Activity of hepatic fatty acid oxidation enzymes in rats fed alpha-linolenic acid

An Oil Rich in γ-Linolenic Acid Differently Affects Hepatic Fatty Acid Oxidation in Mice and Rats

The effects of different dietary fats on hepatic fatty acid oxidation were compared in male ICR mice and Sprague-Dawley rats. Animals were fed diets containing 100 g/kg of either palm oil (saturated fat), safflower oil (rich in linoleic acid), an oil of evening primrose origin (γ-linolenic acid, GLA oil), perilla oil (α-linolenic acid) or fish oil (eicosapentaenoic and doxosahexaenoic acids) for 21 d. GLA, perilla and fish oils, compared with palm and safflower oils, increased the activity of fatty acid oxidation enzymes in both mice and rats, with some exceptions. In mice, GLA and fish oils greatly increased the peroxisomal palmitoyl-CoA oxidation rate, and the activity of acyl-CoA oxidase and enoyl-CoA hydratase to the same degree. The effects were much smaller with perilla oil. In rats, enhancing effects were more notable with fish oil than with GLA and perilla oils, excluding the activity of enoyl-CoA hydratase, and were comparable between GLA and perilla oils. In mice, strong enhancing effects of GLA oil, which were greater than with perilla oil and comparable to those of fish oil, were confirmed on mRNA levels of peroxisomal but not mitochondrial fatty acid oxidation enzymes. In rats, the effects of GLA and perilla oils on mRNA levels of peroxisomal and mitochondrial enzymes were indistinguishable, and lower than those observed with fish oil. Therefore, considerable diversity in the response to dietary polyunsaturated fats, especially the oil rich in γ-linolenic acid and fish oil, of hepatic fatty acid oxidation pathway exists between mice and rats.

Inuit metabolism revisited: what drove the selective sweep of CPT1a L479?

This article reassesses historical studies of Inuit metabolism in light of recent developments in evolutionary genetics. It discusses the possible selective advantage of a variant of CPT1a, which encodes the rate limiting enzyme in hepatic fatty acid oxidation. The L479 variant of CPT1a underwent one of the strongest known selective sweeps in human history and is specific to Inuit and Yu'pik populations. Recent hypotheses predict that this variant may have been selected in response to possible detrimental effects of chronic ketosis in communities with very low carbohydrate consumption. Assessing these hypotheses alongside several alternative explanations of the selective sweep, this article challenges the notion that the selection of L479 is linked to predicted detrimental effects of ketosis. Bringing together for the first time data from biochemical, metabolic, and physiological studies inside and outside the Inuit sphere, it aims to provide a broader interpretative framework and a more comprehensive way to understand the selective sweep. It suggests that L479 may have provided a selective advantage in glucose conservation as part of a metabolic adaptation to very low carbohydrate and high protein consumption, but not necessarily a ketogenic state, in an extremely cold environment. A high intake of n-3 fatty acids may be linked to selection through the mitigation of a detrimental effect of the mutation that arises in the fasted state. The implications of these conclusions for our broader understanding of very low carbohydrate metabolism, and for dietary recommendations for Inuit and non-Inuit populations, are discussed.

Saturated or unsaturated fat supplemented maternal diets influence omental adipose tissue proteome of suckling goat-kids

The aim of the present study was to investigate how maternal diet can influence the adipose tissue of goat kids. Omental adipose tissue proteomes of goat-kids from mothers fed with diet enriched with stearic acid (ST-kids), fish oil (FO-kids) and standard diets (CTRL) were determined by quantitative iTRAQ 2D-LC-MS/MS analysis. Twenty proteins were found to be differentially expressed in suckling kids' omental adipose tissue. Stearic acid induces changes in a higher number of proteins when compared to fish oil. Eleven proteins, namely AARS, ECl1, PMSC2, CP, HSPA8, GPD1, RPL7, OGDH, RPL24, FGA and RPL5 were decreased in ST-kids only. Four proteins, namely DLST, EEF1G, BCAP31 and RALA were decreased in FO-kids only, and one, NUCKS1, was increased. Four proteins, namely PMSC1, PPIB, TUB5×2 and EIF5A1, were be less abundant in both ST- and FO- kids. Most of the protein whose abundance was decreased in ST kids (10 out of 15) are involved in protein metabolism and catabolism pathways. Qualitative gene expression analysis confirmed that all the proteins identified by mass spectrometry, with the exception of FGA, were produced by adipose tissue. Quantitative gene expression analysis demonstrated that two proteins, namely CP, a minor acute phase protein, and ECl1, involved in fatty acid beta oxidation, were downregulated at mRNA level as well. ECl1 gene expression was downregulated in ST-kids AT as compared to Ctrl-kids and CP was downregulated in both ST- and FO-kids. The present results demonstrate that it is possible to influence adipose goat-kid proteome by modifying the maternal diet.

Consumption of alpha-linolenic acid-enriched diacylglycerol induces increase in dietary fat oxidation compared with alpha-linolenic acid-enriched triacylglycerol: A randomized, double-blind trial

Fat metabolism is an important consideration in obesity. Alpha-linolenic acid-enriched diacylglycerol (ALA-DAG), which mainly occurs as ALA esterifies to 1,3-diacyl-sn-glycerol (1,3-DAG), has beneficial effects on fat metabolism and body weight compared with triacylglycerol (TAG). Moreover, compared with ALA-TAG, ALA-DAG enhances β-oxidation activity in the small intestine and liver in rodents. We hypothesized that ALA-DAG consumption may increase dietary fat oxidation compared with ALA-TAG in humans. To examine this hypothesis, we conducted a randomized double-blind cross-over trial in 17 normal and moderately obese men and women (BMI: 25.7±2.0 kg/m², mean±SD). Each participant was assigned to a 4-week intervention period with 2.5 g/day of ALA-DAG or ALA-TAG consumption, followed by a 4-week washout period between consumption of each diet. Dietary fat oxidation, assessed based on the ¹³CO₂ recovery rate in the breath, was significantly increased by ALA-DAG consumption compared with ALA-TAG consumption (17.0±4.5% and 14.1±5.9%, respectively, P<.05). In addition, ALA-DAG consumption significantly decreased the visceral fat area compared with ALA-TAG (102.9±51.9 cm² and 110.9±51.7 cm², respectively; P<.05). These results indicate that ALA-DAG consumption may be useful for preventing obesity.

Diacylglycerol Enhances the Effects of Alpha-Linolenic Acid Against Visceral Fat: A Double-Blind Randomized Controlled Trial

OBJECTIVE

To investigate the effect of alpha-linolenic acid-rich diacylglycerol (ALA-DAG) compared with alpha-linolenic acid-rich triacylglycerol (ALA-TAG) on visceral fat area (VFA) in people with overweight.

METHODS

Subjects with overweight were recruited to a randomized, double-blind, controlled, parallel-group designed trial and randomly allocated to two groups that consumed either 2.5 g/d ALA-TAG or ALA-DAG for 12 weeks. Two 4-week nontreatment periods were placed before and after the treatment period. One hundred fourteen subjects (n = 57 in the ALA-TAG group, n = 57 in the ALA-DAG group) were enrolled into the analysis set for efficacy evaluation.

