Regulation of gene expression by dietary fat

Effects of hexosamines and omega-3/omega-6 fatty acids on pH regulation by interleukin 1-treated isolated bovine articular chondrocytes

Previous work has shown that interleukin 1 (IL-1) increases the activity of acid extruders in articular chondrocytes, while the H+-adenosine triphosphatase (ATPase) inhibitor bafilomycin can prevent aggrecanase-mediated cartilage degradation. The H+ transport induced by IL-1 may therefore be required for proteinase activity. In the present study, the effects of hexosamines and fish oils on H+-ATPase activity have been characterised for isolated bovine articular chondrocytes. Cells isolated in the presence of IL-1 were acidified, and the fraction of acid extrusion mediated by Na+-H+ exchange and an H+-ATPase were determined using specific inhibitors. Exposure to IL-1 significantly enhanced both components of acid extrusion. Co-incubation with glucosamine or mannosamine attenuated the H+-ATPase fraction of efflux. The addition of glucosamine at 9 h after exposure to IL-1--when H+-ATPase activation is already apparent--was also able to abolish H+-ATPase activity, implying that hexosamines do not exert effects at the level of protein synthesis. Co-incubation with the glucose transport inhibitor phloretin elicited similar effects to the hexosamines, suggesting that modulation of adenosine triphosphate levels may underlie their effects on H+-ATPase function. The omega-3 fish oil linolenic acid but not the omega-6 fish oil linoleic acid reduced H+-ATPase activity to levels seen in IL-1-untreated cells, although total efflux remained elevated, as a result of an enhanced H+ leak. These observations support a model whereby IL-1 stimulates an H+-ATPase-dependent system, possibly involved in aggrecanase activation, which appears to be one of the target mechanisms interrupted by dietary supplements reported to have symptom-modifying effects on osteoarthritis.

The opposing effects of n-3 and n-6 fatty acids

Polyunsaturated fatty acids (PUFAs) can be classified in n-3 fatty acids and n-6 fatty acids, and in westernized diet the predominant dietary PUFAs are n-6 fatty acids. Both types of fatty acids are precursors of signaling molecules with opposing effects, that modulate membrane microdomain composition, receptor signaling and gene expression. The predominant n-6 fatty acid is arachidonic acid, which is converted to prostaglandins, leukotrienes and other lipoxygenase or cyclooxygenase products. These products are important regulators of cellular functions with inflammatory, atherogenic and prothrombotic effects. Typical n-3 fatty acids are docosahexaenoic acid and eicosapentaenoic acid, which are competitive substrates for the enzymes and products of arachidonic acid metabolism. Docosahexaenoic acid- and eicosapentaenoic acid-derived eicosanoids antagonize the pro-inflammatory effects of n-6 fatty acids. n-3 and n-6 fatty acids are ligands/modulators for the nuclear receptors NFkappaB, PPAR and SREBP-1c, which control various genes of inflammatory signaling and lipid metabolism. n-3 Fatty acids down-regulate inflammatory genes and lipid synthesis, and stimulate fatty acid degradation. In addition, the n-3/n-6 PUFA content of cell and organelle membranes, as well as membrane microdomains strongly influences membrane function and numerous cellular processes such as cell death and survival.

Nutrition and Cardiovascular Disease

The major cardiovascular diseases affecting the developed world have at their core atherosclerosis and hypertension, both of which are profoundly affected by diet and can be approached, at least in part, from a nutritional point of view, as can the increasing “epidemic” of obesity. Diet is a multi-component mixture of many nutrients, which may interact with one another. The definitive study of nutrients and their impact on cardiovascular disease can be a daunting enterprise. Many dietary risk factors contribute to these diseases in various environmental and ethnic settings. These risk factors are often in evidence in youth so that preventive measures must be initiated early in life. Although most of the information about nutritional risk factors and cardiovascular disease derives from studies in the developed world, the situation is rapidly evolving toward epidemic proportions in the developing world where a major burden on the economy and health services will be imposed.

Fatty acids in component of milk enhance the expression of the cAMP-response-element-binding-protein-binding protein (CBP)/p300 gene in developing rats

Fatty acids in milk are thought to play an important role in intestinal maturation and gene expression in the rat small intestine during the suckling-weaning period. In the present study, we determined the jejunal mRNA level of the cAMP-response-element-binding-protein-binding protein (CBP)/p300, which is one of the chromatin remodelling factors and regulates histone acetylation, during the postnatal period in rats. The mRNA level of CBP/p300 was high during the suckling and middle of the weaning period (day 5 to 20) and then declined sharply to a low level at the end of the weaning period and after weaning. In situ hybridisation also showed that CBP/p300 mRNA levels in the villus as well as the basal membrane clearly decreased after weaning. Rat pups at age 17 d, weaned to a high-fat diet, showed higher levels of CBP/p300 mRNA than those weaned to a low-fat diet. Oral administration of caprylic acid, oleic acid and linoleic acid, which are major fatty acid components in milk, induced jejunal CBP/p300 gene expression. The present results suggest that fatty acids in components of milk enhance expression of the CBP/p300 genes in the small intestine.

Hepatic Lipid Metabolism in Transition Dairy Cows Fed Flaxseed

Thirty-three Holstein cows averaging 687 kg of body weight were allotted 6 wk before the expected date of parturition to 11 groups of 3 cows blocked within parity for similar calving dates to determine the effects of feeding different sources of fatty acids on blood parameters related to fatty liver and profile of fatty acids in plasma and liver. Cows were fed lipid supplements from 6 wk before the expected date of parturition until d 28 of lactation. Cows within each block were assigned to 1 of 3 isonitrogenous and isoenergetic dietary supplements: control with no added lipids (CO); unsaturated lipids supplied as whole flaxseed (FL; 3.3 and 11.0% of the dry matter in prepartum and postpartum diets, respectively); and saturated lipids supplied as Energy Booster (EB; 1.7 and 3.5% of the DM in prepartum and postpartum diets, respectively). Diets EB and FL had similar ether extract concentrations. Multiparous cows fed EB had lower dry matter intake and milk production, higher concentrations of nonesterified fatty acids and beta-hydroxybutyrate in plasma and triglycerides (TG) and total lipids in liver, and lower concentrations of plasma glucose and liver glycogen than those fed FL and CO. Production of 4% fat-corrected milk was similar among treatments. Multiparous cows fed FL had the highest liver concentrations of glycogen on wk 2 and 4 after calving and lowest concentrations of TG on wk 4 after calving. Liver C16:0 relative percentages in multiparous cows increased after calving whereas those of C18:0 decreased. Relative percentages of liver C16:0 were higher in wk 2 and 4 postpartum for multiparous cows fed EB compared with those fed CO and FL; those of C18:0 were lower in wk 4 postpartum for cows fed EB compared with those fed CO and FL. Liver C18:1 relative percentages of multiparous cows increased after calving and were higher in wk 4 for cows fed EB compared with those fed CO and FL. The inverse was observed for liver C18:2 relative percentages. In general, diets had more significant effects on plasma concentrations of nonesterified fatty acids, beta-hydroxybutyrate, and glucose and liver profiles of fatty acids, TG, total lipids, and glycogen of multiparous than primiparous cows. These data suggest that feeding a source of saturated fatty acids increased the risk of fatty liver in the transition cow compared with feeding no lipids or whole flaxseed. Feeding flaxseed compared with no lipids or a source of saturated fatty acids from 6 wk before calving could be a useful strategy to increase liver concentrations of glycogen and decrease liver concentrations of TG after calving, which may prevent the development of fatty liver in the transition dairy cow.

Bovine milk in human nutrition--a review

Milk and milk products are nutritious food items containing numerous essential nutrients, but in the western societies the consumption of milk has decreased partly due to claimed negative health effects. The content of oleic acid, conjugated linoleic acid, omega-3 fatty acids, short- and medium chain fatty acids, vitamins, minerals and bioactive compounds may promote positive health effects. Full-fat milk has been shown to increase the mean gastric emptying time compared to half-skimmed milk, thereby increasing the gastrointestinal transit time. Also the low pH in fermented milk may delay the gastric emptying. Hence, it may be suggested that ingesting full-fat milk or fermented milk might be favourable for glycaemic (and appetite?) regulation. For some persons milk proteins, fat and milk sugar may be of health concern. The interaction between carbohydrates (both natural milk sugar and added sugar) and protein in milk exposed to heat may give products, whose effects on health should be further studied, and the increasing use of sweetened milk products should be questioned. The concentration in milk of several nutrients can be manipulated through feeding regimes. There is no evidence that moderate intake of milk fat gives increased risk of diseases.

