Osteoprotegerin in relation to bone mass density and vascular complications in patients with diabetes

Abstract EN

Background-Identification of the OPG / RANK / RANKL axis [Osteoprotegerin / Receptor Activator of Nuclear Factor Kappa B / RANK ligand] which are essential for osteoclastogenesis / osteoblastogenesis balance, has led to better understanding of bone biology and human metabolic bone disease.

Beside regulating bone mass, OPG / RANK / RANKL axis mediates important and complex links between vascular, skeletal, and immune systems.

Diabetes is now viewed as vascular disease, moreover there is strong evidence that type 1 and type 2 diabetic patients have increased risk of certain types of fractures.

Objective-the aim of the present study is to study the relation between serum OPG levels and both bone density and vascular complications in diabetic patients. Study Design-90 subjects were classified as: Group I Diabetic patients with osteoporosis, that was subdivided into 2 subgroups, Group Ia 15 patients with long term vascular complications Group Ib 15 patients without vascular complications.

Group II Diabetic patients without osteoporosis, which was subdivided into 2 subgroups: Group IIa 15 patients with long term vascular complications.

Group IIb 15 patients without vascular complications Group III: 15 Non diabetic patients with osteoporosis and Group IV: 15 Healthy controls.

All subjects were submitted to full history and thorough physical examination, laboratory investigations in the form of FBG, PPBG, HbA1c, serum calcium, phosphorus ,alkaline phosphatase, 24hour urinary albumin excretion and, serum osteoprotegerin.

Bone mass density using dual emission x ray densitometry (DEXA), fundus examination, fluorescence angiography, coronary angiography, arterial duplex study of lower limbs were also done for all subjects. Results-there is a significant positive correlation between serum OPG and bone mineral density of lumber spine and neck femur in the diabetic patients (r =0.468 r=0.289 respectively).

Also, there was a significant positive correlation between serum OPG and bone mineral density of lumber spine only in all subjects included in the study (r = 0.351).

There is a statistically significant difference in serum OPG between diabetic patients with osteoporosis [35.97±13.253 pmol / L] and diabetic patients without osteoporosis [50.11±19.36 pmol / L], (F value-3.469, p < 0.001).

The osteoporotic populations in this study whether diabetic or not had lower OPG levels, than nonosteoporotic individuals.

The level was lower (28.33±12.79 pmol / L) in Group Ia Diabetic osteoporotic vascular (complicated group), compared to Group Ib (Diabetic osteoporotic non-complicated group) (37.46±10.72 pmol / L) and Group III (osteoporotic non-diabetic group) 42.13 ±12.94 pmol / L.

Serum OPG was highest in group IIa Diabetic non-osteoporotic complicated group) 59.2 ±25 pmol / L.

Another remarkable finding was that group IV (Healthy controls) and group II b Diabetic non-complicated) non-osteoporotic) showed no statistically significant difference when compared with each other as regard serum OPG (F=5.8 and P>0.005).

In the present study there was no significant correlation between serum OPG and glycemic indices of diabetes including duration of diabetes, fasting blood glucose, postprandial blood sugar and HbAıс.

Finally there was a statistically significant difference as regard serum OPG and the incidence of diabetic retinopathy (F=3.224, P<0.005), yet serum OPG showed no correlation with 24 hour urinary albumin (r=0.034).

Conclusion-OPG is clearly linked to osteoporosis.

In diabetes, OPG might be linked to long term vascular complications.

Diabetic osteopathy or vascular complications are associated with changes in serum OPG, yet its use as a biomarker for diagnosis, risk stratification or therapeutic monitoring of diabetic bone and vascular disease awaits further validation.