Elevated serum tumor necrosis factor-alpha concentrations and bioactivity in Type 2 diabetics and patients with android type obesity

Effects of anti-inflammatory therapies on glycemic control in type 2 diabetes mellitus

Background

The overall evidence base of anti-inflammatory therapies in patients with type 2 diabetes mellitus (T2DM) has not been systematically evaluated. The purpose of this study was to assess the effects of anti-inflammatory therapies on glycemic control in patients with T2DM.

Methods

PubMed, Embase, Web of Science, and Cochrane Library were searched up to 21 September 2022 for randomized controlled trials (RCTs) with anti-inflammatory therapies targeting the proinflammatory cytokines, cytokine receptors, and inflammation-associated nuclear transcription factors in the pathogenic processes of diabetes, such as interleukin-1β (IL-1β), interleukin-1β receptor (IL-1βR), tumor necrosis factor-α (TNF-α), and nuclear factor-κB (NF-κB). We synthesized data using mean difference (MD) and 95% confidence interval (CI). Heterogeneity between studies was assessed by I² tests. Sensitivity and subgroup analyses were also conducted.

Results

We included 16 RCTs comprising 3729 subjects in the meta-analyses. Anti-inflammatory therapies can significantly reduce the level of fasting plasma glucose (FPG) (MD = - 10.04; 95% CI: -17.69, - 2.40; P = 0.01), glycated haemoglobin (HbA1c) (MD = - 0.37; 95% CI: - 0.51, - 0.23; P < 0.00001), and C-reactive protein (CRP) (MD = - 1.05; 95% CI: - 1.50, - 0.60; P < 0.00001) compared with control, and therapies targeting IL-1β in combination with TNF-α have better effects on T2DM than targeting IL-1β or TNF-α alone. Subgroup analyses suggested that patients with short duration of T2DM may benefit more from anti-inflammatory therapies.

Conclusion

Our meta-analyses indicate that anti-inflammatory therapies targeting the pathogenic processes of diabetes can significantly reduce the level of FPG, HbA1c, and CRP in patients with T2DM.

Anti- and non-tumor necrosis factor-α-targeted therapies effects on insulin resistance in rheumatoid arthritis, psoriatic arthritis and ankylosing spondylitis

In addition to β-cell failure with inadequate insulin secretion, the crucial mechanism leading to establishment of diabetes mellitus (DM) is the resistance of target cells to insulin, i.e. insulin resistance (IR), indicating a requirement of beyond-normal insulin concentrations to maintain euglycemic status and an ineffective strength of transduction signaling from the receptor, downstream to the substrates of insulin action. IR is a common feature of most metabolic disorders, particularly type II DM as well as some cases of type I DM. A variety of human inflammatory disorders with increased levels of proinflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β, have been reported to be associated with an increased risk of IR. Autoimmune-mediated arthritis conditions, including rheumatoid arthritis (RA), psoriatic arthritis (PsA) and ankylosing spondylitis (AS), with the involvement of proinflammatory cytokines as their central pathogenesis, have been demonstrated to be associated with IR, especially during the active disease state. There is an increasing trend towards using biologic agents and small molecule-targeted drugs to treat such disorders. In this review, we focus on the effects of anti-TNF-α- and non-TNF-α-targeted therapies on IR in patients with RA, PsA and AS. Anti-TNF-α therapy, IL-1 blockade, IL-6 antagonist, Janus kinase inhibitor and phospho-diesterase type 4 blocker can reduce IR and improve diabetic hyper-glycemia in autoimmune-mediated arthritis.

Neuroprotective potential of solanesol in intracerebroventricular propionic acid induced experimental model of autism: Insights from behavioral and biochemical evidence

Autism is the category used within the newest edition of the diagnostic and statistical manual of neurodevelopmental disorders. Autism is a spectrum of disorder where a variety of behavioural patterns observed in autistic patients, such as stereotypes and repetitive behavior, hyperexcitability, depression-like symptoms, and memory and cognitive dysfunctions. Neuropathological hallmarks that associated with autism are mitochondrial dysfunction, oxidative stress, neuroinflammation, Neuro-excitation, abnormal synapse formation, overexpression of glial cells in specific brain regions like cerebellum, cerebral cortex, amygdala, and hippocampus. ICV injection of propionic acid (PPA) (4 μl/0.26 M) mimics autistic-like behavioral and biochemical alterations in rats. Literature findings reveal that there is a link between autism neuronal mitochondrial coenzyme-Q10 (CoQ10) and ETC-complexes dysfunctions are the keys pathogenic events for autism. Therefore, in the current study, we explore the neuroprotective interventions of Solanesol (SNL) 40 and 60 mg/kg alone and in combination with standard drugs Aripiprazole (ARP) 5 mg/kg, Citalopram (CTP) 10 mg/kg, Memantine (MEM) 5 mg/kg and Donepezil (DNP) 3 mg/kg to overcome behavioral and biochemical alterations in PPA induced experimental model of Autism. Chronic treatment with SNL 60 mg/kg in combination with standard drug shows a marked improvement in locomotion, muscle coordination, long-term memory and the decrease in depressive behavior. While, chronic treatment of SNL alone and in combination with standard drug aripiprazole, citalopram, donepezil, and memantine shows the Neuroprotective potential by enhancing the cognitive deficits, biochemical alterations along with reducing the level of inflammatory mediators and oxidative stress.

RING finger protein 10 is a potential drug target for diabetic vascular complications

Vascular remodeling induced by long-term hyperglycaemia is the main pathological process in diabetic vascular complications. Thus, vascular remodeling may be a potential therapeutic target in diabetes mellitus (DM) with macrovascular disease. The present study aimed to investigate the effect of RING finger protein 10 (RNF10) on vascular remodeling under conditions of chronic hyperglycaemia stimulation. We found that overexpression of RNF10 clearly decreased intimal thickness and attenuated vascular remodeling in DM. TUNEL staining showed that apoptosis was clearly inhibited, an effect that may be mediated by decreases in Bcl-2 protein expression. Quantitative analysis demonstrated that overexpression of RNF10 could suppress inflammation by reducing the levels of TNF-α, and MCP-1 mRNA and NF-κB protein. Meanwhile, overexpression of RNF10 prevented vascular smooth muscle cell (VSMC) hyperproliferation through the downregulation of cyclin D1 and CDK4 proteins. Notably, short hairpin RNF10 (shRNF10) greatly aggravated the pathological responses of diabetic vascular remodeling. These outcomes revealed that the differential expression of RNF10 had a completely opposite effect on vascular damage under hyperglycaemia, further displaying the core function of RNF10 in regulating vascular remodeling induced by diabetes. Consequently, RNF10 could be a novel target for the treatment of diabetic vascular complications.

