Gougeon R, Pencharz P B, Sigal R J
McGill Nutrition and Food Science Centre, Royal Victoria Hospital, Montréal, Québec, Canada.
Am J Clin Nutr. 1997 Mar;65(3):861-70. doi: 10.1093/ajcn/65.3.861.
We postulated whether interventions capable of restoring euglycemia would correct whole-body protein metabolism, shown previously to be elevated in hyperglycemic persons with non-insulin-dependent diabetes (NIDDM). The kinetics of protein metabolism were estimated in obese subjects with NIDDM in the hyper- and normoglycemic states during isoenergetic feeding and in the normoglycemic state induced by 4 wk of a very-low-energy diet (VLED) with constant protein intake. Seven NIDDM subjects [three males and four females with a body mass index (in kg/m2) of 39 +/- 2] were given a weight-maintaining, liquid formula providing 95 g protein/d for 15 d, followed in six subjects (two males and four females) for 27 d by a diet providing 1.7 MJ, 93 g protein derived from casein-soy, 13 g carbohydrate, 2 g fat, multivitamins and minerals, and a potassium bicarbonate supplement (32 mmol) per day. Exogenous insulin was given to achieve normoglycemia during the first 8 d of isoenergetic feeding. On days 6-8, 12-14, and 25-27, nitrogen flux rate was calculated from the urine [15N]urea enrichment by using the 60-h oral [15N]glycine method to obtain "integrated" feeding and fasting values. Rates of synthesis and breakdown were calculated from nitrogen flux. During isoenergetic feeding, normoglycemia was associated with more positive nitrogen balance (2.6 +/- 0.5 compared with -0.6 +/- 0.6 g N/d, P < 0.05); 18-23% lower nitrogen flux, and synthesis and breakdown rates (P < 0.05), and a 3% decrease in resting energy expenditure (P < 0.05). During the VLED, euglycemia was achieved but nitrogen balance, although it became less negative with time, never reached equilibrium. This was associated with significant (P < 0.05) decreases in the synthesis rate, resulting in net protein losses. Thus, the altered protein metabolism in moderately hyperglycemic NIDDM subjects was improved with exogenous insulin in doses sufficient to restore normoglycemia in the isoenergetic fed state, but it remained abnormal with a reduced non-protein energy intake. This suggests that protein metabolism is more sensitive to insulinization than was thought previously.
我们推测，能够恢复血糖正常的干预措施是否会纠正全身蛋白质代谢，此前研究表明，非胰岛素依赖型糖尿病（NIDDM）患者在高血糖状态下全身蛋白质代谢会增强。我们评估了肥胖NIDDM患者在等能量喂养的高血糖和正常血糖状态下以及在持续蛋白质摄入量不变的极低能量饮食（VLED）4周诱导的正常血糖状态下的蛋白质代谢动力学。7名NIDDM患者[3名男性和4名女性，体重指数（kg/m²）为39±2]接受维持体重的液体配方，每天提供95克蛋白质，持续15天，随后6名患者（2名男性和4名女性）接受一种饮食，每天提供1.7兆焦耳能量、93克源自酪蛋白-大豆的蛋白质、13克碳水化合物、2克脂肪、多种维生素和矿物质以及碳酸氢钾补充剂（32毫摩尔），持续27天。在等能量喂养的前8天给予外源性胰岛素以实现血糖正常。在第6 - 8天、12 - 14天和25 - 27天，通过使用60小时口服[¹⁵N]甘氨酸方法从尿液[¹⁵N]尿素富集量计算氮通量率，以获得“综合”的进食和空腹值。根据氮通量计算合成和分解速率。在等能量喂养期间，血糖正常与更正向的氮平衡相关（分别为每日2.6±0.5克氮和 - 0.6±0.6克氮，P < 0.05）；氮通量、合成和分解速率降低18 - 23%（P < 0.05），静息能量消耗降低3%（P < 0.05）。在VLED期间，实现了血糖正常，但氮平衡虽然随时间变得不那么负，但从未达到平衡。这与合成速率显著降低（P < 0.05）相关，导致蛋白质净损失。因此，中度高血糖NIDDM患者改变的蛋白质代谢在等能量喂养状态下，通过足以恢复血糖正常的外源性胰岛素剂量得到改善，但在非蛋白质能量摄入减少时仍保持异常。这表明蛋白质代谢对胰岛素化比之前认为的更敏感。
