Effects of insulin sensitivity, body composition, and fitness on lipoprotein particle sizes and concentrations determined by nuclear magnetic resonance

Context: Insulin resistance has been reported to be associated with development of atherogenic dyslipidemia. However, the confounding effects that obesity and low levels of cardiorespiratory fitness have on the relationship between insulin resistance and the development of atherogenic dyslipidemia remain to be adequately addressed. Objective: This study sought to examine the independent and combined effects of insulin sensitivity, body composition, and cardiorespiratory fitness on lipoprotein particle sizes and concentrations. Methods: Eight-four healthy, nondiabetic men (n = 43) and women (n = 41) were studied. The participants had a wide range of ages (18-30 and 65-80 yr), body composition (7.2-52.8% fat), and cardiorespiratory fitness (VO2 peak, 13.5-66.2 ml/kg=min). Body composition, cardiorespiratory fitness, insulin sensitivity, and lipoprotein particle profiles were assessed using dual-energy x-ray absorptiometry, cardiopulmonary exercise testing, a hyperinsulinemic-euglycemic clamp, and nuclear magnetic resonance spectroscopy, respectively. Results: Low levels of insulin sensitivity and cardiorespiratory fitness and higher levels of adiposity were associated with the accumulation of small, dense, low-density lipoprotein particles; small high-density lipoprotein particles; triglycerides; and very low-density lipoprotein particles. Multivariate forward-stepwise regression revealed that higher levels of adiposity, in particular truncal fat, were the strongest predictor of the lipoprotein particle size and concentration data, followed by insulin sensitivity. Conclusions: As expected, the accumulation of atherogenic lipoprotein particles (e.g. small, dense, low-density lipoprotein particles and small, high-density lipoprotein particles) was associated with low levels of insulin sensitivity, cardiorespiratory fitness, and higher levels of adiposity. However, multivariate forward-stepwise regression revealed that triglycerides, followed by truncal fat mass, were the strongest predictors of the lipoprotein particle size and concentration data.