Studies on lipogenesis in vivo: Comparison of cholesterol and fatty acid synthesis in rats and mice

1. The importance of fatty acid synthesis as a pathway for the disposal of ingested glucose has been evaluated in rats and mice given a purified diet high in glucose and low in fat. [U-¹⁴C]Glucose was either added to the diet and fed for 24hr. or given by stomach tube as a 250mg. (mice) or 1000mg. (rats) meal. The two methods of isotope administration gave similar results. 2. Under the conditions employed fatty acid synthesis appeared to be a more important pathway for glucose disposal in mice than in rats. In mice 15·3% of ingested [U-¹⁴C]glucose was converted into fatty acid and in rats the corresponding value was 8·6%. In contrast, the conversion of [U-¹⁴C]glucose into cholesterol, as a percentage of dose, was twice as high in rats as in mice. 3. The effect of 20% of corn oil in the diet on the conversion of dietary [U-¹⁴C]glucose into fat was also investigated. Mice given diets containing 1% or 20% of corn oil converted 14·6% or 7·0% respectively of dietary [U-¹⁴C]glucose into fatty acid over a 24hr. period. There was no effect of fat on the incorporation of the isotope into cholesterol. 4. In mice given diets containing 1% or 20% of corn oil approx. 10% and 2% respectively of newly synthesized fatty acids were found in the liver. Hepatic fatty acid synthesis appears to be more sensitive to dietary fat than is extrahepatic synthesis.     

Dietary fat modifies lipid metabolism in the adipose tissue of metabolic syndrome patients

Adipose tissue (AT) is a key organ in the regulation of total body lipid homeostasis, which is responsible for the storage and release of fatty acids according to metabolic needs. We aimed to investigate the effect of the quantity and quality of dietary fat on the lipogenesis and lipolysis processes in the AT of metabolic syndrome (MetS) patients. A randomized, controlled trial conducted within the LIPGENE study assigned MetS patients to one of four diets: (a) high-saturated fatty acid (HSFA) (b) high-monounsaturated fatty acid, and (c, d) two low-fat, high-complex carbohydrate diets supplemented with long chain (LC) n-3 (LFHCC n-3) polyunsaturated fatty acids (PUFA) or placebo (LFHCC), for 12 weeks each. A fat challenge reflecting the same fatty acid composition as the original diets was conducted post-intervention. Long-term consumption of the LFHCC diet induced an increase in the fasting expression levels of the sterol regulatory element binding protein-1 and stearoyl-CoA desaturase D9-desaturase genes, whereas the supplementation of this diet with n-3 PUFA reversed this effect (p = 0.007). In contrast, long-term consumption of the HSFA diet increased the expression of the adipose triglyceride lipase (ATGL) gene, at both fasting and postprandial states (both, p < 0.001). Our results showed the anti-lipogenic effect exerted by LC n-3 PUFA when administered together with a LFHCC diet. Conversely, a diet high in saturated fat increased the expression of the lipolytic gene ATGL relative to the other diets.

Electronic supplementary material

The online version of this article (doi:10.1007/s12263-014-0409-3) contains supplementary material, which is available to authorized users.     

Effect of maternal diet on fetal hepatic lipogenesis.

