Physical activity prevents alterations in mitochondrial ultrastructure and glucometabolic parameters in a high-sugar diet model

Potential regulatory role of PGC-1α within the skeletal muscle during metabolic adaptations in response to high-fat diet feeding in animal models

High-fat diet (HFD) feeding in rodents has become an essential tool to critically analyze and study the pathological effects of obesity, including mitochondrial dysfunction and insulin resistance. Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) regulates cellular energy metabolism to influence insulin sensitivity, beyond its active role in stimulating mitochondrial biogenesis to facilitate skeletal muscle adaptations in response to HFD feeding. Here, some of the major electronic databases like PubMed, Embase, and Web of Science were accessed to update and critically discuss information on the potential role of PGC-1α during metabolic adaptations within the skeletal muscle in response to HFD feeding in rodents. In fact, available evidence suggests that partial exposure to HFD feeding (potentially during the early stages of disease development) is associated with impaired metabolic adaptations within the skeletal muscle, including mitochondrial dysfunction and reduced insulin sensitivity. In terms of implicated molecular mechanisms, these negative effects are partially associated with reduced activity of PGC-1α, together with the phosphorylation of protein kinase B and altered expression of genes involving nuclear respiratory factor 1 and mitochondrial transcription factor A within the skeletal muscle. Notably, metabolic abnormalities observed with chronic exposure to HFD (likely during the late stages of disease development) may potentially occur independently of PGC-1α regulation within the muscle of rodents. Summarized evidence suggests the causal relationship between PGC-1α regulation and effective modulations of mitochondrial biogenesis and metabolic flexibility during the different stages of disease development. It further indicates that prominent interventions like caloric restriction and physical exercise may affect PGC-1α regulation during effective modulation of metabolic processes.

Serum factors mediate changes in mitochondrial bioenergetics associated with diet and exercise interventions

Mitochondrial improvements resulting from behavioral interventions, such as diet and exercise, are systemic and apparent across multiple tissues. Here, we test the hypothesis that factors present in serum, and therefore circulating throughout the body, can mediate changes in mitochondrial function in response to intervention. To investigate this, we used stored serum from a clinical trial comparing resistance training (RT) and RT plus caloric restriction (RT + CR) to examine effects of blood borne circulating factors on myoblasts in vitro. We report that exposure to dilute serum is sufficient to mediate bioenergetic benefits of these interventions. Additionally, serum-mediated bioenergetic changes can differentiate between interventions, recapitulate sex differences in bioenergetic responses, and is linked to improvements in physical function and inflammation. Using metabolomics, we identified circulating factors associated with changes in mitochondrial bioenergetics and the effects of interventions. This study provides new evidence that circulating factors play a role in the beneficial effects of interventions that improve healthspan among older adults. Understanding the factors that drive improvements in mitochondrial function is a key step towards predicting intervention outcomes and developing strategies to countermand systemic age-related bioenergetic decline.

Superior cardiometabolic and cellular adaptive responses to multiple versus single daily sessions of high-intensity interval training in Wistar rats

This study aimed to compare in rats the cardiometabolic and cellular adaptative responses to 8 weeks of high-intensity interval training (HIIT) performed in a single (1xHIIT) or three shorter daily sessions (3xHIIT). Male Wistar rats were assigned to untrained (n = 10), 1xHIIT (n = 10), and 3xHIIT (n = 10) groups. Both HIIT groups performed 15 min of a treadmill run five times per week for 8 weeks. The 1xHIIT performed single daily sessions of 15 min, and the 3xHIIT performed three daily sessions of 5 min with an interval of 4 h between sessions. Resting VO₂ and VO₂max were measured using a metabolic chamber; blood pressure and heart rate were measured by plethysmography; body composition was estimated by DEXA; Glucose and insulin tolerance tests were performed; after euthanasia, hearts, gastrocnemius, and visceral fat were harvested for analysis of cardiac function, histology, and morphology. Mitochondrial densities of the gastrocnemius and left ventricle muscles were determined by electron microscopy. 3xHIIT induced similar positive adaptative responses to 1xHIIT on resting VO₂ and VO₂max, cardiac function, and mitochondria density. 3xHIIT was superior to 1xHIIT in reducing visceral fat weight and adipocyte size and improving insulin tolerance. Multiple short daily bouts of HIIT may be superior to single HIIT daily sessions in improving cardiometabolic and cellular adaptations in rats.

