Swimming training beneficial effects in a mice model of nonalcoholic fatty liver disease. ACTA ACUST UNITED AC. 2012;64:273-282. [PMID: 20869214 DOI: 10.1016/j.etp.2010.08.019]

Mechanisms underpinning the effect of exercise on the non-alcoholic fatty liver disease: review

Non-alcoholic Fatty Liver Disease (NAFLD) - whose terminology was recently replaced by metabolic liver disease (MAFLD) - is an accumulation of triglycerides in the liver of >5 % of its weight. Epidemiological studies indicated an association between NAFLD and reduced physical activity. In addition, exercise has been shown to improve NAFLD independently of weight loss. In this paper, we aim to systematically review molecular changes in sedentary experimental NAFLD models vs. those subjected to exercise. We utilized the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist and standard review techniques. Studies were considered for inclusion if they addressed the primary question: the mechanisms by which exercise influenced NAFLD. This review summarized experimental evidence of improvements in NAFLD with exercise in the absence of weight loss. The pathways involved appeared to have AMPK as a common denominator. See also the graphical abstract(Fig. 1).

Exercise, mTOR Activation, and Potential Impacts on the Liver in Rodents

The literature offers a consensus on the association between exercise training (ET) protocols based on the adequate parameters of intensity and frequency, and several adaptive alterations in the liver. Indeed, regular ET can reverse glucose and lipid metabolism disorders, especially from aerobic modalities, which can decrease intrahepatic fat formation. In terms of molecular mechanisms, the regulation of hepatic fat formation would be directly related to the modulation of the mechanistic target of rapamycin (mTOR), which would be stimulated by insulin signaling and Akt activation, from the following three different primary signaling pathways: (I) growth factor, (II) energy/ATP-sensitive, and (III) amino acid-sensitive signaling pathways, respectively. Hyperactivation of the Akt/mTORC1 pathway induces lipogenesis by regulating the action of sterol regulatory element binding protein-1 (SREBP-1). Exercise training interventions have been associated with multiple metabolic and tissue benefits. However, it is worth highlighting that the mTOR signaling in the liver in response to exercise interventions remains unclear. Hepatic adaptive alterations seem to be most outstanding when sustained by chronic interventions or high-intensity exercise protocols.

Chronic exercise improves hepatic acylcarnitine handling

Exercise mediates tissue metabolic function through direct and indirect adaptations to acylcarnitine (AC) metabolism, but the exact mechanisms are unclear. We found that circulating medium-chain acylcarnitines (AC) (C12-C16) are lower in active/endurance trained human subjects compared to sedentary controls, and this is correlated with elevated cardiorespiratory fitness and reduced adiposity. In mice, exercise reduced serum AC and increased liver AC, and this was accompanied by a marked increase in expression of genes involved in hepatic AC metabolism and mitochondrial β-oxidation. Primary hepatocytes from high-fat fed, exercise trained mice had increased basal respiration compared to hepatocytes from high-fat fed sedentary mice, which may be attributed to increased Ca2+ cycling and lipid uptake into mitochondria. The addition of specific medium- and long-chain AC to sedentary hepatocytes increased mitochondrial respiration, mirroring the exercise phenotype. These data indicate that AC redistribution is an exercise-induced mechanism to improve hepatic function and metabolism.

Quantification of the liver structure of zebrafish (Danio rerio) submitted to different diets and physical exercise

The zebrafish has been used in research for over 80 years. In the last three decades, discoveries about the fundamental properties of development, regeneration, cancer, and other diseases have established the zebrafish as an important model organism in biomedical research. This study aimed to evaluate liver alterations in zebrafish by quantitatively assessing the areas occupied by hepatocytes, as well as connective and adipose tissues. Forty-eight adult Danio rerio (38 males and 10 females) of approximately 13 months of age were used. They were divided into four groups, with 12 animals each. The fish were randomly distributed to form the groups, which received a maintenance and/or hypercaloric diet, with or without the addition of physical exercise. The animals underwent six hours of forced exercise (5 cm/s) for thirteen weeks. The animals that practiced physical exercise had a higher volumetric density of the area occupied by hepatocytes (65.92%±1.81 - GMex and 50.75%±2.24 GHex) among the groups. The GH group had a higher volumetric density of the area occupied by connective tissue (15.12%±0.72), followed by the GHex group (13.53%±1.43). Regarding the volumetric density of the area occupied by adipose tissue, the GH group had a higher density (27.21%±1.36), followed by the GHex group (21.66%±1.11) with statistically significant differences. The GMex had a volumetric density of the area occupied by adipose tissue of 3.5%±0.76, while the GM had 5.7%±0.5, with statistical difference. In relation to the animals in the GHex group, they had 20.39% less fat than the animals in the GH group. The animals in the GMex group had 72.47% less fat than those in the GM group. It is concluded that the different dietary constitutions and the imposition of physical exercise were able to modify the structural architecture of the liver of Danio rerio. These are acceptable criteria for modulations, thus aiming at the control and possible interferences directly related to the metabolism of the species and therefore the control of diseases.

Aerobic exercise and vitamin E improve high-fat diet-induced NAFLD in rats by regulating the AMPK pathway and oxidative stress

BACKGROUND AND AIMS

Non-alcoholic fatty liver disease (NAFLD) has emerged as a major chronic liver disease. We explored simple and effective ways to improve NAFLD and investigate the mechanism of action.

METHODS

NAFLD was induced in 40 rats fed a high-fat diet (HFD). Magnetic resonance imaging was used to evaluate the progression and improvement of NAFLD. The treatment-related interventions included aerobic exercise (E) and vitamin E (VE) supplementation. Expression levels of proteins related to fat metabolism were also assessed. The activities of antioxidant enzymes in the liver and serum lipid metabolism were analyzed using biochemical methods.

