Rohit Loomba, MD, MHSc (PI) is a hepatologist and Assistant Professor of Medicine at the University of California-San Diego. Dr. Loomba's long-term goal is to develop an independent research career in the genetic epidemiology of nonalcoholic fatty liver disease (NAFLD) by combining patient- centered research with clinical epidemiology. He is interested in underpinning genetic and environmental risk factors that are associated with NAFLD and identify novel mechanistic pathways that are linked with progressive form of NAFLD, which is termed as nonalcoholic steatohepatitis (NASH). NAFLD is the most common liver disease in the United States. It is associated with metabolic syndrome traits including hypertension (HTN), insulin resistance (IR), and hypertriglyceridemia. These metabolic traits predict increased risk of NASH, which can lead to cirrhosis. A critical barrier to progress in the field and to management of patients with NAFLD is that the mechanism underlying the association between metabolic traits and NAFLD, and those associated with progression of NAFLD, are not well understood. In order to fill this gap in knowledge, Dr. Loomba, under the mentorship of Drs. Daniel O'Connor, Elizabeth Barrett-Connor, and David Brenner, proposes to measure liver fat, quantitatively, by a novel magnetic resonance imaging (MRI) technique, in a large, previously well-characterized, existing, twin-pair cohort in humans: (specific aim 1) To examine genetic co-variance between NAFLD and metabolic risk factors including hypertension (HTN), insulin resistance (IR), and elevated triglycerides (TG), which would be assessed by using multivariate generalized estimating equations after adjustment for age and sex. Previous studies suggest that adrenergic system has a strong genetic association with HTN, IR &TG;and in-vitro and in-vivo studies suggest that norepinephrine (increased adrenergic activity) activates hepatic stellate cells &induces fibrogenesis in mice model of diet-induced fibrosis and NAFLD. Therefore, we hypothesize that adrenergic genes are associated with human NAFLD and may be responsible for the shared gene effects between NAFLD and HTN, IR, &TG. (specific aim 2) To examine if the genes in the adrenergic system (already genotyped: preliminary data suggests 2-2 adrenergic gene effect with serum gamma-glutamyl transpeptidase (GGT), a marker of NAFLD, in this twin cohort) are associated with NAFLD. This twin-pair study, which includes both mono-zygotic and di-zygotic twins, allows us to tease out the genetic versus environmental co-variance between the metabolic traits and NAFLD. Furthermore, we will be utilizing a cutting-edge MRI technique to quantify the liver fat fraction as a non-invasive biomarker of hepatic triglyceride content. These innovations would advance the knowledge in the field. In order to gain expertise in genetic epidemiology and twin studies, a rigorous career development plan is proposed that benefits from a multi-disciplinary approach designed to provide a closely mentored, patient-oriented research experience in association with a comprehensively structured didactic curriculum in genetic and advanced epidemiology. This unique twin study design would shed light on shared gene effects between NAFLD and these metabolic syndrome traits and help in identifying novel genetic variations in adrenergic genes that may explain this shared gene effect. These findings may be exploited in assessing liver disease progression and development of novel targets for treatment of NAFLD and associated metabolic complications. The long- term goal of the proposed research program is to reduce the burden of NAFLD and halt progression of NAFLD to NASH.

Public Health Relevance

NAFLD affects one out of every three Americans. The proposed twin study will improve our understanding of disease progression in NAFLD. This study would lead to discovery of specific adrenergic genotypes that are associated with NAFLD, which may be exploited to develop new prognostic models for predicting disease progression and develop newer targets of therapy.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Mentored Patient-Oriented Research Career Development Award (K23)
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Special Emphasis Panel (ZDK1)
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Podskalny, Judith M,
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University of California San Diego
Internal Medicine/Medicine
Schools of Medicine
La Jolla
United States
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Loomba, Rohit; Cui, Jeffrey; Wolfson, Tanya et al. (2016) Novel 3D Magnetic Resonance Elastography for the Noninvasive Diagnosis of Advanced Fibrosis in NAFLD: A Prospective Study. Am J Gastroenterol 111:986-94
Doycheva, I; Cui, J; Nguyen, P et al. (2016) Non-invasive screening of diabetics in primary care for NAFLD and advanced fibrosis by MRI and MRE. Aliment Pharmacol Ther 43:83-95
Lin, Steven C; Ang, Brandon; Hernandez, Carolyn et al. (2016) Cardiovascular risk assessment in the treatment of nonalcoholic steatohepatitis: a secondary analysis of the MOZART trial. Therap Adv Gastroenterol 9:152-61
Jayakumar, Saumya; Harrison, Stephen A; Loomba, Rohit (2016) Noninvasive Markers of Fibrosis and Inflammation in Nonalcoholic Fatty Liver Disease. Curr Hepatol Rep 15:86-95
Dulai, Parambir S; Sirlin, Claude B; Loomba, Rohit (2016) MRI and MRE for non-invasive quantitative assessment of hepatic steatosis and fibrosis in NAFLD and NASH: Clinical trials to clinical practice. J Hepatol 65:1006-1016
Zarrinpar, Amir; Gupta, Shakti; Maurya, Mano R et al. (2016) Serum microRNAs explain discordance of non-alcoholic fatty liver disease in monozygotic and dizygotic twins: a prospective study. Gut 65:1546-54
Patel, Janki; Bettencourt, Ricki; Cui, Jeffrey et al. (2016) Association of noninvasive quantitative decline in liver fat content on MRI with histologic response in nonalcoholic steatohepatitis. Therap Adv Gastroenterol 9:692-701
Heba, Elhamy R; Desai, Ajinkya; Zand, Kevin A et al. (2016) Accuracy and the effect of possible subject-based confounders of magnitude-based MRI for estimating hepatic proton density fat fraction in adults, using MR spectroscopy as reference. J Magn Reson Imaging 43:398-406
Singh, Siddharth; Venkatesh, Sudhakar K; Loomba, Rohit et al. (2016) Magnetic resonance elastography for staging liver fibrosis in non-alcoholic fatty liver disease: a diagnostic accuracy systematic review and individual participant data pooled analysis. Eur Radiol 26:1431-40
Cui, Jeffrey; Heba, Elhamy; Hernandez, Carolyn et al. (2016) Magnetic resonance elastography is superior to acoustic radiation force impulse for the Diagnosis of fibrosis in patients with biopsy-proven nonalcoholic fatty liver disease: A prospective study. Hepatology 63:453-61

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