Presented at the Neonatal Society 2013 Spring Meeting.
Parkinson JRC1, Vasu V2, Hyde MJ1, Fitz-Simon N1, Thomas EL3, Bell JD3, Modi N1
1 Section of Neonatal Medicine, Chelsea and Westminster Campus, Imperial College London, UK
2 Department of Child Health, William Harvey Hospital, Ashford, Kent, UK
3 Metabolic and Molecular Imaging Group, Hammersmith Hospital, Imperial College London, UK
Background: In adults, there is a positive association between intrahepatocellular lipid (IHCL) and internal abdominal adipose tissue (IAAT) (1), with both depots linked to insulin resistance and type 2 diabetes (2, 3). Previous work from our group has shown elevated levels of both IHCL and IAAT in ex-preterm adults (4). However, the relationship between IHCL and IAAT in preterm infants is unknown. The aim of this study was to describe the relationship between IHCL and total/regional AT depots in preterm infants at term age.
Methods: We utilised data from two research ethic approved studies. Preterm infants (<32 weeks GA at birth) underwent whole body magnetic resonance (MR) imaging and 1H MR spectroscopy of the liver at term age according to a previously described and established protocol (1). Total and regional AT volumes were calculated by Vardis (http://vardisgroup.com) using a thresholding technique. IHCL values were adjusted for T1 & T2 effects using hepatic water as an internal standard (4). IHCL data was log transformed for analysis and linear regression performed in SPSS 20, adjusting for GA at scan.
Results: 24 preterm infants (11 male) were evaluated. Birth weight and birth GA were (mean (SD)) 1.32kg (0.35kg) and 29.3 weeks (2.3 weeks) respectively. The results of linear regression analysis between log-transformed IHCL and individual adipose depots are shown in Table 1. A non-significant trend towards an association was observed between IHCL and both deep subcutaneous AT (% change in IHCL per 1ml of DSCA (95% CI): 5.4 (-1.0, 106.4, p=0.054) and IAAT (5.0 (-6.4, 103.7), p=0.08) with wide confidence intervals observed for both depots (Table 1).
Table: Linear Regression Analysis. Percentage change in IHCL per 1ml change in adipose tissue (adjusted for gestational age at time of MR imaging).
Conclusion: These data indicate no clear association between adipose tissue depots and IHCL in preterm infants at term age. From a functional standpoint, deep subcutaneous AT behaves similarly to IAAT in adults. The trend towards an association with IHCL may anticipate the relationship in adulthood indicative of adverse metabolic health. Studies examining the natural progression of IHCL deposition and AT depots are required to test this hypothesis.
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1. Thomas, E. L et al. (2012) The missing risk: MRI and MRS phenotyping of abdominal adiposity and ectopic fat, Obesity (Silver.Spring). 20(1), 76-87
2. Fabbrini, E et al. (2009) Intrahepatic fat, not visceral fat, is linked with metabolic complications of obesity, Proc Natl Acad Sci U S A 106, 15430-15435
3. Despres, J. P. et al. (2006) Abdominal obesity and metabolic syndrome, Nature, 881-887
4. Thomas, E. L et al. (2011) Aberrant adiposity and ectopic lipid deposition characterize the adult phenotype of the preterm infant, Pediatr.Res. 70(5), 507-512