TNF[alpha] and leptin inhibit basal and glucose-stimulated insulin secretion and gene transcription in the HIT-T15 pancreatic cells

• Published in: International Journal of Obesity and Related Disorders 2001-07, Vol.25 (7), p.1018
• Main Authors: Tsiotra, P C, Tsigos, C, Raptis, S A
• Format: Article
• Language: English
• Subjects: Adipose tissue; Body fat; Cytokines; Diabetes; Glucose; Insulin resistance; Metabolism; Obesity; Polymerase chain reaction; Tumor necrosis factor-TNF
• ISSN: 0307-0565; 1476-5497
• DOI: 10.1038/sj.ijo.0801657

BACKGROUND:: Tumor necrosis factor [alpha] (TNF[alpha]), a cytokine produced at inflammatory sites and in adipose tissue, is known primarily for its detrimental effects on insulin action. There is evidence to suggest that TNF[alpha] may also influence β-cell function. Leptin is another adipose tissue-derived hormone that might also act on β-cells. OBJECTIVE:: We explored the independent and combined effects of TNF[alpha] and leptin upon basal and glucose-stimulated insulin transcription and secretion in the HIT-T15 pancreatic β cell line. METHODS:: Cells were cultured for 40 h in the presence of near-normal basal (7 mM) or high (16.7 mM) glucose and treated with either TNF[alpha] (1, 10 and 50 ng/ml) or leptin (10, 50 and 100 ng/ml) or both together. Insulin concentrations were measured by radioimmunoassay. Insulin mRNA levels were evaluated by a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) method, after normalization with β-actin mRNA. RESULTS:: TNF[alpha] significantly suppressed basal and glucose-stimulated insulin secretion and proinsulin mRNA transcription in a dose-dependent manner, an effect that was more powerful in the presence of high glucose. Leptin also inhibited dose-dependent insulin mRNA and protein at both glucose concentrations, but did not appear to further potentiate the suppressive effects of TNF[alpha]. CONCLUSION:: TNF[alpha] suppresses both basal and glucose-stimulated insulin transcription and secretion in HIT-T15 cells, an effect that is enhanced significantly by high glucose. Leptin also independently inhibits basal and glucose-stimulated insulin secretion and transcription but does not modify TNF[alpha] effects. These effects might contribute to the abnormalities of glucose metabolism that characterize conditions of increased TNF[alpha] and/or leptin production. INTERNATIONAL JOURNAL OF OBESITY: (2001) 25, 1018--1026