Specific deletion of CLK2 in GABA neurons: impact on the energy metabolism of mice

Author(s)

Sónia Maria Norberto Alves

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Ciências Médicas
• Defense date: 2021-11-12

Examining board members

Patrícia de Oliveira Prada; Carla Roberta de Oliveira Carvalho; Bruno de Melo Carvalho; Marcelo Alves Mori; Guilherme Zweig Rocha

• Advisor: Patrícia de Oliveira Prada

Abstract

Obesity and associated comorbidities are related to metabolic changes resulting from an energy imbalance. Our research team recently showed that hypothalamic neurons express CLK2 (Cdc-like kinase 2). CLK2 can be phosphorylated in response to insulin and leptin, contributing to the control of energy balance. However, we did not investigate which neurons express CLK2 and the metabolic or behavioral participation involving the CLK2 in specific subpopulations of neurons. Given the abundance of neurons expressing ?-aminobutyric acid (GABA) and its potential to control energy and behavioral homeostasis, we used mice with specific deletion of CLK2 in GABA neurons (Clk2flox/flox.VgatCre) in the present study. We aimed to 1) generate Clk2flox/flox.VgatCre mice and their controls (Clk2flox/flox); investigate in these mice, of both genders: 2) body weight and body composition, food intake, energy expenditure, fasting glycemia, insulin and leptinemia, tolerance to glucose, insulin, and pyruvate of animals submitted to the chow diet (chow) or high-fat diet (HFD); 3) investigate leptin and insulin action and signaling; 4) investigate the gene expression of some genes related to the control of energy metabolism in the hypothalamus, such as Npy, Agrp, Pomc and Crh and; 5) explore the behavior. The deletion of CLK2 induced the obese phenotype in Clk2flox/flox.VgatCre females fed with chow, evidenced by increased adiposity, maybe due to hyperphagia. The mechanisms behind differences in food intake were partially due to insulin resistance in the hypothalamus besides NPY and AGRP expression changes. Energy expenditure did not change. We observed a reduction in glucose tolerance and less anxious behavior in Clk2flox/flox.VgatCre females on chow. Those changes were independent of global insulin sensitivity (ITT). In males, the deletion of CLK2 leads to a dysregulation of Crh mRNA levels and a significant increase in energy expenditure, however, resulting in a similar metabolic phenotype among groups. We observed that both genders of Clk2flox/flox.VgatCre under HFD developed an obese phenotype compared to the groups on chow. The metabolic profile of Clk2flox/flox.VgatCre females under HFD compared to chow displayed an increased daily energy intake, reduced energy expenditure (light phase), glucose intolerance, insulin resistance, hyperleptinemia, and increased hepatic glucose production accompanied by increased PEPCK protein expression in the liver. The obese phenotype of Clk2flox/flox.VgatCre males under HFD, in comparison to Clk2flox/flox.VgatCre on chow was defined by increased adiposity, hyperleptinemia, hyperinsulinemia, insulin resistance, and increased liver production of glucose (indirectly accessed by PTT). The central action of leptin was CLK2-independent in both genders fed chow. However, the anorexigenic effect of leptin was lost in mice fed an HFD. Overall, our data corroborate the participation of the CLK2 in energy homeostasis. Additionally, for the first time, our data demonstrate the metabolic and behavioral phenotype of mice lacking CLK2 in GABA neurons according to the animal's gender. We conclude that CLK2 presents itself as a promising therapeutic target for combating obesity associated with psychological disorders (AU)

• FAPESP's process: 18/18341-2 - Specific deletion of Clk2 in GABA neurons: impact on mice energy metabolism
• Grantee: Sónia Maria Norberto Alves
• Support Opportunities: Scholarships in Brazil - Doctorate