The role of Wnt signaling in the regulation of GLUT1 and GLUT3 glucose transporters in the hypothalamus and hippocampus from prediabetic and obese C57BL/6 mice

• Grant number: 24/21726-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2025
• End date: January 31, 2026
• Field of knowledge: Biological Sciences - Physiology - Physiology of Organs and Systems
• Principal Investigator: Helena Cristina de Lima Barbosa
• Grantee: Isabela de Oliveira e Silva Campos Abreu
• Host Institution: Instituto de Biologia (IB). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Alzheimer disease (AD) is one of the most important modern epidemics, being a neurodegeneration not only associated with aging, but also to external factors, such as obesity and Type 2 Diabetes Mellitus (DM2). Among the most common molecular markers, one can list amyloid-beta (Abeta) deposits in plaques, formation of neurofibrillary tangles (NFTs) and insulin deficiency and resistance in the brain, resulting in oxidative stress, synaptic failure and death of neurons, which cause cognitive impairment in patients. To better understand the initial dysfunctions that result in neurodegeneration, we chose to study a group of proteins known as Wnts, responsible for synaptic plasticity regulation and memory in the nervous system, as well as maintaining homeostasis in various organs and tissues. Moreover, Wnt signaling is involved in the expression of membrane transporters known as GLUT, responsible for importing glucose through the blood-brain barrier (BBB) and into neurons. Factors such as aging, obesity and DM2 can disturb these proteins' functionality, resulting in signaling deregulation and impairments in glucose uptake by the brain. A known inhibitor of the Wnt/beta-catenin pathway, called GSK-3beta, is increased in conditions such as inflammation, hyperglycemia and DM2, in addition to being involved in failures in the insulin signaling pathway, affecting glucose homeostasis. Preliminary data in our research group show an expressive increase in gene expression of GSK-3beta in the hippocampus of prediabetic mice in relation to a control group. In conclusion, in this project we wish to further understand which Wnts are largely affected by aging, obesity and DM2, and, with that knowledge, evaluate if and how the dysfunction of these proteins' signaling can cause glucose deficiency in the nervous system through the reduction of GLUT transporters. For that, we chose to use adult, obese and prediabetic mice, in order to evaluate if those conditions can promote, in the brain, typical modifications related to Alzheimer disease, such as the increase in GSK-3beta. Using immunofluorescence, we can analyze the location of glucose transporters GLUT1 and 3 in hippocampus, hypothalamus and BBB samples. In addition, qPCR will be used to evaluate gene expression of the most common Wnts in the nervous system, as well as GLUTs and junction proteins of the blood-brain barrier, in order to evaluate if dysfunctions in the BBB can be associated with Wnt signaling. Western Blotting will also be used, to analyze the protein content of GLUTs from the brain., intending to identify possible deregulations associated with obesity and DM2. In conclusion, knowing that there is a direct correlation between the neurodegeneration associated with Alzheimer disease and deficient insulin signaling in the brain (mostly due to hypothalamic inflammation), and that this situation, similar to the one observed with DM2, is related to a reduction in Wnt signaling, this work aims to elucidate some of the molecular details that connect the processes mentioned above. By understanding the molecular dysfunctions in the central nervous system, we can explore a new field of study, correlating Wnts, GLUTs, blood-brain barrier and insulin signaling, focusing not only in mitigating the neurodegeneration hallmarks, but also in possible therapies to alleviate and slow the disease's progression.