Signal transducer and activator of transcription 3 (STAT3) exists in the cytoplasm, nucleus, mitochondria, and mitochondria associated endoplasmic reticulum membranes, which is a signal transduction protein involved in various physiological processes such as cell proliferation, differentiation, migration, and immune regulation. This article provides an overview of the structures and types of STAT3 and the pathways through which STAT3 enters mitochondria, and elaborates on the regulatory effect of STAT3 on cellular homeostasis including the anti-apoptotic effect mediated by endoplasmic reticulum Ca²⁺ transport, the mechanism of action in maintaining mitochondrial function, and the regulatory mechanism on lipid synthesis and catabolism. Furthermore, this paper explores the regulatory mechanism of STAT3 on meat color from the perspective of regulating hematopoietic stem cells, skeletal muscle, mitochondrial homeostasis, and lipid synthesis and metabolism in order to provide a theoretical reference for improving meat color.

Postmortem muscle is highly susceptible to oxidative conditions, thus leading to deterioration of meat quality in terms of tenderness, color, and water-holding capacity (WHC). Therefore, the regulation of the oxidation mechanism is a major concern in research on postmortem meat quality. Reactive nitrogen species (RNS) are free radicals and nitro compounds with high oxidation activity derived from the interaction between nitric oxide (NO) and compounds including reactive oxygen species (ROS). RNS not only regulates mitochondria to promote cellular metabolic function, but also mediates mitochondrial damage to induce cell apoptosis, thereby regulating the quality of postmortem meat. Relevant research results need to be summarized urgently. Therefore, this paper provides an overview of the production and metabolism of RNS in cells, elaborates on the mechanism by which RNS regulates normal physiological functions of cells through mitochondria, induces cell apoptosis through causing mitochondrial damage and mediates oxidation mechanism including lipid peroxidation and protein oxidation, and discusses the mechanism by which RNS affect the tenderness, color, and WHC of postmortem muscle. We anticipate that this review will provide a theoretical reference for improving postmortem ageing.