Diabetes Mellitus and Atrial Fibrillation: Mechanistic Insights and Therapeutic Impacts of Glucose-Lowering Drugs

<b>Background/Objectives:</b> Diabetes mellitus (DM) represents a major global public health challenge and is consistently associated with an increased risk of atrial fibrillation (AF). Despite extensive epidemiological evidence linking the two conditions, the underlying mechanisms and the influence of glucose-lowering therapies on AF susceptibility remain incompletely defined. This review aims to summarize the current knowledge on the pathophysiological pathways linking DM and AF and to assess the impact of commonly used antidiabetic therapies on arrhythmic risk. We conducted a narrative review of epidemiological studies, mechanistic research, and cardiovascular outcome trials that evaluate the association between DM and AF. We included data addressing structural, electrical, autonomic, metabolic, and inflammatory mechanisms of AF in diabetes, as well as clinical evidence regarding the impact of metformin, insulin, dipeptidyl peptidase-4 (DPP-4) inhibitors, sodium-glucose cotransporter-2 (SGLT-2) inhibitors, and glucagon-like peptide-1 (GLP-1) receptor agonists on AF incidence or recurrence. <b>Results:</b> DM promotes AF development through multiple complementary mechanisms, including atrial fibrosis, electrical conduction abnormalities, autonomic dysfunction, inflammation, glycemic fluctuations, oxidative stress, and expansion of epicardial adipose tissue. These changes create a vulnerable atrial substrate that facilitates both initiation and maintenance of AF. Evidence from recent trials indicates that the arrhythmic effects of glucose-lowering therapies are heterogeneous. Metformin and SGLT-2 inhibitors appear to offer favorable or neutral effects on AF risk. GLP-1 receptor agonists provide substantial cardiovascular benefits, although their specific impact on AF remains under investigation. Insulin therapy has been linked to a higher AF risk, whereas DPP-4 inhibitors show an overall neutral effect with inconsistent findings across studies. <b>Conclusions:</b> AF in patients with DM results from complex interactions between metabolic disturbances, structural remodeling, and inflammatory activation. Although several antidiabetic drugs appear to have potential antiarrhythmic effects, further dedicated research is needed to clarify their role in AF prevention and management.