Molecular characterisation of carbohydrate digestion and absorption in equine small intestine.

The research article focuses on the molecular mechanisms of carbohydrate digestion and absorption in the equine small intestine. The study posits that the digestion and absorption of dietary carbohydrates in a horse’s small intestine, when done efficiently, can provide a substantial fraction of the animal’s energy required for metabolism.

Study Objective and Methodology

• The main objective of the study was to understand the mechanisms, properties, and locations of carbohydrate digestive and absorptive functions in the equine small intestine.
• The researchers set out to determine this at a molecular level, focusing on the small intestinal brush-border membrane of the horse.
• The study involved evaluating expression levels of certain digestive enzymes and a specific transport protein in different sections of the small intestine.

Key Findings

• The enzymes sucrase, lactase, and maltase which break down certain types of sugars were found to be expressed at varying levels along the length of the intestine.
• The study revealed that D-glucose is moved across the equine intestinal brush-border membrane via a Na+/glucose cotransporter type 1 isoform (SGLT1), which has high affinity but low capacity.
• The rate of transport of glucose was the highest in the duodenum, followed by the jejunum and the ileum.

Additional Research and Implications

• The researchers cloned and sequenced the cDNA encoding equine SGLT1. Comparison with SGLT1 sequences from other species pointed to an 85-89% similarity at the nucleotide level, and 84-87% similarity at the amino acid level.
• They also found that the amount of functional SGLT1 protein correlated with the abundance of SGLT1 mRNA along with the length of the small intestine.
• This suggests that glucose absorption primarily occurs in the proximal intestine in horses maintained on traditional grass-based diets. It also indicates that SGLT1 expression is regulated at the mRNA level along the length of the intestine.
• The data from this study provides the first insights on the capacity of the equine intestine to digest and absorb soluble carbohydrates. This information could potentially aid better feed management, and contribute to the development of pharmaceuticals and diet supplementation for horses, especially following intestinal resection.