Abstract
Background
The influence of diabetic therapies on myocardial substrate selection during cardiac
surgery is unknown but may be important to ensure optimal surgical outcomes. We hypothesized
that metformin and insulin alter myocardial substrate selection during cardiac surgery
and may affect reperfusion cardiac function.
Methods
Rat hearts (n = 8 per group) were evaluated under 3 metabolic conditions: normokalemia, cardioplegia,
or bypass. Groups were perfused with Krebs-Henseleit buffer in the presence of no
additives, metformin, insulin, or both insulin and metformin. Perfusion buffer containing
physiologic concentrations of energetic substrates with different carbon-13 (13C) labeling patterns were used to determine substrate oxidation preferences using
13C magnetic resonance spectroscopy and glutamate isotopomer analysis. Rate pressure
product and oxygen consumption were measured.
Results
Myocardial function was not different between groups. For normokalemia, ketone oxidation
was reduced in the presence of insulin and the combination of metformin and insulin
reduced fatty acid oxidation. Metformin reduced fatty acid and ketone oxidation during
cardioplegia. Fatty acid oxidation was increased in the bypass group compared with
all other conditions.
Conclusion
Metformin and insulin affect substrate utilization and reduce fatty acid oxidation
before reperfusion. These alterations in substrate oxidation did not affect myocardial
function in otherwise normal hearts.
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Article info
Publication history
Published online: December 11, 2017
Accepted:
October 10,
2017
Footnotes
Funding support from American Heart Association South-Central Affiliate, 11BGIA5590007.
Presented at the 12th Annual Academic Surgical Congress in Las Vegas, NV February 7–9, 2017.
Identification
Copyright
© 2017 Elsevier Inc. All rights reserved.
