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Prohibitins are highly conserved proteins mainly implicated in the maintenance of mitochondrial function and architecture. Their dysfunctions are associated with aging, cancer, obesity, and inflammation. However, their possible role in pancreatic β-cells remains unknown. The current study documents the expression of prohibitins in human and rodent islets and their key role for β-cell function and survival. Ablation of Phb2 in mouse β-cells sequentially resulted in impairment of mitochondrial function and insulin secretion, loss of β-cells, progressive alteration of glucose homeostasis, and, ultimately, severe diabetes. Remarkably, these events progressed over a 3-week period of time after weaning. Defective insulin supply in β-Phb2−/− mice was contributed by both β-cell dysfunction and apoptosis, temporarily compensated by increased β-cell proliferation. At the molecular level, we observed that deletion of Phb2 caused mitochondrial abnormalities, including reduction of mitochondrial DNA copy number and respiratory chain complex IV levels, altered mitochondrial activity, cleavage of L-optic atrophy 1, and mitochondrial fragmentation. Overall, our data demonstrate that Phb2 is essential for metabolic activation of mitochondria and, as a consequence, for function and survival of β-cells.

Identification of pre-diabetic individuals with decreased functional ß-cell mass is essential for the prevention of diabetes. However, in vivo detection of early asymptomatic ß-cell defect remains unsuccessful. Metabolomics emerged as a powerful tool in providing read-outs of early disease states before clinical manifestation. We aimed at identifying novel plasma biomarkers for loss of functional ß-cell mass in the asymptomatic pre-diabetic stage. Non-targeted and targeted metabolomics were applied on both lean ß-Phb2 -/mice (ß-cell-specific prohibitin-2 knockout) and obese db/db mice (leptin receptor mutant), two distinct mouse models requiring neither chemical nor diet treatments to induce spontaneous decline of functional ß-cell mass promoting progressive diabetes development.Non-targeted metabolomics on ß-Phb2 -/mice identified 48 and 82 significantly affected metabolites in liver and plasma, respectively. Machine learning analysis pointed to deoxyhexose sugars consistently reduced at the asymptomatic pre-diabetic stage, including in db/db mice, showing strong correlation with the gradual loss of ß-cells. Further targeted metabolomics by GC-MS uncovered the identity of the deoxyhexose with 1,5-anhydroglucitol displaying the most significant changes. In conclusion, this study identified 1,5-anhydroglucitol associated with the loss of functional ß-cell mass and uncovered metabolic similarities between liver and plasma, providing insights into the systemic effects caused by early decline in ß-cells.

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