The effects of: a, maternal diet; b, cyclic-3',5'-adenosinemonophosphate (cyclic AMP) and c, clofibrate on hepatic lipogenesis in fetal rats were studied. The experimental diets contained 22% protein, 40--50% carbohydrate, adequate vitamins, and minerals. In addition, the fat-containing diets were supplemented with either 15% corn oil, 25% corn oil, or 5% cholesterol + 10% oleic acid. In the clofibrate feeding studies, 0.3% (w/v) of the ethyl ester was added to a stock ration or to fat-free diet. Lipogenesis was measured in liver slices incubated with [2-14C]pyruvate, [1-14C]acetate, or 3H2O. In addition, activities of lipogenic enzymes were measured in cytosol fractions from liver homogenates. The effec-s of the experimental diets on liver composition were also examined. Lipogenic activity was higher in fetal than in maternal liver. When 15% corn oil was added to the maternal diet, fatty acid synthesis in fetal liver did not decrease as it did in maternal liver. Maternal fasting decreased fetal fatty acid synthesys by 50% when measured with 14C and less than 10% when measured with 3H2O. Although the addition of cholesterol to the maternal diet decreased cholesterol synthesis in maternal liver, no such decrease was observed in fetal liver. Changes in enzyme activities paralleled alterations in lipogenesis in maternal but not in fetal liver. Corn oil feeding or fasting increased the rate of transfer of linoleate from the dam to the fetus. However, accumulation of linoleate in fetal liver did not correlate with a decreased rate of fatty acid synthesis as it did in maternal liver. Maternal hepatic glycogen stores were depleted by fasting, but glycogen levels in fetal liver remained high under these conditions.     

Effects of dietary corn oil and salmon oil on the oxidation of fatty acids and prostaglandin E2 in rat gastric mucosa

The investigations previously carried out by Grataroli and colleagues (1) to elucidate the relationships between dietary fatty acids, lipid composition, prostaglandin E2 production and phospholipase A2 activity in the rat gastric mucosa are, here, extended. In the present investigations, fatty acid and prostaglandin E2 catabolizing enzymes were assayed in gastric mucosa from rats fed either a low fat diet (corn oil: 4.4% w/w) (referred as control group), a corn oil-enriched diet (17%) or a salmon oil-enriched diet (12.5%) supplemented with corn oil (4.5%) (referred as groups of treated animals) for eight weeks.Peroxisomal fatty acyl-CoA β-oxidation was induced in the treated animals whereas the activities of catalase and mitochondrial tyramine oxidase were increased and normal, respectively. Mitochondrial acyl-CoA dehydrogenations occured at higher rates and carnitine acyltransferase activities were enhanced. In addition, the induction of peroxisomal but not mitochondrial prostaglandoyl-E2-CoA β-oxidation could be demonstrated. Induction of peroxisomal oxidation of fatty acids and prostaglandins is suggested to contribute to the decrease of prostaglandin E2 production in the treated animals, especially those receiving the salmon oil diet, that the above mentioned authors originally reported.     

An interaction effect between glucokinase gene variation and carbohydrate intakes modulates the plasma triglyceride response to a fish oil supplementation

A large inter-individual variability in the plasma triglyceride (TG) response to fish oil consumption has been observed. The objective was to investigate the gene–diet interaction effects between single-nucleotide polymorphisms (SNPs) within glucokinase (GCK) gene and dietary carbohydrate intakes (CHO) on the plasma TG response to a fish oil supplementation. Two hundred and eight participants were recruited in the greater Quebec City area. The participants completed a 6-week fish oil supplementation (5 g fish oil/day: 1.9–2.2 g EPA and 1.1 g DHA). Thirteen SNPs within GCK gene were genotyped using TAQMAN methodology. A gene–diet interaction effect on the plasma TG response was observed with rs741038 and CHO adjusted for age, sex and BMI (p = 0.008). In order to compare the plasma TG response between genotypes according to CHO, participants were divided according to median CHO. Homozygotes of the minor C allele of rs741038 with high CHO >48.59 % had a greater decrease in their plasma TG concentrations following the intake of fish oil (p < 0.05) than C/C homozygotes with low CHO and also than the other genotypes either with high or low CHO. The plasma TG response to a fish oil supplementation may be modulated by gene–diet interaction effects involving GCK gene and CHO.

Electronic supplementary material

The online version of this article (doi:10.1007/s12263-014-0395-5) contains supplementary material, which is available to authorized users.     

