Hypoabsorptive surgeries cause limb-dependent changes in the gut endocannabinoidome and microbiome in association with beneficial metabolic effects.

OBJECTIVE: To determine whether the metabolic benefits of hypoabsorptive surgeries are associated with changes in the gut endocannabinoidome (eCBome) and microbiome. METHODS: Biliopancreatic diversion with duodenal switch (BPD-DS) and single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S) were performed in diet-induced obese (DIO) male Wistar rats. Control groups fed a high-fat diet (HF) included sham-operated (SHAM HF) and SHAM HF-pair-weighed to BPD-DS (SHAM HF-PW). Body weight, fat mass gain, fecal energy loss, HOMA-IR, and gut-secreted hormone levels were measured. The levels of eCBome lipid mediators and prostaglandins were quantified in different intestinal segments by LC-MS/MS, while expression levels of genes encoding eCBome metabolic enzymes and receptors were determined by RT-qPCR. Metataxonomic (16S rRNA) analysis was performed on residual distal jejunum, proximal jejunum, and ileum contents. RESULTS: BPD-DS and SADI-S reduced fat gain and HOMA-IR, while increasing glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) levels in HF-fed rats. Both surgeries induced potent limb-dependent alterations in eCBome mediators and in gut microbial ecology. In response to BPD-DS and SADI-S, changes in gut microbiota were significantly correlated with those of eCBome mediators. Principal component analyses revealed connections between PYY, N-oleoylethanolamine (OEA), N-linoleoylethanolamine (LEA), Clostridium, and Enterobacteriaceae_g_2 in the proximal and distal jejunum and in the ileum. CONCLUSIONS: BPD-DS and SADI-S caused limb-dependent changes in the gut eCBome and microbiome. The present results indicate that these variables could significantly influence the beneficial metabolic outcome of hypoabsorptive bariatric surgeries.

Consistent gut bacterial and short-chain fatty acid signatures in hypoabsorptive bariatric surgeries correlate with metabolic benefits in rats.

OBJECTIVE: The study aimed at comparing how changes in the gut microbiota are associated to the beneficial effects of the most clinically efficient hypoabsorptive bariatric procedures, namely Roux-en-Y gastric bypass (RYGB), biliopancreatic diversion with duodenal switch (BPD-DS) and single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S). METHODS: Diet-induced obese (DIO) male Wistar rats were divided into seven groups. In addition to the groups subjected to RYGB, BPD-DS and SADI-S, the following four control groups were included: SHAM-operated rats fed a high-fat diet (SHAM HF), SHAM fed a low-fat diet (SHAM LF), SHAM HF-pair-weighed to BPD-DS (SHAM HF-PW) and sleeve-gastrectomy (SG) rats. Body weight, food intake, glucose tolerance, insulin sensitivity/resistance, and L-cell secretion were assessed. The gut microbiota (16 S ribosomal RNA gene sequencing) as well as the fecal and cæcal contents of short-chain fatty acids (SCFAs) were also analyzed prior to, and after the surgeries. RESULTS: The present study demonstrates the beneficial effect of RYGB, BPD-DS and SADI-S on fat mass gain and glucose metabolism in DIO rats. These benefits were proportional to the effect of the surgeries on food digestibility (BPD-DS > SADI-S > RYGB). Notably, hypoabsorptive surgeries led to consonant microbial signatures characterized by decreased abundance of the Ruminococcaceae (Oscillospira and Ruminococcus), Oscillospiraceae (Oscillibacter) and Christensenellaceae, and increased abundance of the Clostridiaceae (Clostridium), Sutterellaceae (Sutterella) and Enterobacteriaceae. The gut bacteria following hypoabsorptive surgeries were associated with higher fecal levels of propionate, butyrate, isobutyrate and isovalerate. Increases in the fecal SCFAs were in turn positively and strongly correlated with the levels of peptide tyrosine-tyrosine (PYY) and with the beneficial effects of the surgery. CONCLUSION: The present study emphasizes the consistency with which the three major hypoabsorptive bariatric procedures RYGB, BPD-DS and SADI-S create a gut microbial environment capable of producing a SCFA profile favorable to the secretion of PYY and to beneficial metabolic effects.

Two weeks of western diet disrupts liver molecular markers of cholesterol metabolism in rats.

