Exercise intensity, inflammatory signaling, and insulin resistance in obese rats

2,4-dichlorophenoxyacetic acid (2,4-D) exposure during postnatal development alters the effects of western diet on mouse prostate

Western diet (WD), abundant in saturated fats and simple carbohydrates, has been associated with the development of prostate diseases. In addition, 2,4-dichlorophenoxyacetic acid (2,4-D), an herbicide used in agricultural and non-agricultural settings, may interfere with the endocrine system impacting reproductive health. The association of both factors is something common in everyday life, however, there are no relevant studies associating them as possible modulators of prostatic diseases. This study evaluated the action of the herbicide 2,4-D on the postnatal development of the prostate in mice fed with WD. Male C57Bl/6J mice received simultaneously a WD and 2,4-D at doses of 0.02, 2.0, or 20.0 mg/kg b.w./day for 6 months. The prolongated WD intake induced obesity and glucose intolerance, increasing body weight and fat. WD induced morphological changes and increased PCNA-positive epithelial cells in prostate. Additionally, the WD increased gene expression of AR, antioxidant targets, inflammation-related cytokines, cell repair and turnover, and targets related to methylation and miRNAs biosynthesis compared to the counterpart (basal diet). 2,4-D (0.02 and 2.0) changed prostate morphology and gene expression evoked by WD. In contrast, the WD group exposed to 20 mg/kg of 2,4-D reduced feed intake and body weight, and increased expression of androgen receptor and genes related to cell repair and DNA methylation compared to the negative control. Our results showed that 2,4-D was able to modulate the effects caused by WD, mainly at lower doses. However, further studies are needed to elucidate the mechanisms of 2,4-D on the obesogenic environment caused by the WD.

The Early Impact of Diets Enriched with Saturated and Unsaturated Fatty Acids on Intestinal Inflammation and Tight Junctions

The gut has been suggested as the first organ to be affected by unbalanced diets contributing to the obesogenic process. This study aimed to test a short time-course exposition model to a known pro- or anti-inflammatory enriched fatty diet to understand the early gut alterations. Male mice were exposed to the chow diet (CT), high-fat (HF) diet, or a high-fat diet partially replaced on flaxseed oil (FS), rich in omega-3 (ω3), for 14 days. HF and FS increased the total body weight mass compared with the CT group, but FS reduced the epididymal fat depot compared to HF. The bioinformatics from mice and human databases showed the Zo1-Ocln-Cldn7 tight junctions as the main protein-triad. In the ileum, the HF diet has increased IL1β transcript and IL1β, TNFα, and CD11b proteins, but reduced the tight junctions (Zo1, Ocln, and Cld7) compared to the CT group. Despite the FS diet being partially efficient in protecting the ileum against inflammation, the tight junctions were increased, compared to the HF group. The GPR120 and GPR40 receptors were unaffected by diets, but GPR120 was co-localized on the surface of ileum macrophages. The short period of a high-fat diet was enough to start the obesogenic process, ileum inflammation, and reduce the tight junctions. Flaxseed oil did not protect efficiently against dysmetabolism. Still, it increased the tight junctions, even without alteration on inflammatory parameters, suggesting the protection against gut permeability during early obesity development.

High-fat, high-sucrose, and combined high-fat/high-sucrose diets effects in oxidative stress and inflammation in male rats under presence or absence of obesity

The study examines the influence of three types of hypercaloric diets on metabolic parameters, inflammatory markers, and oxidative stress in experimental model. Male Wistar rats (n = 40) were randomized in control (C), high-sucrose (HS), high-fat (HF), and high-fat with sucrose (HFHS) for 20 weeks. Nutritional, metabolic, hormonal, and biochemical profiles, as well as histological analysis of adipose and hepatic tissues were performed. Inflammation and oxidative stress were determined. HF model caused obesity and comorbidities as glucose intolerance and arterial hypertension. In relation to hormonal and biochemical parameters, there was no significant difference between the groups. All groups showed increased deposition of fat droplets in the hepatic tissue, even though adipocyte areas were similar. Biomarkers of oxidative stress in serum and adipose tissues were similar among the groups. HF model was effective in triggering associated obesity and comorbidities in male rats, but all hypercaloric diets were unable to promote oxidative stress and inflammation.