RESULTS

The VFA and BMI were significantly decreased by the ALA-DAG treatment with a treatment-by-time interaction compared with the ALA-TAG treatment (P < 0.05). Additionally, the change from baseline of the fasting serum TAG concentration at week 12 was significantly decreased by ALA-DAG treatment compared with ALA-TAG treatment (P < 0.05). Safety parameters such as urinary measurements, hematologic parameters and blood biochemistry, and the incidence of adverse events did not differ significantly between groups, and no ALA-DAG-associated adverse effects were detected.

CONCLUSIONS

Incorporation of ALA-DAG in a regular diet for 12 weeks may lead to a reduction in VFA, BMI, and serum TAG in men and women with overweight.

Impaired hepatic lipid synthesis from polyunsaturated fatty acids in TM6SF2 E167K variant carriers with NAFLD

BACKGROUND

Carriers of the transmembrane 6 superfamily member 2 E167K gene variant (TM6SF2^EK/KK) have decreased expression of the TM6SF2 gene and increased risk of NAFLD and NASH. Unlike common 'obese/metabolic' NAFLD, these subjects lack hypertriglyceridemia and have lower risk of cardiovascular disease. In animals, phosphatidylcholine (PC) deficiency results in a similar phenotype. PCs surround the core of VLDL consisting of triglycerides (TGs) and cholesteryl-esters (CEs). We determined the effect of the TM6SF2 E167K on these lipids in the human liver and serum and on hepatic gene expression and studied the effect of TM6SF2 knockdown on hepatocyte handling of these lipids.

METHODS

Liver biopsies were taken from subjects characterized with respect to the TM6SF2 genotype, serum and liver lipidome, gene expression and histology. In vitro, after TM6SF2 knockdown in HuH-7 cells, we compared incorporation of different fatty acids into TGs, CEs, and PCs.

RESULTS

The TM6SF2^EK/KK and TM6SF2^EE groups had similar age, gender, BMI and HOMA-IR. Liver TGs and CEs were higher and liver PCs lower in the TM6SF2^EK/KK than the TM6SF2^EE group (p<0.05). Polyunsaturated fatty acids (PUFA) were deficient in liver and serum TGs and liver PCs but hepatic free fatty acids were relatively enriched in PUFA (p<0.05). Incorporation of PUFA into TGs and PCs in TM6SF2 knockdown hepatocytes was decreased (p<0.05). Hepatic expression of TM6SF2 was decreased in variant carriers, and was co-expressed with genes regulated by PUFAs.

CONCLUSIONS

Hepatic lipid synthesis from PUFAs is impaired and could contribute to deficiency in PCs and increased intrahepatic TG in TM6SF2 E167K variant carriers.

Lipid-lowering effects of Zanthoxylum schinifolium Siebold & Zucc. seed oil (ZSO) in hyperlipidemic rats and lipolytic effects in 3T3-L1 adipocytes

On the basis of the antiatherosclerotic effect of Zanthoxylum schinifolium, the therapeutic potential of Zanthoxylum schinifolium seed oil (ZSO) was tested in terms of the blood lipid profile and obesity in rats. The lipolytic effects of ZSO were determined in adipocytes and the total body and liver weight were decreased in rats. Compared with the high-cholesterol high-fat (HCHF) group, the rats in the HCHF+ZSO group showed improved levels of hyperlipidemia indicators. Furthermore, western blot analysis confirmed that the improvement of hyperlipidemia indicators was induced by stimulation of lipoprotein lipase expression. Additional results indicated that the reduction in body weight was likely caused by phosphorylation of hormone-sensitive lipase (HSL) via the protein kinase A pathway, ultimately leading to lipolysis. In conclusion, the results of the in vivo experiment showed that ZSO improved the lipid profiles in the blood, lowering cardiovascular disease and arteriosclerosis and degrading cellular lipids by activating HSL.

Activity and mRNA Levels of Enzymes Involved in Hepatic Fatty Acid Synthesis in Rats Fed Naringenin

We investigated the physiological activity of naringenin in affecting hepatic lipogenesis and serum and liver lipid levels in rats. Rats were fed diets containing 0, 1, or 2.5 g/kg naringenin for 15 d. Naringenin at a dietary level of 2.5 g/kg significantly decreased the activities and the mRNA levels of various lipogenic enzymes and sterol regulatory element binding protein-1c (SREBP-1c) mRNA level. The activities and the mRNA levels were also 9-22% and 12-38% lower, respectively, in rats fed a 1 g/kg naringenin diet than in the animals fed a naringenin-free diet, although the differences were not significant in many cases. Naringenin at 2.5 g/kg significantly lowered serum triacylglycerol, cholesterol, and phospholipid and hepatic triacylglycerol and cholesterol. This flavonoid at 1.0 g/kg also significantly lowered these parameters except for serum triacylglycerol. Naringenin levels in serum and liver dose-dependently increased, and hepatic concentrations reached levels that can affect various signaling pathways.

Optimized rapeseed oils rich in endogenous micronutrients ameliorate risk factors of atherosclerosis in high fat diet fed rats

BACKGROUND

Micronutrients in rapeseed such as polyphenols, tocopherols, phytosterols and phospholipids in rapeseed exert potential benefit to atherosclerosis. Some part of these healthy components substantially lost during the conventional refining processing. Thus some new processing technologies have been developed to produce various endogenous micronutrient-enriched optimized rapeseed oils. The aim of this study is to assess whether optimized rapeseed oils have positive effects on the atherosclerosis risk factors in rats fed a high-fat diet.

METHODS

Rats received experiment diets containing 20% fat and refined rapeseed oil or optimized rapeseed oils obtained with various processing technologies as lipid source. After 10 weeks of treatment, plasma was assayed for oxidative stress, lipid profiles and imflammation.

RESULTS

Micronutrients enhancement in optimized rapeseed oils significantly reduced plasma oxidative stress, as evaluated by the significant elevation in the activities of CAT and GPx as well as the level of GSH, and the significant decline in lipid peroxidation. Optimized rapeseed oil with the highest micronutrient contents obtained by microwave pretreatment-cold pressing reduced the levels of TG, TC and LDL-C as well as IL-6 and CRP in plasma.

CONCLUSIONS

These results suggest that optimized rapeseed oils may contribute to prevent atherogenesis and make them very promising functional food in cardiovascular health promotion.

