Expression of cytokine-sensitive genes in islets from diabetes-prone mice

Genome-wide association studies in human type 2 diabetes (T2D) have renewed interest in the pancreatic islet as a major site of T2D risk. In this study, microarray data collected from mouse islets were used to identify genes that are regulated by cytokines at levels consistent with the chronic low-grade inflammation observed in T2D. The most cytokine-sensitive genes were then examined for association of single nucleotide polymorphisms (SNPs) with acute insulin response to glucose (AIRg) measured in the Genetics UndeRlying DIAbetes in HispaNics (GUARDIAN) study. In GUARDIAN, there was evidence of association of AIRg with SNPs in ARAP3 (5q31.3), F13A1 (6p25.3), KLHL6 (3q27.1), NID1 (1q42.3), PAMR1 (11p13), RIPK2 (8q21.3), and STEAP4 (7q21.12). These data support the mouse islet microarray data in detection of seven novel genes with potential importance to islet dysfunction in T2D. To further assess each gene, murine islets were exposed for 48-hrs to the following stressors representing models of beta-cell failure: 20nM rotenone (oxidative stress), 100nM thapsigargin (ER stress), 10pg/ml IL-1B + 20pg/ml IL-6 (cytokines/low-grade inflammation), 28mM glucose (hyperglycemia), or 50uM palmitate + 100uM oleate + 50uM linoleate (lipotoxicity). RT-PCR revealed that F13a1 was downregulated 3.3-fold by cytokines (P<0.05) and 2.6-fold by rotenone (P<0.05), Klhl6 was upregulated 4.3-fold by thapsigargin (P<0.01), Ripk2 was mildly (1.5-3-fold) but significantly upregulated by all stressors (P<0.05), and STEAP4 was profoundly cytokine-sensitive (167-fold upregulation, P<0.01). These findings reveal promising leads in elucidating islet dysfunction during the development of T2D.

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Sharma PR, Mackey AJ, Dejene EA, Ramadan JW, Langefeld CD, Palmer ND, Taylor KD, Wagenknecht LE, Watanabe RM, Rich SS, Nunemaker CS