IDENTIFICATION AND CHARACTERIZATION OF A FAMILIAL HYPERLIPOPROTEINEMIA IN MINIATURE SCHNAUZER DOGS

The plasma lipoproteins of 6 clinically healthy lipemic miniature schnauzers (HLMS), 11 clinically healthy non-lipemic miniature schnauzers (HNMS), and 3 diabetic lipemic miniature schnauzers (DLMS) were evaluated through the use of ultracentrifugation, lipoprotein electrophoresis, and biochemical tests. For comparison, the plasma lipoproteins of 8 healthy dogs of other breeds (HDOB) and 3 diabetic dogs of other breeds (DDOB) were similarly evaluated. Lipemia ranged from slight to marked in the HLMSs, and was marked in the DLMSs. The HDOBs and DDOBs all had clear plasma. Four of the HNMSs had historical evidence of fasting lipemia, yet had clear plasma when sampled for the present study. The lipemic miniature schnauzers (HLMSs and DLMSs) all had hypertriglyceridemia associated with excess VLDL, and the most markedly lipemic dogs had chylomicronemia as well. Hypercholesterolemia and hyperphospholipidemia were present in dogs with marked lipemia; all or most of these excess lipids were associated with the VLDL and chylomicrons. Four of the HLMSs lacked detectable amounts of LDL. Four of the HNMSs had mild hypertriglyceridemias associated with increased amounts of VLDL, and all 4 of these dogs lacked LDL. Two of the hypertriglyceridemic HNMSs were dogs with historical evidence of fasting lipemia. The plasma lipoproteins of the DDOBs were essentially indistinguishable from those of the HDOBs, whereas the lipoproteins of the DLMSs were very similar to those of the most markedly lipemic HLMSs. The results indicate that the hyperlipidemia of miniature schnauzers is due to a familial disorder resulting in delayed clearance of triglyceride-rich lipoproteins from the circulation. It appears likely that, while some affected dogs have only a type IV hyperlipoproteinemia due to the effects of the familial disorder alone, others have converted to type V hyperlipoproteinemia because of complicating conditions, such as a high fat diet or development of acquired diseases that also cause hypertriglyceridemia. The familial disorder of the miniature schnauzers bears similarities to familial hypertriglyceridemia in humans. Affected dogs may be at risk of developing pancreatitis and/or diabetes mellitus