Leptin measurement in urine in children and its relationship to other growth peptides in serum and urine

Fecal and Urinary Adipokines as Disease Biomarkers

The use of biomarkers is of great clinical value for the diagnosis and prognosis of disease and the assessment of treatment efficacy. In this context, adipokines secreted from adipose tissue are of interest, as their elevated circulating levels are associated with a range of metabolic dysfunctions, inflammation, renal and hepatic diseases and cancers. In addition to serum, adipokines can also be detected in the urine and feces, and current experimental evidence on the analysis of fecal and urinary adipokine levels points to their potential as disease biomarkers. This includes increased urinary adiponectin, lipocalin-2, leptin and interleukin-6 (IL-6) levels in renal diseases and an association of elevated urinary chemerin as well as urinary and fecal lipocalin-2 levels with active inflammatory bowel diseases. Urinary IL-6 levels are also upregulated in rheumatoid arthritis and may become an early marker for kidney transplant rejection, while fecal IL-6 levels are increased in decompensated liver cirrhosis and acute gastroenteritis. In addition, galectin-3 levels in urine and stool may emerge as a biomarker for several cancers. With the analysis of urine and feces from patients being cost-efficient and non-invasive, the identification and utilization of adipokine levels as urinary and fecal biomarkers could become a great advantage for disease diagnosis and predicting treatment outcomes. This review article highlights data on the abundance of selected adipokines in urine and feces, underscoring their potential to serve as diagnostic and prognostic biomarkers.

Urinary levels of energy metabolism hormones in association with the proportional intake of maternal milk and weight gain in very preterm neonates

BACKGROUND

This study prospectively investigated the levels of energy metabolism hormones in very preterm neonates to identify their change over time, association with intake of maternal milk, and weight gain velocity.

METHODS

We measured and compared the leptin, adiponectin, ghrelin, and insulin-like growth factor I (IGF-1) levels in the urine of 70 very preterm neonates, before the initiation of any enteral feeding (baseline level) and twice within 14 days on full enteral feeding (FEF). Regression models identified the role of intake of maternal milk on the levels of the tested energy metabolism hormones in the enteral-fed infants. We also analyzed the adequacy of the weight gain velocity defined by the fetal-infant growth reference (FIGR). We also collected and analyzed the infants' clinical and feeding characteristics during the birth hospitalization.

RESULTS

The preterm infants' baseline levels of the energy metabolism hormones significantly predicted their increase at the end of two weeks of observation on FEF. The leptin level was associated with increased intake of maternal milk, whereas the feeding volume was associated with increased ghrelin and IGF-1, and decreased leptin and adiponectin. Infants with comparable FIGR had higher leptin levels than those with inadequate weight gain velocity.

CONCLUSION

Early postnatal levels of leptin, adiponectin, ghrelin, and IGF-1 predicted the increase of these hormones in the fully enteral fed very preterm neonates. Moreover, greater intake of maternal milk by the study infants contributed to an increased leptin-associated weight gain velocity.

Contrasting short-term temperature effects on the profiling of metabolic and stress hormones in non-obese healthy adults: A randomized cross-over trial

The manifestation of elevated and sustained air temperature gradient profiles in urban dwellings represents an emerging planetary health phenomenon. There is currently limited evidence about the effect of elevated air temperatures on metabolic health. The aim of this work was to assess changes in metabolic and stress hormonal profiles during a short-term stay in a mountainous, climate-cooler setting against those observed in the urban setting. A prospective, randomized, 2 x 2 cross-over trial of non-obese healthy adults in urban and mountainous areas of a Mediterranean country (Cyprus) was set up during summer, under real-life conditions. The intervention was a short-term stay (mean ± SD: 7 ± 3 days) in a mountainous, climate-cooler setting (altitude range: 650-1200 m), being ~1-h drive away from the main urban centres of Cyprus. The primary endpoint was the change in metabolic hormones levels (leptin and adiponectin) and stress hormone levels (cortisol) between the two settings. Personal air and skin temperature sensors were deployed while biospecimen were collected in each setting. A total of 41 participants between 20 and 60 years old were enrolled and randomized during July 2018, of whom 39 received the allocated intervention, 8 were lost to follow up or excluded from analysis and a total of 31 participants were analysed. A significant leptin reduction (β = -0.255; 95% CI: -0.472, -0.038; p = 0.024) was observed for non-obese healthy adults during their short-term stay in the mountainous environment. The intervention effect on adiponectin or cortisol levels was not statistically significant (β = 0.058; 95% CI: -0.237, 0.353; p = 0.702), and (β = -0.026; 95% CI: -0.530, 0.478; p = 0.920), respectively. In additional analyses, daily max skin temperature surrogate measures were significantly associated with leptin levels (β = 0.34; 95% CI: 0.051, 0.633; p = 0.024). During summer season, a short-term stay in climatologically cooler areas improved the leptin levels of non-obese healthy adults who permanently reside in urban areas of a Mediterranean country. A larger sample is needed to confirm the trial findings that could provide the rationale for such public health interventions in climate-impacted urban areas of our planet.

