Enhanced amelioration of high-fat diet-induced fatty liver by docosahexaenoic acid and lysine supplementations

Ellagic acid alleviates high-fructose diet-induced non-alcoholic fatty liver disease by modulating liver metabolic profiles and gut microbiota

This study integrated analyses of gut microbiota and metabolomics to investigate the impact of ellagic acid (EA) on non-alcoholic fatty liver disease (NAFLD). Compared to the high-fructose diet (HFruD) group, the EA group exhibited reduced body weight and fat mass, alongside improvements in blood glucose and lipid metabolism. Liver metabolomics analysis revealed that EA increased the abundance of metabolites in pathways related to unsaturated fatty acids, amino acids and bile acids. Furthermore, EA induced alterations in the composition and structure of gut microbiota, notably decreasing bacterial genera enriched by HFruD while promoting beneficial bacteria such as Faecalibaculum. Correlation analysis demonstrated significant associations among NAFLD markers, gut microbiota and liver metabolites influenced by EA. This study provides new insights into the anti-NAFLD effects of EA, suggesting EA as a promising nutraceutical for improving NAFLD.

Molecular mechanism and therapeutic significance of essential amino acids in metabolically associated fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), also known as metabolically associated fatty liver disease (MAFLD), is a systemic metabolic disease characterized by lipid accumulation in the liver, lipid toxicity, insulin resistance, intestinal dysbiosis, and inflammation that can progress from simple steatosis to nonalcoholic steatohepatitis (NASH) and even cirrhosis or cancer. It is the most prevalent illness threatening world health. Currently, there are almost no approved drug interventions for MAFLD, mainly dietary changes and exercise to control weight and regulate metabolic disorders. Meanwhile, the metabolic pathway involved in amino acid metabolism also influences the onset and development of MAFLD in the body, and most amino acid metabolism takes place in the liver. Essential amino acids are those amino acids that must be supplemented from outside the diet and that cannot be synthesized in the body or cannot be synthesized at a rate sufficient to meet the body's needs, including leucine, isoleucine, valine (collectively known as branched-chain amino acids), tryptophan, phenylalanine (which are aromatic amino acids), histidine, methionine, threonine and lysine. The metabolic balance of the body is closely linked to these essential amino acids, and essential amino acids are closely linked to the pathophysiological process of MAFLD. In this paper, we will focus on the metabolism of essential amino acids in the body and further explore the therapeutic strategies for MAFLD based on the studies conducted in recent years.

L-lysine supplementation attenuates experimental autoimmune hepatitis in a chronic murine model

The incidence of autoimmune hepatitis (AIH) has increased significantly worldwide. The present study aims to explore the protective effect of L-lysine supplementation against AIH and to investigate its potential underlying mechanisms. A chronic experimental AIH mouse model was established by repeated tail vein injection of human cytochrome P450 2D6 (CYP2D6) plasmid. Starting from day 14 of the modeling, mice in the CYP2D6-AIH +L-lysine group were given 200 µl of purified water containing 10 mg/kg L-lysine by gavage until day27, once a day, and mice in the healthy control group and model group were given an equal volume of purified water by gavage. Our results showed that L-lysine supplementation partially reversed the liver injury mediated by CYP2D6 overexpression. These effects were consistent with the restraining impacts of L-lysine supplementation on decreasing pro-inflammatory cytokines expression level and CD4+ and CD8+ T lymphocytes infiltration, as well as curbing hepatic oxidative stress. Furthermore, L-lysine supplement relieved liver fibrosis in the context of AIH. In conclusion, L-lysine supplementation attenuates CYP2D6-induced immune liver injury in mice, which may serve as a novel nutrition support approach for AIH.

Effects of Lysine-Lysine Dipeptide on Serum Amino Acid Profiles, Intestinal Morphology, and Microbiome in Suckling Piglets

Aims

Small peptides are more energy-saving and efficiently absorbed compared to amino acids. Our study aimed to evaluate the effect of the Lys-Lys dipeptide on the improvement of growth performance, amino acid metabolism, and gut development in suckling piglets.

