Loos Caroline M M, Urschel Kristine L, Vanzant Eric S, Oberhaus Erin L, Bohannan Adam D, Klotz James L, McLeod Kyle R
Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, United States.
School of Animal Sciences, Louisiana State University, Baton Rouge, LA, United States.
Front Vet Sci. 2022 May 31;9:889888. doi: 10.3389/fvets.2022.889888. eCollection 2022.
The objectives of the study were to study the effects of the synthetic ergot alkaloid (EA), bromocriptine, on glucose and lipid metabolism in insulin dysregulated (ID, = 7) and non-ID ( = 8) mares. Horses were individually housed and fed timothy grass hay and two daily concentrate meals so that the total diet provided 120% of daily DE requirements for maintenance. All horses were given intramuscular bromocriptine injections (0.1 mg/kg BW) every 3 days for 14 days. Before and after 14 days of treatment horses underwent a combined glucose-insulin tolerance test (CGIT) to assess insulin sensitivity and a feed challenge (1 g starch/kg BW from whole oats) to evaluate postprandial glycemic and insulinemic responses. ID horses had higher basal plasma concentrations of insulin ( = 0.01) and triglycerides ( = 0.02), and lower concentrations of adiponectin ( = 0.05) compared with non-ID horses. The CGIT response curve showed that ID horses had slower glucose clearance rates ( = 0.02) resulting in a longer time in positive phase ( = 0.03) and had higher insulin concentrations at 75 min ( = 0.0002) compared with non-ID horses. Glucose ( = 0.02) and insulin ( = 0.04) responses to the feeding challenge were lower in non-ID compared to ID horses. Regardless of insulin status, bromocriptine administration increased hay intake ( = 0.03) and decreased grain ( < 0.0001) and total DE ( = 0.0002) intake. Bromocriptine treatment decreased plasma prolactin ( = 0.0002) and cholesterol ( = 0.10) and increased ( = 0.02) adiponectin concentrations in all horses. Moreover, in both groups of horses, bromocriptine decreased glucose clearance rates ( = 0.02), increased time in positive phase ( = 0.04) of the CGIT and increased insulin concentrations at 75 min ( = 0.001). The postprandial glycemic ( = 0.01) and insulinemic ( = 0.001) response following the oats meal was lower after bromocriptine treatment in all horses. In conclusion, in contrast to data in humans and rodents, bromocriptine treatment reduced insulin sensitivity in all horses, regardless of their insulin status. These results indicate that the physiological effects of EA might be different in horses compared to other species. Moreover, because bromocriptine shares a high degree of homology with natural EA, further investigation is warranted in horses grazing endophyte-infected grasses.
本研究的目的是研究合成麦角生物碱（EA）溴隐亭对胰岛素调节异常（ID，n = 7）和非ID（n = 8）母马葡萄糖和脂质代谢的影响。马匹单独饲养，饲喂提摩西草干草和每日两顿精料，以使总日粮提供维持所需每日消化能（DE）的120%。所有马匹每3天接受一次溴隐亭肌肉注射（0.1 mg/kg体重），共14天。在治疗14天前后，马匹接受联合葡萄糖-胰岛素耐量试验（CGIT）以评估胰岛素敏感性，并进行饲料挑战（来自全燕麦的1 g淀粉/kg体重）以评估餐后血糖和胰岛素反应。与非ID马匹相比，ID马匹的基础血浆胰岛素（P = 0.01）和甘油三酯（P = 0.02）浓度较高，脂联素浓度较低（P = 0.05）。CGIT反应曲线显示，与非ID马匹相比，ID马匹的葡萄糖清除率较慢（P = 0.02），导致阳性期时间较长（P = 0.03），且在75分钟时胰岛素浓度较高（P = 0.0002）。与ID马匹相比，非ID马匹对饲料挑战的葡萄糖（P = 0.02）和胰岛素（P = 0.04）反应较低。无论胰岛素状态如何，给予溴隐亭均增加了干草摄入量（P = 0.03），减少了谷物摄入量（P < 0.0001）和总DE摄入量（P = 0.0002）。溴隐亭治疗降低了所有马匹的血浆催乳素（P = 0.0002）和胆固醇（P = 0.10）浓度，并增加了脂联素浓度（P = 0.02）。此外，在两组马匹中，溴隐亭均降低了葡萄糖清除率（P = 0.02），增加了CGIT阳性期时间（P = 0.04），并增加了75分钟时的胰岛素浓度（P = 0.001）。在所有马匹中，溴隐亭治疗后燕麦餐后的餐后血糖（P = 0.01）和胰岛素（P = 0.001）反应均较低。总之，与人类和啮齿动物的数据相反，溴隐亭治疗降低了所有马匹的胰岛素敏感性，无论其胰岛素状态如何。这些结果表明，与其他物种相比，EA在马匹中的生理作用可能不同。此外，由于溴隐亭与天然EA具有高度同源性，因此有必要对放牧感染内生真菌的草的马匹进行进一步研究。
