Associations of IGF-1 gene variants and milk protein intake with IGF-I concentrations in infants at age 6 months - results from a randomized clinical trial

Assessing conflict of interest reporting and quality of clinical trials on infant formula: a systematic review

OBJECTIVES

This study aims to assess the quality, risk of bias, and conflicts of interest (COIs) of clinical trials conducted on the effects of fortified infant formula.

STUDY DESIGN AND SETTTING

Systematic review including all randomized clinical trials targeting healthy children and using three arms: fortified infant formula; standard formula; and breastfeeding. We performed a descriptive analysis of the studies reviewed, assessed their quality using the "Risk of Bias 2- RoB 2" tool, and identified COIs.

RESULTS

A total of 40 studies were included. All showed a high overall risk of bias, with this being especially noteworthy in the "deviations from intention to treat" and "missing outcome data" domains. Of the total included studies, 29 reported conclusions in favor of the fortified formula; 15 studies reported multiple conclusions that were either contradictory or not in line with the results. COIs with industry were identified in 33 studies, and in 17 studies, these conflicts were not declared in the appropriate section.

CONCLUSION

From a methodological perspective, studies on fortified infant formula display low quality, made evident by the high risk of bias. Additionally, there are frequent COIs. These aspects must be considered by health professionals and the population when drawing up recommendations for the use of this product.

Higher versus lower protein intake in formula-fed term infants

BACKGROUND

Many infants are fed infant formulas to promote growth. Some formulas have a high protein content (≥ 2.5 g per 100 kcal) to accelerate weight gain during the first year of life. The risk-benefit balance of these formulas is unclear.

OBJECTIVES

To evaluate the benefits and harms of higher protein intake versus lower protein intake in healthy, formula-fed term infants.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, LILACS, OpenGrey, clinical trial registries, and conference proceedings in October 2022.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) of healthy formula-fed infants (those fed only formula and those given formula as a complementary food). We included infants of any sex or ethnicity who were fed infant formula for at least three consecutive months at any time from birth. We excluded quasi-randomized trials, observational studies, and infants with congenital malformations or serious underlying diseases. We defined high protein content as 2.5 g or more per 100 kcal, and low protein content as less than 1.8 g per 100 kcal (for exclusive formula feeding) or less than 1.7 g per 100 kcal (for complementary formula feeding).

DATA COLLECTION AND ANALYSIS

Four review authors independently assessed the risk of bias and extracted data from trials, and a fifth review author resolved discrepancies. We performed random-effects meta-analyses, calculating risk ratios (RRs) or Peto odds ratios (Peto ORs) with 95% confidence intervals (CIs) for dichotomous outcomes, and mean differences (MDs) with 95% CIs for continuous outcomes. We used the GRADE approach to evaluate the certainty of the evidence.

