Inhibition of microsomal lipid peroxidation by α-tocopherol and α-tocopherol acetate

1. The antioxidant effects of α-tocopherol and α-tocopherol acetate were assayed for the (a) oxygen uptake, (b) chemiluminescence and (c) malondialdehyde formation, of tert-butyl hydroperoxide-supplemented rat liver microsomes.

2. Oxygen uptake was inhibited 60% by both α-tocopherol and α-tocopherol acetate with the half-maximal effect at 5 nmol tocopherol/mg protein. Chemiluminescence and malondialdehyde formation were equally inhibited 35% by both tocopherols with half-maximal effects at 2 nmol tocopherol/mg protein.

3. The rate of O₂ uptake by tocopherol-supplemented microsomes was dependent on O₂ concentration. A 60% inhibition by 5 nmol tocopherol/mg protein at 0.2 mM O₂ is decreased to 5% inhibition at 0.6 mM O₂.

4. The inhibition of O₂ uptake, chemiluminescence and malondialdehyde formation indicate that both α-tocopherol and α-tocopherol acetate have similar effects as free radical traps in the hydrophobic domain of biomembranes. The different inhibition observed at different O₂ concentrations indicate competition between vitamin E and O₂ by unoxygenated lipid radicals.     

Protective effects of α-tocopherol and ischemic preconditioning on hepatic reperfusion injury

This study evaluated the effect of alpha-tocopherol (alpha-TC), ischemic preconditioning (IPC) or a combination on the extent of mitochondrial injury caused by hepatic ischemia/reperfusion (I/R). Rats were pretreated with alpha-TC (20 mg/kg per day, i.p.) for 3 days before sustained ischemia. A rat liver was preconditioned with 10 min of ischemia and 10 min of reperfusion, and was then subjected to 90 min of ischemia followed by 5 h or 24 h of reperfusion. I/R increased the aminotransferase activity and mitochondrial lipid peroxidation, whereas it decreased the mitochondrial glutamate dehydrogenase activity. alpha-TC and IPC individually attenuated these changes. alpha-TC combined with IPC (alpha-TC+IPC) did not further attenuate the changes. The mitochondrial glutathione content decreased after 5 h reperfusion. This decrease was attenuated by alpha-TC, IPC, and alpha-TC+IPC. The significant production of peroxides observed after 10 min reperfusion subsequent to sustained ischemia was attenuated by alpha-TC, IPC, and alpha-TC+IPC. The mitochondria isolated after I/R were rapidly swollen. However, this swelling rate was reduced by alpha-TC, IPC, and alpha-TC+IPC. These results suggest that either alpha-TC or IPC reduces the level of mitochondrial damage associated with oxidative stress caused by hepatic I/R, but alpha-TC combined with IPC offers no significant additional protection.     

Dietary α-tocopherol prevents dehydroepiandrosterone-induced lipid peroxidation in rat liver microsomes and mitochondria

Dehydroepiandrosterone (DHEA), an adrenal steroid, causes lipid peroxidation in rat liver microsomes and mitochondria and induces hepatocarcinogenesis. It was investigated whether α-tocopherol, a naturally occurring free radical chain terminator, could decrease lipid peroxidation. When DHEA-free diet supplemented with increasing concentrations of α-tocopherol (25, 50, 100, 200, 400 and 1000 mg/kg diet) was fed to rats for 7 days, a marked lipid peroxidation (measured as thiobarbituric acid reactive substances formation) was observed at concentrations 25 and 50 mg/kg in liver microsomes and mitochondria isolated from these animals. Lipid peroxidation was significantly reduced at concentrations ≥ 100 mg/kg. When DHEA (500 mg/kg diet) was fed to rats simultaneously with increasing concentrations of α-tocopherol, strong lipid peroxidation was observed at a-tocopherol concentrations ≤ 200 mg/kg diet. However, microsomes and mitochondria isolated from livers of rats fed a-tocopherol at doses of 400 and 1000 mg/kg diet produced only negligible amounts of thiobarbituric acid reactive substances. The data show that high concentrations of α-tocopherol in the diet decrease DHEA-induced microsomal and mitochondrial lipid peroxidation. Our results support the concept thatα-tocopherol can protect against DHEA-induced lipid peroxidation and consequently against steroid-induced liver cell damage and, perhaps, also tumour development.     

