Brain-Type Glycogen Phosphorylase Is Crucial for Astrocytic Glycogen Accumulation in Chronic Social Defeat Stress-Induced Depression in Mice

Abstract

Astrocytic glycogen plays an important role in brain energy metabolism. However, the contribution of glycogen metabolism to stress-induced depression remains unclear. Chronic social defeat stress was used to induce depression-like behaviors in mice, assessed with behavioral tests. Glycogen concentration in the medial prefrontal cortex (mPFC) and the expression of key enzymes of the glycogen metabolism were investigated using Western blots, immunofluorescent staining, electron microscopy, and biochemical assays. Stereotaxic surgery and viral-mediated gene transfer were applied to knockdown or overexpress brain-type glycogen phosphorylase (PYGB) in the mPFC. The glycogen content increased in the mPFC after stress. Glycogenolytic dysfunction due to inactivation of PYGB was responsible for glycogen accumulation. Behavioral tests on astrocyte-specific PYGB overexpression mice showed that augmenting astrocytic PYGB reduces susceptibility to depression when compared with stress-susceptible mice. Conversely, PYGB genetic down-regulation in the mPFC was sufficient to induce glycogen accumulation and depression-like behaviors. Furthermore, PYGB overexpression in the mPFC decreases susceptibility to depression, at least partially by rescuing glycogen phosphorylase activity to maintain glycogen metabolism homeostasis during stress. These findings indicate that (1) glycogen accumulation occurs in mice following stress and (2) glycogenolysis reprogramming leads to glycogen accumulation in astrocytes and PYGB contributes to stress-induced depression-like behaviors. Pharmacological tools acting on glycogenolysis might constitute a promising therapy for depression.

Behavioral state-dependent oscillatory activity in prefrontal cortex induced by chronic social defeat stress

“…Advancement in molecular research revealed that social defeat stress specifically increases c-Fos expression (a marker for neuronal activity) in the PFC ( Numa et al, 2019 ), and social stress-induced behavioral deficits are mediated by molecular adaptations in the prefrontal cortical circuit involving ΔFosB and cholecystokinin ( Vialou et al, 2014 ). Besides, dopamine D2 receptor dimerization ( Bagalkot et al, 2015 ) and astrocytic glycogen accumulation ( Zhu et al, 2021 ) in PFC is also closely related to stress-induced depression-like behavior.…”

Brain-Type Glycogen Phosphorylase (PYGB) in the Pathologies of Diseases: A Systematic Review

“…The inactivation of PYGB leads to the dysfunction of glycogen decomposition and, thus, glycogen storage. PYGB contributes to stress-induced depression-like behaviors and is a promising therapeutic target for the treatment of depression [105].…”

Modern Insights into Muscle Glycogen Phosphorylase Activity

“…While the GPh activity assay is well-established using high performance liquid chromatography (4,5), these enzyme assays with commercially available alternatives have low sensitivity, are complex and lack versatility in their application. While the assay is well-established for liver and brain tissue (5)(6)(7), its applicability to muscle, another significant site of glycogen storage, has been less explored.…”