MAIN RESULTS

We included 11 RCTs (1185 infants) conducted in high-income countries. Seven trials (1629 infants) compared high-protein formula against standard-protein formula, and four trials (256 infants) compared standard-protein formula against low-protein formula. The longest follow-up was 11 years. High-protein formula versus standard-protein formula We found very low-certainty evidence that feeding healthy term infants high-protein formula compared to standard-protein formula has little or no effect on underweight (MD in weight-for-age z-score 0.05 SDs, 95% CI -0.09 to 0.19; P = 0.51, I2 = 61%; 7 studies, 1629 participants), stunting (MD in height-for-age z-score 0.15 SDs, 95% CI -0.05 to 0.35; P = 0.14, I2 = 73%; 7 studies, 1629 participants), and wasting (MD in weight-for-height z-score -0.12 SDs, 95% CI -0.31 to 0.07; P = 0.20, I2 = 94%; 7 studies, 1629 participants) in the first year of life. We found very low-certainty evidence that feeding healthy infants high-protein formula compared to standard-protein formula has little or no effect on the occurrence of overweight (RR 1.26, 95% CI 0.63 to 2.51; P = 0.51; 1 study, 1090 participants) or obesity (RR 1.96, 95% CI 0.59 to 6.48; P = 0.27; 1 study, 1090 participants) at five years of follow-up. No studies reported all-cause mortality. Feeding healthy infants high-protein formula compared to standard-protein formula may have little or no effect on the occurrence of adverse events such as diarrhea, vomiting, or milk hypersensitivity (RR 0.93, 95% CI 0.76 to 1.13; P = 0.44, I2 = 0%; 4 studies, 445 participants; low-certainty evidence) in the first year of life. Standard-protein formula versus low-protein formula We found very low-certainty evidence that feeding healthy infants standard-protein formula compared to low-protein formula has little or no effect on underweight (MD in weight-for-age z-score 0.0, 95% CI -0.43 to 0.43; P = 0.99, I2 = 81%; 4 studies, 256 participants), stunting (MD in height-for-age z-score -0.01, 95% CI -0.36 to 0.35; P = 0.96, I2 = 73%; 4 studies, 256 participants), and wasting (MD in weight-for-height z-score 0.13, 95% CI -0.29 to 0.56; P = 0.54, I2 = 95%; 4 studies, 256 participants) in the first year of life. No studies reported overweight, obesity, or all-cause mortality. Feeding healthy infants standard-protein formula compared to low-protein formula may have little or no effect on the occurrence of adverse events such as diarrhea, vomiting, or milk hypersensitivity (Peto OR 1.55, 95% CI 0.70 to 3.40; P = 0.28, I2 = 0%; 2 studies, 206 participants; low-certainty evidence) in the first four months of life.

AUTHORS' CONCLUSIONS

We are unsure if feeding healthy infants high-protein formula compared to standard-protein formula has an effect on undernutrition, overweight, or obesity. There may be little or no difference in the risk of adverse effects between infants fed with high-protein formula versus those fed with standard-protein formula. We are unsure if feeding healthy infants standard-protein formula compared to low-protein formula has any effect on undernutrition. There may be little or no difference in the risk of adverse effects between infants fed with standard-protein formula versus those fed with low-protein formula. The findings of six ongoing studies and two studies awaiting classification studies may change the conclusions of this review.

Quantity and Source of Protein during Complementary Feeding and Infant Growth: Evidence from a Population Facing Double Burden of Malnutrition

BACKGROUND

While high protein intake during infancy may increase obesity risk, low qualities and quantities of protein contribute to undernutrition. This study aimed to investigate the impact of the amount and source of protein on infant growth during complementary feeding (CF) in a country where under- and overnutrition co-exist as the so-called the double burden of malnutrition.

METHODS

A multicenter, prospective cohort was conducted. Healthy term infants were enrolled with dietary and anthropometric assessments at 6, 9 and 12 months (M). Blood samples were collected at 12M for IGF-1, IGFBP-3 and insulin analyses.

RESULTS

A total of 145 infants were enrolled (49.7% female). Animal source foods (ASFs) were the main protein source and showed a positive, dose-response relationship with weight-for-age, weight-for-length and BMI z-scores after adjusting for potential confounders. However, dairy protein had a greater impact on those parameters than non-dairy ASFs, while plant-based protein had no effect. These findings were supported by higher levels of IGF-1, IGFBP-3 and insulin following a higher intake of dairy protein. None of the protein sources were associated with linear growth.

CONCLUSIONS

This study showed the distinctive impact of different protein sources during CF on infant growth. A high intake of dairy protein, mainly from infant formula, had a greater impact on weight gain and growth-related hormones.

Effect of milk protein content in Toddler formula on later BMI and obesity risk: protocol of the multicentre randomised controlled Toddler Milk Intervention (ToMI) trial

INTRODUCTION

Reduction of milk protein content in infant formula provided during the first year of life has been shown to reduce early weight gain and obesity later in life. While rapid weight gain during the first 2 years of life is one of the strongest early predictors of obesity, the role of animal protein intake beyond the first year of life is unclear. The aim of this study is to examine the role of milk protein during the second year of life in healthy children on weight gain and obesity risk in preschool age.