Effects of BHA,d-α-tocopherol and retinol acetate on TCDD-mediated changes in lipid peroxidation,glutathione peroxidase activity and survival

1. Daily treatment of female rats with butylated hydroxyanisole (BHA) protected against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity. This protective effect was associated with reduced microsomal lipid peroxidation, increased glutathione peroxidase (GSH-PX) activity and decreased aryl hydrocarbon hydroxylase (AHH) activity.

2. Retinol acetate (vitamin A) inhibited lipid peroxidation, elevated GSH-PX activity, and enhanced AHH activity. Thirty per cent of vitamin A-treated animals were alive 25 d after a lethal dose of TCDD.

3. d-α-Tocopherol (vitamin E) inhibited markedly microsomal lipid peroxidation, enhanced AHH activity, and had no effect on GSH-PX activity. Only 10% of the vitamin E-treated animals were alive 25 d after a lethal dose of TCDD.

4. The mechanism of TCDD toxicity may involve in part inhibition of GSH-PX activity with resultant lipid peroxidation by hydrogen peroxide.     

Melatonin prevents endothelial dysfunction in SLE by activating the nuclear receptor retinoic acid-related orphan receptor-α

Atherosclerotic cardiovascular disease confers significant morbidity and mortality in patients with systemic lupus erythematosus (SLE). A substantial proportion of patients with SLE display accelerated endothelial dysfunction, which precedes cardiovascular disease. Melatonin and its nuclear receptor retinoid-related orphan receptor alpha (RORα) have been reported to have some protective effects on the development of atherosclerosis. However, the function of melatonin in SLE-induced endothelial dysfunction and the role that RORα plays are still unknown. In this study, we found that RORα protein expression was decreased in aortas of lupus-prone mice and in human umbilical vein endothelial cells (HUVECs) cultured with medium containing sera of patients with SLE. Melatonin-treated HUVECs showed a decrease of pro-inflammatory mRNAs [interleukin-1beta (IL-1β), interferon-gamma (IFN-γ), and tumor necrosis factor-alpha (TNF-α)] under the stimulation of SLE medium. Melatonin increased nitric oxide and antioxidant mRNAs (SOD1, GPX1, and CAT) and downregulated reactive oxygen species (ROS) level in HUVECs, which may subsequently delay endothelial senescence and promote HUVEC proliferation and repair after injury. Melatonin inhibited SLE medium-induced RAW264.7 macrophage migration. HUVECs pretreated with melatonin expressed less adhesion-related proteins (ICAM-1 and VCAM-1); as a result, these cells adhered to fewer peripheral blood monocytes. In addition, we also showed that the protective effects of melatonin on endothelial cells were largely diminished when RORα was knockdown in HUVECs. In conclusion, by targeting the nuclear receptor RORα, melatonin preserves normal functions of endothelium in SLE by its anti-inflammatory, antioxidant, and anti-senescence effects. RORα may have the potential to become a prophylactic or therapeutic target in preventing endothelial dysfunction and atherosclerotic cardiovascular disease in patients with SLE.     

Inhibition of calpain prevents NMDA-induced cell death and β-amyloid-induced synaptic dysfunction in hippocampal slice cultures

Background and purpose:

Alzheimer''s disease (AD) is a multifactorial, neurodegenerative disease, which is in part caused by an impairment of synaptic function, probably mediated by oligomeric forms of amyloid-β (Aβ). While the Aβ pathology mainly affects the physiology of neurotransmission, neuronal decline is caused by excitotoxic cell death, which is mediated by the NMDA receptor. A comprehensive therapeutic approach should address both Aβ-induced synaptic deficits, as well as NMDA receptor-mediated neurodegeneration, via one molecular target. This study was designed to test whether calpain could be involved in both pathological pathways, which would offer a promising avenue for new treatments.

Experimental approach:

Application of the specific, water-soluble calpain inhibitor A-705253 was used to inhibit calpain in hippocampal slice cultures. We examined whether inhibition of calpain would prevent Aβ-induced deficits in neurotransmission in CA1, as well as NMDA-induced neuronal cell death.

