The isolation of high-quality RNA from endocrine pancreas sections represents a considerable challenge largely due to the high ribonuclease levels. Laser capture microdissection (LCM) of mammalian islets, in association with RNA extraction protocols, has emerged as a feasible approach to characterizing their genetic and proteomic profiles. However, a validated protocol to obtain high-quality RNA from LCM-derived human pancreas specimens that is appropriate for next-generation sequencing analysis is still lacking. In this study, we applied four methods (Picopure extraction kit, Qiazol protocol, Qiazol + Clean-up kit, and RNeasy Microkit + Carrier) to extract RNA from human islets obtained from both non-diabetic individuals and patients with type 2 diabetes who had undergone partial pancreatectomy, as well as handpicked islets from both non-diabetic and diabetic organ donors. The yield and purity of total RNA were determined by 260/280 absorbance using Nanodrop 100 and the RNA integrity number with a bioanalyzer. The results indicated that among the four methods, the RNeasy MicroKit + Carrier (Qiagen) provides the highest yield and purity.

Takatani T, Shirakawa J, Shibue K, Gupta MK, Kim H, Lu S, Hu J, White MF, Kennedy RT, Kulkarni RN. Insulin receptor substrate 1, but not IRS2, plays a dominant role in regulating pancreatic alpha cell function in mice. The Journal of biological chemistry. 2021;296:100646.

Dysregulated glucagon secretion deteriorates glycemic control in type 1 and type 2 diabetes. Although insulin is known to regulate glucagon secretion via its cognate receptor (insulin receptor, INSR) in pancreatic alpha cells, the role of downstream proteins and signaling pathways underlying insulin's activities are not fully defined. Using in vivo (knockout) and in vitro (knockdown) studies targeting insulin receptor substrate (IRS) proteins, we compared the relative roles of IRS1 and IRS2 in regulating alpha cell function. Alpha cell-specific IRS1-knockout mice exhibited glucose intolerance and inappropriate glucagon suppression during glucose tolerance tests. In contrast, alpha cell-specific IRS2-knockout animals manifested normal glucose tolerance and suppression of glucagon secretion after glucose administration. Alpha cell lines with stable IRS1 knockdown could not repress glucagon mRNA expression and exhibited a reduction in phosphorylation of AKT Ser/Thr kinase (AKT, at Ser-473 and Thr-308). AlphaIRS1KD cells also displayed suppressed global protein translation, including reduced glucagon expression, impaired cytoplasmic Ca2+ response, and mitochondrial dysfunction. This was supported by the identification of novel IRS1-specific downstream target genes, Trpc3 and Cartpt, that are associated with glucagon regulation in alpha cells. These results provide evidence that IRS1, rather than IRS2, is a dominant regulator of pancreatic alpha cell function.


Shirakawa J, Tajima K, Okuyama T, Kyohara M, Togashi Y, De Jesus DF, Basile G, Kin T, Shapiro AMJ, Kulkarni RN, et al. Luseogliflozin increases beta cell proliferation through humoral factors that activate an insulin receptor- and IGF-1 receptor-independent pathway. Diabetologia. 2020;63(3):577-587.

AIMS/HYPOTHESIS: Sodium-glucose cotransporter 2 (SGLT2) inhibitors, which prevent the renal reabsorption of glucose, decrease blood glucose levels in an insulin-independent manner. We previously reported creating a mouse model of systemic inhibition of target receptors for both insulin and IGF-1 by treating animals with OSI-906, a dual insulin/IGF-1 receptor inhibitor, for 7 days. The OSI-906-treated mice exhibited an increased beta cell mass, hepatic steatosis and adipose tissue atrophy, accompanied by hyperglycaemia and hyperinsulinaemia. In the present study, we investigated the effects of an SGLT2 inhibitor, luseogliflozin, on these changes in OSI-906-treated mice.

METHODS: We treated C57BL/6J male mice either with vehicle, luseogliflozin, OSI-906 or OSI-906 plus luseogliflozin for 7 days, and phenotyping was performed to determine beta cell mass and proliferation. Subsequently, we tested whether serum-derived factors have an effect on beta cell proliferation in genetically engineered beta cells, mouse islets or human islets.

