Increased visceral fat and impaired glucose tolerance predict the increased risk of metabolic syndrome in Japanese middle-aged men.

BACKGROUND

Impaired glucose tolerance (IGT) represents a stage of pre-diabetes and is a risk factor for future cardiovascular disease (CVD) which is a major cause of death in type 2 diabetes. The metabolic risk factors such as elevated blood pressure (elevated BP), abdominal obesity, dyslipidemia (elevated levels of total triglycerides [TG] and low levels of HDL cholesterol), and hyperglycemia precede the onset of the metabolic syndrome that increases the risk for CVD. This clustering is commonly associated with pre-diabetic hyperinsulinemia and it reflects peripheral insulin resistance. The present study documented that a visceral fat area (VFA) >/= 100 cm (2) can replace waist-to-hip ratios (WHR) associated with IGT or IFG/IGT as a critical risk for the development of the metabolic syndrome in Japanese middle-aged men.

MATERIALS AND METHODS

A total of 575 middle-aged Japanese men with fasting plasma glucose levels of 6.1 - 6.9 mmol/l (impaired fasting glucose; IFG) were enrolled in the study. After a 75-g oral glucose tolerance test (OGTT), blood samples were collected 0 - 2 h later for determination of plasma glucose, insulin concentrations and other variables. Based on the results of an OGTT, the subjects were subgrouped into categories of glucose tolerance for further study.

RESULTS

Subjects with IGT or IFG/IGT had significantly higher levels of metabolic abnormalities such as high BMI, increased AUC glucose, elevated HbA1c, high VFA, elevated BP, and increased TG levels when compared to NGT (normal glucose tolerance) (p < 0.001). Compensatory hyper-secretion of insulin was seen in all pre-diabetic subjects, and was higher in IFG/IGT subjects (681 +/- 33 pmol . h/l) than NGT (480 +/- 22 pmol . h/l) (p < 0.01). The metabolic clustering including abnormal VFA, TG, HDL-C, and BP was strongly associated with the development of metabolic syndrome. Interestingly, VFA >/= 100 cm (2) adjusted for the Japanese correlates strongly with the development of the metabolic syndrome in preclinical IGT or IFG/IGT subjects, with odds ratios of 2.7 and higher.

CONCLUSION

VFA >/= 100 cm (2) strongly correlates with prediabetic IGT or IFG/IGT which is possibly associated with underlying insulin resistance, and is a critical risk factor linked to the development of metabolic syndrome in Japanese middle-aged subjects with IGT or IFG/IGT.