THE LIPOTROPIC ACTION OF COLD: 2. THE INFLUENCE OF COLD AND CHOLINE DEFICIENCY ON SERUM LIPIDS OF RATS AT DIFFERENT INTAKES OF DIETARY METHIONINE

Abstract

The effect of exposure of rats to cold for a 10-day period on the concentration of serum lipids in control and choline-deficient animals was studied at four dietary intakes of methionine. Changes in total lipids, total and free cholesterol, phospholipid, and triglyceride levels were measured.In control (choline-fed) animals, phospholipid, cholesterol, and the ratio of free:ester cholesterol levels were not altered by cold exposure, but a marked decrease (25–30%, P < 0.01) in the levels of total serum lipids occurred. This was a result of a 45–70% decrease in triglyceride levels. The concentration of the triglyceride-rich low-density lipoproteins (S_f10–400) in the serum fell in the cold-exposed animals as indicated by lowered triglyceride:cholesterol ratios.Although cold exposure prevented fatty livers in choline-deficient rats at high methionine intakes, it did not prevent the characteristic decrease in serum lipids found in choline deficiency at any of the methionine intakes studied. Decreases in total lipids (20–40%), triglyceride (10–50%), cholesterol (15–40%), and phospholipids (15–40%) were found. It was concluded that the ability of cold exposure to overcome choline deficiency is limited, apparently, to the fatty liver syndrome and has no effect on the decreased serum lipid levels.