VLDL metabolism in rats is affected by the concentration and source of dietary protein

Protein malnutrition in BALB/C mice: A model mimicking clinical scenario of marasmic-kwashiorkor malnutrition

Protein malnutrition continues to be a major global issue. A stable animal model to address protein malnutrition and its effect on various disease conditions is necessary. In the present study, we have formulated and standardized a low protein diet (LPD) to develop a protein malnutrition model using Balb/C mice. Healthy male Balb/C mice were weaned and exposed to LPD combinations while another group exposed to normal diet (18% protein). Animal survival, change in body weight, body mass index (BMI), biochemical parameters, antioxidant status, and liver histopathology were used to confirm the development of malnourished mice model (marasmic-kwashiorkor). Mice receiving 10% protein diet showed moderate weight gain, higher BMI, and no mortality compared to the 6% protein group. The former group showed remarkable differences in BMI, biochemical and antioxidant parameters. Further, histopathological changes against the normal group at weeks 20 and 30 confirmed the development of protein malnutrition in mice on 10% protein diet. The study confirms the development of a stable, economical, reproducible, and clinically relevant protein malnutrition model using the formulated 10% protein diet. Further, the model can be used for short and long-term studies to investigate the pathophysiology of malnutrition in any disease/condition.

Legumes as Functional Food for Cardiovascular Disease

Legumes are an essential food source worldwide. Their high-quality proteins, complex carbohydrates, dietary fiber, and relatively low-fat content make these an important functional food. Known to possess a multitude of health benefits, legume consumption is associated with the prevention and treatment of cardiovascular diseases (CVD). Legume crude protein isolates and purified peptides possess many cardiopreventive properties. Here, we review selected economically valued legumes, their taxonomy and distribution, biochemical composition, and their protein components and the mechanism(s) of action associated with cardiovascular health. Most of the legume protein studies had shown upregulation of low-density lipoprotein (LDL) receptor leading to increased binding and uptake, in effect significantly reducing total lipid levels in the blood serum and liver. This is followed by decreased biosynthesis of cholesterol and fatty acids. To understand the relationship of identified genes from legume studies, we performed gene network analysis, pathway, and gene ontology (GO) enrichment. Results showed that the genes were functionally interrelated while enrichment and pathway analysis revealed involvement in lipid transport, fatty acid and triglyceride metabolic processes, and regulatory processes. This review is the first attempt to collate all known mechanisms of action of legume proteins associated with cardiovascular health. This also provides a snapshot of possible targets leading to systems-level approaches to further investigate the cardiometabolic potentials of legumes.

Hypocholesterolemic efficacy of royal jelly in healthy mild hypercholesterolemic adults

CONTEXT

Royal jelly (RJ) has been reported for its health promoting factors such as antioxidant, anti-inflammatory and lipid lowering activities.

OBJECTIVE

The present randomized, placebo-controlled study examines the hypolipidemic beneficial effect of RJ through evaluating anthropometric measurements, lipid profile and various hormone levels in mildly hypercholesterolemic participants.

MATERIALS AND METHODS

Forty subjects with mild hypercholesterolemia (180-200 mg/dL) were randomly selected and divided into two groups as experimental or placebo, who requested to intake nine capsules (350 mg/capsule) of RJ or placebo/day, respectively, for three months with one month of follow-up without any supplementation.

RESULTS

No significant changes were noted in any of the anthropometric parameters like body weight, waist and body fat. The serum total cholesterol (TC; 207.05-183.15 mg/dL) and low-density lipoprotein cholesterol (LDL-c; 126.44-120.31 mg/dL) levels were reduced significantly (p < 0.05) after administration of RJ. However, triglyceride (TG) and high-density lipoprotein cholesterol (HDL-c) levels were not considerably altered. Moreover, three months of RJ consumption significantly ameliorated (p < 0.05) the concentration of sex hormones like dehydroepiandrosterone sulphate (DHEA-S; 1788.09-1992.31 ng/mL). Also, intake of RJ did not elicit any hepatic or renal damage.

DISCUSSION AND CONCLUSION

Intervention with RJ for three months considerably lowered the TC and LDL-c levels through improving the levels of DHEA-S and thus alleviates the risk of cardiovascular disease (CVD).

