Chronic stress alters hepatic metabolism and thermodynamic respiratory efficiency affecting epigenetics in C57BL/6 mice.

Chronic stress episodes increase metabolic disease risk even after recovery. We propose that persistent stress detrimentally impacts hepatic metabolic reprogramming, particularly mitochondrial function. In male C57BL/6 mice chronic variable stress (Cvs) reduced energy expenditure (EE) and body mass despite increased energy intake versus controls. This coincided with decreased glucose metabolism and increased lipid ß-oxidation, correlating with EE. After Cvs, mitochondrial function revealed increased thermodynamic efficiency (ƞ-opt) of complex CI, positively correlating with blood glucose and NEFA and inversely with EE. After Cvs recovery, the metabolic flexibility of hepatocytes was lost. Reduced CI-driving NAD+/NADH ratio, and diminished methylation-related one-carbon cycle components hinted at epigenetic regulation. Although initial DNA methylation differences were minimal after Cvs, they diverged during the recovery phase. Here, the altered enrichment of mitochondrial DNA methylation and linked transcriptional networks were observed. In conclusion, Cvs rapidly initiates the reprogramming of hepatic energy metabolism, supported by lasting epigenetic modifications.

Chronic stress targets mitochondrial respiratory efficiency in the skeletal muscle of C57BL/6 mice.

Episodes of chronic stress can result in psychic disorders like post-traumatic stress disorder, but also promote the development of metabolic syndrome and type 2 diabetes. We hypothesize that muscle, as main regulator of whole-body energy expenditure, is a central target of acute and adaptive molecular effects of stress in this context. Here, we investigate the immediate effect of a stress period on energy metabolism in Musculus gastrocnemius in our established C57BL/6 chronic variable stress (Cvs) mouse model. Cvs decreased lean body mass despite increased energy intake, reduced circadian energy expenditure (EE), and substrate utilization. Cvs altered the proteome of metabolic components but not of the oxidative phosphorylation system (OXPHOS), or other mitochondrial structural components. Functionally, Cvs impaired the electron transport chain (ETC) capacity of complex I and complex II, and reduces respiratory capacity of the ETC from complex I to ATP synthase. Complex I-OXPHOS correlated to diurnal EE and complex II-maximal uncoupled respiration correlated to diurnal and reduced nocturnal EE. Bioenergetics assessment revealed higher optimal thermodynamic efficiencies (ƞ-opt) of mitochondria via complex II after Cvs. Interestingly, transcriptome and methylome were unaffected by Cvs, thus excluding major contributions to supposed metabolic adaptation processes. In summary, the preclinical Cvs model shows that metabolic pressure by Cvs is initially compensated by adaptation of mitochondria function associated with high thermodynamic efficiency and decreased EE to manage the energy balance. This counter-regulation of mitochondrial complex II may be the driving force to longitudinal metabolic changes of muscle physiological adaptation as the basis of stress memory.