BACKGROUND: The present study was designed to test the hypothesis that in the liver, excessive fat accumulation impairs cholesterol metabolism mainly by altering the low-density lipoprotein-receptor (LDL-R) pathway. METHOD: Young male Wistar rats were fed standard (SD), high fat (HFD; 60% kcal) or Western (WD; 40% fat + 35% sucrose (17.5% fructose)) diets for 2 or 6 weeks. RESULTS: Weight gain (~ 40 g) was observed only following 6 weeks of the obesogenic diets (P < 0.01). Compared to the 2-week treatment, obesogenic diets tripled fat pad weight (~ 20 vs 7 g) after 6 weeks. Hepatic triglyceride (TG) levels were greater in response to both the WD and HFD compared to the SD (P < 0.01) at 2 and 6 weeks and their concentrations were greater (P < 0.05) in WD than HFD at 2 weeks. Plasma total cholesterol levels were higher (P < 0.05) in animals submitted to WD. After 2 and 6 weeks, liver expression of LDL-R, proprotein convertase subtilisin/kexin 9 (PCSKk9) and sterol regulatory element binding protein 2 (SREBP2), involved in LDL-cholesterol uptake, was lower in animals submitted to WD than in others treated with HFD or SD (P < 0.01). Similarly, low-density lipoprotein-receptor-related protein 1 (LRP1) and acyl-CoA cholesterol acyltransferase-2 (ACAT-2) mRNA levels were lower (P < 0.01) among WD compared to SD-fed rats. Expression of the gene coding the main regulator of endogenous cholesterol synthesis, 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCoAR) was reduced in response to WD compared to SD and HFD at 2 (P < 0.001) and 6 (P < 0.05) weeks. Being enriched in fructose, the WD strongly promoted the expression of carbohydrate-response element binding protein (ChREBP) and acetyl-CoA carboxylase (ACC), two key regulators of de novo lipogenesis. CONCLUSION: These results show that the WD promptly increased TG levels in the liver by potentiating fat storage. This impaired the pathway of hepatic cholesterol uptake via the LDL-R axis, promoting a rapid increase in plasma total cholesterol levels. These results indicate that liver fat content is a factor involved in the regulation of plasma cholesterol.

Timing of high-intensity intermittent exercise affects ad libitum energy intake in overweight inactive men.

The present study sought to clarify the impact of exercise intensity and timing on energy intake and appetite-related blood variables. Fourteen inactive overweight men were included in the study. Firstly, maximal aerobic power (MAP) was measured. Then, participants randomly performed 5 experimental sessions consisting of 30 min of steady-state exercise (SSE) at 50% of MAP, high-intensity intermittent exercise (HIIE) with 30s repetitions at MAP and 30s of passive recovery or no exercise (CTRL). Sessions were performed 1h (SSE1h and HIIE1h) or 2.5h (SSE2.5h and HIIE2.5h) after the consumption of a standardized breakfast. An ad libitum buffet was offered 3.5h after the completion of the breakfast. Absolute energy intake (EI) and relative energy intake (REI) (relative energy intake = energy intake - energy expenditure from exercise) were measured. Appetite (hunger, fullness and desire for specific foods) scores and circulating concentration of insulin and IL-6 were determined at 1h, 1.75h, 2.5h and 3.25h after breakfast while lactate was measured post-exercise. EI was greater after the CTRL session compared to HIIE2.5h (5045.9 ±â€¯1873.5 kJ vs. 3716.1 ±â€¯1688.7 kJ). REI was greater for the CTRL session (5045.9 ±â€¯1873.5 kJ) than HIIE1h (3386.5 ±â€¯1660.1 kJ), HIIE2.5h (2508.5 ±â€¯1709.3 kJ) and SSE2.5h (3426.6 ±â€¯1788.0 kJ). Higher hunger scores were observed following the CRTL session with respect to those of HIIE2.5h. Insulin and IL-6 concentrations were greater after HIIE1h and SSE1h with respect to those obtained after HIIE2.5h, SSE2.5h and CTRL. Lactate concentrations were higher in HIIE1h and HIIE2.5h compared to those of SSE1h and SSE2.5h. These results show that HIIE performed 2.5h after a breakfast reduced appetite (hunger scores) and EI through mechanism that need to be characterized. This approach can be applied to individuals aiming to create an energetic deficit.

Crosstalk between intestinal microbiota, adipose tissue and skeletal muscle as an early event in systemic low-grade inflammation and the development of obesity and diabetes.

