RELATIONS OF PLASMA TG AND HDL-C CONCENTRATIONS TO BODY-COMPOSITION AND PLASMA-INSULIN LEVELS ARE ALTERED IN MEN WITH SMALL LDL PARTICLES

Low-density lipoprotein (LDL) subclass pattern B is characterized by a predominance of small, dense LDL particles (LDL peak particle size le ss than or equal to 255 Angstrom), increased plasma triglyceride (TG) levels, reduced high-density lipoprotein (HDL) cholesterol levels, and glucose intolerance. This study tested the hypothesis that there are differences in the regulation of TG and HDL metabolism by insulin in p atients with LDL pattern B. The study group comprised 160 healthy olde r (60+/-8 years, mean+/-SD) men. Forty-nine of the men (31%) had LDL p attern B. These men had a higher waist-to-hip ratio (WHR) (0.98+/-0.06 versus 0.95+/-0.06, P<.005) and lower maximal aerobic capacity (VO(2) max) (P<.005) than the 111 men of compa- rable age with a predominance of larger LDL particles (LDL peak particle size >255 Angstrom, LDL pa ttern A). Men with LDL pattern B also had higher TG (1.76+/-0.60 versu s 1.03+/-0.41 mmol/L, P<.0001) and lower HDL cholesterol (0.83+/-0.13 versus 1.06+/-0.29 mmol/L, P<.0001) and percent HDL, subspecies (by gr adient gel electrophoresis) (31+/-4 versus 43+/-6, P<.0001) levels tha n men with LDL pattern A, but the total cholesterol and LDL cholestero l levels did not differ between groups. Fasting glucose and insulin le vels also did not differ between groups, but plasma glucose and insuli n levels measured at 90 and 120 minutes during an oral glucose toleran ce test were significantly higher in men with LDL pattern B. This was associated with a higher prevalence of impaired glucose tolerance in m en with LDL B compared with men with LDL A (49% versus 24%, P<.005). T he differences in lipoprotein lipid levels and glucose tolerance betwe en groups persisted after correcting for differences (by ANCOVA) in WH R and VO(2)max. Multiple linear regression analyses with interaction t erms demonstrated that the regression equations delineating the relati ons of plasma TG and HDL to insulin levels differed significantly; men with LDL pattern B had higher plasma TG and lower HDL cholesterol lev els at each plasma insulin level than men with LDL pattern A (P<.001). The relation between HDL and TG levels and body composition also diff ered: men with LDL pattern B had lower HDL cholesterol levels at each percent body fat (P<.005) and higher TG levels at each WHR than men wi th LDL pattern A (P<.001). These results suggested that glucose intole rance and genetic differences in the regulation of TG and HDL metaboli sm by insulin reduce plasma HDL and raise TG levels in men with small LDL particles.