Regulatory cycles of orexin and glucagon-Like peptide-1 in postviral syndromes.

Postviral syndromes are heterogeneous multisystem diseases without a uniform etiology that occur as a result of acute viral infections. During the COVID-19 pandemic, the number of patients increased dramatically due to infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This is known as postacute sequelae of COVID-19 (PASC), with many cases also meeting the criteria for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), the most severe form of a postviral disease, characterized by severe fatigue, postexertional malaise (PEM), unrefreshing sleep, neurocognitive impairment, and autonomic and immune dysregulation. Orexin (OX) neuropeptides, which regulate arousal, metabolism, and neuroendocrine functions, may serve as a central link among stress, immune activation, and metabolic changes in these syndromes. Notable phenotypic similarities between OX system dysfunction and core features of PASC and ME/CFS, including fatigue, sleep issues, impaired glucose metabolism, and neuropsychiatric symptoms, support a mechanistic model in which impaired OX signaling contributes to postviral endocrine and metabolic dysfunction. This review examines the role of OX in regulating glucose metabolism, HPA axis activity, and systemic homeostasis, with a specific focus on sexually dimorphic expression and function in relation to postviral syndromes. We also highlight the effect of glucagon-like peptide-1 (GLP-1), another key player in metabolism, which also has neuroprotective, anti-inflammatory, vasoprotective, and immunomodulatory effects. We further emphasize emerging therapeutic strategies, such as GLP-1 receptor agonists (GLP-1RAs) and drugs targeting the OX system. Together, these insights provide an integrated framework for understanding and targeting the neuroendocrine-metabolic underpinnings of PASC, ME/CFS, and other postviral syndromes.