RESULTS

Aerobic exercise and vitamin E effectively improved NAFLD in rats, resulting in decreased hepatic fat accumulation, reduced hepatocyte ballooning, and decreased triglyceride levels. Combination therapy achieved the best effect. Both aerobic exercise and vitamin E activate the AMPK pathway to phosphorylate acetyl-CoA carboxylase (ACC) and reduce fatty acid synthesis. The expression of sterol regulatory element-binding protein-1 (SREBP-1) was decreased significantly in the treated groups, particularly in the E + VE + HFD group. The expression of carnitine palmitoyl-transferase 1C (CPT1C) significantly increased in the treated groups, particularly in the E + VE + HFD group. Compared with the control group, reactive oxygen species (ROS) in the E + HFD group were slightly decreased, while that in the VE + HFD group were significantly decreased, with the even greater reduction observed in the E + VE + HFD group.

CONCLUSION

Aerobic exercise and vitamin E supplementation can improve HFD-induced NAFLD in rats by regulating the AMPK pathway and reducing oxidative stress.

Exercise training rescues adipose tissue spexin expression and secretion in diet-induced obese mice

Exercise training improves obesity-induced metabolic diseases through regulation of adipokines. Previous studies have shown that adipocyte-spexin participates in metabolic diseases such as obesity and diabetes via the modulation of energy homeostasis and insulin resistance. The objective of this research was to investigate the effects of swimming exercise on the levels of adipocyte-spexin and the underlying mechanisms. The normal chow diet (NC)-fed and high-fat diet (HFD)-fed mice were divided into exercise or sedentary groups. The expression and secretion of spexin in adipose tissue were assessed by quantitative real-time PCR and ELISA. The present findings uncovered the effect of exercise-induced spexin expression in the adipose tissue of obese mice. Besides, chronic exercise-induced upregulation of adipose spexin may be mediated by COUP-TF2 and KLF9. In addition, constant-moderate intensity exercise increased the levels of GLUT4, SIRT1 and PGC-1α in the skeletal muscles of mice. These results suggest that spexin is a potential mediator for exercise to ameliorate obesity-induced insulin resistance, namely, the beneficial effect of exercise on insulin sensitivity is at least partly mediated by spexin. Thus, exercise restores spexin production and release, which increases insulin sensitivity and maintains metabolic balance in the adipose tissues of HFD-induced obese mice.

Imaging the Effects of Whole-Body Vibration on the Progression of Hepatic Steatosis by Quantitative Ultrasound Based on Backscatter Envelope Statistics

Hepatic steatosis causes nonalcoholic fatty liver disease. Whole-body vibration (WBV) has been recommended to allow patients who have difficulty engaging in exercise to improve the grade of hepatic steatosis. This study proposed using ultrasound parametric imaging of the homodyned K (HK) distribution to evaluate the effectiveness of WBV treatments in alleviating hepatic steatosis. Sixty mice were assigned to control (n = 6), sedentary (n = 18), WBV (n = 18), and exercise (swimming) (n = 18) groups. Mice were fed a high-fat diet to induce hepatic steatosis and underwent the intervention for 4, 8, and 16 weeks. Ultrasound scanning was performed in vivo on each mouse after the interventions for ultrasound HK imaging using the parameter μ (the scatterer clustering parameter). Histopathological examinations and the intraperitoneal glucose tolerance test were carried out for comparisons with ultrasound findings. At the 16th week, WBV and exercise groups demonstrated lower body weights, glucose concentrations, histopathological scores (steatosis and steatohepatitis), and μ parameters than the control group (p < 0.05). The steatosis grade was significantly lower in the WBV group (mild) than in the exercise group (moderate) (p < 0.05), corresponding to a reduction in the μ parameter. A further analysis revealed that the correlation between the steatosis grade and the μ parameter was 0.84 (p < 0.05). From this animal study we conclude that WBV may be more effective than exercise in reducing the progression of hepatic steatosis, and ultrasound HK parametric imaging is an appropriate method for evaluating WBV’s effect on hepatic steatosis.

Changes in mitochondrial biogenesis and fatty liver indicators in rat following continuous and high intensity interval training

BACKGROUND

Oxidative stress and mitochondrial dysfunction can be tracked down in most liver diseases like non-alcoholic fatty liver disease (NAFLD). The most recommended preventative method is lifestyle modification, especially exercise. The aim of this study was the investigation of changes in the indexes of mitochondrial biogenesis and fatty liver indicators in rat following continuous and high intensity interval training.

METHODS

Thirty healthy male rats were divided into three control (C=10), Continuous swimming training (CT=10) and High intensity interval swimming training groups (HIIT=10). The training groups performed their specific exercises 5 days a week for 8 weeks. 24 h after the last training session in order to prepare the serum, a blood sample was taken from the left ventricle of the rats. In addition, liver tissue was extracted and the SIRT3, PGC-1α, GSH:GSSG, MDA, LDL, HDL, LDL:HDL, TG, TC, AST, ALT and FBS variables were measured by ELISA and analysis of blood biochemistry.

RESULTS

Continuous training (CT) increased the levels of PGC-1α, SIRT3 and significantly reduced LDL, LDL:HDL, TG and FBS (P<0.05) levels. High-intensity interval training (HIIT) caused a significant increase in SIRT3 and a significant decrease in FBS (P<0.05) levels.

CONCLUSIONS

Adaptations resulting from further aerobic exercise can increase mitochondrial biogenesis factors such as PGC-1α and SIRT3 in hepatocytes, improve this process in hepatocytes, and ultimately improve the fatty liver markers. Therefore, CT may be more effective than HIIT in preventing fatty liver disease.

Obese mice weight loss role on nonalcoholic fatty liver disease and endoplasmic reticulum stress treated by a GLP-1 receptor agonist

BACKGROUND/OBJECTIVES

The weight loss following Semaglutide treatment, a GLP-1 receptor agonist, might be responsible for some effects observed on the nonalcoholic fatty liver disease of obese mice.

SUBJECTS/METHODS

Two groups of C57BL/6 male mice (n = 30/group) were fed the diets Control (C) or high-fat (HF) for 16 weeks. Then, separated into six new groups for an additional four weeks (n = 10/group) and treated with Semaglutide (S, 40 µg/kg) or paired feeding (PF) with S groups (C; C-S; C-PF; HF; HF-S; HF-PF).

