Kadokawa H, Briegel J R, Blackberry M A, Blache D, Martin G B, Adams N R
CSIRO Division of Livestock Industries, Private Bag #5, PO Wembley, WA 6913, Australia.
Domest Anim Endocrinol. 2003 Apr;24(3):219-29. doi: 10.1016/s0739-7240(02)00237-0.
To study the regulation of leptin secretion in sheep, we infused glucose (0.32 g/h/kg for 12 h) into GH-transgenic animals (n = 8) that have chronically high plasma concentrations of ovine GH and insulin, but low body condition and low plasma leptin concentrations, and compared the responses with those in controls (n = 8). In both groups, the infusion increased plasma concentrations of glucose and insulin within 1 h and maintained high levels throughout the infusion period (P < 0.0001). Compared with controls, GH-transgenics had higher concentrations of insulin, IGF-1, GH (all P < 0.0001) and cortisol (P < 0.05), but lower GH pulse frequency (P < 0.0001). Overall, leptin concentrations were lower in GH-transgenics than in controls (P < 0.01). A postprandial increase in leptin concentrations was observed in both groups, independently of glucose treatment, after which the values remained elevated in animals infused with glucose, but returned to basal levels in those infused with saline, independently of transgene status. In both GH-transgenics and controls, glucose infusion did not affect the concentrations of GH, IGF-1, or cortisol. In conclusion, GH-transgenic and control sheep show similar responses to glucose infusion for leptin and other metabolic hormones, despite differences between them in body condition and basal levels of these hormones. Glucose, insulin, GH, IGF-1 and cortisol are probably not major factors in the acute control of leptin secretion in sheep, although sustained high concentrations of GH and IGF-1 might reduce adipose tissue mass or inhibit leptin gene expression.
为研究绵羊中瘦素分泌的调节机制，我们向生长激素转基因动物（n = 8）输注葡萄糖（0.32 g/h/kg，持续12小时），这些动物血浆中绵羊生长激素和胰岛素浓度长期处于高水平，但身体状况较差且血浆瘦素浓度较低，并将其反应与对照组动物（n = 8）进行比较。在两组中，输注在1小时内使血浆葡萄糖和胰岛素浓度升高，并在整个输注期间维持在高水平（P < 0.0001）。与对照组相比，生长激素转基因动物的胰岛素、胰岛素样生长因子-1、生长激素（均P < 0.0001）和皮质醇浓度更高（P < 0.05），但生长激素脉冲频率更低（P < 0.0001）。总体而言，生长激素转基因动物的瘦素浓度低于对照组（P < 0.01）。两组均观察到餐后瘦素浓度升高，且与葡萄糖处理无关，之后，输注葡萄糖的动物瘦素值仍保持升高，但输注生理盐水的动物瘦素值则恢复至基础水平，与转基因状态无关。在生长激素转基因动物和对照组中，葡萄糖输注均未影响生长激素、胰岛素样生长因子-1或皮质醇的浓度。总之，尽管生长激素转基因绵羊和对照绵羊在身体状况和这些激素的基础水平上存在差异，但它们对葡萄糖输注时瘦素和其他代谢激素的反应相似。葡萄糖、胰岛素、生长激素、胰岛素样生长因子-1和皮质醇可能不是绵羊瘦素分泌急性调节的主要因素，但持续高浓度的生长激素和胰岛素样生长因子-1可能会减少脂肪组织量或抑制瘦素基因表达。