The superior beneficial effects of exercise training versus hormone replacement therapy on skeletal muscle of ovariectomized rats

Previous studies have highlighted the positive effects of Estradiol (E2) replacement therapy and physical exercise on skeletal muscle during menopause. However, the comparison effects of exercise training (ET) and estradiol replacement therapy during menopause on skeletal muscle have not been investigated to date. This study aimed to compare the effects of endurance exercise training versus E2 replacement therapy on mitochondrial density, redox status, and inflammatory biomarkers in the skeletal muscle of ovariectomized rats. Thirty female Wistar rats (12-week-old) were randomly assigned into three groups: Untrained ovariectomized rats (UN-OVX, n = 10); untrained ovariectomized rats treated with estradiol replacement therapy (E2-OVX); and, trained ovariectomized rats (TR-OVX). After ovariectomy, the E2-OVX rats were treated subcutaneously with E2 (implanted Silastic® capsule containing 360 μg of 17β-estradiol/mL) while the TR-OVX group performed an exercise training protocol (50–70% of maximal running speed on a treadmill, 60 min/day, 5 days/week for 8 weeks). After euthanasia, the soleus muscle was processed for histological and biochemical evaluations. Only exercise prevented the reduction of maximal oxygen consumption and increased mechanical efficiency (ME). While mitochondrial muscle density, total antioxidant capacity (FRAP), catalase (CAT) activity, and interleukin 10 levels were higher in TR-OVX, only OVX-E2 presented higher CAT activity and lower interleukin 6 levels. Endurance exercise training compared with E2 replacement therapy maintains the aerobic capacity improving the ME of OVX rats. In addition, only endurance exercise training raises the skeletal muscle mitochondrial content and tends to balance the redox and inflammatory status in the skeletal muscle of OVX rats.

Increasing energy expenditure through exercise and low ambient temperature offers oxidative protection to the hypothalamus after high-fat feeding to mice

The effects of weight loss produced by increased energy expenditure on measures of oxidative stress and mitochondrial damage have not been investigated in the hypothalamus of diet-induced obese mice. The present study aimed to characterize the effects of either a low housing temperature of 17°C or daily exercise on a treadmill on high-fat diet (HFD)-induced abnormalities in the hypothalamic tissue of mice. Exercise and low ambient temperature protocols were designed to produce energy deficit through increased energy expenditure. Forty mice aged 8 weeks were assigned to one of four conditions: chow diet (n = 10), HFD (n = 10), HFD and 5 weeks of either exercise training (ET; n = 10) or an ambient temperature of 17°C (n = 10). Mice were killed at the age of 31 weeks. In comparison with HFD treatment alone, both interventions reduced body adiposity (14.6% and 27.6% reduction for the ET and 17°C groups, respectively). Moreover, exposing obese mice to ET and 17°C restored mitochondrial DNA content (41.3% and 32.6% increase for the ET and 17°C groups, respectively), decreased level of lipid peroxidation as assessed by the detection of 4-hydroxy-nonenal protein adducts (12.8% and 29.4% reduction for the ET and 17°C groups, respectively) and normalized the expression levels of proinflammatory cytokines (Tnfα: 73.9% and 62%; Il1β: 54.5% and 39.6%; Il6: 33.1% and 35.6% reduction for the ET and 17°C groups, respectively), as well as several proteins associated with mitochondrial respiratory chain (OxPhos Complex I: 75.7% and 53.9%; Complex III: 33% and 36%; Complex V: 42% and 36.9% reduction for the ET and 17°C groups, respectively) in hypothalamic cells. Negative energy balance induced through either lower ambient temperature or exercise resulted in substantial and similar improvements in markers of inflammation and mitochondrial damage in the hypothalamus of mice with diet-induced obesity, potentially by reducing oxidative stress.

Aerobic exercise training prevents impairment in renal parameters and in body composition of rats fed a high sucrose diet

OBJECTIVE

This study aimed to evaluate the effect of swimming training (T) on the renal system and body composition parameters in young animals treated with a high sucrose diet (SUD) during 12 weeks.