METHODS AND ANALYSIS

This randomised, double-blinded study enrolled 1618 children aged 11.5-13.5 months in Spain and Germany into two groups receiving isocaloric toddler milk with differing protein content during the second year of life. The experimental formula contains 1.5 g/100 kcal and the control formula 6.15 g/100 kcal protein and otherwise equal formula composition, except for modified fat content to achieve equal energy density. The primary endpoint is body mass index (BMI)-for-age z-score at the age of 24 months adjusted for BMI at 12 months of age. The children are followed until 6 years of age.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the ethical committees of the LMU University Hospital Munich, Germany (Nr. 555-15) and at Institut d'Investigació Sanitaria Pere Virgili, Reus, Spain (Ref. CEIm IISPV 013/2016). We aim at publishing results in peer-reviewed journals and sharing of results with study participants.

TRIAL REGISTRATION NUMBER

NCT02907502.

Long-term effects of a modified, low-protein infant formula on growth and body composition: Follow-up of a randomized, double-blind, equivalence trial

BACKGROUND & AIM

High protein intake in early life is associated with an increased risk of childhood obesity. Feeding a modified lower-protein (mLP) infant formula (1.7 g protein/100 kcal) until the age of 6 months is safe and supports adequate growth. The aim of the present study is to assess longer-term anthropometry with BMI at 1 and 2 years as primary outcome parameter and body composition in children fed mLP formula.

METHODS

Healthy term-born infants received mLP or control formula (CTRL) (2.1 g protein/100 kcal) until 6 months of age in a double-blinded RCT. A breast-fed (BF) group served as a reference. Anthropometry data were obtained at 1 and 2 years of age. At the age of 2 years, body composition was measured with air-displacement plethysmography. Groups were compared using linear mixed model analysis.

RESULTS

At 1 and 2 years of age, anthropometry, including BMI, and body composition did not differ between the formula groups (n = 74 mLP; n = 69 CTRL). Compared to the BF group (n = 51), both formula-fed groups had higher z scores for weight for age, length for age, waist circumference for age, and mid-upper arm circumference for age at 1 year of age, but not at 2 years of age (except for z score of weight for age in the mLP group). In comparison to the BF group, only the mLP group had higher fat mass, fat-free mass, and fat mass index. However, % body fat did not differ between feeding groups.

CONCLUSIONS

In this follow-up study, no significant differences in anthropometry or body composition were observed until 2 years of age between infants fed mLP and CTRL formula, despite the significantly lower protein intake in the mLP group during the intervention period. The observed differences in growth and body composition between the mLP group and the BF reference group makes it necessary to execute new trials evaluating infant formulas with improved protein quality together with further reductions in protein content.

CLINICAL TRIAL REGISTRY

This trial was registered in the Dutch Trial Register (Study ID number NTR4829, trial number NL4677). https://www.trialregister.nl/trial/4677.

Early-Life Metabolic and Hormonal Markers in Blood and Growth until Age 2 Years: Results from a Randomized Controlled Trial in Healthy Infants Fed a Modified Low-Protein Infant Formula

Background: High protein intake in early life is associated with an increased risk of childhood obesity. Dietary protein intake may be a key mechanistic modulator through alterations in endocrine and metabolic responses. Objective: We aimed to determine the impact of different protein intake of infants on blood metabolic and hormonal markers at the age of four months. We further aimed to investigate the association between these markers and anthropometric parameters and body composition until the age of two years. Design: Term infants received a modified low-protein formula (mLP) (1.7 g protein/100 kcal) or a specifically designed control formula (CTRL) (2.1 g protein/100 kcal) until 6 months of age in a double blinded RCT. The outcomes were compared with a breast-fed (BF) group. Glucose, insulin, leptin, IGF-1, IGF-BP1, -BP2, and -BP3 levels were measured at the age of 4 months. Anthropometric parameters and body composition were assessed until the age of 2 years. Groups were compared using linear regression analysis. Results: No significant differences were observed in any of the blood parameters between the formula groups (n = 53 mLP; n = 44 CTRL) despite a significant difference in protein intake. Insulin and HOMA-IR were higher in both formula groups compared to the BF group (n = 36) (p < 0.001). IGF-BP1 was lower in both formula groups compared to the BF group (p < 0.01). We found a lower IGF-BP2 level in the CTRL group compared to the BF group (p < 0.01) and a higher IGF-BP3 level in the mLP group compared to the BF group (p = 0.03). There were no significant differences in glucose, leptin, and IGF-1 between the three feeding groups. We found specific associations of all early-life metabolic and hormonal blood parameters with long-term growth and body composition except for IGF-1. Conclusions: Reducing protein intake by 20% did not result in a different metabolic profile in formula-fed infants at 4 months of age. Formula-fed infants had a lower insulin sensitivity compared to breast-fed infants. We found associations between all metabolic and hormonal markers (except for IGF-1) determined at age 4 months and growth and body composition up to two years of age.