A Survey of Pennsylvania Horse Management: Part Two - Exercise

Understanding the frequency, duration, and intensity of exercise is important for determining the optimal diet and management of horses. The objective of the study was to characterize the exercise management of horses in Pennsylvania. An online survey was distributed from February 27th to August 31st, 2020. Respondents were asked to place their horse in an exercise category, as well as report on frequency and duration of exercise and time spent at each gait. Nonparametric statistics (mdn=median) and tests were used when data were not normally distributed. Of the 470 horses, 68% were regularly exercised. The exercised horses were classified as 49% (135/275) in light, 41% (113/275) in moderate, and 12% (32/275) in heavy/very heavy exercise. Of those exercised, 43% (120/278) were ridden recreationally (not used for competition). The median minutes per week spent exercising was 180 minutes (IQR=183). The average number of exercise sessions per week was 3.6 ± 2.2. Horses in heavy/very heavy (mdn=220 min, IQR=272) and moderate exercise (mdn=180 min, IQR=180) spent more minutes exercising per week compared to light exercise (mdn=120 minute, IQR=180; P< .05). Total number of exercise sessions completed per week differed between horses in light (mdn=2 sessions, IQR=3), moderate (mdn=4 sessions, IQR=2), and heavy/very heavy exercise (mdn=6 sessions, IQR=2; P < .05). Horses were exercised for a similar duration and frequency per week compared to previous studies. Some challenges exist for placing horses in NRC exercise categories based on self-reports only.

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.

Effect of two hypercaloric diets on the hormonal and metabolic profile of the adrenal gland

OBJECTIVES

Who disrupts who? It is not clear what the interaction is between a high calorie diet (HCD) and adrenal axis activation in obesity. The goal was to assess the effect of two hypercaloric diets commercialized in Algeria on the hormonal and metabolic profile of the adrenal gland in rabbits.

METHODS

Two classes of local male adult rabbits (n=16) and a finishing diet (FD) as a control for 15 weeks.

RESULTS

It has been shown that HCD-received animals have developed visceral obesity, dyslipidemia and insulin resistance IR by dramatically increasing body weight, visceral fat tissue and adrenal weight, combined with elevated plasma levels of ACTH, cortisol, leptin and insulin. The HCD diet increased the levels of cortisol in the visceral adipose tissue (VAT), in peri-adrenal adipose tissue (PAAT), and decreased cortisol levels in the liver. HCD also causes the process of inflammatory fibrosis associated with the migration and spread of chromaffin cells in the adrenal gland.

CONCLUSIONS

This study gives new insights into how diet-induced obesity studied on local rabbits affects the biology of the adrenal gland. The correlation of these changes with paracrine connections between the chromaffin cell and glomerulosa indicates potential therapeutic methods for obese-related steroid hormone dysfunction.

Impact of Different Physical Exercises on the Expression of Autophagy Markers in Mice

Although physical exercise-induced autophagy activation has been considered a therapeutic target to enhance tissue health and extend lifespan, the effects of different exercise models on autophagy in specific metabolic tissues are not completely understood. This descriptive investigation compared the acute effects of endurance (END), exhaustive (ET), strength (ST), and concurrent (CC) physical exercise protocols on markers of autophagy, genes, and proteins in the gastrocnemius muscle, heart, and liver of mice. The animals were euthanized immediately (0 h) and six hours (6 h) after the acute exercise for the measurement of glycogen levels, mRNA expression of Prkaa1, Ppargc1a, Mtor, Ulk1, Becn1, Atg5, Map1lc3b, Sqstm1, and protein levels of Beclin 1 and ATG5. The markers of autophagy were measured by quantifying the protein levels of LC3II and Sqstm1/p62 in response to three consecutive days of intraperitoneal injections of colchicine. In summary, for gastrocnemius muscle samples, the main alterations in mRNA expressions were observed after 6 h and for the ST group, and the markers of autophagy for the CC group were increased (i.e., LC3II and Sqstm1/p62). In the heart, the Beclin 1 and ATG5 levels were downregulated for the ET group. Regarding the markers of autophagy, the Sqstm1/p62 in the heart tissue was upregulated for the END and ST groups, highlighting the beneficial effects of these exercise models. The liver protein levels of ATG5 were downregulated for the ET group. After the colchicine treatment, the liver protein levels of Sqstm1/p62 were decreased for the END and ET groups compared to the CT, ST, and CC groups. These results could be related to diabetes and obesity development or liver dysfunction improvement, demanding further investigations.

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.

The Influence of Physical Activity on the Bioactive Lipids Metabolism in Obesity-Induced Muscle Insulin Resistance

High-fat diet consumption and lack of physical activity are important risk factors for metabolic disorders such as insulin resistance and cardiovascular diseases. Insulin resistance is a state of a weakened response of tissues such as skeletal muscle, adipose tissue, and liver to insulin, which causes an increase in blood glucose levels. This condition is the result of inhibition of the intracellular insulin signaling pathway. Skeletal muscle is an important insulin-sensitive tissue that accounts for about 80% of insulin-dependent glucose uptake. Although the exact mechanism by which insulin resistance is induced has not been thoroughly understood, it is known that insulin resistance is most commonly associated with obesity. Therefore, it is believed that lipids may play an important role in inducing insulin resistance. Among lipids, researchers’ attention is mainly focused on biologically active lipids: diacylglycerols (DAG) and ceramides. These lipids are able to regulate the activity of intracellular enzymes, including those involved in insulin signaling. Available data indicate that physical activity affects lipid metabolism and has a positive effect on insulin sensitivity in skeletal muscles. In this review, we have presented the current state of knowledge about the impact of physical activity on insulin resistance and metabolism of biologically active lipids.

