1. Five patients with hyperlipoproteinaemia type IV and five normolipaemic controls were maintained on diets containing either a fat or a carbohydrate content of approximately 60%. Leg exchanges of triglycerides, free fatty acid (NEFA), glucose and other metabolites were measured in the basal state. The metabolic response to an intravenous glucose load and the turnover of intravenously infused [14C]oleic acid were determined. Individual fatty acids were analysed in plasma NEFA and very-low-density lipoprotein triglyceride.
2. No differences were detected between patients and controls with regard to leg uptake of triglyceride or NEFA on either diet. On shifting from a fat-rich to a carbohydrate-rich diet, the control subjects showed reduced values for arterial NEFA and for NEFA turnover, accompanied by a lowered release of NEFA and glycerol from the leg. In patients, on the other hand, the arterial concentration and turnover of NEFA remained unchanged and the release of glycerol from the leg increased. Glucose administration gave a less-pronounced fall of arterial NEFA on either diet in the patients and the incorporation of [14C]oleic acid into triglycerides after glucose administration was more marked than in the controls.
3. No difference in net uptake of triglyceride by the leg was demonstrable between patients and controls.
4. It is concluded that hyperlipaemic patients show an altered metabolic response to a carbohydrate-rich diet, possibly contributing to the development of a hyperlipaemic state, and that acute glucose loading results in a greater incorporation of circulating NEFA into very-low-density lipoproteins in these patients.