Study On The Association Between Serum 25-hydroxyvitamin D And Type 2 Diabetic Nephropathy

Objectives: To observe the serum level of 25-hydroxyvitamin D in patients with type 2 diabetes and diabetic nephropathy(DN).To evaluate the relationship between serum 25-hydroxyvitamin D and type 2 diabetic nephropathy,and to explore the possible mechanism of vitamin D satats affecting diabetic nephropathy.Methods: 234 patients with type 2 diabetes were enrolled according to the study criteria.According to the presence or absence of diabetic nephropathy,the patients were divided into simple diabetes group(NDN group,n=99)and diabetic nephropathy group(DN group,n=135).Based on the level of urinary albumin excretion rate(UAER),the patients of diabetic nephropathy group were divided into microalbuminuria group(30?UAER <300mg/24 h,n=72)and macroalbuminuria group(UAER?300mg/24 h,n=63).General data such as age,sex,height,weight were collected.Serum 25(OH)D concentration,serum calcium(SCa),low density lipoprotein cholesterol(LDL-C),serum creatinine(SCr),?2-microglobulin(?2MG)and other fasting biochemical indicators were also measured.Calculate the body mass index(BMI)and the homeostasis model of insulin resistance(HOMA-IR)of the patients.24-hour urine samples were collected for urinary albumin quantification.The differences of the clinical data and laboratory parameters among the groups were compared,and the distribution of serum 25(OH)D levels among the groups was observed.When comparing the quantitative data of normal distribution and equal variances,use the t-test or one-way analysis of variance.For quantitative data that didn't meet the above conditions,Mann-Whitney U test was performed.Chi-square test was used to analysis categorical variables.Binary logistic regression analysis was used to evaluate the risk factors associated with diabetic nephropathy.Spearman and Pearson correlation analysis were used to calculate the correlations between 25(OH)D and other indicators such as UAER.Results: 1.The serum 25(OH)D concentration in DN group was significantly lower than that in the NDN group,which were(20.87±5.55)ng/ml and(26.88±5.51)ng/ml,respectively,and the difference was statistically significant(P<0.001).Compared with patients in microalbuminuria group,the serum 25(OH)D concentration in patients with macroalbuminuria was significantly lower,which was(18.86±5.09)ng/ml,and the difference was statistically significant(P<0.001).2.A binary logistic regression analysis of the influencing factors of type 2 diabetic nephropathy revealed that 25(OH)D(OR 0.829,P<0.001),diabetic duration(OR 1.062,P=0.026),smoking history(OR 2.103,P= 0.043),hypertension(OR 2.583,P=0.011),SCr(OR 1.051,P=0.003),and Hb A1c(OR 1.259,P=0.026)entered the final regression model.It was suggested that 25(OH)D,diabetes duration,smoking history,hypertension,SCr,Hb A1 c may be the influencing factors of DN,and 25(OH)D is a protective factor for DN.3.Serum 25(OH)D was negatively correlated with UAER,duration of diabetes,age,systolic blood pressure,TC,LDL-C,SCr,?2MG,and HOMA-IR,and positively correlated with SCa(P<0.05).Conclusions: 1.There is a high prevalence of vitamin D sufficiency and deficiency in patients with type 2 diabetes.Vitamin D reduction is more obvious in patients with diabetic nephropathy,especially those with macroalbuminuria.2.25(OH)D is associated with type 2 diabetic nephropathy and may be a protective factor for it.3.25(OH)D is negatively associated with UAER,which may reflect the severity of diabetic nephropathy.