Dietary (n-6) and (n-3) fatty acids and energy restriction modulate mesenteric lymph node lymphocyte function in autoimmune-prone (NZB x NZW)F1 mice

We previously showed that dietary fish oil (FO) and energy restriction (R) have beneficial anti-inflammatory properties in the peripheral blood and spleens of (NZB x NZW)F1 (B/W) lupus-prone mice. Furthermore, unsaturated fatty acids also were shown in the past to influence mesenteric lymph node (MLN) lymphocyte function in healthy young rats. The MLN play a pivotal role in mediating food allergy. To date, the effect of R on intestinal immunity is not well understood; therefore we determined the effect of diet on MLN lymphocyte function. Mice were given either free access to a 5 g/100 g corn oil (CO) or fish oil (FO) diet or the same corn oil (CR) or fish oil (FR) diets restricted to 60% of the intake of the control group. At the age of 4 (young) and 8 (old) mo, MLN lymphocytes were isolated and B- (CD19(+)) and T-lymphocyte subsets (CD4(+) and CD8(+)) were determined by flow cytometry. Additional MLN lymphocytes were placed in culture with or without concanavalin A and culture supernatants collected after 72 h for cytokine and immunoglobulin (Ig) quantitation by ELISA. Aging significantly (P < 0.05) decreased both CD4(+) and CD8(+) T-lymphocytes. Spontaneous and activation-induced interleukin-4 (IL-4), IL-10, and interferon-gamma secretion were greater while IL-2 was lower in CO-fed old mice compared to CO-fed young mice. In contrast, CR or FO alone partially blunted the age-dependent alterations in T-lymphocyte ratios including cytokine and Ig secretion, whereas the FR diet significantly (P < 0.005) normalized the accelerated aging effects on these immune variables. We show for the first time that FR is a far more potent anti-inflammatory therapy than either CR or FO alone in modulating MLN lymphocyte function.     

Inflammation: roles in aging and sarcopenia

Aging is associated with inflammatory chronic conditions such as obesity, cardiovascular disease, insulin resistance, and arthritis. Sarcopenia-muscle loss with aging-is multifactorial with contributing factors that may include loss of alpha-motor neuron input, changes in anabolic hormones, decreased intake of dietary protein, and decline in physical activity. Research findings suggest that sarcopenia is a smoldering inflammatory state driven by cytokines and oxidative stress. Elevated levels of interleukin-6 and C-reactive protein are often detected. Sarcopenic obesity manifests the added inflammatory burden of adiposity and associated adipokines. Potential interventions for sarcopenia include nutritional supplements, physical activity/resistance exercise, caloric restriction, anabolic hormones, anti-inflammatory agents, and antioxidants. A key question is whether sarcopenia is truly a distinct syndrome or a milder form of a cachexia continuum.     

Protein and exercise in the prevention of sarcopenia and aging

Aging is associated with a progressive decline in skeletal muscle mass and strength. The decline, known as sarcopenia, could lead to physical disability, poor quality of life, and death. In addition, the older population usually experiences age-related muscle changes that affect muscle mass, muscular strength, and functional abilities. The purpose of this review is to describe the role of protein and exercise in slowing the progression of sarcopenia. It will also discuss whether age-related changes can be attenuated by dietary protein and exercise in the older population. This review will also cover one of the possible mechanisms of how dietary protein and exercise are involved in sarcopenia prevention, as well as the available measurement tools. Based on the findings of this review, the adequate amount of protein required for older men and women needs to be revised and likely be higher. Moreover, studies are required to explore some inconclusive findings concerning sarcopenia in the older population. Further research is required to investigate the following: (1) the safety and effectiveness concerning the consumption of 1.4 g of protein/kg of body weight (or more) in this vulnerable population; (2) the effectiveness of amino acid supplementation in reducing progression of sarcopenia over time through longitudinal studies; (3) the preferred source and timing of protein for the older population to maintain muscular strength and attenuate sarcopenia; (4) exercise interventions, especially those of longer duration, in the attenuation of sarcopenia; (5) other types of exercise and their effects on age-related muscle changes; (6) the mechanism of how protein and exercise prevent muscle loss with aging; and (7) determine the best method to diagnose sarcopenia.     

