Adiponectin levels measured in dried blood spot samples from neonates born small and appropriate for gestational age

Methods applied to neonatal dried blood spot samples for secondary research purposes: a scoping review

This scoping review aimed to synthesize the analytical techniques used and methodological limitations encountered when undertaking secondary research using residual neonatal dried blood spot (DBS) samples. Studies that used residual neonatal DBS samples for secondary research (i.e. research not related to newborn screening for inherited genetic and metabolic disorders) were identified from six electronic databases: Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Embase, Medline, PubMed and Scopus. Inclusion was restricted to studies published from 1973 and written in or translated into English that reported the storage, extraction and testing of neonatal DBS samples. Sixty-seven studies were eligible for inclusion. Included studies were predominantly methodological in nature and measured various analytes, including nucleic acids, proteins, metabolites, environmental pollutants, markers of prenatal substance use and medications. Neonatal DBS samples were stored over a range of temperatures (ambient temperature, cold storage or frozen) and durations (two weeks to 40.5 years), both of which impacted the recovery of some analytes, particularly amino acids, antibodies and environmental pollutants. The size of DBS sample used and potential contamination were also cited as methodological limitations. Residual neonatal DBS samples retained by newborn screening programs are a promising resource for secondary research purposes, with many studies reporting the successful measurement of analytes even from neonatal DBS samples stored for long periods of time in suboptimal temperatures and conditions.

FGF21 via mitochondrial lipid oxidation promotes physiological vascularization in a mouse model of Phase I ROP

Hyperglycemia in early postnatal life of preterm infants with incompletely vascularized retinas is associated with increased risk of potentially blinding neovascular retinopathy of prematurity (ROP). Neovascular ROP (Phase II ROP) is a compensatory but ultimately pathological response to the suppression of physiological postnatal retinal vascular development (Phase I ROP). Hyperglycemia in neonatal mice which suppresses physiological retinal vascular growth is associated with decreased expression of systemic and retinal fibroblast growth factor 21 (FGF21). FGF21 administration promoted and FGF21 deficiency suppressed the physiological retinal vessel growth. FGF21 increased serum adiponectin (APN) levels and loss of APN abolished FGF21 promotion of physiological retinal vascular development. Blocking mitochondrial fatty acid oxidation also abolished FGF21 protection against delayed physiological retinal vessel growth. Clinically, preterm infants developing severe neovascular ROP (versus non-severe ROP) had a lower total lipid intake with more parenteral and less enteral during the first 4 weeks of life. Our data suggest that increasing FGF21 levels in the presence of adequate enteral lipids may help prevent Phase I retinopathy (and therefore prevent neovascular disease).

Effect of multiple pregnancy and laterality on infant neurodevelopment

OBJECTIVE

The objective of this study is to investigate the effect of type of pregnancy (singleton, dizygotic, and monozygotic) on infant neurodevelopment and to explore how laterality operates in this relationship.

METHODS

We constructed a prospective cohort of low-risk women with singleton, monozygotic, and dizygotic pregnancies. Laterality was evaluated using the Edinburgh's scale of laterality, while neurodevelopment was assessed using the Ages & Stages Questionnaire (ASQ). The confounding, modifying, and mediating effect of laterality on the relationship between multiple pregnancy and neurodevelopment was explored by linear regression.

RESULTS

We included 207 singletons, 77 dizygotic, and 75 monozygotic pregnancies. The mean age (SD) at assessment of neurodevelopment was 48.5 (7.5) months. There was a significant trend to poorer neurodevelopment across singleton, dizygotic and monozygotic pregnancies in communication (52.2, 47.6 and 42.3; p < .001) and fine movements (49.6, 44.5 and 35.2; p < .001) even after adjusting for confounders. As compared to singletons, both dizygotic (39.6% vs. 22.7%; p < .001) and monozygotic (39.3% vs. 22.7%; p < .001) pregnancies had a higher frequency of non-right laterality. Laterality was not associated with neurodevelopment, nor confounded, mediated or modified the effect of multiple pregnancy on neurodevelopment.

CONCLUSION

The association of multiple pregnancy to poorer neurodevelopment was independent of children laterality.

