RETRACTED: Reversion of hepatic steatosis by exercise training in obese mice: The role of sterol regulatory element-binding protein-1c

Exercise Is Medicine for Nonalcoholic Fatty Liver Disease: Exploration of Putative Mechanisms

Exercise remains a key component of nonalcoholic fatty liver disease (NAFLD) treatment. The mechanisms that underpin improvements in NAFLD remain the focus of much exploration in our attempt to better understand how exercise benefits patients with NAFLD. In this review, we summarize the available scientific literature in terms of mechanistic studies which explore the role of exercise training in modulating fatty acid metabolism, reducing hepatic inflammation, and improving liver fibrosis. This review highlights that beyond simple energy expenditure, the activation of key receptors and pathways may influence the degree of NAFLD-related improvements with some pathways being sensitive to exercise type, intensity, and volume. Importantly, each therapeutic target of exercise training in this review is also the focus of previous or ongoing drug development studies in patients with nonalcoholic steatohepatitis (NASH), and even when a regulatory-agency-approved drug comes to market, exercise will likely remain an integral component in the clinical management of patients with NAFLD and NASH.

Effect of Aerobic Exercise Alone or in Conjunction With Diet on Liver Function, Insulin Resistance and Lipids in Non-Alcoholic Fatty Liver Disease

BACKGROUND

Physical exercises are the first step of therapy for people with non-alcoholic fatty liver disease (NAFLD).

OBJECTIVE

The purpose of this meta-analysis is to evaluate the efficacy of aerobic exercise training with or without diet to ameliorate liver function, insulin resistance, and lipids in adults.

DATA SOURCES

We searched relevant databases up to 10 June 2021 for conducting a systematic review and meta-analysis of controlled trials lasting 4 or more weeks that investigated the effects of aerobic exercise alone or accompanied by diet on change in liver enzymes, intrahepatic fat (IHF), insulin resistance, and lipids.

RESULTS

Sixteen studies including 2255 participants were included. There was a significant pooled weighted mean differences (MD) for the comparison between aerobic exercise versus control in alanine aminotransferase (ALT; p = 0.003), aspartate aminotransferase (AST; p = 0.006), IHF (p = 0.0004), body mass (p = 0.0003), and body mass index (p = 0.004). Moreover, there was a significant pooled MD for the comparison between aerobic exercise plus diet versus control in ALT (p < 0.0001), AST (p = 0.01), IHF (p = 0.02), GGT (p < 0.00001), insulin (p < 0.0001), HOMA-IR (p < 0.00001), body mass (p < 0.0001), and BMI (p = 0.01).

CONCLUSION

Our findings demonstrate a role for aerobic exercise with and without diet protocol as a therapeutic purpose, and suggest that evaluation of aerobic training levels and aerobic training prescription plus diet should be routine in NAFLD.

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.

AMPKα pathway involved in hepatic triglyceride metabolism disorder in diet-induced obesity mice following Escherichia coli Infection

To investigate the different effects of acute pulmonary infection induced by Escherichia coli (E. coli) on lipid metabolism between diet-induced obesity (DIO, fed with high-fat diet) mice and lean mice. A total of 180 ICR mice were selected to be challenged intranasally with phosphate-buffered saline or 10⁹ CFUs/mL of E. coli, and the body character indexes, biochemical indexes and expressions of genes and proteins involved in lipid metabolism were examined pre- and post-infection. Results revealed that, before infection, DIO mice had significantly higher body weight, adipose and liver indexes, free fatty acid and triglyceride contents than lean mice. After infection, increased free fatty acid and triglyceride contents, increased expressions of resistin, SREBP-1c, ACC1, FAS and SCD-1, and declined PPARα, CPT-1α expressions and AMPKα phosphorylation were detected in the infected group, while the change rates were more serious in the lean mice than the DIO mice. The above-mentioned findings verified that, after being infected with E. coli, hepatic lipid metabolism disorder was aggravated by activating SREBP-1c related lipid synthesis pathway and inhibiting PPARα related fatty acid oxidation pathway. However, infection-induced lipid metabolic disorders was slighter in the DIO mice than the lean mice through AMPKα pathway.

