Short-term high-fat diet modulates several inflammatory, ER stress, and apoptosis markers in the hippocampus of young mice

The consumption of saturated fatty acids is one of the leading risk factors for Alzheimer's Disease (AD) development. Indeed, the short-term consumption of a high-fat diet (HFD) is related to increased inflammatory signals in the hippocampus; however, the potential molecular mechanisms linking it to AD pathogenesis are not fully elucidated. In our study, we investigated the effects of short-term HFD feeding (within 3, 7 and 10 days) in AD markers and neuroinflammation in the hippocampus of mice. The short period of HFD increased fasting glucose and HOMA-IR. Also, mice fed HFD increased the protein content of β-Amyloid, pTau, TNFα, IL1β, pJNK, PTP1B, peIF2α, CHOP, Caspase3, Cleaved-Caspase3 and Alzheimer-related genes (Bax, PS1, PEN2, Aph1b). At 10 days, both neuronal (N2a) and microglial (BV2) cells presented higher expression of inflammatory and apoptotic genes when stimulated with palmitate. These findings suggest that a short period of consumption of a diet rich in saturated fat is associated with activation of inflammatory, ER stress and apoptotic signals in the hippocampus of young mice.

Diets Containing α-Linolenic (ω3) or Oleic (ω9) Fatty Acids Rescues Obese Mice From Insulin Resistance

Subclinical systemic inflammation is a hallmark of obesity and insulin resistance. The results obtained from a number of experimental studies suggest that targeting different components of the inflammatory machinery may result in the improvement of the metabolic phenotype. Unsaturated fatty acids exert antiinflammatory activity through several distinct mechanisms. Here, we tested the capacity of ω3 and ω9 fatty acids, directly from their food matrix, to exert antiinflammatory activity through the G protein-coupled receptor (GPR)120 and GPR40 pathways. GPR120 was activated in liver, skeletal muscle, and adipose tissues, reverting inflammation and insulin resistance in obese mice. Part of this action was also mediated by GPR40 on muscle, as a novel mechanism described. Pair-feeding and immunoneutralization experiments reinforced the pivotal role of GPR120 as a mediator in the response to the nutrients. The improvement in insulin sensitivity in the high-fat substituted diets was associated with a marked reduction in tissue inflammation, decreased macrophage infiltration, and increased IL-10 levels. Furthermore, improved glucose homeostasis was accompanied by the reduced expression of hepatic gluconeogenic enzymes and reduced body mass. Thus, our data indicate that GPR120 and GPR40 play a critical role as mediators of the beneficial effects of dietary unsaturated fatty acids in the context of obesity-induced insulin resistance.

Endurance exercise training increases APPL1 expression and improves insulin signaling in the hepatic tissue of diet-induced obese mice, independently of weight loss

Hepatic insulin resistance is the major contributor to fasting hyperglycemia in type 2 diabetes. The protein kinase Akt plays a central role in the suppression of gluconeogenesis involving forkhead box O1 (Foxo1) and peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α), and in the control of glycogen synthesis involving the glycogen synthase kinase beta (GSK3β) in the liver. It has been demonstrated that endosomal adaptor protein APPL1 interacts with Akt and blocks the association of Akt with its endogenous inhibitor, tribbles-related protein 3 (TRB3), improving the action of insulin in the liver. Here, we demonstrated that chronic exercise increased the basal levels and insulin-induced Akt serine phosphorylation in the liver of diet-induced obese mice. Endurance training was able to increase APPL1 expression and the interaction between APPL1 and Akt. Conversely, training reduced both TRB3 expression and TRB3 and Akt association. The positive effects of exercise on insulin action are reinforced by our findings that showed that trained mice presented an increase in Foxo1 phosphorylation and Foxo1/PGC-1α association, which was accompanied by a reduction in gluconeogenic gene expressions (PEPCK and G6Pase). Finally, exercised animals demonstrated increased at basal and insulin-induced GSK3β phosphorylation levels and glycogen content at 24 h after the last session of exercise. Our findings demonstrate that exercise increases insulin action, at least in part, through the enhancement of APPL1 and the reduction of TRB3 expression in the liver of obese mice, independently of weight loss.

