Investigation of the expression and localization of glucose transporter 4 and fatty acid translocase/CD36 in equine skeletal muscle.

The research investigates the location and level of expression of glucose transporter 4 (GLUT4) and fatty acid translocase (FAT/CD36) in horse skeletal muscle, with results indicating that their expression varies depending on the type of muscle fiber.

Methodology

• The study was conducted on muscle biopsy specimens obtained from 5 healthy Dutch Warmblood horses. The study sites were the vastus lateralis, pectoralis descendens, and triceps brachii muscles.
• The scientists used a method of cryosectioning, a technique where the tissue specimens are frozen to facilitate their cutting into thin slices for microscopic analysis.
• The cryosections were then stained using either combinations of GLUT4 and myosin heavy chain (MHC) specific antibodies or FAT/CD36 and MHC antibodies.
• This staining enabled the researchers to visualize and observe the specific fiber expression of GLUT4 and FAT/CD36 in horse skeletal muscle using indirect immunofluorescent microscopy.

Findings

• Analysis of the stained sections revealed that GLUT4 was mostly expressed in the cytosol of fast type 2B fibers of the equine skeletal muscle. However, several type 1 fibers in the vastus lateralis muscle also expressed GLUT4.
• FAT/CD36 was found to be strongly expressed in all muscle fibers examined, particularly in the sarcolemma (a fine transparent tubular sheath that envelops the fibers of skeletal muscles) and capillaries.
• Though type 1 muscle fibers also showed some internal presence of FAT/CD36, no internal FAT/CD36 presence was found in type 2 muscle fibers.

Conclusions

• The study concludes that in horse skeletal muscles, GLUT4 and FAT/CD36 are expressed in a fiber type-specific manner. This means their expression is not uniform across different types of muscle fibers, but varies depending on the specific type of muscle fiber.
• This variation in expression indicates the potential for unique metabolic functions and requirements in different types of muscle fibers. It opens up the possibility for further investigation into these variations and the implications they might have on horse muscle physiology.