Detrimental effects of a high fat diet in early renal injury are ameliorated by fish oil in Han:SPRD-cy rats

Dietary fish oils containing (n-3) fatty acids can modulate renal inflammatory injury. We previously demonstrated that a high fat (HF) diet worsens early renal disease progression in the Han:SPRD-cy rat model of polycystic kidney disease (PKD). Therefore, using HF (20 g/100 g diet) and low fat (LF; 5 g/100 g diet) diets, we compared the effects of menhaden oil (MO), soybean oil (SO) and cottonseed oil (CO) on renal function and histology in male Han:SPRD-cy rats fed the diets for 6 wk in the early stages of renal disease. Overall, rats fed HF compared with those fed LF diets had larger kidneys, more renal fibrosis and lower creatinine clearance (main effects of fat level).Rats fed MO rather than CO and SO diets had significantly lower kidney weights, kidney water content, cyst volumes and serum cholesterol and triglyceride concentrations (main effects of fat type). Rats fed MO diets also had less renal fibrosis than those fed CO diets, but the least fibrosis was in rats fed SO diets. Analysis of simple effects (due to interactions between fat level and type) revealed that HF diets increased renal inflammation in rats fed CO diets, but reduced inflammation was present in those fed SO and MO diets; HF diets also increased compared with LF diets serum urea nitrogen concentrations in rats fed the MO and CO diets, but not the SO diet. These results confirm that high dietary fat worsens early disease progression in this model of renal disease, and further demonstrate that diets with oils containing (n-3) fatty acids ameliorate some of the detrimental effects of a high fat diet.     

Effect of increasing the dietary (n-3) to (n-6) polyunsaturated fatty acid ratio on murine liver and peritoneal cell fatty acids and eicosanoid formation

An incremental increase in the dietary (n-3):(n-6) polyunsaturated fatty acid (PUFA) ratio from 0 to 1.93 in diets containing 15% fat (wt/wt) decreased the total (n-6) PUFA content of phospholipids of the liver and peritoneal cells (macrophage) in mice from 43.1 and 33.6 mol/100 mol to 16.0 and 12.3 mol/100 mol with a concomitant increase of 27.6 and 16.1 mol/100 mol in (n-3) PUFA, respectively. Consumption of (n-3) PUFA increased hepatic (n-3) PUFA levels without changing total PUFA (46.35 vs. 46.87 mol/100 mol), whereas macrophage PUFA levels were decreased. The synthesis of sulfidopeptide leukotrienes (SP-LT) (LTC4 and LTE4) was progressively reduced by increasing dietary (n-3) PUFA, i.e., there was a reduction of 76% in mice fed a diet containing a (n-3):(n-6) PUFA ratio of 1.93 compared with the control diet. The 5-series SP-LT (LTC5 and LTF5) were produced in all animals consuming (n-3) PUFA and accounted for 62% of all SP-LT synthesized in mice fed the diet containing a 1.93 (n-3):(n-6) PUFA ratio. Synthesis of 6-keto-prostaglandin F1 alpha decreased 81% in mice fed a diet containing a (n-3):(n-6) PUFA ratio of 1.93 whereas prostaglandin E2 synthesis decreased 44% in mice fed diets with (n-3):(n-6) ratios ranging from 0.41 to 1.93.     

Disparate effects of dietary fatty acids on activity of 5'-nucleotidase of rat liver plasma membrane

The effects of incorporation of dietary n-3 polyunsaturated fatty acids (PUFA) into rat liver plasma membrane on the activity of 5'-nucleotidase (EC 3.1.3.5) was studied. The membrane phospholipids from rats fed a diet containing 10% by weight menhaden oil (MO) for 3 wk contained more n-3 PUFA and less n-6 PUFA in phospholipids classes, i.e., 24% and 65% less linoleic and arachidonic acid in phosphatidylcholine, than in rats fed 10% coconut oil (CNO) diets. The specific activity of 5'-nucleotidase in n-3 PUFA-enriched hepatic plasma membranes was 1.6- to 2-fold higher than that in rats fed CNO or corn oil (CO). Lineweaver-Burk plots for 5'-nucleotidase in liver plasma membranes isolated from rats fed MO and CNO showed no significant differences in Km values but the Vmax was increased by 67% in MO-fed rats. Arrhenius plots showed a break point in 5'-nucleotidase activity at 28.3 degrees C and 30.8 degrees C in plasma membranes from MO- and CNO-fed rats, respectively. The implications of this in the generation of adenosine and its possible impact on physiological functions are discussed.     

