Young Chul Kim

Betaine is a methyl donor utilized in regeneration of methionine from homocysteine in a metabolic reaction catalyzed by betaine-homocysteine methyltransferase (BHMT), an enzyme mostly localized in the liver. However, we recently showed that the metabolism of sulfur-containing amino acids in the kidney was also influenced by betaine, which is attributable to elevation of renal methionine availability resulting from an increase in its supply through blood. In this study we investigated the change in pulmonary sulfur-containing amino acid metabolism by betaine and its potential beneficial effect on paraquat (PQ)-induced lung injury. Male rats were provided with betaine for 2 weeks prior to an intratracheal instillation of PQ (0.3 mg/500 μl kg⁻¹). Two weeks after PQ exposure, histopathological assessment revealed severe fibrotic lesions accompanied with elevation of 4-hydroxyproline in the lung, which were all prevented effectively by betaine supplementation. PQ-induced DNA fragmentation in lymphocytes, reduction of oxidant scavenging capacity, expression of heme oxygenase 1 and inducible nitric oxide synthase in the lung, and elevation of serum transforming growth factor beta 1 were also inhibited. PQ instillation increased cysteine, but depleted glutathione in the lung. Betaine supplementation before PQ exposure suppressed the cysteine accumulation and increased the glutathione synthesis. The polyamine synthesis, which requires decarboxylated S-adenosylmethionine as a substrate, was also increased significantly. The results suggest that betaine may enhance pulmonary antioxidant capacity by modulating the metabolism of sulfur-containing amino acids and related substances despite the lack of BHMT in the lung.

We determined the alterations in metabolic conversion of cysteine into glutathione and taurine in liver of rats treated with ethanol acutely. Ethanol treatment reduced cysteine as well as glutathione levels in liver for 24 h. However, cysteine dioxygenase was up-regulated rapidly, and hypotaurine/taurine levels were significantly higher than those found in the saline-treated rats. It is therefore suggested that enhancement of cysteine catabolism into taurine contributes to the depletion of hepatic glutathione, which could exacerbate the ethanol-induced oxidative liver injury.

Earlier studies have shown that betaine administration may modulate the metabolism of sulfur amino acids in the liver. In this study, we determined the changes in the metabolomics of sulfur-containing substances induced by betaine in the kidney, the other major organ actively involved in the transsulfuration reactions. Male rats received betaine (1 %) in drinking water for 2 weeks before killing. Betaine intake did not affect betaine–homocysteine methyltransferase activity or its protein expression in the renal tissue. Expression of methionine synthase was also unchanged. However, methionine levels were increased significantly both in plasma and kidney. Renal methionine adenosyltransferase activity and S-adenosylmethionine concentrations were increased, but there were no changes in S-adenosylhomocysteine, homocysteine, cysteine levels or cystathionine β-synthase expression. γ-Glutamylcysteine synthetase expression or glutathione levels were not altered, but cysteine dioxygenase and taurine levels were decreased significantly. In contrast, betaine administration induced cysteine sulfinate decarboxylase and its metabolic product, hypotaurine. These results indicate that the metabolomics of sulfur-containing substances in the kidney is altered extensively by betaine, although the renal capacity for methionine synthesis is unresponsive to this substance unlike that of the liver. It is suggested that the increased methionine availability due to an enhancement of its uptake from plasma may account for the alterations in the metabolomics of sulfur-containing substances in the kidney. Further studies need to be conducted to clarify the physiological/pharmacological significance of these findings.

It has been known that silymarin exhibits protective activity against oxidative liver injury induced by various hepatotoxicants, but the underlying mechanism of its beneficial action remains unclear. We determined the alterations in sulfur-containing amino acid metabolism induced by silymarin in association with its effects on the antioxidant capacity of liver. Male mice were treated with silymarin (100 or 200 mg/kg, p. o.) every 12 h for a total of 3 doses, and sacrificed 6 h after the final dosing. The hepatic methionine level was increased, but the activity and protein expression of methionine adenosyltransferase were decreased by silymarin in a dose-dependent manner. S-Adenosylmethionine or homocysteine concentration was not changed, whereas the sulfur-containing metabolites generated from homocysteine in the transsulfuration pathway including cystathionine, cysteine, and glutathione were increased significantly. Cystathionine β-synthase was induced, but cysteine dioxygenase was downregulated, both of which would contribute to the elevation of cysteine and its product, glutathione, in liver. Oxygen radical scavenging capacity of liver cytosol against peroxyl radical and peroxynitrite was increased, and also hepatic lipid peroxidation was diminished in the silymarin-treated mice. Taken together, the results demonstrate that silymarin enhances hepatic glutathione generation by elevating cysteine availability via an increment in cysteine synthesis and an inhibition of its catabolism to taurine, which may subsequently contribute to the antioxidant defense of liver.