Key results:

A-705253 dose-dependently prevented excitotoxicity-induced neurodegeneration at low nanomolar concentrations, determined by propidium iodide histochemistry. Inhibition of the NMDA receptor similarly protected from neuronal damage. Caspase staining indicated that calpain inhibition was protective by reducing apoptosis. Electrophysiological analysis revealed that inhibition of calpain by A-705253 also fully prevented Aβ oligomer-induced deficits in neurotransmission. The protective effect of calpain was compared to the clinically available NMDA receptor antagonist memantine, which was also effective in this model.

Conclusions and implications:

We suggest that inhibition of calpain exhibits a promising strategy to address several aspects of the pathology of AD that may go beyond the available therapeutic intervention by memantine.     

Different starting times of α-tocopherol and γ-tocotrienol supplementation and tumor marker enzyme activities in-the rat chemically induced with cancer

• 1.1. α-Tocopherol (α-T) and γ-tocotrienol (γ-T) were supplemented continuously for 8 weeks in the diets of normal rats and rats chemically induced with cancer using diethylnitrosamine (DEN), 2-acetylaminofluorene (AAF) and partial hepatectomy. Hepatocarcinogenesis was followed by determining the plasma γ-glutamyl-transpeptidase (GGT) and alkaline phosphatase (ALP) activities as well as placental glutathione S-transferase (PGST) and GGT activities histochemically, at 4-week intervals.
• 2.2. Male Rattus norvegicus were supplemented α-T and γ-T at two different doses of 30 and 300 mg/kg diet. The supplementation was started at three different times: simultaneously with DEN administration; 4 weeks; and 8 weeks after DEN administration.
• 3.3. Elevation of plasma GGT activities and formation of PGST and GGT positive foci were attenuated significantly (P< 0.05) when α-T and γ-T were supplemented simultaneously with cancer induction. Supplementation begun 4 and 8 weeks after cancer induction did not affect plasma enzyme activities and formation of enzyme-positive foci.
• 4.4. α-T was more effective than γ-T, and a lower dose of 30 mg/kg was found to be more effective in reducing the severity of hepatocarcinogenesis.

     

Olive oil supplementation prevents extracellular matrix deposition and reduces prooxidant markers and apoptosis in the offspring´s heart of diabetic rats

Maternal diabetes induces fetal programming of cardiovascular diseases. Diabetes induced-cardiac fibrosis is a process that may start in utero and may be related to the prooxidant/proinflammatory environment. The aim of this study was to investigate the effect of a maternal diet enriched in olive oil on the levels of components and regulators of the extracellular matrix, on prooxidant markers and on apoptosis rate in the heart of 21-day-old offspring of diabetic rats. Maternal diabetes was induced by neonatal administration of streptozotocin. During pregnancy, diabetic and control rats were fed with diets supplemented or not with 6% olive oil. The heart of the offspring was studied at 21 days of age. We found increased deposition of collagen IV and fibronectin in the offspring´s heart of diabetic rats, which was prevented by the maternal diets enriched in olive oil. Increases in connective tissue growth factor were also prevented by the maternal diets enriched in olive oil. Prooxidant markers as well as apoptosis, which were increased in the heart of the offspring of diabetic rats, were prevented by the maternal olive oil dietary treatment. Our findings identified powerful effects of a maternal diet enriched in olive oil on the prevention of increased extracellular matrix deposition and increased prooxidant markers in the heart of 21-day-old offspring of diabetic rats.     

CCM111 prevents hepatic fibrosis via cooperative inhibition of TGF-β, Wnt and STAT3 signaling pathways

CCM111 is an aqueous extract of Antrodia cinnamomea (AC) that has exhibited anti-liver fibrosis functions. However, the detailed mechanisms of AC action against liver fibrosis have not been elucidated yet. The present research showed that CCM111 significantly lowered the levels of the hepatic enzyme markers glutamate oxaloacetate transaminase (GOT) and glutamic pyruvic transaminase (GPT), prevented liver damage and collagen deposition, and downregulated TGF-β/Smad signaling in a dose-dependent manner compared with CCl₄ treatment alone. CCM111 markedly inhibited TGF-β, Wnt and STAT3 signaling pathway-regulated downstream genes in the liver by next-generation sequencing. The antifibrotic mechanisms of CCM111 were further demonstrated in HSC-T6 cells. Our data demonstrated for the first time that CCM111 can protect against CCl₄-induced liver fibrosis by the cooperative inhibition of TGF-β-, Wnt- and STAT3-dependent proinflammatory and profibrotic mediators, suggesting that CCM111 might be a candidate for preventing and treating chronic fibrotic liver diseases.     

