Berberine hydrochloride (BBR) has been reported to improve insulin resistance. However, the underlying mechanism remains largely elusive. We therefore investigate the anti-inflammatory role of BBR and the cell signaling pathways that involved.
C2C12 myoblasts were treated with IL-1β (10ng/mL) alone or in combination with TNF-α (50 ng/mL) in the presence or absence of BBR (10 µM) for 24 hours. Western blot analysis was used to assess the protein level. In vivo study is conducted using C57BL/6 mice fed with high fat high sucrose (HFHS) diet to induce insulin resistance. Skeletal muscle was collected after 4 weeks treatment with either 5 mg/kg BBR or vehicle.
BBR reduced activity of iNOS, and stress-related kinases, including p38 MAPK, NF-kB, SAP/JNK, MMK4 and C-JUN that was induced by cytokines in C2C12 myoblast. Furthermore, BBR reversed cytokine mediated suppression of AMPK-α, augmented activity of SIRT-1 and PGC-1α. Antioxidant enzyme or transcription factor, nuclear factor like 2 (NRF-2) were also elevated after BBR treatment. In addition, BBR improved insulin signaling in C2C12 myoblast. HFHS diet induced iNOS expression was reversed by BBR in skeletal muscle. Augmentation of the activity of uncoupled protein-3 (UCP-3) and PPARα in HFHS diet skeletal muscle was observed.
Our results demonstrate that BBR ameliorates cytokine induced inflammation and oxidative stress. BBR improves mitochondrial function, promotes insulin sensitivity. The anti-inflammatory effect of BBR in skeletal muscle may mediated through multiple pathways including activation of AMPKα-SIRT-1-PGC-1α pathway, and inhibition of MMK4- SAP/JUNK-C-JUN pathway. BBR is a potential medication in treating obesity induced insulin resistance.
A. Poudel: None. J. Zhou: None. S. Massey: None. L. Li: None.