Enhanced nutrition improves growth and increases blood adiponectin concentrations in very low birth weight infants

Background

Adequate nutrient supply is essential for optimal postnatal growth in very low birth weight (VLBW, birth weight<1,500 g) infants. Early growth may influence the risk of metabolic syndrome later in life.

Objective

To evaluate growth and blood metabolic markers (adiponectin, leptin, and insulin-like growth factor-1 (IGF-1)) in VLBW infants participating in a randomized nutritional intervention study.

Design

Fifty VLBW infants were randomized to an enhanced nutrient supply or a standard nutrient supply. Thirty-seven infants were evaluated with growth measurements until 2 years corrected age (CA). Metabolic markers were measured at birth and 5 months CA.

Results

Weight gain and head growth were different in the two groups from birth to 2 years CA (weight gain: p_interaction=0.006; head growth: p_interaction=0.002). The intervention group improved their growth z-scores after birth, whereas the control group had a pronounced decline, followed by an increase and caught up with the intervention group after discharge. At 5 months CA, adiponectin concentrations were higher in the intervention group and correlated with weight gain before term (r=0.35) and nutrient supply (0.35≤r≤0.45). Leptin concentrations correlated with weight gain after term and IGF-1 concentrations with length growth before and after term and head growth after term (0.36≤r≤0.53).

Conclusion

Enhanced nutrient supply improved early postnatal growth and may have prevented rapid catch-up growth later in infancy. Adiponectin concentration at 5 months CA was higher in the intervention group and correlated positively with early weight gain and nutrient supply. Early nutrition and growth may affect metabolic markers in infancy.

Clinical Trial Registration (ClinicalTrials.gov) no.: NCT01103219

Newborn Adipokines and Birth Outcomes

BACKGROUND

Adipokines can serve as a measure of adipose tissue activity. Although birthweight correlates with neonatal adiposity, findings for cord blood levels of adipokines and birth outcomes have been conflicted. Therefore, we determined the cross-sectional associations between adipokines measured in newborn dried blood spots (DBS) and birth outcomes.

METHODS

The Upstate KIDS study enrolled mothers and infants from 2008 to 2010. Among infants whose parents consented to the use of residual DBS from newborn screening, 2397 singletons and 1240 twins had adipokine measurements from the Human Obesity Panel (R&D Systems) by Luminex. Odds ratios were estimated by multivariable logistic regression for risk of birth outcomes of preterm delivery (<37 weeks for singletons, <32 for twins) and small-for-gestational age (SGA <10th for singletons and <3rd for twins age- and sex-specific percentiles) by adipokine quintiles. Generalised estimating equations were applied to account for correlations between twins.

RESULTS

Singletons in the lowest compared with the highest quintile of adiponectin were more likely preterm (adjusted odds ratio 3.26; 95% confidence interval [CI] 1.99, 5.34) and SGA (1.81; [95% CI 1.18, 2.77]). Similar associations were observed among twins. Resistin was associated with preterm birth (Q1 vs. Q5: 2.08; [95% CI 1.20, 3.62]) only among singletons. Adipsin had inconsistent associations after adjustment.

CONCLUSIONS

This large population-based study demonstrates that newborn DBS-measured adipokines are associated with birth outcomes, particularly preterm birth and SGA among those with lower adiponectin levels regardless of plurality.

Early Surge in Circulatory Adiponectin Is Associated With Improved Growth at Near Term in Very Preterm Infants

CONTEXT

Adiponectin enhances insulin sensitivity and may play a role in fetal and postnatal growth.

OBJECTIVE

This study aimed to determine whether early postnatal adiponectin concentration change is related to postnatal growth in very preterm infants.

SETTING, DESIGN, AND PATIENTS

This was an in-hospital, prospective, longitudinal cohort study of 52 preterm infants with a gestational age (GA) of 26.0 ± 1.9 (SD) weeks and birth weight (BW) of 889 ± 284 g.

