Selective COX2 inhibition improves whole body and muscular insulin resistance in fructose-fed rats

[Current challenges for therapy of comorbid patients: a new look at celecoxib. A review]

The use of non-steroidal anti-inflammatory drugs (NSAIDs) for a wide range of diseases is increasing, in part due to an increasing elderly population. Elderly patients are more vulnerable to adverse drug reactions, including side effects and adverse effects of drug-drug interactions, often occurring in this category of patients due to multimorbidity and polypharmacy. One of the most popular NSAIDs in the world is celecoxib. It is a selective cyclooxygenase (COX)-2 inhibitor with 375 times more COX-2 inhibitory activity than COX-1. As a result, celecoxib has a better gastrointestinal tract safety profile than non-selective NSAIDs. Gastrointestinal tolerance is an essential factor that physicians should consider when selecting NSAIDs for elderly patients. Celecoxib can be used in a wide range of diseases of the musculoskeletal system and rheumatological diseases, for the treatment of acute pain in women with primary dysmenorrhea, etc. It is also increasingly used as part of a multimodal perioperative analgesia regimen. There is strong evidence that COX-2 is actively involved in the pathogenesis of ischemic brain damage, as well as in the development and progression of neurodegenerative diseases, such as Alzheimer's disease. NSAIDs are first-line therapy in the treatment of acute migraine attacks. Celecoxib is well tolerated in patients with risk factors for NSAID-associated nephropathy. It does not decrease the glomerular filtration rate in elderly patients and patients with chronic renal failure. Many meta-analyses and epidemiological studies have not confirmed the increased risk of cardiovascular events reported in previous clinical studies and have not shown an increased risk of cardiovascular events with celecoxib, irrespective of dose. COX-2 activation is one of the key factors contributing to obesity-related inflammation. Specific inhibition of COX-2 by celecoxib increases insulin sensitivity in overweight or obese patients. Combination therapies may be a promising new area of treatment for obesity and diabetes.

Selective COX-2 Inhibitors: Road from Success to Controversy and the Quest for Repurposing

The introduction of selective COX-2 inhibitors (so-called 'coxibs') has demonstrated tremendous commercial success due to their claimed lower potential of serious gastrointestinal adverse effects than traditional NSAIDs. However, following the repeated questioning on safety concerns, the coxibs 'controversial me-too' saga increased substantially, inferring to the risk of cardiovascular complications, subsequently leading to the voluntary withdrawal of coxibs (e.g., rofecoxib and valdecoxib) from the market. For instance, the makers (Pfizer and Merck) had to allegedly settle individual claims of cardiovascular hazards from celecoxib and valdecoxib. Undoubtedly, the lessons drawn from this saga revealed the flaws in drug surveillance and regulation, and taught science to pursue a more integrated translational approach for data acquisition and interpretation, prompting science-based strategies of risk avoidance in order to sustain the value of such drugs, rather than their withdrawal. Looking forward, coxibs are now being studied for repurposing, given their possible implications in the management of a myriad of diseases, including cancer, epilepsy, psychiatric disorders, obesity, Alzheimer's disease, and so on. This article briefly summarizes the development of COX-2 inhibitors to their market impression, followed by the controversy related to their toxicity. In addition, the events recollected in hindsight (the past lessons), the optimistic step towards drug repurposing (the present), and the potential for forthcoming success (the future) are also discussed.

Direct and indirect modulation of LPS-induced cytokine production by insulin in human macrophages

Overweight and obesity are accompanied by insulin resistance, impaired intestinal barrier function resulting in increased lipopolysaccharide (LPS) levels, and a low-grade chronic inflammation that results in macrophage activation. Macrophages produce a range of interleukins as well as prostaglandin E₂ (PGE₂). To cope with insulin resistance, hyperinsulinemia develops. The purpose of the study was to elucidate how LPS, insulin and PGE₂ might interact to modulate the inflammatory response in macrophages. Human macrophages were either derived by differentiation from U937 cells or isolated from blood mononuclear cells. The macrophages were stimulated with LPS, insulin and PGE₂. Insulin significantly enhanced the LPS-dependent expression of interleukin-1β and interleukin-8 on both the mRNA and protein levels. Additionally, insulin increased the LPS-dependent induction of enzymes involved in the PGE₂-synthesis and the production of PGE₂ by macrophages. PGE₂ in turn further enhanced the LPS-dependent expression of cytokines via its G_s-coupled receptors EP2 and EP4, the latter of which appeared to be more relevant. The combination of all three stimuli resulted in an even higher induction than the combination of LPS plus insulin or LPS plus PGE₂. Thus, the compensatory hyperinsulinemia might directly and indirectly enhance the LPS-dependent cytokine production in obese individuals.

