Individual and combined effects of peroxisome proliferator-activated receptor and {gamma} agonists, fenofibrate and rosiglitazone, on biomarkers of lipid and glucose metabolism in healthy nondiabetic volunteers.

This open-label, randomized, placebo-controlled, incomplete-block, 3-period crossover pilot study investigated the effects of peroxisome proliferator-activated receptor alpha- and gamma-agonists on biomarkers of lipid and glucose metabolism in 12 nondiabetic subjects. Plasma samples were collected before and after each 14-day treatment with placebo, fenofibrate (201 mg/d), rosiglitazone (4 mg twice daily), and combined fenofibrate (201 mg/d) plus rosiglitazone (4 mg twice daily). Except for triglycerides (P < .042) and free fatty acids (P < .074), no significant interaction was demonstrated between fenofibrate and rosiglitazone; thus, the effect due to each drug alone was evaluated (presence/absence of drug). Fenofibrate significantly (P < .050) increased lipoprotein lipase activity (35%) and decreased apolipoproteins B (13%) and C-III (20%). Rosiglitazone significantly (P < .050) decreased fasting glucose (7.3%) and increased apolipoprotein C-III (19%) and adiponectin (137%). Fenofibrate and rosiglitazone also produced effects on triglycerides and free fatty acids, but it was not possible to determine if these effects were synergistic in nature.

The influence of different preservation and sterilisation steps on the histological properties of amnion allografts--light and scanning electron microscopic studies.

Despite thorough donor screening and preparation under aseptic conditions, conventional methods of preservation do not exclude the probability of a contamination with pathogenic germs. The purpose of this study was to investigate the changes of histological parameters of amnion transplants (ATs) through different methods of sterilisation and preservation. Therefore 10 different procedures for sterilisation and preservation of ATs were described. Specimens of each group were studied using different histological procedures such as light microscopy and scanning electron microscopy. General staining (Haematoxylin-eosin stain, periodic-acid-Schiff, Domack) and immunohistochemical methods have been applied in order to gain additional information concerning the structure of the amniotic epithelium and the basement membrane but also the distribution of collagens and intermediate filaments. Furthermore, the measurement of the ATs thickness was included in order to study the influence of the manufacturing procedures to this property. As a result we found that the histological appearance of the ATs is closely related to the applied sterilisation and preservation procedures. Although the basement membrane remained intact, especially the amniotic epithelium was partially destroyed by irradiation sterilisation. Further, the dissolution of the connective tissue layers into single fibre bundles was clearly visible. Procedures with and without peracetic acid sterilisation (PAA) preserved the tissue structure. Our results showed a significant variation in the tissue's thickness after different preservation procedures. Air- and freeze-dried ATs were found to be the thinnest tissues varying from 20 to 30 microm, the thickest ATs preserved in glycerol varied from 45 to 50 microm. Because ATs showed a preserved tissue structure after PAA sterilisation it can be recommended as an alternative for methods previously described in literature. Depending on the specific use of the AT one may choose from thinner or thicker allografts.

Application of sterilised human amnion for reconstruction of the ocular surface.

BACKGROUND: Despite improved surgical techniques and the use of new medication, healing of corneal and conjunctival defects cannot always be achieved. In this connection the clinical use of human amnion, produced by different techniques, has represented a successful alternative for the past ten years. The purpose of the present investigation was the development of a clinically secure, therapeutically efficient, and easy-to-handle (transport, storage, application) allogenic amnion transplant. PATIENTS AND METHODS: A new method for an amnion preparation, which contains a sterilisation process in peracetic acid and a drying process in a laminar flow cabinet, was developed as an alternative to previous techniques described in the literature. Amnion transplantation was used to treat 41 patients, 36 of them with corneal ulcer. Further indications for amnion transplantation were symblepharon, descemetocele, as well as dehiscence of conjunctiva after cerclage. RESULTS: Seventy-three percent of cases showed postoperative improvement evidenced by constant vision, while 15 percent showed decreased vision. CONCLUSIONS: The study confirms the observations of previous investigators who consider amnion transplantation an efficient therapeutic method for a multitude of eye diseases. The new method described in this report, guarantees patients' safety by using a validated new sterilisation process against infections that can be transmitted by human tissue. At present this method constitutes the only process available in Germany, and is approved by the Federal Institute for Drugs and Medical Products (BfArM) for the manufacture of human amnion transplants as a finished medical product.

