Sex-specific role of high-fat diet and stress on behavior, energy metabolism, and the ventromedial hypothalamus.

BACKGROUND

Scientific evidence highlights the influence of biological sex on the relationship between stress and metabolic dysfunctions. However, there is limited understanding of how diet and stress concurrently contribute to metabolic dysregulation in both males and females. Our study aimed to investigate the combined effects of high-fat diet (HFD) induced obesity and repeated stress on fear-related behaviors, metabolic, immune, and hypothalamic outcomes in male and female mice.

METHODS

To investigate this, we used a highly reliable rodent behavioral model that faithfully recapitulates key aspects of post-traumatic stress disorder (PTSD)-like fear. We subjected mice to footshock stressor followed by a weekly singular footshock stressor or no stressor for 14 weeks while on either an HFD or chow diet. At weeks 10 and 14 we conducted glucose tolerance and insulin sensitivity measurements. Additionally, we placed the mice in metabolic chambers to perform indirect calorimetric measurements. Finally, we collected brain and peripheral tissues for cellular analysis.

RESULTS

We observed that HFD-induced obesity disrupted fear memory extinction, increased glucose intolerance, and affected energy expenditure specifically in male mice. Conversely, female mice on HFD exhibited reduced respiratory exchange ratio (RER), and a significant defect in glucose tolerance only when subjected to repeated stress. Furthermore, the combination of repeated stress and HFD led to sex-specific alterations in proinflammatory markers and hematopoietic stem cells across various peripheral metabolic tissues. Single-nuclei RNA sequencing (snRNAseq) analysis of the ventromedial hypothalamus (VMH) revealed microglial activation in female mice on HFD, while male mice on HFD exhibited astrocytic activation under repeated stress.

CONCLUSIONS

Overall, our findings provide insights into complex interplay between repeated stress, high-fat diet regimen, and their cumulative effects on health, including their potential contribution to the development of PTSD-like stress and metabolic dysfunctions, emphasizing the need for further research to fully understand these interconnected pathways and their implications for health.