Could osteoprotegerin serve as a marker of metabolic syndrome?

Abstract

There has been a dramatic increase in the worldwide prevalence of obesity, which is associated with the development of several chronic diseases such as metabolic syndrome, type 2 diabetes and cardiovascular diseases. Osteoprotegerin is a glycoprotein mainly secreted by bone but produced also by heart muscle and blood vessels. It inhibits the recruitment, proliferation, and activation of osteoclasts. The role of osteoprotegerin in the pathogenesis of metabolic syndrome, type 2 diabetes and cardiovascular diseases is still discussed. The study was carried out on 62 patients with metabolic syndrome aged 35-83 (34F and 28M). Type 2 diabetes was diagnosed in 76% of subjects and 62% of them suffered from coronary artery disease as a macrovascular complication.

Determinations of biochemical parameters and anthropometric measurements were performed in the studied group. The relationships between serum osteoprotegerin concentrations and components of metabolic syndrome and total cholesterol, LDL-cholesterol, HbA1C, BMI, levels of calcium and phosphate in the blood and 24-hour urinary calcium have been analysed. Diabetics had higher osteoprotegerin concentrations than patients without diabetes (5.570 pmol/l vs 4.690 pmol/l). Osteoprotegerin levels in patients with diabetes and coronary artery disease were significantly higher (6.640pmol/l) than in those without macrovascular complications (5.295 pmol/l) (Z=1.986; p=0.047). Furthermore, the associations between osteoprotegerin and calcium and phosphate levels in the blood and 24-hour urinary calcium have been shown. A lower calcium level in the blood was negative but a lower phosphate level was positive correlated with OPG serum concentration (respectively: 6.825 pmol/l vs 5.195 pmol/l, Z=2.656, p=0.008; 4.250pmol/l vs 5.640 pmol/l, Z=2.718, p=0.007). What’s more, the inverse correlations between OPG concentrations and 24-hour urinary calcium and diastolic blood pressure have been observed. No associations between osteoprotegerin and waist circumference, BMI, cholesterol levels and HbA1C, were found. In summary, osteoprotegerin is not a use ful marker of all components of metabolic syndrome. It is level depends on the presence of hypertension, type 2 diabetes and coronary artery disease. This glycoprotein may serve a a marker of calcium and phosphate homeostasis. We concluded that the relationship between osteoprotegerin concentrations and calcification of atherosclerotic plaques in patients with metabolic syndrome and type 2 diabetes should be analysed in further investigations.