Sedentary horses, like humans, have an increased risk of developing metabolic syndrome characterized by obesity and abnormal elevations in insulin concentrations (hyperinsulinemia). Insulin is a hormone released from the pancreas that is responsible for lowering blood sugar after a meal by promoting the uptake of glucose into tissues. People and animals with insulin resistance are not able to respond normally to the hormone resulting in high blood sugar.   

Sphingolipids are thought to be involved in the development of hyperinsulinemia in horses as well as humans. Ceramides are a type of sphingolipid that can be produced by multiple tissues in the body and are known to block the actions of insulin in tissues. In fact, levels of ceramide are elevated in horses with hyperinsulinemia.   

A recent study published in American Journal of Physiology – Regulatory, Integrative and Comparative Physiology aimed to examine the profile of sphingolipids in the blood, liver and adipose tissues of Icelandic horses (pictured above). Not surprisingly, the types of sphingolipids differed in each of these tissues as well as between different adipose tissue depots. These findings suggest that blood samples may be a poor indicator of ceramide concentrations in the liver and adipose tissues of these animals.

Comparing Icelandic horses with normal levels of insulin to those with hyperinsulinemia, the researchers found that the sphingolipid profile in the plasma and retroperitoneal fat depot, in particular, could be used to predict whether an animal had hyperinsulinemia. Retroperitoneal fat is a type of white visceral fat that is found in the back of the abdominal cavity near the kidneys and intestines.

The findings from this study implicate ceramide-derived from retroperitoneal fat in the development of metabolic syndrome, at least in Icelandic horses.

Source:

E Jorge-Smeding, T Warnken, AJ Grob, K Feige, T Pudert, YH Leung, YY Go, A Kenez. Sphingolipidome of plasma, liver, and adipose tissues and its association with insulin response to oral glucose testing in Icelandic horses. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology. 323(4): R397-R409, 2022. https://doi.org/10.1152/ajpregu.00018.2022

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Categories: Agriculture, Aquaculture, and Livestock, Diet and Exercise