Age-Dependent Increase in Small Intestinal Permeability and Sex-Dependent Absorptive Capacity in Cats (Felis catus)

Age-associated changes in intestinal permeability and function have not been studied in domestic cats, leaving a key factor in the relationship between age and digestive health in cats unexplored. Due to factors not currently understood, mature and senior cats may experience a loss of fat and protein digestibility, along with a loss of body weight (BW), impacting lifespan and quality of life. Therefore, to establish the relationship between age and intestinal health, intestinal permeability and absorptive capacity were quantified in young and senior cats using a differential sugar absorption test (SAT) on cat plasma. A solution containing four different sized sugars was orally administered to 36 healthy mixed-breed domestic shorthair cats (male (n = 21) and female (n = 15)) split into two groups by age, young 2.40 ± 0.758 (n = 21) and senior 11.23 ± 1.896 (n = 15) years (mean ± SD). Blood was collected before and again 3 h after dosage and plasma was analysed using liquid chromatography mass-spectrometry (LC-MS). Intestinal permeability was higher (p = 0.004) in senior cats than young cats, and was not affected by sex (p = 0.288), sampling date (p = 0.652), or BW (p = 0.951). Absorptive capacity was higher (p = 0.033) in male cats than females, and was not affected by age class (p = 0.440), sampling date (p = 0.580), or BW (p = 0.652). In conclusion, intestinal permeability was higher in older cats and suggests age-related changes in intestinal barrier structure and function. These findings highlight the need to further consider increased intestinal permeability as a cause of reduced nutrient digestibility in older cats, offering a new target for interventions to enhance their health and well-being.