摘要
Available data suggest a possible link between abnormalvitamin D level and abnormal glucose homeostasis,two of the most common chronic medical conditions.Both conditions are associated with inflammation,and the exact mechanism for role of either on the other is not well clear.Literature investigating the link between vitamin D and either pre-diabetic states or diabetes is reviewed.Vitamin D deficiency is detrimental to insulin synthesis and secretion in animal and human studies.In humans,it has been shown by majority of observational studies,that vitamin D is positively correlated with insulin sensitivity and its role is mediated both by direct mechanism through the availability of vitamin D receptors in several tissues and indirectly through the changes in calcium levels.Large number of,but not all,variable samples cross sectional human trials have demonstrated an inverse relation between vitamin D status and impaired glucose tolerance,insulin resistance or diabetes.To compliment this conclusively,evidence from intervention studies is critically warranted before we can frankly state that vitamin D plays a role in diabetes prevention or treatment.Absence of both sizable prospective observational trials utilizing 25(OH)D as the main variable and the non-availability of randomized studies specifically designed to assess the effects of vitamin D on pre-diabetes and diabetes states,are the main obstacles to draw solid and conclusive relationships.
Available data suggest a possible link between abnormal vitamin D level and abnormal glucose homeostasis,two of the most common chronic medical conditions.Both conditions are associated with inflammation, andthe exact mechanism for role of either on the other isnot well clear. Literature investigating the link betweenvitamin D and either pre-diabetic states or diabetes isreviewed. Vitamin D deficiency is detrimental to insulinsynthesis and secretion in animal and human studies. Inhumans, it has been shown by majority of observationalstudies, that vitamin D is positively correlated withinsulin sensitivity and its role is mediated both bydirect mechanism through the availability of vitamin Dreceptors in several tissues and indirectly through thechanges in calcium levels. Large number of, but notall, variable samples cross sectional human trials havedemonstrated an inverse relation between vitamin Dstatus and impaired glucose tolerance, insulin resistanceor diabetes. To compliment this conclusively, evidencefrom intervention studies is critically warranted before wecan frankly state that vitamin D plays a role in diabetesprevention or treatment. Absence of both sizableprospective observational trials utilizing 25（OH）D as themain variable and the non-availability of randomizedstudies specifically designed to assess the effects ofvitamin D on pre-diabetes and diabetes states, are themain obstacles to draw solid and conclusive relationships.
