The Impact of Sex Hormones on Renal Mitochondrial Bioenergetics in Aging

Abstract

Introduction. Aging is accompanied by changes in multiple factors, such as accumulation of mitochondrial dysfunction and the decline of sex hormone levels throughout life. Females are generally protected from renal diseases until menopause, potentially as a result of the presence of female sex hormones. Sex hormones govern a plethora of crucial renal processes, including metabolism and mitochondrial bioenergetics. However, there remains a gap in knowledge regarding the role of sex hormones in mitochondrial bioenergetics in renal aging. We hypothesized in this study that removal of sex hormones will exacerbate the aging-induced decline in renal mitochondrial function. Methods. Male and female Sprague Dawley (SD) rats were randomly divided into groups, and gonadectomy or sham surgery was performed before 4 wks of age. At 6 and 12 months of age kidneys were perfused to remove blood, then cortical tissues were immediately collected for mitochondrial isolations using differential centrifugation or snap-frozen/fixed for biochemical assays. Spectrofluorimetry was utilized to measure mitochondrial membrane potential (ΔΨm) and H2O2 production using TMRM and Amplex Red. Seahorse assay was done to measure oxygen consumption rate (OCR). OriginPro was used for statistical analysis (two-way ANOVA with Holm-Sidak post hoc). Results. Male OCR parameters (basal, ADP-linked, maximal and spare capacity) were lower than OCR observed in females at both 6 and 12 months of age (p<0.05). Orchiectomy resulted in an increase in male OCR parameters at both ages (p<0.05); ovariectomy did not affect renal cortical OCR (p>0.05 for both ages). Of note, gonadectomy in males increased the OCR up to the female level (p>0.05 for both ages). Cortical mitochondrial ΔΨm displayed similar values at 6 months across all groups. However, at 12 months we report lower ΔΨm in males vs female shams (p<0.001). Of note, the male gonadectomy increased ΔΨm up to the level of female values, while ovariectomy had no effect (p=0.3). Female cortical H2O2 production was higher than in males (p<0.001), whereas ovariectomy lowered H2O2 at both time points (p<0.001), indicative of ΔΨm-independent ROS sources. Interestingly, the effect of testosterone on H2O2 production was dependent on age. At 6 months old, orchiectomy did not alter H2O2 production compared to shams, while at 12 months, orchiectomy led to higher H2O2 production (p<0.001). Conclusions. Renal mitochondrial OCR was found to be independent of age in either sex at 6 and 12 months of age. Gonadectomy data allowed us to speculate that testosterone suppresses renal OCR, and the decreased membrane potential in males is likely driving the OCR changes. The observed ΔΨm-independent sources of H2O2 remain to be explored in future experiments. These data established the impact of sex hormones on mitochondrial bioenergetics and will help elucidate sex-specific targets that can mitigate the effects of aging on kidney function. Funding for this project came from 1U54HL169191. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.