Vitamin D Deficiency in Metabolic Syndrome Patients

Dr. Maria Aziz. Vitamin D has an essential role in calcium metabolism and bone health. Vitamin D3 or cholecalciferol is synthesized from 7-dehydrocholesterol or provitamin D3, by sunlight ultraviolet radiation to the skin. 7dehydrocholesterol is subsequently hydroxylated in the liver and then in the kidney to produce 1,25-(OH)2D3, the active metabolite that binds to specific receptors (VDR) in target tissues, mainly bone and intestine. Other tissues, such as the immune and cardiovascular system, have also VDR. Vitamin D deficiency can induce rickets in children and osteomalacia and osteoporosis in adults. A possible inverse association between vitamin D levels and the prevalence of metabolic syndrome has been proposed. Vitamin D deficiency increases the risk of type 1 diabetes, insulin resistance, and hypertension, key components of this syndrome.This clinical research study focuses on correlation between Vitamin D and Metabolic syndrome.


Introduction:-
The prevalence of common obesity has become a public health concern in many countries as phenomenological approaches to the understanding of pathogenesis have failed to achieve any long term effect on prevention or treatment.
There is evidence for a central control mechanism which maintains body-weight to a set-point by the regulation of energy intake and energy expenditure through homeostatic pathways. It is suggested that common obesity occurs when the set-point is raised and that accumulation of fat mass functions to increase body size. Larger body size confers a survival advantage in the cold ambient temperatures and food scarcity of the winter climate by reducing surface area to volume ratio and by providing an energy store in the form of fat mass. In addition, it is suggested that the phenotypic metabolic and physiological changes observed as the metabolic syndrome, including hypertension and insulin resistance, could result from a winter metabolism which increases thermogenic capacity. Common obesity and the metabolic syndrome may therefore result from an anomalous adaptive winter response.
The stimulus for the winter response is proposed to be a fall in vitamin D. the synthesis of Vitamin D is dependent upon the absorption of radiation in the ultraviolet-B range of sunlight. At ground level at midlatitudes, UV-B radiation falls in the autumn and becomes negligible in winter. Vitamin D in the form of is the stimulus for the winter consists of an accumulation of fat mass (obesity) and the induction of a winter metabolism (the metabolic syndrome). Vitamin D deficiency can account for the secular trends in the prevalence of obesity and for individual differences in its onset and severity. It may be possible to reverse the increasing prevalence of obesity by improving vitamin D status.
In accord with this hypothesis, many studies have been done across the globe, most of which have found a negative correlation between vitamin D level and BMI. These studies were done in populations belonging to a particular region. In this context there is scarcity of data on Indian population and no such Indian study could be traced.

Controls
Mean serum 25 OH vit D level in cases (21.34 ng/ml) was less than those in controls (26.94 ng/ml). The significance of difference between both means was calculated using students unpaired "t" test. "t" value was 2.02 which was significant at 5% level but was not significant at 1% level (0.05>p<0.01).

Discussion:-
For the last two to three decadesvitamin D deficiency has been associated with obesity and metabolic syndrome. Many studies have been done to establish association between vitamin D levels and occurrence of obesity/metabolic syndrome. According to a publication 22 years back [168] . Body weight increases with higher latitude with lower altitude ad in winter. Different explanations exist for all three associations but vitamin D provides a parsimonious explanation as vitamin D decreases with higher latitude, lower altitude and with winter. In a south Carolina study [169] all obese subjects had vitamin D levels (<2.2 ng/ml) lower than non obese subjects (>8ng/ml). These two studies suggested a inverse relation between vitamin D level and obesity but no causal relationship was explained and no insight into the pathogenesis was made. However, these landmark publications set the stage for further studies to establish this apparent relationship between vitamin D level and obesity.
In present study patients of metabolic syndrome had lower serum 25 OH vitamin D levels than healthy controls the difference was statistically significant at 5% level 44% of patients of metabolic syndrome were vitamin D deficient as compared t 24% of healthy controls. These results were similar to previous studies of Reis et al [79] , Lu et al [80] & Kim et al [81] .  [94] &Lagunova et al [95] .
Serum 25 OH vitamin D had inverse correlation with waist circumference. The correlation coefficient was -0.54 and the association was statistically significant at 1% level. This correlates well with the study done by Elizondo et al [96].
Serum 25 OH vitamin D had inverse correlation with FBS, mean B.P. and serum triglyceride level & a direct correlation with HDL cholesterol. The pearsons correlation coefficient was -0.3854, -0.3838, -0.3824 & 0.2266 respectively. The association of FBS, mean B.P. and serum triglyceride level with serum 25 OH vitamin D level was significant at 1% level which correlates well with the studies of kamycheva et al [94] &Lagunova et al [95] . The correlation between HDL cholesterol & serum 25 OH vitamin D level could not reach statistical significance which contrasts with the study of kamycheva et al [94] &Lagunova et al [95] , the reason for this contrast could be s small study group of present study (which results in a lower "t" value for a particular correlation coefficient). If prospective studies reveals that vitamin D deficiency is causally related to obesity and metabolic syndrome, then it might be possible to reduce the prevalence of obesity and metabolic syndrome globally by vitamin D supplementation.