Metabolic Adaptation in Obesity and Type II Diabetes: Myokines, Adipokines and Hepatokines

Obesity and type II diabetes are characterized by insulin resistance in peripheral tissues. A high caloric intake combined with a sedentary lifestyle is the leading cause of these conditions. Whole-body insulin resistance and its improvement are the result of the combined actions of each insulin-sensitive organ. Among the fundamental molecular mechanisms by which each organ is able to communicate and engage in cross-talk are cytokines or peptides which stem from secretory organs. Recently, it was reported that several cytokines or peptides are secreted from muscle (myokines), adipose tissue (adipokines) and liver (hepatokines) in response to certain nutrition and/or physical activity conditions. Cytokines exert autocrine, paracrine or endocrine effects for the maintenance of energy homeostasis. The present review is focused on the relationship and cross-talk amongst muscle, adipose tissue and the liver as secretory organs in metabolic diseases.

Human experimental endotoxemia in modeling the pathophysiology, genomics, and therapeutics of innate immunity in complex cardiometabolic diseases

Inflammation is a fundamental feature of several complex cardiometabolic diseases. Indeed, obesity, insulin resistance, metabolic dyslipidemia, and atherosclerosis are all closely linked inflammatory states. Increasing evidence suggests that the infectious, biome-related, or endogenous activation of the innate immune system may contribute to the development of metabolic syndrome and cardiovascular disease. Here, we describe the human experimental endotoxemia model for the specific study of innate immunity in understanding further the pathogenesis of cardiometabolic disease. In a controlled, experimental setting, administration of an intravenous bolus of purified Escherichia coli endotoxin activates innate immunity in healthy human volunteers. During endotoxemia, changes emerge in glucose metabolism, lipoprotein composition, and lipoprotein functions that closely resemble those observed chronically in inflammatory cardiovascular disease risk states. In this review, we describe the transient systemic inflammation and specific metabolic consequences that develop during human endotoxemia. Such a model provides a controlled induction of systemic inflammation, eliminates confounding, undermines reverse causation, and possesses unique potential as a starting point for genomic screening and testing of novel therapeutics for treatment of the inflammatory underpinning of cardiometabolic disease.

Fractalkine (CX3CL1), a new factor protecting β-cells against TNFα

Objective

We have previously shown the existence of a muscle–pancreas intercommunication axis in which CX3CL1 (fractalkine), a CX3C chemokine produced by skeletal muscle cells, could be implicated. It has recently been shown that the fractalkine system modulates murine β-cell function. However, the impact of CX3CL1 on human islet cells especially regarding a protective role against cytokine-induced apoptosis remains to be investigated.

Methods

Gene expression was determined using RNA sequencing in human islets, sorted β- and non-β-cells. Glucose-stimulated insulin secretion (GSIS) and glucagon secretion from human islets was measured following 24 h exposure to 1–50 ng/ml CX3CL1. GSIS and specific protein phosphorylation were measured in rat sorted β-cells exposed to CX3CL1 for 48 h alone or in the presence of TNFα (20 ng/ml). Rat and human β-cell apoptosis (TUNEL) and rat β-cell proliferation (BrdU incorporation) were assessed after 24 h treatment with increasing concentrations of CX3CL1.

Results

Both CX3CL1 and its receptor CX3CR1 are expressed in human islets. However, CX3CL1 is more expressed in non-β-cells than in β-cells while its receptor is more expressed in β-cells. CX3CL1 decreased human (but not rat) β-cell apoptosis. CX3CL1 inhibited human islet glucagon secretion stimulated by low glucose but did not impact human islet and rat sorted β-cell GSIS. However, CX3CL1 completely prevented the adverse effect of TNFα on GSIS and on molecular mechanisms involved in insulin granule trafficking by restoring the phosphorylation (Akt, AS160, paxillin) and expression (IRS2, ICAM-1, Sorcin, PCSK1) of key proteins involved in these processes.

Conclusions

We demonstrate for the first time that human islets express and secrete CX3CL1 and CX3CL1 impacts them by decreasing glucagon secretion without affecting insulin secretion. Moreover, CX3CL1 decreases basal apoptosis of human β-cells. We further demonstrate that CX3CL1 protects β-cells from the adverse effects of TNFα on their function by restoring the expression and phosphorylation of key proteins of the insulin secretion pathway.

Exercise induced adipokine changes and the metabolic syndrome

The lack of adequate physical activity and obesity created a worldwide pandemic. Obesity is characterized by the deposition of adipose tissue in various parts of the body; it is now evident that adipose tissue also acts as an endocrine organ capable of secreting many cytokines that are though to be involved in the pathophysiology of obesity, insulin resistance, and metabolic syndrome. Adipokines, or adipose tissue-derived proteins, play a pivotal role in this scenario. Increased secretion of proinflammatory adipokines leads to a chronic inflammatory state that is accompanied by insulin resistance and glucose intolerance. Lifestyle change in terms of increased physical activity and exercise is the best nonpharmacological treatment for obesity since these can reduce insulin resistance, counteract the inflammatory state, and improve the lipid profile. There is growing evidence that exercise exerts its beneficial effects partly through alterations in the adipokine profile; that is, exercise increases secretion of anti-inflammatory adipokines and reduces proinflammatory cytokines. In this paper we briefly describe the pathophysiologic role of four important adipokines (adiponectin, leptin, TNF-α, and IL-6) in the metabolic syndrome and review some of the clinical trials that monitored these adipokines as a clinical outcome before and after exercise.

Effects of rosiglitazone on inflammation in Otsuka long-evans Tokushima Fatty rats

Background

Inflammation plays a role in the response to metabolic stress in type 2 diabetes. However, the effects of rosiglitazone on inflammation of skeletal muscle have not been fully examined in type 2 diabetes.

Methods

We investigated the effects of the insulin-sensitizing anti-diabetic agent, rosiglitazone, on the progression of skeletal muscle inflammation in Otsuka Long-Evans Tokushima Fatty (OLETF) type 2 diabetic rats. We examined the expression of serologic markers (serum glucose, insulin and free fatty acid) and inflammatory cytokines (tumor-necrosis factor-α, interleukin [IL]-1β and IL-6) in OLETF rats from early to advanced diabetic stage (from 28 to 40 weeks of age).

Results

Serum glucose and insulin concentrations were significantly decreased in rosiglitazone-treated OLETF rats compared to untreated OLETF rats. Rosiglitazone treatment significantly decreased the concentrations of serum inflammatory cytokines from 28 to 40 weeks of age. The mRNA expression of various cytokines in skeletal muscle was reduced in rosiglitazone-treated OLETF rats compared with untreated OLETF rats. Furthermore, rosiglitazone treatment resulted in the downregulation of ERK1/2 phosphorylation and NF-κB expression in the skeletal muscle of OLETF rats.

Conclusion

These results suggest that rosiglitazone may improve insulin sensitivity with its anti-inflammatory effects on skeletal muscle.

