Presented at the Neonatal Society 2005 Spring Meeting.
Thomas EL1, Uthaya S2, Bell J1, Modi N2
1 MRC Clinical Sciences Centre, Imperial College London, UK
2 Faculty of Medicine, Imperial College London, UK
Introduction: Proton magnetic resonance spectroscopy (1H MRS) offers a novel, non-invasive means to assess intrahepatocellular (IHCL) lipid content (1). Increased hepatic lipid is associated with excessive adiposity, particularly intra-abdominal adiposity, insulin resistance and type II diabetes. We have recently shown that adipose tissue (AT) distribution is altered in the preterm infant at term, with significantly increased intra-abdominal AT (2). This aim of this study was establish the feasibility of investigating IHCL deposition in infants using 1H MRS.
Methods: Whole body MR AT imaging was performed as previously described (2) on a 1.5T Eclipse multinuclear system. We studied preterm infants at term and term-born infants within a week of birth. 1H MR spectra (fig 1) were obtained from the right lobe of the liver using a PRESS sequence (TR 1500ms, TE 135ms) without water saturation (1). IHCL content is presented relative to liver water content, after correcting for T1 and T2. We employed one way analysis of variance for these preliminary analyses. The study was approved by the local research ethics committee.
Results: To date we have studied 9 infants, 5 born preterm at a gestational age ranging from 29 to 31 weeks, and 4 healthy term-born infants. These were compared with 5 healthy control adults. Preterm infants had significantly elevated IHCL compared with term infants and adults (Kruskal Wallis, p=0.016, fig 2), though adults had a highly significant increased content of total AT (p=0.008) with an increased ratio of intra-abdominal to subcutaneous AT (p=0.028). We found no relationship between total AT content or distribution and IHCL. Within the preterm group there was no obvious relationship between IHCL, rate of postnatal weight gain, parenteral nutrition use or illness severity.
Discussion: We have demonstrated the feasibility of obtaining hepatic 1H MR spectra for quantification of IHCL in infants. The clinical relevance of increased hepatic lipid in preterm infants is as yet unknown. It may be transient and represent recovery from previous nutrient deprivation. Alternatively, persisting increase in IHCL might underlie the observed abnormalities in insulin sensitivity in adolescence in children born preterm (3).
References
1. Thomas et al Gut 2005; 54:122-127.
2. Uthaya et al Pediatr Res 2005; 57:1-6.
3 Hofman et al NEJM 2004; 351:2179-86