• Gabriel Manjarrez-Gutiérrez, José Antonio Mondragón-Herrera, and Jorge Hernández-Rodríguez.
• Neurological Disorders Research Unit, Specialty Hospital, Centro Médico Nacional Siglo XXI (CMN-SXXI), Instituto Mexicano del Seguro Social (IMSS), Mexico City.
• Gac Med Mex. 2022 Jan 1; 158 (4): 182-189.

IntroductionDiabetes mellitus (DM) inhibits brain serotonin biosynthesis through changes in tryptophan-5-hydroxylase (TPH) activity and expression.ObjectivesTo determine whether DM-induced changes in brain TPH1 or TPH2 expression and in the number of serotonergic neurons return to normal in diabetic rats treated with insulin.MethodsRats with streptozotocin-induced diabetes were divided in two groups: one treated with insulin and the other without treatment. On day 14, brain stems were obtained in order to quantify L-tryptophan and 5-hydroxytryptamine levels, as well as to determine TPH activity. The expression of TPH1 and TPH2 by West-ern blot, and the number of serotonergic neurons by immunohistochemistry.ResultsIn diabetic rats, a decrease in the levels of L-tryptophan, 5-hydroxytryptamine, and TPH activity was confirmed, as well as lower TPH1 and TPH2 expression and lower numbers of serotonergic neurons. When diabetic rats were treated with insulin, L-tryptophan returned to normal, but not 5-hy-droxytryptamine, TPH expression, or the number of serotonergic neurons.ConclusionsDM chronically inhibits the synthesis of brain 5-hydroxytryptamine through changes in TPH1 and TPH2 expression and a decrease in the number of serotonergic neurons, which persist despite insulin treatment.Copyright: © 2022 Permanyer.

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