The effects of chronic fish oil feeding in rats on protein catabolism induced by recombinant mediators

Fish oil administration combined with resistance exercise training improves strength, resting metabolic rate, and inflammation in older adults

BACKGROUND

While fish oil (FO) has attracted great attention due to their health-enhancing properties, its potential to enhance benefits from resistance exercise training (RET) has not been fully elucidated yet.

AIMS

The aim of this study was to investigate effects of FO administration during 12 weeks of programmed RET on muscular strength, resting metabolic rate (RMR), and systemic inflammation in healthy older adults.

METHODS

Twenty-eight healthy older adults were randomly assigned to three experimental groups: sedentary control (CON), resistance exercise training (RET), or RET combined with FO (RET-FO). A one-repetition (1RM) of maximum muscle strength, RMR, substrate oxidation, and blood inflammatory biomarkers were assessed before and after the intervention. Statistical significance was set at p ≤ 0.05.

RESULTS

1RM muscle strength was significantly increased in RET and RET-FO while substantially decreased in CON. RMR greatly increased in RET and RET-FO with no change in CON. RET-FO exhibited significantly increased fatty acid oxidation, but no change was found in CON and RET. Systemic interleukin 6 (IL-6) and C-reactive protein (CRP) were significantly decreased from baseline in RET-FO while no change was observed in CON and RET.

CONCLUSION

Our data indicate chronic RET reversed aging-induced loss of muscle strength and improved RMR, while FO administration combined with RET appears to enhance fat metabolism and mildly reduce some indicators of systemic inflammation.

Chronic Fish Oil Consumption with Resistance Training Improves Grip Strength, Physical Function, and Blood Pressure in Community-Dwelling Older Adults

Fish oil (FO) has received great attention for its health-enhancing properties. However, its potential synergistic effects with resistance training (RT) are not well established. The purpose of this study was to investigate the effects of FO supplementation during 12-weeks of RT on handgrip strength, physical function, and blood pressure (BP) in community-dwelling older adults. Twenty-eight healthy older adults (10 males, 18 females; 66.5 ± 5.0 years) were randomly assigned to three groups: Control (CON), resistance training (RT), resistance training with FO (RTFO). Handgrip strength, physical function [five times sit-to-stand (5T-STS), timed up and go (TUG), 6-m walk (6MW), 30-s sit-to-stand (30S-STS)], and BP were measured pre- and post-intervention. ANOVA was used with significance set at P ≤ 0.05. Handgrip strength significantly increased in RT (+5.3%) and RTFO (+9.4%) but decreased in CON (−3.9%). All physical function outcomes increased in RT and RTFO. CON exhibited significantly decreased TUG and 30S-STS with no change in 5T-STS and 6MW. BP substantially decreased only in RTFO, systolic blood pressure (−7.8 mmHg), diastolic blood pressure (−4.5 mmHg), mean arterial pressure (−5.6 mmHg), while no change was found in CON and RT. Chronic RT enhanced strength and physical function, while FO consumption combined with RT improved BP in community-dwelling older adults.

Effect of dietary fish oil supplementation on fever and cytokine production in human volunteers

The effect of dietary fish oil supplementation on acute phase responses to intramuscular injection of typhoid vaccine, and in vitro cytokine production, was investigated in human volunteers. Half of the subjects supplemented their normal diet with 4.5 g/day of fish oil for 6-8 weeks. Injection of typhoid vaccine in unsupplemented subjects caused an increase in white cell count, resting heart rate, metabolic rate, oxygen consumption, and oral temperature. Fish oil supplementation inhibited the tachycardia and attenuated the maximal increases in oral temperature and metabolic rate following typhoid vaccine. However, interpretation of these latter results were complicated by similarly attenuated responses in saline-injected subjects. The in vitro production of interleukin-1 and interleukin-6 from whole blood was suppressed by fish oil supplementation, however, production of tumor necrosis factor alpha was not significantly altered. Fish oil supplementation may therefore provide a non-pharmacological approach of attenuating several of the responses associated with injury and infection and this may be related to reduced cytokine (IL-1 and IL-6) production.

