Effect of Glutathione on Lipogenesis in Liver Slices from Rats Fed on Low Casein Diet

To study the mechanism of fatty infiltration in the liver due to added sulfur-containing amino acids to low casein diet, the effect of sulfur-containing amino acids and glutathione (GSH) on the incorporation of acetate-l-¹⁴C into lipid fractions were studied in liver slices from rats fed on 8% casein diet (Basal diet) with or without added methionine (Met).

The liver acetyl Co A carboxylase activities of rats on basal diet with or without added Met were similar.

Addition of Met, cystine or cysteine to the incubation medium had little effect on lipogenesis of slices. On addition of GSH to liver slices from rats fed on basal diet, lipid formation increased appreciably. On the other hand, addition of GSH to liver slices from rats fed on Met supplemented diet showed no accelerative effect on lipogenesis.

Addition of GSH to the incubation medium of liver slices from rats fed on basal diet tended to reduce the incorporation of acetate into the phospholipid fraction and to increase into the fatty acid fraction of liver slices.

The content of liver GSH was lower in rats on basal diet than in those on Met supplemented diet. The higher GSH level in rats on Met supplemented diet may be one factor causing fatty infiltration in the liver of these animals.     

Changes in Gut Microbiota in Rats Fed a High Fat Diet Correlate with Obesity-Associated Metabolic Parameters

The gut microbiota is emerging as a new factor in the development of obesity. Many studies have described changes in microbiota composition in response to obesity and high fat diet (HFD) at the phylum level. In this study we used 16s RNA high throughput sequencing on faecal samples from rats chronically fed HFD or control chow (n = 10 per group, 16 weeks) to investigate changes in gut microbiota composition at the species level. 53.17% dissimilarity between groups was observed at the species level. Lactobacillus intestinalis dominated the microbiota in rats under the chow diet. However this species was considerably less abundant in rats fed HFD (P<0.0001), this being compensated by an increase in abundance of propionate/acetate producing species. To further understand the influence of these species on the development of the obese phenotype, we correlated their abundance with metabolic parameters associated with obesity. Of the taxa contributing the most to dissimilarity between groups, 10 presented significant correlations with at least one of the tested parameters, three of them correlated positively with all metabolic parameters: Phascolarctobacterium, Proteus mirabilis and Veillonellaceae, all propionate/acetate producers. Lactobacillus intestinalis was the only species whose abundance was negatively correlated with change in body weight and fat mass. This species decreased drastically in response to HFD, favouring propionate/acetate producing bacterial species whose abundance was strongly correlated with adiposity and deterioration of metabolic factors. Our observations suggest that these species may play a key role in the development of obesity in response to a HFD.     

Lipid Metabolism in the Fatty Liver of Rats Fed a Threonine-deficient Diet

Feeding of a threonine-deficient diet to rats weighing approximately 53 g or 99 g caused a significant rise in liver lipids compared to the control diet containing 7% amino acid mixture. Whereas, when rats weighing approximately 155 g were fed either the control diet or the threonine-deficient diet, liver lipid content was essentially the same for both groups. Therefore, in the present paper, young rats were used to clarify the mechanism of liver lipid accumulation in threonine-deficiency. The increase in dietary fat content of the threonine-deficient diet did not prevent the lipid accumulation in rat liver. The rates of in vivo incorporation from radioactive acetate into liver lipids, body lipids and respiratory CO₂ of rats fed either the control diet or the threonine-deficient diet were measured. The threonine-deficient group tended to be lower in total activity of both the liver lipids and body lipids than those of the control group. Thus, these results suggest that the development of this type of fatty liver might not be due to the stimulation of lipid synthesis in the liver. In the serum of rats fed the threonine-deficient diet, the protein content of β-lipoproteins was significantly lower and free fatty acid level tended to be lower than the values of the control animals, respectively. From these results, decreased trasport of lipids from the liver may thus be considered a potential major factor responsible for the excessive lipid accumulation in the liver of rats fed the threonine-deficient diet.     

