AN1284 attenuates steatosis, lipogenesis, and fibrosis in mice with pre-existing non-alcoholic steatohepatitis and directly affects aryl hydrocarbon receptor in a hepatic cell line.

Non-alcoholic steatohepatitis (NASH) is an aggressive form of fatty liver disease with hepatic inflammation and fibrosis for which there is currently no drug treatment. This study determined whether an indoline derivative, AN1284, which significantly reduced damage in a model of acute liver disease, can reverse steatosis and fibrosis in mice with pre-existing NASH and explore its mechanism of action. The mouse model of dietary-induced NASH reproduces most of the liver pathology seen in human subjects. This was confirmed by RNA-sequencing analysis. The Western diet, given for 4 months, caused steatosis, inflammation, and liver fibrosis. AN1284 (1 mg or 5 mg/kg/day) was administered for the last 2 months of the diet by micro-osmotic-pumps (mps). Both doses significantly decreased hepatic damage, liver weight, hepatic fat content, triglyceride, serum alanine transaminase, and fibrosis. AN1284 (1 mg/kg/day) given by mps or in the drinking fluid significantly reduced fibrosis produced by carbon tetrachloride injections. In human HUH7 hepatoma cells incubated with palmitic acid, AN1284 (2.1 and 6.3 ng/ml), concentrations compatible with those in the liver of mice treated with AN1284, decreased lipid formation by causing nuclear translocation of the aryl hydrocarbon receptor (AhR). AN1284 downregulated fatty acid synthase (FASN) and sterol regulatory element-binding protein 1c (SREBP-1c) and upregulated Acyl-CoA Oxidase 1 and Cytochrome P450-a1, genes involved in lipid metabolism. In conclusion, chronic treatment with AN1284 (1mg/kg/day) reduced pre-existing steatosis and fibrosis through AhR, which affects several contributors to the development of fatty liver disease. Additional pathways are also influenced by AN1284 treatment.

Detection of cleaved alpha-fodrin autoantigen in Sjögren's syndrome: apoptosis and co-localisation of cleaved alpha-fodrin with activated caspase-3 and cleaved poly(ADP-ribose) polymerase (PARP) in labial salivary glands.

UNLABELLED: Sjögren's syndrome (SS) is a systemic autoimmune disease which targets the exocrine glands and is associated with autoantibodies. The mechanism of salivary gland destruction or autoantibody production is poorly understood but it is increasingly accepted that apoptosis plays a role. OBJECTIVE: The objective of this study is to demonstrate the presence of cleaved alpha-fodrin autoantigen and apoptosis in the salivary glands of patients with primary Sjögren's syndrome. METHODS: 18 patients with primary Sjögren's syndrome provided tissues from a labial salivary gland biopsy. Using terminal deoxynucleotidyl transferase mediated dUTP nick end labelling (TUNEL) assays to detect DNA fragmentation followed by sequential immunoperoxidase assays in the same patient biopsy to detect cleaved alpha-fodrin, Poly(ADP-ribose) polymerase (PARP), and caspase-3, we show a co-localisation between apoptotic markers and disease. RESULTS: Co-localisation of cleaved alpha-fodrin, PARP and caspase-3 expression was demonstrated primarily in the ducts along with DNA fragmentation in 16/18 salivary gland biopsies from Sjögren's syndrome patients. None of these apoptotic markers was strongly expressed in healthy tissues. CONCLUSION: Apoptotic signals may provide useful therapeutic targets and cleaved alpha-fodrin may prove to be a marker of disease in primary Sjögren's syndrome. Further studies are required to ascertain the specific association of cleaved alpha-fodrin with primary and secondary Sjögren's syndrome.

Can application of exogenous fibronectin enhance periodontal regeneration?