The effect of a moderate zinc deficiency and dietary fat source on the activity and expression of the Δ(3)Δ (2)-enoyl-CoA isomerase in the liver of growing rats

Auxiliary enzymes participate in β-oxidation of unsaturated fatty acids. The objective of the study was to investigate the impact of a moderate zinc deficiency and a high intake of polyunsaturated fat on Δ(3)Δ(2)-enoyl-CoA isomerase (ECI) in the liver and other tissues. Five groups of eight weanling rats each were fed moderately zinc-deficient (ZD) or zinc-adequate (ZA) semisynthetic diets (7 or 50 mg Zn/kg) enriched with 22 % cocoa butter (CB) or 22 % safflower oil (SO) for 4 weeks: (1) ZD-CB, fed free choice; (2) ZA-CBR, ZA-CB diet fed in equivalent amounts consumed by the ZD-CB group; (3) ZD-SO, fed free choice; (4) ZA-SOR, ZA-SO diet fed in equivalent amounts consumed by the ZD-SO group; and (5) ZA-SO, fed free choice. Growth and Zn status markers were markedly reduced in the ZD groups. ECI activity in the liver of the animals fed the ZD- and ZA-SO diets were significantly higher (approximately 2- and 3-fold, respectively) as compared with the CB-fed animals, whereas activities in extrahepatic tissues (kidneys, heart, skeletal muscle, testes, adipose tissue) were not altered by dietary treatments. Transcript levels of the mitochondrial Eci gene in the liver did not significantly differ between ZD and ZA rats, but were 1.6-fold higher in the ZA-SO- than in the ZD-CB-fed animals (P < 0.05). It is concluded that diets enriched with safflower oil as a source high in linoleic acid induce markedly increased hepatic ECI activities and that a moderate Zn deficiency does not affect transcription of the mitochondrial Eci gene in the liver.

A combination of flaxseed oil and astaxanthin alleviates atherosclerosis risk factors in high fat diet fed rats

Background

Atherosclerosis is the most common pathologic process underlying cardiovascular disease. Both flaxseed oil (FO) and astaxanthin (ASX) are believed to benefit cardiovascular system. The combined effect of FO and ASX on the atherosclerosis risk factors in rats fed a high-fat diet was investigated.

Methods

Astaxanthin was dissolved in flaxseed oil to a final concentration of 1g/kg (FO + ASX). Male Sprague–Dawley rats were fed a rodent diet contained 20% fat whose source was lard (HFD) or 75% lard and 25% FO + ASX (50 mg ASX/kg diet) or 50% lard and 50% FO + ASX (100 mg ASX/kg diet) or FO + ASX (200 mg ASX/kg diet) for 10 weeks.

Results

The combination of FO and ASX significantly increased the antioxidant defense capacity and decreased lipid peroxidation in plasma. Evident decreases in the levels TG, TC and LDL-C contents, as well as IL-6 and CRP were also observed in plasma of FO and ASX fed rats.

Conclusion

The combination of FO and ASX can improve oxidative stress, lipid abnormalities and inflammation, providing evidence that the combination of FO and ASX could be a promising functional food in cardiovascular health promotion.

Flaxseed oil and α-lipoic acid combination reduces atherosclerosis risk factors in rats fed a high-fat diet

BACKGROUND

Atherosclerosis is a major manifestation of the pathophysiology underlying cardiovascular disease. Flaxseed oil (FO) and α-lipoic acid (LA) have been reported to exert potential benefit to cardiovascular system. This study tried to assess the effect of supplement of FO and LA combination on the atherosclerosis risk factors in rats fed a high-fat diet.

METHODS

LA was dissolved in flaxseed oil to a final concentration of 8 g/kg (FO+LA) when used. The rodent diet contained 20% fat. One-fifth of the fat was soybean oil and the others were lard (HFD group), or 75% lard and 25% FO+LA (L-FO+LA group), or 50% lard and 50% FO+LA (M-FO+LA group), or FO+LA (H-FO+LA group). Animals were fed for 10 weeks and then killed for blood collection.

RESULTS

Supplement of FO and LA combination significantly enhanced plasma antioxidant defense capacities, as evaluated by the marked increase in the activities of SOD, CAT and GPx as well as the level of GSH, and the significant reduction in lipid peroxidation. Simultaneous intake of FO and LA also reduced plasma TG, TC and LDL-C contents and elevated the ratio of HDL-C/LDL-C. Besides, in parallel with the increase of FO and LA combination, plasma IL-6 and CRP levels were remarkably reduced.

CONCLUSION

Supplement of FO and LA combination may contribute to prevent atherogenesis by improving plasma oxidative stress, lipid profile and inflammation.

Rat liver mitochondrial membrane characteristics and mitochondrial functions are more profoundly altered by dietary lipid quantity than by dietary lipid quality: effect of different nutritional lipid patterns

Dietary lipids are known to affect the composition of the biological membrane and functions that are involved in cell death and survival. The mitochondrial respiratory chain enzymes are membrane protein complexes whose function depends on the composition and fluidity of the mitochondrial membrane lipid. The present study aimed at investigating the impact of different nutritional patterns of dietary lipids on liver mitochondrial functions. A total of forty-eight Wistar male rats were divided into six groups and fed for 12 weeks with a basal diet, lard diet or fish oil diet, containing either 50 or 300 g lipid/kg. The 30 % lipid intake increased liver NEFA, TAG and cholesterol levels, increased mitochondrial NEFA and TAG, and decreased phospholipid (PL) levels. SFA, PUFA and unsaturation index (UI) increased, whereas MUFA and trans-fatty acids (FA) decreased in the mitochondrial membrane PL in 30 % fat diet-fed rats compared with 5 % lipid diet-fed rats. PL UI increased with fish oil diet v. basal and lard-rich diets, and PL trans-FA increased with lard diet v. basal and fish oil diets. The 30 % lipid diet intake increased mitochondrial membrane potential, membrane fluidity, mitochondrial respiration and complex V activity, and decreased complex III and IV activities. With regard to lipid quality effects, β-oxidation decreased with the intake of basal or fish oil diets compared with that of the lard diet. The intake of a fish oil diet decreased complex III and IV activities compared with both the basal and lard diets. In conclusion, the characteristics and mitochondrial functions of the rat liver mitochondrial membrane are more profoundly altered by the quantity of dietary lipid than by its quality, which may have profound impacts on the pathogenesis and development of non-alcoholic fatty liver disease.

Dietary chia seed (Salvia hispanica L.) rich in alpha-linolenic acid improves adiposity and normalises hypertriacylglycerolaemia and insulin resistance in dyslipaemic rats

The present study investigates the benefits of the dietary intake of chia seed (Salvia hispanica L.) rich in alpha-linolenic acid and fibre upon dyslipidaemia and insulin resistance (IR), induced by intake of a sucrose-rich (62.5 %) diet (SRD). To achieve these goals two sets of experiments were designed: (i) to study the prevention of onset of dyslipidaemia and IR in Wistar rats fed during 3 weeks with a SRD in which chia seed was the dietary source of fat; (ii) to analyse the effectiveness of chia seed in improving or reversing the metabolic abnormalities described above. Rats were fed a SRD during 3 months; by the end of this period, stable dyslipidaemia and IR were present in the animals. From months 3-5, half the animals continued with the SRD and the other half were fed a SRD in which the source of fat was substituted by chia seed (SRD+chia). The control group received a diet in which sucrose was replaced by maize starch. The results showed that: (i) dietary chia seed prevented the onset of dyslipidaemia and IR in the rats fed the SRD for 3 weeks--glycaemia did not change; (ii) dyslipidaemia and IR in the long-term SRD-fed rats were normalised without changes in insulinaemia when chia seed provided the dietary fat during the last 2 months of the feeding period. Dietary chia seed reduced the visceral adiposity present in the SRD rats. The present study provides new data regarding the beneficial effect of chia seed upon lipid and glucose homeostasis in an experimental model of dislipidaemia and IR.

