Hepatic steatosis is associated with an increased risk of carotid atherosclerosis

Lack of a relationship between circulating gamma-glutamyltransferase levels and carotid intima media thickness in hypertensive and diabetic patients

BACKGROUND

By increasing the intracellular prooxidant burden, gamma-glutamyltransferase (GGT) may accelerate atherosclerotic vascular disease. That noxious influence may be reflected by circulating enzyme levels, a correlate of cardiovascular risk factors, and a predictor of incident events. To evaluate this hypothesis, we tested the association between circulating GGT and common carotid intima-media thickness (CIMT), a surrogate index of systemic atherosclerotic involvement, in a large and well-characterized group of patients at risk of cardiovascular disease (CVD).

PATIENTS

This study analyzed 548 patients with hypertension and/or diabetes and a widely prevalent history of CVD. Subjects with known hepatic disease and abnormal GGT values were excluded.

METHODS

CIMT (B-mode ultrasonography) values were the mean of four far-wall measurements at both common carotids. Metabolic syndrome (MetS) was diagnosed according to National Cholesterol Education Program-Adult Treatment Panel III criteria. Due to inherent sex-related differences in GGT levels, the data were analyzed separately in males and females in samples dichotomized by the median.

RESULTS

The age-adjusted CIMT values did not differ by GGT levels in males or females. In contrast, the carotid wall was consistently thicker in patients with a history of CVD and MetS independent of age and concurrent GGT values. In both sexes, GGT was associated with key components of the MetS such as triglycerides, fasting plasma glucose, and body mass index.

CONCLUSION

The data collected in this mixed group of hypertensive and/or diabetic patients with widely prevalent history of CVD do not support the concept of a direct pathophysiological link between GGT levels within reference limits and atherosclerotic involvement.

Fatty liver index, gamma-glutamyltransferase, and early carotid plaques

An association between fatty liver and carotid atherosclerosis has been established; however, it is not clear whether this relationship is a consequence of shared conventional risk factors or whether it is determined by specific circulating factors originating from liver or adipose tissue. To identify the factors possibly linking fatty liver and atherosclerosis, we assessed, in 1,012 subjects free of confounding diseases (e.g., hypertension, diabetes, cardiovascular diseases, and dyslipidemia) and metabolic syndrome, the relationship between the presence of early plaques at carotid bifurcation and fatty liver index (FLI; a validated surrogate marker of fatty liver), as well as the associations between carotid plaque presence and established atherosclerotic risk factors, family history of cardiovascular disease (FH-CVD) or diabetes, insulin sensitivity, serum liver enzymes, adipokines, fatty free acids, and high-sensitivity C-reactive protein (hsCRP). A total of 55 of 1,012 subjects (5.4%) had small plaque at carotid bifurcation. Subjects with plaque were older and had higher prevalence of FLI ≥60 and FH-CVD, higher blood pressure, plasma low-density lipoprotein cholesterol, glucose, gamma-glutamyltransferase (GGT), and hsCRP, as compared to subjects without plaques (P < 0.05). In a logistic regression model, adjusted for sex, liver transaminase, and alcohol consumption, the independent predictors of plaque presence were age (P < 0.0005), FLI ≥60 (P < 0.0005), and current smoking (P < 0.05). When FLI in the model was replaced by variables used in its equation (e.g., body mass index, waist circumference, plasma triglycerides, and GGT), the independent determinants of plaque presence were age (P < 0.001), GGT (P = 0.001), and current smoking (P < 0.05).

CONCLUSIONS

Our cross-sectional study suggests that subjects with FLI ≥60 are at higher risk of atherosclerotic lesions, independently of established risk factors, and that serum GGT may represent a link between fatty liver and the development of early atherosclerosis.

Protective and therapeutic effect of ozone on diet-induced nonalcoholic steatohepatitis in rabbits

AIM: To assess whether ozone exerts a protective and therapeutic effect on inflammatory injury in nonalcoholic fatty liver disease (NAFLD) and atherosclerosis in rabbits.

METHODS: Twenty-four male New Zealand rabbits were randomly divided into three groups: model group (n = 10), ozone group (n = 4), and pravastatin plus aspirin group (n = 10). The experimental duration is 12 weeks. Rabbits were weighed once per week. Rabbits of all groups were given a high fat diet, and the ozone group and pravastatin plus aspirin group were additionally given ozone and pravastatin plus aspirin from the second week to the end of the experiment, respectively. The intimal-medial thickness (IMT) of the carotid artery and abdominal aorta was measured by ultrasound at weeks 2, 5, 8 and 12. HE staining was used to examine pathological changes in the carotid artery, aorta, liver, heart and kidney during the formation of NAFLD and AS. The contents of serum TC, LDL, HDL, ALT, γ-GT, Cr and UA were determined. ELISA was used to determine the changes in serum contents of 8-OHdG, TRX, 4-HNE, 8-iso-PGF2a, LEP, ADPN, FFA, ET, IL-6, TNF-α, MDA, MCP-1, hs-CRP, NOS, NO, GSH, reduced glutathione and GSH-Px.

RESULTS: At the end of the experiment, intimal thickening was observed, which suggests that nonalcoholic steatohepatitis was induced successfully. The body weight of rabbits in the ozone group was significantly lower than that in other groups. The percentage of area of aortic lipid deposition in the intima was statistically significant among the three groups (P = 0.037, P < 0.05), but no statistically significant difference was found in the thickness of lipid deposition (P > 0.05). The degree of balloon-like degeneration in the liver differed significantly among the three groups (P < 0.05); however, the degree of hepatic steatosis showed no statistically significant difference (P > 0.05). The degree of lipid deposition in the heart and lipid degeneration of tubular epithelial cells in the kidney showed no statistically significant difference among different groups. Compared to the model group, serum levels of LEP, ADPN, IL-6, TNF-α, MCP-1, hs-CRP, NOS, TRX, MDA, 4-HNE and 8-iso-PGF2a significantly increased and those of NO and reduced glutathione content decreased in the ozone group (all P < 0.05).

CONCLUSION: Ozone reduces inflammatory injury in nonalcoholic steatohepatitis and may be useful in preventing atherosclerosis. Ozone as an antioxidant does not cause visible damage to the liver, kidney and heart. Ozone can improve serum levels of inflammatory cytokines which are involved in oxidative stress and lipid peroxidation.

Role of obesity and lipotoxicity in the development of nonalcoholic steatohepatitis: pathophysiology and clinical implications

As obesity reaches epidemic proportions, nonalcoholic fatty liver disease (NAFLD) is becoming a frequent cause of patient referral to gastroenterologists. There is a close link between dysfunctional adipose tissue in NAFLD and common conditions such as metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. This review focuses on the pathophysiology of interactions between adipose tissue and target organs in obesity and the resulting clinical implications for the management of nonalcoholic steatohepatitis. The release of fatty acids from dysfunctional and insulin-resistant adipocytes results in lipotoxicity, caused by the accumulation of triglyceride-derived toxic metabolites in ectopic tissues (liver, muscle, pancreatic beta cells) and subsequent activation of inflammatory pathways, cellular dysfunction, and lipoapoptosis. The cross talk between dysfunctional adipocytes and the liver involves multiple cell populations, including macrophages and other immune cells, that in concert promote the development of lipotoxic liver disease, a term that more accurately describes the pathophysiology of nonalcoholic steatohepatitis. At the clinical level, adipose tissue insulin resistance contributes to type 2 diabetes mellitus and cardiovascular disease. Treatments that rescue the liver from lipotoxicity by restoring adipose tissue insulin sensitivity (eg, significant weight loss, exercise, thiazolidinediones) or preventing activation of inflammatory pathways and oxidative stress (ie, vitamin E, thiazolidinediones) hold promise in the treatment of NAFLD, although their long-term safety and efficacy remain to be established. Better understanding of pathways that link dysregulated adipose tissue, metabolic dysfunction, and liver lipotoxicity will result in improvements in the clinical management of these challenging patients.

