Thought experiment:you're starving,huddled in the fetal position in a hole in the ground,with no sense of the world around you,except that you are really,really cold.In fact,your internal temperature can go as low...Thought experiment:you're starving,huddled in the fetal position in a hole in the ground,with no sense of the world around you,except that you are really,really cold.In fact,your internal temperature can go as low as–2.9℃,which is as dangerous as it sounds,and somehow,you are not freaking out.展开更多
Changes in protein abundance and reversible protein phosphorylation(RPP)play important roles in regulating hypometabolism but have never been documented in overwintering frogs at high altitudes.To test the hypothesis ...Changes in protein abundance and reversible protein phosphorylation(RPP)play important roles in regulating hypometabolism but have never been documented in overwintering frogs at high altitudes.To test the hypothesis that protein abundance and phosphorylation change in response to winter hibernation,we conducted a comprehensive and quantitative proteomic and phosphoproteomic analysis of the liver of the Xizang plateau frog,Nanorana parkeri,living on the Qinghai-Xizang Plateau.In total,5170 proteins and 5695 phosphorylation sites in 1938 proteins were quantified.Based on proteomic analysis,674 differentially expressed proteins(438 up-regulated,236 down-regulated)were screened in hibernating N.parkeri versus summer individuals.Functional enrichment analysis revealed that higher expressed proteins in winter were significantly enriched in immune-related signaling pathways,whereas lower expressed proteins were mainly involved in metabolic processes.A total of 4251 modified sites(4147 up-regulated,104 down-regulated)belonging to 1638 phosphoproteins(1555 up-regulated,83 down-regulated)were significantly changed in the liver.During hibernation,RPP regulated a diverse array of proteins involved in multiple functions,including metabolic enzymatic activity,ion transport,protein turnover,signal transduction,and alternative splicing.These changes contribute to enhancing protection,suppressing energy-consuming processes,and inducing metabolic depression.Moreover,the activities of phosphofructokinase,glutamate dehydrogenase,and ATPase were all significantly lower in winter compared to summer.In conclusion,our results support the hypothesis and demonstrate the importance of RPP as a regulatory mechanism when animals transition into a hypometabolic state.展开更多
Adaptative strategies of the frog, Nanorana parkeri, to extreme environments at high altitude are linked with the evolution of their own genetic mechanisms and phenotypic traits. However, to date, the roles of symbiot...Adaptative strategies of the frog, Nanorana parkeri, to extreme environments at high altitude are linked with the evolution of their own genetic mechanisms and phenotypic traits. However, to date, the roles of symbiotic microbiomes in host adaptation to environmental extremes remain enigmatic. In the present study, the 16S rRNA gene amplicon coupled with metagenomic sequencing was used to explore composition as well as potential functions of microbiomes in the gut of N. parkeri collected at both low(3 400 m above sea level(a.s.l.)) and high(4 600 m a.s.l.)altitudes on the Qinghai-Xizang Plateau. We found that the phylum Firmicutes and genera,such as unclassified_Peptostreptococcaceae,unclassified_Lachnospiraceae, Breznakia, and unclassified_Ruminococcaceae, dominated the core gut microbiomes at both altitudes. High-altitude frogs have a lower alpha diversity of gut microbiome than low-altitude individuals. Moreover, two potentially butyrate-producing bacterial genera, Anaerovorax and Pygmaiobacter, exhibited higher relative abundances in high-altitude individuals versus low-altitude frogs.Notably, at high altitude, families such as antibacterial GH90 and GT103, associated with inflammation attenuation, showed a significantly high relative abundance, whereas GT48, contributing to the synthesis of fungal cell walls, exhibited a significant decrease in the relative abundance. The current study provides novel insights into the role of gut microbiomes in the adaptation of amphibians to high-altitude environments.展开更多
Muscle wasting is common in mammals during extended periods of immobility. However, many small hibernating mammals manage to avoid muscle atrophy despite remaining stationary for long periods during hibernation. Recen...Muscle wasting is common in mammals during extended periods of immobility. However, many small hibernating mammals manage to avoid muscle atrophy despite remaining stationary for long periods during hibernation. Recent research has highlighted roles for short non-coding microRNAs （miRNAs） in the regulation of stress tolerance. We proposed that they could also play an important role in muscle maintenance during hibernation. To explore this possibility, a group of 10 miRNAs known to be normally expressed in skeletal muscle of non-hibernating mammals were analyzed by RT-PCR in hibernating little brown bats, Myotis lucifugus. We then compared the expression of these miRNAs in euthermic control bats and bats in torpor. Our results showed that compared to euthermic controls, sig- nificant, albeit modest （1.2-1.6 fold）, increases in transcript expression were observed for eight mature miRNAs, including miR-la-1, miR-29b, miR-181b, miR-15a, miR-20a, miR-206 and miR-128-1, in the pectoral muscle of torpid bats. Conversely, expression of miR-21 decreased by 80% during torpor, while expression of miR-107 remained unaffected. Interestingly, these miRNAs have been either validated or predicted to affect multiple muscle-specific factors, including myostatin, FoxO3a, HDAC4 and SMADT, and are likely involved in the preservation of pectoral muscle mass and functionality during bat hibernation.展开更多
