Effect of tumor necrosis factor-alpha on triglyceride and phospholipid content and fatty acid composition of liver and carcass in rats

Metabolic signature of HepaRG cells exposed to ethanol and tumor necrosis factor alpha to study alcoholic steatohepatitis by LC-MS-based untargeted metabolomics

Despite the high prevalence of alcoholic liver disease, its identification and characterization remain poor, especially in early stages such as alcoholic fatty liver disease and alcoholic steatohepatitis. This latter implies diagnostic difficulties, few therapeutic options and unclear mechanisms of action. To elucidate the metabolic alterations and pinpoint affected biochemical pathways, alcoholic steatohepatitis was simulated in vitro by exposing HepaRG cells to ethanol (IC₁₀, 368 mM) and tumor necrosis factor alpha (TNF-α, 50 ng/mL) for 24 h. This combined exposure was compared to solely ethanol-exposed as well as -nonexposed cells. Four different metabolomics platforms were used combining liquid chromatography, high-resolution mass spectrometry and drift tube ion mobility to elucidate both intracellular and extracellular metabolic alterations. Some of the key findings include the influence of TNF-α in the upregulation of hepatic triglycerides and the downregulation of hepatic phosphatidylethanolamines and phosphatidylcholines. S-Adenosylmethionine showed to play a central role in the progression of alcoholic steatohepatitis. In addition, fatty acyl esters of hydroxy fatty acid (FAHFA)-containing triglycerides were detected for the first time in human hepatocytes and their alterations showed a potentially important role during the progression of alcoholic steatohepatitis. Ethoxylated phosphorylcholine was identified as a potential new biomarker of ethanol exposure.

The role of pro-inflammatory cytokines in lipid metabolism of metabolic diseases

Adipose tissue has been considered as a crucial source of certain pro-inflammatory cytokines; conversely, these pro-inflammatory cytokines are involved in regulating the proliferation and apoptosis of adipocytes, promoting lipolysis, inhibiting lipid synthesis and decreasing blood lipids, etc. In recent decades, extensive studies have indicated that pro-inflammatory cytokines play important roles in the development of lipid metabolism of metabolic diseases, including obesity, atherosclerosis, steatohepatitis and hyperlipoproteinemia. However, the involved pro-inflammatory cytokines types and the underlying mechanisms remain largely unknown. The "re-discovery" of cancer as a metabolic disorder largely occurred in the last five years. Although pro-inflammatory cytokines have been intensively investigated in cancer research, there are very few studies about the roles of pro-inflammatory cytokines in the lipid metabolism of cancer. In the current review, we provide an overview of the progress that has been made in the roles of different pro-inflammatory cytokines in lipid metabolism of metabolic diseases including cancer.

Phospholipid Fatty Acid Composition and Diamine Oxidase Activity of Intestinal Mucosa From Rats Treated With Irinotecan Hydrochloride (CPT-11) under Vegetable Oil–Enriched Diets: Comparison Between Perilla Oil and Corn Oil

BACKGROUND

Irinotecan hydrochloride (CPT-11), a topoisomerase I inhibitor highly effective for various cancers, has its dosage limited by diffuse mucosal damage with increased prostaglandin (PG) E(2). However, an analysis of intestinal phospholipid fatty acid composition after CPT-11 treatment has not been reported. This study aimed to evaluate intestinal phospholipid fatty acid composition in relation to intestinal mucosal integrity and plasma and mucosal PGE(2) levels after CPT-11 treatment. The effect of dietary vegetable oil supplementation, perilla oil vs corn oil, was also evaluated.

METHODS

Intestinal phospholipid fatty acid composition, PGE(2) level, mucosal diamine oxidase (DAO) activity, diarrhea, and blood tests were evaluated in rats injected with CPT-11 under a conventional diet. The same parameters were compared among 3 different dietary vegetable oil supplementations: perilla oil, corn oil, and a 1:3, respectively, mixture with a semisynthetic diet during 14 days.

RESULTS

CPT-11 treatment caused severe diarrhea, and intestinal mucosal fatty acid composition changed with increased PGE(2) level and decreased DAO activity. Decreases in eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and EPA/arachidonic acid (AA) ratio in colonic mucosa were observed. Perilla oil increased omega-3 polyunsaturated fatty acids, alpha-linolenic acid, EPA, and EPA/AA ratio and decreased plasma PGE(2). But the amounts used were not enough to attenuate intestinal damage from CPT-11 treatment.

CONCLUSIONS

CPT-11 induced changes of intestinal mucosal fatty acid composition with increased PGE(2) level and decreased intestinal integrity; perilla oil shows the possibility of being able to attenuate those changes.

