IL-6 is a pleiotropic cytokine with complex roles in inflammation and metabolic disease. The role of IL-6 as a pro- or anti-inflammatory cytokine is still unclear. Within the pancreatic islet, IL-6 stimulates secretion of the prosurvival incretin hormone glucagon-like peptide 1 (GLP-1) by α cells and acts directly on β cells to stimulate insulin secretion Uncovering physiologic mechanisms promoting β-cell survival under conditions of inflammation and stress can identify important pathways for diabetes prevention and treatment. Given the established role of GLP-1 in promoting β-cell survival, we hypothesized that IL-6 may also directly protect β cells from apoptosis. Herein, we show that IL-6 robustly activates signal transducer and activator of transcription 3 (STAT3), a transcription factor that is involved in autophagy. IL-6 stimulates LC3 conversion and autophagosome formation in cultured β cells. IL-6 infusion stimulates a robust increase in lysosomes in the pancreas that is restricted to the islet. Autophagy is critical for β-cell homeostasis, particularly under conditions of stress and increased insulin demand. The stimulation of autophagy by IL-6 is regulated multiple complementary mechanisms including inhibition of mammalian target of rapamycin complex 1 (mTORC1) and activation of Akt, ultimately leading to increases in autophagy enzyme production. Pretreatment with IL-6 renders β cells resistant to apoptosis induced by proinflammatory cytokines, and inhibition of autophagy with chloroquine prevents the ability of IL-6 to protect from apoptosis. Importantly, we find that IL-6 can activate STAT3 and the autophagy enzyme GABARAPL1 in human islets. We also see evidence of decreased IL-6 pathway signaling in islets from donors with type 2 diabetes. On the basis of our results, we propose direct stimulation of autophagy as a novel mechanism for IL-6-mediated protection of β cells from stress-induced apoptosis.-Linnemann, A. K., Blumer, J., Marasco, M. R., Battiola, T. J., Umhoefer, H. M., Han, J. Y., Lamming, D. W., Davis, D. B. Interleukin 6 protects pancreatic β cells from apoptosis by stimulation of autophagy.

Risk of type 1 diabetes at 3 years is high for initially multiple and single Ab+ IT and multiple Ab+ NT. Genetic predisposition, age, and male sex are significant risk factors for development of Ab+ in twins.

Transcription factor 19 (TCF19) is a gene associated with type 1 diabetes (T1DM) and type 2 diabetes (T2DM) in genome-wide association studies. Prior studies have demonstrated that Tcf19 knockdown impairs β-cell proliferation and increases apoptosis. However, little is known about its role in diabetes pathogenesis or the effects of TCF19 gain-of-function. The aim of this study was to examine the impact of TCF19 overexpression in INS-1 β-cells and human islets on proliferation and gene expression. With TCF19 overexpression, there was an increase in nucleotide incorporation without any change in cell cycle gene expression, alluding to an alternate process of nucleotide incorporation. Analysis of RNA-seq of TCF19 overexpressing cells revealed increased expression of several DNA damage response (DDR) genes, as well as a tightly linked set of genes involved in viral responses, immune system processes, and inflammation. This connectivity between DNA damage and inflammatory gene expression has not been well studied in the β-cell and suggests a novel role for TCF19 in regulating these pathways. Future studies determining how TCF19 may modulate these pathways can provide potential targets for improving β-cell survival.

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Transcription factor 19 (Tcf19) is a putative transcription factor associated with both Type 1 and Type 2 diabetes. Tcf19 is expressed in human and rodent pancreatic β‐cells and is upregulated in proliferating islets and obesity. We generated a whole body knockout (wbKO) of Tcf19 and the resulting lean, 15‐week‐old mice have normal fasting glucose, insulin secretion, and glucose tolerance compared to control. RNASeq led to the identification of 733 upregulated and 763 downregulated genes in wbKO islets compared to control. Overrepresented GO terms include upregulated apoptotic process, and negative regulation of cell proliferation, and downregulated vesicle‐mediated transport. We verified markers of proliferation, β‐cell identity, cell stress, and pro‐apoptosis using RTqPCR. Ki67, Pdx1, Nkx6.1, and Nkx2.2 were significantly decreased while Chop, Bak, Gadd45α, and Dtx3l were significantly increased in islets from wbKO mice. Whole pancreas was harvested to measure β‐cell area and although total area is not different, wbKO mice have altered islet size distribution with an increased number of small islets. Next, β‐cell proliferation and apoptosis were measured in frozen pancreatic sections using Ki67 and TUNEL staining, which revealed significantly less proliferation with no change in apoptosis rates in wbKO mice. In adulthood, β‐cell mass expansion occurs due to proliferation as an early compensation for insulin resistance in response to obesity. To determine the role of Tcf19 in this adaptive response wbKO and control mice were put on a one‐week high fat diet (HFD). After one week on HFD, islets from wbKO do not appropriately upregulate Ki67 and cyclin D2 as measured by RTqPCR. In summary, Tcf19 is involved in proliferation and stress related processes both of which are involved in regulating β‐cell mass, which declines in Type 1 and Type 2 diabetes. Support or Funding Information VA Merit Award 1I01BX001880VA Merit Award 1I01BX004715TL1 Award TR000429ICTR Clinical and Translational Science Award UL1TR000427NIDDK 5R01DK110324

