The purposes of this study were (1) to determine the association between lipoprotein subfraction profiles and metabolically healthy overweight (MHO) phenotype, as defined by visceral adiposity; and (2) to identify the strongest predictor of metabolic health among the lipoprotein measurements.

Insulin resistance constitutes a pathophysiologic link between obesity, atherosclerosis, and/or cardiovascular complications. Retinol binding protein 4 (RBP4) is a newly discovered adipocyte product that modulates glucose metabolism and consequently induces insulin resistance. We investigated the association between serum RBP4 levels and insulin resistance in obese and nonobese adolescents. A total of 87 nonobese (60 males and 27 females) and 85 obese (62 males and 23 females) apparently healthy adolescents, 12 to 18 years old, were included in this study. A questionnaire was used to obtain participant medical history and lifestyle information, such as smoking and alcohol ingestion habits. Subjects' anthropometric measurements were taken to calculate for body mass index and waist-to-hip ratio. Serum RBP4 levels were measured by an enzyme immunoassay kit. High-sensitivity C-reactive protein, fasting glucose, total cholesterol, triglycerides, high-density lipoprotein cholesterol, and fasting insulin were measured. Low-density lipoprotein cholesterol level and homeostatic model assessment of insulin resistance (HOMA-IR) were calculated. Males had significantly higher RBP4 levels than females. Serum RBP4 levels were significantly higher in the obese group compared with the nonobese group. In all subjects, RBP4 was positively correlated with adiposity index (body mass index, waist circumference, waist-to-hip ratio), systolic and diastolic blood pressures, glucose tolerance index (fasting glucose, insulin, HOMA-IR), lipid profile (total cholesterol, triglycerides), and inflammatory indices (high-sensitivity C-reactive protein, white blood cell count). In multiple linear regression analysis, RBP4 was independently associated with age, HOMA-IR, and triglyceride levels in the nonobese group and with sex and triglyceride levels in the obese group. These results suggest that serum RBP4 might have clinical implications for lipid metabolism and insulin action in adolescents.

Adiponectin levels are significantly lower in obese adult patients with type 2 diabetes mellitus, essential hypertension, dyslipidemia, and cardiovascular disease. However, the role of hypoadiponectinemia in nonobese healthy adults has not been fully elucidated. In this study, we examined the association between hypoadiponectinemia and cardiovascular risk factors and estimated plasma adiponectin values in nonobese, apparently healthy adults. A total of 204 male and 214 female healthy individuals aged 20 to 80 years, with a body mass index (BMI) of less than 25 kg/m2, were included in this study. We measured patients' plasma adiponectin levels, serum lipid profiles, high-sensitivity C-reactive protein (hs-CRP) levels, fasting glucose levels, and fasting insulin levels. Mean values of plasma adiponectin were 5.45 +/- 3.3 microg/mL in male and 8.16 +/- 4.6 microg/mL in female subjects. The hypoadiponectinemia group (< 4.0 microg/mL) had significantly higher levels (P < .01) of BMI, fasting glucose, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), and triglycerides, but lower levels of high-density lipoprotein cholesterol (HDL-C). In males, plasma adiponectin levels were inversely correlated with BMI (r = -0.32, P < .01), HOMA-IR (r = -0.14, P < .05), triglyceride levels (r = -0.17, P < .05), and hs-CRP levels (r = -0.15, P < .05), and positively correlated with HDL-C (r = 0.24, P < .01). In females, plasma adiponectin levels were negatively correlated with BMI (r = -0.31, P < .01), fasting glucose (r = -0.18, P < .01), fasting insulin (r = -0.23, P < .01), HOMA-IR (r = -0.24, P < .01), and triglyceride (r = -0.18, P < .01) levels, and positively correlated with HDL-C (r = 0.37, P < .01). Sex, age, BMI, and HDL-C (P < .01 for each) were found to be independent factors associated with plasma adiponectin levels in multivariate analysis. Hypoadiponectinemia is significantly associated with cardiovascular risk factors such as insulin resistance and atherogenic lipid profiles in nonobese, apparently healthy subjects.