Pezeshki Adel, Fahim Andrew, Chelikani Prasanth K
Department of Production Animal Health, Faculty of Veterinary Medicine, Gastrointestinal Research Group, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Canada.
Department of Production Animal Health, Faculty of Veterinary Medicine, Gastrointestinal Research Group, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Canada
J Nutr. 2015 Oct;145(10):2236-44. doi: 10.3945/jn.115.213843. Epub 2015 Aug 26.
Dietary whey and casein proteins decrease food intake and body weight and improve glycemic control; however, little is known about the underlying mechanisms.
We determined the effects of dietary whey, casein, and a combination of the 2 on energy balance, hormones, glucose metabolism, and taste preference in rats.
In Expt. 1, Obesity Prone CD (OP-CD) rats were fed a high-fat control diet (33% fat energy) for 8 wk, and then randomly assigned to 4 isocaloric dietary treatments (n = 12/group): the control treatment (CO; 14% protein energy from egg white), the whey treatment (WH; 26% whey + 14% egg white), the casein treatment (CA; 26% casein + 14% egg white), or the whey plus casein treatment (WHCA; 13% whey + 13% casein + 14% egg white) for 28 d. Measurements included food intake, energy expenditure, body composition, metabolic hormones, glucose tolerance and key tissue markers of glucose and energy metabolism. In Expt. 2, naïve OP-CD rats were randomly assigned to 3 groups (n = 8/group). During an 8 d conditioning period, each group received on alternate days either the CO or WH, CO or CA, or CO or WHCA. Subsequently, preferences for the test diets were assessed on 2 consecutive days with food intake measurements at regular intervals.
In Expt. 1, food intake was decreased by 17-37% for the first 14 d in the WH and CA rats, and by 18-34% only for the first 4 d in the WHCA compared with the CO rats. Fat mass decreased by 21-28% for the WH rats and 17-33% for the CA rats from day 14 onward, but by 30% only on day 28 in WHCA rats, relative to CO rats. Thus, food intake, body weight, and fat mass decreased more rapidly in WH and CA rats than in WHCA rats. Energy expenditure in WH rats decreased for the first 4 d compared with CA and WHCA rats, and for the first 7 d compared with the CO rats. Circulating leptin, glucose-dependent insulinotropic polypeptide, interleukin 6, and glucose concentrations were lower in WH, CA, and WHCA rats than in CO rats. Plasma glucagon-like peptide 1 concentrations were greater in WH than in CA or WHCA rats. The improvements in glucose tolerance were greater in WH than in WHCA rats. The plasma membrane glucose transporter 4 (GLUT4)-to-total GLUT4 ratio in skeletal muscle was greater in CA and WHCA rats than in CO rats; other markers of glucose and energy metabolism in the adipose and cardiac tissues did not differ. In Expt. 2, during 4 conditioning trials, daily food intake was decreased in WH, CA, and WHCA rats by 26-37%, 30-43%, and 23-33%, respectively, compared with CO rats. Preferences for WH and CA rats were 45% and 31% lower, respectively, than those for CO rats, but that for WHCA rats did not differ.
Together, these data demonstrate that in obese rats, whey, casein, and their combination improve energy balance through differential effects on food intake, taste preference, energy expenditure, glucose tolerance, and gut hormone secretion.
膳食中的乳清蛋白和酪蛋白可减少食物摄入量和体重，并改善血糖控制；然而，其潜在机制尚不清楚。
我们确定了膳食中的乳清蛋白、酪蛋白及其组合对大鼠能量平衡、激素、葡萄糖代谢和味觉偏好的影响。
在实验1中，将肥胖易感CD（OP-CD）大鼠喂饲高脂对照饮食（脂肪能量占33%）8周，然后随机分为4种等热量饮食处理组（每组n = 12）：对照处理组（CO；14%的蛋白能量来自蛋清）、乳清蛋白处理组（WH；26%乳清蛋白 + 14%蛋清）、酪蛋白处理组（CA；26%酪蛋白 + 14%蛋清）或乳清蛋白加酪蛋白处理组（WHCA；13%乳清蛋白 + 13%酪蛋白 + 14%蛋清），持续28天。测量指标包括食物摄入量、能量消耗、身体组成、代谢激素、葡萄糖耐量以及葡萄糖和能量代谢的关键组织标志物。在实验2中，将未处理的OP-CD大鼠随机分为3组（每组n = 8）。在8天的适应期内，每组隔天分别给予CO或WH、CO或CA、或CO或WHCA。随后，连续两天评估对试验饮食的偏好，并定期测量食物摄入量。
在实验1中，与CO组大鼠相比，WH组和CA组大鼠在最初14天食物摄入量减少了17 - 37%，而WHCA组仅在最初4天减少了18 - 34%。从第14天起，WH组大鼠的脂肪量减少了21 - 28%，CA组大鼠减少了17 - 33%，但WHCA组大鼠仅在第28天减少了30%。因此，WH组和CA组大鼠的食物摄入量、体重和脂肪量比WHCA组大鼠下降得更快。与CA组和WHCA组大鼠相比，WH组大鼠在最初4天能量消耗减少，与CO组大鼠相比，在最初7天能量消耗减少。WH组、CA组和WHCA组大鼠的循环瘦素、葡萄糖依赖性促胰岛素多肽、白细胞介素6和葡萄糖浓度均低于CO组大鼠。WH组大鼠血浆胰高血糖素样肽1浓度高于CA组或WHCA组大鼠。WH组大鼠葡萄糖耐量的改善程度大于WHCA组大鼠。CA组和WHCA组大鼠骨骼肌中质膜葡萄糖转运蛋白4（GLUT4）与总GLUT4的比值高于CO组大鼠；脂肪组织和心脏组织中葡萄糖和能量代谢的其他标志物无差异。在实验2中，在4次适应试验期间，与CO组大鼠相比，WH组、CA组和WHCA组大鼠的每日食物摄入量分别减少了26 - 37%、30 - 43%和23 - 33%。WH组和CA组大鼠的偏好分别比CO组大鼠低45%和31%，但WHCA组大鼠的偏好无差异。
总之，这些数据表明，在肥胖大鼠中，乳清蛋白、酪蛋白及其组合通过对食物摄入量、味觉偏好、能量消耗、葡萄糖耐量和肠道激素分泌的不同影响来改善能量平衡。
