C3-epi-25(OH)D3 percentage, not level, may be a potential biomarker to reflect its pathological increase in multiple diseases: a cross-sectional case-control study

Abstract

National surveys in developed countries have examined the presence of C3-epimer of 25-hydroxyvitamin D3 [C3-epi-25(OH)D3]. However, controversy remains regarding its association with disease occurrence due to its high correlation with 25-hydroxyvitamin D3 [25(OH)D3]. This study aims to investigate whether %C3-epi-25(OH)D3 can serve as an indicator for this relationship with various diseases. A total of 3086 healthy participants and 4120 patients were included in this study. We investigated the association between C3-epi-25(OH)D3 and %C3-epi-25(OH)D3 levels with gender, age, and season; compared the performance of C3-epi-25(OH)D3 and %C3-epi-25(OH)D3 across different disease conditions; and explored the correlation between %C3-epi-25(OH)D3 and various diseases. Results indicated that C3-epi-25(OH)D3 varied significantly by gender, age, and season (z/χ2 = 3.765, 10.163, and 150.975, all P < 0.01), while only season for %C3-epi-25(OH)D3 (χ2 = 233.098, P < 0.001). In contrast to the significant decrease in C3-epi-25(OH)D3, %C3-epi-25(OH)D3 showed a significant increase in 8 out of 11 disease categories (z = 3.464 ~ 11.543, all Padj < 0.05). Similar opposite changes were also observed in most of the investigated 32 specific diseases. Moreover, an elevation in %C3-epi-25(OH)D3 was found to be significantly associated with 29 specific diseases both in univariate analysis (OR = 1.16 ~ 2.10, all P < 0.05) and after adjusting for gender, age, and season (OR = 1.15 ~ 1.50, all P < 0.05). However, after further adjustment for 25(OH)D3 levels, the association remained significant only for 15 specific diseases (OR = 1.11 ~ 1.50, all P < 0.05). Seasonal stratification analysis further supports the consistent association of %C3-epi-25(OH)D3 with disease across all or nearly all four seasons. In conclusion, %C3-epi-25(OH)D3 may better reflect the production of C3-epi-25(OH)D3 in disease conditions, thereby offering a more applicable approach to investigate its association with diseases. However, the interpretation of this relationship may be confounded by 25(OH)D3 as a potential covariate.

Figure 1

The gender, age, and season differences in C3-epi-25(OH)D3 level and percentage. Note: The Box height represents a median, and the top and bottom lines of I shape represent the 95%CI of the median. By the Mann–Whitney U test for two gender groups and the Kruskal–Wallis for multiple age and seasonal groups test, our results showed that C3-epi-25(OH)D3 had significant differences in gender, age, and season. But %C3-epi-25(OH)D3 had only seasonal differences.

Figure 2

Seasonally stratified verification of %C3-epi-25(OH)D3 differences in gender and age. Note: The Box height represents a median, and the top and bottom lines of I shape represent the 95%CI of the median. By the Mann–Whitney U test for two gender groups and the Kruskal–Wallis test for multiple age groups, our results showed that %C3-epi-25(OH)D3 had no differences in gender and age during the other seasons except for in summer.

Figure 3

The Box plot of C3-epi-25(OH)D3 level and percentage in various diseases. Note: The Box height represents a median, and the top and bottom lines of I shape represent the 95%CI of the median. The Kruskal–Wallis test and Post-Hoc multiple comparisons was used for multiple groups comparison and pairwise comparison, respectively. In most diseases, the overall level of C3-epi-25(OH)D3 levels exhibited a decreasing trend, possibly due to its highly-tracking to 25(OH)D3 levels. However, %C3-epi-25(OH)D3 showed an increasing trend, suggesting that it may accurately reflect the pathological increase in C3-epi-25(OH)D3 generation.