Obesity is associated with a systemic chronic low-grade inflammation that contributes to the development of metabolic disorders such as cardiovascular diseases and type 2 diabetes. However, the etiology of this obesity-related pro-inflammatory process remains unclear. Most studies have focused on adipose tissue dysfunctions and/or insulin resistance in skeletal muscle cells as well as changes in adipokine profile and macrophage recruitment as potential sources of inflammation. However, low-grade systemic inflammation probably involves a complex network of signals interconnecting several organs. Recent evidences have suggested that disturbances in the composition of the gut microbial flora and alterations in levels of gut peptides following the ingestion of a high-fat diet may be a cause of low-grade systemic inflammation that may even precede and predispose to obesity, metabolic disorders or type 2 diabetes. This hypothesis is appealing because the gastrointestinal system is first exposed to nutrients and may thereby represent the first link in the chain of events leading to the development of obesity-associated systemic inflammation. Therefore, the present review will summarize the latest advances interconnecting intestinal mucosal bacteria-mediated inflammation, adipose tissue and skeletal muscle in a coordinated circuitry favouring the onset of a high-fat diet-related systemic low-grade inflammation preceding obesity and predisposing to metabolic disorders and/or type 2 diabetes. A particular emphasis will be given to high-fat diet-induced alterations of gut homeostasis as an early initiator event of mucosal inflammation and adverse consequences contributing to the promotion of extended systemic inflammation, especially in adipose and muscular tissues.

Effect of an Acute High Carbohydrate Diet on Body Composition Using DXA in Young Men.

AIM: The aim of this study is to investigate the effect of a 3-day high-carbohydrate diet (≥75% of total calories) on body composition using dual-energy X-ray absorptiometry (DXA). METHODS: Twenty non-obese young men (age 22.7 ± 2.6 years, BMI 23.5 ± 2.1 kg/m(2)) completed the study. Two DXA tests were performed for the measurement of total body weight, body mass index (BMI), body fat percentage as well as total, appendicular and central lean body mass (LBM) before and after a high-carbohydrate diet for 3 days. In addition, the participants completed a food diary during the 3-day high-carbohydrate diet to determine the mean percentage of carbohydrates consumed from total kilocalories. RESULTS: The mean percentage of carbohydrate intake over 3 days was 83.7 ± 8.4%. Our results showed a significant increase in total body weight, BMI as well as total and appendicular LBM after the high-carbohydrate diet (p < 0.01). In addition, we observed a strong tendency for lower body fat percentage values after the intervention (p = 0.05). No significant difference was observed for central LBM. CONCLUSIONS: These results indicate that the effect of an acute high carbohydrate diet seems to affect body composition values using DXA, such as total LBM. This study may lead to the need of standardizing a diet prior to using DXA.

Substance P decreases fat storage and increases adipocytokine production in 3T3-L1 adipocytes.

Obesity, inflammation, and insulin resistance are closely linked. Substance P (SP), via its neurokinin 1 receptor (NK1R), mediates inflammatory and, possibly, neuroendocrine processes. We examined SP effects on lipid storage and cytokine production in 3T3-L1 adipocytes and adipose tissues. 3T3-L1 adipocytes and preadipocytes express NK1R, and 8 days of SP supplementation during differentiation to 3T3-L1 preadipocytes decreased lipid droplet accumulation. SP (10 nM, 24 h) increased lipolysis in primary adipocytes (138 ± 7%, P < 0.05) and reduced fatty acid uptake (-31 ± 7%, P < 0.05) and mRNA expression of the differentiation-related transcription factors peroxisome proliferator-activated receptor-γ type 2 (-64 ± 2%, P < 0.001) and CCAAT enhancer-binding protein (CEBP)-α (-65 ± 2%, P < 0.001) and the lipid storage genes fatty acid-binding protein type 4 (-59 ± 2%, P < 0.001) and diacylglycerol O-acyltransferase-1 (-45 ± 2%, P < 0.01) in 3T3-L1 adipocytes, while CD36, a fatty acid transporter (+82 ± 19%, P < 0.01), was augmented. SP increased secretion of complement C3 (148 ± 15%, P < 0.04), monocyte chemoattractant protein-1 (156 ± 16%, P < 0.03), and keratinocyte-derived chemokine (148 ± 18%, P = 0.045) in 3T3-L1 adipocytes and monocyte chemoattractant protein-1 (496 ± 142%, P < 0.02) and complement C3 (152 ± 25%, P < 0.04) in adipose tissue and primary adipocytes, respectively. These SP effects were accompanied by downregulation of insulin receptor substrate 1 (-82 ± 2%, P < 0.01) and GLUT4 (-76 ± 2%, P < 0.01) mRNA expression, and SP acutely blocked insulin-mediated stimulation of fatty acid uptake and Akt phosphorylation. Although adiponectin secretion was unchanged, mRNA expression was decreased (-86 ± 8%, P < 0.001). In humans, NK1R expression correlates positively with plasma insulin, fatty acid, and complement C3 and negatively with adiponectin, CEBPα, CEBPß, and peroxisome proliferator-activated receptor-γ mRNA expression in omental, but not subcutaneous, adipose tissue. Our results suggest that, beyond its neuroendocrine and inflammatory effects, SP could also be involved in targeting adipose tissue and influencing insulin resistance.

