Zinc deficiency increases lung inflammation and fibrosis in obese mice by promoting oxidative stress.

Background: Zinc deficiency can lead to multiple organ damage. In this study, we investigated the effects of zinc deficiency on obesity-related lung damage.

Methods: C57BL/6 J mice were fed a diet with differing amounts of zinc and fat over a 6-month period. Palmitic acid was used to stimulate A549 cells to construct a high-fat alveolar epithelial cell model. Western blotting and histopathological staining were performed on animal tissues. Nuclear expression of nuclear factor erythroid 2-related factor 2 (Nrf2) was detected in cultured cells. A reactive oxygen species (ROS) assay kit was used to detect intracellular ROS. Furthermore, Nrf2 siRNA was used to examine zinc deficiency effects on A549 cells.

Results: Pathological results showed significant damage to the lung structure of mice in the high-fat and low-zinc diet group, with a significant increase in the expression of inflammatory (IL-6, TNF-α) and fibrosis (TGFβ1, PAI-1) factors, combined with a decrease in the expression of Nrf2, HO-1 and NQO1 in the antioxidant pathway. In A549 cells, high fat and low zinc levels aggravated ROS production. Western blot and immunofluorescence results showed that high fat and zinc deficiency inhibited Nrf2 expression. After Nrf2-specific knockout in A549 cells, the protective effect of zinc on oxidant conditions induced by high fat was reduced. Phosphorylated Akt and PI3K levels were downregulated on the high-fat and low-zinc group compared with the high-fat group.

Conclusions: Zinc attenuated lung oxidative damage in obesity-related lung injury and Nrf2 activation is one of the important mechanisms of this effect.

General Significance: Regulating zinc homeostasis through dietary modifications or supplemental nutritional therapy can contribute to the prevention and treatment of obesity-related lung injury.