Maintenance of long-term adequate levels of vitamin d lowers HbA1c in African American patients with type 2 diabetes.

OBJECTIVES: We examined the long-term effects of enhanced Vitamin D (VitD) supplementation on parameters of type 2 diabetes mellitus (T2DM): serum hemoglobin A1c, low density lipoprotein, high density lipoprotein, and triglyceride for the purpose of determining beneficial VitD levels in T2DM African Americans (AA). DESIGN AND METHODS: Following inclusion criteria, retrospective charts of patients aged > or = 30 years were reviewed. VitD supplementation was given to patients as part of drug regimen over a three year continuum. Pearson correlations were used to assess the relationship between VitD levels and levels of each parameter. Repeated measure analysis of variance was conducted to identify difference in mean levels of each parameter between years with VitD included as part of therapy. RESULTS: Vitamin D supplementation was inversely associated with HbA1c (r = -.286, P = .031). No correlation was found between levels of VitD and levels of LDL, HDL or TG. Hemoglobin A1c levels were found to be significantly different under VitD treatment between year 1 (mean VitD 24.75 microg/mL, mean HbA1c 9.15%, P = .000) and year 2 (mean VitD 33.84 microg/mL, mean HbA1c 7.91%, P = .000) and between year 1 and year 3 (mean VitD 34.46 microg/mL, mean 7.98% HbA1c P = .000). CONCLUSION: In T2DM AA, significant improvements in HbA1c are obtained with enhanced VitD supplementation as part of drug regimen over time. Our investigation provides the first known evidence of a relationship between enhanced VitD supplementation as part of a pre-existing medical regimen taken over long term and determinants of T2DM in a group of overweight and obese AA with T2DM.

Significance of plasma C-peptide in obese African American adolescents.

BACKGROUND: C-peptide blood levels can indicate whether or not a person is producing insulin and roughly how much. C-peptide is secreted as a byproduct of the biosynthesis of insulin from proinsulin. C-peptide has proposed biological activity and a well-established diagnostic value. The significance of C-peptide concentration in the plasma and urine in the pediatric population needs further delineation. AIM: To determine the significance of plasma C-peptide in obese African American adolescents with mild insulin resistance but no evidence of diabetes. METHODS: This study included 19 African American adolescents with body mass index (BMI) in at least the 85th percentile evaluated with anthropometric measurements, Homeostatic Model Assessment-Insulin Resistance (HOMA-IR) score, and oral glucose tolerance test (OGTT), and 24-hour urine collections. The study also included an age-matched control group of 15 healthy African American adolescent controls and were not subjected for OGTT. The correlation among BMI, fasting plasma C-peptide concentrations, and 24-hour-urine C-peptide concentrations was calculated. T Tests were conducted to compare plasma C-peptide and 24-hour-urine C-peptide concentrations for the test group and controls. RESULTS: Mean HOMA score (3.96 +/- 1.84) signified mild insulin resistance among the adolescent test group. The test subjects exhibited adequate glucose tolerance (glucose range, 89.4-122.5 mg/dL) during the OGTT. A significant positive relationship was observed between BMI and fasting plasma C-peptide concentration in the control group (r = 0.537) but not the test group (r = 0.335). An insignificant positive relationship was exhibited between BMI and 24-hour-urine C-peptide concentration in the test group (r = 0.150) and controls (r = 0.254). CONCLUSIONS: The positive relationship among BMI, plasma C-peptide, and urine C-peptide is worth further evaluation in studies conducting multiple rounds of OGTT with a larger sample of pediatric subjects. The potential diagnostic value of C-peptide may facilitate early detection of insulin resistance in the pediatric population.