Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Japan.
Domest Anim Endocrinol. 2012 Nov;43(4):299-306. doi: 10.1016/j.domaniend.2012.05.003. Epub 2012 May 27.
Glucagon-like peptide-1 (7-36) amide (GLP-1), secreted by the small intestine, has insulinotropic and glucose-lowering action. Basal plasma GLP-1 concentrations were measured in calves around the weaning period, the effect of short-chain fatty acids (SCFA) on plasma GLP-1 concentrations was examined, and the effects of GLP-1 administration on plasma insulin, glucagon, and glucose concentrations were measured. Thirteen Holstein bull calves were fed whole milk and solid feed and weaned at 7 wk of age. Preprandial plasma samples were obtained from 5 calves once a week from week 0 to 13 to measure basal concentrations of plasma GLP-1 and insulin (experiment 1). Four calves were intravenously administered with a mixed solution of SCFA (2.4 mmol/kg body weight [BW]) in week 2 and 11 to measure plasma GLP-1 concentrations (experiment 2). Another 4 calves were intravenously injected with GLP-1 (1.0 μg/kg BW) to elucidate the response of plasma insulin, glucagon, and glucose concentrations in week 1, 2, 4, 6, 7, 9, 11, and 13 (experiment 3). In experiment 1, age and weaning did not affect preprandial basal concentrations of plasma GLP-1 throughout the experimental period. Preprandial insulin concentrations increased after weaning (P < 0.05), and GLP-1 and insulin were more strongly correlated postweaning than preweaning. In experiment 2, intravenous treatment with SCFA increased plasma GLP-1 concentrations in both week 2 and 11 (P < 0.05.) In experiment 3, intravenous GLP-1 treatment decreased plasma glucose concentrations throughout the experiment (P < 0.05), but increased plasma insulin concentrations only after weaning (P < 0.05). Treatment with GLP-1 did not affect plasma glucagon concentrations, regardless of age. These results indicate that preprandial basal concentrations of plasma GLP-1 in calves are not changed by weaning, but SCFA stimulate GLP-1 secretion. The insulinotropic action of GLP-1 is detected only after weaning, but the glucose-lowering action of GLP-1 is not affected by weaning.
胰高血糖素样肽-1（7-36）酰胺（GLP-1）由小肠分泌，具有胰岛素促分泌和降血糖作用。在断奶期前后测量了小牛的基础血浆 GLP-1 浓度，研究了短链脂肪酸（SCFA）对血浆 GLP-1 浓度的影响，并测量了 GLP-1 给药对血浆胰岛素、胰高血糖素和血糖浓度的影响。13 头荷斯坦公牛犊在 7 周龄时用全脂牛奶和固体饲料喂养并断奶。在第 0 周到第 13 周期间，每周从 5 头小牛身上采集餐前血浆样本，以测量基础血浆 GLP-1 和胰岛素浓度（实验 1）。在第 2 周和第 11 周，4 头小牛静脉内给予混合 SCFA 溶液（2.4mmol/kg 体重[BW]），以测量血浆 GLP-1 浓度（实验 2）。在第 1、2、4、6、7、9、11 和 13 周，另 4 头小牛静脉注射 GLP-1（1.0μg/kg BW）以阐明血浆胰岛素、胰高血糖素和血糖浓度的反应（实验 3）。在实验 1 中，年龄和断奶在整个实验期间均未影响餐前基础血浆 GLP-1 浓度。断奶后餐前胰岛素浓度升高（P<0.05），且断奶后 GLP-1 与胰岛素的相关性强于断奶前。在实验 2 中，静脉内给予 SCFA 增加了第 2 周和第 11 周的血浆 GLP-1 浓度（P<0.05）。在实验 3 中，静脉内 GLP-1 治疗使整个实验过程中的血浆葡萄糖浓度降低（P<0.05），但仅在断奶后增加血浆胰岛素浓度（P<0.05）。GLP-1 治疗不影响血浆胰高血糖素浓度，与年龄无关。这些结果表明，断奶前后小牛餐前基础血浆 GLP-1 浓度不受断奶影响，但 SCFA 刺激 GLP-1 分泌。仅在断奶后才检测到 GLP-1 的胰岛素促分泌作用，但 GLP-1 的降血糖作用不受断奶影响。