PPARalpha expression protects male mice from high fat-induced nonalcoholic fatty liver

Emerging evidence suggests that the lack of PPARα enhances hepatic steatosis and inflammation in Ppara-null mice when fed a high-fat diet (HFD). Thus, the aim of this study was to determine whether Ppara-null mice are more susceptible to nonalcoholic steatohepatitis (NASH) than their wild-type (WT) counterparts following short-term feeding with a HFD. Age-matched male WT and Ppara-null mice were randomly assigned to consume ad libitum a standard Lieber-DeCarli liquid diet (STD) (35% energy from fat) or a HFD (71% energy from fat) for 3 wk. Liver histology, plasma transaminase levels, and indicators of oxidative/nitrosative stress and inflammatory cytokines were evaluated in all groups. Levels of lobular inflammation and the NASH activity score were greater in HFD-exposed Ppara-null mice than in the other 3 groups. Biochemical analysis revealed elevated levels of ethanol-inducible cytochrome P450 2E1 and TNFα accompanied by increased levels of malondialdehyde as well as oxidized and nitrated proteins in Ppara-null mice. Elevated oxidative stress and inflammation were associated with activation of c-Jun-N-terminal kinase and p38 kinase, resulting in increased hepatocyte apoptosis in Ppara-null mice fed a HFD. These results, with increased steatosis, oxidative stress, and inflammation observed in Ppara-null mice fed a HFD, demonstrate that inhibition of PPARα functions may increase susceptibility to high fat-induced NASH.     

Menhaden oil, but not safflower or soybean oil, aids in restoring the polyunsaturated fatty acid profile in the novel [increment]-6-desaturase null mouse

ABSTRACT: BACKGROUND: Polyunsaturated fatty acids (PUFA) have diverse biological effects, from promoting inflammation to preventing cancer and heart disease. Growing evidence suggests that individual PUFA may have independent effects in health and disease. The individual roles of the two essential PUFA, linoleic acid (LA) and alpha-linolenic acid (ALA), have been difficult to discern from the actions of their highly unsaturated fatty acid (HUFA) downstream metabolites. This issue has recently been addressed through the development of the [increment]-6 desaturase knock out (D6KO) mouse, which lacks the rate limiting [increment]-6 desaturase enzyme and therefore cannot metabolize LA or ALA. However, a potential confounder in this model is the production of novel [increment]-5 desaturase (D5D) derived fatty acids when D6KO mice are fed diets containing LA and ALA, but void of arachidonic acid. OBJECTIVE: The aim of the present study was to characterize how the D6KO model differentially responds to diets containing the essential n-6 and n-3 PUFA, and whether the direct provision of downstream HUFA can rescue the phenotype and prevent the production of D5D fatty acids. Methodology Liver and serum phospholipid (PL) fatty acid composition was examined in D6KO and wild type mice fed i) 10% safflower oil diet (SF, LA rich) ii) 10% soy diet (SO, LA+ALA) or iii) 3% menhaden oil +7% SF diet (MD, HUFA rich) for 28 days (n = 3-7/group). RESULTS: Novel D5D fatty acids were found in liver PL of D6KO fed SF or SO-fed mice, but differed in the type of D5D fatty acid depending on diet. Conversely, MD-fed D6KO mice had a liver PL fatty acid profile similar to wild-type mice. CONCLUSIONS: Through careful consideration of the dietary fatty acid composition, and especially the HUFA content in order to prevent the synthesis of D5D fatty acids, the D6KO model has the potential to elucidate the independent biological and health effects of the parent n-6 and n-3 fatty acids, LA and ALA.     

