Stress-impaired transcription factor expression and insulin secretion in transplanted human islets
Chunhua Dai ... Roland Stein, Alvin C. Powers
Chunhua Dai ... Roland Stein, Alvin C. Powers
Published May 2, 2016
Citation Information: J Clin Invest. 2016;126(5):1857-1870. doi:10.1172/JCI83657.
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Categories: Research Article Endocrinology

Stress-impaired transcription factor expression and insulin secretion in transplanted human islets

Abstract

Type 2 diabetes is characterized by insulin resistance, hyperglycemia, and progressive β cell dysfunction. Excess glucose and lipid impair β cell function in islet cell lines, cultured rodent and human islets, and in vivo rodent models. Here, we examined the mechanistic consequences of glucotoxic and lipotoxic conditions on human islets in vivo and developed and/or used 3 complementary models that allowed comparison of the effects of hyperglycemic and/or insulin-resistant metabolic stress conditions on human and mouse islets, which responded quite differently to these challenges. Hyperglycemia and/or insulin resistance impaired insulin secretion only from human islets in vivo. In human grafts, chronic insulin resistance decreased antioxidant enzyme expression and increased superoxide and amyloid formation. In human islet grafts, expression of transcription factors NKX6.1 and MAFB was decreased by chronic insulin resistance, but only MAFB decreased under chronic hyperglycemia. Knockdown of NKX6.1 or MAFB expression in a human β cell line recapitulated the insulin secretion defect seen in vivo. Contrary to rodent islet studies, neither insulin resistance nor hyperglycemia led to human β cell proliferation or apoptosis. These results demonstrate profound differences in how excess glucose or lipid influence mouse and human insulin secretion and β cell activity and show that reduced expression of key islet-enriched transcription factors is an important mediator of glucotoxicity and lipotoxicity.

Authors

Chunhua Dai, Nora S. Kayton, Alena Shostak, Greg Poffenberger, Holly A. Cyphert, Radhika Aramandla, Courtney Thompson, Ioannis G. Papagiannis, Christopher Emfinger, Masakazu Shiota, John M. Stafford, Dale L. Greiner, Pedro L. Herrera, Leonard D. Shultz, Roland Stein, Alvin C. Powers

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Models of chronic metabolic stress. (A) Experimental design. After islet...

Figure 1

Models of chronic metabolic stress.

(A) Experimental design. After islet engraftment period, NSG-DTR mice were injected with 5 ng DT or saline and monitored for 4 weeks; NSG mice were placed on HFD or RD for 12 weeks. (B) Experimental timeline of S961 model. Two weeks after islet transplantation, S961 is delivered by implantation of osmotic pump. Analyses were performed at 1 or 2 weeks after pump implantation. (C) Isolated human islet preparations (n = 13) perifused, prior to transplantation, with media containing 5.6 mM or 16.7 mM glucose (G 5.6 and G 16.7), then 16.7 mM glucose with the phosphodiesterase inhibitor IBMX; some of these were part of previously published perifusion data sets (35, 102). (D) Random blood glucose of NSG-DTR groups after DT injection (n = 6/ group). Nephrectomy indicates survival surgery to remove graft-containing kidney. (E) Pancreatic insulin content in NSG-DTR mice 4 weeks after DT injection (n = 4–6/group). ***P < 0.001, DT-NG or DT-HG vs. PBS. (F) Mouse body weight change after 12 weeks of diet (RD, n = 29; HFD, n = 30). ***P < 0.001. (G) Fat mass (NSG-RD, n = 29; NSG-HFD, n = 30). (H) Serum triglyceride and cholesterol levels after 11 weeks on diet (NSG-RD, n = 8; NSG-HFD, n = 9). (I) Random blood glucose after 8 weeks of diet (RD, n = 20; HFD, n = 21) (J) Glucose tolerance test after 8 weeks on diet (NSG-RD, n = 31; NSG-HFD, n = 33). ***P < 0.001. (K) Random blood glucose measurements of S961- and PBS-treated mice from 0 to 7 days after pump implantation. ***P < 0.001. (L) Random (nonfasting) mouse insulin values. ***P < 0.001. PBS, n = 8; S961, n = 12. Unpaired 2-tailed Student’s t test or 1-way ANOVA followed by Newman-Keuls multiple comparison test (E) was used for analysis of statistical significance. Blue represents the NSG-DTR model, red the NSG-HFD model, and green the NSG-S961 model. DT-HG, hyperglycemia after DT; DT-NG, normoglycemia after DT; PBS, animals given PBS instead of DT.