Consumption of pork-liver protein hydrolysate reduces body fat in Otsuka Long-Evans Tokushima Fatty rats by suppressing hepatic lipogenesis

Antioxidant Capacity of Proteins and Hydrolysates from the Liver of Newborn Piglets, and Their Inhibitory Effects on Steatosis in vitro

Research background

Non-alcoholic steatohepatitis is a potentially progressive hepatic disorder that can lead to end-stage liver disease and hepatocellular carcinoma. The inhibitory effects of proteins and hydrolysates from the liver of newborn piglets on hepatic steatosis in oleic acid-induced hepatocellular carcinoma (HepG2) cells were investigated in vitro.

Experimental approach

The extracted proteins from the liver of newborn piglets were hydrolysed with papain, pepsin, trypsin and Alcalase. Based on the comparison of different enzyme digestion conditions, a protein hydrolysis protocol was established to obtain hydrolysates with lipid-lowering effect.

Results and conclusions

Trypsin-digested liver protein hydrolysate from newborn piglets exhibited strong antioxidant activity and good inhibitory effects against lipogenesis and cholesterol accumulation in HepG2 cells at the concentration of 150 μg/mL, with a triglyceride decrease of (43±3) % and cholesterol decrease of (31±5) %, compared with model group induced with 0.75 mM oleic acid. The addition of trypsin-digested liver protein hydrolysate from newborn piglets (300 μg/mL) decreased alanine aminotransferase and aspartate aminotransferase activities and increased superoxide dismutase activity.

Novelty and scientific contribution

This study demonstrated that the trypsin-digested liver protein hydrolysate from newborn piglets has a potential preventive effect against non-alcoholic fatty liver disease in its early stage, and a potential use as the modulator of lipid overaccumulation in form of food supplements.

Meta-Analysis for Correlating Structure of Bioactive Peptides in Foods of Animal Origin with Regard to Effect and Stability

Amino acid (AA) sequences of 807 bioactive peptides from foods of animal origin were examined in order to correlate peptide structure with activity (antihypertensive, antioxidative, immunomodulatory, antimicrobial, hypolipidemic, antithrombotic, and opioid) and stability in vivo. Food sources, such as milk, meat, eggs, and marine products, show different frequencies of bioactive peptides exhibiting specific effects. There is a correlation of peptide structure and effect, depending on type and position of AA. Opioid peptides contain a high percentage of aromatic AA residues, while antimicrobial peptides show an excess of positively charged AAs. AA residue position is significant, with those in the first and penultimate positions having the biggest effects on peptide activity. Peptides that have activity in vivo contain a high percentage (67%) of proline residues, but the positions of proline in the sequence depend on the length of the peptide. We also discuss the influence of processing on activity of these peptides, as well as methods for predicting release from the source protein and activity of peptides.

Antioxidant properties of porcine liver proteins hydrolyzed using Monascus purpureus

In this study, the antioxidant activities of porcine liver proteins, hydrolyzed using Alcalase^®, papain, pepsin, or a microbial suspension of Monascus purpureus (APLH, PaPLH, PePLH, and MPLH, respectively), were investigated. The results indicated that the yield and degree of hydrolysis (DH) of hydrolysates increased with hydrolysis time. The highest yield and peptide content were obtained from APLH, whereas the DH of PaPLH was higher than that of the others. MPLH exhibited the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and reducing power, whereas APLH and PaPLH exhibited the higher ferrous ion-chelating ability than that of the MPLH. The molecular weights of all the hydrolysates were <10 kDa. The PaPLH exhibited the highest contents of total amino acids and hydrophobic amino acids. Fifteen antioxidant fractions obtained from MPLH contained one or more of the following amino acids in their sequences: Tyr, Trp, Ala, Pro, Met, Lys, Asp, Cys, Val, Leu, and His.

Optimization of ultrasonic-assisted enzymatic hydrolysis conditions for the production of antioxidant hydrolysates from porcine liver by using response surface methodology

Objective

The objective of this study was to optimize ultrasonic-assisted enzymatic hydrolysis conditions, including enzyme-to-substrate (E/S) ratio, pH, and temperature, for producing porcine liver hydrolysates (PLHs) with the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity by using response surface methodology (RSM).

Methods

The study used RSM to determine the combination of hydrolysis parameters that maximized the antioxidant activity of our PLHs. Temperature (40°C, 54°C, and 68°C), pH (8.5, 9.5, and 10.5), and E/S ratio (0.1%, 2.1%, and 4.1%) were selected as the independent variables and analyzed according to the preliminary experiment results, whereas DPPH free radical scavenging activity was selected as the dependent variable.

Results

Analysis of variance showed that E/S ratio, pH, and temperature significantly affected the hydrolysis process (p<0.01). The optimal conditions for producing PLHs with the highest scavenging activity were as follows: E/S ratio, 1.4% (v/w); temperature, 55.5°C; and initial pH, 10.15. Under these conditions, the degree of hydrolysis, DPPH free radical scavenging activity, ferrous ion chelating ability, and reducing power of PLHs were 24.12%, 79%, 98.18%, and 0.601 absorbance unit, respectively. The molecular weight of most PLHs produced under these optimal conditions was less than 5,400 Da and contained 45.7% hydrophobic amino acids.

