Lipid homeostasis in exercise

Proteome Analysis Related to Unsaturated Fatty Acid Synthesis by Interfering with Bovine Adipocyte ACSL1 Gene

Unsaturated fatty acids (UFAs) in beef play a vital role in promoting human health. Long-chain fatty acyl-CoA synthase 1 (ACSL1) is a crucial gene for UFA synthesis in bovine adipocytes. To investigate the protein expression profile during UFA synthesis, we performed a proteomic analysis of bovine adipocytes by RNA interference and non-interference with ACSL1 using label-free techniques. A total of 3558 proteins were identified in both the NC and si-treated groups, of which 1428 were differentially expressed proteins (DEPs; fold change ≥ 1.2 or ≤ 0.83 and p-value < 0.05). The enrichment analysis of the DEPs revealed signaling pathways related to UFA synthesis or metabolism, including cAMP, oxytocin, fatty acid degradation, glycerol metabolism, insulin, and the regulation of lipolysis in adipocytes (p-value < 0.05). Furthermore, based on the enrichment analysis of the DEPs, we screened 50 DEPs that potentially influence the synthesis of UFAs and constructed an interaction network. Moreover, by integrating our previously published transcriptome data, this study established a regulatory network involving differentially expressed long non-coding RNAs (DELs), highlighting 21 DEPs and 13 DELs as key genes involved in UFA synthesis. These findings present potential candidate genes for further investigation into the molecular mechanisms underlying UFA synthesis in bovines, thereby offering insights to enhance the quality of beef and contribute to consumer health in future studies.

Targeted Lipidomics and Inflammation Response to Six Weeks of Sprint Interval Training in Male Adolescents

Lipids play an important role in coordinating and regulating metabolic and inflammatory processes. Sprint interval training (SIT) is widely used to improve sports performance and health outcomes, but the current understanding of SIT-induced lipid metabolism and the corresponding systemic inflammatory status modification remains controversial and limited, especially in male adolescents. To answer these questions, twelve untrained male adolescents were recruited and underwent 6 weeks of SIT. The pre- and post-training testing included analyses of peak oxygen consumption (VO2peak), biometric data (weight and body composition), serum biochemical parameters (fasting blood glucose, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triacylglycerol, testosterone, and cortisol), inflammatory markers, and targeted lipidomics. After the 6-week SIT, the serum C-reactive protein (CRP), interleukin (IL)-1β, IL-2, IL-4, IL-10, tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β significantly decreased (p < 0.05), whereas IL-6 and IL-10/TNF-α significantly increased (p < 0.05). In addition, the targeted lipidomics revealed changes in 296 lipids, of which 33 changed significantly (p < 0.05, fold change > 1.2 or <1/1.2). The correlation analysis revealed that the changes in the inflammatory markers were closely correlated with the changes in some of the lipids, such as LPC, HexCer, and FFA. In conclusion, the 6-week SIT induced significant changes in the inflammatory markers and circulating lipid composition, offering health benefits to the population.

Skeletal Muscle Mitochondrial and Perilipin Content in a Cohort of Obese Subjects Undergoing Moderate and High Intensity Training

Obesity is a complex condition characterized by abnormal and excessive fat accumulation, resulting in an increased risk for severe health problems. Skeletal muscles play a major role in movement and fat catabolism, but the insulin resistance that comes with obesity makes it difficult to fulfill these tasks. In this study, we analyse two types of training protocols, moderate intensity continuous training (MICT) versus high intensity interval training (HIIT), in a cohort of obese subjects to establish which muscle adaptations favour fat consumption in response to exercise. Mitochondria play a role in fat oxidation. We found protein upregulation of mitochondrial biomarkers, TOMM20 and Cox-4, in HIIT but not in MICT, without detecting any shifts in fibre composition phenotype of the vastus lateralis in both training groups. Interestingly, both MICT and HIIT protocols showed increased protein levels of perilipin PLIN2, which is involved in the delivery and consumption of fats. HIIT also augmented perilipin PLIN5. Perilipins are involved in fat storage in skeletal muscles and their upregulation, along with the analysis of circulatory lipid profiles reported in the present study, suggest important adaptations induced by the two types of training protocols that favour fat consumption and weight loss in obese subjects.

