Non-alcoholic fatty liver disease and cardiovascular risk

The AST/ALT (De-Ritis) ratio: A novel marker for critical limb ischemia in peripheral arterial occlusive disease patients

The aspartat aminotransferase (AST)/alanin aminotransferase (ALT) (De-Ritis) ratio (AAR) is an easily applicable blood test. An elevated AAR on the one hand has been associated with an increase in nonalcoholic fatty liver disease (NAFLD). NAFLD on the other hand is associated with an increase in cardiovascular disease, all-cause mortality, and diabetes. As the AAR is also elevated in case of muscular damage, we investigated AAR and its association with critical limb ischemia (CLI) in peripheral arterial occlusive disease (PAOD) patients.In our cross-sectional study, we included 1782 PAOD patients treated at our institution from 2005 to 2010. Patients with chronic alcohol consumption (>20 g/day) were excluded. AAR was calculated and the cohort was categorized into tertiles according to the AAR. An optimal cut-off value for the continuous AAR was calculated by applying a receiver operating curve analysis to discriminate between CLI and non-CLI.In our cohort, occurrence of CLI significantly increased with an elevation in AAR. As an optimal cut-off value, an AAR of 1.67 (sensitivity 34.1%, specificity 81.0%) was identified. Two groups were categorized, 1st group containing 1385 patients (AAR < 1.67) and a 2nd group with 397 patients (AAR > 1.67). CLI was more frequent in AAR > 1.67 patients (166 [41.9%]) compared to AAR < 1.67 patients (329 [23.8%]) (P < 0.001), as was prior myocardial infarction (28 [7.1%] vs 54 [3.9%], P = 0.01). Regarding inflammatory parameters, C-reactive protein (median 8.1 mg/L [2.9-28.23] vs median 4.3 mg/L [2.0-11.5]) and fibrinogen (median 427.5 mg/dL [344.25-530.0] vs 388.0 mg/dL [327.0-493.0]) also significantly differed in the 2 patient groups (both P < 0.001). Finally, an AAR > 1.67 was associated with an odds ratio (OR) of 2.0 (95% confidence interval [CI] 1.7-2.3) for CLI even after adjustment for other well-established vascular risk factors.An increased AAR is significantly associated with patients at high risk for CLI and other cardiovascular endpoints. The AAR is a broadly available and cheap marker, which might be useful to highlight patients at high risk for vascular endpoints.

Nonalcoholic Fatty Liver Disease is Associated with Increased Carotid Intima-Media Thickness in Type 1 Diabetic Patients

A growing body of evidence suggests that NAFLD is associated with an increased risk of incident CVD events both in patients without diabetes and in those with type 2 diabetes (T2DM). However, no published data are available regarding the association between NAFLD and C-IMT in T1DM. A total of 722 patients (371 men) with T1DM were included in this cross-sectional study. The main outcome measures were detection of NAFLD, C-IMT and classical risk factors. The mean age of the subjects was 46.2 years, and 51.1% were male. The prevalence of NAFLD was 15.9%. NAFLD patients had a markedly greater C-IMT (0.81 ± 0.25 vs. 0.69 ± 0.18 mm; p < 0.001) and frequency of carotid plaque (28.9% vs. 16.9%; p < 0.05) than those without fatty liver. Moreover, the differences in C-IMT remained after adjusting for potential confounders. A stepwise linear regression analysis revealed that age (standardized β, 0.326; p < 0.001), NAFLD (standardized β, 0.151, p < 0.001), and hsCRP (standardized β, 0.115, p = 0.008) were independently associated with C-IMT in all subjects. Our data show NAFLD is associated with elevated C-IMT in T1DM independent of conventional cardiovascular disease risk factors.

Insulin resistance in development and progression of nonalcoholic fatty liver disease

Although insulin resistance (IR) is strongly associated with nonalcoholic fatty liver disease (NAFLD), the association of IR and NAFLD is not universal and correlation between IR and severity of NAFLD is still controversial. In this review, we summarize recent evidence that partially dissociates insulin resistance from NAFLD. It has also been reported that single-nucleotide polymorphisms in the diacylglycerol acyltransferase gene, rather than IR, account for the variability in liver fat content. Polymorphisms of the patatin-like phospholipase 3 gene have also been reported to be associated with NAFLD without metabolic syndrome, which suggests that genetic conditions that promote the development of fatty changes in the liver may occur independently of IR. Moreover, environmental factors such as nutrition and physical activity as well as small intestinal bacterial overgrowth have been linked to the pathogenesis of NAFLD, although some of the data are conflicting. Therefore, findings from both genetically engineered animal models and humans with genetic conditions, as well as recent studies that have explored the role of environmental factors, have confirmed the view that NAFLD is a polygenic disease process caused by both genetic and environmental factors. Therefore, IR is not the sole predictor of the pathogenesis of NAFLD.