Non-alcoholic fatty liver disease: a new and important cardiovascular risk factor?

Non-alcoholic fatty liver disease (NAFLD) affects up to a third of the population worldwide and may confer increased cardiometabolic risk with consequent adverse cardiovascular outcomes independent of traditional cardiovascular risk factors and the metabolic syndrome. It is characterized almost universally by insulin resistance and is strongly associated with type 2 diabetes and obesity. Non-alcoholic fatty liver disease is a marker of pathological ectopic fat accumulation combined with a low-grade chronic inflammatory state. This results in several deleterious pathophysiological processes including abnormal glucose, fatty acid and lipoprotein metabolism, increased oxidative stress, deranged adipokine profile, hypercoaguability, endothelial dysfunction, and accelerated progression of atherosclerosis. This ultimately leads to a dysfunctional cardiometabolic phenotype with cardiovascular mortality representing the main mode of premature death in NAFLD. This review is aimed at introducing NAFLD to the clinical cardiologist by discussing in-depth the evidence to date linking NAFLD with cardiovascular disease, reviewing the likely mechanisms underlying this association, as well as summarizing from a cardiologist's perspective, current and potential future treatment options for this increasingly prevalent disease.

Metabolic syndrome and risk factors for non-alcoholic fatty liver disease

CONTEXT: Non-alcoholic fatty liver disease (NAFLD), hepatic manifestation of metabolic syndrome, has been considered the most common liver disease nowadays, which is also the most frequent cause of elevated transaminases and cryptogenic cirrhosis. The greatest input of fatty acids into the liver and consequent increased beta-oxidation contribute to the formation of free radicals, release of inflammatory cytokines and varying degrees of hepatocytic aggression, whose histological expression may vary from steatosis (HS) to non-alcoholic steatohepatitis (NASH). The differentiation of these forms is required by the potential risk of progression to cirrhosis and development of hepatocellular carcinoma. OBJECTIVE: To review the literature about the major risk factors for NAFLD in the context of metabolic syndrome, focusing on underlying mechanisms and prevention. METHOD: PubMed, MEDLINE and SciELO data basis analysis was performed to identify studies describing the link between risk factors for metabolic syndrome and NAFLD. A combination of descriptors was used, non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, metabolic syndrome and risk factors. At the end, 96 clinical and experimental studies, cohorts, meta-analysis and systematic reviews of great impact and scientific relevance to the topic, were selected. RESULTS: The final analysis of all these data, pointed out the central obesity, type 2 diabetes, dyslipidemia and hypertension as the best risk factors related to NAFLD. However, other factors were highlighted, such as gender differences, ethnicity, genetic factors and the role of innate immunity system. How these additional factors may be involved in the installation, progression and disease prognosis is discussed. CONCLUSION: Risk factors for NAFLD in the context of metabolic syndrome expands the prospects to 1) recognize patients with metabolic syndrome at high risk for NAFLD, 2) elucidate pathways common to other co-morbidities, 3) determine risk factors associated with a worse prognosis, 4) develop therapeutic strategies with goal of reducing risk factors, 5) apply acquired knowledge in public health policies focusing on preventive strategies.

Chronic HCV infection is a risk of atherosclerosis. Role of HCV and HCV-related steatosis

OBJECTIVES

HCV and NAFLD are associated with atherosclerosis in general population. The prevalence of atherosclerosis in chronic hepatitis C (CHC) patients is unknown. We hypothesized that HCV per se and HCV-related steatosis could favour atherosclerosis. Thus, in CHC patients we assessed: (a) the prevalence of atherosclerosis; (b) the role of HCV, cardio-metabolic risk factors and hepatic histology.

METHODS

Overall, 803 subjects were enrolled: (A) 326 patients with liver biopsy-proven treatment naive CHC (175 with and 151 without steatosis); (B) 477 age and gender matched controls, including 292 healthy subjects without steatosis (B1) and 185 with NAFLD (B2). Carotid atherosclerosis (CA), assessed by high-resolution B-mode ultrasonography, was categorized as either intima-media thickness (IMT: >1mm) or plaques (≥ 1.5mm).

RESULTS

CHC patients had a higher prevalence of CA than controls (53.7% vs 34.3%; p<0.0001). Younger CHC (<50 years) had a higher prevalence of CA than controls (34.0% vs 16.0%; p<0.04). CHC patients without steatosis had a higher prevalence of CA than B1 controls (26.0% vs 14.8%; p<0.02). CHC with steatosis had a higher prevalence of CA than NAFLD patients (77.7% vs 57.8%, p<0.0001). Viral load was associated with serum CRP and fibrinogen levels; steatosis with metabolic syndrome, HOMA-IR, hyperhomocysteinemia and liver fibrosis. Viral load and steatosis were independently associated with CA. Diabetes and metabolic syndrome were associated with plaques.

CONCLUSION

HCV infection is a risk factor for earlier and facilitated occurrence of CA via viral load and steatosis which modulate atherogenic factors such as inflammation and dysmetabolic milieu.

Diabetes-induced alterations in the extracellular matrix and their impact on myocardial function

Diabetes is an increasing public health problem that is expected to escalate in the future due to the growing incidence of obesity in the western world. While this disease is well known for its devastating effects on the kidneys and vascular system, diabetic individuals can develop cardiac dysfunction, termed diabetic cardiomyopathy, in the absence of other cardiovascular risk factors such as hypertension or atherosclerosis. While much effort has gone into understanding the effects of elevated glucose or altered insulin sensitivity on cellular components within the heart, significant changes in the cardiac extracellular matrix (ECM) have also been noted. In this review article we highlight what is currently known regarding the effects diabetes has on both the expression and chemical modification of proteins within the ECM and how the fibrotic response often observed as a consequence of this disease can contribute to reduced cardiac function.

Nonalcoholic fatty liver disease and cardiovascular disease: has the time come for cardiologists to be hepatologists?

