Acute exercise modulates Trim63 and Bmal1 in the skeletal muscle of IL-10 knockout mice

The anti-inflammatory role of physical exercise is mediated by interleukin 10 (IL-10), and their release is possibly upregulated in response to IL-6. Previous studies demonstrated that mice lacking IL-6 (IL-6 KO mice) exhibited diminished exercise tolerance, and reduced strength. Rev-erbα, a transcriptional suppressor involved in circadian rhythm, has been discovered to inhibit the expression of genes linked to bodily functions, encompassing inflammation and metabolism. It also plays a significant role in skeletal muscle and exercise performance capacity. Given the potential association between Rev-erbα and the immune system and the fact that both pathways are modulated following acute aerobic exercise, we examined the physical performance of IL-10 KO mice and analyzed the modulation of the atrophy and Rev-erbα pathways in the muscle of wild type (WT) and IL-10 KO mice following one session of acute exercise. For each phenotype, WT and IL-10 KO were divided into two subgroups (Control and Exercise). The acute exercise session started at 6 m/min, followed by 3 m/min increments every 3 min until animal exhaustion. Two hours after the end of the exercise protocol, the gastrocnemius muscle was removed and prepared for the reverse transcription-quantitative polymerase chain reaction (RT-q-PCR) and immunoblotting technique. In summary, compared to WT, the IL-10 KO animals showed lower body weight and grip strength in the baseline. The IL-10 control group presented a lower protein content of BMAL1. After the exercise protocol, the IL-10 KO group had higher mRNA levels of Trim63 (atrophy signaling pathway) and lower mRNA levels of Clock and Bmal1 (Rev-erbα signaling pathway). This is the first study showing the relationship between Rev-erbα and atrophy in IL-10 KO mice. Also, we accessed a public database that analyzed the gastrocnemius of MuRF KO mice submitted to two processes of muscle atrophy, a denervation surgery and dexamethasone (Dexa) injections. Independently of knockout, the denervation demonstrated lower Nr1d1 levels. In conclusion, IL-10 seems to be a determinant in the Rev-erbα pathway and atrophy after acute exercise, with no modulation in the baseline state.

Parkin is a critical player in the effects of caffeine over mitochondrial quality control pathways during skeletal muscle regeneration in mice

AIM

This study aimed to investigate the effects of caffeine on pathways associated with mitochondrial quality control and mitochondrial capacity during skeletal muscle regeneration, focusing on the role of Parkin, a key protein involved in mitophagy.

METHODS

We used in vitro C2C12 myoblast during differentiation with and without caffeine in the medium, and we evaluated several markers of mitochondrial quality control pathways and myotube growth. In vivo experiments, we used C57BL/6J (WT) and Parkintm 1Shn lineage (Parkin-/- ) mice and injured tibial anterior muscle. The mice regenerated TA muscle for 3, 10, and 21 days with or without caffeine ingestion. TA muscle was used to analyze the protein content of several markers of mitochondrial quality pathways, muscle satellite cell differentiation, and protein synthesis. Furthermore, it analyzed mtDNA, mitochondrial respiration, and myofiber growth.

RESULTS

C2C12 differentiation experiments showed that caffeine decreased Parkin content, potentially leading to increased DRP1 and PGC-1α content and altered mitochondrial population, thereby enhancing growth capacity. Using Parkin-/- mice, we found that caffeine intake during the regenerative process induces an increase in AMPKα phosphorylation and PGC-1α and TFAM content, changes that were partly Parkin-dependent. In addition, the absence of Parkin potentiates the ergogenic effect of caffeine by increasing mitochondrial capacity and myotube growth. Those effects are related to increased ATF4 content and activation of protein synthesis pathways, such as increased 4E-BP1 phosphorylation.

CONCLUSION

These findings demonstrate that caffeine ingestion changes mitochondrial quality control during skeletal muscle regeneration, and Parkin is a central player in those mechanisms.

Intermittent fasting combined with exercise training reduces body mass and alleviates hypothalamic disorders induced by high-fat diet intake

High-fat diet consumption causes hypothalamic inflammation, dysregulating the leptin pathway, which, in turn, compromises the modulation of hypothalamic neuronal activities and predisposes obesity development. Intermittent fasting (IF) and exercise training (ET) have been demonstrated as efficient interventions to modulate hypothalamic inflammation and neuronal activity. However, no studies have evaluated whether combining these interventions could induce better results in reestablishing hypothalamic homeostasis disrupted by high-fat diet intake. The 8-week-old male C57BL/6 mice were randomly assigned into two groups: sedentary mice fed a standard diet (CT), and sedentary mice fed a high-fat diet (HF). After 8 weeks of an HF diet, part of the HF group (now 16 weeks old) was randomly subjected to different interventions for 6 weeks: HF-IF = HF diet mice submitted to IF; HF-T = HF diet mice submitted to ET; HF-IFT = HF diet mice submitted to IF and ET. All interventions decreased the body weight gain induced by high-fat diet intake, associated with reduced calorie consumption in week 14. Only the HF-IFT group presented improved serum insulin, leptin, resistin, and Tnf-alpha levels concomitantly with decreased hypothalamic inflammation. The HF-IFT group also demonstrated increased Pomc mRNA expression associated with enhanced pSTAT3 expression in the hypothalamic arcuate and ventromedial hypothalamic nuclei. Our data indicate that the beneficial effects of the combination of IF and ET on energy homeostasis are associated with increased leptin sensitivity in the hypothalamic arcuate nucleus and ventromedial hypothalamic nucleus, which is likely due to an improvement in hypothalamic inflammatory pathways in these nuclei.

The dual and emerging role of physical exercise-induced TFEB activation in the protection against Alzheimer's disease

The mechanisms of autophagy have been related to Alzheimer's disease (AD) pathogenesis by the endosomal-lysosomal system, having a critical function in forming amyloid-β (Aβ) plaques. Nevertheless, the exact mechanisms mediating disease pathogenesis remain unclear. The transcription factor EB (TFEB), a primary transcriptional autophagy regulator, improves gene expression, mediating lysosome function, autophagic flux, and autophagosome biogenesis. In this review, we present for the first time the hypothesis of how TFEB, autophagy, and mitochondrial function are interconnected in AD, providing a logical foundation for unraveling the critical role of chronic physical exercise in this process. Aerobic exercise training promotes Adiponectin Receptor 1 (AdipoR1)/AMP-activated protein kinase (AMPK)/TFEB axis activation in the brain of the AD animal model, which contributes to alleviated Aβ deposition and neuronal apoptosis while improving cognitive function. Moreover, TFEB upregulates Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and nuclear factor erythroid 2-related factor 2 (NRF-2), improving mitochondrial biogenesis and redox status. In addition, tissue contraction activates calcineurin in skeletal muscle, which induces TFEB nuclear translocation, raising the hypothesis that the same would occur in the brain. Thus, a deep and comprehensive exploration of the TFEB could provide new directions and strategies for preventing AD. We conclude that chronic exercise can be an effective TFEB activator, inducing autophagy and mitochondrial biogenesis, representing a potential nonpharmacological strategy contributing to brain health.

Short-term physical exercise controls age-related hyperinsulinemia and improves hepatic metabolism in aged rodents

PURPOSE

Aging is associated with changes in glucose homeostasis related to both decreased insulin secretion and/or impaired insulin action, contributing to the high prevalence of type 2 diabetes (T2D) in the elderly population. Additionally, studies are showing that chronically high levels of circulating insulin can also lead to insulin resistance. In contrast, physical exercise has been a strategy used to improve insulin sensitivity and metabolic health. However, the molecular alterations resulting from the effects of physical exercise in the liver on age-related hyperinsulinemia conditions are not yet fully established. This study aimed to investigate the effects of 7 days of aerobic exercise on hepatic metabolism in aged hyperinsulinemic rats (i.e., Wistar and F344) and in Slc2a4^+/- mice (hyperglycemic and hyperinsulinemic mice).