INTERVENTIONS

An analysis of adiponectin was performed on cord blood at birth and peripheral blood at 72 hours, day 7, and then weekly until postmenstrual age (PMA) 40 weeks. Weight, length, and head circumference (HC) measurement was performed weekly and SD scores (SDS) calculated. Energy and protein intake was calculated daily from birth until PMA 35 weeks.

RESULTS

Mean adiponectin concentration increased from 6.8 ± 4.4 μg/mL at 72 hours to 37.4 ± 22.2 μg/mL at 3 weeks; during days 3-21, it was 21.4 ± 12 μg/mL and correlated with GA at birth (r = 0.46, P = .001; BW: r = 0.71, P < .001; BW(SDS): r = 0.42, P = .003). Furthermore, mean adiponectin during days 3-21 correlated with weight(SDS), length(SDS), and HC(SDS) (r = 0.62, 0.65, and 0.62, respectively; all P < .001) at PMA 35 wk). Energy intake (kcal/kg/d) correlated with mean adiponectin during days 3-21 (r = 0.35, P < .013).

CONCLUSIONS

In very preterm infants, adiponectin concentrations increased markedly in the first 3 weeks, and a greater increase was associated with improved postnatal growth.

Filter paper blood spot enzyme linked immunoassay for adiponectin and application in the evaluation of determinants of child insulin sensitivity

BACKGROUND

Adiponectin is an adipocyte-derived hormone that acts as a marker of insulin sensitivity. Bloodspot sampling by fingerstick onto filter paper may increase the feasibility of large-scale studies of the determinants of insulin sensitivity. We first describe the validation of an enzyme-linked immunoassay (ELISA) for quantifying adiponectin from dried blood spots and then demonstrate its application in a large trial (PROBIT).

METHODS

We quantified adiponectin from 3-mm diameter discs (≈3 µL of blood) punched from dried blood spots obtained from: i) whole blood standards (validation); and ii) PROBIT trial samples (application) in which paediatricians collected blood spots from 13,879 children aged 11.5 years from 31 sites across Belarus. We examined the distribution of bloodspot adiponectin by demographic and anthropometric factors, fasting insulin and glucose.

RESULTS

In the validation study, mean intra-assay coefficients of variation (n=162) were 15%, 13% and 10% for 'low' (6.78 µg/ml), 'medium' (18.18 µg/ml) and 'high' (33.13 µg/ml) internal quality control (IQC) samples, respectively; the respective inter-assay values (n=40) were 23%, 21% and 14%. The correlation coefficient between 50 paired whole bloodspot versus plasma samples, collected simultaneously, was 0.87 (95% CI: 0.78 to 0.93). Recovery of known quantities of adiponectin (between 4.5 to 36 µg/ml) was 100.3-133%. Bloodspot adiponectin was stable for at least 30 months at -80°C. In PROBIT, we successfully quantified fasting adiponectin from dried blood spots in 13,329 of 13,879 (96%) children. Mean adiponectin (standard deviation) concentrations were 17.34 µg/ml (7.54) in boys and 18.41 µg/ml (7.92) in girls and were inversely associated with body mass index, fat mass, triceps and subscapular skin-fold thickness, waist circumference, height and fasting glucose.

CONCLUSIONS

Bloodspot ELISA is suitable for measuring adiponectin in very small volumes of blood collected on filter paper and can be applied to large-scale studies.

Cytokine assays: an assessment of the preparation and treatment of blood and tissue samples

Cytokines are key components of the innate and adaptive immune system. As pivotal players in the progression or regression of a pathological process, these molecules provide a window through which diseases can be monitored and can thus act as biomarkers. In order to measure cytokine levels, a plethora of protocols can be applied. These methods include bioassays, protein microarrays, high-performance liquid chromatography (HPLC), sandwich enzyme-linked immunosorbent assay (ELISA), Meso Scale Discovery (MSD) electrochemiluminescence and bead based multiplex immunoassays (MIA). Due to the interaction and activity of cytokines, multiplex immunoassays are at the forefront of cytokine analysis by allowing multiple cytokines to be measured in parallel. However, even with optimized protocols, sample standardization needs to occur before these proteins can optimally act as biomarkers. This review describes various factors influencing the levels of cytokines measured in plasma, serum, dried blood spots and tissue biopsies, focusing on sample collection and handling, long term storage and the repetitive use of samples. By analyzing how each of these factors influences protein levels, it is concluded that samples should be stored at low temperatures in order to maintain cytokine stability. In addition, within a study, sample manipulations should be kept the same, with measurement protocols being chosen for their compatibility with the research in question. By having a clear understanding of what factors influence cytokine levels and how to overcome these technical issues, minimally confounded data can be obtained and cytokines can achieve optimal biomarker activity.

