Comizio R, Pietrobelli A, Tan Y X, Wang Z, Withers R T, Heymsfield S B, Boozer C N
Obesity Research Center, St. Luke's-Roosevelt Hospital, Columbia University College of Physicians and Surgeons, New York, New York 10025, USA.
Am J Physiol. 1998 May;274(5):E860-6. doi: 10.1152/ajpendo.1998.274.5.E860.
Although the study of human body composition is advancing rapidly, confusion still prevails regarding the molecular-level lipid component. Most molecular-level body composition models are presently based on the overall hypothesis that nontriglyceride lipids constitute an insignificant proportion of total body lipid. A single lipid or "fat" component consisting of triglycerides is thus assumed in most molecular-level body composition models. To test this hypothesis, the present study, carried out in adult rats, was designed to examine two questions: 1) What is the proportion of total lipids as triglycerides? and 2) Is this proportion constant or does it change with negative energy balance and weight loss produced by calorie restriction and increased exercise? Results indicated that with negative energy balance and weight loss there were progressive losses of total body triglyceride and lipid. The proportion of total lipids as triglyceride was 0.83 +/- 0.08 (SD) in control animals, with reductions at 2 and 9 wk of energy restriction [0.82 +/- 0.04 (P = NS vs. control) and 0.70 +/- 0.15 (P = 0.05)] and at 9 wk for energy restriction plus exercise [0.67 +/- 0.09 (P = 0.003)]. Nontriglyceride lipids comprised 2.8% of carcass weight at baseline and decreased to 2.2% by 9 wk of energy restriction and exercise (P = NS). Substantial differences were observed between body composition ratios expressed as percentages of the lipid-free body mass (LFM) and triglyceride-free body mass (TGFM); (e.g., total body water/LFM and TGFM in controls = 72.7 +/- 0.7 and 70.4 +/- 2.2, respectively; P = 0.02). These observations strongly support the existence and importance of nontriglyceride lipids as a body composition component that responds independently from storage triglycerides, with negative energy balance produced by food restriction and exercise.
尽管人体成分研究正在迅速发展，但在分子水平的脂质成分方面仍然存在混淆。目前，大多数分子水平的人体成分模型基于这样一个总体假设，即非甘油三酯脂质在全身脂质中所占比例微不足道。因此，在大多数分子水平的人体成分模型中，假定单一脂质或由甘油三酯组成的“脂肪”成分。为了验证这一假设，本研究以成年大鼠为对象，旨在探讨两个问题：1）甘油三酯占总脂质的比例是多少？2）这个比例是恒定的，还是会随着热量限制和运动量增加导致的负能量平衡和体重减轻而变化？结果表明，随着负能量平衡和体重减轻，全身甘油三酯和脂质逐渐减少。对照动物中甘油三酯占总脂质的比例为0.83±0.08（标准差），在能量限制2周和9周时降低[0.82±0.04（与对照组相比，P=无显著性差异）和0.70±0.15（P=0.05）]，在能量限制加运动9周时为0.67±0.09（P=0.003）。非甘油三酯脂质在基线时占胴体重量的2.8%，在能量限制和运动9周后降至2.2%（P=无显著性差异）。以无脂体重（LFM）和无甘油三酯体重（TGFM）的百分比表示的身体成分比率之间观察到显著差异；（例如，对照组全身水/LFM和TGFM分别为72.7±0.7和70.4±2.2；P=0.02）。这些观察结果有力地支持了非甘油三酯脂质作为一种身体成分的存在及其重要性，它独立于储存的甘油三酯做出反应，在食物限制和运动产生负能量平衡时。