Elevation of tumor necrosis factor-alpha induces the overproduction of postprandial intestinal apolipoprotein B48-containing very low-density lipoprotein particles: evidence for related gene expression of inflammatory, insulin and lipoprotein signaling in enterocytes

The aim of this study was to determine whether systemic elevation of tumor necrosis factor (TNF)-alpha induces intestinal-derived apolipoprotein B (apoB)48-containing very low-density lipoprotein (VLDL) production in hamsters after fat loading and whether TNF-alpha disturbs the related mRNA expression in inflammatory, insulin and lipoprotein signaling pathways in primary enterocytes. In vivo TNF-alpha and Triton-WR1339 infusion, Western blotting and reverse transcriptase-polymerase chain reaction were combined to explore the mechanisms underlying intestinal overproduction of apoB48-containing chylomicrons and VLDL(1) particles by TNF-alpha. TNF-alpha infusion increased intestinal production of chylomicron and VLDL(1)-apoB48 in postprandial (fat load) states. Following TNF-alpha-treatment in enterocytes, there was enhanced gene expression of Il1alpha and beta, Il6 and Tnf and decreased mRNA levels of components of the insulin signaling pathway including the insulin receptor (Ir), Ir substrate-1 and 2, PI3 k, and Akt, but increased phosphatase and tensin homolog deleted on chromosome ten (Pten) protein and mRNA expression. TNF-alpha also induced Cd36 and peroxisome proliferators-activated receptor (Ppar)gamma expression, as well as microsomal triglyceride transfer protein (Mtp) protein and mRNA, but suppressed the sterol regulatory element binding protein (Srebp)1c protein and mRNA level. Systemic elevation of TNF-alpha stimulates the postprandial overproduction of apoB48-containing chylomicrons and VLDL(1) particles by disturbing intestinal gene expression of the inflammatory, insulin and lipoprotein pathways. These findings provide mechanistic links among the inflammatory factor, TNF-alpha, intestinal inflammatory/insulin insensitivity and the overproduction of intestinal apoB48-containing lipoproteins.

Silencing mitogen-activated protein 4 kinase 4 (MAP4K4) protects beta cells from tumor necrosis factor-alpha-induced decrease of IRS-2 and inhibition of glucose-stimulated insulin secretion

Obesity and type 2 diabetes present partially overlapping phenotypes with systemic inflammation as a common feature, raising the hypothesis that elevated cytokine levels may contribute to peripheral insulin resistance as well as the decreased beta cell functional mass observed in type 2 diabetes. In healthy humans, TNF-alpha infusion induces skeletal muscle insulin resistance. We now explore the impact of TNF-alpha on primary beta cell function and the underlying signaling pathways. Human and rat primary beta cells were sorted by FACS and cultured for 24 h +/- 20 ng/ml TNF-alpha to explore the impact on apoptosis, proliferation, and short-term insulin secretion (1 h, 2.8 mm glucose followed by 1 h, 16.7 mm glucose at the end of the 24-h culture period) as well as key signaling protein phosphorylation and expression. Prior exposure to TNF-alpha for 24 h inhibits glucose-stimulated insulin secretion from primary beta cells. This is associated with a decrease in glucose-stimulated phosphorylation of key proteins in the insulin signaling pathway including Akt, AS160, and other Akt substrates, ERK as well as the insulin receptor. Strikingly, TNF-alpha treatment decreased IRS-2 protein level by 46 +/- 7% versus control, although mRNA expression was unchanged. While TNF-alpha treatment increased MAP4K4 mRNA expression by 33 +/- 5%, knockdown of MAP4K4 by siRNA-protected beta cells against the detrimental effects of TNF-alpha on both insulin secretion and signaling. We thus identify MAP4K4 as a key upstream mediator of TNF-alpha action on the beta cell, making it a potential therapeutic target for preservation of beta cell function in type 2 diabetes.

Chronic pain and obesity in elderly people: results from the Einstein aging study

OBJECTIVES

To determine the prevalence of chronic pain in elderly people and its relationship with obesity and associated comorbidities and risk factors.

DESIGN

Cross-sectional.

SETTING

Community.

PARTICIPANTS

A representative community sample of 840 subjects aged 70 and older.

MEASUREMENTS

The prevalence of chronic pain and its relationship with obesity (categories defined according to body mass index (BMI)), other medical risk factors, and psychiatric comorbidities were examined. Chronic pain was defined as pain of at least moderate severity (> or =4 on a 10-point scale) some, most, or all of the time for the previous 3 months.

RESULTS

The sample was mostly female (62.8%), and the average age was 80 (range 70-101). The prevalence of chronic pain was 52% (39.7% in men; 58.9% in women). Subjects with chronic pain were more likely to report a diagnosis of depression (odds ratio (OR)=2.5, 95% confidence interval (CI)=1.40-4.55) and anxiety (OR=2.3, 95% CI=1.22-4.64). Obese subjects (BMI 30-34.9) were twice as likely (OR=2.1, 95%CI=1.33-3.28) and severely obese subjects (BMI> or =35) were more than four times as likely (OR=4.5, 95% CI=1.85-12.63) as those of normal weight (BMI 18.5-24.9) to have chronic pain. Obese subjects were significantly more likely to have chronic pain in the head, neck or shoulder, back, legs or feet, and abdomen or pelvis than subjects who were not obese. In multivariate models, obesity (OR=2.0, 95% CI=1.27-3.26) and severe obesity (OR=4.1, 95% CI=1.57-10.82) were associated with chronic pain after adjusting for age, sex, diabetes mellitus, hypertension, depression, anxiety, and education.

CONCLUSION

Chronic pain is common in this elderly population, affects women more than men, and is highly associated with obesity.

Adipose inflammation, insulin resistance, and cardiovascular disease

Adiposity-associated inflammation and insulin resistance are strongly implicated in the development of type 2 diabetes and atherosclerotic cardiovascular disease. This article reviews the mechanisms of adipose inflammation, because these may represent therapeutic targets for insulin resistance and for prevention of metabolic and cardiovascular consequences of obesity. The initial insult in adipose inflammation and insulin resistance, mediated by macrophage recruitment and endogenous ligand activation of Toll-like receptors, is perpetuated through chemokine secretion, adipose retention of macrophages, and elaboration of pro-inflammatory adipocytokines. Activation of various kinases modulates adipocyte transcription factors, including peroxisome proliferator-activated receptor-gamma and NFkappaB, attenuating insulin signaling and increasing adipocytokine and free fatty acid secretion. Inflammation retards adipocyte differentiation and further exacerbates adipose dysfunction and inflammation. Paracrine and endocrine adipose inflammatory events induce a local and systemic inflammatory, insulin-resistant state promoting meta-bolic dyslipidemia, type 2 diabetes, and cardiovascular disease. Developing therapeutic strategies that target both adipose inflammation and insulin resistance may help to prevent type 2 diabetes and cardiovascular disease in the emerging epidemic of obesity.

Reducing the weight of cancer: mechanistic targets for breaking the obesity-carcinogenesis link

The prevalence of obesity, an established epidemiologic risk factor for many cancers, has risen steadily for the past several decades in the US. The increasing rates of obesity among children are especially alarming and suggest continuing increases in the rates of obesity-related cancers for many years to come. Unfortunately, the mechanisms underlying the association between obesity and cancer are not well understood. In particular, the effects on the carcinogenesis process and mechanistic targets of interventions that modulate energy balance, such as reduced-calorie diets and physical activity, have not been well characterized. The purpose of this review is to provide a strong foundation for the translation of mechanism-based research in this area by describing key animal and human studies of energy balance modulations involving diet or physical activity and by focusing on the interrelated pathways affected by alterations in energy balance. Particular attention is placed on signaling through the insulin and insulin-like growth factor-1 receptors, including components of the Akt and mammalian target of rapamycin (mTOR) signaling pathways downstream of these growth factor receptors. These pathways have emerged as potential targets for disrupting the obesity-cancer link. The ultimate goal of this work is to provide the missing mechanistic information necessary to identify targets for the prevention and control of cancers related to or caused by excess body weight.