Rhynchophylline prevents cardiac dysfunction and improves survival in lipopolysaccharide-challenged mice via suppressing macrophage I-κBα phosphorylation

Myocardial dysfunction is a common complication during sepsis and significantly contributes to the mortality of patients with septic shock. However, none of the available therapeutic strategies proven to be effective in patients with severe sepsis are designed specifically to target myocardial dysfunction. The purpose of the present study is to investigate the effect of rhynchophylline (Rhy) on LPS-induced myocardial dysfunction in mice. We found that pretreatment with Rhy significantly improved cardiac systolic dysfunction, increased stroke volume and cardiac output in mice challenged with LPS. LPS induced cardiac inhibitor-κBα (I-κBα) phosphorylation, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) mRNA expression, and in turn increased cardiac TNF-α and IL-1β protein production, all of which were attenuated by pretreatment with Rhy. Immunohistochemistry revealed that TNF-α was found in infiltrated macrophages (F4/80(+)) and myocardium, and Rhy reduced TNF-α immunostaining in cardiac infiltrated macrophages in LPS-challenged mice. Furthermore, Rhy inhibited LPS-induced I-κBα phosphorylation and TNF-α production in cultured mouse peritoneal macrophages, but not in neonatal mouse cardiomyocytes. Pretreatment with Rhy significantly decreased the mortality of LPS-challenged mice. These results indicate that Rhy reduces cardiac dysfunction and improves survival via suppression of macrophage I-κBα phosphorylation in LPS-challenged mice, and suggest that Rhy may be a potential agent for the treatment of septic cardiac dysfunction.     

Synthesis and in vivo lead detoxification evaluation of Poly-α,β-dl-aspartyl-l-methionine

To increase the metal selectivity of polyaspartic acid, a so-called green chelant, poly-α,β-dl-aspartyl-l-methionine (PDM) was synthesized as a novel lead chelating agent. The phosphoric acid (80%) catalyzed thermal poly condensation of dl-aspartic acid provided poly succinimide, which was amidated with l-methionine to form PDM (MW: 29161). At the doses of 0.1, 1.0, and 10.0 nmol/kg, either by intraperitoneal injection (i.p.) or oral administration, PDM removed Pb from the spleens, hearts, and kidneys of mice, especially dose-dependently decreasing the accumulation of Pb in the brains, livers, and femurs of the mice, and did not interfere with the essential metals, including Cu, Fe, Mn, and Ca. Even at the dose of 0.1 nmol/kg, the i.p. injection of PDM removed Pb from the spleens, hearts, and kidneys of mice and increased the amount of urinary volume and urinary Pb, and the amount of fecal matter and the amount of fecal Pb, resulting in effective removal of Pb from the body of mice given Pb by i.p. injection. Our findings revealed that in aqueous solution PDM formed diverse nanospecies.     

The NF-κB inhibitor celastrol attenuates acute hepatic dysfunction induced by cecal ligation and puncture in rats

Acute hepatic dysfunction associating sepsis is mediated mainly by toll-like receptor-4 (TLR-4)/nuclear factor kappa‐B (NF-κB) inflammatory pathway. This study explores potential hepatoprotective effect of the NF-κB inhibitor celastrol in cecal ligation and puncture (CLP) model in rats.Protective effect of celastrol (1 mg/kg, i.p., 1 h before CLP) was illustrated after 24 h by preventing CLP‐induced hepatic histopathological changes and elevation in serum hepatic biomarkers [alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TB) and gamma aminotransferase (γ-GT)] without affecting mortality. Celastrol anti‐inflammatory effect was illustrated by inhibiting increased serum and hepatic mRNA expression of interleukin-6 (IL-6) without affecting IL-10 elevation. Furthermore, celastrol inhibited CLP-induced elevations in hepatic mRNA expression of nuclear factor inhibitory protein kappa-B alpha (NFκBia), TLR-4, 5‐lipoxygenase (5-LOX) and prevented NF‐κB/p65 nuclear translocation and activation.In conclusion, celastrol prevented CLP-induced acute hepatic dysfunction through its anti-inflammatory effect by attenuating NF-κB activation, TLR-4 and 5-LOX expression with subsequent reduction in pro-inflammatory IL-6.     