Exercise ameliorates insulin resistance and improves SIRT6-mediated insulin signaling transduction in liver of obese rats

Physical exercise is essential for the amelioration of insulin resistance (IR). The mechanisms in charge of improved IR, regulated by exercise, are insufficiently studied. Previous research revealed that Sirtuin 6 (SIRT6) - mediated insulin signaling acts a crucial element in hepatic IR. The objective of our research was to determine the effects of exercise on SIRT6-mediated insulin signaling in liver of IR rats. Forty male Sprague Dawley rats were randomly assigned to four groups (n = 10 rats each): control rats fed with standard chow (Lean group); sedentary rats fed with a high-fat diet (HFD-SED); rats fed with HFD and submitted to 8 week chronic swimming exercise training (HFD-CE); and rats fed HFD and submitted to one acute swimming exercise training (HFD-AE). HFD feeding lead to increased body weight, accumulation of hepatic triglyceride and serum free fatty acids, and enhanced gluconeogenesis. Besides, HFD feeding decreased body insulin sensitivity. Hepatic USP10 and SIRT6 protein levels decreased under obese status. Both chronic and acute exercise intervention alleviated physiological and metabolic status, increased hepatic USP10 and SIRT6 levels, improved insulin signaling transduction, and inhibited gluconeogenesis. These results showed that exercise intervention regulated SIRT6-mediated insulin signaling, which contributes to our understanding of the molecular mechanisms behind IR, in that a regular exercise can mitigate the effects of IR.

Biochemical and Molecular Mechanisms of Glucose Uptake Stimulated by Physical Exercise in Insulin Resistance State: Role of Inflammation

Obesity associated with systemic inflammation induces insulin resistance (IR), with consequent chronic hyperglycemia. A series of reactions are involved in this process, including increased release of proinflammatory cytokines, and activation of c-Jun N-terminal kinase (JNK), nuclear factor-kappa B (NF-κB) and toll-like receptor 4 (TLR4) receptors. Among the therapeutic tools available nowadays, physical exercise (PE) has a known hypoglycemic effect explained by complex molecular mechanisms, including an increase in insulin receptor phosphorylation, in AMP-activated protein kinase (AMPK) activity, in the Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) pathway, with subsequent activation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), Rac1, TBC1 domain family member 1 and 4 (TBC1D1 and TBC1D4), in addition to a variety of signaling molecules, such as GTPases, Rab and soluble N-ethylmaleimide-sensitive factor attached protein receptor (SNARE) proteins. These pathways promote greater translocation of GLUT4 and consequent glucose uptake by the skeletal muscle. Phosphoinositide-dependent kinase (PDK), atypical protein kinase C (aPKC) and some of its isoforms, such as PKC-iota/lambda also seem to play a fundamental role in the transport of glucose. In this sense, the association between autophagy and exercise has also demonstrated a relevant role in the uptake of muscle glucose. Insulin, in turn, uses a phosphoinositide 3-kinase (PI3K)-dependent mechanism, while exercise signal may be triggered by the release of calcium from the sarcoplasmic reticulum. The objective of this review is to describe the main molecular mechanisms of IR and the relationship between PE and glucose uptake.

Towards a personalised approach in exercise-based cardiovascular rehabilitation: How can translational research help? A 'call to action' from the Section on Secondary Prevention and Cardiac Rehabilitation of the European Association of Preventive Cardiology

The benefit of regular physical activity and exercise training for the prevention of cardiovascular and metabolic diseases is undisputed. Many molecular mechanisms mediating exercise effects have been deciphered. Personalised exercise prescription can help patients in achieving their individual greatest benefit from an exercise-based cardiovascular rehabilitation programme. Yet, we still struggle to provide truly personalised exercise prescriptions to our patients. In this position paper, we address novel basic and translational research concepts that can help us understand the principles underlying the inter-individual differences in the response to exercise, and identify early on who would most likely benefit from which exercise intervention. This includes hereditary, non-hereditary and sex-specific concepts. Recent insights have helped us to take on a more holistic view, integrating exercise-mediated molecular mechanisms with those influenced by metabolism and immunity. Unfortunately, while the outline is recognisable, many details are still lacking to turn the understanding of a concept into a roadmap ready to be used in clinical routine. This position paper therefore also investigates perspectives on how the advent of 'big data' and the use of animal models could help unravel inter-individual responses to exercise parameters and thus influence hypothesis-building for translational research in exercise-based cardiovascular rehabilitation.