Physical activity and cancer prevention : pathways and targets for intervention

The prevalence of obesity, an established epidemiological risk factor for many cancers, has risen steadily for the past several decades in the US and many other countries. Particularly alarming are the increasing rates of obesity among children, portending continuing increases in the rates of obesity and obesity-related cancers for many years to come. Modulation of energy balance, via increased physical activity, has been shown in numerous comprehensive epidemiological reviews to reduce cancer risk. Unfortunately, the effects and mechanistic targets of physical activity interventions on the carcinogenesis process have not been thoroughly characterized. Studies to date suggest that exercise can exert its cancer-preventive effects at many stages during the process of carcinogenesis, including both tumour initiation and progression. As discussed in this review, exercise may be altering tumour initiation events by modifying carcinogen activation, specifically by enhancing the cytochrome P450 system and by enhancing selective enzymes in the carcinogen detoxification pathway, including, but not limited to, glutathione-S-transferases. Furthermore, exercise may reduce oxidative damage by increasing a variety of anti-oxidant enzymes, enhancing DNA repair systems and improving intracellular protein repair systems. In addition to altering processes related to tumour initiation, exercise may also exert a cancer-preventive effect by dampening the processes involved in the promotion and progression stages of carcinogenesis, including scavenging reactive oxygen species (ROS); altering cell proliferation, apoptosis and differentiation; decreasing inflammation; enhancing immune function; and suppressing angiogenesis. A paucity of data exists as to whether exercise may be working as an anti-promotion strategy via altering ROS in initiated or preneoplastic models; therefore, no conclusions can be made about this possible mechanism. The studies directly examining cell proliferation and apoptosis have shown that exercise can enhance both processes, which is difficult to interpret in the context of carcinogenesis. Studies examining the relationship between exercise and chronic inflammation suggest that exercise may reduce pro-inflammatory mediators and reduce the state of low-grade, chronic inflammation. Additionally, exercise has been shown to enhance components of the innate immune response (i.e. macrophage and natural killer cell function). Finally, only a limited number of studies have explored the relationship between exercise and angiogenesis; therefore, no conclusions can be made currently about the role of exercise in the angiogenesis process as it relates to tumour progression. In summary, exercise can alter biological processes that contribute to both anti-initiation and anti-progression events in the carcinogenesis process. However, more sophisticated, detailed studies are needed to examine each of the potential mechanisms contributing to an exercise-induced decrease in carcinogenesis in order to determine the minimum dose, duration and frequency of exercise needed to yield significant cancer-preventive effects, and whether exercise can be used prescriptively to reverse the obesity-induced physiological changes that increase cancer risk.

Type 2 diabetes mellitus, resistance training, and innate immunity: is there a common link?

Type 2 diabetes mellitus is a serious chronic disease that is very prevalent in the developed world. The etiology of this disease is not well understood. Recently, the role of the innate immune system in the pathogenesis of type 2 diabetes and its complications has received a great deal of attention. Cytokines, acute phase proteins, and phagocytes have been implicated in this model. Resistance training has known benefits in type 2 diabetic patients and older adults, such as improved insulin action, insulin sensitivity, fasting blood glucose and insulin, and glucose tolerance levels. Actions of pro-inflammatory mediators linked to dysregulated innate immune activity have been associated with type 2 diabetes. The immunomodulatory effects of exercise, and in particular approaches such as resistance training, may provide a strategy to counter these pro-inflammatory effectors. However, the effects of resistance training on innate immunity have not been studied extensively in adults with type 2 diabetes or in older adults who are at increased risk for development of type 2 diabetes. This review discusses the possibility that resistance training may have positive effects on innate immunity in this population and so may provide benefits in addition to improving strength and functional abilities. In particular, the potential of resistance training to modulate pro-inflammatory parameters associated with type 2 diabetes, as a strategy that could provide multiple beneficial health outcomes, is addressed.

Associations between insulin resistance and TNF-alpha in plasma, skeletal muscle and adipose tissue in humans with and without type 2 diabetes

AIMS/HYPOTHESIS

Clear evidence exists that TNF-alpha inhibits insulin signalling and thereby glucose uptake in myocytes and adipocytes. However, conflicting results exist with regard to the role of TNF-alpha in type 2 diabetes.

METHODS

We obtained blood and biopsy samples from skeletal muscle and subcutaneous adipose tissue in patients with type 2 diabetes (n = 96) and healthy controls matched for age, sex and BMI (n = 103).

RESULTS

Patients with type 2 diabetes had higher plasma levels of fasting insulin (p < 0.0001) and glucose (p < 0.0001) compared with controls, but there was no difference between groups with regard to fat mass. Plasma levels of TNF-alpha (p = 0.0009) and soluble TNF receptor 2 (sTNFR2; p = 0.002) were elevated in diabetic patients. Insulin sensitivity was correlated with quartiles of plasma TNF-alpha after adjustment for age, sex, obesity, WHR, neutrophils, IL-6 and maximum O(2) uptake (VO2/kg) in the diabetes group (p < 0.05). The TNF mRNA content of adipose or muscle tissue did not differ between the groups, whereas muscle TNF-alpha protein content, evaluated by western blotting, was higher in type 2 diabetic patients. Immunohistochemistry revealed more TNF-alpha protein in type 2 than in type 1 muscle fibres.

CONCLUSIONS/INTERPRETATION

After adjustment for multiple confounders, plasma TNF-alpha is associated with insulin resistance. This supports the idea that TNF-alpha plays a significant role in the pathogenesis of chronic insulin resistance in humans. However, findings on the TNF-alpha protein levels in plasma and skeletal muscle indicate that measurement of TNF mRNA content in adipose or muscle tissue provides no information with regard to the degree of insulin resistance.

Insulin resistance in patients with rheumatoid arthritis: effect of anti-TNFalpha therapy

OBJECTIVES

We undertook this study to test the hypotheses that patients with active rheumatoid arthritis (RA) are insulin resistant and that anti-tumour necrosis factor-alpha (TNFalpha) therapy improves not only the clinical state of these patients but also their glucose metabolism.

METHODS

Nine RA patients with active disease and nine healthy subjects, matched for sex, age, and body mass index (BMI), underwent a hyperinsulinaemic euglycaemic clamp. The RA patients received anti-TNFalpha therapy with Humira(adalimumab) and had the insulin clamp re-evaluated after 8 weeks of treatment.

RESULTS

Patients with RA had marked insulin resistance (glucose infusion rate (GIR) area under the curve (AUC) was 499+/-55 mg/kg in the RA group compared to 710+/-77 mg/kg in the control group; p<0.05). However, insulin sensitivity did not differ before and after 8 weeks of adalimumab therapy. The RA patients demonstrated a reduction in C-reactive protein (CRP) and interleukin-6 (IL-6) levels after the therapy as compared to pretreatment values, but there was no concomitant effect on plasma levels of TNFalpha.

