Daily Endocrinology Research Analysis

Glucagon-like peptide-1 receptor (GLP-1R) agonists (GLP-1RAs) ameliorate mitochondrial health by increasing mitochondrial turnover in metabolically relevant tissues. Mitochondrial adaptation to metabolic stress is crucial to maintain pancreatic β-cell function and prevent type 2 diabetes (T2D) progression. While the GLP-1R is well-known to stimulate cAMP production leading to Protein Kinase A (PKA) and Exchange Protein Activated by cyclic AMP 2 (Epac2) activation, there is a lack of understanding of the molecular mechanisms linking GLP-1R signalling with mitochondrial and β-cell functional adaptation. Here, we present a comprehensive study in β-cell lines and primary islets that demonstrates that, following GLP-1RA stimulation, GLP-1R-positive endosomes associate with the endoplasmic reticulum (ER) membrane contact site (MCS) tether VAPB at ER-mitochondria MCSs (ERMCSs), where active GLP-1R engages with SPHKAP, an A-kinase anchoring protein (AKAP) previously linked to T2D and adiposity risk in genome-wide association studies (GWAS). The inter-organelle complex formed by endosomal GLP-1R, ER VAPB and SPHKAP triggers a pool of ERMCS-localised cAMP/PKA signalling via the formation of a PKA-RIα biomolecular condensate which leads to changes in mitochondrial contact site and cristae organising system (MICOS) complex phosphorylation, mitochondrial remodelling, and β-cell functional adaptation, with important consequences for the regulation of β-cell insulin secretion and survival to stress.

Pluripotent stem cell (SC)-derived islets offer hope as a renewable source for β cell replacement for type 1 diabetes (T1D), yet functional and metabolic immaturity may limit their long-term therapeutic potential. Here, we show that limitations in mitochondrial transcriptional programming impede the formation of SC-derived β (SC-β) cells. Utilizing transcriptomic profiling, assessments of chromatin accessibility, mitochondrial phenotyping, and lipidomics analyses, we observe that SC-β cells exhibit reduced oxidative and mitochondrial fatty acid metabolism compared to primary human islets that are related to limitations in key mitochondrial transcriptional networks. Surprisingly, we find that reductions in glucose-stimulated mitochondrial respiration in SC-islets were not associated with alterations in mitochondrial mass, structure, or genome integrity. In contrast, SC-islets show limited expression of targets of PPARα, which regulate mitochondrial programming, yet whose functions in β cell differentiation are unknown. Importantly, treatment with WY14643, a potent PPARα agonist, induces expression of mitochondrial targets, improves insulin secretion, and increases the formation of SC-β cells both in vitro and following transplantation. Thus, PPARα-dependent mitochondrial programming promotes the differentiation of SC-β cells and may be a promising target to improve β cell replacement efforts for T1D.

OBJECTIVE: To examine the effects of oral semaglutide on kidney outcomes in people with type 2 diabetes (T2D) and atherosclerotic cardiovascular disease (ASCVD) and/or chronic kidney disease (CKD). RESEARCH DESIGN AND METHODS: SOUL (NCT03914326), a double-blind randomized controlled trial, compared oral semaglutide with placebo in people with T2D, ASCVD, and/or CKD, showing a 14% reduction in risk of major adverse cardiovascular (CV) events. Prespecified kidney outcomes included a five-point composite (≥50% decrease in estimated glomerular filtration rate [eGFR], persistent eGFR <15 mL/min/1.73 m2, initiation of chronic kidney replacement therapy, or death from kidney or CV causes); a four-point composite (excluding CV death); and eGFR decline. Prespecified subgroups were also assessed, including those with eGFR <60 mL/min/1.73 m2 at baseline. RESULTS: Among 9,650 participants, mean eGFR was 73.8 mL/min/1.73 m2, and follow-up was 47.5 months. The five-point outcome occurred in 403 (8.4%) and 435 (9.0%) participants taking oral semaglutide versus placebo, respectively (hazard ratio [HR] 0.91; 95% CI 0.80, 1.05; P = 0.19). The four-point outcome occurred in 112 (2.3%) and 129 (2.7%) participants, respectively (HR 0.86; 95% CI 0.66, 1.10; P = 0.22). Mean annual eGFR decline was less with oral semaglutide than placebo (-1.67 vs. -2.06 mL/min/1.73 m2; estimated treatment difference 0.40 [95% CI 0.27, 0.53; P < 0.0001). These effects were similar across most subgroups, including those with eGFR <60 mL/min/1.73 m2. Serious adverse events occurred at similar rates in both groups. CONCLUSIONS: In people with T2D and ASCVD and/or CKD but with overall mostly preserved eGFR, orally administered semaglutide, compared with placebo, did not significantly reduce adverse kidney outcomes but did slow the decline in eGFR.