Effects of egg yolk choline intake on cognitive functions and plasma choline levels in healthy middle-aged and older Japanese: a randomized double-blinded placebo-controlled parallel-group study.

BACKGROUND: Choline, as a neurotransmitter acetylcholine precursor, is reportedly associated with cognitive function. Although there are several cohort and animal studies on choline-containing foods and cognitive function, only a few interventional studies were reported. Egg yolk is a rich source of different choline-containing chemical forms, such as phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and α-glycerophosphocholine (α-GPC). This study aimed to investigate the effect of consuming 300 mg of egg yolk choline per day on cognitive function of Japanese adults. METHODS: A 12-week, randomized, double-blind, placebo-controlled, parallel-group study was conducted in 41 middle-aged and elderly males and females (43.9% female) aged ≥ 60 years and ≤ 80 years without dementia. Participants were randomly assigned to placebo and choline groups. The choline group received a supplement containing egg yolk choline (300 mg/day), and the placebo group received an egg yolk supplement free from choline for 12 weeks. Assessments of Cognitrax, Trail Making Tests (TMT) part A and B, the MOS 36-Item Short-Form Health Survey (SF-36), the Simplified Japanese Version of the WHO-Five Well-Being Index (WHO-5), and plasma choline levels were performed before and 6 and 12 weeks after supplement intake. In the present study, 19 subjects (9 in the placebo group and 10 in the choline group) were excluded due to the violation of the discontinuation criteria or participant compliance, and 41 subjects were analyzed. RESULTS: The change amount of verbal memory scores and verbal memory test-correct hit (delay) was significantly higher in the choline group than in the placebo group at baseline-6 and baseline-12 weeks. The plasma free choline level was significantly higher in the choline group compared with the placebo group at 6 weeks. Conversely, the choline group showed significantly lower Cognitrax processing speed scores, symbol digit coding testing correct responses, and SF-36 physical quality of life summary scores compared to the placebo group at 6 weeks. CONCLUSIONS: The results suggested that continued 300 mg/day intake of egg yolk choline improved verbal memory, which is a part of cognitive functions. To confirm the observed effects of egg yolk choline, more well-designed and large-scale studies are warranted. TRIAL REGISTRATION: Study protocols were pre-registered in the Clinical Trials Registration System (UMIN-CTR) (UMIN 000045050).

Comparing effects of soybean oil- and palm olein-based mayonnaise consumption on the plasma lipid and lipoprotein profiles in human subjects: a double-blind randomized controlled trial with cross-over design.

BACKGROUND: Mayonnaise is used widely in contemporary human diet with widespread use as a salad dressing or spread on breads. Vegetable oils used in its formulation may be a rich source of ω-6 PUFAs and the higher-PUFA content of mayonnaise may be beneficial in mediating a hypocholesterolemic effect. This study, therefore, evaluated the functionality of mayonnaise on cardiometabolic risk within a regular human consumption scenario. METHODS: Subjects underwent a randomized double-blind crossover trial, consuming diets supplemented with 20 g/day of either soybean oil-based mayonnaise (SB-mayo) or palm olein-based mayonnaise (PO-mayo) for 4 weeks each with a 2-week wash-out period. The magnitude of changes for metabolic outcomes between dietary treatments was compared with PO-mayo serving as the control. The data was analyzed by ANCOVA using the GLM model. Analysis was adjusted for weight changes. RESULTS: Treatments resulted in significant reductions in TC (diff = -0.25 mmol/L; P = 0.001), LDL-C (diff = -0.17 mmol/L; P = 0.016) and HDL-C (diff = -0.12 mmol/L; P < 0.001) in SB-mayo compared to PO-mayo without affecting LDL-C:HDL-C ratio (P > 0.05). Lipoprotein particle change was significant with large LDL particles increasing after PO-mayo (diff = +63.2 nmol/L; P = 0.007) compared to SB-mayo but small LDL particles remained unaffected. Plasma glucose, apolipoproteins and oxidative stress markers remained unchanged. CONCLUSIONS: Daily use with 20 g of linoleic acid-rich SB-mayo elicited reductions in TC and LDL-C concentrations without significantly changing LDL-C:HDL-C ratio or small LDL particle distributions compared to the PO-mayo diet. TRIAL REGISTRATION: This clinical trial was retrospectively registered with the National Medical Research Register, National Institute of Health, Ministry of Health Malaysia, (NMRR-15-40-24035; registered on 29/01/2015; https://www.nmrr.gov.my/fwbPage.jsp?fwbPageId=ResearchISRForm&fwbAction=Update&fwbStep=10&pk.researchID=24035&fwbVMenu=3&fwbResearchAction=Update ). Ethical approval was obtained from the National University of Malaysia's Medical Ethics Committee (UKM 1.5.3.5/244/SPP/NN-054-2011, approved on 25/05/2011).

