Abstract Body (Do not enter title and authors here):
Background: Monocytes have been implicated in the initiation and progression of cardiovascular (CV) complications of type 2 diabetes (T2D).

Aim: We investigated diabetes-induced methylation changes and enriched pathways in circulating monocytes of T2D patients. We compared T2D vs. non-T2D participants and analyzed T2D patients according to diabetes control. Further, we assessed methylation changes in a subset of patients with poor diabetes control and high CV risk following a 6-month treatment intensification.

Methods: We recruited consecutively 200 participants, 160 with T2D and 40 non-diabetes controls. Circulating monocytes were sorted using the FACSAria2 ™ cell sorter. Samples were sequenced using enhanced reduced representation bisulfite sequencing. Methylation data was processed with Lumi and limma R packages to obtain batch and covariate corrected differential expression values for the indicated comparisons. Ingenuity Pathway Analysis (Qiagen) was used to identify enriched pathways for each tested condition. Differentially methylated genes used for pathway analysis were those with a p-value < 0.05 and an absolute logFC value ≥ 0.5.

Results: There were 1122 differentially methylated genes when comparing T2D to non-T2D patients. Among the top five enriched canonical pathways, apoptosis signaling was predicted to be activated, while the RHO GTPase cycle and LPS-stimulated MAPK signaling pathways were predicted to be inhibited. Within patients with diabetes, there were 1670 differentially methylated genes comparing those with poor control (HbA1c ≥ 7%) vs. good control (HbA1c<7%). Among the top five enriched pathways, synthesis of DNA, DNA replication signaling, and cell cycle checkpoints were activated while inhibition of ARE-mediated mRNA degradation pathway was inhibited. In patients who responded to treatment intensification (Δ HbA1c = -1.5%, p= 0.02), 1377 differentially methylated genes and differentially inhibited pathways such as non-homologous end-joining and cellular response to heat stress were identified. In non-responders, we identified 1582 differentially methylated genes and activated pathways, including inhibition of mRNA degradation pathways and p14/p19 ARF signaling.

Conclusion: Treatment intensification in T2D patients with CVD and poor control showed the presence of differentially methylated genes affecting pathways regulating cell proliferation and inflammation and are known to be associated with diabetic CVD complications.