# Effects of Blue Light Exposure on Hepatic Inflammation and Gut Microbiota in Mice Consuming a High-Fat, High-Fructose Diet

## TL;DR

This study shows that long-term blue light exposure worsens fatty liver disease in mice on a high-fat, high-fructose diet by increasing inflammation and oxidative stress.

## Contribution

The study reveals blue light exposure exacerbates fatty liver disease under unhealthy diets, independent of the TLR4 pathway.

## Key findings

- Blue light exposure increased oxidative stress and inflammation in the liver of mice on a high-fat, high-fructose diet.
- Blue light exposure altered gut microbiota composition in mice.
- The TLR4 signaling pathway was not involved in the observed effects of blue light exposure.

## Abstract

Background: High-fat or high-fructose consumption may cause abnormal lipid accumulation in the liver, resulting in fatty liver disease, and the intervention of other stress factors may accelerate the progression of this condition. Many studies have demonstrated that long-term exposure to blue light may not only injure the eyes but also cause an increase in oxidative stress, which has been related to metabolic and gut microbiota disorders. However, current research on whether blue light exposure exacerbates fatty liver disease still remains limited. Objective: Therefore, the aim of this study is to investigate the effect of a high-fat, high-fructose diet combined with blue light exposure on fatty liver disease progression. Method: In the first part of the study, we observed that 16 weeks of blue light exposure alone did not achieve significant effects in the liver of male, female, or OVX mice. Therefore, in the second part, we fed ICR mice a high-fat, high-fructose (HFHF) diet to investigate the effect of simultaneous 16-week exposure to blue light. The mice were assigned to three groups, control group (C), HFHF diet group (H), and HFHF diet plus blue light exposure group (HB), to investigate the intervention of unhealthy diet composition and blue light exposure on hepatic oxidative and inflammatory makers and gut microbiota composition. Results: The results showed that exposure to blue light exacerbates oxidative stress (hepatic MDA, p < 0.009), and inflammatory damage (lobular inflammation score, p < 0.0001; hepatic TNF-α, p = 0.0074) caused by an HFHF diet, but this mechanism is not mediated by the TLR4 signaling pathway. Furthermore, exposure to blue light may also partially affect the composition of the gut microbiota. Conclusions: The results of the study suggested that under unhealthy dietary conditions, long-term blue light exposure may be one of the risk factors accelerating the progression of fatty liver disease.