RESULTS

Both aged models showed alterations in insulin and glucose tolerance, which were associated with essential changes in hepatic fat metabolism (lipogenesis, gluconeogenesis, and inflammation). In contrast, 7 days of physical exercise was efficient in improving whole-body glucose and insulin sensitivity, and hepatic metabolism. The Slc2a4^+/- mice presented significant metabolic impairments (insulin resistance and hepatic fat accumulation) that were improved by short-term exercise training. In this scenario, high circulating insulin may be an important contributor to age-related insulin resistance and hepatic disarrangements in some specific conditions.

CONCLUSION

In conclusion, our data demonstrated that short-term aerobic exercise was able to control mechanisms related to hepatic fat accumulation and insulin sensitivity in aged rodents. These effects could contribute to late-life metabolic health and prevent the development/progression of age-related T2D.

Exercise training restores weight gain and attenuates hepatic inflammation in a rat model of non-celiac gluten sensitivity

Gluten intolerance is associated with several disorders in the body. Although research has grown in recent years, the understanding of its impact on different tissues and the effects of physical exercise in mitigating health problems in the condition of gluten intolerance are still limited. Therefore, our objective was to test whether gliadin would affect metabolism and inflammation in liver tissue and whether aerobic physical exercise would mitigate the negative impacts of gliadin administration in rodents. Wistar rats were divided into exercised gliadin, gliadin, and control groups. Gliadin was administered by gavage from birth to 60 days of age. The rats in the exercised gliadin group performed an aerobic running exercise training protocol for 15 days. At the end of the experiments, physiological, histological, and molecular analyzes were performed in the study. Compared to the control group, the gliadin group had impaired weight gain and increased gluconeogenesis, lipogenesis, and inflammatory biomarkers in the liver. On the other hand, compared to the gliadin group, animals in the exercise-gliadin group had a recovery in body weight, improved insulin sensitivity, and a reduction in some gluconeogenesis, lipogenesis, and inflammatory biomarkers in the liver. In conclusion, our results revealed that the administration of gliadin from birth impaired weight gain and induced an increase in hepatic inflammatory cytokines, which was associated with an impairment of glycemic homeostasis in the liver, all of which were attenuated by adding aerobic exercise training in the gliadin group.

Aging reduces ABHD5 protein content in the adipose tissue of mice: The reversal effect of exercise

Dysfunction of the adipose tissue metabolism is considered as a significant hallmark of aging. It has been proposed that α-β hydrolase domain containing 5 (ABHD5) plays a critical role in the control of lipolysis. However, the role of ABHD5 in the control of lipolysis during aging or exercise is unknown. Here we combined the experimental mouse model with transcriptomic analyzes by using murine and human databases to explore the role of ABHD5 in the adipose tissue during aging and in response to exercise. Transcriptomic data revealed a downregulation of Abhd5 messenger RNA levels in the subcutaneous white adipose tissue (scWAT) over time in individuals from 20 to 69 years old. Aged mice displayed dramatic reduction of ABHD5 protein content and lipolytic-related proteins in the scWAT. Interestingly, 4 weeks of high-intensity interval training increased ABHD5 protein level and restored the lipolytic pathway in the scWAT of aged mice. Altogether, our findings demonstrated that aging affects ABHD5 content in the adipose tissue of mice and humans. Conversely, exercise increases ABHD5 activity, recovering the lipolytic activity in aged mice.

Genetic ablation of Toll-like Receptor 4 seems to activate the apoptosis pathway in the skeletal muscle of mice after acute physical exercise

Many conditions, such as inflammation and physical exercise, can induce endoplasmic reticulum (ER) stress. Toll-like Receptor 4 (TLR4) can trigger inflammation and ER stress events. However, there are still no data in the literature regarding the role of TLR4 in ER stress during exercise in skeletal muscle. Therefore, the current investigation aimed to verify the responses of ER stress markers in wild-type (WT) and Tlr4 global knockout (KO) mice after acute and chronic physical exercise protocols. Eight-week-old male WT and KO mice were submitted to acute (moderate or high intensity) and chronic (4-week protocol) treadmill exercises. Under basal conditions, KO mice showed lower performance in the rotarod test. Acute high-intensity exercise increased eIF2α protein in the WT group. After the acute high-intensity exercise, there was an increase in Casp3 and Ddit3 mRNA for the KO mice. Acute moderate exercise increased the cleaved Caspase-3/Caspase-3 in the KO group. In response to chronic exercise, the KO group showed no improvement in any performance evaluation. The 4-week chronic protocol did not generate changes in ATF6, CHOP, p-IRE1α, p-eIF2α/eIF2α, and cleaved Caspase-3/Caspase-3 ratio but reduced BiP protein compared with the KO-Sedentary group. These results demonstrate the global deletion of Tlr4 seems to have the same effects on UPR markers of WT animals after acute and chronic exercise protocols but decreased performance. The cleaved Caspase-3/Caspase-3 ratio may be activated by another pathway other than ER stress in Tlr4 KO animals.

IL-6 deletion decreased REV-ERBα protein and influenced autophagy and mitochondrial markers in the skeletal muscle after acute exercise

Interleukin 6 (IL-6) acts as a pro and anti-inflammatory cytokine, has an intense correlation with exercise intensity, and activates various pathways such as autophagy and mitochondrial unfolded protein response. Also, IL-6 is interconnected to circadian clock-related inflammation and can be suppressed by the nuclear receptor subfamily 1, group D, member 1 (Nr1d1, protein product REV-ERBα). Since IL-6 is linked to physical exercise-modulated metabolic pathways such as autophagy and mitochondrial metabolism, we investigated the relationship of IL-6 with REV-ERBα in the adaptations of these molecular pathways in response to acute intense physical exercise in skeletal muscle. The present study was divided into three experiments. In the first one, wild-type (WT) and IL-6 knockout (IL-6 KO) mice were divided into three groups: Basal time (Basal; sacrificed before the acute exercise), 1 hour (1hr post-Ex; sacrificed 1 hour after the acute exercise), and 3 hours (3hr post-Ex; sacrificed 3 hours after the acute exercise). In the second experiment, C2C12 cells received IL-6 physiological concentrations or REV-ERBα agonist, SR9009. In the last experiment, WT mice received SR9009 injections. After the protocols, the gastrocnemius muscle or the cells were collected for reverse transcription-quantitative polymerase chain reaction (RTq-PCR) and immunoblotting techniques. In summary, the downregulation of REV-ERBα, autophagic flux, and most mitochondrial genes was verified in the IL-6 KO mice independent of exercise. The WT and IL-6 KO treated with SR9009 showed an upregulation of autophagic genes. C2C12 cells receiving IL-6 did not modulate the Nr1d1 mRNA levels but upregulated the expression of some mitochondrial genes. However, when treated with SR9009, IL-6 and mitochondrial gene expression were upregulated in C2C12 cells. The autophagic flux in C2C12 suggest the participation of REV-ERBα protein in the IL-6-induced autophagy. In conclusion, the present study verified that the adaptations required through physical exercise (increases in mitochondrial content and improvement of autophagy machinery) might be intermediated by an interaction between IL-6 and REVERBα.

