Immune dysregulation in type 2 diabetes mellitus: Implications for tuberculosis, COVID-19, and HIV/AIDS

Diabetes mellitus (DM) is a complex and multifactorial disorder associated with elevated blood sugar levels, poor insulin sensitivity, and inadequate insulin production. It has a major impact on the immune system, making a person more susceptible to and influenced by a variety of infectious illnesses. This narrative review summarizes the relationship between chronic inflammation and high glucose levels in DM, on susceptibility and outcomes in endemic infectious diseases. We focused on impact of DM on disease progression, and treatment response in these infections. Literature was identified through searches of PubMed, Scopus, and Google Scholar, focusing on epidemiologic, clinical, and mechanistic studies. The evidences suggest that immune modulation in DM has profound inverse relations with the outcome of infectious diseases including tuberculosis, COVID-19, and HIV/AIDS. DM increases the risk of developing severe forms of infectious diseases due to downregulation of the immune system which is associated with glycemic control. There is a need to understand the relationship between DM and immunological control for developing methods to reduce these risks and improve outcomes for the affected population.