|Year : 2016 | Volume
| Issue : 1 | Page : 11-15
Study of atherosclerotic risk markers in patients with nonalcoholic fatty liver disease
Ritu Karoli, Jalees Fatima, Vaibhav Shukla, Ahraz Ahmad Khan, Mahima Pandey, Ritu Mishra
Department of Medicine, ERA's Lucknow Medical College, Lucknow, Uttar Pradesh, India
|Date of Submission||07-Jun-2015|
|Date of Decision||19-Feb-2016|
|Date of Acceptance||24-Feb-2016|
|Date of Web Publication||16-Jun-2016|
Department of Medicine, ERA's Lucknow Medical College, Sarfarazganj, Hardoi Road, Lucknow - 226 003, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Introduction: Nonalcoholic fatty liver disease (NAFLD) is described as hepatic component of metabolic syndrome as close association exists between the two. It has gained lots of importance in midst of rising epidemic of obesity worldwide in recent times as one of the predisposing risk factors of cardiovascular events. Study Design: The study design was a cross-sectional hospital-based study. Materials and Methods: Forty-eight patients diagnosed to have NAFLD were assessed for insulin resistance (IR) and noninvasive markers of subclinical atherosclerosis and compared with age, gender, and body mass index-matched controls. Results: The patients with NAFLD had significantly higher waist circumference, diastolic blood pressure, fasting insulin, homeostasis model assessment-IR, and significantly lower levels of high-density lipoprotein-cholesterol. They also had significantly higher carotid intima media thickness (CIMT) than controls. Mean CIMT was 0.76 ± 0.12 mm in patients with NAFLD and 0.54 ± 0.18 mm in controls. This difference was statistically significant (P = 0.001). The mean increase in brachial artery diameter was 0.26 ± 0.13 mm in patients and 0.48 ± 0.09 mm in controls. Conclusion: Patients with NAFLD have greater propensity to develop cardiovascular disease in view of the presence of subclinical atherosclerotic markers compared to controls.
Keywords: Atherosclerosis, carotid intima media thickness, nonalcoholic fatty liver disease
|How to cite this article:|
Karoli R, Fatima J, Shukla V, Khan AA, Pandey M, Mishra R. Study of atherosclerotic risk markers in patients with nonalcoholic fatty liver disease. J Obes Metab Res 2016;3:11-5
|How to cite this URL:|
Karoli R, Fatima J, Shukla V, Khan AA, Pandey M, Mishra R. Study of atherosclerotic risk markers in patients with nonalcoholic fatty liver disease. J Obes Metab Res [serial online] 2016 [cited 2017 Dec 14];3:11-5. Available from: http://www.jomrjournal.org/text.asp?2016/3/1/11/184100
| Introduction|| |
Nonalcoholic fatty liver disease (NAFLD) is described as a hepatic component of metabolic syndrome as close association exists between the two. It has gained lots of importance in the midst of rising epidemic of obesity worldwide in recent times. The prevalence of fatty liver in general population of India ,, has been shown to be similar to the estimates reported from the Western countries. , It is emerging as the most common chronic liver disease in Western countries  with higher prevalence in obese and patients with Type 2 diabetes mellitus. NAFLD being asymptomatic in most of the patients encompasses a histological spectrum ranging from steatosis to steatohepatitis, advanced fibrosis, and cirrhosis in the absence of consumption of significant alcohol. Subsets of NAFLD which progress to cirrhosis are being increasingly recognized as a major cause of liver-related morbidity and mortality with the potential to progress to liver failure. 