RESULTS

Semaglutide reduced energy consumption leading to weight loss. Simultaneously it improved glucose intolerance, glycated hemoglobin, insulin resistance/sensitivity, plasma lipids, and gastric inhibitory polypeptide. Semaglutide and paired feeding mitigated liver steatosis and adipose differentiation-related protein (Plin2) expression. Semaglutide also improved hormones and adipokines, reduced lipogenesis and inflammation, and increased beta-oxidation. Semaglutide lessened liver glucose uptake and endoplasmic reticulum (ER) stress. Among the 14 genes analyzed, 13 were modified by Semaglutide (93 %, six genes were changed exclusively by Semaglutide, and seven other genes were affected by the combination of Semaglutide and paired feeding). In seven genes, the paired diet showed no effect (50% of the genes tested). No marker was affected exclusively by paired feeding.

CONCLUSIONS

Semaglutide and the consequent weight loss reduced obese mice liver inflammation, insulin resistance, and ER stress. However, weight loss alone did show few or no action on some significant study findings, like liver steatosis, leptin, insulin, resistin, and amylin. Furthermore, hepatic inflammation mediated by MCP-1 and partially by TNF-alpha and IL6 were also not reduced by weight loss. Furthermore, weight loss alone did not lessen hepatic lipogenesis as determined by the findings of SREBP-1c, CHREBP, PPAR-alpha, and SIRT1. Semaglutide was implicated in improving glucose uptake and lessening ER stress by reducing GADD45, independent of weight loss.

Effects of Long-Term DHA Supplementation and Physical Exercise on Non-Alcoholic Fatty Liver Development in Obese Aged Female Mice

Obesity and aging are associated to non-alcoholic fatty liver disease (NAFLD) development. Here, we investigate whether long-term feeding with a docosahexaenoic acid (DHA)-enriched diet and aerobic exercise, alone or in combination, are effective in ameliorating NAFLD in aged obese mice. Two-month-old female C57BL/6J mice received control or high fat diet (HFD) for 4 months. Then, the diet-induced obese (DIO) mice were distributed into four groups: DIO, DIO + DHA (15% dietary lipids replaced by a DHA-rich concentrate), DIO + EX (treadmill running), and DIO + DHA + EX up to 18 months. The DHA-rich diet reduced liver steatosis in DIO mice, decreasing lipogenic genes (Dgat2, Scd1, Srebp1c), and upregulated lipid catabolism genes (Hsl/Acox) expression. A similar pattern was observed in the DIO + EX group. The combination of DHA + exercise potentiated an increase in Cpt1a and Ppara genes, and AMPK activation, key regulators of fatty acid oxidation. Exercise, alone or in combination with DHA, significantly reversed the induction of proinflammatory genes (Mcp1, Il6, Tnfα, Tlr4) in DIO mice. DHA supplementation was effective in preventing the alterations induced by the HFD in endoplasmic reticulum stress-related genes (Ern1/Xbp1) and autophagy markers (LC3II/I ratio, p62, Atg7). In summary, long-term DHA supplementation and/or exercise could be helpful to delay NAFLD progression during aging in obesity.

Maternal swimming mitigates liver damage caused by paternal obesity

OBJECTIVES

Parents' lifestyle and nutrition can program offspring obesity in adulthood. We hypothesized that maternal swimming has beneficial effects on the adversity caused by paternal obesity on offspring.

METHODS

Twelve-week-old male C57 BL/6 J mice (fed a high-fat diet, obese father [ObFa], or control diet, lean father [LFa]) were mated with female mice fed only the control diet. Mothers were trained (TMo) or untrained (UMo): swimming for 6 wk before and the first 2 wk of gestation. Pups were fed only the control diet.

RESULTS

Fathers showed different body mass (BM) at copulation, but not the mothers. The ObFa had 20% higher BM than the LFa. Twelve-week-old ObFa/UMo offspring showed a higher BM gain than the LFa/UMo and ObFa/TMo. There was BM sexual dimorphism in the LFa/UMo (female mice +24% than male mice). There was hyperglycemia and hyperinsulinemia in the ObFa/UMo, but low glycemia and insulin levels were seen in the ObFa/TMo. There was augmented liver steatosis in the ObFa/UMo compared with the LFa/UMo, and the ObFa/TMo compared with the LFa/TMo, but reduced steatosis in the ObFa/TMo compared with the ObFa/UMo. In addition, lipogenic markers were more expressed and beta-oxidation markers less expressed in the ObFa/UMo compared with the LFa/UMo, but the opposite was observed in the ObFa/TMo compared with the ObFa/UMo. Proinflammatory markers were higher in the liver of the ObFa/UMo compared with the LFa/UMo and lower in the ObFa/TMo compared with the ObFa/UMo.

CONCLUSIONS

Obese fathers produced offspring that were overweight and had altered fasting glycemia and insulin sensitivity, leading to higher liver lipogenesis and inflammation, as well as lower beta-oxidation. The swimming mother mitigated these adverse effects in mice offspring.

The effects of different types of aquatic exercise training interventions on a high-fructose diet-fed mice

Gradual weight gain in modern people and a lowering onset age of metabolic disease are highly correlated with the intake of sugary drinks and sweets. Long-term excessive fructose consumption can lead to hyperglycemia, hyperlipidemia and accumulation of visceral fat. Abdominal obesity is more severe in females than in males. In this study, we used a high-fructose-diet-induced model of obesity in female mice. We investigated the effects of aquatic exercise training on body weight and body composition. After 1 week of acclimatization, female ICR mice were randomly divided into two groups: a normal group (n=8) fed standard diet (control), and a high-fructose diet (HFD) group (n=24) fed a HFD. After 4 weeks of induction followed by 4 weeks of aquatic exercise training, the 24 obese mice were divided into 3 groups (n=8 per group): HFD with sedentary control (HFD), HFD with aquatic strength exercise training (HFD+SE), and HFD with aquatic aerobic exercise training (HFD+AE). We conducted serum biochemical profile analysis, weighed the white adipose tissue, and performed organ histopathology. After 4 weeks of induction and 4 weeks of aquatic exercise training, there was no significant difference in body weight among the HFD, HFD+SE and HFD+AE groups. Serum triglyceride (TG), AST, ALT, and uric acid level were significantly lower in the HFD+SE and HFD+AE groups than in the HFD group. The weight of the perirenal fat pad was significantly lower in the HFD+AE group than in the HFD group. Hepatic TG and total cholesterol (TC) were significantly lower in the HFD+AE group than in the other groups. Long-term intake of a high-fructose diet can lead to obesity and increase the risk of metabolic disease. Based on our findings, we speculate that aquatic exercise training can effectively promote health and fitness. However, aquatic aerobic exercise training appears to have greater benefits than aquatic strength exercise training.

