A potential link between endothelial function, cardiovascular risk, and metabolic syndrome in patients with Non-alcoholic fatty liver disease

The association between metabolic dysfunction-associated steatotic liver disease, cardiovascular and cerebrovascular diseases and the thickness of carotid plaque

BACKGROUND

The relationship between metabolic dysfunction-associated steatotic liver disease (MASLD) and atherosclerosis has been controversial, which has become a hit of recent research. The study aimed to explore the association between MASLD, cardiovascular and cerebrovascular diseases (CCVD), and the thickness of carotid plaque which was assessed by ultrasound.

METHODS

From September 2018 to June 2019, 3543 patients were enrolled. We asked participants to complete questionnaires to obtain information. All patients underwent liver ultrasound and bilateral carotid ultrasound to obtain carotid intima-media thickness (IMT) and maximum carotid plaque thickness (CPT). Hepatic steatosis was quantified during examination according to Hamaguchi's ultrasonographic score, from 0 to 6 points. A score < 2 was defined as without fatty liver, and a score ≥ 2 was defined as fatty liver. Information about blood lipids was collected based on the medical records.

RESULTS

We found common risk factors for CCVD events, MASLD, and atherosclerosis. There was a significant correlation between MASLD and carotid plaque, but not with CPT. No association was found between MASLD and CCVD events. CPT and IMT were thicker in CCVD patients than in non-CCVD patients. No significant difference was found between IMT and CPT in MASLD patients and non-MASLD patients. CCVD was independently and consistently associated with higher IMT, and free fatty acid (FFA).

CONCLUSIONS

According to our results, we recommend carotid ultrasound examination of the patients when FFA is increased, regardless of the presence of risk factors and MASLD. Due to the distribution of CPT of both CCVD and MASLD patients in the CPT 2-4 mm group, contrast-enhanced ultrasound is necessary to assess the vulnerability of the plaque when CPT ≥ 2 mm. Timely treatment of vulnerable plaques may reduce the incidence of future CCVD events.

Endothelial Cell Dysfunction and Nonalcoholic Fatty Liver Disease (NAFLD): A Concise Review

Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases worldwide. It is strongly associated with obesity, type 2 diabetes (T2DM), and other metabolic syndrome features. Reflecting the underlying pathogenesis and the cardiometabolic disorders associated with NAFLD, the term metabolic (dysfunction)-associated fatty liver disease (MAFLD) has recently been proposed. Indeed, over the past few years, growing evidence supports a strong correlation between NAFLD and increased cardiovascular disease (CVD) risk, independent of the presence of diabetes, hypertension, and obesity. This implies that NAFLD may also be directly involved in the pathogenesis of CVD. Notably, liver sinusoidal endothelial cell (LSEC) dysfunction appears to be implicated in the progression of NAFLD via numerous mechanisms, including the regulation of the inflammatory process, hepatic stellate activation, augmented vascular resistance, and the distortion of microcirculation, resulting in the progression of NAFLD. Vice versa, the liver secretes inflammatory molecules that are considered pro-atherogenic and may contribute to vascular endothelial dysfunction, resulting in atherosclerosis and CVD. In this review, we provide current evidence supporting the role of endothelial cell dysfunction in the pathogenesis of NAFLD and NAFLD-associated atherosclerosis. Endothelial cells could thus represent a "golden target" for the development of new treatment strategies for NAFLD and its comorbid CVD.