Nutritional B vitamin deficiency alters the expression of key proteins associated with vascular smooth muscle cell proliferation and migration in the aorta of atherosclerotic apolipoprotein E null mice

Low B vitamin status is linked with human vascular disease. We employed a proteomic and biochemical approach to determine whether nutritional folate deficiency and/or hyperhomocysteinemia altered metabolic processes linked with atherosclerosis in ApoE null mice. Animals were fed either a control fat (C; 4 % w/w lard) or a high-fat [HF; 21 % w/w lard and cholesterol (0/15 % w/w)] diet with different B vitamin compositions for 16 weeks. Aorta tissue was prepared and global protein expression, B vitamin, homocysteine and lipoprotein status measured. Changes in the expression of aorta proteins were detected in response to multiple B vitamin deficiency combined with a high-fat diet (P < 0.05) and were strongly linked with lipoprotein concentrations measured directly in the aorta adventitia (P < 0.001). Pathway analysis revealed treatment effects in the aorta-related primarily to cytoskeletal organisation, smooth muscle cell adhesion and invasiveness (e.g., fibrinogen, moesin, transgelin, vimentin). Combined B vitamin deficiency induced striking quantitative changes in the expression of aorta proteins in atherosclerotic ApoE null mice. Deregulated expression of these proteins is associated with human atherosclerosis. Cellular pathways altered by B vitamin status included cytoskeletal organisation, cell differentiation and migration, oxidative stress and chronic inflammation. These findings provide new insight into the molecular mechanisms through which B vitamin deficiency may accelerate atherosclerosis.

Electronic supplementary material

The online version of this article (doi:10.1007/s12263-014-0446-y) contains supplementary material, which is available to authorized users.     

Effect of chronic consumption of a high-fat diet on mammary metabolism

Rats have been fed semi-synthetic diets containing 4 and 20% (w/w) corn oil for periods of 9-12 weeks covering two lactations. The mean maternal and pup weights at day-14 of the second lactation on the diets were not significantly different. The milk fatty acids of the rats on the high-fat diet contained 39 mol% linoleic acid and only 20 mol% medium-chain acids compared with over 40% for the low-fat diet. With the exception of "malic" enzyme, none of five enzymes assayed in mammary supernatants was significantly altered by the diet fed. These results suggest that the synthesis of these enzymes in the mammary gland is insensitive to dietary lipid.     

Effect of olive oil- and corn oil-enriched diets on the tissue mineral content in mice

The mineral content (zinc, iron, magnesium, and calcium) in the liver, spleen, and thymus of male Balb/C mice was analyzed. Animals were fed, over 21 d, diets enriched with corn oil (FCO diet) or olive oil (FOO diet) (5% addition to standard pellet, w/w). Olive oil with predominant oleic acid (C18:1, n-9) had a quite different composition than corn oil, in which linoleic acid (C18:2, n-6) prevails. The zinc and magnesium tissue concentrations were not changed in either group. The calcium concentration in liver as well as the calcium concentration in spleen increased in mice fed both the FCO and FOO diets. Furthermore, mice fed both the FOO and FCO diets had increased spleen iron concentration. Mice fed the FCO diet had increased thymus calcium concentration compared to controls. The results show the effect of diets with unsaturated, particularly polyunsaturated fatty acids, on the calcium and iron concentration in some organs.     

ELOVL2 gene polymorphisms are associated with increases in plasma eicosapentaenoic and docosahexaenoic acid proportions after fish oil supplement

Fish oil supplementation provides an inconsistent degree of protection from cardiovascular disease (CVD), which may be attributed to genetic variation. Single nucleotide polymorphisms (SNPs) in the elongation-of-very-long-chain-fatty-acids-2 (ELOVL2) gene have been strongly associated with plasma proportions of n-3 long-chain polyunsaturated fatty acids (LC-PUFA). We investigated the effect of genotype interaction with fish oil dosage on plasma n-3 LC-PUFA proportions in a parallel double-blind controlled trial, involving 367 subjects randomised to treatment with 0.45, 0.9 and 1.8 g/day eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (1.51:1) or olive oil placebo for 6 months. We genotyped 310 subjects for ELOVL2 gene SNPs rs3734398, rs2236212 and rs953413. At baseline, carriers of all minor alleles had lower proportions of plasma DHA than non-carriers (P = 0.021–0.030). Interaction between genotype and treatment was a significant determinant of plasma EPA (P < 0.0001) and DHA (P = 0.004–0.032). After the 1.8 g/day dose, carriers of ELOVL2 SNP minor alleles had approximately 30 % higher proportions of EPA (P = 0.002–0.004) and 9 % higher DHA (P = 0.013–0.017) than non-carriers. Minor allele carriers could therefore particularly benefit from a high intake of EPA and DHA in maintaining high levels of plasma n-3 PUFA conducive to protection from CVD.