Supplementation with 1% energy trans fatty acids had little effect on serum cholesterol levels in healthy young Japanese women.

The World Health Organization (WHO) has recommended that trans fatty acid (TFA) intake should be less than 1% of total energy intake, but few data are available as to the influence of energy TFA intake of as low as 1% on blood cholesterol levels. A randomized, double-blind, parallel trial was conducted to assess the effects of 1% TFA dietary supplementation on serum cholesterol levels in healthy young women. Sixty-five volunteers consumed cookies containing 1% (TFA) or 0.04% (control) energy of TFA for 4 weeks and blood was harvested after overnight fasting. There were no significant differences in serum LDL- or HDL-cholesterol levels between the two groups. The hemoglobin A1c level was not influenced by dietary TFA. These results suggest that energy of TFAs at less than 1% has little effect on serum cholesterol or hemoglobin A1c levels in healthy young women. This confirms the correctness of the WHO recommendation.

Health Functions of Egg Protein.

Egg protein is a remarkably abundant source of protein, with an amino acid score of 100 and the highest net protein utilization rate. However, there have been relatively fewer studies investigating the health benefits of egg protein. In this review, we have summarized the available information regarding the health benefits of egg proteins based on human studies. In particular, studies conducted on the characteristics of egg whites, as they are high in pure protein, have reported their various health functions, such as increases in muscle mass and strength enhancement, lowering of cholesterol, and visceral fat reduction. Moreover, to facilitate and encourage the use of egg white protein in future, we also discuss its health functions. These benefits were determined by developing an egg white hydrolysate and lactic-fermented egg whites, with the latter treatment simultaneously improving the egg flavor. The health benefits of the protein hydrolysates from the egg yolk (bone growth effect) and eggshell membrane (knee join pain-lowering effect) have been limited in animal studies. Therefore, the consumption of egg protein may contribute to the prevention of physical frailty and metabolic syndromes.

Antihypertensive Effect of Dietary ß-Conglycinin in the Spontaneously Hypertensive Rat (SHR).

Dietary ß-conglycinin has been shown to increase plasma adiponectin concentration and decrease visceral adipose tissue weight in rats. Since adiponectin is one of the factors regulating blood pressure, as well as modulating lipid metabolism, we examined whether dietary ß-conglycinin affects blood pressure in spontaneously hypertensive rats. The experimental diets were prepared according to the AIN-93G formula containing 20% protein, either casein (Control) or casein replaced with soy protein isolate (SOY) or ß-conglycinin (ß-CON) at the proportion of 50%. Male rats (SHR/Izm, 6 wk-old) were fed the diets for 7 weeks. The SOY compared with the Control significantly suppressed the blood pressure both at week 4 (p = 0.011, Control vs. SOY) and thereafter, and ß-CON had even higher suppression (p = 0.0002, Control vs. ß-CON). SOY and ß-CON increased plasma adiponectin concentration followed by an increase in plasma nitric oxide and possibly a decreasing trend of gene expressions of angiotensinogen in the liver and renin in the kidney. The results indicated suppression by ß-conglycinin of increasing blood pressure through an enhancement of plasma adiponectin, probably in combination with a regulation of the renin-angiotensin system in spontaneously hypertensive rats.

Effect of a 0.6% energy trans fatty acid intake on serum cholesterol concentrations in healthy young Japanese subjects.

A randomized crossover study in healthy young Japanese showed no significant effects of a 0.6% energy trans fatty acid (TFA) intake on the serum cholesterol concentrations and parameters of glucose metabolism. The results indicate that TFAs at this dietary level may have no adverse metabolic effects on healthy young Japanese.

Nutritional Viewpoints on Eggs and Cholesterol.