Endothelial Dysfunction in Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis

Individuals with nonalcoholic fatty liver disease (NAFLD) are characterized by increased cardiovascular risk. Endothelial dysfunction, a mechanism implicated in those processes, may constitute the missing link in this interaction. Therefore, this systematic review and meta-analysis aims to evaluate the association of endothelial dysfunction, assessed by flow-mediated dilation (FMD) of the brachial artery, with NAFLD. We conducted a systematic literature search for studies assessing the difference in FMD between patients with NAFLD and controls. Exclusion criteria consisted of preclinical studies, studies in children/adolescents, no FMD assessment, and the absence of an NAFLD/control group. The database search identified 96 studies. Following the application of the exclusion criteria, 22 studies were included in the meta-analysis (NAFLD: 2164 subjects; control: 3322 subjects). Compared with controls, patients with NAFLD had significantly lower FMD% values (SMD: −1.37, 95% CI −1.91 to −0.83, p < 0.001, I2: 98%). Results remained unaffected after exclusion of any single study. Subgroup analysis revealed significantly decreased FMD in NAFLD subjects diagnosed with liver ultrasound or liver biopsy compared with method combination or other methods, while no differences were observed according to the chosen cuff inflation threshold, the presence of a significant difference in obesity measures between the groups, or the type of the control group (age- and sex-matched vs. other). Funnel plot asymmetry was not observed. Finally, compared with patients with pure steatosis, individuals with nonalcoholic steatohepatitis had significantly lower FMD (SMD: −0.81, 95% CI −1.51 to −0.31, p = 0.003, I2: 81%). In conclusion, FMD of the brachial artery, indicative of endothelial dysfunction, was significantly reduced in subjects with nonalcoholic fatty liver disease. Patients with nonalcoholic steatohepatitis might be facing a more pronounced endothelial impairment.

Coagulation and Endothelial Dysfunction Associated with NAFLD: Current Status and Therapeutic Implications

Non-alcoholic fatty liver disease (NAFLD) is closely related to insulin resistance, type 2 diabetes mellitus and obesity. It is considered a multisystem disease and there is a strong association with cardiovascular disease and arterial hypertension, which interfere with changes in the coagulation system. Coagulation disorders are common in patients with hepatic impairment and are dependent on the degree of liver damage. Through a review of the literature, we consider and discuss possible disorders in the coagulation cascade and fibrinolysis, endothelial dysfunction and platelet abnormalities in patients with NAFLD.

Integrated analysis of potential gene crosstalk between non-alcoholic fatty liver disease and diabetic nephropathy

BACKGROUND

Growing evidence indicates that non-alcoholic fatty liver disease (NAFLD) is related to the occurrence and development of diabetic nephropathy (DN). This bioinformatics study aimed to explore optimal crosstalk genes and related pathways between NAFLD and DN.

METHODS

Gene expression profiles were downloaded from Gene Expression Omnibus. CIBERSORT algorithm was employed to analyze the similarity of infiltrating immunocytes between the two diseases. Protein-protein interaction (PPI) co-expression network and functional enrichment analysis were conducted based on the identification of common differentially expressed genes (DEGs). Least absolute shrinkage and selection operator (LASSO) regression and Boruta algorithm were implemented to initially screen crosstalk genes. Machine learning models, including support vector machine, random forest model, and generalized linear model, were utilized to further identify the optimal crosstalk genes between DN and NAFLD. An integrated network containing crosstalk genes, transcription factors, and associated pathways was developed.

RESULTS

Four gene expression datasets, including GSE66676 and GSE48452 for NAFLD and GSE30122 and GSE1009 for DN, were involved in this study. There were 80 common DEGs between the two diseases in total. The PPI network built with the 80 common genes included 77 nodes and 83 edges. Ten optimal crosstalk genes were selected by LASSO regression and Boruta algorithm, including CD36, WIPI1, CBX7, FCN1, SLC35D2, CP, ZDHHC3, PTPN3, LPL, and SPP1. Among these genes, LPL and SPP1 were the most significant according to NAFLD-transcription factor network. Five hundred twenty-nine nodes and 1,113 edges comprised the PPI network of activated pathway-gene. In addition, 14 common pathways of these two diseases were recognized using Gene Ontology (GO) analysis; among them, regulation of the lipid metabolic process is closely related to both two diseases.

CONCLUSIONS

This study offers hints that NAFLD and DN have a common pathogenesis, and LPL and SPP1 are the most relevant crosstalk genes. Based on the common pathways and optimal crosstalk genes, our proposal carried out further research to disclose the etiology and pathology between the two diseases.