Aerobic training improves NAFLD markers and insulin resistance through AMPK-PPAR-α signaling in obese mice

Liver steatosis is one of the main drivers for the development of whole-body insulin resistance. Conversely, aerobic training (AT) has been suggested as non-pharmacological tool to improve liver steatosis, however, the underlying molecular mechanism remains unclear. Therefore, the aim of this study was to analyze the effect of 8-weeks AT in non-alcoholic liver disease (NAFLD) outcomes in obese mice. Male C57BL/6 J wild type (WT) were fed with standard (SD) or high-fat diet (HFD) for 12-weeks. Another group fed with HFD underwent 8-weeks of AT (60% of maximum velocity), initiated at the 5th week of experimental protocol. We measured metabolic, body composition parameters, protein and gene expression inflammatory and metabolic mediators. We found that AT attenuates the weight gain, but not body fat accumulation. AT improved triacylglycerol and non-esterified fatty acid plasma concentrations, and also whole-body insulin resistance. Regarding NAFLD, AT decreased the progression of macrovesicular steatosis and inflammation through the upregulation of AMPK Thr172 phosphorylation and PPAR-α protein expression. Moreover, although no effects of intervention in PPAR-γ protein concentration were observed, we found increased levels of its target genes Cd36 and Scd1 in exercised group, demonstrating augmented transcriptional activity. AT reduced liver cytokines concentrations, such as TNF-α, IL-10, MCP-1 and IL-6, regardless of increased Ser536 NF-κB phosphorylation. In fact, none of the interventions regulated NF-κB target genes Il1b and Cccl2, demonstrating its low transcriptional activity. Therefore, we conclude that AT attenuates the progression of liver macrovesicular steatosis and inflammation through AMPK-PPAR-α signaling and PPAR-γ activation, respectively, improving insulin resistance in obese mice.

Four weeks exercise training enhanced the hepatic insulin sensitivity in high fat- and high carbohydrate-diet fed hyperinsulinemic rats

Aim

Hyperinsulinemia is considered the primary defect underlying the development of type 2 diabetes. The liver is essential for the regular glucose homeostasis. In this study, we examined the effect of physical training on the insulin signaling, oxidative stress enzymes and Glucose-6-phosphatase(G6Pase) activity in the liver of Wistar rats.

Methods

Adult male Wistar rats were divided into Control diet group(C), High carbohydrate diet(HCD), High fat diet(HFD), HCD and HFD with training(HCD Ex & HFD Ex). HFD Ex and HCD Ex were trained on a small animal treadmill running at 20 m/min for 30 min, 5 days/wk. The present work investigated the effect of training on hepatic insulin receptor(InsR) signaling events, oxidative stress marker expressions and G6Pase activity in hyperinsulinemic rats.

Results

High carbohydrate and fat feeding led to hyperinsulinemic status with increased hepatic G6Pase activity and impaired phosphorylation of insulin receptor substrate 1(IRS1) and reduced expression of antioxidant enzymes.Training significantly reduced hepatic G6Pase activity, upregulated phosphoinositide 3 kinase(PI3K) docking site phosphorylation and downregulated the negative IRS1 phosphorylations thereby increasing the glucose transporter(GLUT) expressions (aa(P < 0.001) when compared to HFD, b(P < 0.01),bb (P < 0.001 when compared to HCD). Anti oxidant enzymes like CAT, SOD, eNOS expression were increased with reduction in the expression of inflammatory enzymes like TNF-α and COX-2 (*(P < 0.05),**(P < 0.01),***(P < 0.001) when compared to control, †(P < 0.05),††(P < 0.01),†††(P < 0.001) when compared to HFD and HCD).

Conclusion

Thus, our study shows that four weeks training enhanced the hepatic insulin sensitivity in high fat and high carbohydrate-diet fed hyperinsulinemic rats.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-020-00694-y.

Morphological evaluation of the effects of exercise on high-fat-diet-induced liver damage in rats

BACKGROUND/AIMS

This study was aimed to investigate the protective effects of swimming exercise on nonalcoholic fatty liver disease (NAFLD) associated with high fat diet-induced obesity, using microscopical and biochemical parameters.

MATERIALS AND METHODS

Sprague Dawley male rats were fed either standard chow (STD group; 6% fat) or high-fat diet (HFD group; 45% fat) for 18 weeks. Animals were divided into four groups, STD, STD + EXC, HFD, HFD + EXC. Exercise groups were submitted to swimming training 5 days of week and 1h of per day, during the last 6 weeks of the experiment. At the end of the experiment, liver samples were evaluated for morphologically and ultrastructurally. Moreover, malondialdehyde (MDA) and glutathione (GSH) levels were evaluated in liver samples.

RESULTS

Normal morphology of liver parancyma with hepatocytes and sinusoids was observed in the STD and STD+EXC groups. Steatosis, lipid accumulation, ballooned hepatocytes, decrease of glycogen deposits and fibrosis in periportal area were observed in HFD group. Liver MDA level was increased and GSH level was decreased in HFD group. Exercise treatment ameliorated these morphological and oxidative changes in HFD induced liver damage.

