Beta cells from nondiabetic mice transfer secretory vesicles to phagocytic cells. The passage was shown in culture studies where the transfer was probed with CD4 T cells reactive to insulin peptides. Two sets of vesicles were transferred, one containing insulin and another containing catabolites of insulin. The passage required live beta cells in a close cell contact interaction with the phagocytes. It was increased by high glucose concentration and required mobilization of intracellular Ca 2+ . Live images of beta cell-phagocyte interactions documented the intimacy of the membrane contact and the passage of the granules. The passage was found in beta cells isolated from islets of young nonobese diabetic (NOD) mice and nondiabetic mice as well as from nondiabetic humans. Ultrastructural analysis showed intraislet phagocytes containing vesicles having the distinct morphology of dense-core granules. These findings document a process whereby the contents of secretory granules become available to the immune system. autoimmune diabetes | autoimmunity | insulin reactivity | insulin-reactive T cells

Recombinant human IL 1X1 inhibits glucose-induced insulin secretion from isolated pancreatic islets and from purified j3-cells obtained by fluorescence-activated cell sorting (FACS) of dispersed islet cells. Brief (1 h) exposure of isolated islets to IL I produces sustained inhibition of insulin secretion for at least 17 h after the IL 1 has been removed from the culture medium. An inhibitory effect of IL 1 on insulin secretion is not observed when islets are coincubated with an inhibitor of DNA transcription (actinomycin D). This finding indicates that the inhibitory effect of IL 1 on insulin secretion requires transcription of one or more genes during the first hour of exposure of islets to IL 1. The inhibitory effect of IL 1 on insulin secretion also requires mRNA translation, because three structurally distinct inhibitors of protein synthesis (cycloheximide, anisomycin, and puromycin) prevent IL 1-induced inhibition of insulin secretion when added to islets after the 1-h exposure to IL 1. Two-dimensional gel electrophoresis of islet proteins metabolically labeled with I35Slmethionine demonstrates that IL 1 augments the expression of a 65-kD (pl 6.5) protein by > 2.5-fold. These findings indicate that biochemical events occurring within 1 h of exposure of islets to IL 1 lead to an inhibition of insulin secretion that persists for at least 17 h after the removal of IL 1. One of the early biochemical effects of IL 1 on islets is gene transcription (0-1 h), which is followed by mRNA translation (after 1 h). Our results suggest that the inhibitory effect of IL 1 on insulin secretion is mediated by protein(s) whose synthesis is induced by IL 1. (J. Clin. Invest.

Primary cilia are specialized cell-surface organelles that mediate sensory perception and, in contrast to motile cilia and flagella, are thought to lack motility function. Here we show that primary cilia in pancreatic beta cells exhibit movement that is required for glucose-dependent insulin secretion. Beta cell cilia contain motor proteins conserved from those found in classic motile cilia, and their 3D motion is dynein-driven and dependent on ATP and glucose metabolism. Inhibition of cilia motion blocks beta cell calcium influx and insulin secretion. Beta cells from humans with type 2 diabetes have altered expression of cilia motility genes. Our findings redefine primary cilia as dynamic structures possessing both sensory and motile function and establish that pancreatic beta cell cilia movement plays a critical role in controlling insulin secretion.

Subcutaneous transplants of embryonic brown adipose tissue (BAT) lead to euglycemia without insulin in mouse models of T1D [Diabetes 2012 61:674]. Euglycemia is accompanied by normalized plasma glucagon levels, restored healthy white adipose tissue, reduced inflammatory cytokines, and increased anti-inflammatory adipokines. Elevated IGF-1 was shown to play a role in successful transplants, putatively by direct stimulation of the insulin receptor [Am. J. Physiol. Endocrinol. Metab. 2015 308:E1043]. However, the mechanism underlying this effect remained unknown. We hypothesized that a secreted product from the transplanted BAT communicates with the recipient allowing a new metabolic equilibrium in the absence of insulin. We tested this using buffer conditioned by cultured immortalized BAT cells. We injected this buffer into diabetic NOD mice once daily for 7 consecutive days. In 5 of the 9 animals studied, blood glucose levels dropped back to the normal range (∼150 mg/dl) for at least 2 months with one animal remaining euglycemic for 5 months with no further intervention. As in embryonic BAT transplants, conditioned buffer injections led to a rapid decrease in plasma glucagon. We found that applying this conditioned buffer to isolated mouse and human islets lowers glucagon secretion directly (without significant changes in insulin or somatostatin). To purify and identify the active BAT-secreted compound, we established a multi-step fractionation protocol using size exclusion, ion exchange, and hydrophobicity columns to concentrate the active compound ∼10 million-fold over the initial BAT-conditioned buffer. Protease, denaturation, and spectroscopy experiments revealed a modified peptide of ∼1600 Da. Initial screening of GPCR targets [Nat Struct Mol Biol. 2015 22:362] revealed binding to the μ-opioid receptor, which is expressed preferentially in α-cells within the islet of Langerhans. Thus, these data suggest a novel path towards clinical antagonism of glucagon secretion. Disclosure D.W. Piston: Consultant; Self; Pfizer Inc. A. Ustione: None. S.C. Gunawardana: None. J. Hughes: None. Funding National Institutes of Health (DK098659); The Leona M. and Harry B. Helmsley Charitable Trust

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