Leucine and Hypertension
Leucine is being touted as a key player in this newly uncovered ‘communications hub’ in the brain that controls blood pressure and appears to affect weight gain and blood sugar homeostasis. The branch chain amino acid (BCAA) has, however, long been used by weightlifters and bodybuilders as an anabolic supplement, often alongside the other two branch chain amino acids, valine and isoleucine but sometimes taken in isolation. Mixed into liquid as sports powders before, during and after a workout these amino acids are regarded as an effective tool to boost muscle mass and promote lean weight gain but new evidence suggests that leucine may actually encourage obesity as well as causing serious underlying health consequences working silently against those engaged in such a fitness regime.
Heart Disease and Leucine’s Effect on the Brain
Cardiovascular disease (CVD) remains the leading cause of death in the US and worldwide and chronic hypertension (high blood pressure) is one of the primary factors putting people at risk of CVD. Author of this latest leucine study, Kamal Rahmouni, UI associate professor of pharmacology and internal medicine, and colleagues identified a protein called mTORC1 in the hypothalamus as being significant in the body’s control of blood pressure. The hypothalamus, a small area of the brain, is already known as the control centre for body temperature and blood glucose as well as for other homeostatic processes. Previous research found that activating of the mTORC1 pathway can affect food intake and body weight, causing animals to consume more food that they would ordinarily.
Leucine and Kidney Function
A metabolite of leucine, beta-hydroxy-beta-methylbutyrate (sold as HMB for athletes and bodybuilders), has been found to increase anabolic muscle signalling thus reducing muscle protein breakdown and increasing muscle protein synthesis. Leucine itself has been seen to increase muscle protein synthesis in poultry and other animals, making it a favoured supplement for many food manufacturers looking to boost growth for faster sales of animal products. This rapid growth is not, however, necessarily healthy and the new study, published this month in Cell Metabolism, demonstrated the activation of mTORC1 protein by leucine and the resulting effect of stimulating nerve signals to the kidneys, thus increasing blood pressure quite dramatically as water and nutrients are excreted at a higher rate. Blocking the action of leucine on the mTORC1 protein had the opposite effect, inhibiting the hypertensive action of the BCAA.
mTORC1, Leucine and High Blood Pressure
Patients with high blood pressure have been found to have elevated leucine levels in their blood and this latest research may offer an explanatory mechanism explaining the connection. In addition to the hypertensive effects of mTORC1 activation on the brain/kidney signalling pathway, scientists have also noted that the protein in the hypothalamus affects leptin, a hormone thought to be involved in obesity-related high blood pressure.
How Safe is Leucine?
Leucine is an essential amino acid, meaning that we humans cannot synthesise it ourselves from other amino acids that make up the protein in our foodstuffs. A variety of foods contain plentiful leucine, including nuts, oats, beans, lentils, soy, rice and corn, meaning that it is extremely unlikely that anyone is leucine-deficient if they eat a balanced and varied diet with plenty of plant proteins. When ingested as part of such proteins, leucine is likely to be combined with isoleucine and valine, the other BCAAs, as well as a number of other essential, conditionally essential and non-essential amino acids. Taking leucine supplements may, however, compromise the absorption and use of other amino acids and nutrients, including the BCAAs and certain B vitamins (leucine has been connected to the occurrence of Pellagra in some cases).
Risks and Benefits of Leucine Supplementation
Anyone considering taking such supplements promoted for bodybuilding should first discuss their general health with their physician and closely monitor for signs of cardiovascular disease. Leucine may be essential for healthy muscle-building and the processes of healing and repair in the body, along with a variety of other functions but this newly discovered link between leucine and risk factors for cardiovascular disease certainly warrants caution. It may be that a metabolite of leucine, HMB, is a preferred option to help maintain lean muscle mass, especially in the convalescent, but further research needs to be carried out to establish if this supplement has a similar effect to leucine, now suspected of raising the risk of heart disease.
Shannon M. Harlan, Deng-Fu Guo, Donald A. Morgan, Caroline Fernandes-Santos, Kamal Rahmouni.Hypothalamic mTORC1 Signaling Controls Sympathetic Nerve Activity and Arterial Pressure and Mediates Leptin Effects. Cell Metabolism, 2013; 17 (4).
Wang, S., Khondowe, P., et al, Effects of “Bioactive” amino acids leucine, glutamate, arginine and tryptophan on feed intake and mRNA expression of relative neuropeptides in broiler chicks, J Anim Sci Biotechnol. 2012; 3(1): 27.
López N, Sánchez J, Picó C, Palou A, Serra F., Dietary l-leucine supplementation of lactating rats results in a tendency to increase lean/fat ratio associated to lower orexigenic neuropeptide expression in hypothalamus. Peptides. 2010 Jul;31(7):1361-7.
Wilkinson DJ, Hossain T, Hill DS, Phillips BE, Crossland H, Williams J, Loughna P, Churchward-Venne TA, Breen L, Phillips SM, Etheridge T, Rathmacher JA,Smith K, Szewczyk NJ, Atherton PJ. Effects of Leucine and its metabolite, β-hydroxy-β-methylbutyrate (HMB) on human skeletal muscle protein metabolism. J Physiol. 2013 Apr 8.