Plasma carnosine concentration: diurnal variation and effects of age, exercise and muscle damage.

The research investigates the relationship between plasma carnosine concentration and factors including age, exercise, and muscle damage in Thoroughbred horses. It concludes that the plasma carnosine levels increase after exercise-induced muscle damage and could potentially serve as a new clinical indicator for muscle damage.

Study Overview

The study was conducted as a component of a broader study focusing on carnosine metabolism and function in Thoroughbred horses. The researchers aimed to explore if plasma carnosine concentration could be used to report on muscle carnosine status.

• The study acknowledges that, unlike in humans, carnosine exists in horse plasma. That implies the absence of plasma carnosinase, an enzyme that serves to degrade carnosine in humans.
• A major area of focus was the effect of age on plasma carnosine concentration. Noticeably higher concentrations were found in horses of 3 years of age and older compared to foals and yearlings, implying a correlation between age and carnosine concentration in horses.
• The study also determined that there were no significant fluctuations in plasma carnosine concentration within a day among fed and fasting horses.

Effects of Exercise on Carnosine levels

Another element of the research was exploring exercise and its effects on plasma carnosine concentration.

• The study reported a small but significant increase in plasma carnosine concentrations following intense exercise.
• However, following the onset of exercise-induced rhadomyolysis (ERS) — a condition associated with rapid muscle breakdown — substantially greater increases in plasma carnosine were observed.

Plasma Carnosine as a Potential Indicator of Muscle Damage

By looking at the relationship between elevated plasma carnosine and increased plasma enzymes (CK and AST activities), the researchers observed an apparent association that triggered subsequent conclusions.

• The study concludes an elevated plasma carnosine level, especially during instances of ERS, could potentially signal muscle damage. However, the severity of the conditions could not be determined solely by checking plasma carnosine concentrations.
• Moreover, plasma carnosine measurements combined with plasma taurine measurements might indicate selective type 1 or type 2 muscle fibre damage.
• Despite the potential of plasma carnosine measurements as a clinical indicator of muscle damage, it’s important to note that due to the complexity of the analytical process, this approach would likely be limited to specialist research centers.