RESULTS: SGLT2 inhibition with luseogliflozin significantly ameliorated hyperglycaemia, but not hyperinsulinaemia, in the OSI-906-treated mice. Liver steatosis and adipose tissue atrophy induced by OSI-906 were not altered by treatment with luseogliflozin. Beta cell mass and proliferation were further increased by SGLT2 inhibition with luseogliflozin in the OSI-906-treated mice. Luseogliflozin upregulated gene expression related to the forkhead box M1 (FoxM1)/polo-like kinase 1 (PLK1)/centromere protein A (CENP-A) pathway in the islets of OSI-906-treated mice. The increase in beta cell proliferation was recapitulated in a co-culture of Irs2 knockout and Insr/IR knockout (βIRKO) beta cells with serum from both luseogliflozin- and OSI-906-treated mice, but not after SGLT2 inhibition in beta cells. Circulating factors in both luseogliflozin- and OSI-906-treated mice promoted beta cell proliferation in both mouse islets and cadaveric human islets.

CONCLUSIONS/INTERPRETATION: These results suggest that luseogliflozin can increase beta cell proliferation through the activation of the FoxM1/PLK1/CENP-A pathway via humoral factors that act in an insulin/IGF-1 receptor-independent manner.

Nakayasu ES, Syed F, Tersey SA, Gritsenko MA, Mitchell HD, Chan CY, Dirice E, Turatsinze J-V, Cui Y, Kulkarni RN, et al. Comprehensive Proteomics Analysis of Stressed Human Islets Identifies GDF15 as a Target for Type 1 Diabetes Intervention. Cell metabolism. 2020;31(2):363-374.e6.

Type 1 diabetes (T1D) results from the progressive loss of β cells, a process propagated by pro-inflammatory cytokine signaling that disrupts the balance between pro- and anti-apoptotic proteins. To identify proteins involved in this process, we performed comprehensive proteomics of human pancreatic islets treated with interleukin-1β and interferon-γ, leading to the identification of 11,324 proteins, of which 387 were significantly regulated by treatment. We then tested the function of growth/differentiation factor 15 (GDF15), which was repressed by the treatment. We found that GDF15 translation was blocked during inflammation, and it was depleted in islets from individuals with T1D. The addition of exogenous GDF15 inhibited interleukin-1β+interferon-γ-induced apoptosis of human islets. Administration of GDF15 reduced by 53% the incidence of diabetes in NOD mice. Our approach provides a unique resource for the identification of the human islet proteins regulated by cytokines and was effective in discovering a potential target for T1D therapy.

Pradas-Juni M, Hansmeier NR, Link JC, Schmidt E, Larsen BD, Klemm P, Meola N, Topel H, Loureiro R, Dhaouadi I, et al. A MAFG-lncRNA axis links systemic nutrient abundance to hepatic glucose metabolism. Nature communications. 2020;11(1):644.

Obesity and type 2 diabetes mellitus are global emergencies and long noncoding RNAs (lncRNAs) are regulatory transcripts with elusive functions in metabolism. Here we show that a high fraction of lncRNAs, but not protein-coding mRNAs, are repressed during diet-induced obesity (DIO) and refeeding, whilst nutrient deprivation induced lncRNAs in mouse liver. Similarly, lncRNAs are lost in diabetic humans. LncRNA promoter analyses, global cistrome and gain-of-function analyses confirm that increased MAFG signaling during DIO curbs lncRNA expression. Silencing Mafg in mouse hepatocytes and obese mice elicits a fasting-like gene expression profile, improves glucose metabolism, de-represses lncRNAs and impairs mammalian target of rapamycin (mTOR) activation. We find that obesity-repressed LincIRS2 is controlled by MAFG and observe that genetic and RNAi-mediated LincIRS2 loss causes elevated blood glucose, insulin resistance and aberrant glucose output in lean mice. Taken together, we identify a MAFG-lncRNA axis controlling hepatic glucose metabolism in health and metabolic disease.

Zheng J, Alves-Wagner AB, Stanford KI, Prince NB, So K, Mul JD, Dirice E, Hirshman MF, Kulkarni RN, Goodyear LJ. Maternal and paternal exercise regulate offspring metabolic health and beta cell phenotype. BMJ open diabetes research & care. 2020;8(1).