Effects of soy protein and isoflavone on hepatic fatty acid synthesis and oxidation and mRNA expression of uncoupling proteins and peroxisome proliferator-activated receptor gamma in adipose tissues of rats

Soy protein rich in isoflavones profoundly affects lipid metabolism in experimental animals. To distinguish the roles of the protein and isoflavone components of a soy protein preparation in regulating lipid metabolism, we compared the effects of diets containing methanol-washed soy protein low in isoflavone supplemented with a 0-, 0.5- and 4-g/kg isoflavone preparation on hepatic fatty acid metabolism and adipose tissue gene expression in rats. Diets containing soy protein irrespective of the isoflavone levels decreased the activities and mRNA expression of enzymes involved in hepatic fatty acid synthesis to similar levels. Methanol-washed soy protein compared to casein increased the mRNA expression of peroxisome proliferator-activated receptor (PPAR) alpha, and supplementing the soy protein diet with isoflavone further increased this parameter dose-dependently. However, methanol-washed soy protein compared to casein was totally ineffective in altering the activities and mRNA levels of enzymes involved in fatty acid oxidation. Supplementation of soy protein diets with isoflavone slightly increased these parameters. The mRNA level of uncoupling protein (UCP) 1 in brown adipose tissue was significantly increased and mRNA levels of UCP2 and 3, and PPARgamma2 tended to be higher in rats fed methanol-washed soy protein not supplemented with isoflavone than in the animals fed casein. Adding isoflavone to the soy protein diets dose-dependently increased these parameters. These results suggested that the protein rather than isoflavone component is primarily responsible for the physiological activity of soy protein rich in isoflavones in reducing hepatic lipogenesis. However, isoflavones may have a role in regulating heptic fatty acid oxidation and adipose tissue gene expression.

The effect of six different C18 fatty acids on body fat and energy metabolism in mice

We studied the effects of five high-fat semi-purified diets varying at a 4 % (w/w) level in either stearic, oleic, linoleic, α-linolenic, or γ-linolenic acid on body fat and energy metabolism in BALB/c mice. A diet containing caprylic, capric, lauric, and myristic acid was used as a reference diet and a diet with 4 % conjugated linoleic acid (CLA) was used as a positive control as it is known to effectively lower body fat in mice. The diets were fed for 35 d. Body fat was significantly lower in the CLA group than in the other groups but was not significantly different among the non-CLA groups. Among the non-CLA groups, the linoleic acid group tended to have the highest and the α-linolenic acid group the lowest proportion of body fat. In energy-balance studies, the percentage of energy intake that was stored in the body was significantly lower in the CLA group compared with the other dietary groups. The percentage of energy intake eliminated in excreta was highest in the stearic acid group followed by the γ-linolenic acid group. These results were reflected in apparent fat digestibility, which was lowest in the stearic acid group. The percentage of energy intake expended as heat was highest in the CLA-fed mice. The results of the present study suggest that body fat and energy accretion in mice fed diets containing different C18 fatty acids is by far the lowest with CLA and that linoleic acid produced the highest fat intake and energy accretion.

The influence of dietary linoleic and alpha-linolenic acid on body composition and the activities of key enzymes of hepatic lipogenesis and fatty acid oxidation in mice

We have recently suggested that feeding the C18 polyunsaturated fatty acid, alpha-linolenic acid (ALA), instead of linoleic acid (LA) reduced body fat in mice. However, the difference in body fat did not reach statistical significance, which prompted us to carry out this study using more animals and diets with higher contents of ALA and LA so that the contrast would be greater. The diets contained either 12% (w/w) LA and 3% ALA or 12% ALA and 4% LA. A low-fat diet was used as control. The diets were fed for 35 days. The proportion of body fat was not influenced by the type of dietary fatty acid. Plasma total cholesterol and phospholipids were significantly lower in ALA-fed mice than in mice fed LA. Activities of enzymes in the fatty acid oxidation pathway were significantly raised by these two diets when compared with the control diet. alpha-Linolenic acid vs. LA did not affect fatty acid oxidation enzymes. In mice fed the diet with LA activities of enzymes of de novo fatty acid synthesis were significantly decreased when compared with mice fed the control diet. alpha-Linolenic acid vs. LA feeding did not influence lipogenic enzymes. It is concluded that feeding mice for 35 days with diets either rich in LA or ALA did not significantly influence body composition.

Consequences of food energy excess and positive energy balance

This paper discusses possible consequences of energy excess throughout the life cycle. Firstly we consider the effects of foods on hunger, satiety and satiation. Also, the changes in food availability and consumption in relation to changes in social and economic determinants of energy excess. The relationship between physical activity and energy intake (EI) is also considered. Secondly we explore the definition of energy excess and the metabolic effects of macronutrients (mainly in relation to fuel partitioning oxidation/storage) on energy balance. The cellular and molecular regulation determined by specific genes involved in lipogenesis, fuel partitioning and/or in energy dissipation are explored. Thirdly, we examine the main consequences induced by energy excess and positive energy balance, starting with the alterations in glucose utilisation (insulin resistance) leading to type 2 diabetes and the linkage of energy excess with other non-communicable diseases (NCDs). Biological, social and psychological consequences during perinatal, childhood and adolescence periods are specifically analysed. Fourthly, the transition from energy deficit to excess, under the optic of a developing country is analysed with country examples drawn from Latin America. The possible role of supplementary food programmes in determining positive energy balance is discussed especially in relation to pre-school and school feeding programmes. Fifthly, we deal with the economic costs of energy excess and obesity related diseases. Finally, some areas where further research is needed are described; biological and genetic determinants of individual and population energy requirements, foods and food preparations as actually consumed, consumer education and research needs on social determinants of energy imbalances.

Polyunsaturated fats attenuate the dietary phytol-induced increase in hepatic fatty acid oxidation in mice

The effects of dietary phytol and the type of dietary fat on hepatic fatty acid oxidation were examined in male ICR mice. Mice were fed diets containing 0 or 5 g/kg phytol and 100 g/kg palm, safflower, or fish oil for 21 d. Among the groups fed phytol-free diets, the activities and mRNA abundance of various enzymes involved in fatty acid oxidation were greater in mice fed fish oil than in those fed palm or safflower oil. Dietary phytol profoundly increased the activities and mRNA abundance of hepatic fatty acid oxidation enzymes in mice fed palm oil. However, safflower and fish oils, especially the latter, greatly attenuated the phytol-dependent increase in hepatic fatty acid oxidation. The hepatic concentration of phytanic acid, a metabolite of phytol that is the ligand and activator of retinoid X receptors and peroxisome proliferator-activated receptors, was higher in mice fed fish oil than safflower or palm oil, and in those administered safflower oil than palm oil. The hepatic mRNA abundance of sterol carrier protein-2, a lipid-binding protein involved in phytol metabolism, was inversely correlated with the hepatic concentration of phytanic acid. We demonstrated that polyunsaturated fats attenuate the enhancing effect of dietary phytol on hepatic fatty acid oxidation. Dietary fat-dependent changes in the hepatic phytanic acid concentration cannot account for this phenomenon.