Nonalcoholic fatty liver disease (NAFLD) is prevalent in people with the metabolic syndrome and type 2 diabetes and is present in up to one-third of the general population. Evidence is now accumulating that NAFLD is associated with obesity and diabetes and may serve as a predictor of cardiovascular disease (CVD). The possible mechanisms linking NAFLD and CVD include inflammation and oxidative stress, hyperlipidaemia, insulin resistance, and direct impact of NAFLD on coronary arteries and left ventricular dysfunction. In addition, several studies suggest that NAFLD is associated with high risk of CVD and atherosclerosis such as carotid artery wall thickness and lower endothelial flow-mediated vasodilation independently of classical risk factors and components of the metabolic syndrome. It is not yet clear how treatment of NAFLD will modulate the risk of CVD. Furthermore, studies are urgently needed to establish (i) the pathophysiology of CVD with NAFLD and (ii) the benefit of early diagnosis and treatment of CVD in patients with NAFLD. In the absence of biochemical markers, it is crucial that screening and surveillance strategies are adopted in clinical practice in the growing number of patients with NAFLD and at risk of developing CVD. Importantly, the current evidence suggest that statins are safe and effective treatment for CVD in individuals with NAFLD.

The severity of Fatty liver disease relating to metabolic abnormalities independently predicts coronary calcification

Background. Nonalcoholic fatty liver disease (NAFLD) is one of the metabolic disorders presented in liver. The relationship between severity of NAFLD and coronary atherosclerotic burden remains largely unknown. Methods and Materials. We analyzed subjects undergoing coronary calcium score evaluation by computed tomography (MDCT) and fatty liver assessment using abdominal ultrasonography. Framingham risk score (FRS) and metabolic risk score (MRS) were obtained in all subjects. A graded, semiquantitative score was established to quantify the severity of NAFLD. Multivariate logistic regression analysis was used to depict the association between NAFLD and calcium score. Results. Of all, 342 participants (female: 22.5%, mean age: 48.7 ± 7.0 years) met the sufficient information rendering detailed analysis. The severity of NAFLD was positively associated with MRS (X² = 6.12, trend P < 0.001) and FRS (X² = 5.88, trend P < 0.001). After multivariable adjustment for clinical variables and life styles, the existence of moderate to severe NAFLD was independently associated with abnormal calcium score (P < 0.05). Conclusion. The severity of NAFLD correlated well with metabolic abnormality and was independently predict coronary calcification beyond clinical factors. Our data suggests that NAFLD based on ultrasonogram could positively reflect the burden of coronary calcification.

Association of serum lipoprotein-associated phospholipase A2 level with nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome and is one of the most common causes of chronic liver disease, worldwide. Lipoprotein-associated phospholipase A2 (Lp-PLA2) was recently characterized as a novel inflammatory biomarker that is correlated with several components constituting the metabolic syndrome.

METHODS

In this study, we determined the serum levels of Lp-PLA2 in patients with definite nonalcoholic steatohepatitis (NASH, n=25), borderline NASH (n=22), simple fatty liver (n=10), and healthy controls without evidence of liver disease (n=38). The levels of Lp-PLA2 were measured by enzyme-linked immunosorbent assay and compared in the four study groups. Moreover, concentrations of Lp-PLA2 were assessed in relation to the general characteristics of the study participants and the results of liver biopsy.

RESULTS

Concentrations of Lp-PLA2 were significantly higher in patients with definite NASH (161.8±0.9 μg/L, P<0.001), borderline NASH (135.4±47.7 μg/L, P=0.001), and simple fatty liver (132.4±46.2 μg/L, P=0.042) compared with healthy controls (86.2±40.7 μg/L). Furthermore, the serum Lp-PLA2 level was strongly associated to histological steatosis scores in patients with NAFLD (β=0.32, t=2.50, P=0.016).

CONCLUSION

Although subject to future confirmation, our data suggest that Lp-PLA2 levels are elevated in NAFLD.

Evaluation of atherosclerotic findings in patients with nonalcoholic fatty liver disease

Background

Nonalcoholic fatty liver disease (NAFLD), a highly prevalent condition, is a feature of metabolic syndrome and is characterized by excessive accumulation of fat in the liver cells. The purpose of this study was to investigate the association between NAFLD and carotid intima-media thickness (CIMT) as an independent risk factor for atherosclerosis.

Methods

We examined 250 consecutive patients with ultrasonographically confirmed NAFLD and 85 age-matched and gender-matched controls with normal parenchymal liver echogenicity for determination of CIMT and presence of carotid atherosclerotic plaque.

Results

Compared with control subjects, patients with NAFLD showed an increased mean CIMT (0.81 ± 0.14 mm) compared with control subjects (0.58 ± 0.15 mm). This difference was statistically significant (P = 0.001). After performing multivariate analysis, the presence of NAFLD was associated with abnormal CIMT independent of other atherogenic risk factors or its association with metabolic syndrome.

Conclusion

NAFLD can be an independent risk factor for developing atherosclerosis. Therefore, NAFLD with and without metabolic syndrome can be associated with increased CIMT and increased risk of cardiovascular events in patients with NAFLD incidentally diagnosed on abdominal ultrasonography.

Treatment of atherogenic liver based on the pathogenesis of nonalcoholic fatty liver disease: a novel approach to reduce cardiovascular risk?

Nonalcoholic fatty liver disease (NAFLD), which spans a spectrum of conditions ranging from simple steatosis to progressive nonalcoholic steatohepatitis (NASH), is the most common chronic liver disease and a relevant public health issue. The prevalence of NAFLD depends on adiposity, age, gender and ethnicity. The natural history of liver disease in those with NAFLD critically depends on liver histological changes. However, cardiovascular mortality is increased in NAFLD, particularly in middle-aged adults. Against such a background, this review consists of three sections. First, data on NAFLD as a novel mechanism of increased cardiovascular risk via hyperinsulinism, pro-thrombotic potential, and subclinical inflammation are summarized. Next, the role of atherogenic liver in the development of manifestations of oxidative stress and atherosclerosis is emphasized. Finally, whether and how treating NAFLD will mechanistically result in reduced cardiovascular risk through ameliorated metabolic syndrome is discussed.

Subjects with sonographical hepatic steatosis should be excluded from studies to establish upper reference levels of serum transaminases

BACKGROUND AND AIMS

Correct upper reference limits (URL) of serum liver enzyme activities are used to select individuals in whom further diagnostic procedures for suspected liver disorders are warranted and to compare the prevalence and incidence of increased serum liver enzyme levels within and among populations. We sought to establish URL in a general adult population by not only generating a disease-free population but also further excluding subjects with ultrasonographical diagnosis of hepatic steatosis.

METHODS

We used data from 4,242 subjects (2,154 women) aged 20-79 years recruited for the population-based Study of Health in Pomerania. A reference population was selected comprising 1,953 subjects (1,129 women). Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and γ-glutamyltransferase (GGT) were measured photometrically.

RESULTS

The exclusion of 630 subjects with hepatic steatosis and 20 subjects with equivocal data on liver ultrasound from the reference population predominantly affected the URL for serum ALT and GGT levels in younger age groups. URL for serum ALT, AST and GGT levels were 1.00 μmol/L/s (60 U/L), 0.55 μmol/L/s (33 U/L) and 1.11 μmol/L/s (67 U/L), respectively, in men as well as 0.57 μmol/L/s (34 U/L), μmol/L/s (25 U/L) and μmol/L/s (39 U/L), respectively, in women.

CONCLUSIONS

URL for serum liver enzyme activities are higher than recommended previously. Creating a reference population for establishing URL for serum liver enzyme activities should include liver ultrasound in order to exclude subjects with subclinical hepatic steatosis.

