Metabolomics is an important component of system biology complementing genomics, transcriptomis, ... more Metabolomics is an important component of system biology complementing genomics, transcriptomis, and proteomics. The project is to determine the effects of 6-month green tea polyphenols (GTP) suppl...
Hibernation is a mammalian strategy that uses metabolic plasticity to reduce energy demands and e... more Hibernation is a mammalian strategy that uses metabolic plasticity to reduce energy demands and enable long-term fasting. Fasting mitigates winter food scarcity but eliminates dietary nitrogen, jeopardizing body protein balance. Here, we reveal gut microbiome-mediated urea nitrogen recycling in hibernating thirteen-lined ground squirrels (Ictidomys tridecemlineatus). Ureolytic gut microbes incorporate urea nitrogen into metabolites that are absorbed by the host, with the nitrogen reincorporated into the squirrel’s protein pool. Urea nitrogen recycling is greatest after prolonged fasting in late winter, when urea transporter abundance in gut tissue and urease gene abundance in the microbiome are highest. These results reveal a functional role for the gut microbiome during hibernation and suggest mechanisms by which urea nitrogen recycling may contribute to protein balance in other monogastric animals.
Animals that undergo seasonal cycles of feeding and fasting have adaptations that maintain integr... more Animals that undergo seasonal cycles of feeding and fasting have adaptations that maintain integrity of organ systems when dietary nutrients are lacking. Food deprivation also challenges the gut microbiota, which relies heavily on host diet for metabolic substrates and the gastrointestinal tract, which is influenced by enteral nutrients and microbial activity. Winter fasting in hibernators shifts the microbiota to favor taxa with the capacity to degrade and utilize host-derived substrates and disfavor taxa that prefer complex plant polysaccharides. Microbiome alterations may contribute to hibernation-induced changes in the intestinal immune system, epithelial barrier function, and other host features that are affected by microbial short-chain fatty acids and other metabolites. Understanding mechanisms by which the hibernator host and its gut symbionts adapt to the altered nutritional landscape during winter fasting may provide insights into protective mechanisms that are compromised when nonhibernating species, such as humans, undergo long periods of enteral nutrient deprivation.
Host diet influences the gut microbiota in species that regularly consume food. We showed that wi... more Host diet influences the gut microbiota in species that regularly consume food. We showed that winter fasting in hibernating ground squirrels increases relative abundance of bacterial taxa that can degrade host glycans (e.g., mucins) and reduces abundance of taxa that prefer plant glycans. Here we determined the functional significance of seasonally changing microbiotas by gavaging summer squirrels and aroused hibernators in early and late winter with 13C-inulin (25 mg/kg), a plant-derived fiber resistant to digestion by mammalian enzymes. Subsequent measurement of δ13CO2 in breath over 2-4 h was used an index of bacterial degradation of 13C-inulin. Compared with summer, peak changes in δ13CO2 in hibernators were delayed and/or reduced by 60-90% after 1 month of hibernation (early winter) and nearly abolished after 4 months (late winter). Intraperitoneal injection of 13C-inulin in summer squirrels produced minimal changes in breath δ13CO2, confirming the bacterial nature of the δ13C signal. The results su...
Host diet influences the structure and function of the microbiota in species that regularly consu... more Host diet influences the structure and function of the microbiota in species that regularly consume food. To measure the functional contribution of microbiotas, we developed a metabolome‐microbiome platform (MMP) and novel stable isotopic labeling to trace microbiotas' metabolism in breath, cecum, and host tissues. We combined cavity ringdown spectroscopy to measure real‐time breath biomarkers and NMR‐based metabolomics to analyze metabolome profiles in tissues. We applied MMP to hibernating ground squirrels to assess the role of bacterial metabolism contributing to seasonal changes in diet. Previously, we showed that the long‐term fast of hibernation decreases relative abundance of bacterial taxa that are adept at degrading abundant plant glycans in summer versus their reduction in winter. Here, we determined the functional significance of seasonally changing microbiotas by gavaging Spring and Summer squirrels and aroused hibernators in Winter with 13C‐labeled complex and simple carbohydrates, and comparing against their respective intraperitoneal and antibiotics applications. Measurement of 13CO2/12CO2(δ13C) in breath was used as an index of bacterial degradation of 13C‐substrates and linked to observed changes in 1H‐[13C]‐metabolome profiles. Compared with robust responses in Summer changes in δ13C after 13C‐inulin gavage in hibernators were nearly abolished, whereas squirrels in Early Winter and Spring showed variable responses consistent with their transitional microbiotas. Metabolome profiles mirrored seasonal changes in 13C‐labeled short‐chain fatty acids. These suggest that during hibernation, the gut microbiota gradually loses the capacity to degrade a plant‐derived glycan, and a shift away from taxa that prefer dietary substrates. The results suggest MMP is a powerful tool in analysis of host‐microbe relationships.Support or Funding InformationSupported by funds from NSF (IOS1558044), UW‐Madison Graduate and Veterinary Medicine.