Decreasing Effect of Chitosan on the Apparent Fat Digestibility by Rats Fed on a High-fat Diet

We investigated the effects of various dietary fibers or their likenesses on the apparent fat digestibility by rats fed on a high-fat diet. Each of 23 different fibers was added at 5% (w/w) to a purified diet containing 20% (w/w) corn oil. The rats were fed these diets for 2 weeks, and the feces were collected from each animal during the last 3 days. When compared with cellulose (control), 10 of the tested fibers significantly increased the fecal lipid excretion. Among these fibers, chitosan markedly increased the fecal lipid excretion and reduced the apparent fat digestibility to about a half relative to the control. The apparent protein digestibility was not greatly affected by chitosan. The fatty acid composition of the fecal lipids closely reflected that of the dietary fat. These results suggest that chitosan has potency for interfering with fat digestion and absorption in the intestinal tract, and for facilitating the excretion of dietary fat into the feces.     

Comparison of the Activity of the Tryptophan-NAD Pathway between Rats Fed a Fat-free Diet and a Fat Diet

The effect of dietary fat on tryptophan-NAD metabolism was investigated. Weanling male rats of the Sprague Dawley strain were fed a 40% casein diet (nicotinic acid-free) with or without 20% fat for 13 days. Although the food intake in 13 days was significantly higher in the fat-free group than in the fat group, the gains in body weight in the two groups were almost the same, because of the same energy intakes. The urinary excretion of tryptophan metabolites such as quinolinic acid, niacin and N¹-methylnicotinamide was greatly increased in the fat group in comparison with that in the fat-free group. The urinary excretion of xanthurenic acid was almost the same in the two groups. The blood NAD level of the fat group was significantly increased. The activities of liver amino-carboxymuconate-semialdehyde decarboxylase and liver nicotinamide methyltransferase in the fat group were significantly reduced, and that of liver NMN adenylyltransferase was significantly increased. The changes of these three enzymes could be advantageous for the increased formation of NAD from tryptophan. As a result, the feeding of a high fat diet to rats increased the formation of niacin and niacin-related compounds.     

High Fat Diet Induces Liver Steatosis and Early Dysregulation of Iron Metabolism in Rats

This paper is dedicated to the memory of our wonderful colleague Professor Alfredo Colonna, who passed away the same day of its acceptance. Fatty liver accumulation, inflammatory process and insulin resistance appear to be crucial in non-alcoholic fatty liver disease (NAFLD), nevertheless emerging findings pointed an important role also for iron overload. Here, we investigate the molecular mechanisms of hepatic iron metabolism in the onset of steatosis to understand whether its impairment could be an early event of liver inflammatory injury. Rats were fed with control diet or high fat diet (HFD) for 5 or 8 weeks, after which liver morphology, serum lipid profile, transaminases levels and hepatic iron content (HIC), were evaluated. In liver of HFD fed animals an increased time-dependent activity of iron regulatory protein 1 (IRP1) was evidenced, associated with the increase in transferrin receptor-1 (TfR1) expression and ferritin down-regulation. Moreover, ferroportin (FPN-1), the main protein involved in iron export, was down-regulated accordingly with hepcidin increase. These findings were indicative of an increased iron content into hepatocytes, which leads to an increase of harmful free-iron also related to the reduction of hepatic ferritin content. The progressive inflammatory damage was evidenced by the increase of hepatic TNF-α, IL-6 and leptin, in parallel to increased iron content and oxidative stress. The major finding that emerged of this study is the impairment of iron homeostasis in the ongoing and sustaining of liver steatosis, suggesting a strong link between iron metabolism unbalance, inflammatory damage and progression of disease.     

A Model of Metabolic Syndrome and Related Diseases with Intestinal Endotoxemia in Rats Fed a High Fat and High Sucrose Diet

Aim

We sought develop and characterize a diet-induced model of metabolic syndrome and its related diseases.

Methods

The experimental animals (Spague-Dawley rats) were randomly divided into two groups, and each group was fed a different feed for 48 weeks as follows: 1) standard control diet (SC), and 2) a high sucrose and high fat diet (HSHF). The blood, small intestine, liver, pancreas, and adipose tissues were sampled for analysis and characterization.