Impact of Breaking up of Sitting Time on Anti-inflammatory Response Induced by Extracellular Vesicles.

Physical inactivity and sedentary behaviors (SB) have promoted a dramatic increase in the incidence of a host of chronic disorders over the last century. The breaking up of sitting time (i.e., sitting to standing up transition) has been proposed as a promising solution in several epidemiological and clinical studies. In parallel to the large interest it initially created, there is a growing body of evidence indicating that breaking up prolonged sedentary time (i.e., > 7 h in sitting time) could reduce overall mortality risks by normalizing the inflammatory profile and cardiometabolic functions. Recent advances suggest that the latter health benefits, may be mediated through the immunomodulatory properties of extracellular vesicles. Primarily composed of miRNA, lipids, mRNA and proteins, these vesicles would influence metabolism and immune system functions by promoting M1 to M2 macrophage polarization (i.e., from a pro-inflammatory to anti-inflammatory phenotype) and improving endothelial function. The outcomes of interrupting prolonged sitting time may be attributed to molecular mechanisms induced by circulating angiogenic cells. Functionally, circulating angiogenic cells contribute to repair and remodel the vasculature. This effect is proposed to be mediated through the secretion of paracrine factors. The present review article intends to clarify the beneficial contributions of breaking up sitting time on extracellular vesicles formation and macrophage polarization (M1 and M2 phenotypes). Hence, it will highlight key mechanistic information regarding how breaking up sitting time protocols improves endothelial health by promoting antioxidant and anti-inflammatory responses in human organs and tissues.

Motilin stimulates preadipocyte proliferation and differentiation and adipocyte lipid storage.

Motilin is a circulating gastrointestinal peptide secreted primarily by duodenal mucosal M cells and recognized for its prokinetic effects on gastrointestinal tissues. Little information is available regarding effects on insulin/glucose homeostasis or adipocyte function. Our aim was to evaluate the effects of motilin on adipocyte proliferation, differentiation, lipolysis, and macronutrient uptake in adipocytes. 3T3-L1 cells and primary rat adipocytes were treated acutely and chronically with varying motilin concentrations, and effects were compared with vehicle alone (control), set as 100% for all assays. In preadipocytes, motilin stimulated proliferation ([(3)H]thymidine incorporation) and mitochondrial activity (141 ± 10%, P < 0.001 and 158 ± 10%, respectively, P < 0.001), in a concentration-dependent manner. Chronic supplementation with motilin during differentiation further increased lipogenesis (Oil red O staining 191 ± 27%, P < 0.05) and was associated with an upregulation of PPARγ (148 ± 8%, P < 0.01), C/EBPα (142 ± 17%, P < 0.05), and Cav3 (166 ± 20%, P < 0.05) expression. In mature 3T3-L1 adipocytes motilin increased fatty acid uptake/incorporation (≤ 202 ± 12%; P < 0.01) and glucose uptake (146 ± 9% P < 0.05) and decreased net fatty acid release (maximal -31%, P < 0.05) without influencing total lipolysis (glycerol release). Similar effects were obtained in primary rat adipocytes. Motilin acutely increased expression of PPARγ, CEBPß, DGAT1, and CD36 while decreasing adiponectin mRNA and secretion. In human adipose tissue, motilin receptor GPR38 correlated with HOMA-IR and GHSR1 (r = 0.876, P < 0.0001). Motilin binding and fatty acid incorporation into adipocytes were inhibited by antagonists MB10 and [D-lys3]-GRP6 and PI 3-kinase inhibitor wortmannin. Taken together, these results suggest that motilin may directly influence adipocyte functions by stimulating energy storage.

Brain activation following peripheral administration of the GLP-1 receptor agonist exendin-4.

