Cell-cell and intracellular lactate shuttles.

Prior research has shown lactate to be a byproduct of anaerobic glycolysis in muscle. However, this understanding did not account for its continuous production and use in aerobic conditions. Established knowledge suggested lactate was a waste product, not a functional substrate. That uncertainty drove the need to re-examine lactate's role in energy metabolism. No prior work had resolved how lactate functions as both a fuel and a signaling molecule. This gap motivated a closer look at lactate shuttles across and within cells. Researchers proposed lactate may act as a substrate and signaling agent in multiple tissues. This paper aims to clarify lactate's role in aerobic metabolism and intercellular communication.

The study aims to explore lactate's function beyond anaerobic conditions. It focuses on how lactate serves as a substrate and signaling molecule. The researchers investigate lactate shuttles in both intracellular and intercellular contexts. They examine how lactate is exchanged between muscle fibers and other organs. The goal is to understand lactate's role in maintaining redox balance and metabolic regulation. The study also addresses how lactate influences mitochondrial function and gene expression. It seeks to demonstrate the interconnected nature of glycolytic and oxidative pathways. This work challenges the outdated view of lactate as a mere waste product.

The researchers reviewed existing literature on lactate metabolism. They analyzed lactate shuttles between white and red muscle fibers. They also considered exchanges between muscle and heart, brain, liver, and kidneys. The study examined intracellular shuttles involving mitochondria and peroxisomes. They looked at lactate's impact on redox state and ROS generation. The team assessed lactate's role in inhibiting lipolysis through G-protein receptors. They evaluated how lactate accumulation affects MCT1 and mitochondrial gene expression. The analysis included in vitro and in vivo studies to support their conclusions.

Lactate shuttles exist between glycolytic and oxidative muscle fibers. Lactate is exchanged between working muscle and heart, brain, liver, and kidneys. Mitochondria and peroxisomes participate in intracellular lactate shuttles. Lactate exchanges influence cell redox state and may generate ROS. High lactate levels in blood reduce glucose and FFA utilization. Lactate binding to G-protein receptors in adipocytes inhibits lipolysis. In vitro, lactate increases MCT1 and mitochondrial reticulum gene expression. These findings show lactate is a preferred substrate and signaling molecule.

The authors propose lactate shuttles are essential for metabolic coordination. They argue glycolytic and oxidative pathways are linked, not alternative. Lactate serves as both a substrate and a signaling agent in multiple tissues. The study highlights lactate's role in maintaining redox balance and energy homeostasis. Researchers suggest lactate influences mitochondrial function and gene expression. They note lactate's impact on FFA availability through G-protein receptor binding. The findings challenge the traditional view of lactate as a waste product. The authors conclude lactate is a central component of aerobic metabolism.