Conclusion

Ultrasonic-assisted enzymatic hydrolysis can be applied to obtain favorable antioxidant hydrolysates from porcine liver with potential applications in food products for preventing lipid oxidation.

Dietary freshwater clam (Corbicula fluminea) extract suppresses accumulation of hepatic lipids and increases in serum cholesterol and aminotransferase activities induced by dietary chloretone in rats

We investigated the ameliorative effect of freshwater clam extract (FCE) on fatty liver, hypercholesterolemia, and liver injury in rats exposed to chloretone. Furthermore, we examined the effects of major FCE components (fat and protein fractions) to determine the active components in FCE. Chloretone increased serum aminotransferase activities and led to hepatic lipid accumulation. Serum aminotransferase activities and hepatic lipid content were lower in rats fed total FCE or fat/protein fractions of FCE. Expression of fatty acid synthase and fatty acid desaturase genes was upregulated by chloretone. Total FCE and fat/protein fractions of FCE suppressed the increase in gene expression involved in fatty acid synthesis. Serum cholesterol levels increased twofold upon chloretone exposure. Total FCE or fat/protein fractions of FCE showed hypocholesterolemic effects in rats with hypercholesterolemia induced by chloretone. These suggest that FCE contains at least two active components against fatty liver, hypercholesterolemia, and liver injury in rats exposed to chloretone.

Mechanisms and prospects of food protein hydrolysates and peptide-induced hypolipidaemia

Hyperlipidaemia is an important risk factor for developing cardiovascular disease, a leading global health issue. While pharmaceutical interventions have proved efficacious in acute conditions, many hypolipidaemic drugs are known to induce adverse side effects. Due to a strong positive link between functional food components and human health, emerging research has explored the application of natural food-based strategies in disease management. One of such strategies involves the use of food proteins as precursors of peptides with a wide variety of beneficial health functions. Some plant, animal and marine-derived protein hydrolysates and peptides have shown promising hypolipidaemic properties when evaluated in vitro, in cultured mammalian cells and animal models. The products exert their functions via bile acid-binding and disruption of cholesterol micelles in the gastrointestinal tract, and by altering hepatic and adipocytic enzyme activity and gene expression of lipogenic proteins, which can modulate aberrant physiological lipid profiles. The activity of the protein hydrolysates and peptides depends on their physicochemical properties including hydrophobicity of amino acid residues but there is knowledge gap on detailed structure-function relationships and efficacy in hyperlipidaemic human subjects. Based on the prospects, commercial functional food products containing hypolipidaemic peptides have been developed for enhancement of cardiovascular health.

Rodent models for metabolic syndrome research

Rodents are widely used to mimic human diseases to improve understanding of the causes and progression of disease symptoms and to test potential therapeutic interventions. Chronic diseases such as obesity, diabetes and hypertension, together known as the metabolic syndrome, are causing increasing morbidity and mortality. To control these diseases, research in rodent models that closely mimic the changes in humans is essential. This review will examine the adequacy of the many rodent models of metabolic syndrome to mimic the causes and progression of the disease in humans. The primary criterion will be whether a rodent model initiates all of the signs, especially obesity, diabetes, hypertension and dysfunction of the heart, blood vessels, liver and kidney, primarily by diet since these are the diet-induced signs in humans with metabolic syndrome. We conclude that the model that comes closest to fulfilling this criterion is the high carbohydrate, high fat-fed male rodent.

Antihyperglycemic effect of stem bark powder from paper mulberry (Broussonetia kazinoki Sieb.) in type 2 diabetic Otsuka Long-Evans Tokushima fatty rats

The effect of stem bark powder from paper mulberry (PMSB) on serum glucose, insulin, fructosamine, and lipid concentrations, as well as enzyme activities that serve as liver injury markers, was investigated in genetically diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats. Both nondiabetic Long-Evans Tokushima Otsuka (LETO) rats and diabetic OLETF rats (30 weeks old) were fed a semisynthetic diet with or without 50 g/kg PMSB for 8 weeks and then compared. The OLETF control rats showed a high amount of daily water intake in comparison to those in the LETO group. The concentrations of glucose, fructosamine, total lipid, triglyceride, total cholesterol, and high-density lipoprotein-cholesterol and the activities of aspartate aminotransferase and alanine aminotransferase (ALT) in serum were higher in the OLETF control rats than those in the LETO control rats. However, PMSB ingestion decreased the serum levels of glucose, fructosamine, triglyceride, and total cholesterol and the activity of ALT in the OLETF rats, but not in the LETO rats. The concentration of serum insulin was also significantly increased by PMSB consumption in the OLETF rats compared to the OLETF control rats. These results suggest that PMSB might have an antihyperglycemic effect in the OLETF rat and that the increased blood insulin level would be an important regulatory factor for improving hyperglycemia in the current animal model.