α-Linolenic acid prevents hepatic steatosis and improves glucose tolerance in mice fed a high-fat diet

OBJECTIVES: Dietary omega-3 fatty acids have been efficacious in decreasing serum cholesterol levels and reducing the risk of cardiovascular disease. However, the metabolic and molecular changes induced by the omega-3 fatty acid α-linolenic acid (ALA), which is found in linseed oil, are not fully understood. In this study, we showed a correlation between ALA and insulin resistance, inflammation and endoplasmic reticulum stress (ERS). METHODS: We studied 40 male mice (C57/BL6) divided into 4 groups: a control (C) group, a control + omega-3/ALA (CA) group, a high-fat diet (HFD) (H) group and a high-fat diet + omega-3/ALA (HA) group. For 8 weeks, the animals in the H and HA groups were fed a high-fat (60%) diet, while the animals in the C and CA groups received regular chow. The diets of the CA and HA groups were supplemented with 10% lyophilized ALA. RESULTS: ALA supplementation improved glucose tolerance and reduced insulin resistance, as measured by intraperitoneal glucose tolerance tests and the homeostasis model assessment for insulin resistance, respectively. In addition, ALA reduced hepatic steatosis and modified the standard fat concentration in the liver of animals fed an HFD. Dietary ALA supplementation reduced the serum levels of interleukin 6 (IL-6), interleukin 1 beta (IL-1β) and monocyte chemoattractant protein-1 (MCP-1), increased the expression of important chaperones such as binding immunoglobulin protein (BIP) and heat shock protein 70 (HSP70) and reduced the expression of C/EBP-homologous protein (CHOP) and X-box binding protein 1 (XBP1) in hepatic tissues, suggesting an ERS adaptation in response to ALA supplementation. CONCLUSIONS: Dietary ALA supplementation is effective in preventing hepatic steatosis; is associated with a reduction in insulin resistance, inflammation and ERS; and represents an alternative for improving liver function and obtaining metabolic benefits.

Conjugated linoleic acid supplementation does not maximize motor performance and abdominal and trunk fat loss induced by aerobic training in overweight women / Suplementação de ácido linoléico conjugado não maximiza o desempenho motor e a perda de gordura de tronco e abdominal induzida pelo treinamento aeróbio em mulheres com excesso de peso

ABSTRACT Objective: To analyze the effect of eight weeks of conjugated linoleic acid supplementation on physical performance, and trunk and abdominal fat in overweight women submitted to an aerobic training program. Methods: Twenty-eight overweight women (body mass index ³25 kg/m2) were divided randomly and double-blindly to receive conjugated linoleic acid or placebo, both associated with an aerobic exercise program (frequency = three times a week, duration=30 min/session, intensity=80% of maximum heart rate). Conjugated linoleic acid (3.2 g) and placebo (4.0 g) supplements were consumed daily (four capsules) for eight weeks. Maximum speed and time to exhaustion were determined in incremental treadmill test. Trunk fat was estimated by dual-energy X-Ray absorptiometry. Waist circumference was used as indicator of abdominal fat. Results: Main effect of time (p<0.05) showed increased maximum speed (conjugated linoleic acid=+6.3% vs. placebo=+7.5%) and time to exhaustion (conjugated linoleic acid=+7.1% vs. placebo=+8.6%) in the incremental treadmill test, with no differences between the groups (p>0.05). Similarly, significant reductions (p<0.05) in trunk fat (conjugated linoleic acid=-1.7% vs. placebo=-1.5%) and abdominal fat (conjugated linoleic acid=-4.7% vs. placebo=-4.0%) were found after eight weeks of intervention, with no differences between the groups (p>0.05). Conclusion: The results of this study suggest that conjugated linoleic acid supplementation does not maximize motor performance, and loss of body and abdominal fat induced by aerobic training in overweight women.

