Diabetes 57:899-908, 2008 DOI: 10.2337/db07-0790 © 2008 by the American Diabetes Association
Physiological and Molecular Determinants of Insulin Action in the Baboon
1 Diabetes Division, University of Texas Health Science Center at San Antonio, San Antonio, Texas Address correspondence and reprint requests to Franco Folli, MD, PhD, Diabetes Division, Department of Medicine, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229. E-mail: folli{at}uthscsa.edu
Abbreviations:
FFA, free fatty acid; FFM, fat-free mass; FPG, fasting plasma glucose; FPI, fasting plasma insulin; HOMA-β, homeostasis model assessment of β-cell function; HOMA-IR, homeostasis model assessment of insulin resistance; IRS, insulin receptor substrate; PI 3-kinase, phosphatidylinositol 3-kinase; Rd, glucose disposal rate
OBJECTIVE—To quantitate insulin sensitivity in lean and obese nondiabetic baboons and examine the underlying cellular/molecular mechanisms responsible for impaired insulin action to characterize a baboon model of insulin resistance. RESEARCH DESIGN AND METHODS—Twenty baboons received a hyperinsulinemic-euglycemic clamp with skeletal muscle and visceral adipose tissue biopsies at baseline and at 30 and 120 min after insulin. Genes and protein expression of key molecules involved in the insulin signaling cascade (insulin receptor, insulin receptor substrate-1, p85, phosphatidylinositol 3-kinase, Akt, and AS160) were sequenced, and insulin-mediated changes were analyzed.
RESULTS—Overall, baboons show a wide range of insulin sensitivity (6.2 ± 4.8 mg · kg–1 · min–1), and there is a strong inverse correlation between indexes of adiposity and insulin sensitivity (r = –0.946, P < 0.001 for % body fat; r = –0.72, P < 0.001 for waist circumference). The genes and protein sequences analyzed were found to have CONCLUSIONS—The obese baboon is a pertinent nonhuman primate model to examine the underlying cellular/molecular mechanisms responsible for insulin resistance and eventual development of type 2 diabetes.
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