Exploration of vitamin D hydroxy metabolites C3 epimers in patients with cardiovascular disease: an observational study.

Roughly 90% of the Polish population experiences vitamin D deficiency. The 3-epi-25(OH)D2 and 3-epi-25(OH)D3 are stereoisomers of 25(OH)D2 and 25(OH)D3, and they can inadvertently be included in measurements of 25(OH)D levels, potentially leading to its overestimating. We aimed to measure 25(OH)D2 and 25(OH)D3, their epimers 3-epi-25(OH)D2 and 3-epi-25(OH)D3, and biologically active 1,25(OH)2D3 in patients with cardiovascular disease and healthy volunteers. We enrolled 27 adult patients with cardiovascular disease (64 ± 15 years) and 35 healthy volunteers (36.37 ± 12.29 years). We used a validated ultra-performance liquid chromatography-mass spectrometry/mass spectrometry (UPLC-MS/MS) method to measure 25(OH)D2/3 concentrations and their epimers. Plasma concentrations of 1α,25(OH)2D3 were determined by sensitive and quantitative enzyme immunoassay following intra- and inter-day validation. Vitamin D insufficiency was observed in approximately 52% of the patients and 37% of healthy volunteers. Comparable levels of 25(OH)D3 and 25(OH)D2 were seen in both groups. The observed levels of the epimeric form 3-epi-25(OH)D3 appeared approximately 1.7 times higher in healthy volunteers, accounting for 9% misclassified according to vitamin D status. Also, patients had lower concentrations of 1,25(OH)2D3, and their 3-epi-25(OH)D2 levels were below the detection limit (2 ng/mL). In all studied subjects, 25(OH)D3 was negatively correlated with % 3-epi-25(OH)D3 (R=-0.758; P<0.001), and 3-epi-25(OH)D2 was negatively correlated with % 3-epi-25(OH)D2 (R = -0.842; P = 0.002). While the mechanism of how vitamin D epimeric forms influence diseases remains unclear, we recommend maintaining 25(OH)D3 levels above 20 ng/mL.