RESUMO Objetivo: Analisar o efeito de oito semanas de suplementação de ácido linoleico conjugado sobre o desempenho físico, a gordura de tronco e abdominal em mulheres com excesso de peso submetidas a um programa de treinamento aeróbio. Métodos: Vinte e oito mulheres com excesso de peso (índice de massa corporal ³ 25 kg/m2) foram separadas aleatoriamente por meio de um delineamento duplo cego para receber suplementação de ácido linoleico ou placebo associado a um programa de exercícios aeróbios (frequência = três sessões semanais, duração=30 min/sessão, intensidade=80% da frequência cardíaca máxima). A suplementação de ácido linoleico (3,2 g) ou de placebo (4,0 g) foi consumida diariamente (quatro cápsulas), durante oito semanas. As variáveis velocidade máxima atingida e tempo de permanência até a exaustão foram determinadas em teste incremental em esteira. A gordura de tronco foi estimada por absortometria radiológica de dupla energia. A circunferência de cintura foi utilizada como indicador de gordura abdominal. Resultados: Efeito principal do tempo (p<0,05) revelou aumento da velocidade máxima atingida (suplementação de ácido linoleico=+6,3% versus placebo=+7,5%) e tempo de duração até a exaustão (suplementação de ácido linoleico=+7,1% versus placebo=+8,6%) em teste incremental em esteira, sem diferenças entre os grupos (p>0,05). De forma similar, uma redução significante (p<0,05) na gordura relativa de tronco (suplementação de ácido linoleico=-1,7% versus placebo=-1,5%) e na gordura abdominal (suplementação de ácido linoleico=-4,7% versus placebo=-4,0%) foi encontrada após oito semanas de intervenção, sem diferenças entre os grupos (p>0,05). Conclusão: Os resultados do presente estudo sugerem que a suplementação de ácido linoleico não maximiza o desempenho motor e a redução da gordura de tronco e abdominal induzida pelo treinamento aeróbio em mulheres com excesso de peso.

Diet high in alpha-linolenic acid up-regulate PPAR-gamma gene expression in the liver of goats

Background There is little information on the effects of diets containing high α-linolenic acid (C18:3n-3) on liver lipid composition and lipogenic gene expressions. In this study fourteen goats (Capra aegagrus hircus) were fed either a flaxseed oil (FSO) supplemented diet containing high α-linolenic acid or a control diet without added flaxseed oil (CON) for 100-d to evaluate the effects on liver lipid composition and the gene expression of peroxisome proliferator-activated receptors (PPAR-α) and stearoyl-CoA-desaturase (SCD) in the liver. Results An increase in the levels of C18:3n-3 and C20:5n-3, C22:5n-3, C22:6n-3 was observed in the liver of FSO-treated goats. There was a significant (P < 0.05) up-regulation of PPAR-α gene expression and downregulation of SCD gene in the liver of goats fed the high α-linolenic acid diet. Conclusions In conclusion, genes associated with the control of fatty acid (FA) conversion (SCD and PPAR) were affected by the α-linolenic acid supplementation in the goat diet. It is suggested that PPAR-α is the key messenger responsible for the translation of nutritional stimuli into changes in hepatic gene expression.

Metabolic evaluation of dairy cows submitted to three different strategies to decrease the effects of negative energy balance in early postpartum / Avaliação metabólica de vacas leiteiras submetidas a três estratégias para diminuir os efeitos do balanço energético negativo no pós-parto inicial

In early lactation dairy cattle suffer metabolic alterations caused by negative energy balance, which predisposes to fatty liver and ketosis. The aim of this study was to evaluate the metabolic condition of high yielding dairy cows subjected to three treatments for preventing severe lipomobilization and ketosis in early lactation. Fifty four multiparous Holstein cows yielding >30 L/day were divided into four groups: control (CN= no treatment), glucose precursor (PG= propylene-glycol), hepatic protector (Mp= Mercepton®), and energy supplement with salts of linolenic and linoleic faty acids (Mg-E= Megalac-E®). Treatments were administrated randomly at moment of calving until 8 weeks postpartum. Blood samples were collected on days 1, 7, 14, 21, 28, 35, 42 and 49 postpartum. Body condition score (BCS) was evaluated at the same periods and milk yield was recorded at 2nd, 4th, 5th, 6th, 7th, and 8th weeks of lactation. Concentrations of non-esterified fatty acids (NEFA), albumin, AST, ß-hydroxybutyrate (BHBA), cholesterol, glucose, total protein, urea and triglycerides were analyzed in blood samples. Cut-off points for subclinical ketosis were defined when BHBA >1.4 mmol/L and NEFA >0.7 mmol/L. General occurrence of subclinical ketosis was 24 percent during the period. An ascendant curve of cholesterol and glucose was observed from the 1st to the 8th week of lactation, while any tendency was observed with BHBA and NEFA, although differences among treatments were detected (p<0.05). BCS decreased from a mean of 3.85 at 1st week to 2.53 at 8th week of lactation (p=0.001). Milk yield was higher in the Mg-E group compared with the other treatment groups (p<0.05) Compared with the CN group, the treatments with Mp and PG did not show significant differences in blood biochemistry and milk yield. Cows receiving PG and Mg-E showed higher values of BHBA and NEFA (P<0.05), indicating accentuated lipomobilization. Supplementation with Mg-E also resulted in significant higher concentrations of cholesterol, BHBA, urea, AST and lower values of glycemia. This performance may be explained by the highest milk yield observed with this treatment. Treatments with PG and Mp did not improve milk yield, compared with control cows, but did not show metabolic evidence of ketosis, fat mobilization or fatty liver. These results suggest that treatment with Mg-E improves milk production but induces a higher negative energy balance leading to moderated lipomobilization and ketone bodies production, increasing the risk of fatty liver.

