Longitudinal changes in vitamin D concentrations and the association with type 2 diabetes mellitus: the Tromsø Study

Dose-Response Relationship Between Serum 25(OH)D and the Risk of Abnormal Glycemic Status in Chinese Older Adults

BACKGROUND/OBJECTIVES

The relationship between serum 25-hydroxyvitaminD (25(OH)D) concentration and the risk of abnormal glycemic status remains contradictory. Whether sufficient 25(OH)D plays a role in reducing the risk of diabetes and prediabetes is debatable. Its dose-response relationship and the optimal 25(OH)D threshold are not clear. This study investigated the relationship between serum 25(OH)D and the risk of abnormal glycemic status to explore the optimal cut-off value.

METHODS

This study included 5856 Chinese older adults aged 60 years and above from the China Adult Chronic Disease and Nutrition Survey (CACDNS 2015-2017). Serum 25(OH)D concentration was measured via an enzyme-linked immuosorbent assay. Abnormal glycemic status in the present study includes diabetes and prediabetes. Statistical methods such as a locally weighted regression and smoothing scatterplot (LOESS), restricted cubic spline regression (RCS) and binary and trend logistic regression were used to explore the dose-response relationship and the optimal 25(OH)D threshold.

RESULTS

The concentration of 25(OH)D was nonlinearly related to the levels of FPG and HbA1C in the LOESS curves. The nonlinear relation between 25(OH)D and the risk of diabetes and prediabetes was illustrated in the RCS curves and the optimal 25(OH)D threshold beneficial for diabetes was preliminarily explored to be 29.06 ng/mL, but no threshold for prediabetes was found. The dose-response results showed that for each 1 ng/mL increase in 25(OH)D, the risk of the fasting glucose type of diabetes reduced by 2.1%, the risk of the abnormal HbA1C type of diabetes reduced by 2.2% and the risk of the mixed type of diabetes reduced by 1.7%, whereas a dose-response relationship was not found for prediabetes.

CONCLUSIONS

Higher serum 25(OH)D concentrations in Chinese older adults were associated with a reduced risk of glycemic abnormalities. The optimal 25(OH)D cut-off value was sufficiently beneficial if the diseased diabetes risk was 29.06 ng/mL, but no threshold was found for prediabetes.

Longitudinal assessment of classic and 11-oxygenated androgen concentrations and their association with type 2 diabetes mellitus development: the Tromsø study

AIM

We aimed to investigate changes in pre-diagnostic concentrations of classic and 11-oxygenated androgens in type 2 diabetes (T2DM) cases and healthy controls, associations between androgen concentrations and T2DM, and the potential for androgens to improve the prediction of T2DM when considered in combination with established risk factors.

METHODS

Androgen concentrations were analysed in serum samples from 116 T2DM cases and 138 controls at 3, pre-diagnostic time-points: 1986/87 (T1), 1994/95 (T2), and 2001 (T3). Generalised estimating equations were used to longitudinally examine androgen concentrations, and logistic regression models were used to estimate the odds ratios (OR) of T2DM at each time-point. Logistic regression models were also used to calculate area under the receiver operating characteristics curve (AROC) from models including established risk factors alone (ERF model) and established risk factors plus each androgen, respectively, which were compared to identify improvements in predictive ability.

RESULTS

For women, no significant associations were observed between any of the investigated androgens and T2DM after adjusting for confounders. For men, after adjusting for confounders, concentrations of all investigated 11-oxygenated androgens were higher in cases than controls at one or several time-points. We observed associations between T2DM and concentrations of 11-ketoandrostenedione (OR: 1.59) and 11-ketotestosterone (OR: 1.62) at T1; and 11-hydroxyandrostenedione (OR: 2.00), 11-hydroxytestosterone (OR: 1.76), 11-ketoandrostenedione (OR: 1.84), 11-ketotestosterone (OR: 1.78) and testosterone (OR: 0.45) at T3 in men. The addition of these androgens (including 11-hydroxytestosterone at T2) to the ERF model resulted in an improved ability to predict T2DM in men (AROC: 0.79-0.82). We did not observe significant differences in changes in androgen concentrations over time between cases and controls in either sex.

CONCLUSION

Our results demonstrate that testosterone and 11-oxygenated androgens are associated with T2DM in men before diagnosis and may be potential biomarkers in T2DM risk assessment.