Therapeutic approaches targeting inflammation for diabetes and associated cardiovascular risk

Obesity-related sub-acute chronic inflammation has been associated with incident type 2 diabetes and atherosclerotic cardiovascular disease. Inflammation is increasingly considered to be a pathologic mediator of these commonly co-occurring diseases. A growing number of preclinical and clinical studies support the inflammatory hypothesis, but clinical trials to confirm the therapeutic potential to target inflammation to treat or prevent cardiometabolic conditions are still ongoing. There are multiple inflammatory signaling pathways. Regulation is complex, with substantial crosstalk across these multiple pathways. The activity of select pathways may be differentially regulated in different tissues. Pharmacologic approaches to diabetes management may have direct or indirect antiinflammatory effects, the latter potentially attributable to an improved metabolic state. Conversely, some antiinflammatory approaches may affect glucose metabolism and cardiovascular health. To date, clinical trials suggest that targeting one portion of the inflammatory cascade may differentially affect dysglycemia and atherothrombosis. Understanding the underlying biological processes may contribute to the development of safe and effective therapies, although a single approach may not be sufficient for optimal management of both metabolic and athrothrombotic disease states.

Comparative Proteomic Study of Fatty Acid-treated Myoblasts Reveals Role of Cox-2 in Palmitate-induced Insulin Resistance

Accumulated studies demonstrate that saturated fatty acids (FAs) such as palmitic acid (PA) inhibit insulin signaling in skeletal muscle cells and monounsaturated fatty acids such as oleic acid (OA) reverse the effect of PA on insulin signaling. The detailed molecular mechanism of these opposite effects remains elusive. Here we provide a comparative proteomic study of skeletal myoblast cell line C2C12 that were untreated or treated with PA, and PA plus OA. A total of 3437 proteins were quantified using SILAC in this study and 29 proteins fall into the pattern that OA reverses PA effect. Expression of some these proteins were verified using qRT-PCR and Western blot. The most significant change was cyclooxygenase-2 (Cox-2). In addition to whole cell comparative proteomic study, we also compared lipid droplet (LD)-associated proteins and identified that Cox-2 was one of three major altered proteins under the FA treatment. This finding was then confirmed using immunofluorescence. Finally, Cox-2 selective inhibitor, celecoxib protected cells from PA-reduced insulin signaling Akt phosphorylation. Together, these results not only provide a dataset of protein expression change in FA treatment but also suggest that Cox-2 and lipid droplets (LDs) are potential players in PA- and OA-mediated cellular processes.

Hepatic cyclooxygenase-2 expression protects against diet-induced steatosis, obesity, and insulin resistance

Accumulation evidence links obesity-induced inflammation as an important contributor to the development of insulin resistance, which plays a key role in the pathophysiology of obesity-related diseases such as type 2 diabetes and nonalcoholic fatty liver disease. Cyclooxygenase (COX)-1 and -2 catalyze the first step in prostanoid biosynthesis. Because adult hepatocytes fail to induce COX-2 expression regardless of the proinflammatory stimuli used, we have evaluated whether this lack of expression under mild proinflammatory conditions might constitute a permissive condition for the onset of insulin resistance. Our results show that constitutive expression of human COX-2 (hCOX-2) in hepatocytes protects against adiposity, inflammation, and, hence, insulin resistance induced by a high-fat diet, as demonstrated by decreased hepatic steatosis, adiposity, plasmatic and hepatic triglycerides and free fatty acids, increased adiponectin-to-leptin ratio, and decreased levels of proinflammatory cytokines, together with an enhancement of insulin sensitivity and glucose tolerance. Furthermore, hCOX-2 transgenic mice exhibited increased whole-body energy expenditure due in part by induction of thermogenesis and fatty acid oxidation. The analysis of hepatic insulin signaling revealed an increase in insulin receptor-mediated Akt phosphorylation in hCOX-2 transgenic mice. In conclusion, our results point to COX-2 as a potential therapeutic target against obesity-associated metabolic dysfunction.

