So as we worry we weigh: Visible burrow system stress and visceral adiposity

Abstract

The visible borrow system (VBS) simulates a natural rodent habitat that supports genuine stress provoking social interactions. This model allows investigation of behavioral, neural and endocrine alterations caused by chronic stress. The Sakai lab further used this model to investigate metabolic outcomes of stress in relation to dominance hierarchies formed within the VBS. Communal social conflict occurs among all VBS rats, but only the SUB rats succumb to the redistribution of lipids in the visceral cavity and consequent metabolic dysregulation, such as hyper-insulinemia. These increases in visceral adipose tissue occur after two cycles of VBS stress and recovery bouts and are associated with decreases in subcutaneous adipose tissue. Traditionally, distribution shift in lipid deposition is predominately thought to occur by characteristics specific to the visceral depot, but evidence supports that decreased subcutaneous adipose tissue deposition may be linked to enhanced visceral adipose expansion. This review will discuss VBS stress and redirection of adipose tissue in SUB rats. There will be specific focus on the enhanced adipogenic capacity of visceral adipose tissue as driven by glucocorticoid receptor density, 11-hydroxysteroid dehydrogenase type 1 (11-HSD1) and lipoprotein lipase (LPL). Additionally, the proposed contribution of decreased subcutaneous adipose expansion via stress-induced inhibition of lipid uptake, storage and cellularity will be discussed. Overall, this review will summarize how stress-induced visceral obesity may result from a combination of maladaptive responses within the visceral and subcutaneous depot.