# Multi-Omics Analysis and Comparison of the Developmental Characteristics of Muscle Fiber Types Between Huainan and Large White Pigs in Early Postnatal Period

## TL;DR

This study compares muscle fiber development in two pig breeds, finding that Huainan pigs have better meat quality due to higher oxidative fibers and specific genes and metabolites.

## Contribution

The study identifies a novel AMPK-mediated gene-metabolite loop involving KLF4 and citrulline that enhances mitochondrial function and muscle fiber differentiation in Huainan pigs.

## Key findings

- Huainan pigs have a higher proportion of oxidative muscle fibers, supporting superior aerobic metabolism and meat quality.
- Key genes like KLF4, NOS1, SH3KBP1, and TRARG1 are upregulated in Huainan pigs, influencing mitochondrial function and metabolism.
- Metabolites such as carnosine, citrulline, and glycerol-3-phosphate are elevated in Huainan pigs, promoting energy supply and muscle fiber transformation.

## Abstract

This study compared the characteristics of muscle fiber types of the longissimus dorsi muscle between the Huainan pigs and the Large White pigs at four postnatal stages (0, 7, 14, and 21 days). Using myosin ATPase staining, transcriptomics, and metabolomics analysis, we found that Huainan pigs had a higher proportion of oxidative muscle fibers, which support superior aerobic energy metabolism and contribute to tender, flavorful meat. Key genes such as KLF4, NOS1, SH3KBP1, and TRARG1 showed higher expression in Huainan pigs, regulating muscle fiber type composition by enhancing mitochondrial function, promoting nitric oxide synthesis, and modulating nutrient metabolism. Metabolomics analysis revealed significantly higher levels of carnosine, citrulline, and glycerol-3-phosphate in Huainan muscle, which enhance energy supply, antioxidant capacity, and fatty acid oxidation to promote muscle fiber transformation. Notably, an “energy-sensing” regulatory loop involving KLF4 and citrulline (mediated by the AMPK pathway) was identified in Huainan pigs, synergistically enhancing mitochondrial function and fiber differentiation. These findings elucidate how genetic background influences muscle development and meat quality, providing novel targets for breeding high-quality pork breeds.

To investigate the molecular mechanisms underlying muscle fiber development in different pig breeds and their impact on meat quality, this study collected the longissimus dorsi muscle of the indigenous Huainan pig and the commercial Large White pig at four developmental stages (0, 7, 14, and 21 days postnatal). Muscle fiber types were identified using myosin ATPase staining, while transcriptomics and non-targeted metabolomics were employed to analyze differences in gene expression and metabolite composition. The results showed that the Huainan pig had a higher proportion of oxidative muscle fibers, indicating superior aerobic metabolic capacity and meat quality. Transcriptome data identified 18 differentially expressed genes common to both pig breeds, including KLF4, NOS1, SH3KBP1, and TRARG1, which were upregulated in Huainan pigs to regulate muscle fiber type composition and meat quality by influencing mitochondrial function, nitric oxide synthesis, and glucose/lipid metabolism. Metabolomics analysis revealed significantly elevated levels of carnosine, citrulline, serine, and glycerol-3-phosphate in Huainan pigs, which are associated with metabolic pathways promoting muscle fiber transformation via enhancing energy supply, antioxidant capacity, and fatty acid oxidation. Notably, integrated transcriptome–metabolome analysis showed that oxidative metabolism genes (e.g., KLF4) and metabolites (e.g., citrulline) formed an AMPK-mediated ‘gene–metabolite’ loop in Huainan pigs, which synergistically promotes mitochondrial function and fiber differentiation. In summary, this study provides new insights into the molecular mechanisms underlying meat quality differences between pig breeds and offers a theoretical basis for the breeding and development of high-quality pork.