1. A significant proportion of diabetic patients develop diabetic nephropathy which can eventually progress to end-stage renal disease despite established conventional therapy for glycemic control, blood pressure control, and the use of inhibitors of the renin-angiotension- aldosterone system. Residual proteinuria is associated with progression of kidney disease, indicating the need for additional treatment. Vitamin D therapies have been used for over 50 years in chronic kidney disease (CKD) patients for treatment of renal osteodystrophy. The prevalence of low vitamin D levels is increasing globally. Epidemiological studies have shown that low vitamin D level are common in patients with albuminuria. There is emerging evidence indicating that vitamin D may have antiproteinuric and renoprotective effects in patients with CKD. Previous studies have shown that the selective vitamin D receptor activator, paricalcitol, and large dose of cholecalciferol effectively reduced proteinuria in patients with type 2 DM. Long-term study of the use of regular doses of oral supplementation of vitamin D and the effect on albuminuria and kidney function has never been studied. INTRODUCTION Baseline1 yearP value 25(OH)Vitamin D level20.78SD 7.3533.11SD 10.910.0001 Creatinine0.91SD 0.300.88SD 0.260.0006 eGFR78.91SD 23.8681.32SD 23.100.02 Urine microalbumin23.83SD 38.3135.43SD 165.030.34 Hb A1C7.302SD 1.407.374SD 1.300.24 LDL88.82SD 27.0681.88SD 26.160.002 HDL43.84SD 10.6644.54SD 11.440.23 Triglyceride122.61SD 61.69126.89SD 68.090.37 Vit D at baseline Low < 30 n = 147 Normal >30 n = 13 Vit D at 1 yr Low < 30 n = 58 Normal > 30 n = 89 Low < 30 n = 4 Normal > 30 n = 9 Group1234P value Mean ∆Vit D 4.328SD 7.9619.112SD 11.01-11.5SD 5.747.444SD 5.620.0001 Mean ∆Cr -0.010SD 0.097-0.045SD 0.130SD 0.08-0.067SD 0.120.25 Mean ∆eGFR 0.32SD 10.443.84SD 13.81-7.528SD 21.196.226SD 15.90.13 Mean ∆U Microalb 16.61 SD 116.78-0.646SD 32.34-13.188SD 21.087.028SD 28.430.56 RESULTS This study aims to evaluate the effect of vitamin D on kidney function (GFR) and urine microalbumin in type 2 diabetic population. OBJECTIVE Over 2,000 type 2 diabetic patients seen in the clinic from January 2009 to December 2013 were screened. Total of 160 patients aged between 40 to 65 years old who meet inclusion criteria were included in the study. Vitamin D level, urine microalbumin, Hb A1C, LDL, HDL, and triglyceride were collected at baseline and 1 year after. All patients had been on stable dose of ACEI or ARB before study period and maintained on the same dose during 1 year study period. Data were analyzed for significant changes between baseline and at 1 year follow up. Patients were divided into 4 groups based on vitamin D levels for further analysis. Statistical analyses were performed using JMP software version 10.0. Data are expressed as the mean +/- Standard deviation (SD) or mean +/- inter quartile range for continuous variables and as frequency and percentage for categorical variables. Comparisons between groups were performed using analysis of variance (ANOVA). METHOD There were increases in vitamin D level and eGFR, decreases in creatinine level, and LDL at 1 year follow up with P value < 0.01 (Table1). However, there were no statistical differences for the change in urine microalbumin, Hb A1C, HDL, and triglyceride. It is unclear that the change in LDL is related to vitamin D supplementation or other factors as some of our patients had been on statin therapy with different intensities and had dose adjusted during study period. In subgroup analysis (Table 2 and Figure 1), the decreases in creatinine and urine microalbumin, or the improvement in eGFR were not associated with the improvement in vitamin D level. Non-significant results can be possibly due to a small sample size in each sub-group. The linear regression analysis showed positive correlation between ∆vitamin D and ∆eGFR, and negative correlation between ∆vitamin D and ∆Cr, ∆urine microalbumin. However, these correlations were not statistically significant. (Figure 2) Previous studies demonstrated a potential therapeutic effect of vitamin D in decreasing albuminuria. Our results are not consistent with some previous studies. This inconsistency might be due to different types (active vs nutritional) and doses of vitamin D supplementation as well as duration of supplementation in our subjects. Further randomized controlled trial are needed to establish the correlation and long-term outcome. DISCUSSION Based on our research analysis, low vitamin D levels were common in type 2 diabetic patients, and vitamin D repletion was shown to improve renal function (GFR) without antiproteinuric effect. Vitamin D level should be routinely checked in type 2 diabetic patients as appropriate vitamin D supplementation may help slow the progression of CKD. CONCLUSION 1. de Zeeuw, D., et al., Selective vitamin D receptor activation with paricalcitol for reduction of albuminuria in patients with type 2 diabetes (VITAL study): a randomised controlled trial. Lancet, 2010. 376(9752): p. 1543-51. 2. de Boer, I.H., et al., Serum 25-hydroxyvitamin D and change in estimated glomerular filtration rate. Clin J Am Soc Nephrol, 2011. 6(9): p. 2141-9. 3. Huang, Y., et al., Oral supplementation with cholecalciferol 800 IU ameliorates albuminuria in Chinese type 2 diabetic patients with nephropathy. PLoS One, 2012. 7(11): p. e50510. 4. Kim, M.J., et al., Oral cholecalciferol decreases albuminuria and urinary TGF-beta1 in patients with type 2 diabetic nephropathy on established renin-angiotensin-aldosterone system inhibition. Kidney Int, 2011. 80(8): p. 851-60. REFERENCES Table 1 Summary of follow-up resultsTable 2 Subgroup analysis Figure 1 Subgroup analysis Microalbuminuria year1-year0 Creatinine year1-year0 GFR year1-year0 Vitamin D year1-year0 1 2 3 4 Figure 2 Correlation analysis p = 0.5602p = 0.2484p = 0.1326p < 0.0001 p = 0.7981 p = 0.3227 p = 0.4590