Effects of physical exercise on muscle metabolism and meat quality characteristics of Mongolian sheep

The objective of this study was to investigate the effects of exercise training on muscle metabolism, fatty acid composition, carcass traits, and meat quality characteristics of Mongolian sheep. Fourteen Mongolian sheep were randomly divided into two groups (7 sheep in each) and placed in two adjacent livestock pens. One group of sheep was kept in the pen (Control [C] group) and the other group of sheep (Training [T] group) were driven away in a field to walk twice a day. The results showed a reduction in pH measured 45 min post mortem, L*, a*, and b* value, intramuscular fat, and carcass length, and an increase in the ultimate pH value and shear force in the meat of T group in comparison with that of C group (p < .050). Also, exercise training moderately affected the fatty acid composition of LT muscle. Compared with C group, the concentrations of myristoleic acid (C14:1) and stearic acid (C18:0) were increased (p < .050), while the concentrations of C20:3 n‐6, neurolic acid (C24:1), and n‐3 polyunsaturated fatty acid (PUFA) were decreased in T group (p < .050). Transcriptome analysis highlighted 621 genes differentially expressed in two groups, including 385 were up‐regulated (e.g., GLUT4 and PGC‐1α) and 236 were down‐regulated (e.g., PLIN1 and ACSL3) in T with respect to C group. Besides, considering these genes, a number of enrichment pathways related to muscle metabolic processes, involving carbohydrate metabolism, lipid metabolism, oxidation reduction process, and muscle tissue development, were highlighted. In conclusion, these results contributed to a better understanding of the possible biological and molecular processes underlying the effects of exercise training on muscle metabolism and meat quality in Mongolian sheep, and provide useful information for contributing to understand the phenotypic and functional differences in meat quality of sheep.

The Effects of Supervised Exercise Training on Weight Control and Other Metabolic Outcomes in Patients With Type 2 Diabetes: A Meta-Analysis

Few studies have investigated the dose-response relationship between exercise and weight control. This study aimed to assess the effects of different types of supervised exercise training on weight control and other metabolic outcomes in patients with type 2 diabetes mellitus and explore the dose-response relationship between exercise volume/duration and these outcomes. PubMed/MEDLINE, Embase, and Cochrane databases were searched for studies between January 1980 and June 2019. Randomized control trials in type 2 diabetes mellitus patients with supervised exercise training versus control treatment were included. The primary outcome was changes in body weight (kg). The secondary outcomes included changes in waist circumference (cm) and total body fat percentage (%). Forty-two randomized control trials, including 3,625 patients with type 2 diabetes mellitus were included. Overall, exercise treatment was associated with significant reduction in body weight (weighted mean differences, -1.10 kg; 95% CI [-1.58, -0.62], p < .01), waist circumference (weighted mean differences, -2.51 cm; 95% CI [-3.25, -1.77], p < .01), and total body fat (weighted mean differences, -1.16%; 95% CI [-1.58%, -0.75%], p < .01). The percentage of total body fat was reduced by all types of exercise, with a significant difference between aerobic exercise and resistance exercise (p = .02) and a significant difference between combined exercise and resistance exercise (p < .01). A higher volume of aerobic exercise and a higher volume of resistance exercise were superior in reducing body weight. In conclusion, supervised exercise training improved metabolic outcomes in general, while different types and volume of exercises have their own merits.

Effects of Lifestyle Intervention in Tissue-Specific Lipidomic Profile of Formerly Obese Mice

Lipids are highly diverse in their composition, properties and distribution in different biological entities. We aim to establish the lipidomes of several insulin-sensitive tissues and to test their plasticity when divergent feeding regimens and lifestyles are imposed. Here, we report a proton nuclear magnetic resonance (1H-NMR) study of lipid abundance across 4 tissues of C57Bl6J male mice that includes the changes in the lipid profile after every lifestyle intervention. Every tissue analysed presented a specific lipid profile irrespective of interventions. Glycerolipids and fatty acids were most abundant in epididymal white adipose tissue (eWAT) followed by liver, whereas sterol lipids and phosphoglycerolipids were highly enriched in hypothalamus, and gastrocnemius had the lowest content in all lipid species compared to the other tissues. Both when subjected to a high-fat diet (HFD) and after a subsequent lifestyle intervention (INT), the lipidome of hypothalamus showed no changes. Gastrocnemius and liver revealed a pattern of increase in content in many lipid species after HFD followed by a regression to basal levels after INT, while eWAT lipidome was affected mainly by the fat composition of the administered diets and not their caloric density. Thus, the present study demonstrates a unique lipidome for each tissue modulated by caloric intake and dietary composition.