We studied the significance of alterations in the metabolomics of sulfur-containing substances in rapidly regenerating rat livers. Male rats were subjected to two-thirds partial hepatectomy (PHx), and the changes in hepatic levels of major sulfur-containing amino acids and related substances were monitored for 2 weeks. Liver weight began to increase from 24 h after the surgery, and appeared to recover fully in 2 weeks. Serum alanine aminotransferase and aspartate aminotransferase activities were elevated immediately after the surgery and returned slowly to normal levels in 2 weeks. Methionine, S-adenosylmethionine (SAM), cystathionine and cysteine were increased rapidly and remained elevated for longer than 1 week. Hepatic glutathione concentration was increased gradually for 24 h, and then decreased thereafter, whereas hypotaurine was elevated drastically right after the surgery. Hepatic concentrations of polyamines were altered significantly by PHx. In the hepatectomized livers putrescine concentration was elevated rapidly, reaching a level 40- to 50-fold greater than normal in 6–12 h. Ornithine, the metabolic substrate for putrescine synthesis, was also elevated markedly. Spermidine was increased significantly, whereas spermine was depressed below normal, which appeared to be due to the increased consumption of decarboxylated SAM for spermidine biosynthesis. The results show that the metabolomics of sulfur-containing amino acids and related substances is altered profoundly in regenerating rat livers until the original weight is recovered. Hepatic concentrations of polyamines after PHx are closely associated with the alteration in the metabolomics of sulfur-containing substances. The implication of these changes in the progression of liver regeneration is discussed.

The ability of 80% ethanol extracts from five medicinal plants, Aralia continentalis, Paeonia suffruticosa, Magnolia denudata, Anemarrhena asphodeloides, and Schizonepeta tenuifolia, to neutralize hydroxyl radical, peroxyl radical and peroxynitrite was examined using the total oxyradical scavenging capacity (TOSC) assay. Peroxyl radical was generated from thermal homolysis of 2,2'-azobis (2-methylpropionamidine) dihydrochloride (ABAP) ; hydroxyl radical by an iron-ascorbate Fenton reaction; peroxynitrite by spontaneous decomposition of 3-morpholinosydnonimine N-ethylcarbamide (SIN-1) . The oxidants generated react with α-keto-γ-methiolbutyric acid (KMBA) to yield ethylene, and the TOSC of the substances tested is quantified from their ability to inhibit ethylene formation. Extracts from P. suffruticosa, M. denudata,and S. tenuifolia were determined to be potent peroxyl radical scavenging agents with a specific TOSC (sTOSC) being at least six-fold greater than that of glutathione (GSH) . These three plants also showed sTOSCs toward peroxynitrite markedly greater than sTOSC of GSH, however, only P. suffruticosa revealed a significant hydroxyl radical scavenging capacity. Seven major active constituents isolated from P. suffruticosa, quercetin, (+) -catechin, methyl gallate, gallic acid, benzoic acid, benzoyl paeoniflorin and paeoniflorin, were determined for their antioxidant potential toward peroxynitrite, peroxyl and hydroxyl radicals. Quercetin, (+) -catechin, methyl gallate, and gallic acid exhibited sTOSCs 40~85 times greater than sTOSC of GSH. These four components also showed a peroxynitrite scavenging capacity higher than at least 10-fold of GSH. For antioxidant activity against hydroxyl radical, methyl gallate was greatest followed by gallic acid and quercetin. Further studies need to be conducted to substantiate the significance of scavenging a specific oxidant in the prevention of cellular injury and disease states caused by the reactive free radical species.

The pharmacokinetics and metabolism of KBH-A40, a novel δ-lactam-based histone deacetylase inhibitor, were characterized in male Sprague–Dawley rats. KBH-A40 exhibited a high clearance (12.0 ± 2.8 ...

We determined the ability of extracts and active components isolated from nine medicinal plants, Poncirus trifoliata, Astragalus membranaceus, Magnolia obovata, Salvia miltiorrhiza, Angelica dahurica, Cornus officinalis, Cnidium officinale, Pueraria lobata and Ostericum koreanum, to neutralize peroxyl radicals using the total oxyradical scavenging capacity (TOSC) assay. Peroxyl radicals were generated from thermal homolysis of 2,2′-azobis(2-methylpropionamidine) dihydrochloride, which oxidize α-keto-γ-methiolbutyric acid to yield ethylene, and the TOSC of the substances tested is quantified from their ability to inhibit ethylene formation. Extracts from S. miltiorrhiza, M. obovata and P. lobata were determined to be potent peroxyl radical scavenging agents with a specific TOSC (sTOSC) being at least threefold greater than that of glutathione. Major constituents of the three plants, tanshinone, cryptotanshinone, 15,16-dihydrotanshinone, syringin, honokiol, magnolol, daidzein, puerarin and genistein, were examined for the antioxidant potential toward peroxyl radical. Puerarin and genistein were shown to have μM sTOSCs at least ten-fold greater than sTOSC of glutathione. Daidzein, syringin and honokiol demonstrated the peroxyl radical scavenging capacity comparable to that of glutathione. The implication of peroxyl radical in lipid peroxidation and other cellular damage suggests a possible protective role for the extracts and isolated components in oxidative stress caused by this reactive oxygen species.