SOCS3 methylation mediated the effect of sedentary time on type 2 diabetes mellitus: The Henan Rural Cohort study

Mendelian Randomization Analysis of the Association of SOCS3 Methylation with Abdominal Obesity

This study was conducted to evaluate the potential causality association of SOCS3 methylation with abdominal obesity using Mendelian randomization. A case-control study, including 1064 participants, was carried out on Chinese subjects aged 18 to 79. MethylTargetTM was used to detect the methylation level for each CpG site of SOCS3, and SNPscan^® was applied to measure the single-nucleotide polymorphism (SNP) genotyping. The logistic regression was used to assess the relationship of SOCS3 methylation level and SNP genotyping with abdominal obesity. Three types of Mendelian randomization methods were implemented to examine the potential causality between SOCS3 methylation and obesity based on the SNP of SOCS3 as instrumental variables. SOCS3 methylation levels were inversely associated with abdominal obesity in five CpG sites (effect estimates ranged from 0.786 (Chr17:76356054) to 0.851 (Chr17:76356084)), and demonstrated positively association in 18 CpG sites (effect estimates ranged from 1.243 (Chr17:76354990) to 1.325 (Chr17:76355061)). The causal relationship between SOCS3 methylation and abdominal obesity was found using the maximum-likelihood method and Mendelian randomization method of penalized inverse variance weighted (MR-IVW), and the β values (95% CI) were 5.342 (0.215, 10.469) and 4.911 (0.259, 9.564), respectively. The causality was found between the SOCS3 methylation level and abdominal obesity in the Chinese population.

SOCS3 Regulates Dectin-2-Induced Inflammation in PBMCs of Diabetic Patients

The C-type lectin receptors (CLRs) Dectin-1 and Dectin-2 are involved in several innate immune responses and are expressed mainly in dendritic cells, monocytes, and macrophages. Dectin-1 activation exacerbates obesity, inflammation, and insulin resistance/type 2 diabetes (T2D). However, the role of Dectin-2 is not clear in T2D. This study aims to evaluate the expression and function of Dectin-2 in peripheral blood mononuclear cells (PBMCs) isolated from diabetic patients and non-diabetic controls. Flow-cytometry and qRT-PCR were performed to evaluate the expression of Dectin-2 in different leukocyte subpopulations isolated from T2D patients (n = 10) and matched non-diabetic controls (n = 11). The functional activity of Dectin-2 was identified in PBMCs. CRP, IL-1β, and TNF-α concentrations were determined by ELISA. siRNA transfection and Western blotting were performed to assess p-Syk and p-NF-kB expression. siRNA transfection was performed to knock down the gene of interest. Our results show that Dectin-2 expression was the highest in monocytes compared with other leukocyte subpopulations. The expression of Dectin-2 was significantly increased in the monocytes of T2D patients compared with non-diabetic controls. Dectin-2 expression positively correlated with markers of glucose homeostasis, including HOMA-IR and HbA1c. The expression of inflammatory markers was elevated in the PBMCs of T2D patients. Interestingly, SOCS3, a negative regulator of inflammation, was expressed significantly lowlier in the PBMCs of T2D patients. Moreover, SOCS3 expression was negatively correlated with Dectin-2 expression level. The further analysis of inflammatory signaling pathways showed a persistent activation of the Dectin-2-Syk-NFkB pathway that was instigated by the diminished expression of SOCS3. Dectin-2 activation failed to induce SOCS3 expression and suppress subsequent inflammatory responses in the PBMCs of diabetic patients. siRNA-mediated knockdown of SOCS3 in PBMCs displayed a similar inflammatory phenotype to diabetic PBMCs when exposed to Dectin-2 ligands. Altogether, our findings suggest that elevated Dectin-2 and its relationship with SOCS3 could be involved in the abnormal immune response observed in T2D patients.

Janus kinase 2 (JAK2) methylation and obesity: A Mendelian randomization study

BACKGROUND AND AIMS

Janus kinase 2 (JAK2) play an important role in the energy metabolism. Whether there is a causal relationship between JAK2 methylation levels and obesity remains unclear. Based on the instrumental variables of 5 SNP sites, this study was aimed to explore the causal relationship between JAK2 methylation levels and obesity by Mendelian randomization analysis.

METHODS AND RESULTS

A total of 1021 participants (511 cases and 510 controls defined by body mass index (BMI) ≥ 28.0 kg/m²) was conducted from the Henan Rural Cohort study. SNPscan® was performed to test the SNP genotyping and MethylTarget™ was applied to detect the DNA methylation level. The logistic regression model was used to evaluate the associations between SNP or methylation of JAK2 and obesity (according to BMI). Mendelian randomization analysis was used to assess the potential causal association between JAK2 methylation and obesity. According to the logistic regression model, 1 CpG sit in the promotor was related to an increased risk of obesity (P < 0.05). 10 CpG sites in the exon were associated with decreased risk of obesity (P < 0.05). Mendelian randomization analysis showed a causal association between the methylated level of JAK2 and obesity, based on the instrumental variables of 5 SNPs (P < 0.05).