Statin modulates insulin signaling and insulin resistance in liver and muscle of rats fed a high-fat diet

Recent studies have shown that statins might have relevant effects on insulin resistance in animal models and in humans. However, the molecular mechanisms that account for this improvement in insulin sensitivity are not well established. The aim of the present study was to investigate the effect of a statin on insulin sensitivity and insulin signaling in liver and muscle of rats fed on a high-fat diet (HFD) for 4 weeks, treated or not with lovastatin during the last week. Our data show that treatment with lovastatin results in a marked improvement in insulin sensitivity characterized by an increase in glucose disappearance rate during the insulin tolerance test. This increase in insulin sensitivity was associated with an increase in insulin-induced insulin receptor (IR) tyrosine phosphorylation and, in parallel, a decrease in IR serine phosphorylation and association with PTP1B. Our data also show that lovastatin treatment was associated with an increase in insulin-stimulated insulin receptor substrate (IRS) 1/phosphatidylinositol 3-kinase/Akt pathway in the liver and muscle of HFD-fed rats in parallel with a decrease in the inflammatory pathway (c-jun N-terminal kinase and I kappa beta kinase (IKKbeta)/inhibitor of kappaB/nuclear factor kappaB) related to insulin resistance. In summary, statin treatment improves insulin sensitivity in HFD-fed rats by reversing the decrease in the insulin-stimulated IRS-1/phosphatidylinositol 3-kinase/Akt pathway in liver and muscle. The effect of statins on insulin action is further supported by our findings that HFD rats treated with statin show a reduction in IRS-1 serine phosphorylation, I kappa kinase (IKK)/inhibitor of kappaB/nuclear factor kappaB pathway, and c-jun N-terminal kinase activity, associated with an improvement in insulin action. Overall, these results provide important new insight into the mechanism of statin action in insulin sensitivity.

Aspirin attenuates insulin resistance in muscle of diet-induced obese rats by inhibiting inducible nitric oxide synthase production and S-nitrosylation of IRbeta/IRS-1 and Akt

AIM/HYPOTHESIS

High-dose aspirin treatment improves fasting and postprandial hyperglycaemia in patients with type 2 diabetes, as well as in animal models of insulin resistance associated with obesity and sepsis. In this study, we investigated the effects of aspirin treatment on inducible nitric oxide synthase (iNOS)-mediated insulin resistance and on S-nitrosylation of insulin receptor (IR)-beta, IRS-1 and protein kinase B (Akt) in the muscle of diet-induced obese rats and also in iNos (also known as Nos2)-/- mice on high fat diet.

METHODS

Aspirin (120 mg kg-1 day-1 for 2 days) or iNOS inhibitor (L-NIL; 80 mg/kg body weight) were administered to diet-induced obese rats or mice and iNOS production and insulin signalling were investigated. S-nitrosylation of IRbeta/IRS-1 and Akt was investigated using the biotin switch method.

RESULTS

iNOS protein levels increased in the muscle of diet-induced obese rats, associated with an increase in S-nitrosylation of IRbeta, IRS-1 and Akt. These alterations were reversed by aspirin treatment, in parallel with an improvement in insulin signalling and sensitivity, as measured by insulin tolerance test and glucose clamp. Conversely, while aspirin reversed the increased phosphorylation of IkappaB kinase beta and c-Jun amino-terminal kinase, as well as IRS-1 serine phosphorylation in diet-induced obese rats and iNos -/- mice on high-fat diet, these alterations were not associated with the improvement of insulin action induced by this drug.

CONCLUSIONS/INTERPRETATION

Our data demonstrate that aspirin treatment not only reduces iNOS protein levels, but also S-nitrosylation of IRbeta, IRS-1 and Akt. These changes are associated with improved insulin resistance and signalling, suggesting a novel mechanism of insulin sensitisation evoked by aspirin treatment.

Acute exercise reverses aged-induced impairments in insulin signaling in rodent skeletal muscle

The insulin resistance associated with aging is improved by exercise, but the molecular mechanisms of this improvement are not fully understood. We investigated whether the improvement in insulin action, associated with acute exercise in old rats is dependent on the modulation of pIRS-1Ser307, JNK, IkBalpha and PTP-1B. Aging rats were subjected to swimming for two 1.5-h long bouts, separated by a 45min rest period. Sixteen hours after the exercise, the rats were killed and proteins from the insulin signaling pathway were analyzed by immunoblotting. Our results show that the reduction in glucose disappearance rate (Kitt), observed in aged rats, was restored at 16h after exercise. Aging led to an increase in Ser307 phosphorylation of IRS-1, and this was reversed by exercise in the skeletal muscle, in parallel with a reduction in pJNK and IkBalpha degradation. Moreover, aging induced an increase in the expression of PTP-1B and attenuated insulin signaling in the muscle of rats, a phenomenon that was reversed by exercise. Interestingly, the decrease in PTP-1B expression in the muscle of exercised old rats was accompanied by an increase in SIRT1 expression. These results provide new insights into the mechanisms by which exercise restores insulin sensitivity during aging.

