Cardiovascular activity of milk casein-derived tripeptides and plant sterols in spontaneously hypertensive rats

The effect of chronic treatment with fermented milk products containing bioactive tripeptides and plant sterols on blood pressure and vascular function was investigated in spontaneously hypertensive rats (SHR). Six-weeks old male SHR (n=36) were randomized into 4 groups by body weight and blood pressure to receive either Lactobacillus helveticus fermented standard milk product (containing tripeptides Ile-Pro-Pro, Val-Pro-Pro and Leu-Pro-Pro), test product with enzymatically produced tripeptides without or with plant sterols or control product without the active constituents for 8 weeks. Systolic blood pressure (SBP) was measured weekly using the tail-cuff method. Thoracic aorta and mesenteric artery were excised for vascular response measurements. At the end, SBP values vs. control product group were: standard product group -14 mmHg (P<0.05), test product group -12 mmHg and test product +sterols group -7 mmHg. The average daily tripeptide dose was 2.8-5.2 mg/kg. Total serum cholesterol in the test product +sterols group tended to be lower than in the test product group (P=0.10) whereas serum plant sterol (campesterol, sitosterol) concentrations were higher (P<0.001). In conclusion, bioactive tripeptide-containing milk products attenuated the blood pressure development in SHR. The plant sterols did not improve this effect. Vascular responses did not markedly differ between the groups, except that endothelium-derived hyperpolarizing factor (EDHF) -related aortic relaxation was demonstrated in the test product +sterols group.