BACKGROUND: Although fibronectin (FN) is an important extracellular glycoprotein involved in periodontal wound healing, it is not clear whether the application of exogenous fibronectin (ExoFN) offers any clinical benefit. The purpose of this preliminary in vitro study was to determine the binding of FN from three different sources, viz. endogenous EDTA-plasma, endogenous serum and exogenous commercial purified human fibronectin in PBS buffer, to demineralized and non-demineralized root powder. METHOD: The binding of FN to a known quantity of mineralized and non-demineralized root powder by overnight incubation at 15 degrees C was studied by enzyme immunoassay (EIA) technique. The criteria for optimal performance of EIA procedure for the determination of FN was established. Particle size of powdered root structure was standardized using a Vibratory Sieve Shaker. RESULTS: The EDTA-plasma and the serum FN exhibited binding of (17.8 +/- 2.1 microg) and (6.5 +/- 4.5 microg), respectively, to the non-demineralized root powder. However, the binding was only significant for the EDTA-plasma FN (p < 0.01) when compared to controls. In the demineralized group there was no ascertainable binding of FN from either endogenous or exogenous sources. ExoFN in buffer exhibited no binding at all to the non-demineralized or demineralized root powder. CONCLUSION: The preliminary data suggest that additional plasma and serum factors may facilitate the binding of FN to root powder. High levels of FN in blood do not necessarily indicate that FN is available for binding to the root surface during periodontal surgery.

Growth factor-stimulated phosphorylation of Akt and p70(S6K) is differentially inhibited by LY294002 and Wortmannin.

The phosphoinositide 3-kinase (PI3K) inhibitors, LY294002 (LY) and wortmannin (WM), are widely used to examine the role of PI3K in growth factor signaling. These compounds inhibit the kinase action of PI3K, thus preventing the accumulation of PI(3,4,5)P3 and PI(3,4)P2 (PIs) and subsequent phosphorylation and activation of the downstream effectors of PI3K, Akt and p70(S6K). The efficacy of these inhibitors has been demonstrated by measuring cellular levels of PIs or the kinase activity of immunoprecipitated PI3K. However, their effects on activation of Akt and p70(S6K), more widely used markers of PI3K activation, has not been formally tested. We have examined the effects of LY and WM on phosphorylation of Akt and p70(S6K) by insulin-like growth factor-I, insulin, and platelet-derived growth factor in skeletal muscle cells. LY is much less effective in blocking the phosphorylation of Akt than p70(S6K); at concentrations which completely inhibit phosphorylation of p70(S6K), phosphorylation of Akt is only partially inhibited by LY. WM also inhibits IGF-I-stimulated phosphorylation of Akt and p70(S6K) with unequal potency but is equally effective in blocking insulin-stimulated phosphorylation of these peptides. Our data demonstrate that inhibiting PI3K signaling through one of its downstream mediators (p70(S6K)) may not indicate complete blockage of the PI3K pathway which may be signaling through an alternate downstream branch (Akt). These findings indicate that the efficacy of LY and WM in blocking PI3K-activation of Akt and p70(S6K) must be tested within the context of every experiment, and that the results obtained with the use of these inhibitors must be interpreted according to their specific effects on the PI3K/Akt and PI3K/p70(S6K) signaling pathways.

Functional inactivation of the IGF-I receptor delays differentiation of skeletal muscle cells.

Skeletal myoblasts are inherently programmed to leave the cell cycle and begin the differentiation process following removal of exogenous growth factors. Serum withdrawal results in a marked induction of IGF production which is essential for skeletal muscle differentiation in vitro. However, the potential role of the tyrosine kinase IGF-I receptor (thought to be the principal mediator of both IGF-I and II signaling in skeletal muscle) in the decision of myoblasts to begin differentiation following serum withdrawal is unknown. To explore the role of the IGF-I receptor in this decision by skeletal myoblasts, we functionally inactivated endogenous IGF-I receptors in mouse C2C12 cells using a dominant negative, kinase-inactive IGF-I receptor in which the ATP-binding site lysine (K) at residue 1003 has been mutated to alanine (A). Cell lines with the greatest degree of mutant IGF-I receptor expression (A/K cells) demonstrated functional inactivation of endogenous IGF-I receptors as determined by their impaired ability to phosphorylate the principal substrate of the IGF-I receptor, IRS-1, in response to treatment with IGF-I. In addition, the proliferative response of myoblasts to IGF-I was completely abolished in A/K cells. Following withdrawal of exogenous growth factors, A/K cells demonstrated a marked delay in the induction of the gene expression of myogenin, a skeletal muscle-specific transcription factor essential for differentiation, and a subsequent delay in the induction of muscle creatine kinase activity. Delayed differentiation in A/K cells was associated with prolonged phosphorylation of the cell cycle regulatory retinoblastoma (Rb) protein; it is the un- (or hypo-) phosphorylated form of Rb which is known to promote differentiation in skeletal myoblasts. Thus, the IGF-I receptor regulates the timing of myoblast differentiation induced by serum withdrawal. The delayed differentiation of skeletal myoblasts with functionally inactive IGF-I receptors may result, at least in part, from delayed induction of myogenin gene expression and prolonged phosphorylation of the Rb protein.