CONCLUSION

Based on morphological and biochemical analysis, we could conclude that swimming training ameliorated obesity-induced liver damage by regulating lipid accumulation and oxidative damage.

AMPKα2 Deficiency Does Not Affect the Exercise-Induced Improvements in Glucose Tolerance and Metabolic Disorders in Mice Fed a High-Fat Diet

Exercise can improve obesity and metabolic disorders in mice fed a high-fat diet (HFD), but the role of AMPKα2 in the process remains unclear. The aim of this study was to investigate the role of AMPKα2 in the exercise-induced improvements in glucose tolerance and metabolic turnover in obesity mice. Male wild-type mice (n=12) and AMPKα2 knockout (AMPKα2 KO) mice (n=12) were fed a HFD for 16 wk and were then randomly divided into four groups: WT HFD group (WT HF), AMPKα2 KO HFD group (AMPKα2 KO HF), WT HFD exercise group (WT HE), and AMPK HFD exercise group (AMPKα2 KO HE). The HF groups continue to be fed a HFD from 16 wk to 24 wk, and the HE groups were fed a HFD and performed exercise training. After 8 wk of exercise, all mice were placed in an energy metabolism chamber to test their metabolic turnover, include locomotor activity, food intake, oxygen consumption (VO₂), carbon dioxide production (VCO₂), energy expenditure (EE) and respiratory exchange ratio (RER), over a period of 3 d. Exercise improved glucose tolerance, VO₂, VCO₂ and EE in mice fed a HFD (p<0.05). The VO₂, VCO₂ and EE in AMPKα2 KO HE group were lower than these in WT HE group (p<0.05). Our findings revealed exercise improved glucose tolerance and metabolic disorders in C57 and AMPKα2 KO mice fed a HFD. AMPKα2 is not essential for exercise-induced improvements in glucose tolerance and metabolic disorders.

Beneficial effects of maternal swimming during pregnancy on offspring metabolism when the father is obese

We aimed to evaluate the impact of maternal exercise training on the offspring metabolism and body size caused by father obesity. C57BL/6 male 4-week-old mice were fed a high-fat diet (HF father) or control diet (C father), while equal age female mice were fed only a C diet and were separated into two groups: trained (T mother) and non-trained (NT mother), and at 12 weeks of age mice were mated. A continuous swimming protocol was applied for 10 weeks (before and during gestation), and offspring were followed since weaning until sacrifice (at 12 weeks of age). HF father, compared to C father, showed obesity, elevated total cholesterol (TC) and triglycerides (TG), and glucose intolerance. Both sexes HF/NT offspring showed hyperglycemia, glucose intolerance and high levels of TC and TG, without obesity. However, HF/T offspring showed data close to C/NT, demonstrating the beneficial effect of maternal exercise in the offspring of obese fathers.

Treadmill running suppresses the vulnerability of dopamine D2 receptor deficiency to obesity and metabolic complications: a pilot study

[Purpose]

To investigate the effect of treadmill running on D₂R deficiency related susceptibility to high fat diet (HFD )-induced obesity and its metabolic complications.

[Methods]

D₂R-/-and +/-mice were obtained by backcrossing D₂R+/-heterozygotes on wild type (WT) littermates (C57BL/6J background) for >10 generations. Mice were randomly assigned to 1) WT mice with standard chow (SC) (WT+SC); 2) WT mice with high-fat diet (WT+HFD); 3) WT mice with high-fat diet plus exercise (WT+HFD+EX), 4) heterozygous (HET) D₂R mice with SC (HET+SC); 5) heterozygous D₂R mice with HFD (HET+HFD); and 6) heterozygous D₂R mice with HFD plus exercise (HET+HFD+EX). In addition, mice assigned to EX groups were subjected to running on a motor-driven rodent treadmill with a frequency of 5 days per week.

[Results]

After a 10-week HFD treatment, HET D₂R (+/-) mice exhibited significantly higher values for hepatic steatosis (p<0.001), areas under the curves (AUCs) for the glucose tolerance test (GTT) and the insulin tolerance test (ITT) (p<0.001 & p<0.001 respectively), serum leptin (p=0.005) and total cholesterol (TC ) (p=0.009), in conjunction with decreased locomotor activity (p=0.031), compared to HET mice exposed to standard chow. However, these HFD-induced elevations in hepatic steatosis (p<0.001), AUCs for GTT and ITT (p=0.032 & p=0.018, respectively), serum leptin (p=0.038) and TC (p=0.038) were significantly alleviated after 10 weeks of treadmill running.

[Conclusion]

The current findings of the study provide experimental evidence of treadmill running as an effective and non-pharmacologic strategy to treat the susceptibility of brain D₂R deficiency to HFD-induced obesity and metabolic disorders.

PGC-1α in hepatic UPR during high-fat high-fructose diet and exercise training in mice

Diet-induced obesity is associated with hepatic steatosis, which has been linked with activation of the unfolded protein response (UPR). PGC-1α is a transcriptional coactivator involved in exercise training-induced adaptations in muscle and liver. Therefore, the aim of this study was to test the hypothesis that PGC-1α is required for exercise training-mediated prevention of diet-induced steatosis and UPR activation in liver. Male liver-specific PGC-1α knockout (LKO) and littermate floxed (lox/lox) mice were divided into two groups receiving either control diet (CON) or high-fat high-fructose diet (HFF). After 9 weeks, half of the HFF mice were treadmill exercise trained for 4 weeks (HFF+ExT), while the rest were kept sedentary. HFF resulted in increased body and liver weight, adiposity, hepatic steatosis and whole body glucose intolerance as well as decreased hepatic IRE1α phosphorylation. Exercise training prevented the HFF-induced weight gain and partially prevented increased liver weight, adiposity and glucose intolerance, but with no effect on liver triglycerides. In addition, BiP protein and CHOP mRNA content increased with exercise training compared with CON and HFF, respectively. Lack of PGC-1α in the liver only resulted in minor changes in the PERK pathway. In conclusion, this study provides evidence for dissociation between diet-induced hepatic triglyceride accumulation and hepatic UPR activation. In addition, PGC-1α was not required for maintenance of basal UPR in the liver and due to only minor exercise training effects on UPR further studies are needed to conclude on the potential role of PGC-1α in exercise training-induced adaptations in hepatic UPR.

