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If leucine isn't stimulating muscle growth, try combining it with glycine

All bodybuilders and fitness fanatics know leucine. Many studies have shown that it stimulates anabolic processes in muscle cells, but others suggest that leucine doesn't always work. Aging, long periods of inactivity and other conditions under which the body produces large amounts of inflammatory factors and oxidants can eliminate the anabolic effect of leucine. Under these circumstances, adding glycine as a supplement may offer a solution, Australian physiologists discovered.

Leucine & glycine

Leucine stimulates the anabolic machinery of muscle cells, but it's not a magic bullet. Leucine only works in combination with other essential amino acids, and probably not during caloric restriction. For other posts on leucine click here.

Glycine is a non-essential amino acid that sports scientists generally don't pay much attention to, but according to recent studies it does actually have some interesting characteristics. Some basic research studies suggest that glycine rejuvenates old cells and protects muscle tissue against breakdown caused by cancer, probably because glycine blocks inflammatory factors. For other posts on glycine click here.

In their publication, which has been published in the American Journal of Physiology - Endocrinology and Metabolism, the researchers write that they injected mice with lipopolysaccharide [LPS]. This substance induces a cascade of inflammatory processes that prevent muscle tissue from being able to grow and also make it insensitive to nearly all anabolic stimuli.

Some of the lab animals were given the amino acid alanine [ALA] a few hours before being given lipopolysaccharide. Alanine has an anti-inflammatory effect. Another group of animals were given glycine.

Several hours after administration the researchers gave the mice leucine, and then looked at the effects this had on the animals' muscle tissue.

The administration of lipopolysaccharide inhibited the muscle growth and synthesis of muscle proteins. The combination of leucine and glycine neutralised this effect to a large extent.

If leucine isn't stimulating muscle growth, try combining it with glycine

If leucine isn't stimulating muscle growth, try combining it with glycine

CON = mice given no lipopolysaccharide, no alanine and no glycine.

Lipopolysaccharide inhibited the key anabolic molecule mTOR, but the leucine-glycine combination neutralised this effect.

If leucine isn't stimulating muscle growth, try combining it with glycine

"Our data show that glycine can restore the anabolic response to leucine during acute inflammation in skeletal muscle", the researchers wrote. "These observations support the view that attempting to stimulate protein synthesis by increasing leucine availability alone constitutes an ineffective strategy to counteract anabolic resistance in muscle wasting conditions."

"Further work is required to elucidate the key signaling pathways responsible for the beneficial effect of glycine."

"The identification of glycine as a novel nutritional intervention to restore the anabolic sensitivity of skeletal muscle to leucine has potential implications for a range of muscle wasting conditions."

The researchers administered the leucine and glycine in a ratio of 1:2. If we were to make an estimate of a human equivalent of the doses used, we'd say 4-5 g leucine and 8-10 g glycine.

Am J Physiol Endocrinol Metab. 2016 Jun 1;310(11):E970-81.

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Nutrition & Strength Training
Amino Acids