FOXO1 is downregulated in obese mice subjected to short-term strength training

Obesity is a worldwide health problem and is directly associated with insulin resistance and type 2 diabetes. The liver is an important organ for the control of healthy glycemic levels, since insulin resistance in this organ reduces phosphorylation of forkhead box protein 1 (FOXO1) protein, leading to higher hepatic glucose production (HGP) and fasting hyperglycemia. Aerobic physical training is known as an important strategy in increasing the insulin action in the liver by increasing FOXO1 phosphorylation and reducing gluconeogenesis. However, little is known about the effects of strength training in this context. This study aimed to investigate the effects of short-term strength training on hepatic insulin sensitivity and glycogen synthase kinase-3β (GSK3β) and FOXO1 phosphorylation in obese (OB) mice. To achieve this goal, OB Swiss mice performed the strength training protocol (one daily session for 15 days). Short-term strength training increased the phosphorylation of protein kinase B and GSK3β in the liver after insulin stimulus and improved the control of HGP during the pyruvate tolerance test. On the other hand, sedentary OB animals reduced FOXO1 phosphorylation and increased the levels of nuclear FOXO1 in the liver, increasing the phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) content. The bioinformatics analysis also showed positive correlations between hepatic FOXO1 levels and gluconeogenic genes, reinforcing our findings. However, strength-trained animals reverted to this scenario, regardless of body adiposity changes. In conclusion, short-term strength training is an efficient strategy to enhance the insulin action in the liver of OB mice, contributing to glycemic control by reducing the activity of hepatic FOXO1 and lowering PEPCK and G6Pase contents.

Muscle endoplasmic reticulum stress in exercise

The endoplasmic reticulum (ER) is an organelle responsible for the post-translational folding and modification of proteins. Under stress conditions, such as physical exercise, there is accumulation of misfolded proteins. The increased load of proteins in the ER results in ER stress, which activates the unfolded protein response (UPR). UPR is comprised of three parallel pathways, responsible for ensuring the quality of secreted proteins. Scientific studies show that resistance or endurance acute physical exercise can induce ER stress and activate the UPR pathways. On the other hand, regular moderate-intensity exercise can attenuate the responses of genes and proteins related to ER stress. However, these positive adaptations do not occur when exercise intensity and volume increase without adequate rest periods, which is observed in overtraining. The current review discusses the frontier-of-knowledge findings on the effects of different acute and chronic physical exercise protocols on skeletal muscle ER stress and its metabolic consequences.

Genetic deletion of IL-6 increases CK-MB, a classic cardiac damage marker, and decreases UPRmt genes after exhaustive exercise

The intensity, duration, type of contraction, and muscle damage influence interleukin-6 (IL-6) response to acute exercise. However, in response to an exhaustive exercise session, the upregulation of IL-6 in the serum and heart is associated with an inflammatory condition and can inhibit autophagy. This study aimed to investigate the role of IL-6 in autophagy pathway responses and mitochondrial function in the heart of mice submitted to acute exhaustive physical exercise. The mice were allocated into three groups, five animals per group, for the wild type (WT) and the IL-6 knockout (IL-6 KO): Basal (sedentary; Basal), 1 h (after 1 h of the acute exercise; 1 h), and 3 h (after 3 h of the acute exercise; 3 h). After the specific time for each group, the blood was collected, each mouse heart was removed, and the left ventricle (LV) was isolated. In summary, under basal conditions, without the influence of the acute exercise, the IL-6 KO group showed lower number of nuclei in the cardiac tissue, but higher collagen deposition; lower messenger RNA (mRNA) levels of Prkaa1 and Mtco1, but higher mRNA levels of Ulk1; and higher protein levels of the ratio p-AMPK/AMPK in the heart when compared to WT at the same time point. After the acute exercise (1 and 3 h), the IL-6 KO group had lower mRNA levels of Tfam, Mtnd1, Mtco1, and Nampt in the heart when compared to WT after exercise; higher serum levels of creatine kinase (CK), CK-MB, and lactate dehydrogenase for the IL-6 group when compared to the WT group after the exercise. Specifically, the heat-shock protein 60 protein levels in the heart increased 3 h after exhaustive exercise in the WT group, but not in the IL-6 KO group. The study emphasizes that IL-6 may offer cardioprotective effects, including mitochondrial adaptations in response to acute exhaustive exercise.

Physical Exercise and Liver Autophagy: Potential Roles of IL-6 and Irisin

Autophagic dysregulation contributes to liver diseases. Although some investigations have examined the effects of endurance and resistance exercise on autophagy activation, potential myokines responsible for skeletal muscle-liver crosstalk are still unknown. Based on experimental studies and bioinformatics, we hypothesized that interleukin 6 (IL-6) and irisin might be key players in the contraction-induced release of molecules that regulate liver autophagic responses.

Using Intermittent Fasting as a Non-pharmacological Strategy to Alleviate Obesity-Induced Hypothalamic Molecular Pathway Disruption

Intermittent fasting (IF) is a popular intervention used to fight overweight/obesity. This condition is accompanied by hypothalamic inflammation, limiting the proper signaling of molecular pathways, with consequent dysregulation of food intake and energy homeostasis. This mini-review explored the therapeutic modulation potential of IF regarding the disruption of these molecular pathways. IF seems to modulate inflammatory pathways in the brain, which may also be correlated with the brain-microbiota axis, improving hypothalamic signaling of leptin and insulin, and inducing the autophagic pathway in hypothalamic neurons, contributing to weight loss in obesity. Evidence also suggests that when an IF protocol is performed without respecting the circadian cycle, it can lead to dysregulation in the expression of circadian cycle regulatory genes, with potential health damage. In conclusion, IF may have the potential to be an adjuvant treatment to improve the reestablishment of hypothalamic responses in obesity.

TLR4 deletion increases basal energy expenditure and attenuates heart apoptosis and ER stress but mitigates the training-induced cardiac function and performance improvement

Strategies capable of attenuating TLR4 can attenuate metabolic processes such as inflammation, endoplasmic reticulum (ER) stress, and apoptosis in the body. Physical exercise has been a cornerstone in suppressing inflammation and dysmetabolic outcomes caused by TRL4 activation. Thus, the present study aimed to evaluate the effects of a chronic physical exercise protocol on the TLR4 expression and its repercussion in the inflammation, ER stress, and apoptosis pathways in mice hearts. Echocardiogram, RT-qPCR, immunoblotting, and histological techniques were used to evaluate the left ventricle of wild-type (WT) and Tlr4 knockout (TLR4 KO) mice submitted to a 4-week physical exercise protocol. Moreover, we performed a bioinformatics analysis to expand the relationship of Tlr4 mRNA in the heart with inflammation, ER stress, and apoptosis-related genes of several isogenic strains of BXD mice. The TLR4 KO mice had higher energy expenditure and heart rate in the control state but lower activation of apoptosis and ER stress pathways. The bioinformatics analysis reinforced these data. In the exercised state, the WT mice improved performance and cardiac function. However, these responses were blunted in the KO group. In conclusion, TLR4 has an essential role in the inhibition of apoptosis and ER stress pathways, as well as in the training-induced beneficial adaptations.

Taurine upregulates insulin signaling and mitochondrial metabolism in vitro but not in adipocytes of obese women

OBJECTIVES

Based on taurine's beneficial roles in metabolic diseases in rodents and obese individuals, we investigated the effects of taurine supplementation on adipose tissue using transcriptome analysis, 3T3-L1 adipocytes, and subcutaneous white adipose tissue (scWAT) of obese women.

