Oxidative stress induces insulin resistance by activating the nuclear factor-kappa B pathway and disrupting normal subcellular distribution of phosphatidylinositol 3-kinase

Trilobatin contributes to the improvement of myopathy in a mouse model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) occurs due to genetic mutations that lead to a deficiency in dystrophin production and consequent progressive degeneration of skeletal muscle fibres, through oxidative stress and an exacerbated inflammatory process. The flavonoid trilobatin (TLB) demonstrates antioxidant and anti-inflammatory potential. Its high safety profile and effective action make it a potent therapy for the process of dystrophic muscle myonecrosis. Thus, we sought to investigate the action of TLB on damage in a DMD model, the mdx mouse. Eight-week-old male animals were treated with 160 mg/kg/day of trilobatin for 8 weeks. Control animals were treated with saline. Following treatment, muscle strength, serum creatine kinase (CK) levels, histopathology (necrotic myofibres, regenerated fibres/central nuclei, Feret's diameter and inflammatory area) and the levels of catalase and NF-κB (western blotting) of the quadriceps (QUA), diaphragm (DIA) and tibialis anterior (TA) muscles were measured. TLB was able to significantly increase muscle strength and reduce serum CK levels in dystrophic animals. The QUA of mdx mice showed a reduction in catalase and the number of fibres with a centralized nucleus after treatment with TLB. In the DIA of dystrophic animals, TLB reduced the necrotic myofibres, inflammatory area and NF-κB and increased the number of regenerated fibres and the total fibre diameter. In TA, TLB increased the number of regenerated fibres and reduced catalase levels in these animals. It is concluded that in the mdx experimental model, treatment with TLB was beneficial in the treatment of DMD.

Targeting the Metabolic Paradigms in Cancer and Diabetes

Dysregulated metabolic dynamics are evident in both cancer and diabetes, with metabolic alterations representing a facet of the myriad changes observed in these conditions. This review delves into the commonalities in metabolism between cancer and type 2 diabetes (T2D), focusing specifically on the contrasting roles of oxidative phosphorylation (OXPHOS) and glycolysis as primary energy-generating pathways within cells. Building on earlier research, we explore how a shift towards one pathway over the other serves as a foundational aspect in the development of cancer and T2D. Unlike previous reviews, we posit that this shift may occur in seemingly opposing yet complementary directions, akin to the Yin and Yang concept. These metabolic fluctuations reveal an intricate network of underlying defective signaling pathways, orchestrating the pathogenesis and progression of each disease. The Warburg phenomenon, characterized by the prevalence of aerobic glycolysis over minimal to no OXPHOS, emerges as the predominant metabolic phenotype in cancer. Conversely, in T2D, the prevailing metabolic paradigm has traditionally been perceived in terms of discrete irregularities rather than an OXPHOS-to-glycolysis shift. Throughout T2D pathogenesis, OXPHOS remains consistently heightened due to chronic hyperglycemia or hyperinsulinemia. In advanced insulin resistance and T2D, the metabolic landscape becomes more complex, featuring differential tissue-specific alterations that affect OXPHOS. Recent findings suggest that addressing the metabolic imbalance in both cancer and diabetes could offer an effective treatment strategy. Numerous pharmaceutical and nutritional modalities exhibiting therapeutic effects in both conditions ultimately modulate the OXPHOS-glycolysis axis. Noteworthy nutritional adjuncts, such as alpha-lipoic acid, flavonoids, and glutamine, demonstrate the ability to reprogram metabolism, exerting anti-tumor and anti-diabetic effects. Similarly, pharmacological agents like metformin exhibit therapeutic efficacy in both T2D and cancer. This review discusses the molecular mechanisms underlying these metabolic shifts and explores promising therapeutic strategies aimed at reversing the metabolic imbalance in both disease scenarios.

Redox Balance in Type 2 Diabetes: Therapeutic Potential and the Challenge of Antioxidant-Based Therapy

Oxidative stress is an important factor in the development of type 2 diabetes (T2D) and associated complications. Unfortunately, most clinical studies have failed to provide sufficient evidence regarding the benefits of antioxidants (AOXs) in treating this disease. Based on the known complexity of reactive oxygen species (ROS) functions in both the physiology and pathophysiology of glucose homeostasis, it is suggested that inappropriate dosing leads to the failure of AOXs in T2D treatment. To support this hypothesis, the role of oxidative stress in the pathophysiology of T2D is described, together with a summary of the evidence for the failure of AOXs in the management of diabetes. A comparison of preclinical and clinical studies indicates that suboptimal dosing of AOXs might explain the lack of benefits of AOXs. Conversely, the possibility that glycemic control might be adversely affected by excess AOXs is also considered, based on the role of ROS in insulin signaling. We suggest that AOX therapy should be given in a personalized manner according to the need, which is the presence and severity of oxidative stress. With the development of gold-standard biomarkers for oxidative stress, optimization of AOX therapy may be achieved to maximize the therapeutic potential of these agents.

Therapeutic effects of icariin and icariside II on diabetes mellitus and its complications

Diabetes mellitus (DM) is a global health issue in the twenty-first century, and there are numerous challenges in preventing and alleviating its chronic complications. The herb Epimedium has beneficial therapeutic effects on various human diseases, including DM. Its major flavonoid component, icariin, has significant anti-DM activity and may help improve pancreatic β-cell dysfunction and insulin resistance. Furthermore, preclinical evidence has shown that icariin and its in vivo bioactive form, icariside II, have preventive and therapeutic effects on several diabetic complications, including diabetic cardiomyopathy, diabetic vascular endothelial disorder, diabetic nephropathy, and diabetic erectile dysfunction. In this review, we present the general and toxicological information concerning icariin and icariside II and review the anti-DM effects of icariin from a molecular perspective. Additionally, we discuss the potential benefits of icariin and icariside II on the important pathological mechanisms of various diabetic complications. Despite positive preclinical evidence, additional investigations are needed before relevant clinical studies can be conducted. Therefore, we conclude with suggestions for future research. Hopefully, this review will provide a comprehensive molecular perspective for future research and product development related to icariin and icariside II in treating DM and diabetic complications.

