Is genetically transmitted obesity due to an adipose tissue defect?

Area of Science:

• Obesity Research
• Cell Biology
• Genetics

Background:

• Obesity is characterized by enlarged fat cells (adipocytes).
• The relative contribution of intrinsic cellular factors versus the surrounding environment to adipocyte size in obesity remains unclear.
• Several rodent models exhibit obesity due to distinct genetic or induced factors.

Purpose of the Study:

• To determine whether fat cell enlargement in obesity originates from intrinsic fat cell properties or the external environment.
• To investigate the role of the cellular environment in regulating adipocyte size across diverse models of rodent obesity.

Main Methods:

• Transplantation of gonadal fat from obese or lean rodents into hosts of either obese or lean genotype.
• Histological examination of transplanted fat to measure adipocyte diameter and calculate adipocyte mass.
• Utilized syngeneic mouse models and F1 hybrids to prevent immunological rejection of grafts.

Main Results:

• 'Lean' fat cells increased in size when transplanted into an obese environment, adopting characteristics of obese adipocytes.
• 'Obese' fat cells decreased in size when transplanted into a lean environment, resembling lean adipocytes.
• These environmental influences on fat cell size were observed across all studied rodent models, including mutant mice (db/db, dbad/dbad, Ay/+) and gold thioglucose-induced obese mice.

Conclusions:

• The cellular environment plays a crucial role in determining fat cell size in all investigated rodent models of obesity.
• Environmental factors are of paramount importance in regulating adipocyte size, with intrinsic fat cell factors contributing negligibly.
• These findings highlight the significant impact of the microenvironment on adipocyte hypertrophy in the context of obesity.