Electronic supplementary material

The online version of this article (doi:10.1007/s12263-013-0362-6) contains supplementary material, which is available to authorized users.     

Growth and fatty acid composition of freshwater prawn, Macrobrachium rosenbergii, larvae fed diets containing various ratios of cod liver oil–corn oil mixture

A feeding trial was conducted to determine the effect of replacing costly cod liver oil with corn oil as a source of dietary lipid on the growth and fatty acid composition of the larval freshwater prawn, Macrobrachium rosenbergii de Man. Prawn larvae were weaned to artificial diets containing cod liver oil and corn oil either singly or in various combinations (2 : 1, 1 : 1, 1 : 2, w/w). Weaning to artificial diets from Artemia nauplii commenced at larval stage III with complete substitution by stage X. The reference group was reared solely on Artemia nauplii during the entire experiment. Incorporation of corn oil at 33–67% of dietary supplemental oil did not have significant effects on the post‐larval production. However, larvae fed with corn oil alone revealed a significantly lower post‐larval production compared to other experimental diets as well as to the reference group. No significant differences (P > 0.05) were observed in dry weight, protein and lipid concentration among larvae fed on various dietary treatments. Palmitic (16 : 0) and oleic/vaccenic (18 : 1) acids were the dominant saturated and monounsaturated fatty acids in larval tissues, respectively, whereas the polyunsaturated fraction was dominated by eicosapentaenoic (20 : 5n‐3) acid. The polyunsaturated fatty acid composition was dominated by n‐3 acids rather than n‐6 fatty acids. The fatty acid composition of the prawn in general reflected that of the diet. Larvae on diets containing higher concentrations of corn oil rich in linoleic (18 : 2n‐6) acid showed a higher concentration of this acid in their tissues. No evidence of de novo synthesis of linoleic (18 : 2n‐6) acid was found. Higher levels of stearic (18 : 0), arachidonic (20 : 4n‐6) and eicosapentaenoic (20 : 5n‐3) acids found in larvae as compared with those fed Artemia and artificial diets strongly indicated the larval ability in chain elongation and desaturation of palmitic (16 : 0), linoleic (18 : 2n‐6) or linolenic (18 : 3n‐3) acids, respectively. Despite a large variation of n‐3 to n‐6 ratios of the live and artificial diets, larval n‐3 to n‐6 ratios were relatively stable among different dietary treatments, possibly indicative of the importance of such a ratio in the larval fatty acid metabolism.     

Effect of Feeding Palm Oil By-Products Based Diets on Muscle Fatty Acid Composition in Goats

The present study aims to evaluate the effects of feeding palm oil by-products based diets on different muscle fatty acid profiles in goats. Thirty-two Cacang × Boer goats were randomly assigned to four dietary treatments: (1) control diet (CD), (2) 80% decanter cake diet (DCD), (3) 80% palm kernel cake diet (PKCD) and (4) CD plus 5% palm oil (PO) supplemented diet (CPOD). After 100 days of feeding, four goats from each group were slaughtered and longissimus dorsi (LD), infraspinatus (IS) and biceps femoris (BF) were sampled for analysis of fatty acids. Goats fed the PKCD had higher (P<0.05) concentration of lauric acid (C12:0) than those fed the other diets in all the muscles tested. Compared to the other diets, the concentrations of palmitic acid (C16:0) and stearic acid (C18:0) were lower (P<0.05) and that of linoleic acid (C18:2 n-6) was higher (P<0.05) in the muscles from goats fed the CD. It was concluded that palm kernel cake and decanter cake can be included in the diet of goats up to 80% with more beneficial than detrimental effects on the fatty acid profile of their meat.     

