Novel equation to determine the hepatic triglyceride concentration in humans by MRI: diagnosis and monitoring of NAFLD in obese patients before and after bariatric surgery

Raúl Jiménez-Agüero¹², José I Emparanza², Adolfo Beguiristain¹, Luis Bujanda¹³, José M Alustiza¹⁴, Elisabeth García⁴, Elizabeth Hijona¹³, Lander Gallego¹, Javier Sánchez-González⁵, María J Perugorria¹³⁶, José I Asensio¹, Santiago Larburu¹, Maddi Garmendia⁷,Mikel Larzabal⁷, María P Portillo⁸, Leixuri Aguirre⁸ and Jesús M Banales¹³⁶^*

*Corresponding author: Jesús M Banales jesus.banales@biodonostia.org

Author Affiliations

¹Department of Liver and Gastrointestinal Diseases, Biodonostia Research Institute, Donostia University Hospital (HUD), University of the Basque Country (UPV/EHU), San Sebastian, Spain

²Clinical Epidemiology Unit, CASPe, CIBER-ESP, Biodonostia Research Institute – HUD, San Sebastian, Spain

³National Institute for the Study of Liver and Gastrointestinal Diseases (CIBERehd), Barcelona, Spain

⁴Osatek SA, San Sebastian, Spain

⁵Philips Healthcare, Iberia, Madrid, Spain

⁶IKERBASQUE, Basque Foundation for Science, Bilbao, Spain

⁷Department of Pathology, HUD, San Sebastian, Spain

⁸Department of Nutrition and Food Science, Faculty of Pharmacy, UPV/EHU, CIBER-obn, Vitoria, Spain

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BMC Medicine 2014, 12:137 doi:10.1186/s12916-014-0137-y

The electronic version of this article is the complete one and can be found online at:http://www.biomedcentral.com/1741-7015/12/137

Received:	25 April 2014
Accepted:	23 July 2014
Published:	26 August 2014

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Abstract

Background

Non-alcoholic fatty liver disease (NAFLD) is caused by abnormal accumulation of lipids within liver cells. Its prevalence is increasing in developed countries in association with obesity, and it represents a risk factor for non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma. Since NAFLD is usually asymptomatic at diagnosis, new non-invasive approaches are needed to determine the hepatic lipid content in terms of diagnosis, treatment and control of disease progression. Here, we investigated the potential of magnetic resonance imaging (MRI) to quantitate and monitor the hepatic triglyceride concentration in humans.

Methods

A prospective study of diagnostic accuracy was conducted among 129 consecutive adult patients (97 obesity and 32 non-obese) to compare multi-echo MRI fat fraction, grade of steatosis estimated by histopathology, and biochemical measurement of hepatic triglyceride concentration (that is, Folch value).

Results

MRI fat fraction positively correlates with the grade of steatosis estimated on a 0 to 3 scale by histopathology. However, this correlation value was stronger when MRI fat fraction was linked to the Folch value, resulting in a novel equation to predict the hepatic triglyceride concentration (mg of triglycerides/g of liver tissue = 5.082 + (432.104 * multi-echo MRI fat fraction)). Validation of this formula in 31 additional patients (24 obese and 7 controls) resulted in robust correlation between the measured and estimated Folch values. Multivariate analysis showed that none of the variables investigated improves the Folch prediction capacity of the equation. Obese patients show increased steatosis compared to controls using MRI fat fraction and Folch value. Bariatric surgery improved MRI fat fraction values and the Folch value estimated in obese patients one year after surgery.

Conclusions

Multi-echo MRI is an accurate approach to determine the hepatic lipid concentration by using our novel equation, representing an economic non-invasive method to diagnose and monitor steatosis in humans.