Functional evaluation of nuclear respiration factor-1 (Nrf1) in hypothalamic prooopiomelanocortin neurons

• Grant number: 24/01619-9
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: March 01, 2024
• End date: February 28, 2026
• Field of knowledge: Biological Sciences - Biochemistry - Metabolism and Bioenergetics
• Principal Investigator: Licio Augusto Velloso
• Grantee: Lara Regina Ferreira
• Host Institution: Faculdade de Ciências Médicas (FCM). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 13/07607-8 - OCRC - Obesity and Comorbidities Research Center, AP.CEPID

Abstract

Pro-opiomelanocortin (POMC) neurons in the hypothalamus act as first-order sensors for systemic signals that indicate energy reserves in the body. When active, these neurons coordinate catabolic responses, reducing hunger and increasing energy expenditure. Previous studies indicate that in animal models of diet-induced obesity, there is a functional and structural loss of POMC neurons, generating a state of anabolism that contributes to increased weight gain and, consequently, obesity. In this way, POMC neurons play a central role in the genesis of obesity and constitute potential targets for the development of preventive and therapeutic interventions for this disease. Furthermore, POMC neurons have a high energy demand, therefore, mitochondrial quality in these neurons is fundamental. During the planning of this project, we usedbioinformatics tools to identify transcripts encoding proteins potentially involved in the protection of POMC neurons against harmful stimuli. Using this method, we identified the nuclear respiration factor-1 (Nrf1) transcript, encoding the NRF1 protein, which plays an important role in mitochondrial DNA replication, mitochondrial respiration and cell growth. However, despite Nrf1 being an important regulator of fundamental aspects of mitochondrial quality, no previous study has evaluated the role of Nrf1 in POMC neurons. In this project, we put forward the hypothesis that, as it is a gene with an important role in the structural and functional regulation of mitochondria, Nrf1 could participate in the protection of POMC neurons against the harmful effects resulting from the consumption of a diet rich in saturated fatty acids. To explore this hypothesis, we will use strainsdistinct from transgenic mice reporter for mitochondria (PhAM-floxed), reporter for POMC (Pomc-cre), with deletion and overexpression of Nrf1 specifically in POMC neurons. In a first step, we will use a cell line of POMC neurons (mHypoA/POMC-GFP-1) and evaluate the impact of exposure to treatment with saturated fatty acid (palmitate) on Nrf1 expression. In parallel, we will usePOMC reporter mice fed a high-fat diet to, using confocal fluorescence microscopy, evaluate the expression of Nrf1 specifically in POMC neurons. In a second step, we will use plasmids to inhibit and overexpress Nrf1 in the cell line and in POMC reporter mice. Faced with inhibition and specific overexpression of Nrf1, we will evaluate the respiratory phenotype and mitochondrial structure in vitro. In mice, we will evaluate the metabolic phenotype, determining weight gain, food intake, O2 consumption, energy expenditure, spontaneous movement, function of brown adipose tissue and structure of POMC neurons. Finally, Pomc-Cre mice will be mated with mitochondria reporter mice (PhAM-Floxed), infected with cre-dependent adenovirus with inhibitory function and Nrf1 overexpression; The mice will then be fed a high-fat diet and the mitochondrial phenotype of POMC neurons will be evaluated. We believe that the elucidation of the role of Nrf1 in POMC neurons may contribute to advances in the understanding of the hypothalamic pathophysiology of obesity and eventually to the identification of new potentially interesting targets for prophylactic and therapeutic interventions of the disease.