Several recent studies of vertebrate adaptation to environmental stress have suggested roles for microRNAs （miRNAs） in regulating glo- bal suppression of protein synthesis and/or restructuring protein expression pat...Several recent studies of vertebrate adaptation to environmental stress have suggested roles for microRNAs （miRNAs） in regulating glo- bal suppression of protein synthesis and/or restructuring protein expression patterns. The present study is the first to characterize stress- responsive alterations in the expression of miRNAs during natural freezing or anoxia exposures in an invertebrate species, the intertidal gastropod Littorina littorea. These snails are exposed to anoxia and freezing conditions as their environment constantly fluctuates on both a tidal and seasonal basis. The expression of selected miRNAs that are known to influence the cell cycle, cellular signaling pathways, carbohydrate metabolism and apoptosis was evaluated using RT-PCR. Compared to controls, significant changes in expression were observed for miR-la-1, miR-34a and miR-29b in hepatopancreas and for miR-la-1, miR-34a, miR-133a, miR-125b, miR-29b and miR-2a in foot muscle after freezing exposure at -6 ~C for 24 h （P 〈 0.05）. In addition, in response to anoxia stress for 24 h, significant changes in expression were also observed for miR-la-1, miR-210 and miR-29b in hepatopancreas and for miR-1 a-1, miR-34a, miR-133a, miR-29b and miR-2a in foot muscle （P 〈 0.05）. Moreover, protein expression of Dicer, an enzyme responsible for mature microRNA processing, was increased in foot muscle during freezing and anoxia and in hepatopancreas during freezing. Alterations in expression of these miRNAs in L. littorea tissues may contribute to organismal survival under freezing and anoxia.展开更多
Micro RNAs（mi RNAs） are small non-coding RNAs that are important in regulating metabolic stress. In this study, we determined the expression and structural characteristics of 20 mi RNAs in brown（BAT） and white adi...Micro RNAs（mi RNAs） are small non-coding RNAs that are important in regulating metabolic stress. In this study, we determined the expression and structural characteristics of 20 mi RNAs in brown（BAT） and white adipose tissue（WAT） during torpor in thirteen-lined ground squirrels. Using a modified stem-loop technique, we found that during torpor, expression of six mi RNAs including let-7a, let-7b, mi R-107, mi R-150, mi R-222 and mi R-31 was significantly downregulated in WAT（P 〈 0.05）, which was 16%–54% of euthermic non-torpid control squirrels,whereas expression of three mi RNAs including mi R-143, mi R-200 a and mi R-519 d was found to be upregulated by 1.32–2.34-fold. Similarly, expression of more mi RNAs was downregulated in BAT during torpor. We detected reduced expression of 6 mi RNAs including mi R-103 a, mi R-107, mi R-125 b, mi R-21, mi R-221 and mi R-31（48%–70% of control）, while only expression of mi R-138 was significantly upregulated（2.91 ± 0.8-fold of the control, P 〈 0.05）. Interestingly,mi RNAs found to be downregulated in WAT during torpor were similar to those dysregulated in obese humans for increased adipogenesis, whereas mi RNAs with altered expression in BAT during torpor were linked to mitochondrial b-oxidation. mi RPath target prediction analysis showed that mi RNAs downregulated in both WAT and BAT were associated with the regulation of mitogen-activated protein kinase（MAPK） signaling, while the mi RNAs upregulated in WAT were linked to transforming growth factor b（TGFb） signaling. Compared to mouse sequences, no unique nucleotide substitutions within the stem-loop region were discovered for the associated pre-mi RNAs for the mi RNAs used in this study, suggesting no structure-influenced changes in pre-mi RNA processing efficiency in the squirrel. As well, the expression of mi RNA processingenzyme Dicer remained unchanged in both tissues during torpor. Overall, our findings suggest that changes of mi RNA expression in adipose tissues may be linked to distinct biological roles in WAT and BAT during hibernation and may involve the regulation of signaling cascades.展开更多
Metabolic rate depression is an important survival strategy for many animal species and a common element of hibernation,torpor,estivation,anoxia and diapause.Studies of the molecular mechanisms that regulate reversibl...Metabolic rate depression is an important survival strategy for many animal species and a common element of hibernation,torpor,estivation,anoxia and diapause.Studies of the molecular mechanisms that regulate reversible transitions to and from hypometabolic states have identified principles of regulatory control.These control mechanisms are conserved among biologically diverse organisms and include the coordinated reduction of specific groups of key regulatory enzymes or proteins in the cell,a process likely driven by microRNA target repression/degradation.The present review focuses on a growing area of research in hypometabolism and mechanisms involving the rapid and reversible control of translation facilitated by microRNAs.The analysis draws primarily from current research on three animal models:hibernating mammals,anoxic turtles and freeze-tolerant frogs(with selected examples from multiple other sources).Here,we demonstrate a link between metabolic rate depression,a well-documented response to periods of environmental stress,and microRNA expression.Microarray-based expression profiles and PCR-driven studies have revealed that specific microRNAs are induced in response to environmental stress.Selected members of this group decrease pro-apoptotic signaling,reduce muscle wasting and reduce protein translation,whereas other members contribute to cell cycle arrest and mitogen-activated protein kinase signaling.Many of the same microRNAs are frequently deregulated in numerous disease pathologies and,hence,the hypometabolism model could provide a novel approach for the treatment of stroke and heart attack in humans.展开更多
A natural tolerance of various environmental stresses is typically supported by various cytoprotective mechanisms that protect macromolecules and promote extended viability. Among these are antioxidant defenses that h...A natural tolerance of various environmental stresses is typically supported by various cytoprotective mechanisms that protect macromolecules and promote extended viability. Among these are antioxidant defenses that help to limit damage from reactive oxygen species and chaperones that help to minimize protein misfolding or unfolding under stress conditions. To understand the molecular mechanisms that act to protect cells during primate torpor, the present study characterizes antioxidant and heat shock protein（HSP） responses in various organs of control（aroused）and torpid gray mouse lemurs, Microcebus murinus. Protein expression of HSP70 and HSP90 a was elevated to 1.26 and 1.49 fold, respectively, in brown adipose tissue during torpor as compared with control animals, whereas HSP60 in liver of torpid animals was 1.15 fold of that in control（P 〈 0.05）. Among antioxidant enzymes, protein levels of thioredoxin 1 were elevated to 2.19 fold in white adipose tissue during torpor, whereas Cu–Zn superoxide dismutase 1 levels rose to 1.1 fold in skeletal muscle（P 〈 0.05）. Additionally, total antioxidant capacity was increased to 1.6 fold in liver during torpor（P 〈 0.05）, while remaining unchanged in the five other tissues. Overall, our data suggest that antioxidant and HSP responses are modified in a tissue-specific manner during daily torpor in gray mouse lemurs. Furthermore, our data also show that cytoprotective strategies employed during primate torpor are distinct from the strategies in rodent hibernation as reported in previous studies.展开更多