Protective molecular mechanisms of clusterin against apoptosis in cardiomyocytes

Loss of cardiomyocytes occurs with aging and contributes to cardiovascular complications. In the present study, we highlighted the role of clusterin, a protein that has recently been associated with the protection of cardiomyocytes from apoptosis. Clusterin protects cardiac cells against damage from myocardial infarction, transplant, or myocarditis. Clusterin can act directly or indirectly on apoptosis by regulating several intracellular pathways. These pathways include (1) the oxidant and inflammatory program, (2) insulin growth factor 1 (IGF-1) pathway, (3) KU70 / BCL-2-associated X protein (BAX) pathway, (4) tumor necrosis factor alpha (TNF-α) pathway, (5) BCL-2 antagonist of cell death (BAD) pathway, and (6) mitogen-activated protein kinase (MAPK) pathway. Given the key role of clusterin in preventing loss of cardiac tissue, modulating the expression and function of this protein carries the potential of improving cardiovascular care in the future.

Omega-3 from Flaxseed Oil Protects Obese Mice Against Diabetic Retinopathy Through GPR120 Receptor

The chronic and low-grade inflammation induced by obesity seem to be the “first hit” to retinopathy associated to diabetes type 2. Herein, we hypothesized that omega-3 fatty acids from flaxseed oil enriched diet disrupt the pro-inflammatory status in the retina, protecting against retinopathy development. For eight weeks under a high-fat diet (HF), several physiological parameters were monitored to follow the metabolic homeostasis disruption. After this period, mice were treated with a HF substituted in part of lard by flaxseed oil (FS) for another eight weeks. Food behavior, weight gain, glucose and insulin sensitivity, electroretinography, RT-qPCR and western blots were carried out. The HF was able to induce a pro-inflammatory background in the retina, changing IL1β and TNFα. VEGF, a master piece of retinopathy, had early onset increased also induced by HF. The FS-diet was able to decrease inflammation and retinopathy and improved retinal electro stimuli compared to HF group. GPR120 and GPR40 (G Protein-Coupled Receptors 120 and 40), an omega-3 fatty acid receptors, were detected in the retina for the first time. FS-diet modulated the gene expression and protein content of these receptors. Thus, unsaturated fatty acids protect the retina from diabetes type 2 mice model from disease progression.

12,13-diHOME as a new therapeutic target for metabolic diseases

Lipokines are bioactive compounds, derived from adipose tissue depots, that control several molecular signaling pathways. Recently, 12,13-dihydroxy-9Z-octadecenoic acid (12,13-diHOME), an oxylipin, has gained prominence in the scientific literature. An increase in circulating 12,13-diHOME has been associated with improved metabolic health, and the action of this molecule appears to be mediated by brown adipose tissue (BAT). Scientific evidence indicates that the increase in serum levels of 12,13-diHOME caused by stimuli such as physical exercise and exposure to cold may favor the absorption of fatty acids by brown adipose tissue and stimulate the browning process in white adipose tissue (WAT). Thus, strategies capable of increasing 12,13-diHOME levels may be promising for the prevention and treatment of obesity and metabolic diseases. This review explores the relationship of 12,13-diHOME with brown adipose tissue and its role in the metabolic health context, as well as the signaling pathways involved between 12,13-diHOME and BAT.

