Non-alcoholic fatty liver disease (NAFLD) is associated with low level of physical activity: a population-based study

Non-alcoholic Fatty Liver Disease (NAFLD) is associated with impairment of Health Related Quality of Life (HRQOL)

BACKGROUND

NAFLD impacts patient reported outcomes (PROs). Our aim was to assess the impact of NAFLD on patients' HRQOL.

METHODS

National Health and Nutrition Examination Survey (NHANES) 2001-2011 data were used to identify adult patients with NAFLD [Fatty Liver Index (FLI) > 60 in absence of other liver disease and excessive alcohol >20 g/day for men, >10 g/day for women]. Patients with other chronic diseases (ex. HIV, cancer, end-stage kidney disease) were excluded. Subjects without any of these conditions were healthy controls. HCV RNA (+) patients were HCV-controls. All patients completed NHANES HRQOL-4 questionnaire. Linear regression determined the association between NAFLD and HRQOL components adjusting for age, gender, race, and BMI.

RESULTS

Participants with complete data were included (n = 9661); 3333 NAFLD (age 51 years and BMI 34 kg/m(2)); 346 HCV+ (age 49 years; BMI 27 kg/m(2)) and 5982 healthy controls (age 48 years and BMI 26 kg/m(2)). The proportion of subjects rating their health as "fair" or "poor" in descending order were HCV controls (30 %) NAFLD (20 %) and healthy controls (10 %) (p < 0.001). HRQOL-4 components scores 2-4 were lowest for HCV, followed by NAFLD and then healthy controls (p-values p = 0.011 to < .0001). After adjustment for age, gender, race, and BMI, NAFLD patients were 18-20 % more likely to report days when their physical health wasn't good or were unable to perform daily activities as a result (p < .0001).

CONCLUSIONS

NAFLD causes impairment of HRQOL. As NAFLD is becoming the most important cause of CLD, its clinical and PRO impact must be assessed.

Objectively Quantified Physical Activity and Sedentary Behavior in Predicting Visceral Adiposity and Liver Fat

Objective. Epidemiologic studies suggest an inverse relationship between nonalcoholic fatty liver disease (NAFLD), visceral adipose tissue (VAT), and self-reported physical activity levels. However, subjective measurements can be inaccurate and prone to reporter bias. We investigated whether objectively quantified physical activity levels predicted liver fat and VAT in overweight/obese adults. Methods. Habitual physical activity was measured by triaxial accelerometry for four days (n = 82). Time spent in sedentary behavior (MET < 1.6) and light (MET 1.6 < 3), moderate (MET 3 < 6), and vigorous (MET 6 < 9) physical activity was quantified. Magnetic resonance imaging and spectroscopy were used to quantify visceral and liver fat. Bivariate correlations and hierarchical multiple regression analyses were performed. Results. There were no associations between physical activity or sedentary behavior and liver lipid. Sedentary behavior and moderate and vigorous physical activity accounted for just 3% of variance for VAT (p = 0.14) and 0.003% for liver fat (p = 0.96). Higher levels of VAT were associated with time spent in moderate activity (r = 0.294, p = 0.007), but there was no association with sedentary behavior. Known risk factors for obesity-related NAFLD accounted for 62% and 40% of variance in VAT and liver fat, respectively (p < 0.01). Conclusion. Objectively measured levels of habitual physical activity and sedentary behavior did not influence VAT or liver fat.

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.

