Development Of Diabetic Nephropathy And Relations To Dietary Protein Intake And Uric Acid Metabolism

ObjectiveTo investigate characteristics of dietary protein intake and uric acid metabolismin type2diabetic patients. Possible effects of protein intake on uric acid metabolismand renal function are also cross-sectionally evaluated.MethodsEighty-four patients with type2diabetes (T2DM) were divided into3groupsaccording to their24h amounts of urinary albumin excretion:37with normalalbuminuria（Normo-MA）,26with microalbuminuria（Micro-MA） and21withmacroalbuminuria（Macro-MA）. General clinical data including age, blood pressureand body mass index (BMI) were recorded. All patients stored their24-hour urine fortesting urinary microalbumin (UMA)、urinary urea nitrogen (UUN)、urinary urinecreatinine (UCrea) and urinary uric acid (UUA). Serum uric acid (SUA), serumcreatinine (Crea), blood urea nitrogen (BUN), xanthine oxidase (XOD) and otherbiochemical indices were detected in fasting blood samples. According to the aboveparameters, clearance rate of creatinine (Ccr), excretion rate of UA(Eua), clearancerate of uric acid (Cua), the amend of uric acid clearance rate (ACua) and dietaryprotein intake (DPI) were calculated. Possible effects of protein intake on uric acidmetabolism and renal function were then cross-sectionally evaluated.Results1. Data comparisons between different UMA groupsDPI (0.94±0.22vs.1.04±0.28vs.0.88±0.23g/kg/d) and Cua (6.02±2.52vs.7.48±6.27vs.4.58±2.50ml/min) were both in high level but comparable between Normo-MA, Micro-MA and Macro-MA group (P>0.05). SUA of the Macro-MApatients was the highest among three groups (303.9±99.4vs.364.8±139.8vs.384.4±119.2μmol/L from Normo-MA to Macro-MA group respectively, P=0.038).ACua of Macro-MA group (13.1±6.3%) and the Micro-MA group （13.4±8.5%）were compared but both higher than Normo-MA group (9.5±3.5%, P=0.047and P=0.03respectively).2. Correlations between ln_UMA and other indicatorsUMA was natural-logarithmatically converted to ln-UMA for its normaldistribution. The ln_UMA increased along with the increasing of concentrations ofSUA(r=0.226, P=0.039)、 ACua (r=0.278, P=0.010), and age (r=0.334, P=0.002). A stepwise multiple linear regression in which lnUMA serving as thedependent variable showed that Age, ACua and SUA were all independent risk factorsfor diabetic nephropathy.3. Correlations between DPI and indicators related to uric acid metabolismAlong with the increasing of DPI，UUA、Cua and EUA increased remarkably (r=0.596，0.405and0.724respectively, all p=0.000). DPI showed no significantrelations with XO activity (r=-0.200，P=0.068) and so as to SUA (r=-0.018,P=0.101).4. Correlations between DPI and indicators related to renal functionAlong with the increasing of DPI, Ccr, UUN and UCcrea increased significantly(r=0.584、r=0.858and0.517respectively, all P=0.000), while Crea showed adownward trend (r=-0.262, P=0.016), BUN and UMA had no significant correlationwith DPI (r=-0.151, P=0.170and r=-0.045, P=0.683).Conclusions1. DPI of T2DM patients in our study is significantly high.2. Increased uric acid synthesis and hyperuricemia may be independent factors fordeterioration of diabetic nephropathy.3. Increased DPI stimulates in vivo uric acid synthesis and aggravates glomerularhyperfiltration and renal nitrogen excretion in T2DM patients.