β-cell 14-3-3-ζ and sex are key regulators of α-cell form and function.

α-cells exhibit heterogeneity in their hormone production, whereby distinct α-cell subpopulations can be induced to produce active glucagon-like peptide-1 (GLP-1). However, the mechanisms that govern α-cell GLP-1 production remain poorly defined and whether these differ between sex is unknown. We previously identified 14-3-3-ζ as an indirect negative regulator of α-cell GLP-1 production in vitro. Therefore, we tested the hypothesis that β-cell 14-3-3-ζ ablation exerts sex-dependent protection against metabolic disease through alteration of the α-cell endocrine profile. Male and female mice with targeted manipulation of GLP-1 production in α-cells and 14-3-3-ζ expression in β-cells were studied. Further, publicly available human pancreas data were analyzed to identify sex-dependent differences in islet cell populations. Loss of α-cell-derived GLP-1 impaired β-cell compensation in response to high-fat diet-induced metabolic stress, and β-cell 14-3-3-ζ ablation improved glucose tolerance during a mixed-meal tolerance test in male, but not female, mice. Conversely, overexpression of 14-3-3-ζ blunted the effect of a GLP-1 receptor agonist to promote insulin secretion in male, but not female, mice. Further, β-cell 14-3-3-ζ ablation increased α-cell abundance in male mice while enhancing α-cell GLP-1 production and secretion in both sexes. Finally, α-cell numbers were higher in females compared to males in both mouse and human islets, and α-cell GLP-1 production was higher in females compared to male mice. Together, these findings identify β-cell 14-3-3-ζ as an upstream constraint on α-cell GLP-1 production and reveal sex-dependent regulation of α-cell abundance, establishing β-cell 14-3-3-ζ and biological sex as key determinants of α-cell GLP-1 production.