Subcutaneous adipose tissue in relation to subclinical atherosclerosis and cardiometabolic risk factors in midlife women

BACKGROUND

Limited data suggest that the effects of abdominal subcutaneous adipose tissue (SAT) on cardiovascular disease risk may depend on accompanying amounts of abdominal visceral adipose tissue (VAT).

OBJECTIVE

The objective was to examine whether abdominal VAT area modifies the effects of abdominal SAT area on subclinical atherosclerosis and cardiometabolic risk factors in both whites and African Americans.

DESIGN

Computed tomographic measures of abdominal SAT and VAT were examined in relation to carotid intima-media thickness (cIMT) and cardiometabolic risk factor levels in 500 African American and white women in midlife. A VAT × SAT interaction term was evaluated.

RESULTS

The mean (±SD) age of the sample was 51.0 ± 2.9 y, and 37% were African American. Higher amounts of SAT and VAT were associated with higher cIMT, blood pressure, homeostasis model assessment insulin resistance index (HOMA-IR), and concentrations of glucose, triglycerides, and insulin and with lower concentrations of HDL cholesterol. However, in African Americans, but not in whites, higher amounts of VAT significantly attenuated associations between higher amounts of SAT and higher insulin concentrations (P for interaction = 0.032) and HOMA-IR (P for interaction = 0.011) and reversed associations with cIMT (P for interaction = 0.005) and glucose (P for interaction = 0.044).

CONCLUSIONS

These results suggest that in midlife African American but not white women, adverse associations between abdominal SAT and cardiometabolic risk factors are attenuated and, in the case of subclinical atherosclerosis, are reversed as VAT amounts increase. Given that African American women suffer disproportionately from obesity and cardiovascular disease, further research into the role of this effect modification on obesity-associated vascular disease in African American women is warranted.

Recent advances in imaging hepatic fibrosis and steatosis

Liver disease is an increasing cause of morbidity and mortality worldwide. Currently, the gold standard for diagnosis and assessment of parenchymal disease is histopathological assessment of a percutaneous or transjugular liver biopsy. The risks and limitations of this technique are well recognized and as a result, significant effort has gone into the development of novel noninvasive methods of diagnosis and longitudinal assessment. Imaging techniques have improved significantly over the past decade and new technologies are beginning to enter clinical practice. Ultrasound, computed tomography and MRI are the main modalities currently used, but novel MRI-based techniques will have an increasing role. While there has been extensive research into the imaging of focal liver disease, the evidence base for imaging in diffuse disease has also undergone recent rapid development, particularly in the assessment of fibrosis and steatosis. Both of these abnormalities of the parenchyma can lead to cirrhosis and/or hepatocellular carcinoma and represent an important opportunity for detection of early liver disease. We discuss the recent advances in liver imaging techniques and their role in the diagnosis and monitoring of diffuse liver disease, with a focus on their current and potential clinical relevance and whether they may replace or augment liver biopsy. We also discuss techniques currently under development and their potential clinical applications in the future.

The association between fatty liver disease and blood pressure in a population-based prospective longitudinal study

OBJECTIVE

The aim of the present study was to investigate the association of fatty liver disease (FLD) with blood pressure (BP) and hypertension in a general population sample with prospective 5-year follow-up examinations.

DESIGN AND METHODS

We used data from the Study of Health in Pomerania, conducted in the northeastern part of Germany. The study population comprised 3191 individuals aged 20-79 years. FLD was defined as the presence of a hyperechogenic pattern of the liver and increased serum alanine transferase (ALT) levels.

RESULTS

Multivariable analyses revealed that FLD was associated with increased DBP and hypertension at baseline and with increased SBP and hypertension at follow-up. In individuals with FLD, the chance of hypertension at baseline and follow-up was three-fold higher [odds ratio (OR) 2.8; 95% confidence interval (CI) 1.3-6.2 and OR 3.1; 95% CI 1.7-5.8, respectively] compared to individuals without FLD. In the subgroup of individuals not receiving antihypertensive medication, FLD was associated with all BP-related variables at baseline and follow-up. Analyses further suggest that these associations were independent of alcohol consumption and further confounders.

CONCLUSION

FLD defined by liver hyperechogenity and increased ALT levels is associated with progression of BP over time and incident hypertension. In individuals with FLD, BP should be checked regularly and interventions addressing behavioural risk factors for FLD and hypertension should be initiated if necessary. Ultrasound should be implemented as a method to detect FLD in individuals with increased ALT levels in routine medical care.

Increased arterial stiffness in nonalcoholic fatty liver disease: the Cardio-GOOSE study

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) is a very frequent disease in Western countries. NAFLD shares with metabolic syndrome the same etiologic factors, such as obesity, diabetes, and dyslipidemia, which are also major cardiovascular risk factors. Cardio-GOOSE (Cardio-Gambettola ObservatOry liver Steatosis Estimation) is a population-based cohort study finalized to evaluate the relationship between NAFLD, subclinical vascular damage, and arterial stiffness.

METHODS

The study population consisted of 220 participants (123 women), aged between 30 and 70 years, who participated in the GOOSE study. Arterial stiffness was determined by measuring the carotid-femoral pulse wave velocity (PWV) by means of the PulsePen device. Preclinical atherosclerosis was detected by carotid intima-media thickness (IMT) measurement.

RESULTS

NAFLD was associated with metabolic syndrome in 48% of cases. IMT values were strongly related to metabolic syndrome factors. No significant differences in IMT were found between controls and patients with isolated NAFLD (0.77 +/- 0.15 mm versus 0.76 +/- 0.14 mm). Conversely, in patients with NAFLD associated with metabolic syndrome, IMT values were significantly higher than in patients with NAFLD alone (0.85 +/- 0.16 mm, P < 0.005). PWV values were significantly lower in controls compared to patients with isolated NAFLD (7.40 +/- 1.47 versus 7.98 +/- 1.51 m/s, P < 0.05) as well as patients with both NAFLD and metabolic syndrome (8.29 +/- 2.2 m/s, P < 0.001). The prevalence in NAFLD was increased in patients with the highest PWV values, and persisted after adjustment for factors determining metabolic syndrome (P < 0.05).

CONCLUSIONS

This study has shown a possible independent role of NAFLD in determining arterial stiffness.

Increased arterial stiffness and impaired endothelial function in nonalcoholic Fatty liver disease: a pilot study

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease both in the general and pediatric population and has been associated with increased cardiovascular risk. Arterial function and early atherosclerotic changes are markers of cardiovascular disease and independent predictors of the corresponding risk. Through a global approach, we investigated the relationships between NAFLD and functional arterial changes and early atherosclerosis.

METHODS

A total of 23 consecutive patients (mean age 55 ± 14 years, 11 males) with biopsy evidence of NAFLD and 28 control subjects matched for age, gender, body mass index, and other cardiovascular risk factors participated in the study.

