Protective Glycine

Also see:
Thyroid peroxidase activity is inhibited by amino acids
Gelatin, Glycine, and Metabolism
Gelatin > Whey

The selection of proteins should minimize the amino acids tryptophan (which is the precursor of serotonin) and cysteine (which, like tryptophan, suppresses thyroid function, by including gelatin and fruits. Gelatin is 22% glycine, which protects the lungs and other organs against toxins and inflammatory agents, and many fruits are “deficient” in tryptophan and cysteine. -Ray Peat, PhD

Am J Physiol. 1999 Nov;277(5 Pt 1):L952-9.
Production of superoxide and TNF-alpha from alveolar macrophages is blunted by glycine.
Wheeler MD, Thurman RG.
Glycine blunts lipopolysaccharide (LPS)-induced increases in intracellular calcium concentration ([Ca(2+)](i)) and tumor necrosis factor-alpha (TNF-alpha) production by Kupffer cells through a glycine-gated chloride channel. Alveolar macrophages, which have a similar origin as Kupffer cells, play a significant role in the pathogenesis of several lung diseases including asthma, endotoxemia, and acute inflammation due to inhaled bacterial particles and dusts. Therefore, studies were designed here to test the hypothesis that alveolar macrophages could be inactivated by glycine via a glycine-gated chloride channel. The ability of glycine to prevent endotoxin [lipopolysaccharide (LPS)]-induced increases in [Ca(2+)](i) and subsequent production of superoxide and TNF-alpha in alveolar macrophages was examined. LPS caused a transient increase in intracellular calcium to nearly 200 nM, with EC(50) values slightly greater than 25 ng/ml. Glycine, in a dose-dependent manner, blunted the increase in [Ca(2+)](i), with an IC(50) less than 100 microM. Like the glycine-gated chloride channel in the central nervous system, the effects of glycine on [Ca(2+)](i) were both strychnine sensitive and chloride dependent. Glycine also caused a dose-dependent influx of radiolabeled chloride with EC(50) values near 10 microM, a phenomenon which was also inhibited by strychnine (1 microM). LPS-induced superoxide production was also blunted in a dose-dependent manner by glycine and was reduced approximately 50% with 10 microM glycine. Moreover, TNF-alpha production was also inhibited by glycine and also required nearly 10 microM glycine for half-inhibition. These data provide strong pharmacological evidence that alveolar macrophages contain glycine-gated chloride channels and that their activation is protective against the LPS-induced increase in [Ca(2+)](i) and subsequent production of toxic radicals and cytokines.

Am J Physiol Regul Integr Comp Physiol. 2004 Dec;287(6):R1387-93. Epub 2004 Aug 26.
Glycine intake decreases plasma free fatty acids, adipose cell size, and blood pressure in sucrose-fed rats.
El Hafidi M, Pérez I, Zamora J, Soto V, Carvajal-Sandoval G, Baños G.
The study investigated the mechanism by which glycine protects against increased circulating nonesterified fatty acids (NEFA), fat cell size, intra-abdominal fat accumulation, and blood pressure (BP) induced in male Wistar rats by sucrose ingestion. The addition of 1% glycine to the drinking water containing 30% sucrose, for 4 wk, markedly reduced high BP in sucrose-fed rats (SFR) (122.3 +/- 5.6 vs. 147.6 +/- 5.4 mmHg in SFR without glycine, P < 0.001). Decreases in plasma triglyceride (TG) levels (0.9 +/- 0.3 vs. 1.4 +/- 0.3 mM, P < 0.001), intra-abdominal fat (6.8 +/- 2.16 vs. 14.8 +/- 4.0 g, P < 0.01), and adipose cell size were observed in SFR treated with glycine compared with SFR without treatment. Total NEFA concentration in the plasma of SFR was significantly decreased by glycine intake (0.64 +/- 0.08 vs. 1.11 +/- 0.09 mM in SFR without glycine, P < 0.001). In control animals, glycine decreased glucose, TGs, and total NEFA but without reaching significance. In SFR treated with glycine, mitochondrial respiration, as an indicator of the rate of fat oxidation, showed an increase in the state IV oxidation rate of the beta-oxidation substrates octanoic acid and palmitoyl carnitine. This suggests an enhancement of hepatic fatty acid metabolism, i.e., in their transport, activation, or beta-oxidation. These findings imply that the protection by glycine against elevated BP might be attributed to its effect in increasing fatty acid oxidation, reducing intra-abdominal fat accumulation and circulating NEFA, which have been proposed as links between obesity and hypertension.