Role of fatty acid binding proteins and long chain fatty acids in modulating nuclear receptors and gene transcription

Abnormal energy regulation may significantly contribute to the pathogenesis of obesity, diabetes mellitus, cardiovascular disease, and cancer. For rapid control of energy homeostasis, allosteric and posttranslational events activate or alter activity of key metabolic enzymes. For longer impact, transcriptional regulation is more effective, especially in response to nutrients such as long chain fatty acids (LCFA). Recent advances provide insights into how poorly water-soluble lipid nutrients [LCFA; retinoic acid (RA)] and their metabolites (long chain fatty acyl Coenzyme A, LCFA-CoA) reach nuclei, bind their cognate ligand-activated receptors, and regulate transcription for signaling lipid and glucose catabolism or storage: (i) while serum and cytoplasmic LCFA levels are in the 200 mircroM-mM range, real-time imaging recently revealed that LCFA and LCFA-CoA are also located within nuclei (nM range); (ii) sensitive fluorescence binding assays show that LCFA-activated nuclear receptors [peroxisome proliferator-activated receptor-alpha (PPARalpha) and hepatocyte nuclear factor 4alpha (HNF4alpha)] exhibit high affinity (low nM KdS) for LCFA (PPARalpha) and/or LCFA-CoA (PPARalpha, HNF4alpha)-in the same range as nuclear levels of these ligands; (iii) live and fixed cell immunolabeling and imaging revealed that some cytoplasmic lipid binding proteins [liver fatty acid binding protein (L-FABP), acyl CoA binding protein (ACBP), cellular retinoic acid binding protein-2 (CRABP-2)] enter nuclei, bind nuclear receptors (PPARalpha, HNF4alpha, CRABP-2), and activate transcription of genes in fatty acid and glucose metabolism; and (iv) studies with gene ablated mice provided physiological relevance of LCFA and LCFA-CoA binding proteins in nuclear signaling. This led to the hypothesis that cytoplasmic lipid binding proteins transfer and channel lipidic ligands into nuclei for initiating nuclear receptor transcriptional activity to provide new lipid nutrient signaling pathways that affect lipid and glucose catabolism and storage.

Discriminating coding, non-coding and regulatory regions using rescaled range and detrended fluctuation analysis

In this paper we analyse the efficiency of two methods, rescaled range analysis and detrended fluctuation analysis, in distinguishing between coding DNA, regulatory DNA and non-coding non-regulatory DNA of Drosophila melanogaster. Both methods were used to estimate the degree of sequential dependence (or persistence) among nucleotides. We found that these three types of DNA can be discriminated by both methods, although rescaled range analysis performs slightly better than detrended fluctuation analysis. On average, non-coding, non-regulatory DNA has the highest degree of sequential persistence. Coding DNA could be characterised as being anti-persistent, which is in line with earlier findings of latent periodicity. Regulatory regions are shown to possess intermediate sequential dependency. Together with other available methods, rescaled range and detrended fluctuation analysis on the basis of a combined purine/pyrimidine and weak/strong classification of the nucleotides are useful tools for refined structural and functional segmentation of DNA.

Nutritional intervention to reduce the n−6/n−3 fatty acid ratio increases adiponectin concentration and fatty acid oxidation in healthy subjects

BACKGROUND/OBJECTIVES

Consumption of n-3 polyunsaturated fatty acids (PUFA) has a favourable impact on inflammation and cardiovascular disease. However, the Western diet is characterized by a low n-3 PUFA intake and an imbalance in the n-6/n-3 PUFA ratio. Study the effect 10-week of diet modification to decrease the n-6/n-3 PUFA ratio on cardiovascular risk factors and resting energy expenditure.

SUBJECTS AND METHODS

Ten-week dietary intervention in 17 healthy subjects. Dietary intake, euglycemic hyperinsulinemic clamp, indirect calorimetry, lipid profile, hormones, inflammatory markers and erythrocyte membrane fatty acid composition were recorded before and at the end of the intervention. Comparisons are between baseline and post-treatment levels.

RESULTS

Dietary records of the linoleic acid/alpha-linolenic acid ratio (baseline: 32.2 (s.d. 3.7) vs post-intervention: 2.2 (s.d. 0.1), P<0.0001) and erythrocyte membrane fatty acid composition reflected good compliance. Dietary intervention was associated with significant reductions in TNF-alpha (baseline: 2.2 (s.d. 0.3), post-intervention: 1.5 (s.d. 0.3) pg/ml, P=0.01) and low-density lipoprotein-cholesterol (baseline: 2.5 (s.d. 0.2), post-intervention: 2.3 (s.d. 0.1) mmol/l, P=0.03) and increased adiponectin (baseline: 6.5 (s.d. 0.7), post-intervention: 7.6 (s.d. 0.6) microg/ml, P=0.02). Fasting lipid oxidation was increased (baseline: 0.7 (s.d. 0.1), post-intervention: 0.9 (s.d. 0.1) mg/kg x min, P=0.01), whereas glucose oxidation decreased in both fasting (baseline: 1.6 (s.d. 0.1), post-intervention: 1.3 (s.d. 0.1) mg/kg x min, P=0.02) and hyperinsulinaemic conditions (baseline: 3.6 (s.d. 0.1), post-intervention: 3.3 (s.d. 0.1) mg/kg x min, P=0.04). Insulin sensitivity was not affected by the intervention.

CONCLUSION

A decreased n-6/n-3 PUFA ratio can be achieved with simple dietary counselling, resulting in multiple, potentially favourable effects on the metabolic and inflammatory profiles.

Fatty acid supplied as triglyceride regulates SRE-mediated gene expression as efficiently as free fatty acids

Sterol regulatory element binding proteins (SREBPs) are key transcription proteins that bind to sterol regulatory elements (SRE) of genes essential for cellular cholesterol and fatty acid homeostasis. Polyunsaturated fatty acids (PUFA) strongly inhibit SREBP processing at post-transcriptional levels. We questioned if delivering PUFA as part of a triglyceride (TG) molecule would have similar effects and efficiency as free non-esterified PUFA. CHO cells stably transfected with an SRE-promoter linked to the luciferase reporter gene were incubated for 8-24 h with linoleic acid (LA) complexed to BSA (molar ratios 0.5-4:1), VLDL-sized trilinolein emulsions (TL, 25-200 microg/ml), and chylomicron-sized soy oil emulsions in the presence and absence of apoE. Effects of LA and TL on decreasing SRE-luciferase activity were similar and dose and time dependent. Both TL and LA significantly and rapidly (<or=2-12 h) reduced SRE-mediated gene expression by up to 75%. At equal fatty acid concentrations, SRE inhibition by TL was as effective as LA. ApoE addition increased inhibition by TL. Inhibition of gene expression was highly correlated to cell TG accumulation. We conclude that TG like fatty acids are rapid and efficient modulators of SRE-mediated gene expression.

Association of the FADS2 Gene withω-6 andω-3 PUFA Concentration in the Egg Yolk of Japanese Quail

This study focused on the association of polymorphisms of the FADS2 gene with fatty acid profiles in egg yolk of eight Japanese quail lines selected for high and low omega-6:omega-3 PUFA ratio (h2 = 0.36-0.38). For the identification of polymorphisms within the FADS2 gene 1350 bp of cDNA sequence were obtained encoding 404 amino acids. Five synonymous SNPs were found by comparative sequencing of animals of the high and low lines. These SNPs were genotyped by single base extension on 160 Japanese quail. The association analysis, comprising analysis of variance and family based association test (FBAT), revealed significant effects of SNP3 and SNP4 genotypes on the egg yolk fatty acid profiles, especially the omega-6 and omega-3 PUFAs (P < 0.05). No effects of the other SNPs were found - indicating that these are not in linkage disequilibrium with the causal polymorphism. The results of this study promote FADS2 as a functional candidate gene for traits related to omega-6 and omega-3 PUFA concentration in the egg yolk.