RESULTS

Compared to controls, NAFLD subjects had significantly higher carotid-femoral pulse wave velocity (PWV; 8.2 ± 1.3 m/s vs. 6.9 ± 1.3 m/s, P = 0.001), higher carotid intima-media thickness (IMT; 0.79 ± 0.18 mm vs. 0.67 ± 0.13 mm, P = 0.01), and reduced flow-mediated dilatation (FMD; 1.92 ± 2.11% vs. 4.8 ± 2.43%, P < 0.001). In multivariable analysis, presence of NAFLD was an independent determinant of both PWV and FMD, whereas leptin was an independent determinant of PWV (B = 0.036, P < 0.05), and adiponectin was independently associated with FMD (B = 0.104, P < 0.05). In addition, histological activity of liver disease expressed by the global Brunt Grade was associated independently with FMD (B = -1.054, P < 0.05).

CONCLUSIONS

NAFLD is associated with arterial stiffness and endothelial dysfunction. Given the important independent prognostic role of these arterial indexes, these findings have important implications for increased cardiovascular risk in patients with NAFLD.

Mean platelet volume and its relationship with carotid atherosclerosis in subjects with non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is linked to an increased risk of cardiovascular disease. Mean platelet volume (MPV), a determinant of platelet activation, is an emerging risk factor for atherothrombosis.

AIMS

The aim of this study was to investigate the levels of MPV in subjects with NAFLD having no confounding factors for atherosclerosis such as obesity, diabetes mellitus, and hypertension. In addition, the possible relationship between MPV and carotid artery intima media thickness (CIMT), a well known marker of subclinical atherosclerosis, was also studied.

METHODS

MPV and CIMT levels were measured in 60 biopsy-proven NAFLD subjects and 54 healthy controls. Age and sex were similar between two groups.

RESULTS

Body mass index and waist circumference levels were higher in the NAFLD group when compared to the controls. There were no differences between the two groups regarding LDL cholesterol levels, whereas HDL cholesterol levels were lower in the NAFLD group. MPV and CIMT levels were not different between the two groups. According to the correlation analyses, CIMT levels were positively correlated to age in patients with NAFLD. However, no significant correlation was found between MPV and CIMT levels.

CONCLUSIONS

The results of this study do not show any difference in MPV levels between subjects with NAFLD and controls. These finding suggests that in the absence of other metabolic risk factors, MPV might not be involved in the mechanism(s) of increased cardiovascular risk in NAFLD.

Non-Alcoholic Fatty Liver Disease (NAFLD): new challenge for general practitioners and important burden for health authorities?

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of hepatic dysfunction encountered in general practice. A large proportion of individuals with type 2 diabetes and the metabolic syndrome develop NAFLD. NAFLD is associated with severe insulin resistance and increased risk of cardiovascular disease and can progress to non-alcoholic steato-hepatitis, liver cirrhosis and cancer. Currently the only known effective treatments for NAFLD are lifestyle changes including stable weight loss and a diet low in calories. General practitioners will increasingly play a key role in dealing with this evolving but serious epidemic of NAFLD and associated metabolic complications. However, success will depend on the appropriate systems and mechanisms being in place in primary care and the proper motivation, support and education of the patient. This review provides the primary care physician with: (a) a step-by step guide of how to identify NAFLD, (b) information to exclude common other causes of liver fat accumulation and (c) additional insight into relationships between NAFLD and other conditions such as obesity, cardiovascular disease and type 2 diabetes.

Ectopic fat and cardiovascular disease: what is the link?

AIM

of this paper is to review the recent literature on the relationship between ectopic fat accumulation and cardiovascular disease.

DATA SYNTHESIS

Ectopic fat is an important predictor of metabolic (in particular insulin resistance) and cardiovascular disease, carrying more risk than general fat accumulation. Recent studies have shown a link between ectopic fat accumulation, as cardiac (epicardial or intra-myocardial fat) and/or visceral and/or hepatic fat, and development of atherosclerosis, coronary heart disease and hypertension.

CONCLUSIONS

Ectopic fat accumulation is not only a marker of cardiometabolic disease, since through the release of adipocitokines, lipotoxic and glucotoxic agents, participates in the crosstalk with insulin-sensitive organs leading to metabolic, cardiac and vascular dysfunctions.

Cardiovascular risk factors, nonalcoholic fatty liver disease, and carotid artery intima-media thickness in an adolescent population in southern Italy

The objective of this study was to determine, in an adolescent population, the prevalence of nonalcoholic fatty liver disease (NAFLD) and the association of NAFLD and cardiovascular risk factors with carotid artery intima-media thickness (IMT), a marker of subclinical atherosclerosis. The authors conducted a population-based study among 642 randomly selected adolescents aged 11-13 years in Reggio Calabria, southern Italy, between November 2007 and October 2008. Prevalences of overweight and obesity were 30.5% and 13.5%, respectively. The overall prevalence of NAFLD was 12.5%, increasing to 23.0% in overweight/obese adolescents. In univariate analysis, increased IMT was positively associated with the presence of NAFLD, body mass index (BMI), waist circumference, systolic blood pressure (all P's < 0.001), diastolic blood pressure (P = 0.006), gamma-glutamyl transpeptidase (P = 0.006), alanine aminotransferase (P = 0.007), and C-reactive protein (P = 0.008) and was inversely associated with high density lipoprotein cholesterol (P < 0.001). In multivariate analysis, NAFLD (P = 0.002), BMI (P = 0.004), waist circumference (P = 0.003), and systolic blood pressure (P = 0.005) retained significant associations. The authors conclude that NAFLD, BMI, waist circumference, and systolic blood pressure are independent markers of increased IMT in a random sample of adolescents.

Presence of gallstones or kidney stones and risk of type 2 diabetes

Recent evidence suggests that gallstones and kidney stones are associated with insulin resistance, but the relation between stone diseases and the risk of developing type 2 diabetes mellitus is not clear. Participants in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam Study (Potsdam, Germany) provided information about the presence of gallstones and kidney stones at recruitment between 1994 and 1998. On biennial questionnaires, participants reported newly diagnosed type 2 diabetes mellitus, and confirmation was obtained from treating physicians. During a mean follow-up period of 7.0 years between 1994 and 2005, 849 incident cases of type 2 diabetes were identified among 25,166 participants. After adjustment for sex, age, waist circumference, and lifestyle risk factors, persons with reported gallstones (n = 3,293) had an increased risk of type 2 diabetes (relative risk = 1.42, 95% confidence interval: 1.21, 1.68). Among the 23,817 participants with information on reported kidney stones (784 cases of incident diabetes), those who developed kidney stones (n = 2,468) were not at increased risk of diabetes in multivariable-adjusted models (relative risk = 1.05, 95% confidence interval: 0.86, 1.27). These findings suggest that gallstones, but not kidney stones, may predict the risk of developing type 2 diabetes, providing physicians with an interventional opportunity to implement adequate prevention measures.

Hepatic steatosis, carotid atherosclerosis and metabolic syndrome: the STEATO Study

PURPOSE

Hepatic steatosis is frequently observed in subjects with metabolic syndrome (MS). In type 2 diabetics, it is independently associated with cardiovascular diseases. In order to confirm and extend this finding, a large group of patients with risk factors for atherosclerosis was studied.

METHODS

Carotid atherosclerosis was investigated by echo-Doppler, and hepatic steatosis by ultrasound and transaminase values. Strict exclusion criteria were chosen in order to avoid secondary forms of fatty liver and interference on transaminase values.

