Monocyte-mediated inflammation and cardiovascular risk factors in type 2 diabetes mellitus: A systematic review and meta-analysis of pre-clinical and clinical studies

BACKGROUND: Monocyte-mediated inflammation increases the risk of developing type 2 diabetes mellitus and cardiovascular disease. This is the first systematic review and meta-analysis of studies reporting on monocyte-mediated inflammation in type 2 diabetes mellitus. METHODS: This systematic review and meta-analysis was registered in the international prospective register of a systematic review: CRD42019132902. The MEDLINE, EMBASE and Google scholar electronic databases were searched, and a random-effects model was used to generate pooled standardised mean differences between patients with type 2 diabetes mellitus and healthy controls. RESULTS: The clinical studies (n = 20) comprised of 1065 patients with type 2 diabetes mellitus and 1103 healthy controls. Notably, the levels of monocyte activation were higher in patients with type 2 diabetes mellitus compared to healthy controls (standardised mean difference = 0.47, 95% confidence interval (0.10, 0.84), p = 0.01) (χ(2) = 65.72, I(2) = 83%, p < 0.00001). Patients with type 2 diabetes mellitus had an increased risk of cardiovascular disease compared to healthy controls (standardised mean difference = 0.37, 95% confidence interval (0.13, 0.61), p = 0.003) (χ(2) = 958.77, I(2) = 95%, p < 0.00001). All included pre-clinical studies reported on the C57BL/6 mice strain, with a majority of the studies 57% of reporting on high fat diet-induced C57BL/6 mice model. The overall quality of the studies was good with a median score and range of 16 (13–19). CONCLUSION: Our meta-analysis suggests that there is increased monocyte activation in patients with type 2 diabetes mellitus.