Effects of Conjugated Linoleic Acid on Myogenic and Inflammatory Responses in a Human Primary Muscle and Tumor Coculture Model

The antiproliferative and anti-inflammatory properties of conjugated linoleic acid (CLA) make it a potentially novel treatment in chronic inflammatory muscle wasting disease, particularly cancer cachexia. Human primary muscle cells were grown in coculture with MIA PaCa-2 pancreatic tumor cells and exposed to varying concentrations of c9,t11 and t10,c12 CLA. Expression of myogenic (Myf5, MyoD, myogenin, and myostatin) and inflammatory genes (CCL-2, COX-2, IL-8, and TNF-α) were measured by real-time PCR. The t10,c12 CLA isomer, but not the c9,t11 isomer, significantly decreased MIA PaCa-2 proliferation by between 15% and 19%. There was a marked decrease in muscle MyoD and myogenin expression (78% and 62%, respectively), but no change in either Myf5 or myostatin, in myotubes grown in coculture with MIA PaCa-2 cells. CLA had limited influence on these responses. A similar pattern of myogenic gene expression changes was observed in myotubes treated with TNF-α alone. Several-fold significant increases in CCL-2, COX-2, IL-8, and TNF-α expression in myotubes were observed with MIA PaCa-2 coculture. The c9,t11 CLA isomer significantly decreased basal expression of TNF-α in myotubes and could ameliorate its tumor-induced rise. The study provides insight into the anti-inflammatory and antiproliferative actions of CLA and its application as a therapeutic agent in inflammatory disease states.     

Insulin-like growth factor-I, but not growth hormone, is dependent on a high protein intake to increase nitrogen balance in the rat.

The aim of the present study was to investigate the influence of dietary protein level on the protein anabolic effects of growth hormone (GH) and insulin-like growth factor-I (IGF-I). Female growing rats were fed on either a high- or a low-protein diet with crude protein contents of 222 and 83 g/kg respectively. The diets contained the same amount of metabolizable energy (15.1 MJ/kg) and were given during a 14 d period. During the same time, three groups of rats (n 8) on each diet received subcutaneous infusions of either saline, recombinant human GH (rhGH) or recombinant human IGF-I (rhIGF-I). rhGH and rhIGF-I were given in doses of 360 and 500 micrograms/d respectively. The low-protein diet alone reduced significantly (P < 0.05) IGF-I concentrations in serum and in tissue taken from the gastrocnemius muscle as well as IGF-I mRNA from the same muscle. The responses to rhGH and rhIGF-I in terms of muscle IGF-I and its mRNA were variable. However, when rhIGF-I was infused into rats on the high-protein diet, significantly elevated levels of IGF-I in muscle tissues could be observed. This was associated with a significantly (P < 0.05) increased N balance, whereas rhGH significantly (P < 0.05) enhanced the N balance in rats on the low-protein diet. Thus, it can be concluded that the level of dietary protein ingested regulates not only the effect of IGF-I on whole-body N economy but also the regulation of IGF-I gene expression in muscles. The exact mechanism by which GH exerts its protein anabolic effect, however, remains to be elucidated.     

Muscle protein metabolism during compensatory growth with changing dietary lysine levels from deficient to sufficient in growing rats

Livestock and laboratory animals show compensatory growth when they are fed ad libitum following a period of restriction feeding. Lysine is a major limiting essential amino acid in the diets both for humans and animals. We hypothesized that changing dietary lysine levels from deficient to sufficient induced compensatory growth in young rats. We elucidated the effect of lysine sufficiency on the dynamics of hormones, relevant to muscle protein synthesis and degradation, insulin-like growth factor-I (IGF-I) and corticosterone, and on the expression of proteolytic-related genes in skeletal muscle during compensatory growth. Lysine sufficiency where the dietary lysine level was increased from 0.46% to 1.30% after 2 wk of subjecting the rats to the lower lysine level induced 80% enhancement of growth rate of rats. During compensatory growth with the lysine sufficiency, fractional muscle protein synthesis rates were higher whereas fractional muscle protein degradation rates were lower than those of the control group (p<0.05). After lysine sufficiency, the expression of atrogin-1/MAFbx mRNA was decreased in gastrocnemius muscle (p<0.05). With the lysine sufficiency, serum IGF-I concentration increased (p<0.05) whereas serum corticosterone decreased (p<0.05). These findings suggest that compensatory growth with lysine sufficiency is due to a change of hormone levels before and after changing diets, resulting in incrementation of protein synthesis and suppression of protein degradation of skeletal muscle.     