[The effect of N-stearoylethanolamine on liver phospholipid composition of rats with insulin resistance caused by alimentary obesity]

We used alimentary obesity-induced insulin resistance (IR) model in rats to investigate the influence of N-stearoylethanolamine on the content of phospholipids and their fatty acid composition. Our results show that prolonged high-fat diet triggers considerable aberrations in the composition of main phospholipids in the liver and can be one of the causes of IR in rats. In particular, the increase of phosphatidylcholine, phosphatidylethanolamine and significant decrease of other phospholipids: lysophosphatidylcholine, lysophosphatidylethanolamine, sphingomyelin, phosphatidylinositol, phosphatidylserine and diphosphaglicerol were observed. The levels of monounsaturated (erucic, nervonic, oleic) and polyunsaturated (eicosatrienoic, docosatrienoic, arachidonic) fatty acids were increased; meanwhile the content of diunsaturated acids was decreased. The NSE administration (50 mg/kg of body weight) caused restoration of the phospholipids content in the liver of rats with diet-induced IR that highly correlated with the decrease in plasma insulin level and the improvement of insulin sensitivity. Moreover, the effect of NSE was accompanied by the normalization of fatty acids composition of phospholipids that could be related to modulating influence of NSE on the activity of the main fatty acid desaturases. It is known that the imbalance in phospholipid composition of the rat liver causes substantial metabolic alterations that are associated with the development of IR. Accordingly, the compensations of the imbalance by NSE can help to restore insulin sensitivity, inhibit the development of obesity, IR and type 2 diabetes.

TNF-alpha, a potent lipid metabolism regulator

As a multifunctional cytokine, tumor necrosis factor alpha (TNF-alpha) exerts a series of biological actions in different cells, tissues, organs, and species and has been demonstrated to regulate and interfere with energy metabolism, especially lipid homeostasis. A large body of researches suggested that the effects of TNF-alpha on lipid metabolism mainly include five aspects: (1) suppresses free fatty acid (FFA) uptake and promotes lipogenesis; (2) induces lipolysis; (3) inhibits lipid-metabolism-related enzymes activity; (4) regulates cholesterol metabolism; (5) regulates other adipocyte-derived adipokines. The molecular mechanisms underlying these actions are complex and several signal transduction pathways might be involved. Regulation of metabolism-related gene expression at transcriptional and protein levels and impact on enzymes activity might be of importance. Identification and verification of these pathways might provide novel potential strategies and drug targets for dyslipidemia therapy. However, the inconsistent and even conflict conclusions on lipid profile drawn from human subjects after infliximab therapy poses the possibility that the effect of TNF-alpha on lipid metabolism might be more complicated than it appeared to be.

High-density lipoproteins in sepsis and septic shock: metabolism, actions, and therapeutic applications

Sepsis and septic shock are important causes of morbidity and lethality in noncoronary intensive care units. Circulating levels of high-density lipoproteins (HDLs) are reduced in sepsis/septic shock, and the magnitude of this reduction is positively correlated with the severity of the illness. The mechanisms underlying this phenomenon are incompletely understood, although increased levels of several acute-phase proteins, including serum amyloid A (SAA) and secretory phospholipase A2 (sPLA2), may contribute to the decrease in plasma HDLs. It has been suggested that HDLs possess anti-inflammatory properties and, hence, may play a crucial role in innate immunity by regulating the inflammatory response as well as being capable of reducing the severity of organ injury in animals and patients with septic shock. These protective effects of HDLs are mediated mainly via (a) lipopolysaccharide (LPS) binding and neutralization, (b) the HDL-associated enzymes, plasma paraoxonase (PON1) and platelet-activating factor acetylhydrolase (PAF-AH), which protect low-density lipoproteins against peroxidative damage, (c) inhibition of the expression of endothelial cell adhesion molecules and release of proinflammatory cytokines, which prevents inflammatory cell infiltration and subsequent multiple organ dysfunction, and (d) stimulation of the expression of endothelial nitric oxide synthase (eNOS). Thus, HDL exerts potent anti-inflammatory effects, some of which are independent of endotoxin binding and might be useful in the treatment of patients with not only sepsis/septic shock but also other conditions associated with an uncontrolled inflammatory response, such as ischemia-reperfusion injury and hemorrhagic shock.

Dietary 18:3ω3 influences immune function and the tissue fatty acid response to antigens and adjuvant

