Diurnal changes in serum triglycerides as related to changes in lipolytic enzymes, (apo) lipoproteins and hormones in normal subjects on a carbohydrate‐rich diet

Abstract

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.

Weight reduction increases adipose tissue lipoprotein lipase responsiveness in obese women.

“…The limited increase in ATLPL to food before weight loss was similar to that reported in obese women by Iverius and Brunzell (36). Yet, in the reduced-obese state, the marked increase in ATLPL responsiveness in the present study was even greater than that reported in normal-weight men 8 h after the ingestion of four high carbohydrate meals (37). In the current study, the meal intake pattern was aimed to simulate a "routine" or outpatient setting wherein 1750 calories, or -55% of the estimated daily caloric consumption (35 kcal/kg), were administered over a 6-h period.…”

Familial longevity is characterized by high circadian rhythmicity of serum cholesterol in healthy elderly individuals

“…Previous studies on the daily variation in serum cholesterol concentrations have been conflicting. Some studies reported no variation during the day (Mirani‐Oostdijk et al ., ; Persson et al ., ), while others reported circadian variation in serum cholesterol with a CV up to 4% (Rivera‐Coll et al ., ) and circadian variation in cholesterol precursors (Miettinen, ) or cholesterol production rate (Jones & Schoeller, ). However, in all these studies, sampling frequency was at most every 1.5 h and the study populations included up to 25 young adults, and the studies showing no circadian rhythm in cholesterol included only five individuals.…”

Different patterns of brisk walking are equally effective in decreasing postprandial lipaemia

“…Over a day of rest during which subjects consume three meals there is little change to skeletal muscle LPL activity, 26 probably because insulin inhibits LPL activity in this tissue. 28 However, exercise leads to an increase in muscle LPL activity which apparently counteracts its downregulation by insulin.…”

“…Thus, when three meals are consumed during the day, adipose tissue LPL activity is highest in the late afternoon and early evening. 26 The reduction in TAG concentrations with walking became apparent only during the late afternoon and early evening, more than 5 h after breakfast. This coincides with the period of maximal TAG extraction and suggests that the lower concentrations during the walking trials may be attributable mainly to an effect on TAG clearance.…”