The Effects of Physical Exercise on Fatty Liver Disease

The increasing prevalence of obesity has made nonalcoholic fatty liver disease (NAFLD) the most common chronic liver disease. As a consequence, NAFLD and especially its inflammatory form nonalcoholic steatohepatitis (NASH) are the fastest increasing etiology of end-stage liver disease and hepatocellular carcinoma. Physical inactivity is related to the severity of fatty liver disease irrespective of body weight, supporting the hypothesis that increasing physical activity through exercise can improve fatty liver disease. This review summarizes the evidence for the effects of physical exercise on NAFLD and NASH. Several clinical trials have shown that both aerobic and resistance exercise reduce the hepatic fat content. From clinical and basic scientific studies, it is evident that exercise affects fatty liver disease through various pathways. Improved peripheral insulin resistance reduces the excess delivery of free fatty acids and glucose for free fatty acid synthesis to the liver. In the liver, exercise increases fatty acid oxidation, decreases fatty acid synthesis, and prevents mitochondrial and hepatocellular damage through a reduction of the release of damage-associated molecular patterns. In conclusion, physical exercise is a proven therapeutic strategy to improve fatty liver disease.

Nonalcoholic fatty liver disease remission in men through regular exercise

Recent cross-sectional and randomized controlled studies of small sample sizes revealed that regular exercise is effective for improving nonalcoholic fatty liver disease. However, there has been no large-scale longitudinal study addressing the effect of regular exercise on remission of nonalcoholic fatty liver disease. Thus, we investigated the impact of exercise on the natural history of nonalcoholic fatty liver disease. We analyzed 1,010 (860 men and 150 women) Japanese participants who received health checkups repeatedly over 10 years by a historical cohort study and were diagnosed with nonalcoholic fatty liver disease at baseline. Regular exercise was defined as participating in any kind of sports at least once a week. Nonalcoholic fatty liver disease was diagnosed by ultrasonographic images. During 10 years of follow-up, remission of nonalcoholic fatty liver disease was observed in 46.0% (396/860) of men and 48.7% (73/150) of women. In men, the adjusted hazard ratio of regular exercise for remission of nonalcoholic fatty liver disease was 1.46 (95% confidence interval 1.10–1.95, p = 0.010). However, this was not significant in women. Exercise at least once a week is implicated in the remission of nonalcoholic fatty liver disease in men.

Exercise-Induced Autophagy in Fatty Liver Disease

Hepatic steatosis prevails each year. Autophagy is integral in mitochondrial quality control and lipid homeostasis in the liver. No pharmacological strategies are currently available to reduce hepatic steatosis, but exercise has been known to improve clinical outcomes of chronic liver disease, particularly nonalcoholic fatty liver disease (NAFLD). Recent studies suggest that exercise may improve NAFLD through enhancing autophagy.

Cassia auriculata flower extract attenuates hyperlipidemia in male Wistar rats by regulating the hepatic cholesterol metabolism

Hyperlipidemia in the male albino Wistar rats was induced by Triton WR - 1339. The treatment of the hyperlipidemic animals with the ethanol extract of Cassia auriculata flower (Et-CAF) exhibited a dose dependent reduction in serum triacylglycerol, total cholesterol, low density lipoprotein (LDL), very low density lipoprotein (VLDL) similar to the hyperlipidemic animals treated with standard drug atorvastatin. Hyperlipidemia altered the protein and mRNA expression levels of the key genes (SREBP-1c, ACC1, SREBP-2, HMGR, HMGS, CYP7A1, and ABCA1) in lipid metabolism and the treatment with Et-CAF (300mg/kg b. wt) reverted these levels similar to that observed with atorvastatin treated hyperlipidemic animals. These results revealed that Et-CAF extract served as an efficient anti-hyperlipidemic drug.