Corn oil supplementation to steers grazing endophyte-free tall fescue. II. Effects on longissimus muscle and subcutaneous adipose fatty acid composition and stearoyl-CoA desaturase activity and expression

Eighteen steers were used to evaluate the effect of supplemental corn oil level to steers grazing endophyte-free tall fescue on fatty acid composition of LM, stearoyl CoA desaturase (SCD) activity and expression as well as cellularity in s.c. adipose. Corn oil was supplemented (g/kg of BW) at 0 (none), 0.75 (medium), and 1.5 (high). Cottonseed hulls were used as a carrier for the corn oil and were supplemented according to pasture availability (0.7 to 1% of BW). Steers were finished on a rotationally grazed, tall fescue pasture for 116 d. Fatty acid composition of LM, s.c. adipose, and diet was determined by GLC. Total linoleic acid intake increased linearly (P < 0.01) with corn oil supplementation (90.7, 265.1, and 406.7 g in none, medium, and high, respectively). Oil supplementation linearly reduced (P < 0.05) myristic, palmitic, and linolenic acid percentage in LM and s.c. adipose. Vaccenic acid (C18:1 t11; VA) percentage was 46 and 32% greater (linear, P = 0.02; quadratic, P = 0.01) for medium and high, respectively, than none, regardless of tissue. Effect of oil supplementation on CLA cis-9, trans-11 was affected by type of adipose tissue (P < 0.01). In the LM, CLA cis-9, trans-11 isomer was 25% greater for medium than for none and intermediate for high, whereas CLA cis-9, trans-11 CLA isomer was 48 and 33% greater in s.c. adipose tissue for medium and high than for none, respectively. Corn oil linearly increased (P </= 0.01) trans-10 octadecenoic acid and CLA trans-10, cis-12; however, values were low (<0.35 and <0.035% of total fatty acids, respectively). Oil supplementation did not change (P > 0.05) the percentage of total SFA, MUFA, or PUFA but linearly increased (P = 0.03) n-6:n-3 ratio from 2.4 to 2.9 in none and high, respectively. Among tissues, total SFA and MUFA were greater in s.c. adipose than LM, whereas total PUFA, n-6, and n-3 fatty acids and the n-6:n-3 ratio were lower. Trans-10 octadecenoic acid, VA, and CLA trans-10, cis-12 were greater (P < 0.01) in s.c. adipose than in LM. Oil supplementation did not alter (P > 0.05) stearoyl CoA desaturase activity or mRNA expression. Corn oil supplementation to grazing steers reduced the percentages of highly atherogenic fatty acids (myristic and palmitic acids) and increased the percentages of antiatherogenic and anticarcinogenic fatty acids (VA and cis-9, trans-11 CLA).

Veterinary aspects and perspectives of nutrigenomics: a critical review

Nutrigenomics examines nutrient-gene interactions on a genome-wide scale. Increased dietary fat or higher non-esterified fatty acids (NEFA) from starvation-induced mobilisation may enhance hepatic oxidation and decrease esterification of fatty acids by reducing the expression of the fatty acid synthase gene. The key factors are the peroxisome proliferator-activated receptors (PPARs). Dietary carbohydrates--both independently and through insulin effect--influence the transcription of the fatty acid synthase gene. Oleic acid or n-3 fatty acids downregulate the expression of leptin, fatty acid synthase and lipoprotein lipase in retroperitoneal adipose tissue. Protein-rich diets entail a shortage of mRNA necessary for expression of the fatty acid synthase gene in the adipocytes. Conjugated linoleic acids (CLAs) are activators of PPAR and also induce apoptosis in adipocytes. Altered rumen microflora produces CLAs that are efficient inhibitors of milk fat synthesis in the mammary gland ('biohydrogenation theory'). Oral zinc or cadmium application enhances transcription rate in the metallothionein gene. Supplemental CLA in pig diets was found to decrease feed intake and body fat by activating PPARgamma-responsive genes in the adipose tissue. To prevent obesity and type II diabetes, the direct modulation of gene expression by nutrients is also possible. Nutrigenomics may help in the early diagnosis of genetically determined metabolic disorders and in designing individualised diets for companion animals.

Differential cerebral cortex transcriptomes of baboon neonates consuming moderate and high docosahexaenoic acid formulas

BACKGROUND

Docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (ARA, 20:4n-6) are the major long chain polyunsaturated fatty acids (LCPUFA) of the central nervous system (CNS). These nutrients are present in most infant formulas at modest levels, intended to support visual and neural development. There are no investigations in primates of the biological consequences of dietary DHA at levels above those present in formulas but within normal breastmilk levels.

METHODS AND FINDINGS

Twelve baboons were divided into three formula groups: Control, with no DHA-ARA; "L", LCPUFA, with 0.33%DHA-0.67%ARA; "L3", LCPUFA, with 1.00%DHA-0.67%ARA. All the samples are from the precentral gyrus of cerebral cortex brain regions. At 12 weeks of age, changes in gene expression were detected in 1,108 of 54,000 probe sets (2.05%), with most showing <2-fold change. Gene ontology analysis assigns them to diverse biological functions, notably lipid metabolism and transport, G-protein and signal transduction, development, visual perception, cytoskeleton, peptidases, stress response, transcription regulation, and 400 transcripts having no defined function. PLA2G6, a phospholipase recently associated with infantile neuroaxonal dystrophy, was downregulated in both LCPUFA groups. ELOVL5, a PUFA elongase, was the only LCPUFA biosynthetic enzyme that was differentially expressed. Mitochondrial fatty acid carrier, CPT2, was among several genes associated with mitochondrial fatty acid oxidation to be downregulated by high DHA, while the mitochondrial proton carrier, UCP2, was upregulated. TIMM8A, also known as deafness/dystonia peptide 1, was among several differentially expressed neural development genes. LUM and TIMP3, associated with corneal structure and age-related macular degeneration, respectively, were among visual perception genes influenced by LCPUFA. TIA1, a silencer of COX2 gene translation, is upregulated by high DHA. Ingenuity pathway analysis identified a highly significant nervous system network, with epidermal growth factor receptor (EGFR) as the outstanding interaction partner.

CONCLUSIONS

These data indicate that LCPUFA concentrations within the normal range of human breastmilk induce global changes in gene expression across a wide array of processes, in addition to changes in visual and neural function normally associated with formula LCPUFA.

Beyond lipids, pharmacological PPARalpha activation has important effects on amino acid metabolism as studied in the rat

PPARalpha agonists have been characterized largely in terms of their effects on lipids and glucose metabolism, whereas little has been reported about effects on amino acid metabolism. We studied responses to the PPARalpha agonist WY 14,643 (30 micromol x kg(-1) x day(-1) for 4 wk) in rats fed a saturated fat diet. Plasma and urine were analyzed with proton NMR. Plasma amino acids were measured using HPLC, and hepatic gene expression was assessed with DNA arrays. The high-fat diet elevated plasma levels of insulin and triglycerides (TG), and WY 14,643 treatment ameliorated this insulin resistance and dyslipidemia, lowering plasma insulin and TG levels. In addition, treatment decreased body weight gain, without altering cumulative food intake, and increased liver mass. WY 14,643 increased plasma levels of 12 of 22 amino acids, including glucogenic and some ketogenic amino acids, whereas arginine was significantly decreased. There was no alteration in branched-chain amino acid levels. Compared with the fat-fed control animals, WY 14,643-treated animals had raised plasma urea and ammonia levels as well as raised urine levels of N-methylnicotinamide and dimethylglycine. WY 14,643 induced changes in a number of key genes involved in amino acid metabolism in addition to expected effects on hepatic genes involved in lipid catabolism and ketone body formation. In conclusion, the present results suggest that, in rodents, effects of pharmacological PPARalpha activation extend beyond control of lipid metabolism to include important effects on whole body amino acid mobilization and hepatic amino acid metabolism.