Stimulation of acyl-CoA oxidase by α-linolenic acid-rich perilla oil lowers plasma triacylglycerol level in rats

The effect of dietary polyunsaturated fatty acids (PUFA) on hepatic peroxisomal oxidation was investigated with respect to the postprandial triacylglycerol levels. Male Sprague--Dawley rats were fed semipurified diets containing either 1% (w/w) corn oil, or 10% each of beef tallow, corn oil, perilla oil, and fish oil for 4 weeks and 4 days. Hepatic and plasma triacylglycerol levels were reduced in rats fed fish and perilla oil diets compared with corn oil and beef tallow diets. The peroxisomal beta-oxidation, catalase activity, and acyl-CoA oxidase (AOX) activity were markedly increased by fish oil feeding. To a lesser extent, perilla oil elevated AOX activity in a 4-day feeding although the effect gradually decreased in a 4-week feeding. Similarly, the mRNA levels were increased in rats fed fish and perilla oils. AOX activity was negatively correlated with postprandial triacylglycerol levels. In addition, the stimulation of AOX was highly associated with the content of long chain n-3 PUFA such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in hepatic microsome. These effects were evident within 4 days of initiating feeding. Therefore, alpha-linolenic perilla oil exerts a similar effect to fish oil in stimulating hepatic activity and gene expression of AOX by enriching long chain n-3 PUFA in hepatic membrane fraction, which can partly account for the reduction of postprandial triglyceridemia.

Dose effect of alpha-linolenic acid on lipid metabolism in the hamster

In order to meet dietary requirements, the consumption of alpha-linolenic acid (ALA, 18:3 n-3) must be promoted. However, its effects on triglyceride (TG) and cholesterol metabolism are still controversial, and may be dose-dependent. The effects of increasing dietary ALA intakes (1%, 10%, 20% and 40% of total FA) were investigated in male hamsters. ALA replaced oleic acid while linoleic and saturated FA were kept constant. Triglyceridemia decreased by 45% in response to 10% dietary ALA and was not affected by higher intakes. It was associated with lower hepatic total activities of acetyl-CoA-carboxylase (up to -29%) and malic enzyme (up to -42%), which were negatively correlated to ALA intake (r(2) = 0.33 and r(2) = 0.38, respectively). Adipose tissue lipogenesis was 2-6 fold lower than in the liver and was not affected by dietary treatment. Substitution of 10% ALA for oleic acid increased cholesterolemia by 15% but, as in TG, higher ALA intakes did not amplify the response. The highest ALA intake (40%) dramatically modified the hepatobiliary metabolism of sterols: cholesterol content fell by 45% in the liver and increased by 28% in the faeces. Besides, faecal bile acids decreased by 61%, and contained more hydrophobic and less secondary bile acids. Thus, replacing 10% oleic acid by ALA is sufficient to exert a beneficial hypotriglyceridemic effect, which may be counteracted by the slight increase in cholesterolemia. Higher intakes did not modify these parameters, but a very high dose resulted in adverse effects on sterol metabolism.

Supplementation with alpha-linolenic acid-rich diacylglycerol suppresses fatty liver formation accompanied by an up-regulation of beta-oxidation in Zucker fatty rats

Insulin resistance-related obesity and diabetes mellitus are the predominant causes of fatty liver disease. Here we examine the effects of dietary diacylglycerol (DG), which is a minor component of plant oils, on lipid accumulation and the expression of genes involved in lipid metabolism in the liver. The animals were fed diets containing either 10% triacylglycerol (TG), 10% TG + 4% alpha-linolenic acid-rich TG (ALATG) or 10% TG + 4% alpha-linolenic acid-rich diacylglycerol (ALADG) for a period of 1 month. Supplementation with ALADG significantly inhibited hepatic triglyceride accumulation; this was accompanied by the up-regulation of beta-oxidation activity, and acyl-CoA oxidase (ACO) and medium-chain acyl-CoA dehydrogenase (MCAD) mRNA levels. By contrast, no significant changes were observed in the levels of peroxisome proliferator-activated receptor-alpha (PPARalpha) and sterol regulatory element-binding protein-1 (SREBP-1) mRNAs. These results indicate that ALADG might be useful in the prevention of fatty liver formation; this effect could be closely related to the stimulation of lipid catabolism in the liver. In addition, our findings suggest that both acylglycerol structure (that is, the structural difference between TG and DG) and fatty-acid species affect the nutritional behaviour of dietary lipids.

Suppression of hepatic fatty acid synthase by feeding alpha-linolenic acid rich perilla oil lowers plasma triacylglycerol level in rats

This study was performed to determine the effects of dietary perilla oil, a n-3 alpha-linolenic acid (ALA) source, on hepatic lipogenesis as a possible mechanism of lowering triacylglycerol (TG) levels. Male Sprague-Dawley rats were trained for a 3-hour feeding protocol and fed one of five semipurified diets as follows: 1% (w/w) corn oil control diet, or one of four diets supplemented with 10% each of beef tallow, corn oil, perilla oil, and fish oil. Two separate experiments were performed to compare the effects of feeding periods, 4 weeks and 4 days. Hepatic and plasma TG levels were decreased in rats fed perilla oil and fish oil diets, compared with corn oil and beef tallow diets. The activities of hepatic lipogenic enzymes such as fatty acid synthase (FAS), glucose-6-phosphate dehydrogenase, and malic enzyme were suppressed in the fish oil, perilla oil, and corn oil-fed groups, and the effect was the most significant in the fish oil-fed group. Also, the activities of glycolytic enzymes, glucokinase, and L-pyruvate kinase showed the similar trend as that of lipogenic enzymes. The activity of FAS, the key regulatory enzyme in lipogenesis, was positively correlated with hepatic and plasma TG levels and reduced significantly in the perilla oil-fed group compared with corn oil-fed group. In addition, the FAS activity was negatively correlated with the hepatic microsomal content of EPA and DHA. In conclusion, suppression of FAS plays a significant role in the hypolipidemic effects observed in rats fed ALA rich perilla oil and these effects were associated with the increase of hepatic microsomal EPA and DHA contents.