Durante o início da lactação as vacas leiteiras sofrem transtornos metabólicos causados pelo balanço energético negativo, o que predispõe a infiltração gordurosa hepática e cetose. O objetivo deste estudo foi avaliar o status metabólico de vacas leiteiras de alta produção submetidas a três tratamentos para prevenir severa lipomobilização e cetose no início da lactação. Cinquenta e quatro vacas de raça Holandesa multíparas produzindo >30 L/dia foram divididas em quatro grupos: controle (CN= sem tratamento), precursor de glicose (PG= propileno-glicol), protetor hepático (Mp= Mercepton®) e suplementação com sais de ácidos linolênico e linoléico (Mg-E= Megalac-E®). Amostras de sangue foram coletadas nos dias 1, 7, 14, 21, 28, 35, 42 e 49 do pós-parto. A condição corporal foi avaliada nos mesmos períodos e a produção de leite foi registrada nas semanas 2, 4, 5, 6, 7 e 8 de lactação. As concentrações de ácidos graxos não esterificados (AGNE), albumina, AST, ß-hidroxibutirato (BHB), colesterol, glicose, proteína total, uréia e triglicerídeos foram determinadas nas amostras de sangue. Pontos de corte para diagnosticar cetose subclínica foram definidos quando BHB >1,4mmol/L e AGNE >0,7mmol/L. A ocorrência geral de cetose subclínica foi de 24 por cento durante o período. Uma curva ascendente de colesterol e de glicose foi observada desde a 1ª até a 8ª semana de lactação, enquanto que nenhuma tendência foi observada com BHB e AGNE, embora diferenças entre os tratamentos foram detectadas (p<0,05). A condição corporal diminuiu de uma media de 3,85 na 1ª semana até 2,53 na 8ª semana de lactação (p=0,001). A produção de leite foi superior no grupo de Mg-E comparado com os demais tratamentos. Comparado com o grupo CN, os tratamentos de Mp e PG não mostraram diferenças significativas na bioquímica sanguínea nem na produção de leite (p<0,05) As vacas que receberam PG e Mg-E mostraram maiores valores de AGNE, indicando uma acentuada lipomobilização. A suplementação com Mg-E também resultou em maiores concentrações de colesterol, BHB, uréia, AST e menores valores de glicemia. Este resultado pode ser explicado pela maior produção de leite observada com este tratamento. Os tratamentos com PG e Mp não melhoraram a produção de leite, comparados ao grupo CN, mas também não mostraram evidências metabólicas de cetose, alta lipomobilização nem infiltração gordurosa hepática. Os resultados sugerem que o tratamento com Mg-E melhora a produção de leite, mas induz um balance energético negativo maior levando a moderada lipomobilização e produção de corpos cetônicos, aumentando o risco de fígado gorduroso.

Exclusión del ácido alfalinolénico de la dieta de la rata durante varias generaciones. I. Efecto en la reproducción y crecimiento postnatal / Exclusion of alpha-linolenic acid from diets for rats during several generations. I. Effect on reproduction and postnatal growth

The effects of a dietary alphalinolenic acid (18: 3w3) deficiency on reproduction and post natal growth in rats during 3 successive generations were studied. Female rats received respectively a diet with sunflower oil at 10 (deficient diet) or a diet with soya oil at 10 (control diet). The results showed that in our experimental conditions deficient diet affects: fecundity, fertility, post natal growth and cause a high rates of perinatal mortality from birth to post partum day 3: Perinatal mortality increased with successive gestation from 14.6 to 18.6 compared with the survival of control. The fatty acid composition of placenta phospholipids and milk lipids reflected the nature of the dietary oil. The possibility that 18: 3w3 might function in a way different from the EFA role of 18: 2w6 in reproduction at least in rats has been discussed.