Background Hyperinsulinemia is independently associated with increased risk and mortality of pancreatic cancer. We recently reported that genetically reduced insulin production resulted in ~ 50% suppression of pancreatic intraepithelial neoplasia (PanIN) precancerous lesions in mice. However, only female mice remained normoglycemic, and only the gene dosage of the rodent-specific Ins1 alleles was tested in our previous model. Moreover, we did not delve into the molecular and cellular mechanisms associated with modulating hyperinsulinemia. Methods We studied how reduced Ins2 gene dosage affects PanIN lesion development in both male and female Ptf1aCreER;KrasLSL-G12D mice lacking the rodent-specific Ins1 gene (Ins1-/-). We generated control mice having two alleles of the wild-type Ins2 gene (Ptf1aCreER;KrasLSL-G12D;Ins1-/-;Ins2+/+) and experimental mice having one allele of Ins2 gene (Ptf1aCreER;KrasLSL-G12D;Ins1-/-;Ins2+/-). We then performed thorough histopathological analyses and single-cell transcriptomics for both genotypes and sexes. Results High-fat diet–induced hyperinsulinemia was transiently or modestly reduced in female and male mice, respectively, with only one allele of Ins2. This occurred without dramatically affecting glucose tolerance. Genetic reduction of insulin production resulted in mice with a tendency for less PanIN and acinar-to-ductal metaplasia (ADM) lesions. Using single-cell transcriptomics, we found hyperinsulinemia affected multiple cell types in the pancreas, with the most statistically significant effects on local immune cell types that were highly represented in our sampled cell population. Specifically, hyperinsulinemia modulated pathways associated with protein translation, MAPK-ERK signaling, and PI3K-AKT signaling, which were changed in epithelial cells and subsets of immune cells. Conclusions These data suggest a potential role for the immune microenvironment in hyperinsulinemia-driven PanIN development. Together with our previous work, we propose that mild suppression of insulin levels may be useful in preventing pancreatic cancer by acting on multiple cell types.

The rising incidence of pancreatic cancer is largely driven by increased prevalence of obesity and type 2 diabetes (T2D). Hyperinsulinemia is a cardinal feature of obesity and T2D, and is associated with increased cancer incidence and mortality. Genetic reduction of insulin production suppresses formation of pancreatic intraepithelial neoplasia (PanIN) pre-cancerous lesions in mice with mutant Kras. However, it remained unclear whether hyperinsulinemia exerts its tumorigenic effects directly on the cells that give rise to PanINs or indirectly on the tumor microenvironment. Here, we tested whether diet-induced hyperinsulinemia contributes to pancreatic cancer directly through insulin receptor (Insr) signaling in KrasG12D-expressing pancreatic acinar cells. Loss of insulin receptors in wild-type or KrasG12D-expressing acinar cells did not significantly influence fasting glucose or insulin. Strikingly, mice lacking Insr in KrasG12D-expressing acinar cells and their progeny had a significant reduction in PanIN plus tumor area in males (2.7-fold) and females (5.3-fold) compared to control mice. Mechanistically, proteome analyses implicated a reduction in digestive enzymes among altered protein networks in mice protected from PanINs, and together with phospho-proteome analysis, linked the spliceosome, ribosome, and secretory pathway to insulin signaling in context of pancreatic cancer initiation. Collectively, these data demonstrate that insulin receptor signaling in acinar cells promotes PanIN initiation in the context of obesity.

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The critical oxygen tension of whole-animal oxygen uptake rate, or P crit , has historically been defined as the oxygen partial pressure ( P O 2 ) at which aerobic scope falls to zero and further declines in P O 2 require substrate-level phosphorylation to meet shortfalls in aerobic ATP production, thereby time-limiting survival. Despite the inclusion of aerobic scope and anaerobic ATP production in the definition, little effort has been made to verify that P crit measurements, the vast majority of which are obtained using respirometry in resting animals, actually reflect the predictions of zero aerobic scope and a transition to increasing reliance on anaerobic ATP production. To test these predictions, we compared aerobic scope and levels of whole-body lactate at oxygen partial pressures ( P O 2 s) bracketing P crit obtained in resting fish during progressive hypoxia in the tidepool sculpin, Oligocottus maculosus . We found that aerobic scope falls to zero at P crit and, in resting fish exposed to P O 2 s < P crit , whole-body lactate accumulated pointing to an increased reliance on anaerobic ATP production. These results support the interpretation of P crit as a key oxygen threshold at which aerobic scope falls to nil and, below P crit , survival is time-limited based on anaerobic metabolic capacity.