Plasma acylation stimulating protein concentration and subcutaneous adipose tissue C3 mRNA expression in nondiabetic and type 2 diabetic men

We studied the effect of an oral fat load on plasma acylation stimulating p rotein (ASP) concentrations in 9 lean healthy (age 59 +/-2 years, body mass index [BMI] 23.2 +/-0.4 kg/m(2) both mean +/- SEM), 9 obese nondiabetic (5 8 +/-2 years, BMI29.4 +/-0.5 kg/m(2)), and 12 type 2 diabetic (60 +/-2 year s, BMI 29.6 +/-1.0 kg/m(2)) men. Because ASP is a cleavage product of compl ement protein C3 (C3adesArg) and its secretion is regulated by insulin, we also examined the subcutaneous adipose tissue expression of C3 mRNA before and after a 240-minute euglycemic hyperinsulinemic clamp in a subgroup of t hese men. Plasma ASP concentration and adipose tissue C3 mRNA expression we re higher in the obese groups than in the lean men. Plasma ASP concentratio n did not change significantly after the fat load. Fasting plasma ASP conce ntration and C3 mRNA expression were correlated negatively with insulin sen sitivity and positively with the magnitude of postprandial lipemia in nondi abetic but not in type 2 diabetic men. The expression of C3 mRNA was not re gulated by insulin. These data suggest that ASP is associated with whole-bo dy glucose and lipid metabolism in nondiabetic individuals, whereas metabol ic disturbances in diabetes may overcome the regulatory role of ASP in lipi d and glucose metabolism.