Differential effects of interleukin-1 and tumor necrosis factor on ketogenesis.

To determine the role of cytokines in mediating the decrease in ketones associated with infection, we studied the effect of endotoxin (LPS), interleukin-1 (IL-1), and tumor necrosis factor (TNF) on serum and hepatic ketone body levels (KB), serum free fatty acids (FFA), and hepatic malonyl-CoA levels. LPS decreased serum and hepatic KB in C57Bl/6 (LPS sensitive) mice, whereas it had little effect in C3H/HeJ (LPS resistant) mice, whose macrophages lack the ability to produce IL-1 and TNF in response to LPS, suggesting that IL-1 and TNF may mediate this effect. IL-1 and TNF decreased serum KB in both strains of mice. As seen with LPS, IL-1 decreased hepatic KB, whereas TNF had no such effect. LPS, IL-1, and TNF increased hepatic malonyl-CoA levels. TNF acutely raised serum FFA, whereas LPS and IL-1 did not. Postulating that the TNF-induced increase in FFA overrides the inhibitory effect of malonyl-CoA on fatty acid oxidation and ketogenesis, we used R-2-phenylisopropyladenosine to block TNF-induced lipolysis and demonstrated that in the absence of increased fatty acid flux, TNF inhibits KB formation. As seen with LPS, IL-1, but not TNF, decreased KB in the fasting state. These data suggest that IL-1 and TNF may mediate the antiketogenic effect of infection and that IL-1 has properties closest to that of LPS.

Role for monokines in the metabolic effects of endotoxin. Interferon-gamma restores responsiveness of C3H/HeJ mice in vivo.

To examine the role of cytokines in mediating the lipogenic effects of endotoxin (LPS), we studied the effects of LPS and cytokines on hepatic fatty acid synthesis in LPS-sensitive C3H/OuJ mice and in LPS-resistant C3H/HeJ mice, whose macrophages are defective in the ability to produce tumor necrosis factor (TNF) and IL-1 in response to LPS. HeJ mice were 16-fold less sensitive than OuJ mice to the lipogenic effect of LPS. In OuJ mice, 10 micrograms of LPS caused a maximal increase in hepatic lipogenesis (3.86 +/- 0.41-fold), whereas in HeJ mice the maximal increase was only 1.79 +/- 0.32-fold after 100 micrograms of LPS. This lipogenic response paralleled the decreased ability of LPS to increase hepatic and splenic levels of mRNAs for TNF and IL-1 and serum levels of TNF in HeJ mice. In contrast, the maximal effect of TNF on lipogenesis was greater and the sensitivity to TNF was increased 2.4-fold in HeJ mice compared to OuJ mice. Administration of IFN-gamma before LPS in HeJ mice had no effect on IL-1 mRNA, but partially restored the LPS-induced increase in hepatic and splenic mRNA for TNF and serum TNF levels, which may account for the partial restoration of sensitivity to the lipogenic effect of LPS after IFN-gamma treatment. These results indicate that cytokines produced by mononuclear leukocytes mediate the lipogenic effects of LPS.

Direct and sex-specific enhancement of bone formation and calcification by sex steroids in fetal mice long bone in vitro (biochemical and morphometric study.

The study was carried out to examine the direct effect of the sex hormones 17 beta-estradiol (E2) and testosterone on the modeling of cultured fetal mouse long bones separated according to their sex. The culture system used allowed for the simultaneous assessment of bone growth, mineralization, and resorption on each bone. Bones from 16-day-old male and female mouse fetuses were cultured in BGJ medium, supplemented with either 10% fetal calf serum or 4 mg/ml BSA (serum-free medium) for 48 h. The bones were harvested, and their length; the length of their diaphyses; their hydroxyproline, calcium, and phosphorus contents; and their 45Ca release were measured. Histomorphometric analyses on midlongitudinal sections of bones from parallel experiments were also performed. The results indicate that in medium supplemented with 10% fetal calf serum, E2 had a dose-dependent stimulatory effect on bone formation and mineralization at 10(-7) and 10(-9) M, with no effect on bone resorption. This effect was specific to bones from female mice and to E2, since 17-alpha-estradiol had no effect. Testosterone had similar effects specific to bones from male mice, resulting in the stimulation of bone formation and mineralization at 10(-7)- and 10(-9)-M concentrations. These effects were absent when serum-free medium was used. E2 and testosterone had an anabolic effect on endochondral and periosteal bone formation and mineralization, but no effect on bone resorption. This effect is dependent on the presence of a serum factor(s).