Am J Physiol Lung Cell Mol Physiol. 2000 Aug;279(2):L390-8.
Dietary glycine blunts lung inflammatory cell influx following acute endotoxin.
Wheeler MD, Rose ML, Yamashima S, Enomoto N, Seabra V, Madren J, Thurman RG.
Mortality associated with endotoxin shock is likely mediated by Kupffer cells, alveolar macrophages, and circulating neutrophils. Acute dietary glycine prevents mortality and blunts increases in serum tumor necrosis factor-alpha (TNF-alpha) following endotoxin in rats. Furthermore, acute glycine blunts activation of Kupffer cells, alveolar macrophages, and neutrophils by activating a glycine-gated chloride channel. However, in neuronal tissue, glycine rapidly downregulates chloride channel function. Therefore, the long-term effects of a glycine-containing diet on survival following endotoxin shock were investigated. Dietary glycine for 4 wk improved survival after endotoxin but did not improve liver pathology, decrease serum alanine transaminase, or effect TNF-alpha levels compared with animals fed control diet. Interestingly, dietary glycine largely prevented inflammation and injury in the lung following endotoxin. Surprisingly, Kupffer cells from animals fed glycine for 4 wk were no longer inactivated by glycine in vitro; however, isolated alveolar macrophages and neutrophils from the same animals were sensitive to glycine. These data are consistent with the hypothesis that glycine downregulates chloride channels on Kupffer cells but not on alveolar macrophages or neutrophils. Importantly, glycine diet for 4 wk protected against lung inflammation due to endotoxin. Chronic glycine improves survival by unknown mechanisms, but reduction of lung inflammation is likely involved.

Glycine protects against fat accumulation in the alcohol-induced liver injury (Senthilkumar, et al., 2003), suggesting that dietary gelatin would complement the protective effects of saturated fats. -Ray Peat, PhD

Both proline and glycine (which are major amino acids in gelatin) are very protective for the liver, increasing albumin, and stopping oxidative damage. -Ray Peat, PhD

Pol J Pharmacol. 2003 Jul-Aug;55(4):603-11.
Glycine modulates hepatic lipid accumulation in alcohol-induced liver injury.
Senthilkumar R, Viswanathan P, Nalini N.
We studied the effect of administering glycine, a non-essential amino acid, on serum and tissue lipids in experimental hepatotoxic Wistar rats. All the rats were fed standard pellet diet. Hepatotoxicity was induced by administering ethanol (7.9 g kg(-1)) for 30 days by intragastric intubation. Control rats were given isocaloric glucose solution. Glycine was subsequently administered at a dose of 0.6 g kg(-1) every day by intragastric intubation for the next 30 days. Average body weight gain at the end of the total experimental period of 60 days was significantly lower in rats supplemented with alcohol, but improved on glycine treatment. Feeding alcohol significantly elevated the levels of cholesterol, phospholipids, free fatty acids and triglycerides in the serum, liver and brain as compared with those of the control rats. Subsequent glycine supplementation to alcohol-fed rats significantly lowered the serum and tissue lipid levels to near those of the control rats. Microscopic examination of alcohol-treated rat liver showed inflammatory cell infiltrates and fatty changes, which were alleviated on treatment with glycine. Alcohol-treated rat brain demonstrated edema, which was significantly lowered on treatment with glycine. In conclusion, this study shows that oral administration of glycine to alcohol-supplemented rats markedly reduced the accumulation of cholesterol, phospholipids, free fatty acids and triglycerides in the circulation, liver and brain, which was associated with a reversal of steatosis in the liver and edema in the brain.

