The effect of rs9939609 polymorphism of the FTO A23525T gene on obesity in patients with chronic hepatitis C

Introduction

Chronic hepatitis C (CHC) remains a global public health issue, being a leading cause of cirrhosis, hepatocellular carcinoma, and the need for liver transplantation [1]. Despite the therapeutic revolution brought about by interferon-free regimens based on direct-acting antivirals (DAAs), the issues of comorbidity and modifiable risk factors for disease progression remain highly relevant [2]. A key factor among these is obesity, the prevalence of which has reached pandemic proportions worldwide. The combination of CHC and obesity exerts a synergistic negative effect, significantly impairing the response to antiviral therapy and the disease prognosis. Therefore, an in-depth investigation of the pathogenetic mechanisms underlying this relationship, particularly the role of genetic factors, represents a critically important direction in modern hepatology [3].

HCV infection and obesity are widespread in the general population, resulting in a high likelihood of their co-occurrence. According to WHO, over 650 million adults are obese, while at least 58 million of these individuals are infected with the hepatitis C virus [4]. Hepatitis C virus and obesity act as independent yet mutually aggravating factors of hepatocyte injury. Obesity itself underlies the pathogenesis of non-alcoholic fatty liver disease (NAFLD), characterized by lipid accumulation in hepatocytes (steatosis), which triggers a cascade of reactions (oxidative stress, inflammation, insulin resistance) leading to fibrosis. It should be noted that the HCV virus itself can induce metabolic disturbances, including insulin resistance and hepatic steatosis [5]. Consequently, in patients with CHC and obesity, steatosis, inflammation, and fibrosis progress significantly more rapidly than in the presence of only one of these factors.

Despite the evident clinical significance of this problem, it remains incompletely understood why some patients with CHC and obesity experience rapid fibrosis progression, while others exhibit a relatively favorable disease course. This observation suggests the existence of individual, including genetically determined, mechanisms.

Currently, several gene polymorphisms associated with obesity risk have been identified. The most extensively studied is the FTO gene, located at locus 16q12.2. This gene is involved in the regulation of eating behavior, and carriage of specific allelic variants, particularly the rs9939609 polymorphism, is recognized as a significant risk factor for the development of excess body weight [6, 7, 8].

Objective

To investigate the effect of the rs9939609 (A23525T) polymorphism of the FTO gene on obesity in patients with chronic hepatitis C.

Materials and Methods

This study examined the association between the rs9939609 polymorphism of the FTO gene and obesity in patients with CHC. The survey was conducted in the day hospital of the Regional Clinical Infectious Diseases Hospital and the clinical diagnostic laboratory of the Institute of Pharmacy, Yaroslavl State Medical University, Ministry of Health of the Russian Federation. The study included 240 patients aged 18 to 60 years. Informed consent to participate in the study was obtained from all patients. The main group consisted of 124 adults with CHC and obesity, and the comparison group comprised 116 patients with CHC without obesity. In this study, body mass index (BMI) served as the primary selection criterion. Patients underwent a physical examination, including anthropometry (height, weight, waist circumference, body mass index). To determine the type of obesity, waist circumference (WC) was measured in a standing position, with the landmark placed midway between the top of the iliac crest and the lower edge of the ribs. BMI was calculated using the formula: BMI = weight (kg) / height (m²). BMI values allowed for the determination of the degree of obesity (Table 1) [4].

Table 1. WHO classification of degrees of excess body weight

A biochemical blood test was performed to determine the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). The activity of chronic hepatitis was assessed according to the international classification of chronic viral hepatitis (Los Angeles, 1999). Molecular genetic analysis of the candidate gene FTO (A23525T) polymorphism was performed using real-time PCR on an iCycler iQ5 instrument (BioRad, USA) with the SNP-express-RV reagent kit (NPF Litekh, Russia). Liver fibrosis (elastometry) was evaluated using a FibroScan 502 device (Echosens), with fibrosis stages interpreted according to the METAVIR scale: F0 (no fibrosis) <5.8 kPa; F1 (minimal fibrosis) – 5.9–7.2 kPa; F2 (moderate fibrosis) – 7.3–9.5 kPa; F3 (severe fibrosis) – 9.6–12.0 kPa; F4 (cirrhosis) >12.0 kPa [10].

Data processing was performed using IBM SPSS Statistics (version 21) and Statistica (version 64). The following statistical methods were applied in data analysis: standard descriptive statistics (mean, standard deviation for normal distribution; median, quartiles for non-normal distribution). Comparisons between study groups for each gene separately were performed using the Mann–Whitney U test for quantitative variables and the chi-square test for categorical variables. Regression analysis was used to assess the effect of gene expression on metabolic syndrome parameters. The type of regression analysis varied depending on the type of metabolic syndrome indicator. Statistically significant results were illustrated using stacked bar charts for categorical variables and box plots for quantitative variables. Significance levels of 0.05, 0.01, and 0.001 were used for decision-making. Calculations were performed using the statistical software package IBM SPSS version 26.