RESULTS

The SUD impaired the physical performance, increased the body adiposity index (BAI), Lee index (LI) and retroperitoneal adipose tissue (RAT) weight, plasma creatinine and number renal cells nuclei, decreased urinary volume and urinary creatinine excretion besides creatinine clearance. The T reversed the increased the BAI, LI, RAT weight, plasma and urinary creatinine, creatinine clearance and number renal cells nuclei in addition to promoting decrease in urinary protein excretion. This study found that eight weeks of swimming physical training protected renal function and restored normal glomerular filtration rate (GFR) values. Swimming training also contributed to prevention of the onset of a renal inflammatory process and caused a decrease in the risk of development of obesity promoted by SUD decreasing the body composition parameters (BAI, LI, and RAT weight).

Sucrose-Sweetened Drinks Reduce the Physical Performance and Increase the Cardiovascular Risk in Physically Active Males

INTRODUCTION

The intake of sugar-sweetened beverages (SSBs) has increased rapidly, but the effects of this habit on health and physical performance are unknown. This study assessed the effect of excessive SSB intake on biochemical, physical performance, and biochemical and cardiovascular parameters of physically active males.

METHODS

Seventeen volunteers consumed a placebo drink (Pd; carbohydrate free) and an excessive SSB drink (eSSBd = Pd plus 300 g sucrose). In a blind randomized crossover study, the subjects were assigned to Pd or eSSBd groups for 15 days. After an interval of 7 days, subjects were reassigned to the other condition.

RESULTS

After eSSBd intake, there was an increase in weight (69.34 ± 13.71 vs. 70.62 ± 14.06), body mass index (24.49 ± 4.01 vs. 24.97 ± 4.13), waist circumference (75.33 ± 11.22 vs. 76.79 ± 11.51), VLDL (19.54 ± 9.50 vs. 25.52 ± 11.18), triglycerides (78.94 ± 23.79 vs. 114.77 ± 43.65), and peak systolic blood pressure (178.57 ± 26.56 vs. 200.71 ± 24.64). The cardiorespiratory response to exercise (VO2max) (48.15 ± 10.42 vs. 40.98 ± 11.20), peak heart rate (186.64 ± 8.00 vs. 179.64 ± 6.28), total exercise time (15.02 ± 1.57 vs. 14.00 ± 2.18), and mechanical work (15.83 ± 4.53 vs. 13.68 ± 5.67) decreased after eSSBd intake (all values expressed in initial mean ± DP vs. final). The rates of perceived exertion were higher (1.300 vs.1.661 slope and -0.7186 vs. -1.118 y-intercept) after eSSBd intake.

CONCLUSION

The present study shows that 15 days of eSSBd intake may negatively modulate biochemical parameters associated with cardiovascular risk. In addition, this overintake can impair the physical performance and cardiovascular responses to physical exercise.

Melatonin reverses the loss of the anticontractile effect of perivascular adipose tissue in obese rats

Perivascular adipose tissue (PVAT) undergoes functional changes in obesity. Increased oxidative stress is a central mechanism whereby obesity induces loss of the anticontractile effect of PVAT. Melatonin is an antioxidant that displays vasoprotective action in cardiovascular disease. Here, we sought to investigate whether melatonin would restore the anticontractile effect of periaortic PVAT in obesity. Male Wistar Hannover rats were treated for 10 weeks with a high-calorie diet. Melatonin (5 mg/kg/d, p.o., gavage) was administered for 2 weeks. Functional findings showed that obesity-induced loss of the anticontractile effect of PVAT and treatment with melatonin reversed this response. Tiron [a scavenger of superoxide anion (O₂ ^- )] restored the anticontractile effect of PVAT in aortas from obese rats, suggesting a role for reactive oxygen species (ROS) in such response. Decreased superoxide dismutase (SOD) activity and augmented levels of ROS were detected in periaortic PVAT from obese rats. These responses were accompanied by decreased levels of nitric oxide (NO) in PVAT. Treatment with melatonin restored SOD activity, decreased ROS levels, and increased NO bioavailability in PVAT from obese rats. Here, we first reported the beneficial effects of melatonin in periaortic PVAT in obesity. Melatonin reversed the adverse effects of obesity in PVAT that included overproduction of ROS, reduced SOD activity, and decreased bioavailability of NO. Therefore, PVAT may constitute an important target for the treatment of obesity-induced vascular dysfunction and melatonin emerges as a potential tool in the management of the vascular complications induced by obesity.

