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iDEA: DREXEL LIBRARIES E-REPOSITORY AND ARCHIVES

iDEA: DREXEL LIBRARIES E-REPOSITORY AND ARCHIVES

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Association Between Serum 25-Hydroxyvitamin D Concentration And Type 2 Diabetes Mellitus

Details
Title
Association Between Serum 25-Hydroxyvitamin D Concentration And Type 2 Diabetes Mellitus: Interaction By Race/Ethnicity And Mediation By Inflammation
Author(s)
Kabadi, Shaum Mohan
Advisor(s)
Liu, Longjian
Keywords
Public Health
Date
201206
Publisher
Drexel University
Thesis
Ph.D., Epidemiology -- Drexel University, 2012
Abstract
Diabetes mellitus affects 25.6 million adults and is the seventh leading cause of death in the United States. Recent evidence indicates that vitamin D may alter glucose metabolism, which suggests it may play a role in reducing risk of prediabetes and type 2 diabetes. Although observational studies support pancreatic β-cell dysfunction and insulin resistance as pathways by which vitamin D influences glucose homeostasis, a mechanism involving systemic inflammation remains obscure. We hypothesized that vitamin D was associated with inflammation, prediabetes, and type 2 diabetes. In the present investigation, we analyzed data from the National Health and Nutrition Examination Survey (NHANES) conducted from 2001-2006 among adults over 20 years of age. We evaluated the association between 25-hydroxyvitamin D [25(OH)D], a serum biomarker of vitamin D status, and prediabetes or type 2 diabetes. In addition, we assessed the association by subgroups of gender and race/ethnicity and evaluated interaction using joint effects. We determined the association between 25(OH)D and three biomarkers of inflammation, including C-reactive protein (CRP), and further assessed mediation by CRP on the association between 25(OH)D and hemoglobin A1c [HbA1c], a biomarker of glucose homeostasis. Using piecewise regression, it was determined that 25(OH)D was inversely associated with CRP when 25(OH)D < 20 ng/mL, but directly associated when 25(OH)D ≥ 20 ng/mL. There was significant interaction by age, gender, race/ethnicity, and abdominal obesity. Furthermore, 25(OH)D was not associated with fibrinogen but inversely associated with homocysteine. Results from path analysis indicate that CRP mediated 14.9% of the association between 25(OH)D and HbA1c in males. We determined that 25(OH)D sufficiency was associated with type 2 diabetes. However, the association was not significant in non-Hispanic Blacks which suggests that 25(OH)D sufficiency as defined by the Institute of Medicine may be inadequate for this subgroup. Our finding that vitamin D may prevent diabetes is consistent with prospective studies which supports a temporal association. Although these findings need to be confirmed in prospective studies and intervention trials, our results may be of large public health value in controlling the current unfavorable diabetes epidemic.
URI
http://hdl.handle.net/1860/idea:6727
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