The gray mouse lemur（Microcebus murinus） is one of few primate species that is able to enter daily torpor or prolonged hibernation in response to environmental stresses. With an emerging significance to human health...The gray mouse lemur（Microcebus murinus） is one of few primate species that is able to enter daily torpor or prolonged hibernation in response to environmental stresses. With an emerging significance to human health research, lemurs present an optimal model for exploring molecular adaptations that regulate primate hypometabolism. A fundamental challenge is how to effectively regulate energy expensive cellular processes（e.g., transcription and translation） during transitionsto/from torpor without disrupting cellular homeostasis. One such regulatory mechanism is reversible posttranslational modification of selected protein targets that offers fine cellular control without the energetic burden. This study investigates the role of phosphorylation and/or acetylation in regulating key factors involved in energy homeostasis（AMP-activated protein kinase, or AMPK, signaling pathway）, m RNA translation（eukaryotic initiation factor 2a or e IF2 a, eukaryotic initiation factor 4E or e IF4 E, and initiation factor 4E binding protein or 4EBP）, and gene transcription（histone H3） in six tissues of torpid and aroused gray mouse lemurs. Our results indicated selective tissue-specific changes of these regulatory proteins. The relative level of Thr172-phosphorylated AMPKa was significantly elevated in the heart but reduced in brown adipose tissue during daily torpor, as compared to the aroused lemurs, implicating the regulation of AMPK activity during daily torpor in these tissues. Interestingly, the levels of the phosphorylated e IFs were largely unaltered between aroused and torpid animals. Phosphorylation and acetylation of histone H3 were examined as a marker for transcriptional regulation. Compared to the aroused lemurs, level of Ser10-phosphorylated histone H3 decreased significantly in white adipose tissue during torpor, suggesting global suppression of gene transcription. However, a significant increase in acetyl-histone H3 in the heart of torpid lemurs indicated a possible stimulation of transcriptional activity of this tissue. Overall, our study demonstrates that AMPK signaling and posttranslational regulation of selected proteins may play crucial roles in the control of transcription/translation during daily torpor in mouse lemurs.展开更多
Very few selected species of primates are known to be capable of entering torpor. This exciting discovery means that the ability to enter a natural state of dormancy is an ancestral trait among primates and, in phylog...Very few selected species of primates are known to be capable of entering torpor. This exciting discovery means that the ability to enter a natural state of dormancy is an ancestral trait among primates and, in phylogenetic terms, is very close to the human lineage. To explore the regulatory mechanisms that underlie primate torpor, we analyzed signal transduction cascades to discover those involved in coordinating tissue responses during torpor. The responses of mitogen-activated protein kinase（MAPK） family members to primate torpor were compared in six organs of control（aroused） versus torpid gray mouse lemurs, Microcebus murinus. The proteins examined include extracellular signal-regulated kinases（ERKs）, c-jun NH2-terminal kinases（JNKs）, MAPK kinase（MEK）, and p38, in addition to stress-related proteins p53 and heat shock protein 27（HSP27）. The activation of specific MAPK signal transduction pathways may provide a mechanism to regulate the expression of torpor-responsive genes or the regulation of selected downstream cellular processes. In response to torpor, each MAPK subfamily responded differently during torpor and each showed organ-specific patterns of response. For example, skeletal muscle displayed elevated relative phosphorylation of ERK1/2 during torpor. Interestingly, adipose tissues showed the highest degree of MAPK activation. Brown adipose tissue displayed an activation of ERK1/2 and p38, whereas white adipose tissue showed activation of ERK1/2, p38, MEK, and JNK during torpor. Importantly, both adipose tissues possess specialized functions that are critical for torpor, with brown adipose required for non-shivering thermogenesis and white adipose utilized as the primary source of lipid fuel for torpor. Overall, these data indicate crucial roles of MAPKs in the regulation of primate organs during torpor.展开更多
Different responses or tolerance to thermal stress between invasive and native species can affect the outcome of interactions between climate change and biological invasion.However,knowledge about the physiological me...Different responses or tolerance to thermal stress between invasive and native species can affect the outcome of interactions between climate change and biological invasion.However,knowledge about the physiological mechanisms that modulate the interspecific differences in thermal tolerance is limited.The present study analyzes the metabolic responses to thermal stress by the globally invasive turtle,Trachemys scripta elegans,as compared with two co-occurring native turtle species in China,Pelodiscus sinensis and Mauremys reevesii.Changes in metabolite contents and the expression or enzyme activities of genes involved in energy sensing,glucose metabolism,lipid metabolism,and tricarboxylic acid(TCA)cycle after exposure to gradient temperatures were assessed in turtle juveniles.Invasive and native turtles showed distinct metabolic responses to thermal stress.T.scripta elegans showed greater transcriptional regulation of energy sensors than the native turtles.Enhanced anaerobic metabolism was needed by all three species under extreme heat conditions,but phosphoenolpyruvate carboxykinase and lactate dehydrogenase in the invader showed stronger upregulation or stable responses than the native species,which showed inhibition by high temperatures.These contrasts were pronounced in the muscles of the three species.Regulation of lipid metabolism was observed in both T.scripta elegans and P.sinensis but not in M.reevesii under thermal stress.Thermal stress did not inhibit the TCA cycle in turtles.Different metabolic responses to thermal stress may contribute to interspecific differences in thermal tolerance.Overall,our study further suggested the potential role of physiological differences in mediating interactions between climate change and biological invasion.展开更多