Assessment of Diet and Physical Activity in Paediatric Non-Alcoholic Fatty Liver Disease Patients: A United Kingdom Case Control Study

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in children, with prevalence rising alongside childhood obesity rates. This study aimed to characterise the habitual diet and activity behaviours of children with NAFLD compared to obese children without liver disease in the United Kingdom (UK). Twenty-four biopsy-proven paediatric NAFLD cases and eight obese controls without biochemical or radiological evidence of NAFLD completed a 24-h dietary recall, a Physical Activity Questionnaire (PAQ), a Dutch Eating Behavior Questionnaire (DEBQ) and a 7-day food and activity diary (FAD), in conjunction with wearing a pedometer. Groups were well matched for age and gender. Obese children had higher BMI z-scores (p = 0.006) and BMI centiles (p = 0.002) than participants with NAFLD. After adjusting for multiple hypotheses testing and controlling for differences in BMI, no differences in macro- or micronutrient intake were observed as assessed using either 24-h recall or 7-day FAD (p > 0.001). Under-reporting was prevalent (NAFLD 75%, Obese Control 87%: p = 0.15). Restrained eating behaviours were significantly higher in the NAFLD group (p = 0.005), who also recorded more steps per day than the obese controls (p = 0.01). In conclusion, this is the first study to assess dietary and activity patterns in a UK paediatric NAFLD population. Only a minority of cases and controls were meeting current dietary and physical activity recommendations. Our findings do not support development of specific dietary/ physical activity guidelines for children with NAFLD; promoting adherence with current general paediatric recommendations for health should remain the focus of clinical management.

Relationship of sitting time and physical activity with non-alcoholic fatty liver disease

BACKGROUND & AIMS

The goal of this study was to examine the association of sitting time and physical activity level with non-alcoholic fatty liver disease (NAFLD) in Korean men and women and to explore whether any observed associations were mediated by adiposity.

METHODS

A cross-sectional study was performed on 139,056 Koreans, who underwent a health examination between March 2011 and December 2013. Physical activity level and sitting time were assessed using the validated Korean version of the international Physical Activity Questionnaire Short Form. The presence of fatty liver was determined using ultrasonographic findings. Poisson regression models with robust variance were used to evaluate the association of sitting time and physical activity level with NAFLD.

RESULTS

Of the 139,056 subjects, 39,257 had NAFLD. In a multivariable-adjusted model, both prolonged sitting time and decreased physical activity level were independently associated with increasing prevalence of NAFLD. The prevalence ratios (95% CIs) for NAFLD comparing 5-9 and ⩾10 h/day sitting time to <5h/day were 1.04 (1.02-1.07) and 1.09 (1.06-1.11), respectively (p for trend <0.001). These associations were still observed in subjects with BMI <23 kg/m(2). The prevalence ratios (95% CIs) for NAFLD comparing minimally active and health-enhancing physically active groups to the inactive group were 0.94 (0.92-0.95) and 0.80 (0.78-0.82), respectively (p for trend <0.001).

CONCLUSIONS

Prolonged sitting time and decreased physical activity level were positively associated with the prevalence of NAFLD in a large sample of middle-aged Koreans, supporting the importance of reducing time spent sitting in addition to promoting physical activity.

Physical activity as a treatment of non-alcoholic fatty liver disease: A systematic review

AIM

To review the effectiveness of exercise as a therapy for nonalcoholic fatty liver disease (NAFLD) and potential benefits in treating insulin resistance and atherosclerosis.

METHODS

Medline (EBSCOhost) and PubMed were searched for English-language randomized controlled trials and prospective cohort studies in human adults aged ≥ 18 which investigated the various effects of exercise alone, a combination of exercise and diet, or exercise and diet coupled with behavioral modification on NAFLD from 2010 to Feburary 2015.

RESULTS

Eighteen of 2298 available studies were chosen for critical review, which included 6925 patients. Nine (50%) studies were randomized controlled trials. Five (27.8%) studies utilized biopsy to examine the effects of physical activity on hepatic histology. The most commonly employed imaging modality to determine change in hepatic steatosis was hydrogen-magnetic resonance spectroscopy. Only two studies examined the effects of low impact physical activity for patients with significant mobility limitations and one compared the efficacy of aerobic and resistance exercise. No studies examined the exact duration of exercise required for hepatic and metabolic improvement in NAFLD.

