Inhibition of tumor necrosis factor-alpha with anti-diabetic agents

Therapeutic Potentials of Colocasia affinis Leaf Extract for the Alleviation of Streptozotocin-Induced Diabetes and Diabetic Complications: In vivo and in silico-Based Studies

INTRODUCTION

Hypoglycemia in diabetes mellitus (DM) correlates with hepatic impairment, nephropathy, lipid abnormalities, and oxidative stress and subsequently complicates the disease pathogenesis. Medicinal plants have been used for the management of diabetes since ancient times. In this study, we explored the potentials of Colocasia affinis (CA), a plant known to possess anti-allergic and anti-inflammatory activities, as a remedy for diabetes and related complications.

METHODS

We induced diabetes in rats using a single intraperitoneal dose (65 mg/kg) of streptozotocin (STZ). We next treated the rats with an ethanolic extract of leaves of CA to reveal its antidiabetic and organ-protective potentials. Biomarkers of diabetes, inflammation, and oxidative stress were measured using biochemical and histopathological analysis. We also performed molecular docking for three major phytochemicals (kaempferol, myricetin, and rosmarinic acid) of CA.

RESULTS

Oral administration of the CA leaves extract at 250 mg/kg and 500 mg/kg doses decreased blood glucose level significantly (p<0.05) in STZ-induced diabetic rats. The extract also considerably attenuated plasma HbA1c levels and normalized blood lipids, glycogen, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Additionally, treatment with the extract improved kidney complications by decreasing serum creatinine and blood urea nitrogen (BUN) levels. Furthermore, CA leaves extract normalized nitric oxide (NO) and advance oxidative protein products (AOPP) in diabetic rats. The extract also showed significant improvement of the antioxidant enzymes glutathione dismutase (GSH) and superoxide dismutase (SOD) at a dose of 500 mg/kg. Besides, histological investigation demonstrated attenuation of inflammation of the vital organs, including the liver and the kidney. In silico studies revealed that three major phytochemicals (kaempferol, myricetin, and rosmarinic acid) of the ethanolic extract of leaves of CA can inhibit several molecular targets of diabetes and inflammation.

CONCLUSION

Collectively, our results demonstrated the therapeutic potentials of CA for the mitigation of diabetes and diabetic complications.

Sulfonylurea derivatives and cancer, friend or foe?

Type 2 diabetes mellitus (T2DM) is associated with a higher risk of cancer and cancer-related mortality. Increased blood glucose and insulin levels in T2DM patients may be, at least in part, responsible for this effect. Indeed, lowering glucose and/or insulin levels pharmacologically appears to reduce cancer risk and progression, as has been demonstrated for the biguanide metformin in observational studies. Studies investigating the influence of sulfonylurea derivatives (SUs) on cancer risk have provided conflicting results, partly due to comparisons with metformin. Furthermore, little attention has been paid to within-class differences in systemic and off-target effects of the SUs. The aim of this systematic review is to discuss the available preclinical and clinical evidence on how the different SUs influence cancer development and risk. Databases including PubMed, Cochrane, Database of Abstracts on Reviews and Effectiveness, and trial registries were systematically searched for available clinical and preclinical evidence on within-class differences of SUs and cancer risk. The overall preclinical and clinical evidence suggest that the influence of SUs on cancer risk in T2DM patients differs between the various SUs. Potential mechanisms include differing affinities for the sulfonylurea receptors and thus differential systemic insulin exposure and off-target anti-cancer effects mediated for example through potassium transporters and drug export pumps. Preclinical evidence supports potential anti-cancer effects of SUs, which are of interest for further studies and potentially repurposing of SUs. At this time, the evidence on differences in cancer risk between SUs is not strong enough to guide clinical decision making.

Synergistic action of ursolic acid and metformin in experimental model of insulin resistance and related behavioral alterations

Chronic restraint stress (CRS) is known to cause metabolic and neurological complications in a number of ways. Prolonged exposure to stress evident by increased corticosterone level led to impaired altered insulin signaling and oxidative stress in mice, in the present study. Impaired insulin signaling or insulin resistance was characterized by hyperglycemia, hyperinsulinemia, hyperlipidemia, hypoadiponectinemia, increased glycosylated haemoglobin and HOMA-IR. It was also associated with increased proinflammatory cytokine TNF-α levels. CRS also caused significant increase in acetylcholinesterase activity and oxidative stress in brain along with cognitive impairment in behavioral test. Ursolic acid, metformin, gliclazide and their combinations when administered daily for 30 days significantly improved insulin sensitivity apart from behavioral and biochemical alterations in stressed mice. Treatment with drugs also decreased serum corticosterone and TNF-α levels. The findings of our study revealed that improvement in insulin sensitivity, learning and cognitive performance in stressed mice was attributed to attenuation of proinflammatory cytokines and oxidative stress. Moreover, combination of [Metformin (150 mg/kg) + Ursolic acid (10 mg/kg)] produced enhanced improvement in insulin sensitivity and cognitive impairment as compared to their individual effects, suggesting possibly the common mode of anti-inflammatory and antioxidant mechanisms.

Anti-TNF-α antibody alleviates insulin resistance in rats with sepsis-induced stress hyperglycemia

PURPOSE

To explore the effects and mechanisms of anti-tumor necrosis factor-α (TNF-α) antibody on insulin resistance (IR) in rats with sepsis-induced stress hyperglycemia.

METHODS

The sepsis-induced stress hyperglycemic rat model was constructed by cecal ligation and puncture combined with the intraperitoneal injection of lipopolysaccharide. The rats were randomly divided into six groups: normal control (NC) group, surgical rats (Cntl) group, high-dose anti-TNF-α antibody therapy (TNF, 6 mg/kg) group, low-dose anti-TNF-α antibody therapy (Tnf, 3 mg/kg) group, insulin therapy (INS) group, and INS + Tnf group. The blood glucose and serum insulin concentrations were detected, followed by analysis of intraperitoneal glucose tolerance test (IPGTT) and hyperinsulinemic-euglycemic clamp. Finally, the expression levels of phospho-Akt (p-Akt), Akt, p-mTOR, mTOR, nuclear factor-κB (NFκB), I kappa beta kinase (IKKβ), and suppressor of cytokine signaling (SOCS-3) were detected by western blotting.