METHODS

First, we applied bioinformatics analysis to evaluate the effect of the taurine synthesis pathway on the adipose tissue of several BXD mice strains. After that, using 3T3-L1 adipocytes, we investigated the effects of different taurine doses in proteins related to insulin signaling, lipid oxidation, and mitochondrial function. Finally, we evaluated the effects of taurine supplementation (3 grams, 8 wk) on the same proteins in the scWAT of obese women.

RESULTS

The transcriptome analysis showed that the taurine biosynthesis pathway was positively associated with insulin signaling and mitochondrial metabolism in the scWAT of BXD mice. The experiments using 3T3-L1 cells highlighted that the taurine dosage has an essential function in taurine synthesis, insulin, and mitochondrial markers. In contrast, the 8-wk taurine administration did not change the basal insulin, proteins of the taurine synthesis or insulin pathways, lipid oxidation, or mitochondrial metabolism in the scWAT of obese women.

CONCLUSIONS

For the first time, to our knowledge, we showed that supplementation with 3 g of taurine for 8 wk promoted no effect in the insulin signaling pathway in the scWAT of obese women. These findings bring new perspectives to investigate different taurine doses and the intervention period for human studies owing to the potential antiobesity activity of taurine.

Exercise Counterbalances Rho/ROCK2 Signaling Impairment in the Skeletal Muscle and Ameliorates Insulin Sensitivity in Obese Mice

Physical exercise is considered a fundamental strategy in improving insulin sensitivity and glucose uptake in skeletal muscle. However, the molecular mechanisms underlying this regulation, primarily on skeletal muscle glucose uptake, are not fully understood. Recent evidence has shown that Rho-kinase (ROCK) isoforms play a pivotal role in regulating skeletal muscle glucose uptake and systemic glucose homeostasis. The current study evaluated the effect of physical exercise on ROCK2 signaling in skeletal muscle of insulin-resistant obese animals. Physiological (ITT) and molecular analysis (immunoblotting, and RT-qPCR) were performed. The contents of RhoA and ROCK2 protein were decreased in skeletal muscle of obese mice compared to control mice but were restored to normal levels in response to physical exercise. The exercised animals also showed higher phosphorylation of insulin receptor substrate 1 (IRS1 Serine 632/635) and protein kinase B (Akt) in the skeletal muscle. However, phosphatase and tensin homolog (PTEN) and protein-tyrosine phosphatase-1B (PTP-1B), both inhibitory regulators for insulin action, were increased in obesity but decreased after exercise. The impact of ROCK2 action on muscle insulin signaling is further underscored by the fact that impaired IRS1 and Akt phosphorylation caused by palmitate in C2C12 myotubes was entirely restored by ROCK2 overexpression. These results suggest that the exercise-induced upregulation of RhoA-ROCK2 signaling in skeletal muscle is associated with increased systemic insulin sensitivity in obese mice and further implicate that muscle ROCK2 could be a potential target for treating obesity-linked metabolic disorders.

Interleukin-6 ablation does not alter morphofunctional heart characteristics but modulates physiological and inflammatory markers after strenuous exercise

Interleukin-6 (IL-6) is associated with pathological cardiac hypertrophy and can be dramatically increased in serum after an acute strenuous exercise session. However, IL-6 is also associated with the increased production and release of anti-inflammatory cytokines and the inhibition of tumor necrosis factor-alpha (TNF-α) after chronic moderate exercise. To elucidate the relevance of IL-6 in inflammatory and hypertrophic signaling in the heart in response to an acute strenuous exercise session, we combined transcriptome analysis using the BXD mice database and exercised IL-6 knockout mice (IL-6KO). Bioinformatic analysis demonstrated that low or high-levels of Il6 mRNA in the heart did not change the inflammation- and hypertrophy-related genes in BXD mice strains. On the other hand, bioinformatic analysis revealed a strong positive correlation between Il6 gene expression in skeletal muscle with inflammation-related genes in cardiac tissue in several BXD mouse strains, suggesting that skeletal muscle-derived IL-6 could alter the heart's intracellular signals, particularly the inflammatory signaling. As expected, an acute strenuous exercise session increased IL-6 levels in wild-type, but not in IL-6KO mice. Despite not showing morphofunctional differences in the heart at rest, the IL-6KO group presented a reduction in physical performance and attenuated IL-6, TNF-α, and IL-1beta kinetics in serum, as well as lower p38MAPK phosphorylation, Ampkalpha expression, and higher Acta1 and Tnf gene expressions in the left ventricle in the basal condition. In response to strenuous exercise, IL-6 ablation was linked to a reduction in the pro-inflammatory response and higher activation of classical physiological cardiac hypertrophy proteins.

Acute physical exercise increases PI3K-p110α protein content in the hypothalamus of obese mice

The anatomy of the hypothalamus includes many nuclei and a complex network of neurocircuits. In this context, some hypothalamic nuclei reside closer to the blood-brain barrier, allowing communication with the peripheral organs through some molecules, such as leptin. Leptin is considered the main adipokine for energy homeostasis control. Furthermore, leptin signalling in the hypothalamus can communicate with insulin signalling through the activation of phosphoinositide 3-kinase (PI3k). Previous data suggest that isoforms of PI3k are necessary to mediate insulin action in the hypothalamus. However, obese animals show impairment in the central signalling of these hormones. Thus, in the current study, we evaluated the role of acute exercise in the leptin and insulin pathways in the hypothalamus, as well as in food intake control in obese mice. Although acute physical exercise was not able to modulate leptin signalling, this protocol suppressed the increase in the suppressor of cytokine signalling 3 (SOCS3) protein levels. In addition, acute exercise increased the content of PI3k-p110α protein in the hypothalamus. The exercised animals showed a strong tendency to reduction in cumulative food intake. For the first time, our results indicate physical exercise can increase PI3k-p110α protein content in the hypothalamus of obese mice and regulate food intake.

Aerobic Exercise Training Induces the Mitonuclear Imbalance and UPRmt in the Skeletal Muscle of Aged Mice

The impairment of the mitochondrial functions is a hallmark of aging. During aging, there is a downregulation of two mechanisms strictly associated with mitochondrial integrity, including the mitonuclear imbalance (eg, imbalance in mitochondrial- versus nuclear-encoded mitochondrial proteins) and the mitochondrial unfolded protein response (UPRmt). Here, we evaluated the effects of aerobic exercise in the mitonuclear imbalance and UPRmt markers in the skeletal muscle of old mice. We combined the physiological tests, molecular and bioinformatic analyzes to evaluate the effects of 4 weeks of aerobic exercise training on mitonuclear imbalance and UPRmt markers in the skeletal muscle of young (2 months) and aged (24 months) C57BL/6J mice. Initially, we found that aging reduced several mitochondrial genes in the gastrocnemius muscle, and it was accompanied by the low levels of UPRmt markers, including Yme1l1 and Clpp mRNA. As expected, physical training improved the whole-body metabolism and physical performance of aged mice. The aerobic exercise increased key proteins involved in the mitochondrial biogenesis/functions (VDAC and SIRT1) along with mitochondrial-encoded genes (mtNd1, mtCytB, and mtD-Loop) in the skeletal muscle of old mice. Interestingly, aerobic exercise induced the mitonuclear imbalance, increasing MTCO1/ATP5a ratio and UPRmt markers in the skeletal muscle, including HSP60, Lonp1, and Yme1L1 protein levels in the gastrocnemius muscle of aged mice. These data demonstrate that aerobic exercise training induced mitonuclear imbalance and UPRmt in the skeletal muscle during aging. These phenomena could be involved in the improvement of the mitochondrial metabolism and oxidative capacity in aged individuals.

