Effect of glycine on tissue fatty acid composition in an experimental model of alcohol-induced hepatotoxicity

Integration of proteomics and metabolomics reveals energy and metabolic alterations induced by glucokinase (GCK) partial inactivation in hepatocytes

AIMS

Glucokinase (GCK) acts as the glucose sensor in maintaining glucose homeostasis. The inactivating mutation of the GCK gene leads to glucokinase-maturity onset diabetes of the young (GCK-MODY). This study aims to gain further insights into the molecular alterations triggered by GCK partial inactivation in hepatocytes, potentially underlying the favorable prognosis of GCK-MODY.

MAIN METHODS

A GCK knockdown HepG2 cell model was established, and the integration of proteomics and metabolomics was used to gain a comprehensive understanding of the molecular pathway changes caused by GCK inactivation in the liver.

KEY FINDINGS

Proteomic analysis identified 257 differential proteins. KEGG pathway enrichment analysis showed that protein expression changes in the GCK knockdown group were significantly enriched in central carbon metabolism, the TCA cycle, amino acid metabolism and the oxidative phosphorylation pathway. Among them, enzymes in the TCA cycle (PC, IDH2, SDH) were significantly downregulated in GCK-knockdown group. Targeted metabolomics revealed that in the GCK knockdown hepatocytes, TCA cycle intermediates were significantly decreased, including pyruvate, oxaloacetate, citrate and succinic acid, and three metabolites increased including glycine, betaine and homocysteine. These metabolic alterations in turn reduced the accumulation of reactive oxygen species in GCK knockdown hepatocytes. Correlation analysis indicated that TCA cycle metabolites were positively correlated with proteins involved in the TCA cycle, carbon metabolism, glycolysis, Ras signaling, fibrosis and inflammation.

SIGNIFICANCE

In conclusion, GCK knockdown reduced TCA cycle flux and oxidative stress in hepatocytes by influencing the levels of key transcription factors and enzymes, providing a comprehensive understanding of the effects of GCK partial inactivation on liver metabolism and molecular mechanisms.

Multifarious Beneficial Effect of Nonessential Amino Acid, Glycine: A Review

Glycine is most important and simple, nonessential amino acid in humans, animals, and many mammals. Generally, glycine is synthesized from choline, serine, hydroxyproline, and threonine through interorgan metabolism in which kidneys and liver are the primarily involved. Generally in common feeding conditions, glycine is not sufficiently synthesized in humans, animals, and birds. Glycine acts as precursor for several key metabolites of low molecular weight such as creatine, glutathione, haem, purines, and porphyrins. Glycine is very effective in improving the health and supports the growth and well-being of humans and animals. There are overwhelming reports supporting the role of supplementary glycine in prevention of many diseases and disorders including cancer. Dietary supplementation of proper dose of glycine is effectual in treating metabolic disorders in patients with cardiovascular diseases, several inflammatory diseases, obesity, cancers, and diabetes. Glycine also has the property to enhance the quality of sleep and neurological functions. In this review we will focus on the metabolism of glycine in humans and animals and the recent findings and advances about the beneficial effects and protection of glycine in different disease states.

Protective effect of puerarin on rats with alcoholic hepatitis

AIM: To investigate mechanism of puerarin on alcoholic hepatitis in rats.

METHODS: Twenty-one Wistar rats were divided into three groups randomly, with intragastric administration of the control group by corn oil + 500 g/L glucose 20 mL/(kg•d); intragastric administration of the model group by 400 mL/L alcohol 8 g/(kg•d)+ corn oil; peritoneal injection of the puerarin group by puerarin 5 mg/(kg•d); After thirty days. Serum and liver tissue samples were prepared, and the levels of alanine transaminase (ALT), aspartate transaminase (AST), and γ-glutamyltranspeptidase (GST) were determined by chromatometry, serum PGE2, TNF-α and IL-6 by radioimmunity method, and COX-2 expression on the hepatic tissue by Western blot. Pathological changes on hepatic tissue was determined by light microscopy.

RESULTS: The serum ALT, AST and GST was significantly higher in model group than in control group (107.5 ± 6.81 vs 33.20 ± 10.55, 138.29 ± 9.72 vs 47.86 ± 14.3, 3.57 ± 0.53 vs 1.43 ± 0.43, all P < 0.01). The serum ALT and AST was significantly lower in puerarin group than in model group (52.33 ± 13.19, 63.33 ± 7.03, P < 0.01). The serum GST level was lower, but not significantly. The levels of serum PGE2, TNF-α and IL-6 were significantly higher in model group than in control group (274.13 ± 26.15 vs 193.84 ± 23.97, 1.85 ± 0.11 vs 0.90±0.18, 68.07 ± 12.64 vs 40.50 ± 5.09, all P < 0.01), and the levels of the serum PGE2, TNF-α and IL-6 were significantly lower in puerarin group than in model group (227.05 ± 21.55, 1.35 ± 0.19, 53.16 ± 5.62, all P < 0.01). Expression of COX-2, was weak, but had high expression in model group(P < 0.01). The expression of COX-2 in puerarin group was down regulated, compared with model group (P < 0.01).

CONCLUSION: Puerarin has effects on hepatic injury in alcoholic hepatitis.

Effect of dietary epigallocatechin-3-gallate on cytochrome P450 2E1-dependent alcoholic liver damage: enhancement of fatty acid oxidation

This study was designed to determine whether dietary epigallocatechin-3-gallate (EGCG), the most abundant catechin polyphenol in green tea, can protect the liver from cytochrome P450 2E1 (CYP2E1)-dependent alcoholic liver damage. Compared with an ethanol group, when EGCG was present in the ethanol diet, the formation of a fatty liver was significantly reduced and the serum aspartate transaminase (AST) and alanine transaminase (ALT) levels were much lower. Ethanol treatment significantly elevated hepatic CYP2E1 expression while simultaneously reducing hepatic phospho-acetyl CoA carboxylase (p-ACC) and carnitine palmitoyl-transferase 1 (CPT-1) levels. While EGCG markedly reversed the effect of ethanol on hepatic p-ACC and CPT-1 levels, it had no effect on the ethanol-induced elevation in CYP2E1 expression. EGCG prevents ethanol-induced hepatotoxicity and inhibits the development of a fatty liver. These effects were associated with improvements in p-ACC and CPT-1 levels. The use of EGCG might be useful in treating patients with an alcoholic fatty liver.