Influence of a Protein Concentrate from Amaranthus cruentus Seeds on Lipid Metabolism

It is widely known that elevated cholesterol and triglycerides levels favor the development of heart disease. In this paper we studied the effect of a protein concentrate from Amaranthus cruentus (Ac) on the lipid content in serum and liver tissue of male Wistar rats. The animals were separated into two groups, each group with 16 rats. The control diet had casein as protein source (CD), and the experimental one had Ac protein concentrate (PCAcD). The diets contained 1% cholesterol. Parameters of oxidative stress in liver with CD and PCAcD were also evaluated. No significant differences were observed in serum total cholesterol, whereas LDL decreased and HDL increased (P < 0.001), and the amount of triglycerides decreased in PCAcD as compared to CD. In liver, a decrease of total cholesterol and triglycerides (P < 0.001) was observed in the experimental group in relation to control. Fatty acid synthase (FAS) activity decreased significantly in the experimental group. The mRNA of HMG-CoA reductase did not change, and mRNA of FAS decreased in rat liver fed with PCAcD compared with CD. The excretion of total lipids in feces increased with PCAcD compared to CD (P < 0.001). The activity of reactive substances to thiobarbituric acid in liver showed no significant differences between the control and experimental diets. However, total glutathione and reduced glutathione increased in PCAcD compared to CD (P < 0.001). It can be concluded that PCAcD has a hypotriglyceridemic effect, affects the metabolism of liver lipids, and increases parameters of antioxidant protection in male Wistar rats.

Purified chickpea or lentil proteins impair VLDL metabolism and lipoprotein lipase activity in epididymal fat, but not in muscle, compared to casein, in growing rats

BACKGROUND

It is well known that the legume proteins have a lowering effect on plasma cholesterol and triacylglycerols (TG) concentrations compared to animal proteins. The protein itself, as well as non-protein constituents, naturally present in legumes may be implicated.

AIM OF THE STUDY

The effects of various dietary purified legumes proteins compared to casein, were determined on plasma TG level, VLDL concentration and composition. Moreover, lipoprotein lipase (LPL) activity in epididymal fat, gastrocnemius and heart was investigated to evaluate in these tissues their capacity to release free fatty acids from their TG substrate and the liver capacity to stock the TG.

METHODS

Weaning male Wistar rats were fed ad libitum one of the following diets: 200 g/kg diet of purified proteins of lentil (L), or chickpea (CP) or casein (CAS). At day 28, VLDL were isolated from plasma sample by a single ultracentrifugation flotation. Hepatic lipase and LPL activity in epididymal fat, gastrocnemius and heart were measured by using glycerol tri [9-10(n)-(3)H] oleate emulsion as substrate.

RESULTS

Compared with CAS diet, the CP and L protein diets exhibited similar cholesterolemia, but lower triglyceridemia (1.9-fold and 2.5-fold) and VLDL particle number, as measured by their reduced contents of TG and apolipoproteins. CP and L protein diets reduced liver TG and cholesterol by 31 and 45%, respectively compared to CAS diet. Furthermore, LPL activity in adipose tissue of rats fed CP or L was 1.6-fold lower than that of rats fed CAS. There was no significant difference in heart and gastrocnemius LPL activities with the three proteins. In contrast, hepatic lipase activity was higher in rats fed CP and L diets.

CONCLUSION

The low food efficiency ratio of purified CP and L proteins related to CAS is associated with decreased plasma VLDL and adipose tissue LPL activity. The low liver TG concomitant with reduced TG and apolipoproteins contents of VLDL confirm that hypotriglyceridemia is essentially due to impaired synthesis, exportation and transport of TG by VLDL which prevent lipid storage in adipose tissue.

Royal jelly supplementation improves lipoprotein metabolism in humans

Royal jelly (RJ) has several physiological effects and is widely used in commercial medical products and health foods. We examined the effects of RJ supplementation on serum lipoprotein metabolism in humans. Fifteen volunteers were divided into an RJ intake group (n=7) and a control group (n=8). The RJ group took 6 g per day for 4 wk. Their serum total cholesterol (TC) and serum low-density lipoprotein (LDL) decreased significantly compared with those of the control group (p<0.05). There were no significant differences in serum high-density lipoprotein (HDL) or triglyceride concentrations. Moreover, the relationship between the serum cholesterol and lipoprotein levels was investigated. Among the lipoprotein fractions, small very-low-density lipoprotein was decreased (p<0.05) after RJ intake. Our results suggest that dietary RJ decreases TC and LDL by lowering small VLDL levels.