Role of PPARs in the regulation of obesity-related insulin sensitivity and inflammation.

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptor isoforms with key roles in the regulation of lipid and glucose metabolism. Synthetic ligands for PPAR gamma (and PPAR alpha) have effects of promoting insulin sensitization in the context of obesity. Recent evidence suggests that activation of PPAR delta might produce similar effects. Both PPAR gamma and PPAR alpha have also been shown to produce selected anti-inflammatory effects and to reduce the progression of atherosclerosis in animals (alpha and gamma) or in humans (alpha). Mechanisms underlying insulin-sensitizing effects are complex. For PPAR gamma, direct effects on adipose tissue lipid metabolism with secondary benefits in liver and/or muscle (lipid levels and insulin signaling) have been implicated. For PPAR alpha, accelerated lipid catabolism may contribute to reduced muscle or liver 'steatosis'. Anti-inflammatory mechanisms as contributors to the beneficial metabolic effects of PPAR activation are also worth considering for the following reasons: (1) obesity and insulin resistance are associated with a proinflammatory milieu. (2) PPAR gamma has clear effects to oppose the effects of tumor necrosis factor-alpha (TNFalpha) in adipocytes. (3) effects of PPAR ligands on cytokine-mediated signaling (eg via NF-kappa B) may be expected to enhance insulin action. (4) Adipose production of several molecules that are implicated as markers or mediators of inflammation is reduced. (5) In humans, treatment with either PPAR alpha or PPAR gamma agonists has been shown to reduce circulating levels of proteins that serve as markers of inflammation. (6) Adiponectin, a fat-derived circulating factor that has been implicated as having anti-inflammatory activity, is induced by PPAR gamma agonism.

Involvement of peripheral arteries in giant cell arteritis: a color Doppler sonography study.

OBJECTIVE: To investigate the involvement of arteries other than the temporal arteries in active giant cell arteritis using color Doppler sonography. METHODS: The occipital, facial, vertebral, carotid, subclavian, axillary, brachial, ulnar radial, femoral, popliteal, posterior tibial, and dorsal pedal arteries, and the abdominal aorta of 33 consecutive patients with acute giant cell arteritis and 33 age- and sex-matched controls were investigated. RESULTS: In 10 patients (30%), but in none of the controls, a characteristic inflammatory mural thickening (halo) could be demonstrated in these arteries. The subclavian, external carotid, and/or facial arteries were involved in 4 patients, the occipital and/or axillary arteries in 3 patients, the brachial and/or ulnar arteries in 2 patients, and the common carotid, vertebral, popliteal, and/or radial arteries in 1 patient each. Two patients had symptomatic large vessel giant cell arteritis with arm claudication. The other patients were asymptomatic concerning the involved arteries. Furthermore the ulnar artery was occluded in 3 cases, the posterior tibial artery in 2 cases, and the dorsal pedal and the vertebral artery in 1 case each. No occlusions were found in the controls. Occlusion of the temporal arteries occurred more frequently in patients with peripheral artery involvement than in those without peripheral involvement (60% versus 26%). In most of the non-stenotic, small arteries the halo disappeared within 9 to 21 days. Mural thickening remained in large, stenotic arteries. CONCLUSION: Peripheral artery involvement occurs more frequently in acute temporal arteritis than has been assumed up to now. Color Doppler sonography offers a new method to evaluate this peripheral involvement.

New drug targets for type 2 diabetes and the metabolic syndrome.

An insidious increase in features of the 'metabolic syndrome' - obesity, insulin resistance and dyslipidaemia -- has conspired to produce a worldwide epidemic of type 2 insulin-resistant diabetes mellitus. Most current therapies for this disease were developed in the absence of defined molecular targets or an understanding of disease pathogenesis. Emerging knowledge of key pathogenic mechanisms, such as the impairment of glucose-stimulated insulin secretion and the role of 'lipotoxicity' as a probable cause of hepatic and muscle resistance to insulin's effects on glucose metabolism, has led to a host of new molecular drug targets. Several have been validated through genetic engineering in mice or the preliminary use of lead compounds and therapeutic agents in animals and humans.

Role of AMP-activated protein kinase in mechanism of metformin action.

