Osteoprotegerin : an atherosclerosis risk factor in type 2 diabetes

Abstract EN

The bone related peptide, osteoprotegerin (OPG) has recently been found in increased amounts in the vasculature in diabetes.

It is produced by vascular smooth muscles and endothelial cells, and may be implicated in the development of vascular calcification.

OPG is also present in the circulation, where increased amounts have been observed in patients with diabetes. Aim of The Work: In this study, we aimed to investigate the relationship between plasma OPG, inflammatory markers, including high sensitivity C-reactive protein (hsCRP)) and interleukin-6 (IL-6) and early atherosclerosis as assessed by carotid intima media thickness (IMT) in a group of type 2 diabetic patients. Material and Methods: This study was conducted on 50 patients with type 2 diabetes mellitus (Group I), they were 30 males and 20 females with age ranged from 42–63 years.

They were divided into 2 subgroups according to the absence (Group Ia, n=30) or presence (Group Ib, n=20) of microvascular diabetic complications (neuropathy, nephropathy and retinopathy).

Twenty age and sex-matched healthy subjects were also included as a control group (Group II); they were 12 males and 8 females.

All studied subjects underwent anthropometric measures, body mass index (BMI), waist circumference (WC), ultrasonograhic measurement of carotid IMT, in addition to disease variables, markers of inflammation and serum OPG. Results: Our results showed that OPG level was significantly higher in patients with type 2 diabetes (Group I) than in the control group (Group II) (P<0.001), also it was significantly higher in the group of patients with microvascular diabetic complications (Group Ib) compared to the uncomplicated group (Group Ia) (P<0.001).

In our results we could find that OPG was significantly positively correlated with age (r= 0.57, P<0.05), BMI (r= 0.49, P<0.05), WC (r= 0.47, P<0.05), disease duration (r= 0.58, P<0.05), hemoglobin A1c (HbA1c) (r= 0.55, P<0.05), fasting insulin level (r= 0.42, P<0.05), homeostatic model assessment of insulin resistance (HOMA-IR) (r=0.44, P<0.05), hsCRP (r= 0.48, P<0.05) and IL-6 (r= 0.51, P<0.05).

There is also strong positive correlation between OPG and carotid IMT (r=0.73, P<0.001) and urinary albumin/creatinine excretion ratio (ACR) (r= 0.68, P<0.001). Conclusion and Recommendations: Serum OPG level was found to be increased in diabetic patients and it was positively correlated with inflammatory markers and early atherosclerosis as assessed by carotid IMT.

Thus, high OPG may act as a causal risk factor of/or represent a counter-regulatory protective response to atherosclerosis.

Further studies to clarify the precise nature of the association between OPG and atherosclerosis in type 2 diabetes are warranted.

The use of OPG as a simple test for identifying high risk type 2 diabetes also merits further investigations.