Antihypertensive effects of dietary protein and its mechanism

Abstract

Hypertension is a leading cause of morbidity and mortality worldwide. Individuals with hypertension are at increased risk of stroke, heart disease and kidney failure. Both genetic and lifestyle factors, particularly diet, have been attributed an important role in the development of hypertension. Reducing dietary sugar and salt intake can help lower blood pressure; similarly, adequate protein intake may also attenuate hypertension. Observational, cross-sectional and longitudinal epidemiological studies, and controlled clinical trials, have documented significant inverse associations between protein intake and blood pressure. Human and animal studies have shown that specific amino acids within proteins may have antihypertensive effects. Cysteine, glutathione (a tripeptide), glutamate and arginine attenuate and prevent alterations that cause hypertension including insulin resistance, decreased nitric oxide bioavailability, altered renin angiotensin system function, increased oxidative stress and formation of advanced glycation end products. Leucine increases protein synthesis in skeletal muscle and improves insulin resistance by modulating hepatic gluconeogenesis. Taurine and tryptophan attenuate sympathetic nervous system activity. Soy protein helps lower blood pressure through its high arginine content and antioxidant activity exhibited by isoflavones. A diet containing an ample amount of protein may be a beneficial lifestyle choice for individuals with hypertension; one example is the Dietary Approaches to Stop Hypertension (DASH) diet, which is low in salt and saturated fat; includes whole grains, lean meat, poultry, fish and nuts; and is rich in vegetables, fruits and low-fat dairy products, which are good sources of antioxidant vitamins, minerals and fibre. Including an adequate supply of soy in the diet should also be encouraged.

Figure 1)

Mechanism of hypertension. Hypertension develops from a combination of genetic and lifestyle factors, such as diet. Diets high in salt and sugar, and low in antioxidants and protein, have been implicated in hypertension. Insulin resistance, altered glucose metabolism with an increase in advanced glycation end products (AGEs), increased oxidative stress, decreased bioavailability of nitric oxide (NO), alteration of renin-angiotensin system (RAS) function, altered renal function and endothelial dysfunction are all mechanisms that contribute to the development of hypertension

Figure 2)

Antihypertensive mechanism of cysteine, arginine, glutamate and glutathione (GSH). These amino acids from dietary sources help to lower blood pressure by improving insulin resistance, decreasing oxidative stress, decreasing advanced glycation end product (AGE) formation, improving nitric oxide (NO) bioavailability and modulating the renin-angiotensin system (RAS)

Figure 3)

Antihypertensive mechanism of dietary leucine. Leucine lowers blood pressure by helping to decrease body fat, attenuating insulin resistance and maintaining muscle mass by increasing protein synthesis

Figure 4)

The antihypertensive mechanism of dietary protein and amino acids. The blood pressure-lowering effect of protein is performed by its amino acids. Arginine, cysteine, glutamate, glutathi-one, leucine, taurine and tryptophan all help to attenuate insulin resistance and improve glucose metabolism. This in turn helps to decrease advanced glycation end products (AGEs), improve oxidative stress, decrease vascular intracellular calcium and increase nitric oxide production. This all contributes to improving endothelial function and decreasing peripheral vascular resistance, resulting in decreased blood pressure