Liver fat content might be an appropriate measure for estimation of cardiovascular disease risk in non-alcoholic steatohepatitis patients

Background: Non-alcoholic steatohepatitis (NASH) is increasing worldwide due to the metabolic syndrome epidemy. According to the current evidence, a higher cardiovascular disease risk (CVDR) is observed in NASH individuals than the general population. Objective: The relationship between liver fat content (LFC) and CVDR in a cohort of NASH patients was evaluated in this research. Methods: Consecutively selected patients with increased aminotransferase levels and fatty change in liver ultrasonography were enrolled in the study. Those with known causes of viral hepatitis, any hepatotoxic medications or alcohol consumption, autoimmune hepatitis, cigarette smoking, and ischemic heart disease were excluded from the project. The remaining was presumed to have NASH. The Framingham risk score (FRS) and LFC were calculated by means of an online calculator and a valid formula, respectively. The correlation between LFC and independent variables was measured using the Pearson correlation test. The P-value of less than 0.05 was considered significant. The statistical analysis was performed using SPSS program version 18. Results: Finally, two hundred NASH patients were included in the study. Considering diabetes mellitus as a confounder, there was a fair relationship between LFC and FRS (R=0.26 and 0.23, respectively, p<0.05) in the second and third visits. Even after adjustment for known cardiovascular risk factors, LFC was associated with increased CVDR (OR=9.181; 95% CI: 2.00-42.14, p=0.01). The cut-off value of 9.1% for LFC had a sensitivity of 92% and a specificity of 87% for discrimination of the FRS >20% and <20%. Conclusion: LFC might independently be correlated with CVDR in NASH patients. If further research confirmed this relationship, the inclusion of LFC into the FRS formula would provide an appropriate CVDR estimation tool in NASH.

Association between smoking and non-alcoholic fatty liver disease: A systematic review and meta-analysis

Background/aims

Non-alcoholic fatty liver disease is one of the most common chronic liver diseases. Some risk factors are known to influence the development of non-alcoholic fatty liver disease, but the effect of tobacco smoking on the progression of non-alcoholic fatty liver disease is controversial. The main goal of this systematic review and meta-analysis is to investigate the association between smoking and non-alcoholic fatty liver disease.

Method

Electronic databases (PubMed, Scopus, and ISI Web of Science) were searched to find published articles on non-alcoholic fatty liver disease and smoking until December 2016. All relevant studies were screened by inclusion and exclusion criteria and compatible studies were chosen. The Newcastle-Ottawa Scale was used to assess the methodological quality of eligible articles. Subsequently, information was gathered based on the following: author, publication year, keywords, country, inclusion and exclusion criteria, main results, study design, conclusion, and confounder variables (age, body mass index, gender, ethnicity, and diabetes). Finally, analyses were performed using Comprehensive Meta-Analysis Software.

Results

Data were extracted from 20 observational studies (9 cross-sectional, 6 case-control, 4 cohort studies, and 1 retrospective cohort study). A significant association was observed between smoking and non-alcoholic fatty liver disease with a pooled odds ratio of 1.110 (95% confidence interval, 1.028-1.199), p-value = 0.008. The statistical heterogeneity was medium with an I2 of 40.012%, p-heterogeneity = 0.074. Also there was a significant relation between non-alcoholic fatty liver disease and passive smoking with a pooled odds ratio of 1.380 (95% confidence interval, 1.199-1.588; p-value = 0.001; I2 = 59.41; p-heterogeneity = 0.117).

Conclusion

Our meta-analysis demonstrated that smoking is significantly associated with non-alcoholic fatty liver disease. Further prospective studies exploring the underlying mechanisms of this association should be pursued. Also passive smoking increases the risk of non-alcoholic fatty liver disease about 1.38-fold. The effects of smoking cigarettes on active smokers (current smoker, former smoker, and total smoker) are less than passive smokers. Further studies are needed to compare the of effects of passive and active smoking on non-alcoholic fatty liver disease.