Δ8-Tetrahydrocannabivarin prevents hepatic ischaemia/reperfusion injury by decreasing oxidative stress and inflammatory responses through cannabinoid CB2 receptors

BACKGROUND AND PURPOSE

Activation of cannabinoid CB₂ receptors protects against various forms of ischaemia-reperfusion (I/R) injury. Δ⁸-Tetrahydrocannabivarin (Δ⁸-THCV) is a synthetic analogue of the plant cannabinoid Δ⁹-tetrahydrocannabivarin, which exhibits anti-inflammatory effects in rodents involving activation of CB₂ receptors. Here, we assessed effects of Δ⁸-THCV and its metabolite 11-OH-Δ⁸-THCV on CB₂ receptors and against hepatic I/R injury.

EXPERIMENTAL APPROACH

Effects in vitro were measured with human CB₂ receptors expressed in CHO cells. Hepatic I/R injury was assessed in mice with 1h ischaemia and 2, 6 or 24h reperfusion in vivo.

KEY RESULTS

Displacement of [³H]CP55940 by Δ⁸-THCV or 11-OH-Δ⁸-THCV from specific binding sites in CHO cell membranes transfected with human CB₂ receptors (hCB₂) yielded K_i values of 68.4 and 59.95 nM respectively. Δ⁸-THCV or 11-OH-Δ⁸-THCV inhibited forskolin-stimulated cAMP production by hCB₂ CHO cells (EC₅₀= 12.95 and 14.3 nM respectively). Δ⁸-THCV, given before induction of I/R, attenuated hepatic injury (measured by serum alanine aminotransferase and aspartate aminotransferase levels), decreased tissue protein carbonyl adducts, 4-hydroxy-2-nonenal, the chemokines CCL3 and CXCL2,TNF-α, intercellular adhesion molecule 1 (CD54) mRNA levels, tissue neutrophil infiltration, caspase 3/7 activity and DNA fragmentation. Protective effects of Δ⁸-THCV against liver damage were still present when the compound was given at the beginning of reperfusion. Pretreatment with a CB₂ receptor antagonist attenuated the protective effects of Δ⁸-THCV, while a CB₁ antagonist tended to enhance it.

CONCLUSIONS AND IMPLICATIONS

Δ⁸-THCV activated CB₂ receptors in vitro, and decreased tissue injury and inflammation in vivo, associated with I/R partly via CB₂ receptor activation.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7     

α-Tocopheryl hemisuccinate administration increases rat liver subcellular α-tocopherol levels and protects against carbon tetrachloride-induced hepatotoxicity

Rats were administered a series of tocopherol analogs 18 h prior to a hepatotoxic dose of carbon tetrachloride (CCl₄). Of the compounds tested, only d-α-tocopheryl hemisuccinate (TS) provided significant protection against CCl₄-induced hepatotoxicity. No protection was observed with either d-α-tocopherol (α-T) or a tocopherol succinate ether derivative, d-α-tocopheryloxybutyric acid (TSE). None of the tocopherol analogs significantly inhibited CYP2E1 activity as measured by oxidation of p-nitrophenol. Liver homogenates and subcellular fractions (cytosol, nuclei, plasma membranes, mitochondria and microsomes) were collected 18 h after tocopherol analog administration in the absence of CCl₄. Homogenate and subcellular α-T levels were not significantly increased following TSE administration but were increased 2–3 fold following TS and α-T administration. Total tocopherol levels (α-T+TS+TSE) in liver homogenates and subcellular fractions were highest in rats supplemented with TS. In these animals, TS was detected in all subcellular fractions and total tocopherol levels were increased from 6–23 fold over those seen in controls and 2–9 fold over α-T treated rats. In vitro studies in which liver homogenates and subcellular fractions were peroxidized with ascorbate and ADP/Fe suggest that increasing levels of α-T but not TS correlates with increased protection against lipid peroxidation. These results suggest that the ability of TS to protect against CCl₄-induced hepatotoxicity relates to its enhanced hepatic accumulation and subsequent hydrolysis to α-T.     

