Effect of dietary fish oil on the sensitivity of hepatic lipid metabolism to regulation by insulin

Crosstalk Between Dietary Pattern, Anthropometric Parameters, and Adiponectin Concentration Among Patients with Metabolic Syndrome

Background: Adiponectin is known to mediate antidiabetic and cardioprotective metabolic effects. Current evidence suggests that diet, both its quantity and quality, affects adiponectin concentration. Methods: The purpose of this study was to evaluate the association of adiponectin with cardiometabolic risk factors, anthropometric features, and diet characteristics in obese patients with multiple cardiometabolic risk factors. The group of 113 nondiabetic patients (90 males, mean age: 48 ± 9 years) fulfilling the criteria of metabolic syndrome (IDF, 2005) was divided into 2 subgroups according to median adiponectin concentration calculated for that cohort (6.83 μg/mL)-low-adiponectin (LA) and high-adiponectin (HA) subgroup. Biochemical and anthropometric measurements were recorded and nutrients intake was assessed using 24-hr dietary recall method and diet history questionnaire. Results: No significant differences between LA and HA were noted regarding the anthropometric parameters. However, there were significant differences in biochemical indices, and HA was characterized by a more favorable insulin level, homeostasis model assessment of insulin resistance (HOMA-IR) value, and plasma lipid profile than LA. Both LA and HA subgroups were comparable in terms of energy, protein, carbohydrate, and total fat intake, but there were significant differences between the level of polyunsaturated fatty acids (PUFA) consumption (6.06 ± 1.0 and 6.37 ± 1.1, respectively) and omega-3/omega-6 ratio (as follows: 0.09 ± 0.01 and 0.16 ± 0.04). Conclusions: These results highlight interactions between diet, adiponectin concentration, and biochemical profile. Nondiabetic patients with metabolic syndrome with higher PUFA consumption, including higher omega-3/omega-6 ratio, were characterized by higher circulating adiponectin level and more favorable biochemical profile. Thus, it might be assumed that the protective role of omega-3 fatty acids might be mediated by adiponectin in patients with metabolic syndrome.

Effect of omega-3 fatty acids on glucose homeostasis: role of free fatty acid receptor 1

Insulin resistance is a worldwide health problem. This study investigated the acute effects of eicosapentanoic acid (EPA) on glucose homeostasis focusing on the role of free fatty acid receptor 1 (FFAR1) and the chronic effects of fish oil omega-3 fatty acids on insulin resistance. Insulin resistance was induced by feeding mice high-fructose, high-fat diet (HFrHFD) for 16 weeks. In the first part, the acute effects of EPA alone and in combination with GW1100 and DC260126 (FFAR1 blockers) on glucose homeostasis and hepatic phosphatidyl-inositol 4,5-bisphosphate (PIP2) and diacylglycerol (DAG) were investigated in standard chow diet (SCD)- and HFrHFD-fed mice. In the second part, mice were treated with fish oil omega-3 fatty acids for 4 weeks starting at the week 13 of feeding HFrHFD. Changes in the blood- and liver tissue-insulin resistance markers and FFAR1 downstream signals were recorded at the end of experiment. Results showed that EPA increased 0 and 30 min blood glucose levels after glucose load in SCD-fed mice but improved glucose tolerance in HFrHFD-fed mice. Moreover, FFAR1 blockers reduced EPA effects on glucose tolerance and hepatic PIP2 and DAG levels. On the other hand, chronic use of fish oil omega-3 fatty acids increased FBG levels and decreased serum insulin and triglycerides levels without improving the index of insulin resistance. Also, they increased hepatic β-arrestin-2, PIP2, and pS473 Akt levels but decreased DAG levels. In conclusion, EPA acutely improved glucose homeostasis in HFrHFD-fed mice by modulating the activity of FFAR1. However, the chronic use of fish oil omega-3 fatty acids did not improve the insulin resistance.