Results

Typical metabolic syndrome (MS), non-alcoholic fatty liver disease (NAFLD), and type II diabetes (T2DM) were common in the HSHF group after a 48 week feeding period. The rats fed HSHF exhibited signs of obesity, dyslipidemia, hyperglycaemia, glucose intolerance, and insulin resistance (IR). At the same time, these animals had significantly increased levels of circulating LPS, TNFα, and IL-6 and increased ALP in their intestinal tissue homogenates. These animals also showed a significant reduction in the expression of occluding protein. The HSHF rats showed fatty degeneration, inflammation, fibrosis, cirrhosis, and lipid accumulation when their liver pathologies were examined. The HSHF rats also displayed increased islet diameters from 12 to 24 weeks, while reduced islet diameters occurred from 36 to 48 weeks with inflammatory cell infiltration and islet fat deposition. The morphometry of adipocytes in HSHF rats showed hypertrophy and inflammatory cell infiltration. HSHF CD68 analysis showed macrophage infiltration and significant increases in fat and pancreas size. HSHF Tunel analysis showed significant increases in liver and pancreas cell apoptosis.

Conclusions

This work demonstrated the following: 1) a characteristic rat model of metabolic syndrome (MS) can be induced by a high sucrose and high fat diet, 2) this model can be used to research metabolic syndrome and its related diseases, such as NAFLD and T2DM, and 3) intestinal endotoxemia (IETM) may play an important role in the pathogenesis of MS and related diseases, such as NAFLD and T2DM.     

Effects of Dietary Glutathione on Plasma and Liver Lipid Levels in Rats Fed on a High Cholesterol Diet

The effects of dietary glutathione (GSH) on plasma and liver lipid concentrations were investigated with rats fed on a high cholesterol diet. When graded levels of GSH, 0.75 to 5.0%, were added to the 25% casein basal diet, the plasma total cholesterol level was significantly decreased and the HDL-cholesterol level was inversely increased in all addition levels without influence on the growth of animals except for the 5% addition level; the dietary addition of 5% GSH markedly depressed the growth and food consumption of rats and caused a slight diarrhea. Plasma triglyceride and phospholipid levels were decreased by the dietary addition of GSH. The contents of cholesterol and triglyceride in the liver were decreased as the dietary addition level of GSH was increased. The dietary addition of a mixture of glutamic acid, cysteine and glycine, or cysteine alone corresponding to 2.5% GSH resulted in a cholesterol-lowering effect which could not be distinguished from the effect of GSH in rats fed on the 25% casein diet. When 1.5% GSH was added to a low (10%) casein diet, the plasma cholesterol-lowering effect of GSH was also observed and the effect was comparable to that of cysteine. These results indicate that dietary-added GSH has a plasma and liver cholesterol-lowering efficacy and that this effect is largely attributable to the cysteine residue of GSH rather than to the tripeptide itself or the other amino acid residues.     

Alleviation Effect of Grape Seed Proanthocyanidins on Neuronal Apoptosis in Rats with Iron Overload

Biological Trace Element Research - We aimed to evaluate the effect of grape seed proanthocyanidins (GSPCs) on neuronal apoptosis, particularly through their roles in maintaining divalent mineral...     

Photoperiod Regulates Lean Mass Accretion,but Not Adiposity,in Growing F344 Rats Fed a High Fat Diet

In this study the effects of photoperiod and diet, and their interaction, were examined for their effects on growth and body composition in juvenile F344 rats over a 4-week period. On long (16L:8D), relative to short (8L:16D), photoperiod food intake and growth rate were increased, but percentage adiposity remained constant (ca 3-4%). On a high fat diet (HFD), containing 22.8% fat (45% energy as fat), food intake was reduced, but energy intake increased on both photoperiods. This led to a small increase in adiposity (up to 10%) without overt change in body weight. These changes were also reflected in plasma leptin and lipid levels. Importantly while both lean and adipose tissue were strongly regulated by photoperiod on a chow diet, this regulation was lost for adipose, but not lean tissue, on HFD. This implies that a primary effect of photoperiod is the regulation of growth and lean mass accretion. Consistent with this both hypothalamic GHRH gene expression and serum IGF-1 levels were photoperiod dependent. As for other animals and humans, there was evidence of central hyposomatotropism in response to obesity, as GHRH gene expression was suppressed by the HFD. Gene expression of hypothalamic AgRP and CRH, but not NPY nor POMC, accorded with the energy balance status on long and short photoperiod. However, there was a general dissociation between plasma leptin levels and expression of these hypothalamic energy balance genes. Similarly there was no interaction between the HFD and photoperiod at the level of the genes involved in thyroid hormone metabolism (Dio2, Dio3, TSHβ or NMU), which are important mediators of the photoperiodic response. These data suggest that photoperiod and HFD influence body weight and body composition through independent mechanisms but in each case the role of the hypothalamic energy balance genes is not predictable based on their known function.     