Research hypotheses on muscle wasting, aging, loss of function and disability

Advancing age is accompanied by modifications in body composition such as increase in fat and decrease in bone and muscle mass. Loss of muscle mass or sarcopenia is characterized by a decrease in the total number of muscle fibers, a reduced cross-sectional area of the thigh, and decreased muscle density associated with increased intramuscular fat. Loss of skeletal muscle mass may be a common pathway by which multiple diseases contribute to the risk of disability. Decreases in muscle mass are associated with an increased risk of morbidity, mortality and disability in old age, but the mechanisms by which this occurs are not fully understood. Inflammatory cytokines interfere with muscle contraction and are linked with sarcopenia. Recent evidence showing that decline in left ventricular function is accompanied by sarcopenia and an increase in cytokines might help to understand the role of cytokines in muscle loss in aging and disease. The Health and Body Changes (Health ABC) study, a large population-based cohort study sponsored by the National Institute on Aging, will prospectively address the issues related to sarcopenia and incident disability. Defining modifiable risk factors of sarcopenia is the first step towards the identification of interventions for preventing or reversing disability in older persons.     

Magnesium Lithospermate B Attenuates High-Fat Diet-Induced Muscle Atrophy in C57BL/6J Mice

Magnesium lithospermate B (MLB) is a primary hydrophilic component of Danshen, the dried root of Salvia miltiorrhiza used in traditional medicine, and its beneficial effects on obesity-associated metabolic abnormalities were reported in our previous study. The present study investigated the anti-muscle atrophy potential of MLB in mice with high-fat diet (HFD)-induced obesity. In addition to metabolic abnormalities, the HFD mice had a net loss of skeletal muscle weight and muscle fibers and high levels of muscle-specific ubiquitin E3 ligases, namely the muscle atrophy F-box (MAFbx) and muscle RING finger protein 1 (MuRF-1). MLB supplementation alleviated those health concerns. Parallel changes were revealed in high circulating tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), skeletal TNF receptor I (TNFRI), nuclear factor-kappa light chain enhancer of activated B cells (NF-κB), p65 phosphorylation, and Forkhead box protein O1 (FoxO1) as well as low skeletal phosphoinositide 3-kinase (PI3K) and protein kinase B (Akt) phosphorylation. The study revealed that MLB prevented obesity-associated skeletal muscle atrophy, likely through the inhibition of MAFbx/MuRF-1-mediated muscular degradation. The activation of the PI3K-Akt-FoxO1 pathway and inhibition of the TNF-α/TNFRI/NF-κB pathway were assumed to be beneficial effects of MLB.     

Antioxidant supplementation restores defective leucine stimulation of protein synthesis in skeletal muscle from old rats

Aging is characterized by a progressive loss of muscle mass that could be partly explained by a defect in the anabolic effect of food intake. We previously reported that this defect resulted from a decrease in the protein synthesis response to leucine in muscles from old rats. Because aging is associated with changes in oxidative status, we hypothesized that reactive oxygen species-induced oxidative damage may be involved in the impairment of the anabolic effect of leucine with age. The present study assessed the effect of antioxidant supplementation on leucine-regulated protein metabolism in muscles from adult and old rats. Four groups of 8- and 20-mo-old male rats were supplemented or not for 7 wk with an antioxidant mixture containing rutin, vitamin E, vitamin A, zinc, and selenium. At the end of supplementation, muscle protein metabolism was examined in vitro using epitrochlearis muscles incubated with increasing leucine concentrations. In old rats, the ability of leucine to stimulate muscle protein synthesis was significantly decreased compared with adults. This defect was reversed when old rats were supplemented with antioxidants. It was not related to increased oxidative damage to 70-kDa ribosomal protein S6 kinase that is involved in amino acid signaling. These effects could be mediated through a reduction in the inflammatory state, which decreased with antioxidant supplementation. Antioxidant supplementation could benefit muscle protein metabolism during aging, but further studies are needed to determine the mechanism involved and to establish if it could be a useful nutritional tool to slow down sarcopenia with longer supplementation.     

