Progress of olfactory changes in metabolic diseases and the mechanisms

Abstract

Metabolic disorders, characterized by a complex pathogenesis, are experiencing a rising prevalence globally and a trend toward younger populations, making them a significant public health concern. Olfaction, a crucial sensory function, plays a pivotal role in an individual′s nutrition and quality of life. There is a bidirectional relationship between obesity and olfactory function. Olfaction is influenced by nutritional status; simultaneously, it plays a vital role in the regulation of food intake, energy expenditure, and lipid metabolism. Moreover, individuals with metabolic disorders such as type 2 diabetes and obstructive sleep apnea syndrome exhibit olfactory dysfunction. Mechanisms underlying olfactory changes in metabolic disorders involve alterations in metabolic states such as hyperglycemia and insulin resistance. These changes can lead to dysregulation of peptide hormones, adipocyte factors, and neurotransmitters, which may potentially act as mediators between metabolic disorders and olfactory dysfunction. Vascular and neural alterations resulting from metabolic disorders can directly damage olfactory nerves or induce abnormal neural transmission. Furthermore, dysbiosis in the gut microbiota induced by metabolic disorders is a potential mechanism for olfactory dysfunction. Cognitive dysfunction is a significant complication of metabolic disorders. Olfactory dysfunction can serve as an early clinical manifestation of cognitive impairment and contributes to early identification and assessment of diseases. This article reviews recent researches on the relationship between metabolic diseases and olfactory changes and the potential mechanisms.

Keywords

• obesity
• diabetes mellitus
• olfactory function
• metabolic diseases
• cognitive impairment