Physical Exercise and Alzheimer's Disease: Effects on Pathophysiological Molecular Pathways of the Disease

Alzheimer’s disease (AD), the most common form of neurodegenerative dementia in adults worldwide, is a multifactorial and heterogeneous disorder characterized by the interaction of genetic and epigenetic factors and the dysregulation of numerous intracellular signaling and cellular/molecular pathways. The introduction of the systems biology framework is revolutionizing the study of complex diseases by allowing the identification and integration of cellular/molecular pathways and networks of interaction. Here, we reviewed the relationship between physical activity and the next pathophysiological processes involved in the risk of developing AD, based on some crucial molecular pathways and biological process dysregulated in AD: (1) Immune system and inflammation; (2) Endothelial function and cerebrovascular insufficiency; (3) Apoptosis and cell death; (4) Intercellular communication; (5) Metabolism, oxidative stress and neurotoxicity; (6) DNA damage and repair; (7) Cytoskeleton and membrane proteins; (8) Synaptic plasticity. Moreover, we highlighted the increasingly relevant role played by advanced neuroimaging technologies, including structural/functional magnetic resonance imaging, diffusion tensor imaging, and arterial spin labelling, in exploring the link between AD and physical exercise. Regular physical exercise seems to have a protective effect against AD by inhibiting different pathophysiological molecular pathways implicated in AD.

Aerobic training induces differential expression of genes involved in lipid metabolism in skeletal muscle and white adipose tissues

Aerobic training induces adaptive responses in skeletal muscles and white adipose tissues, thus facilitating lipid utilization as energy substrates during a physical exercise session. However, the effects of training on cytokines levels and on transcription factors involved in lipid metabolism in muscle and different white adipose depots are still unclear; therefore, these were the aims of the present study. Nineteen adult male Wistar rats were randomly assigned to a trained group or a control, non-trained group. The 10-week training protocol consisted of running on a treadmill, during 1 hour per day, 5 days per week, at 75% of maximum aerobic speed. As expected, trained rats improved their aerobic performance and had augmented citrate synthase activity in the soleus, while the control rats did not. Although body weight was not different between groups, the adiposity index and white adipose depots (ie, epididymal and retroperitoneal) were reduced in trained rats. Training reduced serum concentration of insulin, but failed to change serum concentrations of glucose, triacylglycerol, total cholesterol, and nonesterified fatty acids. Training increased sterol regulatory element-binding protein-1c expression in the gastrocnemius and epididymal adipose tissue, and reduced peroxisome proliferator-activated receptor γ (PPARγ) expression in most of the tissues analyzed. The expression of PPARα and carnitine palmitoyltransferase 1 increased in the gastrocnemius and mesenteric adipose tissue but reduced in epididymal adipose tissue. Triacylglycerol content and tribbles 3 expression reduced in the gastrocnemius of trained rats. Tumor necrosis factor-α and interleukin-6 were increased in all adipose depots evaluated. Collectively, our data indicate that the 10-week aerobic training changed gene expression to improve muscle oxidative metabolism and facilitate lipid degradation in adipose tissues. Our data also highlight the existence of adaptive responses that are distinct between the skeletal muscle and white adipose tissue and between different adipose depots.

Skeletal Muscle Lipid Droplets and the Athlete's Paradox

The lipid droplet (LD) is an organelle enveloped by a monolayer phospholipid membrane with a core of neutral lipids, which is conserved from bacteria to humans. The available evidence suggests that the LD is essential to maintaining lipid homeostasis in almost all organisms. As a consequence, LDs also play an important role in pathological metabolic processes involving the ectopic storage of neutral lipids, including type 2 diabetes mellitus (T2DM), atherosclerosis, steatosis, and obesity. The degree of insulin resistance in T2DM patients is positively correlated with the size of skeletal muscle LDs. Aerobic exercise can reduce the occurrence and development of various metabolic diseases. However, trained athletes accumulate lipids in their skeletal muscle, and LD size in their muscle tissue is positively correlated with insulin sensitivity. This phenomenon is called the athlete’s paradox. This review will summarize previous studies on the relationship between LDs in skeletal muscle and metabolic diseases and will discuss the paradox at the level of LDs.

Acute Postexercise Change in Circulating Irisin Is Related to More Favorable Lipid Profile in Pregnant Women Attending a Structured Exercise Program and to Less Favorable Lipid Profile in Controls: An Experimental Study with Two Groups

INTRODUCTION

The blood irisin concentrations may be affected both by exercise and pregnancy. We aimed to determine acute responses in serum irisin after a single exercise session and relationships between exercise-induced changes in this hormone and lipid profile in pregnancy.

MATERIAL AND METHODS

It was an experimental study in 20 Caucasian women in normal pregnancy (age 30 ± 3 years, 28 ± 6 weeks of gestation; mean ± SD). Participants were assigned to training (n = 8) and control groups (n = 12). Before the experiment, women from the training group attended a structured exercise program 3 times a week for 6 weeks. Blood samples were collected before and 30 minutes after a single bout of 60-minute moderate- to high-intensity exercise to determine serum levels of irisin, insulin, glucose concentration, and lipid profile.