NAFLD is also now believed to be an integral part of metabolic syndrome which comprises a cluster of abnormalities such as abdominal obesity, atherogenic dyslipidemia, hypertension, elevated plasma glucose, and a prothrombotic and a proinflammatory state that greatly increases individual's probability of developing atherosclerotic cardiovascular disease (CVD) and Type 2 diabetes mellitus. ,, Insulin resistance (IR) is a key pathogenic factor in both NAFLD and metabolic syndrome. ,
In recent times, certain surrogate markers of atherosclerosis have been devised which can help to assess the cardiovascular risk noninvasively. Assessment of carotid intima media thickness (CIMT)  and endothelial dysfunction  is considered as a potential tool for predicting coronary atherosclerosis and future cardiovascular events. Hepatic steatosis being a common incidental finding in subjects undergoing abdominal ultrasonography for any other reason has been shown to be associated with carotid plaques and increased CIMT by several cross-sectional studies. ,, Targher et al.  reported in a prospective nested case-control study that NAFLD is a strong predictor of future cardiovascular events among Type 2 diabetes mellitus. Targher et al. in another study also showed a correlation between higher CIMT and severity of liver disease assessed by histological grades. 
Assessment of endothelial dysfunction by measuring flow-mediated dilatation (FMD) of the brachial artery is being considered as a potential tool for predicting coronary artery disease with recent data showing it to be a predictor of cardiovascular events. , There are not much published data regarding the association between NAFLD and subclinical atherosclerosis in our patient population, so the present study was designed to characterize various causes of hepatomegaly in medical outpatient department (OPD) and wards, prevalence of NAFLD, various metabolic covariates including IR, obesity, dyslipidemia, hypertension, endothelial dysfunction, and CIMT in patients with NAFLD.
| Materials and methods|| |
In a cross-sectional study, all consecutive patients >18 years old with hepatomegaly detected on clinical  and/or ultrasonographic examination  attending as OPD or admitted in medical wards of the of ERA's Lucknow Medical College between January 2010 to December 2010 were enrolled. Exclusion criteria included pregnancy or patients who were not willing to participate. A written informed consent was taken from all the participants and study protocol was approved by the Institutional Ethics Committee.
Each patient of the study population had been subjected to detailed history that included symptoms, history of alcohol consumption, drug history, high-risk behavior (illicit/intravenous drug abuse, sexual promiscuity, and tattooing), blood/blood product transfusion, needle prick or other modes of blood-borne transmission, history of travel, consumption of contaminated food and water, systemic illness, and detailed family history of significant systemic illnesses. Detailed general examination including anthropometric measurements and systemic examination was done in each patient.
Depending on the clinical diagnosis based on detailed history and clinical examination, patients were subjected to hematological and biochemical investigations as required and when feasible. Hematological parameters included hemoglobin, complete blood counts, coagulation profile, peripheral blood smear for parasites, stool examination, Widal test, viral markers for hepatitis, serology for dengue and amebiasis, and blood, urine, sputum cultures were done. Abdominal ultrasonography was performed in all the patients whereas chest skiagram, electrocardiography, and echocardiography were done when required. Biochemical tests comprised plasma glucose, electrolytes, lipid profile, renal and liver function tests.
The diagnosis of NAFLD was based on the presence of hepatic steatosis as bright/echogenic liver on abdominal ultrasound after exclusion of alcohol consumption, smoking, positive hepatic markers of viral hepatitis, autoimmune hepatitis, Wilson's disease, hemochromatosis alpha-1 anti-trypsin deficiency, and medications known to cause fatty liver (methotrexate, estrogens, amiodarone, and tamoxifen). Ultrasonography was performed by the same radiologist who was blinded for subject's medical history and diagnosis. A high-resolution B-mode scanner of General Electric Logic 5 with a 3.5 MHz convex-array probe was used. Hepatic steatosis was defined as diffuse increase in fine echoes in liver parenchyma with impaired visualization of intrahepatic vessels and the diaphragm. 
The patients who were diagnosed to have NAFLD were evaluated for fasting insulin, flow-mediated vasodilatation of brachial artery, and CIMT, and compared with controls. The controls were age, sex, and body mass index (BMI) matched healthy individuals who had ultrasonographically normal liver echogenicity and normal liver function tests enrolled from the hospital staff and their relatives. Homeostasis model assessment (HOMA) method for IR was calculated by the formula: Fasting serum insulin (microunits/ml) fasting serum glucose (mmol/L)/22.5.