Prevalence of Non Alcoholic Fatty Liver Disease and its Association with Diabetic Nephropathy in Patients with Type 2 Diabetes Mellitus

INTRODUCTION

Non Alcoholic Fatty Liver Disease (NAFLD) and Type 2 Diabetes Mellitus (T2DM) are two common problems affecting global health as these two conditions can influence each other. There is very little information about the possible association between NAFLD and diabetic microvascular complications such as diabetic nephropathy.

AIM

The aim of this study was to evaluate the prevalence of NAFLD in patients with T2DM and to investigate the association between NAFLD and diabetic nephropathy in these patients.

MATERIALS AND METHODS

This cross-sectional study was conducted on 255 patients with T2DM, with minimum age being 30 years. Hepatic ultrasonography using a 3.5 MHz probe was performed in all subjects. Fatty liver based on standard criteria was diagnosed with liver brightness, contrast between the echogenicity of the liver, kidneys and the blood vessels fading rate. Screening for microalbuminuria was performed by the preferred method, measurement of the Urine Albumin-To-Creatinine (UACR) ratio in a random spot collection.

RESULTS

In this study, 255 patients with T2DM were enrolled of which 173 (68%) were females and 82 (32%) were males. Of these 221 subjects (86.66%) had NAFLD. Diabetic nephropathy was observed among 33% of individuals, microalbuminuria among 32% and macroalbuminuria in 10% of all individuals. Duration of diabetes, Body Mass Index (BMI), hypertriglyceridemia, and HbA1c were significantly associated with incidence of NAFLD. Also, duration of diabetes and HbA1c were significantly associated with diabetic nephropathy in patients with T2DM.

CONCLUSION

NAFLD in patients with T2DM is extremely common. NAFLD is not considered as a risk factor for diabetic nephropathy. To better understand the pathogenesis of NAFLD and its causal relationship with complications of diabetes such as diabetic nephropathy, prospective studies and long term follow up are needed.

Dimethylarginine Dimethylaminohydrolase 1 Protects Against High-Fat Diet-Induced Hepatic Steatosis and Insulin Resistance in Mice

AIMS

High plasma concentrations of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, are associated with hepatic dysfunction in patients with nonalcoholic fatty liver disease (NAFLD). However, it is unknown whether ADMA is involved in the pathogenesis of NAFLD. Dimethylarginine dimethylaminohydrolase 1 (DDAH1) is an enzyme that degrades ADMA. In this study, we used Ddah1^-/- mice to investigate the effects of the ADMA/DDAH1 pathway on high-fat diet (HFD)-induced hepatic steatosis.

RESULTS

After HFD feeding for 20 weeks, Ddah1^-/- mice were more obese and had developed more severe hepatic steatosis and worse insulin resistance compared with wild-type (WT) mice. In the livers of HFD-fed mice, loss of DDAH1 resulted in higher levels of lipogenic genes, lower expression of β-oxidation genes, and greater induction of oxidative stress, endoplasmic reticulum stress, and inflammation than in the WT livers. Furthermore, ADMA treatment in HepG2 cells led to oxidative stress and steatosis, whereas overexpression of DDAH1 attenuated palmitic acid-induced steatosis, oxidative stress, and inflammation. Innovation and Conclusion: Our results provide the first direct evidence that the ADMA/DDAH1 pathway has a marked effect on hepatic lipogenesis and steatosis induced by HFD feeding. Our findings suggest that strategies to increase DDAH1 activity in hepatocytes may provide a novel approach to attenuate NAFLD development. Antioxid. Redox Signal. 26, 598-609.

