Abstract
The serum lecithin-cholesterol acyltransferase (LCAT) esterifies circulating cholesterol. Recently positive correlation of serum LCAT activity with relative body weight has been reported, however, the relationship between the change of body weight and serum LCAT activity has not been clarified.
The present study was designed to elucidate the relationship between serum LCAT activity and serum lipids after the change of body weight in obese and lean subjects.
The results are as follows.
(A) Measurement of LCAT activity
1. As the substrate for the LCAT assay plasma d>1.063 fraction (HDL) is preferable to whole plasma.
2. The reaction of cholesterol esterification using that substrate plasma proceeded linearly for 6 hours incubation. There was also linear relationship between it's reaction and the LCAT concentration up to 40μl/ml medium.
3. Unesterified cholesterol in the incubation medium did not affect on the assay system, if LCAT activity was expressed as μg/ml/hr.
4. When the serum sample was frozen and maintained at-15°C until the LCAT assay, the activity of LCAT did not decrease at least for 16 weeks.
(B) The LCAT activity and serum lipids were measured in nine obese and four lean subjects before and after the change of body weight
1. The LCAT activity in obese subjects decreased significantly together with weight loss by diet restriction, while it's activity increased following weight gain in lean subjects by high calorie diet. The serum LCAT activity was found to correlate with the relative body weight before and after the change of body weight. There was also a significant positive correlation between serum LCAT activity and the change of body weight.
2. Serum total cholesterol and cholesterol ester in obese subjects became significantly lower following weight loss by diet restriction. Serum triglyceride and serum unesterified cholesterol in obese subjects decreased after weight reduction and they increased mostly after weight gain in lean subjects, though it was not significant.