Effect of proteins from beef, pork, and turkey meat on plasma and liver lipids of rats compared with casein and soy protein

OBJECTIVE

We assessed the effect of dietary proteins isolated from beef, pork, and turkey meat on concentrations of cholesterol and triacylglycerols in plasma, lipoproteins, and liver and the composition of the microsomal membrane (fatty acids, phosphatidylcholine/phosphatidylethanolamine ratio) compared with that of casein and soy protein in rats.

METHODS

Five groups of 12 rats each were fed semisynthetic diets for 20 d that contained 200 g/kg of proteins isolated from beef, pork, or turkey meat or, as controls, casein or soy protein.

RESULTS

Rats fed beef, pork, or turkey proteins did not differ in cholesterol concentrations of plasma, lipoproteins, and liver and in composition of microsomal membrane from rats fed the casein diet. All groups fed a protein from an animal source had higher very low-density lipoprotein (VLDL) and liver cholesterol concentrations than did rats fed soy protein. However, rats fed pork protein had lower concentrations of triacylglycerols in liver, plasma, and VLDL and lower mRNA concentrations of sterol regulatory element binding protein-1 and glucose-6-phosphate dehydrogenase than did rats fed casein. However, concentrations of plasma and VLDL triacylglycerols in rats fed pork protein were not as low as those observed in rats fed soy protein.

CONCLUSION

Proteins isolated from beef, pork, or turkey meat do not differ from casein in their effects on cholesterol metabolism. Pork protein decreases plasma triacylglycerol concentrations compared with casein but not compared with soy protein. The triacylglycerol-lowering effect of pork protein compared with casein is suggested to be caused by decreased hepatic fatty acid synthesis.

Rat adult offspring serum lipoproteins are altered by maternal consumption of a liquid diet

Palatable liquid diets for the administration of ethanol (EtOH) to animals have proven to be a major advance for the study of the effects of EtOH consumption under conditions of isocaloric nutrition of the control animals. Using a liquid diet, the original aim of the reported studies was to examine the effect of maternal EtOH consumption during pregnancy on the lipoprotein (Lp) profiles of the adult offspring measured by means of nuclear magnetic resonance spectroscopy. However, initial data suggested that compared to a maternal chow diet, the basal maternal liquid diet (without EtOH) had a significant effect on specific serum Lp of the adult offspring. The adult offspring of mothers who had consumed a basal liquid diet without EtOH exhibited significant increases in their plasma triglycerides (TG) and cholesterol content compared to adult offspring whose mothers consumed a chow diet. Further, there were significant increases in the offspring's VLDL and low density Lp (LDL) subfractions' particle number, regardless of whether the maternal liquid diet was ad libitum-fed, pair-fed, or EtOH-containing. The increase in offspring plasma TG was due to increases in specific VLDL subfraction particle numbers and not to increased TG content per particle. Similarly, the increase in plasma cholesterol was the result of elevated level of the very small LDL particles but not to an increased amount of cholesterol per LDL particle. These findings should be further examined in light of the widespread use of liquid diets in research to administer EtOH, especially for studies of fetal alcohol syndrome.

A long-term high-protein diet markedly reduces adipose tissue without major side effects in Wistar male rats

Although there is a considerable interest of high-protein, low-carbohydrate diets to manage weight control, their safety is still the subject of considerable debate. They are suspected to be detrimental to the renal and hepatic functions, calcium balance, and insulin sensitivity. However, the long-term effects of a high-protein diet on a broad range of parameters have not been investigated. We studied the effects of a high-protein diet in rats over a period of 6 mo. Forty-eight Wistar male rats received either a normal-protein (NP: 14% protein) or high-protein (HP: 50% protein) diet. Detailed body composition, plasma hormones and nutrients, liver and kidney histopathology, hepatic markers of oxidative stress and detoxification, and the calcium balance were investigated. No major alterations of the liver and kidneys were found in HP rats, whereas NP rats exhibited massive hepatic steatosis. The calcium balance was unchanged, and detoxification markers (GSH and GST) were enhanced moderately in the HP group. In contrast, HP rats showed a sharp reduction in white adipose tissue and lower basal concentrations of triglycerides, glucose, leptin, and insulin. Our study suggests that the long-term consumption of an HP diet in male rats has no deleterious effects and could prevent metabolic syndrome.