Consumption of Low Dose Fucoxanthin Does Not Prevent Hepatic and Adipose Inflammation and Fibrosis in Mouse Models of Diet-Induced Obesity

Fucoxanthin (FCX) is a xanthophyll carotenoid present in brown seaweed. The goal of this study was to examine whether FCX supplementation could attenuate obesity-associated metabolic abnormalities, fibrosis, and inflammation in two diet-induced obesity (DIO) mouse models. C57BL/6J mice were fed either a high-fat/high-sucrose/high-cholesterol (HFC) diet or a high-fat/high-sucrose (HFS) diet. The former induces more severe liver injury than the latter model. In the first study, male C57BL/6J mice were fed an HFC diet, or an HFC diet containing 0.015% or 0.03% (w/w) FCX powder for 12 weeks to develop obesity-induced nonalcoholic steatohepatitis (NASH). In the second study, mice were fed an HFS diet or an HFS diet containing 0.01% FCX powder for 8 weeks. FCX did not change body weight gain and serum lipid profiles compared to the HFC or HFS controls. No significant differences were present in liver triglyceride and total cholesterol, hepatic fat accumulation, and serum alanine aminotransferase levels between control and FCX-fed mice regardless of whether they were on an HFC or HFS diet. FCX did not mitigate mRNA abundance of genes involved in lipid synthesis, cholesterol metabolism, inflammation, and fibrosis in the liver and white adipose tissue, while hepatic fatty acid β-oxidation genes were significantly elevated by FCX in both HFC and HFS feeding studies. Additionally, in the soleus muscle, FCX supplementation significantly elevated genes that regulate mitochondrial biogenesis and fatty acid β-oxidation, concomitantly increasing mitochondrial DNA copy number, compared with HFC. In summary, FCX supplementation had minor effects on hepatic and white adipose inflammation and fibrosis in two different DIO mouse models.     

Green tea extract suppresses NFκB activation and inflammatory responses in diet-induced obese rats with nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is characterized by oxidative stress and inflammatory responses that exacerbate liver injury. The objective of this study was to determine whether the antioxidant and antiinflammatory activities of green tea extract (GTE) would protect against NASH in a model of diet-induced obesity. Adult Wistar rats were fed a low-fat (LF) diet or high-fat (HF) diet containing no GTE or GTE at 1% or 2% (HF+2GTE) for 8 wk. The HF group had greater (P ≤ 0.05) serum alanine (ALT) and aspartate aminotransferases and hepatic lipids than the LF group. Both GTE groups had lower ALT and hepatic lipid than the HF group. In liver and epididymal adipose, the HF group had lower glutathione as well as greater mRNA and protein expression of TNFα and monocyte chemoattractant protein-1 (MCP-1) and NFκB binding activity than the LF group. Compared to the HF group, the HF+2GTE group had greater glutathione and lower protein and mRNA levels of inflammatory cytokines in both tissues. NFκB binding activities at liver and adipose were also lower, likely by inhibiting the phosphorylation of inhibitor of NFκB. NFκB binding activities in liver and adipose (P ≤ 0.05; r = 0.62 and 0.46, respectively) were correlated with ALT, and hepatic NFκB binding activity was inversely related to liver glutathione (r = -0.35). These results suggest that GTE-mediated improvements in glutathione status are associated with the inhibition of hepatic and adipose inflammatory responses mediated by NFκB, thereby protecting against NASH.     

Dietary n-3 polyunsaturated fatty acids: rate and extent of modification of fatty acyl composition of lipid classes of mouse lung and kidney