Short-term strength training reduces gluconeogenesis and NAFLD in obese mice

Non-alcoholic fatty liver disease (NAFLD) has a positive correlation with obesity, insulin resistance and type 2 diabetes mellitus (T2D). The aerobic training is an important tool in combating NAFLD. However, no studies have demonstrated the molecular effects of short-term strength training on the accumulation of hepatic fat in obese mice. This study aimed to investigate the effects of short-term strength training on the mechanisms of oxidation and lipid synthesis in the liver of obese mice. The short duration protocol was used to avoid changing the amount of adipose tissue. Swiss mice were separated into three groups: lean control (CTL), sedentary obese (OB) and strength training obese (STO). The obese groups were fed a high-fat diet (HFD) and the STO group performed the strength training protocol 1 session/day for 15 days. The short-term strength training reduced hepatic fat accumulation, increasing hepatic insulin sensitivity and controlling hepatic glucose production. The obese animals increased the mRNA of lipogenic genes Fasn and Scd1 and reduced the oxidative genes Cpt1a and Ppara. On the other hand, the STO group presented the opposite results. Finally, the obese animals presented higher levels of lipogenic proteins (ACC and FAS) and proinflammatory cytokines (TNF-α and IL-1β), but the short-term strength training was efficient in reducing this condition, regardless of body weight loss. In conclusion, there was a reduction of obesity-related hepatic lipogenesis and inflammation after short-term strength training, independent of weight loss, leading to improvements in hepatic insulin sensitivity and glycemic homeostasis in obese mice. Key points: (1) Short-term strength training (STST) reduced fat accumulation and inflammation in the liver; (2) Hepatic insulin sensitivity and HPG control were increased with STST; (3) The content and activity of ACC and content of FAS were reduced with STST; (4) STST improved hepatic fat accumulation and glycemic homeostasis; (5) STST effects were observed independently of body weight change.

Acute exercise decreases PTP-1B protein level and improves insulin signaling in the liver of old rats

It is now commonly accepted that chronic inflammation associated with obesity during aging induces insulin resistance in the liver. In the present study, we investigated whether the improvement in insulin sensitivity and insulin signaling, mediated by acute exercise, could be associated with modulation of protein-tyrosine phosphatase 1B (PTP-1B) in the liver of old rats. Aging rats were subjected to swimming for two 1.5-h long bouts, separated by a 45 min rest period. Sixteen hours after the exercise, the rats were sacrificed and proteins from the insulin signaling pathway were analyzed by immunoblotting. Our results show that the fat mass was increased in old rats. The reduction in glucose disappearance rate (Kitt) observed in aged rats was restored 16 h after exercise. Aging increased the content of PTP-1B and attenuated insulin signaling in the liver of rats, a phenomenon that was reversed by exercise. Aging rats also increased the IRβ/PTP-1B and IRS-1/PTP-1B association in the liver when compared with young rats. Conversely, in the liver of exercised old rats, IRβ/PTP-1B and IRS-1/PTP-1B association was markedly decreased. Moreover, in the hepatic tissue of old rats, the insulin signalling was decreased and PEPCK and G6Pase levels were increased when compared with young rats. Interestingly, 16 h after acute exercise, the PEPCK and G6Pase protein level were decreased in the old exercised group. These results provide new insights into the mechanisms by which exercise restores insulin signalling in liver during aging.

Exercise training decreases mitogen-activated protein kinase phosphatase-3 expression and suppresses hepatic gluconeogenesis in obese mice

Insulin plays an important role in the control of hepatic glucose production. Insulin resistant states are commonly associated with excessive hepatic glucose production, which contributes to both fasting hyperglycaemia and exaggerated postprandial hyperglycaemia. In this regard, increased activity of phosphatases may contribute to the dysregulation of gluconeogenesis. Mitogen-activated protein kinase phosphatase-3 (MKP-3) is a key protein involved in the control of gluconeogenesis. MKP-3-mediated dephosphorylation activates FoxO1 (a member of the forkhead family of transcription factors) and subsequently promotes its nuclear translocation and binding to the promoters of gluconeogenic genes such as phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase). In this study, we investigated the effects of exercise training on the expression of MKP-3 and its interaction with FoxO1 in the livers of obese animals. We found that exercised obese mice had a lower expression of MKP-3 and FoxO1/MKP-3 association in the liver. Further, the exercise training decreased FoxO1 phosphorylation and protein levels of Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and gluconeogenic enzymes (PEPCK and G6Pase). These molecular results were accompanied by physiological changes, including increased insulin sensitivity and reduced hyperglycaemia, which were not caused by reductions in total body mass. Similar results were also observed with oligonucleotide antisense (ASO) treatment. However, our results showed that only exercise training could reduce an obesity-induced increase in HNF-4α protein levels while ASO treatment alone had no effect. These findings could explain, at least in part, why additive effects of exercise training treatment and ASO treatment were not observed. Finally, the suppressive effects of exercise training on MKP-3 protein levels appear to be related, at least in part, to the reduced phosphorylation of Extracellular signal-regulated kinases (ERK) in the livers of obese mice.

