Presented at the Neonatal Society 2004 Autumn Meeting.
Modi N1, Thomas EL2, Harrington TAM1, Uthaya S1, Doré C3, Bell J2
1 Chelsea & Westminster Campus, Imperial College London, UK
2 Clinical Sciences Centre, London, UK
3 MRC Clinical Trials Unit, London, UK
Background: The suggestion that increased adiposity may be linked with growth early in development has aroused considerable interest. Attention has largely focused on size at birth (used as an index of intrauterine growth), postnatal growth and infant nutrition, but disentangling these variables has proved difficult. Outcomes have usually been assessed in childhood or adult life, with little attention paid to alterations in adiposity during normal growth in infancy.
Aim: We have previously presented details of alterations in adipose tissue (AT) distribution between birth and 6 weeks to the Society. Here we aimed to examine changes in adipose tissue content in relation to postnatal growth in healthy term-born infants.
Methods: The study was approved by the hospital research ethics committee and parental consent was obtained. We classified infants at birth as appropriately grown for gestational age (AG) or malnourished (MG) if they had evidence of deceleration of growth in utero, a characteristic clinical phenotype (loose thin skin with prominent ribs, a scaphoid abdomen, and muscle wasting over the cheeks, arms, buttocks and thighs) and a birth weight below the 10th centile. We measured weight, length and head circumference (HC) and carried out whole body AT magnetic resonance imaging at birth and at 6 weeks as previously described by our group (1). We expressed each anthropometric index as standard deviation score (SDS) and growth between birth and 6 weeks as SDS gain (SDSG) calculated using commercially available software based on the 1990 British growth reference (2). SDSG is the change in SDS adjusted for sex and reference correlations between measurements at two time points (3). We coded infant diet as exclusively breast fed, breast and formula fed, and exclusively formula fed. We converted total AT to mass, given a density of AT of 0.9g/cm3 and expressed this as a percentage of body weight (%ATM). Data were analysed using SPSS version 10.5.
Results: We studied 29 term-born infants. We found a striking correlation between %ATM at 6 weeks and length SDSG (r = 0.712, p < 0.001), a weaker correlation with weight SDSG (r = 0.464, p = 0.011), and no correlation with HC SDSG (r=0.009, p=0.965). Greater than 80% of the variance in %ATM at 6 weeks (R2 = 0.876, adjusted R2 = 0. 826), was explained by length SDSG and the interaction between MG status and exclusive breast feeding, allowing for baseline (birth) length SDS and %ATM. The highest %ATM at 6 weeks, allowing for these variables, was seen in MG infants who were exclusively breast fed (mean, 95%CI: 33.5%, 29.5 to 37.5) and the lowest in MG infants who had received mixed breast and formula feeds (24.1%, 20.8 to 27.5).
Conclusion: Increasing adiposity accompanies accelerated growth in length or weight regardless of size at birth. This is the first direct demonstration of this effect and supports epidemiological observations pointing to such an association.
Speculation: The physiological and cellular determinants of accelerated or catch-up growth have not been fully elucidated. Our observations suggest the possibility of an adipokine-mediated, positive feedback process with total AT quantity signalling promotion of growth and adiposity.
References
1 Harrington TAM et al, Pediatr Res 2004; 55:437-441
2 Child Growth Foundation, 2 Mayfield Avenue, London W4 1PW
3 Cole TJ Arch Dis Child 1995; 73:8-16