Epidemiology of Nonalcoholic Fatty Liver Disease and Nonalcoholic Steatohepatitis in the United States and the Rest of the World

Nonalcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease with increasing prevalence, which can progress to cirrhosis and liver failure. Because of the obesity epidemic and increasing prevalence of metabolic syndrome, NAFLD and its progressive form, nonalcoholic steatohepatitis, are seen more commonly in different parts of the world. This article reviews the worldwide epidemiology of NAFLD and nonalcoholic steatohepatitis. The PubMed database was used to identify studies related to epidemiology of NAFLD in the adult population. It is estimated that the epidemic of obesity will continue to fuel the burden of NAFLD and its long-term complications.

Correlation between homocysteine level and carotid artery intima-media thickness in patients with nonalcoholic steatohepatitis

AIM: To evaluate the relationship between carotid artery intimae-media thickness (C-IMT) and plasma homocysteine (Hcy) level in non-alcoholic fatty hepatitis (NASH) patients.

METHODS: Eighty patients with NASH proven by liver biopsy, 80 patients with non-alcoholic fatty liver (NAFL) and 50 healthy controls were included. Blood lipids, liver biochemical indexes, serum homocysteine and carotid artery intimae-media thickness were measured and analyzed by correlation analysis.

RESULTS: In the NASH group, Hcy level was significantly higher in the NASH and NAFL groups than in the control group (P < 0.05), and in the NASH group than in the NAFL group. Correlation analysis showed that C-IMT was positively correlated with body mass index (BMI), total cholesterol (TC), triacylglycerol (TG), aspartate transaminase (AST) and Hcy. Multiple linear regression analysis showed that NASH, hypertension, metabolic syndrome (MS), and Hcy were risk factors for C-IMT (standardized regression coefficients = 1.515, 2.066, 3.270, and 1.240; P = 0.001, 0.032, 0.009, and 0.039, respectively).

CONCLUSION: Hey levels in patients with non-alcoholic fatty hepatitis are closely related to C-IMT and could be a risk factor for cardiovascular disease.

Tetradecylthiopropionic acid induces hepatic mitochondrial dysfunction and steatosis, accompanied by increased plasma homocysteine in mice

BACKGROUND

Hepatic mitochondrial dysfunction plays an important role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Methyl donor supplementation has been shown to alleviate NAFLD, connecting the condition to the one-carbon metabolism. Thus, the objective was to investigate regulation of homocysteine (Hcy) and metabolites along the choline oxidation pathway during induction of hepatic steatosis by the fatty acid analogue tetradecylthiopropionic acid (TTP), an inhibitor of mitochondrial fatty acid oxidation.

METHODS

Mice were fed a control diet, or diets containing 0.3 %, 0.6 %, or 0.9 % (w/w) TTP for 14 days. Blood and liver samples were collected, enzyme activities and gene expression were analyzed in liver, lipid and fatty acid composition in liver and plasma, one-carbon metabolites, B-vitamin status, carnitine and acylcarnitines were analyzed in plasma.

RESULTS

Liver mitochondrial fatty acid oxidation decreased by 40 % and steatosis was induced in a dose dependent manner; total lipids increased 1.6-fold in animals treated with 0.3 % TTP, 2-fold with 0.6 % TTP and 2.1 fold with 0.9 % TTP compared to control. The higher hepatic concentration of fatty acids was associated with shortening of carbon-length. Furthermore, the inhibited fatty acid oxidation led to a 30-fold decrease in plasma carnitine and 9.3-fold decrease in acetylcarnitine at the highest dose of TTP, whereas an accumulation of palmitoylcarnitine resulted. Compared to the control diet, TTP administration was associated with elevated plasma total Hcy (control: 7.2 ± 0.3 umol/L, 0.9 % TTP: 30.5 ± 5.9 umol/L) and 1.4-1.6 fold increase in the one-carbon metabolites betaine, dimethylglycine, sarcosine and glycine, accompanied by changes in gene expression of the different B-vitamin dependent pathways of Hcy and choline metabolism. A positive correlation between total Hcy and hepatic triacylglycerol resulted.

CONCLUSIONS

The TTP-induced inhibition of mitochondrial fatty acid oxidation was not associated with increased hepatic oxidative stress or inflammation. Our data suggest a link between mitochondrial dysfunction and the methylation processes within the one-carbon metabolism in mice.