PDE5 inhibitors enhance celecoxib killing in multiple tumor types

The present studies determined whether clinically relevant phosphodiesterase 5 (PDE5) inhibitors interacted with a clinically relevant NSAID, celecoxib, to kill tumor cells. Celecoxib and PDE5 inhibitors interacted in a greater than additive fashion to kill multiple tumor cell types. Celecoxib and sildenafil killed ex vivo primary human glioma cells as well as their associated activated microglia. Knock down of PDE5 recapitulated the effects of PDE5 inhibitor treatment; the nitric oxide synthase inhibitor L-NAME suppressed drug combination toxicity. The effects of celecoxib were COX2 independent. Over-expression of c-FLIP-s or knock down of CD95/FADD significantly reduced killing by the drug combination. CD95 activation was dependent on nitric oxide and ceramide signaling. CD95 signaling activated the JNK pathway and inhibition of JNK suppressed cell killing. The drug combination inactivated mTOR and increased the levels of autophagy and knock down of Beclin1 or ATG5 strongly suppressed killing by the drug combination. The drug combination caused an ER stress response; knock down of IRE1α/XBP1 enhanced killing whereas knock down of eIF2α/ATF4/CHOP suppressed killing. Sildenafil and celecoxib treatment suppressed the growth of mammary tumors in vivo. Collectively our data demonstrate that clinically achievable concentrations of celecoxib and sildenafil have the potential to be a new therapeutic approach for cancer.

Effects of cyclooxygenase inhibition on insulin release and pancreatic islet blood flow in rats

OBJECTIVES

To examine the effects of inhibition of cyclooxygenase (COX) on islet hormone secretion in vitro and on pancreatic islet blood flow in vivo.

METHODS

Insulin release was measured in a static incubation system of islets isolated from Wistar-F rats after inhibition of COX-1 and COX-2 with SC 560 (COX-1), FR 122047 (COX-1), rofecoxib (COX-2), or indomethacin (both COX-1 and COX-2). In other rats organ blood flow values were measured with a microsphere technique during both normo- and hyperglycemia after administration of these enzyme inhibitors.

RESULTS

Serum insulin values were lower after pretreatment with a COX-1 inhibitor or a non-selective COX inhibitor in both control and glucose-injected rats in vivo, whereas COX-2 inhibition had no such effects. However, inhibition of COX had only minor effects on insulin release in vitro. Inhibition of COX affected neither total pancreatic nor islet blood flow in normoglycemic rats. Hyperglycemia caused an increase in both these flow values and in the duodenum. The increase in total pancreatic and duodenal blood flow was prevented by inhibition of COX-2 or non-selective COX inhibition. However, no effects on islet blood flow were seen after COX inhibition.

CONCLUSION

Inhibition of COX affects insulin release and blood glucose concentrations in vivo. However, COX inhibition has only minor effects on pancreatic islet blood flow, but prevents the glucose-induced increase in total pancreatic blood flow.

NOD1 expression is increased in the adipose tissue of women with gestational diabetes

