Effect of exercise, training, circadian rhythm, age, and sex on insulin-like growth factor-1 in the horse.

The research paper investigates the factors influencing the concentration of Insulin-like growth factor-1 (IGF-1), a potential diagnostic or forensic marker in horses, such as the impact of exercise, training, circadian rhythm, age, and sex.

Objective and Methodology

• The researchers aimed to comprehend the physiological regulation of IGF-1 in horses to increase its diagnostic, selection, and forensic utilization.
• The study was conducted on six geldings (castrated horses) over a nine-week training program. The research involved monitoring IGF-1 concentrations throughout different physical and environmental scenarios.

Investigation of Factors Affecting IGF-1 Concentration

• The report shows that regular fitness training maintained a mean IGF-1 concentration of 302 +/- 29 ng/mL in horses. This means that the concentration of IGF-1 remained relatively stable irrespective of fitness training.
• When the researchers compared the pre-and post-exercise values of IGF-1, they found that moderate or high-intensity exercise had no significant impact on IGF-1 concentrations.
• The study also investigated the impact of the time of day by tracking IGF-1 concentration changes over a 24-hour period. While they observed some variation in concentrations, they found no clear diurnal rhythm affecting IGF-1 levels.

Population Study and Effect of Sex and Age

• The researchers measured IGF-1 concentrations in a large population of thoroughbred horses (1,880) on three continents to gain a broader understanding of the implicated factors.
• On factors such as sex, the global mean IGF-1 concentration was slightly higher in gonad-intact males (336 +/- 5.6 ng/mL) compared to females (303 +/- 3.2 ng/mL) or geldings (302 +/- 3.2 ng/mL). This suggests that intact male horses may inherently have a higher concentration of IGF-1.
• The study also evaluated age as an influencing factor. In mares and geldings, the team observed a gradual decrease in IGF-1 concentrations with advancing age. However, the aging impact on IGF-1 concentration was not as apparent in stallions.

Research Findings

• The study concluded that IGF-1 concentrations in horses are stable when compared with growth hormone (GH) concentrations. This information is useful in suggesting that a meaningful measure of IGF-1 status can be taken from a daily serum sample without disruptions.