Prevalence of Abnormal Serum Alanine Aminotransferase Levels in Type 2 Diabetic Patients in Iran

INTRODUCTION

Diabetes and obesity are the most prevalent causes of nonalcoholic steatohepatitis (NASH). NASH is the main cases of chronic liver disease and AST and ALT as primary screening test for NASH (Daniel et al., 1999).

Among patients with diabetes, the risk of chronic liver disease is doubled; independent of alcoholic liver disease or viral hepatitis (El-Serag et al., 2004). Diabetes also increases the risk of primary liver cancers (Davila et al., 2005; Shaib et al., 2005) and death from liver cirrhosis (de Marco et al., 1999; Trombetta et al., 2005).

Type 2 diabetes, a frequent complication of obesity, has been described in 34 to 75% of patients with NASH (Hermos et al., 2008).

Aminotransferase, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST), measure the concentration of intracellular hepatic enzymes that have leaked into the circulation and serve as a marker of hepatocyte injury (Erbey et al., 2000).

The aminotransferases AST and ALT are normally between 5-40 U L^-1 (Kaplan, 2002; Prati et al., 2002). Chronic mild elevation of transaminases is frequently found in type 2 diabetic patients. Despite this, the sources of this elevation did not well known and epidemiological study of this type is not very popular (Piton et al., 1998). Erbey et al. (2000) analyzed 18,825 non-institutionalized patients in the United States. Of those with type 2 diabetes, the prevalence of elevated ALT was 7.8%, compared to 3.8% in those without diabetes (Erbey et al., 2000). Salmela et al. (1984) study (1984) in Finland multivariate analysis showed BMI more than 25 kg m^-2 and poor diabetic control (fasting blood glucose >11.88 mmol L^-1) were the most significant clinical variables associated with elevated ALT (Salmela et al., 1984). This study was conducted to assess the prevalence of elevated AST and ALT in type 2 diabetic patients and determine the relations between this elevation to age, gender and other metabolic parameters.

MATERIALS AND METHODS

In this cross-sectional study 348 patients with type 2 diabetes, who attended the diabetic clinic of Diabetes Research Center (Yazd, Iran), were studied from October 2004 to December 2005.

The criteria for diagnosis of type 2 diabetes were the American Diabetes Association criteria (2004), fasting blood sugar of 126 mg dL^-1 at two occasions or random blood sugar of 200 mg dL^-1 with diabetic symptoms or taking hypoglycemic drugs or insulin and did not have any episodes of ketosis in the past.

The institution`s Research Ethics Committee approval was obtained prior to study enrollment. Informed consent was obtained in all subjects. Clinical data of all patients which included sex, height, weight, age at onset of diabetes, duration of diabetes, family history of diabetes and liver diseases, as well as a history of medication, were obtained by reviewing the medical records and direct patient interview.

The patients were excluded if their history indicated the presence of any of the following conditions: (1) history of known liver disease or other medical problems thought to cause an elevation in liver enzymes, (2) history of viral hepatitis and /or significant alcohol consumption, defined as greater than one alcoholic beverage per day and (3) history of any medication use thought to cause elevation in liver enzymes such as Corticosteroids, Amiodarone, Bleomycin, Methotrexate ,Tamoxifen and Sodium valporate. Moreover those with a diagnosis of Maturity Onset Diabetes of the Young, secondary diabetes, gestational diabetes or uncertain type of diabetes were excluded.

Blood sampling and biochemical analysis: Venous blood samples were collected after an overnight fasting, Plasma glucose, glycated hemoglobin (HbA_1C) and triglyceride as determined by enzymatic methods (PARS AZMON-Iran). AST and ALT were estimated using enzymatic methods (PARS AZMON kit -Iran). We defined Alt and AST more than 40 U L^-1 as abnormal. A complementary viral test performed in patients who have elevated AST and ALT. Ultrasonography was performed in patients who have two times elevation in ALT and also viral profile to rule out viral infection.

Statistical analysis: Statistical analysis were performed using SPSS for windows, version 11.5. Data are presented as Mean ± SD. Two unrelated samples were compared by student t-test. A significant level of p<0.05 was used for univariate test. ANOVA, Pierson and Tokay test were used for evaluating the relationship between mean of AST and ALT and metabolic parameters.