CONCLUSION

While exercise improved hepatic steatosis and underlying metabolic abnormalities in NAFLD, more studies are needed to define the most beneficial form and duration of exercise treatment.

Hepatic steatosis is associated with lower levels of physical activity measured via accelerometry

OBJECTIVE

Prior studies on the association of physical activity (PA) and nonalcoholic fatty liver disease are limited by reliance on subjective measures of PA. We examined the association between objectively measured PA and hepatic steatosis defined by computed tomography (CT).

METHODS

We conducted a cross-sectional study of 1,060 Framingham Heart Study participants who participated in the Multidetector CT 2 substudy and who underwent assessment of PA via accelerometry. Hepatic steatosis was estimated by liver attenuation, as measured by CT. We explored the relationship between liver attenuation and PA using multivariable regression models.

RESULTS

In multivariable-adjusted models, we observed an inverse association between PA and liver attenuation. Each 30 minutes/day increase in moderate to vigorous PA (MVPA) was associated with a reduced odds of hepatic steatosis (OR = 0.62, P < 0.001). This association was attenuated and no longer statistically significant after adjustment for body mass index (BMI) (OR = 0.77, P = 0.05) or visceral adipose tissue (VAT) (OR = 0.83, P = 0.18). Participants who met the national PA recommendations of engaging in ≥150 minutes/week of MVPA had the lowest odds of hepatic steatosis, even after adjusting for BMI (OR = 0.63, P = 0.007) or VAT (OR = 0.67, P = 0.03).

CONCLUSIONS

There is an inverse association between PA and hepatic steatosis. Participants who met the national PA guidelines had the lowest prevalence of hepatic steatosis.

Diagnosis and management of cardiovascular risk in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is increasingly recognized as an important cardiovascular risk (CVR) factor. This is a narrative clinical review aimed at answering how diagnosis and management of CVR should be conducted in the individual patient with NAFLD. To this end, the authors performed an extensive search of the existing literature on PubMed (1993-2014) using pertinent keywords. To date, CVR among patients with NAFLD might be assessed with the Framingham risk score equation or other risk calculators, to be adapted to the true CVR in the specific population being assessed; however, the use of these CVR calculators needs to be validated by future studies in larger cohorts of NAFLD patients of various ethnic backgrounds in order to substantiate their clinical relevance as a foundation for the primary prevention of cardiovascular diseases in this group of patients. Early and aggressive drug treatment of CVR should be started in NAFLD patients with a history of cardiovascular events, established diabetes or who are at high (calculated) CVR. Whether such an aggressive pharmacological approach is also justified in patients with NAFLD, who are at intermediate or low CVR, remains debatable. Currently, there are no clinical trials showing that the treatment of NAFLD per se (either associated or unassociated with traditional CVR factors) will result in decreased risk of cardiovascular events. Accordingly, drug treatment should be better individualized, aiming at correcting all the coexisting cardio-metabolic risk factors of the individual patient with NAFLD. To this end, an overview of the lifestyle interventions and the available drugs is offered, emphasis being conveyed to statins and metformin, which promise to cover worrying complications of NAFLD such as the risk of developing hepatocellular carcinoma.

Nonalcoholic fatty liver disease: a precursor of the metabolic syndrome

The conventional paradigm of nonalcoholic fatty liver disease representing the "hepatic manifestation of the metabolic syndrome" is outdated. We identified and summarized longitudinal studies that, supporting the association of nonalcoholic fatty liver disease with either type 2 diabetes mellitus or metabolic syndrome, suggest that nonalcoholic fatty liver disease precedes the development of both conditions. Online Medical databases were searched, relevant articles were identified, their references were further assessed and tabulated data were checked. Although several cross-sectional studies linked nonalcoholic fatty liver disease to either diabetes and other components of the metabolic syndrome, we focused on 28 longitudinal studies which provided evidence for nonalcoholic fatty liver disease as a risk factor for the future development of diabetes. Moreover, additional 19 longitudinal reported that nonalcoholic fatty liver disease precedes and is a risk factor for the future development of the metabolic syndrome. Finally, molecular and genetic studies are discussed supporting the view that aetiology of steatosis and lipid intra-hepatocytic compartmentation are a major determinant of whether fatty liver is/is not associated with insulin resistance and metabolic syndrome. Data support the novel paradigm of nonalcoholic fatty liver disease as a strong determinant for the development of the metabolic syndrome, which has potentially relevant clinical implications for diagnosing, preventing and treating metabolic syndrome.

