Alterations of SOCS1 and SOCS3 transcript levels, but not promoter methylation levels in subcutaneous adipose tissues in obese women

Abstract

Background: Animal model studies suggest that change in the members of the suppressor of the cytokine signaling (SOCS) family (mainly SOCS1 and SOCS3) is linked to the pathogenesis of obesity-related metabolic disorders. Moreover, epigenetic modification is involved in the transcriptional regulation of the SOCS gene family. Here, we aimed to evaluate the mRNA expression as well as gene promoter methylation of SOCS1 and SOCS3 in subcutaneous adipose tissue (SAT) from obese women compared to normal-weight subjects. We also intend to identify the possible association of SOCS1 and SOCS3 transcript levels with metabolic parameters in the context of obesity.

Methods: This study was conducted on women with obesity (n = 24) [body mass index (BMI) ≥ 30 kg/m ²] and women with normal-weight (n = 22) (BMI < 25 kg/m ²). Transcript levels of SOCS1 and SOCS3 were evaluated by real-time PCR in SAT from all participants. After bisulfite treatment of DNA, methylation-specific PCR was used to assess the putative methylation of 10 CpG sites in the promoter of SOCS1 and 13 CpG sites in SOCS3 in SAT from women with obesity and normal weight.

Results: It was found that unlike SOCS3, which disclosed an elevating expression pattern, the expression level of SOCS1 was lower in the women with obesity as compared with their non-obese counterparts (P-value = 0.03 for SOCS1 transcript level and P-value = 0.011 for SOCS3 transcript level). As for the analysis of promoter methylation, it was found that SOCS1 and SOCS3 methylation were not significantly different between the individuals with obesity and normal weight (P-value = 0.45 and P-value = 0.89). Correlation analysis indicated that the transcript level of SOCS1 mRNA expression had an inverse correlation with BMI, hs-CRP levels, HOMA-IR, and insulin levels. However, the SOCS3 transcript level showed a positive correlation with BMI, waist-to-height ratio, waist circumference, hip circumference, hs-CRP, HOMA-IR, insulin, fasting blood glucose, and total cholesterol. Interestingly, HOMA-IR is the predictor of the transcript level of SOCS1 (β = - 0.448, P-value = 0.003) and SOCS3 (β = 0.465, P-value = 0.002) in SAT of all participants.

Conclusions: Our findings point to alterations of SOCS1 and SOCS3 transcript levels, but not promoter methylation levels in subcutaneous adipose tissues from women with obesity. Moreover, mRNA expression of SOCS1 and SOCS3 in SAT was associated with known obesity indices, insulin resistance, and hs-CRP, suggesting the contribution of SOCS1 and SOCS3 in the pathogenesis of obesity-related metabolic abnormalities. However, further studies are required to establish this concept.

Keywords: Expresseion; Methylation; Obesity, Insulin resistance; SOCS1; SOCS3, Adipose tissue.

Fig. 1

Bioinformatic analysis of SOCS1 and SOCS3 regulatory regions. The regulatory regions (grey) and CpG islands (light blue) are shown relative to the transcription start sites (+ 1). SOCS1, suppressor of cytokine signaling 1; SOCS3, suppressor of cytokine signaling 3

Fig. 2

Expression of SOCS1 (a) and SOCS3 (b) genes in the subcutaneous adipose tissues (SAT) of women with obesity (O) and ones with normal weight (NW). Results, normalized to the corresponding value of housekeeping genes (β-actin), are shown as median (interquartile). Fold changes in gene expression of women with obesity relative to the controls were calculated by the 2-^ΔΔCt method. The p-value was determined by Mann–Whitney U test

Fig. 3

Methylation status of regulatory regions of SOCS1 (a) and SOCS3 (b) genes in the subcutaneous adipose tissues (SAT) of women with obesity (O) and ones with normal weight (NW). The methylated level of DNA is expressed as the estimated amount of methylated DNA to the unmethylated DNA levels ratio calculated for each sample using the fluorescence threshold cycle. The results were s expressed as fold change relative to the controls. Results were shown as median (interquartile ranges). The p-value was determined by Mann–Whitney U test