Diabetes Care：低碳水化合物饮食可以保护肾功能

为了探讨各种饮食，特别是低碳水化合物高蛋白饮食，对有或没有2型糖尿病的患者肾功能的长期影响。来自以色列本古里安大学Iris Shai教授及其团队进行了一项研究，该研究发现在有或没有2型糖尿病、基线血清肌酐＜176umol/l的中度肥胖患者中，低碳水化合物饮食与地中海饮食或低脂饮食在保护/改善肾功能方面一样安全。该研究结果在线发表在2013年5月20日的《糖尿病治疗》（Diabetes Care）杂志上。

该研究中，在2年饮食干预随机对照试验（DIRECT）中，318例(年龄：51岁；男性86%；BMI 31kg/m²；平均估算肾小球滤过率[eGFR] 70.5ml/min/1.73m²；平均尿微量白蛋白与肌酐比值12:12)血清肌酐＜176unol/l（eGFR≥30ml/min/1.73m²）的患者被随机分到低脂饮食、地中海饮食、或低碳水化合物饮食中。2年依从性为85%，并且，尽在低碳水化合物饮食组中，蛋白摄入占总能量的比例显著增加，至22%（与低脂饮食和地中海饮食相比，P＜0.05）。检测尿微量白蛋白和eGFR变化，使用肾脏疾病饮食调整和慢性肾脏疾病流行病学协作公式对尿微量白蛋白和eGFR变化进行评估。

该研究结果表明，在低碳水化合物饮食（+5.3%[95%CI 2.1–8.5]）、地中海饮食（+5.2%[2.1–8.5]）、以及低脂饮食（+4.0%[0.9–7.1]）中，eGFR显著改善（组内P＜0.05），在各个饮食组间有相似的变化(P＞0.05)。与eGFR≥60ml/min/1.73m²（+3.7%）的受试者相比，有（+6.7%）或没有（+4.5%）2型糖尿病，以及那些基线肾功能较低、eGFR＜60ml/min/1.73m²（+7.1%）的受试者的eGFR至少显著增加。在校正年龄、性别、饮食组、2型糖尿病、ACE抑制剂使用、2年体重下降、以及蛋白摄入变化（混杂因素和单变量预测因子）的多变量模型中，仅有空腹胰岛素（β=-0.211；P=0.004）和收缩压（β=-0.25；P＜0.001）下降与eGFR的增加独立相关。在各个饮食组之间，尿微量白蛋白与肌酐比值有相似的改善，特别是在基线微量白蛋白性别校正的受试者之间，平均变化为-24.8（P＜0.05）。

该研究发现，在有或没有2型糖尿病、基线血清肌酐＜176umol/l的中度肥胖患者中，低碳水化合物饮食与地中海饮食或低脂饮食在保护/改善肾功能方面一样可靠。潜在的改善有可能是通过体重下降诱导胰岛素敏感性和血压的改善介导。

Renal Function Following Three Distinct Weight Loss Dietary Strategies During 2 Years of Randomized Controlled Trial.
Abstract
OBJECTIVE This study addressed the long-term effect of various diets, particularly low-carbohydrate high-protein, on renal function on participants with or without type 2 diabetes.RESEARCH DESIGN AND METHODS In the 2-year Dietary Intervention Randomized Controlled Trial (DIRECT), 318 participants (age, 51 years; 86% men; BMI, 31 kg/m2; mean estimated glomerular filtration rate [eGFR], 70.5 mL/min/1.73 m2; mean urine microalbumin-to-creatinine ratio, 12:12) with serum creatinine <176 μmol/L (eGFR ≥30 mL/min/1.73 m2) were randomized to low-fat, Mediterranean, or low-carbohydrate diets. The 2-year compliance was 85%, and the proportion of protein intake significantly increased to 22% of energy only in the low-carbohydrate diet (P < 0.05 vs. low-fat and Mediterranean). We examined changes in urinary microalbumin and eGFR, estimated by Modification of Diet in Renal Disease and Chronic Kidney Disease Epidemiology Collaboration formulas.RESULTS Significant (P < 0.05 within groups) improvements in eGFR were achieved in low-carbohydrate (+5.3% [95% CI 2.1-8.5]), Mediterranean (+5.2% [3.0-7.4]), and low-fat diets (+4.0% [0.9-7.1]) with similar magnitude (P > 0.05) across diet groups. The increased eGFR was at least as prominent in participants with (+6.7%) or without (+4.5%) type 2 diabetes or those with lower baseline renal function of eGFR <60 mL/min/1.73 m2 (+7.1%) versus eGFR ≥60 mL/min/1.73 m2 (+3.7%). In a multivariable model adjusted for age, sex, diet-group, type 2 diabetes, use of ACE inhibitors, 2-year weight loss, and change in protein intake (confounders and univariate predictors), only a decrease in fasting insulin (β = -0.211; P = 0.004) and systolic blood pressure (β = -0.25; P < 0.001) were independently associated with increased eGFR. The urine microalbumin-to-creatinine ratio improved similarly across the diets, particularly among participants with baseline sex-adjusted microalbuminuria, with a mean change of -24.8 (P < 0.05).CONCLUSIONS A low-carbohydrate diet is as safe as Mediterranean or low-fat diets in preserving/improving renal function among moderately obese participants with or without type 2 diabetes, with baseline serum creatinine <176 μmol/L. Potential improvement is likely to be mediated by weight loss-induced improvements in insulin sensitivity and blood pressure.