A systemic review and meta-analysis of human case -control studies examining the association between toxoplasma gondii and type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) continues to be a major challenge for public health authorities worldwide. An emerging field of research is starting to examine the association of infectious and environmental pathogens with diabetes. In particular, the potential of these pathogens to cause low-grade inflammation that may facilitate the risk and development of T2DM. An understudied pathogen of potential interest is the protozoan parasite Toxoplasma gondii (T. gondii). There is some clinical evidence supporting an association between chronic T. gondii infection and the development of T2DM in both animals and humans. The objective of this review is to comprehensively assess the seroprevalence rates of T. gondii in subjects with T2DM in comparison to healthy controls to determine the risk of T2DM due to T. gondii infection. Six electronic databases (Google Scholar, Science Direct, Embase, PubMed, PLOS ONE, and Scopus) were searched using specific Medical Subject Headings terms without language or date restrictions. Fixed and random effects models were used to determine odds ratios with statistical significance being set at 5.0%. Among 1,963 studies, four studies reporting prevalence of T. gondii infection in 1,158 subjects with T2DM and 603 healthy controls met the eligibility criteria. The overall weighted prevalence of T. gondii infection in subjects with T2DM was 55.4% (range: 42.7 - 60.4%) in comparison to 32.1% (range: 21.8 - 50.6%) of healthy controls. Because of significant heterogeneity (Q = 25.529, p \u3c 0.001, I2 = 88.25%), the common odds ratio was calculated using a random effects model at 2.34 (95% CI: 1.17 - 4.64, p = 0.016). Regardless of the limited number of studies and a lack of data, T. gondii infection should continue to be regarded as a contributing factor to T2DM disease development. Further high quality studies that include inflammatory biomarker analysis are warranted to determine the specific role of this parasite in the pathogenesis of T2DM