RESULTS

There was no significant difference in blood glucose concentrations among these groups, while the serum insulin concentration in TNF and Tnf groups was lower than that in the Cntl group at postoperative 6 h (P < 0.05). IPGTT analysis revealed that blood glucose level was lower in the TNF group than that in the Cntl group (P < 0.05). The glucose infusion rate in the Cntl group was lower than that in the Tnf and TNF groups (P < 0.05). The p-Akt/Akt, p-mTOR/mTOR ratio, and expression levels of NFκB, IKKβ and SOCS-3 were lower in the drug intervention than that in the Cntl group (P < 0.05).

CONCLUSIONS

Anti-TNF-α antibody could reduce IR by inhibiting AKt/mTOR signaling pathway and the expression levels of NFκB, IKKβ, and SOCS-3 in rats with sepsis-induced stress hyperglycemia.

Serum concentrations and renal expressions of IL-1 and TNF-a early after hemorrhage in rats under the effect of glibenclamide

PURPOSE

To investigate changes in the serum concentration and renal expression of IL-1 and TNF-α cytokines in rats that received sevoflurane and glibenclamide prior to hemorrhage.

METHODS

Two groups of sevoflurane-anesthetized Wistar rats (n=10): G1 (control) and G2 (glibenclamide, 1 µg/g i.v.); hemorrhage of 30% blood volume (10% every 10 min), with replacement using Ringer solution, 5 ml/kg/h. Serum concentrations of IL-1 and TNF-α were studied in the first hemorrhage (T1) and 50 min later (T2), renal expression, at T2.

RESULTS

In serum, G1 TNF-α (pg/mL) was T1=178.6±33.5, T2=509.2±118.8 (p<0.05); IL-1 (pg/mL) was T1=148.8±31.3, T2=322.6±115.4 (p<0.05); in G2, TNF-α was T1=486.2±83.6, T2=261.8±79.5 (p<0.05); IL-1 was T1=347.0±72.0, T2= 327.3±90.9 (p>0.05). The expression of TNF-α and IL-1 in the glomerular and tubular cells was significantly higher in the G2 group.

CONCLUSIONS

Hemorrhage and glibenclamide elevated TNF-α and IL-1 concentrations in serum and kidneys. High levels of TNF-α already present before the hemorrhage in the glibenclamide group may have attenuated the damages found in the kidneys after the ischemia event.

Metabolic syndrome in rheumatoid arthritis

Insulin resistance is an essential feature of the metabolic syndrome that has been linked to rheumatoid arthritis (RA). Understanding how inflammation arising in one tissue affects the physiology and pathology of other organs remains an unanswered question with therapeutic implications for chronic conditions including obesity, diabetes mellitus, atherosclerosis, and RA. Adipokines may play a role in the development of atherogenesis in patients with RA. Biologic therapies, such as TNF-α antagonists, that block proinflammatory cytokines have beneficial effects on the insulin resistance that is often observed in patients with RA.

Vitamins D, C, and E in the prevention of type 2 diabetes mellitus: modulation of inflammation and oxidative stress

The incidence of type 2 diabetes mellitus (T2DM) is increasing worldwide, and certain population subgroups are especially vulnerable to the disease. To reduce T2DM risk and progression at the population level, preventative strategies are needed that can be implemented on a population-wide scale with minimal cost and effort. Chronic low-grade inflammation resulting from oxidative stress and imbalances in the innate immune system has been associated with obesity, metabolic syndrome, and insulin resistance – critical stages in the development and progression of T2DM. Therefore, inflammation may play a causal role in the pathogenesis of T2DM, and reducing it via modulation of oxidative stress and the innate immune response could lead to a status of improved insulin sensitivity and delayed disease onset. Dietary supplementation with anti-inflammatory and antioxidant nutritional factors, such as micronutrients, might present a novel strategy toward the prevention and control of T2DM at the population level. This review examines current knowledge linking oxidation, inflammatory signaling pathways, and vitamin supplementation or intake to the risk of T2DM. The concept that micronutrients, via attenuation of inflammation, could be employed as a novel preventive measure for T2DM is evaluated in the context of its relevance to public health.

Type 2 diabetes mellitus and inflammation: Prospects for biomarkers of risk and nutritional intervention

Obesity is a major risk factor for type 2 diabetes mellitus (T2DM), which is a significant health problem worldwide. Active disease is associated with low-grade chronic inflammation resulting in part from the activation of the innate immune system. In obesity, this activation leads to the release of pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin-1β and interleukin-6 that block major anabolic cascades downstream of insulin signaling and thus disrupt insulin homeostasis and action. Cytokines also trigger the production of acute-phase reactants such as C-reactive protein, plasminogen activator inhibitor-1, serum amyloid-A, and haptoglobin. The elevated synthesis of pro-inflammatory cytokines and acute-phase proteins (inflammatory network) characterizes the early (or pre-clinical) stages of T2DM and exhibits a graded increase with the disease progression. Current evidence suggests that understanding inflammatory networks can point to new biomarkers that may permit capturing the interaction between genetic and environmental risk factors in the pathogenesis of T2DM. Such biomarkers have a significant public health potential in the prediction of disease occurrence beyond risk factors presently monitored, such as family history, lifestyle assessment and standard clinical chemistry profiles. Furthermore, inflammatory markers may assist in the evaluation of novel strategies for prevention, particularly in relation to micronutrients. This review discusses the current knowledge linking T2DM risk to inflammatory signaling pathways interacting with the innate immunity system and the prospect of inflammatory markers serving as molecular targets for prevention and/or biomarkers for early risk prediction of T2DM. The potential of micronutrients replenishment to improve insulin action by attenuating inflammation is also evaluated in the context of the public health relevance of this approach.