Application of N-carbamylglutamate in Rex rabbits to reduce body fat deposition and its possible mechanism

N-Carbamylglutamate (NCG) has been shown to enhance arginine synthesis and improve growth performance in animals. However, the effect of NCG on body fat deposition remains unknown. This study examined the effects of NCG on body fat deposition and evaluated the potential mechanisms involved. Rex rabbits (3 months old) were assigned to one of four dietary groups and supplemented with NCG at the following different concentrations in a feeding trial that lasted 67 d: 0 (control), 0·04, 0·08, and 0·12 %. NCG supplementation increased serum concentrations of arginine and proline by activating intestinal carbamoylphosphate synthase-І at the posttranscriptional level. Final body weights and growth performance were not affected by dietary NCG levels. However, NCG-treated rabbits had lower perirenal and subcutaneous fat percentages, serum TAG content, and hepatic fatty acid synthase (FAS) activity and increased NO synthase activity and serum levels of NO, growth hormone (GH), and insulin-like growth factor 1 (IGF-1). There were significant positive correlations between TAG content and perirenal fat percentage, as well as FAS activity and perirenal fat percentage, but significant negative correlations between TAG and NO levels, and FAS activity and IGF-1 level in rabbits after NCG treatment. NCG supplementation did not affect hepatic health indicators, except for serum ammonia concentrations, which were decreased in NCG-treated rabbits. Our results suggest that NCG can serve as a dietary supplement to reduce unfavourable fat deposition through inhibiting hepatic lipogenesis in animals since it appears to have no negative effects on growth performance or hepatic health.

Saturated and monounsaturated fatty acids in membranes are determined by the gene expression of their metabolizing enzymes SCD1 and ELOVL6 regulated by the intake of dietary fat

PURPOSE

We investigated the effect of dietary fats on the incorporation of saturated (SAFAs) and monounsaturated dietary fatty acids (MUFAs) into plasma phospholipids and the regulation of the expression of lipid-metabolizing enzymes in the liver.

METHODS

Mice were fed different diets containing commonly used dietary fats/oils (coconut fat, margarine, fish oil, sunflower oil, or olive oil) for 4 weeks (n = 6 per diet group). In a second experiment, mice (n = 6 per group) were treated for 7 days with synthetic ligands to activate specific nuclear hormone receptors (NHRs) and the hepatic gene expression of CYP26A1 was investigated. Hepatic gene expression of stearoyl-coenzyme A desaturase 1 (SCD1), elongase 6 (ELOVL6), and CYP26A1 was examined using quantitative real-time PCR (QRT-PCR). Fatty acid composition in mouse plasma phospholipids was analyzed by gas chromatography (GC).

RESULTS

We found significantly reduced hepatic gene expression of SCD1 and ELOVL6 after the fish oil diet compared with the other diets. This resulted in reduced enzyme-specific fatty acid ratios, e.g., 18:1n9/18:0 for SCD1 and 18:0/16:0 and 18:1n7/16:1n7 for ELOVL6 in plasma phospholipids. Furthermore, CYP26A1 a retinoic acid receptor-specific target was revealed as a new player mediating the suppressive effect of fish oil-supplemented diet on SCD1 and ELOVL6 hepatic gene expression.

CONCLUSION

Plasma levels of MUFAs and SAFAs strongly reflect an altered hepatic fatty acid-metabolizing enzyme expression after supplementation with different dietary fats/oils.

