Estimation of Titanium Dioxide Intake by Diet and Stool Assessment among US Healthy Adults

Food-grade titanium dioxide exposure between age groups and in global regions: a systematic review and meta-analysis

Food-grade titanium dioxide (TiO2), also known as food additive E171, is widely used for its opacifying and coloring properties in food, feed, and pharmaceuticals. Despite its ban in food within the European Union (EU), TiO2 remains prevalent globally amidst safety debates. This study conducted a systematic search and meta-analysis to assess oral TiO2 intake across different age groups in the EU, North America, and East Asia. Analyzing ten studies, we found that mean oral TiO2 intake ranged from 0.045 to 10.5 mg/kg body weight (bw)/day, with the lowest exposures in East Asia and a lifelong weighted average TiO2 exposure of 1.43 mg/kgbw/day. Higher TiO2 exposures were observed in children compared to adults, with Standardized Mean Differences (SMD) of 1.05 (general comparison) and 2.15 (ages 3-9 vs. 18-64 years). This discrepancy diminishes with age as adolescents (10-17 years) exposures approach adult levels (SMD = 0.49). The heightened TiO2 exposure in children may be due to lower body weight and higher consumption of TiO2-containing products. Regional disparities in exposure levels reflect dietary habits and legislative standards. Given concerns over TiO2's potential health impacts and regulatory differences, this study provides a comprehensive review to assist in refined health risk assessments.

Absolute quantitative lipidomics reveals the disturbance of lipid metabolism induced by oral exposure of titanium dioxide nanoparticles

The widespread use of titanium dioxide nanoparticles (TiO2 NPs) as a white pigment in consumer goods increases the possibility of its release into the environment, which poses a great health risk to human beings. Many studies have proved the liver damage caused by TiO2 NPs, but the research about the potential effects of TiO2 NPs on liver lipid metabolism has been limited. Therefore, we selected Sprague-Dawley (SD) rats to explore the effects of long-term exposure to TiO2 NPs on lipid metabolism. Rats were exposed to TiO2 NPs at 0, 2, 10, 50 mg/kg body weight daily for 90 consecutive days. Subsequently, absolute quantitative lipidomics was used to ascertain variation of differential lipid metabolites in rat liver and serum. The results showed that TiO2 NPs (50 mg/kg) changed 22 lipid metabolites such as DAG (18:2/20:5) and TAG (58:10/FA18:2) in rat liver. In the serum, the alteration of 119 lipid metabolites such as DAG (18:0/18:2) were more significant. There was a significant correlation between the different lipid metabolites in liver and serum. At the same time, it was observed that the relative expression levels of oxidative stress-related genes Nrf-2 and Ho-1 changed significantly, and they were closely related to differential metabolites. In conclusion, oral exposure of TiO2 NPs has changed the lipid metabolomics of liver and serum, and the strong induction of oxidative stress may be related to it. TAG and DAG are key metabolites and metabolic pathways in two distinct biological samples, serving as potential indicators of liver injury to a certain extent.

Titanium dioxide nanoparticles induce apoptosis through ROS-Ca2+-p38/AKT/mTOR pathway in TM4 cells