The rate and extent of modification of fatty acid composition of mice lung and kidney by dietary menhaden oil (MO) was investigated. White mice were fed 2 wt% safflower oil and either 10 wt% MO or 10 wt% hydrogenated coconut oil (HCO) for 23 d. The stability of dietary MO-induced fatty acid modifications was assessed by replacing the MO diet of a group of mice after 23 d with the HCO diet for an additional 10 d. Mice were sacrificed on d 0, 1, 3, 5, 7, 14, 23 and 33. The n-3 polyunsaturated fatty acid (PUFA), 20:5n-3 and 22:6n-3 were rapidly incorporated into lung and kidney phosphoglyceride (PL) classes during the first 7 d of MO ingestion relative to the controls. After 1 wk of MO consumption, the rate of incorporation either plateaued at an elevated level or continued to increase at a much more gradual rate. A marked increase in the content of 22:5n-3 in lung and kidney was observed. A concomitant and rapid decrease was observed in the n-6 PUFA, 20:4n-6, 22:5n-6 and 18:2n-6. The minimum content of 20:4n-6 was reached between 1 and 2 wk, whereas the minimum levels of 18:2n-6 and 22:5n-6 occurred within 72 h. The n-6/n-3 PUFA ratio in lung and kidney and PL classes increased in mice fed HCO and decreased in mice fed dietary MO. When dietary MO was removed, the n-3 PUFA levels decreased with a concomitant increase in n-6 PUFA after 10 d of HCO consumption.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dietary gamma-linolenic acid suppresses aortic smooth muscle cell proliferation and modifies atherosclerotic lesions in apolipoprotein E knockout mice

The present study was conducted to evaluate the antiatherogenic effects of dietary gamma-linolenic acid (GLA) (primrose oil) in apolipoprotein E (apoE) genetic knockout mice. Five-wk-old male mice were fed cholesterol-free diets containing 10 g/100 g lipid as corn oil (CO) [control diet, 0 mol/100 mol GLA and (n-3) polyunsaturated fatty acids (PUFA)], primrose oil (PO, 10 mol/100 mol GLA), fish oil-CO mix [FC; 9:1 wt/wt, 0 mol/100 mol GLA and 17 mol/100 mol (n-3) PUFA] or fish oil-PO mix [FP, 1:3 wt/wt, 8 mol/100 mol GLA and 5 mol/100 mol (n-3) PUFA] for 15 wk. Subsequently, diets were supplemented with cholesterol (1.25 g/100 g) and sodium cholate (0.5 g/100 g) and fed for an additional 10 and 16 wk. Plasma cholesterol and triglyceride levels generally did not differ among groups at 20, 30 and 36 wk of age. Mice fed GLA-containing diets (PO and FP) had significantly (P < 0.05) higher liver phospholipid levels of dihomo-gamma-linolenic acid, the elongated product of GLA, relative to CO and FC groups. Consumption of GLA (PO and FP diets) significantly reduced (P < 0.05) aortic vessel wall medial layer thickness at 20 and 30 wk. A parallel GLA-dependent suppression in the number of proliferating (proliferating cell nuclear antigen positive) aortic smooth muscle cells was also observed. Diets containing either GLA or (n-3) PUFA reduced (P < 0.05) atherosclerotic lesion size in 30-wk-old mice. These results indicate that dietary GLA can suppress smooth muscle cell proliferation in vivo and retard the development of diet-induced atherosclerosis in apoE knockout mice.     

Metabolic responses to high-fat diets rich in n-3 or n-6 long-chain polyunsaturated fatty acids in mice selected for either high body weight or leanness explain different health outcomes

Background

Increasing evidence suggests that diets high in polyunsaturated fatty acids (PUFA) confer health benefits by improving insulin sensitivity and lipid metabolism in liver, muscle and adipose tissue.

Methods

The present study investigates metabolic responses in two different lines of mice either selected for high body weight (DU6) leading to rapid obesity development, or selected for high treadmill performance (DUhTP) leading to a lean phenotype. At 29 days of age the mice were fed standard chow (7.2% fat, 25.7% protein), or a high-fat diet rich in n-3 PUFA (n-3 HFD, 27.7% fat, 19% protein) or a high-fat diet rich in n-6 PUFA (n-6 HFD, 27.7% fat, 18.6% protein) for 8 weeks. The aim of the study was to determine the effect of these PUFA-rich high-fat diets on the fatty acid profile and on the protein expression of key components of insulin signalling pathways.

Results

Plasma concentrations of leptin and insulin were higher in DU6 in comparison with DUhTP mice. The high-fat diets stimulated a strong increase in leptin levels and body fat only in DU6 mice. Muscle and liver fatty acid composition were clearly changed by dietary lipid composition. In both lines of mice n-3 HFD feeding significantly reduced the hepatic insulin receptor β protein concentration which may explain decreased insulin action in liver. In contrast, protein kinase C ζ expression increased strongly in abdominal fat of n-3 HFD fed DUhTP mice, indicating enhanced insulin sensitivity in adipose tissue.