CONCLUSIONS

This study supported that the methylation degree of JAK2 has a complex relationship with obesity, which might be related to the region of methylation. A causal relationship exists between the methylated level of JAK2 and obesity.

Combined effects of progesterone and SOCS3 DNA methylation on T2DM: a case-control study

BACKGROUND

This study aims to investigate the independent and combined effects of progesterone and suppressor of cytokine signaling (SOCS)-3 DNA methylation on type 2 diabetes mellitus (T2DM) among men and postmenopausal women in rural China.

METHODS

A case-control study with 914 participants (329 T2DM, 585 controls) was conducted. Serum progesterone was detected with liquid chromatography-tandem mass spectrometry. DNA methylation of SOCS3 was determined by MethylTarget™. Linear regression was applied to evaluate the associations of progesterone and SOCS3 methylation with marks of glucose metabolism. Logistic regression was employed to investigate the independent and combined effects of progesterone and SOCS3 methylation with T2DM in men and postmenopausal women.

RESULTS

After multiple adjustment, progesterone was positively associated with T2DM in both men (odds ratio (OR) (95% confidence interval (CI)): 2.77 (1.79, 4.29)) and postmenopausal women (OR (95% CI): 1.85 (1.26, 2.72)). Methylation level of Chr17:76,356,190 or Chr17:76,356,199 (SOCS3) was negatively associated with T2DM in both men (OR (95% CI): 0.58 (0.39, 0.86) or 0.27 (0.14, 0.51)) and postmenopausal women (OR (95% CI): 0.43 (0.29, 0.65) or 0.53 (0.28, 0.99)). Subjects with high progesterone and low Chr17:76,356,190 or Chr17:76,356,199 methylation were more susceptible to have a higher prevalence of T2DM (men: OR (95% CI): 5.20 (2.49, 10.85) or 5.62 (2.74, 11.54); postmenopausal women: OR (95% CI): 3.66 (1.85, 7.26) or 3.27 (1.66, 6.45)).

CONCLUSIONS

The independent and combined effects of progesterone and SOCS3 methylation on T2DM were found among men and postmenopausal women, suggesting that ensuring low levels of progesterone and high methylation of SOCS3 could reduce the prevalence of T2DM. Trial registration The Chinese Clinical Trial registration: The Henan Rural Cohort Study, ChiCTR-OOC-15006699. Registered 06 July 2015, http://www.chictr.org.cn/showproj.aspx?proj=11375.

The mediation role of SOCS3 methylation in the effect of serum testosterone on type 2 diabetes

BACKGROUND

Previous studies reported that testosterone and DNA methylation of suppressor of cytokine signaling-3 (SOCS3) were associated with type 2 diabetes (T2D). Testosterone affects SOCS3 gene expression. Therefore, we aimed to investigate how the SOCS3 methylation mediates the relationship between testosterone and T2D among Chinese rural adults.

METHODS

A case-control study comprised 365 T2D patients and 651 controls was conducted. Liquid chromatography-tandem mass spectrometry and MethylTarget were used to determine the levels of serum testosterone and DNA methylation of SOCS3 gene, respectively. The odds ratio (OR) of testosterone or SOCS3 methylation for T2D was calculated using logistic regression models, and β value of testosterone for SOCS3 methylation was evaluated by linear regression models. Furthermore, through mediation analysis the mediating effect of SOCS3 methylation on the association of testosterone with T2D was estimated.

RESULTS

After adjusting for multiple variables, the protective effect of testosterone on T2D was found in men (OR = 0.61, 95% confidence interval [CI]: 0.47-0.80), and the methylation of Chr17:76356190 or Chr17:76356199 was negatively related to T2D in both men and women. Moreover, testosterone was positively associated with Chr17:76356190 methylation in men and Chr17:76356199 methylation in women (both P < .05). The mediation analysis showed that the Chr17:76356190 methylation partly mediated effect of testosterone on T2D in men was approximately 8.2%.

CONCLUSIONS

High levels of serum testosterone in men and Chr17:76356190 and Chr17:76356199 (SOCS3) methylation were related to a lower prevalent T2D. In addition, Chr17:76356190 methylation partially mediated the effect of testosterone on T2D in Chinese rural men.

