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.

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Diurnal levels of serum triglyceride (TG), cholesterol, free fatty acids (FFA), glucose and insulin were measured in three type IV hyperlipidemic patients on a fixed solid 65 % carbohydrate and a 65 % fat diet when in steady state conditions in a metabolic unit. The carbohydrate-rich food was divided into either three or eight equivalent portions, differently spaced over the day and night. The fatrich food was given in three equivalent portions only. The diurnal TG profiles on these diets showed the same characteristics as those found in normals, but increments and mean levels were considerably higher. On the carbohydrate-rich diet, mean TG levels decreased during the study. This was not seen either on the fat-rich diet or in normals. In contrast to our findings in normals, chylomicrons formed the major contribution to the serum TG pattern. FFA levels were markedly higher on the high-fat than on the carbohydrate-rich diet, but not different from those in normals. Postprandial glucose responses did not differ significantly between the diets. Insulin responses were markedly higher on the carbohydrate-rich than on the fat-rich food. Glucose levels did not differ from those in normals. Insulin levels were significantly higher in the patients. Cholesterol showed minimal fluctuations, parallel to the TG pattern, which could be attributed to chylomicron cholesterol.Abbreviations: HTG = hypertriglyceridemia, T C = triglyceride, FFA = fre fatty acid, VLDL = very low density lipoprotein, LDL = low density lipoprotein, HDL = high density lipoprotein. Acta Mcd Scnnd 210

Diurnal levels of serum triglyceride (TG) were measured in six normal persons consuming a fixed solid 65% fat diet under steady state conditions in a metabolic unit. The food was divided into either three or eight similar portions, differently spaced over the day and night. The diurnal TG-profiles on this diet were practically identical to those found under comparable conditions on a 65% carbohydrate diet [1]. Mean diurnal TG values did not significantly differ with varying meal frequency. Free fatty acid levels, however, were significantly higher on a high fat diet. Post-prandial glucose and insulin reponses did not significantly differ whether a high fat diet or a high carbohydrate diet was consumed. We conclude that the composition of the diet is of little importance in determining diurnal TG patterns when the diet consists of normal food stuffs, but that these patterns are dependent on meal frequency and distribution.