Hyperglycaemia Induces Trained Immunity in Macrophages and Their Precursors and Promotes Atherosclerosis.

Cardiovascular risk in diabetes remains elevated despite glucose lowering therapies. We hypothesised that hyperglycaemia induces trained immunity in macrophages, promoting persistent pro-atherogenic characteristics. Bone marrow derived macrophages from control and mice with diabetes were grown in physiological glucose (5 mM) and subject to RNA-sequencing (n=6), ATAC-sequencing (n=6) and ChIP-sequencing (n=6) for determination of hyperglycaemia-induced trained immunity. Bone marrow transplantation from mice with (n=9) or without (n=6) diabetes into [normoglycaemic] Ldlr mice was used to assess its functional significance . Evidence of hyperglycaemia-induced trained immunity was sought in human peripheral blood mononuclear cells (PBMCs) from patients with diabetes (n=8) compared with case controls (n=16) and in human atherosclerotic plaque macrophages excised by laser capture microdissection. In macrophages, high extracellular glucose promoted pro-inflammatory gene expression and pro-atherogenic functional characteristics, through glycolysis-dependent mechanisms. Bone marrow-derived macrophages (BMDM) from diabetic mice, retained these characteristics, even when cultured in physiological glucose, indicating hyperglycaemia-induced trained immunity. Bone marrow transplantation from diabetic mice into [normoglycaemic] mice increased aortic root atherosclerosis, confirming a disease-relevant and persistent form of trained innate immunity. Integrated ATAC-seq, ChIP-seq and RNA-seq analyses of haematopoietic stem cells and BMDM revealed a pro-inflammatory “priming effect” in diabetes. The pattern of open chromatin implicated transcription factor, RUNX1, while transcriptomes of atherosclerotic plaque macrophages and peripheral leukocytes in patients with type 2 diabetes were enriched for RUNX1 targets, consistent with a potential role in human disease. Pharmacological inhibition of RUNX1 inhibited the trained phenotype. Hyperglycaemia-induced trained immunity may explain why targeting elevated glucose is ineffective in reducing macrovascular risk in diabetes and suggests new targets for disease prevention and therapy.