Association of Sarcopenia and Expression of Interleukin-16 in Gastric Cancer Survival

We designed the present work to explore the connection between sarcopenia and interleukin-16 (IL-16) expression and their integrated relation with gastric cancer (GC) survival. We deemed the sex-specific third lumbar vertebra skeletal muscle index cutoffs for sarcopenia to be ≤40.8 and ≤34.9 cm²/m² in male and female patients, respectively. Immunohistochemistry was carried out to detect IL-16 levels among GC tissues of the patients. We determined overall survival (OS) and relapse-free survival (RFS) by univariate and multivariate analyses. This study included 225 GC cases, with an average age of 62.7 years. There were 41 (18.2%) female patients, and 107 (47.5%) patients had sarcopenia. Sarcopenia and high IL-16 expression were identified as independent factors to predict OS (hazard ratios [HR] = 1.64 and 1.79, 95% confidence interval [CI] = 1.25–2.23 and 1.16–2.78, respectively) and RFS (HR = 1.43 and 1.60, 95% CI = 1.15–2.95 and 1.10–2.37, respectively). There were more cases showing high IL-16 expression detected in the sarcopenia group (55.7% vs. 37.3%, p = 0.003). Later, we grouped the patients with sarcopenia and IL-16 expression and discovered that the patients with sarcopenia and IL-16 upregulation displayed the poorest OS (HR = 3.02; 95% CI = 1.64–5.91) and RFS (HR = 2.34; 95% CI = 1.47–4.69). In conclusion, more IL-16 upregulation was noted in GC patients with sarcopenia. Sarcopenia accompanied by high IL-16 expression remarkably indicates a dismal prognosis in GC patients. This suggests that these biomarkers may be able to identify patients with GC with poor prognosis and enhance prognostication.     

Does Long‐Term Intermittent Treatment With Glutamine Improve the Well‐being of Fed and Fasted Very Old Rats?

BACKGROUND: Glutamine is known to have a specific role in very old rats (>25 months of age). For this reason, we have orally supplemented female rats with glutamine (20% of diet protein) intermittently. The treatment started before animals became very old and lasted 5 months. Very old rats were studied in fed state or after 5-day fasting after the last glutamine cure. The aim of this study was to determine whether this in vivo pretreatment improves the well-being of very old rats (muscle sarcopenia decrease, gut integrity improvement, decrease of the known up-regulated glutamine synthetase observed regardless of nutrition state). METHODS: Protein turnover was measured in epitrochlearis muscle, whereas glutamine synthetase (GS) activities were assessed in tibialis anterior muscle from fed and 5-days-fasted female Wistar adult (6 months) and very old (27 months) rats, pretreated or not with glutamine. Furthermore, gut was dissected and weighed. RESULTS: Long-term treatment with glutamine had positive effects on very old rats: (1) it prevented the loss of body weight, but, (2) it did not prevent the inevitable sarcopenia regardless of nutrition state, and (3) it maintained the gut mass. Surprisingly, the muscle up-regulated GS activity observed in fed and fasted very old rats was only decreased in the fed state when rats were supplemented, without change in plasma and muscle glutamine concentrations. CONCLUSIONS: Long-term treatment with glutamine started before advanced age had essentially a beneficial role on the gut. It may play a role in maintaining intestine integrity and intestinal immune function. Further investigations would be warranted to explore these mechanisms.     

Attenuation of Oxidative Stress and Inflammatory Response by Chronic Cannabidiol Administration Is Associated with Improved n-6/n-3 PUFA Ratio in the White and Red Skeletal Muscle in a Rat Model of High-Fat Diet-Induced Obesity

The consumption of fatty acids has increased drastically, exceeding the nutritional requirements of an individual and leading to numerous metabolic disorders. Recent data indicate a growing interest in using cannabidiol (CBD) as an agent with beneficial effects in the treatment of obesity. Therefore, our aim was to investigate the influence of chronic CBD administration on the n-6/n-3 polyunsaturated fatty acids (PUFAs) ratio in different lipid fractions, inflammatory pathway and oxidative stress parameters in the white and red gastrocnemius muscle. All the designed experiments were performed on Wistar rats fed a high-fat diet (HFD) or a standard rodent diet for seven weeks and subsequently injected with CBD (10 mg/kg once daily for two weeks) or its vehicle. Lipid content and oxidative stress parameters were assessed using gas–liquid chromatography (GLC), colorimetric and/or immunoenzymatic methods, respectively. The total expression of proteins of an inflammatory pathway was measured by Western blotting. Our results revealed that fatty acids (FAs) oversupply is associated with an increasing oxidative stress and inflammatory response, which results in an excessive accumulation of FAs, especially of n-6 PUFAs, in skeletal muscles. We showed that CBD significantly improved the n-6/n-3 PUFA ratio and shifted the equilibrium towards anti-inflammatory n-3 PUFAs, particularly in the red gastrocnemius muscle. Additionally, CBD prevented generation of lipid peroxidation products and attenuated inflammatory response in both types of skeletal muscle. In summary, the results mentioned above indicate that CBD presents potential therapeutic properties with respect to the treatment of obesity and related disturbances.     