Conclusions

A diet high in n-3 PUFA may facilitate a shift from fuel deposition in liver to fuel storage as fat in adipose tissue in mice. Tissue specific changes in insulin sensitivity may describe, at least in part, the health improving properties of dietary n-3 PUFA. However, important genotype-diet interactions may explain why such diets have little effect in some population groups.     

Lipid profile of rats fed high-fat diets based on flaxseed, peanut, trout, or chicken skin

OBJECTIVE: Dietary saturated fatty acids are associated with coronary disease. Conversely, dietary monounsaturated polyunsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) seem to exert a protective effect. This study evaluated the lipid profile of rats fed high-fat (HF) diets, with fat added as different sources of PUFA (flaxseed and trout), MUFA (peanut), and saturated fatty acid (chicken skin). METHODS: Adult male Wistar rats were placed into six dietary groups (n = 10): control (normal); high fat, with 1% cholesterol, 10% soy oil, and 5% lard; and four groups fed similar HF diets, with 10% lipid as trout, flaxseed, peanut, or chicken skin. After 28 d the animals were killed. Blood, livers, and adipose tissue samples were collected. RESULTS: A higher level (P < 0.05) of total serum cholesterol was observed in rats fed the normal diet (93.57 +/- 14.95 mg/dL) compared with those fed the HF diet (67.57 +/- 12.54 mg/dL). Total cholesterol levels in rats fed the flaxseed diet were lower (P < 0.05) than in rats fed the other fats. No difference was observed in cholesterol levels between groups fed the peanut and chicken skin diets (P > 0.05). Animals fed the peanut diet showed decreased body weight gain than did animals in the other treatment groups. There were large lipid and cholesterol depositions in livers of rats fed the HF diet. Lipid deposition in adipose tissue followed the same dietary fatty acid profile, i.e., high levels of omega-3 PUFA in the flaxseed group, high levels of MUFA in the peanut and chicken skin groups and high levels of omega-6 PUFA in the trout group. CONCLUSIONS: These data indicate that flaxseed is promising for dietary manipulation of hyperlipidemia.     

Behavioral responses are altered in piglets with decreased frontal cortex docosahexaenoic acid

Docosahexaenoic acid [22:6(n-3)] is required in large amounts for membrane lipid synthesis during brain growth. The functional importance of differences in dietary fatty acid intakes that alter brain 22:6(n-3), however, is not well understood. We used a dietary approach to manipulate 22:6(n-3) in piglet brain and assessed the effects on behavior and change in behavior on an elevated plus maze after administration of L-dihydroxyphenylalanine (L-Dopa) or sulperide, a dopamine D2 receptor blocker. Piglets were fed 1.2% energy 18:2(n-6) and 0.05% energy 18:3(n-3) (low PUFA), or 10.7% energy 18:2(n-6), 1.1% energy 18:3(n-3), 0.3% energy 20:4(n-6) and 0.3% energy 22:6(n-3) (high PUFA) from 1 d of age and behavior assessed at 18-22 d of age. At 30 d of age, frontal cortex dopamine, and phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidyethanolamine (PE) and phosphatidylinositol (PI) fatty acids were quantified. Piglets fed the low PUFA diet had fewer arm entries on the maze than piglets fed the high PUFA diet, P = 0.02. L-Dopa increased the open (P = 0.005) and closed (P = 0.04) arm entries by piglets fed the low PUFA diet. Behavior did not differ between piglets fed the low and high PUFA diets when given L-Dopa. Frontal cortex PC, PS and PE 22:6(n-3) was lower and 22:5(n-6) was higher in piglets fed the low compared with the high PUFA diet, P < 0.01. Our work establishes the neonatal piglet as a model with which to study the behavioral effects of diet-induced changes in brain 22:6(n-3), and provides functional evidence that brain 22:6(n-3) is important in central dopamine metabolism.     