Liver Nonprotein Sulfhydryl and Taurine Concentrations,and Fat Content of Rats Fed a Low Protein Diet Supplemented with Sulfur-containing Amino Acids

The relative excess of some catabolites of sulfur-containing amino acids in the liver of rats fed a low protein diet might be one of the factors which cause the liver fat accumulation. To investigate the possibility were studied relationships between changes in concentrations of some metabolites of sulfur-containing amino acids and those in fat contents of rats fed a low protein diet consisting of heated soybean flour, casein or wheat flour with or without added methionine, threonine or lysine. The addition of 0.6% methionine to the 25% heated soybean flour diet increased the nonprotein-sulfhydryl (NP–SH) concentration and fat content in the liver. These changes were prevented by the further addition of 0.5% threonine to the diet, although the NP–SH concentration was remarkably higher than that of rats fed the unsupplemented diet. The addition of 0.6% cystine HC1 to the 25% heated soybean flour diet containing sufficient choline elevated the NP–SH concentration and fat content in the liver, which were not affected by the further addition of 0.5% threonine. The addition of 0.6% cystine HC1 to the 10% casein diet significantly increased the fat content, and NP–SH and taurine concentrations in the liver. The further addition of 0.5 % threonine completely decreased the fat content, and partially reduced the NP–SH and taurine concentrations. Effects of supplementation of 0.4% lysine HC1 to the 70% wheat flour diet on the fat content and NP–SH concentration in the liver demonstrated the trends similar to those of supplementation of cystine to the 10% casein diet. The further addition of threonine remarkably decreased the fat content, NP–SH and taurine concentrations in the liver.     

Effects of Cricket Extract on Lipid Metabolism and Body Fat Content in High- Fat Diet Fed Rats

The effect of cricket extract on high‐fat diet fed rat was observed. It was shown that cricket extract prevented the increment of body weight by high‐fat diet. The extract also decreased the value of AST in liver. The most significant effect of the extract was shown on lipid metabolism. The contents of total lipid and total cholesterol in liver and feces were reduced by the extract on dose‐dependent. These statistically significant results were clear in 3% extract treated group (HFD3) while were slight in 1% extract treated group (HFD1). The same result was also shown in body fat content.     

Triglyceride Release and Fatty Acid Oxidation by the Perfused Liver of Rats Fed a Low Protein Diet

Livers of growing rats fed a 5 or 20 protein calories percent (PC %) diet containing purified whole egg protein for three weeks were perfused in situ and the release of triglycerides (TG) and the oxidation of fatty acid by the liver alone were estimated by infusing palmitic acid-l-¹⁴C to the perfusion medium.

The release of TG from the liver of the 5 PC% group was significantly lower in both unfractionated perfusate plasma and perfusate plasma very low density lipoprotein (VLDL) than that of the 20 PC% group, whereas the content of liver TG of the 5 PC% group was higher than that of the 20 PC% group. Significantly lower radioactivity appeared in TG of both unfractionated perfusate plasma and perfusate plasma VLDL of the 5 PC% group than that of the 20 PC% group, while total radioactivity of liver TG was higher in the 5 PC% group than in the 20 PC% group. The ¹⁴CO₂ production in the perfused liver of the 5 PC% group increased gradually with time rather than decreased in comparison with that of the 20 PC% group.

These findings suggest that a major factor responsible for the liver lipid accumulation in rats fed the low protein diet is not an impaired fatty acid oxidation in the liver but an impaired secretion of TG from the liver.     