Interleukin 4 inhibits stimulation of hepatic lipogenesis by tumor necrosis factor, interleukin 1, and interleukin 6 but not by interferon-alpha.

Multiple cytokines stimulate hepatic lipogenesis in rodents. We have previously shown that lipogenic cytokines can be divided into 2 classes by their mechanism of action and their synergistic interactions. We now report the effects of interleukin 4, a cytokine known to inhibit the synthesis and action of other cytokines. Interleukin 4 by itself did not alter hepatic lipogenesis. However, interleukin 4 inhibited the characteristic stimulation of hepatic lipogenesis that is seen with tumor necrosis factor, interleukin 1, and interleukin 6. These 3 cytokines stimulate hepatic lipogenesis by the same mechanism, increasing hepatic levels of citrate, a key allosteric activator of acetyl CoA carboxylase, the rate-limiting enzyme of fatty acid synthesis. Interleukin 4 blocks the ability of tumor necrosis factor to increase hepatic citrate. In contrast, interleukin 4 does not block the stimulation of hepatic lipogenesis by interferon-alpha, a cytokine that increases hepatic lipogenesis by a mechanism other than increasing hepatic citrate levels. These results demonstrate that interleukin 4 can inhibit the metabolic action of selected cytokines, which provides strong support for our proposal that lipogenic cytokines operate through 2 distinct mechanisms of action and can therefore be divided into 2 separate classes based on their interactions. These results also emphasize the multiple relationships between the immune response and lipid metabolism.

Effect of interleukin-1 on lipid metabolism in the rat. Similarities to and differences from tumor necrosis factor.

Infection and inflammation are associated with hypertriglyceridemia, which is thought to be mediated by cytokines. Previous studies at our laboratory and others have shown that tumor necrosis factor acutely increases serum triglyceride levels primarily by stimulating hepatic lipid synthesis and secretion. The role of interleukin-1 (IL-1), a cytokine that is also secreted by stimulated macrophages and that has many actions that overlap those of tumor necrosis factor, has not been studied in depth. The present study demonstrates that IL-1, at doses similar to those that cause fever and anorexia and that stimulate adrenocorticotropic hormone secretion, rapidly increases serum triglyceride levels; this elevation persists for at least 17 hours. Serum cholesterol levels are not altered by IL-1. Neither is the clearance of triglyceride-rich lipoproteins affected by IL-1. However, hepatic triglyceride secretion, measured by the Triton WR-1339 technique, is increased in IL-1-treated animals. Accompanying this stimulation in hepatic lipid secretion is an increase in de novo fatty acid synthesis in the liver. IL-1 does not increase serum free fatty acid and glycerol levels, suggesting that IL-1 does not stimulate lipolysis in vivo. Additionally, inhibition of lipolysis does not prevent the increase in serum triglyceride levels, providing further evidence that lipolysis does not play a crucial role in the increased hepatic lipid synthesis and secretion induced by IL-1. In contrast, tumor necrosis factor increases lipolysis, which contributes to the increase in serum triglycerides. That multiple cytokines rapidly elevate plasma triglyceride levels suggest that these changes in lipid metabolism may play an important role in the organism's response to infection and inflammation.

Tumor necrosis factor-increased hepatic very-low-density lipoprotein production and increased serum triglyceride levels in diabetic rats.

