Equine insulin receptor and insulin-like growth factor-1 receptor expression in digital lamellar tissue and insulin target tissues.

The research article investigates the role of hyperinsulinaemia, caused by intake of dietary nonstructural carbohydrate (NSC), in the occurrence of endocrinopathic laminitis in horses. It specifically explores the mRNA expression of the two insulin receptor isoforms, the insulin-like growth factor-1 receptor, and the hybrid version, in the lamellar tissue and other insulin responsive tissues.

Objective of the Study

• The overarching aim of this research was to examine and characterise the expression of InsR-A, InsR-B, IGF-1R, and the Hybrid receptor in the lamellar tissue (LT) and insulin-responsive tissues in horses.
• A further objective was to examine how the intake of dietary nonstructural carbohydrate (NSC) impacts these receptor’s mRNA expressions in LT, skeletal muscle, liver, and two adipose tissues of lean and obese ponies.

Methods Employed in the Study

• This in vivo experiment used lamellar tissue samples, where the researchers applied a quantitative reverse transcription polymerase chain reaction (RT-qPCR) to evaluate the mRNA expression of the receptor.
• Furthermore, immunoblotting was utilized to identify protein expression.
• The researchers used archived LT, skeletal muscle, liver, and adipose tissue from lean and obese mixed-breed ponies fed either a low or high NSC diet for an evaluation period of 7 days.
• The aim was to determine how the body condition and diet affect the receptor expression in different tissues.

Significant Findings

• The results show that the LT does express both InsR isoforms, IGF-1R, and Hybrid.
• Among these, the expression of the IGF-1R gene was more prevalent than either InsR isoform, and the InsR-A expression was more than InsR-B.
• Obesity was found to significantly suppress IGF-1R, InsR-A, and InsR-B mRNA expression in LT and InsR-A in tailhead adipose tissue.
• Alongside this, a high NSC diet was found to reduce the expression of all three receptor types in the liver, and IGF-1R and InsR-A in LT and InsR-A in tailhead adipose tissue.

Study Conclusion

• The study concluded by confirming that the LT expresses IGF-1R, InsR isoforms, and Hybrids.
• However, it also recommends further exploration of these receptors’ functional characteristics and their possible role in endocrinopathic laminitis.