Influence of vagus nerve and spleen ablation on brown adipose tissue histology of hypothalamic obese and non-obese male Wistar rats

Abstract

Vagus nerve and spleen can influence metabolic function and adiposity. Brown adipose tissue is an organ specialized in thermogenesis, a biochemistry process of lipids degradation that results in heat production, elevating energy expenditure and contributing to anti-obesity effects. Aim: Here, we evaluated the impact of vagus nerve and spleen absence on histology and lipid deposition of brown adipose tissue from non-obese and hypothalamic obese male Wistar rats. Methods: Hypothalamic obesity was induced by neonatal glutamate L-monosodium (4g/Kg) administration during the first post-natal days. Control rats received equimolar saline. At 60 days of life, obese and control groups underwent surgery: vagotomy, splenectomy, and sham. At 150 days of life, the animals were weighed and measured. Blood was collected for biochemistry analysis of glucose and triglycerides, and insulin resistance evaluated. Moreover, white adipose tissue and brown adipose tissue depots were removed and weighed. Brown adipose tissue was histologically analyzed. Results: In obese animals, elevated adiposity, hypertriglyceridemia, insulin resistance and higher lipid deposition in brown adipose tissue were noted. Vagus nerve ablation displayed more pronounced anti-adiposity effects, improving triglyceride plasma levels and insulin resistance in the obese rats compared to the control group. Moreover, spleen absence, especially in the obese group, raises nuclei number and reduced adipocyte size. These responses were amplified by vagus nerve ablation. Conclusion: Hypothalamic obese rats show excessive adiposity and metabolic dysfunctions related to brown adipose tissue hypofunction. Vagus nerve and spleen absence reduced lipid deposition on brown adipose tissue of obese rats, suggesting reactivation of thermogenesis.