To determine whether AMPK plays a critical role in structural formation and maintenance of neurons, axons, and dendritic branches, which ultimately leads to synapse formation and signal transduction.

In highly energetic neuronal cells, manipulation of a well-known energy sensor, AMPK, has been proposed as an effective therapeutic modality for age-related and neurodegenerative brain function loss. A safe, well-established anti-diabetic medication, metformin, is known to modulate AMPK activity and exerts effects on brain function. We targeted AMPKα and AMPKα2, which are most abundant in neurons. Manipulating such a specific energy sensor subunit may impact neurons’ cellular and morphological integrity.

Cerebellar purkinje cells (PC) from post-mortem AMPKα2 knock out mice were assessed using immunohistochemistry. Further, dorsomorphin (DMD) as an AMPK inhibitor and metformin as an AMPK activator were used in primary hippocampal neuron-based studies. The neuronal morphological quantification for cell body perimeter and dendritic branches was carried out using figure scale and manual tracing in ImageJ software.

DMD treatment led to dendrite loss in primary hippocampal neuron cultures, which could be reversed by metformin. Interestingly, DMD and metformin co-treatment did not prevent loss of dendritic branches and overall lengths. On the contrary, soma size of primary neurons grew progressively with DMD, DMD washout then metformin, and DMD with metformin co-treatment, respectively. Additionally, PCs of AMPKα2-KO demonstrated increased soma size and decreased dendritic branching and neurite length compared to WT littermates.

AMPKα is a critical determinant of neuron structure and dendritic branching. Our results suggest temporary inhibition by DMD is recoverable by metformin’s AMPK activation. Increased soma size in all cellular insults and especially in cotreatment suggests a possible storming interaction between DMD and metformin. The loss of neurite branching and increased soma size in AMPKα2-KO PCs may represent either acute effects or rebound compensation due to loss of AMPKα2 function.