Energy-matched moderate and high intensity exercise training improves nonalcoholic fatty liver disease risk independent of changes in body mass or abdominal adiposity - A randomized trial

BACKGROUND AND PURPOSE

Exercise training is commonly prescribed for individuals diagnosed with nonalcoholic fatty liver disease (NAFLD); however, consensus regarding the volume and intensity of exercise for optimal benefits is lacking. Thus, we determined whether high intensity interval exercise training (HIIT) produced greater reductions in intrahepatic lipid (IHL) content and NAFLD risk factors compared with energy-matched moderate intensity continuous exercise training (MICT) in obese adults with liver steatosis.

METHODS

Eighteen obese adults were randomized to either 4weeks of HIIT (4min 80% VO₂peak/3min, 50% VO₂peak) or MICT (55% VO₂peak, ~60min), matched for energy expenditure (~400kcal/session) and compared to five non-exercising age-matched control subjects. IHL was measured by ¹H-MRS and frequent blood samples were analyzed for glucose, insulin, c-peptide, and NEFA levels during a liquid meal test (180min) to characterize metabolic phenotype.

RESULTS

Baseline body weight, visceral abdominal adiposity, and fasting insulin concentrations were greater in the MICT vs HIIT group (P<0.05), while IHL was tightly matched between MICT and HIIT subjects (P>0.05), albeit higher than control subjects (P<0.01). Visceral abdominal adiposity, body mass, liver aminotransferases (ALT, AST), and hepatic apoptotic/inflammatory markers (cytokeratin 18 and fetuin a) were not reduced with either exercise training intervention (P>0.05). Both HIIT and MICT lowered IHL (HIIT, -37.0±12.4%; MICT, -20.1±6.6%, P<0.05); however, the reduction in IHL was not statistically different between exercise intensities (P=0.25). Furthermore, exercise training decreased postprandial insulin, c-peptide, and lipid peroxidation levels (iAUC, P<0.05).

CONCLUSIONS

Collectively, these findings indicate that energy-matched high intensity and moderate intensity exercise are effective at decreasing IHL and NAFLD risk that is not contingent upon reductions in abdominal adiposity or body mass.

Treating fructose-induced metabolic changes in mice with high-intensity interval training: insights in the liver, white adipose tissue, and skeletal muscle

Fructose-rich caloric sweeteners induce adverse changes in the metabolism of humans. The study evaluated the effects of high-intensity interval training (HIIT) on a fructose feeding model, focusing on the liver, white adipose tissue (WAT), skeletal muscle, and their interplay. Male C57BL/6 mice were fed for 18 wk one of the following diets: control (C; 5% of total energy from fructose) or fructose (F; 55% of total energy from fructose). In the 10th week, for an additional 8-wk period, the groups were divided into nontrained (NT) or HIIT groups, totaling four groups: C-NT, C-HIIT, F-NT, and F-HIIT. At the end of the experiment, fructose consumption in the F-NT group led to a high systolic blood pressure, high plasma triglycerides, insulin resistance with glucose intolerance, and lower insulin sensitivity. We also observed liver steatosis, adipocyte hypertrophy, and diminished gene expressions of peroxisome proliferator-activated receptor-γ coactivator 1-α and fibronectin type III domain containing 5 (FNDC5; irisin) in this F-NT group. These results were accompanied by decreased gene expressions of nuclear respiratory factor 1 and mitochondrial transcription factor A (markers of mitochondrial biogenesis), and peroxisome proliferator-activated receptor-α and carnitine palmitoyltransferase 1 (markers of β-oxidation). HIIT improved all of these data in the C-HIIT and F-HIIT groups. In conclusion, in mice fed a fructose diet, HIIT improved body mass, blood pressure, glucose metabolism, and plasma triglycerides. Liver, WAT, and skeletal muscle were positively modulated by HIIT, indicating HIIT as a coadjutant treatment for diseases affecting these tissues.NEW & NOTEWORTHY We investigated the effects of high-intensity interval training (HIIT) in mice fed a fructose-rich diet and the resulting severe negative effect on the liver, white adipose tissue (WAT), and skeletal muscle, which reduced the expression of fibronectin type III domain containing 5 (FNDC5, irisin) and PGC1α and, consequently, affected markers of mitochondrial biogenesis and β-oxidation. Because HIIT may block these adverse effects in all of these three tissues, it might be suggested that it functions as a coadjutant treatment in combatting the alterations caused by high-fructose intake.

Effects of endurance and endurance-strength exercise on biochemical parameters of liver function in women with abdominal obesity

INTRODUCTION

Obesity is a risk factor of nonalcoholic fatty liver disease. Although the standard therapy for obesity involves physical exercise, well-planned studies of the changes in liver function in response to different exercise intensities in obese subjects are scarce. The aim of the present study was to examine a question of how does exercise mode affect the liver function.

MATERIAL AND METHODS

44 women with abdominal obesity were randomized into two exercise groups: endurance (group A) and endurance-strength (group B). Women in each group exercised for 60min 3 times/week for a 3-month period. Markers of liver function: serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltranspeptidase (GGT), alkaline phosphatase (ALP) activities, and bilirubin levels were quantified.

RESULTS

We found significant differences in ALT (p<0.01) and AST (p<0.05) activities between group A and B after training exercise. Blood ALT and AST tended to decrease in group B, increase in group A. Significant reduction in serum GGT level after exercise in both groups was observed (p<0.001, group A; p<0.01, group B). Neither endurance nor endurance-strength exercise led to changes in serum ALP activity and total or direct bilirubin level. However, endurance-strength training resulted in significant decreases in serum indirect bilirubin (p<0.05). Strong positive correlations between serum indirect bilirubin and body mass (r=0.615; p=0.0085) and BMI (r=0.576; p=0.0154) were found after endurance-strength exercise (group B).