PGC-1α in aging and lifelong exercise training-mediated regulation of UPR in mouse liver

Aging is associated with changes in several metabolic pathways affecting liver function including the adaptive unfolded protein response (UPR). On the other hand, exercise training has been shown to exert beneficial effects on metabolism in the liver and exercise training has been reported to affect hepatic UPR. PGC-1α is a transcriptional coactivator involved in exercise training-induced adaptations in skeletal muscle and liver. Therefore, the aim of the present study was to examine the impact of PGC-1α in aging and lifelong exercise training-induced hepatic UPR in mice. Liver was obtained from young (3months old), aged (15months old) and lifelong exercise trained aged wild-type (WT) and whole-body PGC-1α knockout (KO) mice. Hepatic BiP, IRE1α and cleaved ATF6 protein content increased, whereas PERK protein content was reduced with aging indicating both increased and decreased capacity of specific UPR pathways and increased activity of the ATF6 pathway in the liver with aging. Lifelong exercise training prevented the age-associated change in BiP and IRE1α protein, but not cleaved ATF6 protein and resulted in further decreased PERK protein. Taken together, the present study provides evidence that the capacity and activity of the three UPR pathways are differentially regulated in the liver with aging and lifelong exercise training. In addition, PGC-1α does not seem to regulate the activity of hepatic UPR in response to exercise training, but to influence the capacity of the liver to induce UPR in a pathway specific manner.

Exercise-Induced Release of Pharmacologically Active Substances and Their Relevance for Therapy of Hepatic Injury

Chronic liver disease (CLD) features constant parenchymal injury and repair together with an increasing hepatic impairment, finally leading to fibrosis and cirrhosis and a heightened risk of hepatocellular carcinoma (HCC). Closely related to the rise in obesity, the worldwide prevalence of nonalcoholic fatty liver disease, the most common form of CLD, has reached an epidemic dimension and is estimated to afflict up to 46% of the general population, including more than one out of three U.S. citizens. Up to now there is no effective drug treatment available, which is why recommendations encompass both exercise programs and changes in dietary habits. Exercise is well-known for unleashing potent anti-inflammatory effects, which can principally counteract liver inflammation and chronic low-grade inflammation. This review article summarizes the underlying mechanisms responsible for the exercise-mediated anti-inflammatory effects, illustrates the application in animal models as well as in humans, and highlights the therapeutic value when possible. Based on the available results there is no doubt that exercise can even be beneficial in an advanced stage of liver disease and it is the goal of this review article to provide evidence for the therapeutic impact on fibrosis, cirrhosis, and HCC and to assess whether exercise might be of value as adjuvant therapy in the treatment of CLD. In principle, all exercise programs carried out in these high-risk patients should be guided and observed by qualified healthcare professionals to guarantee the patients’ safety. Nevertheless, it is also necessary to additionally determine the optimal amount and intensity of exercise to maximize its value, which is why further studies are essential.

Whole Body Vibration Improves Insulin Resistance in db/db Mice: Amelioration of Lipid Accumulation and Oxidative Stress

Insulin resistance (IR) is the hallmark of type 2 diabetes mellitus (T2DM), which is one of the most important chronic noncommunicable diseases. Effective and feasible strategies to treat IR are still urgently needed. Previous research studies reported that whole body vibration (WBV) was beneficial for IR in clinical; however, its underlying mechanisms remains unknown. In the present study, db/db mice were treated with WBV administration 60 min/day for 12 weeks and the impaired insulin sensitivity was improved. Besides, liver steatosis was also ameliorated. Further explorations revealed that WBV could reduce the expression of SREBP1c and increase the expression of GSH-Px and consequently suppress oxidative stress. In conclusion, WBV attenuates oxidative stress to ameliorate liver steatosis and thus improves insulin resistance in db/db mice. Therefore, WBV administration is a promising treatment for individuals who suffered from central obesity and IR.

