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Diurnal levels of serum triglyceride, cholesterol, free fatty acids, glucose, and cortisol were measured in four normal persons on a fixed solid 65% carbohydrate diet under steady state conditions in a metabolic unit. Triglyceride levels in all subjects showed similar patterns, which unexpectedly did not bear a simple relation to meal frequency or distribution. With three equivalent meals per day at 09.00, 12.00 and 17.00 hours, 'fasting' triglyceride levels increased by about 0.3 g/l from a minimum value between 03.00 and 05.00 hours in the morning till before breakfast. After breakfast there was a continued rise till about 15.00 hours and then a overall fall in spite of the meal at 17.00 hours. Isocaloric change to eight equivalent meals, consumed between 09.00 and 23.00 hours, resulted in a similar although slightly more even triglyceride pattern. On eight equivalent meals, spaced evenly over the entire 24 h period, a different pattern was found with lower triglyceride values at daytime than at night. Increase in meal frequency did not result in a lowering of mean diurnal triglyceride levels. The cholesterol pattern followed the triglyceride pattern most clearly in subjects with high triglyceride levels. Glucose showed the expected postprandial increments. Cortisol rhythm did not change on varying meal frequency.

Normal subjects in steady state on a carbohydrate-rich diet (three equivalent meals a day at 9.00, 13.00 and 17.00 h), show a wave-like serum triglyceride (TG) pattern with a peak at 14.00 h. Post-heparin lipoprotein lipase (LPL) activity increased from a mean value of 49 mU/ml +/- 13 (SD) in the fasting state to 127 mU/ml +/- 18 in the fed state (P less than 0.005). This was due to an increase in adipose tissue LPL activity which, at 16.30 and 21.30 h, was significantly higher than basal levels (128.3 +/- 81.5 and 87.7 +/- 23.2 v. 43.3 +/- 9.3 mU/g, P less than 0.05 and P less than 0.01, respectively). Skeletal muscle LPL activity was low (5.8 mU/g +/- 2.3, mean +/- SD) and showed no diurnal change. The observed changes in TG-hydrolysing capacity in the course of the day might explain the TG-pattern. High density lipoprotein (HDL) subfractions HDL2 and HDL3 were separated by density gradient ultracentrifugation and had mean hydrated densities of 1.088 and 1.135 g/ml, respectively. While HDL2 showed no diurnal change, HDL3-cholesterol and-phospholipid significantly increased during the day (P less than 0.005 and P less than 0.001 respectively), reaching their highest levels in the evening. Since te rise in HDL3-lipids follows the fall in serum TG, this provides further indication that the metabolism of these fractions in mutually related.

Ery~hrocyte aggregation, plasma fibrinogen concentrations and serum protein fractions have been studied in 19 diabetic patients without retinopathy, 18 patients with retinopathy and 41 non-diabetic controls.-Significant differences in the parameters were observed between diabetics and controls. The differences between the diabetics with and without retinopathy were not significant.-The role of abnormal erythrocyte aggregation in the development of diabetic retinopathy is discussed.-Striking parallels were found with similar findings concerning platolet aggregation in diabetics.