Intra-individual variation of plasma lipids and lipoproteins in prepubescent children

High-Intensity Running and Energy Restriction Reduce Postprandial Lipemia in Girls

PURPOSE

This study examined the potency of combining acute high-intensity exercise and energy intake restriction on postprandial triacylglycerol concentrations ([TAG]) in healthy girls.

METHODS

Sixteen 11- to 13-yr-old girls (mean (SD) body mass, 45.1 (7.6) kg; peak oxygen uptake (V˙O2), 43 (6) mL·kg(-1)·min(-1)) completed three 2-d conditions in a counterbalanced crossover design separated by 14 d. On day 1, participants completed 10 × 1-min interval runs (HIIR) or 5 × 1-min interval runs combined with 0.82 (0.19) MJ energy intake restriction (HIIR-ER) or rested (CON). Exercise was completed at 100% maximal aerobic speed determined from an incremental peak V˙O2 test, with 1-min recovery between intervals. On day 2, capillary blood samples were taken in the fasted state and at predetermined intervals throughout the 6.5-h postprandial period. A standardized breakfast and lunch were consumed immediately and 4 h after the fasting sample, respectively.

RESULTS

Based on ratios of the geometric means (95% confidence intervals (CI) for ratios), fasting [TAG] was 16% and 8% lower than CON in HIIR (-24% to -7%; effect size (ES), 0.49; P = 0.002) and HIIR-ER (-17% to 1%; ES, 0.24; P = 0.09), respectively; HIIR was 8% lower than HIIR-ER (-17% to 1%; ES, 0.25; P = 0.08). The total area under the [TAG] versus time curve was 10% and 9% lower than CON in HIIR (-16% to -3%; ES, 0.30; P = 0.01) and HIIR-ER (-15% to -2%; ES, 0.28; P = 0.01), respectively; HIIR-ER and HIIR were similar (-1%; -8% to 6%; P = 0.80).

CONCLUSIONS

Manipulations of HIIR and ER reduce postprandial [TAG] in girls. The magnitude of effect was marginally, although not meaningfully, greater after HIIR than that after HIIR-ER.

Energy replacement diminishes the effect of exercise on postprandial lipemia in boys

PURPOSE

Acute bouts of exercise reduce postprandial triacylglycerol concentrations ([TAG]) in healthy boys and girls; however, it is not known whether this effect is mediated by the energy deficit. This study examined whether the exercise-induced reduction in postprandial [TAG] persists after immediate dietary replacement of the exercise energy expenditure (EE).

METHODS

Eighteen healthy 11- to 13-year-old boys (mean (SD): body mass 41.3 (8.4)kg; peak oxygen uptake (V̇O2) 55 (5)mL·kg(-1)·min(-1)) completed three, 2-day conditions in a within-measures, crossover design separated by 14days. On day 1, participants rested (CON), exercised at 60% peak V̇O2 inducing a net EE of 32kJ·kg(-1) body mass (EX-DEF) or completed the same exercise with the net EE replaced immediately (EX-REP). On day 2, capillary blood samples were taken in the fasted state and at pre-determined intervals throughout the 6.5h postprandial period. A standardised breakfast and lunch meal were consumed immediately and 4h, respectively, after the fasting sample.

RESULTS

Based on ratios of the geometric means (95% confidence intervals (CI) for ratios), EX-DEF fasting [TAG] was 19% and 15% lower than CON (-32 to -4%, ES=1.15, P=0.02) and EX-REP (-29 to 0%, ES=0.91, P=0.05) respectively; CON and EX-REP were similar (-4%; P=0.59). The EX-DEF total area under the [TAG] versus time curve was 15% and 16% lower than CON (-27 to 0%, ES=0.55, P=0.05) and EX-REP (-29 to -2%, ES=0.62, P=0.03) respectively; CON and EX-REP were not different (2%; -13 to 20%, P=0.80).

CONCLUSION

Immediate replacement of the exercise-induced energy deficit negates the reduction in postprandial [TAG] in boys; this highlights the importance of maintaining a negative energy balance immediately post-exercise to maximise the metabolic health benefits of exercise.

Effect of energy expenditure on postprandial triacylglycerol in adolescent boys

This study examined the effects of 30 and 60 min of moderate intensity exercise on postprandial triacylglycerol concentration [TAG] in 11 healthy, 13-year-old boys. The boys completed three counterbalanced conditions. On day 1, they either rested (CON), or jogged for 30 min (EX30) or 60 min (EX60) at 55% peak [Formula: see text] Following a 12-h fast, on day 2 a capillary blood sample was taken for fasting [TAG] before a high fat milkshake was consumed. Further blood samples were taken every hour over a 6-h postprandial rest period for [TAG]. The estimated energy expenditure for EX30 (982 kJ) was doubled in EX60 (1967 kJ). Differences in fasting [TAG] between the conditions were small (ES = 0.23, P = 0.35). Differences in postprandial TAG over time between conditions were identified (ES = 0.41, P = 0.03). Mean [TAG] was lower in EX60 than CON (-33 to -3%, P = 0.03) with a similar strong trend for EX30 (-29 to 1%, P = 0.06); EX60 and EX30 were not different from each other (-21 to 14%, P = 0.62). The total area under the [TAG] versus time curve was different between conditions (ES = 0.42, P = 0.03). Again, EX60 was lower than CON (-31 to -2%, P = 0.02) with a strong trend for EX30 (-31 to 4%, P = 0.06); EX30 and EX60 were not different from each other (-17 to 16%, P = 0.58). This study shows for the first time that both 30 and 60 min of jogging, with energy expenditures equivalent to 982 and 1,967 kJ, attenuates postprandial [TAG] in adolescent boys, but not in a dose-dependent manner.