Physical activity and liver diseases

Regular physical activity beneficially impacts the risk of onset and progression of several chronic diseases. However, research regarding the effects of exercising on chronic liver diseases is relatively recent. Most researchers focused on nonalcoholic fatty liver disease (NAFLD), in which increasing clinical and experimental data indicate that skeletal muscle crosstalking to the adipose tissue and the liver regulates intrahepatic fat storage. In this setting, physical activity is considered to be required in combination with calories restriction to allow an effective decrease of intrahepatic lipid component, and despite that evidence is not conclusive, some studies suggest that vigorous activity might be more beneficial than moderate activity to improve NAFLD/nonalcoholic steatohepatitis. Evidence regarding the effects of exercise on the risk of hepatocellular carcinoma is scarce; some epidemiological studies indicate a lower risk in patients regularly and vigorously exercising. In compensated cirrhosis, exercise acutely increases portal pressure, but in the longer term it has been proved safe and probably beneficial. Decreased aerobic capacity (VO2 ) correlates with mortality in patients with decompensated cirrhosis, who are almost invariably sarcopenic. In these patients, VO2 is improved by physical activity, which might also reduce the risk of hepatic encephalopathy through an increase in skeletal muscle mass. In solid organ transplantation recipients, exercise is able to improve lean mass, muscle strength, and, as a consequence, aerobic capacity. Few data exist in liver transplant recipients, in whom exercise should be an object of future studies given its high potential of providing long-term beneficial effects.

CONCLUSIONS

Despite that evidence is far from complete, physical activity should be seen as an important part of the management of patients with liver disease in order to improve their clinical outcome.

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.

miR-212 downregulation contributes to the protective effect of exercise against non-alcoholic fatty liver via targeting FGF-21

Non-alcoholic fatty liver disease (NAFLD) is associated with obesity and lifestyle, while exercise is beneficial for NAFLD. Dysregulated microRNAs (miRs) control the pathogenesis of NAFLD. However, whether exercise could prevent NAFLD via targeting microRNA is unknown. In this study, normal or high-fat diet (HF) mice were either subjected to a 16-week running program or kept sedentary. Exercise attenuated liver steatosis in HF mice. MicroRNA array and qRT-PCR demonstrated that miR-212 was overexpressed in HF liver, while reduced by exercise. Next, we investigated the role of miR-212 in lipogenesis using HepG2 cells with/without long-chain fatty acid treatment (± FFA). FFA increased miR-212 in HepG2 cells. Moreover, miR-212 promoted lipogenesis in HepG2 cells (± FFA). Fibroblast growth factor (FGF)-21, a key regulator for lipid metabolism, was negatively regulated by miR-212 at protein level in HepG2 cells. Meanwhile, FFA downregulated FGF-21 both at mRNA and protein levels in HepG2 cells. Also, FGF-21 protein level was reduced in HF liver, while reversed by exercise in vivo. Furthermore, siRNA-FGF-21 abolished the lipogenesis-reducing effect of miR-212 inhibitor in HepG2 cells (± FFA), validating FGF-21 as a target gene of miR-212. These data link the benefit of exercise and miR-212 downregulation in preventing NAFLD via targeting FGF-21.

High intensity interval training improves liver and adipose tissue insulin sensitivity

Objective

Endurance exercise training reduces insulin resistance, adipose tissue inflammation and non-alcoholic fatty liver disease (NAFLD), an effect often associated with modest weight loss. Recent studies have indicated that high-intensity interval training (HIIT) lowers blood glucose in individuals with type 2 diabetes independently of weight loss; however, the organs affected and mechanisms mediating the glucose lowering effects are not known. Intense exercise increases phosphorylation and inhibition of acetyl-CoA carboxylase (ACC) by AMP-activated protein kinase (AMPK) in muscle, adipose tissue and liver. AMPK and ACC are key enzymes regulating fatty acid metabolism, liver fat content, adipose tissue inflammation and insulin sensitivity but the importance of this pathway in regulating insulin sensitivity with HIIT is unknown.

Methods

In the current study, the effects of 6 weeks of HIIT were examined using obese mice with serine–alanine knock-in mutations on the AMPK phosphorylation sites of ACC1 and ACC2 (AccDKI) or wild-type (WT) controls.