Ablation of Akt2 and AMPKα2 rescues high fat diet-induced obesity and hepatic steatosis through Parkin-mediated mitophagy

Given the opposing effects of Akt and AMP-activated protein kinase (AMPK) on metabolic homeostasis, this study examined the effects of deletion of Akt2 and AMPKα2 on fat diet-induced hepatic steatosis. Akt2–Ampkα2 double knockout (DKO) mice were placed on high fat diet for 5 months. Glucose metabolism, energy homeostasis, cardiac function, lipid accumulation, and hepatic steatosis were examined. DKO mice were lean without anthropometric defects. High fat intake led to adiposity and decreased respiratory exchange ratio (RER) in wild-type (WT) mice, which were ablated in DKO but not Akt2^−/− and Ampkα2^−/− mice. High fat intake increased blood and hepatic triglycerides and cholesterol, promoted hepatic steatosis and injury in WT mice. These effects were eliminated in DKO but not Akt2^−/− and Ampkα2^−/− mice. Fat diet promoted fat accumulation, and enlarged adipocyte size, the effect was negated in DKO mice. Fat intake elevated fatty acid synthase (FAS), carbohydrate-responsive element-binding protein (CHREBP), sterol regulatory element-binding protein 1 (SREBP1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), peroxisome proliferator-activated receptor-α (PPARα), PPARγ, stearoyl-CoA desaturase 1 (SCD-1), phosphoenolpyruvate carboxykinase (PEPCK), glucose 6-phosphatase (G6Pase), and diglyceride O-acyltransferase 1 (DGAT1), the effect was absent in DKO but not Akt2^−/− and Ampkα2^−/− mice. Fat diet dampened mitophagy, promoted inflammation and phosphorylation of forkhead box protein O1 (FoxO1) and AMPKα1 (Ser⁴⁸⁵), the effects were eradicated by DKO. Deletion of Parkin effectively nullified DKO-induced metabolic benefits against high fat intake. Liver samples from obese humans displayed lowered microtubule-associated proteins 1A/1B light chain 3B (LC3B), Pink1, Parkin, as well as enhanced phosphorylation of Akt, AMPK (Ser⁴⁸⁵), and FoxO1, which were consolidated by RNA sequencing (RNAseq) and mass spectrometry analyses from rodent and human livers. These data suggest that concurrent deletion of Akt2 and AMPKα2 offers resilience to fat diet-induced obesity and hepatic steatosis, possibly through preservation of Parkin-mediated mitophagy and lipid metabolism.     

Inhibition of NF-κB and the oxidative stress -dependent caspase-3 apoptotic pathway by betaine supplementation attenuates hepatic injury mediated by cisplatin in rats

BackgroundCisplatin is a major anti-cancer drug commonly used in the treatment of various cancers; nevertheless, the associated hepatotoxicity has limited its clinical application. The aim of this investigation is to test the impact of betaine supplementation on cisplatin-induced hepatotoxicity.MethodsAnimals were allocated into four groups; normal control group (control betaine group (250 mg/kg/day, po for twenty six days), cisplatin group (single injection of 7 mg/kg, ip) and betaine + cisplatin group (received betaine for twenty one days before cisplatin injection and daily after cisplatin for five days).ResultsCisplatin-induced liver injury was confirmed by increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Cisplatin elevated lipid peroxides, and reduced the concentrations of reduced glutathione (GSH), glutathione peroxidase (GSH-Px), catalase and superoxide dismutase (SOD) in hepatic tissues. Cisplatin increased the inflammatory mediators; nitrite and tumor necrosis factor-α (TNF- α) in hepatic tissues. Increased gene expressions of the apoptotic marker, caspase-3 and nuclear factor-kappa B (NF-κB) were observed in hepatic tissues of cisplatin-treated rats. All these changes were further confirmed by histopathological findings in cisplatin group. Pre-treatment with betaine reduced serum aminotransferases (ALT and AST), and lowered hepatic concentrations of lipid peroxides, nitrite and TNF-α while increased SOD, GSH, catalase, and GSH-Px concentrations. Moreover, the histological and immunohistochemical changes were improved.ConclusionThe suppression of NF-κβ-mediated inflammation, oxidative stress, and caspase-3 induced apoptosis are possible mechanisms to the observed hepatoprotective effect of betaine.     