Maternal peripheral insulin resistance and increased inflammation are two features of pregnancies, complicated by gestational diabetes mellitus (GDM). The nucleotide-binding oligomerisation domain (NOD) intracellular molecules recognise a wide range of microbial products, as well as other intracellular danger signals, thereby initiating inflammation through activation of nuclear factor κB (NFκB). The aim of this study was to determine whether levels of NOD1 and NOD2 are increased in adipose tissue of women with GDM. The effect of NOD1 and NOD2 activation on inflammation and the insulin signalling pathway was also assessed. NOD1, but not NOD2, expression was higher in omental and subcutaneous adipose tissues obtained from women with GDM when compared with those from women with normal glucose tolerance (NGT). In both omental and subcutaneous adipose tissues from NGT and GDM women, the NOD1 ligand g-d-glutamyl-meso-diaminopimelic acid (iE-DAP) significantly induced the expression and secretion of the pro-inflammatory cytokine interleukin 6 (IL6) and chemokine IL8; COX2 (PTGS2) gene expression and subsequent prostaglandin production; the expression and secretion of the extracellular matrix remodelling enzyme matrix metalloproteinase 9 (MMP9) and the gene expression and secretion of the adhesion molecules ICAM1 and VCAM1. There was no effect of the NOD2 ligand muramyl dipeptide on any of the endpoints tested. The effects of the NOD1 ligand iE-DAP were mediated via NFκB, as the NFκB inhibitor BAY 11-7082 significantly attenuated iE-DAP-induced expression and secretion of pro-inflammatory cytokines, COX2 gene expression and subsequent prostaglandin production, MMP9 expression and secretion and ICAM1 and VCAM1 gene expression and secretion. In conclusion, the present findings describe an important role for NOD1 in the development of insulin resistance and inflammation in pregnancies complicated by GDM.

Inflammatory mediators involved in the progression of the metabolic syndrome

The metabolic syndrome is often associated with type 2 diabetes mellitus, dyslipidemia, atherosclerosis, hypertension, steatosis of the liver and other organs, as well as hypertension, type 2 diabetes mellitus, and atherosclerosis. Recent studies have implicated a number of inflammatory mediators including cytokines, adipokines and eicosanoids in the inflammatory responses that accompany the metabolic syndrome. Measurements of the circulating levels of the inflammatory molecules that accompany this syndrome might provide leads to therapeutic approaches to modulate the inflammatory responses and thereby alter disease progression. In this review, we summarize recent studies on classical and newer inflammatory mediators in the pathogenesis of the metabolic syndrome in humans and experimental models.

α-Lipoic acid prevents mild portal endotoxaemia-induced hepatic inflammation and β cell dysfunction

BACKGROUND

This study was undertaken to evaluate the preventive effect of α-lipoic acid (LA) on chronic mild portal endotoxaemia-mediated subacute hepatic inflammation and pancreatic β cell dysfunction in rats.

MATERIALS AND METHODS

Male Sprague-Dawley rats were randomly assigned into four groups: those with intraportal vehicle (saline) or low-dose lipopolysaccharide (LPS) (0·42 ng/kg/min) infusion, combined with oral administration of vehicle or LA, a potent antioxidant (60 mg/kg/day) for 4 weeks. The hyperglycaemic clamp and euglycaemic clamp techniques were used to access the glucose-stimulated insulin secretion and systemic insulin sensitivity in vivo.

RESULTS

Body weight, fasting plasma glucose and insulin were not different among groups. In rats with chronic intraportal LPS infusion, plasma C-reactive protein, amylase, superoxide levels, the contents of thiobarbituric acid-reactive substance, tumour necrosis factor α and interleukin 6 in liver and pancreas and also the gene expression of Toll-like receptor 4 in liver were significantly increased as compared with those with LA cotreatment. The histopathological examination showed that inflammatory changes were clearly visible in liver and pancreatic islets of LPS-infused rats and rarely observed in those cotreated with LA. In addition, low-dose intraportal LPS infusion also significantly impaired glucose-stimulated insulin secretion but not affect the systemic insulin sensitivity and metabolic clearance rate of insulin. LA administration markedly reversed LPS-induced β cell dysfunction.

CONCLUSIONS

α-Lipoic acid cotreatment could significantly prevent mild portal endotoxaemia-induced chronic hepatic inflammation and impaired pancreatic insulin secretion in absence of changing systemic insulin resistance.

The importance of cyclooxygenase 2-mediated oxidative stress in obesity-induced muscular insulin resistance in high-fat-fed rats

AIM

This study was undertaken to examine the effect of cyclooxygenase (COX) 2 inhibition on the development of muscular insulin resistance in high-fat-induced obese rats.