Type 1 and Type 2 diabetes (TID and TIID) differ in etiology, but both have decreased functional pancreatic β‐cell mass. Genome‐wide association studies identified transcription factor 19 (Tcf19) as a potential causal gene for both TID and TIID. Tcf19 is expressed in both humans and rodents, most highly in the pancreatic islet and upregulated in mouse models of non‐diabetic obesity. We showed that TCF19 is necessary for β‐cell proliferation and survival in INS1 cells. Thus, we hypothesized that TCF19 regulates β‐cell mass developmentally and in adaptive response to stress. A germline whole‐body knockout (wbTcf19KO) of Tcf19 mouse model was generated. wbTcf19KO and control (C57BL6/N) mice were fed a chow diet. Lean wbTcf19KO are metabolically similar to controls other than significantly higher body weights. Markers of proliferation (Ki67) and β‐cell identity (Pdx1, Nkx6.1, Nkx2.2) were significantly decreased while markers of pro‐apoptosis (Chop) and DNA damage response (Bak, Gadd45a, Dtx3l) were significantly increased in islets from wbTcf19KO mice. DNA damage is significantly elevated in wbTcf19KO islets as measured by y‐H2AX Western blot. Islet size distribution is significantly altered in wbTcf19KO islets, skewed by many very small islets. wbTcf19KO and control male mice were challenged with high fat diet (HFD; 1‐week & 10‐week) feeding. These mice failed to appropriately upregulate proliferation markers (Ki67, CyclinD2) in islets after 1‐week of HFD. Glucose intolerance and elevated fasting glucose develop in these mice after 10‐weeks of HFD. Female mice, less susceptible to diet induced hyperglycemia, were stressed with long‐term high fat high sucrose diet (HFHS) feeding to induce insulin resistance. After 8‐weeks of HFHS feeding wbTcf19KO females became significantly more glucose intolerant than control HFHS fed female mice. Ongoing studies will examine the impact of Tcf19 knockout on β‐cell mass during pregnancy in these HFHS‐fed females. Overall, loss of Tcf19 reveals changes in proliferation and DNA damage, which may be critical in stress‐induced β‐cell mass regulation.

Transcription factor 19, TCF19, is a novel gene associated with type 1 and type 2 diabetes. We have previously shown that Tcf19 is involved in the regulation of proliferation and apoptosis in the INS1 β-cell line. To determine the role of Tcf19 in diabetes pathogenesis, we generated germline whole body Tcf19 knockout mice (wbTcf19KO). Lean wbTcf19KO mice have slightly increased fasting glucose and decreased in vivo glucose-stimulated insulin secretion. We focused on the pancreatic islet in further analysis of this model due to the high expression of Tcf19 in the mouse islet and our preliminary findings in a β-cell line. RNAseq from wbTcf19KO mouse islets identified significantly decreased expression of genes involved in maintaining β-cell identity, vesicle docking, and Ca2+ sensing (Nkx6.1, Nkx2.2, Pdx1, Sort1, Syt7). Additionally, the proliferative marker, Ki67, was downregulated by 3-fold. Similarly, with immunohistochemistry of pancreatic sections, there was a 20% decrease in Ki67+ β-cells in wbTcf19KO mice. Despite no difference in overall β-cell mass compared to control mice, wbTcf19KO mice have an altered islet size distribution with an increased quantity of small islets. In addition, wbTcf19KO mice fail to increase proliferative genes in the islet, such as cyclinD2 and Ki67, in response to a short term high fat diet (HFD). Islet RNA seq analysis also showed an upregulation of genes involved in the DNA damage pathway, inflammation, and pro apoptotic genes (Ddx60, Gadd45a, Dtx3l, Chop, Bak, Ifit1, Cxcl10). Baseline levels of DNA damage in the wbTcf19KO islets are increased, as measured by γH2AX on western blot. wbTcf19KO mouse islets also have increased DNA damage after in vivo challenge with extended HFD feeding or ex vivo after cytokine exposure. Taken together, we conclude that Tcf19 plays an important role in regulating β-cell DNA damage repair pathways to prevent apoptosis and allow proliferation. Disclosure G.H. Yang: None. J. Han: None. S. Lodh: None. J.T. Blumer: None. D. Fontaine: None. D.B. Davis: None.

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