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Hibernation is a complex phenotype that enables animals to fast for several months during periods... more Hibernation is a complex phenotype that enables animals to fast for several months during periods of food scarcity. During this time, less of the hibernator's protein is degraded than would be predicted and, in the 13‐lined ground squirrel (Ictidomys tridecemlineatus), muscle volume and protein synthesis rise near the end of the hibernation season despite continued fasting and loss of body mass. With no exogenous nitrogen intake, one nitrogen source to support protein synthesis in late winter could be from urea nitrogen salvage (UNS), a nitrogen recycling process mediated by the ureolytic activity of the hibernator's gut microbiota. We hypothesized that the contribution of UNS to skeletal muscle growth in 13‐lined ground squirrels increases over the hibernation season, and tested this by comparing UNS processes in summer, early hibernation (1 month), and late hibernation (>3 months) squirrels. Data collected thus far suggest that expression of the urea transporter (UT‐B) in cecal tissue is 3‐fold greater in late winter than in summer squirrels (P<0.001; n=12 per group), indicating a greater capacity for transport of urea into the cecum during winter fasting. Real‐time measurement of microbial ureolytic activity using cavity ring‐down spectrometry on squirrels I.P.‐injected with 13C,15N‐labeled urea confirmed the bacterial origin of UNS, because δ13C in breath is substantially reduced in antibiotic‐depleted microbiotas. Isotope ratio mass spectrometry showed that tissues of squirrels treated with 13C,15N‐urea accumulated up to 200x more 15N as saline‐treated control squirrels, confirming that urea‐derived nitrogen is recycled and incorporated into host tissues. Together, these results corroborate UNS in active and hibernating 13‐lined ground squirrels and suggest that this mechanism for nitrogen recycling is a key aspect of the host‐microbe symbiosis in hibernating mammals that helps prepare the squirrels for spring emergence.Support or Funding InformationThis work is supported by NSF award IOS1558044This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Metabolomics is an important component of system biology complementing genomics, transcriptomis, ... more Metabolomics is an important component of system biology complementing genomics, transcriptomis, and proteomics. The project is to determine the effects of 6-month green tea polyphenols (GTP) suppl...
Hibernation is a mammalian strategy that uses metabolic plasticity to reduce energy demands and e... more Hibernation is a mammalian strategy that uses metabolic plasticity to reduce energy demands and enable long-term fasting. Fasting mitigates winter food scarcity but eliminates dietary nitrogen, jeopardizing body protein balance. Here, we reveal gut microbiome-mediated urea nitrogen recycling in hibernating thirteen-lined ground squirrels (Ictidomys tridecemlineatus). Ureolytic gut microbes incorporate urea nitrogen into metabolites that are absorbed by the host, with the nitrogen reincorporated into the squirrel’s protein pool. Urea nitrogen recycling is greatest after prolonged fasting in late winter, when urea transporter abundance in gut tissue and urease gene abundance in the microbiome are highest. These results reveal a functional role for the gut microbiome during hibernation and suggest mechanisms by which urea nitrogen recycling may contribute to protein balance in other monogastric animals.
Animals that undergo seasonal cycles of feeding and fasting have adaptations that maintain integr... more Animals that undergo seasonal cycles of feeding and fasting have adaptations that maintain integrity of organ systems when dietary nutrients are lacking. Food deprivation also challenges the gut microbiota, which relies heavily on host diet for metabolic substrates and the gastrointestinal tract, which is influenced by enteral nutrients and microbial activity. Winter fasting in hibernators shifts the microbiota to favor taxa with the capacity to degrade and utilize host-derived substrates and disfavor taxa that prefer complex plant polysaccharides. Microbiome alterations may contribute to hibernation-induced changes in the intestinal immune system, epithelial barrier function, and other host features that are affected by microbial short-chain fatty acids and other metabolites. Understanding mechanisms by which the hibernator host and its gut symbionts adapt to the altered nutritional landscape during winter fasting may provide insights into protective mechanisms that are compromised when nonhibernating species, such as humans, undergo long periods of enteral nutrient deprivation.