Gray mouse lemurs（Microcebus murinus） from Madagascar present an excellent model for studies of torpor regulation in a primate species. In the present study, we analyzed the response of the insulin signaling pathway...Gray mouse lemurs（Microcebus murinus） from Madagascar present an excellent model for studies of torpor regulation in a primate species. In the present study, we analyzed the response of the insulin signaling pathway as well as controls on carbohydrate sparing in six different tissues of torpid versus aroused gray mouse lemurs. We found that the relative level of phospho-insulin receptor substrate（IRS-1） was significantly increased in muscle, whereas the level of phospho-insulin receptor（IR） was decreased in white adipose tissue（WAT） of torpid animals, both suggesting an inhibition of insulin/insulin-like growth factor-1（IGF-1） signaling during torpor in these tissues. By contrast, the level of phospho-IR was increased in the liver. Interestingly, muscle,WAT, and liver occupy central roles in whole body homeostasis and each displays regulatory controls operating at the plasma membrane. Changes in other tissues included an increase in phosphoglycogen synthase kinase 3a（GSK3a） and decrease in phospho-ribosomal protein S6（RPS6） in the heart, and a decrease in phospho-mammalian target of rapamycin（m TOR） in the kidney. Pyruvate dehydrogenase（PDH） that gates carbohydrate entry into mitochondria is inhibited via phosphorylation by pyruvate dehydrogenase kinase（e.g., PDK4）. In the skeletal muscle, the protein expression of PDK4 and phosphorylated PDH at Ser 300 was increased, suggesting inhibition during torpor. In contrast, there were no changes in levels of PDH expression and phosphorylation in other tissues comparing torpid and aroused animals. Information gained from these studies highlight the molecular controls that help to regulate metabolic rate depression and balance energetics during primate torpor.展开更多
The use of daily torpor and/or of multi-day torpor bouts during a hibernation season are energy-saving survival strategies that have been well-studied for many years,particularly for small mammals living in seasonally...The use of daily torpor and/or of multi-day torpor bouts during a hibernation season are energy-saving survival strategies that have been well-studied for many years,particularly for small mammals living in seasonally-cold environments.Both phenomena are characterized by a regulated suppression of metabolic rate,展开更多
During food shortages, the gray mouse lemur（Microcebus murinus） of Madagascar experiences daily torpor thereby reducing energy expenditures. The present study aimed to understand the impacts of torpor on the immune ...During food shortages, the gray mouse lemur（Microcebus murinus） of Madagascar experiences daily torpor thereby reducing energy expenditures. The present study aimed to understand the impacts of torpor on the immune system and antioxidant response in the gut of these animals.This interaction may be of critical importance given the trade-off between the energetically costly immune response and the need to defend against pathogen entry during hypometabolism. The protein levels of cytokines and antioxidants were measured in the small intestine（duodenum, jejunum,and ileum） and large intestine of aroused and torpid lemurs. While there was a significant decrease of some pro-inflammatory cytokines（IL-6 and TNF-a） in the duodenum and jejunum during torpor as compared to aroused animals, there was no change in anti-inflammatory cytokines. We observed decreased levels of cytokines（IL-12p70 and M-CSF）, and several chemokines（MCP-1and MIP-2） but an increase in MIP-1a in the jejunum of the torpid animals. In addition, we evaluated antioxidant response by examining the protein levels of antioxidant enzymes and total antioxidant capacity provided by metabolites such as glutathione（and others）. Our results indicatedthat levels of antioxidant enzymes did not change between torpor and aroused states, although antioxidant capacity was significantly higher in the ileum during torpor. These data suggest a suppression of the immune response, likely as an energy conservation measure, and a limited role of antioxidant defenses in supporting torpor in lemur intestine.展开更多
A variety of mammals employ torpor as an energy-saving strategy in environments of marginal or severe stress either on a daily basis during their inactive period or on a seasonal basis during prolonged multi-day hiber...A variety of mammals employ torpor as an energy-saving strategy in environments of marginal or severe stress either on a daily basis during their inactive period or on a seasonal basis during prolonged multi-day hibernation. Recently, a few Madagascar lemur species have been identified as the only primates that exhibit torpor; one of these is the gray mouse lemur（Microcebus murinus）. To explore the regulatory mechanisms that underlie daily torpor in a primate, we analyzed the expression of 28 selected genes that represent crucial survival pathways known to be involved in squirrel and bat hibernation. Array-based real-time PCR was used to compare gene expression in control（aroused） versus torpid lemurs in five tissues including the liver, kidney,skeletal muscle, heart, and brown adipose tissue. Significant differences in gene expression during torpor were revealed among genes involved in glycolysis, fatty acid metabolism, antioxidant defense, apoptosis, hypoxia signaling, and protein protection. The results showed upregulation of select genes primarily in liver and brown adipose tissue. For instance, both tissues showed elevated gene expression of peroxisome proliferator activated receptor gamma（ppargc）, ferritin（fth1）, and protein chaperones during torpor. Overall, the data show that the expression of only a few genes changed during lemur daily torpor, as compared with the broader expression changes reported for hibernation in ground squirrels. These results provide an indication that the alterations in gene expression required for torpor in lemurs are not as extensive as those needed for winter hibernation in squirrel models. However, identification of crucial genes with altered expression that support lemur torpor provides key targets to be explored and manipulated toward a goal of translational applications of inducible torpor as a treatment option in human biomedicine.展开更多
基金a Discovery grant from the Natural Sciences and Engineering Research Council(NSERC)of Canada(6793)awarded to KBS,and by NSERC doctoral scholarship awarded to SML.