One Bout of Aerobic Exercise Can Enhance the Expression of Nr1d1 in Oxidative Skeletal Muscle Samples

The nuclear receptor subfamily 1, group D member 1 (Nr1d1), plays a role in the skeletal muscle’s oxidative capacity, mitochondrial biogenesis, atrophy genes, and muscle fiber size. In light of the effects of physical exercise, the present study investigates the acute response of Nr1d1 and genes related to atrophy and mitochondrial biogenesis on endurance and resistance exercise protocols. In this investigation, we observed, after one bout of endurance exercise, an upregulation of Nr1d1 in soleus muscle, but not in the gastrocnemius, and some genes related to mitochondrial biogenesis and atrophy were enhanced as well. Also, analysis of muscle transcripts from diverse isogenic BXD mice families revealed that the strains with higher Nr1d1 gene expression displayed upregulation of AMPK signaling and mitochondrial-related genes. In summary, a single session of endurance exercise can enhance the Nr1d1 mRNA levels in an oxidative muscle.

Hepatic LC3 II/I ratio is not modulated in exercised mice

Autophagy plays an essential role in body homeostasis achievement. One of the main proteins involved in this process is the LC3I, which, after lipidation, leads to the formation of LC3II that participates in the formation and maturation of autophagosome. This descriptive study verified the responses of LC3II to LC3I proteins, as well as the time-course of this ratio in mice livers after different types of acute physical exercise protocols. Eight-week-old male C57BL/6 mice were maintained three per cage with controlled temperature (22±2 °C) on a 12:12-h light-dark normal cycle with food (Purina chow) and water ad libitum. Mice were randomly divided into four groups: control (CT, sedentary mice), resistance (RE, submitted to a single bout of resistance exercise), endurance (EE, submitted to a single bout of endurance exercise), and concurrent (CE, submitted to a single bout of endurance combined with resistance exercise). The mice livers were extracted and used for the immunoblotting technique. The hepatic LC3B II/I ratio for the RE and EE groups were not altered during the different time-points. For the CE group, there was a decrease in this ratio 12h after exercise compared to time 0 and 18h. Also, the hepatic LC3B II/I ratios were not different among the acute physical exercise protocols along the time-course. The hepatic LC3B II/I ratio was not influenced by the endurance and resistance protocols but decreased in response to the concurrent protocol at 12h after the stimulus.

Moderate, but Not Excessive, Training Attenuates Autophagy Machinery in Metabolic Tissues

The protective effects of chronic moderate exercise-mediated autophagy include the prevention and treatment of several diseases and the extension of lifespan. In addition, physical exercise may impair cellular structures, requiring the action of the autophagy mechanism for clearance and renovation of damaged cellular components. For the first time, we investigated the adaptations on basal autophagy flux in vivo in mice's liver, heart, and skeletal muscle tissues submitted to four different chronic exercise models: endurance, resistance, concurrent, and overtraining. Measuring the autophagy flux in vivo is crucial to access the functionality of the autophagy pathway since changes in this pathway can occur in more than five steps. Moreover, the responses of metabolic, performance, and functional parameters, as well as genes and proteins related to the autophagy pathway, were addressed. In summary, the regular exercise models exhibited normal/enhanced adaptations with reduced autophagy-related proteins in all tissues. On the other hand, the overtrained group presented higher expression of Sqstm1 and Bnip3 with negative morphological and physical performance adaptations for the liver and heart, respectively. The groups showed different adaptions in autophagy flux in skeletal muscle, suggesting the activation or inhibition of basal autophagy may not always be related to improvement or impairment of performance.

Role of TLR4 in physical exercise and cardiovascular diseases

Cardiovascular diseases are a leading cause of death for adults worldwide. Published articles have shown that toll-like receptor 4 (TLR4), a member of the toll-like receptor (TLR) family, is involved in several cardiovascular diseases and can be modulated by physical exercise. TLR4 is the most expressed TLR in cardiac tissue and is an essential mediator of the inflammatory and apoptosis processes in the heart, playing a pivotal role in the development of cardiovascular diseases. Physical exercise is recognized as a non-pharmacological strategy for the prevention and treatment of these diseases. In addition, physical exercise can modulate the TLR4 in the mice heart, and its absence attenuates apoptosis, endoplasmic reticulum stress, and inflammation. However, the relationship between TLR4 and physical exercise-induced cardiac adaptations has barely been explored. Thus, the objective of this brief review was to discuss studies describing how TLR4 influences cardiac responses to physical exercise and present a link between these responses and cardiovascular diseases, showing physical activity improves the cardiac function of individuals with cardiovascular diseases through the TLR4 modulation.

Role of interleukin-6 in inhibiting hepatic autophagy markers in exercised mice

BACKGROUND

Based on the crosstalk of inflammation with apoptosis, autophagy, and endoplasmic reticulum (ER) stress, the main objective of this study was to explore the role of interleukin-6 (IL-6) on genes and proteins related to these phenomena in the livers of mice submitted to acute exhaustive exercise.

METHODS

Reverse transcription-quantitative polymerase chain reaction and immunoblotting technique were used to evaluate the livers of wild-type (WT) and IL-6 knockout (KO) mice at baseline (BL) and 3 h after the acute exhaustive physical exercise (EE).

RESULTS

Compared to the WT at baseline, the IL-6 KO had lower exhaustion velocity, mRNA levels of Mtor, Ulk1, Map1lc3b, and Mapk14, and protein contents of ATG5 and p-p70S6K/p70S6K. For the WT group, the EE decreased glycemia, mRNA levels of Casp3, Mtor, Ulk1, Foxo1a, Mapk14, and Ppargc1a, and protein contents of ATG5 and p-p70S6K/p70S6K, but increased mRNA levels of Sqstm1. For the IL-6 KO group, the EE decreased glycemia, mRNA levels of Casp3 and Foxo1a, and protein contents of pAkt/Akt and Mature/Pro IL-1beta, but increased mRNA levels of Sqstm1, and protein contents of p-AMPK/AMPK.

CONCLUSION

The inhibition of the hepatic autophagy markers induced by the acute EE was attenuated in IL-6 KO mice, highlighting a new function of this cytokine.

The Combination of Fasting, Acute Resistance Exercise, and Protein Ingestion Led to Different Responses of Autophagy Markers in Gastrocnemius and Liver Samples

The present study verified the responses of proteins related to the autophagy pathway after 10 h of fast with resistance exercise and protein ingestion in skeletal muscle and liver samples. The rats were distributed into five experimental groups: control (CT; sedentary and without gavage after fast), exercise immediately (EXE-imm; after fast, rats were submitted to the resistance protocol and received water by gavage immediately after exercise), exercise after 1 h (EXE-1h; after fast, rats were submitted to the resistance protocol and received water by gavage 1 h after exercise), exercise and supplementation immediately after exercise (EXE/Suppl-imm; after fast, rats were submitted to the resistance protocol and received a mix of casein: whey protein 1:1 (w/w) by gavage immediately after exercise), exercise and supplementation 1 h after exercise (EXE/Suppl-1h; after fast, rats were submitted to the resistance protocol and received a mix of casein: whey protein 1:1 (w/w) by gavage 1 h after exercise). In summary, the current findings show that the combination of fasting, acute resistance exercise, and protein blend ingestion (immediately or 1 h after the exercise stimulus) increased the serum levels of leucine, insulin, and glucose, as well as the autophagy protein contents in skeletal muscle, but decreased other proteins related to the autophagic pathway in the liver. These results deserve further mechanistic investigations since athletes are combining fasting with physical exercise to enhance health and performance outcomes.

