Diurnal triglyceride profiles: a novel approach to study triglyceride changes

Fasting plasma triglycerides (TG) show a high intra-individual variability, and therefore, repeated measurements and alternative methodology are neces sary when studying TG metabolism. In search for novel approaches to study T G changes, we evaluated the feasibility of determining ambulatory capillary TG. In addition, well-known characteristics (e.g. gender differences) of T G metabolism in healthy subjects were determined. In 18 subjects with a wid e range of fasting plasma TG, the results of standardised oral fat loading tests (50 g m(-2)) were compared to their diurnal capillary TG profiles, me asured on 3 different days, six times each day in an out-patient clinic set ting. The diurnal TG-profile was calculated as area under the capillary TG curve (TGc-AUC) and as incremental area (dTGc-AUC). Clearance of plasma TG after the acute oral fat load correlated well with the diurnal TGc-AUC (r = 0.77; P < 0.01). In addition, hypertriglyceridemic subjects (plasma TG > 2 .0 mmol l(-1)) had a higher diurnal triglyceridemia (49.83 +/- 15.37 h mmol l(-1)) as well as a higher response of plasma TG to the oral fat load (42. 10 +/- 15.37 h mmol l(-1)), than the subjects with normal fasting plasma TG (29.83 +/- 11.75 h mmol l(-1) (P < 0.05) and 20.75 +/- 5.89 h mmol l(-1) ( P < 0.01), respectively). In an observational study, 106 volunteers (54 fem ales and 52 males) measured capillary triglycerides. Food intake was record ed and fasting blood was drawn once at the start of the study. Body composi tion was assessed by anthropometric parameters and body-impedance. Repeated measurements of diurnal triglyceridemia tended to be less variable than fa sting capillary triglycerides (mean coefficients of variation 15.1% (range: 0.60-45.9%) and 24.9% (range: 1.44-72.7%), respectively; P = 0.09) for the whole group and in males (18.6% (0.60-45.9%) and 24.0% (1.4-58.2%), respec tively; P = 0.07). The mean diurnal TGc-AUC and dTGc-AUC were lower in fema les (16.50 +/- 4.85 and 1.82 +/- 3.46 h mmol l(-1), respectively) than in m ales (23.44 +/- 6.50 and 6.93 +/- 4.67 h mmol l(-1); P < 0.001 for each). T he total daily energy intake was lower in females (8911 +/- 1905 kJ) than i n males (11042 +/- 2604 kJ, P < 0.001) because of a lower intake of all nut rients. In females, estrogen status determined significantly the capillary TG profiles. Stepwise multiple regression analysis for females and males, w ith TGc-AUC as the dependent variable, showed that the best predictors were fasting capillary TG, gender, systolic blood pressure and mean daily energ y intake, explaining 72% of the variation. Incremental triglyceridemia was best described by gender, mean daily protein intake and systolic blood pres sure, explaining 42% of the variation. Diurnal capillary TG profiles may be used to estimate the total daily load of potential atherogenic particles t o which individuals are subjected during the day without the need for metab olic ward studies. (C) 2001 Elsevier Science Ireland Ltd. All rights reserv ed.