Triglyceride uptake in muscles in rats

Area of Science:

• Metabolism and Nutrition
• Physiology

Background:

• Exogenous lipid assimilation varies across adipose tissue regions and physiological states (fasting/fed).
• The quantitative role of lipid uptake in muscle tissue remains largely unevaluated.

Purpose of the Study:

• To quantify exogenous lipid uptake in non-adipose tissues, specifically skeletal muscles.
• To compare lipid assimilation patterns in various tissues, including adipose tissue, liver, heart, and different muscle types.

Main Methods:

• Oral administration of U14C-oleic acid in sesame oil to conscious rats.
• Measurement of lipid label radioactivity in serum, heart, liver, adipose depots, and distinct muscle groups over 24 hours.
• Calculation of lipid uptake in total adipose tissue, muscle tissue, and liver based on extracted lipid radioactivity.

Main Results:

• Heart and serum lipid radioactivity peaked early and declined rapidly.
• Liver radioactivity peaked at or before 4 hours and decreased swiftly.
• Adipose tissue showed gradual uptake peaking around 16 hours; muscle radioactivity varied, with red gastrocnemius showing the highest uptake at 4 hours.
• Muscle radioactivity per unit mass correlated with oxidative capacity.

Conclusions:

• Skeletal muscles, particularly oxidative types, actively assimilate exogenous lipids.
• Lipid uptake dynamics differ significantly between muscle, adipose, and liver tissues.
• Oxidative capacity is a key determinant of lipid uptake in skeletal muscle.