Astaxanthin Carotenoid Modulates Oxidative Stress in Adipose-Derived Stromal Cells Isolated from Equine Metabolic Syndrome Affected Horses by Targeting Mitochondrial Biogenesis

Astaxanthin is gaining recognition as a natural bioactive component. This study aimed to test whether astaxanthin could protect adipose-derived stromal stem cells (ASCs) from apoptosis, mitochondrial dysfunction and oxidative stress. Phaffia rhodozyma was used to extract astaxanthin, whose biocompatibility was tested after 24, 48 and 72 h of incubation with the cells; no harmful impact was found. ASCs were treated with optimal concentrations of astaxanthin. Several parameters were examined: cell viability, apoptosis, reactive oxygen levels, mitochondrial dynamics and metabolism, superoxide dismutase activity, and astaxanthin’s antioxidant capacity. A RT PCR analysis was performed after each test. The astaxanthin treatment significantly reduced apoptosis by modifying the normalized caspase activity of pro-apoptotic pathways (p21, p53, and Bax). Furthermore, by regulating the expression of related master factors SOD1, SOD2, PARKIN, PINK 1, and MFN 1, astaxanthin alleviated the oxidative stress and mitochondrial dynamics failure caused by EMS. Astaxanthin restored mitochondrial oxidative phosphorylation by stimulating markers associated with the OXPHOS machinery: COX4I1, COX4I2, UQCRC2, NDUFA9, and TFAM. Our results suggest that astaxanthin has the potential to open new possibilities for potential bio-drugs to control and suppress oxidative stress, thereby improving the overall metabolic status of equine ASCs suffering from metabolic syndrome.

Quercetin: an effective polyphenol in alleviating diabetes and diabetic complications

Various studies, especially in recent years, have shown that quercetin has beneficial therapeutic effects in various human diseases, including diabetes. Quercetin has significant anti-diabetic effects and may be helpful in lowering blood sugar and increasing insulin sensitivity. Quercetin appears to affect many factors and signaling pathways involved in insulin resistance and the pathogenesis of type 2 of diabetes. TNFα, NFKB, AMPK, AKT, and NRF2 are among the factors that are affected by quercetin. In addition, quercetin can be effective in preventing and ameliorating the diabetic complications, including diabetic nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy, and affects the key mechanisms involved in the pathogenesis of these complications. These positive effects of quercetin may be related to its anti-inflammatory and anti-oxidant properties. In this article, after a brief review of the pathogenesis of insulin resistance and type 2 diabetes, we will review the latest findings on the anti-diabetic effects of quercetin with a molecular perspective. Then we will review the effects of quercetin on the key mechanisms of pathogenesis of diabetes complications including nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy. Finally, clinical trials investigating the effect of quercetin on diabetes and diabetes complications will be reviewed.

Berberine promotes peri-implant osteogenesis in diabetic rats by ROS-mediated IRS-1 pathway

Accompanying with diabetes mellitus-induced osteoporosis (DM-OS), diabetic patients show poor peri-implant osteogenesis after implantation for dentition defect. Berberine (BBR), a candidate oral hypoglycemic agent, is a promising agent for treating DM-OS. In this study, BBR was applied on DM rats and high-glucose-cultured bone mesenchymal stem cells (BMSCs) to investigate its therapeutic mechanism on DM-OS, thus laying a theoretical basis for the future application of BBR in implant restoration. Phenotypes were assessed in the DM rats after 4 w of gavage with BBR. Furthermore, BMSCs were cultured with high glucose and BBR. Cell Counting Kit-8, 2',7'-dichlorofluorescin diacetate (H2 DCF-DA), quantitative real-time PCR (qRT-PCR), and western blot were performed to estimate the cell proliferation, oxidative stress, and osteogenic differentiation. Moreover, the DM rats treated with BBR and insulin receptor substrate-1 anti-sense oligonucleotide (IRS-1-ASO) underwent a 4-w implant-healing period and then micro computed tomography (Micro-CT) and histology were performed to verify the mechanism. Results showed that the 4-w administration of BBR markedly improved the glucose metabolism and bone metabolism in the DM rats. in vitro experiments revealed that BBR alleviated high-glucose-inhibited osteogenesis of the BMSCs by upregulating reactive oxygen species (ROS)-mediated IRS-1 signaling. Besides, injection of IRS-1-ASO abolished the BBR promotion of implant osseointegration in the DM rats. In conclusion, targeting ROS-mediated IRS-1 signaling, BBR acted as an efficient agent to advance osseointegration in DM, which indicated that BBR use is a good strategy for future implants restoration in diabetic patients.

Host-Parasite Interaction in Sarcoptes scabiei Infestation in Porcine Model with a Preliminary Note on Its Genetic Lineage from India

Simple Summary

Scabies or mange caused by Sarcoptess cabiei is the latest addition of WHO’s list oftropical neglected diseases. It causes severe itching to the host. It has a wide host range including humans, farm animals, companion animals, and wild animals. It is anemerging/re-emerging disease with high prevalence in underdeveloped and developing countries. The disease has zoonotic importance and is of significant public health concern as cross-transmission or species jumping is very common. To date, fifteen Sarcoptes varieties have been reported as per host origin. Differential diagnosis at variety level is very crucial for epidemiological study and scratching future eradication program of the disease. As morphotaxonomy fails to differentiate varieties, use of molecular markers is crucial. Moreover, it is very important to understand the host-parasite interaction at the systemic level for a better understanding on the pathogenicity of the disease. Here, we report the genetic characterization of S. scabiei from India and host-parasite interaction in a porcine model.

Abstract

The burrowing mite Sarcoptes scabiei causes scabies in humans or mange in animals. It infests a wide range of mammalian species including livestock, companion animals, wild animals, and humans. Differential diagnosis of Sarcoptes varieties is key for epidemiological studies and for formulation of an eradication program. Host-parasite interaction at the systemic level is very important to understand the pathogenicity of the mite. This communication deals with the preliminary report on the genetic characterization of S. scabiei from India. Moreover, the effect of S. scabiei infestation on host physiology with special emphasis on serum biochemical parameters, lipid profile, oxidant/antioxidant balance, stress parameters, and immune responses were evaluated in a porcine model. Cytochrome C oxidase 1 and voltage-sensitive sodium channel based phylogenetic study could distinguish human and animals isolates but could not distinguish host or geographical specific isolates belonging to animal origin. An absence of host-specific cluster among animal isolates argues against the hypothesis of delineating S. scabiei as per host origin. Elevated levels of markers of liver function such as albumin, AST, ALT, ALP, and LDH in infested animals indicated impaired liver function in infested animals. S. scabiei infestation induced atherogenic dyslipidemia indicated by elevated levels of total cholesterol, low-density lipoprotein cholesterol and triglycerides, and a decreased level of high-density lipoprotein cholesterol. Oxidative stress in infested animals was indicated by a high level of nitric oxide and serum MDA as oxidative stress markers and low antioxidant capacity. S. scabiei triggered stress response and elevated levels of serum cortisol and heat shock proteins were recorded in infested animals. S. scabiei infestation increased the serum concentration of immunoglobulins and was associated with up-regulation of IL-2, IFN-γ, IL-1β, and IL-4 indicating both Th1 and Th2 response. The results of the study will be helpful for a better understanding of host-parasite interaction at the systemic level in crusted scabies in pigs.

