Pan Li1, Liqin Ding2, Shijie Cao2, Xinchi Feng3, Qiang Zhang2, Yuwei Chen1, Nan Zhang1, Feng Qiu4. 1. School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, Tianjin, 301617, China; State Key Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 301617, China. 2. State Key Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 301617, China. 3. School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, Tianjin, 301617, China. 4. School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, Tianjin, 301617, China; State Key Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 301617, China. Electronic address: fengqiu20070118@163.com.
Abstract
ETHNOPHARMACOLOGICAL EVIDENCE: Curcumin (CUR) is the active ingredient of Traditional Chinese Medicine turmeric (Curcuma longa L.), which has been used for treatment of diabetes in Ayurveda and China. CUR exerts potent anti-insulin-resistant effects in various cell lines. However, previous studies indicated CUR was metabolized extensively in vivo and massively degraded in a medium alkaline buffer solution. The real active component of the anti-insulin-resistant activity of CUR in vitro is not clear. AIM OF THE STUDY: Our study identified the functional contribution of the metabolites of CUR and the related molecular mechanism in improving insulin sensitivity. MATERIALS AND METHODS: HPLC and UPLC-QQQ-MS analyses were used to investigate the stability and metabolism of CUR in HepG2 cells. The effect of the metabolic products of CUR on insulin sensitivity was evaluated in high glucose (HG)-induced insulin-resistant HepG2 cells. A network pharmacology approach was used to examine the potential targets of the metabolites, and Western blotting was performed to verify changes in the targets. RESULTS: CUR was unstable in the cell culture medium, but the prototypes, metabolites and degradation products of CUR coexisted in the HepG2 cell culture experiment. The insulin sensitivity assay demonstrated that CUR and its metabolites enhanced insulin sensitivity in HG-induced insulin-resistant HepG2 cells, but the total degradation products of CUR may not play the major role. Similar to CUR, hexahydrocurcumin (HHC) and octahydrocurcumin (OHC) improved insulin sensitivity by strengthening the PI3K-AKT-GSK3B signal and suppressing the phosphorylation of ERK/JNK in HG-induced insulin-resistant HepG2 cells. CONCLUSIONS: Metabolites of CUR played a critical role in counteracting insulin resistance in HG-induced HepG2 cells. CUR exerted anti-insulin resistance effect in HepG2 cells in a multi-component, multi-target, and multi-pathway manner.
ETHNOPHARMACOLOGICAL EVIDENCE: Curcumin (CUR) is the active ingredient of Traditional Chinese Medicine turmeric (Curcuma longa L.), which has been used for treatment of diabetes in Ayurveda and China. CUR exerts potent anti-insulin-resistant effects in various cell lines. However, previous studies indicated CUR was metabolized extensively in vivo and massively degraded in a medium alkaline buffer solution. The real active component of the anti-insulin-resistant activity of CUR in vitro is not clear. AIM OF THE STUDY: Our study identified the functional contribution of the metabolites of CUR and the related molecular mechanism in improving insulin sensitivity. MATERIALS AND METHODS: HPLC and UPLC-QQQ-MS analyses were used to investigate the stability and metabolism of CUR in HepG2 cells. The effect of the metabolic products of CUR on insulin sensitivity was evaluated in high glucose (HG)-induced insulin-resistant HepG2 cells. A network pharmacology approach was used to examine the potential targets of the metabolites, and Western blotting was performed to verify changes in the targets. RESULTS: CUR was unstable in the cell culture medium, but the prototypes, metabolites and degradation products of CUR coexisted in the HepG2 cell culture experiment. The insulin sensitivity assay demonstrated that CUR and its metabolites enhanced insulin sensitivity in HG-induced insulin-resistant HepG2 cells, but the total degradation products of CUR may not play the major role. Similar to CUR, hexahydrocurcumin (HHC) and octahydrocurcumin (OHC) improved insulin sensitivity by strengthening the PI3K-AKT-GSK3B signal and suppressing the phosphorylation of ERK/JNK in HG-induced insulin-resistant HepG2 cells. CONCLUSIONS: Metabolites of CUR played a critical role in counteracting insulin resistance in HG-induced HepG2 cells. CUR exerted anti-insulin resistance effect in HepG2 cells in a multi-component, multi-target, and multi-pathway manner.