Muscular resistance, hypertrophy and strength training equally reduce adiposity, inflammation and insulin resistance in mice with diet-induced obesity

Objective

To evaluate the effect of three types of muscular resistance training on adiposity, inflammation levels and insulin activity in Swiss mice with fat-rich diet-induced obesity.

Methods

Lean and obese male Swiss mice were selected and allocated to one of eight groups comprising eight mice each, as follows: standard diet + no training; standard diet + muscular resistance training; standard diet + hypertrophy training; standard diet + strength training; high-fat diet + no training; high-fat diet + muscular resistance training; high-fat diet + hypertrophy training; high-fat diet + strength training. The training protocol consisted of stair climbing for a 10-week period. Blood samples were collected for lactate analysis, glucose level measurement and insulin tolerance test. After euthanasia, adipose tissues were removed and weighed for adiposity index determination. Fragments of epididymal adipose tissue were then embedded for histological analysis or homogenized for tumor necrosis factor alpha level determination using the ELISA method.

Results

Ausency of differences in total training volume and blood lactate levels overall emphasize the similarity between the different resistance training protocols. Body weight loss, reduced adipocyte area and lower adiposity index were observed in trained obese mice, regardless of training modality. Different training protocols also improved insulin sensitivity and reduced inflammation levels.

Conclusion

Resistance training protocols were equally effective in reducing body fat, inflammation levels and insulin resistance in obese mice.

Dynamic, Not Isometric Resistance Training Improves Muscle Inflammation, Oxidative Stress and Hypertrophy in Rats

This study aimed to compare the effects of dynamic (DRT) and isometric (IRT) resistance training on blood glucose, muscle redox capacity, inflammatory state, and muscle strength and hypertrophy. Fifteen 12-week-old male Wistar rats were randomly allocated into three groups: control group (CTL), DRT, and IRT, n = 5 animals per group. The animals were submitted to a maximal weight carried (MWC; every 15 days) and maximum isometric resistance (MIR; pre- and post-training) tests. Both training protocols were performed five times a week during 12 weeks, consisting of one set of eight uninterrupted climbs for 1 min with a 30% overload of MWC. The animals in the IRT group remained under isometry for 1 min. The DRT group experienced greater MWC from pre- to post-training compared to the CTL and IRT groups (p < 0.0001). The DRT and IRT groups displayed similar gains in MIR (p = 0.3658). The DRT group exhibited improved glycemic homeostasis (p = 0.0111), redox (p < 0.0001), and inflammatory (p < 0.0001) balance as compared with CTL and IRT groups. In addition, the improved glycemic profile was associated with an increase in muscle strength and hypertrophy, improvement in redox balance and inflammation status. We conclude that DRT was more effective than IRT on increasing cross-sectional area, but not muscle strength, in parallel to improved blood glucose, inflammatory status, and redox balance.

Modelos animais na síndrome metabólica

RESUMO O conhecimento sobre modelos animais para estudo metabólico representa a base da pesquisa nessa área. Este trabalho tem por objetivo revisar os principais modelos animais a serem utilizados no estudo da obesidade e da síndrome metabólica. Para isso, pesquisa no banco de dados Pubmed foi realizada usando as palavras-chave “animal models”, “obesity”, "metabolic syndrome”, e “bariatric surgery”. Várias espécies de animais podem ser usadas para o estudo de distúrbios metabólicos, no entanto, os roedores, tanto modelos monogênicos quanto modelos de obesidade induzida por dieta (DIO), são os animais mais utilizados nessa área. Animais monogênicos são a melhor escolha se apenas um aspecto estiver sendo avaliado. Animais DIO tendem a demonstrar melhor a interação entre doença, ambiente e gene. No entanto, eles ainda não são totalmente eficazes para a compreensão de todos os mecanismos dessa doença.

Physical training reverses changes in hepatic mitochondrial diameter of Alloxan-induced diabetic rats

OBJECTIVE

To investigate the effects of physical training on metabolic and morphological parameters of diabetic rats.

METHODS

Wistar rats were randomized into four groups: sedentary control, trained control, sedentary diabetic and trained diabetic. Diabetes mellitus was induced by Alloxan (35mg/kg) administration for sedentary diabetic and Trained Diabetic Groups. The exercise protocol consisted of swimming with a load of 2.5% of body weight for 60 minutes per day (5 days per week) for the trained control and Trained Diabetic Groups, during 6 weeks. At the end of the experiment, the rats were sacrificed and blood was collected for determinations of serum glucose, insulin, albumin and total protein. Liver samples were extracted for measurements of glycogen, protein, DNA and mitochondrial diameter determination.

RESULTS

The sedentary diabetic animals presented decreased body weight, blood insulin, and hepatic glycogen, as well as increased glycemia and mitochondrial diameter. The physical training protocol in diabetic animals was efficient to recovery body weight and liver glycogen, and to decrease the hepatic mitochondrial diameter.