MCD diet-induced steatohepatitis is associated with alterations in asymmetric dimethylarginine (ADMA) and its transporters

Using an experimental model of NASH induced by a methionine-choline-deficient (MCD) diet, we investigated whether changes occur in serum and tissue levels of asymmetric dimethylarginine (ADMA). Male Wistar rats underwent NASH induced by 8-week feeding with an MCD diet. Serum and hepatic biopsies at 2, 4 and 8 weeks were taken, and serum enzymes, ADMA and nitrate/nitrite (NOx), were evaluated. Hepatic biopsies were used for mRNA and protein expression analysis of dimethylarginine dimethylaminohydrolase-1 (DDAH-1) and protein methyltransferases (PRMT-1), enzymes involved in ADMA metabolism and synthesis, respectively, and ADMA transporters (CAT-1, CAT-2A and CAT-2B). Lipid peroxides (TBARS), glutathione, ATP/ADP and DDAH activity were quantified. An increase in serum AST and ALT was detected in MCD animals. A time-dependent decrease in serum and tissue ADMA and increase in mRNA expression of DDAH-1 and PRMT-1 as well as higher rates of mRNA expression of CAT-1 and lower rates of CAT-2A and CAT-2B were found after 8-week MCD diet. An increase in serum NOx and no changes in protein expression in DDAH-1 and CAT-1 and higher content in CAT-2 and PRMT-1 were found at 8 weeks. Hepatic DDAH activity decreased with a concomitant increase in oxidative stress, as demonstrated by high TBARS levels and low glutathione content. In conclusion, a decrease in serum and tissue ADMA levels in the MCD rats was found associated with a reduction in DDAH activity due to the marked oxidative stress observed. Changes in ADMA levels and its transporters are innovative factors in the onset and progression of hepatic alterations correlated with MCD diet-induced NASH.

The association of circulating levels of complement-C1q TNF-related protein 5 (CTRP5) with nonalcoholic fatty liver disease and type 2 diabetes: a case-control study

BACKGROUND

It is well-established that nonalcoholic fatty liver disease (NAFLD) is associated with type 2 diabetes mellitus (T2DM). Complement-C1q TNF-related protein 5 (CTRP5) is a novel adipokine involved in the regulation of lipid and glucose metabolism. We aimed to assess plasma levels of CTRP5 in patients with NAFLD (n = 22), T2DM (n = 22) and NAFLD with T2DM (NAFLD + T2DM) (n = 22) in comparison with healthy subjects (n = 21) and also to study the association between CTRP5 levels and NAFLD and diabetes-related parameters.

METHODS

All subjects underwent anthropometric assessment, biochemical evaluation and liver stiffness (LS) measurement. Insulin resistance (IR) was determined by the homeostasis model assessment (HOMA). Plasma CTRP5 levels were measured by enzyme-linked immunosorbent assay.

RESULTS

We found significantly lower plasma levels of CTRP5 in patients with NAFLD + T2DM, NAFLD and T2DM (122.52 ± 1.92, 124.7 ± 1.82 and 118.31 ± 1.99 ng/ml, respectively) in comparison with controls (164.96 ± 2.95 ng/ml). In the whole study population, there was a significant negative correlations between CTRP5 and body mass index (r = -0.337; p = 0.002), fasting blood glucose (FBG) (r = -0.488; p < 0.001), triglyceride (TG) (r = -0.245; p = 0.031), HOMA-IR (r = -0.492; p < 0.001), insulin(r = -0.338; p = 0.002), LS (r = -0.544; p < 0.001), alanine aminotransferase (ALT) (r = -0.251; p = 0.027), waist-to-hip ratio (WHR) (r = -0.352; p = 0.002) and waist circumference (WC) (r = -0.357; p = 0.001). After adjustment for BMI, decrease in circulating levels of CTRP5 remained as a significant risk factor for NAFLD, T2DM and NAFLD + T2DM. The receiver operating characteristic (ROC) curves of circulating CTRP5 in predicting NAFLD and T2DM demonstrated an area under the curve (AUC) of 0.763 in T2DM, and 0.659 in NAFLD + T2DM.

CONCLUSIONS

It appears that the decreased levels of CTRP5 contribute to the increased risk of T2DM and NAFLD.