Diminished bioavailability of nitric oxide (NO), the gaseous signaling molecule involved in the regulation of numerous vital biological functions, contributes to the development and progression of multiple age- and lifestyle-related diseases. While l-arginine is the precursor for the synthesis of NO by endothelial-nitric oxide synthase (eNOS), oral l-arginine supplementation is largely ineffective at increasing NO synthesis and/or bioavailability for a variety of reasons. l-citrulline, found in high concentrations in watermelon, is a neutral alpha-amino acid formed by enzymes in the mitochondria that also serves as a substrate for recycling l-arginine. Unlike l-arginine, l-citrulline is not quantitatively extracted from the gastrointestinal tract (i.e., enterocytes) or liver and its supplementation is therefore more effective at increasing l-arginine levels and NO synthesis. Supplementation with l-citrulline has shown promise as a blood pressure lowering intervention (both resting and stress-induced) in adults with pre-/hypertension, with pre-clinical (animal) evidence for atherogenic-endothelial protection. Preliminary evidence is also available for l-citrulline-induced benefits to muscle and metabolic health (via vascular and non-vascular pathways) in susceptible/older populations. In this review, we examine the impact of supplementing this important urea cycle intermediate on cardiovascular and metabolic health outcomes and identify future directions for investigating its therapeutic impact on cardiometabolic health. View Full-Text
L-瓜氨酸：一种中性的、非必需的α-氨基酸，是肝脏和肾脏中尿素循环的重要组成部分。一种非蛋白质氨基酸，L-瓜氨酸在食物中很少见，但在西瓜中含量很高。每千克西瓜中的L-瓜氨酸浓度是1.6~3.5克。所以，L-瓜氨酸的最低有效剂量（3克/天），每天需要消耗约1-1.5千克量西瓜，。已证明皮功能障碍起源于L-精氨酸- NO代谢缺乏，并且考虑到L-精氨酸补充对NO代谢相对无效，研发人员已开始研究L-瓜氨酸的潜在治疗益处即：营养保健品级L-瓜氨酸西瓜补充剂，水、提取物等对血管、代谢生理，及心脏代谢健康的潜在益处！