CONCLUSION

Physical training ameliorated hepatic metabolism and promoted important morphologic adaptations as mitochondrial diameter in liver of the diabetic rats.

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.

Excessive training impairs the insulin signal transduction in mice skeletal muscles

The main aim of this investigation was to verify the effects of overtraining (OT) on the insulin and inflammatory signaling pathways in mice skeletal muscles. Rodents were divided into control (CT), overtrained by downhill running (OTR/down), overtrained by uphill running (OTR/up), and overtrained by running without inclination (OTR) groups. Rotarod, incremental load, exhaustive, and grip force tests were used to evaluate performance. Thirty-six hours after the grip force test, the extensor digitorum longus (EDL) and soleus were extracted for subsequent protein analyses. The three OT protocols led to similar responses of all performance evaluation tests. The phosphorylation of insulin receptor beta (pIRβ; Tyr), protein kinase B (pAkt; Ser473), and the protein levels of plasma membrane glucose transporter-4 (GLUT4) were lower in the EDL and soleus after the OTR/down protocol and in the soleus after the OTR/up and OTR protocols. While the pIRβ was lower after the OTR/up and OTR protocols, the pAkt was higher after the OTR/up in the EDL. The phosphorylation of IκB kinase alpha and beta (pIKKα/β; Ser180/181), stress-activated protein kinases/Jun amino-terminal kinases (pSAPK-JNK; Thr183/Tyr185), factor nuclear kappa B (pNFκB p65; Ser536), and insulin receptor substrate 1 (pIRS1; Ser307) were higher after the OTR/down protocol, but were not altered after the two other OT protocols. In summary, these data suggest that OT may lead to skeletal muscle insulin signaling pathway impairment, regardless of the predominance of eccentric contractions, although the insulin signal pathway impairment induced in OTR/up and OTR appeared to be muscle fiber-type specific.

Eccentric exercise leads to performance decrease and insulin signaling impairment

PURPOSE

This study aimed to evaluate the effects of an overtraining (OT) protocol based on eccentric exercise (EE) sessions on the insulin and inflammatory signaling pathways in the skeletal muscles of Swiss mice.

METHODS

Rodents were divided into control (C; sedentary mice), trained (TR; performed the aerobic training protocol), and overtrained (OTR; performed the OT protocol). The incremental load test and exhaustive test were used to measure performances before and after exercise protocols. Twenty-four hours after the exhaustive test performed at the end of week 8, the extensor digitorum longus (EDL) and soleus muscles were removed for subsequent protein analysis by immunoblotting.

RESULTS

The phosphorylation of insulin receptor beta (pIRbeta; Tyr1146) diminished for EDL and soleus muscles in OTR compared with C. The phosphorylation of insulin receptor substrate 1 (pIRS-1; Ser307) increased for EDL and soleus muscles in OTR compared with C and TR. The phosphorylation of protein kinase B (pAkt; Ser473) diminished for EDL and soleus muscles in OTR compared with C and TR. The phosphorylation of IκB kinase alpha and beta (pIKKalpha/beta; Ser176/180), stress-activated protein kinases/Jun amino-terminal kinases (pSAPK/JNK; Thr183/Tyr185), and the protein levels of suppressor of cytokine signaling 3 (SOCS3) increased for EDL and soleus muscles in OTR compared with C and TR.

CONCLUSION

In summary, the current used OT protocol based on eccentric exercise sessions impaired the insulin signaling pathway with concomitant increases of IKK, SAPK/JNK, and SOCS3 protein levels.

Regulation of hepatic TRB3/Akt interaction induced by physical exercise and its effect on the hepatic glucose production in an insulin resistance state

To maintain euglycemia in healthy organisms, hepatic glucose production is increased during fasting and decreased during the postprandial period. This whole process is supported by insulin levels. These responses are associated with the insulin signaling pathway and the reduction in the activity of key gluconeogenic enzymes, resulting in a decrease of hepatic glucose production. On the other hand, defects in the liver insulin signaling pathway might promote inadequate suppression of gluconeogenesis, leading to hyperglycemia during fasting and after meals. The hepatocyte nuclear factor 4, the transcription cofactor PGC1-α, and the transcription factor Foxo1 have fundamental roles in regulating gluconeogenesis. The loss of insulin action is associated with the production of pro-inflammatory biomolecules in obesity conditions. Among the molecular mechanisms involved, we emphasize in this review the participation of TRB3 protein (a mammalian homolog of Drosophila tribbles), which is able to inhibit Akt activity and, thereby, maintain Foxo1 activity in the nucleus of hepatocytes, inducing hyperglycemia. In contrast, physical exercise has been shown as an important tool to reduce insulin resistance in the liver by reducing the inflammatory process, including the inhibition of TRB3 and, therefore, suppressing gluconeogenesis. The understanding of these new mechanisms by which physical exercise regulates glucose homeostasis has critical importance for the understanding and prevention of diabetes.