DNA methylation as a mediator of associations between the environment and chronic diseases: A scoping review on application of mediation analysis

DNA methylation (DNAm) is one of the most studied epigenetic modifications. DNAm has emerged as a key biological mechanism and biomarkers to test associations between environmental exposure and outcomes in epidemiological studies. Although previous studies have focused on associations between DNAm and either exposure/outcomes, it is useful to test for mediation of the association between exposure and outcome by DNAm. The purpose of this scoping review is to introduce the methodological essence of statistical mediation analysis and to examine emerging epidemiological research applying mediation analyses. We conducted this scoping review for published peer-reviewed journals on this topic using online databases (PubMed, Scopus, Cochrane, and CINAHL) ending in December 2020. We extracted a total of 219 articles by initial screening. After reviewing titles, abstracts, and full texts, a total of 69 articles were eligible for this review. The breakdown of studies assigned to each category was 13 for smoking (18.8%), 8 for dietary intake and famine (11.6%), 6 for other lifestyle factors (8.7%), 8 for clinical endpoints (11.6%), 22 for environmental chemical exposures (31.9%), 2 for socioeconomic status (SES) (2.9%), and 10 for genetic factors and race (14.5%). In this review, we provide an exposure-wide summary for the mediation analysis using DNAm levels. However, we found heterogenous methods and interpretations in mediation analysis with typical issues such as different cell compositions and tissue-specificity. Further accumulation of evidence with diverse exposures, populations and with rigorous methodology will be expected to provide further insight in the role of DNAm in disease susceptibility.

Increased PARylation impacts the DNA methylation process in type 2 diabetes mellitus

Background

Epigenetic modifications, such as DNA methylation, can influence the genetic susceptibility to type 2 diabetes mellitus (T2DM) and the progression of the disease. Our previous studies demonstrated that the regulation of the DNA methylation pattern involves the poly(ADP-ribosyl)ation (PARylation) process, a post-translational modification of proteins catalysed by the poly(ADP-ribose) polymerase (PARP) enzymes. Experimental data showed that the hyperactivation of PARylation is associated with impaired glucose metabolism and the development of T2DM. Aims of this case–control study were to investigate the association between PARylation and global and site-specific DNA methylation in T2DM and to evaluate metabolic correlates.

Results

Data were collected from 61 subjects affected by T2DM and 48 healthy individuals, recruited as controls. Global levels of poly(ADP-ribose) (PAR, a surrogate of PARP activity), cytosine methylation (5-methylcytosine, 5mC) and de-methylation intermediates 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) were determined in peripheral blood cells by ELISA-based methodologies. Site-specific DNA methylation profiling of SOCS3, SREBF1 and TXNIP candidate genes was performed by mass spectrometry-based bisulfite sequencing, methyl-sensitive endonucleases digestion and by DNA immuno-precipitation. T2DM subjects presented higher PAR levels than controls. In T2DM individuals, increased PAR levels were significantly associated with higher HbA1c levels and the accumulation of the de-methylation intermediates 5hmC and 5fC in the genome. In addition, T2DM patients with higher PAR levels showed reduced methylation with increased 5hmC and 5fC levels in specific SOCS3 sites, up-regulated SOCS3 expression compared to both T2DM subjects with low PAR levels and controls.

Conclusions

This study demonstrates the activation of PARylation processes in patients with T2DM, particularly in those with poor glycaemic control. PARylation is linked to dysregulation of DNA methylation pattern via activation of the DNA de-methylation cascade and may be at the basis of the differential gene expression observed in presence of diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01099-1.

Androgen receptor DNA methylation is an independent determinant of glucose metabolic disorders in women; testosterone plays a moderating effect

BACKGROUND

We have previously shown that serum testosterone was associated with impaired fasting glucose (IFG) and type 2 diabetes (T2D). Testosterone can be acting through binding the androgen receptor (AR). Therefore, we aimed to explore the independent associations of AR DNA methylation (ARm) with IFG and T2D and the moderation effects of serum testosterone on the associations.

METHODS

A case-control study with 1065 participants including 461 men and 604 women was performed. ARm in peripheral blood sample and serum testosterone were measured using pyrosequeuncing and liquid chromatography-tandem mass, respectively. Multivariable logistic regression was performed to estimate the associations of ARm (including 2 cytosine-phosphoguanine [CpG] islands and average methylation levels) with different glucose status. Serum testosterone was used as a moderator to estimate the moderation effect.

RESULTS

After multivariate adjustment, CpG 1, 2 and CpG average methylation were all significantly associated with IFG (CpG 1: Odds ratio (OR) = 4.80, 95% confidence interval (CI): 2.24-10.27; CpG 2: OR = 4.35, 95% CI: 2.50-7.58; CpG average: OR = 11.73, 95% CI: 5.36-25.67) in women. In addition, testosterone played negative moderation effects in above associations. Moreover, no significant independent associations of methylation levels with T2D was observed both in men and women.

CONCLUSION

Our findings demonstrate that ARm was positively associated with IFG in women and the associations would be weakened by testosterone. The individuals experiencing low testosterone and ARm levels reported a lower state of IFG than those who experienced high levels of testosterone and ARm in women.