Effects of fat feeding and energy level on plasma metabolites and hormones in Shetland ponies.

This research article investigates the effects of a diet supplemented with fats versus a carbohydrate-based diet on lipid metabolism and the enteroinsular axis in Shetland ponies. It was found that a diet enriched with fats, regardless of energy content, significantly reduced plasma triglycerides and improved triglyceride clearance, but impaired glucose tolerance.

Study Objectives and Design

• The primary objective of this study was to understand the impact a fat-enriched diet has on lipid metabolism and the enteroinsular axis (the relationship between the gastrointestinal tract and the insulin-secreting cells of the pancreas) in Shetland ponies, in contrast to a diet rich in carbohydrates.
• The research was conducted in a ‘crossover’ design, allowing the same ponies to be studied under different dietary conditions. This was done in two phases: in the first 10 weeks the ponies were fed according to their caloric requirements and in the following 10 weeks, they were overfed to examine the impact of different energetic content in their diets.

Key Findings

• The study found that a diet rich in fats lead to a significant decrease in plasma triglycerides (fat in the blood), along with an increase in lipoprotein lipase activity, an enzyme that breaks down fat. These findings occurred regardless of the fat-enriched diet’s caloric content.
• The ponies on the fat-enriched diet showed higher blood glucose levels following an oral glucose load, indicating impaired glucose tolerance compared to ponies on a carbohydrate-based diet.
• Interestingly, when given an oral glucose administration after being on the high-energy, fat-rich diet, there was a dramatic 25-fold increase in insulin levels in the ponies’ plasma. Elevated insulin levels can affect numerous bodily functions and may lead to the development of insulin resistance.
• Another noteworthy finding was that glucose-dependent insulinotropic polypeptide (GIP) levels, a hormone that stimulates insulin secretion, were higher in ponies on a fat-enriched diet.

Implications

• Despite the positive influence on triglyceride clearance, the observed detrimental effect on glucose tolerance is an important consideration for the nutrition management of ponies.
• This research provides insights into how dietary fat influences lipid metabolism and the enteroinsular axis in Shetland ponies and lays a foundation for future studies, particularly in the context of equine hyperlipaemia, a serious metabolic disorder in horses. However, the authors recommend further studies involving diseased animals for a more comprehensive understanding.