CONCLUSION

The mode of exercise does matter: endurance-strength exercise led to a greater improvement, compared to endurance exercise, in the liver function in women with abdominal obesity.

Hepatocellular carcinoma and lifestyles

The majority of hepatocellular carcinoma occurs over pre-existing chronic liver diseases that share cirrhosis as an endpoint. In the last decade, a strong association between lifestyle and hepatocellular carcinoma has become evident. Abundance of energy-rich food and sedentary lifestyles have caused metabolic conditions such as obesity and diabetes mellitus to become global epidemics. Obesity and diabetes mellitus are both tightly linked to non-alcoholic fatty liver disease and also increase hepatocellular carcinoma risk independent of cirrhosis. Emerging data suggest that physical activity not only counteracts obesity, diabetes mellitus and non-alcoholic fatty liver disease, but also reduces cancer risk. Physical activity exerts significant anticancer effects in the absence of metabolic disorders. Here, we present a systematic review on lifestyles and hepatocellular carcinoma.

Exercise training improves liver steatosis in mice

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is rapidly turning into the most common liver disorder worldwide. One of the strategies that has been shown to effectively improve NAFLD is regular exercise, which seems to lower steatosis partly independent of weight loss. However, limited data are available about the mechanisms involved. The aim of the present study was to identify the mechanisms underlying the effect of regular exercise on liver steatosis.

METHODS

Non-obese male mice were rendered steatotic by feeding a sucrose-enriched choline-deficient diet. They were then subjected to daily treadmill running for three weeks, whereas the control mice remained sedentary.

RESULTS

Compared to the untrained mice, trained mice showed similar adipose tissue mass but had significantly reduced size of lipid droplets in the liver coupled with a reduction in liver triglyceride content (~30 %, P < 0.05). Levels of various plasma lipid parameters and plasma glucose were similar between the trained and untrained mice, whereas levels of hepatic glycogen were significantly higher in the trained mice. Hepatic triglyceride secretion rate and de novo lipogenesis were unchanged between the two sets of mice, as were indicators of lipolysis and autophagy. Finally, whole genome expression profiling indicated a mild stimulatory effect of exercise training on PPARα-mediated regulation of oxidative metabolism, including fatty acid oxidation.

CONCLUSIONS

Taken together, our study suggests that the lowering of hepatic steatosis by repeated exercise is likely due to activation of fuel oxidation pathways in liver.

Exercise and the Regulation of Hepatic Metabolism

The accelerated metabolic demands of the working muscle cannot be met without a robust response from the liver. If not for the hepatic response, sustained exercise would be impossible. The liver stores, releases, and recycles potential energy. Exercise would result in hypoglycemia if it were not for the accelerated release of energy as glucose. The energetic demands on the liver are largely met by increased oxidation of fatty acids mobilized from adipose tissue. Adaptations immediately following exercise facilitate the replenishment of glycogen stores. Pancreatic glucagon and insulin responses orchestrate the hepatic response during and immediately following exercise. Like skeletal muscle and other physiological systems, liver adapts to repeated demands of exercise by increasing its capacity to produce energy by oxidizing fat. The ability of regular physical activity to increase fat oxidation is protective and can reverse fatty liver disease. Engaging in regular physical exercise has broad ranging positive health implications including those that improve the metabolic health of the liver.

Effect of aerobic exercise training on non-alcoholic fatty liver disease induced by a high fat diet in C57BL/6 mice

[Purpose]

The aim of this study was to investigate the effects of aerobic exercise training on a high fat diet (HFD)-induced fatty liver and its metabolic complications in C57BL/6 mice.

[Methods]

Mice at 5-month old (n = 30) were randomly assigned to standard chow (SC + CON, n = 10) and high-fat diet (HFD, n = 20), and they were subjected to SC and HFD, respectively, for 23-week. After 15-week of HFD, mice in the HFD group were further assigned to HFD (HFD + CON, n = 10) or exercise training (HFD + EX, n = 10) groups. The HFD + EX mice were subjected to aerobic treadmill running during the last 8-week of the 23-week HFD course. Outcomes included hepatic steatosis, insulin resistance, and expression of genes involved in mitochondrial function and/or fatty oxidation as well as de novo lipogenesis and/or triacylglycerol (TAG) synthesis.

[Results]

Treadmill running ameliorated impaired glucose tolerance and insulin resistance secondary to the HFD. The beneficial effects of treadmill running were associated with enhanced molecular markers of mitochondrial function and/or fatty acids oxidation (i.e., PPARα and CPT1a mRNAs, pAMPK/AMPK, pACC, and SIRT1 protein) as well as suppressed expression of de novo lipogenesis and/or TAG synthesis (i.e., SREBP1c, lipin1 and FAS mRNAs) in the liver.

[Conclusion]

The current findings suggest that aerobic exercise training is an effective and non-pharmacological means to combat fatty liver and its metabolic complications in HFD-induced obese mice.

Effect of physical training on liver expression of activin A and follistatin in a nonalcoholic fatty liver disease model in rats

Nonalcoholic fatty liver disease (NAFLD) is characterized by fat accumulation in the liver and is associated with obesity and insulin resistance. Activin A is a member of the transforming growth factor beta (TGF)-β superfamily and inhibits hepatocyte growth. Follistatin antagonizes the biological actions of activin. Exercise is an important therapeutic strategy to reduce the metabolic effects of obesity. We evaluated the pattern of activin A and follistatin liver expression in obese rats subjected to swimming exercise. Control rats (C) and high-fat (HF) diet-fed rats were randomly assigned to a swimming training group (C-Swim and HF-Swim) or a sedentary group (C-Sed and HF-Sed). Activin βA subunit mRNA expression was significantly higher in HF-Swim than in HF-Sed rats. Follistatin mRNA expression was significantly lower in C-Swim and HF-Swim than in either C-Sed or HF-Sed animals. There was no evidence of steatosis or inflammation in C rats. In contrast, in HF animals the severity of steatosis ranged from grade 1 to grade 3. The extent of liver parenchyma damage was less in HF-Swim animals, with the severity of steatosis ranging from grade 0 to grade 1. These data showed that exercise may reduce the deleterious effects of a high-fat diet on the liver, suggesting that the local expression of activin-follistatin may be involved.

