Iranian Red Crescent Medical Journal ORIGINAL ARTICLE

Evaluation of the Correlation between Non-Alcoholic Fatty Liver Disease and Insulin Resistance
O Akha1*, H Fakheri 2, R Abdi3, MR Mahdavi4
1 4

Department of Endocrinology, 2Department of Gastroenterology, 3Department of Radiology, Department of General Laboratory, Mazandaran University of Medical Sciences, Sari, Iran
Abstract
Background: Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent liver diseases, being associated with type II diabetes mellitus, obesity and dyslipidemia. It seems that insulin resistance observed in those with type II diabetes or in obese persons plays an important role in the pathogenesis of NAFLD. The aim of this study was to evaluate the relationship between NAFLD and insulin resistance, disregarding obesity and diabetes. Methods: This case-control study was performed on those patients with NAFLD referring to Sari Imam Khomeini Hospital in 2007 after obtaining informed consent from patients. After repeated sonography and proved fatty liver, 80 patients were enrolled (34 cases and 46 controls) matched for age, gender and body mass index (BMI). NAFLD was documented in the case group, using ultrasonographic indices. Those in the control group were healthy. ALT and AST were normal in both groups. Fasting plasma glucose, fasting insulin, 2-hour oral glucose tolerance test (OGTT) and insulin-resistance were compared between the two groups. Insulin resistance was calculated using HOMA-IR formula. Results: There were 20 men (58.8%) and 14 women (41.2%) in the case group with the mean age of 38.09.4 years. Those in the control group were 27 men (58.7%) and 19 women (41.3%) with the mean age of 39.410.5 years. There was no significant difference between the two groups concerning their age, gender or BMI. The mean level of FPG was 91.88.4 mg/dl in the case and 92.510.1 mg/dl in the control group. The mean level of OGTT was 110.918.8 mg/dl in the case group and 103.125.8 mg/dl in the control group and the difference was not significant. The mean levels of fasting insulin were 16.14.2 mg/dl and 10.34.8 mg/dl in the case and control groups, respectively (p<0.001). Insulin resistance was 3.60.8 u/l.mmol/l in the case and 2.31.2 u/l.mmol/l in the control group. Conclusion: Since the intervening factors were identical in both groups, we can conclude that the role of insulinresistance in the pathogenesis of NAFLD is not dependent on age, gender and BMI. Keywords: Non-alcoholic fatty liver disease; Insulin-resistance; Diabetes mellitus

Introduction Fatty liver is a clinicohistologic term that seems to be related to the injuries caused by alcohol consumption. Therefore, NFALD occurs in patients with no history of alcohol consumption or in those with minimal use. NAFLD includes a histologic spectrum from accumulation of fat in hepatocytes without in*Correspondence: Ozra Akha, MD, Assistant Professor of Endocrinology, Mazandaran University of Medical Sciences, Imam Khomeini Hospital, Sari, Iran. Tel: +98-911-1245156, Fax: +98-1512264044, e-mail: zr_akha@yahoo.com Received: June 23, 2009 Accepted: October 6, 2009

flammation or fibrosis (simple hepatic steatosis) to steatohepatitis with inflammatory necrotizing changes with or without fibrosis. It can be accompanied by the increase in serum aminotransferases and hepatomegaly and even can lead to the inflammation and necrosis of the liver tissue.1 Alcoholic fatty liver disease occurs in those who over-drink alcohol as a habit. NAFLD refers to the non-hemogen distribution of fat in the liver of a person who does not drink alcohol. But the histopathologic pattern of both diseases are the same.2,3 The pathophysiology of NAFLD is related to the accumulation of fat in hepatocytes, and increased oxidative

