Vitamin D in Minorities With Prediabetes

Not Applicable

Completed

Brief Summary: Vitamin D supplementation in minority subjects with both pre-diabetes and low vitamin D levels will delay the development of diabetes.

Detailed Description: Low vitamin D levels 1) are associated with abnormalities in insulin secretion and insulin action, 2) predict the development of diabetes in those without diabetes, and 3) are more common in people with diabetes. Minority populations (African-Americans and Latinos) are more likely to have both low levels of vitamin D and diabetes. This study will identify minority individuals who are at increased risk for diabetes (those with central obesity, family history of diabetes in first degree relatives and either with hypertension or being treated for hypertension), and determine if they have both pre-diabetes, ie, impaired fasting glucose and/or impaired glucose tolerance, and low levels of vitamin D. Those that have both will be randomized to either high doses of vitamin D or placebo and insulin secretion and action as well as changes in the oral glucose tolerance test (reversion to normal, maintenance of pre-diabetes or development of diabetes) will be monitored at 3 month intervals for one year. This study will test the hypothesis that the increased amount of diabetes in minority populations may be due in part to low levels of vitamin D and whether supplementing this vitamin may delay the development of diabetes.

Recruitment & Eligibility

Inclusion Criteria

Age greater than 40.
Impaired fasting glucose (FPG level greater than 100 and less than 126 mg/dl); and/or
Impaired glucose tolerance (2-h plasma glucose concentration after 75 gram glucose load greater than 140 and less than 200 mg/dl)
Serum 25-OHD less than 30 ng/ml
Able and willing to provide informed consent

Exclusion Criteria

FPG greater than 126 mg/dl or 2-hour-OGTT plasma glucose greater than 200 mg/dl
Major psychiatric disorder on medication (excluding successfully treated depression)
Diagnosed diabetes mellitus
HIV/AIDS
Major hematological, hepatic (AST/ALT levels greater than or equal to 2 times normal) or renal eGFR less than 60 ml/min) disorder
History of carcinoma, except skin basal cell or squamous cell skin carcinomas
Heart failure, unstable angina or history of a myocardial infarction
Alcohol or substance abuse
Current treatment with glucocorticoids
Current treatment with diabetes medications, including metformin
Cushing's syndrome
Primary hyperparathyroidism
Nephrolithiasis
Pregnancy or breast-feeding
Regular visits to a tanning salon (unlikely in this minority population)

Arm && Interventions

Group	Intervention	Description
Placebo	placebo	Subjects with low vitamin D levels and pre-diabetes
vitamin D	vitamin D	Subjects with low vitamin D levels and pre-diabetes

Primary Outcome Measures

Name	Time	Method
Percent of Subjects Who Develop Diabetes	one year	Diabetes defined by a FPG\>=126 mg/dl or a 2-hr glucose concentration on an OGTT of \>=200 mg/dl

Secondary Outcome Measures

Name	Time	Method
Disposition Index	Baseline, 3, 6, 9, 12 months	Measure of insulin secretion multiplied by measure of insulin sensitivity,both derived from oral glucose tolerance test; higher values are better