Metformin is a widely used drug for treatment of type 2 diabetes with no defined cellular mechanism of action. Its glucose-lowering effect results from decreased hepatic glucose production and increased glucose utilization. Metformin's beneficial effects on circulating lipids have been linked to reduced fatty liver. AMP-activated protein kinase (AMPK) is a major cellular regulator of lipid and glucose metabolism. Here we report that metformin activates AMPK in hepatocytes; as a result, acetyl-CoA carboxylase (ACC) activity is reduced, fatty acid oxidation is induced, and expression of lipogenic enzymes is suppressed. Activation of AMPK by metformin or an adenosine analogue suppresses expression of SREBP-1, a key lipogenic transcription factor. In metformin-treated rats, hepatic expression of SREBP-1 (and other lipogenic) mRNAs and protein is reduced; activity of the AMPK target, ACC, is also reduced. Using a novel AMPK inhibitor, we find that AMPK activation is required for metformin's inhibitory effect on glucose production by hepatocytes. In isolated rat skeletal muscles, metformin stimulates glucose uptake coincident with AMPK activation. Activation of AMPK provides a unified explanation for the pleiotropic beneficial effects of this drug; these results also suggest that alternative means of modulating AMPK should be useful for the treatment of metabolic disorders.

Hyperglycemia-induced production of acute phase reactants in adipose tissue.

Chronic elevation of systemic levels of acute phase reactants and inflammatory cytokines found in patients with diabetes and the often-associated metabolic syndrome X (hypertriglyceridemia, low serum high density lipoprotein cholesterol, hypertension, and accelerated atherosclerosis) may be responsible for the increased incidence of cardiovascular problems in this population. Here we examine the contribution of adipose tissue to the systemic elevation of acute phase reactants associated with chronic hyperglycemia. We demonstrate that adipose tissue expresses a number of acute phase reactants at high levels, including serum amyloid A3 (SAA3), alphal-acid glycoprotein, the lipocalin 24p3 as well as plasminogen activator inhibitor-1 (PAI-1). Additionally, we show SAA3 is expressed at low levels under normal conditions but in the diabetic state is dramatically up-regulated in adipose tissue while down-regulated in liver. Furthermore, pro-inflammatory stimuli and high glucose can lead to the induction of SAA3 in adipose tissue in vivo as well as in the 3T3-L1 adipocyte cell line. Adipose tissue may therefore play a major role in the pathogenic sequelae of Type II diabetes, in particular the cardiovascular problems associated with prolonged hyperglycemia.

Use of homogeneous time-resolved fluorescence energy transfer in the measurement of nuclear receptor activation.

Nuclear receptors (NRs) are a superfamily of ligand-dependent transcription factors that mediate the effects of hormones and other endogenous ligands to regulate the expression of specific genes. NRs are clearly important targets for drug discovery. Ligand-dependent protein-protein interactions between NRs and NR coactivators (NRCoAs) are a critical step in regulation of transcription. Homogeneous time-resolved fluorescence (HTRF) energy transfer technology is sensitive, homogeneous, and nonradioactive. These characteristics make this approach attractive for developing high-throughput screening assays. The long-lived nature of the fluorescence of europium cryptate combined with a time delay in reading facilitates the homogeneous nature of the assay. Importantly, the introduction of lanthanides (with R0 values as great as 90 A in HTRF) make HTRF amenable to be used for protein-protein interactions. In this article we review, using peroxisome proliferator-activated receptor (PPAR)gamma as a model system, a novel approach for characterizing the ligand-dependent interaction between NR and NRCoA using HTRF technology and its potential uses in small-molecule screening, profiling selectivity of NR-NRCoA paired interactions, and profiling NR ligands as agonists versus partial agonists or antagonists.

Differential gene regulation in human versus rodent hepatocytes by peroxisome proliferator-activated receptor (PPAR) alpha. PPAR alpha fails to induce peroxisome proliferation-associated genes in human cells independently of the level of receptor expresson.

