Mechanism of GDNF Regulation of Hepatic Steatosis

NIH Pandemic-Era Grants

Pandemic Era Grants

2024

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Principal Investigator: Shanthi K Srinivasan
Organization: VETERANS HEALTH ADMINISTRATION
Fiscal Year: 2024
Funding agency: Veterans Affairs

Non-alcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease in veterans and its
prevalence continues to increase, with the growing obesity epidemic. Currently more than 25% of our veterans
are obese and a larger number are overweight. In this proposal, we will examine the pleiotropic effects of Glial
Derived Neurotrophic Factor (GDNF) on hepatocytes. We have demonstrated that GDNF transgenic (GDNF-
Tg) mice fed a high fat diet are protected from obesity and the development of hepatic steatosis despite similar
food intake and physical activity. GDNF-Tg mice overexpress GDNF under the control of the GFAP promoter
expressed in glia and stellate cells. GDNF and its receptor GFRα−1 are expressed in human and murine
hepatocytes. Thus, GDNF present in the liver can act locally on the hepatocytes. We recently demonstrated
that GDNF can enhance autophagy and prevent liver injury. Our preliminary data demonstrate novel effects of
GDNF on the liver that include: (i) Human liver tissue from patients with steatosis and fibrosis have reduced
GDNF expression (ii) Western diet (WD)-fed mice have reduced level of Sirt3 and this is ameliorated in GDNF-
Tg mice fed a WD; (iii) Human hepatocytes treated with GDNF have increased mitophagy. (iv) GDNF prevents
apoptosis in primary human hepatocytes. The signaling pathway for these potentially beneficial effects of
GDNF have yet to be explored. We hypothesize that the mechanism of GDNF prevention of hepatic injury is
through promoting hepatocyte Sirt3 signaling, subsequent improved mitochondrial function leading to
increased hepatocyte survival. Using both genetic and pharmacological approaches we will define the role of
GDNF in inducing mitophagy to lead to improved mitochondrial function, fat reduction and reduced hepatic
injury. To test the hypothesis and further investigate the underlying mechanism(s) of GDNF regulation of
hepatic steatosis, we propose the following interrelated, but independently achievable aims: Specific Aim 1:
To determine the mechanism of GDNF regulation of Sirt3 Preliminary data indicate that GDNF is a potent
inducer of Sirt3 in vivo and in vitro. We have demonstrated that GDNF can activate the ERK signaling pathway
in hepatocytes through its receptor GFRα1. We will establish if the mechanism of GDNF regulation of Sirt3 is
through the GFRα1-ERK-CREB-PGC-1α pathway. WT and GDNF-Tg mice will be fed a Western diet together
with fructose and glucose added in drinking water (WD/FG) for 16 weeks and ERK-CREB-PGC-1α-Sirt3
pathway assessed in hepatocytes. In vitro the necessity and sufficiency of ERK-CREB-PGC-1α in the GDNF
regulation of Sirt3 expression will be determined using gene knock down and overexpression strategies.
Specific Aim 2: To examine the role of mitochondrial function and mitophagy in GDNF-mediated
hepatocyte survival. Our preliminary data demonstrate that GDNF increases mitochondrial function and
mitophagy in hepatocytes. We will establish the role of GDNF in regulating mitochondrial function and
mitophagy using the GDNF-Tg mice and in vitro experiments involving treatment of hepatocytes with GDNF.
We will examine the mechanism of GDNF regulation of mitochondrial health using gene knock down and over-
expression strategies. We will examine the role of GDNF-induced mitophagy in regulating hepatocyte survival.
Specific Aim 3: To establish that GDNF-loaded ginger lipid nanoparticles can prevent hepatic lipid
accumulation and promote hepatocyte survival. Our preliminary data demonstrate our ability to generate
liver-specific natural ginger nanoparticles. We will examine the effect of GDNF-loaded ginger nanoparticles on
hepatic steatosis and hepatocyte cell death and injury. GDNF-loaded ginger nanoparticles will be injected once
a week into WT, Sirt3 KO mice and PINK1 KO to further establish the mechanism of action of GDNF involving
Sirt3 and PINK1. Taken together our data from this proposal may provide novel targets for the treatment or
prevention of hepatic steatosis and injury.

