Pregestational maternal diabetes primes neonatal beta cell dysfunction with structural remodelling, impaired calcium buffering and altered mTORC2–Gαq–PKCα signalling in a pig model

Aims/hypothesis Offspring of mothers with diabetes are at increased risk of developing type 2 diabetes, and this predisposition is established during fetal life. The aim of this study was to define the functional, morphological and molecular alterations in neonatal pancreatic islets associated with maternal hyperglycaemia, with a particular focus on beta cells, an area that remains poorly understood. Given its similarity to humans in endocrine pancreas development, the pig was used as a translational animal model. Methods Using genetically diabetic and beta cell reporter pig models, we performed functional assessments of glucose-stimulated insulin secretion in vivo and in situ using fresh pancreatic tissue slices from neonatal piglets born to hyperglycaemic mothers (PHGs) or normoglycaemic mothers (PNGs). Morphological and molecular profiling, including proteomics and single-cell RNA-seq, were performed to elucidate molecular changes reflecting the developmental impact of maternal diabetes on offspring metabolic health, with a particular focus on neonatal beta cells. Results PHGs were born hyperglycaemic, hyperinsulinaemic and insulin resistant, exhibiting markedly delayed glucose and insulin response curves following oral glucose administration, with more pronounced effects in male piglets. Elevated basal insulin secretion and an almost blunted glucose responsiveness of pancreatic tissue slices were associated with increased insulin and somatostatin content, expansion of beta (+35%) and delta (+47%) cell populations, and organisation into larger islet clusters. Neonatal PHG islets exhibited a molecular profile consistent with intrinsic beta cell dysfunction that partially overlapped with type 2 diabetes (e.g. RBP4 upregulation), together with alterations in glucose sensing (near absence of GLUT2), nutrient metabolism resembling congenital hyperinsulinism (HADH downregulation), and cytosolic Ca 2 ⁺ homeostasis (near absence of the Ca 2 ⁺ buffer calbindin D28K). In addition to an ATF4-dominated stress signature, a shift towards a distinct PHG beta cell subcluster characterised by low expression of ribosomal genes was observed, with an adaptive early-response-gene-mediated transcriptional reactivity. In contrast to the Gαs–adenylyl cyclase–cAMP–PKA signalling axis that dominated in PNG beta cells, neonatal PHG beta cells displayed distinct alterations in Gαq–PLC–PKCα signalling components, the mTORC2 target PKCα, and CREB1, suggesting a restructured signalling architecture. Conclusions/interpretation Our findings reveal altered islet modelling with a unique beta cell dysfunction profile that partially overlaps with, but differs from, that of type 2 diabetes. A shift towards a beta cell subcluster exhibiting an adaptive early-response-gene-mediated transcriptional reactivity and an ATF4-associated transcriptional stress signature provides insight into molecular alterations associated with fetal exposure to maternal diabetes and may contribute to the increased risk of metabolic disease in offspring.