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Plasma 25-hydroxyvitamin D is related to protein signaling involved in glucose homeostasis in a tissue-specific manner

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posted on 2016-10-01, 00:00 authored by Lewan ParkerLewan Parker, I Levinger, A Mousa, Kirsten HowlettKirsten Howlett, B De Courten
Vitamin D has been suggested to play a role in glucose metabolism. However, previous findings are contradictory and mechanistic pathways remain unclear. We examined the relationship between plasma 25-hydroxyvitamin D (25(OH)D), insulin sensitivity, and insulin signaling in skeletal muscle and adipose tissue. Seventeen healthy adults (Body mass index: 26 ± 4; Age: 30 ± 12 years) underwent a hyperinsulinemic-euglycemic clamp, and resting skeletal muscle and adipose tissue biopsies. In this cohort, the plasma 25(OH)D concentration was not associated with insulin sensitivity (r = 0.19, p = 0.56). However, higher plasma 25(OH)D concentrations correlated with lower phosphorylation of glycogen synthase kinase-3 (GSK-3) αSer21 and βSer9 in skeletal muscle (r = −0.66, p = 0.015 and r = −0.53, p = 0.06, respectively) and higher GSK-3 αSer21 and βSer9 phosphorylation in adipose tissue (r = 0.82, p < 0.01 and r = 0.62, p = 0.042, respectively). Furthermore, higher plasma 25(OH)D concentrations were associated with greater phosphorylation of both protein kinase-B (AktSer473) (r = 0.78, p < 0.001) and insulin receptor substrate-1 (IRS-1Ser312) (r = 0.71, p = 0.01) in adipose tissue. No associations were found between plasma 25(OH)D concentration and IRS-1Tyr612 phosphorylation in skeletal muscle and adipose tissue. The divergent findings between muscle and adipose tissue with regard to the association between 25(OH)D and insulin signaling proteins may suggest a tissue-specific interaction with varying effects on glucose homeostasis. Further research is required to elucidate the physiological relevance of 25(OH)D in each tissue.

History

Journal

Nutrients

Volume

8

Season

Article Number : 631

Article number

ARTN 631

Location

Switzerland

ISSN

2072-6643

eISSN

2072-6643

Language

English

Publication classification

C Journal article, C1 Refereed article in a scholarly journal

Copyright notice

2016, The Authors

Issue

10

Publisher

MDPI