Methods and Results

Twenty-eight newborn suckling piglets were orally administrated with 0.1%, 1%, and 5% Lys-Lys dipeptide for 21 days. Our results showed that the Lys-Lys dipeptide has no significant effect on growth performance and intestinal morphology compared with the control group. We also found that the 1% Lys-Lys dipeptide significantly increased the concentrations of serum Lys, Thr, Phe, and Pro while decreasing Cys compared to the control group. Similarly, the 5% Lys-Lys dipeptide markedly increased the concentrations of serum Lys, Iso, Thr, Asp, Glu, and Pro compared to the control group. Moreover, the Lys-Lys dipeptide downregulated the expression of jejunal Slc7a1, Slc7a2, and Slc15a1 and ileal Slc7a2. Additionally, the Lys-Lys dipeptide decreased the microbiota richness indices and relative abundance of Bacteroidales.

Conclusion

In this study, we found that the Lys-Lys dipeptide contributes to the metabolism of amino acids but failed to affect the growth performance of piglets. Additionally, the Lys-Lys dipeptide decreased the relative abundance of Bacteroidales. These results provide a theoretical for the future application and research of Lys-Lys dipeptide in intestinal development of suckling piglets.

The crucial role of lysine in the hepatic metabolism of growing Holstein dairy heifers as revealed by LC-MS-based untargeted metabolomics

The objective of this experiment was to evaluate the effect of supplementing rumen-protected Lys based on a Lys-deficient diet on liver metabolism in growing Holstein heifers. The experiment was conducted for 3 months with 36 Holstein heifers (initial body weight: 200 ± 9.0 kg; 7-month-old). Heifers were randomly assigned to 2 diets based on corn, soybean meal, alfalfa hay, and wheat bran: control, Lys-deficient diet (LD; 0.66% Lys in diet), and Lys-adequate diet (LA; 1.00% Lys in diet). The results showed no difference in growth performance between the 2 groups (P > 0.05). However, there was a clear trend of increasing feed conversion rate with Lys supplementation (0.05 < P < 0.01). The serum urea nitrogen concentration was significantly decreased, and the aspartate aminotransferase-to-alanine aminotransferase ratio was significantly decreased by Lys supplementation (P < 0.05). Moreover, growing heifers fed a Lys-adequate diet had lower levels of urine nitrogen excretion and higher levels of the biological value of nitrogen (P < 0.05). Metabolomic analysis revealed that 5 types of phosphatidylcholine and 3 types of ceramide were significantly increased and enriched in sphingolipid metabolism and glycerophospholipid metabolism (P < 0.05). His, Leu, and Asp levels were significantly decreased in the liver following Lys supplementation (P < 0.05). In conclusion, Lys supplementation may promote the synthesis of body tissue proteins, as evidenced by significantly decreased amino acids in the liver and urine N excretion, it also improves hepatic lipid metabolism by providing lipoprotein precursors.

The effect of the application of diets with varied proportions of arginine and lysine on biochemical and antioxidant status in turkeys

The aim of the study was to determine the effect of two proportions of arginine (95% and 105%) relative to lysine (Lys), where Lys content in the diet is in accordance with NRC (1994) recommendations or 10% higher, on the metabolism, antioxidant status, and growth performance of turkeys. The experiment had a 2x2 factorial design with two levels of Lys and Arg. The diets with a low level of Lys were according to the NRC (1994) requirements. In the diets with a high level of Lys, the content of Lys was increased by 10% relative to the low level Lys. The two Arg levels in the experimental diets were determined so as to provide 95% and 105% Arg relative to the content of dietary Lys. An increase in the amount of Lys in the diet of turkeys by 10% relative to NRC nutritional recommendations (1994) was not shown to improve growth performance, but had beneficial effects on the metabolism and antioxidant status of the birds, as evidenced by the improvement of hepatic indices (reduction of AST and ALT activity at 9th week of life) and renal indices (reduction of UREA at 9th week of life and reduction of TP and increase level of ALB levels at 16th week of life), as well as an increase in the level of glutathione with strong antioxidant properties at 16th week of life. In comparison to the lower level of Arg in the diet, an increase in the amount of this amino acid to 105% Lys did not improve growth performance, metabolism, or antioxidant status. An Arg level of 95% Lys can be used in a diet for turkeys containing 10% more Lys than the level recommended by the NRC (1994).