文摘Thought experiment:you're starving,huddled in the fetal position in a hole in the ground,with no sense of the world around you,except that you are really,really cold.In fact,your internal temperature can go as low as–2.9℃,which is as dangerous as it sounds,and somehow,you are not freaking out.
基金supported by the National Natural Science Foundation of China(32001110)Training Program for Cultivating Highlevel Talents by the China Scholarship Council(2021lxjjw01)Open Project of State Key Laboratory of Plateau Ecology and Agriculture,Qinghai University(2021-KF-004)。
文摘Changes in protein abundance and reversible protein phosphorylation(RPP)play important roles in regulating hypometabolism but have never been documented in overwintering frogs at high altitudes.To test the hypothesis that protein abundance and phosphorylation change in response to winter hibernation,we conducted a comprehensive and quantitative proteomic and phosphoproteomic analysis of the liver of the Xizang plateau frog,Nanorana parkeri,living on the Qinghai-Xizang Plateau.In total,5170 proteins and 5695 phosphorylation sites in 1938 proteins were quantified.Based on proteomic analysis,674 differentially expressed proteins(438 up-regulated,236 down-regulated)were screened in hibernating N.parkeri versus summer individuals.Functional enrichment analysis revealed that higher expressed proteins in winter were significantly enriched in immune-related signaling pathways,whereas lower expressed proteins were mainly involved in metabolic processes.A total of 4251 modified sites(4147 up-regulated,104 down-regulated)belonging to 1638 phosphoproteins(1555 up-regulated,83 down-regulated)were significantly changed in the liver.During hibernation,RPP regulated a diverse array of proteins involved in multiple functions,including metabolic enzymatic activity,ion transport,protein turnover,signal transduction,and alternative splicing.These changes contribute to enhancing protection,suppressing energy-consuming processes,and inducing metabolic depression.Moreover,the activities of phosphofructokinase,glutamate dehydrogenase,and ATPase were all significantly lower in winter compared to summer.In conclusion,our results support the hypothesis and demonstrate the importance of RPP as a regulatory mechanism when animals transition into a hypometabolic state.
文摘Adaptative strategies of the frog, Nanorana parkeri, to extreme environments at high altitude are linked with the evolution of their own genetic mechanisms and phenotypic traits. However, to date, the roles of symbiotic microbiomes in host adaptation to environmental extremes remain enigmatic. In the present study, the 16S rRNA gene amplicon coupled with metagenomic sequencing was used to explore composition as well as potential functions of microbiomes in the gut of N. parkeri collected at both low(3 400 m above sea level(a.s.l.)) and high(4 600 m a.s.l.)altitudes on the Qinghai-Xizang Plateau. We found that the phylum Firmicutes and genera,such as unclassified_Peptostreptococcaceae,unclassified_Lachnospiraceae, Breznakia, and unclassified_Ruminococcaceae, dominated the core gut microbiomes at both altitudes. High-altitude frogs have a lower alpha diversity of gut microbiome than low-altitude individuals. Moreover, two potentially butyrate-producing bacterial genera, Anaerovorax and Pygmaiobacter, exhibited higher relative abundances in high-altitude individuals versus low-altitude frogs.Notably, at high altitude, families such as antibacterial GH90 and GT103, associated with inflammation attenuation, showed a significantly high relative abundance, whereas GT48, contributing to the synthesis of fungal cell walls, exhibited a significant decrease in the relative abundance. The current study provides novel insights into the role of gut microbiomes in the adaptation of amphibians to high-altitude environments.
基金supported by a Discovery grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada (Grant No. 6793)
文摘Muscle wasting is common in mammals during extended periods of immobility. However, many small hibernating mammals manage to avoid muscle atrophy despite remaining stationary for long periods during hibernation. Recent research has highlighted roles for short non-coding microRNAs （miRNAs） in the regulation of stress tolerance. We proposed that they could also play an important role in muscle maintenance during hibernation. To explore this possibility, a group of 10 miRNAs known to be normally expressed in skeletal muscle of non-hibernating mammals were analyzed by RT-PCR in hibernating little brown bats, Myotis lucifugus. We then compared the expression of these miRNAs in euthermic control bats and bats in torpor. Our results showed that compared to euthermic controls, sig- nificant, albeit modest （1.2-1.6 fold）, increases in transcript expression were observed for eight mature miRNAs, including miR-la-1, miR-29b, miR-181b, miR-15a, miR-20a, miR-206 and miR-128-1, in the pectoral muscle of torpid bats. Conversely, expression of miR-21 decreased by 80% during torpor, while expression of miR-107 remained unaffected. Interestingly, these miRNAs have been either validated or predicted to affect multiple muscle-specific factors, including myostatin, FoxO3a, HDAC4 and SMADT, and are likely involved in the preservation of pectoral muscle mass and functionality during bat hibernation.
基金supported by a Discovery Grant from the Natural Sciences and Engineering Research Council (NSERC Grant No. 6793) of CanadaK.K. Biggar held an NSERC postgraduate fellowship, and S.F. Kornfeld and Y. Maistrovski were supported by NSERC undergraduate summer research awards
文摘Several recent studies of vertebrate adaptation to environmental stress have suggested roles for microRNAs （miRNAs） in regulating glo- bal suppression of protein synthesis and/or restructuring protein expression patterns. The present study is the first to characterize stress- responsive alterations in the expression of miRNAs during natural freezing or anoxia exposures in an invertebrate species, the intertidal gastropod Littorina littorea. These snails are exposed to anoxia and freezing conditions as their environment constantly fluctuates on both a tidal and seasonal basis. The expression of selected miRNAs that are known to influence the cell cycle, cellular signaling pathways, carbohydrate metabolism and apoptosis was evaluated using RT-PCR. Compared to controls, significant changes in expression were observed for miR-la-1, miR-34a and miR-29b in hepatopancreas and for miR-la-1, miR-34a, miR-133a, miR-125b, miR-29b and miR-2a in foot muscle after freezing exposure at -6 ~C for 24 h （P 〈 0.05）. In addition, in response to anoxia stress for 24 h, significant changes in expression were also observed for miR-la-1, miR-210 and miR-29b in hepatopancreas and for miR-1 a-1, miR-34a, miR-133a, miR-29b and miR-2a in foot muscle （P 〈 0.05）. Moreover, protein expression of Dicer, an enzyme responsible for mature microRNA processing, was increased in foot muscle during freezing and anoxia and in hepatopancreas during freezing. Alterations in expression of these miRNAs in L. littorea tissues may contribute to organismal survival under freezing and anoxia.