Dietary Fat and Postmenopausal Invasive Breast Cancer in the National Institutes of Health-AARP Diet and Health Study Cohort

BACKGROUND

Although ecologic association and animal studies support a direct effect of dietary fat on the development of breast cancer, results of epidemiologic studies have been inconclusive.

METHODS

We prospectively analyzed the association between fat consumption and the incidence of postmenopausal invasive breast cancer in the National Institutes of Health-AARP Diet and Health Study, a US cohort comprising 188,736 postmenopausal women who completed a 124-item food-frequency questionnaire in 1995-1996. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox proportional hazards regression models with adjustment for energy and potential confounding factors. All statistical tests were two-sided.

RESULTS

Over an average follow-up of 4.4 years, the cohort yielded 3501 cases of invasive breast cancer. The hazard ratio of breast cancer for the highest (median intake, 40.1% energy from total fat; 434 cases per 100,000 person-years) versus the lowest (median intake, 20.3% energy from total fat; 392 cases per 100,000 person-years) quintile of total fat intake was 1.11 (95% CI = 1.00 to 1.24; P(trend) = .017). The corresponding hazard ratio for a twofold increase in percent energy from total fat on the continuous scale was 1.15 (95% CI = 1.05 to 1.26). Positive associations were also found for subtypes of fat (hazard ratio for a twofold increase in percent energy from saturated fat = 1.13; 95% CI = 1.05 to 1.22; from monounsaturated fat, HR = 1.12; 95% CI = 1.03 to 1.21; from polyunsaturated fat, HR = 1.10, 95% CI = 1.01 to 1.20). Correction for measurement error in nutrient intakes, on the basis of a calibration substudy that used two 24-hour dietary recalls, strengthened the associations, yielding an estimated hazard ratio for total fat of 1.32 (95% CI = 1.11 to 1.58). Secondary analyses showed that associations between total, saturated, and monounsaturated fat intakes were confined to women who were not using menopausal hormone therapy at baseline.

CONCLUSION

In this large prospective cohort with a wide range of fat intake, dietary fat intake was directly associated with the risk of postmenopausal invasive breast cancer.

Circulating triacylglycerol and apoE levels in response to EPA and docosahexaenoic acid supplementation in adult human subjects

High doses ofn–3 PUFA found in fish oils can reduce the circulating concentration of triacylglycerol (TG), which may contribute to the positive impact of these fatty acids on the risk of CVD. The present study aimed to establish the differential impact of EPA and docosahexaenoic (DHA) on plasma lipids and apo in adults. Forty-two normolipidaemic adult subjects completed a double-blind placebo controlled parallel study, receiving an EPA-rich oil (4·8 g EPA/d), DHA-rich oil (4·9 g DHA/d) or olive oil as control, for a period of 4 weeks. No effects of treatment on total cholesterol, LDL-cholesterol or HDL-cholesterol were evident. There was a significant 22 % reduction in TG level relative to the control value following the DHA treatment (P=0·032), with the 15 % decrease in the EPA group failing to reach significance (P=0·258). There were no significant inter-group differences in response to treatment for plasma apoA1, -C3 or -E levels, although a significant 15 % within-group increase in apoE was evident in the EPA (P=0·006) and DHA (P=0·003) groups. In addition, a within-group decrease in the apoA1:HDL-cholesterol ratio was observed in the DHA group, suggesting a positive impact of DHA on HDL particle size. The DHA intervention resulted in a significant increase in the proportion of EPAP=0·000 and DHAP=0·000 in plasma phospholipids, whilst significant increases in EPAP=0·000 and docosapentaenoic acidP=0·002, but not DHAP=0·193, were evident following EPA supplementation (P>0·05). Our present results indicate that DHA may be more efficacious than EPA in improving the plasma lipid profile.

The effects of dietary lipids on adrenergically-stimulated lipolysis in perinodal adipose tissue following prolonged activation of a single lymph node

The effects of feeding beef suet (mostly saturated and monoenoic fatty acids), sunflower oil (rich inn-6 fatty acids) and fish oil (rich inn-3 fatty acids) on the response of mesenteric, omental, popliteal and perirenal adipocytes to experimentally-induced local inflammation were studied in adult guinea pigs. After 6 weeks on the experimental diets, the animals were fed standard chow, and lipopolysaccharide was injected unilaterally daily for 4 d to induce swelling of one popliteal lymph node. Basal lipolysis in the perinodal adipocytes of all depots studied was higher in the sunflower oil-fed animals than in the controls fed on standard chow, and lower in those fed on suet or fish oil. Dietary lipids altered rates of lipolysis during incubation with 10-5M noradrenaline in all samples studied from the locally-activated popliteal depot, but only in adipocytes within 5 mm of a large lymph node in the other depots. The fish-oil diet attenuated the spread of increased lipolysis within the locally-activated popliteal adipose tissue, and from this depot to other node-containing depots. These experiments show thatn-6 polyunsaturated fatty acids promote andn-3 fatty acids suppress the spread of immune activation to adipocytes within and between depots, and alter the sensitivity of perinodal adipocytes to noradrenaline. Dietary effects are reduced or absent in adipocytes in sites remote from lymph nodes, and thus such samples do not adequately represent processes in perinodal adipose tissue. These results are consistent with the hypothesis that perinodal adipocytes interact with adjacent lymphoid cells during immune responses.

Several transcription factors are recruited to the glucose-6-phosphatase gene promoter in response to palmitate in rat hepatocytes and H4IIE cells

Fatty acids and glucose are strong modulators of the expression of glucose-6-phosphatase (Glc-6-Pase), an enzyme that plays a key role in glucose homeostasis. PUFA inhibit, whereas SFA and monounsaturated fatty acids induce the expression of the Glc-6-Pase gene. Palmitate and oleate are the most abundant fatty acid species in circulation during food deprivation in mammals. Although dietary fats have been shown to modulate the expression of genes involved in both lipid and carbohydrate metabolism in liver, little is known regarding the molecular mechanism of transcriptional response of the Glc-6-Pase gene to long-chain fatty acids. Using H4IIE hepatoma cells and hepatocytes from adult rats, we investigated the mechanism of the induction of this gene by palmitate and oleate. Both of these fatty acids stimulated Glc-6-Pase gene transcription but did not affect the stability of its mRNA. In transient transfection assays, transcription from the Glc-6-Pase gene promoter was markedly enhanced by both palmitate and oleate but not by arachidonate. Chromatin immunoprecipitation analysis was used to show that palmitate induced the recruitment of an array of transcription factors viz hepatic nuclear factor(NF)-4alpha, CAAT/enhancer binding proteinbeta, PPARalpha, chicken ovalbumin upstream promoter transcription factor (COUP-TF), cAMP regulatory element binding protein, and NF-kappaB to this gene promoter. Although it is presently unclear how these various transcription factors interact at this promoter, the data are consistent with the view that multiple regulatory elements in the Glc-6-Pase gene promoter are responsible for the modulation of gene transcription by fatty acids.

Nutritional strategies to influence adaptations to training

This article highlights new nutritional concerns or practices that may influence the adaptation to training. The discussion is based on the assumption that the adaptation to repeated bouts of training occurs during recovery periods and that if one can train harder, the adaptation will be greater. The goal is to maximize with nutrition the recovery/adaptation that occurs in all rest periods, such that recovery before the next training session is complete. Four issues have been identified where recent scientific information will force sports nutritionists to embrace new issues and reassess old issues and, ultimately, alter the nutritional recommendations they give to athletes. These are: (1) caffeine ingestion; (2) creatine ingestion; (3) the use of intramuscular triacylglycerol (IMTG) as a fuel during exercise and the nutritional effects on IMTG repletion following exercise; and (4) the role nutrition may play in regulating the expression of genes during and after exercise training sessions. Recent findings suggest that low doses of caffeine exert significant ergogenic effects by directly affecting the central nervous system during exercise. Caffeine can cross the blood-brain barrier and antagonize the effects of adenosine, resulting in higher concentrations of stimulatory neurotransmitters. These new data strengthen the case for using low doses of caffeine during training. On the other hand, the data on the role that supplemental creatine ingestion plays in augmenting the increase in skeletal muscle mass and strength during resistance training remain equivocal. Some studies are able to demonstrate increases in muscle fibre size with creatine ingestion and some are not. The final two nutritional topics are new and have not progressed to the point that we can specifically identify strategies to enhance the adaptation to training. However, it is likely that nutritional strategies will be needed to replenish the IMTG that is used during endurance exercise. It is not presently clear whether the IMTG store is chronically reduced when engaging in daily sessions of endurance training or if this impacts negatively on the ability to train. It is also likely that the increased interest in gene and protein expression measurements will lead to nutritional strategies to optimize the adaptations that occur in skeletal muscle during and after exercise training sessions. Research in these areas in the coming years will lead to strategies designed to improve the adaptive response to training.