CONCLUSION

RA patients with active disease showed marked insulin resistance that was not influenced by anti-TNFalpha therapy despite a reduction in systemic inflammation during the treatment.

The significance of tumor necrosis factor-alpha in newly diagnosed type 2 diabetic patients by transient intensive insulin treatment

This study was performed to investigate whether transient intensive insulin therapy with an insulin pump (TIIT) can decrease serum tumor necrosis factor-alpha (TNF-alpha) and explore whether the decrease of serum TNF-alpha has correlation with the improvement of islet beta-Cell function and the decrease of insulin resistance. Thirty healthy volunteers served as control subjects. One hundred and thirty-eight newly diagnosed type 2 diabetic patients had been treated with TIIT for 2 weeks. TNF-alpha, free fatty acids (FFAs), glucose, and insulin (INS) had been measured before and after TIIT, respectively. Homeostasis model assessment (HOMA) was used to estimate insulin resistance (HOMA-IR) and islet beta-Cell function (HOMA-beta). TNF-alpha was significantly increased in diabetes. After TIIT, TNF-alpha, fasting blood glucose, FFAs, and HOMA-IR were significantly decreased. HOMA-beta and the areas under the curves of INS were significantly increased during intravenous glucose tolerance tests. TNF-alpha had not only significant negative correlation with the changes of insulin secretion, but also significant positive correlation with the changes of HOMA-IR after adjustment of blood glucose. Partial correlation analyses demonstrated that there was an indepenent relationship between TNF-alpha and HOMA-IR and HOMA-beta. Our study confirms that TIIT can effectively decrease serum TNF-alpha in type 2 diabetes. It is inferred that the decrease of serum TNF-alpha might be involved in the improvement of beta-Cell function and the decrease of insulin resistance by TIIT.

Intensive treatment of risk factors in patients with type-2 diabetes mellitus is associated with improvement of endothelial function coupled with a reduction in the levels of plasma asymmetric dimethylarginine and endogenous inhibitor of nitric oxide synthase

AIMS

Vascular endothelium is a major organ involved in hyperglycaemia and is affected by plasma asymmetric dimethylarginine (ADMA). ADMA is an endogenous, competitive inhibitor of nitric oxide synthase and is induced by inflammatory cytokines of tumour necrosis factor (TNF)-alpha in vitro. We hypothesized that a tight glycaemic control may restore endothelial function in patients with type-2 diabetes mellitus (DM), in association with modulation of TNF-alpha and/or reduction of ADMA level.

METHODS AND RESULTS

In 24 patients with type-2 DM, the flow-mediated, endothelium-dependent dilation (FMD: %) of brachial arteries during reactive hyperaemia was determined by a high-resolution ultrasound method. Blood samples for glucose, cholesterol, TNF-alpha, and ADMA analyses were also collected from these patients after fasting. No significant glycaemic or FMD changes were observed in 10 patients receiving the conventional therapy. In 14 patients who were hospitalized and intensively treated, there was a significant decrease in glucose level after the treatment [from 190+/-55 to 117+/-21 (mean+/-SD) mg/dL, P<0.01]. After the intensive control of glucose level, FMD increased significantly (from 2.5+/-0.9 to 7.2+/-3.0%), accompanied by a significant (P<0.01) decrease in TNF-alpha (from 29+/-16 to 11+/-9 pg/dL) and ADMA (from 4.8+/-1.5 to 3.5+/-1.1 microM/L) levels. The changes in FMD after treatment correlated inversely with those in TNF-alpha (R=-0.711, P<0.01) and ADMA (R=-0.717, P<0.01) levels.

CONCLUSION

The intensive correction of hyperglycaemia is associated with the improvement of endothelial function, which is coupled with the decrease in the levels of reduction of plasma TNF-alpha and ADMA in patients with type-2 DM. A strict glycaemic control may exert anti-cytokine and anti-atherogenic effects and may therefore be pathophysiologically important.

Metabolic and vascular effects of tumor necrosis factor-alpha blockade with etanercept in obese patients with type 2 diabetes

OBJECTIVE

The pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) impairs insulin action in insulin-sensitive tissues, such as fat, muscle and endothelium, and causes endothelial dysfunction. We hypothesized that TNF-alpha blockade with etanercept could reverse vascular and metabolic insulin resistance.

METHOD AND RESULTS

Twenty obese patients with type 2 diabetes were randomized to etanercept treatment (25 mg subcutaneously twice weekly for 4 weeks) or used as controls in an open parallel study. Forearm blood flow and glucose uptake were measured during intra-arterial infusions of serotonin, sodium nitroprusside and insulin co-infused with serotonin. Beta-cell function was assessed with oral and intra-venous glucose tolerance tests and whole-body insulin sensitivity by hyperinsulinemic euglycemic clamps. Plasma levels of C-reactive protein and interleukin-6 decreased significantly with etanercept (C-reactive protein from 9.9 +/- 3.1 to 4.8 +/- 1.4 mg l(-1), p = 0.04; interleukin-6 from 3.1 +/- 0.4 to 1.9 +/- 0.2 ng l(-1), p = 0.03). Vasodilatory responses to serotonin and sodium nitroprusside infusions remained unchanged. Insulin effect on vasodilatation and on whole-body and forearm glucose uptake remained unchanged as well. Beta-cell function tended to improve.

CONCLUSION

Although short-term etanercept treatment had a significant beneficial effect on systemic inflammatory markers, no improvement of vascular or metabolic insulin sensitivity was observed.

Low serum concentration of sulfatide and presence of sulfated lactosylceramid are associated with Type 2 diabetes. The Skaraborg Project

AIMS

The glycosphingolipid sulfatide (sulfated galactosyl-ceramide) increases exocytosis of beta-cell secretory granules, activates K(ATP)-channels and is thereby able to influence insulin secretion through its presence in the islets. A closely related compound, sulfated lactosylceramide (sulf-lac-cer), is present in the islets during fetal and neonatal life when, as in Type 2 diabetes, insulin is secreted autonomically without the usual first phase response to glucose. The aim was to examine whether serum concentrations of these glycolipids are associated with Type 2 diabetes.

METHODS

A case-control study, comprising 286 women and 283 men, was designed using a population-based sample of patients with Type 2 diabetes and a population survey.

RESULTS

Low serum concentrations of sulfatide were associated with Type 2 diabetes, independent of traditional risk factors for diabetes in a sex-specific analysis: odds ratio (OR) 2.1 (95% confidence interval 1.1, 3.9) in men, and 2.3 (1.2, 4.3) in women, comparing the lowest and the highest tertiles. Type 2 diabetes was also associated with detectable amounts of sulf-lac-cer in serum: OR 1.7 (0.9, 3.4) in men, and 7.6 (3.8, 15.2) in women. After adjustment for confounding from other diabetes risk factors, these associations remained basically unchanged. The connections between sulfatide and Type 2 diabetes, and sulf-lac-cer and Type 2 diabetes were independent of each other. Insulin resistance (HOMA-IR) was negatively correlated with sulfatide concentration and positively correlated with sulf-lac-cer (both P < 0.0001, independently).

