Semaglutide restores astrocyte-vascular interactions and blood-brain barrier integrity in a model of diet-induced metabolic syndrome.

INTRODUCTION: Metabolic syndrome (MetS) is a metabolic disorder related to obesity and insulin resistance and is the primary determinant of the development of low-intensity chronic inflammation. This continuous inflammatory response culminates in neuroimmune-endocrine dysregulation responsible for the metabolic abnormalities and morbidities observed in individuals with MetS. Events such as the accumulation of visceral adipose tissue, increased plasma concentrations of free fatty acids, tissue hypoxia, and sympathetic hyperactivity in individuals with MetS may contribute to the activation of the innate immune response, which compromises cerebral microcirculation and the neurovascular unit, leading to the onset or progression of neurodegenerative diseases. OBJECTIVE: This study aimed to evaluate the effects of chronic treatment with a GLP-1 receptor agonist (semaglutide) on cerebral microcirculation and neurovascular unit (NVU) integrity. METHODS: C57BL/6 mice were fed a standard normolipidic diet or a high-fat diet (HFD) for 24 weeks and then treated for 4 weeks with semaglutide (HFD SEMA) or saline solution (HFD SAL). At the end of pharmacological treatment, biochemical analyses, immunohistochemistry analysis, and intravital microscopy of the brain microcirculation were carried out to quantify leukocyte-endothelium interactions and to assess structural capillary density, astrocyte coverage on cerebral vessels and microglial activation. RESULTS: We observed that SEMA attenuates high-fat diet-induced metabolic alterations in mice fed with HFD for 24 weeks. SEMA also reversed cerebral microcirculation effects of HFD by reducing capillary rarefaction and the interaction of leukocytes in postcapillary brain venules. The HFD-SEMA group exhibited improved astrocyte coverage on vessels. However, SEMA did not reverse microglial activation. CONCLUSIONS: Semaglutide can reverse microvascular rarefaction in metabolic syndrome by restoring the integrity of the neurovascular unit. Adverse dietary stimuli can compromise microglial homeostasis that is not reversed by semaglutide.