Liu Jiankang, da Silva Alexandre A, Tallam Lakshmi S, Hall John E
Department of Physiology and Biophysics, and Center of Excellence in Cardiovascular Renal Research, The University of Mississippi Medical Center, Jackson, Mississippi 39216-4505, USA.
J Hypertens. 2006 Jul;24(7):1391-5. doi: 10.1097/01.hjh.0000234120.71142.6c.
Acute studies suggest that insulin has anorexic and hypertensive actions through direct effects on the central nervous system (CNS). However, the importance of these actions in the long-term regulation of food intake and cardiovascular function is still unclear. The goal of the present study was to determine whether chronic increases in CNS levels of insulin, in the absence of changes in plasma insulin concentration, decrease food intake and raise arterial pressure in rats.
An intracerebroventricular cannula was placed in the lateral ventricle of male Sprague-Dawley rats for chronic insulin or vehicle (artificial cerebrospinal fluid, 0.5 mul/h) infusion, via osmotic minipump, and arterial and venous catheters were implanted for measurement of mean arterial pressure (MAP) and heart rate (HR) 24 h/day and intravenous infusions. After 4 days of control measurements, insulin (6 mU/h, n = 7 or 12 mU/h, n = 6) or vehicle (n = 4) was infused intracerebroventricularly for 7 days.
Insulin infusion at 6 or 12 mU/h caused transient decreases in food intake, but did not significantly alter plasma glucose or insulin concentrations. Insulin intracerebroventricular infusion also did not alter MAP or HR (106 +/- 2 and 105 +/- 5 versus 104 +/- 2 mmHg in control; 411 +/- 9 and 407 +/- 9 versus 410 +/- 7 bpm in control, respectively). Food intake, MAP and HR remained unchanged in the vehicle-treated group.
These findings provide no evidence that insulin plays a major role in the long-term regulation of appetite, arterial pressure or HR. However, the CNS actions of insulin may exert modest acute effects on appetite that could play a role in limiting meal size and influencing caloric balance.
急性研究表明，胰岛素可通过对中枢神经系统（CNS）的直接作用产生厌食和升压作用。然而，这些作用在食物摄入和心血管功能长期调节中的重要性仍不明确。本研究的目的是确定在血浆胰岛素浓度无变化的情况下，中枢神经系统胰岛素水平的慢性升高是否会降低大鼠的食物摄入量并升高动脉血压。
将脑室内插管置于雄性Sprague-Dawley大鼠的侧脑室，通过渗透微型泵进行慢性胰岛素或载体（人工脑脊液，0.5微升/小时）输注，并植入动脉和静脉导管，用于每天24小时测量平均动脉压（MAP）和心率（HR）以及静脉输注。在进行4天的对照测量后，脑室内输注胰岛素（6 mU/小时，n = 7或12 mU/小时，n = 6）或载体（n = 4），持续7天。
以6或12 mU/小时的速度输注胰岛素会导致食物摄入量短暂下降，但不会显著改变血浆葡萄糖或胰岛素浓度。脑室内输注胰岛素也不会改变MAP或HR（对照组分别为106±2和105±5 mmHg，而输注胰岛素组分别为104±2 mmHg；对照组为410±7次/分钟，输注胰岛素组分别为411±9和407±9次/分钟）。载体治疗组的食物摄入量、MAP和HR保持不变。
这些发现没有提供证据表明胰岛素在食欲、动脉血压或心率的长期调节中起主要作用。然而，胰岛素的中枢神经系统作用可能对食欲产生适度的急性影响，这可能在限制餐量和影响热量平衡方面发挥作用。