The effect of diet and exercise on tobacco carcinogen-induced lung cancer

In previous studies, we found that low-carbohydrate (CHO) diets reduced the incidence of tumors in mice genetically predisposed to cancer. However, because >90% of human cancers arise via carcinogen-induced somatic mutations, we investigated, herein, the role that different types and levels of CHO, protein and lipid play in lung cancer induced by the tobacco-specific carcinogen, nicotine-derived nitrosamine ketone (NNK) in A/J mice. We found lowering CHO levels significantly reduced lung nodules and blood glucose levels. We also found that soy protein was superior to casein and that coconut oil was ineffective at reducing lung nodules. Diets containing amylose or inulin (at 15% of total calories), soy protein (at 35%) and fat (at 50%, 30% being fish oil) were the most effective at reducing lung nodules. These fish oil-containing diets increased plasma levels of the ketone body, β-hydroxybutyrate, while reducing both insulin and 8-isoprostane in plasma and bronchoalveolar interleukin-12 and lung PGE2 levels. After only 2 weeks on this diet, the levels of γ-H2AX were significantly reduced, 24 hours after NNK treatment. Housing these mice in two-tiered rat cages with exercise wheels led to similar mouse weights on the different diets, whereas keeping mice in standard mouse cages led to both significant weight differences between the low-CHO, soy protein, fish oil diet and Western diet and substantially more lung nodules than in the two-tiered cages. Our results suggest that low-CHO, soy protein, fish oil-containing diets, together with exercise, may reduce the incidence of lung cancer.

Performance, insulin sensitivity, carcass characteristics, and fatty acid profile of beef from steers fed microalgae

Heterotrophic production of microalgae biomass provides a consistent, high-quality source of docosahexaenoic acid (DHA; C22:6 n-3) in triglyceride oils that could be used as a ration supplement for feedlot steers to improve nutritional qualities of beef. Sixty Angus × Simmental steers (438 ± 6.4 kg) were allotted to two treatments (30 steers each, six pens, five steers/pen) to determine the effects of ForPLUS (DHA-rich microalgae Aurantiochytrium limacinum; 63.6% fat; 17.9% DHA; 30 mg/kg Sel-Plex; Alltech Inc.) on performance, insulin sensitivity, LM fatty acid composition, and meat quality. Steers were fed basal diets containing 45% corn, 30% distillers dried grains with solubles, 20% corn silage, and 5% supplement. Basal diets were formulated to contain 16.1% CP and 1.32 Mcal/kg NEg. Treatments were delivered to steers in a ground corn-based top-dress (454 g total/steer) and contained no microalgae for control steers or 100 g/steer daily of ForPLUS for microalgae steers. A glucose tolerance test (GTT) was performed 10 d prior to slaughter. Steers were slaughtered when a target pen BW of 621 kg was achieved. Fatty acid oxidation potential was determined by measuring thiobarbituric acid reactive substances (TBARS) on LM samples collected 24 h after slaughter and aged for 48 h or 21 d. Weight and BW gain did not differ during the study (P ≥ 0.13); however, steers fed microalgae remained in the feedlot seven more days compared to steers fed the control diet (111 vs. 104 d; P = 0.04). Overall DMI decreased (P = 0.002) and G:F increased during the second half of the study (P = 0.04) in steers fed microalgae compared to steers fed the control diet. Steers fed microalgae secreted less insulin (P = 0.01) and took longer to clear glucose (P = 0.01) during a 2-h GTT. Carcass traits did not differ between treatments (P ≥ 0.23). Microalgae had no effect on n-6 content (P = 0.67), but more than doubled the n-3 fatty acid percentage and the n-3:n-6 ratio of the LM (P < 0.0001). The percentage of n-3 fatty acids C20:5 and C22:6 were increased (P < 0.0001) 4-fold and 6.25-fold, respectively, by microalgae supplementation. Concentration of TBARS did not differ in LM aged for 48 h (P = 0.91); however, when aged for 21 d, steers fed microalgae tended to produce LM with greater TBARS concentration compared to steers fed the control diet (P = 0.08). In conclusion, DHA-rich microalgae decreased DMI of steers, and increased n-3 fatty acids and beef oxidation in steaks aged for 21 d.