RESULTS

At baseline, we recorded slightly lower irisin levels in the training group compared to controls (12.2 ± 2.4 and 13.9 ± 3.3 ng · ml^-1, respectively). Only in the training group all women presented increase in irisin levels after exercise (on average by 14%); and this change was statistically significant (p = 0.002). In the controls, we found positive significant relationships between postexercise irisin change and low-density lipoproteins (R = 0.594; p = 0.04) and total cholesterol (R = 0.734; p = 0.006). Surprisingly, in the training group, these relationships were also significant but inverse (R = -0.738 and p = 0.036; R = -0.833 and p = 0.01, respectively).

CONCLUSIONS

Training and control pregnant women responded differently to a single exercise session, both in the postexercise change in irisin and its relationship to the blood lipids. Only in the training group we observed the postexercise increase in irisin, which was related to more favorable lipid profile. Systematic prenatal physical activity may optimize the postexercise irisin response and lipid metabolism regulated by this hormone. Therefore, exercise programs should be promoted in pregnant women and obstetric care providers.

Expression of the key metabolic regulators in the white adipose tissue of rats; the role of high-fat diet and aerobic training

Lipid metabolism, especially in the white adipose tissue as an active metabolic organ, is tightly regulated by the key transcription factors, such as the sterol regulatory element binding protein 1c (SREBP-1c) and the Farnesoid X Receptor (FXR). We have studied the expression of these genes in the white adipose tissue to see how a high fat diet (HFD) and two intensities of aerobic training change the lipogenic and lipolytic pathways. 44 male Wistar rats randomly divided into the normal (12% calories from fat) and HFD (56% calories from fat) groups. Each group included control (n=6), moderate trained (n=8, ~65% Vo2max) and high intensity trained (n=8, ~75% Vo2max) rats. After 8 weeks of training, the weight changes, plasma insulin and lipid profile levels and the relative gene expression of SREBP-1c and FXR in the adipose tissue was measured. Data were analysed by 2-way ANOVA (P<0.05). HFD fed rats showed higher levels of insulin and dyslipidemia that was correlated with the higher weight gain. Also, the adipose expression of SREBP-1c was higher in the HFD fed rats that it was strongly correlated with the lower FXR expression. Trained rats independent of the intensity of the training showed lower SREBP-1c and higher FXR expression, but no change was observed in the lipid profile levels. HFD-induced dyslipidemia could occur via SREBP-1c activation in the adipose tissue while the aerobic training activates FXR and inhibits the lipogenic pathways. Despite the activation of lipolytic pathways in the trained rats, it seems that diet has more effect on the lipid profile than the aerobic training.

Implications of exercise-induced adipo-myokines in bone metabolism

Physical inactivity has been recognized, by the World Health Organization as the fourth cause of death (5.5 % worldwide). On the contrary, physical activity (PA) has been associated with improved quality of life and decreased risk of several diseases (i.e., stroke, hypertension, myocardial infarction, obesity, malignancies). Bone turnover is profoundly affected from PA both directly (load degree is the key determinant for BMD) and indirectly through the activation of several endocrine axes. Several molecules, secreted by muscle (myokines) and adipose tissues (adipokines) in response to exercise, are involved in the fine regulation of bone metabolism in response to the energy availability. Furthermore, bone regulates energy metabolism by communicating its energetic needs thanks to osteocalcin which acts on pancreatic β-cells and adipocytes. The beneficial effects of exercise on bone metabolism depends on the intermittent exposure to myokines (i.e., irisin, IL-6, LIF, IGF-I) which, instead, act as inflammatory/pro-resorptive mediators when chronically elevated; on the other hand, the reduction in the circulating levels of adipokines (i.e., leptin, visfatin, adiponectin, resistin) sustains these effects as well as improves the whole-body metabolic status. The aim of this review is to highlight the newest findings about the exercise-dependent regulation of these molecules and their role in the fine regulation of bone metabolism.