Modifications of Own Mothers' Milk Fortification Protocol Affect Early Plasma IGF-I and Ghrelin Levels in Preterm Infants. A Randomized Clinical Trial

The aim was to investigate the effect of two own mother’s milk (OMM) fortification protocols on (a) IGF-I and ghrelin plasma levels at 35 post-conceptional weeks (PCW, T2) and whether this effect is maintained after elimination of the differences in OMM fortification, and (b) growth until 12 months corrected age. Forty-eight OMM-fed preterm infants (GA 24–32 weeks) were randomly allocated to the fixed-fortification (FF) group (n = 23) and the protein-targeting fortification (PTF) group (n = 25) targeting the recommended daily protein intake (PI). Plasma IGF-I and ghrelin were assessed at 35 (T2) and 40 (T3) PCW while growth was longitudinally assessed until 12 months corrected age. PTF group had lower IGF-I and higher ghrelin than FF group at T2, while receiving lower daily protein and energy amounts. PI correlated positively to T2-IGF-I and inversely to T3-ghrelin while energy intake (EI) correlated inversely to T2- and T3-ghrelin. Group and PI were independent predictors of adjusted T2-IGF-I, while group and EI were predictors of adjusted and T2-ghrelin. Growth parameter z-scores were comparable between groups up to 12 months corrected age. Modifications of OMM fortification have a transient effect on early plasma IGF-I and ghrelin levels in preterm infants in a way consistent with the previously recognized protein-energy/endocrine balance, indicating a potential programming effect.

Childhood Dietary Intake in Italy: The Epidemiological "MY FOOD DIARY" Survey

Promoting a healthy lifestyle during the first years of life is a key strategy for controlling obesity risk in later life; having good-quality epidemiological data on eating habits of infants and toddlers can improve awareness and possibly the education given by pediatricians to parents and children. With this aim, we performed a survey about the dietary pattern of Italian children in early childhood. We described the intake of energy, macronutrients and fiber, minerals, and vitamins of 443 Italian children (range 6.4–131 months), through a three-day food record filled out by their parents and assessed by family pediatricians. The results were compared with the Italian Dietary Reference Values. The median protein intake, in g/kg per body weight, exceeded the average requirement in all age groups, and in the 12–36 month period, the intake as % of energy was outside the reference range (>15%). The majority of the children consumed quantities of simple carbohydrates (consisting of both natural sugars and free or added sugars, 82.3% of the children in the study) and saturated fats (69% of the children in the study) above the limits of the Italian Dietary Reference Values, with low intake of fiber and polyunsaturated fats. Median mineral intake, in our study, was different depending on age, while vitamin D intake was very low in all age groups. This is one of the few studies reporting on the nutrient intake of Italian children with reference to nutrition recommendations in order to identify the principal nutritional errors. The present results underline the need for healthcare policies starting from the first years of life in order to ameliorate nutrient intake during childhood, possibly impacting long-term health outcomes.

IGF1 gene polymorphisms associated with diabetic retinopathy risk in Chinese Han population

Objective

This study aimed to explore the association of insulin-like growth factor 1 gene (IGF1) polymorphisms with diabetic retinopathy (DR) in a Chinese Han population.

