ABSTRACT
Inhibition of Notch signaling via systemic drug administration triggers conversion of white adipocytes into beige adipocytes (browning) and reduces adiposity. However, translation of this discovery into clinical practice is challenged by potential off-target side effects and lack of control over the location and temporal extent of beige adipocyte biogenesis. Here, we demonstrate an alternative approach to stimulate browning using nanoparticles (NPs) composed of FDA-approved poly(lactide-co-glycolide) that enable sustained local release of a Notch inhibitor (dibenzazepine, DBZ). These DBZ-loaded NPs support rapid cellular internalization and inhibit Notch signaling in adipocytes. Importantly, focal injection of these NPs into the inguinal white adipose tissue depots of diet-induced obese mice results in localized NP retention and browning of adipocytes, consequently improving the glucose homeostasis and attenuating body-weight gain of the treated mice. These findings offer new avenues to develop a potential therapeutic strategy for clinical treatment of obesity and its associated metabolic syndrome.
Subject(s)
Adipose Tissue, Brown/drug effects , Adipose Tissue, White/drug effects , Anti-Obesity Agents/pharmacology , Dibenzazepines/pharmacology , Nanoparticles/chemistry , Obesity/drug therapy , Adipose Tissue, Brown/metabolism , Adipose Tissue, Brown/pathology , Adipose Tissue, White/metabolism , Adipose Tissue, White/pathology , Animals , Anti-Obesity Agents/chemistry , Apoptosis Regulatory Proteins/agonists , Apoptosis Regulatory Proteins/genetics , Apoptosis Regulatory Proteins/metabolism , Basic Helix-Loop-Helix Transcription Factors/antagonists & inhibitors , Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Cell Cycle Proteins/antagonists & inhibitors , Cell Cycle Proteins/genetics , Cell Cycle Proteins/metabolism , Dibenzazepines/chemistry , Drug Carriers , Energy Metabolism/drug effects , Energy Metabolism/genetics , Gene Expression Regulation , Iodide Peroxidase/genetics , Iodide Peroxidase/metabolism , Lactic Acid/chemistry , Lactic Acid/metabolism , Male , Mice , Mice, Inbred C57BL , Mice, Obese , Nanoparticles/metabolism , Obesity/genetics , Obesity/metabolism , Obesity/pathology , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/agonists , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/genetics , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/metabolism , Polyglycolic Acid/chemistry , Polyglycolic Acid/metabolism , Polylactic Acid-Polyglycolic Acid Copolymer , Signal Transduction , Transcription Factor HES-1/antagonists & inhibitors , Transcription Factor HES-1/genetics , Transcription Factor HES-1/metabolism , Iodothyronine Deiodinase Type IIABSTRACT
Brown and beige adipocytes are potent therapeutic agents to increase energy expenditure and reduce risks of obesity and its affiliated metabolic symptoms. One strategy to increase beige adipocyte content is through inhibition of the evolutionarily conserved Notch signaling pathway. However, systemic delivery of Notch inhibitors is associated with off-target effects and multiple dosages of application further faces technical and translational challenges. Here, we report the development of a biodegradable polymeric microsphere-based drug delivery system for sustained, local release of a Notch inhibitor, DBZ. The microsphere-based delivery system was fabricated and optimized using an emulsion/solvent evaporation technique to encapsulate DBZ into poly(lactide-co-glycolide) (PLGA), a commonly used biodegradable polymer for controlled drug release. Release studies revealed the ability of PLGA microspheres to release DBZ in a sustained manner. Co-culture of white adipocytes with and without DBZ-loaded PLGA microspheres demonstrated that the released DBZ retained its bioactivity, and effectively inhibited Notch and promoted browning of white adipocytes. Injection of these DBZ-loaded PLGA microspheres into mouse inguinal white adipose tissue depots resulted in browning in vivo. Our results provide the encouraging proof-of-principle evidence for the application of biodegradable polymers as a controlled release platform for delivery of browning factors, and pave the way for development of new translational therapeutic strategies for treatment of obesity.