Methods for determining pubertal status in research studies: literature review and opinions of experts and adolescents

In lifecourse studies that encompass the adolescent period, the assessment of pubertal status is important, but can be challenging. We aimed to identify current methods for pubertal assessment and assess their appropriateness for population-based research by combining a review of the literature with the views of experts in the field. We searched bibliographic databases, extracted data and assessed study quality to inform a workshop with 21 experts. Acceptability of different approaches was explored with a panel of ten adolescents. We screened 11,935 abstracts, assessed 157 articles and summarised results from 38 articles. Combining these with the opinions of experts, self-assessment was found to be a practical method for use in studies where agreement with the gold standard of clinical assessment by physical examination to within one Tanner stage was acceptable. Serial measures of height and foot size accurately indicated timing of the pubertal growth spurt and age at peak height velocity, and were seen as feasible within longitudinal studies. Hormonal and radiological methods did not offer a practical means of assessing pubertal status. Assessment of voice maturation was promising, but needed validation. Young people thought that self-assessment, foot size and voice assessments were acceptable, and preferred an assessor of the same sex for clinical assessment. This review thus informs researchers working in lifecourse and adolescent health, and identifies future directions in order to improve validity of the methods.

The Relationship between Nocturnal Urinary Leptin and Gonadotrophins as Children Progress towards Puberty

BACKGROUND/AIMS

Leptin is necessary for normal human pubertal development but its exact role in the period leading up to the onset of puberty has not been defined. This study has assessed the relationship between leptin and gonadotrophin secretion over time as children progress into puberty.

SUBJECTS AND METHODS

Twenty children (13 boys and 7 girls) judged to be close to the initiation of puberty were recruited. Three consecutive first morning urine samples were collected from each subject each month over 6 months. At the end of the study, the children were classified into those who remained physically prepubertal (n = 7) and those that had advanced in puberty (n = 13). Leptin and gonadotrophins were measured by immunoradiometric and immunofluorometric assay, respectively.

RESULTS

Total urinary leptin excreted over 6 months was higher in girls than in boys, both prepubertally and in early puberty, and in both sexes, was higher in those advancing into puberty than in those remaining prepubertal (girls 8.0 vs. 3.4 ng/l and boys 3.6 vs. 1.7 ng/l; both p < 0.05). In the whole group, when controlling for gender, there was a significant correlation between both leptin and luteinizing hormone (LH; r = 0.43, p < 0.001) and leptin and follicle-stimulating hormone (FSH; r = 0.32, p = 0.001). The possibility of a lead relationship was explored by pairing leptin values with the gonadotrophin values in the following month. Leptin was significantly correlated with FSH but not LH in both pre- and peripubertal children (prepubertal r = 0.45, p = 0.01; peripubertal r = 0.32, p = 0.01).

CONCLUSIONS

This study has shown that in children approaching and progressing into puberty, leptin is associated with LH and FSH over the same time frame, and with FSH when leptin is acting as the lead hormone. These data imply that leptin is an important facilitator of the early phases of human puberty.

Effects of Acute, Heavy-Resistance Exercise on Urinary Peptide Hormone Excretion in Humans

To examine physical exercise-related changes in urinary excretion of protein/peptide hormones and to correlate modifications with the general increase in post-exercise proteinuria, urine C-peptide, insulin and insulin-like growth factor-I (IGF-I) and their plasma concentrations were measured. Plasma and urinary C-peptide, insulin and IGF-I before (Bex) and at the end (Eex) of physical exercise (a 2.5-hour competition, 102 km) were analysed in 20 young cyclists. At Eex compared with Bex, concentration of urinary C-peptide decreased slightly but significantly (21.3 +/- 2.7 vs. 13.5 +/- 1.7 nmol/l), but urinary insulin and urinary IGF-I concentrations significantly increased at Eex (92.5 +/- 4.2 vs. 131.4 +/- 15.7 pmol/l and 10.0 +/- 2.1 vs. 33.6 +/- 3.8 pmol/l, respectively). Plasma insulin and plasma C-peptide significantly decreased, whereas plasma IGF-I was unchanged. Urinary concentrations of total proteins and creatinine significantly increased. Both Eex urinary C-peptide/urinary protein and urinary C-peptide/urinary creatinine ratios were significantly reduced. The correlation between C-peptide and insulin in plasma was confirmed at Bex as well as Eex, but in urine only at Bex. An increased renal tubular reabsorption of C-peptide at the end of exercise might be suggested, but the expected values considering creatinine excretion were almost three times less. The Eex urinary insulin concentration was higher than expected, considering the circulation levels, but lower when compared with the expected concentration considering creatinine excretion. Physical exercise proteinuria, related to an increased protein filtration and a saturation of the mechanisms responsible for the reabsorption, does not appear similar for all peptide hormones.