Muscle and liver-specific alterations in lipid and acylcarnitine metabolism after a single bout of exercise in mice

Intracellular lipid pools are highly dynamic and tissue-specific. Physical exercise is a strong physiologic modulator of lipid metabolism, but most studies focus on changes induced by long-term training. To assess the acute effects of endurance exercise, mice were subjected to one hour of treadmill running, and (13)C16-palmitate was applied to trace fatty acid incorporation in soleus and gastrocnemius muscle and liver. The amounts of carnitine, FFA, lysophospholipids and diacylglycerol and the post-exercise increase in acetylcarnitine were pronouncedly higher in soleus than in gastrocnemius. In the liver, exercise increased the content of lysophospholipids, plasmalogens and carnitine as well as transcript levels of the carnitine transporter. (13)C16-palmitate was detectable in several lipid and acylcarnitine species, with pronounced levels of tracer-derived palmitoylcarnitine in both muscles and a strikingly high incorporation into triacylglycerol and phosphatidylcholine in the liver. These data illustrate the high lipid storing activity of the liver immediately after exercise whereas in muscle, fatty acids are directed towards oxidation. The observed muscle-specific differences accentuate the need for single-muscle analyses as well as careful consideration of the particular muscle employed when studying lipid metabolism in mice. In addition, our results reveal that lysophospholipids and plasmalogens, potential lipid signalling molecules, are acutely regulated by physical exercise.

Modulation of Hypercholesterolemia-Induced Oxidative/Nitrative Stress in the Heart

Hypercholesterolemia is a frequent metabolic disorder associated with increased risk for cardiovascular morbidity and mortality. In addition to its well-known proatherogenic effect, hypercholesterolemia may exert direct effects on the myocardium resulting in contractile dysfunction, aggravated ischemia/reperfusion injury, and diminished stress adaptation. Both preclinical and clinical studies suggested that elevated oxidative and/or nitrative stress plays a key role in cardiac complications induced by hypercholesterolemia. Therefore, modulation of hypercholesterolemia-induced myocardial oxidative/nitrative stress is a feasible approach to prevent or treat deleterious cardiac consequences. In this review, we discuss the effects of various pharmaceuticals, nutraceuticals, some novel potential pharmacological approaches, and physical exercise on hypercholesterolemia-induced oxidative/nitrative stress and subsequent cardiac dysfunction as well as impaired ischemic stress adaptation of the heart in hypercholesterolemia.

Lipid droplet dynamics in skeletal muscle

The skeletal muscle is subjected to high mechanical and energetic demands. Lipid droplets are an important source of energy substrates for the working muscle. Muscle cells contain a variety of lipid droplets, which are fundamentally smaller than those found in adipocytes. This translates into a greater lipid droplet surface area serving as the interface for intracellular lipid metabolism. The skeletal muscle has a high plasticity, it is subjected to major remodeling following training and detraining. This coincides with adaptations in lipid droplet characteristics and dynamics. The majority of lipid droplets in skeletal muscle are located in the subsarcolemmal region or in-between the myofibrils, in close vicinity to mitochondria. The vastly organized nature of skeletal muscle fibers limits organelle mobility. The high metabolic rate and substrate turnover in skeletal muscle demands a strict coordination of intramyocellular lipid metabolism and LD dynamics, in which lipid droplet coat proteins play an important role. This review provides insights into the characteristics, diversity and dynamics of skeletal muscle lipid droplets.

Sarcolipin overexpression improves muscle energetics and reduces fatigue

Sarcolipin (SLN) is a regulator of sarcoendoplasmic reticulum calcium ATPase in skeletal muscle. Recent studies using SLN-null mice have identified SLN as a key player in muscle thermogenesis and metabolism. In this study, we exploited a SLN overexpression (Sln(OE)) mouse model to determine whether increased SLN level affected muscle contractile properties, exercise capacity/fatigue, and metabolic rate in whole animals and isolated muscle. We found that Sln(OE) mice are more resistant to fatigue and can run significantly longer distances than wild-type (WT). Studies with isolated extensor digitorum longus (EDL) muscles showed that Sln(OE) EDL produced higher twitch force than WT. The force-frequency curves were not different between WT and Sln(OE) EDLs, but at lower frequencies the pyruvate-induced potentiation of force was significantly higher in Sln(OE) EDL. SLN overexpression did not alter the twitch and force-frequency curve in isolated soleus muscle. However, during a 10-min fatigue protocol, both EDL and soleus from Sln(OE) mice fatigued significantly less than WT muscles. Interestingly, Sln(OE) muscles showed higher carnitine palmitoyl transferase-1 protein expression, which could enhance fatty acid metabolism. In addition, lactate dehydrogenase expression was higher in Sln(OE) EDL, suggesting increased glycolytic capacity. We also found an increase in store-operated calcium entry (SOCE) in isolated flexor digitorum brevis fibers of Sln(OE) compared with WT mice. These data allow us to conclude that increased SLN expression improves skeletal muscle performance during prolonged muscle activity by increasing SOCE and muscle energetics.