DHA attenuates postprandial hyperlipidemia via activating PPARα in intestinal epithelial cells

It is known that peroxisome proliferator-activated receptor (PPAR)α, whose activation reduces hyperlipidemia, is highly expressed in intestinal epithelial cells. Docosahexaenoic acid (DHA) could improve postprandial hyperlipidemia, however, its relationship with intestinal PPARα activation is not revealed. In this study, we investigated whether DHA can affect postprandial hyperlipidemia by activating intestinal PPARα using Caco-2 cells and C57BL/6 mice. The genes involved in fatty acid (FA) oxidation and oxygen consumption rate were increased, and the secretion of triacylglyceride (TG) and apolipoprotein B (apoB) was decreased in DHA-treated Caco-2 cells. Additionally, intestinal FA oxidation was induced, and TG and apoB secretion from intestinal epithelial cells was reduced, resulting in the attenuation of plasma TG and apoB levels after oral administration of olive oil in DHA-rich oil-fed mice compared with controls. However, no increase in genes involved in FA oxidation was observed in the liver. Furthermore, the effects of DHA on intestinal lipid secretion and postprandial hyperlipidemia were abolished in PPARα knockout mice. In conclusion, the present work suggests that DHA can inhibit the secretion of TG from intestinal epithelial cells via PPARα activation, which attenuates postprandial hyperlipidemia.

Abdominal adiposity, insulin and bone quality in young male rats fed a high-fat diet containing soybean or canola oil

OBJECTIVES

A low ratio of omega-6/omega-3 polyunsaturated fatty acids is associated with healthy bone properties. However, fatty diets can induce obesity. Our objective was to evaluate intra-abdominal adiposity, insulin, and bone growth in rats fed a high-fat diet containing low ratios of omega-6/omega-3 provided in canola oil.

METHODS

After weaning, rats were grouped and fed either a control diet (7S), a high-fat diet containing soybean oil (19S) or a high-fat diet of canola oil (19C) until they were 60 days old. Differences were considered to be significant if p<0.05.

RESULTS

After 60 days, the 19S and 19C groups showed more energy intake, body density growth and intraabdominal fat mass. However, the 19S group had a higher area (200%) and a lower number (44%) of adipocytes, while the 7S and 19C groups did not differ. The serum concentrations of glucose and insulin and the insulin resistance index were significantly increased in the 19C group (15%, 56%, and 78%, respectively) compared to the 7S group. Bone measurements of the 19S and 19C groups showed a higher femur mass (25%) and a higher lumbar vertebrae mass (11%) and length (5%). Computed tomography analysis revealed more radiodensity in the proximal femoral epiphysis and lumbar vertebrae of 19C group compared to the 7S and 19S groups.

CONCLUSIONS

Our results suggest that the amount and source of fat used in the diet after weaning increase body growth and fat depots and affect insulin resistance and, consequently, bone health.

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.

Suplementação de ácidos graxos ômega 3 em atletas de competição: impacto nos mediadores bioquímicos relacionados com o metabolismo lipídico

OBJETIVO: Avaliar o efeito da suplementação dos ácidos graxos ômega 3 em atletas de natação sobre indicadores bioquímicos. MÉTODOS: Nadadores de elite (n = 14) do sexo masculino foram avaliados em estudo randomizado, controlado por placebo pelo período de seis semanas (45 dias). O grupo placebo (GP) recebeu óleo mineral (n = 6) e o grupo suplementado (n = 8), óleo de peixe (GOP) contendo, no total, 950mg de ácido eicosapentaenóico e 500mg de ácido docosapentaenóico. Amostras de sangue foram coletadas imediatamente antes (T0), aos 15 (T15), aos 30 (T30) e aos 45 (T45) dias de suplementação para análise da composição dos ácidos graxos por cromatografia gasosa e para quantificação das lipoproteínas plasmáticas através de kits comerciais específicos. RESULTADOS: Os resultados revelaram um desajuste na dieta dos atletas considerando a ingestão g/kg de massa corporal dos macronutrientes. A análise do questionário de freqüência de consumo mostrou que os atletas não ingeriram regularmente fontes alimentares de ômega 3 e que o consumo de peixes, em 85% da amostra, era inferior ou igual a uma vez na semana. O perfil de ácidos graxos plasmáticos evidenciou aumento dos ácidos graxos poliinsaturados ômega 3 (P < 0,05) e redução do ácido araquidônico no grupo suplementado (P < 0,05). A suplementação com óleo de peixe ocasionou efeito hipocolesterolêmico, com redução nos teores sanguíneos de VLDL, LDL e colesterol total. Os valores de HDL não apresentaram diferenças significativas entre os grupos em nenhum momento estudado (P > 0,05). CONCLUSÃO: A suplementação de ácidos graxos N-3 em atletas nadadores altera os indicadores bioquímicos do metabolismo lipídico, influenciando na redução das lipoproteínas plasmáticas, ricas em colesterol e na prevenção de doenças cardiovasculares.