Are Alterations in Skeletal Muscle Mitochondria a Cause or Consequence of Insulin Resistance?

As a major site of glucose uptake following a meal, skeletal muscle has an important role in whole-body glucose metabolism. Evidence in humans and animal models of insulin resistance and type 2 diabetes suggests that alterations in mitochondrial characteristics accompany the development of skeletal muscle insulin resistance. However, it is unclear whether changes in mitochondrial content, respiratory function, or substrate oxidation are central to the development of insulin resistance or occur in response to insulin resistance. Thus, this review will aim to evaluate the apparent conflicting information placing mitochondria as a key organelle in the development of insulin resistance in skeletal muscle.

RNA binding protein HuD contributes to β-cell dysfunction by impairing mitochondria dynamics

Imbalanced mitochondrial dynamics in pancreatic β-cells contributes to β-cell dysfunction in diabetes; however, the molecular mechanisms underlying mitochondrial dynamics in the pathology of diabetes are not fully elucidated. We previously reported the reduction of RNA binding protein HuD in pancreatic β-cells of diabetes. Herein, we demonstrate that HuD plays a novel role in the regulation of mitochondrial dynamics by promoting mitochondrial fusion. We show enhanced mitochondrial fragmentation in the pancreas of db/db mice and HuD KO mice. Downregulation of HuD increases the number of cells with fragmented mitochondria and reduces the mitochondrial activity determined by mitochondrial membrane potential and ATP production in mouse insulinoma βTC6 cells. HuD binds to 3'-untraslated region of mitofusin 2 (Mfn2) mRNA and positively regulates its expression. Ectopic expression of Mfn2 in βTC6 cells stably expressing short hairpin RNA against HuD (shHuD) restores HuD-mediated mitochondrial dysfunction. Taken together, our results suggest that HuD regulates mitochondrial dynamics by regulating Mfn2 level and its reduced expression leads to mitochondrial dysfunction in pancreatic β-cells.

High-glucose diets induce mitochondrial dysfunction in Caenorhabditis elegans

Glucose is an important nutrient that dictates the development, fertility and lifespan of all organisms. In humans, a deficit in its homeostatic control might lead to hyperglucemia and the development of obesity and type 2 diabetes, which show a decreased ability to respond to and metabolize glucose. Previously, we have reported that high-glucose diets (HGD) induce alterations in triglyceride content, body size, progeny, and the mRNA accumulation of key regulators of carbohydrate and lipid metabolism, and longevity in Caenorhabditis elegans (PLoS ONE 13(7): e0199888). Herein, we show that increasing amounts of glucose in the diet induce the swelling of both mitochondria in germ and muscle cells. Additionally, HGD alter the enzymatic activities of the different respiratory complexes in an intricate pattern. Finally, we observed a downregulation of ceramide synthases (hyl-1 and hyl-2) and antioxidant genes (gcs-1 and gst-4), while mitophagy genes (pink-1 and dct-1) were upregulated, probably as part of a mitohormetic mechanism in response to glucose toxicity.

Liver-Metabolizing Genes and Their Relationship to the Performance of Elite Spanish Male Endurance Athletes; a Prospective Transversal Study

Background

The genetic profile that is needed to define an endurance athlete has been studied during recent years. The main objective of this work is to approach for the first time the study of genetic variants in liver-metabolizing genes and their role in endurance performance by comparing the allelic and genotypic frequencies in elite endurance athletes to the non-athlete population.

Methods

Genotypic and allelic frequencies were determined in 123 elite endurance athletes (75 professional road cyclists and 48 endurance elite runners) and 122 male non-athlete subjects (sedentary). Genotyping of cytochrome P450 family 2 subfamily D member 6 (CYP2D6 rs3892097), glutathione-S transferase mu isoform 1 (GSTM1), glutathione S-transferase pi (GSTP rs1695) and glutathione S-transferase theta (GSTT) genes was performed by polymerase chain reaction (PCR). The combination of the polymorphisms for the “optimal” polygenic profile has been quantified using the genotype score (GS).