Relation of physical activity to prevalence of nonalcoholic Fatty liver disease independent of cardiometabolic risk

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity and insulin resistance and has been linked with increased cardiovascular risk. Although physical activity (PA) and lifestyle modification are often recommended in patients at cardiovascular risk, the benefit across the cardiometabolic risk spectrum is unclear. We aimed to evaluate the relation of PA and NAFLD independent of metabolic syndrome (MS) or obesity. We evaluated 5,743 healthy Brazilian subjects (43 ± 10 years, 79% men) without clinical coronary heart disease from December 2008 to December 2010. NAFLD was diagnosed using ultrasounds, and self-reported PA was assessed using the International Physical Activity Questionnaire scale. In a multivariate logistic regression adjusted for cardiometabolic risk factors, we evaluated for an independent association of NAFLD and PA. In the total study population, NAFLD prevalence was 36% (n = 2,075), obesity 23% (1,300), and MS 20% (1,152). NAFLD was more prevalent in subjects with MS (74%) than those without (26%) and in those obese (73%) than in those nonobese (25%). Overall, 1,305 (23%) subjects reported low activity, 1,990 (35%) moderate activity, and 2,448 (42%) high activity. NAFLD prevalence was lower at higher levels of reported PA (low 45%, moderate 38%, and high 30%, p <0.001). After adjusting for risk factors, subjects with high activity had lower odds of having NAFLD. The favorable association was independent of obesity or MS. In conclusion, PA presents a dose-response association with NAFLD independent of the MS or obesity. Our results are compatible with the idea that benefits of PA are relevant to everyone regardless of cardiometabolic risk.

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.

Beneficial effects of phosphatidylcholine on high-fat diet-induced obesity, hyperlipidemia and fatty liver in mice

AIMS

Soybean-derived PC is an essential cell membrane phospholipid that is composed of unsaturated fatty acids, including oleic acid. The present study aimed to evaluate the potential alleviation effects of soybean PC on high fat diet (HFD)-induced obesity and its related complications.

MAIN METHODS

We fed C57BL/6 mice a HFD for 12 weeks and administered PC orally for 8 or 12 weeks at different doses. At the end of the experiment, blood was prepared for biochemical analysis and leptin ELISA. Aorta, epididymal and mesenteric fat and liver were removed surgically, weighed and observed for histological or immunohistochemical changes.

KEY FINDINGS

PC significantly prevented body weight gain and lipid accumulation and alleviated hyperlipidemia by decreasing triglyceride (TG) and total cholesterol (TC) levels and the atherogenic index in serum or by increasing the HDL/TC ratio. Aortic apoE expression and serum leptin levels were suppressed by PC treatment in the HFD-induced obese mouse model. Elevated serum aspartate aminotransferase and alanine aminotransferase levels in HFD-fed mice were decreased in the PC groups. PC treatment significantly decreased HFD-induced liver weight and hepatic lipid accumulation.

SIGNIFICANCE

PC treatment alleviated HFD-induced obese status and obesity-related complications such as hyperlipidemic changes that induce cardiovascular disease and NAFLD.

Physical activity and risk of fatty liver in people with different levels of alcohol consumption: a prospective cohort study

OBJECTIVE

To investigate whether physical activity affects the future incidence of fatty liver in people with never-moderate and heavy alcohol consumption.

DESIGN

Prospective cohort study.