Effect of diets on growth,digestibility, carcass and meat quality characteristics of four rabbit breeds

The current study was conducted to evaluate three diets using four rabbit breeds. A total of 320 male weaned rabbits representing four breeds named V-line, Saudi-1, Saudi-2 and Saudi-3 were randomly distributed into three comparable dietary treatments. Three levels of indigenous feedstuffs (IFS) of 42.5%, 65% or 87.5% (alfalfa hay, barley and wheat bran) were substituted for the same levels of non-indigenous feedstuffs in the diet (corn grain, soybean, molasses, and limestone) to form three diets named D1, D2 and D3, respectively. These dietary treatments were used to evaluate post-weaning growth performance, feed intake, feed conversion, carcass and lean composition, and nutrients digestibility in four rabbit breeds.Partial replacement of IFS with non-indigenous feedstuffs attained significant increase in growth performance. The diet containing 87.5% IFS led to significant increase in daily weight gains by 8.4, 4.0, 8.1, 6.2 and 6.7 g at age intervals of 5–6, 7–8, 9–10, 10–11 and 11–12 weeks compared to the control diet, respectively. The diet containing 87.5% IFS showed a significant reduction in feed conversion ratio compared to control diet during the experimental periods. The diet containing 65% IFS showed significant increases in pre-slaughter weight (112 g) and hot carcass weight (89 g), while dressing percent, offal weight and percent, and non-carcass weights and percentages (head, fur, legs + tail, viscera) were not significantly different. The diet containing 87.5% IFS gave an increase of 1.1%, 6.4%, 8.8%, 17.9%, 7.4%, and 19.6% in digestibility coefficients of organic matter (OM), crude protein (CP), neutral detergent fibre (NFD), acid detergent fiber (ADF), hemi-cellulose (HC) and cellulose (C) compared to control diet, respectively.Feed intakes were moderate and ranged from 69 to 124 g for V-line, 77 to 128 g for Saudi-1, 79 to 130 g for Saudi-2, and 76 to 119 g for Saudi-3 along with moderate ratios of feed conversion ranging from 2.65 to 3.80, 2.45 to 3.90, 2.46 to 3.79 and 2.63 to 3.65, respectively. Pre-slaughter weight, hot carcass weight, and offal weight were in favour of Saudi-2 rabbits compared to the other groups. Both Saudi-1 and Saudi-2 rabbits were slightly higher than Saudi-3 in weights and percentages of head, fur, viscera and legs + tail. Lean and bone weights and percentages and meat to bone ratio in Saudi-2 carcasses were slightly higher than those recorded in the other groups, while moisture, DM, CP, EE and ash contents in the lean have shown little differences between groups. Rabbits of Saudi-1 were ranked the first in digestibility coefficients of OM, CP, NDF, ADF, HC, C and cell count compared to other groups.Rabbits of Saudi-2 fed diet containing 87.5% IFS recorded the heaviest body weights and gains since this class showed considerable deviations in body weights of 345, 341, 269, 307, 321, 345 and 347 g at 6, 7, 8, 9, 10, 11 and 12 weeks of age, respectively, in comparison with the lightest class. Both Saudi-2 and Saudi-3 rabbits fed the diet containing 87.5% IFS had favourable estimates of feed conversions ranging from 2.1 to 3.4, while rabbits of Saudi-1 fed the diet containing 87.5% IFS recorded the best digestibility coefficients.     

