Key Laboratory of Animal Genetics, Breeding and Reproduction of Ministry of Education and Key Laboratory of Swine Genetics and Breeding of Ministry of Agriculture, Department of Animal Nutrition and Feed Science, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Br J Nutr. 2010 Mar;103(5):643-51. doi: 10.1017/S0007114509992169. Epub 2010 Jan 12.
The present study was conducted in a one-factorial arrangement to determine the effects of dl-2-hydroxy-4-methylthiobutyrate (dl-HMTB) on the first-pass intestinal metabolism of dietary methionine and its extra-intestinal availability. Barrows (n 6; aged 35 d; weight 8.6 kg), implanted with arterial, portal, mesenteric and gastric catheters, were fed a diet containing dl-methionine (dl-MET) or dl-HMTB once hourly and infused intramesenterically with 1 % p-aminohippurate and intragastrically with [1-13C]methionine at 7.0 mumol/kg body weight per h. Arterial and portal blood samples were taken at hourly intervals until 6 h of tracer infusion and pigs was then killed for collection of muscle, intestine, liver and kidney samples. The net portal appearance of methionine, expressed as the fraction of ingested directly available l-methionine, was higher (P < 0.05) in the dl-HMTB than in the dl-MET diet, and there was no difference (P = 0.26) in the fractional portal balance of [1-13C]methionine between the diets. [1-13C]methionine enrichment (tracer:tracee ratio; mol/100 mol amino acid) in the jejunum, arterial and portal plasma, liver, kidney and muscle was also not different (P>0.05) between the groups. Over the 6 h period after the start of feeding, the average concentration of citrulline both in the arterial and portal plasma was higher (P < 0.05) in the dl-HMTB than in the dl-MET group, and arterial plasma ornithine and taurine concentration was also higher (P < 0.05) in the dl-HMTB than in the dl-MET group. However, plasma urea concentration both in the arterial and portal vein was lower (P < 0.05) in the dl-HMTB than in the dl-MET group. These results suggested that the potential difference in the first-pass use of methionine by the intestine between the dl-HMTB and dl-MET diets might affect intestinal and systemic metabolism of other amino acids, which may provide new important insights into nutritional efficiency of different methionine sources.
本研究采用单因素设计，旨在确定 dl-2-羟基-4-甲基硫丁酸（dl-HMTB）对膳食蛋氨酸的首过肠道代谢及其肠外可用性的影响。将植入动脉、门静脉、肠系膜和胃导管的巴罗（n 6；年龄 35 天；体重 8.6 公斤）每小时喂一次含 dl-蛋氨酸（dl-MET）或 dl-HMTB 的饮食，并每小时通过肠系膜内输注 1%对氨基马尿酸和胃内输注[1-13C]蛋氨酸，以 7.0 微摩尔/公斤体重/小时。在示踪剂输注 6 小时时，每隔 1 小时采集动脉和门静脉血样，然后处死猪，采集肌肉、肠、肝和肾样。蛋氨酸的门静脉净出现量，以摄入的直接可用 l-蛋氨酸的分数表示，在 dl-HMTB 饮食中高于 dl-MET 饮食（P < 0.05），并且两种饮食之间[1-13C]蛋氨酸的门静脉平衡分数无差异（P = 0.26）。空肠、动脉和门静脉血浆、肝、肾和肌肉中的[1-13C]蛋氨酸富集（示踪剂：示踪剂比值；摩尔/100 摩尔氨基酸）在两组之间也没有差异（P>0.05）。在开始喂养后的 6 小时期间，动脉和门静脉血浆中瓜氨酸的平均浓度在 dl-HMTB 饮食中高于 dl-MET 组（P < 0.05），并且 dl-HMTB 饮食中动脉血浆鸟氨酸和牛磺酸浓度也高于 dl-MET 组（P < 0.05）。然而，dl-HMTB 饮食中动脉和门静脉中的血浆尿素浓度均低于 dl-MET 饮食（P < 0.05）。这些结果表明，dl-HMTB 和 dl-MET 饮食之间蛋氨酸的首过肠道利用的潜在差异可能影响其他氨基酸的肠道和全身代谢，这可能为不同蛋氨酸来源的营养效率提供新的重要见解。