SETTING

Health check-up programme at Meiji Yasuda Shinjuku Medical Center in Shinjuku Ward, Tokyo, Japan.

POPULATION

A total of 10,146 people aged 18 years or older without fatty liver enrolled through baseline surveys conducted from 2005 to 2007. They were grouped into never-moderate alcohol drinkers (n=7803) and heavy alcohol drinkers (n=2343) and followed until 2013.

MAIN OUTCOME MEASURE

Incident fatty liver diagnosed by ultrasound.

RESULTS

During a mean follow-up of 4.4 years (34,648 person-years), 1255 never-moderate alcohol drinkers developed fatty liver; 520 heavy alcohol drinkers developed fatty liver during a mean follow-up of 4.1 years (9596 person-years). For never-moderate alcohol drinkers, engaging in >3×/week of low-intensity (HR=0.82, 95% CI 0.71 to 0.96) and moderate-intensity (HR=0.56, 95% CI 0.39 to 0.81) physical activity significantly reduced incident fatty liver compared with those who engaged in physical activity <1×/week. For vigorous-intensity physical activity, frequencies of 2×/week (HR=0.57, 95% CI 0.38 to 0.86) and >3×/week (HR=0.55, 95% CI 0.38 to 0.79) were significantly associated with lower risk of incident fatty liver. In propensity-adjusted models, these significant associations still remained. By contrast, in heavy alcohol drinkers, there were no significant associations between the type or frequency of physical activity and incident fatty liver.

CONCLUSIONS

Physical activity had an independent protective effect on incident fatty liver only in the never-moderate alcohol drinkers, and the preventive effect increased with higher frequencies and intensities of physical activity.

Autophagy protects against palmitate-induced apoptosis in hepatocytes

Background

Non-alcoholic fatty liver disease, one of the most common liver diseases, has obtained increasing attention. Palmitate (PA)-induced liver injury is considered a risk factor for the development of non-alcoholic fatty liver disease. Autophagy, a cellular degradative pathway, is an important self-defense mechanism in response to various stresses. In this study, we investigated whether autophagy plays a protective role in the progression of PA-induced hepatocytes injury.

Results

Annexin V-FITC/PI staining by FCM analysis, TUNEL assay and the detection of PARP and cleaved caspase3 expression levels demonstrated that PA treatment prominently induced the apoptosis of hepatocytes. Meanwhile, treatment of PA strongly induced the formation of GFP-LC3 dots, the conversion from LC3I to LC3II, the decrease of p62 protein levels and the increase of autophagosomes. These results indicated that PA also induced autophagy activation. Autophagy inhibition through chloroquine pretreatment or Atg5shRNA infection led to the increase of cell apoptosis after PA treatment. Moreover, induction of autophagy by pretreatment with rapamycin resulted in distinct decrease of PA-induced apoptosis. Therefore, autophagy can prevent hepatocytes from PA-induced apoptosis. In the further study, we explored pathway of autophagy activation in PA-treated hepatocytes. We found that PA activated PKCα in hepatocytes, and had no influence on mammalian target of rapamycin and endoplasmic reticulum stress pathways.

Conclusions

These results demonstrated that autophagy plays a protective role in PA-induced hepatocytes apoptosis. And PA might induce autophagy through activating PKCα pathway in hepatocytes.

Accelerated infant weight gain and risk for nonalcoholic fatty liver disease in early adulthood

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) is considered the hepatic metabolic syndrome. Some studies demonstrated an association between small size at birth and NAFLD. Rapid catch-up in weight often follows small birth size and has been associated with metabolic syndrome, but its association with NAFLD remained unknown.

PATIENTS AND METHODS

In 268 adults aged 18-24 years, body mass index, waist circumference, triglyceride, γ-glutamyltransferase, alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase levels were determined. Fatty liver index (FLI; 0-100) was calculated. Associations of birth weight SD score and first year gain in weight and length SD scores were determined with FLI and other liver markers. Comparisons were performed between subjects with and without rapid catch-up in weight in the first year of life. Furthermore, a FLI score (low, intermediate, high risk for NAFLD) was assigned to each participant to determine clinical relevance, and ordinal regression analyses were performed.

