This R01 renewal proposal is designed to fully characterize a novel mechanism relevant to the established clinical observation that skeletal muscle lipid accumulation is strongly associated with the development of insulin resistance. Our preliminary studies have identified a potentially exciting role for the transcription factor MondoA in the coordinate control of muscle fuel metabolism and insulin signaling. This discovery was unveiled by an unbiased high-throughput chemical biology screen designed to identify small molecule probes that influence downstream pathways involved in the control of myocyte neutral lipid stores. One such molecule, SBI-477, reduced human skeletal myocyte lipid stores and increased glucose uptake. Our recent results indicate that SBI-477 is a potent inhibitor of fatty acid incorporation into triglyceride (TAG) and activates insulin signaling in human skeletal myocytes and in vivo. The downstream actions of SBI-477 are attributable, at least in part, to inhibition of the transcription factor MondoA resulting in reduced expression of target genes encoding TXNIP and ARRDC4, known suppressors of insulin signaling. These results support the hypothesis that MondoA serves a key metabolic homeostatic function in muscle by controlling fuel substrate availability by regulating genes involved in myocyte lipid storage and glucose import (via insulin signaling) in accordance with nutrient availability. We propose, however, that in states of chronic caloric excess persistent activation of MondoA becomes maladaptive, contributing to a vicious cycle of cellular lipid accumulation and insulin resistance. To test these hypotheses, we will conduct studies in human skeletal myotubes in culture and in vivo in MondoA loss-of-function mice.
In Aim 1, we will delineate MondoA gene targets (direct and indirect) and pathways in human skeletal myocytes using unbiased whole genome chromatin immunoprecipitation sequencing (ChIP-seq) and RNA-seq. The goal of Aim 2 is to validate the function of MondoA-regulated targets and pathways in the control of skeletal myocyte glucose and lipid metabolism under conditions of varied nutrient supply and cellular energy status.
In Aim 3, the metabolic actions of MondoA will be defined in vivo in muscle-specific MondoA-deficient mice under basal conditions and after long-term administration of a high-fat diet to determine whether MondoA participates in the development of muscle lipotoxicity and insulin resistance in the context of chronic nutrient overload. The long-term goal of this project is to identify novel mechanisms and targets relevant to the early-stage treatment of muscle insulin resistance in individuals at risk for developing type 2 diabetes. The mechanistic insights gained from the proposed studies should lead to new approaches for the prevention and treatment of lipotoxic diseases relevant to other tissues including nonalcoholic steatohepatitis (NASH) and heart failure in the diabetic.

Public Health Relevance

We are witnessing a pandemic in obesity-related diabetes. This project seeks to identify new mechanisms, molecules, and metabolic pathways in muscle to guide novel therapeutic approaches aimed at reducing the development of insulin resistance and progression to diabetes in the obese population. The proposed studies also show great promise for developing effective therapeutics to reduce the complications of diabetes including cardiovascular and liver disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK045416-25
Application #
9734034
Study Section
Integrative Physiology of Obesity and Diabetes Study Section (IPOD)
Program Officer
Silva, Corinne M
Project Start
1992-09-30
Project End
2021-04-30
Budget Start
2019-07-01
Budget End
2020-04-30
Support Year
25
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of Pennsylvania
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Zhang, Xiaolei; Trevino, Michelle B; Wang, Miao et al. (2018) Impaired Mitochondrial Energetics Characterize Poor Early Recovery of Muscle Mass Following Hind Limb Unloading in Old Mice. J Gerontol A Biol Sci Med Sci 73:1313-1322
Lee, Samuel; Leone, Teresa C; Rogosa, Lisa et al. (2017) Skeletal muscle PGC-1? signaling is sufficient to drive an endurance exercise phenotype and to counteract components of detraining in mice. Am J Physiol Endocrinol Metab 312:E394-E406
Vega, Rick B; Kelly, Daniel P (2017) Cardiac nuclear receptors: architects of mitochondrial structure and function. J Clin Invest 127:1155-1164
Vega, Rick B; Konhilas, John P; Kelly, Daniel P et al. (2017) Molecular Mechanisms Underlying Cardiac Adaptation to Exercise. Cell Metab 25:1012-1026
Ahn, Byungyong; Soundarapandian, Mangala M; Sessions, Hampton et al. (2016) MondoA coordinately regulates skeletal myocyte lipid homeostasis and insulin signaling. J Clin Invest 126:3567-79
Liang, Xijun; Liu, Lin; Fu, Tingting et al. (2016) Exercise Inducible Lactate Dehydrogenase B Regulates Mitochondrial Function in Skeletal Muscle. J Biol Chem 291:25306-25318
Liu, Jing; Liang, Xijun; Zhou, Danxia et al. (2016) Coupling of mitochondrial function and skeletal muscle fiber type by a miR-499/Fnip1/AMPK circuit. EMBO Mol Med 8:1212-1228
Dorn 2nd, Gerald W; Vega, Rick B; Kelly, Daniel P (2015) Mitochondrial biogenesis and dynamics in the developing and diseased heart. Genes Dev 29:1981-91
Ciron, Carine; Zheng, Lu; Bobela, Wojciech et al. (2015) PGC-1? activity in nigral dopamine neurons determines vulnerability to ?-synuclein. Acta Neuropathol Commun 3:16

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