We examined the effects of the dietary intake of medium- and long-chain triacylglycerol (MLCT) on hyperglycemia in diabetic ob/ob mice. Six-week-old male ob/ob mice were fed a diet containing longchain triacylglycerol (LCT) or MLCT for 3 wks. During the dietary treatment, we determined the plasma glucose and insulin concentrations in the fed state once a week.
View Article and Find Full Text PDFRecent studies have shown that medium-chain triacylglycerol (MCT) improved serum albumin concentration in elderly people with protein-energy malnutrition (PEM) and in malnourished rats. However, the mechanism for this effect has not been clarified. Dietary MCT promotes insulin secretion from the pancreas, and insulin activates mammalian target of rapamycin (mTOR) complex 1 (mTORC1) via the activation of phosphoinositide 3-kinase (PI3K) and its downstream effecter, Akt.
View Article and Find Full Text PDFObjective: Excessive accumulation of visceral fat is strongly associated with insulin resistance. The present investigation examined the effects of dietary intake of medium- and long-chain triacylglycerols (MLCTs), which have been shown to induce significantly lower visceral fat accumulation in rats and humans, on high-fat diet-induced obesity and insulin resistance in rats. These effects were then compared with those observed in long-chain triacylglycerol (LCT)-fed rats.
View Article and Find Full Text PDFTypes of dietary lipid affect the life span of rats. In this study, we investigated the influence of the life-long dietary n-6/n-3 ratio on life span and serum lipid and glucose levels. A semi-purified diet adjusted to a constant saturated : monounsaturated : polyunsaturated fatty acid ratio and an n-6/n-3 ratio of 1 (R1), 4 (R4) or 16 (R16) was fed to rats (n=33) from 4 wk of age until death.
View Article and Find Full Text PDFBiosci Biotechnol Biochem
November 2009
We have hypothesized a suppressive mechanism against dietary docosahexaenoic acid (22:6n-3; DHA)-induced tissue lipid peroxidation, in which the degradation products, including their conjugates, are excreted into the urine by xenobiotic or organic anion transporters. In this study, we employed parent-strain Sprague-Dawley rats (SDRs), together with their mutant strain, Eisai hyperbilirubinuria rats (EHBRs). EHBRs are deficient in multidrug resistance-associated protein (MRP) 2, and show defective urinary excretion of numerous xenobiotics and organic anions.
View Article and Find Full Text PDFAdiponectin, an adipose-specific secretory protein, exhibits antidiabetic and antiatherogenic properties. The effect of alpha-linolenic acid (ALA) on adiponectin has not been revealed. ALA is included abundantly in vegetable oils such as flaxseed oil.
View Article and Find Full Text PDFThe optimal dietary n-6/n-3 ratio has not been fully elucidated. To investigate the influence of the dietary n-6/n-3 ratio on this ratio in the body and on liver beta-oxidation peroxisomal activity, rats were fed diets containing fat at an n-6/n-3 ratio of 1 to 16 for 4 weeks. To investigate whether elevation of the liver peroxisomal beta-oxidation activity increases the n-6/n-3 ratio in the body, rats were fed a diet containing a peroxisome-activating agent, bezafibrate, for 2 weeks, and its influence on the liver n-6/n-3 ratio was examined.
View Article and Find Full Text PDFThe bulk of fatty acids found in our diets consists of long-chain fatty acids (LCFA), which are molecules containing 12 or more carbon atoms. In contrast, medium-chain fatty acids (MCFA) are composed of 8-10 carbon atoms, and are found in palm kernel oil, among other types of foods. MCFA have attracted attention as being part of a healthy diet, because they are absorbed directly into the portal vein, transported rapidly to the liver for beta-oxidation, and thus increase diet-induced thermogenesis.
View Article and Find Full Text PDFWe hypothesized a suppressive mechanism for docosahexaenoic acid (22:6n-3; DHA)-induced tissue lipid peroxidation in which the degradation products, especially aldehydic compounds, are conjugated with glutathione through catalysis by glutathione S-transferases, and then excreted into urine as mercapturic acids. In the present study, ascorbic acid-requiring ODS rats were fed a diet containing DHA (3.6% of total energy) for 31 days.
View Article and Find Full Text PDFIt is well known that the consumption of n-3 polyunsaturated fatty acid (PUFA) decreases the plasma triacylglycerol (TAG) level. The technology of elevating the content of n-3 PUFAs in pig meat has already reached a practical level. In this study, the effects of dietary lard containing higher alpha-linolenic acid (LNA) on plasma TAG were compared with those of normal lard in rats.
View Article and Find Full Text PDFWe investigated the antihypertensive effect and safety of alpha-linolenic acid (ALA) in human subjects. In Experiment 1, subjects with high-normal blood pressure and mild hypertension ingested bread containing 14 g of common blended oil (control oil) or ALA-enriched oil for 12 weeks. The test oil contained 2.