The aim of our study was to investigate the anorectic and brain stimulatory effects of various doses of exendin-4 (Ex-4) and to investigate the role of the vagus nerve in Ex-4-induced brain activation. A dose-related increase in c-fos mRNA expression was observed following Ex-4 administration (0.155-15.5 µg/kg). Doses of Ex-4 that caused anorexia without aversive effects (0.155, 0.775 µg/kg) induced c-fos expression in the hypothalamic arcuate and paraventricular (PVH; parvocellular) nuclei as well as in the limbic and brainstem structures. Doses of Ex-4 that caused aversion (1.55, 15.5 µg/kg) stimulated the same regions (in a more intense way) and additionally activated the magnocellular hypothalamic structures (supraoptic nucleus and PVH magnocellular). The brain c-fos pattern induced by Ex-4 showed both similarities and differences with that induced by refeeding. Subdiaphragmatic vagotomy significantly blunted the stimulation of c-fos mRNA expression induced by Ex-4 in the nodose ganglion, the medial part of nucleus of the solitary tract, and the parvocellular division of the PVH. Pretreatment with Ex-9-39 (330 µg/kg ip) impaired the neuronal activation evoked by Ex-4 in all brain regions and in the nodose ganglion. Effects of Ex-4 on hypothalamic-pituitary-adrenal axis activity were not altered by vagotomy. Results of this study demonstrate and relate the anorectic and brain stimulatory effects of aversive and nonaversive doses of Ex-4 and indicate that the activation of specific central regions induced by the peripheral administration of Ex-4 is, at least in part, dependent on the integrity of the vagus nerve.

Early administration of L-arginine in mdx neonatal mice delays the onset of muscular dystrophy in tibialis anterior (TA) muscle.

Duchenne muscular dystrophy (DMD) is a genetic disorder that results in the absence of dystrophin, a cytoskeletal protein. Individuals with this disease experience progressive muscle destruction, which leads to muscle weakness. Studies have been conducted to find solutions for the relief of individuals with this disease, several of which have shown that utrophin, a protein closely related to dystrophin, when overexpressed in mdx neonatal mice (the murine model of DMD), is able to prevent the progressive muscle destruction observed in the absence of dystrophin. Furthermore, recent studies have shown that L-arginine induces utrophin upregulation in adult mdx mice. We hypothesized that L-arginine treatment also induces utrophin upregulation to prevent the development of muscle weakness in neonatal mdx mice. Hence, L-arginine should also prevent progressive muscle destruction via utrophin upregulation in mdx neonatal mice. Mdx neonatal mice were injected intraperitoneally daily with 800 mg/kg of L-arginine for 6 weeks, whereas control mice were injected with a physiological saline. The following experiments were performed on the tibialis anterior (TA) muscle: muscle contractility and resistance to mechanical stress; central nucleation and peripheral nucleation, utrophin, and creatine kinase quantification as well as a nitric oxide (NO) assay. Our findings show that early administration of L-arginine in mdx neonatal mice prevents the destruction of the tibialis anterior (TA) muscle. However, this improvement was related to nitric oxide (NO) production rather than the expected utrophin upregulation.

Interplay Between Gut Microbiota and Gastrointestinal Peptides: Potential Outcomes on the Regulation of Glucose Control.

A host of gastrointestinal (GI) peptides influence the regulation of vital functions, such as growth, appetite, stress, gut motility, energy expenditure, digestion and inflammation, as well as glucose and lipid homeostasis. Hence, impairments in the synthesis/secretion of glucagon-like peptide-1 (GLP-1), leptin, nesfatin-1, glucose-dependent insulinotropic peptide (GIP), ghrelin (acylated and unacylated forms), oxyntomodulin, vasoactive intestinal peptide, somatostatin, cholecystokinin, peptide tyrosine‒tyrosine, GLP-2 and pancreatic polypeptide were previously associated with the development of obesity-related disorders. It is currently emphasized that the beneficial metabolic outcomes associated with the normalization of the gut microbiota (GM) is influenced by increases in GLP-1 and peptide YY secretion as well as by decreases in acylated ghrelin production. These effects are associated with reductions in body weight and adiposity in combination with the normalization of glucose and lipid metabolism. However, important questions remain unanswered regarding how GLP-1, peptide tyrosine‒tyrosine, acylated ghrelin and other metabolically relevant GI peptides interact with the GM to modulate the host's metabolic functions. In addition, it is likely that the GM and other biologically active GI peptides influence metabolic functions, such as glucose control, although the mechanisms remain ill-defined. In this review, we investigate how GM and GI peptides influence glucose metabolism in experimental models, such as germ-free animals and dietary interventions. Emphasis is placed on pathways through which GM and GI peptides could modulate intestinal permeability, nutrient absorption, short-chain fatty acid production, metabolic endotoxemia, oxidative stress and low-grade inflammation.

Change in plasma acylation stimulating protein during euglycaemic-hyperinsulinaemic clamp in overweight and obese postmenopausal women: a MONET study.