RESULTS

Gain in weight in the first 3 months of life was associated with FLI as a continuous variable, whereas low birth weight was not. There were no significant associations with γ-glutamyltransferase, alanine aminotransferase, or aspartate aminotransferase. Of the subjects with rapid catch-up in weight for length, 27.8% had an intermediate or high FLI at the age of 21 years, compared with 5.3% of subjects with slow catch-up. Rapid catch-up was also associated with a higher FLI score after adjustments (odds ratio, 11.7; P = .016).

CONCLUSION

Accelerated gain in weight for length in the first 3 months of life is associated with a higher risk for NAFLD in early adulthood, whereas small size at birth is not.

Lifestyle interventions for the treatment of non-alcoholic fatty liver disease

The burden of non-alcoholic fatty liver disease (NAFLD) worldwide is a significant clinical and public health issue, affecting approximately one third of the Western population. This review assesses the effect and impact lifestyle interventions have on the treatment of this common condition. We review studies comparing the effect of calorie restriction and exercise programs, as well as comparison of lifestyle intervention with pharmaceutical intervention. Both calorie restriction and exercise programs are shown to be beneficial in improving features of metabolic syndrome and surrogate markers of NAFLD. The paucity of studies using histological improvement hinders the ability to conclude a benefit on improvement of histological NAFLD, although this is shown in a small number of studies. There is a need to extend the intervention period to show a sustained improvement with intervention as most studies have a follow up period of 12 months of less.

Physical activity for the prevention and treatment of metabolic disorders

Metabolic syndrome and its various features (obesity, hypertension, dyslipidemia, diabetes, and nonalcoholic fatty liver disease) are increasing worldwide and constitute a severe risk for the sustainability of the present universal Italian health care system. Lifestyle interventions should be the first therapeutic strategy to prevent/treat metabolic diseases, far before pharmacologic treatment. The role of diet and weight loss has been fully ascertained, whereas the role of physical activity is frequently overlooked both by physicians and by patients. Physical activity has favorable effects on all components of the metabolic syndrome and on the resulting cardiovascular risk, the cornerstone in the development of cardiometabolic diseases. The quantity and the frequency of physical activity necessary to produce beneficial effects has not been defined as yet, but brisk walking is considered particularly appropriate, as it can be practiced by a large number of individuals, without any additional cost, and has a low rate of injury. The effects of exercise and leisure time physical activity extend from prevention to treatment of the various components of the metabolic syndrome, as well as to mood and quality of life. Any effort should be done to favor adherence to protocols of physical activity in the community.

Physical inactivity, insulin resistance, and the oxidative-inflammatory loop

Epidemiological data indicate that physical inactivity, a main factor of global energetic imbalance, is involved in the worldwide epidemic of obesity and metabolic disorders such as insulin resistance. Although the complex pathogenesis of insulin resistance is not fully understood, literature data accumulated during the past decades clearly indicate that the activation of the oxidative-inflammatory loop plays a major role. By activating the oxidative-inflammatory loop in insulin-sensitive tissues, fat gain and adipose tissue dysfunction likely contribute to induce insulin resistance during chronic and prolonged physical inactivity. However, in the past years, evidence has emerged showing that early insulin resistance also occurs after very short-term exposure to physical inactivity (1-7 days) without any fat gain or energetic imbalance. The possible role of liver disturbances or endothelial dysfunction is suggested, but further studies are necessary to really conclude. Inactive skeletal muscle probably constitutes the primary triggering tissue for the development of early insulin resistance. In the present review, we discuss on the current knowledge about the effect of physical inactivity on whole-body and peripheral insulin sensitivity, and how local inflammation and oxidative stress arising with physical inactivity could potentially induce insulin resistance. We assume that early muscle insulin resistance allows the excess nutrients to shift in the storage tissues to withstand starvation through energy storage. We also consider when chronic and prolonged, physical inactivity over an extended period of time is an underestimated contributor to pathological insulin resistance and hence indirectly to numerous chronic diseases.

