Members of a domestic cat colony with chylomicronemia share many phenotypic features with human lipoprotein lipase (LPL) deficiency. Biochemical analysis reveals that these cats do have defective LPL catalytic activity and have a clinical phenotype very similar to human LPL deficiency. To determine the molecular basis underlying this biochemical phenotype, we have cloned the normal and affected cat LPL cDNAs and shown that the affected cat has a nucleotide change resulting in a substitution of arginine for glycine at residue 412 in exon 8. In vitro mutagenesis and expression studies, in addition to segregation analysis, have shown that this DNA change is the cause of LPL deficiency in this cat colony. Reduced body mass, growth rates, and increased stillbirth rates are observed in cats homozygous for this mutation. These findings show that this LPL deficient cat can serve as an animal model of human LPL deficiency and will be useful for in vivo investigation of the relationship between triglyceride rich lipoproteins and atherogenic risk and for the assessment of new approaches for treatment of LPL deficiency, including gene therapy. ( J. Clin. Invest.

Primary hyperlipoproteinaemia (hyperchylomicronaemia with slight very low density lipoprotein elevation) is described in two related male cats. Fasting hyperlipaemia, lipaemia retinalis and subcutaneous xanthomas were detected on clinical examination. In one cat lipoprotein lipase activity measured after heparin activation was significantly reduced compared to the response in a normal cat. The lipid and protein concentration in each of the lipoprotein classes and the lipoprotein distribution of the two hyperlipaemic cats, two normolipaemic relations and 16 normolipaemic adult cats were determined. Plasma cholesterol and triglyceride levels were elevated in the hyperlipaemic cats with the major proportion of triglyceride and cholesterol being present in chylomicrons whereas in normolipaemic cats the majority of triglyceride was contained in very low density lipoprotein. High density lipoprotein was the predominant lipid carrier in both the normolipaemic and the hyperlipaemic cats but the protein content in chylomicrons was elevated in the two affected cats. The lipoprotein distribution in normal cats in this study agrees with previously reported values. The hyperlipaemic cats showed many of the features of familial lipoprotein lipase deficiency (type I hyperlipoproteinaemia, exogenous chylomicronaemia) which is an inherited disease in man.

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Primary hyperlipoproteinaemia (hyperchylomicronaemia) with a slight increase in very low density lipoprotein) is described in 20 cats. Fasting hyperlipaemia, lipaemia retinalis and peripheral neuropathies were the most frequently detected clinical signs. The disease is thought to be inherited as an autosomal recessive trait but the exact mode of inheritance has not been determined. Affected cats showed reduced lipoprotein lipase activity measured after heparin activation compared with the response in normal cats. Plasma triglyceride and cholesterol were increased in all the cats with the major proportion of triglyceride and cholesterol being present in chylomicrons. The peripheral nerve lesions were caused by compression of nerves by lipid granulomata. It is probable that the lipid granulomata result from trauma because the nerves most often affected were at sites like the spinal foraminae where they were susceptible to trauma.

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