Effects of different intensities of physical exercise on insulin sensitivity and protein kinase B/Akt activity in skeletal muscle of obese mice

Objective:

To investigate the effects of different intensities of acute exercise on insulin sensitivity and protein kinase B/Akt activity in skeletal muscle of obese mice.

Methods:

Swiss mice were randomly divided into four groups, and fed either a standard diet (control group) or high fat diet (obese sedentary group and obese exercise group 1 and 2) for 12 weeks. Two different exercise protocols were used: swimming for 1 hour with or without an overload of 5% body weight. The insulin tolerance test was performed to estimate whole-body sensitivity. Western blot technique was used to determine protein levels of protein kinase B/Akt and phosphorylation by protein Kinase B/Akt in mice skeletal muscle.

Results:

A single bout of exercise inhibited the high fat diet-induced insulin resistance. There was increase in phosphorylation by protein kinase B/Akt serine, improve in insulin signaling and reduce of fasting glucose in mice that swam for 1 hour without overload and mice that swan for 1 hour with overload of 5%. However, no significant differences were seen between exercised groups.

Conclusion:

Regardless of intensity, aerobic exercise was able to improve insulin sensitivity and phosphorylation by protein kinase B/Ak, and proved to be a good form of treatment and prevention of type 2 diabetes.

Mechanisms behind the superior effects of interval vs continuous training on glycaemic control in individuals with type 2 diabetes: a randomised controlled trial

AIMS/HYPOTHESIS

By use of a parallel and partly crossover randomised, controlled trial design we sought to elucidate the underlying mechanisms behind the advantageous effects of interval walking training (IWT) compared with continuous walking training (CWT) on glycaemic control in individuals with type 2 diabetes. We hypothesised that IWT, more than CWT, would improve insulin sensitivity including skeletal muscle insulin signalling, insulin secretion and disposition index (DI).

METHODS

By simple randomisation (sequentially numbered, opaque sealed envelopes), eligible individuals (diagnosed with type 2 diabetes, no exogenous insulin treatment) were allocated to three groups: a control group (CON, n = 8), an IWT group (n = 12) and an energy expenditure-matched CWT group (n = 12). Training groups were prescribed free-living training, five sessions per week (60 min/session). A three-stage hyperglycaemic clamp, including glucose isotope tracers and skeletal muscle biopsies, was performed before and after a 4 month intervention in a hospitalised setting. No blinding was performed.

RESULTS

The improved glycaemic control, which was only seen in the IWT group, was consistent with IWT-induced increases in insulin sensitivity index (49.8 ± 14.6%; p < 0.001), peripheral glucose disposal (14.5 ± 4.9%; p < 0.05) and DI (66.2 ± 21.8%; p < 0.001), with no changes in the CWT or CON group. Moreover, only IWT improved insulin signalling in skeletal muscle via increased insulin-stimulated phosphorylation of AS160 (29.0 ± 10.8%; p < 0.05). No changes were seen in insulin secretion during hyperglycaemia alone, hyperglycaemia + glucagon-like peptide 1 infusion or arginine injection.

CONCLUSIONS/INTERPRETATION

IWT maintains insulin secretion and improves insulin sensitivity and DI, in contrast to energy expenditure-matched CWT. These results suggest that training with alternating intensity, and not just training volume and mean intensity, is a key determinant of changes in whole body glucose disposal in individuals with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials (NCT01234155).

Calmodulin dependent protein kinase II activation by exercise regulates saturated & unsaturated fatty acids and improves some metabolic syndrome markers

AIMS

Activation of Calmodulin dependent protein kinase (CaMK)-II by exercise has a plethora of benefits in health. Fatty acids play a pivotal role in the pathogenesis of metabolic syndrome (MetS). Prevention of MetS and treatment of its main characteristics are very significant to fight against type 2 diabetes. CaMKII activation in the regulation of saturated and unsaturated fatty acids in relation to type 2 diabetes and MetS has not been studied, which became the focus of this present study.

MAIN METHODS

Using Gas chromatography-Mass spectrometry, we investigated saturated fatty acids and unsaturated fatty acids. Quantitative real time PCR was also used to assess the gene expression.

KEY FINDINGS

Results indicate that both palmitoleic acid and oleic acid which are monounsaturated fatty acids were increased in response to CaMKII activation. On the other hand, myristic acid and palmitic acid which are saturated fatty acids known to increase the risk factors of MetS and type 2 diabetes were decreased by exercise induction of CaMKII. Conversely, lauric acid also a saturated fatty acid was increased in response to CaMKII activation by exercise. This fatty acid is known to have beneficial effects in alleviating symptoms of both type 2 diabetes and MetS.