View Article and Find Full Text PDFThe present study attempted to clarify the antihypertensive effect and its mechanism when alpha-linolenic acid (ALA) is administered orally. For this purpose, 1 mL of flaxseed oil, which is rich in ALA, and high oleic safflower oil was administered orally to spontaneously hypertensive rats (SHR) of a control and an ALA group on days 1 and 5. Systolic blood pressure was measured on day 1, and blood and liver were collected on day 5.
View Article and Find Full Text PDFPrevious studies demonstrated that, compared with long-chain TAG (LCT), dietary medium-chain TAG (MCT) could improve glucose tolerance in rats and humans. It has been well established that adiponectin acts to increase insulin sensitivity. The effects of dietary MCT on adiponectin serum concentration and mRNA levels in adipose tissue were studied in rats.
View Article and Find Full Text PDFBiosci Biotechnol Biochem
July 2006
To clarify the alternative mechanisms to vitamin E (VE) regulating lipid peroxide accumulation in the liver after docosahexaenoic acid (DHA) ingestion, we examined the relationship between the DHA-induced lipid peroxide formation and induction of the xenobiotic transporters, Ral-binding GTPase-activating protein (RalBP1) and multidrug resistance-associated proteins 1, 2 and 3 (MRP1-3), in the liver of rats fed with DHA. The test diets contained DHA and linoleic acid (LA) (8.7% and 2.
View Article and Find Full Text PDFObjectives: We examined the effects of ascorbic acid (AsA) and glutathione (GSH; experiment 1) and of GSH in acetaminophen-fed rats (experiment 2) on dietary docosahexaenoic acid (DHA)-induced tissue lipid peroxidation.
Methods: In experiment 1, AsA-requiring Osteogenic Disorder Shionogi/Shi-od/od (ODS) rats were fed soybean protein diets containing DHA (10.0% total energy) and AsA at 50 (low) or 300 (normal) mg/kg without (low) or with (normal) methionine at 2 g/kg for 32 d.
We showed in our previous study that docosahexaenoic acid-rich phosphatidylethanolamine in the external layer of small-size liposomes, as a model for biomembranes, protected its docosahexaenoic acid from 2,2'-azobis(2-amidinopropane)dihydrochloride- (AAPH-) mediated lipid peroxidation in vitro. Besides phosphatidylethanolamine, both phosphatidylserine and an alkenyl-acyl analogue of phosphatidylethanolamine, phosphatidylethanolamine plasmalogen, are reported to possess characteristic antioxidant activities. However, there are few reports about the relationship between the protective activity of phosphatidylethanolamine plasmalogen and/or phosphatidylserine against lipid peroxidation and their distribution in a phospholipid bilayer.
View Article and Find Full Text PDFWe examined the relationship between the transbilayer distribution of aminophospholipids, such as phosphatidylethanolamine (PE), PE plasmalogen and phosphatidylserine, and the oxidative stability of polyunsaturated fatty acids (PUFAs) in the aminophospholipids. To modulate the transbilayer distribution of aminophospholipid in liposomes, we used phosphatidylcholine (PC) with two types of acyl chain region: dipalmitoyl (PC16:0) or dioleoyl (PC18:1). In the smaller-sized liposomes, the proportions of aminophospholipid in the liposomal external layer were significantly higher in liposomes containing PC18:1 than in those containing PC16:0.
View Article and Find Full Text PDFWe compared the effect of direct supplementation with docosahexaenoic acid (DHA) on the fatty acid composition of the liver and the rod outer segment (ROS) membranes of the retina in young (five-week-old) and mature (one-year-old) rats. In young rats, a high content of DHA in the diet (9.7% of total energy) effectively increased the proportion of DHA in ROS membranes (41.
View Article and Find Full Text PDFIn previous studies, we showed that docosahexaenoic acid (DHA) ingestion enhanced the susceptibility of rat liver and kidney to lipid peroxidation, but did not increase lipid peroxide formation to the level expected from the relative peroxidizability index (P-index) of the total tissue lipids. The results suggested the existence of some suppressive mechanisms against DHA-induced tissue lipid peroxide formation, as increased tissue ascorbic acid (AsA) and glutathione levels were observed. Therefore, we focused initially on the role of AsA for the suppressive mechanisms.
View Article and Find Full Text PDFMutant male osteogenic disorder Shionogi (ODS) rats, unable to synthesize ascorbic acid, were fed diets containing a high content of docosahexaenoic acid (DHA) and different amounts of ascorbic acid, to study the effect of DHA on peroxidative susceptibility of the retina and possible antioxidant action of ascorbic acid. ODS rats were fed from 7 weeks of age with diets containing high DHA (6.4% of total energy).
View Article and Find Full Text PDFWe have proposed that incorporation of docosahexaenoic acid (DHA) into phosphatidylethanolamine (PE) might enhance resistance to lipid peroxidation in vivo. In this study, we examined the relationship between the transbilayer distribution of PE and the oxidative stability of DHA in PE. Liposomes composed of a phospholipid mixture were used as models for biological membranes.
View Article and Find Full Text PDF