Validity and reliability of perinatal biomarkers of adiposity after storage as dried blood spots on paper

OBJECTIVE

To validate use of chip-based immunoaffinity capillary electrophoresis on dried blood spot samples (DBSS) to measure obesity-related hormones.

METHODS

Chip-based immunoaffinity capillary electrophoresis was used to measure adiponectin, leptin and insulin in capillary serum and DBSS in pregnant women and infant heelstick at birth and six weeks. Concordance of measurements was determined with Pearson's correlation and Bland-Altman plots.

RESULTS

We report high concordance between results obtained from serum and DBSS.

CONCLUSIONS

Ease of sample collection and storage makes DBSS an optimal method for use in studies involving neonates and young children, as well as studies conducted in areas where freezer storage is not available.

Breast milk hormones and regulation of glucose homeostasis

Growing evidence suggests that a complex relationship exists between the central nervous system and peripheral organs involved in energy homeostasis. It consists in the balance between food intake and energy expenditure and includes the regulation of nutrient levels in storage organs, as well as in blood, in particular blood glucose. Therefore, food intake, energy expenditure, and glucose homeostasis are strictly connected to each other. Several hormones, such as leptin, adiponectin, resistin, and ghrelin, are involved in this complex regulation. These hormones play a role in the regulation of glucose metabolism and are involved in the development of obesity, diabetes, and metabolic syndrome. Recently, their presence in breast milk has been detected, suggesting that they may be involved in the regulation of growth in early infancy and could influence the programming of energy balance later in life. This paper focuses on hormones present in breast milk and their role in glucose homeostasis.

Adipokines in breast milk and preterm infants

Studies have shown that the early life environment affects feeding behaviour, food intake and energy balance in later life, suggesting there is a link between foetal and infant growth and the risk of metabolic disorders in adulthood. Although there is an evident epidemiological association between low birth weight and adult-onset diseases, the incidence of metabolic diseases in adulthood among people who were born prematurely is still unknown. Considerable advances have been made during the last years in the scientific knowledge of the benefits of early nutrition, such as breastfeeding, on health and well-being later in life. Nutritional researchers have focussed their attention on the biological characteristics of human breast milk, which represents the main source of nutrients in the first months of life for breastfed infants. Recently, leptin and ghrelin have been detected in the breast milk of mothers of term and preterm infants. Adiponectin and resistin, present in term human milk, have not been investigated in the breast milk of mothers of preterm infants. These hormones are involved in the regulation of energy balance and may have a role in the regulation of growth and development in the neonatal period and infancy, as well as long-term effects on metabolic programming. Leptin, adiponectin and resistin have been found at lower levels in pre-term infants compared with term newborns, whereas there seems to be no difference in ghrelin levels. Future research is necessary to clarify the role of hormones present in breast milk for identifying potential short- and long-term effects of breastfeeding on the health of children born prematurely.

Can hormones contained in mothers' milk account for the beneficial effect of breast-feeding on obesity in children?

Nutrition and growth during infancy are an emerging issue because of their potential link to metabolic health disorders in later life. Moreover, prolonged breast-feeding appears to be associated with a lower risk of obesity than formula feeding. Human milk is a source of various hormones and growth factors, namely adipokines (leptin and adiponectin), ghrelin, resistin and obestatin, which are involved in food intake regulation and energy balance. These compounds are either not found in commercial milk formulas or their presence is still controversial. Diet-related differences during infancy in serum levels of factors involved in energy metabolism might explain anthropometric differences and also differences in dietary habits between breast-fed (BF) and formula-fed (FF) infants later in life, and may thus have long-term health consequences. In this context, the recent finding of higher leptin levels and lower ghrelin levels in BF than in FF infants suggests that differences in hormonal values together with different protein intake could account for the differences in growth between BF and FF infants both during infancy and later in life. In this review, we examine the data related to hormones contained in mothers' milk and their potential protective effect on subsequent obesity and metabolic-related disorders.