Mechanisms of regulation of gene expression by fatty acids

Fatty acids (FA) regulate the expression of genes involved in lipid and energy metabolism. In particular, two transcription factors, sterol regulatory element binding protein-1c (SREBP-1c) and peroxisome proliferator activated receptor alpha (PPARalpha), have emerged as key mediators of gene regulation by FA. SREBP-1c induces a set of lipogenic enzymes in liver. Polyunsaturated fatty acids (PUFA), but not saturated or monounsaturated FA, suppress the induction of lipogenic genes by inhibiting the expression and processing of SREBP-1c. This unique effect of PUFA suggests that SREBP-1c may regulate the synthesis of unsaturated FA for incorporation into glycerolipids and cholesteryl esters. PPARalpha plays an essential role in metabolic adaptation to fasting by inducing the genes for mitochondrial and peroxisomal FA oxidation as well as those for ketogenesis in mitochondria. FA released from adipose tissue during fasting are considered as ligands of PPARalpha. Dietary PUFA, except for 18:2 n-6, are likely to induce FA oxidation enzymes via PPARalpha as a "feed-forward " mechanism. PPARalpha is also required for regulating the synthesis of highly unsaturated FA, indicating pleiotropic functions of PPARalpha in the regulation of lipid metabolic pathways. It is yet to be determined whether FA regulate other transcription factors such as liver-X receptor, hepatocyte nuclear factor 4, and carbohydrate response element binding protein.

Histological alterations in the liver of sea bream, Sparus aurata L., caused by short- or long-term feeding with vegetable oils. Recovery of normal morphology after feeding fish oil as the sole lipid source

This study evaluated the effects of fish oil (FO) replacement by vegetable oils [soybean oil (SO), rapeseed oil (RO), linseed oil (LO)] and subsequent feeding with FO on the liver morphology of sea bream. A short-term trial (3 months) and long-term trial (6 months) were carried out feeding sea bream with the following experimental diets: FO100%; SO60% + FO40%; RO60% +FO40%; LO60% + FO40%; SO + RO +LO60% + FO40%. Finally, all groups from the long-term trial were fed with FO100% for 95 days (washout period). Liver samples were taken for histological and biochemical studies. In both the short- and long-term trials, livers of sea bream fed LO60% and SO + RO + LO60% showed a similar hepatic morphology to that observed in fish fed FO100%. In contrast, sea bream fed SO60% showed an intense steatosis, with foci of swollen hepatocytes containing numerous lipid vacuoles. After the washout period, a considerable reduction of the cytoplasmic vacuolation and the lipid vacuole accumulation were observed in the livers of fish fed the different experimental diets. The results of this study suggested that the type of non-essential fatty acid, characteristic of vegetable oils, induces the appearance of steatosis in the following order: linoleic acid > linolenic acid > oleic acid. However, the liver alterations found during the experimental periods with vegetable oils are reversible when the fish are re-fed with a balanced diet (FO100%), indicating the non-pathological character of these histological changes.

Effects of dietary alpha linolenic acid on cholesterol metabolism in male and female hamsters of the LPN strain

N-3 polyunsaturated fatty acids and estrogens are recognized as protective factors of atherosclerosis, however their interactions on cholesterol metabolism remain unclear. Male and female hamsters were fed for 9 weeks diets containing 12.5% lipids and rich in either alpha-linolenic acid ("linseed" diet) or saturated fatty acids ("butter" diet). Hamsters fed the "linseed" diet exhibited lower plasma concentrations of cholesterol (-29%), total LDL (-35%) and HDL (-17%), glucose (-20%), insulin (-40%) and of the LDL-cholesterol/HDL-cholesterol ratio (-27%) than those fed the "butter" diet. In the liver, cholesterol content was 2.7-fold lower in response to the "linseed" diet, whereas the concentration of HDL receptor (SR-BI) and the activities of HMGCoA reductase and cholesterol 7alpha-hydroxylase were 30 to 50% higher than with the "butter" diet. By contrast, the LDL receptor concentration did not vary with the diet. Females exhibited higher concentration of LDL (+24%), lower concentration of plasma triglycerides (-34%), total VLDL (-46%) and VLDL-cholesterol (-37%) and of biliary phospholipids (-19%). Besides, there was also an interaction between gender and diet: in males fed the "butter" diet, plasma triglycerides and VLDL concentration, were 2 to 4 fold higher than in the other groups. These data suggest that gene and/or metabolic regulations by fatty acids could interact with that of sex hormones and explain why males are more sensitive to dietary fatty acids.

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.

Species differences in the physiological activity of dietary lignan (sesamin and episesamin) in affecting hepatic fatty acid metabolism

The effect of sesame (Sesamum orientale) lignan preparation containing equivalent amounts of sesamin and episesamin on hepatic fatty acid metabolism was compared in rats, mice and hamsters. Animals were fed on either a diet free of lignan or a diet containing 2 g lignan/kg for 15 d. The lignan preparation greatly increased hepatic activity and the mRNA levels of enzymes involved in fatty acid oxidation, while it strongly down-regulated those of enzymes involved in lipogenesis in rats. In contrast, lignan did not modify these variables in mice and hamsters. Changes observed, if any, were more attenuated in these mice and hamsters than in rats. Sesamin and episesamin concentrations in serum and liver of animals fed on lignan-containing diets were significantly greater (P<0.05) in rats than in mice and hamsters. Moreover, sesamin:episesamin values in tissues were far from that expected from the value in the lignan preparation given to the animals and were dependent on the animal species. Liver microsomes from each animal species degraded sesamin and episesamin in the presence of NADPH. The combined value of sesamin and episesamin degradation rates was lower in rats than in mice and hamsters. In addition, there was considerable diversity in the specificity of the enzyme reaction toward sesamin and episesamin among animal species. The differences in the amounts of lignan remaining in the tissues may account for the species dependence of the physiological activity of sesame lignan in affecting hepatic fatty acid oxidation and synthesis.

Divergent effects of eicosapentaenoic and docosahexaenoic acid ethyl esters, and fish oil on hepatic fatty acid oxidation in the rat

The physiological activity of fish oil, and ethyl esters of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) affecting hepatic fatty acid oxidation was compared in rats. Five groups of rats were fed various experimental diets for 15 days. A group fed a diet containing 9.4% palm oil almost devoid of n-3 fatty acids served as a control. The test diets contained 4% n-3 fatty acids mainly as EPA and DHA in the form of triacylglycerol (9.4% fish oil) or ethyl esters (diets containing 4% EPA ethyl ester, 4% DHA ethyl ester, and 1% EPA plus 3% DHA ethyl esters). The lipid content of diets containing EPA and DHA ethyl esters was adjusted to 9.4% by adding palm oil. The fish oil diet and ethyl ester diets, compared to the control diet containing 9.4% palm oil, increased activity and mRNA levels of hepatic mitochondrial and peroxisomal fatty acid oxidation enzymes, though not 3-hydroxyacyl-CoA dehydrogenase activity. The extent of the increase was, however, much greater with the fish oil than with EPA and DHA ethyl esters. EPA and DHA ethyl esters, compared to the control diet, increased 3-hydroxyacyl-CoA dehydrogenase activity, but fish oil strongly reduced it. It is apparent that EPA and DHA in the form of ethyl esters cannot mimic the physiological activity of fish oil at least in affecting hepatic fatty acid oxidation in rat.