SIGNIFICANCE

According to our knowledge, this is the first study to show that CaMKII activation by exercise regulates fatty acids essential in type 2 diabetes and MetS. CaMKII can be an avenue of designing novel therapeutic drugs in the management and treatment of type 2 diabetes and MetS.

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.

Acute exercise suppresses hypothalamic PTP1B protein level and improves insulin and leptin signaling in obese rats

Hypothalamic inflammation is associated with insulin and leptin resistance, hyperphagia, and obesity. In this scenario, hypothalamic protein tyrosine phosphatase 1B (PTP1B) has emerged as the key phosphatase induced by inflammation that is responsible for the central insulin and leptin resistance. Here, we demonstrated that acute exercise reduced inflammation and PTP1B protein level/activity in the hypothalamus of obese rodents. Exercise disrupted the interaction between PTP1B with proteins involved in the early steps of insulin (IRβ and IRS-1) and leptin (JAK2) signaling, increased the tyrosine phosphorylation of these molecules, and restored the anorexigenic effects of insulin and leptin in obese rats. Interestingly, the anti-inflammatory action and the reduction of PTP1B activity mediated by exercise occurred in an interleukin-6 (IL-6)-dependent manner because exercise failed to reduce inflammation and PTP1B protein level after the disruption of hypothalamic-specific IL-6 action in obese rats. Conversely, intracerebroventricular administration of recombinant IL-6 reproduced the effects of exercise, improving hypothalamic insulin and leptin action by reducing the inflammatory signaling and PTP1B activity in obese rats at rest. Taken together, our study reports that physical exercise restores insulin and leptin signaling, at least in part, by reducing hypothalamic PTP1B protein level through the central anti-inflammatory response.

Gastrointestinal morphological alterations in obese rats kept under hypercaloric diets

Hypercaloric diets have been successfully used as experimental models of obesity. This work compared morphological characteristics of inferior gastrointestinal organs. The experiment lasted 10 weeks, during which the rats’ food consumption, body weight, distance between the mouth and neck, distance between mouth and neck, distance between neck and tail, and abdominal circumference were evaluated weekly. After the sacrifice of the rats, 20 variables referring to inferior gastrointestinal morphology were assessed. The results comprised descriptive statistics of the data, analysis of main components, linear correlation, and t-tests. Significant differences were found between the two groups for the variables of abdominal circumference, retroperitoneal fat, ratio between retroperitoneal fat/animal weight, stomach weight, ratio between animal weight/intestine weight and mesentery/animal weight, length of small intestine, length of large intestine, and lateral line of the cecum. The data allow us to state that a hypercaloric diet can be responsible an increase in fat in the abdominal cavity as well as gastrointestinal morphological alterations, principally in stomach development.

Multiple univariate data analysis reveals the inulin effects on the high-fat-diet induced metabolic alterations in rat myocardium and testicles in the preobesity state

Obesity is a worldwide epidemic and a well-known risk factor for many diseases affecting billions of people's health and well-being. However, little information is available for metabolic changes associated with the effects of obesity development and interventions on cardiovascular and reproduction systems. Here, we systematically analyzed the effects of high-fat diet (HFD) and inulin intake on the metabolite compositions of myocardium and testicle using NMR spectroscopy. We developed a useful high-throughput method based on multiple univariate data analysis (MUDA) to visualize and efficiently extract information on metabolites significantly affected by an intervention. We found that HFD caused widespread metabolic changes in both rat myocardium and testicles involving fatty acid β-oxidation together with the metabolisms of choline, amino acids, purines and pyrimidines even before HFD caused significant body-weight increases. Inulin intake ameliorated some of the HFD-induced metabolic changes in both myocardium (3-HB, lactate and guanosine) and testicle tissues (3-HB, inosine and betaine). A remarkable elevation of scyllo-inositol was also observable with inulin intake in both tissues. These findings offered essential information for the inulin effects on the HFD-induced metabolic changes and demonstrated this MUDA method as a powerful alternative to traditionally used multivariate data analysis for metabonomics.

Moderate physical activity from childhood contributes to metabolic health and reduces hepatic fat accumulation in adult rats

BACKGROUND

Obesity, oxidative stress and inflammation, by triggering insulin resistance, may contribute to the accumulation of hepatic fat, and this accumulation by lipotoxicity can lead the organ to fail. Because obesity is growing at an alarming rate and, worryingly, in a precocious way, the present study aimed to investigate the effects of moderate physical training performed from childhood to adulthood on liver fat metabolism in rats.