Insulin resistance in rheumatoid arthritis: the impact of the anti-TNF-alpha therapy

Increased prevalence of insulin resistance has been observed in patients with rheumatoid arthritis (RA). High-grade systemic inflammation is implicated in the development of insulin resistance in these patients. Tumor necrosis factor (TNF)-alpha is a potent proinflammatory cytokine that plays a role in the initiation and progression of inflammation and the mechanisms associated with accelerated atherosclerosis in RA. In assessing data immediately prior to and after intravenous infusion of the anti-TNF-alpha monoclonal antibody-infliximab in RA patients on period treatment with this drug attributable to disease refractory to conventional disease-modifying antirheumatic drugs, a dramatic improvement of insulin resistance and insulin sensitivity was observed. A long-term positive effect of TNF-alpha antagonists infliximab and etanercept on insulin resistance in RA patients with severe disease was also reported. These results highlight the importance of therapies that act blocking TNF-alpha function to reduce the mechanisms implicated in the development of the metabolic syndrome observed in RA.

'Warm-up' phenomenon in diabetic patients with stable angina treated with diet or sulfonylureas

BACKGROUND

Classic sulfonyloureas (SUs) are known to attenuate ischaemic preconditioning. Gliclazide is an SU agent believed to be more protective. We assessed the effects of diet, glibenclamide, or gliclazide on the warm-up effect in type 2 diabetic patients with stable angina.

METHODS

The study group consisted of 64 men, aged 54+/-5 years: 17 patients without diabetes (G I) and 47 diabetic patients: 16 patients treated with glibenclamide (G II), 16 with gliclazide (G III) and 15 patients treated with diet (G IV). After the baseline positive exercise test (ET1), all patients reexercised after 30-min rest (ET2). We analysed exercise duration (ED, s), time to 1 mm ST depression (T-STD, s), max STD (mm), heart rate-systolic blood pressure product at 1 mm STD, or ischaemic threshold (mmHg/min x 100) and the total ischaemic time (s).

RESULTS

In G I, all analysed variables improved significantly during ET2 relative to ET1. Glibenclamide (G II) completely abolished the protective effect of exercise-induced ischaemia because only ED increased during ET2 (431 vs. 451, P<0.05). In G III, however, ED (486 vs. 537, P<0.001), T-STD (364 vs. 388, P<0.05) and max STD (2.5 vs. 2.0, P<0.05) improved significantly during ET2, whereas ischaemic threshold and total ischaemic time did not (PNS). In G IV, similar to G I, all variables improved significantly during ET2 relative to ET1.

CONCLUSION

Warm-up effect is preserved in diabetic patients with stable angina treated with diet, partially preserved in gliclazide-treated and abolished in glibenclamide-treated patients.

Resistance training alters cytokine gene expression in skeletal muscle of adults with type 2 diabetes

Resistance training results in muscle hypertrophy and improves glycemic control in patients with type 2 diabetes. Whether resistance training modulates inflammation in muscles of diabetic patients remains unknown. We examined the expression of genes encoding the cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and transforming growth factor-beta1 (TGF-beta1) as well as the pan-leukocyte marker CD18. Thirty men and women (67+/-7 years) were randomized to either 16 weeks of resistance training and usual diabetes care (EX) or to usual diabetes care only (CON). Muscle biopsies were obtained from the vastus lateralis muscle prior to the 16-week intervention, and 72 h following the maximal strength test post-intervention. Fiber cross-sectional area (CSA) was determined following ATPase staining. Cytokine and CD18 transcript levels were assessed by real-time PCR. Resistance training increased CSA of type I and II fibers (both P <0.05) and IL-1beta transcript levels (P = 0.05). TNF-alpha (P<0.05) and TGF-beta1 transcripts (P<0.05) increased over time in the EX group, but these increases did not differ from those in the CON group. In both groups, the increase in CD18 transcripts remained minimal. The two groups differ by the relationship between changes in CD18 and changes in cytokine transcripts, suggesting that resistance training affects the source of cytokines in muscle. Our studies establish that resistance training in older adults with type 2 diabetes results in muscle fiber hypertrophy, despite a greater accumulation of inflammatory cytokine transcripts in muscle.

Sulfatide increases adiponectin and decreases TNF-alpha, IL-6, and IL-8 in human adipose tissue in vitro

Type 2 diabetes is associated with decreased levels of the glycosphingolipid sulfatide, as well as a state of low-grade inflammation. Sulfatide is reported to have anti-inflammatory properties in other cell-types. In the present study, the effects of sulfatide on adipokine (adiponectin, TNF-alpha, IL-6, and IL-8) production in human adipose tissue (AT) was investigated in vitro. Isolated human adipocytes and AT cultures were incubated with sulfatide isolated from pig brain [sulfatide containing a variety of fatty acids or isoforms of sulfatide with defined, saturated fatty acids with 16 (C16:0) or 24 (C24:0) carbon atoms]. Adiponectin production was increased 50-80%, by all sulfatide preparations. Only the C16:0 isoform decreased TNF-alpha, IL-6, and IL-8 production 20-30%. The C16:0 sulfatide has been shown to activate potassium channels in beta-cells, and glibenclamide, an ATP-sensitive K+-(KATP) channel blocker, reversed the C16:0-induced decrement in stimulated TNF-alpha, IL-6, and IL-8 release in adipocytes. Glibenclamide on its own was without effect on the production of adiponectin, TNF-alpha, IL-6, and IL-8. In conclusion, this study shows that, sulfatide exerts anti-inflammatory effects in human adipocytes and AT in vitro. Accordingly, the reported low serum levels of sulfatide in patients with type 2 diabetes might be of importance in relation to the chronic low-grade inflammatory state found in this disease.