Fructose Mediated Non-Alcoholic Fatty Liver Is Attenuated by HO-1-SIRT1 Module in Murine Hepatocytes and Mice Fed a High Fructose Diet

Background

Oxidative stress underlies the etiopathogenesis of nonalcoholic fatty liver disease (NAFLD), obesity and cardiovascular disease (CVD). Heme Oxygenase-1 (HO-1) is a potent endogenous antioxidant gene that plays a key role in decreasing oxidative stress. Sirtuin1 (SIRT1) belongs to the family of NAD-dependent de-acyetylases and is modulated by cellular redox.

Hypothesis

We hypothesize that fructose-induced obesity creates an inflammatory and oxidative environment conducive to the development of NAFLD and metabolic syndrome. The aim of this study is to determine whether HO-1 acts through SIRT1 to form a functional module within hepatocytes to attenuate steatohepatitis, hepatic fibrosis and cardiovascular dysfunction.

Methods and Results

We examined the effect of fructose, on hepatocyte lipid accumulation and fibrosis in murine hepatocytes and in mice fed a high fructose diet in the presence and absence of CoPP, an inducer of HO-1, and SnMP, an inhibitor of HO activity. Fructose increased oxidative stress markers and decreased HO-1 and SIRT1 levels in hepatocytes (p<0.05). Further fructose supplementation increased FAS, PPARα, pAMPK and triglycerides levels; CoPP negated this increase. Concurrent treatment with CoPP and SIRT1 siRNA in hepatocytes increased FAS, PPARα, pAMPK and triglycerides levels suggesting that HO-1 is upstream of SIRT1 and suppression of SIRT1 attenuates the beneficial effects of HO-1. A high fructose diet increased insulin resistance, blood pressure, markers of oxidative stress and lipogenesis along with fibrotic markers in mice (p<0.05). Increased levels of HO-1 increased SIRT1 levels and ameliorated fructose-mediated lipid accumulation and fibrosis in liver along with decreasing vascular dysfunction (p<0.05 vs. fructose). These beneficial effects of CoPP were reversed by SnMP.

Conclusion

Taken together, our study demonstrates, for the first time, that HO-1 induction attenuates fructose-induced hepatic lipid deposition, prevents the development of hepatic fibrosis and abates NAFLD-associated vascular dysfunction; effects that are mediated by activation of SIRT1 gene expression.     

Increased Oxidant Stress and Decreased Antioxidant Status in Erythrocytes of Rats Fed with Zinc-deficient Diet

The aim of this study was to evaluate the lipid peroxidation, nitric oxide (NO), and free radical scavenging enzyme activities in erythrocytes of zinc (Zn)-deficient rats and to investigate the relationship among these parameters in either group. Sixteen male rats with a weight of 40-50 g were used for the experiment. The rats were divided into control (n = 8) and Zn-deficient groups. At the end of the experiment, the animals were anesthetized with ketamine-HCl (Ketalar, 20 mg/kg(-1), i.p.), and the blood was collected by cardiac puncture after thoracotomy. Blood samples were collected in vacutainer tubes without and with K(3)-EDTA as anticoagulant. Erythrocyte catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GRD), glutathione-S-transferase (GST), superoxide dismutase (SOD) activities, total (enzymatic plus nonenzymatic) superoxide scavenger activity (TSSA), nonenzymatic superoxide scavenger activity (NSSA), antioxidant potential (AOP), and serum zinc (Zn) values in the Zn-deficient group were significantly lower than those of the control group, whereas NO and malondialdehyde (MDA) levels were significantly higher than those of the control group. The results show that Zn deficiency causes a decrease in antioxidant defense system and an increase in oxidative stress in erythrocyte of rats.     

高蛋氨酸饮食对大鼠血管内皮细胞分泌功能的影响

目的:探讨高蛋氨酸饮食对大鼠血管内皮细胞分泌功能的影响。方法:雄性Wistar大鼠随机分为正常饮食对照组(对照组)和高蛋氨酸饮食组(高蛋氨酸组)。对照组喂饲普通饲料,高蛋氨酸组大鼠喂饲含3%蛋氨酸的饲料,共8周。采用高效液相色谱法测定大鼠血浆同型半胱氨酸含量,以MDA、SOD、NO/ET和t-PA/PAI平衡等指标建立研究平台和内皮功能评价体系,同时以扫描电镜观察主动脉弓血管内皮细胞形态。结果:与对照组相比,高蛋氨酸组血浆Hcy含量显著高于对照组,是对照组的2倍以上;血浆MDA和SOD活力显著升高(P<0.05),t-PA/PAI-1和NO/ET比值均显著降低(P<0.05)。扫描电镜显示高蛋氨酸组大鼠内皮细胞呈典型虫蛀样损害,伴有附壁血栓形成和脂质沉积。结论:高蛋氨酸饮食可诱发大鼠高半胱氨酸血症,Hcy可通过氧化应激机制损伤血管内细胞分泌功能,血浆NO/ET和t-PA/PAI-1系统失衡。     

