Chronic and acute effects of kefir: The role of angiotensin converting enzyme inhibition instead of nitric oxide balance

Abstract

Probiotic consumption promotes numerous health benefits. The aim of this study is 1) to evaluate the antihypertensive effect of kefir in a hypertension rat model caused by the administration of the nitric oxide synthesis inhibitor, L-NAME, and 2) to evaluate the acute angiotensin converting enzyme (ACE) inhibitory activity of the soluble nonbacterial fraction (SNBF) of kefir. To develop the first aim, male rats were separated into three groups: control group (C) treated with 0.3 mL/100 g of milk; L-NAME group (LN) received 10 mg/kg of said inhibitor; and Kefir group (K) treated with 0.3 mL/100 g of kefir plus L-NAME (10 mg/kg of said inhibitor). The treatments were given by oral gavage twice a day for four weeks. For the second aim”instead additionally, male rats received angiotensin I (in bolus) in three doses (Ang I: 0.03, 3 and 300 µg/kg) and were separated into two groups: a) received captopril (30 mg/kg i.v.) and b)received SNBF of kefir (5 mL/kg i.v.). Blood pressure were evaluated before and after Ang I. After treatment, hemodynamic parameters were evaluated, heart weight was recorded, and body weight gain was calculated. SNBF of kefir did not decrease the blood pressure for L-NAME-treated animals, and no changes were observed in the cardiac parameters. However, the SNBF of kefir demonstrated acute inhibition of ACE in vivo similar to that of captopril. Thus, our results suggest that kefir may improve human cardiovascular systems by using mechanisms independent of nitric oxide syntheses. Additionally, the renin angiotensin system is probably the most important system involved in kefir effect regarding hypertension.