RESULTS

Among 970 enrolled patients, about 20% were diabetics, half had MS and 76% presented echographic hepatic steatosis. In multivariate analyses, fatty liver and MS were associated with carotid atherosclerosis [odds ratio (95% confidence intervals) 2.15 (1.27-3.63) and 1.72(1.12-2.64), respectively], whereas HOMA index was not. Aspartate aminotransferase and alanine aminotransferase were not independently associated with carotid atherosclerosis, whereas gamma-glutamyl transferase showed a link with atherosclerosis beyond MS and steatosis presence. The analyses of the 780 non diabetics recruited showed similar results.

CONCLUSIONS

The results of the present study demonstrate that hepatic steatosis measured by echography is associated with carotid atherosclerosis in a large population mostly carrying cardiovascular or metabolic risk factors, independently of MS, cardiovascular diseases, diabetes mellitus and/or insulin resistance.

Hepatic steatosis in overweight/obese females: New screening method for those at risk

AIM: To identify which parameters could help to distinguish the “metabolically benign obesity”, which is not accompanied by insulin resistance (IR) and early atherosclerosis.

METHODS: Eighty two of 124 overweight/obese females formed the study population, which was divided into two groups (52 and 30 subjects, respectively) with and without IR according to a HO meostatic Metabolic Assessment (HOMA) cut-off of 2, and were studied in a cross-sectional manner. The main outcome measures were waist circumference, serum uric acid, high-density lipoprotein-cholesterol and triglycerides, alanine aminotransferase, blood pressure and the two imaging parameters, hepatic steatosis and longitudinal diameter of the spleen, which were measured in relation to the presence/absence of IR.

RESULTS: A variable grade of visceral obesity was observed in all subjects with the exception of three. Obesity of a severe grade was represented more in the group of IR individuals (P = 0.01). Hepatic steatosis, revealed at ultrasound, was more pronounced in IR than in non-IR subjects (P = 0.005). The two groups also demonstrated a clear difference in longitudinal spleen diameter and blood pressure, with raised and significant values in the IR group. Metabolic syndrome was frequent in the IR group, and was not modified when adjusted for menopause (P = 0.001). At linear regression, the β values of waist circumference and body mass index predicting HOMA were 0.295, P = 0.007 and 0.41, P = 0.0001, respectively. Measures of spleen longitudinal diameter were well predicted by body mass index (BMI) values, β = 0.35, P = 0.01, and by HOMA, β = 0.41, P = 0.0001. Blood pressure was predicted by HOMA values, β = 0.39, P = 0.0001). HOMA and hepatic steatosis were highly associated (rho = 0.34, P = 0.002). Interestingly, IR patients were almost twice as likely to have hepatic steatosis as non-IR patients. Among the MS criteria, blood pressure was very accurate in identifying the presence of IR (AUROC for systolic blood pressure 0.66, cut-off 125 mm of Hg, sensibility 64%, specificity 75%; AUROC for diastolic blood pressure 0.70, cut-off 85 mm of Hg, sensibility 54.5%, specificity 75%).

CONCLUSION: As health care costs are skyrocketing, reliable and mainly inexpensive tools are advisable to better define subjects who really need to lose weight.

Ultrasonography to quantify hepatic fat content: validation by 1H magnetic resonance spectroscopy

An abundance of fat stored within the liver, or steatosis, is the beginning of a broad hepatological spectrum, usually referred to as fatty liver disease (FLD). For studies on FLD, quantitative hepatic fat ultrasonography would be an appealing study modality. Objective of this study was to develop a technique for quantifying hepatic fat content by ultrasonography and validate this using proton magnetic resonance spectroscopy ((1)H MRS) as gold standard. Eighteen white volunteers (BMI range 21.0-42.9) were scanned by both ultrasonography and (1)H MRS. Altered ultrasound characteristics, present in the case of FLD, were assessed using a specially developed software program. Various attenuation and textural based indices of FLD were extracted from ultrasound images. Using linear regression analysis, the predictive power of several models (consisting of both attenuation and textural based measures) on log 10-transformed hepatic fat content by (1)H MRS were investigated. The best quantitative model was compared with a qualitative ultrasonography method, as used in clinical care. A model with four ultrasound characteristics could modestly predict the amount of liver fat (adjusted explained variance 43.2%, P = 0.021). Expanding the model to seven ultrasound characteristics increased adjusted explained variance to 60% (P = 0.015), with r = 0.789 (P < 0.001). Comparing this quantitative model with qualitative ultrasonography revealed a significant advantage of the quantitative model in predicting hepatic fat content (P < 0.001). This validation study shows that a combination of computer-assessed ultrasound measures from routine ultrasound images can be used to quantitatively assess hepatic fat content.

Ultrasonographic hepatic steatosis increases prediction of mortality risk from elevated serum gamma-glutamyl transpeptidase levels

The aim of the present study was to investigate the association of serum gamma-glutamyltransferase (GGT) levels with all-cause mortality and to assess the impact of ultrasonographic findings of hepatic hyperechogenicity in that association. We used data from 4,160 subjects (2,044 men and 2,116 women) recruited for the population-based Study of Health in Pomerania (SHIP) without baseline hepatitis B and C infections or liver cirrhosis. GGT was divided into age- and sex-dependent quintiles to calculate overall and sex-specific crude incidence mortality rates. Hepatic steatosis was defined by elevated GGT levels (>80%) and the presence of hyperechogenic liver ultrasound. We used multiple-adjusted Cox proportional hazards regression models, first, to assess the direct effect of GGT on all-cause mortality, second, to stratify according to the ultrasonographic finding, and third, to investigate potential mediating effects of cardiometabolic risk factors. During 29,810 person-years (7.3 years, median) of follow-up, 307 individuals (7.5%) died, resulting in a death rate of 0.86 deaths per 1000 person-years. Elevated GGT levels were associated with increased risk of mortality in men (hazard ratio [HR] 1.49; 95% confidence interval [CI], 1.08-2.05), but not in women (HR 1.30; 95% CI, 0.80-2.12). This association was even stronger in men with hepatic steatosis (HR 1.98; 95% CI, 1.21-3.27). Cause-specific mortality analysis by cardiovascular disease deaths confirmed the sex-specific association. Adjustment for cardiometabolic risk factors did not affect the estimates.

CONCLUSION

In the case of increased GGT levels, liver ultrasound should be performed, not only for diagnosis, but also for further risk stratification.

Parametric exploration of the liver by magnetic resonance methods

MRI, as a completely noninvasive technique, can provide quantitative assessment of perfusion, diffusion, viscoelasticity and metabolism, yielding diverse information about liver function. Furthermore, pathological accumulations of iron and lipids can be quantified. Perfusion MRI with various contrast agents is commonly used for the detection and characterization of focal liver disease and the quantification of blood flow parameters. An extended new application is the evaluation of the therapeutic effect of antiangiogenic drugs on liver tumours. Novel, but already widespread, is a histologically validated relaxometry method using five gradient echo sequences for quantifying liver iron content elevation, a measure of inflammation, liver disease and cancer. Because of the high perfusion fraction in the liver, the apparent diffusion coefficients strongly depend on the gradient factors used in diffusion-weighted MRI. While complicating analysis, this offers the opportunity to study perfusion without contrast injection. Another novel method, MR elastography, has already been established as the only technique able to stage fibrosis or diagnose mild disease. Liver fat content is accurately determined with multivoxel MR spectroscopy (MRS) or by faster MRI methods that are, despite their widespread use, prone to systematic error. Focal liver disease characterisation will be of great benefit once multivoxel methods with fat suppression are implemented in proton MRS, in particular on high-field MR systems providing gains in signal-to-noise ratio and spectral resolution.

