Hypovitaminosis D in Chinese type 2 diabetes: Lack of impact on clinical metabolic status and biomarkers of cellular inflammation

Objective: Low vitamin D (25 OH vitamin D) is implicated in the development of diabetes and the metabolic syndrome. We examined whether hypovitaminosis D has a clinically significant impact on glycaemia, metabolic status and inflammatory markers in Chinese patients with established type 2 diabetes. Methods: Characteristics of 109 patients aged over 50 years were stratified by 25 OH vitamin D status. Patients identified as 25 OH vitamin D deficient (<= 50 nmol/L) received cholecalciferol 2,000 IU daily for three months. Measurement of HbA1c, metabolic syndrome parameters, 25 OH vitamin D, calcium, phosphate, PTH, hsCRP and ferritin were taken at baseline and then 25 OH vitamin D, PTH, calcium, phosphate monthly for three months in those on replacement therapy. Results: Vitamin D deficiency was common, affecting 36% of patients. There was no impact of hypovitaminosis D on metabolic syndrome status, HbA1c or insulin use (p >= 0.4 for all) and no association between 250HVitD and ferritin or hsCRP (p >= 0.3 for all). Neither BMI nor the metabolic syndrome affected the incremental rise in 250HVitD levels during supplementation. Conclusion: There is no relationship between hypovitaminosis D and metabolic control or inflammatory markers in established type 2 diabetes. This suggests that at least in Chinese populations, the effect of low vitamin D is not clinically significant once diabetes is established. Future 250HVitD intervention trials should therefore focus on prevention in pre-diabetes.