Effect of protein intake on bone and muscle mass in the elderly

The aging process is frequently characterized by an involuntary loss of muscle (sarcopenia) and bone (osteoporosis) mass. Both chronic diseases are associated with decreased metabolic rate, increased risk of falls/fracture, and, as a result, increased morbidity and loss of independence in the elderly. The quality and quantity of protein intake affects bone and muscle mass in several ways and there is evidence that increased essential amino acid or protein availability can enhance muscle protein synthesis and anabolism, as well as improve bone homeostasis in older subjects. A thorough evaluation of renal function is important, since renal function decreases with age. Finally, protein and calcium intake should be considered in the prevention or treatment of the chronic diseases osteoporosis and sarcopenia.     

Ornithine alpha-ketoglutarate: Could it be a new therapeutic option for sarcopenia?

Our current knowledge on the causes of sarcopenia is still fragmentary. One of the most evident candidates to explain muscle loss in elderly includes imbalance in protein turnover, i.e. decreased muscle protein synthesis rate, notably in the post-prandial state. Nutritional strategies such as leucine supplementation, use of fast digested proteins or a pulse protein intake have been show to enhance the synthesis rate of muscle proteins in older individuals. Ornithine alpha-ketoglutarate (OKG) is a precursor of amino acids such as glutamine, arginine and proline, and increases the secretion of anabolic hormones, i.e. insulin and growth hormone. A beneficial anabolic action of OKG has been demonstrate in several pathological conditions associated with muscle loss. Therefore, OKG may be of a potential interest to modulate muscle protein metabolism and to maintain muscle mass during aging.     

β-Sitosterol Attenuates Dexamethasone-Induced Muscle Atrophy via Regulating FoxO1-Dependent Signaling in C2C12 Cell and Mice Model

Sarcopenia refers to a decline in muscle mass and strength with age, causing significant impairment in the ability to carry out normal daily functions and increased risk of falls and fractures, eventually leading to loss of independence. Maintaining protein homeostasis is an important factor in preventing muscle loss, and the decrease in muscle mass is caused by an imbalance between anabolism and catabolism of muscle proteins. Although β-sitosterol has various effects such as anti-inflammatory, protective effect against nonalcoholic fatty liver disease (NAFLD), antioxidant, and antidiabetic activity, the mechanism of β-sitosterol effect on the catabolic pathway was not well known. β-sitosterol was assessed in vitro and in vivo using a dexamethasone-induced muscle atrophy mice model and C2C12 myoblasts. β-sitosterol protected mice from dexamethasone-induced muscle mass loss. The thickness of gastrocnemius muscle myofibers was increased in dexamethasone with the β-sitosterol treatment group (DS). Grip strength and creatine kinase (CK) activity were also recovered when β-sitosterol was treated. The muscle loss inhibitory efficacy of β-sitosterol in dexamethasone-induced muscle atrophy in C2C12 myotube was also verified in C2C12 myoblast. β-sitosterol also recovered the width of myotubes. The protein expression of muscle atrophy F-box (MAFbx) was increased in dexamethasone-treated animal models and C2C12 myoblast, but it was reduced when β-sitosterol was treated. MuRF1 also showed similar results to MAFbx in the mRNA level of C2C12 myotubes. In addition, in the gastrocnemius and tibialis anterior muscles of mouse models, Forkhead Box O1 (FoxO1) protein was increased in the dexamethasone-treated group (Dexa) compared with the control group and reduced in the DS group. Therefore, β-sitosterol would be a potential treatment agent for aging sarcopenia.     