The Potential of Lactobacillus spp. for Modulating Oxidative Stress in the Gastrointestinal Tract

The gastrointestinal (GI) tract is crucial for food digestion and nutrient absorption in humans. However, the GI tract is usually challenged with oxidative stress that can be induced by various factors, such as exogenous pathogenic microorganisms and dietary alterations. As a part of gut microbiota, Lactobacillus spp. play an important role in modulating oxidative stress in cells and tissues, especially in the GI tract. Oxidative stress is linked with excessive reactive oxygen species (ROS) that can be formed by a few enzymes, such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs). The redox mechanisms of Lactobacillus spp. may contribute to the downregulation of these ROS-forming enzymes. In addition, nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf-2) and nuclear factor kappa B (NF-κB) are two common transcription factors, through which Lactobacillus spp. modulate oxidative stress as well. As oxidative stress is closely associated with inflammation and certain diseases, Lactobacillus spp. could potentially be applied for early treatment and amelioration of these diseases, either individually or together with prebiotics. However, further research is required for revealing their mechanisms of action as well as their extensive application in the future.

Effect of garden cress in reducing blood glucose, improving blood lipids, and reducing oxidative stress in a mouse model of diabetes induced by a high-fat diet and streptozotocin

BACKGROUND

A mouse model in which diabetes mellitus was induced by low-dose streptozotocin (STZ) injection combined with a high-fat diet was used to study the effect of two water cress (Lepidium savitum) preparations. Diabetic mice were treated with dried cress powder or with water-soluble extracts (tested at two doses), together with proper control groups. The mice were evaluated after 4 weeks of continuous intervention for type 2 diabetic and associated markers. We determined blood glucose, body weight, total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), serum insulin levels, and DNA integrity of hepatic cells. The concentrations of malondialdehyde (MDA) and lipid peroxide (LPO) and the activities of four enzymes that are part of the antioxidant defense system were determined in liver samples, as well as gene expression (by semi-quantitative reverse transcription polymerase chain reaction) and enzyme activity of IRS-1, IRS-2, PI3K, AKT-2, and GLUT4.

RESULTS

After 4 weeks of intervention, the levels of TC, TG, and LDL cholesterol were significantly (P < 0.5) decreased and HDL cholesterol was significantly increased. Enzyme activities of liver superoxide dismutase, glutathione, glutathione peroxidase, and catalase were significantly increased, whereas MDA and LPO concentrations were significantly reduced. The transcription level of the five genes assessed was increased, with corresponding increases in protein expression.

CONCLUSION

Oral uptake of garden cress can significantly reduce the blood glucose and improve the blood lipid metabolism of diabetic mice. Considerable improvements in the activity of antioxidant defense enzymes were observed in type 2 diabetic mice that improved the body's antioxidant emergency response. © 2019 Society of Chemical Industry.

Serjanic Acid Improves Immunometabolic Markers in a Diet-Induced Obesity Mouse Model

Plant extracts from Cecropia genus have been used by Latin-American traditional medicine to treat metabolic disorders and diabetes. Previous reports have shown that roots of Cecropia telenitida that contains serjanic acid as one of the most prominent and representative pentacyclic triterpenes. The study aimed to isolate serjanic acid and evaluate its effect in a prediabetic murine model by oral administration. A semi-pilot scale extraction was established and serjanic acid purification was followed using direct MALDI-TOF analysis. A diet induced obesity mouse model was used to determine the impact of serjanic acid over selected immunometabolic markers. Mice treated with serjanic acid showed decreased levels of cholesterol and triacylglycerols, increased blood insulin levels, decreased fasting blood glucose and improved glucose tolerance, and insulin sensitivity. At transcriptional level, the reduction of inflammation markers related to adipocyte differentiation is reported.

Oxidative Stress, Intrauterine Growth Restriction, and Developmental Programming of Type 2 Diabetes

Intrauterine growth restriction (IUGR) leads to reduced birth weight and the development of metabolic diseases such as Type 2 diabetes in adulthood. Mitochondria dysfunction and oxidative stress are commonly found in key tissues (pancreatic islets, liver, and skeletal muscle) of IUGR individuals. In this review, we explore the role of oxidative stress in IUGR-associated diabetes etiology.

Effects of close-up body condition score and selenium-vitamin E injection on lactation performance, blood metabolites, and oxidative status in high-producing dairy cows

High-producing dairy cows with high pre-calving body condition score (BCS) are more susceptible to metabolic disorders and oxidative stress. The aim of present study was to evaluate the effects of close-up BCS and 3 times Se-vitamin E (SeE) injection on BCS change, blood metabolites, oxidative status, and milk yield in high-producing Holstein cows. A total of 136 multiparous cows were divided into 2 groups based on their BCS including high (HB = 4.00 ± 0.20) and moderate (MB = 3.25 ± 0.25) at 3 wk before expected calving time. Then, each group was divided into 2 subgroups: 3 rounds of SeE injection at 21 d before, and 0 and 21 d after calving (+SeE), and no SeE injection (-SeE). Four final experimental groups were HB+SeE, MB+SeE, HB-SeE, and MB-SeE (34 cows each). Results indicated that interaction effect of BCS and SeE affected serum glucose, and the MB+SeE group had the highest level. The HB cows lost more BCS compared with MB cows during the postcalving period. Moreover, serum insulin concentration increased after SeE injection. The HB cows had higher serum nonesterified fatty acids at 14 d after calving. The MB cows tended to have higher activity of blood glutathione peroxidase over the study period. Furthermore, the SeE-injected cows tended to have higher activity of blood glutathione peroxidase at 28 d after calving. Serum albumin level was increased by SeE injection. The HB cows had greater milk production than MB cows, and SeE-injected cows tended to have higher milk fat percentage and higher fat:protein ratio compared with nonsupplemented cows. It was concluded that SeE injection had beneficial effects on some blood metabolites, albumin as a blood antioxidative parameter, and lactation performance in high-producing dairy cows, especially cows with moderate close-up BCS.