Progress in treatment of non-alcoholic fatty liver disease

The improvement of people's living standard, the accelerated pace of life and the decreased amount of exercise have significantly increased the prevalence of metabolic syndrome and fatty liver disease. In particular, some obese children have been diagnosed with non-alcoholic fatty liver disease. This should arouse our enough attention. This article reviews the progress in the treatment of non-alcoholic fatty liver disease.

Combining metformin and aerobic exercise training in the treatment of type 2 diabetes and NAFLD in OLETF rats

Here, we sought to compare the efficacy of combining exercise and metformin for the treatment of type 2 diabetes and nonalcoholic fatty liver disease (NAFLD) in hyperphagic, obese, type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. OLETF rats (age: 20 wk, hyperglycemic and hyperinsulinemic; n = 10/group) were randomly assigned to sedentary (O-SED), SED plus metformin (O-SED + M; 300 mg·kg(-1)·day(-1)), moderate-intensity exercise training (O-EndEx; 20 m/min, 60 min/day, 5 days/wk treadmill running), or O-EndEx + M groups for 12 wk. Long-Evans Tokushima Otsuka (L-SED) rats served as nonhyperphagic controls. O-SED + M, O-EndEx, and O-EndEx + M were effective in the management of type 2 diabetes, and all three treatments lowered hepatic steatosis and serum markers of liver injury; however, O-EndEx lowered liver triglyceride content and fasting hyperglycemia more than O-SED + M. In addition, exercise elicited greater improvements compared with metformin alone on postchallenge glycemic control, liver diacylglycerol content, hepatic mitochondrial palmitate oxidation, citrate synthase, and β-HAD activities and in the attenuation of markers of hepatic fatty acid uptake and de novo fatty acid synthesis. Surprisingly, combining metformin and aerobic exercise training offered little added benefit to these outcomes, and in fact, metformin actually blunted exercise-induced increases in complete mitochondrial palmitate oxidation and β-HAD activity. In conclusion, aerobic exercise training was more effective than metformin administration in the management of type 2 diabetes and NAFLD outcomes in obese hyperphagic OLETF rats. Combining therapies offered little additional benefit beyond exercise alone, and findings suggest that metformin potentially impairs exercise-induced hepatic mitochondrial adaptations.

The effect of dietary α-lipoic acid, betaine,l-carnitine, and swimming on the obesity of mice induced by a high-fat diet

We evaluate the effect of supplementation, at 300 mg kg⁻¹body weight (BW), with the antioxidants α-lipoic acid (AL), betaine (BT),l-carnitine (LC), and the combination of these and exercise on obesity induced by a 9 week high-fat diet (HFD) in mice.

Hepatic adverse effects of fructose consumption independent of overweight/obesity

The chronic intake of fructose has been linked to insulin resistance, obesity, dyslipidemia and nonalcoholic fatty liver disease (NAFLD), which in turn, may progress to nonalcoholic steatohepatitis (NASH). We aimed to evaluate the magnitude of the effects of the chronic consumption of high-fructose (HFr) and high fat (HF) alone or combined. Four groups of male mice were fed different diets for 16 weeks: standard chow (9% fat: SC), HF diet (42% fat), HFr diet (34% fructose) and HF/HFr diet (42% fat, 34% fructose). The food intake was not different among the groups, and the body mass was not greater in the HFr group than in the SC group. The homeostasis model assessment for insulin resistance (HOMA-IR), as well as plasmatic total cholesterol and triglycerides were greater in the groups HF, HFr, and HF/HFr group than in the SC group. We observed in the groups HF, HFr and HF/HFr, compared to the group SC, nonalcoholic fatty liver disease (NAFLD) with a predominance of lipogenesis mediated by SREBP-1c and PPAR-γ, and a reduction of the oxidation mediated by PPAR-α. We also observed an increase in gluconeogenesis mediated by the GLUT-2 and the PEPCK. Importantly, we identified areas of necroinflammation indicating a transition from NAFLD to nonalcoholic steatohepatitis in the HFr and HF/HFr groups. This study is relevant in demonstrating that fructose consumption, even in the absence of obesity, causes serious and deleterious changes in the liver with the presence of the dyslipidemia, insulin resistance (IR), and NAFLD with areas of necroinflammation. These conditions are associated with a poor prognosis.

Exercise as a therapeutic tool to prevent mitochondrial degeneration in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease, encompassing hepatic steatosis, nonalcoholic steatohepatitis (NASH), fibrosis and cirrhosis, is a significant health problem associated with modern lifestyle, based on caloric overconsumption and physical inactivity. Although the mechanisms associated with progression from the 'benign' steatosis to NASH are still elusive, mitochondrial dysfunction seems to play an important role in this degenerative process. Degeneration of mitochondrial function during NASH has been associated with impaired β-oxidation, oxidative phosphorylation and increased reactive oxygen species production, contributing to hepatocyte death and inflammatory response. Despite the fact that several therapeutic approaches can be used in the context of NASH, including insulin-sensitizing agents, anti-obesity drugs, lipid-lowering drugs or mitochondrial-targeted drugs, dietary and physical activity are still the most effective strategies. In fact, active lifestyles decrease insulin resistance and body weight and result in decreased histological signs of liver injury. In fatty liver, physical activity prevents the disease progression through mitochondrial adaptations, namely by increasing cytochrome c content, enzyme activities and fatty acid oxidation, which are lost after some days of physical inactivity. However, less is known about the effect of physical activity on NASH-associated mitochondrial dysfunction. After a brief characterization of NASH and its association with liver mitochondrial (dys)function, the present review addresses the impact of physical (in)activity on NASH and, particularly, the possible contribution of active lifestyles to the modulation of liver mitochondrial dysfunction.