A high-cholesterol, n-3 polyunsaturated fatty acid diet causes different responses in rats and hamsters

This study was designed to investigate the response to a high-cholesterol, n-3 polyunsaturated fatty acid (PUFA) or n-6 PUFA diet in rats and hamsters. Animals were fed n-3 or n-6 PUFA with a cholesterol-free diet, or with a diet enriched with cholesterol (0.5%, w/w) for 2 weeks. In rats and hamsters fed a cholesterol-free diet, plasma cholesterol, triglycerides and very-low-density lipoprotein (VLDL)-triglyceride levels in n-3 PUFA group were significantly lower than those in n-6 PUFA group. In contrast, when diets were supplemented with 0.5% cholesterol, the plasma cholesterol- and triglyceride-lowering effect of dietary n-3 PUFA disappeared. In hamsters fed with the atherogenic diet (0.5% dietary cholesterol) for 2 weeks, n-3 PUFA induced hypercholesterolemia more than n-6 PUFA, the increase being in the VLDL and low-density lipoprotein (LDL) fractions. Our data thus indicate that elevation of VLDL- and LDL-cholesterol in hamsters by n-3 PUFA, compared with n-6 PUFA, is dependent on 0.5% dietary cholesterol supplementation. In rats, on the other hand, dietary n-3 PUFA did not induce hypercholesterolemia more than n-6 PUFA when 0.5% cholesterol was supplemented. Although the effects of n-3 PUFA on plasma cholesterol, triglycerides and VLDL-triglycerides were similar in hamsters and rats, the interactive effects of n-3 PUFA and cholesterol on plasma and lipoprotein cholesterol levels differed in the two species. It was also found that plasma triglycerides, cholesterol and lipoprotein cholesterol levels in hamsters are higher than in rats in the presence and absence of dietary cholesterol. In addition, cholesterol feeding induces hypertriglyceridemia and hypercholesterolemia only in hamsters. Moreover, liver triglyceride concentrations increased in rats fed a cholesterol-rich diet and hepatic triglyceride levels of the n-3 PUFA-fed rats were significantly lower than those in the n-6 PUFA-fed rats in the presence and absence of dietary cholesterol. However, triglycerides did not accumulate in the liver in hamsters fed a cholesterol-rich diet and hepatic triglyceride levels of the n-3 PUFA-fed hamsters were not significantly different from those in the n-6 PUFA-fed hamsters in the presence and absence of dietary cholesterol. Therefore, these studies confirm marked species differences in response to the interactive effects of dietary n-3 PUFA and cholesterol.