Contribution of glucose tolerance and gender to cardiac adiposity

CONTEXT AND OBJECTIVE

To examine whether pericardial and myocardial fat depots may contribute to the association between diabetes and cardiovascular risk, including sex-related differences, and the role of adiponectin, we evaluated data in patients with obesity and without diabetes [nondiabetic (ND)] or with impaired glucose tolerance or type 2 diabetes and in lean ND controls.

METHODS

Magnetic resonance imaging and spectroscopy were used to measure left ventricular (LV) function and abdominal sc and visceral fat areas to estimate respective masses, pericardial fat depots, and myocardial triglyceride content in 53 subjects (10 lean ND, 25 obese ND, six impaired-glucose-tolerance, and 12 type 2 diabetic patients with macrovascular disease); gender effects and adiponectin levels were evaluated in the available subset of subjects.

RESULTS

Myocardial and pericardial fat increased progressively across study groups. They were lower in obese women than men (P = 0.002), but cardiac steatosis caught up in hyperglycemic women (+81% vs. ND, P = 0.01). Adiponectin was inversely related with both fat depots (P < 0.01) and LV mass (P = 0.003) and positively with LV function (P = 0.03). In multiple regression analysis, myocardial and pericardial fat were independently related with plasma glucose levels, only pericardial fat mass was associated with visceral adiposity and myocardial fat with cardiac output and work.

CONCLUSIONS

We conclude that glycemia, gender, adiponectin, and cardiac workload are associated with, and hyperglycemia and male gender are independent positive predictors of, heart adiposity. Once glucose tolerance becomes impaired, the evolution of cardiac steatosis is more pronounced in women.

Carotid lesions in outpatients with nonalcoholic fatty liver disease

AIM: To ascertain whether carotid lesions are more prevalent in outpatients with incidental findings of nonalcoholic fatty liver disease (NAFLD) at abdominal ultrasound (US).

METHODS: One hundred and fifty-four consecutive outpatients (age range 24-90 years, both sexes) referred by general practitioners for abdominal US, and drinking less than 20 g alcohol/day, underwent carotid US for an assessment of carotid intima-media thickness (c-IMT) and carotid plaque prevalence. Hepatic steatosis, visceral fat thickness and subcutaneous fat thickness were also assessed at ultrasonography.

RESULTS: Higher c-IMT values were found in the presence of NAFLD (90 patients), even after adjustment for indices of general and abdominal obesity and for the principal cardiovascular risk factors (0.84 ± 0.10 mm vs 0.71 ± 0.10 mm, P < 0.001). The prevalence of carotid plaques was 57.8% in the patients with NAFLD vs 37.5% in the patients without this condition (P = 0.02). The adjusted relative risk of having carotid plaques for patients with NAFLD was 1.85 (95% CI: 1.33-2.57, P < 0.001).

CONCLUSION: An incidental finding of hepatic steatosis may suggest the presence of silent carotid atherosclerotic lesions.

Relationships of PAI-1 levels to central obesity and liver steatosis in a sample of adult male population in southern Italy

To analyse the relationship of PAI-1 plasma levels to echographically determined liver steatosis and cardiometabolic risk factors in a randomly selected sample of 254 adult male participants of the Olivetti Heart Study. Accounting for age and ongoing pharmacological treatment, PAI-1 levels were directly (P < 0.005) associated with body mass index (BMI), waist circumference (WC), serum triglyceride (TG), total cholesterol, insulin, homeostasis model assessment index, gamma-glutamyl transpeptidase and peritoneal fat. At multiple linear regression (MLR) analysis, measures of adiposity and TG exerted significant and quantitatively similar effects on PAI-1 levels. A progressive rise in PAI-1 level was detected with increasing degree of steatosis. A stepwise MLR model was used to evaluate the relative power of cardiometabolic risk factors and liver steatosis on PAI-1 levels. Adjusting for alcohol intake, BMI, WC and peritoneal fat were alternatively included in the model with other variables found to be significantly associated with plasma PAI-1 level. Liver steatosis, serum TG and various indexes of adiposity each had a significant independent impact on PAI-1 plasma level and explained overall 23% of its variability. Abdominal fat, liver steatosis and serum TG levels were significant and independent determinants of PAI-1 plasma level in an unselected sample of adult male population upon adjustment for age and therapy.

Non-alcoholic fatty liver disease is associated with cardiovascular disease risk markers

Recognition of the link between non-alcoholic fatty liver disease (NAFLD) and cardiovascular disease (CVD) has boosted research in this area. The main objective of this paper is to review the literature on NAFLD in the context of CVD, focussing on underlying mechanisms and treatment. Besides excessive fatty acid influx, etiologic factors may include components of the metabolic syndrome, cytokines and mitochondrial dysfunction. NAFLD is associated with both hepatic and systemic insulin resistance. In the case of NAFLD, the liver overproduces several atherogenic factors, notably inflammatory cytokines, glucose, lipoproteins and coagulation factors, and factors increasing blood pressure. Intervention studies on diet and laparoscopic surgery revealed improvements of hepatic fat content and CVD risk profile. Pharmacological approaches with potential benefit have been developed as well, but effects are often confounded by weight change. NAFLD is associated with an increased CVD risk profile (and hepatic risk). In order to improve CVD risk profile, prevention and treatment of NAFLD seem advisable. However, well-designed intervention studies, randomized clinical trials and long-term follow-up studies are scarce.

Nonalcoholic fatty liver disease as a comorbidity of childhood obesity

Childhood obesity is a worldwide health problem associated with an increase in the prevalence and severity of comorbid conditions including nonalcoholic fatty liver disease (NAFLD). The increasing number of children with NAFLD presents a major public health concern. This review focuses on the recent advancements in the understanding of the epidemiology, diagnosis, histology, pathogenesis and treatment of pediatric NAFLD and highlights ongoing challenges and unmet needs in the area.

Nonalcoholic fatty liver disease and cardiovascular risk

Nonalcoholic fatty liver disease (NAFLD) is a very common cause of chronic liver disease in the United States. A large proportion of patients with NAFLD have coexisting metabolic syndrome, a major risk factor for cardiovascular disease. A strong association between NAFLD and cardiovascular disease has been long suspected, and recent studies have confirmed that cardiovascular disease is the single most important cause of mortality in this patient population. NAFLD may pose cardiovascular risk beyond the risk conferred by traditional factors such as dyslipidemia, diabetes, and smoking. Health care providers managing patients with NAFLD should recognize this increased cardiovascular risk and should undertake early, aggressive risk factor modification.

