Assessment of diabetics by the quantification of essential elements and stable isotope ratios of carbon and nitrogen in scalp hair

Mercury Exposure and Risk of Type 2 Diabetes: A Systematic Review and Meta-Analysis

“…The systematic search of databases yielded a total of 778 studies. After excluding duplicate publications ( n = 168) and unrelated studies by titles/abstracts ( n = 559), 51 publications underwent full-text screening, of which 17 studies [ 14 – 16 , 18 , 19 , 28 , 29 , 32 – 36 , 40 – 44 ], with a total sample size of 42,917 participants (5,545 cases of T2DM), published between 1984 and 2021, were eligible to be included in the current meta-analysis according to the inclusion criteria. The flowchart reporting the process of screening is presented in Figure 1 .…”

“…Some included studies reported different effect sizes based on their studied subgroups; for these studies, we extracted and analyzed all suitable effect sizes. Of the included studies, data on Hg levels in T2DM patients vs. healthy controls were reported in 10 studies with 15 effect sizes [ 14 – 16 , 19 , 32 , 33 , 40 – 42 , 44 ], and 11 studies (3 prospective cohorts and 8 case-control) with 17 effect sizes [ 15 , 18 , 28 , 29 , 32 , 34 – 36 , 42 – 44 ] reported risk estimates for the association between Hg exposure and the risk of T2DM. All studies reporting risk estimates for T2DM adjusted the analysis for the potential confounders.…”

“…The sample size of the analyzed studies ranged between 53 and 15,327 subjects. Regarding the sex of participants, 5 studies reported data for subgroups of males and females separately [ 14 , 18 , 35 , 36 , 41 ], 1 study just included males [ 19 ], 1 study just included females [ 15 ], and the remaining studies were performed on a combination of both genders. The quality of studies was medium to high, with scores ranging from 4 to 9.…”

“…In the pooled analysis of all eligible studies, Hg levels were significantly higher in T2DM patients compared with non-T2DM controls (random effects, SMD = 1.07; 95% CI = 0.59 to 1.55, P ≤ 0.001) ( Figure 2 ), with a significant heterogeneity across studies (I2 = 96.1%; P =≤0.001). In the stratified analysis by type of sample, compared with healthy controls, Hg levels were also significantly higher in blood (7 studies [ 16 , 19 , 32 , 40 – 42 , 44 ], SMD = 0.64 μ g/L; 95% CI = 0.05 to 1.22, P =0.03) and hair (3 studies [ 14 , 33 , 41 ], SMD = 3.15 μ g/L; 95% CI = 1.49 to 4.82, P ≤ 0.001) of patients with T2DM, but not in urine samples (based on 1 study [ 15 ]) ( Figure 2 ).…”

“…Several mechanisms are introduced such as altering Ca 2+ homeostasis, activation of phosphatidylinositol 3-kinase (PI3K) Akt signaling pathway, and reactive oxygen species (ROS) production [ 5 ]. Some studies have assessed the presence of this metal in diabetic patient's scalp hair [ 14 ], urine [ 15 ], and blood [ 16 – 19 ] to examine any relationships between its levels with T2DM markers, but the results were heterogeneous. While some studies demonstrated positive relationships between T2DM and Hg levels in blood [ 20 – 25 ], urine [ 26 ], hair [ 27 ], and toenail [ 28 ], some other studies did not observe any relationship [ 29 – 36 ].…”