GJA1 and Hyperglycemia: However, the FAS/FASL pathway is not the only extrinsic pathway activated by hyperglycemia; previously, Chang et al. [13] reported an upregulation of the extrinsic pathway proteins TRAIL and KILLER in the diabetic mouse ovary and related this overexpression to a reduction in the gap junction protein connexin 43, which is fundamental for metabolic communication between granulosa cells and oocytes [13].