Results

Statistical differences were found in the genetic distributions between elite endurance athletes and non-athletes in CYP2D6 (p < 0.001) and GSTT (p = 0.014) genes. The binary logistic regression model showed a favourable OR (odds ratio) of being an elite endurance runner against a professional road cyclist (OR: 2.403, 95% CI: 1.213–4.760 (p = 0.002)) in the polymorphisms studied.

Conclusions

Genotypic distribution of liver-metabolizing genes in elite endurance athletes is different to non-athlete subjects, with a favourable gene profile in elite endurance athletes in terms of detoxification capacity.

Effect of Polyhexamethylene Biguanide Solution on Bacterial Load and Biofilm in Venous Leg Ulcers: A Randomized Controlled Trial

PURPOSE

The purpose of this study was to investigate the effect of polyhexamethylene biguanide (PHMB) solution as a wound cleanser on bacterial load and bacterial biofilm in venous leg ulcers.

DESIGN

Randomized controlled trial.

SUBJECTS AND SETTING

The target population was adults attending the dermatology outpatient clinic of the Clinical Hospital of the Federal University of Minas Gerais, Brazil. The sample comprised 44 patients with venous leg ulcers recruited over a 6-month period.

METHODS

Participants were divided into 2 groups: the intervention group had their wounds cleansed with PHMB, and the control group had their wound cleansed with a 0.9% saline solution. Tissue fragments of the wounds were collected for bacteriological analysis; transmission electron microscopy was used to identify the presence of biofilm.

RESULTS

The bacterial load was reduced in both groups compared to baseline values; no significant difference was found when groups were compared. Correlation analysis between wound duration (months), wound area (cm²), necrosis (%), variables, and bacterial count (colony forming units [CFUs]/g) after cleansing showed a significant relationship between area of the wound and CFUs/g (P = .0070, r = 0.51). Transmission electron microscopy revealed the presence of bacterial biofilm in the wounds after cleansing with both solutions.

CONCLUSIONS

The results of this study indicate that both PHMB and saline solution are effective in reducing the bacterial load in venous leg ulcers. However, bacterial biofilm was present after cleansing with both solutions. These findings provide important evidence regarding effectiveness of 2 common wound cleansers on bacterial presence in wounds.

Swimming improves cognitive reserve in ovariectomized rats and enhances neuroprotection after global cerebral ischemia

Cognitive reserve has been proposed to account for different responses to brain damage or pathology. Factors implicated to influence cognitive reserve include cognitive engagement, physical activity, leisure activities, stress levels, and diet. Furthermore, long-term ovariectomy (OVX), such as occurs in women that have underwent surgical menopause, has been reported to increase the risk of cognitive impairment. In the current study, we examined whether swimming improves cognitive function in long-term OVX-rats. We also examined the neuroprotective effect of swimming after global cerebral ischemia (GCI) and explored the effect of swimming preconditioning on activation of the MAPK cascade signaling pathway, synaptic proteins and brain-derived growth factor (BDNF) - all factors implicated in regulating synaptic plasticity and neuroprotection in the brain. Adult Sprague-Dawley OVX-rats were randomly assigned into four groups: Sham (Sh), Sham + Swimming (Sh + Sw), Ischemia/Reperfusion (IR) and IR + Sw. Our results revealed that (1) Morris water maze and shuttle box test analysis revealed that swimming improved cognitive function in OVX-rats, (2) The levels of PSD95 and synaptophysin, as well as the protein expression of p-ERK, p-CREB and BDNF were all increased in the hippocampus after swimming with or without GCI, and (3) Swimming also increased the number of surviving neurons and IL4 protein expression, while decreasing the Iba1 (a microglia marker) level in the hippocampus. In conclusion, our study demonstrates that swimming improves memory in OVX-rats, and that swimming preconditioning enhances the neuroprotective ERK1/2/CREB/BDNF pathway signaling and ameliorates brain damage after GCI in OVX-rats, which may be closely related to induction of an IL4-mediated anti-inflammatory mechanism.