Comparison of isotope ratio mass spectrometry and cavity ring-down spectroscopy procedures and precision of the doubly labeled water method in different physiological specimens

RATIONALE

This study determines if saliva collection procedures for the doubly labeled water (DLW) method, used for measuring total energy expenditure (TEE), are comparable to urine and plasma collection. Both the cavity ring-down spectroscopy (CRDS) and isotope ratio mass spectrometry (IRMS) analyses techniques are compared.

METHODS

Saliva specimens were collected from participants for the DLW method. The specimens were collected under different conditions: after consumption of tap water, after chewing gum, and during exposure to conditions of high and low relative humidity. The isotopes in saliva were compared with simultaneous plasma and urine collection. TEE calculated from saliva and analyzed using CRDS was compared to that of plasma analyzed using IRMS.

RESULTS

The within-individual variances were not significantly different between the saliva specimens (0.4‰) and plasma (0.3‰). After the oral dose of DLW, the saliva specimens displayed a shorter equilibration time to urine. When participants consumed 500 mL of tap water, the enrichment of saliva specimens reached a new plateau value faster than urine. Saliva collection exposed to high ambient humidity conditions was slightly less enriched as compared to low-humidity conditions while urine enrichment was unaffected. In contrast, whereas the within-individual effects of gum chewing during saliva collection on ¹⁸ O were unaffected, the abundance of ² H in saliva was slightly lower after chewing the gum. The within-individual difference between TEE calculated from saliva and that calculated from plasma analyzed using IRMS did not differ from zero, and the standard deviation was not different from that predicted by a propagation of error analysis based on analytical error alone.

CONCLUSIONS

Our findings support using saliva specimens for the DLW method. The analysis of plasma and urine, however, requires reducing the memory effect resulting from contaminants. Also, it should be performed in a manner that minimizes exposure to air where specimens may be exposed to evaporation or contamination from water vapor during sampling.

Health-related quality of life and well-being in parents of infants and toddlers with cancer

Background

The unique psychosocial needs of parents and caregivers of young children with cancer are poorly understood. The aims of the present study were to examine health-related quality of life (hrqol), stress, and psychological distress in parents of young children (0-4 years) diagnosed with cancer; and the associations between parent psychosocial functioning and child treatment characteristics.

Methods

Parents (n = 35) with a child (n = 19 male, 54.3%) 0-48 months of age (median: 31.06 months) on active cancer therapy were recruited. Parents completed questionnaires related to demographics, parent hrqol, parenting stress, posttraumatic stress symptoms, and parent psychological distress.

Results

Parents reported clinically elevated parenting stress (5.9%), posttraumatic stress symptoms (18.2%), and psychological distress (21.9%). Compared with population norms, parents reported lower hrqol in the vitality (t = 5.37, p < 0.001), mental health (t = 4.02, p < 0.001), role limitation-emotional (t = 3.52, p < 0.001), and general health perceptions (t = 2.25, p = 0.025) domains. Social functioning (β = 0.33, p = 0.041) predicted general health perceptions; vitality (β = 0.30, p = 0.134) and parent mental health (β = 0.24, p = 0.285) did not [F _(3,29) = 12.64, p < 0.001, R ² = 0.57].

Conclusions

A subset of parents of young children on active cancer treatment experience clinically elevated psychosocial symptoms. Having poor social connections put parents at risk of perceiving their health more poorly in general. Supports that focus on preventing the emergence of clinically significant distress should focus on parents of young children with cancer who are most at risk of poor outcomes.

Quality of life in pediatric cancer survivors: contributions of parental distress and psychosocial family risk

Background

Pediatric survivors of childhood cancer are at increased risk of poor quality of life and social-emotional outcomes following treatment. The relationship between parent psychological distress and child adjustment in pediatric cancer survivors has been well established. However, limited research has examined the factors that may buffer this association. The current study examined the associations between psychosocial family risk factors, parental psychological distress, and health-related quality of life (hrql) in pediatric cancer survivors.

Methods

Fifty-two pediatric cancer survivors (34 males, 18 females, mean age = 11.92) and their parents were recruited from a long-term cancer survivor clinic. Children and their parents who consented to participate completed the Pediatric Quality of Life Inventory 4.0. Parents completed a demographic information form, the Psychosocial Assessment Tool (pat 2.0) and the Brief Symptom Inventory (bsi). The Intensity of Treatment Rating (itr-3) was evaluated by the research team.

