Patients with type 1 diabetes mellitus have impaired IL-1β production in response to Mycobacterium tuberculosis

E. Lachmandas, K. Thiem, C. van den Heuvel, A. Hijmans, B. E. de Galan, C. J. Tack, M. G. Netea, R. van Crevel, J. A. van Diepen

Patients with diabetes mellitus have an increased risk of developing tuberculosis. Although the underlying mechanism is unclear, evidence suggests a role for chronic hyperglycaemia. We examined the influence of hyperglycaemia on Mycobacterium tuberculosis-induced cytokine responses in patients with type 1 diabetes mellitus (T1D). Peripheral blood mononuclear cells (PBMCs) from 24 male T1D patients with sub-optimal glucose control [HbA1c > 7.0% (53 mmol/L)] and from 24 age-matched male healthy controls were stimulated with M. tuberculosis lysate. Cytokine analysis, assessment of aerobic glycolysis, receptor recognition and serum cross-over experiments were performed to explore the mechanistic differences. PBMCs from T1D patients produced less bioactive interleukin (IL)-1β in response to M. tuberculosis. IL-6 and interferon (IFN)-γ production trended towards a decrease, whilst other cytokines such as tumour necrosis factor (TNF)-α, IL-17 and IL-1Ra were normal. The decrease in cytokine production was not correlated to HbA1c or plasma glucose levels. Cross-over serum experiments did not alter the cytokine profile of T1D or control patients, arguing for an intrinsic cellular defect. Cellular metabolism and the expression of M. tuberculosis-related pattern recognition receptors (PRRs) such as TLR2, TLR4 and NOD2 did not differ between T1D patients and healthy controls. Compared to matched controls, T1D patients have a reduced capacity to produce pro-inflammatory cytokines in response to M. tuberculosis. The impaired IL-1β production in T1D patients may contribute to the increased susceptibility to tuberculosis. This effect appears not to be related to prevailing glucose levels but to an intrinsic cellular deficit.