Winter to summer change in vitamin D status reduces systemic inflammation and bioenergetic activity of human peripheral blood mononuclear cells

Abstract

Background: Vitamin D status [25(OH)D] has recently been reported to be associated with altered cellular bioenergetic profiles of peripheral blood mononuclear cells (PBMCs). No study has tracked the seasonal variation of 25(OH)D and its putative influence on whole body energy metabolism, cellular bioenergetic profiles, inflammatory markers and clinical chemistry. Material and methods: Whole body energy metabolism and substrate utilisation were measured by indirect calorimetry. PBMCs obtained from the same subjects were isolated from whole blood, counted and freshly seeded. Bioenergetic analysis (mitochondrial stress test and glycolysis stress test) was performed using the Seahorse XFe96 flux analyser. 25(OH)D was assessed using the Architect immunoassay method. Results: 25(OH)D increased by a median (IQR) of 14.40 (20.13) nmol/L (p75 nmol/L. The absolute change in 25(OH)D was not associated with altered bioenergetics. Conclusion: Seasonal improvements in 25(OH)D was associated with reduced systemic inflammation, PBMC bioenergetic profiles and whole body energy metabolism. These observational changes in PBMC bioenergetics were most pronounced in those who had insufficient 25(OH)D in winter. The data warrants confirmation through cause and effect study designs. Keywords: Peripheral blood mononuclear cells, Bioenergetics, Vitamin D, Season, Inflammation, Insulin sensitivity