Effect of gliclazide modified release on adiponectin, interleukin-6, and tumor necrosis factor-alpha plasma levels in individuals with type 2 diabetes mellitus

OBJECTIVE

The aim of the study was to evaluate the effect of gliclazide modified release (MR) treatment on adiponectin, interleukin 6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) plasma concentrations in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

24 randomly selected type 2 diabetic patients, aged 61.2 +/- 15.4 years, with poorly controlled glucose level (mean glycated hemoglobin [HbA1c] 7.6 +/- 1.1%) despite treatment with diet and/or oral hypoglycemic agents, were included in the study. All of the patients, after a 2-week run-in period, were given gliclazide MR for 12 weeks. At baseline, and after gliclazide MR treatment, HbA(1c) and plasma concentrations of IL-6, TNF-alpha, and adiponectin were measured.

RESULTS

Gliclazide MR treatment produced significant reductions in fasting plasma glucose (from 7.6 +/- 1.4 to 6.6 +/- 1.2 mmol/L, p < 0.01), HbA(1c) (from 7.6 +/- 1.1 to 6.9 +/- 0.8%, p < 0.01), and plasma IL-6 concentrations (from 2.5 +/- 1.8 to 1.8 +/- 1.2 pg/mL, p < 0.05). A significant increase in plasma adiponectin level was noted (from 6.4 +/- 3.3 to 7.6 +/- 4.4 mug/mL, p < 0.05). Plasma TNF-alpha concentrations and homeostasis model assessment of insulin resistance (HOMA-IR) decreased after treatment, but these changes did not reach statistical significance.

CONCLUSIONS

Gliclazide MR improves glycemic control and, in addition, has a positive influence on the plasma level of some inflammatory markers and adiponectin. Increased plasma adiponectin and decreased plasma IL-6, and TNF-alpha levels may explain, at least in part, the anti-atherogenic action of this drug reported elsewhere.

TNF-alpha induces endothelial dysfunction in diabetic adults, an effect reversible by the PPAR-gamma agonist pioglitazone

AIMS

Inflammation contributes to the pathogenesis of cardiovascular disease. Tumour necrosis factor (TNF)-alpha, in particular, is a key mediator of inflammation and vascular dysfunction and progression of atherosclerotic disease. Pioglitazone, a peroxisome proliferator-activated receptor-gamma agonist, not only improves insulin sensitivity, but may also have anti-inflammatory effects. The aims of this study were to investigate the acute effects of local intra-arterial infusion with low-dose TNF-alpha on resistance vessel endothelial function in type 2 diabetes and to determine whether short-term pioglitazone treatment protects against vascular dysfunction induced by this inflammatory stimulus.

METHODS AND RESULTS

A randomized, parallel, placebo-controlled, double blind trial with 30 mg pioglitazone once daily for 4 weeks was performed in 16 male patients with recently diagnosed type 2 diabetes. Forearm plethysmography (FBF) was used to evaluate the effect on resistance vessel responses of intra-arterial administration of serotonin (NO-dependent vasodilation) and nitroprusside (endothelium-independent vasodilation) followed by another FBF-measurement during the second hour of intra-arterial infusion with TNF-alpha (10 ng/100 mL forearm volume/min for 2 h). Endothelial-dependent FBF of type 2 diabetic patients was significantly impaired (25.4%) by intra-arterial TNF-alpha infusion (P = 0.01), whereas nitroprusside-induced vasodilation did not change. Treatment with pioglitazone for 4 weeks completely blocked TNF-alpha-induced impairment of endothelial-dependent FBF compared with placebo. No significant changes in plasma concentrations of TNF-alpha, interleukin-6, soluble TNF-alpha-receptors, or CD40L were observed.

CONCLUSION

Pioglitazone treatment can convey direct protection against cytokine (TNF-alpha)-induced endothelial dysfunction in humans with an increased cardiovascular risk due to type 2 diabetes.

Gliclazide inhibits differentiation-associated biologic events in human monocyte-derived macrophages

We investigated the in vitro effect of gliclazide on human monocyte-derived macrophage scavenger receptor expression and activity, foam cell formation, and lipopolysaccharide-induced cytokine production. Differentiation of human monocytes into macrophages in the presence of gliclazide (1-10 microg/mL) decreased CD36 expression by 20% to 50%, with maximal effect occurring at 2.5 microg/mL (P<.05). This effect was mimicked by vitamin E (50 micromol/L) and N-acetyl-L-cysteine (10 mmol/L). Incubation of the cells with gliclazide and N-acetyl-L-cysteine also reduced CD36 activity by 30% (P<.02). Despite these effects, neither gliclazide nor vitamin E did affect foam cell formation. In contrast, gliclazide significantly reduced lipopolysaccharide-stimulated macrophage tumor necrosis factor alpha and interleukin 6 secretion (P<.05). Overall, these data indicate that gliclazide, at concentrations in the therapeutic range, may regulate some key biologic events associated with the process of monocyte differentiation into macrophages.

Differential effect of saturated, monounsaturated, and polyunsaturated fatty acids on alloxan-induced diabetes mellitus

Earlier, we reported that oils rich in omega-3 eicosapentaenoic acid and docosahexaenoic acid and omega-6 gamma-linolenic acid and arachidonic acid prevented the development of alloxan-induced diabetes mellitus in experimental animals. Here we report the results of our studies with pure saturated stearic acid (SA), monounsaturated oleic acid (OA) and omega-6 arachidonic acid (AA) on alloxan-induced diabetes mellitus in Wistar male rats. Prior oral supplementation with AA prevented alloxan-induced diabetes mellitus, whereas both SA and OA were ineffective. Cyclo-oxygenase (COX) and lipoxygenase (LO) inhibitors did not block this protective action of AA against alloxan-induced diabetes, suggesting that both prostaglandins and leukotrienes are not involved, and that AA by itself is effective. Furthermore, AA restored the anti-oxidant status to normal range in various tissues. These results suggest that AA protects pancreatic beta cells against alloxan-induced diabetes in experimental animals by attenuating oxidant stress.