Metabolic syndrome was diagnosed in patients with NAFLD and controls based on the presence of three or more of the following: (i) Waist circumference >102 cm for men and >88 cm for women (ii) serum triglyceride >150 mg/dl (iii) high-density lipoprotein (HDL) cholesterol <50 mg/dl (iv) serum fasting glucose >100 mg/dl (v) blood pressure ≥ 130/85 mmHg according to National Cholesterol Education Program/Adult Treatment Panel III, 2001 criteria. 
Flow-mediated dilatation measurement
Endothelial function was measured noninvasively by ultraonographic assessment of right brachial artery dimensions.  The diameter of the right brachial artery was measured twice, first at rest then after inducing reactive hyperemia with the help of pneumatic cuff. It was carried out by a blinded sonologist after an overnight fast in a cool, quiet room with B-mode ultrasound scanner (Siemens, Germany) using 10 MHz linear transducer. The diameter of right brachial artery was measured 2-8 cm above the antecubital space in the end diastolic phase from one media-adventitia interface to the other at the clearest part 3 times and an average was taken. After the detection of the right transducer position, skin was marked and arm was kept in the same position. The blood pressure cuff was tied on the upper arm and inflated to suprasystolic levels kept inflated for 4 min. Sixty seconds after the cuff was released, brachial artery dimensions were again measured. The maximum diameter measurement was defined as the average of three consecutive diameters measurements.
CIMT - It was measured by B-mode ultrasound using linear probe at a frequency of 10 MHz. The common carotid arteries were scanned at the level of bifurcation on either sides and mean value was used for analysis. The CIMT was measured in the far wall of the arteries at sites identified as diffuse and continuous projections with the greatest distance between the luminal intimal interface and media adventitial interface but without atherosclerotic plaques. Localized lesions >2 mm thickness were considered to be atherosclerotic plaques. CIMT was assessed by single observer who was blinded for the diagnosis.
The Statistical Package for the Social Sciences (SPSS version 13.0, SPSS Inc., Chicago, IL) was used for statistical analysis. Data were expressed as percentages, mean values (with standard deviations), or differences between groups were analyzed with Chi-square test for proportions and the Student's t-test for means. Results were defined as statistically significant when the P value (two-sided) was <0.05. Chi-square test of goodness of fit has been applied for seasonal variation. Analysis of correlations between parameters was performed by using Pearson's correlation coefficient and regression analysis was done to predict FMD and CIMT. Multiple regression analysis with CIMT as the dependent variable was used for adjustment of predictor variables that had been shown to have P < 0.05 in univariate analysis.
| Results|| |
Forty-eight patients with NAFLD were compared with age-, sex- and BMI-matched healthy controls [Table 1]. The patients with NAFLD had significantly higher waist circumference, diastolic blood pressure, fasting insulin, HOMA-IR, and significantly lower levels of HDL-cholesterol. They also had significantly higher CIMT than controls.
|Table 1: Clinical and biochemical characteristics of patients with nonalcoholic fatty liver disease and controls |
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Mean CIMT was 0.76 ± 0.12 mm in patients with NAFLD and 0.54 ± 0.18 mm in controls. This difference was statistically significant (P = 0.001). The mean increase in brachial artery diameter was 0.26 ± 0.13 mm in patients and 0.48 ± 0.09 mm in controls. This difference was statistically significant (P = 0.001), indicating an increase in diameter with ischemia. Mean brachial artery diameter at baseline was 3.8 ± 1.9 mm in patients and 3.67 ± 2.3 mm in controls. The difference was not statistically significant (P = 0.5). Mean FMD was 8.12 ± 2.56% and 13.26 ± 2.8% in patients with NAFLD and in controls, respectively [Table 2]. The difference was statistically significant (P = 0.01). In univariate analysis, CIMT was positively correlated with age (r = 0.36, P = 0.03), BMI (r = 0.46, P = 0.01), waist circumference (r = 0.52, P = 0.001), and HOMA (r = 0.31, P = 0.04).
