# Mitochondrial Haplogroups Influence Mitochondrial Structure and Function, Oxidative Stress, Autophagy, and Lipid Metabolism of Chicken Hepatocytes in Response to Energy Stimulation

## TL;DR

This study shows how different mitochondrial haplogroups in chickens affect liver cell function, stress response, and fat metabolism when exposed to energy changes.

## Contribution

The study reveals how mitochondrial haplogroups influence maternal effects through changes in mitochondrial structure, autophagy, and lipid metabolism in chicken hepatocytes.

## Key findings

- E-group mitochondria showed shorter perimeters and lengths during refeeding compared to A-group.
- E-group cells had higher reactive oxygen species levels and lower autophagy markers after energy stimulation.
- Mitochondrial haplogroups affect lipid accumulation and structural integrity in response to fasting and refeeding.

## Abstract

This article reports the effects of mitochondrial haplogroups on the structure and function of mitochondria, the level of oxidative stress, and fat content in chicken hepatocytes. Mitochondrial haplogroups are classified based on differences in the base sequences of the mitochondrial genome, and since mitochondria are important carriers of maternal effects, mitochondrial haplogroups may have an impact on maternal effects. The aim of this study was to elucidate the mechanism by which mitochondrial haplogroups affect maternal effects. By comparing the differences in mitochondrial structure and function, oxidative stress levels and fat content between mitochondrial haplogroups in chicken hepatocytes stimulated by nutrient or energy factors, this study found that the capabilities of mitochondrial fusion, renewal and autophagy, the resistance to oxidative stress, the capacity for fat deposition, and the ability to cope with energy stress in the cell were affected by mitochondrial haplogroups. These findings contribute to the understanding of how maternal effects influence animal physiological function and how mitochondrial haplogroup-based selection can improve animal production performance.

Mitochondria are crucial carriers of maternal effects, and their function is closely related to energy metabolism and disease occurrence. Previous studies have shown that chickens with different mitochondrial haplogroups exhibit differences in production performance, but the underlying mechanism remains unclear. This study investigates the differences in mitochondrial structure and function-related indices between the A and E mitochondrial haplogroups (referred to as A-group and E-group) in recessive white-feathered chickens. It was achieved using in vivo fasting/refeeding models and an in vitro model of treating hepatocytes with nutritional factors (glucose and fatty acids). In vivo study indicated that compared to A-group chicken hepatocytes, E-group hepatocytes had shorter perimeters of mitochondria and shorter lengths of mitochondria associated with the endoplasmic reticulum membrane during refeeding (p < 0.05); mitochondria were more abundant (p = 0.05) but displayed compromised structural integrity during fasting; mitochondrial swelling was more severe during both refeeding and fasting (p < 0.01, p < 0.05); the protein level of mitofusin 2 (MFN2) was lower during fasting (p < 0.05); and there were more vacuoles and lipid accumulation in liver sections during refeeding (p < 0.05). In cultured hepatocytes, compared to A-group cells, E-group cells had higher reactive oxygen species (ROS) level after oleic acid treatments (p < 0.001); the protein level of microtubule-associated protein 1A/1B-light chain 3 beta (LC3) was lower after glucose treatment (p < 0.01), and the protein levels of MFN2 and LC3 were lower after oleic acid treatment (p < 0.01, p < 0.05). These findings suggest that mitochondrial haplogroups are associated with mitochondrial structure and function, oxidative stress, autophagy, and lipid metabolism of chicken hepatocytes in response to energy stimulation. The findings may explain how mitochondrial haplogroups affect chicken production performance.