Inflammation and the etiology of type 2 diabetes

Type 2 diabetes is increasingly common worldwide and is beginning to strike younger age groups. Almost 90% of all patients with diabetes show insulin resistance, which also precedes the first symptoms of diabetes. The mechanisms underlying the development of insulin resistance are not well understood. In recent years, several studies have been published that implicate subclinical chronic inflammation as an important pathogenetic factor in the development of insulin resistance and type 2 diabetes. This opens new perspectives for diagnosis and treatment of early insulin resistance and incipient glucose intolerance. Surrogate markers for this low-grade chronic inflammation include CRP, IL-6 and TNF-alpha. Some antidiabetic agents, for example, glitazones that reduce insulin resistance, and insulin itself, reduce inflammation. Conversely, antiinflammatory drugs (ASA/NSAID) may improve glucose tolerance. Vasoactive drugs that are often prescribed to people with diabetes, for example, statins and ACE inhibitors/angiotensin receptor antagonists, also counteract inflammation and reduce the risk of type 2 diabetes. More specific and sensitive biomarkers should be identified, which may predict early disturbances in insulin sensitivity and cardiovascular risk. Also, inflammatory signalling pathways need to be explored in greater detail, and may form the basis of drugable targets against the epidemic of insulin resistance and atherosclerosis.

Rheumatoid arthritis: a disease associated with accelerated atherogenesis

OBJECTIVES

Rheumatoid arthritis (RA) is a systemic inflammatory disease associated with an increased prevalence of coronary heart disease and a high cardiovascular (CV) mortality. In this article, a review of mechanisms implicated in the development of accelerated atherogenesis in RA was performed. The potential role of treatment to reduce the incidence of CV events in RA was also discussed.

METHODS

Retrospective review of the literature. The potential mechanisms implicated in the development of accelerated atherogenesis in RA, information on carotid ultrasonography, and the potential implication of treatment to prevent accelerated atherogenesis in individuals with RA were examined.

RESULTS

Endothelial dysfunction, which is an early step in the development of atherosclerosis, has been observed in patients with RA. Deleterious effects resulting from persistent chronic inflammation may lead to endothelial dysfunction, insulin resistance, and a dyslipidemic pattern in these patients. Other mechanisms different from those related to classic atherogenesis risk factors, such as hyperhomocysteinemia and increased oxidative stress, are considered to be implicated in the pathogenesis of atherosclerosis in RA. Increased carotid intima-media thickness and carotid plaques have been found in RA patients compared with matched controls. Active MTX treatment of the disease has been associated with decreased CV mortality. Additional drugs such as statins may be considered in the management of these patients.

CONCLUSIONS

The increased prevalence of CV mortality rate in RA cannot only be explained by the presence of traditional atherosclerotic risk factors. A chronic inflammatory response may promote the development of accelerated atherogenesis in these patients. Active treatment of the disease is required to reduce the risk of developing CV complications in individuals with RA.

Secondary sulfonylurea failure: comparison of period until insulin treatment between diabetic patients treated with gliclazide and glibenclamide

We retrospectively evaluated a possible difference in periods until start of insulin treatment between type 2 diabetic patients treated with gliclazide (GCZ) and glibenclamide (GBC), because GCZ might be protective for beta cells than GBC. Subjects were Japanese patients. GCZ group consisted of patients treated with GCZ alone or with GCZ and GBC in the separate treatment periods in combination with or without other oral hypoglycemic agents (OHAs), while GBC group consisted of patients with GBC alone or in combination with other OHAs except GCZ. The periods until the treatment of insulin commenced were calculated using the Kaplan-Meier method. Proportional hazards models were used to adjust the differing variables between GCZ and GBC groups. The periods until the start of insulin treatment from diabetes onset, diabetes treatment, or GCZ or GBC treatment were significantly longer in the GCZ group than those in GBC group (P<0.001 in each group). Independent variables affecting the period were average HbA1c levels during GCZ or GBC treatment (hazard ratio=2.5 per %), other OHAs combined (hazard ratio=1.9 on combination), and difference between GCZ and GBC groups (hazard ratio=0.5 on GCZ). These results imply that GCZ may be more protective against secondary beta cell failure than GBC.

An immune origin of type 2 diabetes?

Subclinical, low-grade systemic inflammation has been observed in patients with type 2 diabetes and in those at increased risk of the disease. This may be more than an epiphenomenon. Alleles of genes encoding immune/inflammatory mediators are associated with the disease, and the two major environmental factors the contribute to the risk of type 2 diabetes-diet and physical activity-have a direct impact on levels of systemic immune mediators. In animal models, targeting of immune genes enhanced or suppressed the development of obesity or diabetes. Obesity is associated with the infiltration and proinflammatory activity of macrophages in adipose tissue, and immune mediators may be important regulators of insulin resistance, mitochondrial function, ectopic lipid storage and beta cell dysfunction or death. Intervention studies targeting these pathways would help to determine the contribution of an activated innate immune system to the development of type 2 diabetes.

