Dorsomorphin Dihydrochloride (Dorsomorphin) Inhibits AMPK to Block ABA-Stimulated Muscle Glucose Uptake
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Kinase signaling mechanisms underlying non-insulin-dependent glucose disposal represent a major area of investigation in metabolic physiology. Skeletal muscle serves as the primary site for postprandial glucose uptake, operating through both insulin-dependent signaling cascades involving phosphatidylinositol 3-kinase (PI3K) and Akt, and insulin-independent mechanisms driven by AMP-activated protein kinase (AMPK). AMPK acts as a cellular energy sensor, responding to alterations in AMP-to-ATP ratios by initiating pathways that promote ATP generation while suppressing energy-consuming biosynthetic processes. Recent findings have identified the endogenous phytohormone abscisic acid (ABA) as an activator of AMPK signaling in mammalian skeletal muscle cells, operating independently of classical insulin receptor activation. To delineate the precise requirement of AMPK in mediating ABA-induced glucose uptake, small-molecule pharmacological tools are essential. Among these reagents, Dorsomorphin Dihydrochloride—a highly selective, ATP-competitive inhibitor of AMPK—provides a precise mechanism to dissect downstream signaling events.
The small molecule, commonly referred to as Dorsomorphin, acts by reversibly competing with ATP for binding at the catalytic kinase domain of the AMPK α subunit. By occupying this catalytic cleft, the compound prevents the phosphorylation of key downstream substrates and halts signaling cascades initiated by physiological and pharmacological AMPK activators. In vitro experiments conducted in L6 myoblasts revealed that exposure to low nanomolar concentrations of abscisic acid increases the phosphorylation of AMPK at its critical activation loop residue, Thr172. This activation event is accompanied by an increase in total AMPK protein expression and upregulation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a master regulator of mitochondrial biogenesis and oxidative metabolism. Furthermore, stimulation with ABA triggers the translocation of glucose transporter 4 (GLUT4) storage vesicles from intracellular pools to the plasma membrane, facilitating enhanced transport of 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-D-glucose (2-NBDG) and [18F]fluorodeoxyglucose (FDG) into the cytoplasm.
Application of Dorsomorphin Dihydrochloride in these myoblast assays completely abrogated ABA-induced 2-NBDG and FDG cellular uptake. The loss of ABA-stimulated glucose influx in the presence of the inhibitor demonstrates that AMPK activity is an absolute requirement for ABA-mediated metabolic actions in muscle cells. Upstream signaling analysis indicated that ABA binds to lanthionine synthetase C-like protein 2 (LANCL2), initiating a membrane-associated cascade that converges on AMPK activation. When AMPK enzymatic activity is blocked by Dorsomorphin, the LANCL2-initiated cascade fails to execute downstream GLUT4 translocation, confirming that AMPK functions as the obligatory intermediate bridge between initial receptor engagement and physical glucose transporter insertion at the sarcolemma.
To validate these cellular findings within intact physiological tissue, ex vivo experiments were performed using isolated skeletal muscle biopsies from murine models. Incubation of mouse soleus and extensor digitorum longus muscle preparations with low-dose ABA resulted in heightened Thr172 phosphorylation and elevated rates of glucose transport under basal, non-insulin-stimulated conditions. Addition of Dorsomorphin to the organ bath cultures efficiently blocked Thr172 phosphorylation and eliminated ABA-enhanced hexose transport. These ex vivo results mirror the responses observed in cultured L6 myoblasts, establishing that the LANCL2-AMPK-GLUT4 signaling axis operates in native, differentiated skeletal muscle fibers under physiological tissue architecture.
Complementary in vivo studies provided broader physiological context regarding the systemic effects of ABA administration. In mouse models subjected to high-glucose dietary regimens, oral administration of ABA significantly improved systemic blood glucose clearance during oral glucose tolerance tests (OGTT). Muscle tissue harvested from treated mice exhibited elevated glycogen accumulation and enhanced mitochondrial enzyme activity, reflecting sustained activation of PGC-1α and oxidative metabolic pathways. In addition, physical performance assessments demonstrated that ABA treatment extended treadmill running time to exhaustion in treated animals compared to vehicle controls. Notably, ABA maintained its efficacy in hypoinsulinemic TRPM2-knockout mouse models, confirming that its glucoregulatory actions bypass functional pancreatic beta-cell insulin secretion.
The combined in vitro, ex vivo, and in vivo evidence establishes that low-dose abscisic acid promotes skeletal muscle glucose uptake through a LANCL2-dependent activation of AMPK and subsequent GLUT4 translocation. The absolute sensitivity of this axis to inhibition by Dorsomorphin Dihydrochloride highlights AMPK as the indispensable enzymatic hub governing insulin-independent glucose disposition. Utilizing selective pharmacological tools like Dorsomorphin enables clear mechanistic dissection of alternative metabolic pathways, offering molecular insights into non-canonical signaling networks in skeletal muscle.
Pharmacological Blockade of AMPK-Mediated Metabolic Flux
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Dorsomorphin Dihydrochloride selectively inhibits AMP-activated protein kinase (AMPK) by competing with ATP at the catalytic domain. Blockade of AMPK abrogates abscisic acid (ABA)-induced phosphorylation at Thr172, preventing downstream upregulation of PGC-1α and GLUT4 translocation to the plasma membrane. Consequently, ABA-stimulated 2-NBDG and FDG uptake is completely suppressed in skeletal myoblasts and ex vivo muscle tissue.
Thr172 Phosphorylation Blockade Prevents Downstream GLUT4 Translocation
In L6 myoblast cultures, abscisic acid elevated Thr172 phosphorylation of AMP-activated protein kinase. Pretreatment with Dorsomorphin abolished this activation cascade. Downstream GLUT4 translocation to the cell surface ceased completely under competitive AMPK inhibition. Hexose uptake measured via 2-NBDG fluorescence dropped to baseline values in treated cultures. PGC-1α upregulation was similarly suppressed upon target engagement. These observations demonstrate that abscisic acid relies on intact kinase activity to drive non-insulin-dependent glucose uptake. In ex vivo murine soleus muscle strips, identical inhibitory patterns confirmed pathway conservation across tissue types.
Oral Abscisic Acid Normalizes Glycemia in Diabetic Mouse Models
In vivo metabolic assays demonstrated clear systemic effects of phytohormone administration. High-glucose-fed mice receiving oral abscisic acid showed accelerated blood glucose clearance during oral glucose tolerance tests. Skeletal muscle glycogen content increased significantly in wild-type animals. In hypoinsulinemic TRPM2-knockout mice, the compound maintained its glucoregulatory efficacy without requiring endogenous insulin secretion. Treadmill exhaustion trials revealed improved physical endurance following daily dosing regimens. These therapeutic outcomes remained dependent on LANCL2-AMPK axis integrity across all evaluated cohorts.