Dietary omega-3 fatty acid supplementation increases the rate of muscle protein synthesis in older adults: a randomized controlled trial

BACKGROUND

Loss of muscle mass with aging is a major public health concern. Omega-3 (n-3) fatty acids stimulate protein anabolism in animals and might therefore be useful for the treatment of sarcopenia. However, the effect of omega-3 fatty acids on human protein metabolism is unknown.

OBJECTIVE

The objective of this study was to evaluate the effect of omega-3 fatty acid supplementation on the rate of muscle protein synthesis in older adults.

DESIGN

Sixteen healthy, older adults were randomly assigned to receive either omega-3 fatty acids or corn oil for 8 wk. The rate of muscle protein synthesis and the phosphorylation of key elements of the anabolic signaling pathway were evaluated before and after supplementation during basal, postabsorptive conditions and during a hyperaminoacidemic-hyperinsulinemic clamp.

RESULTS

Corn oil supplementation had no effect on the muscle protein synthesis rate and the extent of anabolic signaling element phosphorylation in muscle. Omega-3 fatty acid supplementation had no effect on the basal rate of muscle protein synthesis (mean ± SEM: 0.051 ± 0.005%/h compared with 0.053 ± 0.008%/h before and after supplementation, respectively; P = 0.80) but augmented the hyperaminoacidemia-hyperinsulinemia-induced increase in the rate of muscle protein synthesis (from 0.009 ± 0.005%/h above basal values to 0.031 ± 0.003%/h above basal values; P < 0.01), which was accompanied by greater increases in muscle mTOR(Ser2448) (P = 0.08) and p70s6k(Thr389) (P < 0.01) phosphorylation.

CONCLUSION

Omega-3 fatty acids stimulate muscle protein synthesis in older adults and may be useful for the prevention and treatment of sarcopenia. This trial was registered at clinical trials.gov as NCT00794079.

Medium-chain triglyceride and n-3 polyunsaturated fatty acid-containing emulsions in intravenous nutrition

Medium-chain triglycerides and n-3 polyunsaturated fatty acid emulsions as a physical mixture have attracted increasing interest for use in parenteral nutrition and may play an important role in the development of structured triglycerides in a future generation of new lipids. Over the past two decades, the clinical use of intravenous emulsion for the nutritional support of hospitalized patients has relied exclusively on long-chain triglycerides providing both a safe, calorically dense alternative to dextrose and a source of essential fatty acids needed for biological membranes and maintenance of the immune function. During the past decade, the development of new triglycerides (medium- and long-chain triglyceride emulsions and structured triglyceride emulsions) for parenteral use have provided useful advances and opportunities to enhance nutritional and metabolic support. Medium-chain triglycerides and n-3 polyunsaturated fatty acid emulsions possess unique physical, chemical, and metabolic properties that make them theoretically advantageous over the conventional long-chain triglycerides. The physical mixture of medium- and long-chain triglycerides have been used clinically in patients with critical illness, liver disease, immunosuppression, pulmonary disease, and in premature infants, with good tolerance and the avoidance of some of the problems encountered with long-chain triglycerides alone.

Influence of n-6 and n-3 polyunsaturated fatty acids on the resistance to experimental tuberculosis

It has previously been shown that the n-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (20:5(n-3)) and docosahexaenoic acid (22:6(n-3)) possess antiinflammatory properties and can interfere with immune functions. To evaluate whether this would affect resistance to infection, we studied the influence of different types of fatty acids (FAs) on experimental tuberculosis in an animal model. Three groups of 26 weanling guinea pigs were fed isocaloric diets with 26 cal% fat that differed in FA composition with respect to saturated FAs, linoleic acid (18:2(n-6)), eicosapentaenoic acid (20:5(n-3)), and docosanexaenoic acid (22:6(n-3)) as follows: (1) reference (REF) group: 14.8 cal% saturated FAs and 2.8 cal% linoleic acid; (2) n-6 group: 4.6 cal% saturated FAs and 15.4 cal% linoleic acid; (3) n-3 group: 6.3 cal% saturated FAs, 10 cal% linoleic acid, 1.4 cal% eicosapentaenoic acid, and 0.9 cal% docosahexaenoic acid. After 13 weeks, 18 animals from each group were intramuscularly injected with 180 colony-forming units (CFU) Mycobacterium tuberculosis strain H37Rv. Eight noninfected animals per group served as controls. Seven weeks later, the mean number of mycobacteria recovered from the spleens of the n-3 group (log 4.34 CFU, standard error of the mean [SEM], 0.12) was significantly higher than from the REF group (log 3.90 CFU; SEM, 0.15) and the n-8 group (log 3.93 CFU; SEM, 0.13; P < .05). In addition, the Root Index of Virulence (RIV) showed the most pronounced progression of the disease in the n-3 group. The mean size of the tuberculin reaction was larger in the n-3 group than in the other groups (P < .05). There was no significant difference between the n-6 group and the REF group. We conclude that supplementing the diet with n-3 FAs eicosapentaenoic acid and docosahexaenoic acid can affect resistance to M tuberculosis, whereas supplementing with n-6 FAs does not.

