Tightly linked to the obesity epidemic, disorders along the nonalcoholic fatty liver disease (NAFLD) spectrum, including nonalcoholic steatohepatitis (NASH), occur with nearly 30% prevalence among all adults in the United States. NAFLD dramatically increases the risks of developing type 2 diabetes and cardiovascular disease, and its natural history is heavily influenced by genomic and environmental inputs that are still incompletely understood. In particular, the role of mitochondrial metabolism, which governs the oxidative `disposal' of fats, has only been partially characterized. Mitochondrial ketone body generation (ketogenesis) is generally viewed as a passive metabolic overflow conduit through which products of ?-oxidation pass when carbohydrates and insulin are in short supply, with little known feedback on interwoven pathways including the Krebs (tricarboxylic acid, TCA) cycle, glucose production, and lipid metabolism. On the contrary, our preliminary data indicate that (i) hepatic ketogenic capacity directly influences these metabolic pathways in liver, even in the carbohydrate-laden fed state; (ii) in contradistinction to type 1 diabetes, NAFLD/NASH and insulin resistance are states in which ketogenesis is relatively underutilized, and (iii) geneticaly-induced ketogenic insufficiency alone predisposes to increased hepatic steatosis, hepatocellular injury, and glycemia. Together our preliminary data support the central hypotheses that (i) ketogenesis is not a passive overflow pathway but rather a dynamic node in hepatic and integrated physiological homeostasis, and (ii) prudent ketogenic augmentation can mitigate NAFLD/NASH and disordered hepatic glucose metabolism, which will be tested through two Specific Aims.
In Aim 1, we will demonstrate the mechanisms by which hepatic ketogenesis governs hepatic metabolic homeostasis and mitochondrial function. We will use mouse models of ketogenic insufficiency, high resolution nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography coupled to high mass accuracy mass spectrometry (LC/MS)-guided metabolomics in mice treated with stable isotopically-labeled metabolic fuels. Targeted and untargeted computational metabolomics and lipidomics approaches will be leveraged to comprehensively quantify the biochemical space through which ketogenesis regulates integrated organelle metabolic homeostasis. Genetic and pharmacological provocations will reveal mechanistic connections among hepatocyte metabolism, mitochondrial function, and NAFLD/NASH pathogenesis.
In Aim 2, we will demonstrate that increasing hepatic ketogenesis ameliorates NAFLD pathogenesis and disordered hepatic glucose metabolism. Wild-type or constitutively hyperactive mutated versions of the fate-committing ketogenic mitochondrial enzyme 3-hydroxymethylglutaryl-CoA synthase will be expressed in mouse models of fatty liver injury in vivo. The effects of varying hepatic ketogenesis on hepatic injury and inflammation, fatty acid oxidation, de novo lipogenesis, and glucose production will be quantified by NMR spectroscopy, comprehensive LC/MS metabolomics, and systems physiological approaches.

Public Health Relevance

Nonalcoholic fatty liver disease and type 2 diabetes both pose major unmet needs with escalating personal and economic burdens. The proposed experiments will be the first to use highly sophisticated and convergent chemical profiling and powerful genetic animal models to demonstrate that metabolism of ketone bodies might be safely leveraged as a safe conduit for caloric disposal that prevents and treats these epidemic disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK091538-10
Application #
9433641
Study Section
Integrative Physiology of Obesity and Diabetes Study Section (IPOD)
Program Officer
Teff, Karen L
Project Start
2011-04-01
Project End
2020-03-31
Budget Start
2018-04-01
Budget End
2019-03-31
Support Year
10
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Minnesota Twin Cities
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
555917996
City
Minneapolis
State
MN
Country
United States
Zip Code
55455
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Schugar, Rebecca C; Huang, Xiaojing; Moll, Ashley R et al. (2013) Role of choline deficiency in the Fatty liver phenotype of mice fed a low protein, very low carbohydrate ketogenic diet. PLoS One 8:e74806
Cotter, David G; Ercal, Baris; d'Avignon, D André et al. (2013) Impact of peripheral ketolytic deficiency on hepatic ketogenesis and gluconeogenesis during the transition to birth. J Biol Chem 288:19739-49
Cotter, David G; Schugar, Rebecca C; Wentz, Anna E et al. (2013) Successful adaptation to ketosis by mice with tissue-specific deficiency of ketone body oxidation. Am J Physiol Endocrinol Metab 304:E363-74

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