Niveles de Retinol Hepatico y óseo en cadáveres de Adolescentes y Adultos Guatemaltecos (Liver and Bone Retinol Levels in Guatemalan Adolescents and Adults)

Objectives:

1. To determine the post mortem concentration of hepatic and bone VA in corpses of adolescent, young and elderly adults as an indicator of exposure to dietary VA
2. To assess the effect of high VA exposure on key enzymes in liver and bone tissue and to assess the risk of hypervitaminosis A in people exposed to compulsory mass vitamin A fortification program in Guatemala.

Methodology:

Setting and sampling The corpses for this study will be obtained from the National Institute of Forensic Sciences' (INACIF) departmental morgues in 2 hospitals in Guatemala City. The study population will be 150 cadavers sampled for VA tissue concentration; gene expression analysis combined with histopathology.

Sample collection process and duration All samples will be collected during necropsies carried out at the INACIF forensic morgue. During necropsy, the liver will be weighed and the information recorded. A range of up to 10 x 3 g samples of the liver's right lobe will be obtained. Each sample will be properly labelled with previously prepared codes. Liver samples for histopathological analysis will be stored in 10% buffered formalin for 24 hours prior to transfer to ethanol before embedding, sectioning and staining. All samples collected for retinoid analysis will be frozen on dry ice in the morgue, transported as such to the laboratory and subsequently stored at -80˚C. Liver samples for gene expression analysis will be collected in RNAlater solution to protect RNA stability and subsequently stored at -80˚C until shipment to Newcastle University. The hepatic VA analysis will be done in Newcastle University using established High Perfromance Liquid Chromatography (HPLC) methods. Samples for analysis of gene expression will be sent on dry ice to Newcastle for RNA extraction and quantification. Since it is possible to obtain good quality RNA suitable for Quantitative Polymerase Chain Reaction (q-PCR) based analyses from post mortem tissue up to 72 hours after death, tissue samples stored in RNAlater within 24 hours of death will be adequate for gene expression analysis. Furthermore, experience from the investigators human biobank in Newcastle shows that tissue RNA can be extracted successfully after the demise of a patient up to 72 hours after death as long as the tissue has a pH of over 6. Gene expression of key regulatory proteins, such as LRAT and CYP26A1 will be performed in Newcastle. Choice of genes was based on the fact that LRAT may become saturated at very high levels of VA, leading to increasing levels of free circulating VA that can be metabolized to retinoic acid and other metabolites via CYP26A. Histopathological analysis will be carried out by pathologists in Guatemala with digitised slides being sent to the pathologist within Newcastle University - these slides will be analysed by both pathologists independently.