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stress may be related to insulin resistance.4 NAFLD is probably the most common liver disease.5,6 The prevalence of fatty liver, being commonly diagnosed by ultrasonography, is about 20% in Japan, east of Europe and America.7 In a study performed in 2002, the prevalence of NAFLD was reported to be 24% in American population. 8 Patients with NAFLD are usually symptomfree, but may have different symptoms according to the grade of fat infiltration, the duration of the disease and the responsible cause. They sometimes have fatigue and 75% have hepatomegaly. The obese or diabetic patients with the chronic accumulation of fat in the liver are usually without any symptom and just feel a little pain while palpating their large liver. Severe steatohepatitis can also cause icterus, coagulopathy or fever. 9 Different studies have shown that NAFLD is associated with older age, diabetes mellitus, obesity and dyslipidemia (especially increased triglyceride).1,10-15 Type II diabetes mellitus, being the most common condition in association with insulin resistance, is found in 30% of patients with NAFLD.16 It seems that 28-55% of patients with diabetes mellitus have fatty liver disease. 17 It is also reported that 21-78% of diabetic patients show fatty liver changes in their sonographic evaluation.18 Some other studies have also shown that obesity is related to insulin-resistance and the presence of biochemical markers of insulin resistance in obese or diabetic patients supports this subject.19,20 Regarding the presence of insulin resistance in those with diabetes or obesity, we decided to assess whether there is a relationship between insulinresistance and NAFLD disregarding obesity and diabetes and selected patients with normal liver enzyme.

(heterogen echogenicity or nodular pattern of liver, the presence of ascites or portal vein diameter more than 8 mm on ultrasonography), history of chronic liver disease, alcohol consumption or using drugs that cause hepatic steatosis. The people in both groups were evaluated by one sinologist. Those with sonographic criteria of fatty liver (bright liver) were included in the case group and those without the above criteria were included in the control group. The two groups were matched according to their age (age groups of 20-39 years, 40-59 years and above 60 years), gender (male or female) and BMI (less than 25, 25-30 and more than 30 kg/m). The medical histories of all of them were taken and they were all physically examined. The data including demographic data (age, gender, height, weight and BMI) were gathered in a questionnaire and laboratory tests including fasting plasma glucose (FPG), 2-hour OGTT, albumin, prothrombin time, bilirubin, serum levels of insulin, cholesterol and triglyceride and High-density lipoprotein (HDL). Those with FPG more than 100 mg/dl or 2-hour OGTT more than 140 mg/dl, PT more than 17 seconds, serum albumin less than 3.5 mg/dl or total bilirubin more than 1.5 mg/dl were excluded from the study. Insulin-resistance was calculated using the HOMA-IR formula.20 HOMA-IR= fasting insulin (u/L) FPG (mmol/l) /22.5
Insulin - resistance = fastinginsulin (mIu / l ) FPG (mol / l ) 22.5

Materials and Methods This casecontrol study was performed on 80 persons (34 in the case and 46 in the control group) referring to the Gastroenterology Clinic of Imam Khomini Hospital in Sari in 2007. The case group underwent repeated sonographies and with a proved fatty liver by a fixed radiologist and a fixed instrument was enrolled. The control group included those people referring to Gastroenterology Clinic due to other problems. The exclusion criteria in both groups were increased levels of serum Alanine aminotransferase or Aspartate aminotransferase, diabetus mellitus, cirrhosis

Accordingly, the patients were included in these 3 groups: i) HOMA- IR<2.24: these are assumed as insulinsensitive people, ii) 2.24 HOMA-IR 3.59: these are assumed as intermediate people, iii) HOMA-IR>3.59: These are assumed as insulin resistant people. The collected data were analyzed using SPSS software (version 15, Chicago, IL, USA) and descriptive statistical tests (mean value and standard deviation) and t-test.

Results 58.8% of the patients in the case group were male and 41.2% were female, and the mean age was 38.09.4 years. 58.7% of those in the control group were male and 41.3% were female, with the mean age of 39.4 10.5 years. There was no significant difference between the two groups concerning their age, gender or BMI (Table 1).

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Table 1: The frequency of intervening factors in the case and control groups Variant Case (No.=34) Control (No.=46) P value No. (%) No. (%) Gender 0.95 19 (41.3) 14 (41.2) Female 27 (58.7) 20 (58.8) Male Age (year) 0.46 27 (58.7) 21 (61.8) 20-39 17 (37) 13 (38.2) 40-59 2 (4.3) 0 60 BMI 0.93 18 (39.1) 14 (41.2) <25 26 (56.5) 19 (55.9) 25 BMI<30 2 (4.4) 1(2.9) 30

As shown in Table 2, the mean values of serum albumin, bilirubin, cholesterol, triglyceride and HDL did not show a significant difference between the two groups. The mean level of FPG and 2-hour OGTT also did not show any statistically significant difference between the two groups. The mean level of fasting insulin was 16.14.2 mg/dl in the case group and 10.34.8 mg/dl in the control group, showing a statistically significant difference between the two groups (p<0.001). The insulin-resistance, using HOMA-IR formula, was 3.60.8 u/l.mmol/l in the case group and 2.31.2 u/l.mmol/l in the control group (p<0.001) (Table 3). Data analysis showed that insulin-resistance was not

statistically different between males and females (3.151.4 vs. 2.661.2 u/l.mmol/l). Also, insulinresistance was not significantly different between those being over or under 35 years of age (2.741.1 vs. 31.2 u/l.mmol/l). Insulin-resistance was not also statistically different between those having BMI > 25 kg/m or less than 25 kg/m (3.231.1 vs. 2.721.2 u/l.mmol/l).

