Osaka, Japan - Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide and can progress to liver cirrhosis, liver failure or cancer. Currently, nonalcoholic steatohepatitis (NASH) diagnosis requires an invasive liver biopsy which can lead to procedural complications. Now, researchers at Osaka University working with international collaborators have identified a noninvasive biomarker that can identify patients at risk of NAFLD complications using a simple blood test.
Owing to the increasing prevalence of obesity worldwide, as many as one in four humans has NAFLD. Unrelated to alcohol intake by definition, the early stage - NAFL (nonalcoholic fatty liver) - is asymptomatic. Unfortunately, progression to NASH incurs inflammatory damage and eventually liver fibrosis occurs; this may further lead to adverse outcomes. Liver deterioration can be deferred by lifestyle modifications comprising diet and exercise; therefore, early diagnosis is key.
Diagnostic confirmation requires a needle biopsy; however, the disadvantages include expense and variability in sampling and interpretation. The research team investigated whether they could devise a diagnostic screen using transcriptomics, the emerging science of analyzing the 'transcriptome,' the entire array of an organism's messenger RNA molecules derived from expression of the genome.
"We obtained liver tissue from over 300 Japanese and European patients with biopsy-proven NAFLD and performed global RNA sequencing," co-first author Kazuhiro Kozumi explains. "Remarkably, from the protein patterns we could not only distinguish NASH from NAFL, but also determine the molecular hallmarks of NASH pathology. Specifically, we pinpointed that levels of thrombospondin-2 (TSP-2), a glycoprotein encoded by the THBS2 gene, were increased in both NASH and advanced fibrosis."
The researchers established that THBS2 expression in liver cells paralleled the clinical indicators conventionally used to categorize the pathological changes including serum enzyme levels, NAFLD Activity Score and NAFLD Fibrosis Score. "Serum levels of TSP-2 in NAFLD patients were significantly higher in NASH than in NAFL," co-first author Takahiro Kodama claims, "and, interestingly, the increase tallied with the degree of fibrosis."
Corresponding author Tetsuo Takehara explains the clinical relevance of their research findings. "Both hepatic THBS2 gene expression in the liver and serum protein levels of TSP-2 can diagnose cases of NASH and/or advanced fibrosis. A simple and convenient blood test can provide a clinically useful early warning system for complications of NAFLD and inform lifestyle modifications or other interventions that may alter the course of the disease and improve the prognosis."
The article, "Transcriptomics identify thrombospondin-2 as a biomarker for nonalcoholic steatohepatitis and advanced liver fibrosis" was published in Hepatology at DOI: https://doi.org/10.1002/hep.31995
About Osaka University
Osaka University was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world, being named Japan's most innovative university in 2015 (Reuters 2015 Top 100) and one of the most innovative institutions in the world in 2017 (Innovative Universities and the Nature Index Innovation 2017). Now, Osaka University is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.