Dietary whey and egg proteins interact with inulin fiber to modulate energy balance and gut microbiota in obese rats

Diets supplemented with protein and fiber are well known to reduce food intake and weight gain; however, less is known about the combined effects of protein and prebiotic fiber on energy balance and gut microbiota composition. We compared effects of diets containing high egg or whey protein with cellulose or prebiotic (inulin) fiber on energy balance, gut microbiota, hormones, and metabolites. Male obese rats (n=8/group) were allocated to four diets: Egg albumen+Cellulose (EC), Egg albumen+Inulin (EI), Whey protein+Cellulose (WC), and Whey protein+Inulin (WI). Results revealed that diet-induced hypophagia was transient with EC and prolonged with EI and WI, compared to WC. Importantly, CCK-1 receptor antagonist (Devazepide) attenuated the hypophagic effects of EC, EI, and WI. Further, EC, EI and WI decreased respiratory quotient, energy expenditure, weight and adiposity gains, and improved glycemia, relative to WC. Propranolol (β₁-β₂-receptor blocker) attenuated diet-induced changes in energy expenditure. Transcript abundance of thermogenic markers in brown adipose tissue, plasma hormones, and metabolites especially acyl-carnitines and glycerophospholipids, were differentially altered by diets. Diet explained 25% of compositional differences in cecal microbiomes, but diets with same fiber type did not differ. Microbiota differing between groups also strongly correlated with gut hormones and metabolites. Species most strongly correlated to a marker for butyrate production were in highest abundance in inulin diets. Together, these findings indicate that inulin enriched diets containing egg or whey protein improved energy balance, decreased adiposity, and modulated gut microbiota and metabolites, with CCK signaling partly mediating the satiety effects of diets.

A novel chicken model of fatty liver disease induced by high cholesterol and low choline diets

Fatty liver diseases, common metabolic diseases in chickens, can lead to a decrease in egg production and sudden death of chickens. To solve problems caused by the diseases, reliable chicken models of fatty liver disease are required. To generate chicken models of fatty liver, 7-week-old ISA female chickens were fed with a control diet (17% protein, 5.3% fat, and 1,300 mg/kg choline), a low protein and high fat diet (LPHF, 13% protein, 9.1% fat, and 1,300 mg/kg choline), a high cholesterol with low choline diet (CLC, 17% protein, 7.6% fat with additional 2% cholesterol, and 800 mg/kg choline), a low protein, high fat, high cholesterol, and low choline diet (LPHFCLC, 13% protein, 12.6% fat with additional 2% cholesterol, and 800 mg/kg choline) for 4 wk. Our data showed that the CLC and LPHFCLC diets induced hyperlipidemia. Histological examination and the content of hepatic lipids indicated that the CLC and LPHFCLC diets induced hepatic steatosis. Plasma dipeptidyl peptidase 4, a biomarker of fatty liver diseases in laying hens, increased in chickens fed with the CLC or LPHFCLC diets. Hepatic ballooning and immune infiltration were observed in these livers accompanied by elevated interleukin 1 beta and lipopolysaccharide induced tumor necrosis factor mRNAs suggesting that the CLC and LPHFCLC diets also caused steatohepatitis in these livers. These diets also induced hepatic steatosis in Plymouth Rock chickens. Thus, the CLC and LPHFCLC diets can be used to generate models for fatty liver diseases in different strains of chickens. In ISA chickens fed with the CLC diet, peroxisome proliferator-activated receptor γ, sterol regulatory element binding transcription factor 1, and fatty acid synthase mRNAs increased in the livers, suggesting that lipogenesis was enhanced by the CLC treatment. Our data show that treatment with CLC or LPHFCLC for 4 wk induces fatty liver disease in chickens. These diets can be utilized to rapidly generate chicken models for fatty liver research.