Host diet influences the gut microbiota in species that regularly consume food. We showed that wi... more Host diet influences the gut microbiota in species that regularly consume food. We showed that winter fasting in hibernating ground squirrels increases relative abundance of bacterial taxa that can degrade host glycans (e.g., mucins) and reduces abundance of taxa that prefer plant glycans. Here we determined the functional significance of seasonally changing microbiotas by gavaging summer squirrels and aroused hibernators in early and late winter with 13C-inulin (25 mg/kg), a plant-derived fiber resistant to digestion by mammalian enzymes. Subsequent measurement of δ13CO2 in breath over 2-4 h was used an index of bacterial degradation of 13C-inulin. Compared with summer, peak changes in δ13CO2 in hibernators were delayed and/or reduced by 60-90% after 1 month of hibernation (early winter) and nearly abolished after 4 months (late winter). Intraperitoneal injection of 13C-inulin in summer squirrels produced minimal changes in breath δ13CO2, confirming the bacterial nature of the δ13C signal. The results su...
Host diet influences the structure and function of the microbiota in species that regularly consu... more Host diet influences the structure and function of the microbiota in species that regularly consume food. To measure the functional contribution of microbiotas, we developed a metabolome‐microbiome platform (MMP) and novel stable isotopic labeling to trace microbiotas' metabolism in breath, cecum, and host tissues. We combined cavity ringdown spectroscopy to measure real‐time breath biomarkers and NMR‐based metabolomics to analyze metabolome profiles in tissues. We applied MMP to hibernating ground squirrels to assess the role of bacterial metabolism contributing to seasonal changes in diet. Previously, we showed that the long‐term fast of hibernation decreases relative abundance of bacterial taxa that are adept at degrading abundant plant glycans in summer versus their reduction in winter. Here, we determined the functional significance of seasonally changing microbiotas by gavaging Spring and Summer squirrels and aroused hibernators in Winter with 13C‐labeled complex and simple carbohydrates, and comparing against their respective intraperitoneal and antibiotics applications. Measurement of 13CO2/12CO2(δ13C) in breath was used as an index of bacterial degradation of 13C‐substrates and linked to observed changes in 1H‐[13C]‐metabolome profiles. Compared with robust responses in Summer changes in δ13C after 13C‐inulin gavage in hibernators were nearly abolished, whereas squirrels in Early Winter and Spring showed variable responses consistent with their transitional microbiotas. Metabolome profiles mirrored seasonal changes in 13C‐labeled short‐chain fatty acids. These suggest that during hibernation, the gut microbiota gradually loses the capacity to degrade a plant‐derived glycan, and a shift away from taxa that prefer dietary substrates. The results suggest MMP is a powerful tool in analysis of host‐microbe relationships.Support or Funding InformationSupported by funds from NSF (IOS1558044), UW‐Madison Graduate and Veterinary Medicine.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Hibernation is a complex phenotype that enables animals to fast for several months during periods... more Hibernation is a complex phenotype that enables animals to fast for several months during periods of food scarcity. During this time, less of the hibernator's protein is degraded than would be predicted and, in the 13‐lined ground squirrel (Ictidomys tridecemlineatus), muscle volume and protein synthesis rise near the end of the hibernation season despite continued fasting and loss of body mass. With no exogenous nitrogen intake, one nitrogen source to support protein synthesis in late winter could be from urea nitrogen salvage (UNS), a nitrogen recycling process mediated by the ureolytic activity of the hibernator's gut microbiota. We hypothesized that the contribution of UNS to skeletal muscle growth in 13‐lined ground squirrels increases over the hibernation season, and tested this by comparing UNS processes in summer, early hibernation (1 month), and late hibernation (>3 months) squirrels. Data collected thus far suggest that expression of the urea transporter (UT‐B) in cecal tissue is 3‐fold greater in late winter than in summer squirrels (P<0.001; n=12 per group), indicating a greater capacity for transport of urea into the cecum during winter fasting. Real‐time measurement of microbial ureolytic activity using cavity ring‐down spectrometry on squirrels I.P.‐injected with 13C,15N‐labeled urea confirmed the bacterial origin of UNS, because δ13C in breath is substantially reduced in antibiotic‐depleted microbiotas. Isotope ratio mass spectrometry showed that tissues of squirrels treated with 13C,15N‐urea accumulated up to 200x more 15N as saline‐treated control squirrels, confirming that urea‐derived nitrogen is recycled and incorporated into host tissues. Together, these results corroborate UNS in active and hibernating 13‐lined ground squirrels and suggest that this mechanism for nitrogen recycling is a key aspect of the host‐microbe symbiosis in hibernating mammals that helps prepare the squirrels for spring emergence.Support or Funding InformationThis work is supported by NSF award IOS1558044This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
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