Methods

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used for genotyping. Genotype frequencies were compared by chi-square test. Odds ratio (OR) with 95% confidence interval (95%CI) was calculated to express the risk intensity of DR. Linkage disequilibrium between IGF1 polymorphisms was analyzed by Haploview. Serum IGF1 concentration was measured by enzyme-linked immunosorbent assays (ELISA) and assessed by student's t test.

Results

AG genotype of rs6218 and TT genotype of rs35767 were significantly associated with the elevated risk of DR (rs6218: OR=1.77, P=0.04; rs35767: OR=2.32, P=0.03) and type II diabetes mellitus (T2DM) (rs6218: OR=1.92, P=0.00. rs35767: OR=2.29, P=0.02). Only T allele of rs35767 significantly increased the risk of DR (OR=1.45, P=0.04), however, rs6218 (OR=1.92, P=0.00), rs35767 (OR=0.02, P=0.02) and rs5742612 (OR=2.21, P=0.04) showed obvious association with T2DM. Haplotypes were only associated with T2DM, but not DR. Minor allele homozygote of rs35767 was obviously correlated with serum IGF1 level.

Conclusion

IGF1 rs6218 and rs35767 polymorphisms contribute to the risk of DR. IGF1 rs35767 polymorphism may participate in the regulation of serum IGF1 concentration in DR.

Long-Term Health Impact of Early Nutrition: The Power of Programming

The Power of Programming conference 2016 at Ludwig-Maximilians-Universität Munich brought together about 600 researchers and other stakeholders from around the world who reviewed the recent evidence on the lasting health impact of environment and nutrition during early life, from pre-pregnancy to early childhood. The conference was hosted by the Early Nutrition Project, a multidisciplinary research collaboration funded by the European Commission with collaborating researchers from 35 institutions in 15 countries in Europe, the United States and Australia. The project explores the early origins of obesity, adiposity and associated non-communicable diseases, underlying mechanisms and opportunities for prevention. The project also proactively supports translational application of research findings. In fact, some existing evidence has already been rapidly adopted into policy, regulatory standards and practice. Further, broad dissemination of findings is achieved through the established digital eLearning platform of the Early Nutrition eAcademy, video clip-based learning and graphically supported messaging to consumers. The project demonstrated powerful effects of early metabolic programming on later health. Compared to other common prevention strategies, modifying risk trajectories in early life can achieve a much larger risk reduction and be more cost-effective. While some effective prevention strategies have been promptly implemented in policy and guidelines, legislation and practice, in other areas, the uptake is limited by a paucity of quality human intervention trials and insufficient evaluation of the feasibility of implementation and econometric impact. This needs to be strengthened by future collaborative research work.

Novel genetic loci underlying human intracranial volume identified through genome-wide association

Intracranial volume reflects the maximally attained brain size during development, and remains stable with loss of tissue in late life. It is highly heritable, but the underlying genes remain largely undetermined. In a genome-wide association study of 32,438 adults, we discovered five previously unknown loci for intracranial volume and confirmed two known signals. Four of the loci were also associated with adult human stature, but these remained associated with intracranial volume after adjusting for height. We found a high genetic correlation with child head circumference (ρgenetic = 0.748), which indicates a similar genetic background and allowed us to identify four additional loci through meta-analysis (Ncombined = 37,345). Variants for intracranial volume were also related to childhood and adult cognitive function, and Parkinson's disease, and were enriched near genes involved in growth pathways, including PI3K-AKT signaling. These findings identify the biological underpinnings of intracranial volume and their link to physiological and pathological traits.

Protein intakes and their nutritional sources during the first 2 years of life: secondary data evaluation from the European Childhood Obesity Project

BACKGROUND/OBJECTIVES

High protein intake in infancy affects future obesity risk and other health outcomes. We aim to describe total protein intake and its sources in a birth cohort in five European countries over the first 2 years of life.