Metabolic disturbances in non-alcoholic fatty liver disease

NAFLD (non-alcoholic fatty liver disease) refers to a wide spectrum of liver damage, ranging from simple steatosis to NASH (non-alcoholic steatohepatitis), advanced fibrosis and cirrhosis. NAFLD is strongly associated with insulin resistance and is defined by accumulation of liver fat >5% per liver weight in the presence of <10 g of daily alcohol consumption. The exact prevalence of NAFLD is uncertain because of the absence of simple non-invasive diagnostic tests to facilitate an estimate of prevalence. In certain subgroups of patients, such as those with Type 2 diabetes, the prevalence of NAFLD, defined by ultrasound, may be as high as 70%. NASH is an important subgroup within the spectrum of NAFLD that progresses over time with worsening fibrosis and cirrhosis, and is associated with increased risk for cardiovascular disease. It is, therefore, important to understand the pathogenesis of NASH and, in particular, to develop strategies for interventions to treat this condition. Currently, the 'gold standard' for the diagnosis of NASH is liver biopsy, and the need to undertake a biopsy has impeded research in subjects in this field. Limited results suggest that the prevalence of NASH could be as high as 11% in the general population, suggesting there is a worsening future public health problem in this field of medicine. With a burgeoning epidemic of diabetes in an aging population, it is likely that the prevalence of NASH will continue to increase over time as both factors are important risk factors for liver fibrosis. The purpose of this review is to: (i) briefly discuss the epidemiology of NAFLD to describe the magnitude of the future potential public health problem; and (ii) to discuss extra- and intra-hepatic mechanisms contributing to the pathogenesis of NAFLD, a better understanding of which may help in the development of novel treatments for this condition.

Recent advances in nonalcoholic fatty liver disease

PURPOSE OF REVIEW

This review focuses on recent advances in the study of the epidemiology, pathogenesis, natural history and treatment of nonalcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

Study of hepatic lipid metabolism with respect to the contribution of de-novo lipogenesis to hepatic steatosis and insulin resistance and the dysregulation of cellular adaptive response to stress, that is, the unfolded protein response has added to our current understanding of NAFLD. microRNA has recently emerged and has been shown to be differentially expressed in patients with nonalcoholic steatohepatitis. Its mechanism of action remains to be further explored. There is no proven pharmacotherapy for the treatment of NAFLD. Lifestyle intervention to achieve weight loss and increase exercise is persistently associated with improved liver histology. The diagnostic utility of noninvasive markers and imaging modalities in assessing fibrosis remains to be elucidated.

SUMMARY

The underlying mechanism and pathogenesis of NAFLD remain elusive. Although research effort has advanced the understanding of the natural history, pathogenesis and management of the disease, there is no proven therapy for this medical condition. At present, treatment concentrates on managing underlying metabolic risk factors.

Fatty liver is associated with insulin resistance, risk of coronary heart disease, and early atherosclerosis in a large European population

Patients with fatty liver (FL) disease have a high risk of developing diabetes and cardiovascular diseases. The aim was to evaluate the association between FL, insulin resistance (IR), coronary heart disease (CHD) risk, and early atherosclerosis in a large European population (RISC Study). In 1,307 nondiabetic subjects (age 30-60 years) recruited at 19 centers, we evaluated liver enzymes, lipids, insulin sensitivity (by euglycemic-hyperinsulinemic clamp), glucose tolerance (by 75 g oral glucose tolerance test), carotid atherosclerosis as intima media thickness (IMT), CHD risk by the Framingham Heart study prediction score, and physical activity (by accelerometer). The presence of FL was estimated using the fatty liver index (FLI; >60, likelihood >78% presence FL; FLI <20 likelihood >91% absence of FL). Subjects were divided into three groups: G1: FLI <20 (n = 608); G3: FLI >60 (n = 234), G2: intermediate group (n = 465). Compared to G1, G3 included more men (70% versus 24%) and people with impaired glucose tolerance (23% versus 5%). IMT increased with FLI (G3 = 0.64 +/- 0.08 versus G1 = 0.58 +/- 0.08 mm, P < 0.0001). FLI was associated with increased CHD risk (r = 0.48), low-density lipoprotein cholesterol (r = 0.33), alanine aminotransferase (r = 0.48), aspartate aminotransferase (r = 0.25), systolic blood pressure (r = 0.39) and IMT (r = 0.30), and reduced insulin sensitivity (r = -0.43), high-density lipoprotein cholesterol (r = -0.50), adiponectin (r = -0.42), and physical activity (r = -0.16, all P < 0.0001). The correlations hold also in multivariate analysis after adjusting for age, gender, and recruiting center.

CONCLUSION

In middle-age nondiabetic subjects, increased IMT, CHD risk, and reduced insulin sensitivity are associated with high values of FLI.

Hepatic steatosis is associated with low serum testosterone and high serum DHEAS levels in men

Obesity and metabolic syndrome are associated with low serum testosterone levels. Hepatic steatosis contributes to the metabolic syndrome and might be regarded as its hepatic manifestation. In this study, we sought to investigate the relationship between hepatic steatosis, serum testosterone and dehydroepiandrosterone sulphate (DHEAS) levels in men. This is a cross-sectional population-based study. We used data of 1912 men recruited for the population-based Study of Health in Pomerania, which was conducted in a region with high prevalence of metabolic syndrome and related diseases. Hepatic steatosis was defined according to sonographic criteria. The relationship of hepatic steatosis with serum testosterone and DHEAS levels was analysed by multivariable logistic regression. Men with low serum testosterone levels had a higher risk of hepatic steatosis than men with high serum testosterone levels. Adjustment for age and further confounders attenuated this association, but did not affect statistical significance (odds ratio 2.36; 95% confidence interval 1.66-3.37; p < 0.05). In the full model, the highest risk of hepatic steatosis was found in subjects with the highest serum DHEAS levels (odds ratio 1.59; 95% confidence interval 1.04-2.43; p < 0.05). Exclusion of men with high alcohol consumption did not affect these results substantially. Hepatic steatosis is associated with low serum testosterone and high serum DHEAS levels. These associations are independent of alcohol consumption.

Non alcoholic fatty liver disease and metabolic syndrome

Non-alcoholic fatty liver disease (NAFLD) is a clinicopathologic entity increasingly recognized as a major health burden in developed countries. It includes a spectrum of liver damage ranging from simple steatosis to nonalcoholic steatohepatitis (NASH), advanced fibrosis, and rarely, progression to cirrhosis. Recent studies emphasize the role of insulin resistance, oxidative stress and subsequent lipid peroxidation, proinflammatory cytokines, adipokines and mitochondrial dysfunction in the development and progression of NAFLD. Furthermore, accumulating evidence supports an association between NAFLD and metabolic syndrome. Although the data are mainly epidemiological, the pathogenesis of NAFLD and metabolic syndrome seems to have common pathophysiological mechanisms, with focus on insulin resistance as a key factor. This review summarizes the current knowledge on the epidemiology, pathophysiology and diagnosis of both NAFLD and metabolic syndrome and the findings that strongly support the association of nonalcoholic fatty liver disease as a possible component in the cluster of metabolic syndrome.