Adiponectin and leptin concentrations in dichorionic twins with discordant and concordant growth

CONTEXT

Discordant twin gestation, in which one fetus is growth restricted, is a unique model that can elucidate the mechanism(s) by which the intrauterine environment affects fetal growth.

OBJECTIVE

The objective of the study was to determine the cord blood adiponectin and leptin concentrations and evaluate their association with birth weight in dichorionic twins, with and without growth discordance. DESIGN, SETTING, PARTICIPANTS, AND MAIN OUTCOME MEASURE: In this cross-sectional study, arterial cord blood adiponectin and leptin concentrations were determined in two groups of newborns: 1) discordant twins, in which one of the twins is growth restricted (small for gestation age and abnormal umbilical arteries Doppler) and the other is appropriate for gestation age (AGA) (n = 14 pairs); and 2) concordant twins, in which both twins are AGA (n = 15 pairs).

RESULTS

Results were: 1) within the discordant twins group, the median adiponectin concentration was significantly lower in the growth-restricted newborns than in their cotwins (P = 0.004); 2) within the concordant twin group, there was no significant difference in the median cord blood adiponectin concentration between the two AGA twins; 3) the median leptin concentration did not differ between the twins pairs in both study groups; 4) a positive correlation between cord blood adiponectin concentrations and both birth weight (r = 0.7, P < 0.001) and gestational age (r = 0.6, P < 0.02) was found only in the small-for-gestational-age newborns; 5) linear regression model revealed that birth weight is independently associated with circulating adiponectin concentration.

CONCLUSIONS

Low circulating adiponectin concentrations, previously reported in adults, children, and infants who were born small for gestational age, characterize fetuses with growth restriction and are independently associated with birth weight.

High plasma C-reactive protein (CRP) is related to low paraoxonase-I (PON-I) activity independently of high leptin and low adiponectin in type 2 diabetes mellitus

OBJECTIVES

In type 2 diabetes mellitus, circulating C-reactive protein (CRP) is increased, whereas the high density lipoprotein (HDL)-associated, anti-oxidative and anti-inflammatory enzyme, paraoxonase-I, is decreased. Both high CRP and low paraoxonase-I activity may predict cardiovascular disease. It is unknown whether lower paraoxonase-I activity contributes to higher CRP levels in diabetes. In type 2 diabetic and control subjects, we determined the relationship of CRP with paraoxonase-I when taking account of plasma levels of pro- and anti-inflammatory adipokines.

DESIGN AND PATIENTS

In 81 type 2 diabetic patients and 89 control subjects, plasma high-sensitive CRP, serum paraoxonase-I activity (arylesterase activity, assayed as the rate of hydrolysis of phenyl acetate into phenol), plasma leptin, adiponectin, resistin and lipids were determined.

RESULTS

Body mass index (BMI), waist, insulin resistance, triglycerides, CRP, leptin and resistin levels were higher (P < 0.05 to P < 0.001), whereas HDL cholesterol, paraoxonase-I activity and adiponectin levels were lower (P = 0.02 to P < 0.001) in diabetic compared to control subjects. Multiple linear regression analysis demonstrated that, after controlling for age and gender, CRP was inversely related to paraoxonase-I activity (beta = -0.15, P = 0.028) and adiponectin (beta = -0.18, P = 0.009), and positively to leptin (beta = 0.33, P < 0.001) and BMI (beta = 0.22, P = 0.007), independently of the diabetic state (or of fasting glucose or HbA1c), insulin resistance and lipids (P > 0.20 for all).

CONCLUSIONS

Low paraoxonase-I activity is related to higher CRP, independently of adipokines, as well as of obesity and lipids. Low paraoxonase-I activity in type 2 diabetes mellitus may contribute to increased cardiovascular risk via an effect on enhanced systemic low-grade inflammation.