OBJECTIVE: Poor maternal and paternal environments increase the risk for obesity and diabetes in offspring, whereas maternal and paternal exercise in mice can improve offspring metabolic health. We determined the effects of combined maternal and paternal exercise on offspring health and the effects of parental exercise on offspring pancreas phenotype, a major tissue regulating glucose homeostasis.

RESEARCH DESIGN AND METHODS: Breeders were high fat fed and housed±running wheels before breeding (males) and before and during gestation (females). Offspring groups were: both parents sedentary (Sed); maternal exercise only (Mat Ex); paternal exercise only (Pat Ex); and maternal+paternal exercise (Mat+Pat Ex). Offspring were sedentary, chow fed, and studied at weaning, 12, 20 and 52 weeks.

RESULTS: While there was no effect of parental exercise on glucose tolerance at younger ages, at 52 weeks, offspring of Mat Ex, Pat Ex and Mat+Pat Ex displayed lower glycemia and improved glucose tolerance. The greatest effects were in offspring from parents that both exercised (Mat+Pat Ex). Offspring from Mat Ex, Pat Ex, and Mat+Pat Ex had decreased beta cell size, whereas islet size and beta cell mass only decreased in Mat+Pat Ex offspring.

CONCLUSIONS: Maternal and paternal exercise have additive effects to improve glucose tolerance in offspring as they age, accompanied by changes in the offspring endocrine pancreas. These findings have important implications for the prevention and treatment of type 2 diabetes.

Lee M, Maji B, Manna D, Kahraman S, Elgamal RM, Small J, Kokkonda P, Vetere A, Goldberg JM, Lippard SJ, et al. Native Zinc Catalyzes Selective and Traceless Release of Small Molecules in β-Cells. Journal of the American Chemical Society. 2020;142(14):6477-6482.

The loss of insulin-producing β-cells is the central pathological event in type 1 and 2 diabetes, which has led to efforts to identify molecules to promote β-cell proliferation, protection, and imaging. However, the lack of β-cell specificity of these molecules jeopardizes their therapeutic potential. A general platform for selective release of small-molecule cargoes in β-cells over other islet cells ex vivo or other cell-types in an organismal context will be immensely valuable in advancing diabetes research and therapeutic development. Here, we leverage the unusually high Zn(II) concentration in β-cells to develop a Zn(II)-based prodrug system to selectively and tracelessly deliver bioactive small molecules and fluorophores to β-cells. The Zn(II)-targeting mechanism enriches the inactive cargo in β-cells as compared to other pancreatic cells; importantly, Zn(II)-mediated hydrolysis triggers cargo activation. This prodrug system, with modular components that allow for fine-tuning selectivity, should enable the safer and more effective targeting of β-cells.

De Jesus DF, Orime K, Kaminska D, Kimura T, Basile G, Wang C-H, Haertle L, Riemens R, Brown NK, Hu J, et al. Parental metabolic syndrome epigenetically reprograms offspring hepatic lipid metabolism in mice. The Journal of clinical investigation. 2020;130(5):2391-2407.

The prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing worldwide. Although gene-environment interactions have been implicated in the etiology of several disorders, the impact of paternal and/or maternal metabolic syndrome on the clinical phenotypes of offspring and the underlying genetic and epigenetic contributors of NAFLD have not been fully explored. To this end, we used the liver-specific insulin receptor knockout (LIRKO) mouse, a unique nondietary model manifesting 3 hallmarks that confer high risk for the development of NAFLD: hyperglycemia, insulin resistance, and dyslipidemia. We report that parental metabolic syndrome epigenetically reprograms members of the TGF-β family, including neuronal regeneration-related protein (NREP) and growth differentiation factor 15 (GDF15). NREP and GDF15 modulate the expression of several genes involved in the regulation of hepatic lipid metabolism. In particular, NREP downregulation increases the protein abundance of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and ATP-citrate lyase (ACLY) in a TGF-β receptor/PI3K/protein kinase B-dependent manner, to regulate hepatic acetyl-CoA and cholesterol synthesis. Reduced hepatic expression of NREP in patients with NAFLD and substantial correlations between low serum NREP levels and the presence of steatosis and nonalcoholic steatohepatitis highlight the clinical translational relevance of our findings in the context of recent preclinical trials implicating ACLY in NAFLD progression.