Long-chain polyunsaturated fatty acids and chemically induced diabetes mellitus. Effect of omega-3 fatty acids

In a previous study, we showed that prior oral feeding of oils rich in omega-3 eicosapentaenoic acid and docosahexaenoic acid and omega-6 gamma-linolenic acid and arachidonic acid prevent the development of alloxan-induced diabetes mellitus in experimental animals. We also observed that 99% pure omega-6 fatty acids gamma-linolenic acid and arachidonic acid protect against chemically induced diabetes mellitus. Here we report the results of our studies with omega-3 fatty acids. Alloxan-induced in vitro cytotoxicity and apoptosis in an insulin-secreting rat insulinoma cell line, RIN, was prevented by prior exposure of these cells to alpha-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid. Prior oral supplementation with alpha-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid prevented alloxan-induced diabetes mellitus. alpha-Linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid not only attenuated chemical-induced diabetes mellitus but also restored the anti-oxidant status to normal range in various tissues. These results suggested that omega-3 fatty acids can abrogate chemically induced diabetes in experimental animals and attenuate the oxidant stress that occurs in diabetes mellitus.

Long-chain polyunsaturated fatty acids and chemically induced diabetes mellitus: effect of omega-6 fatty acids

OBJECTIVE

We previously showed that prior oral supplementation of oils rich in omega-3, eicosapentaenoic acid and docosahexaenoic acid, and omega-6, gamma-linolenic acid and arachidonic acid, can prevent the development of alloxan-induced diabetes mellitus in experimental animals. But the effect of individual fatty acids on chemically induced diabetes mellitus is not known. We report the results of our studies with omega-6 fatty acids.

METHODS

Alloxan-induced in vitro cytotoxicity and apoptosis in an insulin-secreting rat insulinoma cell line, RIN, was prevented by prior exposure of these cells to linoleic acid, gamma-linolenic acid, and arachidonic acid (AA) but not to dihomo-gamma-linolenic acid. Cyclo-oxygenase and lipoxygenase inhibitors did not block this protective action of AA. Prior oral supplementation with gamma-linolenic acid and pre- and simultaneous treatments with AA prevented alloxan-induced diabetes mellitus.

RESULTS

Even though pretreatment with linoleic acid and dihomo-gamma-linolenic acid and simultaneous treatment with linoleic acid, gamma-linolenic acid, and dihomo-gamma-linolenic acid did not prevent the development of diabetes mellitus, the severity of diabetes was much less. The saturated fatty acid stearic acid and the monounsaturated fatty acid oleic acid were ineffective in preventing alloxan-induced diabetes mellitus. gamma-Linolenic acid and AA not only attenuated chemically induced diabetes mellitus but also restored the antioxidant status to normal range in various tissues. Changes in the concentrations of various fatty acids of the phospholipid fraction of plasma that occurred as a result of alloxan-induced diabetes mellitus also reverted to normal in the AA-treated animals.

CONCLUSIONS

These results suggest that polyunsaturated fatty acids can prevent chemically induced diabetes in experimental animals and attenuate the oxidant stress that occurs in diabetes mellitus.

Absence of peripheral blood mononuclear cells priming in hemodialysis patients

As a consequence of the proinflammatory environment occurring in dialytic patients, cytokine overproduction has been implicated in hemodialysis co-morbidity. However, there are discrepancies among the various studies that have analyzed TNF-alpha synthesis and the presence of peripheral blood mononuclear cell (PBMC) priming in this clinical setting. We measured bioactive cytokine by the L929 cell bioassay, and evaluated PBMC TNF-alpha production by 32 hemodialysis patients (HP) and 51 controls. No difference in TNF-alpha secretion was observed between controls and HP (859 +/- 141 vs 697 +/- 130 U/10(6) cells). Lipopolysaccharide (5 microg/ml) did not induce any further TNF-alpha release, showing no PBMC priming. Paraformaldehyde-fixed HP PBMC were not cytotoxic to L929 cells, suggesting the absence of membrane-anchored TNF-alpha. Cycloheximide inhibited PBMC cytotoxicity in HP and controls, indicating lack of a PBMC TNF-alpha pool, and dependence on de novo cytokine synthesis. Actinomycin D reduced TNF-alpha production in HP, but had no effect on controls. Therefore, our data imply that TNF-a production is an intrinsic activity of normal PBMC and is not altered in HP. Moreover, TNF-alpha is a product of de novo synthesis by PBMC and is not constitutively expressed on HP cell membranes. The effect of actinomycin D suggests a putative tighter control of TNF-alpha mRNA turnover in HP. This increased dependence on TNF-alpha RNA transcription in HP may reflect an adaptive response to hemodialysis stimuli.

Type 2 diabetes, cardiovascular risk, and the link to insulin resistance

BACKGROUND

Patients with type 2 diabetes mellitus frequently have coexistent dyslipidemia, hypertension, and obesity, and are at risk for microvascular and macrovascular disease complications such as myocardial infarction, stroke, retinopathy, and microalbuminuria. To optimize cardiovascular health outcomes for patients with type 2 diabetes, strategies to reduce the risks of microvascular and macrovascular disease are needed in clinical practice.

OBJECTIVE

This article provides an overview of the cardiovascular risk profile of patients with type 2 diabetes and discusses the cardiovascular consequences of use of the thiazolidinediones (insulin-sensitizing agents) in the treatment of type 2 diabetes.

METHODS

A literature search of MEDLINE/PubMed was performed to identify relevant articles published from 1966 to April 2003. Search terms used were diabetes, cardiovascular disease, atherosclerosis, dyslipidemia, obesity, hypertension, blood pressure, hyperglycemia, inflammation, C-reactive protein, fibrinolysis, plasminogen activator inhibitor type-1, microalbuminuria, thiazolidinediones, safety, hepatotoxicity, and edema. Bibliographies within the identified articles were also evaluated for additional relevant articles and information.

RESULTS

Recommendations for cardiovascular risk reduction through preventive and therapeutic strategies that target the symptoms of insulin resistance may reduce the microvascular and macrovascular sequelae of diabetes and ameliorate the impact of other components of the metabolic syndrome, including hypertension, hyperglycemia, and obesity. In this regard, thiazolidinediones are promising therapies.

CONCLUSIONS

Early data suggest that, in addition to reducing hyperglycemia, pioglitazone and rosiglitazone effect changes in the dyslipidemic profile, hemodynamics, vascular inflammation, and endothelial functioning of patients with type 2 diabetes. Additional research is needed to further distinguish the cardiovascular benefits of these drugs.

