SAT-LB108 Brown Adipose Tissue Activity in Different Insulin Resistance Models in Rats: Lean Goto-Kakizaki and Diet-Induced Obese Wistar Rats
Authors: Serdan Tamires Duarte Afonso 
Published: May 2020

Abstract
Obesity is growing worldwide and one of the main causes of death. It is highly associated with the development of type 2 diabetes mellitus, insulin resistance, cardiovascular disease, metabolic syndrome, and certain forms of cancer. The presence of two types of adipose tissue, which have the opposing function, has been known for a long time. White adipose tissue (WAT) is the tissue of energy expenditure storage, while Brown adipose tissue (BAT) is characterized to dissipates energy as heat and is required for non-shivering thermoregulation, presents a high thermogenesis capacity, regulating systemic metabolism and participating of the glycemic homeostasis, and displayed a high metabolic activity, which is due the presence of UCP1 (uncoupling protein-1) and through this the ability to dissipate energy, to burn away (extra) food, and it had been a proposal as a potential target to obesity treatment. Was identification a novel type of adipocytes, brite/beige adipocytes, localized within the WAT depots and possess the ability to increase energy expenditure. The BAT activity is regulated by the adrenergic receptor and Sympathetic Nervous System; however, its regulation by the insulin resistance state is not completely elucidated yet. In this study, we evaluated the BAT activity and response different animal models of insulin resistance: lean type 2 diabetic Goto-Kakizaki rats and high-fat diet-induced obese Wistar rats. Animals at eight weeks-old were fed ad libitum with a control diet (Wistar-Control and GK-CD), high-fat diet (Wistar-HFD) and/ or plus condensed milk (wistar-HFD+CM) for eight weeks. To evaluate the BAT activity, 18F-FDG small-animal PET/CT was performed at 30 min after CL316,243 or saline injection. The activity of brown adipose tissue by 18F-FDG uptake sob basal conditions, when injecting saline, not shown a significant difference between the groups, however, shown lower 18F-FDG uptake in animals GK than compared with other groups. After CL 316,243 stimuli a highly specific beta 3- adrenoceptor agonist, the animals GK showed decreased 18F-FDG uptake in brown adipose tissue than the control group (by 56%). The analyze between to the groups sob saline or CL 316, 243 conditions by two-way ANOVA test, showed after stimuli that control group showed increased 18F-FDG uptake when compared to the HFD +CM and GK (by 68,9%) and (by 71%), respectively. The GK animals showed lower 18F-FDG uptake when compared with HFD and HFD+CM groups (by 62,3%) and (by 51%). The 18F-FGD showed decreased BAT activity after CL316,243 stimuli in GK animals. The encephalon18F-FDG uptake, under saline, showed higher uptake the animals HFD when compared with the GK group (by 171,3%). After stimuli CL 316, 243, the HFD group displayed higher 18F-FDG uptake than CM+HFD group and control group (by 35,3%) and (by 56,2%), respectively. The analyze between groups, baseline or CL 316, 243, showed that the baseline the HFD group displayed higher 18F-FDG uptake when compared with GK and CM+HFD group (by 63,1%) and (by 73,4%), respectively. These data showed decreased 18F-FDG uptake in response the stimuli CL 316, 243 in all groups, except GK group. These findings suggest a transition from brown to white adipose tissue in GK rats, a process known as “whitening”.