MondoA coordinately regulates skeletal myocyte lipid homeostasis and insulin signaling
Byungyong Ahn, Mangala M. Soundarapandian, Hampton Sessions, Satyamaheshwar Peddibhotla, Gregory P. Roth, Jian-Liang Li, Eliot Sugarman, Ada Koo, Siobhan Malany, Miao Wang, Kyungmoo Yea, Jeanne Brooks, Teresa C. Leone, Xianlin Han, Rick B. Vega, Daniel P. Kelly
Byungyong Ahn, Mangala M. Soundarapandian, Hampton Sessions, Satyamaheshwar Peddibhotla, Gregory P. Roth, Jian-Liang Li, Eliot Sugarman, Ada Koo, Siobhan Malany, Miao Wang, Kyungmoo Yea, Jeanne Brooks, Teresa C. Leone, Xianlin Han, Rick B. Vega, Daniel P. Kelly
View: Text | PDF
Research Article Metabolism

MondoA coordinately regulates skeletal myocyte lipid homeostasis and insulin signaling

Abstract

Intramuscular lipid accumulation is a common manifestation of chronic caloric excess and obesity that is strongly associated with insulin resistance. The mechanistic links between lipid accumulation in myocytes and insulin resistance are not completely understood. In this work, we used a high-throughput chemical biology screen to identify a small-molecule probe, SBI-477, that coordinately inhibited triacylglyceride (TAG) synthesis and enhanced basal glucose uptake in human skeletal myocytes. We then determined that SBI-477 stimulated insulin signaling by deactivating the transcription factor MondoA, leading to reduced expression of the insulin pathway suppressors thioredoxin-interacting protein (TXNIP) and arrestin domain–containing 4 (ARRDC4). Depleting MondoA in myocytes reproduced the effects of SBI-477 on glucose uptake and myocyte lipid accumulation. Furthermore, an analog of SBI-477 suppressed TXNIP expression, reduced muscle and liver TAG levels, enhanced insulin signaling, and improved glucose tolerance in mice fed a high-fat diet. These results identify a key role for MondoA-directed programs in the coordinated control of myocyte lipid balance and insulin signaling and suggest that this pathway may have potential as a therapeutic target for insulin resistance and lipotoxicity.

Authors

Byungyong Ahn, Mangala M. Soundarapandian, Hampton Sessions, Satyamaheshwar Peddibhotla, Gregory P. Roth, Jian-Liang Li, Eliot Sugarman, Ada Koo, Siobhan Malany, Miao Wang, Kyungmoo Yea, Jeanne Brooks, Teresa C. Leone, Xianlin Han, Rick B. Vega, Daniel P. Kelly

×

Figure 5

SBI-477 inhibits MondoA-mediated activation of the TXNIP gene promoter via effects on nuclear localization.

Options: View larger image (or click on image) Download as PowerPoint
SBI-477 inhibits MondoA-mediated activation of the TXNIP gene promoter v...
(A) A luciferase reporter construct containing approximately 1.5 kb of the human TXNIP promoter (schematic) or a pGL3 control vector was transfected into H9c2 skeletal myocytes. The activity of the TXNIP promoter (relative luciferase units [RLU]) was measured following treatment with SBI-477 at the indicated concentration (n = 5). (B) The activity of WT versus ChoRE mutant TXNIP promoters was measured in the presence and absence of SBI-477 (10 μM) for 24 hours (n = 5). The red “X” denotes inactivity mutations. (C) ChIP–qRT-PCR analysis was performed with anti-MondoA (black bars) or IgG (white bars) control Abs in human skeletal myotubes. Occupancy of MondoA on the ChoRE of the TXNIP or ARRDC4 promoters following treatment with SBI-477 in the absence or presence of oleate is shown (n = 4). Occupation on a MEF2-binding site within the IMPA2 promoter was used as a negative control. (D) Representative images of more than 3 micrographs of MondoA-V5 in human skeletal myoblasts following treatment with 10 μM SBI-477 or DMSO vehicle control for 24 hours. MondoA-V5 staining is shown in red, DAPI in blue. (E) Western blot analysis was performed on total cell lysates and nuclear or cytoplasmic fractions from primary human myotubes treated with 10 μM SBI-477 or DMSO vehicle control for 24 hours. Lamin A/C and GAPDH were included as controls for the nuclear and cytoplasmic fractions, respectively. *P < 0.05 versus vehicle; 1-way ANOVA with Bonferroni’s post-hoc test. Data represent the mean ± SD. HSE, heat shock element; Luc, luciferase.