Although most current epidemiologic studies indicate no significant association between consuming one egg daily and blood cholesterol levels and cardiovascular risk, arguments still persist with a positive association. Since the diet is one of the most influential factors for this association, we illustrate characteristic features in Japanese people whose dietary pattern is distinct from that, for example, the US (United States) population. Available epidemiologic studies in healthy Japanese people show no association between consumption of one egg daily and blood cholesterol level, consistent with those observed in the US population. However, when consumption of major nutrients and food sources of cholesterol are compared to the US population, Japanese people may have an extra-reserve against the influence of eggs on cardiovascular risk markers, despite consuming relatively more eggs. Further discussion on the influence of nutrients contained in the egg and dietary pattern, including interaction with gut microbes, is necessary. In addition, special consideration at the personalized level is needed for judgment regarding dietary cholesterol not only for hypercholesterolemic patients but for hyper-responsive healthy persons. Although randomized controlled trials with long-term follow-up are required to evaluate the association between consumption of eggs and human health, available information, at least from the nutritional viewpoint, suggests that egg is a healthy and cost-efficient food worldwide.

Dietary ß-Conglycinin Modulates Insulin Sensitivity, Body Fat Mass, and Lipid Metabolism in Obese Otsuka Long-Evans Tokushima Fatty (OLETF) Rats.

The physiological effects of dietary ß-conglycinin (ß-CON), one of the major components of soy protein (SOY), were examined in an obese animal model. Prior studies show that ß-CON intake decreases plasma triglycerides and visceral adipose tissue weight, and increases plasma adiponectin in rodents. Since plasma adiponectin is known to affect both lipid and glucose metabolism, feeding a diet containing ß-CON could modulate insulin sensitivity. Therefore, we examined the effects of dietary ß-CON on insulin sensitivity and blood glucose levels, as well as lipid metabolism in obese Otsuka Long-Evans Tokushima Fatty (OLETF) rats (pre-symptomatic stage of type 2 diabetes mellitus). Male OLETF rats (6 weeks old) were fed diets containing 20% protein such as casein (CAS), CAS replaced with soy protein (SOY), or ß-CON at a proportion of 50% for 13 weeks. Fasting blood glucose levels were measured every 3 weeks, and an insulin tolerance test (ITT; 0.75 IU/kg body weight) was conducted at week 12. During the feeding period, fasting blood glucose was comparable among the groups. Insulin sensitivity measured by the ITT revealed that the SOY and ß-CON diets decreased blood glucose levels at 30 min after intraperitoneal insulin injection (vs. CAS diet). In addition, the ß-CON diet increased plasma adiponectin concentrations, hepatic gene expression of insulin receptor substrate (IRS) 2, and muscle gene expression of adiponectin receptor 1 (AdipoR1) and IRS1, and with a decrease in plasma insulin concentration. Finally, the ß-CON diet decreased the mesenteric adipose tissue weight and liver triglyceride concentration compared to the CAS diet. These results suggest that the metabolic effects of dietary ß-CON are mediated by increasing plasma adiponectin to increase insulin sensitivity and influence the hepatic lipid metabolism in obese OLETF rats.

Supplementation with trans fatty acid at 1% energy did not increase serum cholesterol irrespective of the obesity-related genotypes in healthy adult Japanese.

BACKGROUND AND OBJECTIVES: The excessive intake of trans fatty acids increases serum low-density lipoproteincholesterol and reduces high-density lipoprotein-cholesterol. We studied the effects of 1% energy trans fatty acid supplementation on serum lipid concentrations in healthy adult Japanese with different obesity-related gene polymorphisms. METHODS AND STUDY DESIGN: A randomized, double-blind, parallel trial was conducted in 53 healthy adults. The volunteers consumed one cookie containing either 1% energy or <0.01% energy (control) of trans fatty acids every day for 4 weeks, and a blood sample was then obtained after overnight fasting. The single nucleotide polymorphisms of the fat mass- and obesity-associated gene rs9939609 and beta-3 adrenergic receptor rs4994 were genotyped. RESULTS: The mean trans fatty acid intake of the control and trans fatty acid groups corresponded to 0.28% and 1.31 % energy, respectively. There were no significant differences in serum cholesterol (total, low-density lipoprotein and high-density lipoprotein) or triacylglycerol between the control and trans fatty acid groups. The responses of serum cholesterol, triacylglycerol, glucose, insulin and hemoglobinA1c were also independent of the fat mass- and obesity-associated gene and beta-3 adrenergic receptor gene variants. CONCLUSIONS: Our findings indicate that supplementation with 1% energy trans fatty acids has little effect on serum cholesterol in healthy adult Japanese, regardless of genotype of fat mass- and obesity-associated gene or beta-3 adrenergic receptor. More systematic studies, with respect to dietary trans fatty acid intakes above those used here, may be warranted to determine the tolerable upper level of dietary trans fatty acid.