The role of skeletal muscle in development of nonalcoholic Fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is closely correlated with abnormal accumulation of visceral fat, but the role of skeletal muscle remains unclear. The aim of this study was to elucidate the role of skeletal muscle in development of NAFLD.

METHODS

Among 11,116 subjects (6,242 males), we examined the effects of skeletal muscle mass and visceral fat area (VFA, by bioelectric impedance analysis) on NAFLD using by the fatty liver index (FLI).

RESULTS

Of the total subjects (9,565 total, 5,293 males) included, 1,848 were classified as having NALFD (FLI ≥60). Body mass index, lipid profile, fasting plasma glucose, hemoglobin A1c, prevalence of type 2 diabetes (DM), hypertension (HTN), and metabolic syndrome were higher in males than females, but FLI showed no significant difference. The low FLI group showed the lowest VFA and highest skeletal muscle mass of all the groups. Skeletal muscle to visceral fat ratio (SVR) and skeletal muscle index had inverse correlations with FLI, when adjusted for age and gender. In multivariate regression analysis, SVR was negatively associated with FLI. Among SVR quartiles, the highest quartile showed very low risk of NAFLD when adjusted for age, gender, lipid profile, DM, HTN, and high sensitivity C-reactive protein from the lowest quartiles (odds ratio, 0.037; 95% confidence interval, 0.029 to 0.049).

CONCLUSION

Skeletal muscle mass was inversely associated with visceral fat area, and higher skeletal muscle mass may have a beneficial effect in preventing NAFLD. These results suggest that further studies are needed to ameliorate or slow the progression of sarcopenia.

In patients with non-alcoholic fatty liver disease, metabolically abnormal individuals are at a higher risk for mortality while metabolically normal individuals are not

BACKGROUND AND AIM

Non-alcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease and is strongly associated with metabolic syndrome. The aim of this study is to compare the clinical profile and long-term outcome in NAFLD patients with or without metabolic syndrome.

METHODS

The initial cohort (N=6709) was identified from National Health and Nutrition Examination Survey-III (NHANES III, 1988-94) data. Laboratory profiles, body measurement examinations, and mortality data were linked to self-reported questionnaires of demographic and health risk information. NAFLD was defined as significant steatosis on hepatic ultrasound after exclusion of other chronic liver diseases (N=1448). NAFLD patients were classified according to presence or absence of metabolic syndrome. Mortality was determined through December 31, 2006. Cox models were used to estimate hazard ratios and 95% confidence intervals for all-cause, cardiovascular and liver-specific mortality differences between two sub-cohorts of NAFLD with and without metabolic syndrome.

RESULTS

NAFLD participants with metabolic syndrome were more likely to be Non-Hispanic white, older, and have higher aminotransferase levels. All-cause mortality (P<.001) and cardiovascular mortality (P<.001) were higher in NAFLD patients with metabolic syndrome. Furthermore, the presence of metabolic syndrome was independently associated with overall mortality, liver-specific mortality, and cardiovascular mortality. Age was an independent predictor of both all-cause and cardiovascular mortality. Elevated liver enzymes and obesity were two other independent predictors of liver-specific mortality. There were no differences in all-cause, liver-related, or cardiovascular mortality between groups of individuals without liver disease and individuals with NAFLD without metabolic syndrome (metabolically-normal).

CONCLUSIONS

Diagnosis of NAFLD with metabolic syndrome is an independent predictor of all-cause, liver-specific, and cardiovascular mortality. In contrast, mortality of metabolically-normal NAFLD patients is similar to the cohort without liver disease.