Kwame Osei1, Trudy Gaillard, Dara Schuster. 1. Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, 491 McCampbell Hall, The Ohio State University College of Medicine and Public Health, Columbus OH 43210, USA. osei-1@medctr.osu.edu
Abstract
OBJECTIVE: We studied plasma adiponectin, insulin sensitivity, and insulin secretion before and after oral glucose challenge in normal glucose tolerant, impaired glucose tolerant, and type 2 diabetic first degree relatives of African-American patients with type 2 diabetes. RESEARCH METHODS AND PROCEDURES: We studied 19 subjects with normal glucose tolerance (NGT), 8 with impaired glucose tolerance (IGT), and 14 with type 2 diabetes. Serum glucose, insulin, C-peptide, and plasma adiponectin levels were measured before and 2 hours after oral glucose tolerance test. Homeostasis model assessment-insulin resistance index (HOMA-IR) and HOMA-beta cell function were calculated in each subject using HOMA. We empirically defined insulin sensitivity as HOMA-IR<2.68 and insulin resistance as HOMA-IR>2.68. RESULTS: Subjects with IGT and type 2 diabetes were more insulin resistant (as assessed by HOMA-IR) when compared with NGT subjects. Mean plasma fasting adiponectin levels were significantly lower in the type 2 diabetes group when compared with NGT and IGT groups. Plasma adiponectin levels were 2-fold greater (11.09+/-4.98 vs. 6.42+/-3.3811 microg/mL) in insulin-sensitive (HOMA-IR, 1.74+/-0.65) than in insulin-resistant (HOMA-IR, 5.12+/-2.14) NGT subjects. Mean plasma adiponectin levels were significantly lower in the glucose tolerant, insulin-resistant subjects than in the insulin sensitive NGT subjects and were comparable with those of the patients with newly diagnosed type 2 diabetes. We found significant inverse relationships of adiponectin with HOMA-IR (r=-0.502, p=0.046) and with HOMA-beta cell function (r=-0.498, p=0.042) but not with the percentage body fat (r=-0.368, p=0.063), serum glucose, BMI, age, and glycosylated hemoglobin A1C (%A1C). DISCUSSION: In summary, we found that plasma adiponectin levels were significantly lower in insulin-resistant, non-diabetic first degree relatives of African-American patients with type 2 diabetes and in those with newly diagnosed type 2 diabetes. We conclude that a decreased plasma adiponectin and insulin resistance coexist in a genetically prone subset of first degree African-American relatives before development of IGT and type 2 diabetes.
OBJECTIVE: We studied plasma adiponectin, insulin sensitivity, and insulin secretion before and after oral glucose challenge in normal glucose tolerant, impaired glucose tolerant, and type 2 diabetic first degree relatives of African-American patients with type 2 diabetes. RESEARCH METHODS AND PROCEDURES: We studied 19 subjects with normal glucose tolerance (NGT), 8 with impaired glucose tolerance (IGT), and 14 with type 2 diabetes. Serum glucose, insulin, C-peptide, and plasma adiponectin levels were measured before and 2 hours after oral glucose tolerance test. Homeostasis model assessment-insulin resistance index (HOMA-IR) and HOMA-beta cell function were calculated in each subject using HOMA. We empirically defined insulin sensitivity as HOMA-IR<2.68 and insulin resistance as HOMA-IR>2.68. RESULTS: Subjects with IGT and type 2 diabetes were more insulin resistant (as assessed by HOMA-IR) when compared with NGT subjects. Mean plasma fasting adiponectin levels were significantly lower in the type 2 diabetes group when compared with NGT and IGT groups. Plasma adiponectin levels were 2-fold greater (11.09+/-4.98 vs. 6.42+/-3.3811 microg/mL) in insulin-sensitive (HOMA-IR, 1.74+/-0.65) than in insulin-resistant (HOMA-IR, 5.12+/-2.14) NGT subjects. Mean plasma adiponectin levels were significantly lower in the glucose tolerant, insulin-resistant subjects than in the insulin sensitive NGT subjects and were comparable with those of the patients with newly diagnosed type 2 diabetes. We found significant inverse relationships of adiponectin with HOMA-IR (r=-0.502, p=0.046) and with HOMA-beta cell function (r=-0.498, p=0.042) but not with the percentage body fat (r=-0.368, p=0.063), serum glucose, BMI, age, and glycosylated hemoglobin A1C (%A1C). DISCUSSION: In summary, we found that plasma adiponectin levels were significantly lower in insulin-resistant, non-diabetic first degree relatives of African-American patients with type 2 diabetes and in those with newly diagnosed type 2 diabetes. We conclude that a decreased plasma adiponectin and insulin resistance coexist in a genetically prone subset of first degree African-American relatives before development of IGT and type 2 diabetes.
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