Persistent organic pollutants and non-alcoholic fatty liver disease in morbidly obese patients: a cohort study

BACKGROUND

In animal experiments persistent organic pollutants (POPs) cause hepatosteatosis. In epidemiological studies POPs have positive associations with serum markers of nonalcoholic fatty liver disease (NAFLD) and together with obesity synergistic association with insulin resistance. Because insulin resistance and obesity are critical in NAFLD pathogenesis, we investigated the association of serum pollutant levels with liver histology and alanine aminotransferase (ALT) in morbidly obese.

METHODS

Liver biopsies were from 161 participants of the Kuopio Obesity Surgery Study (KOBS) who underwent bariatric surgery 2005-2011. Liver histology was categorized as normal, steatosis and non-alcoholic steatohepatitis (NASH). Liver phenotype at baseline and ALT at baseline and 12 months post-surgery were correlated to serum POP concentrations at respective time points. As lipophilic POPs concentrate to smaller fat volume during weight loss, serum levels before and 12 months after bariatric surgery were compared.

RESULTS

Baseline serum concentration of PCB-118, β-HCH and several PFAAs had an inverse association with lobular inflammation possibly due to changes in bile acid metabolism. ALT had negative associations with many POPs at baseline that turned positive at 12 months after major clinical improvements. There was an interaction between some POPs and sex at 12 months, and in stratified data positive associations were observed mainly in females but not in males.

CONCLUSIONS

We found a negative association between serum concentrations of PCB-118, β-HCH and several PFAAs with lobular inflammation at baseline. Positive POPs-ATL associations at 12 months among women suggest that increased POP concentrations may decrease the degree of liver recovery.

Bariatric surgery, lipoprotein metabolism and cardiovascular risk

PURPOSE OF REVIEW

To summarize recent epidemiological, preclinical and clinical studies on the effects of Roux-en-Y-gastric bypass (RYGBP) surgery on cardiovascular risk factors and the underlying mechanisms.

RECENT FINDINGS

Although RYGBP has mechanical effects on the gastrointestinal tract, the reduced gastric pouch and intestinal calorie absorption cannot fully explain the metabolic improvements.

SUMMARY

Obesity predisposes to cardiovascular risk factors such as dyslipidemia, type 2 diabetes, nonalcoholic fatty liver disease and hypertension. In contrast to the limited success of pharmacological and lifestyle interventions, RYGBP induces sustained weight loss, metabolic improvements and decreases morbidity/mortality. In line, RYGBP reduces cardiovascular risk factors. Although the mechanisms are not entirely understood, RYGBP induces complex changes in the gut affecting other organs through endocrine and metabolic signals from the intestine to all key metabolic organs, which can link RYGBP and decreased cardiovascular risk. Here, we discuss the roles of changes in lipid absorption and metabolism, bile acid metabolism, gut hormones and the microbiote as potential mechanisms in the decreased cardiovascular risk and metabolic improvement after RYGBP.

Challenges and Management of Liver Cirrhosis: Practical Issues in the Therapy of Patients with Cirrhosis due to NAFLD and NASH

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome and comprises a liver disease spectrum ranging from steatosis to nonalcoholic steatohepatitis (NASH) with risk of progression to liver cirrhosis and hepatocellular carcinoma (HCC). Associated metabolic conditions and comorbidities such as obesity, diabetes and cardiovascular diseases are common and require concerted management. Adiponutrin (PNPLA3) variants may help to identify NAFLD patients at higher risk for liver disease progression towards advanced fibrosis and HCC. The therapeutic options in NAFLD/NASH include lifestyle modification, pharmacological treatment, bariatric surgery for patients with morbid obesity and treatment of complications of liver cirrhosis and HCC, including liver transplantation. Insulin sensitizers and antioxidative treatment strategies with vitamin E are among the best-established pharmacological approaches, but both drugs have long-term safety issues and there is limited evidence in cirrhotic patients. Treatment of concomitant/underlying metabolic conditions with statins or metformin may also have beneficial effects on portal hypertension, complications of liver cirrhosis and HCC prevention. The bile acid receptor FXR may be a promising novel therapeutic target for the treatment of NAFLD/NASH, fibrosis and portal hypertension, but the prognostic implications of associated changes in low- and high-density lipoprotein cholesterol require further studies. Morbidly obese NASH patients can benefit from bariatric surgery which may reduce liver fibrosis but carries a risk of decompensation in patients with advanced liver cirrhosis. When carefully selected, patients with NASH cirrhosis undergoing liver transplantation have a good outcome. This review summarizes recent progress in the management of patients with liver cirrhosis due to NASH.