Inhibition of NF-κB activation improves insulin resistance of L6 cells

To explore the role of NF-κB activation in the development of insulin resistance and investigate whether or not that the inhibition of NF-κB activation by PDTC will improve the insulin resistance of L6 cells exposed to H₂O₂. L6 cells were treated with H₂O₂, PDTC or both H₂O₂ and PDTC for 4 hours. The uptake of glucose with stimulation of insulin, the expression of P38-MAPK, p- P38-MAPK, NF-κBp65, p- NF-κBp65, IRS-1, IRS-2, p-IRS-2, PI3K, IκBα, p- IκBα, caspase-8 and GLUT4, the production of ROS, TNF-α, IL-6 and IL-1β as well as the apoptosis rate of L6 cells were determined and compared in L6 treated with H₂O₂ alone or both H₂O₂ and PDTC. Compared with the L6 cells treated with H₂O₂ alone, the L6 cells treated with both H₂O₂ and PDTC showed (1) significantly lower production of ROS, TNF-α, IL-6 and IL-1β; (2) significantly decreased expression of P38-MAPK, p- P38-MAPK and NF-κBp65, p- NF-κBp65, p- IκBα and caspase-8; (3) significantly lower rate of apoptosis; (4) significantly higher expression of IRS-2, p-IRS-2 (Tyr 612), PI3K and GLUT4; (5) significantly higher uptake of glucose with stimulation of insulin; (6) significantly increased expression of Bcl2 and decreased ratio of Bax to Bcl2. Based on the findings of the present study, inhibition of NF-κB activation by PDTC would improve the insulin resistance of L6 cells exposed to H₂O₂.

From physical inactivity to immobilization: Dissecting the role of oxidative stress in skeletal muscle insulin resistance and atrophy

In the literature, the terms physical inactivity and immobilization are largely used as synonyms. The present review emphasizes the need to establish a clear distinction between these two situations. Physical inactivity is a behavior characterized by a lack of physical activity, whereas immobilization is a deprivation of movement for medical purpose. In agreement with these definitions, appropriate models exist to study either physical inactivity or immobilization, leading thereby to distinct conclusions. In this review, we examine the involvement of oxidative stress in skeletal muscle insulin resistance and atrophy induced by, respectively, physical inactivity and immobilization. A large body of evidence demonstrates that immobilization-induced atrophy depends on the chronic overproduction of reactive oxygen and nitrogen species (RONS). On the other hand, the involvement of RONS in physical inactivity-induced insulin resistance has not been investigated. This observation outlines the need to elucidate the mechanism by which physical inactivity promotes insulin resistance.

Peripheral arterial endothelial dysfunction of neurodegenerative diseases

This study evaluates endothelial functions of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), progressive supranuclear palsy (PSP), multiple system atrophy (MSA) and spinocerebellar ataxia (SCA). The reactive hyperemia index (RHI) of peripheral arterial tonometry and serological data were compared between age- and gender-matched normal controls (n=302) and five disease groups (ALS; n=75, PD; n=180, PSP; n=30, MSA; n=35, SCA; n=53). Correlation analyses were performed in ALS with functional rating scale-revised (FRS-R), and in PD with the Hehn-Yahr scale (H-Y) and a heart to mediastinum ratio using (123)I-MIBG scintigraphy (MIBG). The RHI of ALS and PD, but not of PSP, MSA or SCA, were significantly lower than normal controls (p<0.01). ALS showed a negative correlation of RHI with serum triglycerides (TG) and immunoreactive insulin (IRI) levels, but not with disease severity (FRS-R) or rates of disease progression (∆FRS-R). On the other hand, PD showed a negative correlation of RHI with a progressive disease severity (H-Y) and a positive correlation of RHI with early/delayed MIBG scintigraphy, but not with serological data. The present study demonstrated significant declines of peripheral arterial endothelial functions in ALS and PD. The RHI of ALS was more correlated with disease duration and serum parameters while the RHI of PD was more correlated with disease severity and MIBG, suggesting different mechanisms of endothelial dysfunction.

Effect of Parenteral Antioxidant Supplementation During the Dry Period on Postpartum Glucose Tolerance in Dairy Cows

Background

Exacerbated postparturient insulin resistance (IR) has been associated with several pathologic conditions in dairy cattle. Oxidative stress (OS) plays a causative role in IR in humans, and an association, but not direct relationship, between OS and IR recently has been reported in transition dairy cattle.

Hypothesis

Supplementation with antioxidants shortly before calving improves glucose tolerance after parturition in dairy cattle.

Animals

Ten late‐pregnant Holstein cows entering their 2nd to 5th lactation.

Methods

Randomized placebo‐controlled trial: 15 ± 2 days before expected calving, the treatment group received an injection of DL‐alpha‐tocopheryl acetate at a dosage of 6 mg/kg body weight (BW) and 0.06 mg/kg BW of sodium selenite, and the control group was injected with isotonic saline. During the first week after calving, both groups underwent glucose tolerance testing (0.25 g glucose/kg BW). Commercial assays were used to quantify the concentrations of glucose, insulin, nonesterified fatty acids (NEFA), beta‐hydroxybutyrate, and markers of redox status in blood. Data were analyzed using the Mann–Whitney U‐test (α = 0.05).

Results

Supplemented cows showed a lower risk for OS, as reflected by a lower OS index (P = .036), different areas under the curve for the concentrations of glucose (P < .01), insulin (P = .043), and NEFA (P = .041), more rapid elimination rates (P = .080, <.01 and .047 respectively), and shorter half‐lives (P = .040, <.01 and .032) of these metabolites.

Conclusions and Clinical Importance

Supplementation with antioxidants before calving resulted in greater insulin sensitivity after calving, thereby suggesting the role of OS in the development of IR in cattle and the potential benefits of antioxidant supplementation in minimizing the consequences of negative energy balance.

Treatment with atorvastatin attenuates progression of insulin resistance and pancreatic fibrosis in the Otsuka Long-Evans Tokushima fatty rats

PURPOSE

The effects of statins on insulin resistance (IR) and type 2 diabetes mellitus (T2DM) are still controversial and its effects on pancreatic fibrosis are poorly defined. The purpose of this study is to examine the effects of atorvastatin on these issues using the Otsuka Long-Evans Tokushima Fatty (OLETF) rat, an animal model of IR, T2DM and pancreatic fibrosis.

METHODS

Male OLETF rats were divided into 2 groups at 6weeks of age. The first group received a standard diet until the end of experimental period at age 28weeks. The second group was given a diet containing 0.05% atorvastatin from 6weeks of age, before the onset of IR and pancreatic fibrosis. The age-matched Long-Evans Tokushima Otsuka rats without presence of IR, T2DM and pancreatic fibrosis, received a standard diet and were used as a normal control.