基金supported by a Discovery grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada (Grant No. 6793)supported by the NSERC postgraduate fellowships
文摘Micro RNAs（mi RNAs） are small non-coding RNAs that are important in regulating metabolic stress. In this study, we determined the expression and structural characteristics of 20 mi RNAs in brown（BAT） and white adipose tissue（WAT） during torpor in thirteen-lined ground squirrels. Using a modified stem-loop technique, we found that during torpor, expression of six mi RNAs including let-7a, let-7b, mi R-107, mi R-150, mi R-222 and mi R-31 was significantly downregulated in WAT（P 〈 0.05）, which was 16%–54% of euthermic non-torpid control squirrels,whereas expression of three mi RNAs including mi R-143, mi R-200 a and mi R-519 d was found to be upregulated by 1.32–2.34-fold. Similarly, expression of more mi RNAs was downregulated in BAT during torpor. We detected reduced expression of 6 mi RNAs including mi R-103 a, mi R-107, mi R-125 b, mi R-21, mi R-221 and mi R-31（48%–70% of control）, while only expression of mi R-138 was significantly upregulated（2.91 ± 0.8-fold of the control, P 〈 0.05）. Interestingly,mi RNAs found to be downregulated in WAT during torpor were similar to those dysregulated in obese humans for increased adipogenesis, whereas mi RNAs with altered expression in BAT during torpor were linked to mitochondrial b-oxidation. mi RPath target prediction analysis showed that mi RNAs downregulated in both WAT and BAT were associated with the regulation of mitogen-activated protein kinase（MAPK） signaling, while the mi RNAs upregulated in WAT were linked to transforming growth factor b（TGFb） signaling. Compared to mouse sequences, no unique nucleotide substitutions within the stem-loop region were discovered for the associated pre-mi RNAs for the mi RNAs used in this study, suggesting no structure-influenced changes in pre-mi RNA processing efficiency in the squirrel. As well, the expression of mi RNA processingenzyme Dicer remained unchanged in both tissues during torpor. Overall, our findings suggest that changes of mi RNA expression in adipose tissues may be linked to distinct biological roles in WAT and BAT during hibernation and may involve the regulation of signaling cascades.
基金supported by the National Science and Engineering Research Council Canada[grant number 6793].
文摘Metabolic rate depression is an important survival strategy for many animal species and a common element of hibernation,torpor,estivation,anoxia and diapause.Studies of the molecular mechanisms that regulate reversible transitions to and from hypometabolic states have identified principles of regulatory control.These control mechanisms are conserved among biologically diverse organisms and include the coordinated reduction of specific groups of key regulatory enzymes or proteins in the cell,a process likely driven by microRNA target repression/degradation.The present review focuses on a growing area of research in hypometabolism and mechanisms involving the rapid and reversible control of translation facilitated by microRNAs.The analysis draws primarily from current research on three animal models:hibernating mammals,anoxic turtles and freeze-tolerant frogs(with selected examples from multiple other sources).Here,we demonstrate a link between metabolic rate depression,a well-documented response to periods of environmental stress,and microRNA expression.Microarray-based expression profiles and PCR-driven studies have revealed that specific microRNAs are induced in response to environmental stress.Selected members of this group decrease pro-apoptotic signaling,reduce muscle wasting and reduce protein translation,whereas other members contribute to cell cycle arrest and mitogen-activated protein kinase signaling.Many of the same microRNAs are frequently deregulated in numerous disease pathologies and,hence,the hypometabolism model could provide a novel approach for the treatment of stroke and heart attack in humans.
基金supported by a Discovery grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada (Grant No. 6793)a grant from the Heart and Stroke Foundation of Canada (Grant No. G-140005874) to KBS. KBS holds the Canada Research Chair in Molecular PhysiologyCWW, KKB, and SNT all held NSERC postgraduate scholarships
文摘A natural tolerance of various environmental stresses is typically supported by various cytoprotective mechanisms that protect macromolecules and promote extended viability. Among these are antioxidant defenses that help to limit damage from reactive oxygen species and chaperones that help to minimize protein misfolding or unfolding under stress conditions. To understand the molecular mechanisms that act to protect cells during primate torpor, the present study characterizes antioxidant and heat shock protein（HSP） responses in various organs of control（aroused）and torpid gray mouse lemurs, Microcebus murinus. Protein expression of HSP70 and HSP90 a was elevated to 1.26 and 1.49 fold, respectively, in brown adipose tissue during torpor as compared with control animals, whereas HSP60 in liver of torpid animals was 1.15 fold of that in control（P 〈 0.05）. Among antioxidant enzymes, protein levels of thioredoxin 1 were elevated to 2.19 fold in white adipose tissue during torpor, whereas Cu–Zn superoxide dismutase 1 levels rose to 1.1 fold in skeletal muscle（P 〈 0.05）. Additionally, total antioxidant capacity was increased to 1.6 fold in liver during torpor（P 〈 0.05）, while remaining unchanged in the five other tissues. Overall, our data suggest that antioxidant and HSP responses are modified in a tissue-specific manner during daily torpor in gray mouse lemurs. Furthermore, our data also show that cytoprotective strategies employed during primate torpor are distinct from the strategies in rodent hibernation as reported in previous studies.
