Trotta Ronald J, Swanson Kendall C, Klotz James L, Harmon David L
Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, United States.
Department of Animal Science, North Dakota State University, Fargo, ND, United States.
J Nutr. 2023 Oct;153(10):2854-2867. doi: 10.1016/j.tjnut.2023.08.009. Epub 2023 Aug 10.
Increasing luminal carbohydrate flow decreases pancreatic α-amylase activity but can increase jejunal maltase activity, suggesting that regulation of carbohydrase activity is perhaps uncoordinated in response to luminal carbohydrate flow. Increasing luminal casein flow increases pancreatic α-amylase activity in cattle, and exogenous glucagon-like peptide 2 (GLP-2) has been shown to increase small intestinal α-glucosidase activity in nonruminants.
The objective was to evaluate the effects of postruminal casein infusion, exogenous GLP-2, or their combination on endogenous pancreatic and small intestinal carbohydrase activity in cattle postruminally infused with starch.
Holstein steers [n = 24; 250 ± 23 kg body weight (BW)] received a continuous abomasal infusion of 3.94 g raw corn starch/kg of BW combined with either 0 or 1.30 g casein/kg of BW. Steers received subcutaneous injections in 2 equal portions daily of excipient (0.5% bovine serum albumin) or 100 μg GLP-2/kg of BW per day. At the end of the 7-d treatment period, steers were slaughtered for tissue collection. Data were analyzed using the MIXED procedure of SAS version 9.4 (SAS Institute Inc.).
Postruminal casein infusion increased (P ≤ 0.03) pancreatic mass by 12.6%, total pancreatic α-amylase activity by 50%, and postruminal starch disappearance from 96.7% to 99.3%. Exogenous GLP-2 increased (P < 0.01) total small intestinal and mucosal mass by 1.2 kg and 896 g, respectively. Relative to control, GLP-2 and casein + GLP-2 increased (P = 0.04) total small intestinal α-glucosidase activity by 83.5%. Total small intestinal maltase, isomaltase, and glucoamylase activity was 90%, 100%, and 66.7% greater for GLP-2 and casein + GLP-2 steers compared with control.
Casein increased pancreatic α-amylase activity, GLP-2 increased small intestinal α-glucosidase activity, and the combination of casein and GLP-2 increased both pancreatic α-amylase activity and small intestinal α-glucosidase activity. This novel approach provides an in vivo model to evaluate effects of increasing endogenous carbohydrase activity on small intestinal starch digestion.
管腔内碳水化合物流量增加会降低胰腺α-淀粉酶活性，但会增加空肠麦芽糖酶活性，这表明碳水化合物酶活性的调节可能无法响应管腔内碳水化合物流量而协调进行。管腔内酪蛋白流量增加会提高牛的胰腺α-淀粉酶活性，并且已表明外源性胰高血糖素样肽2（GLP-2）可提高非反刍动物小肠α-葡萄糖苷酶活性。
本研究旨在评估瘤胃后注入酪蛋白、外源性GLP-2或二者联合对瘤胃后注入淀粉的牛的内源性胰腺和小肠碳水化合物酶活性的影响。
荷斯坦公牛（n = 24；体重250 ± 23千克）接受连续皱胃输注3.94克生玉米淀粉/千克体重，并分别联合0或1.30克酪蛋白/千克体重。公牛每天分2等份接受皮下注射赋形剂（0.5%牛血清白蛋白）或100微克GLP-2/千克体重。在7天的治疗期结束时，宰杀公牛以收集组织。使用SAS 9.4版（SAS Institute Inc.）的MIXED程序分析数据。
瘤胃后注入酪蛋白使胰腺重量增加（P≤0.03）12.6%，胰腺α-淀粉酶总活性增加50%，瘤胃后淀粉消失率从96.7%提高到99.3%。外源性GLP-2使小肠和黏膜总重量分别增加（P < 0.01）1.2千克和896克。相对于对照组，GLP-2和酪蛋白+GLP-2使小肠α-葡萄糖苷酶总活性增加（P = 0.04）83.5%。与对照组相比，GLP-2组和酪蛋白+GLP-2组公牛的小肠麦芽糖酶、异麦芽糖酶和葡糖淀粉酶总活性分别高90%、100%和66.7%。
酪蛋白提高了胰腺α-淀粉酶活性，GLP-2提高了小肠α-葡萄糖苷酶活性，酪蛋白和GLP-2联合使用既提高了胰腺α-淀粉酶活性又提高了小肠α-葡萄糖苷酶活性。这种新方法提供了一种体内模型，用于评估增加内源性碳水化合物酶活性对小肠淀粉消化的影响。