RESULTS

Atorvastatin slightly decreased serum fasting glucose and insulin levels, but significantly improved index of IR compared with the untreated OLETF rats. In addition, atorvastatin markedly decreased transforming growth factor-β1 mRNA expression, myeloperoxidase activity and proportion of fibrotic area, and elevated superoxide dismutase activity in the pancreas compared with the untreated OLETF rats.

CONCLUSIONS

These findings suggest that atorvastatin exerts favorable influence on progression of IR and pancreatic inflammation and fibrosis via pleiotropic effect such as anti-oxidative property.

Glutathione Decrement Drives Thermogenic Program In Adipose Cells

Adipose tissue metabolically adapts to external stimuli. We demonstrate that the induction of the thermogenic program in white adipocytes, through cold exposure in mice or in vitro adrenergic stimulation, is accompanied by a decrease in the intracellular content of glutathione (GSH). Moreover, the treatment with a GSH depleting agent, buthionine sulfoximine (BSO), recapitulates the effect of cold exposure resulting in the induction of thermogenic program. In particular, BSO treatment leads to enhanced uncoupling respiration as demonstrated by increased expression of thermogenic genes (e.g. Ucp1, Ppargc1a), augmented oxygen consumption and decreased mitochondrial transmembrane potential. Buffering GSH decrement by pre-treatment with GSH ester prevents the up-regulation of typical markers of uncoupling respiration. We demonstrate that FoxO1 activation is responsible for the conversion of white adipocytes into a brown phenotype as the “browning” effects of BSO are completely abrogated in cells down-regulating FoxO1. In mice, the BSO-mediated up-regulation of uncoupling genes results in weight loss that is at least in part ascribed to adipose tissue mass reduction. The induction of thermogenic program has been largely proposed to counteract obesity-related diseases. Based on these findings, we propose GSH as a novel therapeutic target to increase energy expenditure in adipocytes.

Association of oxidative status and insulin sensitivity in periparturient dairy cattle: an observational study

Post-parturient insulin resistance (IR) is a common feature in all mammalian animals. However, in dairy cows, it can be exacerbated because of high milk yield, leading to excessive negative energy balance, which is related with increased disease incidence, reduced milk production and worsened reproductive performance. IR has been extensively investigated in humans suffering from diabetes mellitus. In these subjects, it is known that oxidative stress (OS) plays a causative role in the onset of IR. Although OS occurs in transitional dairy cattle, there are yet no studies that investigated the association between IR and OS in dairy cattle. Therefore, the aim of this study was to investigate whether there is a relationship between OS and IR in dairy cattle. Serum samples were taken repeatedly from 22 dairy cows from 2 months prior to the expected calving date to 2 months after calving and were analysed for markers of metabolic and redox balance. Surrogate indices of insulin sensitivity were also calculated. Generalised linear mixed models revealed an effect of the oxidative status on peripheral insulin concentration and on indices of insulin sensitivity. Hence, field trials should investigate the effectiveness of antioxidant therapy on insulin sensitivity in peripheral tissues during the transition period of dairy cattle.

Skeletal muscle insulin resistance in salt-sensitive hypertension: role of angiotensin II activation of NFκB

Background

We have previously shown that in hypertensive Dahl salt-sensitive (DS) rats, impaired endothelium-dependent relaxation to acetylcholine and to insulin is mechanistically linked to up-regulation of angiotensin (Ang) II actions and the production of reactive oxygen species (ROS) and to activation of the proinflammatory transcription factor (NF)κB. Here we investigated whether Ang II activation of NFκB contributed to insulin resistance in the skeletal muscle of this animal model.

Methods

DS rats were fed either a normal (NS, 0.5% NaCl) or high (HS, 4% NaCl) salt diet for 6 weeks. In addition, 3 separate groups of HS rats were given angiotensin receptor 1 blocker candesartan (ARB, 10 mg/kg/day in drinking water), antioxidant tempol (1 mmol/L in drinking water) or NFκB inhibitor PDTC (150 mg/kg in drinking water).

Results

DS rats manifested an increase in soleus muscle Ang II content, ROS production and phosopho-IκBα/IκBα ratio, ARB or tempol reduced ROS and phospho-IκBα/IκBα ratio. Hypertensive DS rats also manifested a reduction in glucose infusion rate, impaired insulin-induced Akt phosphorylation and Glut-4 translocation in the soleus muscle, which were prevented with treatment of either ARB, tempol, or PDTC. Data from the rat diabetes signaling pathway PCR array showed that 8 genes among 84 target genes were altered in the muscle of hypertensive rats with the increase in gene expression of ACE1 and 5 proinflammatory genes, and decrease of 2 glucose metabolic genes. Incubation of the muscle with NFκB SN50 (a specific peptide inhibitor of NFκB) ex vivo reversed changes in hypertension-induced gene expression.

Conclusion

The current findings strongly suggest that the activation of NFκB inflammatory pathway by Ang II play a critical role in skeletal muscle insulin resistance in salt-sensitive hypertension.

P65 inactivation in adipocytes and macrophages attenuates adipose inflammatory response in lean but not in obese mice

NF-κB induces transcriptional expression of proinflammatory genes and antiapoptotic genes. The two activities of NF-κB remain to be characterized in the mechanism of chronic inflammation in obesity. To address this issue, we inactivated NF-κB in adipose tissue by knocking out p65 (RelA) in mice (F-p65-KO) and examined the inflammation in lean and obese conditions. In the lean condition, KO mice exhibited a reduced inflammation in adipose tissue with a decrease in macrophage infiltration, M1 polarization, and proinflammatory cytokine expression. In the obese condition, KO mice had elevated inflammation with more macrophage infiltration, M1 polarization, and cytokine expression. In the mechanism of enhanced inflammation, adipocytes and macrophages exhibited an increase in cellular apoptosis, which was observed with more formation of crown-like structures (CLS) in fat tissue of KO mice. Body weight, glucose metabolism, and insulin sensitivity were not significantly altered in KO mice under the lean and obese conditions. A modest but significant reduction in body fat mass was observed in KO mice on HFD with an elevation in energy expenditure. The data suggest that in the control of adipose inflammation, NF-κB exhibits different activities in the lean vs. obese condition. NF-κB is required for expression of proinflammatory genes in the lean but not in the obese condition. NF-κB is required for inhibition of apoptosis in the obese condition, in which proinflammation is enhanced by NF-κB inactivation.

Impaired glutathione redox system paradoxically suppresses angiotensin II-induced vascular remodeling

BACKGROUND

Angiotensin II (AII) plays a central role in vascular remodeling via oxidative stress. However, the interaction between AII and reduced glutathione (GSH) redox status in cardiovascular remodeling remains unknown.

