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Plasma free 25-(OH)D linked to insulin sensitivity
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Insulin sensitivity is more strongly associated with plasma free 25-hydroxyvitamin D than with total 25-hydroxyvitamin D, according to findings published in The Journal of Clinical Endocrinology.
Anthony J. Hanley, PhD, of the department of nutritional sciences at the University of Toronto, and colleagues evaluated data from the IRAS Family Study cohort on 1,189 adults (median age, 39 years; 63% Hispanic; 37% black; 57% women) without diabetes to determine the association between 25-(OH)D and insulin sensitivity and beta-cell function. Median plasma free 25-(OH)D was 2.98 pg/mL for all participants, 3.46 pg/mL for Hispanics and 2.19 pg/mL for blacks (ethnic difference, P < .0001). Median plasma total 25-(OH)D was 13 ng/mL for all participants, 16 ng/mL for Hispanics and 10 ng/mL for blacks (P for ethnic difference < .0001).
There was a correlation between plasma free and total 25-(OH)D in all participants (P < .0001), which remained after adjustment for BMI (P < .0001).
Plasma free and total 25-(OH)D were positively correlated with insulin sensitivity, whereas 25-(OH)D was negatively correlated with indexes of adiposity, waist circumference and subcutaneous adipose tissue. Plasma free 25-(OH)D was negatively correlated with visceral adipose tissue. Plasma free 25-(OH)D was positively correlated with deposition index. Researchers observed a negative correlation between acute insulin response and homeostasis model of assessment for insulin resistance (HOMA-IR) and plasma free and total 25-(OH)D.
“Plasma free 25-(OH)D was significantly associated with insulin sensitivity in the IRAS Family Study cohort,” the researchers wrote. “Both free and total 25-(OH)D were low in African Americans based on direct measurement. While the free form of plasma 25-(OH)D appeared to have a modestly stronger association vs. the total form on plasma 25-(OH)D, additional research is needed to confirm this observation.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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