NAD+ precursor increases aerobic performance in mice

PURPOSE

Nicotinamide riboside (NR) acts as a potent NAD⁺ precursor and improves mitochondrial oxidative capacity and mitochondrial biogenesis in several organisms. However, the effects of NR supplementation on aerobic performance remain unclear. Here, we evaluated the effects of NR supplementation on the muscle metabolism and aerobic capacity of sedentary and trained mice.

METHODS

Male C57BL/6 J mice were supplemented with NR (400 mg/Kg/day) over 5 and 10 weeks. The training protocol consisted of 5 weeks of treadmill aerobic exercise, for 60 min a day, 5 days a week. Bioinformatic and physiological assays were combined with biochemical and molecular assays to evaluate the experimental groups.

RESULTS

NR supplementation by itself did not change the aerobic performance, even though 5 weeks of NR supplementation increased NAD⁺ levels in the skeletal muscle. However, combining NR supplementation and aerobic training increased the aerobic performance compared to the trained group. This was accompanied by an increased protein content of NMNAT3, the rate-limiting enzyme for NAD + biosynthesis and mitochondrial proteins, including MTCO1 and ATP5a. Interestingly, the transcriptomic analysis using a large panel of isogenic strains of BXD mice confirmed that the Nmnat3 gene in the skeletal muscle is correlated with several mitochondrial markers and with different phenotypes related to physical exercise. Finally, NR supplementation during aerobic training markedly increased the amount of type I fibers in the skeletal muscle.

CONCLUSION

Taken together, our results indicate that NR may be an interesting strategy to improve mitochondrial metabolism and aerobic capacity.

TGF-β1 downregulation in the hypothalamus of obese mice through acute exercise

Obesity and aging lead to abnormal transforming growth factor-β1 (TGF-β1) signaling in the hypothalamus, triggering the imbalance on glucose metabolism and energy homeostasis. Here, we determine the effect of acute exercise on TGF-β1 expression in the hypothalamus of two models of obesity in mice. The bioinformatics analysis was performed to evaluate the correlation between hypothalamic Tgf-β1 messenger RNA (mRNA) and genes related to thermogenesis in the brown adipose tissue (BAT) by using a large panel of isogenic BXD mice. Thereafter, leptin-deficient (ob/ob) mice and obese C57BL/6 mice fed on a high-fat diet (HFD) were submitted to the acute exercise protocol. Transcriptomic analysis by using BXD mouse reference population database revealed that hypothalamic Tgf-β1 mRNA is negatively correlated with genes related to thermogenesis in brown adipose tissue of BXD mice, such as peroxisome proliferator-activated receptor gamma coactivator and is positively correlated with respiratory exchange ratio. In agreement with these results, leptin-deficient (ob/ob) and HFD-fed mice displayed high levels of Tgf-β1 mRNA in the hypothalamus and reduction of Pgc1α mRNA in BAT. Interestingly, an acute exercise session reduced TGF-β1 expression in the hypothalamus, increased Pgc1α mRNA in the BAT and reduced food consumption in obese mice. Our results demonstrated that acute physical exercise suppressed hypothalamic TGF-β1 expression, increasing Pgc1α mRNA in BAT in obese mice.

CD1 is involved in diet-induced hypothalamic inflammation in obesity

Obesity-associated hypothalamic inflammation plays an important role in the development of defective neuronal control of whole body energy balance. Because dietary fats are the main triggers of hypothalamic inflammation, we hypothesized that CD1, a lipid-presenting protein, may be involved in the hypothalamic inflammatory response in obesity. Here, we show that early after the introduction of a high-fat diet, CD1 expressing cells gradually appear in the mediobasal hypothalamus. The inhibition of hypothalamic CD1 reduces diet-induced hypothalamic inflammation and rescues the obese and glucose-intolerance phenotype of mice fed a high-fat diet. Conversely, the chemical activation of hypothalamic CD1 further increases diet-induced obesity and hypothalamic inflammation. A bioinformatics analysis revealed that hypothalamic CD1 correlates with transcripts encoding for proteins known to be involved in diet-induced hypothalamic abnormalities in obesity. Thus, CD1 is involved in at least part of the hypothalamic inflammatory response in diet-induced obesity and its modulation affects the body mass phenotype of mice.

Excessive treadmill training enhances the insulin signaling pathway and glycogen deposition in mice hearts

Exhaustive and chronic physical exercise leads to peripheral inflammation, which is one of the molecular mechanisms responsible for the impairment of the insulin signaling pathway in the heart. Recently, 3 different running overtraining models performed downhill (OTR/down), uphill (OTR/up), and without inclination (OTR) increased the serum levels of proinflammatory cytokines. This proinflammatory status induced insulin signaling impairment in the skeletal muscle; however, the response of this signaling pathway in the cardiac muscle of overtrained mice was still unknown. Thus, we investigated the effects of OTR/down, OTR/up, and OTR protocols on the protein levels of phosphorylation of insulin receptor β (pIRβ) (Tyr), phosphorylation of protein kinase B (pAkt) (Ser473), plasma membrane glucose transporter-1 (GLUT1) and GLUT4, phosphorylation of insulin receptor substrate-1 (pIRS-1) (Ser307), phosphorylation of IκB kinase α/β) (pIKKα/β (Ser180/181), phosphorylation of p38 mitogen-activated protein kinase (p-p38MAPK) (Thr180/Tyr182), phosphorylation of stress-activated protein kinases-Jun amino-terminal kinases (pSAPK-JNK) (Thr183/Tyr185), and glycogen content in mice hearts. The rodents were divided into naïve (N, sedentary mice), control (CT, sedentary mice submitted to performance evaluations), trained (TR, performed the training protocol), OTR/down, OTR/up, and OTR groups. After the grip force test, the cardiac muscles (ie, left ventricle) were removed and used for immunoblotting and histology. Although the OTR/up and OTR groups exhibited higher cardiac levels of pIRβ (Tyr), only the OTR group exhibited higher cardiac levels of pAkt (Ser473) and plasma membrane GLUT4. On the contrary, the OTR/down group exhibited higher cardiac levels of pIRS-1 (Ser307). The OTR model enhanced the cardiac insulin signaling pathway. All overtraining models increased the left ventricle glycogen content, with this probably acting as a compensatory organ in response to skeletal muscle insulin signaling impairment.

Exhaustive acute exercise-induced ER stress is attenuated in IL-6-knockout mice

The endoplasmic reticulum (ER) stress and inflammation relationship occurs at different levels and is essential for the adequate homeostatic function of cellular systems, becoming harmful when chronically engaged. Intense physical exercise enhances serum levels of interleukin 6 (IL-6). In response to a chronic exhaustive physical exercise protocol, our research group verified an increase of the IL-6 concentration and ER stress proteins in extensor digitorium longus (EDL) and soleus. Based on these results, we hypothesized that IL-6-knockout mice would demonstrate a lower modulation in the ER stress proteins compared to the wild-type mice. To clarify the relationship between exercise-induced IL-6 increased and ER stress, we studied the effects of an acute exhaustive physical exercise protocol on the levels of ER stress proteins in the skeletal muscles of IL-6-knockout (KO) mice. The WT group displayed a higher exhaustion time compared to the IL-6 KO group. After 1 h of the acute exercise protocol, the serum levels of IL-6 and IL-10 were enhanced in the WT group. Independent of the experimental group, the CHOP and cleaved caspase 12/total caspase 12 ratio in EDL as well as ATF6 and CHOP in soleus were sensitive to the acute exercise protocol. Compared to the WT group, the oscillation patterns over time of BiP in EDL and soleus as well as of peIF2-alpha/eIF2-alpha ratio in soleus were attenuated for the IL-6 KO group. In conclusion, IL-6 seems to be related with the ER stress homeostasis, once knockout mice presented attenuation of BiP in EDL and soleus as well as of pEiF2-alpha/EiF2-alpha ratio in soleus after the acute exhaustive physical exercise protocol.

