Betaine, a Potential Therapeutic Alternative for the Treatment of Depression.

Depression is a debilitating psychiatric disorder characterized by loss of interest, anhedonia, and social isolation, which is projected to become the leading cause of disability worldwide by 2030. Despite the greater economic and social burden imposed by depression, the precise pathophysiology underlying the development of depression remains elusive. Betaine (N, N, N-trimethylglycine), an amino acid derivative, is widely distributed in various animals and plants and has been shown to have numerous beneficial effects, including antioxidant activities, anti-inflammatory functions, regulation of energy metabolism, and reduction of endoplasmic reticulum stress. It has been used to treat Alcohol-Associated Liver Disease (AALD), type 2 diabetes, cancer, obesity, and Alzheimer's Disease (AD). Interestingly, accumulating evidence has shown that betaine exerts a significant role in alleviating depressive-like behavior in patients and animals resulting from chronic stress. Although the antidepressant effects of betaine have not been compared with traditional antidepressants with insufficient verification, based on the neurobiological mechanisms of depression, it may be a potential alternative medicine for the treatment of depression. This is the first review aiming to provide a comprehensive overview of the remarkable effects of betaine in the pathophysiology of depression. These pieces of evidence are of great importance for deepening our understanding of the antidepressant mechanism of betaine, so as to develop betaine supplements for the supplementary treatment of depression.