Cholesterol and Bile Pigment Changes Incident to Diets Low in Protein.

Abstract

Variable elevations of blood cholesterol have been observed during the past 5 years both clinically and experimentally where nitrogen balance was disturbed. In order to determine the possible importance of nitrogen balance on cholesterol levels, 6 dogs were placed on diets adequate in regard to minerals, vitamines and calories, but deficient in nitrogen. The nitrogen was limited to 1 gm. per day per animal. On this diet the urinary nitrogen excretion ranged from .99 to 2.2 gm. per day; so that a negative nitrogen balance was established and could be maintained for any desired period.

All dogs placed on this diet showed striking elevations in their total blood cholesterol and a gradual loss of weight. After 2 to 5 weeks on the low nitrogen diet, blood cholesterol began to increase gradually. It increased from the control readings of 125-225 mgm. to 450-550 mgm. after 4 to 12 weeks. If the diet was discontinued, a very slow return of cholesterol to the normal level was observed after many weeks. If the low protein diet was continued, the wasting became marked and a gradual drop in blood cholesterol began. After the cholesterol had dropped near to or below normal, blood lipase 1 (olive oil lipase) ordinarily appeared in increasing amounts. Later the Van den Bergh reaction became positive, soon bile appeared in the urine and the animal would refuse to eat. Cautious feeding of milk followed by a gradual return to the general ration would restore the animal only after several months. Realimentation with liberal amounts of meat was associated with a peculiar toxic state and resulted in the death of one animal not unlike that seen with meat feeding in cirrhosis of the liver in dogs.