基金supported by a Discovery grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada (Grant No. 6793)a grant from the Heart and Stroke Foundation of Canada (Grant No. G-14-0005874) to KBS. KBS holds the Canada Research Chair in Molecular PhysiologySNT, KKB, and CWW all held NSERC postgraduate scholarships
文摘The gray mouse lemur（Microcebus murinus） is one of few primate species that is able to enter daily torpor or prolonged hibernation in response to environmental stresses. With an emerging significance to human health research, lemurs present an optimal model for exploring molecular adaptations that regulate primate hypometabolism. A fundamental challenge is how to effectively regulate energy expensive cellular processes（e.g., transcription and translation） during transitionsto/from torpor without disrupting cellular homeostasis. One such regulatory mechanism is reversible posttranslational modification of selected protein targets that offers fine cellular control without the energetic burden. This study investigates the role of phosphorylation and/or acetylation in regulating key factors involved in energy homeostasis（AMP-activated protein kinase, or AMPK, signaling pathway）, m RNA translation（eukaryotic initiation factor 2a or e IF2 a, eukaryotic initiation factor 4E or e IF4 E, and initiation factor 4E binding protein or 4EBP）, and gene transcription（histone H3） in six tissues of torpid and aroused gray mouse lemurs. Our results indicated selective tissue-specific changes of these regulatory proteins. The relative level of Thr172-phosphorylated AMPKa was significantly elevated in the heart but reduced in brown adipose tissue during daily torpor, as compared to the aroused lemurs, implicating the regulation of AMPK activity during daily torpor in these tissues. Interestingly, the levels of the phosphorylated e IFs were largely unaltered between aroused and torpid animals. Phosphorylation and acetylation of histone H3 were examined as a marker for transcriptional regulation. Compared to the aroused lemurs, level of Ser10-phosphorylated histone H3 decreased significantly in white adipose tissue during torpor, suggesting global suppression of gene transcription. However, a significant increase in acetyl-histone H3 in the heart of torpid lemurs indicated a possible stimulation of transcriptional activity of this tissue. Overall, our study demonstrates that AMPK signaling and posttranslational regulation of selected proteins may play crucial roles in the control of transcription/translation during daily torpor in mouse lemurs.
基金supported by a Discovery grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada (Grant No. 6793)a grant from the Heart and Stroke Foundation of Canada (Grant No. G-140005874) to KBS. KBS holds the Canada Research Chair in Molecular PhysiologyKKB, CWW, and SNT all held NSERC postgraduate scholarships
文摘Very few selected species of primates are known to be capable of entering torpor. This exciting discovery means that the ability to enter a natural state of dormancy is an ancestral trait among primates and, in phylogenetic terms, is very close to the human lineage. To explore the regulatory mechanisms that underlie primate torpor, we analyzed signal transduction cascades to discover those involved in coordinating tissue responses during torpor. The responses of mitogen-activated protein kinase（MAPK） family members to primate torpor were compared in six organs of control（aroused） versus torpid gray mouse lemurs, Microcebus murinus. The proteins examined include extracellular signal-regulated kinases（ERKs）, c-jun NH2-terminal kinases（JNKs）, MAPK kinase（MEK）, and p38, in addition to stress-related proteins p53 and heat shock protein 27（HSP27）. The activation of specific MAPK signal transduction pathways may provide a mechanism to regulate the expression of torpor-responsive genes or the regulation of selected downstream cellular processes. In response to torpor, each MAPK subfamily responded differently during torpor and each showed organ-specific patterns of response. For example, skeletal muscle displayed elevated relative phosphorylation of ERK1/2 during torpor. Interestingly, adipose tissues showed the highest degree of MAPK activation. Brown adipose tissue displayed an activation of ERK1/2 and p38, whereas white adipose tissue showed activation of ERK1/2, p38, MEK, and JNK during torpor. Importantly, both adipose tissues possess specialized functions that are critical for torpor, with brown adipose required for non-shivering thermogenesis and white adipose utilized as the primary source of lipid fuel for torpor. Overall, these data indicate crucial roles of MAPKs in the regulation of primate organs during torpor.
基金funded by the Youth Science Foundation of the National Natural Science Foundation of China(No.31901094)the University Natural Science Foundation of Jiangsu Province(22KJD190002)。
文摘Different responses or tolerance to thermal stress between invasive and native species can affect the outcome of interactions between climate change and biological invasion.However,knowledge about the physiological mechanisms that modulate the interspecific differences in thermal tolerance is limited.The present study analyzes the metabolic responses to thermal stress by the globally invasive turtle,Trachemys scripta elegans,as compared with two co-occurring native turtle species in China,Pelodiscus sinensis and Mauremys reevesii.Changes in metabolite contents and the expression or enzyme activities of genes involved in energy sensing,glucose metabolism,lipid metabolism,and tricarboxylic acid(TCA)cycle after exposure to gradient temperatures were assessed in turtle juveniles.Invasive and native turtles showed distinct metabolic responses to thermal stress.T.scripta elegans showed greater transcriptional regulation of energy sensors than the native turtles.Enhanced anaerobic metabolism was needed by all three species under extreme heat conditions,but phosphoenolpyruvate carboxykinase and lactate dehydrogenase in the invader showed stronger upregulation or stable responses than the native species,which showed inhibition by high temperatures.These contrasts were pronounced in the muscles of the three species.Regulation of lipid metabolism was observed in both T.scripta elegans and P.sinensis but not in M.reevesii under thermal stress.Thermal stress did not inhibit the TCA cycle in turtles.Different metabolic responses to thermal stress may contribute to interspecific differences in thermal tolerance.Overall,our study further suggested the potential role of physiological differences in mediating interactions between climate change and biological invasion.
