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Abstract：
Elevated circulating branched-chain amino acids (BCAAs; isoleucine, leucine, and valine) are associated with obesity and type 2 diabetes (T2D). Reducing circulatory BCAAs by dietary restriction was suggested to mitigate these risks in rodent models, but this is a challenging paradigm to deliver in humans. We aimed to design and assess the feasibility of a diet aimed at reducing circulating BCAA concentrations in humans, while maintaining energy balance and overall energy/protein intake. Twelve healthy individuals were assigned to either a 7-day BCAA-restricted diet or a 7-day control diet. Diets were iso-nitrogenous and iso-caloric, with only BCAA levels differing between the two. The BCAA-restricted diet significantly reduced circulating BCAA concentrations by ~50% i.e., baseline 437 ± 60 to 217 ± 40 µmol/L (p < 0.005). Individually, both valine (245 ± 33 to 105 ± 23 µmol/L; p < 0.0001), and leucine (130 ± 20 to 75 ± 13 µmol/L; p < 0.05), decreased significantly in response to the BCAA-restricted diet. The BCAA-restricted diet marginally lowered Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) levels: baseline 1.5 ± 0.2 to 1.0 ± 0.1; (p = 0.096). We successfully lowered circulating BCAAs by 50% while maintaining iso-nitrogenous, iso-caloric dietary intakes, and while meeting the recommended daily allowances (RDA) for protein requirements. The present pilot study represents a novel dietary means by which to reduce BCAA, and as such, provides a blueprint for a potential dietary therapeutic in obesity/diabetes.
摘要：
升高的循环支链氨基酸（BCAAs；异亮氨酸，亮氨酸,和缬氨酸）与肥胖和2型糖尿病（T2D）有关。在啮齿动物模型中，建议通过饮食限制减少循环BCAA来减轻这些风险。但这对人类来说是一个具有挑战性的范例。我们旨在设计和评估旨在降低人体循环BCAA浓度的饮食的可行性，同时保持能量平衡和整体能量/蛋白质摄入量。12名健康个体被分配到7天BCAA限制饮食或7天控制饮食。饮食是等氮和等热量的，两者之间只有BCAA水平不同。BCAA限制饮食显着降低循环BCAA浓度约50％，即基线437±60至217±40µmol/L（p<0.005）。个别地,两种缬氨酸（245±33至105±23µmol/L；p<0.0001），和亮氨酸（130±20至75±13µmol/L；p<0.05），对BCAA限制饮食的反应显着降低。BCAA限制的饮食略微降低了胰岛素抵抗的稳态模型评估（HOMA-IR）水平：基线1.5±0.2至1.0±0.1；（p=0.096）。我们成功地将循环BCAA降低了50%，同时保持了等氮，等热量膳食摄入量，同时满足蛋白质需求的建议每日配额（RDA）。本试点研究代表了一种新的饮食手段，通过它来减少BCAA，因此，为肥胖/糖尿病的潜在饮食治疗提供了蓝图。