Threonine, but Not Lysine and Methionine, Reduces Fat Accumulation by Regulating Lipid Metabolism in Obese Mice

Some amino acids (AAs) have been proven to suppress fat mass and improve insulin sensitivity. However, the impact of important essential AAs, threonine, lysine, and methionine, on obesity has not been clarified. In the present study, after an 8 week period of obesity induction, mice were grouped to receive either a high-fat diet (HFD) or HFD supplemented with lysine, threonine, or methionine (3% in drinking water) for another 10 weeks. The results showed that dietary supplementation with threonine significantly decreased body weight, epididymal and perirenal fat pad weights, serum concentrations of glucose, triacylglycerols, total cholesterol, and LDL-cholesterol compared to the HFD group. HOMA-IR and serum leptin and adiponectin were improved by threonine supplementation. In epididymal adipose tissue, threonine treatment significantly down-regulated the expression levels of lipogenesis and up-regulated expressions of lipolysis compared to the HFD group. Threonine addition stimulated the expression of UCP-1 and related genes in brown adipose tissue. However, lysine or methionine supplementation showed little effect on body weight, WAT weight, serum lipid profiles, and lipid-metabolism-related gene expressions of HFD-fed mice. These findings suggest that threonine inhibited fat mass and improved lipid metabolism of already obese mice, providing a potential agent in treating obesity.

Dietary supplementation with L-lysine affects body weight and blood hematological and biochemical parameters in rats

L-Lysine (Lys) is a popular additive in foods, but the physiological effects of excess Lys supplementation are poorly understood and upper limits of safe intake have not been established. The objectives of this study were to examine the effects of dietary supplementation with increasing amounts of Lys on body weight (BW), food intake, and various blood hematological and biochemical parameters in rats. Male Sprague-Dawley rats at 10 weeks of age were assigned to ten diet groups (eight rats/group) and fed diets containing either 7% or 20% casein and supplemented with either 0% (Control), 1.5%, 3%, 6% Lys, or 6% Lys + 3% arginine for 1 week. Rats fed 7% casein with ≥ 1.5% Lys supplementation had lower serum albumin and leptin and higher LDL cholesterol (LDLC), ratios of total cholesterol (TC):HDL cholesterol (HDLC) and LDLC:HDLC than those fed 7% casein Control diet (P < 0.05). Rats fed 7% casein diet supplemented with 3% Lys diet had lower BW gain, food intake, serum alkaline phosphatase activity, and increased mean corpuscular hemoglobin concentration, blood urea nitrogen and serum pancreatic polypeptide compared to rats fed the Control diet (P < 0.05). Addition of 6% Lys in 7% casein caused significant BW loss (P < 0.001) and altered additional parameters. Addition of 6% Lys in a 20% casein diet reduced BW gain and food intake and altered numerous parameters. Arg supplementation normalized many of the endpoints changed by Lys. Collectively, these results show that Lys supplementation affects BW, food intake and a number of hematological and biochemical parameters. These effects of Lys supplementation were confined primarily in diets with lower levels of dietary protein. In the context of a low protein diet (7% casein), levels of Lys supplementation ≥ 1.5% may exert adverse health effects in rats.

Role of n-3 Polyunsaturated Fatty Acids in Ameliorating the Obesity-Induced Metabolic Syndrome in Animal Models and Humans

The incidence of obesity and its comorbidities, such as insulin resistance and type II diabetes, are increasing dramatically, perhaps caused by the change in the fatty acid composition of common human diets. Adipose tissue plays a role as the major energy reservoir in the body. An excess of adipose mass accumulation caused by chronic positive energy balance results in obesity. The n-3 polyunsaturated fatty acids (n-3 PUFA), DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) exert numerous beneficial effects to maintain physiological homeostasis. In the current review, the physiology of n-3 PUFA effects in the body is delineated from studies conducted in both human and animal experiments. Although mechanistic studies in human are limited, numerous studies conducted in animals and models in vitro provide potential molecular mechanisms of the effects of these fatty acids. Three aspects of n-3 PUFA in adipocyte regulation are discussed: (1) lipid metabolism, including adipocyte differentiation, lipolysis and lipogenesis; (2) energy expenditure, such as mitochondrial and peroxisomal fatty acid β-oxidation; and (3) inflammation, including adipokines and specialized pro-resolving lipid mediators. Additionally, the mechanisms by which n-3 PUFA regulate gene expression are highlighted. The beneficial effects of n-3 PUFA may help to reduce the incidence of obesity and its comorbidities.