Results and Discussion

The study involved a cohort of 240 patients, with a predominance of males – 124 individuals (52%) compared to females – 116 individuals (48%). Comparative analysis by sex and age revealed statistically significant differences between the groups: in the main group, the proportion of men was significantly higher, and the mean age of patients was significantly lower than in the comparison group (p <0.05). Table 2 presents the distribution of patients by sex and age in the study groups. This study was approved by the Ethics Committee on November 28, 2024 (No. 72).

Table 2. Distribution of patients by gender and age in the study groups

According to the results of the FTO rs9939609 polymorphism (Fig. 1), the homozygous AA genotype was more frequent in patients of the main group – 53 (42%) – than the heterozygous AT – 46 (37%) and homozygous TT – 26 (21%) genotypes. In the comparison group, carriers of the heterozygous AT genotype – 68 (60%) – were more common than homozygous AA – 17 (15%) and TT – 29 (25%).

Fig. 1. Frequency of occurrence of FTO A23525T gene genotypes in patients with CHC

The analysis revealed that none of the gene variants showed an association with sex. A significant correlation of the FTO rs9939609 (A23525T) polymorphism was associated with anthropometric parameters in patients of the main group. Carriers of this gene variant demonstrated a pathological increase in body mass index (exceeding 32.0 kg/m²) and waist circumference (greater than 100 cm). It was found that the AA genotype significantly correlated with the development of class I–II obesity, whereas the AT and TT genotypes were associated with a more severe form – class III obesity (p <0.05).

The study assessed the association between FTO A23525T genotypes and the possible degree of hepatitis C activity and liver fibrosis stage (LF) in patients of the main group. In patients with the homozygous TT genotype, elevated ALT levels were observed (Fig. 2). For the other genotypes, no significant effect was found (p >0.05). AST values did not show statistical significance.

Fig. 2. ALT level in patients with the TT genotype of the FTO A23525T gene

The study identified statistically significant differences in the distribution of LF stages between the groups (p <0.001). In the comparison group, patients with stages F0 (10.3%) and F3 (47.4%) significantly predominated. Conversely, in the obesity group, stages F2 (33.9%) and F4 (18.5%) were significantly more frequently recorded. Fig. 3 shows that in patients with AT and TT genotypes, a greater proportion of patients had LF stages F3–F4.

Fig. 3. Distribution of patients by stages of liver fibrosis depending on the rs9939609 polymorphism of the FTO A23525T gene

Analysis of BMI (kg/m²) showed that overweight was characteristic of patients in the comparison group (median 25.45 [24.35; 28.4] kg/m²), whereas individuals in the main group had obesity indicators (median 32.2 [30.5; 34.8] kg/m²). The distribution by obesity degree demonstrates a clear predominance of class I (37.0%, n=89) over class II (2.9%, n=7) and class III (5.6%, n=7) (Table 3).

Table 3. Distribution of BMI in patients with CHC

Comparison of biochemical parameters revealed that in the main group, both AST and ALT levels significantly exceeded those in the comparison group (p <0.001). Thus, patients with CHC and obesity were characterized by moderate and high degrees of activity, whereas the group without obesity exhibited minimal activity (Fig. 4).

Fig. 4. Distribution of hepatitis C activity in study groups

Moreover, according to the data obtained, transaminase levels in men in both clinical groups significantly exceeded the corresponding values in women (Table 4). This observation is consistent with the results of studies conducted by Russian authors (Tereshchenko Yu.A., Ignatova T.M.) [11, 12].

Table 4. Liver transaminase levels in men and women

Conclusion

• In patients with chronic hepatitis C and concomitant obesity, an association was established between the rs9939609 polymorphism of the FTO gene (A23525T) and anthropometric parameters: BMI >32 kg/m² and waist circumference >100 cm.

• Carriers of the AA genotype showed a correlation with class I–II obesity, while carriers of the AT and TT genotypes showed a correlation with class III obesity.

• The presence of the TT genotype in obese patients was associated with elevated ALT levels and a predominance of moderate and high degrees of hepatitis activity.

• Patients with CHC and obesity exhibited more advanced stages of liver fibrosis – F2 (33.9%) and F4 (18.5%) – compared to the comparison group.

• In carriers of the AT and TT genotypes of the FTO rs9939609 polymorphism, liver fibrosis stages F3–F4 were observed.