Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, UK and Postgraduate Medical School, University of Surrey, Guildford, UK.
Proc Nutr Soc. 2011 Aug;70(3):342-50. doi: 10.1017/S002966511100084X.
Most postprandial studies have investigated the response of a single meal, yet the ingestion of sequential meals is more typical in a Western society. The aim of this review is to explain how natural and stable isotope tracers of fatty acids have been used to investigate the metabolism of dietary fat after single and multiple meals, with a focus on in vivo measurements of adipose tissue metabolism. When stable isotope tracers are combined with arteriovenous difference measurements, very specific measurements of metabolic flux across tissues can be made. We have found that adipose tissue is a net importer of dietary fat for 5 h following a single test meal and for most of the day during a typical three-meal eating pattern. When dietary fat is cleared from plasma, some fatty acids 'spillover' into the plasma and contribute up to 50% of postprandial plasma NEFA concentrations. Therefore, plasma NEFA concentrations after a meal reflect the balance between intracellular and extracellular lipolysis in adipose tissue. This balance is altered after the acute ingestion of fructose. The enzyme lipoprotein lipase is a key modulator of fatty acid flux in adipose tissue and its rate of action is severely diminished in obese men. In conclusion, in vivo studies of human metabolism can quantify the way that adipose tissue fatty acid trafficking modulates plasma lipid concentrations. This has implications for the flux of fatty acids to tissues that are susceptible to ectopic fat deposition such as the liver and muscle.
大多数餐后研究都调查了单一餐的反应，但在西方社会，连续进食更为常见。本综述旨在解释如何使用天然和稳定同位素示踪剂脂肪酸来研究单一餐和多餐餐后脂肪的代谢，重点是体内测量脂肪组织代谢。当稳定同位素示踪剂与动静脉差测量相结合时，可以对组织间代谢通量进行非常具体的测量。我们发现，在单次测试餐后 5 小时内，以及在典型的三餐进食模式下，大部分时间内，脂肪组织都是膳食脂肪的净摄取者。当脂肪从血浆中清除后，一些脂肪酸“溢出”到血浆中，导致餐后血浆非酯化脂肪酸浓度高达 50%。因此，餐后血浆非酯化脂肪酸浓度反映了脂肪组织细胞内和细胞外脂解之间的平衡。这种平衡在急性摄入果糖后会发生改变。脂蛋白脂肪酶是脂肪组织中脂肪酸通量的关键调节剂，其作用速度在肥胖男性中严重降低。总之，人体代谢的体内研究可以定量评估脂肪组织脂肪酸转运如何调节血浆脂质浓度。这对易发生异位脂肪沉积的组织（如肝脏和肌肉）中脂肪酸的通量有影响。
