A catecholamine-independent pathway controlling adaptive adipocyte lipolysis

Area of Science:

• Metabolism
• Endocrinology
• Adipose Tissue Biology

Background:

• Constitutive bone marrow adipose tissue and other fat depots resist typical fat breakdown signals.
• The mechanisms by which the body catabolizes stable adipocytes during starvation, wasting, or cachexia remain largely unknown.

Purpose of the Study:

• To investigate the mechanisms of stable adipocyte catabolism, particularly bone marrow adipose tissue, independent of food intake.
• To identify the neurosystemic pathways regulating the depletion of all adipose tissues.

Main Methods:

• Development of a novel mouse model for brain-evoked fat depletion.
• Utilized genetic, surgical, and chemical approaches to study adipocyte catabolism.
• Investigated the roles of lipolysis, local nerves, sympathetic nervous system, catecholamines, hypoglycemia, and hypoinsulinemia.

Main Results:

• Adipose triglyceride lipase-dependent lipolysis is crucial for stable adipocyte catabolism.
• Catabolism is independent of local nerves, the sympathetic nervous system, and catecholamines.
• Concurrent hypoglycemia and hypoinsulinemia trigger a catabolic state by suppressing lipid storage and promoting catecholamine-independent lipolysis via downregulation of inhibitors like G0s2.
• This pathway effectively delipidates classical adipose depots and is observed in cachectic mice.

Conclusions:

• Stable adipocytes possess unique resistance mechanisms to lipolysis in healthy states.
• A potent catecholamine-independent neurosystemic pathway facilitates rapid catabolism of all adipose tissues during specific physiological conditions.
• This pathway is activated by hypoglycemia and hypoinsulinemia and is relevant to conditions like cachexia.