Changes and variability in high levels of low-density lipoprotein cholesterol among children

OBJECTIVE

A 2008 report from the American Academy of Pediatrics recommended both population and individual approaches (including pharmacologic interventions) for adolescents who had low-density lipoprotein (LDL) cholesterol levels above various cutoff points (130, 160, and 190 mg/dL). However, the tracking and variability of these very high levels have not been investigated.

METHODS

A total of 6827 subjects underwent multiple LDL cholesterol determinations in childhood and adulthood in the Bogalusa Heart Study. The total number of determinations was 26748, and the median interval between examinations was 3 years.

RESULTS

Correlations between initial and subsequent LDL cholesterol levels ranged from r approximately 0.8 for measurements made within the same year to r approximately 0.5 for periods of > or = 20 years. Most children who had very high LDL cholesterol levels, however, had substantially lower levels at the next examination. LDL cholesterol levels between 160 and 189 mg/dL (n = 201) decreased, on average, by 21 mg/dL at the next examination, whereas levels of > or = 190 mg/dL (n = 44) decreased by 34 mg/dL. In contrast, the mean increase for LDL cholesterol levels of <70 mg/dL was 13 mg/dL. These changes were equal to those expected on the basis of regression to the mean.

CONCLUSIONS

There can be large changes in extreme levels of LDL cholesterol because of regression to the mean, and practitioners should be aware that very high levels may decrease substantially in the absence of any intervention.

Lipid-Lipoproteins in Children: An Exercise Dose-Response Study

PURPOSE

To study the effect of exercise volume on pre- and early-pubertal children's lipid-lipoprotein profile.

METHODS

Thirty-four children (15 girls) completed 12 wk of exercise training, preceded by a 12-wk control period. Sixteen (7 girls and 9 boys) expended an additional 422 +/- 5 kJ.kg BM (LOW, 100 kcal.kg), whereas 18 (8 girls and 10 boys) expended an additional 586 +/- 7 kJ.g (MOD, 140 kcal.kg) as a result of the training program. They all exercised on three nonconsecutive days per week at 80 +/- 1% HRpeak. Exercise duration was individualized to match energy expenditure targets. Plasma TG, TC, and HDL-C were measured precontrol, pretraining, and posttraining. LDL-C, TC/HDL-C, and LDL-C/HDL-C were also calculated.

RESULTS

Group mean lipid-lipoprotein concentrations did not change as a result of training energy expenditure in either of the groups (P > 0.05). Dietary composition, habitual physical activity, and body composition were also relatively stable over the intervention period (P > 0.05). In the LOW, but not the MOD group, peak VO2 (mL.kg.min) tended to increase over the intervention period (P = 0.07). Pearson's product moment correlation analyses indicated that pretraining concentrations of TG, TC, LDL-C, TC/HDL-C, and LDL-C/HDL-C were all related to the small changes seen in the lipid-lipoprotein profile (P < 0.01).

CONCLUSION

Additional energy expenditure of 422 or 586 kJ.kg, as a direct result of aerobic exercise training over a 12-wk period, did not cause significant alterations in the lipid-lipoprotein profile in pre- and early-pubertal children. This may indicate that the exercise volume was insufficient, the lipoprotein profiles of the majority of children in this study were classified as "desirable," or more likely a combination of these factors.

Intraindividual variability of children's blood lipid and lipoprotein concentrations: a review

Of the numerous risk factors that have been associated with atherosclerosis and subsequent coronary heart disease, none have caught the public's attention more than plasma cholesterol. An increasing number of studies are focusing on intervention strategies aimed at "improving" the plasma lipid-lipoprotein profile of children. However, the efficacy of these strategies cannot be ascertained unless the biologic and analytic variability of these metabolites has been determined. From the limited available literature, it would appear that the biologic variability of total cholesterol, high- and low-density lipoprotein cholesterol, and triacylglycerol in children is similar to that reported for adults. Yet studies that have directly focused on this important issue with children are scarce, especially those that have included a representative sample and measurements of lipoprotein subfractions. Further research is warranted with children to better establish the extent of intraindividual variation associated with the lipid-lipoprotein profile.

Prevalence of plasma lipid abnormalities in Saudi children

BACKGROUND

Lipid levels in children vary in different populations. Due to a close association between high lipid levels and development of atherosclerosis, considerable interest has been directed to investigating lipid levels in children.

MATERIALS AND METHODS

We conducted this study on 2914 children with ages ranging from 1 year to <15 years, randomly selected during a national household screening program. Fasting blood samples were used for estimation of triglyceride and cholesterol levels.

RESULTS

The overall range for cholesterol was 2.0-5.7 mmol/L and for triglyceride the overall range was 0.1-1.7 mmol/L. The children were separated into 14 groups depending on age, and the cholesterol and triglyceride levels were calculated in each age group. Using published guidelines for estimating "borderline" and "high risk" for coronary artery disease from cholesterol and triglyceride levels, the prevalence of borderline and high-risk groups was calculated. 7.72% of the children fell in the borderline risk group and 1.55% in the high-risk group using cholesterol values, while using triglyceride values, 1.4% and 0.55% fell in the borderline and high-risk groups, respectively. The prevalence of abnormality varied in the different age groups.

CONCLUSION

The paper discusses the need for a lipid awareness program in Saudi children in an attempt to decrease the complications associated with dyslipidemias during adulthood.