Transcript LA - UNL Office of Research - University of Nebraska–Lincoln

Anti-Lipemic Mechanism of (R)-α-Lipoic Acid (LA)
Regis Moreau, Ph.D.
Assistant Professor
Department of Nutrition and Health Sciences
University of Nebraska-Lincoln
LA
Zucker Diabetic Fatty
(ZDF) rats,
model of hypertriglyceridemia
Fit with the COBRE Theme
•
Controlling blood lipid abnormalities is a major public health challenge
•
Hypertriglyceridemia affects 65 million Americans
•
Major risk factor for cardiovascular disease and type-2 diabetes
•
Dietary molecule: (R)-a-lipoic acid (LA)
– Naturally occurring molecule synthesized by plants and animals
– Used therapeutically in diabetics
– Safe in humans
– Lipid-lowering properties have recently been recognized
LA
Zucker Diabetic Fatty
(ZDF) rats,
model of hypertriglyceridemia
Goals of the Project
•
Identify the molecular targets and signaling mechanism of LA
•
Generate interest in the therapeutic use of LA
Central Hypothesis
•
LA corrects hypertriglyceridemia by the combined stimulation of triglyceride
(TG) clearance mediated by FGF21 and inhibition of hepatic TG synthesis
mediated by mTORC1
Novel Molecular Targets of LA
LA
LA
FGFR1
X6
β-Klotho
FGF21
Tf
mTORC1
TSC1/2
Rheb
SREBP1c
ChREBP
Tf
X5
Fgf21
Liver
β-oxidation
genes
Muscle
Lipogenic genes
ACC, FAS, GPAT1, DGAT2
Liver
Fibroblast growth factor-21 (FGF21) mediates the
lipolytic properties of LA
(Tf = Transcription factor)
LA downregulates SREBP1c-mediated
transcription of lipogenic genes through
inactivation mTORC1 (mammalian target of
rapamycin complex 1)
Preliminary Studies
C
A
B
A) Feeding LA to obese rats corrects
hypertriglyceridemia (–70%).
B) Feeding LA to obese rats increases blood
FGF21 levels (+600%).
Butler et al. 2009 ABB; Finlay et al. 2011 AJP
D
C) LA (50 µM) added to liver cells inactivates
mTORC1 via dephosphorylation of mTOR
and loss of Raptor. Ctl = vehicle control.
D) LA lowers hepatic levels of transcription
factors SREBP1c and ChREBP downstream
of mTORC1.
Experimental Models
•
Fgfr1f/f/Cre mice lacking fibroblast growth factor-21 (FGF21) receptor
Cre/
ESR
Gt(ROSA)26Sor
Cre
ESR
+
Tamoxife
n
Fgfr
1
loxP
loxP
Fgfr1 KO
•
Tsc1f/f/Cre mice constitutively expressing mammalian target of rapamycin
complex 1 (mTORC1)
Cre/
ESR
Gt(ROSA)26Sor
Cre
ESR
+
Tamoxife
n
Tsc1
loxP
loxP
Tsc1 KO
Innovation
•
Shift from the current paradigm that LA acts as an antioxidant
•
Novel lipid-lowering mechanisms of LA
– Stimulation of lipid clearance (FGF21)
– Downregulation of triglyceride synthesis (mTORC1)
Outcome
•
Safe and economical alternative to current lipid-lowering therapies
•
Mechanism-based rationale for clinical trials with LA
Timetable of the Proposed Studies
•
The project will span 3 years
•
Two Specific Aims
– Specific Aim 1. Define the role of FGF21 in the mechanism of LA
1A. Elucidate the mechanism by which LA up-regulates FGF21 gene expression
1B. Assess the FGF21 sensitizing properties of LA and consequences on lipolysis
– Specific Aim 2. Define the role of mTORC1 in the mechanism of LA
2A. Elucidate the mechanism by which LA represses mTORC1 activity
2B. Ascertain SREBP1c requirement in mTORC1 repression by LA
2C. Evaluate the consequences of mTORC1 repression by LA on lipogenesis
•
Year 1: Initiate Specific Aims 1A, 1B and 2A, complete Specific Aim 1A
•
Year 2: Complete Specific Aims 1B and 2A, initiate Specific Aims 2C
•
October of Year 2: Submission date for an R01 (NHLBI, NIDDK, NCCAM)
•
Year 3: Complete Specific Aims 2B and 2C
Mentorship Work Plan
•
Primary mentor
– Dr. Janos Zempleni (NHS, UNL)
• Published work on LA
• Collection of chemically defined LA metabolites (structure-function studies)
•
Secondary mentors
– Dr. Edgar Cahoon (Biochemistry, UNL)
• Expert in secondary plant metabolites
• Strategies to increase LA content in plants
– Dr. Mark Wilson (Biochemistry, UNL)
• Expert in X-ray crystallography
• Structure-signaling relationships of LA and signaling protein
Use of UNL Core Research Facilities
•
•
NPOD Epigenetics Core
–
Chromatin immunoprecipitation (ChIP) assay
–
Antibody validation
NPOD Computational and Data Sharing Core
–
•
•
Statistical data analysis
Genomics Core
–
DNA sequencing
–
Primer validation
–
RNA integrity
Animal Research Facility
–
Breeding colonies
–
Feeding trials
NPOD Scientific Collaborations
•
Dr. Dmitri Fomenko (Project Leader 2)
–
•
Thiol disulfide exchange between LA and protein sulfhydryls (COBRE-supported Redox
Biology Center)
Dr. Saraswathi Viswanathan (Project Leader 5)
–
LA-omega 3 fatty acids synergies
Existing Collaborations
•
Dr. Qingsheng Li (COBRE-supported Nebraska Center for Virology)
–
•
Recombinant lentivirus gene knockdown
Dr. David Wasserman (Vanderbilt-NIDDK Mouse Metabolic Phenotyping
Center)
–
Metabolic studies in Fgfr1f/f/Cre mice