Previous studies demonstrated that administration of tumor necrosis factor (TNF) to diabetic rats rapidly increases serum triglyceride levels and stimulates hepatic lipogenesis without affecting the activity of adipose tissue lipoprotein lipase or serum insulin levels. The purpose of this study was to determine the mechanism by which TNF increases serum triglyceride levels and stimulates hepatic fatty acid synthesis in diabetic animals. The maximal increase (approximately 2-fold) in serum triglyceride levels in diabetic rats is seen with a dose of 10 micrograms TNF/200 g body wt, and the half-maximal effect is observed with 5 micrograms TNF/200 g body wt. The clearance of labeled triglyceride-rich lipoproteins from the circulation is not affected by TNF administration (triglyceride t 1/2; diabetic vs. TNF-administered diabetic, 3.5 +/- 0.7 vs. 4.0 +/- 0.6 min, respectively; NS). The production of triglyceride, measured by the Triton WR-1339 technique, is increased twofold in diabetic animals after TNF administration. These results indicate that the rapid increase in serum triglyceride levels after TNF treatment is accounted for by increased hepatic lipoprotein secretion. TNF administration did not alter either the amount or activation state of hepatic acetyl-CoA carboxylase, a key regulatory enzyme in fatty acid synthesis. There was also no change in the hepatic levels of fatty acyl-CoA, an allosteric inhibitor of acetyl-CoA carboxylase. However, there was a 71% increase in hepatic citrate concentrations. Citrate is an allosteric activator of acetyl-CoA carboxylase, and changes in hepatic citrate concentrations have been shown to mediate changes in the rates of fatty acid synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Diet affects the mechanisms by which TNF stimulates hepatic triglyceride production.

Tumor necrosis factor (TNF) induces hyperlipidemia in rodents by increasing hepatic triglyceride production. We now explore the mechanism of this increase. TNF does not increase phosphatidate phosphohydrolase, glycerolphosphate acyltransferase, or diacylglycerol acyltransferase, which are enzymes of triglyceride synthesis. Rather, TNF increases triglyceride production by providing increased fatty acids (FA) as substrate. In chow-fed rats, TNF increases plasma free fatty acids (FFA). The antilipolytic drug, phenylisopropyl adenosine (PIA), prevents the TNF-induced increase in plasma FFA and, most importantly, inhibits the TNF-induced increase in plasma triglycerides. Thus increased lipolysis with delivery of FA to liver contributes to TNF-induced hyperlipidemia in chow-fed animals. In contrast, in rats fed a high-sucrose diet, TNF causes hyperlipidemia without increasing plasma FFA, and PIA has no effect on TNF-induced increases in plasma triglycerides. However, in sucrose-fed rats, TNF markedly stimulates hepatic de novo FA synthesis, which provides FA. This diet determines the mechanism by which TNF stimulates hepatic triglyceride production. The use of multiple mechanisms to increase plasma triglycerides suggests that this TNF action plays an important role in the response to infection or inflammation.

Search for mediators of the lipogenic effects of tumor necrosis factor: potential role for interleukin 6.

The significance of potential second messengers as mediators of the metabolic effects of tumor necrosis factor (TNF) was explored by studying their role in stimulating hepatic lipogenesis. Platelet-activating factor and prostaglandins have previously been suggested to mediate some of the toxic effects of TNF. An inhibitor of platelet-activating factor (WEB 2086) and two inhibitors of the synthesis of prostaglandins (ibuprofen and aspirin) had no effect on the ability of TNF to increase hepatic lipogenesis or serum triglyceride levels in the rat. Another inhibitor of the toxic effects of TNF, pentoxifylline, also had no effect on lipid metabolism in the rat. Catecholamines are increased after TNF administration, but alpha- and beta-adrenergic blockade did not prevent the lipogenic effects of TNF. However, interleukin 6, a cytokine whose synthesis and secretion are induced by TNF, is able to acutely stimulate hepatic lipogenesis in mice. Interleukin 6 stimulates hepatic lipogenesis by increasing hepatic citrate concentrations, the same mechanism by which TNF stimulates hepatic lipogenesis. These data suggest that interleukin 6, but not platelet-activating factor, prostaglandins, or catecholamines, could potentially mediate the lipogenic effects of TNF.

Evidence for two classes of cytokines that stimulate hepatic lipogenesis: relationships among tumor necrosis factor, interleukin-1 and interferon-alpha.

