Regulation of Peroxisome Proliferator-Activated Receptor Pathway During Torpor in the Garden Dormouse, Eliomys quercinus

Investigation of seasonal changes in lipid synthesis and metabolism-related genes in the oviduct of Chinese brown frog (<em>Rana dybowskii</em>)

A peculiar physiological characteristic of the Chinese brown frog (Rana dybowskii) is that its oviduct dilates during pre-brumation rather than during the breeding season. This research aimed to examine the expression of genes connected with lipid synthesis and metabolism in the oviduct of R. dybowskii during both the breeding season and pre-brumation. We observed significant changes in the weight and size of the oviduct between the breeding season and pre-brumation. Furthermore, compared to the breeding season, pre-brumation exhibited significantly lower triglyceride content and a marked increase in free fatty acid content. Immunohistochemical results revealed the spatial distribution of triglyceride synthase (Dgat1), triglyceride hydrolase (Lpl and Hsl), fatty acid synthase (Fasn), and fatty acid oxidases (Cpt1a, Acadl, and Hadh) in oviductal glandular cells and epithelial cells during both the breeding season and pre-brumation. While the mRNA levels of triglycerides and free fatty acid synthesis genes (dgat1 and fasn) did not show a significant difference between the breeding season and pre-brumation, the mRNA levels of genes involved in triglycerides and free fatty acid metabolism (lpl, cpt1a, acadl, acox and hadh) were considerably higher during pre-brumation. Furthermore, the R. dybowskii oviduct's transcriptomic and metabolomic data confirmed differential expression of genes and metabolites enriched in lipid metabolism signaling pathways during both the breeding season and pre-brumation. Overall, these results suggest that alterations in lipid synthesis and metabolism during pre-brumation may potentially influence the expanding size of the oviduct, contributing to the successful overwintering of R. dybowskii.

Fatty acid metabolization and insulin regulation prevent liver injury from lipid accumulation in Himalayan marmots

Fat storage and weight gain are dominant traits for hibernating mammals. However, excessive fat accumulation may cause liver damage. Here, we explore the lipid accumulation and metabolic processes of the Himalayan marmot (Marmota himalayana), a hibernating rodent species. We find that the unsaturated fatty acid (UFA) content in food was consistent with a large increase in the body mass of Himalayan marmots. Metagenomic analysis shows that Firmicutes Bacterium CAG:110 plays a synergistic role by synthesizing UFAs, which is demonstrated by fecal transplantation experiments, indicating that the gut microbiome promotes fat storage in Himalayan marmots for hibernation. Microscopic examination results indicate that the risk of fatty liver appears at maximum weight; however, liver function is not affected. Upregulations of UFA catabolism and insulin-like growth factor binding protein genes provide an entry point for avoiding liver injury.

Elevated plasma phospholipid n-3 docosapentaenoic acid concentrations during hibernation

Factors for initiating hibernation are unknown, but the condition shares some metabolic similarities with consciousness/sleep, which has been associated with n-3 fatty acids in humans. We investigated plasma phospholipid fatty acid profiles during hibernation and summer in free-ranging brown bears (Ursus arctos) and in captive garden dormice (Eliomys quercinus) contrasting in their hibernation patterns. The dormice received three different dietary fatty acid concentrations of linoleic acid (LA) (19%, 36% and 53%), with correspondingly decreased alpha-linolenic acid (ALA) (32%, 17% and 1.4%). Saturated and monounsaturated fatty acids showed small differences between summer and hibernation in both species. The dormice diet influenced n-6 fatty acids and eicosapentaenoic acid (EPA) concentrations in plasma phospholipids. Consistent differences between summer and hibernation in bears and dormice were decreased ALA and EPA and marked increase of n-3 docosapentaenoic acid and a minor increase of docosahexaenoic acid in parallel with several hundred percent increase of the activity index of elongase ELOVL2 transforming C20-22 fatty acids. The highest LA supply was unexpectantly associated with the highest transformation of the n-3 fatty acids. Similar fatty acid patterns in two contrasting hibernating species indicates a link to the hibernation phenotype and requires further studies in relation to consciousness and metabolism.

Mass Spectrometry Imaging of Lipids in the Scent Glands of Muskrat (Ondatra zibethicus) in Different Reproductive Statuses

As a typical seasonal breeding animal, male muskrats have a pair of scent glands that can emit musky odor substances to attract females during the breeding period. The present study aimed to visualize the differences in the distribution of lipids in the scent glands of muskrats during their different reproductive statuses by imaging mass spectrometry and quantitative real-time PCR (qRT-PCR). The results revealed remarkable differences in the expression and spatial distribution of lipids detected in the scent glands of muskrats during the different reproductive statuses. In addition, the expression levels of lipid molecules PC (32:0) and LysoPC (16:0) were found to be significantly higher in the breeding season than in the non-breeding season. Moreover, the mRNA expression levels of lipid synthesis enzyme Pemt and Pla2g4b were higher in the breeding season than in the non-breeding season, and there were positive correlations between the expression intensities of lipid molecules and the expression levels of Pemt and Pla2g4b. The present study investigates the changes and distribution of the endogenous lipid in the scent glands of muskrats and elucidates that the seasonal changes in the lipid metabolism may affect the functions of the scent glands in muskrats.