Discussion The results of this study showed that insulin resistance was significantly higher in those with NAFLD

Table 2: The mean and standard-deviation values of each variant in the case and control groups Variable Case Control P value (mean valueSD*) (mean valueSD*) Albumin (g/dl) 4.380.5 7.040.6 0.20 Bilirubin (mg/dl) 0.290.2 0.330.3 0.66 Triglyceride (mg/dl) 206.2998.6 182.6791.1 0.27 Cholestrol (mg/dl) 209.5954.4 198.5455.3 0.37 LDL (mg/dl)** 131.8839.1 121.2232.58 0.19 HDL (mg/dl)*** 43.6516.5 46.787.3 0.26 *SD: standard deviation, ** LDL: low density lipoprotein, ***HDL: high density lipoprotein

Table 3: The mean and standard-deviation values of fasting plasma glucose, 2 hours OGTT, fasting insulin and insulin resistance in the case and control groups Variable Case Control P value (mean valueSD*) (mean valueSD*) FPG (mg/dl) 91.85 8.4 92.54 10.1 0.74 OGTT (mg/dl) 110.91 18.8 103.15 25.8 0.14 Fasting insulin (u/l) 16.11 4.2 10.37 4.8 <0.001 HOMA-IR (u/l.mmol/l) 3.63 0.8 2.39 1.2 <0.001

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compared with the control group. This shows a relationship between NAFLD and insulin resistance. On the other hand, since the intervening factors of age, gender, and BMI were matched in the 2 groups, we can conclude that the relationship between NAFLD and insulin resistance is not dependent on age, gender or BMI and in all patients liver transaminases were normal (the case and control groups). In one study, a relationship between NAFLD and insulin resistance was reported and the increase in fasting insulin levels resulted in the increase in the probability of insulin resistance. Although most patients were obese (in our study patients did not have obesity), the exclusion of obesity did not cause any difference in the results. 21 But in a study by Ciba et al. in 2007, assessing the insulin-resistance in obese children and teenagers with NAFLD, although the rate of insulin-resistance was high in the study group, it was not significantly different from those being in the control group. 23 This could be due to the method of selecting samples. Those in the control group were also obese. In our study, the mean level of fasting serum insulin in those with NAFLD was more than that in the control group, but the mean levels of FPG and 2-hour OGTT were not significantly different between the two groups. Schwimmer showed that fasting serum insulin levels and insulin-resistance were higher in those with NAFLD, who had been diagnosed using liver biopsy.22 Our study showed identical results. Chan et al. in 2004 reported that the degree of liver involvement in patients with NAFLD according to sonographic findings was positively related to insulin

resistance. Only obese patients were evaluated in that study.24 Mehmet et al. in 2003 found the same results. They reported that normal FPG accompanied by elevated serum insulin levels was the gold standard for diagnosing insulin-resistance.4 The superiority of our study to other studies is that our patients were not obese and were also matched with the control group and in all patients liver transaminases were normal. Besides the factors being related to insulin-resistance, our study also evaluated liver function tests and lipid profile, which were not significantly different between the two groups. Although the pathogenesis of NAFLD is not completely understood, our study, as many other studies, supports the role of insulin resistance as a substantial factor for hepatic steatosis. 11-17 The other opinion is that NAFLD is a hepatic marker of insulin resistance although oxidative stressors can also cause additional oxidative damage. Insulin resistance leads to an increase in lipolysis, triglyceride synthesis, and hepatic absorption of free fatty acids and accumulation of fat in the liver. 21 The strength of this survey was that we matched BMI in the two groups and our limitation was lack of liver biopsy instead of liver sonography for confirming a fatty liver.

Acknowledgement We wish to thank Mazandaran University of Medical Sciences for their financial support. Conflict of interest: None declared.

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