Gene expression of placental hormones regulating energy balance in small for gestational age neonates

OBJECTIVE

Fetal growth restriction is associated with an increased risk for metabolic and cardiovascular disease in later life. To further elucidate mechanisms that might be involved in the process of prenatal programming, we measured the adipokines leptin, resistin, and adiponectin and the GH-releasing hormone ghrelin in the placenta of small for gestational age (SGA) neonates.

STUDY DESIGN

The control group included 24 placentas of appropriate for gestational age (AGA) newborns, in the study group were 16 placentas of SGA neonates. Gene expression of leptin, resistin, adiponectin, and ghrelin was examined. For hormones showing alterations in gene regulation placental protein expression was measured by Western blot.

RESULTS

Placental mRNA expression of leptin was significantly increased in SGA placentas (p=0.0035, related to beta-actin). Protein concentration was increased, as well. There were no differences in placental resistin, adiponectin, or ghrelin gene expressions between SGA neonates and controls. Leptin was the only hormone to demonstrate a significant inverse correlation with birth weight (r=-0.44, p=0.01). Adiponectin correlated significantly with leptin (r=0.53, p=0.0023) and ghrelin (r=0.50, p=0.0045).

CONCLUSIONS

Placental leptin gene expression and protein concentration showed the expected increase in the SGA group. Leptin was inversely correlated with birth weight. Positive correlation of adiponectin with leptin and ghrelin expression suggests an interaction between these hormones in the placenta. However, the unchanged expression of resistin, adiponectin, and ghrelin in SGA placentas and the absence of correlation with birth weight cast doubt whether these hormones produced in the placenta play a key role in fetal programming.

Effects of blood sample handling procedures on measurable inflammatory markers in plasma, serum and dried blood spot samples

The interests in monitoring inflammation by immunoassay determination of blood inflammatory markers call for information on the stability of these markers in relation to the handling of blood samples. The increasing use of stored biobank samples for such ventures that may have been collected and stored for other purposes, justifies the study hereof. Blood samples were stored for 0, 4, 24, and 48 h at 4 degrees C, room temperature (RT), and at 35 degrees C, respectively, before they were separated into serum or plasma and frozen. Dried blood spot samples (DBSS) were stored for 0, 1, 2, 3, 7, and 30 days at the same temperatures. 27 inflammatory markers in serum and plasma and 25 markers in DBSS were measured by a previously validated multiplex sandwich immunoassay using Luminex xMAP technology. The measurable concentrations of several cytokines in serum and plasma were significantly increased when blood samples were stored for a period of time before the centrifugation, for certain cytokines more than 1000 fold compared to serum and plasma isolated and frozen immediately after venepuncture. The concentrations in serum generally increased more than in plasma. The measurable concentrations of inflammatory markers also changed in DBSS stored under various conditions compared to controls frozen immediately after preparation, but to a much lesser degree than in plasma or serum. The study demonstrates that trustworthy measurement of several inflammatory markers relies on handling of whole blood samples at low temperatures and rapid isolation of plasma and serum. Effects of different handling procedures for all markers studied are given. DBSS proved to be a robust and convenient way to handle samples for immunoassay analysis of inflammatory markers in whole blood.

Adipose Tissue: A Metabolic Regulator. Potential Implications for the Metabolic Outcome of Subjects Born Small for Gestational Age (SGA)

Adipose tissue is involved in the regulation of glucose and lipid metabolism, energy balance, inflammation and immune response. Abdominal obesity plays a key role in the development of insulin resistance because of the high lipolytic rate of visceral adipose tissue and its secretion of adipocytokines. Low birth weight subjects are prone to central redistribution of adipose tissue and are at high risk of developing metabolic syndrome, type 2 diabetes and cardiovascular disease. Intrauterine adipogenesis may play a key role in the fetal origin of the pathogenesis of metabolic syndrome, type 2 diabetes and cardiovascular disease. Therefore, knowledge of the behavior of visceral adipose tissue-derived stem cells could provide a greater understanding of the metabolic risk related to intrauterine growth retardation, with potential clinical implications for the prevention of long-term metabolic alterations.