We compared the ability of rat and human hepatocytes to respond to fenofibric acid and a novel potent phenylacetic acid peroxisome proliferator-activated receptor (PPAR) alpha agonist (compound 1). Fatty acyl-CoA oxidase (FACO) activity and mRNA were increased after treatment with either fenofibric acid or compound 1 in rat hepatocytes. In addition, apolipoprotein CIII mRNA was decreased by both fenofibric acid and compound 1 in rat hepatocytes. Both agonists decreased apolipoprotein CIII mRNA in human hepatocytes; however, very little change in FACO activity or mRNA was observed. Furthermore, other peroxisome proliferation (PP)-associated genes including peroxisomal 3-oxoacyl-CoA thiolase (THIO), peroxisomal enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase (HD), peroxisomal membrane protein-70 (PMP-70) were not regulated by PPAR alpha agonists in human hepatocytes. Moreover, other genes that are regulated by PPAR alpha ligands in human hepatocytes such as mitochondrial HMG-CoA synthase and carnitine palmitoyl transferase-1 (CPT-1) were also regulated in HepG2 cells by PPAR alpha agonists. Several stably transfected HepG2 cell lines were established that overexpressed human PPAR alpha to levels between 6- and 26-fold over normal human hepatocytes. These PPAR alpha-overexpressing cells had higher basal mRNA levels of mitochondrial HMG-CoA synthase and CPT-1; however, basal FACO mRNA levels and other PP-associated genes including THIO, HD, or PMP-70 mRNA were not substantially affected. In addition, FACO, THIO, HD, and PMP-70 mRNA levels did not increase in response to PPAR alpha agonist treatment in the PPAR alpha-overexpressing cells, although mitochondrial HMG-CoA synthase and CPT-1 mRNAs were both induced. These results suggest that other factors besides PPAR alpha levels determine the species-specific response of human and rat hepatocytes to the induction of PP.

Peroxisome proliferator-activated receptor-gamma ligands inhibit adipocyte 11beta -hydroxysteroid dehydrogenase type 1 expression and activity.

Peroxisome proliferator-activated receptor-gamma (PPARgamma) has been shown to play an important role in the regulation of expression of a subclass of adipocyte genes and to serve as the molecular target of the thiazolidinedione (TZD) and certain non-TZD antidiabetic agents. Hypercorticosteroidism leads to insulin resistance, a variety of metabolic dysfunctions typically seen in diabetes, and hypertrophy of visceral adipose tissue. In adipocytes, the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1) converts inactive cortisone into the active glucocorticoid cortisol and thereby plays an important role in regulating the actions of corticosteroids in adipose tissue. Here, we show that both TZD and non-TZD PPARgamma agonists markedly reduced 11beta-HSD-1 gene expression in 3T3-L1 adipocytes. This diminution correlated with a significant decrease in the ability of the adipocytes to convert cortisone to cortisol. The half-maximal inhibition of 11beta-HSD-1 mRNA expression by the TZD, rosiglitazone, occurred at a concentration that was similar to its K(d) for binding PPARgamma and EC(50) for inducing adipocyte differentiation thereby indicating that this action was PPARgamma-dependent. The time required for the inhibitory action of the TZD was markedly greater for 11beta-HSD-1 gene expression than for leptin, suggesting that these genes may be down-regulated by different molecular mechanisms. Furthermore, whereas regulation of PPARgamma-inducible genes such as phosphoenolpyruvate carboxykinase was maintained when cellular protein synthesis was abrogated, PPARgamma agonist inhibition of 11beta-HSD-1 and leptin gene expression was ablated, thereby supporting the conclusion that PPARgamma affects the down-regulation of 11beta-HSD-1 indirectly. Finally, treatment of diabetic db/db mice with rosiglitazone inhibited expression of 11beta-HSD-1 in adipose tissue. This decrease in enzyme expression correlated with a significant decline in plasma corticosterone levels. In sum, these data indicate that some of the beneficial effects of PPARgamma antidiabetic agents may result, at least in part, from the down-regulation of 11beta-HSD-1 expression in adipose tissue.

Altered extracellular signal-regulated kinase signaling and glycogen metabolism in skeletal muscle from p90 ribosomal S6 kinase 2 knockout mice.