基金supported by a Discovery grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada (Grant No. 6793)a grant from the Heart and Stroke Foundation of Canada (Grant No. G-14-0005874) to KBS. KBS holds the Canada Research Chair in Molecular PhysiologySNT, KKB, and CWW all held NSERC postgraduate scholarships
文摘Gray mouse lemurs（Microcebus murinus） from Madagascar present an excellent model for studies of torpor regulation in a primate species. In the present study, we analyzed the response of the insulin signaling pathway as well as controls on carbohydrate sparing in six different tissues of torpid versus aroused gray mouse lemurs. We found that the relative level of phospho-insulin receptor substrate（IRS-1） was significantly increased in muscle, whereas the level of phospho-insulin receptor（IR） was decreased in white adipose tissue（WAT） of torpid animals, both suggesting an inhibition of insulin/insulin-like growth factor-1（IGF-1） signaling during torpor in these tissues. By contrast, the level of phospho-IR was increased in the liver. Interestingly, muscle,WAT, and liver occupy central roles in whole body homeostasis and each displays regulatory controls operating at the plasma membrane. Changes in other tissues included an increase in phosphoglycogen synthase kinase 3a（GSK3a） and decrease in phospho-ribosomal protein S6（RPS6） in the heart, and a decrease in phospho-mammalian target of rapamycin（m TOR） in the kidney. Pyruvate dehydrogenase（PDH） that gates carbohydrate entry into mitochondria is inhibited via phosphorylation by pyruvate dehydrogenase kinase（e.g., PDK4）. In the skeletal muscle, the protein expression of PDK4 and phosphorylated PDH at Ser 300 was increased, suggesting inhibition during torpor. In contrast, there were no changes in levels of PDH expression and phosphorylation in other tissues comparing torpid and aroused animals. Information gained from these studies highlight the molecular controls that help to regulate metabolic rate depression and balance energetics during primate torpor.
基金supported by a Discovery grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada (Grant No. 6793)a grant from the Heart and Stroke Foundation of Canada (Grant No. G-14-0005874) to KBS. KBS holds the Canada Research Chair in Molecular Physiology
文摘The use of daily torpor and/or of multi-day torpor bouts during a hibernation season are energy-saving survival strategies that have been well-studied for many years,particularly for small mammals living in seasonally-cold environments.Both phenomena are characterized by a regulated suppression of metabolic rate,
基金supported by a Discovery grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada (Grant No. 6793)a grant from the Heart and Stroke Foundation of Canada (Grant No. G-14-0005874) to KBS. KBS holds the Canada Research Chair in Molecular PhysiologySNT held a NSERC postgraduate scholarship and BAK held a NSERC postdoctoral fellowship
文摘During food shortages, the gray mouse lemur（Microcebus murinus） of Madagascar experiences daily torpor thereby reducing energy expenditures. The present study aimed to understand the impacts of torpor on the immune system and antioxidant response in the gut of these animals.This interaction may be of critical importance given the trade-off between the energetically costly immune response and the need to defend against pathogen entry during hypometabolism. The protein levels of cytokines and antioxidants were measured in the small intestine（duodenum, jejunum,and ileum） and large intestine of aroused and torpid lemurs. While there was a significant decrease of some pro-inflammatory cytokines（IL-6 and TNF-a） in the duodenum and jejunum during torpor as compared to aroused animals, there was no change in anti-inflammatory cytokines. We observed decreased levels of cytokines（IL-12p70 and M-CSF）, and several chemokines（MCP-1and MIP-2） but an increase in MIP-1a in the jejunum of the torpid animals. In addition, we evaluated antioxidant response by examining the protein levels of antioxidant enzymes and total antioxidant capacity provided by metabolites such as glutathione（and others）. Our results indicatedthat levels of antioxidant enzymes did not change between torpor and aroused states, although antioxidant capacity was significantly higher in the ileum during torpor. These data suggest a suppression of the immune response, likely as an energy conservation measure, and a limited role of antioxidant defenses in supporting torpor in lemur intestine.
基金supported by a Discovery grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada (Grant No. 6793)a grant from the Heart and Stroke Foundation of Canada (Grant No. G-140005874) to KBS. KBS holds the Canada Research Chair in Molecular PhysiologySNT, KKB, and CWW all held NSERC postgraduate scholarships
文摘A variety of mammals employ torpor as an energy-saving strategy in environments of marginal or severe stress either on a daily basis during their inactive period or on a seasonal basis during prolonged multi-day hibernation. Recently, a few Madagascar lemur species have been identified as the only primates that exhibit torpor; one of these is the gray mouse lemur（Microcebus murinus）. To explore the regulatory mechanisms that underlie daily torpor in a primate, we analyzed the expression of 28 selected genes that represent crucial survival pathways known to be involved in squirrel and bat hibernation. Array-based real-time PCR was used to compare gene expression in control（aroused） versus torpid lemurs in five tissues including the liver, kidney,skeletal muscle, heart, and brown adipose tissue. Significant differences in gene expression during torpor were revealed among genes involved in glycolysis, fatty acid metabolism, antioxidant defense, apoptosis, hypoxia signaling, and protein protection. The results showed upregulation of select genes primarily in liver and brown adipose tissue. For instance, both tissues showed elevated gene expression of peroxisome proliferator activated receptor gamma（ppargc）, ferritin（fth1）, and protein chaperones during torpor. Overall, the data show that the expression of only a few genes changed during lemur daily torpor, as compared with the broader expression changes reported for hibernation in ground squirrels. These results provide an indication that the alterations in gene expression required for torpor in lemurs are not as extensive as those needed for winter hibernation in squirrel models. However, identification of crucial genes with altered expression that support lemur torpor provides key targets to be explored and manipulated toward a goal of translational applications of inducible torpor as a treatment option in human biomedicine.