Weight gain and increased concentrations of receptor proteins for tumor necrosis factor after patients with symptomatic HIV infection received fortified nutrition support

OBJECTIVE

To determine whether certain nutrients and dietary factors act as modulators of the immune system and improve the nutritional status of immunocompromised patients.

DESIGN

Controlled, double-blind, crossover phase trials of the effects of a fortified formula in patients infected with the human immunodeficiency virus (HIV). Patients consumed a control formula for 4 months and a study formula for 4 months.

SUBJECTS

Ten men with symptomatic HIV infection who were following stable medication regimens and had no malignancies, mycobacteriosis, or additional virus infection requiring systemic treatment.

INTERVENTION

Formula fortified with alpha-linolenic acid (1.8 g/day), arginine (7.8 g/day), and RNA (0.75 g/day) and a standard formula.

MAIN OUTCOME MEASURES

Nutritional status determined by anthropometric, bioelectrical, biochemical, and dietary assessment; energy expenditure determined by indirect calorimetry; disease progression; CD4 lymphocyte counts; HIV p24 antigen plasma concentrations; tumor necrosis factor (TNF) receptor proteins; and compliance control parameters.

STATISTICAL ANALYSES PERFORMED

Student's t tests for paired and unpaired data.

RESULTS

Fortified nutrition resulted in a weight gain (+ 2.9 kg/4 months vs -0.5 kg/4 months with the control formula, P < .05), an incorporation of eicosaenoic acid into erythrocyte cell membranes (+ 47% of baseline values, P < .05), and increased plasma arginine concentrations (96.8 +/- 45.1 vs 51.8 +/- 20.9 mumol/L, P < .01). The serum concentrations of the soluble tumor necrosis factor receptor (sTNFR) proteins increased during the study period (sTNFR 55 = + 0.23 vs -0.40 ng/mL, P < .001; sTNFR 75 = + 0.90 vs -0.36 ng/mL, P < .01), whereas no changes in CD4+ lymphocyte counts were observed.

CONCLUSION

Increasing dietary intakes of n-3 polyunsaturated fatty acids, L-arginine, and RNA increased body weight, possibly by modulating the negative effects of TNF.

Inhibition of the thermogenic and pyrogenic responses to interleukin-1 beta in the rat by dietary N-3 fatty acid supplementation

The thermogenic (increase in oxygen consumption, VO2) and pyrogenic (Tc) responses to the cytokine interleukin-1 beta (IL-1 beta) were studied in rats fed a n-3 fatty acid supplemented diet (8.75% n-3 fatty acids/kg diet). 4-6 weeks after commencing the diets, the n-3 supplemented rats exhibited reduced pyrogenic (0.5 +/- 0.1 degrees C versus 1.1 +/- 0.2 degrees C in control animals) and thermogenic (9 +/- 3% versus 22 +/- 6% in control animals) responses to intraperitoneal (i.p.) injection of IL-1 beta (1 micrograms/rat). However, responses to centrally administered IL-1 beta (5ng intracerebroventricular (i.c.v.)) were similar in both groups at this time. After 8-9 weeks of supplementation, n-3 supplemented animals exhibited attenuated responses to both ip IL-1 beta (VO2 responses reduced by 68% and Tc by 0.8 degrees C) and also i.c.v. IL-1 beta (VO2 responses reduced by 56% and Tc by 0.7 degrees C). N-3 supplementation did not, however, influence the thermogenic capacity of these animals since responses to noradrenaline were similar in control and n-3 fed animals (50% increase in VO2). These findings demonstrate that n-3 supplementation modifies the pyrogenic and thermogenic responses to IL-1 beta, probably via changes in eicosanoid metabolism. Modification of central responses to IL-1 are delayed compared to the effects of peripheral administration indicating separate mechanisms of IL-1 on fever and thermogenesis in the brain and the periphery.