Tumor necrosis factor (TNF) increases serum triglycerides in rats by increasing de novo hepatic fatty acid synthesis and very low density lipoprotein production. We have recently shown that several other cytokines increase hepatic fatty acid synthesis in the mouse. We now explore the mechanism by which these cytokines increase de novo lipogenesis and the interactions between cytokines in fed mice. TNF administration results in increased hepatic levels of citrate, the primary allosteric activator of acetyl-CoA carboxylase, which is the major rate-limiting enzyme for fatty acid synthesis. The TNF-induced increase in citrate occurs within 15 min of administration, early enough to account for the acute rise in hepatic fatty acid synthesis seen by 30 min after TNF administration. IL-1, which also increases hepatic fatty acid synthesis, produces similar increases in hepatic citrate levels. In contrast, another potent stimulator of hepatic fatty acid synthesis, interferon-alpha (IFN alpha), has no effect on hepatic citrate levels. There were no acute effects of TNF or IL-1 on the activation state of acetyl-CoA carboxylase. A trend toward an increase in the activation state of acetyl-CoA carboxylase was seen after IFN alpha administration. Low doses of TNF and IL-1 given in combination show no synergy while maximal doses are not additive. In contrast, when a low dose of either TNF or IL-1 is combined with a low dose of IFN alpha, there is synergy in stimulating hepatic fatty acid synthesis. A maximal dose of TNF or IL-1 and a high dose of IFN alpha produce a further increase in hepatic fatty acid synthesis. These data support the concept that there are two classes of cytokines that stimulate hepatic fatty acid synthesis, those that can increase hepatic citrate levels and those that cannot.

The effect of diet on tumor necrosis factor stimulation of hepatic lipogenesis.

Previous studies have demonstrated that tumor necrosis factor (TNF) acutely increases serum triglyceride levels and stimulates hepatic lipid synthesis. In this study, we determined the effects of TNF on serum lipid levels and hepatic lipid synthesis in animals whose diets and feeding conditions were varied to induce changes in baseline serum lipid levels and/or rates of hepatic lipid synthesis. In animals studied at both the nadir and peak of the diurnal cycle of hepatic lipid synthesis, TNF acutely increases serum triglyceride levels, stimulates hepatic fatty acid synthesis, and increases the quantity of newly synthesized fatty acids found in the serum. Similarly, in animals ingesting either high-sucrose or cholesterol-enriched diets, TNF induces the characteristic rapid increase in serum triglyceride levels, hepatic fatty acid synthesis, and quantity of labeled fatty acids in the serum. In animals fed a diet high in triglycerides, using either corn oil or lard, TNF stimulates hepatic fatty acid synthesis and increases the quantity of newly synthesized fatty acids in the serum, but serum triglyceride levels do not change. However, TNF inhibits gastric emptying, which results in a marked decrease in fat absorption in TNF-treated animals. It is likely that a decrease in the dietary contribution to serum triglyceride levels during high-triglyceride feeding counterbalances the increased hepatic contribution induced by TNF treatment. In animals fasted before TNF administration there was no acute change in either serum lipid levels, hepatic fatty acid synthesis, or the quantity of labeled fatty acids in the serum. Thus, TNF stimulates hepatic fatty acid synthesis and increases serum triglyceride levels under many diverse dietary conditions, suggesting that there is a strong linkage between the immune system and lipid metabolism that is independent of most dietary manipulations and may be of fundamental importance in the body's response to infection.

Tumor necrosis factor stimulates hepatic lipid synthesis and secretion.

Previous studies have shown that tumor necrosis factor (TNF) administration acutely increases serum triglyceride levels and stimulates hepatic de novo fatty acid synthesis. We now demonstrate that 60-90 min after TNF administration the incorporation of glycerol into triglycerides in the liver is increased 57% in chow-fed rats. Additionally, the quantity of labeled lipid in serum is increased 96% in the TNF-treated animals. TNF also acutely increases hepatic lipid synthesis and the quantity of labeled lipids in serum in rats fed a high sucrose diet. Moreover, using the Triton WR-1339 method, from 1-2 h after TNF administration there is a 52% increase in total hepatic triglyceride secretion. In contrast, in animals fasted before TNF administration, the characteristic increase in serum triglyceride levels is not observed, and neither the incorporation of glycerol into hepatic lipids nor the quantity of labeled lipids in the circulation are increased. By 17 h after TNF administration the incorporation of glycerol into hepatic lipid and the quantity of labeled lipid in the serum are no longer increased. These results indicate that in addition to TNF acutely stimulating de novo fatty acid synthesis, TNF also acutely stimulates hepatic triglyceride synthesis. The increase in hepatic triglyceride synthesis leads to increased secretion of lipids into the circulation. These observations provide strong support for our hypothesis that a TNF-induced stimulation of hepatic lipid synthesis and secretion contributes to the TNF-induced hyperlipidemia.