Activity and mRNA levels of enzymes involved in hepatic fatty acid synthesis and oxidation in mice fed conjugated linoleic acid

The effects of dietary conjugated linoleic acid (CLA) on the activity and mRNA levels of hepatic enzymes involved in fatty acid synthesis and oxidation were examined in mice. In the first experiment, male ICR and C57BL/6J mice were fed diets containing either a 1.5% fatty acid preparation rich in CLA or a preparation rich in linoleic acid. In the second experiment, male ICR mice were fed diets containing either 1.5% linoleic acid, palmitic acid or the CLA preparation. After 21 days, CLA relative to linoleic acid greatly decreased white adipose tissue mass but caused hepatomegaly accompanying an approximate 10-fold increase in the tissue triacylglycerol content irrespective of mouse strain. CLA compared to linoleic acid greatly increased the activity and mRNA levels of various lipogenic enzymes in both experiments. Moreover, CLA increased the mRNA expression of Delta6- and Delta5-desaturases, and sterol regulatory element binding protein-1 (SREBP-1). The mitochondrial and peroxisomal palmitoyl-CoA oxidation rate was about 2.5-fold higher in mice fed CLA than in those fed linoleic acid in both experiments. The increase was associated with the up-regulation of the activity and mRNA expression of various fatty acid oxidation enzymes. The palmitic acid diet compared to the linoleic acid diet was rather ineffective in modulating the hepatic lipid levels or activity and mRNA levels of enzymes in fatty acid metabolism. It is apparent that dietary CLA concomitantly increases the activity and mRNA levels of enzymes involved in fatty acid synthesis and oxidation, and desaturation of polyunsaturated fatty acid in the mouse liver. Both the activation of peroxisomal proliferator alpha and up-regulation of SREBP-1 may be responsible for this.

Dietary alpha-linolenic acid-rich diacylglycerols reduce body weight gain accompanying the stimulation of intestinal beta-oxidation and related gene expressions in C57BL/KsJ-db/db mice

Dietary fat contributes to the development of obesity. We examined the effect of dietary diacylglycerol (DG), which is a minor component of edible oils, on the development of obesity and expression of genes involved in energy homeostasis in C57BL/KsJ-db/db mice. Mice were fed diets containing either 14 g/100 g (%) triacylglycerol (TG), 10% TG + 4% alpha-linolenic acid-rich TG (ALATG), or 10% TG + 4% alpha-linolenic acid-rich diacylglycerol (ALADG) for 1 mo. Mice fed ALADG, but not ALATG had less body weight gain and higher rectal temperature than the TG-fed controls. These effects were accompanied by up-regulation of acyl-CoA oxidase, medium-chain acyl-CoA dehydrogenase, fatty acid binding protein, and uncoupling protein (UCP)-2 mRNA and beta-oxidation activity in the small intestine. In contrast, the treatments did not affect beta-oxidation and related gene expressions in the liver or UCP-3 mRNA level in skeletal muscle. These results indicate that stimulation of lipid metabolism in the small intestine might be closely related to the antiobesity and thermogenic effects of dietary DG. In addition, structural differences between DG and TG, not variations in the composition of fatty acids, are responsible for the different effects of the lipids.

Metabolic fate of long-chain unsaturated fatty acids and their effects on palmitic acid metabolism and gluconeogenesis in bovine hepatocytes

The objectives were to determine the metabolic fate of different long-chain fatty acids, and their effects on palmitic acid metabolism and gluconeogenesis in bovine hepatocytes. Hepatocytes were isolated from four ruminating calves and exposed in suspension for 3 h to one of the following treatments: 1 mM palmitic acid (1C16), 2 mM palmitic acid (2C16), or 1 mM palmitic acid plus either 1 mM oleic (C18:1), linoleic (C18:2), linolenic (C18:3), eicosapentaenoic (C20:5), or docosahexaenoic acid (C22:6). Oxidation of [1-(14)C]palmitic acid or one of the [1-(14)C]-labeled treatment fatty acids to CO2 or incorporation into cellular triglycerides (TG), phospholipids, cholesterol, and cholesterol esters were measured. Rates of oxidation to CO2 were 3- to 4-fold higher for C22:6 than for other fatty acids, with the exception of C20:5, which had intermediate rates of oxidation to CO2. In general, treatments 2C16 and C18:1 yielded the highest rates of incorporation into most cellular lipids, whereas the polyunsaturated fatty acids were poor substrates for incorporation into cellular lipids. The most pronounced change was a large reduction of polyunsaturated fatty acid incorporation into cellular TG compared to 1C16, 2C16, and C18:1. The unsaturated fatty acids also influenced palmitic acid metabolism. The addition of C20:5 yielded the highest rates of palmitic acid oxidation to CO2 followed by addition of C18:1 and C22:6. Treatments containing polyunsaturated fatty acids decreased palmitic acid metabolism to TG and total cellular lipids compared with treatments 2C16 and C18:1. Rates of gluconeogenesis from propionate were significantly higher for the treatment containing C18:1. Long-chain fatty acids vary in their routes of metabolism and influence palmitic acid metabolism and gluconeogenesis in bovine hepatocytes.

Comparative effect of sesamin and episesamin on the activity and gene expression of enzymes in fatty acid oxidation and synthesis in rat liver

Sesamin is one of the most abundant lignans in sesame seed. Episesamin, a geometrical isomer of sesamin, is not a naturally occurring compound and is formed during the refining process of non-roasted sesame seed oil. We compared the physiological activities of these compounds in affecting hepatic fatty acid metabolism in rat liver. Rats were fed either a control diet free of lignan or diets containing 0.2% of sesamin or episesamin for 15 days. These lignans increased the mitochondrial and peroxisomal palmitoyl-CoA oxidation rates. However, the magnitude of the increases was greater with episesamin than with sesamin. Sesamin caused 1.7- and 1.6-fold increases in mitochondrial and peroxisomal activity, respectively, while episesamin increased these values 2.3- and 5.1-fold. These lignans also increased the activity and gene expression of various fatty acid oxidation enzymes. Again, the increase was much more exaggerated with episesamin (1.5- to 14-fold) than with sesamin (1.3- to 2.8-fold). Diets containing sesamin and episesamin lowered the activity and gene expression of hepatic lipogenic enzymes to one-half of those obtained in the animals fed a lignan-free diet. However, no significant differences in these parameters were seen between rats fed sesamin and episesamin. Responses to sesamin and episesamin of hepatic lipogenesis are, therefore, considerably different from those observed in fatty acid oxidation. These results show that the physiological activity of the commercial sesamin preparation containing equivalent amounts of both sesamin and episesamin in increasing hepatic fatty acid oxidation observed previously was mainly ascribable to that of episesamin but not to sesamin.