CONCLUSIONS

We report a new, robust and highly significant independent association between Type 2 diabetes and serum concentrations of sulfatide in both sexes, and sulf-lac-cer in females. The associations were also independent of other known diabetes risk factors.

Leptin enhances TNF-alpha production via p38 and JNK MAPK in LPS-stimulated Kupffer cells

Leptin is now recognized as a proinflammatory cytokine and thought to be a progressive factor for non-alcoholic steatohepatitis (NASH). Here we showed the effects of leptin on the production of TNF-alpha (tumor necrosis factor-alpha) by Kupffer cells (KCs) with signal transduction. Leptin enhanced TNF-alpha production accompanied by a dose-dependent increase of MAPK activity in lipopolysaccharide (LPS)-stimulated KCs. SB203580 and JNK inhibitor I, specific inhibitors of P38 and JNK, inhibited TNF-alpha production in KCs but PD98059, an inhibitor of the ERK pathway, did not affect TNF-alpha production by KCs. Recombinant constitutively active adenovirus (Ad)-MKK6 and-MKK7 increased TNF-alpha production in KCs with activation of P38 and JNK without any change by Ad-MEK1 delivery. On the other hand, KCs isolated from the Zucker rat (fa/fa), a leptin receptor-deficient rat, showed reduced production of TNF-alpha on stimulation with LPS. The delivery of Ad-MKK6 and-MKK7, but not Ad-MEK1, increased TNF-alpha production in KCs of Zucker rats with activation of P38 and JNK. Addition of leptin to normal rats increased LPS-induced hepatic TNF-alpha production in vivo and leptin receptor-deficient Zucker rats showed reduced hepatic TNF-alpha production on addition of LPS in vivo. These findings indicate that P38 and JNK pathways are involved in the signal transduction of leptin enhancement of LPS-induced TNF-alpha production.

A prospective study of soluble tumor necrosis factor-alpha receptor II (sTNF-RII) and risk of coronary heart disease among women with type 2 diabetes

OBJECTIVE

Tumor necrosis factor-alpha (TNF-alpha), a cytokine secreted by adipose tissue and other cells, might play a role in insulin resistance.

RESEARCH DESIGN AND METHODS

Of 32,826 women from the Nurses' Health Study who provided blood at baseline, we followed 929 women with type 2 diabetes. During 10 years of follow-up, we documented 124 incident cases of coronary heart disease (CHD).

RESULTS

After adjustment for age, smoking, BMI, and other cardiovascular risk factors, the relative risks (RRs) comparing extreme quartiles of soluble TNF-alpha receptor II (sTNF-RII) were 2.48 (95% CI 1.08-5.69; P = 0.034) for myocardial infarction (MI) and 2.02 (1.17-3.48; P = 0.003) for total CHD. The probability of developing CHD over 10 years was higher among diabetic subjects with substantially higher levels of both sTNF-RII (>75th percentile) and HbA(1c) (>7%), compared with diabetic subjects with lower levels (25% vs. 7%, P < 0.0001). Diabetic subjects with only higher sTNF-RII or HbA(1c) had similar (16-17%) risk. In a multivariate model, diabetic subjects with higher levels of both sTNF-RII and HbA(1c) had an RR of 3.66 (1.85-7.22) for MI and 3.03 (1.82-5.05) for total CHD, compared with those with lower levels of both biomarkers.

CONCLUSIONS

Increased levels of sTNF-RII were strongly associated with risk of CHD among diabetic women, independent of hyperglycemia.

The anti-inflammatory effect of exercise

Regular exercise offers protection against all-cause mortality, primarily by protection against cardiovascular disease and Type 2 diabetes mellitus. The latter disorders have been associated with chronic low-grade systemic inflammation reflected by a two- to threefold elevated level of several cytokines. Adipose tissue contributes to the production of TNF-α, which is reflected by elevated levels of soluble TNF-α receptors, IL-6, IL-1 receptor antagonist, and C-reactive protein. We suggest that TNF-α rather than IL-6 is the driver behind insulin resistance and dyslipidemia and that IL-6 is a marker of the metabolic syndrome, rather than a cause. During exercise, IL-6 is produced by muscle fibers via a TNF-independent pathway. IL-6 stimulates the appearance in the circulation of other anti-inflammatory cytokines such as IL-1ra and IL-10 and inhibits the production of the proinflammatory cytokine TNF-α. In addition, IL-6 enhances lipid turnover, stimulating lipolysis as well as fat oxidation. We suggest that regular exercise induces suppression of TNF-α and thereby offers protection against TNF-α-induced insulin resistance. Recently, IL-6 was introduced as the first myokine, defined as a cytokine that is produced and released by contracting skeletal muscle fibers, exerting its effects in other organs of the body. Here we suggest that myokines may be involved in mediating the health-beneficial effects of exercise and that these in particular are involved in the protection against chronic diseases associated with low-grade inflammation such as diabetes and cardiovascular diseases.

Arterial osteoprotegerin: increased amounts in diabetes and modifiable synthesis from vascular smooth muscle cells by insulin and TNF-alpha

AIMS/HYPOTHESIS

Extracellular matrix modifications and linear medial calcifications are elements of diabetic macroangiopathy. We hypothesised that the bone-related protein osteoprotegerin (OPG) may occur in altered amounts in the arterial wall in diabetes, putatively associated with altered synthesis from vascular cells.

METHODS

The amount of OPG in the thoracic aorta, obtained at autopsy from 21 diabetic and 42 sex- and age-matched controls, was measured in tissue extracts by an ELISA. The production of OPG was estimated in conditioned media by an ELISA, and OPG mRNA was estimated by RT-PCR in vascular cells grown in vitro.

RESULTS

The content of OPG was increased in tunica media samples from diabetic individuals. No differences between diabetic and non-diabetic subjects were observed in tunica intima. Human vascular smooth muscle cells (HVSMCs) produced approximately 30 times more OPG than human umbilical vein endothelial cells. The OPG production into the medium decreased dose- and time-dependently after insulin treatment (maximal effect approximately 60% of control) in HVSMCs, whereas TNF-alpha supplement gave rise to increased OPG synthesis in a time- and dose-dependent manner (maximal effect approximately 200% of control). Similar effects on OPG mRNA expression were observed. Addition of growth hormone (10 ng/ml) or extra glucose (25 mmol/l) to the growth medium had no effect.

CONCLUSIONS/INTERPRETATION

Increased OPG concentrations in the arterial wall in diabetes may be part of generalised matrix alterations, putatively related to the development of vascular calcifications. Altered arterial OPG content may be a consequence of the effects of hormones and cytokines, like insulin and TNF-alpha.

Reductions in plasma cytokine levels with weight loss improve insulin sensitivity in overweight and obese postmenopausal women

OBJECTIVE

The purpose of this study was to determine whether improvements in insulin sensitivity with weight loss are mediated by changes in inflammation in obese, postmenopausal women.

