Vitamin D deficiency and metabolic disorders increase albuminuria risk in type 2 diabetes (ACR 0.1-300 mg/g): a...

This study aimed to investigate the synergistic effect of vitamin D deficiency and metabolic disorders on albuminuria in type 2 diabetes mellitus (T2DM) patients with urinary albumin-to-creatinine ratio (ACR) of 0.1~300 mg/g, and to construct a validated risk stratification nomogram for precise clinical assessment.

A cross-sectional study was conducted on 507 T2DM patients, divided into normal albumin (ACR < 30 mg/g, n=349) and albuminuria groups (ACR ≥ 30 mg/g, n=158; further subdivided into micro- and moderate albuminuria subgroups). Serum 25-hydroxyvitamin D (25-OH-VD) was detected, with deficiency defined as < 50 nmol/L. Interaction analysis, univariate Logistic regression, LASSO regression and multivariate Logistic regression were used to screen core factors and identify independent predictors of albuminuria. A nomogram was constructed and validated by concordance index (C-index), calibration curves and decision curve analysis (DCA) in the total population and ACR subgroups.

The prevalence of vitamin D deficiency was 83.0% in all patients, and was significantly higher in the albuminuria group (91.8%) than the normal group (79.1%, P < 0.001), with the highest rate in moderate albuminuria subgroup (96.8%). ACR levels were significantly negatively correlated with 25-OH-VD levels(ρ=-0.326, P < 0.001). Vitamin D deficiency and elevated HbA1c had a significant positive synergistic effect on albuminuria (multivariate OR = 1.392, 95%CI:1.081~1.789, P = 0.010; univariate OR = 1.426, 95%CI:1.103~1.842, P = 0.007). Age, BMI, HbA1c, 25-OH-VD, LDL-C, eGFR, and the vitamin D deficiency × HbA1c interaction term were identified as independent predictors. The constructed nomogram had excellent discriminative ability (C-index: 0.882 in training set, 0.858 in validation set), with C-indices of 0.845 and 0.861 in micro- and moderate albuminuria subgroups, respectively. Calibration curves showed high consistency between predicted and actual probabilities, and DCA confirmed the nomogram had significantly higher clinical net benefit than traditional and single-index models.

Vitamin D deficiency is highly prevalent in T2DM patients with ACR 0.1~300 mg/g and synergizes with elevated HbA1c to drive albuminuria progression. The constructed nomogram integrates key metabolic predictors and the vitamin D-HbA1c interaction term, exhibiting excellent predictive and stratification ability, and may serve as a precise tool for individualized risk assessment and stratified intervention in T2DM patients.