Multivitamin restriction increases adiposity and disrupts glucose homeostasis in mice

A strong association between obesity and low plasma concentrations of vitamins has been widely reported; however, the causality of this relationship is still not established. Our goal was to evaluate the impact of a multivitamin restriction diet (MRD) on body weight, adiposity and glucose homeostasis in mice. The mice were given a standard diet or a diet containing 50 % of the recommended vitamin intake (MRD) for 12 weeks. At the end of the experiment, total body weight was 6 % higher in MRD animals than in the control group, and the adiposity of the MRD animals more than doubled. The HOMA-IR index of the MRD animals was significantly increased. The adipose tissue of MRD animals had lower expression of mRNA encoding adiponectin and Pnpla2 (47 and 32 %, respectively) and 43 % higher leptin mRNA levels. In the liver, the mRNA levels of Pparα and Pgc1α were reduced (29 and 69 %, respectively) in MRD mice. Finally, the level of β-hydroxybutyrate, a ketonic body reflecting fatty acid oxidation, was decreased by 45 % in MRD mice. Our results suggest that MRD promotes adiposity, possibly by decreasing adipose tissue lipolysis and hepatic β-oxidation. These results could highlight a possible role of vitamin deficiency in the etiology of obesity and associated disorders.

Electronic supplementary material

The online version of this article (doi:10.1007/s12263-014-0410-x) contains supplementary material, which is available to authorized users.     

Relationship between the amino acid release kinetics of feed proteins and nitrogen balance in finishing pigs

In current nutrition requirements of swine, although the protein diets are formulated based on the ileal digestibility of protein and amino acid (AA), there is a difference in nitrogen utilisation among various protein diets, which might be related to the AA release kinetics. To evaluate the relationship between AA release kinetics of feed proteins and nitrogen balance in finishing pigs, pigs were fed diets based on casein (CAS) or corn gluten meal (CGM) at normal or low-protein concentrations, and the AA release patterns were assessed. A 2 × 2 full factorial experimental design was used. 24 pigs (Duroc × Landrace × Yorkshire) with an initial weight of 67.0 ± 1.8 kg were randomly assigned to consume a normal-protein casein-based diet (N.CAS, 10% CP), normal-protein corn gluten meal-based diet (N.CGM, 10% CP), low-protein casein-based diet (L.CAS, 8.5% CP), or low-protein corn gluten meal-based diet (L.CGM, 8.5% CP) for 14 days (n = 6 per group; pigs housed and fed separately). The low-protein diets were associated with a more rapid release of AAs in the early stages of gastric digestion than the normal-protein diets. The N.CAS and L.CAS diets were associated with a peak AA release at approximately 4 h during trypsin digestion, whereas N.CGM and L.CGM were at approximately 16 h. The N.CAS diet was associated with the least dispersed release curves and lowest synchronisation indexes, implying that it was associated with the best AA release synchronism, whereas the L.CGM diet was on the contrary. The nitrogen intake (NI), faecal nitrogen, urine nitrogen (UN), total nitrogen, net protein utilisation and apparent biological value (ABV) of protein of pigs fed the L.CAS or L.CGM diets were lower than those fed the N.CAS or N.CGM diets (P < 0.05). Notably, there was a difference in NI (P < 0.05) and trends with respect to UN and ABV (0.05 < P < 0.1), but no differences in retained nitrogen or apparent nitrogen digestibility between pigs fed the N.CAS or L.CAS diets and those fed the N.CGM or L.CGM diets. Pigs fed the N.CAS or N.CGM diets had higher serum concentrations of UN than pigs fed the L.CAS or L.CGM diets (P < 0.05), but there were no differences in serum total protein, albumin, triglyceride, glucose, alanine transaminase, or aspartate aminotransferase between the groups. In addition, there was an interaction between protein level and protein source on serum globulin (P < 0.05). Therefore, the diet with a better AA release synchronism can improve protein utilisation efficiency in finishing pigs and to reduce environmental pollution.     