RESULTS

Of 348 type 2 diabetic patients, mean age of patients were 58.8 ± 11.5 years. (ranging from 17-82). Mean duration of diabetes mellitus was 8.59 ± 6.65 years that maximum duration of diabetes was 31 years. Mean body weight was 70.48 kg (Ranging from 38-110) and mean BMI was 27.25 (ranging from 42 to 32). Mean of AST and ALT were 24.57 ± 15 and 24.67 ± 23 U L^-1, respectively.

Table 1 shows the characteristics of type 2 diabetic patients studied. Elevated ALT and AST were found in 10.4 and 3.3% of type 2 diabetic patients, respectively. Ninety percent of patients had ALT less than 40 U L^-1 and 9.2% had ALT between 40-80 U L^-1 and only 0.09 had ALT over more than twice the upper limit of normal range.

Although the prevalence of elevated ALT increased with increasing age in subjects, but it was not statistically significant (Table 2). The risk of elevated ALT and AST increased with increasing triglyceride, but it was not significant at 5% level (TG level less than 150 and 150 mg dL^-1 and above). There is no difference in the means of AST and ALT in subgroups of patient with different FBS levels. Also in type 2 diabetic patients, the risk of elevated ALT significantly decreased with increasing duration of diabetes (p = 0.006) (Fig. 1).

BMI is divided in three subgroups: less than 25, 25-30 and over 30 kg m^-2, mean of AST and ALT levels were not different in the subgroup of BMI (p = 0.796).

Table 1:	Characteristics of type 2 diabetic patients studied


Fig. 1:	Mean FBS levels in type 2 diabetic subjects with normal and elevated ALT levels in different age groups

Table 2:	Frequency of ALT and AST levels and ORs in type 2 diabetic patients for various risk factors

*Refrence category

There was negative correlation between ALT and age (r = -0.14, p = 0.007). Moreover, there was a negative significant correlation between AST and FBS (r = - 0.11, p = 0.042) and HDL (r = -0.18, p = 0.001), but no significant correlation between AST and other variables was seen.

In nine patient who had elevated AST, ALT significantly, Hbs Ag and HCV was performed that were negative in all of them. Also ultrasonography was performed that in all of them fatty changes was seen.

DISCUSSION

The prevalence of elevated ALT and AST in type 2 diabetic patients was higher than general population (Mohamadnejad et al., 2003), but lower than studies done in diabetic patients (West et al., 2006). This suggests that aminotrasferase levels should be checked at least once in type 2 diabetic patients and elevated trasaminase levels may need further evaluation for the causes of raised trasaminase levels. One of our limitation was a single measure of trasaminase was performed. As fluctuation in transaminase is recognized in patients with chronic liver disease and a single measurement can underestimate disease burden (Clark and Diehl, 2003).

In non-hepatitis subjects, an elevation of ALT or GGT, even within the normal range, reflects deposition of excess fat in the liver (Wannamethee et al., 2005). High prevalence of transaminase levels in type 2 diabetic patients might be due to high prevalence of uncontrolled diabetic patients in present study (mean FBS: 200.73 ± 68.61 mg dL^-1). As some studies showed hyperglycemia and hyperinsulinemia can promote fatty infiltration of the liver (de Marco et al., 1999).

In this study, only age and duration of diabetes, related to elevation of ALT in diabetic patients and there is no relationship between BMI and FBS levels and elevation of ALT. Elevated ALT was slightly more common in men and increased with increasing triglyceride, but it was not significant. ALT appeared to show some association with dislipidemia and microalbuminuria (West et al., 2006), but they could not show any relation with other risk factors included age, BMI, hypertension, oral hypoglycemic agent, insulin and HbA1c levels. In comparison to Salmela et al. (1984) showed that BMI > 25 kg m^-2 and poor diabetic control (fasting blood glucose > 11.88 mmol L^-1) were the most significant clinical variables associated with elevated ALT, however in present study no relationship was observed between BMI an elevation of ALT (Salmela et al., 1984).

In other study elevation of ALT among older-aged patients, diabetes independently predicted elevated ALT, whereas BMI did not (Hermos et al., 2008). This study is in agreement with present study as ALT levels are significantly different between age lower than 52 year group and upper 64.

CONCLUSION

The prevalence of elevated of ALT in type 2 diabetic patients is 1.6 times higher than general population in Iran unrelated to age, BMI, glycemic control, triglyceride levels. Identification risk factors and mechanisms of these elevations are very important and require further evaluation.

ACKNOWLEDGMENTS

This study was supported by Yazd Diabetes Research Center and Shaheed Sadoughi University of Medical Sciences and Health Services (University Grant No. 626).