Genetically modified rapeseed oil containing cis-9,trans-11,cis-13-octadecatrienoic acid affects body fat mass and lipid metabolism in mice.

Punicic acid, one of the conjugated linolenic acid (CLN) isomers, exerts a body-fat reducing effect. Although punicic acid is found in pomegranate and Tricosanthes kirilowii seeds, the amount of this fatty acid is very low in nature. The goal of this study was to produce a transgenic oil containing punicic acid. A cDNA encoding conjugase that converts linoleic acid to punicic acid was isolated from T. kirilowii, and the plant expression vector, pKN-TkFac, was generated. The pKN-TkFac was introduced into Brassica napus by Agrobacterium-mediated transformation. As a result, a genetically modified rapeseed oil (GMRO) containing punicic acid was obtained, although its proportion to the total fatty acids was very low (approximately 2.5%). The effects of feeding GMRO in ICR CD-1 male mice were then examined. Wild-type rapeseed (B. napus) oil (RSO) containing no CLN was used as a control oil. For reference oils, RSO-based blended oils were prepared by mixing with different levels of pomegranate oil (PO), either 2.5% (RSO + PO) or 5.0% (RSO + 2PO) punicic acid. Mice were fed purified diets containing 10% of either RSO, RSO + PO, RSO + 2PO, or GMRO for 4 weeks, and dietary PO dose-dependently reduced perirenal adipose tissue weight with a significant difference between the RSO group and the RSO + 2PO group. GMRO, as compared to RSO, lowered the adipose tissue weight to the levels observed with RSO + 2PO. The liver triglyceride level of the RSO + 2PO and GMRO groups but not that of the RSO + PO group was lower than that of the RSO group. The RSO + 2PO and GMRO groups, but not the RSO + PO group, had increased carnitine-palmitoyltransferase activity in the liver and brown adipose tissue. These results showed that dietary GMRO, even at a dietary punicic acid level as low as 0.25 wt % of diet, reduced body fat mass and altered liver lipid metabolism in mice and was more effective than an equal amount of punicic acid from PO.

Absorption of dietary cholesterol oxidation products and their downstream metabolic effects are reduced by dietary apple polyphenols.

Exogenous and endogenous cholesterol oxidation products (COPs) perturb various metabolic processes, and thereby they may induce various homeostasis-related disorders. Here, we observed that procyanidin-rich dietary apple polyphenol (APP) from unripe apples alleviates the perturbation of lipid metabolism by decreasing the exogenous COP levels in rats. Dietary COPs may be the greatest source of COPs found in the human body. Rats (4 weeks of age) were fed AIN-purified diets containing 0.3% COPs supplemented with 0.5 or 2.5% APP for 3 weeks. Dietary APP alleviated the growth inhibition action of the exogenous COPs. The modulations of the liver lipid profile by COPs remained unchanged. However, serum total cholesterol, high-density lipoprotein cholesterol, and triglyceride levels increased following the intake of dietary APP. Further, dietary APP inhibited the increase in lipid peroxide levels in the liver and serum by COPs. The activity of hepatic Delta6 desaturase was lowered by dietary APP in a dose-dependent manner, although exogenous COPs generally increased the activity of this enzyme. In keeping with this observation, Delta6 desaturation indices in the phospholipids and cholesteryl esters of the liver and serum lipids were lower in the APP-fed groups than those in the control group. Dietary APP also promoted the excretion of exogenous COPs, cholesterol, and acidic steroids in feces. Therefore, the inhibition of intestinal absorption of COPs may partly contribute to the alleviation of the perturbation of lipid metabolism and lipid peroxidation levels. Thus, APP may be an important removal agent of exogenous toxic material such as COPs contained in processed or fast foods.

Industrial Trans Fatty Acid and Serum Cholesterol: The Allowable Dietary Level.

