The Effect of Vitamin D Status Correction on the Human Milieu Intérieur Proteome: A Year-Long Prospective Interventional Study

Low vitamin D status or hypovitaminosis D has been associated with a plethora of adverse extra-skeletal health consequences, including obesity, metabolic syndrome, cardiovascular disease and cancer. However, a causal molecular link at the serological protein level remains to be established. This proof-of-principle study compared the proteomic profiles of age-matched non-diabetic, overweight and obese females (n=22) and males (n=20) that attained a Vitamin D sufficient status after a 12-month intervention compared to those in women (n=17) and men (n=20) that participated in the same intervention but did not achieve vitamin D sufficiency. The intervention protocol was based on the increased consumption of vitamin D-rich foods and sun exposure. Non-targeted, depletion-free quantitative proteomics with bioinformatics in silico interpretations were used to analyze the whole serum specimens. This novel method profiles more than double the number of proteins otherwise captured by other proteomic methods to date. Over 2500 proteins were profiled of which ~14% changed positively or negatively with vitamin D status correction (p<0.05). The change ranged from negative 2.2 to positive 3.6 on a log₂ ratio, included novel and known proteins, and showed marked sexual dimorphism. These data, thus, provide a sexually dimorphic signature of vitamin D repletion. The known proteins identified are involved in the canonical pathways of intermediary metabolism, blood coagulation, tumorigenesis and apoptosis.  These multiple, mildly modulated proteins and their potentially epistatic functions may on the one hand explain the beneficial effects of vitamin D and on the other the elusive and frequently controversial mainstream clinico-pathological indicators. The identified previously unknown proteins could serve as novel vitamin-D status correction molecular signatures and help create testable hypotheses on its potential metabolic, cardioprotective and anti-cancer effects in men and women.