Effect of papaya (Carica papaya) leaf extract as dietary growth promoter supplement in red hybrid tilapia (Oreochromis mossambicus × Oreochromis niloticus) diet

The purpose of this experiment was to examine the potential use of Carica papaya leaf extract as a supplement to promote growth and improve feed utilization in red hybrid tilapia. Five diets were formulated containing isolipidic (80 g/kg) and isonitrogenic (350 g/kg) levels. All feeds contained similar types and amounts of raw materials but differed in the inclusion of papaya leaf extract (0, 5, 10, 20 and 40 g/kg feed). The initial size of fish used was 2.3 ± 0.01 g. Each diet was performed in triplicate tanks, and the feeding period was 12 weeks. Fish fed diet containing 2% papaya leaf extract (PLE) had the highest final weight, 31.14 ± 1.47 g, followed by 1% PLE (27.27 ± 1.75 g). These two diets (1% and 2%) were also showed significant improvements of weight gain, SGR, and feed efficiency of the red hybrid tilapia (p < 0.05). However, papaya leaf extract did not affect the HSI, VSI, PER, digestive enzymes activity, blood composition, and survival rate. Supplementing the diets with papaya leaf extract lowered serum urea. Findings of this research suggest that adding papaya leaf extract to the diet of red hybrid tilapia improves growth and feed efficiency without adversely affecting blood parameters. Therefore, an inclusion level between 1% and 2% of the papaya leaf extract is recommended as a feed additive to promote red hybrid tilapia fry growth.     

DNBS/TNBS Colitis Models: Providing Insights Into Inflammatory Bowel Disease and Effects of Dietary Fat

Inflammatory Bowel Diseases (IBD), including Crohn''s Disease and Ulcerative Colitis, have long been associated with a genetic basis, and more recently host immune responses to microbial and environmental agents. Dinitrobenzene sulfonic acid (DNBS)-induced colitis allows one to study the pathogenesis of IBD associated environmental triggers such as stress and diet, the effects of potential therapies, and the mechanisms underlying intestinal inflammation and mucosal injury. In this paper, we investigated the effects of dietary n-3 and n-6 fatty acids on the colonic mucosal inflammatory response to DNBS-induced colitis in rats. All rats were fed identical diets with the exception of different types of fatty acids [safflower oil (SO), canola oil (CO), or fish oil (FO)] for three weeks prior to exposure to intrarectal DNBS. Control rats given intrarectal ethanol continued gaining weight over the 5 day study, whereas, DNBS-treated rats fed lipid diets all lost weight with FO and CO fed rats demonstrating significant weight loss by 48 hr and rats fed SO by 72 hr. Weight gain resumed after 72 hr post DNBS, and by 5 days post DNBS, the FO group had a higher body weight than SO or CO groups. Colonic sections collected 5 days post DNBS-treatment showed focal ulceration, crypt destruction, goblet cell depletion, and mucosal infiltration of both acute and chronic inflammatory cells that differed in severity among diet groups. The SO fed group showed the most severe damage followed by the CO, and FO fed groups that showed the mildest degree of tissue injury. Similarly, colonic myeloperoxidase (MPO) activity, a marker of neutrophil activity was significantly higher in SO followed by CO fed rats, with FO fed rats having significantly lower MPO activity. These results demonstrate the use of DNBS-induced colitis, as outlined in this protocol, to determine the impact of diet in the pathogenesis of IBD.     

The role of lipid components of the diet in the regulation of the fatty acid composition of the rat liver endoplasmic reticulum and lipid peroxidation

