VDR and diabetic kidney disease: It has been shown in Table 2 that the risk for DN conferred by VDR gene polymorphisms did not show significant difference in the overall 7 studies (all P values >0.05) (Figs. 2, 3, 4 and 5).In the stratified analysis, there was a relationship between TT genotype and DN risk in Asians in only two studies of 488 patients(TT vs Tt + tt: OR =2.21, 95% CI: 1.05–4.67, p = 0.04), however, p value equals to 0.04 seems not enough to support relationship between genetic variant and diabetic nephropathy.