In multivariate analysis with CIMT as dependent variable, presence of NAFLD, waist circumference, and HOMA retained a significant association. Similarly for FMD, NAFLD and HOMA were the independent predictors.
|Table 2: Atherosclerosis markers in patients with nonalcoholic fatty liver disease and control subjects |
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| Discussion|| |
Nonalcoholic steatohepatitis emerged from an anecdotal disease which was first described by Ludwig et al.  in 1980 to the most common cause of incident chronic liver disease at the end of the current decade. It was thought to be a benign condition, but is now increasingly recognized as a major cause of liver-related morbidity and mortality. NAFLD is commonly associated with components of the metabolic syndrome. This strongly supports the notion that NAFLD is the hepatic manifestation of the syndrome. Mishra et al.  found the prevalence of metabolic syndrome and NAFLD to be 24% and 14.8%, respectively, in nonalcoholic North Indian men. The prevalence of NAFLD in the general population has been reported by Mohan et al.  as 22% in normal glucose tolerance to 55% in patients with Type 2 diabetes.
Increasing recognition of the importance of NAFLD and its strong relationship with the metabolic syndrome has stimulated an interest in the possible role of NAFLD in the development of CVD. 
In the present study, all the patients with NAFLD were evaluated for the presence of components of metabolic syndrome and IR. We observed 25% prevalence of metabolic syndrome in patients with NAFLD as compared to 6% in controls. The patients with NAFLD had significantly higher waist circumference, diastolic blood pressure, fasting insulin, HOMA-IR, and significantly lower levels of HDL-cholesterol. We also made an attempt to assess the markers of subclinical atherosclerosis in them. They also had significantly higher CIMT and endothelial dysfunction than age-, sex- and BMI-matched controls.
The possible mediators linking NAFLD and CVD include the release of pro-atherogenic factors from the liver (C-reactive protein, fibrinogen, plasminogen activator inhibitor-1, and other inflammatory cytokines) as well as the contribution of NAFLD per se, IR, and atherogenic dyslipidemia, in turn favoring CVD progression. The clinical impact of NAFLD on CVD risk deserves particular attention in view of the implications for screening and surveillance strategies in the growing number of patients with NAFLD. Theoretically, the increased risk of cardiovascular events in patients with NAFLD is due to coexistence of this entity with metabolic syndrome.
One of the early processes in the pathophysiology of atherosclerosis is impaired endothelial function. Impaired endothelial function quantified by FMD is a marker of increased cardiovascular risk, due to its correlation with impaired endothelial function in the coronary arteries. The basic mechanism for FMD is to observe vasodilation by sonography after provoking ischemia by inflating blood pressure cuff. After brachial artery occlusion, endothelial nitric oxide is released and vascular smooth muscle relaxation occurs. The results of the present study are similar to those of Vlachopoulos et al.  and Villanova et al.,  who also showed that NAFLD is associated with arterial stiffness and impaired endothelial function.
In recent years, several studies have shown the association between hepatic steatosis and carotid atherosclerosis. Manco et al.  have also observed a significant association between increased CIMT levels and NAFLD, although in a case-control study, they could not derive a suitable cutoff. We could demonstrate that atherosclerosis can affect vascular anatomy and physiology in NAFLD patients, independent of other risk factors. Given that age, gender, and BMI, as well as other cardiovascular risk factors, can influence the pathogenesis of atherosclerosis and its major determinants, i.e., FMD and CIMT, we matched cases and controls to eliminate as far as possible these effects on FMD and CIMT.
There are not much published data regarding the association between NAFLD and subclinical atherosclerotic risk markers in our population, which is the novelty of our study. The limitations of our study are small sample size and its cross-sectional design, so causative nature of the associations could not be established. Hence, large-scale prospective studies are needed to show the time sequence of events and also the association of NAFLD and incident cardiovascular events. Priorities for future research are the optimization of noninvasive screening, the identification of patients at risk of liver disease progression, future cardiovascular events, and management intervention strategies at the earliest.
| Conclusion|| |
NAFLD is a hepatic manifestation of metabolic syndrome. It has an association with subclinical atherosclerosis that increases the risk for future cardiovascular events.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]