Eur Rev Med Pharmacol Sci. 2012 Jun;16(6):728-36.
Glycine alleviates liver injury induced by deficiency in methionine and or choline in rats.
Barakat HA, Hamza AH.
OBJECTIVES:
Nonalcoholic steatohepatitis (NASH) is an advanced stage of non-alcoholic fatty liver disease (NAFLD) from steatosis. Methionine and choline are important amino acids play a key role in many cellular functions. Glycine is a non-essential amino acid having multiple roles in many reactions. This study aimed to investigate liver damage induced by feeding male albino rats either methionine deficient (MD), choline deficient (CD), or MCD diets. And to clarify the alleviatory effect of dietary glycine supplementation (5%) on reduced complications caused by feeding each of the deficient diets.
MATERIAL AND METHODS:
Nutritional status, liver functions, lipids profile, hepatic oxidative stress, hepatic antioxidant enzymes, tumor markers and hepatic fatty acid transport protein gene were assessed.
RESULTS:
Rats fed with either MD or MCD diet had less body weight gain unlike rats fed the CD diet. Liver injury was detected in deficient groups by elevating plasma ALT, AST, ALP, total and direct bilirubin, albumin and protein levels. Lipid accumulation was more prominent in rats fed the MCD or CD diet than in those fed the MD diet. Fatty acid transport protein (FATP) was significantly elevated in the different glycine supplemented groups.
CONCLUSION:
Oral administration of glycine confers a significant protective effect by optimizing all the assessed parameters and gene expression.

Hepatology. 2000 Sep;32(3):542-6.
Glycine prevents apoptosis of rat sinusoidal endothelial cells caused by deprivation of vascular endothelial growth factor.
Zhang Y, Ikejima K, Honda H, Kitamura T, Takei Y, Sato N.
Apoptosis of sinusoidal endothelial cells (SECs) is one of the initial events in the development of ischemia-reperfusion injury of the liver. Glycine has been shown to diminish ischemia-reperfusion injury in the liver and improve graft survival in the rat liver transplantation model. Here, we investigated the effect of glycine on apoptosis of primary cultured rat SECs induced by vascular endothelial growth factor (VEGF) deprivation. Isolated rat SECs were cultured in EBM-2 medium supplemented with 10% fetal bovine serum (FBS) and growth factors including 20 ng/mL VEGF for 3 days. SECs at 3 days of culture showed spindle-like shapes; however, cells started shrinking and detaching from dishes by VEGF deprivation. Apoptosis was detected by terminal deoxynucleotidyl transferase (TdT)-mediated d-uridine triphosphate (dUTP)-biotin nick end labeling (TUNEL) staining in these conditions. Control SECs contained only a few percent of TUNEL-positive cells; however, they started increasing 4 hours after VEGF deprivation, and the percentage of TUNEL-positive cells reached about 50% at 8 hours and almost 100% at 16 hours after VEGF deprivation. Interestingly, this increase in TUNEL-positive cells after VEGF deprivation was prevented significantly when glycine (1-10 mmol/L) was added to the medium, the levels being around 60% of VEGF deprivation without glycine. Furthermore, strychnine (1 micromol/L), a glycine receptor antagonist, inhibited this effect of glycine, suggesting the possible involvement of the glycine receptor/chloride channel in the mechanism. Moreover, Bcl-2 protein levels in SECs were decreased 8 hours after VEGF deprivation, which was prevented almost completely by glycine. It is concluded that glycine prevents apoptosis of primary cultured SECs under VEGF deprivation.