MAIN METHODS

The rats were on a regular chow diet (C) or high-fat enriched diet (HFD) energy-restrictedly (HFr), or ad libitum (HFa) for 12weeks. The rats fed HFD ad libitum were further divided into 3 groups: oral gavage with vehicle (HFa), selective COX-2 inhibitors-celecoxib (HFa+C) or nimesulid (HFa+N), 30mg/kg/day, respectively.

KEY FINDINGS

Increased fasting plasma insulin, triglyceride and 8-isoprostane levels in HFa were significantly suppressed in those of HFa+C and HFa+N. The whole body insulin resistance of HFa indicated by the increased fasting plasma insulin levels and the elevated area under curve of insulin obtained from the oral glucose tolerance test were significantly reversed in those combined with celecoxib and nimesulid administration compared with those in HFr. The gene expression of COX-2 was significantly increased in epididymal fat but not in soleus muscle in HFa and the enhanced adipose COX-2 expression in high-fat fed rats was suppressed by those with drug treatment. Both selective COX-2 inhibitors reversed the diminished insulin-stimulated glucose uptake and GLUT4 translocation in skeletal muscles of HFa. Obesity-induced oxidative stress indicated by the elevated plasma 8-isoprostane,the decreased ratio of GSH/GSSG and increased TBARS in soleus muscle were significantly reversed by COX-2 inhibition.

SIGNIFICANCE

The results suggest that COX-2 inhibition might suppress the muscular insulin resistance indirectly through decreasing the COX-2-mediated systemic oxidative stress in this diet-induced obese model.

Effects of insulin resistance and testosterone on the participation of cyclooxygenase isoforms in vascular reactivity

Testosterone plays an important role in mediating hypertension and altered vascular reactivity associated with insulin resistance. In addition to other pathways, testosterone-dependent changes in aortic cyclooxygenase (COX-2) mRNA levels affect blood pressure following insulin resistance. However their effects on vascular tone are unclear. We studied the changes in contraction response to phenylephrine (PE) in the aorta and superior mesenteric artery (SMA) from intact and gonadectomized fructose-fed rats. Constriction response to PE was studied in tissues incubated with the COX-1 and COX-2-selective antagonists, SC-560 and NS-398, respectively, and indomethacin, in addition to assessing its role in endothelium-dependent relaxation. Finally changes in COX-2 protein expression and plasma thromboxane A2 (TXA2), a downstream vasoconstrictor metabolite of COX-2, were measured. In fructose-fed rats, castration prevented the increase in blood pressure but not insulin resistance. The involvement of COX-2 in mediating the alpha-adrenergic vasoconstriction was higher in intact rat aorta compared to COX-1, which was prevented by castration. However, in the SMA, COX-2 participation was dependent on testosterone alone. Fructose-induced attenuation of endothelial relaxation was restored by indomethacin, which suggests a pro-vasoconstrictor role for COX. Both diet and testosterone did not alter vascular COX-2 expression thus suggesting the involvement of downstream testosterone-dependent pathways. This is supported by increased plasma TXA2 in the castrated rats compared to intact rats. Isoform-specific actions of COX are tissue-selective in states of insulin resistance and involve potential testosterone-dependent downstream targets. Further studies are needed to investigate the role of androgens and insulin resistance in vascular arachidonic acid metabolism.

Suppressive effect of COX2 inhibitor on the progression of adipose inflammation in high-fat-induced obese rats

BACKGROUND

The aim was to examine whether the inhibition of selective cyclooxygenase (COX) 2 activation could suppress the development of inflammatory reaction in visceral and subcutaneous abdominal fats of high-fat-induced obese rats.

MATERIALS AND METHODS

The rats were fed separately regular diet (CONT), high-fat diet ad libitum or energy-restrictedly (HFr) for 12 weeks. Rats fed high-fat diet ad libitum were further divided into those co-treated with vehicle (HFa), a selective COX2 inhibitor-celecoxib (HFa-Cel) or nimesulide (HFa-Nim). Oral glucose tolerance test (OGTT) was performed at the end of weeks 4, 8, 12. Another set of rats with similar grouping was divided into those with a 4-, 8- or 12-week intervention for tissue sampling.