Comparative effects of perilla and fish oils on the activity and gene expression of fatty acid oxidation enzymes in rat liver

The activity and mRNA level of hepatic enzymes in fatty acid oxidation and synthesis were compared in rats fed diets containing either 15% saturated fat (palm oil), safflower oil rich in linoleic acid, perilla oil rich in alpha-linolenic acid or fish oil rich in eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) for 15 days. The mitochondrial fatty acid oxidation rate was 50% higher in rats fed perilla and fish oils than in the other groups. Perilla and fish oils compared to palm and safflower oils approximately doubled and more than tripled, respectively, peroxisomal fatty acid oxidation rate. Compared to palm and safflower oil, both perilla and fish oils caused a 50% increase in carnitine palmitoyltransferase I activity. Dietary fats rich in n-3 fatty acids also increased the activity of other fatty acid oxidation enzymes except for 3-hydroxyacyl-CoA dehydrogenase. The extent of the increase was greater with fish oil than with perilla oil. Interestingly, both perilla and fish oils decreased the activity of 3-hydroxyacyl-CoA dehydrogenase measured using short- and medium-chain substrates. Compared to palm and safflower oils, perilla and fish oils increased the mRNA level of many mitochondrial and peroxisomal enzymes. Increases were generally greater with fish oil than with perilla oil. Fatty acid synthase, glucose-6-phosphate dehydrogenase, and pyruvate kinase activity and mRNA level were higher in rats fed palm oil than in the other groups. Among rats fed polyunsaturated fats, activities and mRNA levels of these enzymes were lower in rats fed fish oil than in the animals fed perilla and safflower oils. The values were comparable between the latter two groups. Safflower and fish oils but not perilla oil, compared to palm oil, also decreased malic enzyme activity and mRNA level. Examination of the fatty acid composition of hepatic phospholipid indicated that dietary alpha-linolenic acid is effectively desaturated and elongated to form EPA and DHA. Dietary perilla oil and fish oil therefore exert similar physiological activity in modulating hepatic fatty acid oxidation, but these dietary fats considerably differ in affecting fatty acid synthesis.

Sesamin, a sesame lignan, is a potent inducer of hepatic fatty acid oxidation in the rat

The effects of sesamin, one of the most abundant lignans in sesame seed, on hepatic fatty acid oxidation were examined in rats that were fed experimental diets containing various amounts (0%, 0.1%, 0.2%, and 0.5%) of sesamin (a 1:1 mixture of sesamin and episesamin) for 15 days. Dietary sesamin dose-dependently increased both mitochondrial and peroxisomal palmitoyl-coenzyme A (CoA) oxidation rates. Mitochondrial activity almost doubled in rats on the 0.5% sesamin diet. Peroxisomal activity increased more than 10-fold in rats fed a 0.5% sesamin diet in relation to rats on the sesamin-free diet. Dietary sesamin greatly increased the hepatic activity of fatty acid oxidation enzymes, including carnitine palmitoyltransferase, acyl-CoA dehydrogenase, acyl-CoA oxidase, 3-hydroxyacyl-CoA dehydrogenase, enoyl-CoA hydratase, and 3-ketoacyl-CoA thiolase. Dietary sesamin also increased the activity of 2,4-dienoyl-CoA reductase and delta3,delta2-enoyl-CoA isomerase, enzymes involved in the auxiliary pathway for beta-oxidation of unsaturated fatty acids dose-dependently. Examination of hepatic mRNA levels using specific cDNA probes showed a sesamin-induced increase in the gene expression of mitochondrial and peroxisomal fatty acid oxidation enzymes. Among these various enzymes, peroxisomal acyl-CoA oxidase and bifunctional enzyme gene expression were affected most by dietary sesamin (15- and 50-fold increase by the 0.5% dietary level). Sesamin-induced alterations in the activity and gene expression of carnitine palmitoyltransferase I and acyl-CoA oxidase were in parallel with changes in the mitochondrial and peroxisomal palmitoyl-CoA oxidation rate, respectively. In contrast, dietary sesamin decreased the hepatic activity and mRNA abundance of fatty acid synthase and pyruvate kinase, the lipogenic enzymes. However, this lignan increased the activity and gene expression of malic enzyme, another lipogenic enzyme. An alteration in hepatic fatty acid metabolism may therefore account for the serum lipid-lowering effect of sesamin in the rat.

Comparative effects of alpha- and gamma-linolenic acids on rat liver fatty acid oxidation

It has been reported that both n-3 and n-6 octadecatrienoic acids can increase hepatic fatty acid oxidation activity. It remains unclear, however, whether different enzymes in fatty acid oxidation show a similar response to n-3 and n-6 octadecatrienoic acids. The activity of hepatic fatty acid oxidation enzymes in rats fed an oil mixture rich in alpha-linolenic acid (18:3n-3) and borage oil rich in gamma-linolenic acid (18:3n-6) was therefore compared to that in rats fed an oil mixture rich in linoleic acid (18:2n-6) and a saturated fat (palm oil) in this study. Linseed oil served as the source of 18:3n-3 for the oil mixture rich in this octadecatrienoic acid and contained 30.6% 18:3n-3 but not 18:3n-6. Borage oil contained 25.7% 18:3n-6 and 4.5% 18:3n-3. Groups of seven rats each were fed diets containing 15% various fats for 15 d. The oxidation rate of palmitoyl-CoA in the peroxisomes was higher in rats fed a fat mixture rich in 18:3n-3 (3.03 nmol/min/mg protein) and borage oil (2.89 nmol/min/mg protein) than in rats fed palm oil (2.08 nmol/min/mg protein) and a fat mixture rich in 18:2n-6 (2.15 nmol/min/mg protein). The mitochondrial palmitoyl-CoA oxidation rate was highest in rats fed a fat mixture rich in 18:3n-3 (1.93 nmol/min/mg protein), but no significant differences in this parameter were seen among the other groups (1.25-1.46 nmol/min/mg protein). Compared to palm oil and fat mixtures rich in 18:2n-6, a fat mixture rich in 18:3n-3 and borage oil significantly increased the hepatic activity of carnitine palmitoyltransferase and acyl-CoA oxidase. Compared to palm oil and a fat mixture rich in 18:2n-6, a fat mixture rich in 18:3n-3, but not fats rich in 18:3n-6, significantly decreased 3-hydroxyacyl-CoA dehydrogenase activity. Compared to palm oil and a fat mixture rich in 18:2n-6, borage oil profoundly decreased mitochondrial acyl-CoA dehydrogenase activity, but a fat mixture rich in 18:3n-3 increased it. 2,4-Dienoyl-CoA reductase activity was significantly lower in rats fed palm oil than in other groups. Compared to other fats, borage oil significantly increased delt3,delta2-enoyl-CoA isomerase activity. Activity was also significantly higher in rats fed 18:2n-6 oil than in those fed palm oil. It was confirmed that both dietary 18:3n-6 and 18:3n-3 increased fatty acid oxidation activity in the liver. These two dietary octadecatrienoic acids differ considerably, however, in how they affect individual fatty acid oxidation enzymes.