The danger of weight loss in the elderly

Aging is generally accompanied by weight loss made up of both fat mass and fat-free mass. As more people, including elderly, are overweight or obese, weight loss is recommended to improve health. Health risks are decreased in overweight children and adults by dieting and exercise, but the health benefits of weight loss in elderly, particularly by calorie restriction, are uncertain. Rapid unintentional weight loss in elderly is usually indicative of underlying disease and accelerates the muscle loss which normally occurs with aging. Intentional weight loss, even when excess fat mass is targeted also includes accelerated muscle loss which has been shown in older persons to correlate negatively with functional capacity for independent living. Sarcopenic obesity, the coexistence of diminished lean mass and increased fat mass, characterizes a population particularly at risk for functional impairment since both sarcopenia (relative deficiency of skeletal muscle mass and strength) and obesity have been shown to predict disability. However, indices of overweight and obesity such as body mass index (BMI) do not correlate as strongly with adverse health outcomes such as cardiovascular disease in elderly as compared to younger individuals. Further, weight loss and low BMI in older persons are associated with mortality in some studies. On the other hand, studies have shown improvement in risk factors after weight loss in overweight/obese elderly. The recent focus on pro-inflammatory factors related to adiposity suggest that fat loss could ameliorate some catabolic conditions of aging since some cytokines may directly impact muscle protein synthesis and breakdown. Simply decreasing weight may also ease mechanical burden on weak joints and muscle, thus improving mobility. However, until a strategy is proven whereby further loss of muscle mass can be prevented, weight loss by caloric restriction in individuals with sarcopenic obesity should likely be avoided.     

The Usefulness of an Alternative Diagnostic Method for Sarcopenia Using Thickness and Echo Intensity of Lower Leg Muscles in Older Males

ObjectivesSarcopenia is diagnosed on the basis of skeletal muscle mass and muscle strength/function; however, simpler and more accurate measures for muscle mass and muscle strength/function should be explored using ultrasonography. This study aimed to investigate a new screening method using ultrasonography to diagnose sarcopenia of lower leg muscles in older males.DesignCross-sectional study.Setting and subjectsA total of 60 males, aged 65 years or older, participated in this study.MeasuresThe muscle thickness (MT) and echo intensity (EI) of the lower leg muscles were measured using ultrasonography, and the physical functions were examined. The MT and EI values of the lower leg muscles for predicting low appendicular skeletal muscle mass index (ASMI) and low grip strength were analyzed using receiver operating characteristic curve analysis and significant cutoff values were observed. A binary logistic regression analysis was performed with an MT below the cutoff value or an EI above the cutoff value as the independent variable, and with sarcopenia according to the Asian Working Group for Sarcopenia criterion as the dependent variable.ResultsUsing the optimal cutoff points of MT and EI for predicting a low ASMI and low grip strength, the MT of the tibialis anterior (TA), the EI of the TA and gastrocnemius, and the MT/EI index of the TA and soleus were found to be associated with sarcopenia after adjusting for age, body mass index, calf circumference, presence of diabetes mellitus, and statin use in the binary logistic regression model. In addition, the combined MT and EI of the TA showed predictability with respect to sarcopenia.Conclusions/RelevanceUltrasonographic assessment of lower leg muscles might be useful as a convenient approach for detecting sarcopenia. In particular, the determination of both MT and EI of the TA should be considered as an alternative method of screening for sarcopenia.     

Dietary fish oil increases tumor necrosis factor secretion but decreases interleukin-10 secretion by murine peritoneal macrophages

Dietary fish oil has immunomodulatory effects that are mediated in part by its effects on cytokines. Secretion of the inflammatory and the anti-inflammatory cytokines tumor necrosis factor (TNF) and interleukin (IL)-10 by murine resident peritoneal macrophages was monitored after ex vivo stimulation with lipopolysaccharide. Macrophages were obtained from mice fed a corn oil diet containing 200 g/kg corn oil or a fish oil diet containing 180 g/kg fish oil and 20 g/kg corn oil. Dietary fish oil increased secretion of the proinflammatory cytokine, TNF, but decreased secretion of the anti-inflammatory cytokine, IL-10. The cytokines appeared in the medium after 1.5 h and peaked at 6-12 h. Neutralizing antibodies against TNF and IL-10 had little effect on secretion of the other cytokine, indicating that the effects of fish oil on TNF and IL-10 secretion by these cells are independent of one another. Furthermore, although inhibiting prostaglandin production enhanced TNF secretion by macrophages from mice fed the corn oil diet, it did not affect IL-10 secretion by macrophages in this group. Blocking leukotriene B(4) production also did not affect IL-10 secretion in macrophages from mice fed a nonpurified diet. These results demonstrate that fish oil has an overall pro-inflammatory effect given its effects on secretion of both inflammatory and anti-inflammatory cytokines by resident peritoneal macrophages.