The role of sphingosine-1-phosphate in skeletal muscle: Physiology, mechanisms, and clinical perspectives

Sphingolipids were discovered more than a century ago and were simply considered as a class of cell membrane lipids for a long time. However, after the discovery of several intracellular functions and their role in the control of many physiological and pathophysiological conditions, these molecules have gained much attention. For instance, the sphingosine-1-phosphate (S1P) is a circulating bioactive sphingolipid capable of triggering strong intracellular reactions through the family of S1P receptors (S1PRs) spread in several cell types and tissues. Recently, the role of S1P in the control of skeletal muscle metabolism, atrophy, regeneration, and metabolic disorders has been widely investigated. In this review, we summarized the knowledge of S1P and its effects in skeletal muscle metabolism, highlighting the role of S1P/S1PRs axis in skeletal muscle regeneration, fatigue, ceramide accumulation, and insulin resistance. Finally, we discussed the physical exercise role in S1P/S1PRs signaling in skeletal muscle cells, and how this nonpharmacological strategy may be prospective for future investigations due to its ability to increase S1P levels.

Abnormal brown adipose tissue mitochondrial structure and function in IL10 deficiency

Background

Inflammation is the most relevant mechanism linking obesity with insulin-resistance and metabolic disease. It impacts the structure and function of tissues and organs involved in metabolism, such as the liver, pancreatic islets and the hypothalamus. Brown adipose tissue has emerged as an important component of whole body energy homeostasis, controlling caloric expenditure through the regulation of non-shivering thermogenesis. However, little is known about the impact of systemic inflammation on the structure and function of brown adipose tissue.

Methods

The relations between IL10 and mitochondria structure/function and also with thermogenesis were evaluated by bioinformatics using human and rodent data. Real-time PCR, immunoblot, fluorescence and transmission electron microscopy were employed to determine the effect of IL10 in the brown adipose tissue of wild type and IL10 knockout mice.

Findings

IL10 knockout mice, a model of systemic inflammation, present severe structural abnormalities of brown adipose tissue mitochondria, which are round-shaped with loss of cristae structure and increased fragmentation. IL10 deficiency leads to newborn cold intolerance and impaired UCP1-dependent brown adipose tissue mitochondrial respiration. The reduction of systemic inflammation with an anti-TNFα monoclonal antibody partially rescued the structural but not the functional abnormalities of brown adipose tissue mitochondria. Using bioinformatics analyses we show that in both humans and mice, IL10 transcripts correlate with mitochondrial lipid metabolism and caspase gene expression.

Interpretation

IL10 and systemic inflammation play a central role in the regulation of brown adipose tissue by controlling mitochondrial structure and function.

Fund

Sao Paulo Research Foundation grant 2013/07607-8.

Downregulation of HIF complex in the hypothalamus exacerbates diet-induced obesity

Hypothalamic hypoxia-inducible factor-1 (HIF-1) can regulate whole-body energy homeostasis in response to changes in blood glucose, suggesting that it acts as a sensor for systemic energy stores. Here, we hypothesized that hypothalamic HIF-1 could be affected by diet-induced obesity (DIO). We used eight-week old, male C57Bl6 mice, fed normal chow diet or with high fat diet for 1, 3, 7, 14 and 28 days. The expression of HIF-1alpha and HIF-1beta was measured by PCR and western blotting and its hypothalamic distribution was evaluated by fluorescence microscopy. Inhibition of HIF-1beta in arcuate nucleus of hypothalamus was performed using stereotaxic injection of shRNA lentiviral particles and animals were grouped under normal chow diet or high fat diet for 14 days. Using bioinformatics, we show that in humans, the levels of HIF-1 transcripts are directly correlated with those of hypothalamic transcripts for proteins involved in inflammation, regulation of apoptosis, autophagy, and the ubiquitin/proteasome system; furthermore, in rodents, hypothalamic HIF-1 expression is directly correlated with the phenotype of increased energy expenditure. In mice, DIO was accompanied by increased HIF-1 expression. The inhibition of hypothalamic HIF-1 by injection of an shRNA resulted in a further increase in body mass, a decreased basal metabolic rate, increased hypothalamic inflammation, and glucose intolerance. Thus, hypothalamic HIF-1 is increased during DIO, and its inhibition worsens the obesity-associated metabolic phenotype. Thus, hypothalamic HIF-1 emerges as a target for therapeutic intervention against obesity.

Excessive training induces molecular signs of pathologic cardiac hypertrophy

Chronic exercise induces cardiac remodeling that promotes left ventricular hypertrophy and cardiac functional improvement, which are mediated by the mammalian or the mechanistic target of rapamycin (mTOR) as well as by the androgen and glucocorticoid receptors (GRs). However, pathological conditions (i.e., chronic heart failure, hypertension, and aortic stenosis, etc.) also induce cardiac hypertrophy, but with detrimental function, high levels of proinflammatory cytokines and myostatin, elevated fibrosis, reduced adenosine monophosphate-activated protein kinase (AMPK) activation, and fetal gene reactivation. Furthermore, recent studies have evidenced that excessive training induced an inflammatory status in the serum, muscle, hypothalamus, and liver, suggesting a pathological condition that could also be detrimental to cardiac tissue. Here, we verified the effects of three running overtraining (OT) models on the molecular parameters related to physiological and pathological cardiac hypertrophy. C57BL/6 mice performed three different OT protocols and were evaluated for molecular parameters related to physiological and pathological cardiac hypertrophy, including immunoblotting, reverse transcription polymerase chain reaction, histology, and immunohistochemistry analyses. In summary, the three OT protocols induced left ventricle (LV) hypertrophy with signs of cardiac fibrosis and negative morphological adaptations. These maladaptations were accompanied by reductions in AMPKalpha (Thr172) phosphorylation, androgen receptor, and GR expressions, as well as by an increase in interleukin-6 expression. Specifically, the downhill running-based OT model reduced the content of some proteins related to the mTOR signaling pathway and upregulated the β-isoform of myosin heavy-chain gene expression, presenting signs of LV pathological hypertrophy development.

The Role of Physical Exercise to Improve the Browning of White Adipose Tissue via POMC Neurons

Obesity is a public health issue that affects more than 600 million adults worldwide. The disease is characterized by fat accumulation, mainly in the abdominal area. The human body is mainly composed of two types of adipose tissue: white adipose tissue (WAT) and brown adipose tissue (BAT); however, the browning process generates a different type of brown fat-like adipocyte in WAT, which similar to BAT has thermogenic capacity by activating UCP-1. The hypothalamic arcuate nucleus plays an important role in WAT browning via POMC neurons, which are influenced by synergistic insulin and leptin signaling. On the other hand, stimulation of AgRP neurons suppresses WAT browning. The hypothalamic inflammatory process that occurs in obesity impairs insulin and leptin signaling in this tissue and, consequently, can decrease WAT browning. In addition, practicing physical exercise may be a great strategy for triggering the browning process since it reduces hypothalamic inflammation and increases POMC neurons gene expression. Moreover, physical exercise stimulates irisin gene expression, which has an important impact on thermogenesis, which in turn culminates in increased gene expression of proteins such as UCP-1 and Cidea, which are related to WAT browning. Furthermore, thermogenetic activation of WAT leads to increased energy expenditure, favoring obesity treatment. Therefore, this mini-review aimed to highlight the most recent studies that link the control of hypothalamic activity with the browning metabolism of adipose tissue in response to physical exercise.