OBJECTIVE: Acylation-stimulating protein (ASP) has been shown to positively stimulate fatty acid esterification and glucose uptake in adipocytes. In vitro studies demonstrate that insulin stimulates ASP secretion from adipocytes. Individuals with obesity and/or metabolic disturbances (insulin resistance and type 2 diabetes) have increased plasma ASP. DESIGN: The present study was designed to evaluate whether ASP levels are influenced by the metabolic profiles of overweight and obese postmenopausal women during a euglycaemic/hyperinsulinaemic clamp (EHC). Patients The study population consisted of 76 overweight and obese sedentary postmenopausal women. MEASUREMENTS: We evaluated insulin sensitivity, plasma ASP levels, body composition including visceral adipose tissue area, blood lipid profiles, liver enzymes, peak aerobic capacity, resting metabolic rate (RMR) and total energy expenditure (TEE). RESULTS: We observed wide interindividual variations of ASP levels during the EHC. Therefore, subjects were divided into three groups based on ASP changes. Negative ASP Responders (NAR; n = 24) showed a -20% or greater decrease in ASP levels while Positive ASP Responders (PAR; n = 42) displayed ASP fluctuations superior to +20%. Ten subjects had little or no ASP change and were considered as Zero ASP responders (ZAR). PAR women displayed a worse metabolic profile than NAR women, including higher BMI, visceral adipose tissue, fasting insulin levels, lean body mass, and alanine aminotransferase (ALT), a marker of impaired liver function. After adjustment for BMI, only ALT remained significantly different, while lean body mass (P = 0.08) and visceral adipose tissue (P = 0.07) remained marginally higher. Correlation analysis of all subjects demonstrated that fasting ASP levels correlated positively with albumin and VO(2 peak) and this association remained significant after adjustments for the effect of BMI. In addition, the percentage maximal change in ASP levels during the EHC was positively associated with BMI, lean body mass, visceral adipose tissue, fasting insulin, HOMA, TEE, RMR, ALT and AST. CONCLUSION: Overall these results suggest that an elevated ASP response during the EHC is associated with metabolic disturbances in overweight and obese postmenopausal women.

Ethical consideration and feasibility demonstration of high-intensity interval training without the use of electrical shocks in mice with and without doxorubicin exposition.

INTRODUCTION: Most protocols intended to stimulate cardiovascular training in mice use electrical shocks that cause psychological stress and interfere with running performance. The aim of this study was to: 1) demonstrate the feasibility of a two-week high-intensity interval training (HIIT) program without the use of electric shocks in mice and 2) show that HIIT without electric shocks is feasible in the specific context of mice exposed to chemotherapy (i.e., doxorubicin). METHODS: Ten C57bl/6 6-week-old female mice underwent a maximal exercise capacity test before and after two weeks of HIIT (five sessions per week) to measure their maximum running speed. The electrical stimulus was substituted by gently lifting the hind legs of the training mice using a tongue depressor. A second sample of ten C57bl/6 10-week-old female mice receiving a single intravenous injection of 20 mg/kg of doxorubicin underwent a single session of HIIT post-DOX using the same gentle stimulation method. RESULTS: After two weeks of HIIT without the use of electric shocks, non-treated mice had a significant increase in their maximal speed (4.4 m•min-1; P = 0.019). In DOX-treated mice, the compliance rate to run went from 100% during the acclimation period prior to doxorubicin treatment to 100% when HIIT was performed after the DOX treatment. Doxorubicin treatment seemed to affect exercise compliance in DOX-treated mice. Our study demonstrated that a two-week HIIT program in non-treated mice and a single HIIT session in DOX-treated mice are feasible. CONCLUSION: The use of electric shocks was not required to obtain acceptable exercise compliance and a significant change in mice physical capacity. Our technique to perform a treadmill maximal exercise capacity test was shown to be feasible, even in specific pathological conditions like chemotherapy infusion, and could become a reference for future research protocols aimed at reducing the impact of psychological stress caused by electric shocks in mice. This model of exercise training in mice introduces an alternative to ethical conduct standards in animal research.

A Short-Term High-Fat Diet Alters Glutathione Levels and IL-6 Gene Expression in Oxidative Skeletal Muscles of Young Rats.