Relationship between n-3 PUFA content and energy metabolism in the flight muscles of a migrating shorebird: evidence for natural doping

During their fall migration from the Arctic to South America, semipalmated sandpipers Calidris pusilla stop in the Bay of Fundy (east coast of Canada) before flying non-stop for ∼4500 km across the ocean. Refueling birds double their body mass by feeding on Corophium volutator, an amphipod containing high amounts of n-3 polyunsaturated fatty acids (n-3 PUFA), particularly eicosapentaenoic (20:5) and docosahexaenoic acid (22:6). In mammals, high dietary intake of n-3 PUFA is known to increase capacity for oxidative metabolism. Therefore, we hypothesized that tissue incorporation of n-3 PUFA would be associated with increases in the activity of key muscle enzymes to upregulate energy metabolism for prolonged exercise.

Birds were collected at various stages of fat loading to monitor changes in lipid composition and flight muscle enzymes simultaneously. Enzymes were measured to assess oxidative capacity [citrate synthase (CS)],β-oxidation [carnitine palmitoyl transferase (CPT) and 3-hydroxyacyl dehydrogenase (HOAD)] and glycolytic capacity [lactate dehydrogenase (LDH)]. Changes in the fatty acid composition of muscle membranes (phospholipids) and fuel reserves (neutral lipids) were measured separately to distinguish between membrane-related and systemic effects of n-3 PUFA. Results show that muscle CS and HOAD are stimulated during refueling and that their activities are correlated with n-3 PUFA content in phospholipids (22:6 for CS, 20:5 for HOAD)and in neutral lipids (20:5 for CS). This suggests that 20:5 and 22:6 have different effects on energy metabolism and that they act via changes in membrane structure and systemic mechanisms. CPT and LDH did not change during refueling, but LDH activity was significantly related to the n-3 PUFA content of fuel reserves. This study shows that oxidative capacity increases rapidly during refueling and supports the idea that dietary n-3 PUFA are used as molecular signals to prime flight muscles of some long-distance migrants for extreme exercise.

Genistein affects adipose tissue deposition in a dose-dependent and gender-specific manner

The soy isoflavone genistein targets adipose tissue and elicits physiological effects that may vary based on dietary intake. We hypothesized that the adipose effects of genistein are dose and gender dependent. Four-week-old C57BL/6 male and female mice received daily oral doses of genistein (50-200,000 microg/kg.d) or 17beta-estradiol (E2) (5 microg/kg.d) for 15 d or a diet containing 800 ppm genistein. Genistein increased epididymal and renal fat pad and adipocyte size at doses up to 50,000 microg/kg.d or at 800 ppm in the diet in males but not in females. The alteration in adipocity correlated with changes in peripheral insulin resistance. These treatments increased genistein serum concentrations from 35+/-6 to 103+/-26 nM 12 h after treatment and lowered plasma triglycerides and cholesterol levels. The 200,000 microg/kg.d genistein dose decreased adipose tissue weight similarly to E2. This genistein dose down-regulated estrogen receptor (beta more than alpha) and progesterone receptor expression and induced estrogen-dependent adipose differentiation factors; it did not change expression of the minimal consensus estrogen-responsive element in ERE-tK-LUC mice, which was positively modulated in other tissues (e.g. the lung). E2 down-regulated almost all examined adipogenic factors. Gene microarray analysis identified factors in fat metabolism and obesity-related phenotypes differentially regulated by low and high doses of genistein, uncovering its adipogenic and antiadipogenic actions. The lower dose induced the phospholipase A2 group 7 and the phospholipid transfer protein genes; the 200,000 microg/kg.d dose inhibited them. The antiadipogenic action of genistein and down-regulation of adipogenic genes required the expression of ERbeta. In conclusion, nutritional doses of genistein are adipogenic in a gender-specific manner, whereas pharmacological doses inhibited adipose deposition.

DHEA enhances effects of weight training on muscle mass and strength in elderly women and men

The plasma levels of dehydroepiandrosterone (DHEA) and its sulfated form (DHEAS) decline approximately 80% between the ages of 25 and 75 yr. Muscle mass and strength also decrease with aging. Published data on the effects of DHEA replacement on muscle mass and strength are conflicting. The goals of this study were to determine whether DHEA replacement increases muscle mass and strength and/or enhances the effects of heavy resistance exercise in elderly women and men. We conducted a randomized, double-blind, placebo-controlled study of the effects of 10 mo of DHEA replacement therapy with the addition of weightlifting exercise training during the last 4 mo of the study (DHEA + exercise group, n = 29; placebo + exercise group, n = 27). DHEA alone for 6 mo did not significantly increase strength or thigh muscle volume. However, DHEA therapy potentiated the effect of 4 mo of weightlifting training on muscle strength, evaluated by means of one-repetition maximum measurement and Cybex dynamometry, and on thigh muscle volume, measured by magnetic resonance imaging. Serum insulin-like growth factor concentration increased in response to DHEA replacement. This study provides evidence that DHEA replacement has the beneficial effect of enhancing the increases in muscle mass and strength induced by heavy resistance exercise in elderly individuals.

Promoting training adaptations through nutritional interventions

Training and nutrition are highly interrelated in that optimal adaptation to the demands of repeated training sessions typically requires a diet that can sustain muscle energy reserves. As nutrient stores (i.e. muscle and liver glycogen) play a predominant role in the performance of prolonged, intense, intermittent exercise typical of the patterns of soccer match-play, and in the replenishment of energy reserves for subsequent training sessions, the extent to which acutely altering substrate availability might modify the training impulse has been a key research area among exercise physiologists and sport nutritionists for several decades. Although the major perturbations to cellular homeostasis and muscle substrate stores occur during exercise, the activation of several major signalling pathways important for chronic training adaptations take place during the first few hours of recovery, returning to baseline values within 24 h after exercise. This has led to the paradigm that many chronic training adaptations are generated by the cumulative effects of the transient events that occur during recovery from each (acute) exercise bout. Evidence is accumulating that nutrient supplementation can serve as a potent modulator of many of the acute responses to both endurance and resistance training. In this article, we review the molecular and cellular events that occur in skeletal muscle during exercise and subsequent recovery, and the potential for nutrient supplementation (e.g. carbohydrate, fat, protein) to affect many of the adaptive responses to training.

Improvements in glucose tolerance and insulin sensitivity after lifestyle intervention are related to changes in serum fatty acid profile and desaturase activities: the SLIM study

AIMS/HYPOTHESIS

The aim of this study was to investigate whether lifestyle intervention-induced changes in serum fatty acid profile of cholesteryl esters and estimated desaturase activities are related to improvements in insulin sensitivity in subjects at risk of type 2 diabetes.

MATERIALS AND METHODS

In the Study on Lifestyle Intervention and Impaired Glucose Tolerance Maastricht (SLIM), 97 men and women with IGT were randomised to a combined diet and exercise programme (47 intervention) or a control group (50 control subjects). At baseline and after 1 year the following assessments were made: an OGTT, an exercise test to determine maximal aerobic capacity, anthropometry, and analysis of the serum fatty acid profile of cholesteryl esters.

