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alpha-Glycerophosphate shuttle in a clonal beta-cell line
M D Meglasson1, K M Smith, D Nelson
1Diabetes Research Center, University of Pennsylvania School of Medicine, Philadelphia 19104.
The American Journal of Physiology
|January 1, 1989
Summary
The alpha-glycerophosphate (alpha-GOP) shuttle aids ATP generation in beta-cells, crucial for glucose-stimulated insulin secretion. This study provides direct evidence for its role in insulin-secreting cells.
Area of Science:
- Biochemistry
- Cell Biology
- Metabolic Regulation
Background:
- The alpha-glycerophosphate (alpha-GOP) shuttle is hypothesized to regulate glycolysis in beta-cells.
- It links cytosolic NADH reoxidation to ATP production via the electron transport chain.
- Direct evidence for its function in beta-cells was previously lacking.
Purpose of the Study:
- To investigate the operation and role of the alpha-GOP shuttle in insulin-secreting cells.
- To determine if the alpha-GOP shuttle contributes to ATP generation and insulin secretion.
Main Methods:
- Investigated the alpha-GOP shuttle in the HIT-T15 insulin-secreting cell line.
- Localized the key enzymes: flavin-linked alpha-GOP dehydrogenase (mitochondrial) and NAD+-dependent alpha-GOP dehydrogenase (cytosolic).
- Utilized amobarbital to preserve shuttle function while blocking NADH oxidation by the respiratory chain.
Main Results:
- Confirmed the presence and localization of alpha-GOP shuttle enzymes in HIT cells.
- In the presence of amobarbital, glucose significantly increased insulin secretion, O2 consumption, and the cellular ATP/ADP ratio.
- These effects were compared to amobarbital treatment alone.
Conclusions:
- The alpha-glycerophosphate (alpha-GOP) shuttle contributes to ATP generation in HIT cells.
- Activation of the alpha-GOP shuttle appears necessary for glucose-induced insulin secretion.
- Provides direct evidence supporting the shuttle's critical role in beta-cell function.