Passion fruit peel intake decreases inflammatory response and reverts lipid peroxidation and adiposity in diet-induced obese rats

This study investigated Passiflora edulis peel flour (PEPF) intake and its effect against high-fat diet-induced obesity. PEPF is a source of fiber and phenolic compounds, which can decrease oxidative stress and inflammatory cytokines, both linked to chronic inflammatory response and fat deposition in obesity. Therefore, we hypothesized that PEPF intake could decrease inflammatory cytokines and oxidative stress observed in obesity, leading to decrease of fatness and chronic inflammatory response. The aims of the study were to evaluate the lipid peroxidation, the expression of antioxidants enzymes, and inflammatory parameters in obese rats. Male Sprague-Dawley rats were divided into 3 groups (n = 8 per group) according to the diets: control (based on AIN-93G), high-fat (HF, 35% fat w/w), and HF with PEPF (HFPF), and the experiment lasted for 10 weeks. PEPF showed high dietary fiber content and bioactive compounds, such as ferulic acid, and β-carotene. PEPF intake was effective in reducing body weight gain (13.31%) and total body fat (22.58%). The lipid peroxidation in the liver and adipose tissue decreased in the HFPF group compared to HF-fed animals, whereas hepatic glutathione peroxidase and glutathione reductase activity and their expressions in the liver were higher in HFPF than HF. In addition, the PEPF intake decreased inflammatory cytokines in serum. These results suggest that PEPF intake decreases oxidative stress, possibly by the increase of antioxidant enzymes expression. Furthermore, PEPF decreases inflammatory response and protects from adiposity. Then, PEPF could act as an adjuvant to control of early parameters in obesity dysfunction.

Time-restricted feeding combined with aerobic exercise training can prevent weight gain and improve metabolic disorders in mice fed a high-fat diet

KEY POINTS

Time-restricted feeding (TRF, in which energy intake is restricted to 8 h/day during the dark phase) alone or combined with aerobic exercise (AE) training can prevent weight gain and metabolic disorders in Swiss mice fed a high-fat diet. The benefits of TRF combined with AE are associated with improved hepatic metabolism and decreased hepatic lipid accumulation. TRF combined with AE training increased fatty acid oxidation and decreased expression of lipogenic and gluconeogenic genes in the liver of young male Swiss mice. TRF combined with AE training attenuated the detrimental effects of high-fat diet feeding on the insulin signalling pathway in the liver.

ABSTRACT

Time-restricted feeding (TRF) or physical exercise have been shown to be efficient in the prevention and treatment of metabolic disorders; however, the additive effects of TRF combined with aerobic exercise (AE) training on liver metabolism have not been widely explored. In this study TRF (8 h in the active phase) and TRF combined with AE (TRF+Exe) were compared in male Swiss mice fed a high-fat diet, with evaluation of the effects on insulin sensitivity and expression of hepatic genes involved in fatty acid oxidation, lipogenesis and gluconeogenesis. As in previous reports, we show that TRF alone (eating only between zeitgeber time 16 and 0) was sufficient to reduce weight and adiposity gain, increase fatty acid oxidation and decrease lipogenesis genes in the liver. In addition, we show that mice of the TRF+Exe group showed additional adaptations such as increased oxygen consumption ( V ̇ O 2 ), carbon dioxide production ( V ̇ C O 2 ) and production of ketone bodies (β-hydroxybutyrate). Also, TRF+Exe attenuated the negative effects of high-fat diet feeding on the insulin signalling pathway (insulin receptor, insulin receptor substrate, Akt), and led to increased fatty acid oxidation (Ppara, Cpt1a) and decreased gluconeogenic (Fbp1, Pck1, Pgc1a) and lipogenic (Srebp1c, Cd36) gene expression in the liver. These molecular results were accompanied by increased glucose metabolism, lower serum triglycerides and reduced hepatic lipid content in the TRF+Exe group. The data presented in this study show that TRF alone has benefits but TRF+Exe has additive benefits and can mitigate the harmful effects of consuming a high-fat diet on body adiposity, liver metabolism and glycaemic homeostasis in young male Swiss mice.

