Identification and validation of N-acetyltransferase 2 as an insulin sensitivity gene

• Text
• PDF

Abstract

Decreased insulin sensitivity, also referred to as insulin resistance (IR), is a fundamental abnormality in patients with type 2 diabetes and a risk factor for cardiovascular disease. While IR predisposition is heritable, the genetic basis remains largely unknown. The GENEticS of Insulin Sensitivity consortium conducted a genome-wide association study (GWAS) for direct measures of insulin sensitivity, such as euglycemic clamp or insulin suppression test, in 2,764 European individuals, with replication in an additional 2,860 individuals. The presence of a nonsynonymous variant of N-acetyltransferase 2 (NAT2) [rs1208 (803A>G, K268R)] was strongly associated with decreased insulin sensitivity that was independent of BMI. The rs1208 “A” allele was nominally associated with IR-related traits, including increased fasting glucose, hemoglobin A1C, total and LDL cholesterol, triglycerides, and coronary artery disease. NAT2 acetylates arylamine and hydrazine drugs and carcinogens, but predicted acetylator NAT2 phenotypes were not associated with insulin sensitivity. In a murine adipocyte cell line, silencing of NAT2 ortholog Nat1 decreased insulin-mediated glucose uptake, increased basal and isoproterenol-stimulated lipolysis, and decreased adipocyte differentiation, while Nat1 overexpression produced opposite effects. Nat1-deficient mice had elevations in fasting blood glucose, insulin, and triglycerides and decreased insulin sensitivity, as measured by glucose and insulin tolerance tests, with intermediate effects in Nat1 heterozygote mice. Our results support a role for NAT2 in insulin sensitivity.

Authors

Joshua W. Knowles, Weijia Xie, Zhongyang Zhang, Indumathi Chennemsetty, Themistocles L. Assimes, Jussi Paananen, Ola Hansson, James Pankow, Mark O. Goodarzi, Ivan Carcamo-Orive, Andrew P. Morris, Yii-Der I. Chen, Ville-Petteri Mäkinen, Andrea Ganna, Anubha Mahajan, Xiuqing Guo, Fahim Abbasi, Danielle M. Greenawalt, Pek Lum, Cliona Molony, Lars Lind, Cecilia Lindgren, Leslie J. Raffel, Philip S. Tsao, The RISC (Relationship between Insulin Sensitivity and Cardiovascular Disease) Consortium, The EUGENE2 (European Network on Functional Genomics of Type 2 Diabetes) Study, The GUARDIAN (Genetics UndeRlying DIAbetes in HispaNics) Consortium, The SAPPHIRe (Stanford Asian and Pacific Program for Hypertension and Insulin Resistance) Study, Eric E. Schadt, Jerome I. Rotter, Alan Sinaiko, Gerald Reaven, Xia Yang, Chao A. Hsiung, Leif Groop, Heather J. Cordell, Markku Laakso, Ke Hao, Erik Ingelsson, Timothy M. Frayling, Michael N. Weedon, Mark Walker, Thomas Quertermous