RESULTS

The lifestyle programme was effective in reducing the intake of total and saturated fat, increasing physical activity, reducing obesity and improving insulin sensitivity and glucose tolerance. Regression analysis of the total population showed that an increase in the C20:4 n-6/C20:3 n-6 ratio (estimated Delta5-desaturase activity) and reductions in the C18:3 n-6/C18:2 n-6 ratio (estimated Delta6-desaturase activity) and the C16:1 n-7/C16:0 ratio (estimated Delta9-desaturase activity or stearoyl-CoA desaturase-1) were significantly associated with a decrease in homeostasis model assessment for insulin resistance. After adjustment for lifestyle changes (change in percentage body fat, aerobic capacity and saturated fat intake), these associations were partly reduced, but remained statistically significant.

CONCLUSIONS/INTERPRETATION

Lifestyle-induced changes in fatty acid profile of cholesteryl esters and desaturase activities were independently related to changes in insulin sensitivity in subjects at risk of type 2 diabetes.

Protein-mediated fatty acid uptake: novel insights from in vivo models

Long-chain fatty acids are both important metabolites as well as signaling molecules. Fatty acid transport proteins are key mediators of cellular fatty acid uptake and recent transgenic and knockout animal models have provided new insights into their contribution to energy homeostasis and to pathological processes, including obesity and insulin desensitization.

Fibrates upregulate TRB3 in lymphocytes independent of PPAR alpha by augmenting CCAAT/enhancer-binding protein beta (C/EBP beta) expression

Fibrates, which function by binding and activating peroxisome proliferator-activated receptor alpha (PPARalpha), have been used successfully to treat hyperlipidemia and atherosclerosis. Increasing evidence suggests that in addition to their lipid lowering activities these medications also function as immunosuppressive agents. Tribbles is a Drosophila protein that slows cell cycle progression, and its mammalian homolog, TRB3 interferes with insulin-induced activation of AKT. In these studies we demonstrate that fibrates upregulate TRB3 expression in mitogen-activated lymphocytes. Interestingly, in lymphocytes fibrates augment TRB3 expression in both PPARalpha wildtype and knockout mice, suggesting that upregulation of this protein occurs in a PPARalpha-independent manner. Fibrates activate a proximal TRB3 promoter construct and mutation or partial deletion of a potential PPAR response element does not alter the ability of fibrates to drive TRB3 expression. Subsequent studies reveal that fibrates upregulate C/EBPbeta and CHOP in lymphocytes and mutation of potential C/EBPbeta and CHOP consensus sequences abrogates the ability of fibrates to upregulate TRB3 promoter activity. Accordingly, fibrates enhance the recruitment of C/EBPbeta and CHOP to the proximal TRB3 promoter. Finally, TRB3 expression in lymphocytes induces G2 cell cycle delay and cellular depletion. These studies outline a novel PPARalpha-independent mechanism of action of fibrates and document for the first time the expression of TRB3 in activated lymphocytes.

Selectivity of fatty acid ligands for PPARalpha which correlates both with binding to cis-element and DNA binding-independent transactivity in Caco-2 cells

It is thought that peroxisome proliferator-activated receptor alpha (PPARalpha) is a major regulator for fatty acid metabolism. Long-chain fatty acids have been shown to induce expression of the genes related to fatty acid metabolism through PPARalpha. However, it is unclear whether the intensity of PPARalpha activation is different among various fatty acids. In this study, we compared various fatty acids in the capability of PPARalpha activation by differential protease sensitivity assay (DPSA), electrophoretic mobility shift assay and GAL4-PPAR chimera reporter assay in intestinal cell line, Caco-2. DPSA revealed that polyunsaturated fatty acids of 18 to 20 carbon groups with 3-5 double bonds strongly induced a PPARalpha conformational change. The ligand-induced changes in the sensitivity to protease corresponded to the enhancement of the binding of PPARalpha-RXRalpha heterodimer to the PPAR-response element (PPRE). The GAL4-PPAR chimera reporter assay revealed that the DNA binding-independent transactivity of PPARalpha was induced by various fatty acids with a wide spectrum of intensity which correlated with the conformational change of PPARalpha. These results suggest that PPARalpha has greater selectivity to certain types of polyunsaturated fatty acids, and that the ligand-induced conformational change of PPARalpha leads to parallel increases in both DNA binding to the PPAR-response element and the DNA binding-independent transactivity.

Mechanisms for the hypotriglyceridemic effect of marine omega-3 fatty acids

A mechanism to explain the hypotriglyceridemic effects of marine omega-3 fatty acids in humans has not been clarified. A working model can be developed at the gene transcriptional level, which involves >or=4 metabolic nuclear receptors. These include liver X receptor, hepatocyte nuclear factor-4alpha (HNF-4alpha), farnesol X receptor, and peroxisome proliferator-activated receptors (PPARs). Each of these receptors is regulated by sterol receptor element binding protein-1c (SREBP-1c), the main genetic switch controlling lipogenesis. Omega-3 fatty acids elicit hypotriglyceridemic effects by coordinately suppressing hepatic lipogenesis through reducing levels of SREBP-1c, upregulating fatty oxidation in the liver and skeletal muscle through PPAR activation, and enhancing flux of glucose to glycogen through downregulation of HNF-4alpha. The net result is the repartitioning of metabolic fuel from triglyceride storage toward oxidation, thereby reducing the substrate available for very-low-density lipoprotein (VLDL) synthesis. By simultaneously downregulating genes encoding proteins that stimulate lipid synthesis and upregulating genes encoding proteins that stimulate fatty acid oxidation, omega-3 fatty acids are more potent hypotriglyceridemic agents than are omega-6 fatty acids, on a carbon-for-carbon basis. Additionally, peroxidation of omega-3 fatty acids may reduce VLDL secretion through stimulating apolipoprotein B degradation. Omega-3 fatty acids may act by enhancing postprandial chylomicron clearance through reduced VLDL secretion and by directly stimulating lipoprotein lipase activity. These combined effects support the use of omega-3 fatty acids as a valuable clinical tool for the treatment of hypertriglyceridemia.

Intestinal mucosal adaptation

Intestinal failure is a condition characterized by malnutrition and/or dehydration as a result of the inadequate digestion and absorption of nutrients. The most common cause of intestinal failure is short bowel syndrome, which occurs when the functional gut mass is reduced below the level necessary for adequate nutrient and water absorption. This condition may be congenital, or may be acquired as a result of a massive resection of the small bowel. Following resection, the intestine is capable of adaptation in response to enteral nutrients as well as other trophic stimuli. Identifying factors that may enhance the process of intestinal adaptation is an exciting area of research with important potential clinical applications.

A newly discovered member of the fatty acid desaturase gene family: a non-coding, antisense RNA gene to delta5-desaturase

The rate limiting steps in the conversion of 18-carbon unsaturated fatty acids to 20- and 22-carbon products are catalyzed by two desaturase enzymes (Delta5-desaturase and Delta6-desaturase) found within a lipid desaturase gene cluster. Careful examination of this cluster revealed the existence of a conventionally spliced (human) and an intronless (mouse and rat) non-coding RNA gene, reverse Delta5-desaturase, which is transcribed from the opposite strand of the Delta5-desaturase gene. The 654 bp human reverse Delta5-desaturase transcript contains 269 nucleotides that are complementary to exon 1 and intron 1 of the Delta5-desaturase transcript, and the 3'-end of this sequence contains a 143 nucleotide stretch that is 100% complementary to the 5'-end of the Delta5-desaturase. The rat and mouse transcripts are 1355 and 690 bp long and complementary to a portion of the first intron and the entire first exon of their respective Delta5-desaturases. All reverse Delta5-desaturase transcripts contain several stop codons in all frames suggesting that they do not encode a peptide. Reverse Delta5-desaturase RNA was detected in all rat tissues where Delta5-desaturase is expressed, and the transition between fasting and refeeding produced a significant increase in reverse Delta5-desaturase RNA relative to Delta5-desaturase mRNA. Transient expression of reverse Delta5-desaturase in CHO cells stably transformed with Delta5-desaturase produced a modest decrease in Delta5-desaturase mRNA (30%), but lowered Delta5-desaturase enzymatic activity by >70%. More importantly, a diet enriched in fish oil produced a reciprocal increase in reverse Delta5-desaturase mRNA and decrease in Delta5-desaturase mRNA that was accompanied by a 5-6-fold decrease in Delta5-desaturase enzyme activity. These findings support a significant role for reverse Delta5-desaturase as a natural antisense regulator of Delta5-desaturase.