A Diet Rich in Docosahexaenoic Acid Restores Liver Arachidonic Acid and Docosahexaenoic Acid Concentrations in Mice Homozygous for the Human Apolipoprotein E ε4 Allele

BACKGROUND

Metabolism of long-chain polyunsaturated fatty acids (LC-PUFAs) is disturbed in carriers of the apolipoprotein E (APOE) ε4 allele (APOE4). More specifically, APOE4 carriers are lower responders to ω-3 (n-3) LC-PUFA supplementation; this might be because LC-PUFA transport into cells or β-oxidation is disturbed. However, high doses of dietary docosahexaenoic acid (DHA) seem to restore DHA homeostasis in APOE4 carriers, but the contribution of hepatic fatty acid (FA) transporters is unknown.

OBJECTIVES

With the use of mice carrying human APOE isoforms, we sought to investigate whether a DHA-rich diet could restore DHA homeostasis in APOE4 mice and whether this involved hepatic FA transporters.

METHODS

Male and female mice homozygous for the APOE ε2 allele, APOE ε3 allele (APOE3), and APOE4 were fed either a diet enriched with DHA (0.7 g DHA/100 g diet) or a control diet for 8 mo and were killed at 12 mo of age. Liver and plasma FA profiles were measured by GC, and FA transporter expression was evaluated by Western immunoblotting.

RESULTS

There was a significant genotype × diet interaction for hepatic concentrations of arachidonic acid (AA) and DHA (P = 0.005 and P = 0.002, respectively) and a trend toward an interaction for liver expression of fatty acid binding protein 1 (FABP1) (P-interaction = 0.05). APOE4 mice had 60-100% higher liver AA, DHA, and FABP1 than did APOE3 mice, but only when fed the control diet. Independent of diet, APOE4 mice had 20-30% lower plasma concentrations of AA and DHA than did APOE3 mice. Overall, mice fed the DHA diet had 50% lower concentrations of liver total FAs than did mice fed the control diet.

CONCLUSIONS

These findings in transgenic mice suggest that a long-term diet rich in DHA suppresses the APOE4-specific disturbances in hepatic transport and concentration of AA and DHA and also reduces hepatic total FA concentrations, regardless of genotype.

Ameliorating effect of Allium Sativum on high-fat diet induced fatty liver in albino rats

Objective:

To assess the hepatoprotective effect provided by fresh garlic on fatty liver induced by high-fat diet.

Methods:

This experimental study was carried out at BMSI, JPMC from October to November 2008. Thirty adult albino rats, 200-240 gram weight, were divided into three groups. Group A received control diet, Group B received high-fat diet (20 mg butter/100 gm diet) and Group C received high-fat diet with fresh garlic (20 mg butter with 6 gm fresh garlic/100 gm diet). The groups were further divided on the basis of duration of treatment, four weeks and eight weeks respectively. The rats were sacrificed, liver removed, weighed and relative liver weight calculated. Hepatic tissue was processed and tissue slides stained with haematoxylin and eosin.

Results:

There was significant increase in relative liver weight in group B animals as compared to the control animals, which decreased significantly in group C. Haematoxylin and eosin stained sections revealed ballooned hepatocytes having vesicular appearance with pyknotic nuclei in high-fat group which were preserved to a great extent in group C animals.

Conclusion:

This study has shown that use of fresh garlic along with high-fat diet prevents its damaging effects on liver to a great extent.

Primary Endodermal Epithelial Cell Culture from the Yolk Sac Membrane of Japanese Quail Embryos

We established an endodermal epithelial cell culture model (EEC) for studying the function of certain enzymes and proteins in mediating nutrient utilization by avian embryos during development. Fertilized Japanese quail eggs were incubated at 37 °C for 5 days and then yolk sac membranes (YSM) were collected to establish the EEC culture system. We isolated the embryonic endoderm layer from YSM, and sliced the membrane into 2 - 3 mm pieces and partially digested with collagenase before seeding in 24-well culture plates. The EECs proliferate out of the tissue and are ready for cell culture studies. We found that the EECs had typical characteristics of YSM in vivo, for example, accumulation of lipid droplets, expression of sterol O-acyltransferase and lipoprotein lipase. The partial digestion treatment significantly increased the successful rate of EEC culture. Utilizing the EECs, we demonstrated that the expression of SOAT1 was regulated by the cAMP dependent protein kinase A related pathway. This primary Japanese quail EEC culture system is a useful tool to study embryonic lipid transportation and to clarify the role of genes involved in mediating nutrient utilization in YSM during avian embryonic development.