Effects of dietary polyunsaturated n-3 fatty acids on dyslipidemia and insulin resistance in rodents and humans. A review

For many years, clinical and animal studies on polyunsaturated n-3 fatty acids (PUFAs), especially those from marine oil, eicosapentaenoic acid (20:5,n-3) and docosahexaenoic acid (22:6,n-3), have reported the impact of their beneficial effects on both health and diseases. Among other things, they regulate lipid levels, cardiovascular and immune functions as well as insulin action. Polyunsaturated fatty acids are vital components of the phospholipids of membrane cells and serve as important mediators of the nuclear events governing the specific gene expression involved in lipid and glucose metabolism and adipogenesis. Besides, dietary n-3 PUFAs seem to play an important protecting role against the adverse symptoms of the Plurimetabolic syndrome. This review highlights some recent advances in the understanding of metabolic and molecular mechanisms concerning the effect of dietary PUFAs (fish oil) and focuses on the prevention and/or improvement of dyslipidemia, insulin resistance, impaired glucose homeostasis, diabetes and obesity in experimental animal models, with some extension to humans.

Regulation of triacylglycerol hydrolase expression by dietary fatty acids and peroxisomal proliferator-activated receptors

Triacylglycerol hydrolase (TGH) is an enzyme that catalyzes the lipolysis of intracellular stored triacylglycerol (TG). Peroxisomal proliferator-activated receptors (PPAR) regulate a multitude of genes involved in lipid homeostasis. Polyunsaturated fatty acids (PUFA) are PPAR ligands and fatty acids are produced via TGH activity, so we studied whether dietary fats and PPAR agonists could regulate TGH expression. In 3T3-L1 adipocytes, TGH expression was increased 10-fold upon differentiation, compared to pre-adipocytes. 3T3-L1 cells incubated with a PPARgamma agonist during the differentiation process resulted in a 5-fold increase in TGH expression compared to control cells. Evidence for direct regulation of TGH expression by PPARgamma could not be demonstrated as TGH expression was not affected by a 24-h incubation of mature 3T3-L1 adipocytes with the PPARgamma agonist. Feeding mice diets enriched in fatty acids for 3 weeks did not affect hepatic TGH expression, though a 3-week diet enriched in fatty acids and cholesterol increased hepatic TGH expression 2-fold. Two weeks of clofibrate feeding did not significantly affect hepatic TGH expression or microsomal lipolytic activities in wild-type or PPARalpha-null mice, indicating that PPARalpha does not regulate hepatic TGH expression. Therefore, TGH expression does not appear to be directly regulated by PPARs or fatty acids in the liver or adipocytes.

Effects of long chain fatty acids on lipid and glucose metabolism in monolayer cultures of bovine hepatocytes

The objectives were to determine the long-term (48 h) effects of specific long chain fatty acids on hepatic lipid and glucose metabolism in monolayer cultures of bovine hepatocytes. From 16 to 64 h after plating, hepatocytes from three 7- to 10-d-old calves were exposed to one of the following treatments: 1 mM palmitic acid (1 mM C16:0), 2 mM palmitic acid (2 mM C16:0), or 1 mM palmitic acid plus 1 mM of either stearic (C18:0), oleic (C18:1), linoleic (C18:2), linolenic (C18:3), eicosapentaenoic (C20:5), or docosahexaenoic (C22:6) acid, or 0.5 mM each of eicosapentaenoic and docosahexaenoic acid (C20:5 + C22:6). The two treatments containing 2 mM of saturated fatty acids, 2 mM C16:0 and 1 mM C16:0 plus 1 mM C18:0, increased beta-hydroxybutyrate concentrations in the medium and [1-(14)C]palmitic acid oxidation to acid-soluble products compared with all other treatments. The treatment containing C22:6 increased total cellular triglyceride content and incorporation of [1-(14)C]palmitic acid into cellular triglycerides. The treatments containing C22:6 or C20:5 + C22:6 increased [1-(14)C]palmitic acid metabolism to phospholipids and cholesterol. The presence of C22:6 in the medium decreased metabolism of [2-(14)C]propionic acid either to glucose in the medium or to cellular glycogen. Overall, fatty acids differed in their effects on lipid and glucose metabolism in monolayer cultures of bovine hepatocytes with C22:6 eliciting the most profound changes.

