Bile acid metabolism in hereditary forms of hypertriglyceridemia: evidence for an increased synthesis rate in monogenic familial hypertriglyceridemia.

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Abstract
This study was undertaken to characterize bile acid metabolism in hereditary forms of hypertriglyceridemia. Ten hypertriglyceridemic patients (type IV phenotype) with familial combined hyperplipidemia and 7 patients with monogenic familial hypertriglyceridemia (FHTG) were compared with 18 healthy controls; all subjects were males. Pool size, synthesis rate, and fractional catabolic rate of cholic and chenodeoxycholic acids were determined with an isotopic dilution technique. Patients with FHTG had synthesis rates of cholic acid, chenodeoxycholic acid, and total bile acids above those seen in normal controls (P < 0.001); also the fractional catabolic rates of both bile acids were increased (P < 0.001). In contrast, bile acid kinetic parameters were-with one exception-within normal limits in patients with familial combined hyperlipidemia. The abnormality of bile acid metabolism could also be identified in a normolipidemic individual presumed to carry the gene for FHTG. The postprandial rise of serum bile acids was blunted in FHTG, indicating that the intestinal uptake of bile acids may be deficient in this condition. We conclude that FHTG, but not familial combined hyperlipidemia, is frequently associated with a defective regulation of bile acid synthesis, resulting in an abnormally high production rate of bile acids. It is hypothesized that this abnormality is important for the subsequent development of hypertriglyceridemia.