Fish oil alleviated high-fat diet-induced non-alcoholic fatty liver disease via regulating hepatic lipids metabolism and metaflammation: a transcriptomic study

Background

Intake of fish oil rich in n-3 polyunsaturated fatty acids (PUFAs) is believed to be beneficial against development of non-alcoholic fatty liver disease (NAFLD). However, the underlying mechanisms remain unclear. This study was to gain further understanding of the potential mechanisms of the protective effects of fish oil against NAFLD.

Methods

Ten male Sprague–Dawley rats were fed a control diet (CON), a Western style high-fat and high-cholesterol diet (WD), or a WD diet containing fish oil (FOH) for 16 weeks respectively. The development of liver steatosis and fibrosis were verified by histological and biochemical examination. Hepatic transcriptome were extracted for RNA-seq analysis, and particular results were confirmed by real-time polymerase chain reaction (PCR).

Results

The consumption of fish oil significantly ameliorated WD-induced dyslipidemia, transaminase elevation, hepatic steatosis, inflammatory infiltration, and fibrosis. Hepatic RNA-Seq analysis showed that long-term intake of fish oil restored the expression of circadian clock-related genes per2 and per3, which were reduced in WD fed animals. Fish oil consumption also corrected the expression levels of genes involved in fatty acid and cholesterol metabolism, such as Srebf1, Fasn, Scd1, Insig2, Cd36, Cyp7a1, Abcg5, Abcg8 and Pcsk9. Moreover, the expression levels of pro-inflammation genes Mcp1, Socs2, Sema4a, and Cd44 in the FOH group were lower than that of WD group, implying that fish oil protects the liver against WD-induced hepatic inflammation.

Conclusion

The present study demonstrates fish oil protects against WD-induced NALFD via improving lipid metabolism and ameliorating hepatic inflammation. Our findings add to the current understanding on the benefits of n-3 PUFAs against NAFLD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-016-0190-y) contains supplementary material, which is available to authorized users.

Potential Therapeutic Agents for the Treatment of Fatty Degeneration of Liver and Atheromatous Plaques: An Experimental Study in Rats

Background:

Since long high fat diet (HFD) is being blamed for causing fatty degeneration of liver and formation of atheromatous plaques. At present, no proper pharmacotherapy is available for both the conditions. In this study, different substances containing monounsaturated fatty acids were used to observe their protective effects in the HFD induced damage to liver and coronary vessels.

Objectives:

To discover effective therapeutic agents for HFD induced fatty degeneration of liver and atheromatous plaques.

Materials and Methods:

The study was conducted from September 2015 to April 2016. In this study, rats were divided into nine groups according to dietary regimen. Each group comprised six rats. Saturated fat was given in the form of butter, and unsaturated fat was given in the form of corn oil, olive oil, Nigella sativa oil, and crushed garlic. Serum samples were taken to estimate lipid profile, liver functions, cardiac functions, and kidney functions. Visceras were removed after animal sacrifice, and histopathological examination was done.

Results and Conclusion:

During the study period, the weight of animals changed significantly in some groups. Those animals which were given crushed garlic along with high saturated fat diet, showed protection against accumulation of lipids in the hepatocytes. Olive oil and Nigella sativa oil were comparatively less effective.

SUMMARY

Consumption of Garlic, Nigella Sativa and Olive oil significantly improved/revised the Fatty Degeneration of liver induced by intake of High Fat Diet.

No fat deposition was found in the liver when Garlic, Nigella Sativa and Olive oil, were given concomitantly with HFD.

Hepatocytes functioned better even in comparison to control and a decrease in liver enzymes was found with use of Garlic.

Use of Garlic, Nigella Sativa and Olive oil, prevented the plaque formation in the vessels and decreased serum lipids.

Beneficial effects of Garlic were significant in comparison to Nigella Sativa and Olive oil.

Abbreviations used: HFD: High Fat Diet; NS: Nigella Sativa; TQ: Thymoquinone; KFMRC: King Fahad Medical Research Center; BUN: Blood Urea Nitrogen; BNF: Buffered Neutral Formalin; G: Group