Results

HIIT lowered blood glucose and increased exercise capacity, food intake, basal activity levels, carbohydrate oxidation and liver and adipose tissue insulin sensitivity in HFD-fed WT and AccDKI mice. These changes occurred independently of weight loss or reductions in adiposity, inflammation and liver lipid content.

Conclusions

These data indicate that HIIT lowers blood glucose levels by improving adipose and liver insulin sensitivity independently of changes in adiposity, adipose tissue inflammation, liver lipid content or AMPK phosphorylation of ACC.

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High-intensity interval training (HIIT) improves exercise capacity and whole-body glucose homeostasis.

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HIIT enhances liver and adipose tissue insulin sensitivity independent of body weight and adiposity.

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HIIT does not change adipose tissue cell size, macrophage infiltration, inflammation and liver lipid content.

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HIIT exercise training improves insulin sensitivity independently of the AMPK-ACC signaling pathway.

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.

Regular exercise decreases liver tumors development in hepatocyte-specific PTEN-deficient mice independently of steatosis

BACKGROUND & AIMS

Unhealthy lifestyles predispose people to non-alcoholic steatohepatitis (NASH), which may further result in the development of hepatocellular carcinoma (HCC). Although NASH patients benefit from physical activity, it is unknown whether regular exercise reduces the risk of developing HCC. Therefore, we studied the effect of regular exercise on the development of HCC in male hepatocyte-specific PTEN-deficient mice (AlbCrePten(flox/flox)), which develop steatohepatitis and HCC spontaneously.

METHODS

Mice were fed a standardized 10% fat diet and were randomly divided into exercise or sedentary groups. The exercise group ran on a motorized treadmill for 60 min/day, 5 days/week during 32 weeks.

RESULTS

After 32 weeks of regular exercise, 71% of exercised mice developed nodules larger than 15 mm(3)vs. 100% of mice in the sedentary group. The mean number of tumors per liver was reduced by exercise, as well as the total tumoral volume per liver. Exercise did not affect steatosis and had no effect on the non-alcoholic fatty liver disease (NAFLD) Activity Score (NAS). Exercise decreased tumor cell proliferation. Mechanistically, exercise stimulated the phosphorylation of AMPK and its substrate raptor, which decreased the kinase activity of mTOR.

CONCLUSIONS

These data show a beneficial effect of regular exercise on the development of HCC in an experimental model of NASH and offer a rationale for encouraging predisposed patients to increase their physical activity for the prevention of HCC.

Beneficial mechanisms of aerobic exercise on hepatic lipid metabolism in non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) refers to any fatty liver disease that is not due to excessive use of alcohol. NAFLD probably results from abnormal hepatic lipid metabolism and insulin resistance. Aerobic exercise is shown to improve NAFLD. This review aimed to evaluate the molecular mechanisms involved in the beneficial effects of aerobic exercise on NAFLD.

DATA SOURCE

We searched articles in English on the role of aerobic exercise in NAFLD therapy in PubMed.

RESULTS

The mechanisms of chronic aerobic exercise in regulating the outcome of NAFLD include: (i) reducing intrahepatic fat content by down-regulating sterol regulatory element-binding protein-1c and up-regulating peroxisome proliferator-activated receptor gamma expression levels; (ii) decreasing hepatic oxidative stress through modulating the reactive oxygen species, and enhancing antioxidant enzymes such as catalase and glutathione peroxidase; (iii) ameliorating hepatic inflammation via the inhibition of pro-inflammatory mediators such as tumor necrosis factor-alpha and interleukin-1 beta; (iv) attenuating mitochondrial dependent apoptosis by reducing cytochrome C released from the mitochondria to the cytosol; and (v) inducing hepato-protective autophagy.

CONCLUSION

Aerobic exercise, via different mechanisms, significantly decreases the fat content of the liver and improves the outcomes of patients with NAFLD.