Obesity: physiologic changes and implications for preoperative management

The proportion of patients defined as obese continues to grow in many westernized nations, particularly the United States (USA). This trend has shifted the perioperative management of obese patients into the realm of routine care. As obese patients present for all types of procedures, it is crucial for anesthesiologists, surgeons, internists, and perioperative health care providers alike to have a firm understanding of their altered multi-organ physiology in order to safely prepare the obese patient for an operation. A careful preoperative evaluation may also serve to identify risk factors for postoperative adverse events. Subsequently, preoperative measures may be implemented to mitigate these complications. In this manuscript we address the major considerations for the preoperative evaluation of the severely obese patient.

Mechanisms of action for arsenic in cardiovascular toxicity and implications for risk assessment

The possibility of an association between inorganic arsenic (iAs) exposure and cardiovascular outcomes has received increasing attention in the literature over the past decade. The United States Environmental Protection Agency (US EPA) is currently revising its Integrated Risk Assessment System (IRIS) review of iAs, and one of the non-cancer endpoints of interest is cardiovascular disease (CVD). Despite the increased interest in this area, substantial gaps remain in the available information, particularly regarding the mechanism of action (MOA) by which iAs could cause or exacerbate CVD. Few studies specifically address the plausibility of an association between iAs and CVD at the low exposure levels which are typical in the United States (i.e., below 100 μg As/L in drinking water). We have conducted a review and evaluation of the animal, mechanistic, and human data relevant to the potential MOAs of iAs and CVD. Specifically, we evaluated the most common proposed MOAs, which include disturbance of endothelial function and hepatic dysfunction. Our analysis of the available evidence indicates that there is not a well-established MOA for iAs in the development or progression of CVD. Few human studies of the potential MOAs have addressed plausibility at low doses and the applicability of extrapolation from animal studies to humans is questionable. However, the available evidence indicates that regardless of the specific MOA, the effects of iAs on physiological processes at the cellular level appear to operate via a threshold mechanism. This finding is consistent with the lack of association of CVD with iAs exposure in humans at levels below 100 μg/L, particularly when considering important exposure and risk modifiers such as nutrition and genetics. Based on this analysis, we conclude that there are no data supporting a linear dose-response relationship between iAs and CVD, indicating this relationship has a threshold.

A concise review of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome and the incidence of which is rising rapidly due to the increasing epidemic of obesity in both adults and children. The initial accumulation of fat followed by subsequent inflammation is central to the development of liver damage, and is critically influenced by host factors including age, gender, presence of diabetes, genetic polymorphisms and more recently by the gut microbiome. An increasing body of data suggest that NAFLD is also an independent risk factor of cardiovascular disease, which remains the commonest cause of mortality in such patients. This review focusses on the pathogenesis of NAFLD, and the evolution of new approaches to the management and treatment of NAFLD.

Nonalcoholic fatty liver disease and vascular disease: State-of-the-art

Nonalcoholic fatty liver disease (NAFLD), the most common of chronic liver disease in Western Country, is closely related to insulin resistance and oxidative stress and includes a wide spectrum of liver diseases ranging from steatosis alone, usually a benign and non-progressive condition, to nonalcoholic steatohepatitis (NASH), which may progress to liver fibrosis and cirrhosis. NAFLD is considered the hepatic manifestation of the metabolic syndrome with which shares several characteristics, however recent data suggest that NAFLD is linked to increased cardiovascular risk independently of the broad spectrum of risk factors of metabolic syndrome. Accumulating evidence suggests that the clinical burden of NAFLD is not restricted to liver-related morbidity and mortality, with the majority of deaths in NAFLD patients related to cardiovascular disease and cancer and not to the progression of liver disease. Retrospective and prospective studies provide evidence of a strong association between NAFLD and subclinical manifestation of atherosclerosis (increased intima-media thickness, endothelial dysfunction, arterial stiffness, impaired left ventricular function and coronary calcification). A general agreement emerging from these studies indicates that patients with NASH are at higher risk of cardiovascular diseases than those with simple steatosis, emphasizing the role of chronic inflammation in the pathogenesis of atherosclerosis of these patients. It is very likely that the different mechanisms involved in the pathogenesis of atherosclerosis in patients with NAFLD have a different relevance in the patients according to individual genetic background. In conclusion, in the presence of NAFLD patients should undergo a complete cardiovascular evaluation to prevent future atherosclerotic complications. Specific life-style modification and aggressive pharmaceutical modification will not only reduce the progression of liver disease, but also reduce morbidity for cardiovascular disease improving overall prognosis and survival.