Trans fatty acid (TFA) from partially hydrogenated oil is regarded as the worst dietary fatty acid per gram due to its role in coronary heart disease. TFA consumption is decreasing worldwide, but some but not all observational studies indicate that TFA intake has little relevance to serum cholesterol levels in populations with low TFA intake (<1% E [percentage of total energy intake],

Lymphatic transport of a physical mixture of medium- and long-chain TAG in rats.

Lymphatic transport of a mixture of medium-chain TAG (MCT) and long-chain TAG (LCT) was studied in lymph-cannulated rats. Animals were administered a test emulsion containing either triolein, tricaprylin, or a 1:1 mixture of triolein and tricaprylin, and the lymph was collected for 24 h. The lymphatic recovery rate of medium-chain FA (MCFA) was significantly higher in rats given the TAG mixture than in those given MCT alone. The lymphatic recovery rate of long-chain FA (LCFA) also was significantly higher in rats given the TAG mixture than in those given LCT alone. No TAG containing three MCFA (i.e., MCT) was detected, and 37.7% of TAG containing one or two MCFA was detected in the lymph TAG when rats were given the TAG mixture. These results indicate that lymphatic transport of MCFA and LCFA can be modified by the combination of MCT and LCT.

Interaction of dietary fat types and sesamin on hepatic fatty acid oxidation in rats.

The interaction of sesamin, one of the most abundant lignans in sesame seed, and types of dietary fats affecting hepatic fatty acid oxidation was examined in rats. Rats were fed purified experimental diets supplemented with 0% or 0.2% sesamin (1:1 mixture of sesamin and episesamin), and containing 8% of either palm, safflower or fish oil for 15 days. Among the groups fed sesamin-free diets, the activity of various fatty acid oxidation enzymes was higher in rats fed fish oil than in those fed palm and safflower oils. Dietary sesamin increased enzyme activities in all groups of rats given different fats. The extent of the increase depended on dietary fat type, and a diet containing sesamin and fish oil in combination appeared to increase many of these parameters synergistically. In particular, the peroxisomal palmitoyl-CoA oxidation rate and acyl-CoA oxidase activity levels were much higher in rats fed sesamin and fish oil in combination than in animals fed sesamin and palm or safflower oil in combination. Analyses of mRNA levels revealed that a diet containing sesamin and fish oil increased the gene expression of various peroxisomal fatty acid oxidation enzymes and PEX11alpha, a peroxisomal membrane protein, in a synergistic manner while it increased the gene expression of mitochondrial fatty acid oxidation enzymes and microsomal cytochrome P-450 IV A1 in an additive manner. It was concluded that a diet containing sesamin and fish oil in combination synergistically increased hepatic fatty acid oxidation primarily through up-regulation of the gene expression of peroxisomal fatty acid oxidation enzymes.

Effects of Aster scaber Seed Oil Containing trans-Δ3 Fatty Acids on Lipid Profiles of Hamsters and Rats.

The effects of Aster scaber seed oil (ASO) on lipid profiles were studied in rats and hamsters. ASO contained considerable amounts of Δ3t-16:1 (11.4%), Δ3t, 9c-18:2 (4.6%), and Δ3t, 9c, 12c-18:3 (11.3%). Young rats and hamsters were fed diets containing ASO, soybean oil (SBO), or olive oil (OLO) as fat sources for 4 weeks in separate experiments with or without cholesterol. In the rat study, there were no significant differences in the concentrations of serum total cholesterol, high-density lipoprotein (HDL)-cholesterol, and triacylglycerol among the groups. The serum but not liver malondialdehyde (MDA) level was significantly lower in the ASO-fed group than it was in the other groups. The biochemical and growth parameters revealed no significant biological damages in the ASO-fed animals. In the hamster study, dietary cholesterol-dependent effects were evident in the serum lipids profiles, whereas the fat-induced effect was only observed in the ratio of serum low-density lipoprotein (LDL)-/HDL-cholesterol. Furthermore, fat- and cholesterol-induced effects were evident in the ratio of serum LDL-/HDL-cholesterol. Significant interactions between dietary fat and cholesterol were observed as evident from the concentration of serum cholesterol and triacylglycerol, as well as the activity of serum cholesterol ester transfer protein. These results suggest that dietary ASO containing trans-Δ3 fatty acids appeared to improve the serum LDL-/HDL-cholesterol ratio more than the SBO did, especially when hamsters were simultaneously fed cholesterol-supplemented diet.