A Prescribed Chinese Herbal Medicine Improves Glucose Profile and Ameliorates Oxidative Stress in Goto-Kakisaki Rats Fed with High Fat Diet

Oxidative stress (OS) plays a role in hyperglycemia induced islet β cell dysfunction, however, studies on classic anti-oxidants didn’t show positive results in treating diabetes. We previously demonstrated that the prescribed Chinese herbal medicine preparation “Qing Huo Yi Hao” (QHYH) improved endothelial function in type 2 diabetic patients. QHYH protected endothelial cells from high glucose-induced damages by scavenging superoxide anion and reducing production of reactive oxygen species. Its active component protected C2C12 myotubes against palmitate-induced oxidative damage and mitochondrial dysfunction. In the present study, we investigated whether QHYH protected islet β cell function exacerbated by high fat diet (HFD) in hyperglycemic GK rats. 4-week-old male rats were randomly divided into high HFD feeding group (n = 20) and chow diet feeding group (n = 10). Each gram of HFD contained 4.8 kcal of energy, 52% of which from fat. Rats on HFD were further divided into 2 groups given either QHYH (3 ml/Kg/d) or saline through gastric tube. After intervention, serum glucose concentrations were monitored; IPGTTs were performed without anesthesia on 5 fasting rats randomly chosen from each group on week 4 and 16. Serum malondialdehyde (MDA) concentrations and activities of serum antioxidant enzymes were measured on week 4 and 16. Islet β cell mass and OS marker staining was done by immunohistochemistry on week 16. QHYH prevented the exacerbation of hyperglycemia in HFD feeding GK rats for 12 weeks. On week 16, it improved the exacerbated glucose tolerance and prevented the further loss of islet β cell mass induced by HFD. QHYH markedly decreased serum MDA concentration, increased serum catalase (CAT) and SOD activities on week 4. However, no differences of serum glucose concentration or OS were observed on week 16. We concluded that QHYH decreased hyperglycemia exacerbated by HFD in GK rats by improving β cell function partly via its antioxidant effect.     

桂皮醛对高脂喂养小鼠糖脂代谢影响的实验研究

目的：探讨口服桂皮醛对高脂喂养小鼠（C57BL/6J 背景）糖脂代谢的影响。方法：采用雄性C57BL/6J小鼠作为研究对象,分 正常对照组（6 只）,高脂组（6 只）,高脂+ 桂皮醛（40 mg/kg,每天1 次）干预组（6 只）。桂皮醛以0.5 %羧甲基纤维素钠（CMC-Na） 溶解后口服灌胃,每天1 次;正常对照组和高脂组给予灌服等体积的CMC-Na,每天1 次,干预时间为3 月。每周观察体重、空腹血 糖,实验结束后观察胰岛素耐量（IPITT）、葡萄糖耐量（IPGTT）,观察各组小鼠的血脂水平（TC,TG,LDL-C,HDL-C）、胰岛素水 平、肠系膜脂肪重量及以HE 染色观察脂肪细胞形态。结果：在脂代谢方面,桂皮醛干预可显著防止高脂喂养小鼠的体重和血脂水 平的升高;高脂喂养小鼠肠系膜脂肪重量显著增加,HE 染色提示脂肪细胞显著增大;桂皮醛可显著防止肠系膜脂肪重量的增加 及脂肪细胞的变大。而在葡萄糖代谢方面,桂皮醛可显著降低高脂喂养小鼠血糖和胰岛素水平,改善小鼠的葡萄糖耐量和胰岛素 敏感性。结论：口服桂皮醛可显著改善高脂喂养小鼠的糖、脂代谢。