The fatty acid compositions of the lipids and the lipid peroxide concentrations and rates of lipid peroxidation were determined in suspensions of liver endoplasmic reticulum isolated from rats fed on synthetic diets in which the fatty acid composition had been varied but the remaining constituents (protein, carbohydrate, vitamins and minerals) kept constant. Stock diet and synthetic diets containing no fat, 10% corn oil, herring oil, coconut oil or lard were used. The fatty acid composition of the liver endoplasmic reticulum lipid was markedly dependent on the fatty acid composition of the dietary lipid. Feeding a herring-oil diet caused incorporation of 8.7% eicosapentaenoic acid (C_20:5) and 17% docosahexaenoic acid (C_22:6), but only 5.1% linoleic acid (C_18:2) and 6.4% arachidonic acid (C_20:4), feeding a corn-oil diet caused incorporation of 25.1% C_18:2, 17.8% C_20:4 and 2.5% C_22:6 fatty acids, and feeding a lard diet caused incorporation of 10.3% C_18:2, 13.5% C_20:4 and 4.3% C_22:6 fatty acids into the liver endoplasmic-reticulum lipids. Phenobarbitone injection (100mg/kg) decreased the incorporation of C_20:4 and C_22:6 fatty acids into the liver endoplasmic reticulum of rats fed on a lard, corn-oil or herring-oil diet. Microsomal lipid peroxide concentrations and rates of peroxidation in the presence of ascorbate depended on the nature and quantity of the polyunsaturated fatty acids in the diet. The lipid peroxide content was 1.82±0.30nmol of malonaldehyde/mg of protein and the rate of peroxidation was 0.60±0.08nmol of malonaldehyde/min per mg of protein after feeding a fat-free diet, and the values were increased to 20.80nmol of malonaldehyde/mg of protein and 3.73nmol of malonaldehyde/min per mg of protein after feeding a 10% herring-oil diet in which polyunsaturated fatty acids formed 24% of the total fatty acids. Addition of α-tocopherol to the diets (120mg/kg of diet) caused a very large decrease in the lipid peroxide concentration and rate of lipid peroxidation in the endoplasmic reticulum, but addition of the synthetic anti-oxidant 2,6-di-t-butyl-4-methylphenol to the diet (100mg/kg of diet) was ineffective. Treatment of the animals with phenobarbitone (1mg/ml of drinking water) caused a sharp fall in the rate of lipid peroxidation. It is concluded that the polyunsaturated fatty acid composition of the diet regulates the fatty acid composition of the liver endoplasmic reticulum, and this in turn is an important factor controlling the rate and extent of lipid peroxidation in vitro and possibly in vivo.     

Effects on metabolic markers are modified by PPARG2 and COX2 polymorphisms in infants randomized to fish oil

Long-chain n-3 fatty acids (n-3 LCPUFA) improve blood pressure (BP) and lipid profile in adults and improve insulin sensitivity in rodents. We have previously shown that n-3 LCPUFA reduces BP and plasma triacylglycerol (TAG) in infants. Few studies have found effects on glucose homeostasis in humans. We explored possible effect modification by FADS, PPARG2, and COX2 genotypes to support potential effects of n-3 LCPUFA on metabolic markers in infants. Danish infants (133) were randomly allocated to daily supplementation with a teaspoon (~5 mL/day) of fish oil (FO) or sunflower oil (SO) from 9 to 18 months of age. Before and after the intervention, we assessed BP, erythrocyte n-3 LCPUFA, plasma lipid profile, insulin, and glucose in addition to functional single nucleotide polymorphisms in FADS, PPARG2, and COX2. At 18 months, plasma TAG was lower in the FO compared with SO group (p = 0.014). This effect was modified by PPARG2-Pro12Ala, as TAG only decreased among heterozygotes. FO supplemented PPARG2 Pro12Ala heterozygotes also had decreased plasma glucose compared with the SO group (p = 0.043). The effect of FO on mean arterial BP at 18 months was gender dependent (p = 0.020) and reduced in boys only (p = 0.028). Diastolic BP was, however, lower among all FO supplemented homozygous COX2-T8473C variant allele carriers compared with the SO group (p = 0.001). In conclusion, our results confirm that FO supplementation in late infancy reduces TAG and BP and indicates that the effects are mediated via peroxisome proliferator-activated receptor-γ and cyclooxygenase-2. Furthermore, FO reduced plasma glucose only in PPARG2 heterozygotes.

Electronic supplementary material

The online version of this article (doi:10.1007/s12263-014-0396-4) contains supplementary material, which is available to authorized users.