RESULTS

Body and epididymal fat weights were increased similarly in HFa, HFa-Cel and HFa-Nim. Time-dependent increases in plasma insulin, triglyceride, impaired OGTT shown in HFa were significantly reversed in HFa-Cel and HFa-Nim. The obese-linked increases in gene expressions of COX-2, monocyte chemoattractant protein-1 (MCP-1) and tumour necrosis factor-alpha (TNF-alpha) in epididymal and subcutaneous fats (especially in the former) were significantly suppressed in HFa-Cel and HFa-Nim. The protein contents of MCP-1 and TNF-alpha in epididymal fats were changed consistently with their gene expressions. Plasma MCP-1 was increased time-dependently in HFa and suppressed in HFa-Cel and HFa-Nim. The increased CD68 positive cells showed in both epididymal and subcutaneous fats of HFa were significantly attenuated in HFa-Cel and HFa-Nim.

CONCLUSIONS

Our findings suggest that COX2 activation is crucially involved in the development of inflammatory response in adipose tissues of high-fat-induced obese rats.

Different impacts of saturated and unsaturated free fatty acids on COX-2 expression in C(2)C(12) myotubes

In skeletal muscle, saturated free fatty acids (FFAs) act as proinflammatory stimuli, and cyclooxygenase-2 (COX-2) is a pro/anti-inflammatory enzyme induced at sites of inflammation, which contributes to prostaglandin production. However, little is known about the regulation of COX-2 expression and its responses to FFAs in skeletal muscle. Herein, we examined the effects of saturated and unsaturated FFAs, including a recently identified lipokine (lipid hormone derived from adipocytes), palmitoleate, on COX-2 expression in C(2)C(12) myotubes as a skeletal muscle model. Exposure of myotubes to saturated FFAs [palmitate (16:0) and stearate (18:0)], but not to unsaturated FFAs [palmitoleate (16:1), oleate (18:1), and linoleate (18:2)], led to a slow-onset induction of COX-2 expression and subsequent prostaglandin E(2) production via mechanisms involving the p38 MAPK and NF-kappaB but not the PKC signaling cascades. Pharmacological modulation of mitochondrial oxidative function failed to interfere with COX-2 expression, suggesting the mitochondrial overload/excessive beta-oxidation contribution to this event to be minimal. On the contrary, unsaturated FFAs appeared to effectively antagonize palmitate-induced COX-2 expression with markedly different potencies (linoleate > oleate > palmitoleate), being highly associated with the suppressive profile of each unsaturated FFA toward palmitate-evoked intracellular signals, including p38, JNK, ERK1/2 MAPKs, and PKCtheta, as well as IkappaB degradation. In addition, our data suggest little involvement of PPAR in the protective actions of unsaturated FFAs against palmitate-induced COX-2 expression. No direct contribution of the increased COX-2 activity in generating palmitate-induced insulin resistance was detected, at least in terms of insulin-responsive Akt phosphorylation and GLUT4 translocation. Taken together, our data provide a novel insight into the molecular mechanisms responsible for the FFA-induced COX-2 expression in skeletal muscle and raise the possibility that, in skeletal myocytes, COX-2 and its product prostaglandins may play an important role in the complex inflammation responses caused by elevated FFAs, for example, in the diabetic state.

The fructose-fed rat: a review on the mechanisms of fructose-induced insulin resistance and hypertension

The metabolic syndrome is an important public health concern that predisposes individuals to the development of cardiovascular disease and/or Type 2 diabetes. The fructose-fed rat is an animal model of acquired systolic hypertension that displays numerous features of the metabolic syndrome. This animal model is used to study the relationship between insulin resistance/compensatory hyperinsulinemia and the development of hypertension. Several mechanisms have been proposed to mediate the link between insulin resistance and hypertension. In this review, we have addressed the role of sympathetic nervous system overactivation, increased production of vasoconstrictors, such as endothelin-1 and angiotensin II, and prostanoids in the development of hypertension in fructose-fed rats. The roles of nitric oxide, impaired endothelium-dependent relaxation and sex hormones in the pathogenesis of the fructose-fed induced hypertensive rats have also been highlighted. More recently, increased formation of reactive oxygen species and elevated levels of uric acid have been reported to contribute to fructose-induced hypertension.