RESEARCH DESIGN AND METHODS

We studied 58 sedentary, overweight, and obese (BMI 33 +/- 1 kg/m(2), means +/- SEM) postmenopausal (58 +/- 1 year) women at baseline and 37 women who completed 6 months of weight loss induced by diet and exercise. The women underwent 3-h hyperinsulinemic-euglycemic clamps (40 mU x m(-2) x min(-1)) to determine glucose utilization (M). Insulin sensitivity was determined as M/I, the amount of glucose metabolized per unit of plasma insulin (I). Visceral adipose tissue (VAT) and plasma concentrations of C-reactive protein (CRP), cytokines interleukin (IL)-6, and tumor necrosis factor (TNF)-alpha, as well as their soluble receptors, were measured.

RESULTS

At baseline, CRP concentration was a predictor of both glucose utilization and insulin sensitivity, independent of adiposity, race, and aerobic fitness (M: partial r = -0.30, P = 0.03, and M/I: partial r = -0.32, P = 0.02). Weight loss resulted in significant reductions in body weight, fat mass, VAT, and fasting glucose and insulin levels (P < 0.05). Both glucose utilization and insulin sensitivity increased by 16% (P < 0.05). CRP, IL-6, and soluble TNF receptor (sTNFR)-1 concentrations decreased (P < 0.05), but concentrations of TNF-alpha, sTNFR-2, and soluble IL-6 receptor (IL-6sR) did not change. In stepwise regression models to predict changes in glucose homeostasis, changes in VAT and sTNF-R1 independently predicted changes in glucose utilization (r = -0.49 and cumulative r = -0.64, P < 0.01), while changes in VAT and IL-6 were both independent predictors of changes in insulin sensitivity (r = -0.57 and cumulative r = -0.68, P < 0.01).

CONCLUSIONS

Improvements in glucose metabolism with weight loss programs are independently associated with decreases in cytokine concentrations, suggesting that a reduction in inflammation is a potential mechanism that mediates improvements in insulin sensitivity.

Serum tumor necrosis factor-alpha levels and components of the metabolic syndrome in obese adolescents

Tumor necrosis factor-alpha (TNF-alpha) seems to be increased in obese subjects, suggesting its role as a proinflammatory cytokine to insulin resistance and metabolic abnormalities in obesity. The aim of this study was to evaluate the relationship between serum TNF-alpha, soluble TNF-alpha receptor 1 (sTNF-R1), TNF-alpha receptor 2 (sTNF-R2), and metabolic syndrome (MS) components and anthropometric indices in obese and non-obese adolescents. A cross-sectional study was performed on obese and non-obese adolescents. We studied 71 adolescents (age, 15 to 16 years old); 39 were obese (obese group; 14 males and 25 females) and 32 were non-obese adolescents (non-obese lean group; 12 males and 20 females). The body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were determined in each subject. The serum TNF-alpha, sTNF-R1, sTNF-R2, fasting plasma glucose (FPG), and lipid profile were also measured. The mean serum TNF-alpha, sTNF-R1, and sTNF-R2 were significantly higher in the obese than the non-obese group (TNF-alpha, 18.15 v 5.88 pg/mL, P < .001; sTNF-R1, 2.01 v 1.40 ng/mL, P < .001; sTNF-R2, 6.06 v 3.70 pg/mL, P < .001). The serum TNF-alpha concentrations were positively correlated with the BMI (TNF-alpha, r = 0.346, P < .05; sTNF-R1, r = 0.624, P < .001; sTNF-R2, r = 0.482, P < .001, respectively) and WC (TNF-alpha, r = 0.525, P < .05; sTNF-R1, r = 0.700, P < .001; sTNF-R2, r = 0.669, P < .001, respectively). The serum TNF-alpha was positively correlated with triglyceride (TG) and DBP, and negatively with high-density lipoprotein-cholesterol (HDLC). The sTNF-R1 and sTNF-R2 were correlated with TG and DBP, and TG, respectively. Obese compared with non-obese adolescents exhibited higher concentrations of TNF-alpha and its soluble receptors, and the higher TNF-alpha concentrations were associated with several components of MS in obese adolescents.

Obesity and the Impact of Chronic Pain

OBJECTIVE

To evaluate obesity as a marker for increased pain severity, disability, and psychologic distress in treatment-seeking, mixed chronic pain patients.

METHODS

Three hundred seventy-two consecutive chronic pain patients seeking evaluation at a university pain clinic were divided into 3 weight categories, based on body mass index (BMI): normal (BMI < 25 kg/m2), overweight (BMI between 25 kg/m and 30 kg/m2), and obese (BMI > or = 30 kg/m2). Patients completed questionnaires to identify pain severity, disability, depression, anxiety, and quality of life.

RESULTS

Pain severity and days per week with pain were similar among the weight groups. Disability was related to increasing weight status, with increased BMI associated with more days per week with both reduced activity and complete disability. Depressive symptoms were also related to weight category, with an average Beck Depression Inventory score of 11.81 +/- 7.55 in normal, 12.88 +/- 11.64 in overweight, and 15.78 +/- 9.88 in obese patients. Anxiety scores were similar among the weight categories. Physical function domain of quality of life was also reduced in relation to weight.

CONCLUSIONS

Weight is associated with co-morbid disability, depression, and reduced quality of life for physical function in chronic pain patients. Calculation of the BMI should become a routine part of the screening evaluation for chronic pain patients, with additional screening for disability and psychologic distress in patients with elevated BMIs.

Insulin receptor substrate-2-dependent interleukin-4 signaling in macrophages is impaired in two models of type 2 diabetes mellitus

We have shown previously that hyperinsulinemia inhibits interferon-alpha-dependent activation of phosphatidylinositol 3-kinase (PI3-kinase) through mammalian target of rapamycin (mTOR)-induced serine phosphorylation of insulin receptor substrate (IRS)-1. Here we report that chronic insulin and high glucose synergistically inhibit interleukin (IL)-4-dependent activation of PI3-kinase in macrophages via the mTOR pathway. Resident peritoneal macrophages (PerMPhis) from diabetic (db/db) mice showed a 44% reduction in IRS-2-associated PI3-kinase activity stimulated by IL-4 compared with PerMPhis from heterozygote (db/+) control mice. IRS-2 from db/db mouse PerMPhis also showed a 78% increase in Ser/Thr-Pro motif phosphorylation without a difference in IRS-2 mass. To investigate the mechanism of this PI3-kinase inhibition, 12-O-tetradecanoylphorbol-13-acetate-matured U937 cells were treated chronically with insulin (1 nm, 18 h) and high glucose (4.5 g/liter, 48 h). In these cells, IL-4-stimulated IRS-2-associated PI3-kinase activity was reduced by 37.5%. Importantly, chronic insulin or high glucose alone did not impact IL-4-activated IRS-2-associated PI3-kinase. Chronic insulin + high glucose did reduce IL-4-dependent IRS-2 tyrosine phosphorylation and p85 association by 54 and 37%, respectively, but did not effect IL-4-activated JAK/STAT signaling. When IRS-2 Ser/Thr-Pro motif phosphorylation was examined, chronic insulin + high glucose resulted in a 92% increase in IRS-2 Ser/Thr-Pro motif phosphorylation without a change in IRS-2 mass. Pretreatment of matured U937 cells with rapamycin blocked chronic insulin + high glucose-dependent IRS-2 Ser/Thr-Pro motif phosphorylation and restored IL-4-dependent IRS-2-associated PI3-kinase activity. Taken together these results indicate that IRS-2-dependent IL-4 signaling in macrophages is impaired in models of type 2 diabetes mellitus through a mechanism that relies on insulin/glucose-dependent Ser/Thr-Pro motif serine phosphorylation mediated by the mTOR pathway.