Hepatic rhythmicity of endoplasmic reticulum stress is disrupted in perinatal and adult mice models of high-fat diet-induced obesity

We investigated the regulation of hepatic ER stress in healthy liver and adult or perinatally programmed diet-induced non-alcoholic fatty liver disease (NAFLD). Female mice were fed either obesogenic or control diet before mating, during pregnancy and lactation. Post-weaning, offspring from each maternal group were divided into either obesogenic or control diet. At six months, offspring were sacrificed at 4-h intervals over 24?h. Offspring fed obesogenic diets developed NAFLD phenotype, and the combination of maternal and offspring obesogenic diets exacerbated this phenotype. UPR signalling pathways (IREα, PERK, ATF6) and their downstream regulators showed different basal rhythmicity, which was modified in offspring exposed to obesogenic diet and maternal programming. The double obesogenic hit increased liver apoptosis measured by TUNEL staining, active caspase-3 and phospho-JNK and GRP78 promoter methylation levels. This study demonstrates that hepatic UPR is rhythmically activated. The combination of maternal obesity (MO) and obesogenic diets in offspring triggered altered UPR rhythmicity, DNA methylation and cellular apoptosis.     

Effects of Three-Month Feeding High Fat Diets with Different Fatty Acid Composition on Myocardial Proteome in Mice

Westernized diet is characterized by a high content of saturated fatty acids (SFA) and a low level of omega-3 polyunsaturated fatty acids (PUFA), often accompanied by an imbalance in the omega-6/omega-3 PUFA ratio. Since increased intake of SFA and n-6 PUFA is considered as a cardiovascular disease risk factor, this study was conducted to determine whether a three-month dietary supplementation of high-fat diets (HFDs) with saturated fatty acids and a significant proportion of various n-6 and n-3 PUFA ratios would affect the architecture and protein expression patterns of the murine heart. Therefore, three HFD (n = 6) feeding groups: rich in SFA, dominated by PUFA with the n-6/n-3–14:1, and n-6/n-3–5:1, ratios were compared to animals fed standard mouse chow. For this purpose, we performed two-dimensional electrophoresis with MALDI-ToF mass spectrometry-based identification of differentially expressed cardiac proteins, and a histological examination of cardiac morphology. The results indicated that mice fed with all HFDs developed signs of hypertrophy and cardiac fibrosis. Animals fed SFA-rich HFD manifested the most severe cardiac hypertrophy and fibrosis lesions, whereas less pronounced changes were observed in the group of animals that ingested the highest amount of omega-3 FA. In general, all HFDs, regardless of FA composition, evoked a comparable pattern of cardiac protein changes and affected the following biological processes: lipid metabolism and FA β-oxidation, glycolysis, TCA cycle, respiratory chain, myocardium contractility, oxidative stress and PUFA eicosanoid metabolism. However, it should be noted that three proteins, namely IDH3A, LDHB, and AK1, were affected differently by various FA contents. High expression of these myocardial proteins found in the group of animals fed a HFD with the highest n-3 PUFA content could be closely related to the observed development of hypertrophy.     

Suppression of altered hepatic foci development by a high fish oil diet compared with a high corn oil diet in rats

