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Theaflavins inhibit the ATP synthase and the respiratory chain without increasing superoxide production.

ABSTRACT: Four dietary polyphenols, theaflavin, theaflavin-3-gallate, theaflavin-3'-gallate and theaflavin-3,3'-digallate (TF3), have been isolated from black tea, and their effects on oxidative phosphorylation and superoxide production in a model system (Escherichia coli) have been examined. The esterified theaflavins were all potent inhibitors of the membrane-bound adenosine triphosphate (ATP) synthase, inhibiting at least 90% of the activity, with IC(50) values in the range of 10-20 μM. ATP-driven proton translocation was inhibited in a similar fashion, as was the purified F(1)-ATPase, indicating that the primary site of inhibition was in the F(1) sector. Computer modeling studies supported this interpretation. All four theaflavins were also inhibitory towards the electron transport chain, whether through complex I (NDH-1) or the alternative NADH dehydrogenase (NDH-2). Inhibition of NDH-1 by TF3 appeared to be competitive with respect to NADH, and this was supported by computer modeling studies. Rates of superoxide production during NADH oxidation by each dehydrogenase were measured. Superoxide production was completely eliminated in the presence of about 15 μM TF3, suggesting that inhibition of the respiratory chain by theaflavins does not contribute to superoxide production.

SUBMITTER: Li B

PROVIDER: S-EPMC8717676 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:New findingsWhat is the central question of this study? Humans with obesity have lower ATP synthesis in muscle along with lower content of the β-subunit of the ATP synthase (β-F1-ATPase), the catalytic component of the ATP synthase. Does lower synthesis rate of β-F1-ATPase in muscle contribute to these responses in humans with obesity? What is the main finding and its importance? Humans with obesity have a lower synthesis rate of β-F1 -ATPase and ATP synthase specific activity in muscle. These findings indicate that reduced production of subunits forming the ATP synthase in muscle may contribute to impaired generation of ATP in obesity.AbstractThe content of the β-subunit of the ATP synthase (β-F1 -ATPase), which forms the catalytic site of the enzyme ATP synthase, is reduced in muscle of obese humans, along with a reduced capacity for ATP synthesis. We studied 18 young (37 ± 8 years) subjects of which nine were lean (BMI = 23 ± 2 kg m-2 ) and nine were obese (BMI = 34 ± 3 kg m-2 ) to determine the fractional synthesis rate (FSR) and gene expression of β-F1 -ATPase, as well as the specific activity of the ATP synthase. FSR of β-F1 -ATPase was determined using a combination of isotope tracer infusion and muscle biopsies. Gene expression of β-F1 -ATPase and specific activity of the ATP synthase were determined in the muscle biopsies. When compared to lean, obese subjects had lower muscle β-F1 -ATPase FSR (0.10 ± 0.05 vs. 0.06 ± 0.03% h-1 ; P < 0.05) and protein expression (P < 0.05), but not mRNA expression (P > 0.05). Across subjects, abundance of β-F1 -ATPase correlated with the FSR of β-F1 -ATPase (P < 0.05). The specific activity of muscle ATP synthase was lower in obese compared to lean subjects (0.035 ± 0.004 vs. 0.042 ± 0.007 arbitrary units; P < 0.05), but this difference was not significant after the activity of the ATP synthase was adjusted to the β-F1 -ATPase content (P > 0.05). Obesity impairs the synthesis of β-F1 -ATPase in muscle at the translational level, reducing the content of β-F1 -ATPase in parallel with reduced capacity for ATP generation via the ATP synthase complex.

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Theaflavins inhibit the ATP synthase and the respiratory chain without increasing superoxide production.

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