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Glycogen synthesis from lactate in a chronically active muscle
R J Talmadge1, J I Scheide, H Silverman
1Department of Zoology and Physiology, Louisiana State University, Baton Rouge 70803.
Summary
Skeletal muscles can directly synthesize glycogen from lactate, especially in the dy2J mouse model. Specific muscle fibers in dy2J mice show a significantly higher rate of lactate-to-glycogen conversion.
Area of Science:
- Biochemistry
- Muscle Physiology
- Metabolic Disorders
Background:
- Gastrocnemius muscles in dy2J mice exhibit altered metabolic profiles compared to normal mice.
- Elevated glycogen and lactate levels are observed in dy2J muscles, suggesting metabolic dysregulation.
Purpose of the Study:
- To investigate the direct synthesis of glycogen from lactate within skeletal muscles.
- To compare the capacity of normal and dy2J muscle fibers to incorporate lactate into glycogen.
Main Methods:
- Utilized an in situ procedure bathing gastrocnemius muscles in [14C]lactate with controlled blood flow.
- Employed autoradiography to visualize and quantify 14C incorporation into muscle glycogen.
- Contralateral gastrocnemius muscles served as controls to account for systemic organ input.
Main Results:
- Both normal and dy2J muscles can synthesize glycogen directly from lactate under high lactate conditions.
- While normal muscle incorporates lactate into glycogen at a higher overall rate, specific high-glycogen fibers in dy2J muscle show a fourfold increased rate of lactate incorporation.
- This indicates a fiber-type-specific metabolic adaptation in dy2J muscle.
Conclusions:
- Skeletal muscle possesses the intrinsic ability to convert lactate into glycogen.
- The dy2J mouse model demonstrates enhanced, fiber-specific capacity for lactate-to-glycogen synthesis, potentially as a compensatory mechanism.