METHODS

In vivo: The cuff-induced vascular injury model was applied to Sprague Dawley rats. Then we administered saline or a GSH inhibitor, buthionine sulfoximine (BSO, 30 mmol/L in drinking water) for a week, subsequently administered 4 more weeks by osmotic pump with saline or AII (200 ng/kg/minute) to the rats. In vitro: Incorporation of bromodeoxyuridine (BrdU) was measured to determine DNA synthesis in cultured rat vascular smooth muscle cells (VSMCs).

RESULTS

BSO reduced whole blood GSH levels. Systolic blood pressure was increased up to 215 ± 4 mmHg by AII at 4 weeks (p<0.01), which was not affected by BSO. Superoxide production in vascular wall was increased by AII and BSO alone, and was markedly enhanced by AII+BSO. The left ventricular weight to body weight ratio was significantly increased in AII and AII+BSO as compared to controls (2.52 ± 0.08, 2.50 ± 0.09 and 2.10 ± 0.07 mg/g respectively, p<0.05). Surprisingly, the co-treatment of BSO totally abolished these morphological changes. Although the vascular circumferential wall stress was well compensated in AII, significantly increased in AII+BSO. The anti-single-stranded DNA staining revealed increasing apoptotic cells in the neointima of injured arteries in BSO groups. BrdU incorporation in cultured VSMCs with AII was increased dose-dependently. Furthermore it was totally abolished by BSO and was reversed by GSH monoethyl ester.

CONCLUSIONS

We demonstrated that a vast oxidative stress in impaired GSH redox system totally abolished AII-induced vascular, not cardiac remodeling via enhancement of apoptosis in the neointima and suppression of cell growth in the media. The drastic suppression of remodeling may result in fragile vasculature intolerable to mechanical stress by AII.

Differences in the redox status of human visceral and subcutaneous adipose tissues--relationships to obesity and metabolic risk

OBJECTIVE

Metabolic homeostasis depends on adipocyte metabolic responses/processes, most of which are redox-regulated. Besides, visceral and subcutaneous adipose tissues (VAT and SAT, respectively) differ metabolically and in their contribution to metabolic complications, but their redox characteristics in humans are still unknown. To understand the molecular mechanisms of metabolic syndrome development, we analysed the redox characteristics of VAT and SAT in groups with various body weights and metabolic risks.

MATERIAL AND METHODS

Fifty premenopausal women were classified according to body mass index into normal-weight and obese groups, and these groups were further sub-classified into metabolically healthy and metabolically obese ("at risk") based on the homeostasis model assessment of insulin resistance (HOMA-IR) index and the triglyceride, total-, LDL- and HDL-cholesterol levels. Antioxidant components, NADPH oxidase protein and 4-hydroxynonenal (4-HNE) levels were analysed in VAT and SAT.

RESULTS

Compared with the SAT, the VAT showed a higher basal level of glutathione (GSH) and GSH-dependent enzyme activities. Compared with the metabolically healthy normal-weight controls, the obese groups of women showed lower GSH levels in both depots. However, in these groups, additional prooxidative changes (increased NADPH oxidase and 4-HNE and decreased levels of SOD and/or CAT) were observed only in VAT.

CONCLUSIONS

Because of the critical role of thiol-redox homeostasis in lipogenesis, interdepot-differences in the GSH-dependent antioxidant part may be connected to the higher metabolic activity found in VAT. Analogously, the lower GSH levels that occur during obesity and the corresponding additional redox imbalance may be signs of VAT metabolic dysfunction that underlie the subsequent metabolic impairment.

Genetic disruption of SOD1 gene causes glucose intolerance and impairs β-cell function

Oxidative stress has been associated with insulin resistance and type 2 diabetes. However, it is not clear whether oxidative damage is a cause or a consequence of the metabolic abnormalities present in diabetic subjects. The goal of this study was to determine whether inducing oxidative damage through genetic ablation of superoxide dismutase 1 (SOD1) leads to abnormalities in glucose homeostasis. We studied SOD1-null mice and wild-type (WT) littermates. Glucose tolerance was evaluated with intraperitoneal glucose tolerance tests. Peripheral and hepatic insulin sensitivity was quantitated with the euglycemic-hyperinsulinemic clamp. β-Cell function was determined with the hyperglycemic clamp and morphometric analysis of pancreatic islets. Genetic ablation of SOD1 caused glucose intolerance, which was associated with reduced in vivo β-cell insulin secretion and decreased β-cell volume. Peripheral and hepatic insulin sensitivity were not significantly altered in SOD1-null mice. High-fat diet caused glucose intolerance in WT mice but did not further worsen the glucose intolerance observed in standard chow-fed SOD1-null mice. Our findings suggest that oxidative stress per se does not play a major role in the pathogenesis of insulin resistance and demonstrate that oxidative stress caused by SOD1 ablation leads to glucose intolerance secondary to β-cell dysfunction.

Mechanisms of insulin resistance in obesity

Obesity increases the risk for type 2 diabetes through induction of insulin resistance. Treatment of type 2 diabetes has been limited by little translational knowledge of insulin resistance although there have been several well-documented hypotheses for insulin resistance. In those hypotheses, inflammation, mitochondrial dysfunction, hyperinsulinemia and lipotoxicity have been the major concepts and have received a lot of attention. Oxidative stress, endoplasmic reticulum (ER) stress, genetic background, aging, fatty liver, hypoxia and lipodystrophy are active subjects in the study of these concepts. However, none of those concepts or views has led to an effective therapy for type 2 diabetes. The reason is that there has been no consensus for a unifying mechanism of insulin resistance. In this review article, literature is critically analyzed and reinterpreted for a new energy-based concept of insulin resistance, in which insulin resistance is a result of energy surplus in cells. The energy surplus signal is mediated by ATP and sensed by adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. Decreasing ATP level by suppression of production or stimulation of utilization is a promising approach in the treatment of insulin resistance. In support, many of existing insulin sensitizing medicines inhibit ATP production in mitochondria. The effective therapies such as weight loss, exercise, and caloric restriction all reduce ATP in insulin sensitive cells. This new concept provides a unifying cellular and molecular mechanism of insulin resistance in obesity, which may apply to insulin resistance in aging and lipodystrophy.

