Effects of tirzepatide, a dual GIP and GLP-1 receptor agonist, on blood pressure, cardiac function, and sympathetic nervous system in stroke-prone spontaneously hypertensive rats.

Tirzepatide, a dual agonist for glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors, has shown robust efficacy in treating diabetes and obesity, and in obese patients with heart failure with preserved ejection fraction (HFpEF), it reduced weight, lowered blood pressure, and improved outcomes. However, its cardiovascular effects in non-obese, non-diabetic hypertension remain unclear. We investigated the impact of tirzepatide on blood pressure, cardiac function, and sympathetic nervous system activity in stroke-prone spontaneously hypertensive rats. Starting at 8 weeks of age, rats received tirzepatide (TZP, 25 nmol/kg, every two days), vehicle (VEH), or pair-fed vehicle (VEH-PF) to control for differences in food intake for 4 weeks. Tirzepatide significantly reduced food intake and body weight. Contrary to prior clinical observations, tirzepatide elevated mean blood pressure (197.4 ± 16.6 vs. 153.7 ± 5.4 mmHg at Day 28; TZP vs. VEH-PF, n = 9 vs. 8; p < 0.05) and increased heart rate, accompanied by left ventricular hypertrophy, myocardial fibrosis, and impaired diastolic function. Sympathetic activation was evident, with higher plasma norepinephrine levels and increased ΔFosB expression-a marker of sustained neuronal excitation-in the parvocellular paraventricular nucleus and the rostral ventrolateral medulla. Moreover, ΔFosB expression was increased in anorexigenic proopiomelanocortin neurons within the hypothalamic arcuate nucleus, which reduce feeding and have been implicated in promoting sympathetic excitation. These findings point to a central mechanism underlying increased sympathetic outflow. In conclusion, tirzepatide increased blood pressure and sympathetic activity in hypertensive rats without cardiac protection, highlighting context-dependent cardiovascular actions. Tirzepatide increased blood pressure, impaired LV diastolic function, and induced cardiac hypertrophy and fibrosis, as well as sympathetic overactivation in SHRSP.