Novos mecanismos pelos quais o exercício físico melhora a resistência à insulina no músculo esquelético

O prejuízo no transporte de glicose estimulada por insulina no músculo constitui um defeito crucial para o estabelecimento da intolerância à glicose e do diabetes tipo 2. Por outro lado, é notório o conhecimento de que tanto o exercício aeróbio agudo quanto o crônico podem ter efeitos benéficos na ação da insulina em estados de resistência à insulina. No entanto, pouco se sabe sobre os efeitos moleculares pós-exercício sobre a sinalização da insulina no músculo esquelético. Assim, esta revisãoapresenta novos entendimentos sobre os mecanismos por meio dos quais o exercício agudo restaura a sensibilidade à insulina, com destaque ao importante papel que proteínas inflamatórias e a S-nitrosação possuem sobre a regulação de proteínas da via de sinalização da insulina no músculo esquelético.

Hypothalamic S1P/S1PR1 axis controls energy homeostasis in Middle-Aged Rodents: the reversal effects of physical exercise

Recently, we demonstrated that the hypothalamic S1PR1/STAT3 axis plays a critical role in the control of food consumption and energy expenditure in rodents. Here, we found that reduction of hypothalamic S1PR1 expression occurs in an age-dependent manner, and was associated with defective thermogenic signaling and weight gain. To address the physiological relevance of these findings, we investigated the effects of chronic and acute exercise on the hypothalamic S1PR1/STAT3 axis. Chronic exercise increased S1PR1 expression and STAT3 phosphorylation in the hypothalamus, restoring the anorexigenic and thermogenic signals in middle-aged mice. Acutely, exercise increased sphingosine-1-phosphate (S1P) levels in the cerebrospinal fluid (CSF) of young rats, whereas the administration of CSF from exercised young rats into the hypothalamus of middle-aged rats at rest was sufficient to reduce the food intake. Finally, the intracerebroventricular (ICV) administration of S1PR1 activators, including the bioactive lipid molecule S1P, and pharmacological S1PR1 activator, SEW2871, induced a potent STAT3 phosphorylation and anorexigenic response in middle-aged rats. Overall, these results suggest that hypothalamic S1PR1 is important for the maintenance of energy balance and provide new insights into the mechanism by which exercise controls the anorexigenic and thermogenic signals in the central nervous system during the aging process.

Overtraining is associated with DNA damage in blood and skeletal muscle cells of Swiss mice

BACKGROUND

The alkaline version of the single-cell gel (comet) assay is a useful method for quantifying DNA damage. Although some studies on chronic and acute effects of exercise on DNA damage measured by the comet assay have been performed, it is unknown if an aerobic training protocol with intensity, volume, and load clearly defined will improve performance without leading to peripheral blood cell DNA damage. In addition, the effects of overtraining on DNA damage are unknown. Therefore, this study aimed to examine the effects of aerobic training and overtraining on DNA damage in peripheral blood and skeletal muscle cells in Swiss mice. To examine possible changes in these parameters with oxidative stress, we measured reduced glutathione (GSH) levels in total blood, and GSH levels and lipid peroxidation in muscle samples.

RESULTS

Performance evaluations (i.e., incremental load and exhaustive tests) showed significant intra and inter-group differences. The overtrained (OTR) group showed a significant increase in the percentage of DNA in the tail compared with the control (C) and trained (TR) groups. GSH levels were significantly lower in the OTR group than in the C and TR groups. The OTR group had significantly higher lipid peroxidation levels compared with the C and TR groups.

CONCLUSIONS

Aerobic and anaerobic performance parameters can be improved in training at maximal lactate steady state during 8 weeks without leading to DNA damage in peripheral blood and skeletal muscle cells or to oxidative stress in skeletal muscle cells. However, overtraining induced by downhill running training sessions is associated with DNA damage in peripheral blood and skeletal muscle cells, and with oxidative stress in skeletal muscle cells and total blood.

Nonfunctional overreaching leads to inflammation and myostatin upregulation in swiss mice

The aims of the this study were a) to verify whether the performance decrease induced by nonfunctional overreaching (NFOR) is linked to high concentrations of cytokines in serum, skeletal muscles and liver; b) to verify muscle myostatin adaptation to NFOR; c) to verify the effects of chronic glucose supplementation on the parameters mentioned above. Mice were divided into control (C), trained (TR), overtrained (OTR) and supplemented overtrained (OTR + S). The incremental load test (ILT) and exhaustive test (ET) were used to measure performances before and after exercise protocols. 24 h after ET, muscles and liver were removed and stored at -80°C for subsequent measurements. Total blood was collected from decapitation for subsequent determination of cytokine concentrations. Generally, OTR and OTR + S presented higher contents of IL-6, TNF-alpha, GLUT-4 and myostatin in muscle samples compared to C and TR. Glucose supplementation attenuated the high contents of IL-6, TNF-alpha and IL-15 in liver, and of IL-6 in serum. In summary, NFOR led to low-grade chronic inflammation and myostatin upregulation.