Terms: <Apoptosis><Apoptosis Pathway><Astroprotein><Autophagocytosis><Biogenesis><Body Tissues><CREB><CREB1><CREB1 gene><Cell Communication and Signaling><Cell Death><Cell Signaling><Cellular injury><D-Glucose><Data><Development><Dextrose><Eating><Fats><Fatty Liver><Fatty acid glycerol esters><Fibrosis><Food Intake><Fructose><GDNF><GDNF gene><GFA-Protein><GFAP><Genes><Genetic><Ginger><Glia><Glial Cells><Glial Fibrillary Acid Protein><Glial Fibrillary Acidic Protein><Glial Intermediate Filament Protein><Glucose><Health><Health Care Systems><Healthcare><Healthcare Systems><Hepatic><Hepatic Cells><Hepatic Parenchymal Cell><Hepatocyte><Hexadecanoates><High Fat Diet><Human><In Vitro><Incidence><Injury to Liver><Intracellular Communication and Signaling><KO mice><Knock-out Mice><Knockout Mice><Kolliker's reticulum><Levulose><Lipids><Liver><Liver Cells><Liver Fibrosis><Liver Steatosis><Mediating><Metabolic syndrome><Mice><Mice Mammals><Mitochondria><Modern Man><Murine><Mus><NAFLD><Neuroglia><Neuroglial Cells><Non-neuronal cell><Nonneuronal cell><Null Mouse><Obesity><Obesity Epidemic><Obesity associated liver disease><Obesity related liver disease><Origin of Life><Over weight><Overweight><PARK6><PARK6 gene><PARK6 protein><PINK1><PINK1 gene><PINK1 gene product><PINK1 protein><PTEN induced kinase 1><PTEN induced putative kinase 1><PTEN-induced putative kinase><Palmitates><Parkinson disease 6 gene><Pathway interactions><Patients><Phosphatase and tensin homolog induced kinase 1><Physical activity><Play><Prevalence><Prevention><Programmed Cell Death><Publishing><Receptor Protein><Regulation><Reporting><Role><Signal Pathway><Signal Transduction><Signal Transduction Systems><Signaling><Testing><Tissues><Transgenic Mice><Veterans><Wild Type Mouse><Zingiber officinale><adiposity><autophagy><biological signal transduction><cAMP Response Element-Binding Protein 1><cell damage><cell injury><cellular damage><chronic hepatic disease><chronic hepatic disorder><chronic liver disease><chronic liver disorder><corpulence><cost><damage to cells><developmental><drinking water><experiment><experimental research><experimental study><experiments><fibrotic liver><glial cell-line derived neurotrophic factor><health care><hepatic body system><hepatic damage><hepatic fibrosis><hepatic injury><hepatic organ system><hepatic steatosis><hepatosteatosis><improved><in vivo><injury to cells><knock-down><knockdown><lipid based nanoparticle><lipid nanoparticle><liver damage><liver injury><military veteran><mitochondrial><nano particle><nano-sized particle><nanoparticle><nanosized particle><necrocytosis><nerve cement><neurotrophic factor><neurotrophin><neutrophin><new drug target><new druggable target><new pharmacotherapy target><new therapeutic target><new therapy target><non-alcohol fatty liver disease><non-alcoholic fatty liver disease><non-alcoholic liver disease><nonalcoholic fatty liver disease><novel><novel drug target><novel druggable target><novel pharmacotherapy target><novel therapeutic target><novel therapy target><obese patients><overexpress><overexpression><pathway><patients with obesity><pharmacologic><pleiotropic effect><pleiotropism><pleiotropy><prevent><preventing><promoter><promotor><protein expression><protein kinase BRPK><protein kinase BRPK gene><receptor><serine/threonine-protein kinase PINK1><social role><stellate cell><veteran population><western diet><western-style diet><western-type diet><wildtype mouse>