Ethanol washing does not attenuate the hypocholesterolemic potential of soy protein.

OBJECTIVE: A feeding study in rats investigated the principal active component for the hypocholesterolemic effect of soy protein isolate (SPI) by comparing the effect before and after ethanol washing. METHODS: Five-week-old male Sprague-Dawley rats were fed cholesterol-enriched AIN-93G diets containing 20% casein (CAS), 20% SPI, 20% ethanol-washed SPI (EWS), 18.4% EWS plus 1.6% ethanol extract (EE), or 20% CAS plus 1.6% EE for 2 wk. RESULTS: Plasma cholesterol concentrations in rats fed EWS and SPI were comparable and were significantly lower than those in rats fed CAS. The addition of EE to EWS and CAS did not influence plasma cholesterol level. Fecal steroid excretion of the three SPI groups was higher than that of the two CAS groups. The addition of EE to EWS and CAS showed a tendency to increase acidic steroid and decrease neutral steroid. CONCLUSIONS: In this experiment which used identifiable protein preparations, a significant fraction of the cholesterol-lowering effect of SPI in rats was attributed to its protein component but not to the ethanol-extractable minor constituents including isoflavones.

Decrease in plasma low-density lipoprotein cholesterol, apolipoprotein B, cholesteryl ester transfer protein, and oxidized low-density lipoprotein by plant stanol ester-containing spread: a randomized, placebo-controlled trial.

OBJECTIVE: The ester of plant stanols significantly reduces plasma levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in Western people. Effects of plant stanol ester-containing spread on plasma levels of TC, LDL-C, and apolipoprotein B (apoB) were studied in a randomized, placebo-controlled trial in Japanese subjects whose diet is low in fat and cholesterol. The effects of plant stanol ester on plasma levels of arteriosclerosis-promoting factors, namely remnants of triacylglycerol (TG)-rich lipoproteins, cholesteryl ester transfer protein (CETP), and oxidized LDL (Ox-LDL), were also studied. The assessment of safety was also made. METHODS: One hundred and five healthy volunteers were assigned randomly to one of three groups: placebo spread (n = 35), 2 g/d of plant stanol (3.4 g of stanol ester; n = 34), and 3 g/d of plant stanol (5.1 g of stanol ester; n = 36). Plasma levels of lipids were measured at start of the study, at 2 and 4 wk (end of trial), and at 8 wk (+4 wk). Plasma apoproteins, cholesterol in remnant-like particles which are equivalent to remnants of TG-rich lipoproteins (RLP-C), CETP mass, and Ox-LDL were measured at the beginning and the end of the trial. Plasma levels of plant steroids and fat-soluble vitamins were also measured for the assessment of safety. RESULTS: Background and dietary composition did not differ among groups. Plasma levels of TC, LDL-C, apoB, apoE, CETP mass, and Ox-LDL were reduced significantly by 6.5%, 9.6%, 8.3%, 4.5%, 6.1%, and 20%, respectively, in the 2 g/d plant stanol group. Plasma levels of TC, LDL-C, apoB, CETP mass, and Ox-LDL were decreased significantly by 5.5%, 7.3%, 5.6%, 3.3%, and 19%, respectively, in the 3 g/d plant stanol group. Plasma levels of plant stanols, plant sterols, retinol, beta-carotene, and alpha-tocopherol did not change in any group, but levels of campestanol increased and alpha-tocopherol decreased slightly in the sitostanol groups. CONCLUSION: Plasma levels of TC and LDL-C were significantly reduced by the plant stanol ester-containing spread. The smaller reduction than in Western studies and the lack of dose dependency in this study might be due to the different basal diets. We concluded that plant stanol ester-containing spread is efficacious in reducing plasma LDL-C, apoB, CETP, and Ox-LDL and that 2 g/d plant stanol is adequate for Japanese people. No significant side effects were observed in any group.

Dietary protein modulates the effect of CLA on lipid metabolism in rats.

