Comparative Study of Bone Specific Alkaline Phosphatase, Bone Mineral Density, and Zinc in Postmenopausal Osteoporosis in Iraqi Type 2 Diabetic Women

Abstract

Background: Osteoporosis is the most common metabolic bone disorder that is common in postmenopausal women with type 2 diabetes.T2DM is linked to an increase in the fracture rate as compared to the non-diabetic population even with normal or raised bone mineral density (BMD). Hence, bone quality plays an important role in the pathogenesis of skeletal fragility due to T2DM. Zinc (Zn) an essential trace element is necessary for the normal mineralization of bone and play role in collagen metabolism, and its levels are altered in diabetes. Osteopenia describes a decrease in BMD below normal reference values, yet not low enough to meet the diagnostic criteria for osteoporosis. BMD is diagnosed via dual-energy X-ray absorptiometry bone scans. Bone alkaline phosphatase (BALP) is an ectoenzyme attached to the outer surface of the cell membrane of osteoblasts. It is partly released into circulation. BALP and liver ALP constitute about 95% of the total ALP (TALP) activity in human serum.

Aims: The aim of the present work is to compare the investigated results of BALP, Total ALP, BMD, T-scor, body mass index (BMI), age, calcium, and Zn between diabetic postmenopausal osteoporosis (diabetic PMOP) and non-diabetic postmenopausal osteopenia to see if there is any influence caused an increase in fracture risk in diabetes patients.

Materials and Methods: We performed a cross-sectional study in Kerbala medical college department of chemistry and biochemistry enrolling 80 subjects, 40 PMOP with T2DM, aged between (50-75) years, and 40 postmenopausal osteopenia without T2DM, aged between (50-76) years. All Patients had been in spontaneous menopause for at least, one year. For each subject we measured serum BALP, total ALP, Zinc, Calcium, BMI, BMD, and T-scor during Nov. 2021 to June, 2022. Diabetic patients were collected from Al-Hassan center for Endocrinology and diabetes mellitus and Osteoporosis center at Al-Hussein Medical City, Kerbala Health Directorates, Kerbala/ Iraq. The mean and standard deviation of the parameters of the two groups were computed and compared by unpaired Student^'s T-test. The relationship between variables was measured by Karl Pearson^'s correlation coefficient. A statistical significance is set at a 5% level of significance (P < 0.05).

Result: Age and TALP were significantly higher in diabetic PMOP compared with non-diabetic osteopenia (62.8 ± 6.8 vs. 56.4 ± 7.37 year), (227.43± 61.46 vs. 201.50 ± 41.47 U/L), P<0.05. BMI was non-significant in diabetic PMOP compared with non-diabetic osteopenia (29± 4.72 vs.30.34 ± 4.64 kg/m2) P>0.05. T-scor was significantly lower in diabetic PMOP compared with non-diabetic osteopenia (-3.04 ± 0.45 vs. -1.64 ± 0.38) P <0.05. BMD and Zinc were significantly lower in diabetic PMOP compared with non-diabetic osteopenia (0.72 ± 0.06 vs. 0.86 ± 0.04 g/cm2), (78.90 ± 7.34 vs. 83.02 ± 7.43 µg/dL) P<0.05. BALP was non-significantly higher in diabetic PMOP compared with non-diabetic osteopenia (52.33 ± 11.62 vs. 49.51 ± 7.64 ng/L) P>0.05. Calcium was non-significantly in diabetic PMOP compared with non-diabetic osteopenia (9.49 ± 0.30 vs. 9.39 ± 0.44 mg/dL) P>0.05. BMD of diabetic PMOP showed a significant strong positive correlation with T-scor and also BMD of non-diabetic osteopenia showed a significant positive correlation with T-scor. BMD of diabetic PMOP and non-diabetic osteopenia showed a non-significant negative correlation with BALP and TALP. BMD of non-diabetic osteopenia showed a significant positive correlation with Zn and in diabetic osteoporosis non-significant positive correlation with Zn.

Conclusions: Type 2 diabetic PMOP have BMD lower than the non-diabetic osteopenia. High zinc level in non-diabetic osteopenia may contribute to high BMD. Serum zinc levels may serve to be important predictors of BMD. Low BMI in diabetic PMOP is an indicator for osteoporosis and its related fracture. In diabetic PMOP, T-scor is only predict by high level of BALP and TALP and low level of zinc. Low levels of BALP, TALP and high level serum zinc are the predictors of T-score in non-diabetic osteopenia.