Effects of Combination of Thiazolidinediones with Melatonin in Dexamethasone-induced Insulin Resistance in Mice

In type 2 Diabetes, oxidative stress plays an important role in development and aggregation of insulin resistance. In the present study, long term administration of the dexamethasone led to the development of insulin resistance in mice. The effect of thiazolidinediones pioglitazone and rosiglitazone, with melatonin on dexamethasone-induced insulin resistance was evaluated in mice. Insulin resistant mice were treated with combination of pioglitazone (10 mg/kg/day, p.o.) or rosiglitazone (5 mg/kg/day, p.o.) with melatonin 10 mg/kg/day p.o. from day 7 to day 22. In the biochemical parameters, the serum glucose, triglyceride levels were significantly lowered (P<0.05) in the combination groups as compared to dexamethasone treated group as well as with individual groups of pioglitazone, rosiglitazone, and melatonin. There was also, significant increased (P<0.05) in the body weight gain in combination treated groups as compared to dexamethasone as well as individual groups. The combination groups proved to be effective in normalizing the levels of superoxide dismutase, catalase, glutathione reductase and lipid peroxidation in liver homogenates may be due to antioxidant effects of melatonin and decreased hyperglycemia induced insulin resistance by thiazolidinediones. The glucose uptake in the isolated hemidiaphragm of mice was significantly increased in combination treated groups (PM and RM) than dexamethasone alone treated mice as well as individual (pioglitazone, rosiglitazone, melatonin) treated groups probably via increased in expression of GLUT-4 by melatonin and thiazolidinediones as well as increased in insulin sensitivity by thiazolidinediones. Hence, it can be concluded that combination of pioglitazone and rosiglitazone, thiazolidinediones, with melatonin may reduces the insulin resistance via decreased in oxidative stress and control on hyperglycemia.

Calorie restriction with a high-fat diet effectively attenuated inflammatory response and oxidative stress-related markers in obese tissues of the high diet fed rats

Obesity characterized by increased mass of adipose tissue leads to systemic inflammation. Calorie restriction (CR) improves parameters associated with immune response and antioxidant defense. We hypothesized that CR with a high fat diet (HFCR) regulates local and systemic inflammation and oxidative stress damage in a high fat diet induced obesity (HF group). We investigated effect of HFCR on inflammation and oxidative stress-related markers in liver and adipose tissues as well as adipokines in plasma. HFCR lowered liver triglyceride levels, total cholesterol levels, and the plasma leptin/adiponectin ratio to normal levels and improved glucose tolerance. HFCR also improved fatty liver and normalized adipocyte size and morphology. HFCR reduced lipid peroxidation and decreased the expression levels of inducible nitric oxide synthetase, cyclooxygenase-2, NF-E2-related factor, and heme oxygenase-1 in the liver. Moreover, HFCR suppressed the expression levels of C- reactive protein and manganese superoxide dismutase in the adipose tissue in the HF group. These results suggest that HFCR may have beneficial effects on inflammation and oxidative stress as well as lipid profiles in the HF diet induced obesity. Moreover, HFCR may be a good way to increase compliance in obese patients and to prevent obesity induced complications without changes in dietary pattern.

Mechanisms underlying skeletal muscle insulin resistance induced by fatty acids: importance of the mitochondrial function

Insulin resistance condition is associated to the development of several syndromes, such as obesity, type 2 diabetes mellitus and metabolic syndrome. Although the factors linking insulin resistance to these syndromes are not precisely defined yet, evidence suggests that the elevated plasma free fatty acid (FFA) level plays an important role in the development of skeletal muscle insulin resistance. Accordantly, in vivo and in vitro exposure of skeletal muscle and myocytes to physiological concentrations of saturated fatty acids is associated with insulin resistance condition. Several mechanisms have been postulated to account for fatty acids-induced muscle insulin resistance, including Randle cycle, oxidative stress, inflammation and mitochondrial dysfunction. Here we reviewed experimental evidence supporting the involvement of each of these propositions in the development of skeletal muscle insulin resistance induced by saturated fatty acids and propose an integrative model placing mitochondrial dysfunction as an important and common factor to the other mechanisms.

Diabetes and pancreatic cancer

Type 2 diabetes mellitus is likely the third modifiable risk factor for pancreatic cancer after cigarette smoking and obesity. Epidemiological investigations have found that long-term type 2 diabetes mellitus is associated with a 1.5-fold to 2.0-fold increase in the risk of pancreatic cancer. A causal relationship between diabetes and pancreatic cancer is also supported by findings from prediagnostic evaluations of glucose and insulin levels in prospective studies. Insulin resistance and associated hyperglycemia, hyperinsulinemia, and inflammation have been suggested to be the underlying mechanisms contributing to development of diabetes-associated pancreatic cancer. Signaling pathways that regulate the metabolic process also play important roles in cell proliferation and tumor growth. Use of the antidiabetic drug metformin has been associated with reduced risk of pancreatic cancer in diabetics and recognized as an antitumor agent with the potential to prevent and treat this cancer. On the other hand, new-onset diabetes may indicate subclinical pancreatic cancer, and patients with new-onset diabetes may constitute a population in whom pancreatic cancer can be detected early. Biomarkers that help define high-risk individuals for clinical screening for pancreatic cancer are urgently needed. Why pancreatic cancer causes diabetes and how diabetes affects the clinical outcome of pancreatic cancer have yet to be fully determined. Improved understanding of the pathological mechanisms shared by diabetes and pancreatic cancer would be the key to the development of novel preventive and therapeutic strategies for this cancer.

Oxidative stress as pathogenesis of cardiovascular risk associated with metabolic syndrome

Metabolic syndrome (MetS) is characterized by accumulation of visceral fat associated with the clustering of metabolic and pathophysiological cardiovascular risk factors: impaired glucose tolerance, dyslipidemia, and hypertension. Although the definition of MetS is different among countries, visceral obesity is an indispensable component of MetS. A growing body of evidence suggests that increased oxidative stress to adipocytes is central to the pathogenesis of cardiovascular disease in MetS. Increased oxidative stress to adipocytes causes dysregulated expression of inflammation-related adipocytokines in MetS, which contributes to obesity-associated vasculopathy and cardiovascular risk primarily through endothelial dysfunction. The purpose of present review is to unravel the mechanistic link between oxidative stress and cardiovascular risk in MetS, focusing on insulin resistance, hypertension, and atherosclerosis. Then, therapeutic opportunities translated from the bench to bedside will be provided to develop novel strategies to cardiovascular risk factors in MetS.