Effects of low corn oil, high corn oil, and high fish oil diets on altered hepatic foci development in female Sprague-Dawley rats were investigated. Rats assigned to Groups 1-4 were initiated with saline as the control and those assigned to Groups 5-7 were initiated with diethylnitrosamine (DEN 15 mg/kg) at 24 hours of age. After weaning, all rats, except those in Group 1, received 500 ppm phenobarbital (PB) in their diet as tumor promoter for three months. Altered hepatic foci development was significantly lower in DEN-initiated rats fed the high fish oil + PB diet than in DEN-initiated rats fed the high corn oil + PB diets. Liver weight and relative liver weight were significantly greater in rats fed the high fish oil + PB diet than in rats fed the other diets, and hepatic biotransformation/detoxification enzyme activities were greater in rats fed the fish oil + PB diets than in rats fed the other diets. These results suggest that the effect of a high fish oil diet on altered hepatic foci may occur through regulation of hepatic biotransformation/detoxification enzyme activities, leading to alteration in the tumor-promoting action of PB. Dietary lipid significantly affected the hepatic phospholipid fatty acid composition of rats. n-3 polyunsaturated fatty acids were incorporated into membrane phospholipid at the expense of n-6 polyunsaturated fatty acids. A high fish oil diet caused greater oxidative stress in rats, as measured by plasma vitamin E level, red blood cell glutathione status, liver lipid peroxidation, and hepatic glutathione reductase activity. Pearson's correlation analysis indicated that the foci number was negatively correlated to the liver thiobarbituric acid-reactive substance and 7-pentoxyresorufin O-dealkylase activity, and the foci area was negatively correlated to the liver thiobarbituric acid-reactive substance activity (p < 0.05) in rats of groups that developed foci. These results suggest that the type of dietary lipid is the more important determinant for gamma-glutamyl transpeptidase-positive foci development than the amount of dietary lipid when rats consumed approximately the same amount of calories in all the dietary groups, and the underlying mechanisms may be partially ascribed to the antioxidant/oxidation status and biotransformation/detoxification system of rats.     

Effects of different quantities of fat on serum and liver lipids, phospholipid class distribution and fatty acid composition in alcohol-treated rats

The present study investigated the quantitative effect of dietary fats and ingestion of alcohol on serum and liver lipids, fatty acid bound to phospholipids and their class distribution of male Wistar rats. The rats in C (control) and A (alcohol) groups were fed a standard laboratory diet, HFC (high fat-control) and HFA (high fat-alcohol) groups were fed a high fat diet (standard diet supplemented with 20 g%w/w, sunflower oil: lard mixture 1: 1) for 6 wk. Alcohol-treated rats consumed alcohol at the rate of 9 g/kgbw/d (15-20% energy). Liver phospholipid (PL) content was decreased, and phospholipid/cholesterol liver molar ratio increased in the alcohol treated rats. The proportion of serum sphingophospholipid (Sph) was significantly lower and proportion of phosphatidylcholin (PC) significantly higher in serum PL in alcohol-treated rats. Phospholipid class distribution was unaffected by alcohol feeding in liver. Significantly lower levels of 16:1n-7 and higher levels of 20:5n-3 and 22:4n-6 in the serum PL were observed in the alcohol-treated rats. The groups on the HF diet increased levels of 20:4n-6, 22:4n-6 and total n-6, polyunsaturated fatty acid (PUFA) and decreased levels of 18:1n-9 and total monounsaturated fatty acids (MUFA)in both liver and serum PL, but n-3 fatty acid increased in serum PL and decreased in liver PL compared to groups on the standard diet. Alcohol fat interaction was evident in MUFA and PUFA/SFA in serum PL and n-6, MUFA, PUFA and polyunsaturated/saturated fatty acid ratios (PUFA/SFA) in liver PL. This study showed that the high fat intake in alcohol-treated rats increased levels of 20:4n-6, 22:4n-6 and 20:4/18:2 ratio, and decreased level of 18:1n-9 in liver and serum phospholipids.     

Dietary n-3 fatty acids affect mRNA level of brown adipose tissue uncoupling protein 1, and white adipose tissue leptin and glucose transporter 4 in the rat

We examined the effect of dietary fats rich in n-3 polyunsaturated fatty acids (PUFA) on mRNA levels in white and brown adipose tissues in rats. Four groups of rats were fed on a low-fat diet (20 g safflower oil/kg) or a high-fat diet (200 g/kg) containing safflower oil, which is rich in n-6 PUFA (linoleic acid), or perilla (alpha-linolenic acid) or fish oil (eicosapentaenoic and docosahexaenoic acids), both of which are rich in n-3 PUFA, for 21 d. Energy intake was higher in rats fed on a high-safflower-oil diet than in those fed on low-fat or high-fish-oil diet, but no other significant differences were detected among the groups. Perirenal white adipose tissue weight was higher and epididymal white adipose tissue weight tended to be higher in rats fed on a high-safflower-oil diet than in those fed on a low-fat diet. However, high-fat diets rich in n-3 PUFA, compared to a low-fat diet, did not increase the white adipose tissue mass. High-fat diets relative to a low-fat diet increased brown adipose tissue uncoupling protein 1 mRNA level. The increases were greater with fats rich in n-3 PUFA than with n-6 PUFA. A high-safflower-oil diet, compared to a low-fat diet, doubled the leptin mRNA level in white adipose tissue. However, high-fat diets rich in n-3 PUFA failed to increase it. Compared to a low-fat diet, high-fat diets down-regulated the glucose transporter 4 mRNA level in white adipose tissue. However, the decreases were attenuated with high-fat diets rich in n-3 PUFA. It is suggested that the alterations in gene expression in adipose tissue contribute to the physiological activities of n-3 PUFA in preventing body fat accumulation and in regulating glucose metabolism in rats.     