Recent advances in pharmacotherapy for hypertriglyceridemia

Elevated plasma triglyceride (TG) concentrations are associated with an increased risk of atherosclerotic cardiovascular disease (CVD), hepatic steatosis and pancreatitis. Existing pharmacotherapies, such as fibrates, n-3 polyunsaturated fatty acids (PUFAs) and niacin, are partially efficacious in correcting elevated plasma TG. However, several new TG-lowering agents are in development that can regulate the transport of triglyceride-rich lipoproteins (TRLs) by modulating key enzymes, receptors or ligands involved in their metabolism. Balanced dual peroxisome proliferator-activated receptor (PPAR) α/γ agonists, inhibitors of microsomal triglyceride transfer protein (MTTP) and acyl-CoA:diacylglycerol acyltransferase-1 (DGAT-1), incretin mimetics, and apolipoprotein (apo) B-targeted antisense oligonucleotides (ASOs) can all decrease the production and secretion of TRLs; inhibitors of cholesteryl ester transfer protein (CETP) and angiopoietin-like proteins (ANGPTLs) 3 and 4, monoclonal antibodies (Mabs) against proprotein convertase subtilisin/kexin type 9 (PCSK9), apoC-III-targeted ASOs, selective peroxisome proliferator-activated receptor modulators (SPPARMs), and lipoprotein lipase (LPL) gene replacement therapy (alipogene tiparvovec) enhance the catabolism and clearance of TRLs; dual PPAR-α/δ agonists and n-3 polyunsaturated fatty acids can lower plasma TG by regulating both TRL secretion and catabolism. Varying degrees of TG reduction have been reported with the use of these therapies, and for some agents such as CETP inhibitors and PCSK9 Mabs findings have not been consistent. Whether they reduce CVD events has not been established. Trials investigating the effect of CETP inhibitors (anacetrapib and evacetrapib) and PCSK9 Mabs (AMG-145 and REGN727/SAR236553) on CVD outcomes are currently in progress, although these agents also regulate LDL metabolism and, in the case of CETP inhibitors, HDL metabolism. Further to CVD risk reduction, these new treatments might also have a potential role in the management of diabetes and non-alcoholic fatty liver disease owing to their insulin-sensitizing action (PPAR-α/γ agonists) and potential capacity to decrease hepatic TG accumulation (PPAR-α/δ agonists and DGAT-1 inhibitors), but this needs to be tested in future trials. We summarize the clinical trial findings regarding the efficacy and safety of these novel therapies for hypertriglyceridemia.

The relation between carotid intima media thickness and serum osteoprotegerin levels in nonalcoholic fatty liver disease

AIM

This study was designed to evaluate carotid intima media thickness (CIMT) and serum osteoprotegerin (OPG) levels in nonalcoholic fatty liver disease (NAFLD) in comparison to healthy controls and to investigate factors predicting the CIMT increase.

MATERIALS AND METHODS

A total of 60 outpatients [median (min-max) age 44.5 (24.0-65.0) years, 63.3% were females] diagnosed with NAFLD via ultrasonography performed during their admission to our hospital for any reason and 30 control subjects [median (min-max) age 39.5 (24.0-57.0) years, 73.3% were females] with normal liver echogenicity in ultrasonography were included in this study. Data on demographic characteristics, anthropometric measurements, biochemical and hematological tests, CIMT measurement, serum levels for OPG, and predictive factors for the CIMT increase were collected.

RESULTS

Median (min-max) CIMT [0.60 (0.40-1.10) vs. 0.50 (0.30-0.60), P<0.001) and OPG (pg/mL) [65.0 (18.1-272.8) vs. 32.0 (10.1-82.3), P<0.001] levels were significantly higher in NAFLD patients compared to controls, while there was a significant positive correlation between CIMT and serum OPG (r=0.42, P<0.001). Mean CIMT value was determined to increase significantly by 0.001 cm (P=0.001) for each 1 pg/mL of increase in OPG levels, by 0.103 cm (P<0.001) in case of concomitant NAFLD (P<0.001), and by 0.006 cm (P<0.001) for each 1 pg/mL of increase in urea levels.

CONCLUSION

Our findings indicate higher levels of serum OPG and CIMT in patients with NAFLD compared to controls along with a positive correlation between serum OPG and CIMT levels. High levels of serum OPG, presence of NAFLD, and high levels of serum urea seem to be the independent risk factors predictive for the CIMT increase.