Obesity and ensuing disorders are increasingly prevalent worldwide. High-fat diets (HFD) and diet-induced obesity have been shown to induce oxidative stress and inflammation while altering metabolic homeostasis in many organs, including the skeletal muscle. We previously observed that 14 days of HFD impairs contractile functions of the soleus (SOL) oxidative skeletal muscle. However, the mechanisms underlying these effects are not clarified. In order to determine the effects of a short-term HFD on skeletal muscle glutathione metabolism, young male Wistar rats (100-125 g) were fed HFD or a regular chow diet (RCD) for 14 days. Reduced (GSH) and disulfide (GSSG) glutathione levels were measured in the SOL. The expression of genes involved in the regulation of glutathione metabolism, oxidative stress, antioxidant defense and inflammation were measured by RNA-Seq. We observed a significant 25% decrease of GSH levels in the SOL muscle. Levels of GSSG and the GSH:GSSG ratio were similar in both groups. Further, we observed a 4.5 fold increase in the expression of pro-inflammatory cytokine interleukin 6 (IL-6) but not of other cytokines or markers of inflammation and oxidative stress. We hereby demonstrate that a short-term HFD significantly lowers SOL muscle GSH levels. This effect could be mediated through the increased expression of IL-6. Further, the skeletal muscle antioxidant defense could be impaired under cellular stress. We surmise that these early alterations could contribute to HFD-induced insulin resistance observed in longer protocols.

The impact of a short-term high-fat diet on mitochondrial respiration, reactive oxygen species production, and dynamics in oxidative and glycolytic skeletal muscles of young rats.

Multiple aspects of mitochondrial function and dynamics remain poorly studied in the skeletal muscle of pediatric models in response to a short-term high-fat diet (HFD). This study investigated the impact of a short-term HFD on mitochondrial function and dynamics in the oxidative soleus (SOL) and glycolytic extensor digitorum longus (EDL) muscles in young rats. Young male Wistar rats were submitted to either HFD or normal chow (NCD) diets for 14 days. Permeabilized myofibers from SOL and EDL were prepared to assess mitochondrial respiration and reactive oxygen species (ROS) production. The expression and content of protein involved in mitochondrial metabolism and dynamics (fusion/fission) were also quantified. While no effects of HFD was observed on mitochondrial respiration when classical complex I and II substrates were used, both SOL and EDL of rats submitted to a HFD displayed higher basal and ADP-stimulated respiration rates when Malate + Palmitoyl-L-carnitine were used as substrates. HFD did not alter ROS production and markers of mitochondrial content. The expression of CPT1b was significantly increased in SOL and EDL of HFD rats. Although the expression of UCP3 was increased in SOL and EDL muscles from HFD rats, mitochondrial coupling efficiency was not altered. In SOL of HFD rats, the transcript levels of Mfn2 and Fis1 were significantly upregulated. The expression and content of proteins regulating mitochondrial dynamics was not modulated by HFD in the EDL. Finally, DRP1 protein content was increased by over fourfold in the SOL of HFD rats. Taken altogether, our findings show that exposing young animals to short-term HFD results in an increased capacity of skeletal muscle mitochondria to oxidize fatty acids, without altering ROS production, coupling efficiency, and mitochondrial content. Our results also highlight that the impact of HFD on mitochondrial dynamics appears to be muscle specific.

Immunometabolic Changes in Hepatocytes Arising from Obesity and the Practice of Physical Exercise.

Over the recent years, a particular interest was shown towards understanding the roles of excessive hepatic fat accumulation and the development of obesity-related diseases. While hepatic triacylglycerol accumulation seems to be a response to the systemic increase of insulin release, fatty acid metabolites contribute to the progression of non-alcoholic fatty liver disease (NAFLD) to non-alcoholic steatohepatitis (NASH). It is widely accepted that NAFLD is a polygenic and multifactorial disease under the influence of critical behavioral factors such as overeating and sedentary lifestyles. The progression of the disease is proposed to include the accumulation of lipids in hepatocytes, but liver damage would be mainly initiated through an exaggerated activation of the immune system. This inflammatory response would be triggered by the increase in cytokine production followed by TLR-4 activation and NF-kB pathways. Interestingly, cytokines as IL-1ra, IL-4, IL-6 and IL-10 act as antiinflammatory in response to exercise and thus, could play an important role in the restoration of liver functions in diseased conditions. Strategies for healthy life behaviors including nutrition and regular physical exercise are recommended to counteract the dreadful effects of NAFLD. To beyond the classical effect of exercise for increasing energy expenditure and/or inducing negative energy balance, exercise also prevents and reverses the effects of disorders related to the immunometabolic profile. This suggests that exercise prescription may be an attractive alternative for the prevention of obesity and NAFLD. Thus, this review seeks to shed light on the inflammatory pathways regulating the beneficial effects of physical activity on obesity and NAFLD. We will clarify how physical activity intervenes to normalize inflammatory processes and prevent obesity and NAFLD. Finally, the exercise interventions should be individualized to facilitate behavioral and cognitive strategies in order to promote long-term adherence. A multidisciplinary approach including lifestyles, diet and exercise training interventions is considered as a "best practice" and displays the strongest liver benefits when it occurs simultaneously with weight loss.

