Association between Post-Transplant Vitamin D, Metabolic Syndrome, and Post-Transplant Diabetes Mellitus

Key Points Metabolic syndrome components after kidney transplant are associated with a higher likelihood of post-transplant diabetes. This predictive association persists independently of other prediabetes markers, including fasting sugar and hemoglobin A1c. Higher vitamin D-25 levels blunt this association; in patients with high metabolic syndrome burden, vitamin D supplementation may be warranted. Background Associations between 25-hydroxyvitamin D (25(OH)D) deficiency and diabetes have been observed in the general population, but are less delineated in kidney transplant recipients (KTRs), especially in the context of highly prevalent metabolic syndrome (MetS) features in KTRs. We hypothesized that vitamin D deficiency may present greater risk in KTRs with greater burden of MetS features. Methods We retrospectively evaluated 1792 KTRs with no treated diabetes at transplant between 1998 and 2018. Vitamin D was measured at ≥3 months post-transplant. MetS features were defined by the National Cholesterol Education Program, Adult Treatment Panel III (NCEP-ATP-III) criteria. The primary outcome was treated post-transplant diabetes mellitus (PTDM) incidence. Results In 1792 nondiabetic KTRs followed for 10,956 patient-years, 237 patients developed PTDM. For KTRs meeting NCEP-ATP-III criteria with fourth-quartile 25(OH)D, there were 1.5 new diagnoses per 100 patient-years versus 4.2 events per 100 patient-years in KTRs with first-quartile 25(OH)D ( P < 0.001). In multivariate survival regression, vitamin D was, accounting for individual NCEP-ATP-III criteria, associated with PTDM (hazard ratio, 0.93 per 10 nmol/ml 25(OH)D, P = 0.007) independently of fasting blood sugar and hemoglobin A1c. In marginal effects analysis, MetS effect on PTDM increased as serum 25(OH)D levels decreased. Conclusions Our study suggests that decreased 25(OH)D is associated with increased PTDM, and this marginal effect worsens as KTRs have an increased burden of MetS.