The p90 ribosomal S6 kinase (RSK), a cytosolic substrate for the extracellular signal-regulated kinase (ERK), is involved in transcriptional regulation, and one isoform (RSK2) has been implicated in the activation of glycogen synthase by insulin. To determine RSK2 function in vivo, mice lacking a functional rsk2 gene were generated and studied in response to insulin and exercise, two potent stimulators of the ERK cascade in skeletal muscle. RSK2 knockout (KO) mice weigh 10% less and are 14% shorter than wild-type (WT) mice. They also have impaired learning and coordination. Hindlimb skeletal muscles were obtained from mice 10, 15, or 30 min after insulin injection or immediately after strenuous treadmill exercise for 60 min. While insulin and exercise significantly increased ERK phosphorylation in skeletal muscle from both WT and KO mice, the increases were twofold greater in the KO animals. This occurred despite 27% lower ERK2 protein expression in skeletal muscle of KO mice. KO mice had 18% less muscle glycogen in the fasted basal state, and insulin increased glycogen synthase activity more in KO than WT mice. The enhanced insulin-stimulated increases in ERK and glycogen synthase activities in KO mice were not associated with higher insulin receptor or with IRS1 tyrosine phosphorylation or with IRS1 binding to phosphatidylinositol 3-kinase. However, insulin-stimulated serine phosphorylation of Akt was significantly higher in the KO animals. c-fos mRNA was increased similarly in muscle from WT and KO mice in response to insulin (2. 5-fold) and exercise (15-fold). In conclusion, RSK2 likely plays a major role in feedback inhibition of the ERK pathway in skeletal muscle. Furthermore, RSK2 is not required for activation of muscle glycogen synthase by insulin but may indirectly modulate muscle glycogen synthase activity and/or glycogen content by other mechanisms, possibly through regulation of Akt. RSK2 knockout mice may be a good animal model for the study of Coffin-Lowry syndrome.

Discovery of a potent, highly selective, and orally efficacious small-molecule activator of the insulin receptor.

A series of 3,6-diaryl-2,5-dihydroxybenzoquinones were synthesized and evaluated for their abilities to selectively activate human insulin receptor tyrosine kinase (IRTK). 2, 5-Dihydroxy-6-(1-methylindol-3-yl)-3-phenyl-1,4-benzoquinone (2h) was identified as a potent, highly selective, and orally active small-molecule insulin receptor activator. It activated IRTK with an EC(50) of 300 nM and did not induce the activation of closely related receptors (IGFIR, EGFR, and PDGFR) at concentrations up to 30 000 nM. Oral administration of the compound to hyperglycemic db/db mice (0.1-10 mg/kg/day) elicited substantial to nearly complete correction of hyperglycemia in a dose-dependent manner. In ob/ob mice, the compound (10 mg/kg) caused significant reduction in hyperinsulinemia. A structurally related compound 2c, inactive in IRTK assay, failed to affect blood glucose level in db/db mice at equivalent exposure levels. Results from additional studies with compound 2h, aimed at evaluating classical quinone-related phenomena, provided sufficient grounds for optimism to allow more extensive toxicologic evaluation.

Activation of insulin signal transduction pathway and anti-diabetic activity of small molecule insulin receptor activators.

We recently described the identification of a non-peptidyl fungal metabolite (l-783,281, compound 1), which induced activation of human insulin receptor (IR) tyrosine kinase and mediated insulin-like effects in cells, as well as decreased blood glucose levels in murine models of Type 2 diabetes (Zhang, B., Salituro, G., Szalkowski, D., Li, Z., Zhang, Y., Royo, I., Vilella, D., Diez, M. T. , Pelaez, F., Ruby, C., Kendall, R. L., Mao, X., Griffin, P., Calaycay, J., Zierath, J. R., Heck, J. V., Smith, R. G. & Moller, D. E. (1999) Science 284, 974-977). Here we report the characterization of an active analog (compound 2) with enhanced IR kinase activation potency and selectivity over related receptors (insulin-like growth factor I receptor, epidermal growth factor receptor, and platelet-derived growth factor receptor). The IR activators stimulated tyrosine kinase activity of partially purified native IR and recombinant IR tyrosine kinase domain. Administration of the IR activators to mice was associated with increased IR tyrosine kinase activity in liver. In vivo oral treatment with compound 2 resulted in significant glucose lowering in several rodent models of diabetes. In db/db mice, oral administration of compound 2 elicited significant correction of hyperglycemia. In a streptozotocin-induced diabetic mouse model, compound 2 potentiated the glucose-lowering effect of insulin. In normal rats, compound 2 improved oral glucose tolerance with significant reduction in insulin release following glucose challenge. A structurally related inactive analog (compound 3) was not effective on insulin receptor activation or glucose lowering in db/db mice. Thus, small molecule IR activators exert insulin mimetic and sensitizing effects in cells and in animal models of diabetes. These results have implications for the future development of new therapies for diabetes mellitus.

Evidence for peroxisome proliferator-activated receptor (PPAR)alpha-independent peroxisome proliferation: effects of PPARgamma/delta-specific agonists in PPARalpha-null mice.

