Effect of supplementation with vitamin D3 on glucose production pathways in human subjects

Scope: Research reports suggest that vitamin D affects glucose and insulin metabolism; however, the exact mechanisms are unclear. H-2 NMR analysis of monoacetone glucose (MAG) after tracer administration provides a non-invasive method of profiling hepatic glucose metabolism. This study examined the effects of supplementation with vitamin D-3 on contribution of glycogenolysis to glucose production. Methods and results: Tracer administration and biofluid collections were performed with eight healthy females before and following a 4-wk vitamin D-3 administration period. Following an overnight fast subjects ingested deuterated water and acetaminophen. Full void urine samples were collected after 4 h. H-2 NMR spectra of urinary monoacetone glucose were acquired to determine the contribution of glycogenolysis to glucose production. The mean contribution of glycogenolysis to glucose production was 60 +/- 13%. Supplementation with vitamin D-3 had no effect on hepatic glucose production. Regression analysis revealed a significant relationship between carbohydrate intake and the contribution of glycogenolysis (beta = 0.914, p = 0.004). Conclusion: In conclusion, we saw no changes in the percentage contribution of glycogenolysis following supplementation with vitamin D-3. The reproducibility of our results and the non-invasive nature of the method highlight the potential for this method in assessing mechanistic modes of action in future nutritional interventions.