INSULIN-RESISTANCE AND FAT PATTERNING WITH AGING - RELATIONSHIP TO METABOLIC RISK-FACTORS FOR CARDIOVASCULAR-DISEASE

Both insulin resistance and abdominal fat patterning are related to ag ing, and have been related to cardiovascular disease (CVD) risk factor s such as dyslipidemia and hypertension. However, previous studies hav e not used direct methods to quantify the independent strength of the association of each of these two putative primary factors with metabol ic outcomes. We quantified overall obesity by the body mass index (BMI ) and used a previously validated magnetic resonance imaging (MRI) met hod to quantify abdominal fat in 63 healthy nondiabetic individuals ag ed 22 to 83 years. We also measured the glucose and insulin response t o an oral glucose tolerance test and the insulin sensitivity ([S-I] by modified minimal model analysis). Body fat patterning was evaluated b y the waist to hip ratio (WHR) and by MRI, which allowed direct measur ement of subcutaneous (SCF) and intraabdominal (IAF) fat depots at the umbilicus in these subjects, These independent parameters were relate d to risk factors for CVD (blood pressure, lipids, and lipoproteins) a nd to plasma concentrations of free fatty acids (FFAs). Measures of ov erall obesity (BMI), total fat [TF], and/or SCF measured at the abdome n by MRI), glucose/insulin metabolism and S-I, and central fat pattern ing (WHR or IAF measured by MRI) were correlated with mean arterial pr essure (MAP), triglyceride (TG), and high-density lipoprotein choleste rol (HDL-C) levels in univariate analysis and after controlling for ag e and gender. An index of central fat patterning (WHR) added to the in formativeness of the insulin area under the curve (IAUC) in explaining 24% of the variability in plasma TG concentration, but measures of ov erall obesity were not independently related. Both the BMI and TF cont ributed to the IAUC in explaining 32% to 34% of the variability in MAP , but central fat patterning was not independently related. No index o f overall obesity, fat patterning, glucose/insulin metabolism, and/or S-I, was independently related to the plasma concentration of HDL-C af ter controlling for any one of the other two. Direct measurement of gl ucose/insulin metabolism and S-I, as well as fat patterning, provides information on their relative associations with CVD risk factors. The measures of glucose/insulin metabolism and S-I were more consistently related to dyslipidemia and hypertension than were the overall obesity and fat patterning in this healthy population. Copyright (C) 1998 by W.B. Saunders Company.