Peroxisome proliferators are a diverse group of compounds that cause hepatic hypertrophy and hyperplasia, increase peroxisome number, and on chronic high-dose administration, lead to rodent liver tumorigenesis. Various lines of evidence have led to the conclusion that these agents induce their pleiotropic effects exclusively via agonism of peroxisome proliferator-activated receptor (PPAR)alpha, a member of the steroid receptor superfamily involved in the regulation of fatty acid metabolism. Recently, agonists of two other members of this receptor family have been identified. PPARgamma is predominantly expressed in adipocytes where it mediates differentiation; PPARdelta is a widely expressed orphan receptor with yet unresolved physiologic functions. In the course of characterizing newer PPAR ligands, we noted that highly selective PPARgamma agonists or dual PPARgamma/PPARdelta agonists, lacking apparent murine PPARalpha agonist activity, cause peroxisome proliferation in CD-1 mice. We therefore made use of PPARalpha knockout mice to investigate whether these effects resulted from agonism of PPARalpha by these agents at very high dose levels or whether PPARgamma (or PPARdelta) agonism alone can result in peroxisome proliferation. We report here that several parameters linked to the hepatic peroxisome proliferation response in mice that were seen with these agents resulted from PPARalpha-independent effects.

[Eye complications in 458 children with rheumatoid arthritis]. / Augenbeteiligung bei 458 Kindern mit Erkrankungen des rheumatischen Formenkreises.

BACKGROUND: Besides arthritis or other systemic manifestations, endogenous inflammation (most commonly uveitis) can be a symptom of rheumatoid arthritis in children. The uveitis of children shows certain differences compared to that in adults. This study will show these differences and their incidences. PATIENTS AND METHODS: Retrospective analysis of the histories of 458 children that were admitted to the pediatric clinic due to rheumatism related diseases. An analysis of the general and pediatric data, laboratory results and therapy were combined with the ophthalmologic data. RESULTS: 45 (9.8%) of the 458 patients suffered from uveitis at least once during the studied time period between 1992 and 1996. Most common complications of the therapy were clouding of the lens up to full cataract (in both eyes in eight out of nine patients). Seven patients underwent cataract operation. Further complications are synechiae, band shaped keratopathy, secondary glaucoma and retinal diseases. CONCLUSION: Since the pediatric uveitis usually does not take an acute course and since children rarely can articulate themselves precisely, a regular ophthalmologic examination of pediatric rheumatology patients is necessary, as well as every uveitis in children should warrant pediatric-rheumatologic diagnostics. The impact of uveitis is much more severe for children when compared to adults, since it not only endangers the vision but the whole development of the child.

New approaches in the treatment of type 2 diabetes.

Type 2 diabetes is a chronic metabolic derangement that results from defects in both insulin action and secretion. New thiazolidinedione insulin sensitizers have been recently launched. New approaches with mechanisms different from current therapies are being explored, including novel ligands of peroxisome proliferator-activated receptor, glucagon receptor antagonists, dipeptidyl peptidase IV inhibitors, and insulin receptor activators.

Potential role of TNF-alpha in the pathogenesis of insulin resistance and type 2 diabetes.

Tumor necrosis factor alpha (TNF-alpha) has well-described effects on lipid metabolism in the context of acute inflammation, as in sepsis. Recently, increased TNF-alpha production has been observed in adipose tissue derived from obese rodents or human subjects and TNF-alpha has been implicated as a causative factor in obesity-associated insulin resistance and the pathogenesis of type 2 diabetes. Thus, current evidence suggests that administration of exogenous TNF-alpha to animals can induce insulin resistance, whereas neutralization of TNF-alpha can improve insulin sensitivity. Importantly, results from knockout mice deficient in TNF-alpha or its receptors have suggested that TNF-alpha has a role in regulating in vivo insulin sensitivity. However, the absence of TNF-alpha action might only partially protect against obesity-induced insulin resistance in mice. Multiple mechanisms have been suggested to account for these metabolic effects of TNF-alpha. These include the downregulation of genes that are required for normal insulin action, direct effects on insulin signaling, induction of elevated free fatty acids via stimulation of lipolysis, and negative regulation of PPAR gamma, an important insulin-sensitizing nuclear receptor. Although current evidence suggests that neutralizing TNF-alpha in type 2 diabetic subjects is not sufficient to cause metabolic improvement, it is still probable that TNF-alpha is a contributing factor in common metabolic disturbances such as insulin resistance and dyslipidemia.