Variations in human body water isotope composition across the United States

Energy expenditure and weight-related behaviors in youth with Down syndrome: a protocol

Background

The consequences of obesity are ominous, yet healthcare professionals are not adequately preventing or treating obesity in youth with Down syndrome (DS). Total daily energy expenditure (TDEE) is the energy expended in 24 h through physical activity and life-sustaining physiologic processes. An individual's TDEE is essential for determining the daily caloric intake needed to maintain or change body weight. Successful prevention and treatment of obesity in youth with DS is severely compromised by the lack of data on TDEE and information on weight-related behaviors for this high-risk population. This manuscript describes the protocol for the federally funded study that is in process to determine daily energy expenditure in a large cohort of children with DS.

Methods

This observational cross-sectional study will include a national sample of 230 youth with DS, stratified by age (5-11 and 12-18 years of age) and sex. Doubly Labeled Water analysis will provide the criterion body fat%, fat-free mass, and TDEE. To increase accessibility and decrease the burden on participants, the entire study, including obtaining consent and data collection, is conducted virtually within the participant's home environment on weekdays and weekends. The study team supervises all data collection via a video conferencing platform, e.g., Zoom. This study will (1) examine and determine average TDEE based on age and sex, (2) develop a prediction equation based on measured TDEE to predict energy requirements with a best-fit model based on fat-free mass, sex, age, and height and/or weight, and (3) use 24-hour dietary recalls, a nutrition and physical activity screener, wearable devices, and sleep questionnaire to describe the patterns and quality of dietary intake, sleep, and physical activity status in youth with DS.

Discussion

The lack of accurate information on energy expenditure and weight-related behaviors in youth with DS significantly impedes the successful prevention and treatment of obesity for this vulnerable population. The findings of this study will provide a further understanding of weight-related behaviors as obesity risk factors, currently not well understood for this population. This study will advance the science of weight management in individuals with disabilities and shift clinical practice paradigms.

Examination of amino acid hydrogen isotope measurements of scalp hair for region-of-origin studies

RATIONALE

Hydrogen isotope (δ2 H) analysis of keratinaceous bulk tissues has been used in forensic science to reconstruct an individual's travel history or determine their region-of-origin. Here, we use a compound-specific approach to examine patterns of individual amino acid δ2 H values in relation to those of local tap water, bulk scalp hair tissues, and region-of-origin.

METHODS

We measured δ2 H values of amino acids in anonymously collected scalp hair (n = 67) and tap water from 28 locations in the United States. Samples were hydrolyzed into their constituent amino acids, derivatized alongside in-house reference materials, and analyzed in triplicate using a GC-C-IRMS system.

RESULTS

Non-essential amino acid (AANESS ) δ2 H values and their corresponding tap water samples varied systematically across continental regions. Hydrogen isotope values of alanine, glutamic acid, and glycine were significantly correlated with tap water and an estimated 42%-51% of the hydrogen atoms in these AANESS were derived from tap water. We used linear discriminate analysis (LDA) to explore regional patterns in scalp hair bulk tissue and amino acid δ2 H values. For the model that included AANESS data, 87% of the variance was explained by the first linear discriminant axis (LD1), and was driven by bulk hair tissue, alanine, and proline. This model had an overall 72% successful reclassification with samples from the south and northwest regions reclassifying correctly 92% and 78% of the time, respectively. For the model that included AAESS data, LD1 explained 81% of the variation and was driven bulk hair, threonine, valine, phenylalanine, and isoleucine. The overall reclassification rate for the model that included AAESS was 70%.

CONCLUSIONS

Our findings suggest that δ2 H analyses of AANESS and AAESS could help improve geolocation models for human and wildlife forensics by simultaneously providing information about both dietary and tap water inputs of hydrogen to tissue synthesis.

Hydration and Nephrolithiasis in Pediatric Populations: Specificities and Current Recommendations

Renal lithiasis is less frequent in children than in adults; in pediatrics, lithiasis may be caused by genetic abnormalities, infections, and complex uropathies, but the association of urological and metabolic abnormalities is not uncommon. The aim of this study is to provide a synthesis of nephrolithiasis in children and to emphasize the role of hydration in its treatment. As an etiology is reported in 50% of cases, with a genetic origin in 10 to 20%, it is proposed to systematically perform a complete metabolic assessment after the first stone in a child. Recent data in the field reported increased incidence of pediatric urolithiasis notably for calcium oxalate stones. These changes in the epidemiology of stone components may be attributable to metabolic and environmental factors, where hydration seems to play a crucial role. In case of pediatric urolithiasis, whatever its cause, it is of utmost importance to increase water intake around 2 to 3 L/m² per day on average. The objective is to obtain a urine density less than 1010 on a dipstick or below 300 mOsm/L, especially with the first morning urine. Some genetic diseases may even require a more active 24 h over-hydration, e.g., primary hyperoxaluria and cystinuria; in such cases naso-gastric tubes or G-tubes may be proposed. Tap water is adapted for children with urolithiasis, with limited ecological impact and low economical cost. For children with low calcium intake, the use of calcium-rich mineral waters may be discussed in some peculiar cases, even in case of urolithiasis. In contrast, sugar-sweetened beverages are not recommended. In conclusion, even if parents and patients sometimes have the feeling that physicians do not propose "fancy" therapeutic drugs, hydration and nutrition remain cornerstones of the management of pediatric urolithiasis.