Physical exercise reduces pyruvate carboxylase (PCB) and contributes to hyperglycemia reduction in obese mice

The present study evaluated the effects of exercise training on pyruvate carboxylase protein (PCB) levels in hepatic tissue and glucose homeostasis control in obese mice. Swiss mice were distributed into three groups: control mice (CTL), fed a standard rodent chow; diet-induced obesity (DIO), fed an obesity-inducing diet; and a third group, which also received an obesity-inducing diet, but was subjected to an exercise training protocol (DIO + EXE). Protocol training was carried out for 1 h/d, 5 d/wk, for 8 weeks, performed at an intensity of 60% of exhaustion velocity. An insulin tolerance test (ITT) was performed in the last experimental week. Twenty-four hours after the last physical exercise session, the animals were euthanized and the liver was harvested for molecular analysis. Firstly, DIO mice showed increased epididymal fat and serum glucose and these results were accompanied by increased PCB and decreased p-Akt in hepatic tissue. On the other hand, physical exercise was able to increase the performance of the mice and attenuate PCB levels and hyperglycemia in DIO + EXE mice. The above findings show that physical exercise seems to be able to regulate hyperglycemia in obese mice, suggesting the participation of PCB, which was enhanced in the obese condition and attenuated after a treadmill running protocol. This is the first study to be aimed at the role of exercise training in hepatic PCB levels, which may be a novel mechanism that can collaborate to reduce the development of hyperglycemia and type 2 diabetes in DIO mice.

Reversion of steatosis by SREBP-1c antisense oligonucleotide did not improve hepatic insulin action in diet-induced obesity mice

The literature has associated hepatic insulin action with NAFLD. In this sense, treatments to revert steatosis and improve hepatic insulin action become important. Our group has demonstrated that inhibition of Sterol Regulatory Element Binding Proteins-1c (SREBP-1c) reverses hepatic steatosis. However, insulin signals after NAFLD reversion require better investigation. Thus, in this study, we investigated if the reversal of NAFLD by SREBP-1c inhibitor results in improvement in the hepatic insulin signal in obesity mice. After installation/achievement of diet-induced obesity and insulin resistance, Swiss mice were divided into 3 groups: i) Lean, ii) D-IHS, diet-induced hepatic steatosis [no treatment with antisense oligonucleotide (ASO)], and iii) RD-IHS, reversion of diet-induced hepatic steatosis (treated with ASO). The mice were treated with ASO SREBP-1c as previously described by our group. After ASO treatment, one set of animals was anesthetized and used for in vivo test, and another mice set was anesthetized and used for histology and Western blot analysis. Reversion of diet-induced hepatic steatosis did not change blood glucose, glucose decay constant (k(ITT)), body weight, or serum insulin levels. In addition, results showed that the protocol did not improve insulin pathway signaling, as confirmed by the absence of changes in IR, IRS1, Akt and Foxo1 phosphorylation in hepatic tissue. In parallel, no alterations were observed in proinflammatory molecules. Thus, our results suggest that the inhibition of SREBP-1c reverts steatosis, but without improving insulin hepatic resistance.

Impaired insulin signaling and spatial learning in middle-aged rats: The role of PTP1B

The insulin and Brain-Derived Neurotrophic Factor (BDNF) signaling in the hippocampus promotes synaptic plasticity and memory formation. On the other hand, aging is related to the cognitive decline and is the main risk factor for Alzheimer's Disease (AD). The Protein-Tyrosine Phosphatase 1B (PTP1B) is related to several deleterious processes in neurons and emerges as a promising target for new therapies. In this context, our study aims to investigate the age-related changes in PTP1B content, insulin signaling, β-amyloid content, and Tau phosphorylation in the hippocampus of middle-aged rats. Young (3 months) and middle-aged (17 months) Wistar rats were submitted to Morris-water maze (MWM) test, insulin tolerance test, and molecular analysis in the hippocampus. Aging resulted in increased body weight, and insulin resistance and decreases learning process in MWM. Interestingly, the middle-aged rats have higher levels of PTP-1B, lower phosphorylation of IRS-1, Akt, GSK3β, mTOR, and TrkB. Also, the aging process increased Tau phosphorylation and β-amyloid content in the hippocampus region. In summary, this study provides new evidence that aging-related PTP1B increasing, contributing to insulin resistance and the onset of the AD.