The mechanisms of inhibitory actions of gliclazide on neutrophils-endothelial cells adhesion and surface expression of endothelial adhesion molecules mediated by a high glucose concentration

BACKGROUND

We previously reported that culture of endothelial cells in the presence of high glucose concentrations (27.8 and 55.5 mM) increase neutrophils adhesion because of the increase in endothelial adhesion molecules expression via activation of a protein kinase C (PKC) pathway. The antidiabetic sulfonylurea gliclazide, but not glibenclamide, inhibited these events, but the mechanisms involved were not clarified then. We present hereafter the results of further investigations of that effect with special reference to PKC activation.

METHODS

Human umbilical vein endothelial cells (HUVEC) were cultured for 48 h in a glucose-rich medium and neutrophils from healthy volunteers were then added and allowed to adhere for 30 min. Adhered neutrophils were quantified by measuring myeloperoxidase (MPO) activities and the surface expression of endothelial adhesion molecules was determined by enzyme immunoassay.

RESULTS

Culture in the presence of a high glucose concentration (27.8 mM for 48 h) increased neutrophils-endothelial cells adhesion and the surface expression of intercellular adhesion molecule-1 (ICAM-1), P-selectin, and E-selectin on the endothelial cells. These phenomena were significantly inhibited by gliclazide (20 microM). On the other hand, phorbol 12-myristate 13-acetate (PMA), a PKC activator, had an effect similar to a high glucose concentration and that effect was also inhibited by gliclazide.

CONCLUSIONS

These data suggest that gliclazide inhibits high glucose-mediated neutrophils-endothelial cells adhesion and expression of endothelial adhesion molecules through inhibition of a PKC pathway.

Tumour necrosis factor-alpha plasma levels in elderly patients with Type 2 diabetes mellitus-observations over 2 years

AIMS

The cytokine tumour necrosis factor-alpha (TNF-alpha) is involved in the development of obesity-linked insulin resistance. TNF-alpha plasma levels rise with increasing age and might thus also be related to metabolic control in Type 2 diabetes mellitus. We have studied the relationship of TNF-alpha plasma levels to glycaemic control in elderly patients with Type 2 diabetes over 2 years.

METHODS

Clinical and laboratory data of 53 patients (26 women, 27 men) with Type 2 diabetes (mean age 71.6 +/- 5.6 years) were regularly evaluated over 2 years, and the relationship to anti-diabetic treatment regimens analysed. TNF-alpha plasma level was measured by a solid-phase enzyme amplified sensitivity immunoassay.

RESULTS

TNF-alpha plasma levels increased significantly from 16.2 +/- 9.6 pg/ml at baseline to 28.0 +/- 13.8 pg/ml after 2 years (P = 0.028). HbA1c values also increased from 6.4 +/- 1.2% to 7.7 +/- 1.6% (P = 0.046). Mean body mass index of the patients remained almost constant, while a moderate increase in the percentage of body fat (34.5 +/- 7.0% to 35.3 +/- 6.9%; P= 0.061) and in waist-hip ratio was observed (0.86 +/- 0.04 to 0.88 +/- 0.04; P= 0.052). After adjustment for covariates multivariate analysis demonstrated that TNF-alpha plasma levels are positively related to the HbA1c values of the whole study population at the baseline control and after 2 years. TNF-alpha also revealed a positive correlation to the percentage of body fat.

CONCLUSIONS

In elderly patients with Type 2 diabetes TNF-alpha plasma levels revealed a continuous increase during an observation period of 2 years. This increase in TNF-alpha plasma levels might add another aspect to the worsening of glycaemic control in the progression of Type 2 diabetes.

Metabolic and additional vascular effects of thiazolidinediones

Several cardiovascular risk factors (dyslipidaemia, hypertension, glucose intolerance, hypercoagulability, obesity, hyperinsulinaemia and low-grade inflammation) cluster in the insulin resistance syndrome. Treatment of these individual risk factors reduces cardiovascular complications. However, targeting the underlying pathophysiological mechanisms of the insulin resistance syndrome is a more rational treatment strategy to further improve cardiovascular outcome. Our understanding of the so-called cardiovascular dysmetabolic syndrome has been improved by the discovery of nuclear peroxisome proliferator-activated receptors (PPARs). PPARs are ligand-activated transcription factors belonging to the nuclear receptor superfamily. As transcription factors, PPARs regulate the expression of numerous genes and affect glycaemic control, lipid metabolism, vascular tone and inflammation. Activation of the subtype PPAR-gamma improves insulin sensitivity. Expression of PPAR-gamma is present in several cell types involved in the process of atherosclerosis. Thus, modulation of PPAR-gamma activity is an interesting therapeutic approach to reduce cardiovascular events. Thiazolidinediones are PPAR-gamma agonists and constitute a new class of pharmacological agents for the treatment of type 2 (non-insulin-dependent) diabetes mellitus. Two such compounds are currently available for clinical use: rosiglitazone and pioglitazone. Thiazolidinediones improve insulin sensitivity and glycaemic control in patients with type 2 diabetes. In addition, improvement in endothelial function, a decrease in inflammatory conditions, a decrease in plasma levels of free fatty acids and lower blood pressure have been observed, which may have important beneficial effects on the vasculature. Several questions remain to be answered about PPAR-gamma agonists, particularly with respect to the role of PPAR-gamma in vascular pathophysiology. More needs to be known about the adverse effects of thiazolidinediones, such as hepatotoxicity, increased low-density lipoprotein cholesterol levels and increased oedema. The paradox of adipocyte differentiation with weight gain concurring with the insulin-sensitising effect of thiazolidinediones is not completely understood. The decrease in blood pressure induced by thiazolidinedione treatment seems incompatible with an increase in the plasma volume, and the discrepancy between the stimulation of the expression of CD36 and the antiatherogenic effects of the thiazolidinediones also needs further explanation. Long-term clinical trials of thiazolidinediones with cardiovascular endpoints are currently in progress. In conclusion, studying the effects of thiazolidinediones may shed more light on the mechanisms involved in the insulin resistance syndrome. Furthermore, thiazolidinediones could have specific, direct effects on processes involved in the development of vascular abnormalities.