Dietary fish oil does not protect rats exposed to restraint or sleep deprivation stress

It has been suggested that fish oil (FO) prevents weight loss caused by physiological stress such as cancer, injury, or cardiovascular disorders. Previously, we observed that a high-fat diet containing corn and coconut oil exaggerated weight loss caused by the mixed physiological and psychological stress of repeated restraint (RR). This experiment tested the effects of a high-fat diet containing FO as the predominant lipid source in rats exposed to the mixed physiological and psychological stress of either RR or sleep deprivation (SD). FO did not prevent stress-induced hypophagia or weight loss in RR or SD rats but exaggerated the negative effects of stress on body weight in SD rats by promoting loss of lean body mass. RR caused a reduction in body fat content irrespective of dietary treatment. In SD rats, both stress and FO independently reduced body fat mass. FO did not have any effect on adrenal and thymus weights during RR or SD and did not influence corticosterone levels after 1 h of RR or after 48 or 96 h of SD. In conclusion, our results suggest that high levels of dietary FO do not improve the response to stress in rats exposed to mixed stressors.

Effects of glucagon and insulin on plasma glucose, triglyceride, and triglyceride-rich lipoprotein concentrations in laying hens fed diets containing different types of fats

The influence of dietary fat supplementations differing in the ratio of n-6 to n-3 polyunsaturated fatty acids (PUFA) on the effects of glucagon and insulin on plasma glucose, triglyceride (TG), and TG-rich lipoprotein concentrations was investigated in laying hens. Birds were fed either a low-fat control diet (LF) or diets supplemented with 4% pumpkin seed oil (PO; rich in n-6 PUFA) or 4% cod liver oil (CO; rich in n-3 PUFA). After 4 wk feeding of the experimental diets, hens were implanted with wing vein catheters and injected with porcine glucagon (20 microg/kg BW) and porcine insulin (0.5 IU/kg BW), 2 to 5 h after oviposition. Plasma glucose, TG, and TG-rich lipoprotein concentrations were determined from 10 min pre-injection to 60 min post-injection. PO diet resulted in a prolonged plasma glucose response to glucagon administration and altered hypoglycemic response to insulin. However, CO diet did not influence plasma glucose response to either glucagon or insulin administration compared to LF diet. The effects of glucagon and insulin on plasma TG and TG-rich lipoproteins were similar for all diets regardless of the amount or type of fat. The results suggest that feeding dietary fats with high n-6 to n-3 PUFA ratio alters the glucagon and insulin sensitivity of plasma glucose in laying hens. Fats rich in n-3 PUFA seem to have no influence on the plasma glucose response to glucagon and insulin.

Characterization of the rodent genes for arylacetamide deacetylase, a putative microsomal lipase, and evidence for transcriptional regulation

In the current study, we have determined the cDNA and the genomic sequences of the arylacetamide deacetylase (AADA) gene in mice and rats. The AADA genes in the rat and mouse consist of five exons and have 2.4 kilobases of homologous promoter sequence upstream of the initiating ATG codon. AADA mRNA is expressed in hepatocytes, intestinal mucosal cells (probably enterocytes), the pancreas and also the adrenal gland. In mice, there is a diurnal rhythm in hepatic AADA mRNA concentration, with a maximum 10 h into the light (post-absorptive) phase. This diurnal regulation is attenuated in peroxisome proliferator-activated receptor alpha knockout mice. Intestinal but not hepatic AADA mRNA was increased following oral administration of the fibrate, Wy-14,643. The homology of AADA with hormone-sensitive lipase and the tissue distribution of AADA are consistent with the view that AADA plays a role in promoting the mobilization of lipids from intracellular stores and in the liver for assembling VLDL. This hypothesis is supported by parallel changes in AADA gene expression in animals with insulin-deficient diabetes and following treatment with orotic acid.