Are the decreases in hepatic cytochrome P-450 and other drug-metabolising enzymes caused by indomethacin in vivo mediated by intestinal bacterial endotoxins?: 16,16-dimethylprostaglandin F2α prevents decreases in hepatic drug-metabolising enzymes due to exogenous endotoxin

Administration of either indomethacin (8.5 mg/kg) or E. coli endotoxin (3.5 mg/kg) to rats caused significant decreases in a variety of drug-metabolising enzyme activities. Either agent markedly decreased biphenyl 4-hydroxylase by 72-80% and caused lesser decreases (21-64%) in cyt. P-450, aminopyrine N-demethylase, ethoxyresorufin O-deethylase (EROD), benzyloxyphenoxazone O-debenzylase (BPOD), cyt. b5, NADPH-cyt. c reductase, NADH-cyt. b5 reductase, epoxide hydrolase (EH) and glucuronyl transferase (GT). The decreases in GT (21-22%) were significantly less than in cyt. P-450 (45-57%). Sulphotransferase was not affected by either indomethacin or endotoxin. The overall pattern of relative decreases in the different enzymes was similar for either indomethacin or endotoxin. Four activities, however, were affected to a significantly greater extent by indomethacin than by endotoxin at 2-6 mg/kg: EROD, BPOD, cyt. b5 and EH. Additionally, hepatic glutathione was decreased by indomethacin but not by endotoxin. Indomethacin or endotoxin caused similar but not identical decreases in selected protein bands in the "cyt. P-450 region" of microsomal SDS-polyacrylamide gel electrophoretograms. Concomitant administration of 16,16-dimethylprostaglandin F2 alpha afforded significant (50-100%) protection against all the above-mentioned effects of indomethacin or endotoxin. The effects of indomethacin on cyt. P-450 were lessened by concomitant administration of a mixture of neomycin, polymyxin B and bacitracin. Throughout the study there was a close correlation between the extent of decrease in hepatic cyt. P-450 and the degree of intestinal ulceration caused by indomethacin. It was concluded that bacterial endotoxins liberated into the portal blood as a result of indomethacin-induced ulceration of the small intestine probably only partially mediated the effects of indomethacin on hepatic drug-metabolising enzymes. The protection afforded by 16,16-dimethylprostaglandin F2 alpha could have been due to both the prevention of ulceration and to a direct cytoprotective effect on the liver.     

TAK-875, a GPR40/FFAR1 agonist,in combination with metformin prevents progression of diabetes and β-cell dysfunction in Zucker diabetic fatty rats

BACKGROUND AND PURPOSE

TAK-875, a selective GPCR40/free fatty acid receptor 1 agonist, improves glycaemic control by increasing glucose-dependent insulin secretion. Metformin is a first-line drug for treatment of type 2 diabetes that improves peripheral insulin resistance. Based on complementary mechanism of action, combining these agents is expected to enhance glycaemic control. Here, we evaluated the chronic effects of TAK-875 monotherapy and combination therapy with metformin in diabetic rats.

EXPERIMENTAL APPROACH

Long-term effects on glycaemic control and β-cell function were evaluated using Zucker diabetic fatty (ZDF) rats, which develop diabetes with hyperlipidaemia and progressive β-cell dysfunction.

KEY RESULTS

Single doses of TAK-875 (3–10 mg·kg⁻¹) and metformin (50–150 mg·kg⁻¹) significantly improved both postprandial and fasting hyperglycaemia, and additive improvements were observed in their combination. Six-week treatment with TAK-875 (10 mg·kg⁻¹, b.i.d.) significantly decreased glycosylated Hb (GHb) by 1.7%, and the effect was additively enhanced by combination with metformin (50 mg·kg⁻¹, q.d.; GHb: −2.4%). This improvement in glycaemic control in the combination group was accompanied by significant 3.2-fold increase in fasting plasma insulin levels. Pancreatic insulin content was maintained at a level comparable to that in normal rats by combination treatment (vehicle: 26, combination: 67.1; normal lean: 69.1 ng·mg⁻¹ pancreas) without affecting pancreatic glucagon content. Immunohistochemical analyses revealed normal morphology, enhanced pancreas duodenum homeobox-1 expression and increased PCNA-positive cells in islets of the combination group.

Conclusion and Implications

Our results indicate that combination therapy with TAK-875 and metformin could be a valuable strategy for glycaemic control and β-cell preservation in type 2 diabetes.