Performance-enhancing role of dietary fatty acids in a long-distance migrant shorebird: the semipalmated sandpiper

At the end of summer, semipalmated sandpipers (Calidris pusilla)traveling from the Arctic stop in the Bay of Fundy (east coast of Canada) to build large fat reserves before a non-stop flight to South America. During a 2-week stopover, the body mass of this small shorebird is doubled (∼20 g to 40 g) by feeding on a burrowing amphipod, Corophium volutator,that contains unusually high levels of n-3 polyunsaturated fatty acids (PUFA). In mammals, high n-3 PUFA content of membrane phospholipids (PL) is linked to improved exercise performance due to increased membrane fluidity that accelerates transmembrane lipid transport. We hypothesized that dietary n-3 PUFA could be used as a natural `performance-enhancing substance' by semipalmated sandpipers to prepare their flight muscles for migration. Also,PUFA stored as fuel in neutral lipids (NL) can be mobilized more quickly than saturated fatty acids, but they contain less energy per unit mass. It is therefore unclear whether dietary fatty acids are modified before storage. Birds were collected at various stages of fat loading to examine changes in the composition of tissue PL (membranes) and NL (fuel stores). Results show that dietary n-3 PUFA are incorporated in tissue lipids in less than 2 weeks. During the stopover, the double bond index of muscle PL increases by 25% and the fatty acid profiles of both muscle PL and adipose NL converge with that of the diet. However, &gt;50% of dietary n-3 PUFA are converted to other fatty acids before storage, mainly to oleate (18:1), possibly because monounsaturates offer a compromise between high energy density and ease of mobilization. This study shows that long-distance migrant birds can (1) use natural diets rich in specific lipids to prime flight muscles for endurance exercise, and (2) modify dietary fatty acids before storing them as fuel.

Regulation of hepatic fatty acid elongase and desaturase expression in diabetes and obesity

Fatty acid elongases and desaturases play an important role in hepatic and whole body lipid composition. We examined the role that key transcription factors played in the control of hepatic elongase and desaturase expression. Studies with peroxisome proliferator-activated receptor alpha (PPARalpha)-deficient mice establish that PPARalpha was required for WY14643-mediated induction of fatty acid elongase-5 (Elovl-5), Elovl-6, and all three desaturases [Delta(5) desaturase (Delta(5)D), Delta(6)D, and Delta(9)D]. Increased nuclear sterol-regulatory element binding protein-1 (SREBP-1) correlated with enhanced expression of Elovl-6, Delta(5)D, Delta(6)D, and Delta(9)D. Only Delta(9)D was also regulated independently by liver X receptor (LXR) agonist. Glucose induction of l-type pyruvate kinase, Delta(9)D, and Elovl-6 expression required the carbohydrate-regulatory element binding protein/MAX-like factor X (ChREBP/MLX) heterodimer. Suppression of Elovl-6 and Delta(9)D expression in livers of streptozotocin-induced diabetic rats and high fat-fed glucose-intolerant mice correlated with low levels of nuclear SREBP-1. In leptin-deficient obese mice (Lep(ob/ob)), increased SREBP-1 and MLX nuclear content correlated with the induction of Elovl-5, Elovl-6, and Delta(9)D expression and the massive accumulation of monounsaturated fatty acids (18:1,n-7 and 18:1,n-9) in neutral lipids. Diabetes- and obesity-induced changes in hepatic lipid composition correlated with changes in elongase and desaturase expression. In conclusion, these studies establish a role for PPARalpha, LXR, SREBP-1, ChREBP, and MLX in the control of hepatic fatty acid elongase and desaturase expression and lipid composition.

Regulation of prostate 5alpha-reductase-2 gene expression and prostate weight by dietary fat and caloric intake in the rat

BACKGROUND

High-fat diet is a major risk factor for prostate cancer. 5alpha-reductases are potential targets of dietary fat.

METHODS

Male ACI/Seg rats given either a low-fat or a high-fat diet at weaning or adulthood were sacrificed at 2, 4, and 10 weeks after dietary treatment. Prostate 5alpha-reductase mRNAs, plasma androgens, food consumption, prostate, and body weight were determined.

RESULTS

Prostate 5alpha-reductase-2 mRNA and plasma dihydrotestosterone levels were elevated at 2 weeks, and prostate weight was increased at 10 weeks in neonatal rats fed the high-fat diet. Animals fed the high-fat diet consumed more calories in the first 4 weeks. 5alpha-reductase-1 mRNA, plasma testosterone, and body weight were not different between the two dietary groups. These dietary effects were not observed in adult rats fed the same diets.

CONCLUSION

A high-dietary fat and caloric intake upregulates prostate 5alpha-reductase-2 gene expression, and stimulates prostate growth in neonatal, but not adult rats.

Microarray analysis of differential gene expression in the liver of lean and fat chickens

Excessive adiposity has become a major drawback in meat-type chicken production. However, few studies were conducted to analyze the liver expression of genes involved in pathways and mechanisms leading to adiposity. A previous study performed by differential display on RNAs extracted from chicken livers from lean and fat lines allowed us to isolate cDNA products of genes with putative differential expression. In this study, a cDNA microarray resource was developed from these products together with cDNAs from genes involved in or related to lipid metabolism. This resource was used to analyze gene expression in the liver from lean and fat chickens. Some genes were found with a difference in expression between lean and fat animals and/or correlated to adipose tissue weight. Cytochrome P450 2C45, thought to play a role in biotransformation of steroids and poly-unsaturated fatty acids, was more expressed in lean chickens whereas fatty acid synthase, stearoyl-CoA desaturase, sterol response element binding factor 1 and hepatocyte nuclear factor 4, respectively involved in lipogenesis and its regulation, were more expressed in fat chickens. These results indicate that mechanisms involved in the expression and regulation of lipogenic genes could play a key role in fatness ontogenesis in chickens from lean and fat lines.

Rediscovery of natural products using genomic tools

A screening methodology called 'genomic screening' was established to identify natural products that can regulate cellular gene expression. Application of genomic screening to Keishi-bukuryo-gan (KBG), a Japanese herbal medicine formulation, identified a previously unnoticed transcriptional effect by linoleic acid, a known KBG component. The approach opens up a possibility to develop cell-permeable molecular tools for functional genomics research and sets a stage to evaluate the potential of natural products for transcription therapies.

The fate and intermediary metabolism of stearic acid

Coming from the Greek for "hard fat," stearic acid represents one of the most abundant FA in the Western diet. Otherwise known as n-octadecanoic acid (18:0), stearate is either obtained in the diet or synthesized by the elongation of palmitate, the principal product of the FA synthase system in animal cells. Stearic acid has been shown to be a very poor substrate for TG synthesis, even as compared with other saturated fats such as myristate and palmitate, and in human studies stearic acid has been shown to generate a lower lipemic response than medium-chain saturated FA. Although it has been proposed that this may be due to less efficient absorption of stearic acid in the gut, such findings have not been consistent. Along with palmitate, stearate is the major substrate for the enzyme stearoyl-CoA desaturase, which catalyzes the conversion of stearate to oleate, the preferred substrate for the synthesis of TG and other complex lipids. In mice, targeted disruption of the stearoyl-CoA desaturase-1 (SCD1) gene results in the generation of a lean mouse that is resistant to diet-induced obesity and insulin resistance. SCD1 also has been shown to be a key target of the anorexigenic hormone leptin, thus underscoring the importance of this enzyme, and consequently the cellular stearate-to-oleate ratio, in lipid metabolism and potentially in the treatment of obesity and related disorders.

Effect of fish oil enriched enteral diet on inflammatory bowel disease tissues in organ culture: differential effects on ulcerative colitis and Crohn's disease

AIM

To investigate the influence of fish oil enriched enteral diet on intestinal tissues taken from Crohn's disease (CD), ulcerative colitis (UC) and non-inflamed non-IBD control patients in vitro.