Overproduction of altered VLDL in an insulin-resistance rat model: Influence of SREBP-1c and PPAR-α

BACKGROUND

In insulin-resistance, VLDL presents alterations that increase its atherogenic potential. The mechanism by which insulin-resistance promotes the production of altered VLDL is still not completely understood. The aim of this study was to evaluate the relationship between the expression of sterol regulatory element binding protein 1c (SREBP-1c) and of peroxisome proliferator-activated receptor-α (PPAR-α), with the features of composition and size of VLDL in an insulin-resistance rat model induced by a sucrose rich diet (SRD).

METHODS

The study was conducted on 12 male Wistar rats (180g) receiving SRD (12 weeks) and 12 controls. Lipid profile, free fatty acids, glucose, and insulin were measured. Lipid content in liver and visceral fat were assessed. Isolated VLDL (d<1.006g/ml) was characterized by its chemical composition and size by HPLC. The respective hepatic expression of SREBP-1c and PPAR-α was determined (Western blot).

RESULTS

As expected, SRD had elevated triglycerides (TG), free fatty acids and insulin levels, and decreased HDL-cholesterol (p<0.05), together with augmented hepatic and visceral fat (p<0.05). SRD showed higher VLDL total mass - with increased TG content - and predominance of large VLDL (p<0.05). SRD showed an increase in SREBP-1c (precursor and mature forms) and decreased PPAR-α expression (p<0.045). SREBP-1c forms were positively associated with VLDL total mass (p<0.04), VLDL-TG% (p<0.019), and large VLDL% (p<0.002). On the other hand, PPAR-α correlated negatively with VLDL total mass (p=0.05), VLDL-TG% (p=0.005), and large VLDL% (p=0.002).

CONCLUSIONS

Insulin-resistance, by coordinated activation of SREBP-1c and reduction of PPAR-α, could promote the secretion of larger and TG over-enriched VLDL particles, with greater atherogenic capacity.

Physical training at sub-threshold intensity reduces the prevalence of hepatic steatosis after high-fat diet in rats

The purpose of the present study was to evaluate the effects of swimming physical training with sub-threshold load on the prevalence of hepatic steatosis in Wistar rats fed high-fat diets (cafeteria or baru). After 2 months of cafeteria diet administration, the rats were separated into 6 groups: Sedentary or Trained Baru diet; Sedentary or Trained Cafeteria diet; Sedentary or Trained standard diet. The trained groups were subjected to swimming exercise at sub-threshold intensity (2% of body weight) during 8 weeks, 5x/week, 1h/day. The body weight and hepatohistological changes were analyzed. Sedentary groups fed high-fat diets presented higher body weight gain when compared to control trained group. The swimming training at the proposed intensity was able to prevent the hepatic steatosis in rats fed high-fat diets.

Silkworm pupae powder ingestion increases fat metabolism in swim-trained rats

[Purpose]

Many researchers are trying to solve the metabolic syndrome by utilizing a variety of nutritional control and exercise. Of those, silkworm pupae peptides are known to inhibit the synthesis of fat. Therefore, we examine the effect of fat metabolism by supplying silkworm pupae (SP) for 5-week in swim-trained rats.

[Methods]

Animals were divided into four groups as a group (n = 32) fed a normal diet (CO) with exercise training (CE); a group fed a silkworm pupa diet (SPC) with an exercise training (SPE), respectively.

[Results]

Abdominal fat pads (abdominal and epididymal) weight were lowest in SPE. The serum triglyceride, total cholesterol concentrations were lower in the SP and the SPE. HDL-cholesterol, however, was not different between groups. Liver AMPK (AMP-activated protein kinase) was increased in the CE and the SPE. Liver PPAR-α (Peroxisome proliferator-activated receptor alpha) was increased in the SPC and SPE. L-FABP (liver fatty acids binding protein) was increased by SP ingestion. Liver CPT-1 (carnitine palmitoyltransferase-1) protein expression was increased by exercise training only.

[Conclusion]

In the present study showed that the silkworm pupae intake and/or swimming exercise training activates fat metabolism to reduce the concentration of serum lipids. Thus, the silkworm pupae intake leads to a reduction in fat storage, this is considered to be effective in the inhibition of the metabolic syndrome.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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