Sports food manufacturers do nothing with the amino acid glycine. To them glycine is at best a pricey filling agent. But this image is not justified, according to an animal study that physiologists at the University of Melbourne published in Clinical Nutrition. According to their study, glycine has an anticatabolic effect.
The figure below summarises what we know about the way the human body metabolises glycine. Glycine functions as a raw material for bile salts, purines, glutathione and even glucose, and can be created from other amino acids.
Less well known is that glycine inhibits inflammatory processes [Curr Opin Clin Nutr Metab Care. 2003 Mar;6(2):229-40.] and protects muscle tissue from withering when the blood circulation falters. [Curr Pharm Des. 2006;12(23):2953-67.] Because of these effects, the Australian researcher Daniel Ham wondered whether glycine might help against cachexia: the catabolic processes that arise in advanced forms of cancer.
Ham injected mice with aggressive tumour cells, and then gave the animals daily glycine injections. Glycine is also easily absorbed orally, so there would be no objection to administering it mixed with food. But Ham used injections to get round the problem of reduced appetite as a result of the cancer.
The daily dose was 1 g glycine per kg bodyweight. Converted to adult humans that would amount to 7-10 g glycine per day.
Administering glycine protected the muscle mass from breakdown and prevented a decline in muscle strength, Ham observed after three weeks.
Glycine supplementation inhibited the activity of catabolic genes such as Atrogin-1 in the muscles.
Ham repeated his experiments with the amino acids alanine and citrulline. These did not offer the muscles any protection. Glycine also inhibited the growth of the tumours and neither of the other amino acids had that effect. Citrulline actually speeded up the growth of the tumour.
“Regardless of the specific mechanism, glycine represents a potential treatment for cancer cachexia, either in isolation or in combination with other nutrients”, the researchers conclude. “Glycine provides protection against cancer-induced reductions in skeletal muscle size and function, reduces the oxidative and inflammatory burden, and reduces the expression of genes associated with muscle protein breakdown in cancer cachexia.”
It’s just possible that glycine would have similar effects in athletes. Perhaps pre-workout products containing – for example – glycine and BCAAs could do interesting things for bodybuilders’ progression.
Glycine administration attenuates skeletal muscle wasting in a mouse model of cancer cachexia.
BACKGROUND AND AIMS:
The non-essential amino acid, glycine, is often considered biologically neutral, but some studies indicate that it could be an effective anti-inflammatory agent. Since inflammation is central to the development of cancer cachexia, glycine supplementation represents a simple, safe and promising treatment. We tested the hypothesis that glycine supplementation reduces skeletal muscle inflammation and preserves muscle mass in tumor-bearing mice.
To induce cachexia, CD2F1 mice received a subcutaneous injection of PBS (control, n = 12) or C26 tumor cells (n = 32) in accordance with the protocols developed by Murphy et al. [Murphy KT, Chee A, Trieu J, Naim T, Lynch GS. Importance of functional and metabolic impairments in the characterization of the C-26 murine model of cancer cachexia. Dis Models Mech 2012;5(4):533-545.]. Subcutaneous injections of glycine (n = 16) or PBS (n = 16) were administered daily for 21 days and at the conclusion of treatment, selected muscles, tumor and adipose tissue were collected and prepared for Real-Time RT-PCR or western blot analysis.
Glycine attenuated the loss of fat and muscle mass, blunted increases in markers of inflammation (F4/80, P = 0.01 & IL-6 mRNA, P = 0.01) and atrophic signaling (MuRF, P = 0.047; atrogin-1, P = 0.04; LC3B, P = 0.06 and; BNIP3, P = 0.10) and tended to attenuate the loss of body mass (P = 0.07), muscle function (P = 0.06), and oxidative stress (GSSG/GSH, P = 0.06 and DHE, P = 0.07) seen in tumor-bearing mice. Preliminary studies that compared the effect of glycine administration with isonitrogenous doses of alanine or citrulline showed that the observed protective effect was specific to glycine.
Glycine protects skeletal muscle from cancer-induced wasting and loss of function, reduces the oxidative and inflammatory burden, and reduces the expression of genes associated with muscle protein breakdown in cancer cachexia. Importantly, these effects were glycine specific.
PMID: 23835111 [PubMed – in process]