Poly(ADP-ribose) polymerase 1 is involved in glucose toxicity through SIRT1 modulation in HepG2 hepatocytes

Accelerated glucose metabolism leads to oxidative stress and DNA damage in cells; these effects are related to glucose toxicity. The precise mechanisms of glucose toxicity are still unclear. The aim of this work was to investigate the mechanism of poly(ADP-ribose) polymerase 1 (PARP1), which is a DNA repair enzyme activated by high-glucose-induced oxidative stress, and its effect on glucose toxicity in HepG2 hepatocytes. HepG2 cells were cultured under normal (5.5 mM) or high (30 mM) glucose conditions for 4 days. PJ34, which is an inhibitor of PARP1, was used to determine the downstream effects of PARP1 activation. PARP1 activity in 30 mM-glucose-treated cells was more than that in 5.5 mM-glucose-treated cells, and the activity correlated with the increase in ROS generation and DNA damage. PJ34 suppressed PARP1 activation and prevented the high-glucose-induced suppression of SIRT1 and AMP-activated protein kinase (AMPK) activity, which was similar to its effect on the restoration of intracellular nicotinamide adenine dinucleotide (NAD) content. Further, the phosphorylation of insulin receptor was attenuated in response to insulin stimulation under high glucose conditions, and PJ34 could reverse this effect. The results of transfection of HepG2 cells with PARP1 small interfering RNA were similar to those obtained by treatment of the cells with PARP1 inhibitor PJ34. These data suggest that high-glucose-induced PARP1 activation might play a role in glucose toxicity by down-regulating SIRT1 and AMPK activity through NAD depletion and resulting in insulin insensitivity.

Studies of gene variants related to inflammation, oxidative stress, dyslipidemia, and obesity: implications for a nutrigenetic approach

Obesity is currently considered a serious public health issue due to its strong impact on health, economy, and quality of life. It is considered a chronic low-grade inflammation state and is directly involved in the genesis of metabolic disturbances, such as insulin resistance and dyslipidemia, which are well-known risk factors for cardiovascular disease. Furthermore, there is evidence that genetic variation that predisposes to inflammation and metabolic disturbances could interact with environmental factors, such as diet, modulating individual susceptibility to developing these conditions. This paper aims to review the possible interactions between diet and single-nucleotide polymorphisms (SNPs) in genes implicated on the inflammatory response, lipoprotein metabolism, and oxidative status. Therefore, the impact of genetic variants of the peroxisome proliferator-activated receptor-(PPAR-)gamma, tumor necrosis factor-(TNF-)alpha, interleukin (IL)-1, IL-6, apolipoprotein (Apo) A1, Apo A2, Apo A5, Apo E, glutathione peroxidases 1, 2, and 4, and selenoprotein P exposed to variations on diet composition is described.

Oxidative stress accumulates in adipose tissue during aging and inhibits adipogenesis

Aging constitutes a major independent risk factor for the development of type 2 diabetes and is accompanied by insulin resistance and adipose tissue dysfunction. One of the most important factors implicitly linked to aging and age-related chronic diseases is the accumulation of oxidative stress. However, the effect of increased oxidative stress on adipose tissue biology remains elusive. In this study, we demonstrate that aging in mice results in a loss of fat mass and the accumulation of oxidative stress in adipose tissue. In vitro, increased oxidative stress through glutathione depletion inhibits preadipocyte differentiation. This inhibition of adipogenesis is at least in part the result of reduced cell proliferation and an inhibition of G₁→S-phase transition during the initial mitotic clonal expansion of the adipocyte differentiation process. While phosphorylation of the retinoblastoma protein (Rb) by cyclin/cdk complexes remains unaffected, oxidative stress decreases the expression of S-phase genes downstream of Rb. This silencing of S phase gene expression by increased oxidative stress is mediated through a transcriptional mechanism involving the inhibition of E2F recruitment and transactivation of its target promoters. Collectively, these data demonstrate a previously unrecognized role of oxidative stress in the regulation of adipogenesis which may contribute to age-associated adipose tissue dysfunction.

Exercise training attenuates oxidative stress and decreases p53 protein content in skeletal muscle of type 2 diabetic Goto-Kakizaki rats

Oxidative stress can impair mitochondrial function and fuel utilization and is closely linked with the development of insulin resistance in skeletal muscle in diabetes mellitus as well as fatty liver disease. In vitro data indicate that cellular levels of reactive oxygen species depend on the expression and activity of p53, which plays a key role in energy metabolism and as a crucial transcription factor for SCO cytochrome oxidase deficient homolog 2 (SCO2) and tumor p53-induced glycolysis and apoptosis regulator (TIGAR), which regulate mitochondrial respiration and glycolysis in cells. The aims of this study were: (1) to investigate whether exercise training could attenuate the development of oxidative stress in skeletal muscle in rats with diabetes mellitus (DM) and (2) to evaluate the potential role of p53 and its transcriptional targets in exercise-induced mitochondrial adaptation in skeletal muscle in rats with DM. Goto-Kakizaki (GK) rats, which develop type 2 DM (T2DM) early in life, were randomly divided into two groups: (1) subjected to regular exercise on a treadmill at 20m/min for 30-60min, 6 days per week for 8 weeks (GK exercising, n=7), and (2) rested controls (GK control, n=7). Exercise training increased serum adiponectin and decreased serum insulin and levels of glycosylated hemoglobin (P<0.05). Skeletal muscle GSH content and GSH:GSSG ratio increased in GK exercising rats vs GK controls (P<0.05). Skeletal muscle COX activity (P<0.05), mtDNA markers (P<0.01), and COXII protein levels (P<0.05) increased in response to exercise training. Exercise training decreased p53 protein levels and TIGAR expression in skeletal muscle (P<0.05), but SCO2 expression was unchanged. These data indicate that exercise training can attenuate oxidative stress and increase mitochondrial DNA content in skeletal muscle in rats with T2DM and that exercise-induced suppression of p53 and TIGAR expression may play a role in preventing oxidative stress in insulin resistance.

Oxidative stress, insulin signaling, and diabetes

Oxidative stress has been implicated as a contributor to both the onset and the progression of diabetes and its associated complications. Some of the consequences of an oxidative environment are the development of insulin resistance, β-cell dysfunction, impaired glucose tolerance, and mitochondrial dysfunction, which can lead ultimately to the diabetic disease state. Experimental and clinical data suggest an inverse association between insulin sensitivity and ROS levels. Oxidative stress can arise from a number of different sources, whether disease state or lifestyle, including episodes of ketosis, sleep restriction, and excessive nutrient intake. Oxidative stress activates a series of stress pathways involving a family of serine/threonine kinases, which in turn have a negative effect on insulin signaling. More experimental evidence is needed to pinpoint the mechanisms contributing to insulin resistance in both type 1 diabetics and nondiabetic individuals. Oxidative stress can be reduced by controlling hyperglycemia and calorie intake. Overall, this review outlines various mechanisms that lead to the development of oxidative stress. Intervention and therapy that alter or disrupt these mechanisms may serve to reduce the risk of insulin resistance and the development of diabetes.