Results

Multiple regression analyses revealed that parental psychological distress negatively predicted parent-reported hrql, while treatment intensity, gender, and psychosocial risk negatively predicted parent and child-reported hrql. Psychosocial risk moderated the association between parent psychological distress and parent-reported child hrql (p = 0.03), whereby parents with high psychological distress but low levels of psychosocial risk reported their children to have higher hrql.

Conclusion

Low levels of family psychosocial risk buffer the impact of parent psychological distress on child hrql in pediatric cancer survivors. The findings highlight the importance of identifying parents and families with at-risk psychological distress and psychosocial risk in order to provide targeted support interventions to mitigate the impact on hrql.

Dilution space ratio of 2H and 18O of doubly labeled water method in humans

Variation of the dilution space ratio (Nd/No) between deuterium ((2)H) and oxygen-18 ((18)O) impacts the calculation of total energy expenditure (TEE) by doubly labeled water (DLW). Our aim was to examine the physiological and methodological sources of variation of Nd/No in humans. We analyzed data from 2,297 humans (0.25-89 yr old). This included the variables Nd/No, total body water, TEE, body mass index (BMI), and percent body fat (%fat). To differentiate between physiologic and methodologic sources of variation, the urine samples from 54 subjects were divided and blinded and analyzed separately, and repeated DLW dosing was performed in an additional 55 participants after 6 mo. Sex, BMI, and %fat did not significantly affect Nd/No, for which the interindividual SD was 0.017. The measurement error from the duplicate urine sample sets was 0.010, and intraindividual SD of Nd/No in repeats experiments was 0.013. An additional SD of 0.008 was contributed by calibration of the DLW dose water. The variation of measured Nd/No in humans was distributed within a small range and measurement error accounted for 68% of this variation. There was no evidence that Nd/No differed with respect to sex, BMI, and age between 1 and 80 yr, and thus use of a constant value is suggested to minimize the effect of stable isotope analysis error on calculation of TEE in the DLW studies in humans. Based on a review of 103 publications, the average dilution space ratio is 1.036 for individuals between 1 and 80 yr of age.

Effect of conjugated linoleic acid on body fat accretion in overweight or obese children

BACKGROUND

Conjugated linoleic acid (CLA) is a supplemental dietary fatty acid that decreases fat mass accretion in young animals.

OBJECTIVE

The aim of this study was to determine CLA's efficacy with regard to change in fat and body mass index (BMI; in kg/m(2)) in children.

DESIGN

We conducted a 7 +/- 0.5-mo randomized, double-blind, placebo-controlled trial of CLA in 62 prepubertal children aged 6-10 y who were overweight or obese but otherwise healthy. The subjects were randomly assigned to receive 3 g/d of 80% CLA (50:50 cis-9,trans-11 and trans-10,cis-12 isomers) or placebo in chocolate milk.

RESULTS

Fifty-three subjects completed the trial (n = 28 in the CLA group, n = 25 in the placebo group). CLA attenuated the increase in BMI (0.5 +/- 0.8) compared with placebo (1.1 +/- 1.1) (P = 0.05). The percentage change in body fat measured by dual-energy X-ray absorptiometry was smaller (P = 0.001) in the CLA group (-0.5 +/- 2.1%) than in the placebo group (1.3 +/- 1.8%). The change in abdominal body fat as a percentage of total body weight was smaller (P = 0.02) in the CLA group (-0.09 +/- 0.9%) than in the placebo group (0.43 +/- 0.6%). There were no significant changes in plasma glucose, insulin, or LDL cholesterol between groups. Plasma HDL cholesterol decreased significantly more (P = 0.05) in the CLA group (-5.1 +/- 7.3 mg/dL) than in the placebo group (-0.7 +/- 8 mg/dL). Bone mineral accretion was lower (P = 0.04) in the CLA group (0.05 +/- 0.03 kg) than in the placebo group (0.07 +/- 0.03 kg). Reported gastrointestinal symptoms did not differ significantly between groups.

CONCLUSIONS

CLA supplementation for 7 +/- 0.5 mo decreased body fatness in 6-10-y-old children who were overweight or obese but did not improve plasma lipids or glucose and decreased HDL more than in the placebo group. Long-term investigation of the safety and efficacy of CLA supplementation in children is recommended.