METHODS

Colonoscopic biopsies from patients with active CD (n = 4), active UC (n = 7), and non-inflamed non-IBD control patients (n = 4) were incubated (three dilutions of 1:20, 1:10, and 1:5) with Waymouth's culture medium and enteral elemental diet (EO28, SHS, Liverpool, UK) modified in the fatty acid composition with fish oil (EF) in an organ culture system for 24 h. In each experimental set-up, incubation with Waymouth's medium alone as control was included. Tissue viability was assessed by adding bromodeoxyuridine (BrdU) to the culture fluid and immunohistochemically staining for BrdU uptake. Cytokine ratio of IL-1ra/IL-1beta (low ratio indicative of inflammation) and production of those cytokines as a percentage of medium control were assayed in the culture supernatant.

RESULTS

Incubation of CD-affected tissue with EF (1:20, 1:10, and 1:5) modestly and non-significantly increased IL-1ra/IL-1beta ratio as compared with medium control (CD 39.1+/-16.1; 26.5+/-7.8, 47.1+/-16.8 vs control 13.0+/-2.2), but incubation of UC-affected tissues increased IL-1ra/IL-1beta ratio significantly in all three dilutions (UC 69.1+/-32.2, P<0.05; 76.1+/-36.4, P = 0.05; 84.5+/-37.3, P<0.02; vs control 10.2+/-3.7). Incubation of non-inflamed non-IBD control tissue did not increase the IL-1ra/IL-1beta ratio in any dilution compared to medium control (69.3+/-47.0, 54.1+/-30.6, 79.4+/-34.0 vs control 76.1+/-37.3). Average percentage production of IL-1beta indexed against medium control was significantly less in UC after EF incubation as compared with CD (UC 24.0+/-4.8 vs CD 51.8+/-8.1; P<0.05). Average percentage production of IL-1ra was markedly higher in UC (135.9+/-3.4) than that in control patients (36.5+/-4.3) (P<0.0001).

CONCLUSION

IBD tissues, after incubation with elemental diet modified in its fatty acid composition with fish oil, show an increase in IL-1ra/IL-1beta cytokine ratio. This effect of omega-3 fatty acid modulation is significantly more marked in UC compared with CD and is accompanied by both a reduction of IL-1beta and increase of IL-1ra. The positive direct anti-inflammatory effect of elemental diet with fish oil in tissue affected with UC suggests dietary treatment of UC may be possible.

Fatty acid metabolism pathway play an important role in carcinogenesis of human colorectal cancers by Microarray-Bioinformatics analysis

The present study systematically explored metabolic pathways and altered expressions of genes speculatively participating in colorectal carcinogenesis by using a Microarray-Bioinformatic analysis methods. The results revealed that 157 genes were up-regulated and 281 genes were down-regulated in colorectal cancer (CRC). Gene Ontology (GO) and relevant bioinformatics tools indicated that the functional category to which 438 genes (12%; 438/3800) of the most frequent alteration belonged was metabolism. The analysis of 10 colorectal cancer tissue specimens demonstrated that genes involved in fatty acid metabolic pathways had high rates of overexpression. In addition, we stimulated CRL-1790 cell line with linoleic acid (a polyunsaturated fatty acid) for 12, 24, 48 and 72 h. Cell proliferation was elevated by 5, 25, 28 and 31% (P<0.05), respectively. Further analyses revealed that the genes increasingly expressed in the cell line included enoyl-Coenzyme A, hydratase/3-hydroxyacyl Coenzyme A dehydrogenase (EHHADH), enoyl Coenzyme A hydratase, short chain, 1, mitochondrial (ECHS1); glutaryl-Coenzyme A dehydrogenase (GCDH), acyl-Coenzyme A oxidase 2, branched chain (ACOX2); acyl-Coenzyme A dehydrogenase, C-2 to C-3 short chain precursor (ACADS); carnitine palmitoyltransferase 1B (CPT1B), acyl-CoA synthetase long-chain family member 5 (ACSL5), and cytochrome P450, family 4, subfamily A, and polypeptide 11 (CYP4A11) genes. This indicated that the stimulating effect of linoleic acid on cell proliferation was due to interference with the metabolic pathway of fatty acid metabolism. In conclusion, genes with altered expression levels in CRC were mainly associated with fatty acid metabolic pathways speculated to have an important role linked to carcinogenesis.

Diet and rheumatoid arthritis: a review of the literature

INTRODUCTION

Rheumatoid arthritis is a common inflammatory condition. A large number of patients seek alternative or complementary therapies of which diet is an important component. This article reviews the evidence for diet in rheumatoid arthritis along with the associated concept of oral tolerization.

METHODS

References were taken from Medline from 1966 to September 2004. The keywords, rheumatoid arthritis, diet, n-3 fatty acids, vitamins, and oral tolerization, were used.

RESULTS

Randomized controlled trials (RCTs) indicate that dietary supplementation with n-3 fatty acids provides modest symptomatic benefit in groups of patients with rheumatoid arthritis. Epidemiological studies and RCTs show cardiovascular benefits in the broader population and patients with ischemic heart disease. A number of mechanisms through which n-3 fats may reduce inflammation have been identified. In a small number of patients with rheumatoid arthritis, other dietary manipulation such as fasting, vegan, and elimination diets may have some benefit. However, many of these diets are impractical or difficult to sustain long term.

CONCLUSIONS

Dietary manipulation provides a means by which patients can a regain a sense of control over their disease. Dietary n-3 supplementation is practical and can be easily achieved with encapsulated or, less expensively, bottled fish oil.

Thermogenesis associated to the intake of a diet non-supplemented or supplemented with n-3 polyunsaturated fatty acid-rich fat, determined in rats receiving the same quantity of metabolizable energy

The beneficial effects of n-3 polyunsaturated fatty acids (PUFA) are well known, but their consumption in western countries is chronically insufficient, and so it is recommended that diets should be supplemented with a fat rich in these fatty acids. However, the effect of such diets on the energy expenditure remains a controversial question. Precise data concerning the effect of using under the same metabolizable energy intake, a diet non-supplemented or supplemented with a fat rich in n-3 PUFA are not available. This type of information was obtained using rats at weaning fed a diet supplemented or non-supplemented with 10% of fish oil. Between the 30th and 60th day after starting the experiment, the energy and protein balance was established by means of the comparative slaughter method. The blood levels of different metabolites were also determined. Although total thermogenesis did not vary between the two groups, consumption of the fish oil diet led to a lower level of thermogenesis associated with the oxidation of protein, and a higher one of that associated with the oxidation of fat. We conclude that the thermic effect of feeding is a combination of independent processes. Due to their specific metabolism, n-3 PUFA may be considered essential compounds to maintain the energy balance.

Overexpression of dopamine receptor genes and their products in the postnatal rat brain following maternal n-3 fatty acid dietary deficiency

A combination of PCR-Select cDNA subtraction and gene array hybridization was used to identify differentially expressed genomic markers in brains of rats fed for 3 weeks in utero and 2 weeks after birth on an n-3 polyunsaturated fatty acid (PUFA)-deficient diet supplied to dams. Total RNA was isolated, switch mechanism at 5'-end of the RNA transcripts (SMART) applied and used for PCR-Select subtraction of PUFA-deficient and adequately-fed control preparations. Subtracted and amplified ds-cDNA end-products were fragmented, terminally labeled with biotin-ddUTP and hybridized with a RN-U34A gene array. A 10-fold increase in potential genes with log2(Tester/Driver) = 1.4 was found compared with traditional gene array technology when the same chip was tested using non-subtracted targets. Reverse transcription-real-time relative PCR confirmed 30% of the transcripts. Among the validated transcripts, D1 and D2 receptors for dopamine (DA), were most prominent among a number of over-expressed neurotransmitter receptors and retinoic acid receptor (RXR alpha-2 and alpha-1). Immunohistochemical staining of brain sections from 2-week-old pups revealed a substantial enrichment of the D2 receptor in discrete regions of the mesolimbic and mesocortical pathways as well as in a large number of brain areas from the n-3 PUFA-deficient pups. Punches of the same areas run on western blots showed similar results. The overwhelming expression of D1 and D2 receptors may be attributed to a behavioral hypersensitivity caused by the possible impairment of DA production during brain development, which may have implications in certain disorders of the nervous system.