Investigating mitochondrial stress as a driver of β-cell identity loss and senescence in male and female mice

Mitochondria play a central role in pancreatic β-cell function by coupling nutrient availability to insulin release. Mitochondrial dysfunction and premature β-cell senescence are both implicated in diabetes progression, yet whether these processes are linked, and whether biological sex influences susceptibility to either, remains poorly understood. Building on our previous work showing that β-cell-specific deletion of Bcl-xL (BclxβKO) impairs PGC-1α-dependent mitochondrial quality control in glucose-stressed male β-cells, we examined mitochondrial stress responses in islets from both male and female BclxβKO mice and BclxβWT littermates. Two complementary stress models were used: prolonged high-glucose culture and pharmacological inhibition of mitochondrial complex I with rotenone. Consistent with our previous findings, male BclxβKO islets showed impaired PGC-1α-associated responses to glucose stress. However, this model also revealed a sex difference, as female islets did not mount the OXPHOS-associated transcriptional response observed in wild-type males. Rotenone-induced complex I inhibition caused a concentration-dependent shift in stress signaling that was largely independent of genotype and sex, progressing from an oxidative stress-associated response towards activation of the mitochondrial integrated stress response, and was accompanied by a concentration-dependent suppression of core β-cell identity genes. Finally, mitochondrial dysfunction, through both Bcl-xL deficiency and complex I inhibition, was associated with induction of senescence hallmarks, with male β-cells showing greater susceptibility to induction of senescence-associated phenotypes. Together, these findings highlight biological sex as an important variable shaping β- cell stress responses and support mitochondrial dysfunction as a potential contributor to β-cell senescence in diabetes.