SUBJECTS/METHODS

A total of 746 formula-fed infants were included. Three-day weighed dietary records at 6, 7, 8, 9, 12, 18 and 24 months of age were used. Kruskal-Wallis, ANOVA and Friedman's tests were used to assess possible differences in nutritional intake among countries and over time.

RESULTS

Dairy products were the main components of the infants' diets. Cow's milk was rarely introduced before 12 months of age, whereas infants' formula was the main contributor of protein intake. Food choices and protein intake differed among countries (P<0.001). Protein intake often exceeded European recommendations from 9 months onwards, partly because of the substitution of dairy protein (mainly infant formula) by meat protein. Two nutritional patterns were identified that were characterised by differences in energy, fat, protein and animal protein intake. Finally, food consumption was not always in line with protein intakes, and thus infants from some countries showed high consumption of specific food groups but relatively low protein intakes.

CONCLUSIONS

During weaning, over-limited substitution of dairy products with other sources (especially meat) resulted in relatively high protein intakes in formula-fed infants. Differences in preferences of specific protein sources from complementary foods existed among European countries. Great opportunities in improving early nutrition were revealed, although cultural and geographical differences should always be considered.

Milk: a postnatal imprinting system stabilizing FoxP3 expression and regulatory T cell differentiation

BACKGROUND

Breastfeeding has protective effects for the development of allergies and atopy. Recent evidence underlines that consumption of unboiled farm milk in early life is a key factor preventing the development of atopic diseases. Farm milk intake has been associated with increased demethylation of FOXP3 and increased numbers of regulatory T cells (Tregs). Thus, the questions arose which components of farm milk control the differentiation and function of Tregs, critical T cell subsets that promote tolerance induction and inhibit the development of allergy and autoimmunity.

FINDINGS

Based on translational research we identified at least six major signalling pathways that could explain milk's biological role controlling stable FoxP3 expression and Treg differentiation: (1) via maintaining appropriate magnitudes of Akt-mTORC1 signalling, (2) via transfer of milk fat-derived long-chain ω-3 fatty acids, (3) via transfer of milk-derived exosomal microRNAs that apparently decrease FOXP3 promoter methylation, (4) via transfer of exosomal transforming growth factor-β, which induces SMAD2/SMAD3-dependent FoxP3 expression, (5) via milk-derived Bifidobacterium and Lactobacillus species that induce interleukin-10 (IL-10)-mediated differentiation of Tregs, and (6) via milk-derived oligosaccharides that serve as selected nutrients for the growth of bifidobacteria in the intestine of the new born infant.

CONCLUSION

Accumulating evidence underlines that milk is a complex signalling and epigenetic imprinting network that promotes stable FoxP3 expression and long-lasting Treg differentiation, crucial postnatal events preventing atopic and autoimmune diseases.

Early Programming by Protein Intake: The Effect of Protein on Adiposity Development and the Growth and Functionality of Vital Organs

This article reviews the role of protein intake on metabolic programming early in life. The observations that breastfeeding in infancy reduces the risk of being overweight and obese later in life and the differences in the protein content between formula milk and human milk have generated the early protein hypothesis. The present review focuses on a mechanistic approach to programmed adiposity and the growth and development of other organs by protein intake in infancy, which may be mediated by branched-chain amino acids, insulin, and insulin-like growth factor 1 via the mammalian target of rapamycin. Observational studies and clinical trials have shown that lowering the protein content in infant and follow-on formulas may reduce the risk of becoming obese later in life. The recent body of evidence is currently being translated into new policies. Therefore, the evolution of European regulatory laws and recommendations by expert panels on the protein content of infant and follow-on formulas are also reviewed. Research gaps, such as the critical window for programming adiposity by protein intake, testing formulas with modified amino acids, and the long-term consequences of differences in protein intake on organ functionality among well-nourished infants, have been identified.

Role of selected amino acids on plasma IGF-I concentration in infants

PURPOSE

Insulin-like growth factor-I (IGF-I) is related to growth and its secretion is modified by protein intake in early infancy. We examined the relationship of dietary protein and circulating amino acids on plasma IGF-I levels and early growth.