Altered Feeding Behaviors and Adiposity Precede Observable Weight Gain in Young Rats Submitted to a Short-Term High-Fat Diet.

Information regarding the early effects of obesogenic diets on feeding patterns and behaviors is limited. To improve knowledge regarding the etiology of obesity, young male Wistar rats were submitted to high-fat (HFD) or regular chow diets (RCDs) for 14 days. Various metabolic parameters were continuously measured using metabolic chambers. Total weight gain was similar between groups, but heavier visceral fat depots and reduced weight of livers were found in HFD rats. Total calorie intake was increased while individual feeding bouts were shorter and of higher calorie intake in response to HFD. Ambulatory activity and sleep duration were decreased in HFD rats during passive and active phase, respectively. Acylated and unacylated ghrelin levels were unaltered by the increased calorie intake and the early changes in body composition. This indicates that at this early stage, the orexigenic signal did not adapt to the high-calorie content of HFD. We hereby demonstrate that, although total weight gain is not affected, a short-term obesogenic diet alters body composition, feeding patterns, satiation, ambulatory activity profiles, and behaviours in a young rat model. Moreover, this effect precedes changes in weight gain, obesity, and ensuing metabolic disorders.

Altered Lipid Metabolism Impairs Skeletal Muscle Force in Young Rats Submitted to a Short-Term High-Fat Diet.

Obesity and ensuing disorders are increasingly prevalent in young populations. Prolonged exposure to high-fat diets (HFD) and excessive lipid accumulation were recently suggested to impair skeletal muscle functions in rodents. We aimed to determine the effects of a short-term HFD on skeletal muscle function in young rats. Young male Wistar rats (100-125 g) were fed HFD or a regular chow diet (RCD) for 14 days. Specific force, resistance to fatigue and recovery were tested in extensor digitorum longus (EDL; glycolytic) and soleus (SOL; oxidative) muscles using an ex vivo muscle contractility system. Muscle fiber typing and insulin signaling were analyzed while intramyocellular lipid droplets (LD) were characterized. Expression of key markers of lipid metabolism was also measured. Weight gain was similar for both groups. Specific force was decreased in SOL, but not in EDL of HFD rats. Muscle resistance to fatigue and force recovery were not altered in response to the diets. Similarly, muscle fiber type distribution and insulin signaling were not influenced by HFD. On the other hand, percent area and average size of intramyocellular LDs were significantly increased in the SOL of HFD rats. These effects were consistent with the increased expression of several mediators of lipid metabolism in the SOL muscle. A short-term HFD impairs specific force and alters lipid metabolism in SOL, but not EDL muscles of young rats. This indicates the importance of clarifying the early mechanisms through which lipid metabolism affects skeletal muscle functions in response to obesogenic diets in young populations.

Association of acylated and nonacylated ghrelin with insulin sensitivity in overweight and obese postmenopausal women.

OBJECTIVE: Ghrelin [acylated (AG) and nonacylated (NAG)] has been shown to play a pivotal role in the regulation of food intake and insulin sensitivity. It is presently unclear whether variation in insulin sensitivity is related to AG and NAG levels in obese individuals. To address this issue, we determined whether insulin-sensitive overweight or obese (ISO) and insulin-resistant overweight or obese (IRO) individuals display different total ghrelin (TotG), AG, and NAG profiles during a euglycemic/hyperinsulinemic clamp (EHC). DESIGN: Eighty-nine nondiabetic overweight and obese postmenopausal women underwent EHC to evaluate insulin sensitivity. Body composition and blood lipid profiles were assessed. Subjects within the highest tertile of insulin sensitivity were described as ISO (n = 31), whereas those within the lowest tertile of insulin sensitivity were considered as IRO (n = 29). Plasma TotG, AG, and NAG profiles were assessed by RIA at 0, 60, 160, 170, and 180 min during the EHC. RESULTS: TotG and NAG levels were significantly decreased for ISO and IRO individuals during the EHC, whereas only ISO subjects displayed a significant reduction of AG concentrations (P < 0.05). AG area under the curve value and the ratio of AG/NAG (fasting and area under the curve) were significantly decreased in ISO individuals. Furthermore, maximal reduction of TotG and AG concentrations was greater in ISO compared with IRO individuals (P < 0.05). Insulin sensitivity was significantly correlated with maximal reduction of TotG (r = 0.36; P < 0.01) and AG (r = 0.36; P < 0.05) concentrations. CONCLUSION: The dysregulation of ghrelin secretion profiles during EHC is associated with insulin resistance. AG may contribute to the variation of insulin sensitivity in overweight or obese postmenopausal women.