Evidence for a neuromuscular circuit involving hypothalamic interleukin-6 in the control of skeletal muscle metabolism

Hypothalamic interleukin-6 (IL6) exerts a broad metabolic control. Here, we demonstrated that IL6 activates the ERK1/2 pathway in the ventromedial hypothalamus (VMH), stimulating AMPK/ACC signaling and fatty acid oxidation in mouse skeletal muscle. Bioinformatics analysis revealed that the hypothalamic IL6/ERK1/2 axis is closely associated with fatty acid oxidation- and mitochondrial-related genes in the skeletal muscle of isogenic BXD mouse strains and humans. We showed that the hypothalamic IL6/ERK1/2 pathway requires the α2-adrenergic pathway to modify fatty acid skeletal muscle metabolism. To address the physiological relevance of these findings, we demonstrated that this neuromuscular circuit is required to underpin AMPK/ACC signaling activation and fatty acid oxidation after exercise. Last, the selective down-regulation of IL6 receptor in VMH abolished the effects of exercise to sustain AMPK and ACC phosphorylation and fatty acid oxidation in the muscle after exercise. Together, these data demonstrated that the IL6/ERK axis in VMH controls fatty acid metabolism in the skeletal muscle.

Rock protein as cardiac hypertrophy modulator in obesity and physical exercise

Obesity and cardiovascular diseases are worldwide public health issues. In this review, we discussed the participation of ROCK protein in cardiac hypertrophy, mainly through the modulation of leptin and insulin signaling pathways. Leptin plays a role in cardiovascular disease development and, through the Rho-associated protein kinase (ROCK), promotes cardiac hypertrophy. ROCK protein, is regulated by small Rho-GTPases and has two isoforms with high homology. ROCK is able to activate the MAP kinase (MAPK) pathway and modulate insulin signaling in the heart, participating in cardiac hypertrophy development of concentric and eccentric left ventricle growth. Although different types of stimulus can lead to morphologically antagonistic heart growth, physical exercise promotes improvements in hemodynamic function, emerging as a promising non-pharmacological tool to improve overall health. Leptin can activate ROCK in a pathological way, increasing MAPK activity and decreasing insulin signaling via insulin receptor substrate 1 (IRS1) serine 307 residue phosphorylation, phosphatase and tensin homolog, and protein kinase Cβ2. In turn, physical exercise decreases leptin levels and positively modulates insulin signaling as well as increases ROCK-dependent IRS1 (Ser632/635) phosphorylation, improving phosphatidylinositol 3-kinase/protein kinase B axis and promoting physiologic heart growth. Currently, there is a lack of studies about differences in ROCK isoforms, especially during exercise and/or obesity. However, the understanding of its biological function and the complex mechanism underlying the distinct types of cardiac hypertrophy development can be a useful tool in the improvement and treatment of cardiovascular outcomes.

Acute physical exercise increases leptin-induced hypothalamic extracellular signal-regulated kinase1/2 phosphorylation and thermogenesis of obese mice

The obesity is a result of energy imbalance and the increase in thermogenesis seems an interesting alternative for the treatment of this disease. The mechanism of energy expenditure through thermogenesis is tightly articulated in the hypothalamus by leptin. The hypothalamic extracellular signal-regulated kinase-1/2 (ERK1/2) is a key mediator of the thermoregulatory effect of leptin and mediates the sympathetic signal to the brown adipose tissue (BAT). In this context, physical exercise is one of the main interventions for the treatment of obesity. Thus, this study aimed to verify the effects of acute physical exercise on leptin-induced hypothalamic ERK1/2 phosphorylation and thermogenesis in obese mice. Here we showed that acute physical exercise reduced the fasting glucose of obese mice and increased leptin-induced hypothalamic p-ERK1/2 and uncoupling protein 1 (UCP1) content in BAT ( P < 0.05). These molecular changes are accompanied by an increased oxygen uptake (VO ₂ ) and heat production in obese exercised mice ( P < 0.05). The increased energy expenditure in the obese exercised animals occurred independently of changes in spontaneous activity. Thus, this is the first study demonstrating that acute physical exercise can increase leptin-induced hypothalamic ERK1/2 phosphorylation and energy expenditure of obese mice.