Exercise decreases CLK2 in the liver of obese mice and prevents hepatic fat accumulation

The accumulation of fatty acids in the liver associated with obesity condition is also known as nonalcoholic fatty liver disease (NAFLD). The impaired fat oxidation in obesity condition leads to increased hepatic fat accumulation and increased metabolic syndrome risk. On the other hand, physical exercise has been demonstrated as a potent strategy in the prevention of NAFLD. Also, these beneficial effects of exercise occur through different mechanisms. Recently, the Cdc2-like kinase (CLK2) protein was associated with the suppression of fatty acid oxidation and hepatic ketogenesis. Thus, obese animals demonstrated elevated levels of hepatic CLK2 and decreased fat acid oxidation. Here, we explored the effects of chronic physical exercise in the hepatic metabolism of obese mice. Swiss mice were distributed in Lean, Obese (fed with high-fat diet during 16 weeks) and Trained Obese group (fed with high-fat diet during 16 weeks and exercised (at 60% exhaustion velocity during 1 h/5 days/week) during 8 weeks. In our results, the obese animals showed insulin resistance, increased hepatic CLK2 content and increased hepatic fat accumulation compared to the Lean group. Otherwise, the chronic physical exercise improved insulin resistance state, prevented the increased CLK2 in the liver and attenuated hepatic fat accumulation. In summary, these data reveal a new protein involved in the prevention of hepatic fat accumulation after chronic physical exercise. More studies can evidence the negative role of CLK2 in the control of liver metabolism, contributing to the improvement of insulin resistance, obesity, and type 2 diabetes.

NAD+ repletion improves muscle function in muscular dystrophy and counters global PARylation

Neuromuscular diseases are often caused by inherited mutations that lead to progressive skeletal muscle weakness and degeneration. In diverse populations of normal healthy mice, we observed correlations between the abundance of mRNA transcripts related to mitochondrial biogenesis, the dystrophin-sarcoglycan complex, and nicotinamide adenine dinucleotide (NAD⁺) synthesis, consistent with a potential role for the essential cofactor NAD⁺ in protecting muscle from metabolic and structural degeneration. Furthermore, the skeletal muscle transcriptomes of patients with Duchene's muscular dystrophy (DMD) and other muscle diseases were enriched for various poly[adenosine 5'-diphosphate (ADP)-ribose] polymerases (PARPs) and for nicotinamide N-methyltransferase (NNMT), enzymes that are major consumers of NAD⁺ and are involved in pleiotropic events, including inflammation. In the mdx mouse model of DMD, we observed significant reductions in muscle NAD⁺ levels, concurrent increases in PARP activity, and reduced expression of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme for NAD⁺ biosynthesis. Replenishing NAD⁺ stores with dietary nicotinamide riboside supplementation improved muscle function and heart pathology in mdx and mdx/Utr^-/- mice and reversed pathology in Caenorhabditis elegans models of DMD. The effects of NAD⁺ repletion in mdx mice relied on the improvement in mitochondrial function and structural protein expression (α-dystrobrevin and δ-sarcoglycan) and on the reductions in general poly(ADP)-ribosylation, inflammation, and fibrosis. In combination, these studies suggest that the replenishment of NAD⁺ may benefit patients with muscular dystrophies or other neuromuscular degenerative conditions characterized by the PARP/NNMT gene expression signatures.

Treadmill Slope Modulates Inflammation, Fiber Type Composition, Androgen, and Glucocorticoid Receptors in the Skeletal Muscle of Overtrained Mice

Overtraining (OT) may be defined as an imbalance between excessive training and adequate recovery period. Recently, a downhill running-based overtraining (OTR/down) protocol induced the nonfunctional overreaching state, which is defined as a performance decrement that may be associated with psychological and hormonal disruptions and promoted intramuscular and systemic inflammation. To discriminate the eccentric contraction effects on interleukin 1beta (IL-1β), IL-6, IL-10, IL-15, and SOCS-3, we compared the release of these cytokines in OTR/down with other two OT protocols with the same external load (i.e., the product between training intensity and volume), but performed in uphill (OTR/up) and without inclination (OTR). Also, we evaluated the effects of these OT models on the muscle morphology and fiber type composition, serum levels of fatigue markers and corticosterone, as well as androgen receptor (AR) and glucocorticoid receptor (GR) expressions. For extensor digitorum longus (EDL), OTR/down and OTR groups increased the cytokines and exhibited micro-injuries with polymorphonuclear infiltration. While OTR/down group increased the cytokines in soleus muscle, OTR/up group only increased IL-6. All OT groups presented micro-injuries with polymorphonuclear infiltration. In serum, while OTR/down and OTR/up protocols increased IL-1β, IL-6, and tumor necrosis factor alpha, OTR group increased IL-1β, IL-6, IL-15, and corticosterone. The type II fibers in EDL and soleus, total and phosphorylated AR levels in soleus, and total GR levels in EDL and soleus were differentially modulated by the OT protocols. In summary, the proinflammatory cytokines were more sensitive for OTR/down than for OTR/up and OTR. Also, the specific treadmill inclination of each OT model influenced most of the other evaluated parameters.

Obesity Increases Mitogen-Activated Protein Kinase Phosphatase-3 Levels in the Hypothalamus of Mice

Mitogen-activated Protein Kinase Phosphatase 3 (MKP-3) has been involved in the negative regulation of insulin signaling. The absence of MKP-3 is also associated with reduced adiposity, increased energy expenditure and improved insulin sensitivity. The MKP-3 is known as the main Erk1/2 phosphatase and FoxO1 activator, which has repercussions on the gluconeogenesis pathway and hyperglycemia in obese mice. Recently, we showed that MKP-3 overexpression decreases FoxO1 phosphorylation in the hypothalamus of lean mice. However, the hypothalamic interaction between MKP-3 and FoxO1 during obesity was not investigated yet. Here, the MKP-3 expression and the effects on food intake and energy expenditure, were investigated in high-fat diet-induced obese mice. The results indicate that obesity in mice increased the MKP-3 protein content in the hypothalamus. This hypothalamic upregulation led to an increase of food intake, adiposity, and body weight. Furthermore, the obese mice with increased MKP-3 showed an insulin signaling impairment with reduction of insulin-induced FoxO1 and Erk1/2 phosphorylation in the hypothalamus. Moreover, a bioinformatics analysis of data demonstrated that hypothalamic MKP-3 mRNA levels were positively correlated with body weight and negatively correlated to oxygen consumption (VO₂) in BXD mice. Taken together, our study reports that obesity is associated with increased protein levels of hypothalamic MKP-3, which is related to the reduction of FoxO1 and Erk1/2 phosphorylation in the hypothalamus as well as to an increase in body weight and a reduction in energy expenditure.

Retraction notice to "Obesity-Induced Increase in Tumor Necrosis Factor-α Leads to Development of Colon Cancer in Mice" Gastroenterology 2012;143:741-753.e4

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief and Deputy Editor-in-Chief following an investigation into the data that were presented in several figures within the article. A number of images used in this article are believed to be duplicated images. The authors stated that they inadvertently inserted images of the wrong blots in several of the figures, resulting in the duplications; however, they did not address all of the concerns raised. Because the editors were no longer confident in the conclusions of the article based on these incorrect data, a decision was made to retract the paper. All authors have been notified of this decision. The University of Campinas (UNICAMP) in São Paulo, Brazil was contacted regarding these concerns, but to date the journal has received no response.