Backes Gunda, Hennig Ulf, Petzke Klaus J, Elsner Angelika, Junghans Peter, Nürnberg Gerd, Metges Cornelia C
Unit Protein Metabolism, German Institute of Human Nutrition, Bergholz-Rehbrücke, Germany.
Am J Clin Nutr. 2002 Dec;76(6):1317-25. doi: 10.1093/ajcn/76.6.1317.
We previously reported microbial lysine contribution to plasma lysine homeostasis in humans with an adequate lysine intake.
We sought to explore whether the low lysine intake from a wheat gluten-based diet is balanced by enhanced microbial lysine contribution in a pig model.
Twenty miniature pigs (minipigs) fitted with ileo-ileal cannulas were fed 2 wheat gluten-based diets. One diet provided 2.7 g lysine/kg diet (WG diet) and one diet was supplemented with crystalline lysine to provide 6.6 g lysine/kg diet (WG+Lys diet). Both diets were fed for 10 or 100 d (n = 5 per group): 10WG+Lys, 10WG, 100WG+Lys, and 100WG diets. Ileal microbial lysine, which we considered to be the precursor pool for absorption, was labeled by oral administration of (15)NH(4)Cl for the final 10 d. On days 10 and 100, a 10-h fast-fed tracer protocol with [1-(13)C]lysine was performed.
Lysine rates of appearance decreased by 25% with the WG diet in the fed state but increased by 50% with the WG+Lys diet in the fasted state (P < 0.05). Daily gross microbial lysine contribution was lower (P < 0.05) with the WG diet (205.3 micro mol. kg(-) (1). d(-)(1)) than with the WG+Lys diet (370.7 micro mol. kg(-) (1). d(-)(1)), irrespective of the adaptation period and was similar to the ileal lysine loss with the WG diet. In the WG groups, incorporation of microbial lysine increased in the duodenum and liver (P < 0.05) but not in whole-body and muscle proteins.
Minipigs fed the WG diet did not adapt by showing an enhanced absorption of microbial lysine to the extrasplanchnic tissues, presumably because microbial lysine continues to be used for splanchnic protein synthesis.
我们之前报道过，在赖氨酸摄入量充足的人类中，微生物来源的赖氨酸对血浆赖氨酸稳态有贡献。
我们试图在猪模型中探究，以小麦面筋为基础的饮食中低赖氨酸摄入量是否会通过增加微生物来源的赖氨酸贡献来达到平衡。
给20头安装了回肠-回肠插管的小型猪（迷你猪）喂食两种以小麦面筋为基础的饮食。一种饮食提供2.7克赖氨酸/千克日粮（WG日粮），另一种饮食添加了结晶赖氨酸，以提供6.6克赖氨酸/千克日粮（WG+Lys日粮）。两种日粮均喂养10天或100天（每组n = 5）：10WG+Lys、10WG、100WG+Lys和100WG日粮。在最后10天通过口服(15)NH(4)Cl标记回肠微生物赖氨酸，我们将其视为吸收的前体库。在第10天和第100天，采用[1-(13)C]赖氨酸进行10小时禁食-喂食示踪方案。
在进食状态下，WG日粮使赖氨酸的出现率降低了25%，但在禁食状态下，WG+Lys日粮使其增加了50%（P < 0.05）。无论适应期如何，WG日粮的每日微生物赖氨酸总贡献量（205.3微摩尔·千克(-1)·天(-1)）均低于WG+Lys日粮（370.7微摩尔·千克(-1)·天(-1)）（P < 0.05），且与WG日粮的回肠赖氨酸损失量相似。在WG组中，十二指肠和肝脏中微生物赖氨酸的掺入增加（P < 0.05），但全身和肌肉蛋白质中未增加。
喂食WG日粮的迷你猪并未通过增强微生物赖氨酸向肠外组织的吸收来适应，推测是因为微生物赖氨酸继续用于内脏蛋白质合成。
