Diabetes mellitus:
Vitamin D deficiency has been observed in the onset of diabetes (type 1
and 2) in world populations (51). The active form of vitamin D
(calcitriol) after binding with its receptor (VDR) plays an important
role in insulin secretion and the insulin sensitivity in the targeted
cells (52).
Some observational studies in Pakistani population showed vitamin D
deficiency in type 2 diabetic subjects (53, 54). A case control study
conducted in a district headquarter hospital Gujranwala, Punjab found
that vitamin D levels were significantly lesser in diabetic patients as
compared with control group but both groups had vitamin D levels less
than 20 ng/mL (55). In another study, vitamin D levels were found
negatively associated with blood glucose levels of type 2 diabetic
patients in Karachi (56). Similarly, another study showed that 62% of
type 2 diabetic patients had elevated levels of HbA1c and poor glycemic
control along with vitamin D deficiency (57). A study was conducted by
our group found that vitamin D levels were negatively correlated with
random blood sugar and HbA1c levels in the diabetic patients. However,
vitamin D levels were not significantly different between good and poor
glycemic control subjects (58).
Elevated levels of HbA1c represent poor glycemic control and it is a
common modality in type 2 diabetic patients (59). A study showed
positive association of vitamin D deficiency with poor glycemic control
in Pakistani population (60).
A randomized clinical trial was conducted to evaluate the effects of
vitamin D administration to improve glycemic control in type 2 diabetic
patients at a tertiary care hospital in Lahore, Punjab (61). Patients
were divided in to two groups. One group was administered only Metformin
500 mg after dinner while, second group was administered 200,000 IU of
vitamin D along with 500 mg Metformin after dinner for six months of
period. The result showed improvement in vitamin D levels in the group
administered with vitamin D and metformin, but HbA1c levels were not
found significantly different after six months between two groups.
Vitamin D deficiency has also been studied with the relevance of
dyslipidemia in type 2 diabetic patients (62). A study conducted to
evaluate the role of statin use with vitamin D levels showed no
significant association with dyslipidemia. But a significant negative
association was found between total cholesterol and vitamin D levels
suggesting an important impact of vitamin D levels with
hypercholesterolemia in the type 2 diabetic patients (63).
Microvascular complications in diabetes such as retinopathy, neuropathy
and nephropathy have been associated with vitamin D deficiency in world
populations (64). The results of meta-analysis revealed that vitamin D
deficiency is associated with the onset of diabetes neuropathy in
Caucasians and Asian populations (65). Microvascular complications are
prevalent in Pakistani population and Vitamin D deficiency was found to
be associated with diabetic retinopathy in type 2 diabetic patients of
Peshawar, KPK (66).