Alpha-linolenic acid (18:3omega3) has many important physiological functions including being beta-oxidized, serving a precursor to the synthesis of other lipids and it has immunomodulation properties. The objective of the present study was to test the effects of immunization and dietary 18:3omega3 on immune function and the fatty acid profile of immunized pig tissues. Piglets suckled from sows consuming either a control or high 18:3omega3 diet until 14 days old when they were weaned onto a similar diet as the sow and were moved to a segregated nursery for the remainder of the study. At 35 days of age, pigs on both diets (2 x 2 factorial design) received either an injection containing hen eggwhite lysozyme (HEWL), killed Mycobacterium tuberculosis and Freund's complete adjuvant (immunized) or phosphate buffered saline (PBS) (non-immunized) into the neck followed by a booster injection 2 weeks later and induction of delayed-type hypersensitivity (DTH) one week later. Immunization increased (compared to non-immunized) while the high 18:3omega3 diet decreased haptoglobin by 30% compared to pigs consuming the control diet. Immunized pigs had a seven-fold increase in antibodies to HEWL and pigs consuming the high 18:3omega3 diet also had transiently higher levels of serum antibodies. There was a diet by immunization interaction on the DTH reaction such that immunized pigs consuming the high 18:3omega3 had the largest DTH reaction. The neck muscle proximal to the site of injection of immunized pigs had 10-30% lower levels of triglyceride and phospholipid linoleic (18:2omega6) and 18:3omega3 compared to non-immunized pigs. Thus, a high 18:3omega3 intake in pigs modulates immune function and tissue fatty acids in response to immunization.

Intramuscular injection of antigens and adjuvant preferentially decreases 18∶2n−6 and 18∶3n−3 in pig neck muscle

Linoleic (18:2n-6) and alpha-linolenic acids (18:3n-3) have many important physiological functions including immunomodulation. We tested how immunization influences the metabolism of 18:2n-6 and 18:3n-3 in the neck muscle of pigs. At 35 d old, pigs received either an intramuscular neck injection containing hen egg white lysozyme (HEWL), killed Mycobacterium tuberculosis, and Freund's complete adjuvant (immunized) or PBS (control). At 49 d old, immunized pigs received a booster injection of HEWL and Freund's incomplete adjuvant, and the control pigs received PBS into the neck. At 56 d old, all pigs received an intradermal injection of Mycobacterium bovis into the hind leg to induce a delayed-type hypersensitivity (DTH) reaction. At 57 d old, immunized pigs had a twofold increase in serum haptoglobin, a 10-fold increase in antibodies to HEWL, and the skinfold at the DTH reaction site was 10 times thicker than the controls. Both 18:2n-6 and 18:3n-3 (% composition) were approximately 25% lower in muscle TG, 40% lower in FFA, 50% lower in phospholipids, but not different in cholesteryl esters of the neck muscle of immunized pigs. The antigens in this model induce an increased response in the innate (haptoglobin), humoral (antibodies), and cellular (DTH) immune systems as well as a preferential decrease of 18:2n-6 and 18:3n-3 in the inflamed neck muscle. It appears that 18:2n-6 and 18:3n-3 are preferentially metabolized (possibly beta-oxidized) in response to antigens.

L-carnitine alleviates alcohol-induced liver damage in rats: role of tumour necrosis factor-alpha

AIMS

Excessive alcohol intake induces hepatic fatty infiltration, which has been suggested to sensitize the liver to further damage. To test this hypothesis, L-carnitine, a constitutional lipotropic compound, was administered to rats chronically treated with ethanol by liquid diet feeding for 10 weeks.

RESULTS

Ethanol administration caused marked steatosis, mild inflammation and elevated plasma alanine aminotransferase and tumour necrosis factor alpha (TNF-alpha) concentrations. Dietary supplementation with L-carnitine significantly reduced all these parameters as well as the hepatic concentration of thiobarbituric acid reactive substances, an indicator of lipid peroxidation products. Pretreatment with L-carnitine also significantly blunted ethanol-induced stimulation of TNF-alpha release by isolated Kupffer cells.

CONCLUSIONS

This study provides direct support for the notion that steatosis sensitizes the liver to further damage and suggests an involvement of TNF-alpha in this process.

Whole-body beta-oxidation of 18:2omega6 and 18:3omega3 in the pig varies markedly with weaning strategy and dietary 18:3omega3

Segregated early weaning (SEW) into a cleaner nursery increases food intake and growth in pigs, presumably because of reduced immune stimulation compared with conventionally reared, nonsegregated pigs (NSW). The aim of the present study was to evaluate the oxidation of linoleic acid (18:2omega6) and alpha-linolenic acid (18:3omega3) in SEW and NSW pigs. Pigs consumed a control or high 18:3omega3 diet (omega6 PUFA/omega3 PUFA; 21.3 vs. 2.5, respectively) and were weaned at either 14 days old into a SEW nursery or at 21 days old into a conventional NSW nursery. The major acute-phase protein of pigs but not haptoglobin increased in 35-day-old NSW pigs. NSW pigs had 15-25% lower carcass 18:2omega6 and 20-30% lower carcass 18:3omega3 (% composition) at 49 days old. Between 35- and 49-days-old, NSW pigs had a higher whole-body oxidation of 18:2omega6 (40-120%) and 18:3omega3 (30-80%). The high 18:3omega3 diet decreased the whole-body oxidation of 18:2omega6 by 73% and of 18:3omega3 by 63% in NSW pigs. We conclude that moderately cleaner housing SEW significantly decreases 18:2omega6 and 18:3omega3 oxidation in pigs.