Role of tumour necrosis factor-alpha in insulin resistance during normal pregnancy

OBJECTIVE

Role of tumour necrosis factor-alpha (TNF-alpha) was studied in insulin resistance during pregnancy.

STUDY DESIGN

Serum TNF-alpha (ELISA) and fasting C-peptide (Cp) (RIA) concentrations were measured in 40 healthy pregnant women (15, 12 and 13 of them in the 1st, 2nd and 3rd trimesters, respectively) and in 25 healthy non-pregnant women in a case-control study.

RESULTS

TNF-alpha (X+/-S.D.: 5.33+/-0.46 pg/ml) and Cp levels (3.37+/-1.30 ng/ml) were significantly higher in the 3rd trimester as compared with matched healthy controls (TNF: 4.07+/-0.26, Cp: 1.05+/-0.36) and to the pregnant women in 1st (TNF: 4.04+/-0.26, Cp: 1.34+/-0.59) and 2nd (TNF: 4.35+/-0.32, Cp: 1.11+/-0.35) trimesters. Significant positive linear correlation was calculated among TNF-alpha, Cp, Cp/blood glucose ratio (indirect parameters of insulin resistance) and body mass indexes (BMIs) of pregnant women (P<0.01).

CONCLUSION

TNF-alpha may contribute to the insulin resistance during the course of normal pregnancy.

Tumor necrosis factor system in insulin resistance in gestational diabetes

OBJECTIVE

The aim of the study was to investigate the pathophysiological role of the tumor necrosis factor (TNF) system in insulin resistance in patients with gestational diabetes (GDM) and during the course of normal pregnancy.

PATIENTS AND METHODS

Thirty women with GDM (16-39 gestational weeks), 35 healthy pregnant women (15 first, nine second and 11 third trimester) and 25 healthy age-matched non-pregnant women were studied. Serum TNF-alpha, and its soluble receptors 1 and 2 (sTNFR-1 and -2) were measured.

RESULTS

In non-diabetic pregnant women in the third trimester all measures were significantly higher (P<0.05 or less) than in the first trimester and in non-pregnant women (BMI 27.6 +/- 4.1 (+/- S.D.), 24.1 +/- 2.6, 22.4 +/- 2.4 kg/m(2)), serum TNF-alpha (4.6 +/- 0.6, 4.1 +/- 0.4, 4.1 +/- 0.4 ng/l), sTNFR-1 (2.7 +/- 0.9, 2.0 +/- 0.5, 2.0 +/- 0.1 microg/l), sTNFR-2 (5.6 +/- 2.6, 4.6 +/- 2.1, 3.3 +/- 0.2 microg/l), C-peptide (3.1 +/- 1.7, 1.1 +/- 0.7, 1.1 +/- 0.8 microg/l), and C-peptide:blood glucose ratio (0.6 +/- 0.2, 0.2 +/- 0.1, 0.2 +/- 0.1 microg/mmol). In GDM these measures were even higher than in any subgroup of healthy pregnant women (BMI) (33.4 +/- 6.4 kg/m(2), TNF-alpha) (6.3 +/- 0.6 microg/l), sTNFR-1 (3.0 +/- 0.5 microg/l), sTNFR-2 (10.0 +/- 6.9 microg/l, C-peptide 6.0 +/- 2.7 microg/l, C-peptide:blood glucose ratio: 1.2 +/- 0.5 microg/mmol, P<0.01). Significant (P<0.01) positive linear correlations were found in gestational diabetic and non-diabetic women between serum TNF-alpha, C-peptide levels, and BMI. In gestational diabetic women, in multivariate analysis studying the dependency of C-peptide only BMI remained significant (r(2)=0.67, P=0.01).

CONCLUSIONS

Our observation emphasizes the obesity-related component of insulin resistance driven by adipocytokines, such as TNF-alpha and its receptors during the course of normal pregnancy and GDM.

The role of the immune system in the insulin resistance syndrome

The complex relationship between immunity and the insulin resistance syndrome is likely mediated to a significant degree by cytokines and the inflammatory proteins they induce. Epidemiologic work has revealed associations between cytokines and clinically evident insulin resistance, and mechanistic studies have yielded insight into the induction of insulin resistance at the cellular level by cytokines such as tumor necrosis factor-alpha. Genetic polymorphisms significantly influence this relationship, and variations in cellular immunity as manifested by T-helper cell phenotype are likely to be important as well. Further elucidation of the link between immunity and insulin resistance may lead to more effective treatment, and potentially prevention, of the insulin resistance syndrome.

Insulin resistance with aging: effects of diet and exercise

Insulin resistance, a reduction in the rate of glucose disposal elicited by a given insulin concentration, is present in individuals who are obese, and those with diabetes mellitus, and may develop with aging. Methods which are utilised to measure insulin sensitivity include the hyperinsulinaemic-euglycaemic and hyperglycaemic clamps and the intravenous glucose tolerance tests. Several hormones and regulatory factors affect insulin action and may contribute to the insulin resistance observed in obesity. In addition, abnormal free fatty acid metabolism plays an important role in insulin resistance and the abnormal carbohydrate metabolism seen in individuals who are obese or diabetic. Thus, the mechanisms underlying the development of insulin resistance are multifactorial, and also involve alterations of the insulin signalling pathway. Aging is associated with an increase in bodyweight and fat mass. Not only is abdominal fat associated with hyperinsulinaemia but visceral adiposity is correlated with insulin resistance as well. Modifications of the changes in body composition with aging by diet and exercise training could delay the onset of insulin resistance. Weight loss and aerobic and resistive exercise training result in losses of total body fat and abdominal fat. Several studies report that bodyweight loss increases insulin sensitivity and improves glucose tolerance. In addition, the insulin resistance observed in aged persons can be modified by physical training. Longitudinal studies indicate significant improvements in glucose metabolism with aerobic exercise training in middle-aged and older men and women. Moreover, the improvements in insulin sensitivity with resistive training are similar in magnitude to those achieved with aerobic exercise. The improvements in glucose metabolism after bodyweight loss and exercise training may in some cases be partially attributed to changes in body composition, including reductions in total and central body fat. Yet, additional changes in skeletal muscle, blood flow and other mechanisms likely interact to modify insulin resistance with exercise training. Lifestyle modifications including bodyweight loss and physical activity provide health benefits and functional gains and should be promoted to increase insulin sensitivity and prevent glucose intolerance and type 2 diabetes mellitus in older adults.

Tumour necrosis factor, a key role in obesity?

Tumour necrosis factor-alpha (TNF) is a pleiotropic cytokine involved in many metabolic responses in both normal and pathophysiological states. In spite of the fact that this cytokine (also known as "cachectin") has been related to many of the metabolic abnormalities associated with cachexia, recent studies suggest that TNF may also have a central role in obesity modulating energy expenditure, fat deposition and insulin resistance. This review deals with the role of TNF in the control of fat mass and obesity.