The effect of the interaction of CLA and type of dietary protein on lipid metabolism was studied in male rats by feeding diets containing casein (CAS) or soy protein (SOY) as dietary protein and either linoleic acid (LA, a control FA) or graded levels of CLA at 0, 0.1, 0.5, and 1.0% for 28 d. CLA reduced the weight of perirenal adipose tissue in a dose-dependent manner, but the magnitude of the reduction was greater when rats were fed SOY. Feeding SOY resulted in a significant reduction of the concentrations of serum total and HDL cholesterol, TG, glucose, and insulin irrespective of dietary CLA. The concentration of serum leptin tended to be lower on the SOY diet free of CLA than in the corresponding CAS diet, but it fell with an increasing dietary level of CLA in the CAS groups. In contrast, serum leptin tended to increase when CLA was added to SOY diets. The concentration of serum adiponectin was higher in the CAS than in the SOY groups, and it tended to increase in response to dietary CLA levels in the CAS-fed rats, whereas CLA showed no effect in SOY-fed rats. The activity of liver mitochondrial carnitine palmitoyltransferase was higher in the SOY than in the CAS groups, but it tended to increase with an increasing dietary level of CLA in both protein groups. Although the body fat-reducing activity of CLA was more effective when the protein source was SOY, rats fed CAS appeared to be more susceptible to CLA than in those fed SOY with respect to cytokines examined. These results suggest that the type of dietary protein may modify the antiobesity activity of CLA.

Dietary conjugated linolenic acid in relation to CLA differently modifies body fat mass and serum and liver lipid levels in rats.

The present study compared the effect of dietary conjugated linolenic acid (CLNA) on body fat and serum and liver lipid levels with that of CLA in rats. FFA rich in linoleic acid, a-linolenic acid, CLA, or CLNA were used as experimental fats. Male Sprague-Dawley rats (4 wk old) were fed purified diets containing 1% of one of these experimental fats. After 4 wk of feeding, adipose tissue weights, serum and liver lipid concentrations, serum tumor necrosis factor (TNF)-alpha and leptin levels, and hepatic beta-oxidation activities were measured. Compared with linoleic acid, CLA and, more potently, CLNA were found to reduce perirenal adipose tissue weight. The same trend was observed in the weight of epididymal adipose tissue. CLNA, but not CLA, was found to significantly increase serum and liver TG concentrations. Serum FFA concentration was also increased in the CLNA group more than in the other groups. The activity of beta-oxidation in liver mitochondria and peroxisomes was significantly higher in the CLNA group than in the other groups. Thus, the amount of liver TG exceeded the ability of hepatic beta-oxidation. Significant positive correlation was found between the adipose tissue weights and serum leptin levels in all animals (vs. perirenal: r = 0.557, P < 0.001; vs. epididymal: r = 0.405, P < 0.05). A less significant correlation was found between adipose tissue weights and serum TNF-alpha level (vs. perirenal: r = 0.069, P > 0.1; vs. epididymal: r = 0.382, P < 0.05). Although the mechanism for the specific effect of CLNA is not clear at present, these findings indicate that in rats CLNA modulated the body fat and TG metabolism differently from CLA.

Dietary restriction downregulates free radical and lipid peroxide production: plausible mechanism for elongation of life span.

Dietary restriction elongates life span by suppressing age-related diseases in experimental animals. It has received a great deal of attention in connection with the relationship between aging, nutrition, and oxidative stress because oxidative injury in several tissues is a prominent feature in the aging process. Although the oxidative stress theory of aging has currently gained popularity, the premise from which this hypothesis was derived is paradoxical because the same oxygen, that supports life in one hand threatens survival and promotes aging in the other. Until recently, no single experimental paradigm could offer satisfactory mechanistic explanations for this complex issue. Recent investigations using the life-extending dietary restriction regimen could offer satisfactory mechanistic explanations for this apparent self-contradiction to life. The modulation of free radical-induced oxidative stress provided sufficient data to support the notion that dietary restriction's antiaging effect may come from its ability to tightly regulate the oxidative status of an organism. The result is the maintenance of cellular homeostasis, a hallmark of dietary restriction's action in the extension of life span. To date, we reported that dietary restriction (maintained on 60% of ad libitum feeding) suppresses age-related oxidative damage by modulating the amount as well as the fatty acid composition of tissue phospholipids. These remarkable findings have been incorporated into the new "membrane peorxidation cycle" concept. The intervention of this cycle appears to be an evolutionary process that the dietary restricted rats have adapted as a strategy to protect the membrane in an oxidative environment.