Proteomic predictors of individualized nutrient-specific insulin secretion in health and disease

HumanIslets: An integrated platform for human islet data access and analysis

Comprehensive molecular and cellular phenotyping of human islets can enable deep mechanistic insights for diabetes research. We established the Human Islet Data Analysis and Sharing (HI-DAS) consortium to advance goals in accessibility, usability, and integration of data from human islets isolated from donors with and without diabetes at the Alberta Diabetes Institute (ADI) IsletCore. Here we introduce HumanIslets.com, an open resource for the research community. This platform, which presently includes data on 547 human islet donors, allows users to access linked datasets describing molecular profiles, islet function and donor phenotypes, and to perform various statistical and functional analyses at the donor, islet and single-cell levels. As an example of the analytic capacity of this resource we show a dissociation between cell culture effects on transcript and protein expression, and an approach to correct for exocrine contamination found in hand-picked islets. Finally, we provide an example workflow and visualization that highlights links between type 2 diabetes status, SERCA3b Ca2+-ATPase levels at the transcript and protein level, insulin secretion and islet cell phenotypes. HumanIslets.com provides a growing and adaptable set of resources and tools to support the metabolism and diabetes research community.

LONP1 regulation of mitochondrial protein folding provides insight into beta cell failure in type 2 diabetes

Proteotoxicity is a contributor to the development of type 2 diabetes (T2D), but it is unknown whether protein misfolding in T2D is generalized or has special features. Here, we report a robust accumulation of misfolded proteins within the mitochondria of human pancreatic islets in T2D and elucidate its impact on β cell viability. Surprisingly, quantitative proteomics studies of protein aggregates reveal that human islets from donors with T2D have a signature more closely resembling mitochondrial rather than ER protein misfolding. The matrix protease LonP1 and its chaperone partner mtHSP70 were among the proteins enriched in protein aggregates. Deletion of LONP1 in mice yields mitochondrial protein misfolding and reduced respiratory function, ultimately leading to β cell apoptosis and hyperglycemia. Intriguingly, LONP1 gain of function ameliorates mitochondrial protein misfolding and restores human β cell survival following glucolipotoxicity via a protease-independent effect requiring LONP1-mtHSP70 chaperone activity. Thus, LONP1 promotes β cell survival and prevents hyperglycemia by facilitating mitochondrial protein folding. These observations may open novel insights into the nature of impaired proteostasis on β cell loss in the pathogenesis of T2D that could be considered as future therapeutic targets.

Amino acid-stimulated insulin secretion: a path forward in type 2 diabetes

Qualitative and quantitatively appropriate insulin secretion is essential for optimal control of blood glucose. Beta-cells of the pancreas produce and secrete insulin in response to glucose and non-glucose stimuli including amino acids. In this manuscript, we review the literature on amino acid-stimulated insulin secretion in oral and intravenous in vivo studies, in addition to the in vitro literature, and describe areas of consensus and gaps in understanding. We find promising evidence that the synergism of amino acid-stimulated insulin secretion could be exploited to develop novel therapeutics, but that a systematic approach to investigating these lines of evidence is lacking. We highlight evidence that supports the relative preservation of amino acid-stimulated insulin secretion compared to glucose-stimulated insulin secretion in type 2 diabetes, and make the case for the therapeutic potential of amino acids. Finally, we make recommendations for research and describe the potential clinical utility of nutrient-based treatments for type 2 diabetes including remission services.