Coenzyme A–mediated degradation of pyruvate dehydrogenase kinase 4 promotes cardiac metabolic flexibility after high-fat feeding in mice

Abstract

Cardiac energy is produced primarily by oxidation of fatty acids and glucose, with the relative contributions of each nutrient being sensitive to changes in substrate availability and energetic demand. A major contributor to cardiac metabolic flexibility is pyruvate dehydrogenase (PDH), which converts glucose-derived pyruvate to acetyl-CoA within the mitochondria. PDH is inhibited by phosphorylation dependent on the competing activities of pyruvate dehydrogenase kinases (PDK1-4) and phosphatases (PDP1-2). A single high-fat meal increases cardiac PDK4 content and subsequently inhibits PDH activity, reducing pyruvate utilization when abundant fatty acids are available. In this study, we demonstrate that diet-induced increases in PDK4 are reversible and characterize a novel pathway that regulates PDK4 degradation in response to the cardiac metabolic environment. We found that PDK4 degradation is promoted by CoA (CoASH), the levels of which declined in mice fed a high-fat diet and normalized following transition to a control diet. We conclude that CoASH functions as a metabolic sensor linking the rate of PDK4 degradation to fatty acid availability in the heart. However, prolonged high-fat feeding followed by return to a low-fat diet resulted in persistent sensitivity of PDH to fatty acid-induced inhibition despite reductions in PDK4 content. Moreover, increases in the levels of proteins responsible for β-oxidation and rates of palmitate oxidation by isolated cardiac mitochondria following long-term consumption of high dietary fat persisted after transition to the control diet. We propose that these changes prime PDH for inhibition upon reintroduction of fatty acids.

Enhancing cardiac glycolysis causes an increase in PDK4 content in response to short-term high-fat diet

“…To better understand the discrepancy between mRNA levels and protein abundance, we next examined factors, CoA and Lon protease, that may affect PDK4 posttranslationally. PDK4 associates with the PDH complex, and this protects it from degradation (18). Upon an increase in the PDH substrate, CoA, PDK4 dissociates from the complex and is degraded by Lon protease (17).…”

“…The primer pair used to quantify Pdk4 mRNA, as validated in Ref. 18, was the following: forward, 5Ј-AGGGAGGTCGAGCTGT-TCTC-3Ј; reverse, 5Ј-GGAGTGTTCACTAAGCGGTCA-3Ј. For Pgc1␣ mRNA, it was as follows: forward, 5Ј-CCCTGCCA-TTGTTAAGAC-3Ј; reverse, 5Ј-GCTGCTGTTCCTGTTTT-C-3Ј, as validated in Ref.…”

“…PDH is therefore highly regulated by multiple mechanisms that include product feedback inhibition and phosphorylation. In the heart, PDH is phosphorylated and inhibited by pyruvate dehydrogenase kinase 4 (PDK4), an enzyme that also fluctuates in both protein content and activity, depending upon the nutrient status (5,(16)(17)(18). For example, under conditions where fatty acid oxidation is elevated, such as with fasting or under high-fat diet feeding, PDK4 levels are elevated.…”

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Induced by Repeated Forced Swimming in Mice

“…PDH is a crucial enzyme localized in the mitochondria matrix linking glycolysis to TCA cycle and oxidative phosphorylation. 8) PDH is inhibited by phosphorylation, which is dependent on the pyruvate dehydrogenase kinase (PDK) activity. 9) PDH activity is impor-tant for muscle function and exercise.…”

Microenvironmental control of glucose metabolism in tumors by regulation of pyruvate dehydrogenase

“…The highly ubiquitous relevance of PDC function in the organism translates into many medical conditions beyond the scope of this review. Further examples include but are not limited to: acute liver failure, nonalcoholic steatohepatitis, obesity, cardiovascular diseases, viral and bacterial infection, and even autism …”