Metabolic differences between white and brown fat from fasting rabbits at physiological temperature

Area of Science:

• Metabolic research
• Adipose tissue biology
• Animal physiology

Background:

• Activated brown adipose tissue (BAT) is known for increased glucose metabolism.
• Limited data exists on BAT metabolic activity during fasting and normal temperatures.
• Understanding adipose tissue metabolism is crucial for metabolic health.

Purpose of the Study:

• To compare energetic metabolism differences between BAT and white adipose tissue (WAT) in rabbits.
• To investigate metabolic activity under physiological temperature and post-fasting conditions.
• To elucidate the metabolic pathways utilized by BAT and WAT during fasting.

Main Methods:

• New Zealand rabbits (n=10) were maintained at 23±2°C for 8 weeks.
• Food was withheld for 24 hours before tissue collection.
• Protein expression of key metabolic enzymes and metabolite levels were analyzed in BAT and WAT.

Main Results:

• WAT showed higher expression of glycolytic proteins (glyceraldehyde-3-phosphate dehydrogenase, pyruvate dehydrogenase) and cytosolic malate dehydrogenase.
• BAT exhibited higher expression of fatty acid oxidation enzymes (CPT1, CPT2, acyl CoA dehydrogenase).
• BAT had significantly higher lactate dehydrogenase expression and lactate content compared to WAT.

Conclusions:

• Rabbit BAT appears to favor anaerobic metabolism for energy during fasting at normal temperatures.
• WAT demonstrates potentiated malate-aspartate shuttle activity, suggesting a preference for gluconeogenesis.
• This study provides novel insights into the distinct metabolic adaptations of BAT and WAT under specific physiological conditions.