*••;••' N A L A R T I C L E Visceral Adiposity, Fasting Plasma Insulin, and Blood Pressure in Japanese- Americans EDWARD J. BOYKO, MD, MPH DONNA L. LEONETTI, PHD RICHARD W. BERGSTROM, MD LAURA NEWELL-MORRIS, PHD WILFRED Y. FUJIMOTO, MD OBJECTIVE— To examine the associations among blood pressure, body mass index (BMI), intra-abdominal fat, and fasting plasma insulin levels among nondiabetic subjects. RESEARCH DESIGN AND METHODS — Second (Nisei, n = 290) and third- (Sansei, n = 230) generation Japanese-American subjects without non-insulin- dependent diabetes mellitus (NIDDM) were selected from a community-based study of NIDDM incidence and complications. A cross-sectional comparison of measures ob- tained at the baseline visit was performed. Intra-abdominal fat (IAF) area was assessed using computed tomography. Associations among blood pressure, fasting insulin, and adiposity measures were assessed by comparison of mean values and multiple linear regression analysis. RESULTS— Hypertensive men and women had significantly higher mean IAF ar- eas. Fasting insulin levels were somewhat higher in hypertensive subjects, with the only significant difference occurring among Sansei men. Both systolic and diastolic blood pressure correlated more strongly with IAF than BMI or skinfold thicknesses among Nisei, whereas among Sansei, IAF and BMI correlated equally well with either blood pressure. Significant positive correlations were found between fasting insulin level and blood pressure among Sansei only, even after adjustment for IAF and BMI (diastolic blood pressure — insulin coefficient = 0.24, P = 0.0043; systolic blood pressure — insulin coefficient = 0.36, P = 0.0025). CONCLUSIONS — IAF correlated more strongly with blood pressure than BMI or skinfold thicknesses among older, second-generation Japanese-Americans and was positively correlated with blood pressure among Sansei independent of fasting insulin level. Fasting insulin was significantly correlated with blood pressure independent of visceral and overall adiposity among third-generation Japanese-Americans. From the Department of Medicine (E.J.B., R.W.B., W.Y.F.), University of Washington School of Medicine; the Medical Service (E.J.B.), Veterans Affairs Medical Center; and the Department of Anthropology (D.L.L., L.N.-M.), University of Washington, Seattle, Washington. Address correspondence and reprint requests to Edward J. Boyko, MD, MPH, VA Medical Center (111 M), 1660 S. Columbian Way, Seattle, WA 98108. Received for publication 2 May 1994 and accepted in revised form 22 September 1994. IAF, intra-abdominal fat; CT, computed tomography; NIDDM, non-insulin-dependent dia- betes mellitus; IGT, impaired glucose tolerance; WHO, World Health Organization; BMI, body mass index. T he clustering of glucose intolerance, hypertriglyceridemia, hypertension, and central obesity in a given indi- vidual has been referred to by Kaplan as "the deadly quartet" (1). An underlying disorder has been sought as the cause of this constellation of metabolic dis- turbances. Insulin resistance and accom- panying hyperinsulinemia have been implicated, given reports that have dem- onstrated a positive association between fasting insulin levels and both dyslipi- demia and hypertension (2,3). Insulin re- sistance and hyperinsulinemia appear to be related not just to total obesity but, in particular, to upper body obesity (4). Intra-abdominal fat (IAF) area measured by computed tomography (CT) may be a more important determinant of glucose intolerance (and associated insu- lin resistance) than other measures of re- gional or generalized obesity. Despres et al. (5) found no association between glu- cose intolerance and total body fat mass measured by hydrostatic weighing after adjustment for CT-measured IAF area. Other studies have reported positive asso- ciations between IAF and 2-h stimulated plasma glucose, and future development of non-insulin-dependent diabetes melli- tus (NIDDM) among nondiabetic sub- jects followed prospectively (6,7). The effect of regional body fat dis- tribution on the association between fast- ing insulin and blood pressure has not been extensively studied. Johnson et al. (8) found that adjustment for CT-mea- sured abdominal fat did not substantially alter a positive association between insu- lin area derived during an oral glucose tolerance test and either systolic or dia- stolic blood pressure. This study focused on relatively young (mean age 36 years) men with normal glucose tolerance. We examined the associations among IAF area, fasting plasma insulin, and blood pressure among second- and third-generation Japanese-Americans with normal or impaired glucose tolerance (IGT). Because the association between hyperinsulinemia and blood pressure has 174 DIABETES CARE, VOLUME 18, NUMBER 2, FEBRUARY 1995 Downloaded from http://diabetesjournals.org/care/article-pdf/18/2/174/443287/18-2-174.pdf by guest on 29 December 2021