Effect of fish oil on glucose metabolism in the interleukin-1 alpha-treated rat

Fish oil has been demonstrated to ameliorate many of the responses to infection. This study was conducted to determine whether fish oil feeding could modify the alterations of glucose metabolism induced by interleukin-1 alpha (IL-1 alpha) infusion in the rat. Male Sprague-Dawley rats were pair-fed for 5 weeks on two experimental diets in which the source of fat was either fish oil or soybean oil and provided 20% of calories; the diets were isonitrogenous and isocaloric. After 5 weeks of feeding, rats from both diet regimens were further divided into two subgroups to receive a 3-hour infusion of either 0.1% albumin in saline or 0.1% albumin in saline containing IL-1 alpha. A total of 20 micrograms/kg IL-1 alpha was administered, and half the dose of IL-1 alpha was given as a bolus and the remaining portion (10 micrograms/kg) was continuously infused into the jugular vein. During the last 2 hours of IL-1 alpha infusion, a primed constant infusion of D-(6-3H)glucose and D-(U-14C)glucose was combined to determine the effects of IL-1 alpha and diet on glucose kinetics. Plasma levels of glucose and insulin, energy expenditure, and respiratory quotient were also measured. IL-1 alpha significantly increased concentrations of plasma insulin and the percentage of glucose carbon recycling, confirming previous findings. Concentrations of glucose and insulin with IL-1 alpha treatment were significantly higher in soybean oil- fed animals compared with fish oil-fed animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutrition support and the human immunodeficiency virus (HIV)

Nutritional support of patients with HIV or acquired immune deficiency syndrome (AIDS) has many similarities to other disease states in that the same nutritional products and techniques are used. Some patients with HIV, and many with AIDS without secondary infection, experience a metabolic milieu similar to patients with cancer cachexia. In providing dietary counselling to the HIV patient, we encounter many of the obstacles that must be overcome to improve nutrition in cancer: anorexia, gastrointestinal discomfort, lethargy, and poor nutrient utilization, which limit the ability for nutritional repletion. When a secondary infection is superimposed on HIV, patients resemble more highly catabolic trauma patients or patients in the intensive care unit (ICU), where, despite aggressive efforts to feed, there is usually a net nitrogen wasting leading to the more rapid development of cachexia. However, even in this setting, feeding will limit substantially net catabolism when compared to total starvation. Because the nutritional needs of HIV patients vary greatly, individual strategies have to be designed as the patient moves through the stages of disease. Patients are generally able to consume adequate nutrition either as regular food or dietary supplements during the latency period of viral replication. Once secondary infections become prevalent, artificial diets administered by tube or by vein may be required during the period of active secondary infections, with dietary supplements often helpful during more quiescent periods. Patients with HIV are among the most challenging for clinicians providing nutritional support. Knowledge from treatment of patients with other diseases may be useful, but more data must be gathered on the unique aspects of aetiology and treatment of the anorexia, malabsorption, and ultimate wasting associated with AIDS.