METHODS

Healthy formula-fed infants (n = 213) were randomly assigned to receive either a protein-reduced infant formula with alpha-lactalbumin-enriched whey and free tryptophan and phenylalanine (IF) or an isocaloric standard formula without free amino acids (CF) for the first 120 days of life. A group of breastfed (BF) infants was studied as a non-randomized reference cohort. Biochemical variables were measured shortly after birth (subpopulation) and at an age of 120 days. A path analysis was used to explore the relationship between IGF-I, insulin and amino acids. Results are derived from secondary analyses of a randomized controlled trial.

RESULTS

Plasma concentrations of IGF-I at 120 days were significantly higher in IF than in CF infants [58.5 (15.0) vs. 53.7 (9.95) ng/mL; p = 0.020]. BF infants showed lower IGF-I concentrations of 41.6 (10.7) ng/mL. All amino acids but Thr and Cit had a more marked effect on insulin than on IGF-I level. Considering weight, sex and feeding group, Trp explained an equal percentage of variance of IGF-I and insulin (total R ² 12.5 % of IGF-I and 12.3 % of insulin), while branched-chain AA explained an up to twofold higher variance of insulin than IGF-I. Compared to CF, IF explained 18.9 % of the IGF-I level (p = 0.03), while for insulin no direct effect was detectable.

CONCLUSION

Higher IGF-I concentrations and growth velocities in infants receiving protein-reduced IF indicate that the protein concentration of an infant formula alone does not control IGF-I levels and growth. Other components (e.g., selected amino acids) of infant formulae might control directly or indirectly via insulin influence IGF-I.

Mediation from multilevel to structural equation modeling

BACKGROUND/AIMS

The purpose of this article is to outline multilevel structural equation modeling (MSEM) for mediation analysis of longitudinal data. The introduction of mediating variables can improve experimental and nonexperimental studies of child growth in several ways as discussed throughout this article. Single-mediator individual-level and multilevel mediation models illustrate several current issues in the estimation of mediation with longitudinal data. The strengths of incorporating structural equation modeling (SEM) with multilevel mediation modeling are described. SUMMARY AND KEY MESSAGES: Longitudinal mediation models are pervasive in many areas of research including child growth. Longitudinal mediation models are ideally modeled as repeated measurements clustered within individuals. Further, the combination of MSEM and SEM provides an ideal approach for several reasons, including the ability to assess effects at different levels of analysis, incorporation of measurement error and possible random effects that vary across individuals.

Rapid growth and childhood obesity are strongly associated with lysoPC(14:0)

BACKGROUND

Despite the growing interest in the early-origins-of-later-disease hypothesis, little is known about the metabolic underpinnings linking infant weight gain and childhood obesity.

OBJECTIVE

To discover biomarkers reflective of weight change in the first 6 months and overweight/obesity at age 6 years via a targeted metabolomics approach.

DESIGN

This analysis comprised 726 infants from a European multicenter randomized trial (Childhood Obesity Programme, CHOP) for whom plasma blood samples at age 6 months and anthropometric data up to the age of 6 years were available. 'Rapid growth' was defined as a positive difference in weight within the first 6 months of life standardized to WHO growth standards. Weight change was regressed on each of 168 metabolites (acylcarnitines, lysophosphatidylcholines, sphingomyelins, and amino acids). Metabolites significant after Bonferroni's correction were tested as predictors of later overweight/obesity.

RESULTS

Among the overall 19 significant metabolites, 4 were associated with rapid growth and 15 were associated with a less-than-ideal weight change. After adjusting for feeding group, only the lysophosphatidylcholine LPCaC14:0 remained significantly associated with rapid weight gain (β = 0.18). Only LPCaC14:0 at age 6 months was predictive of overweight/obesity at age 6 years (OR 1.33; 95% CI 1.04-1.69).

CONCLUSION

LPCa14:0 is strongly related to rapid growth in infancy and childhood overweight/obesity. This suggests that LPCaC14:0 levels may represent a metabolically programmed effect of infant weight gain on the later obesity risk. However, these results require confirmation by independent cohorts.