Influence of age and sex on plasma lipid and lipoprotein concentrations and associated enzyme activities in cats

Objective-To determine effects of age and sex on plasma lipid and lipoprote in metabolism in cats. Animals-33 kittens and 16 adolescent, 23 adult, and 10 senior cats. Procedure-Plasma concentrations of cholesterol, triglyceride, and lipoprote in-cholesterol and activities of lipoprotein lipase, hepatic lipase, and le cithin:cholesterol acyl transferase (LCAT) were measured and compared withi n and among groups. Results-Plasma cholesterol and triglyceride concentrations were significant ly higher in 5- and 7-week-old kittens, compared with the same kittens afte r weaning and cats in the other age groups. Cholesterol concentration was s ignificantly less in 20-week-old kittens, compared with adolescent and adul t cats. Lipid and lipoprotein-cholesterol concentrations were not significa ntly different among the adolescent, adult, and senior groups, nor did sex influence lipid and lipoprotein-cholesterol concentrations in these groups. Activities of lipoprotein and hepatic lipases were significantly less in s enior cats, compared with the other groups. Activity of LCAT was highest in 20-week-old kittens and was greater in sexually intact adult and adolescen t females, compared with their male counterparts. After castration, activit ies of hepatic lipase and LCAT significantly decreased in adolescent male c ats. Conclusions and Clinical Relevance-The upper limits of reference ranges for plasma cholesterol and triglyceride concentrations should be increased for kittens < 8 weeks of age. Low cholesterol concentrations in adolescent cat s likely reflect high tissue demands for growth and steroidogenesis. Decrea se in lipoprotein and hepatic lipase activity in senior cats could predispo se this age group to hypertriglyceridemia, particularly in insulin-resistan t cats or those fed a high fat diet.