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. Author manuscript; available in PMC: 2015 Mar 1.
Published in final edited form as: Endocrinol Metab Clin North Am. 2013 Dec 12;43(1):205–232. doi: 10.1016/j.ecl.2013.09.010

Figure 2.

Figure 2

Vitamin D and insulin action. In peripheral insulin-target cells, vitamin D may directly enhance insulin sensitivity by stimulating the expression of insulin receptors (INS-R) and/or by activating peroxisome proliferator-activated receptor (PPAR-δ), a transcription factor implicated in the regulation of fatty acid metabolism in skeletal muscle and adipose tissue. The effects of vitamin D may be mediated indirectly via its important and well-recognized role in regulating extracellular calcium (Ca2+), calcium flux through the cell and intracellular calcium (Ca2+)i. Vitamin D may promote beta-cell survival by modulating the generation (through inactivation of nuclear factor-kB [NF-kb]) and effects of cytokines. Vitamin D may also affect insulin resistance indirectly through the renin-angiotensin (AII)-aldosterone system.