Dietary fish oil upregulates intestinal lipid metabolism and reduces body weight gain in C57BL/6J mice

Fish oils (FO) rich in (n-3) PUFA exert hypolipidemic and antiobesity effects in association with modulated hepatic lipid metabolism. We recently demonstrated the possible involvement of intestinal lipid metabolism in the development of obesity. In this study, we examined the effect of FO ingestion on intestinal lipid metabolism in relation to obesity. When diet-induced obesity-prone C57BL/6J mice were fed an 8% FO, high-fat (30%) diet for 5 mo, body weight gain was significantly reduced compared with mice fed a 30% triacylglycerol (TG) diet without FO. In addition to modulating messenger RNA (mRNA) levels in the liver, FO ingestion for 2 wk affected the intestinal mRNA levels of lipid metabolism-related genes; those of carnitine palmitoyltransferase 1a, cytochrome P450 4A10, and malic enzyme were significantly higher in mice fed the 8% FO diet compared with mice fed the 30% TG diet. Northern blot analysis revealed that the expression levels of most lipid metabolism-related genes in the small intestine of mice fed the 8% FO diet were comparable to those in the liver. Furthermore, reflecting the difference at the mRNA level, FO ingestion affected lipid metabolism-related enzyme activity; fatty acid beta-oxidation, omega-oxidation, and malic enzyme activities in the small intestine of mice fed the 8% FO diet were 1.2-, 1.6-, and 1.7-fold those in mice fed the 30% TG diet, respectively. These findings suggest that an upregulation of intestinal lipid metabolism is associated with the antiobesity effect of FO.     

Influence of dietary n-6/n-3 polyunsaturated fatty acid balance on the development of tolerance during chronic ethanol intoxication in rats.

The present study addresses the possible interacting effects of dietary n-6/n-3 polyunsaturated fatty acid (PUFA) balance and chronic ethanol intoxication on the synaptic membrane responses to ethanol and the development of tolerance in rats. Wistar rats were fed either a standard lab chow or various semi-synthetic diets: rich in PUFA (from soya oil: SO), deficient in linolenate (from sunflower oil: SFO) or rich in long-chain (n-3) PUFA (cod liver oil: CLO). Male adult rats from the second specially fed generation were submitted to a 3-week alcoholization by daily intubation. Functional tolerance was quantified by the hypothermic response to a challenge dose of ethanol. Synaptic fluidity and sensitivity to ethanol (variations after acute ethanol addition) were assessed by fluorescence polarization (FP) of DPH, TMA-DPH or PROP-DPH. Membrane fatty acid composition was determined by GLC. The fatty acid composition of the synaptic membranes was influenced by the diet, but rearrangements among the lipids occurred, resulting in an apparent stability in brain membrane fluidity parameters. Nevertheless, clear-cut differences were noted in response to ethanol intoxication according to the diet. In the same period of time, rats fed SFO or CLO diets were unable to develop tolerance to ethanol at the membrane level as well as functionally, contrarily to the rats fed SO or standard diets. The structurally specific roles of PUFA are suggested by the negative membrane effects of the alpha-linolenate deficient diet (SFO) and the positive ones of a diet (SO) rich and well balanced in (n-3 + n-6) PUFA. Furthermore, the n-6/n-3 PUFA balance in the synaptic membrane needs to be kept within very narrow limits to allow normal development of the adaptive response to ethanol.