Participation of high glucose concentrations in neutrophil adhesion and surface expression of adhesion molecules on cultured human endothelial cells: effect of antidiabetic medicines

BACKGROUND

Atherosclerosis and vascular inflammation induced by hyperglycemia are important factors in the promotion of diabetic complications. One of the earliest events in the inflammatory process is increased binding of neutrophils to endothelial cells. Since vascular inflammation has been recently reported to be crucial for the onset of atherosclerosis-mediated serious diseases (acute myocardial infarction, stroke), in this study, we examined the effects of high glucose concentrations on endothelial-neutrophil cell adhesion and surface expression of endothelial adhesion molecules. We also evaluated the effects of various antidiabetic medicines on these events.

METHODS

Human umbilical vein endothelial cells (HUVECs) were first cultured for 48 h in the glucose-rich medium, and neutrophils from healthy volunteers were then added and allowed to adhere for 30 min. Adhered neutrophils were quantified by measuring myeloperoxidase (MPO) activities, and surface expression of endothelial adhesion molecules was determined using an enzyme immunoassay.

RESULTS

High glucose concentrations (over 27.8 mM) increased endothelial-neutrophil cell adhesion and expression of endothelial adhesion molecules (intercellular adhesion molecule-1 (ICAM-1), P-selectin, E-selectin). These events were protein kinase C (PKC) dependent, because PKC inhibitors, but not other intracellular second messenger inhibitors, significantly blocked them. Among antidiabetic medicines, a sulfonylurea, gliclazide (but not glibenclamide or glimepiride), and an aldose reductase inhibitor, epalrestat, significantly inhibited these events; however, a new K(ATP)-channel blocker, netegulinide, a biguanide, metformine, or an insulin sensitizer, troglitazone, did not.

CONCLUSIONS

Our data is consistent with hyperglycemia-mediated vascular inflammation through increases in neutrophil adhesion and expression of endothelial adhesion molecules. These events might lead to the onset of atherosclerosis-mediated serious diseases, but could be inhibited by something perhaps, such as gliclazide and epalrestat.

Prevention of chemically induced diabetes mellitus in experimental animals by polyunsaturated fatty acids

Previous studies showed that essential fatty-acid deficiency, conjugated linoleic acid, and a peroxisome proliferator-activated receptor-gamma binding agent such as troglitazone can prevent the development of diabetes mellitus in experimental animals. In the present study, we observed that oral supplementation with oils rich in omega-3 eicosapentaenoic acid and docosahexaenoic acid and omega-6 gamma-linolenic acid and arachidonic acid could protect the animals against alloxan-induced diabetes mellitus. These oils rich in omega-3 and omega-6 fatty acids not only significantly attenuated chemical-induced diabetes mellitus but also restored the antioxidant status to normal range. Changes in the concentrations of different fatty acids shown by the phospholipid fractions of plasma, liver, and muscle tissues that occurred as a result of alloxan-induced diabetes mellitus also reverted to normal in these animals. Based on these results and the known mechanisms of alloxan, we suggest that omega-3 and omega-6 long-chain fatty acids can prevent chemically induced diabetes mellitus by enhancing the antioxidant status and suppressing production of cytokines.

Protective action of arachidonic acid against alloxan-induced cytotoxicity and diabetes mellitus

Previous studies showed that essential fatty acid (EFA) deficiency, conjugated linoleic acid and troglitazone exert a protective effect in animal models of diabetes mellitus. Here we show that alloxan-induced in vitro cytotoxicity and apoptosis in an insulin secreting rat insulinoma, RIN, cells can be prevented by arachidonic acid (AA) and that both cyclo-oxygenase and lipoxygenase inhibitors do not block this protective action. Alloxan-induced diabetes in male Wistar rats was also prevented by oral supplementation of AA, gamma-linolenic acid (GLA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This protective action is best when the animals were pre-treated with the fatty acid. These results suggest that polyunsaturated fatty acids can prevent alloxan-induced diabetes mellitus in experimental animals and may be useful to prevent diabetes mellitus in the high-risk population.

Modulation of tumor necrosis factor-alpha production with anti-hypertensive drugs

It is well known that some anti-hypertensive drugs affect insulin sensitivity and that tumor necrosis factor-alpha (TNF-alpha) is a mediator of obesity-associated insulin resistance. In this study, we have investigated the effect of anti-hypertensive drugs, calcium (Ca) channel blockers (amlodipine, manidipine and nicardipine), an alpha(1)-blocker (doxazosin), a beta(1)-blocker (metoprolol), and a thiazide diuretic (hydrochlorothiazide), on lipopolysaccharide (LPS)-induced TNF-alpha production. TNF-alpha production, measured with a bioassay and an immunoassay, was evaluated both in vivo and in vitro, by utilizing mice and a human peripheral blood mononuclear cell culture, respectively. Nicardipine, or amlodipine, manidipine and doxazosin significantly inhibited TNF-alpha production in mice at doses more than one or ten times higher than those used clinically, respectively. On the other hand, metoprolol increased TNF-alpha production at doses of more than 10 times those used clinically, whereas hydrochlorothiazide did not alter production of the cytokine. The in vivo effects of these drugs were not necessary parallel to the in vitro effects. Because high doses of these drugs in mice correspond to clinical doses and effects in human, these actions may be related to beneficial and/or harmful effects of these drugs on TNF-alpha mediated diseases, including insulin resistance.