The acute-phase response to turpentine-induced abscesses in malnourished rats at different environmental temperatures

An assessment was made of the independent effect environmental temperature (13, 21, and 30 degrees C) and either protein deficiency or energy deficiency on the metabolic response of rats that had aseptic abscesses induced by subcutaneous injections of turpentine. Measurements of food intake, alpha 2-macroglobulin (alpha 2-M; a major acute-phase protein in the rat), albumin, and various circulating metabolites were made 48 hours after turpentine injection in animals acclimatized at 13, 21, and 30 degrees C and compared with pair-fed controls. Despite differences in basal circulating albumin concentrations between controls and protein deficient rats (P less than .001), turpentine produced a similar reduction in all groups of animals (approximately 10 g/L), independent of environmental temperature. The alpha 2-M response to turpentine was attenuated in all protein-deficient animals and also in the energy-restricted animals at 13 degrees C. The increase in circulating 3-hydroxybutyrate (BOH) and nonesterified fatty acid (NEFA) concentrations, which normally occur with reduced dietary intake, was reduced in the turpentine-injected animals to an extent that depended on prior dietary intake. It is concluded that the metabolic response, particularly the acute-phase protein response, to a standard form of "injury" is affected by protein deficiency and possibly by energy restriction under adverse environmental temperature.

Comparative effects of omega-3 and omega-6 polyunsaturated fatty acids on protein metabolism in rats bearing the mammary adenocarcinoma

The comparative effects of diets containing 20% (wt/wt) of either fish oil (FO) or safflower oil (SO) on protein synthesis and catabolism were determined in rats bearing the 7,12-dimethylbenz(a)anthracene (DMBA) 13762 mammary adenocarcinoma in vivo using a 6-hour constant infusion of L-(1-14C)-leucine. Tumor-bearing animals fed FO had significantly lower tumor growth rate (36 +/- 0.5 v 53 +/- 0.7%/d, P less than .05), total tumor protein synthesis (Ts) (1.25 +/- 0.1 v 1.85 +/- 0.1 mumol/h, P less than .05), and tumor protein concentration (12.0 +/- 0.5 v 14.0 +/- 0.7%/d, P less than 0.01). Tumor fractional synthetic rate and total protein breakdown rate of the tumor were unaffected by FO feeding. Both tumor-bearing and saline-control animals fed FO had significantly (P less than .01) lower liver fractional synthetic rate and total protein breakdown rate, and higher liver total protein compared with SO-fed rats. Muscle protein kinetics were unaffected by either treatment or diet. Whole body protein kinetics were not affected by dietary treatment, but the presence of tumor significantly (P less than .001) reduced whole body flux, synthesis, breakdown, and oxidation. Chronic FO feeding for 7 weeks significantly (P less than .001) lowered omega-6 polyunsaturated fatty acids (omega-6 PUFAs) and significantly elevated omega-3 polyunsaturated fatty acids (omega-3 PUFAs) (P less than .001) in both plasma phospholipid and triglycerides. The present study indicates that dietary FO can modulate mammary tumor growth in a manner that reflects changes in protein metabolism in both host and tumor tissues.

Persistence of metabolic effects after long-term oral feeding of a structured triglyceride derived from medium-chain triglyceride and fish oil in burned and normal rats

The persistence of metabolic effects following long-term oral feeding of a structured triglyceride rich in omega-3 fatty acids was studied in burned and normal rats, and compared with controls fed safflower oil, a long-chain triglyceride high in omega-6 fatty acid content. Male Sprague-Dawley rats were pair-fed a high fat diet as either structured triglyceride or safflower oil for 42 days. On day 43, a jugular catheter was placed, and rats received either a dorsal surface scald or sham injury. Following a 48-hour fast, body weight, nitrogen loss, energy metabolism, and liver weight were measured, and whole-body and tissue-specific protein kinetics were studied by constant intravenous infusion of [1-14C]leucine. Plasma albumin, free fatty acids, glucose, insulin, and triglyceride fatty acid composition were determined. Urinary nitrogen loss, energy expenditure, and plasma leucine concentration were elevated in burned rats, confirming the presence of an injury response. Rats previously fed structured triglyceride had greater liver weight, total liver protein, and percentage of leucine flux oxidized, and plasma levels of glucose and insulin were increased. Plasma leucine concentration was decreased in rats previously fed structured triglyceride. Plasma triglyceride and phospholipid fatty acid analysis showed a reduction in arachidonic acid and an increase in omega-3 fatty acids in rats previously fed structured triglyceride. Long-term feeding of structured triglyceride induced major systemic metabolic changes related to the dietary fatty acid composition that persist after the diet is discontinued.