METHODS

Twenty rats that were 28 days old were divided into two groups: control (C) and trained (T). The C Group was kept in cages without exercise, and the T group was submitted to swimming exercise for 1 hour/day, 5 days/week from 28 to 90 days of age (8 weeks) at 80% of the anaerobic threshold determined by the lactate minimum test. At the end of the experiment, the body weight gain, insulin sensitivity (glucose disappearance rate during the insulin tolerance test), concentrations of free fatty acids (FFA) and triglycerides (TG) and hepatic lipogenic rate were analyzed. For the statistical analysis, the Student t-test was used with the level of significance preset at 5%.

RESULTS

The T group showed lower body weight gain, FFA concentrations, fat accumulation, hepatic lipogenic rate and insulin resistance.

CONCLUSION

The regular practice of moderate physical exercise from childhood can contribute to the reduction of obesity and insulin resistance and help prevent the development of accumulation of hepatic fat in adulthood.

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.

A new overtraining protocol for mice based on downhill running sessions

1. The purpose of the present study was to verify whether a downhill running protocol was able to induce non-functional overreaching in > 75% of mice. 2. Mice were divided into control (C), trained (TR) and overtrained (OTR) groups. Bodyweight and food intake were recorded weekly. The incremental load test (ILT) and the exhaustive test (ET) were used to measure performance before and after aerobic training and overtraining protocols. 3. Although the bodyweight of the OTR group was lower than that of the C group at the end of Week 7, the food intake of the OTR group was higher than that of the C and TR groups at the end of Week 8. Evaluation of results from the ILT and ET revealed significant intra- and inter-group differences: whereas the parameters measured by both tests increased significantly in the TR group, they were significantly decreased in the OTR group. 4. In conclusion, this new overtraining protocol based on downhill running sessions induced non-functional overreaching in 100% of mice.

Impact of physical activity on inflammation: effects on cardiovascular disease risk and other inflammatory conditions

Since the 19(th) century, many studies have enlightened the role of inflammation in atherosclerosis, changing our perception of "vessel plaque due to oxidized lipoproteins", similar to a "rusted pipe", towards a disease with involvement of many cell types and cytokines with more complex mechanisms. Although "physical activity" and "physical exercise" are two terms with some differences in meaning, compared to sedentary lifestyle, active people have lower cardiovascular risk and lower inflammatory markers. Activities of skeletal muscle reveal "myokines" which have roles in both the immune system and adipose tissue metabolism. In vitro and ex-vivo studies have shown beneficial effects of exercise on inflammation markers. Meanwhile in clinical studies, some conflicting results suggested that type of activity, exercise duration, body composition, gender, race and age may modulate anti-inflammatory effects of physical exercise. Medical data on patients with inflammatory diseases have shown beneficial effects of exercise on disease activity scores, patient well-being and inflammatory markers. Although the most beneficial type of activity and the most relevant patient group for anti-inflammatory benefits are still not clear, studies in elderly and adult people generally support anti-inflammatory effects of physical activity and moderate exercise could be advised to patients with cardiovascular risk such as patients with metabolic syndrome.

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.

Effects of endurance exercise and high-fat diet on insulin resistance and ceramide contents of skeletal muscle in sprague-dawley rats

Background

We evaluated the effects of endurance exercise and a high-fat diet on insulin resistance and ceramide contents of skeletal muscle in Sprague-Dawley rats.

Methods

We randomly divided 32 rats into four groups: control (CON, n = 8), high fat diet (HF, n = 8), exercise (Ex, 24 m/min for 2 hours, 5 days/wk, n = 8), HF/Ex (n = 8). After 4-week treatments, plasma lipid profiles, glucose and insulin concentrations were measured. The triglycerides (TG), ceramide, and glucose transporter 4 (GLUT-4) contents were measured in the skeletal muscle. The rate of glucose transport was determined under submaximal insulin concentration during the muscle incubation.

Results

Free fatty acid levels were significantly higher in CON and HF than Ex (P = 0.032). Plasma glucose levels in HF were significantly higher than the two Ex groups (P = 0.002), and insulin levels were significantly higher in HF than in other three groups (P = 0.021). Muscular TG concentrations were significantly higher in HF than CON and Ex and also in HF/Ex than Ex, respectively (P = 0.005). Hepatic TG concentrations were significantly higher in HF than other three groups but Ex was significantly lower than HF/Ex (P = 0.000). Muscular ceramide content in HF was significantly greater than that in either Ex or HF/Ex (P = 0.031). GLUT-4 levels in CON and HF were significantly lower than those in Ex and HF/Ex (P = 0.009, P = 0.003). The glucose transport rate in submaximal insulin concentration was lower in CON than in either Ex or HF/Ex (P = 0.043), but not different from HF.

Conclusion

This study suggests that high fat diet for 4 weeks selectively impairs insulin resistance, but not glucose transport rate, GLUT-4 and ceramide content in skeletal muscle per se. However, endurance exercise markedly affects the content of ceramide and insulin resistance in muscle.