Correlation of inflammatory biomarkers with cognitive function and glycemic and lipid profiles in patients with type 2 diabetes mellitus: A meta-analysis

Abstract Background Type 2 diabetes mellitus (T2DM) is associated with an increased risk of cognitive impairment. Accumulating evidence has demonstrated that inflammation is connected to cognitive function and glycemic and lipid profiles in patients with T2DM. However, a quantitative synthesis of empirical studies on the correlation of inflammatory biomarkers with cognitive function and glycemic and lipid profiles is lacking and the reported data has so far been conflicting. The study aimed to examine and estimate previous inconsistent results on the correlation of inflammatory biomarkers with cognitive function and glycemic and lipid profiles in T2DM quantitatively. Methods The databases of PubMed, Web of Science, EMBASE, SCOPUS, CNKI, Wanfang, VIP, and CBM database were searched from inception until September 2022 (PROSPERO protocol CRD42022356889). We included original studies reporting the correlation of inflammatory biomarkers with cognitive function and glycemic and lipid profiles in T2DM patients. The Pearson or Spearman correlation coefficient was collected from each included study, and a meta-analysis was conducted with Comprehensive Meta-Analysis (version 3) software. Results Thirty-two studies were included, with a cumulative sample size of 7483 patients. In the correlation between inflammatory biomarkers and cognitive function, the findings revealed a significant moderate negative correlation between interleukin-6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor-α (TNF-α) levels and MoCA (r = -0.540, P = 0.006; r = -0.434, P < 0.001; r = -0.532, P = 0.015, respectively), and TNF-α level had a moderate negative correlation with MMSE (r = -0.491, P = 0.001). In the correlation between inflammatory biomarkers and glycemic and lipid profile, there was a significant moderate positive correlation between serum CRP and TNF-α levels and HbA1c (r = 0.467, P < 0.001; r = 0.521, P < 0.001, respectively). TNF-α level was also found to have a low positive correlation with FBG (r = 0.265, P < 0.001), CRP level was found to have a low positive correlation with TC (r = 0.286, P < 0.001), and IL-6 level was found to be lowly and positively correlated with TG (r = 0.230, P = 0.015). Conclusions These findings imply that IL-6, CRP, and TNF-α are potential inflammatory biomarkers and modifiable risk factors for T2DM with cognitive impairment, and that these inflammatory markers may be related to alterations in glycemic and lipid levels, including HbA1c, FBG, TC, and TG. Further research and longitudinal studies are required to assess the clinical value of these markers and to investigate potential causal mechanisms underlying this connection.