Titanium dioxide nanoparticles (TiO2 NPs) can cause apoptosis in TM4 cells; however, the underlying mechanism has not been entirely elucidated. The purpose of this study was to investigate the effects of TiO2 NPs on ROS, Ca2+ level, p38/AKT/mTOR pathway, and apoptosis in TM4 cells and to evaluate the role of Ca2+ in p38/AKT/mTOR pathway and apoptosis. After exposure to different concentrations (0, 50, 100, 150, and 200 μg/mL) of TiO2 NPs for 24 h, cell viability, ROS, Ca2+ level, Ca2+-ATPase activity, p38/AKT/mTOR pathway-related proteins, apoptosis rate, and apoptosis-related proteins (Bax, Bcl-2, Caspase 3, Caspase 9, and p53) were detected. The ROS scavenger NAC was used to determine the effect of ROS on Ca2+ level. The Ca2+ chelator BAPTA-AM was used to evaluate the role of Ca2+ in p38/AKT/mTOR pathway and apoptosis. TiO2 NPs significantly inhibited cell viability, increased ROS level, and elevated Ca2+ level while suppressing Ca2+-ATPase activity. TiO2 NPs regulated the p38/AKT/mTOR pathway via increasing p-p38 level and decreasing p-AKT and p-mTOR levels. TiO2 NPs significantly enhanced the apoptosis. NAC attenuated Ca2+ overload and reduction in Ca2+-ATPase activity caused by TiO2 NPs. BAPTA-AM alleviated TiO2 NPs-induced abnormal expression of p38/AKT/mTOR pathway-related proteins. BAPTA-AM assuaged the apoptosis caused by TiO2 NPs. Altogether, this study revealed that TiO2 NPs elevated intracellular Ca2+ level through ROS accumulation. Subsequently, the heightened intracellular Ca2+ level was observed to exert regulation over the p38/AKT/mTOR pathway, ultimately culminating in apoptosis. These results provides a complementary understanding to the mechanism of TiO2 NPs-induced apoptosis in TM4 cells.

Stool titanium dioxide is positively associated with stool alpha-1 antitrypsin and calprotectin in young healthy adults

Titanium dioxide (TiO2/E171) is used widely in foods, primarily as a food additive. Animal models have shown that chronic TiO2 exposure may disturb homeostasis of the gastrointestinal tract by increasing gut permeability, inducing gut inflammation, and increasing the likelihood of microbial infection. Adults have a wide range of ingested TiO2,which span two to three orders of magnitude, with a small portion of individuals consuming near gram quantities of TiO2/day. However, research on the health effects of chronic ingestion of TiO2/E171 in humans is limited. We hypothesized that regularly ingested TiO2/E171 is associated with increased gut inflammation and gut permeability in healthy adults. We tested this hypothesis in a cross-sectional design by measuring clinically established stool markers of gut inflammation (calprotectin, lactoferrin) and gut permeability (alpha-1 antitrypsin; A1AT) in 35 healthy adults, and comparing these markers between relatively high and low TiO2 exposure groups. Participants were stratified by TiO2 stool content (high dry stool TiO2 content: 0.95-9.92 μg/mg, n = 20; low content: 0.01-0.04 μg/mg; n = 15). Differences in gut health markers were tested between high and low exposure groups by independent samples t-test or Mann-Whitney U test. Multivariable linear regression was used to assess the association between TiO2 in dry stool and measured stool alpha-1 antitrypsin (A1AT). Participants in the high stool TiO2 group had greater stool A1AT (42.7 ± 21.6 mg/dL; median: 38.3; range: 1.0-49.2 mg/dL), compared to the low TiO2 group (22.8 ± 13.6 mg/dL; median: 20.9; range: 8.7-93.0 mg/dL), P = 0.003. There was also greater stool calprotectin in the high TiO2 group (51.4 ± 48.6 μg/g; median 29.2 μg/g; range: 15.3-199.0 μg/g) than in the low group (47.5 ± 63.3 μg/g; median 18.8 μg/g; range: 1.6-198.1 μg/g), P = 0.04. No clear difference was observed for lactoferrin (high TiO2 group 1.6 ± 2.1 μg/g; median: 0.68 μg/g; range: 0.01-7.7 μg/g, low TiO2 group: 1.3 ± 2.6 μg/g; median: 0.2; range: 0.01-7.6 μg/g) (P = 0.15). A1AT concentration was positively associated with stool TiO2, after adjusting for confounders (β ± SE: 19.6 ± 7.2; P = 0.01) R2 = 0.38). Community dwelling, healthy adults with the highest TiO2 stool content had higher stool A1AT and calprotectin, compared to those with the lowest TiO2 stool content. Ongoing research is needed to validate these observations in larger groups, and to determine the long-term effects of ingested TiO2 on human gut health, using these and additional health endpoints.