Phytomedicine Plus (Aug 2023)
Bombax ceiba calyx extract promotes insulin sensitivity in L6 myotubes and modulates glucose metabolism in BRL3A cells through multiple pathways: A cell metabolomics approach
Abstract
Background: Bombax ceiba calyces are highly valued as a medicinal and nutritional vegetable, and have been traditionally used to treat various ailments. Recent studies have shown that extracts derived from Bombax ceiba calyces (BCE) can decrease insulin resistance and increase insulin secretion in hyperglycemic conditions, while reducing the formation of advanced glycation end products. However, the mechanism by which BCE promotes insulin sensitivity in high glucose condition remains unclear and requires further investigation. Purpose: In this study, our objective was to elucidate the molecular mechanism responsible for the effects of BCE and high glucose (Glu 33.6 mM) treatments on insulin sensitivity and glucose metabolism in L6 myotubes and BRL3A cells. By investigating these mechanisms, we aim to provide a better understanding of how BCE promotes insulin sensitivity and enhances glucose metabolism under conditions of high glucose. Methods: The insulin-sensitizing activity of BCE (10 µg and 20 µg) was evaluated in L6 myotubes under high glucose conditions (G33.6 mM). After the treatment period, protein isolation was performed, and western blot analysis was conducted to assess the levels of specific markers, including AKT, pAKT, Nrf2, PI3K, and NFκB. Mitochondrial dysfunction was measured by evaluating the activity of complexes I-IV, TCA enzymes such as succinate dehydrogenase (SDH) and aconitase. Additionally, a Q-RT-PCR study was performed to determine the expression levels of PGC1α, PDK4, UCP2, and UCP3. The effect of BCE (10 µg and 20 µg) on glucose utilization and gluconeogenesis was determined by using BRL3A cells under hyperglycemic conditions (G33.6 mM). Glucose uptake and glycogen content were measured, while gluconeogenesis was inhibited by assessing the expression of AKT, pAKT, AMPK, pAMPK, and PEPCK proteins using western blot analysis. Results: Our results indicate that, BCE promotes insulin signaling and enhances insulin sensitivity in L6 myotubes treated with high glucose by activating the PI3K/AKT pathway. Our analysis revealed that BCE restores mitochondrial respiration by restoring complexes I-IV, UCP2, and UCP3, and enhances metabolism through the activation of PGC1α, PDK4, and TCA enzymes such as aconitase and SDH. Moreover, BCE activates antioxidant pathways, such as Nrf2 and NF-kB, in high glucose-treated L6 myotubes, and improves insulin sensitivity by modulating the glycerophospholipid pathway. Furthermore, BCE promotes glycogenesis through AKT and AMPK phosphorylation and inhibits gluconeogenesis by downregulating PEPCK expression in BRL3A cells treated with high glucose. Conclusion: Our study has demonstrated that, BCE promotes insulin sensitivity and modulates glucose metabolism through multiple mechanisms under hyperglycemic conditions. Our findings suggest that BCE has the potential to be used as a functional food for the treatment of hyperglycemia.
