Papain is a proteolytic enzyme present in the leaves, fruits, roots, and latex of the Carica papaya (papaya) plant. Although it exhibits a wide range of activities, there are no reports on the anti-obesity effects of papain. This study examined the anti-obesity effect and obesity-involved anti-inflammatory mechanism of papain in in vivo and in vitro models using high-fat diet (HFD)-induced obese mice and 3T3-L1 preadipocytes. Oral administration of papain reduced HFD-induced weight of the body, liver, and adipose tissues of mice. Papain also reduced hepatic lipid accumulation and adipocyte size. Moreover, serum total cholesterol and triglyceride levels were markedly reduced in papain-treated mice. In addition, papain inhibited the differentiation of preadipocytes and oil accumulation in 3T3-L1 preadipocytes and rat primary preadipocytes. Mechanistically, papain significantly downregulated the protein levels of key adipogenesis regulators and reversed the expression of pro-inflammatory cytokines and adipokines in HFD-induced obese mice and 3T3-L1 preadipocytes. Papain also markedly enhanced activation of the AMP-activated protein kinase pathway in both models. Collectively, these results suggest that papain exerts anti-obesity effects in HFD-induced mice and 3T3-L1 preadipocytes by regulating levels of adipogenic factors involved in lipid metabolism and inflammation; thus, it could be useful in the prevention and treatment of obesity.

The genus Epilobium consists of approximately 200 species that are distributed worldwide. Some of these herbs have been used for the treatment of diarrhea, infection, irritation, and other disorders associated with inflammation. Unlike that of other Epilobium species, there is little scientific understanding of the pharmacological effect of Epilobium amurense subsp. cephalostigma (Hausskn.) C. J. Chen, Hoch & P. H. Raven. In this study, we demonstrated the anti-inflammatory and antioxidative properties of an E. amurense 95% ethanol extract (EACEE) in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages, and observed the underlying mechanism of this effect. We measured the productions of nitric oxide (NO) and reactive oxygen species, and examined the actions of EACEE on transcription factors in the macrophages. EACEE reduced NO production and inducible nitric oxide synthase protein levels via the inhibition of the nuclear factor (NF)-κB pathway. Additionally, EACEE suppressed redundant reactive oxygen species production and regulated nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) signaling. Furthermore, EACEE significantly inhibited the phosphorylation of p38 mitogen-activated protein kinase (MAPK). Overall, these results indicate that EACEE exerts anti-inflammatory and antioxidant effects via the activation of Nrf2/HO-1 and inhibition of NF-κB/p38 MAPK signaling.

Background: The genus Epilobium consists of approximately 200 species that are distributed worldwide. Some of these herbs have been used for the treatment of diarrhea, infection, irritation, and other disorders associated with inflammation. Unlike that of other Epilobium species, there is little scientific understanding of the pharmacological effect of Epilobium amurense subsp. cephalostigma (Hausskn.) C. J. Chen, Hoch & P. H. Raven. Methods: In this study, we demonstrated the anti-inflammatory and anti-oxidative properties of an E. amurense 95% ethanol extract (EACEE) in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages and observed the underlying mechanism of this effect. We measured the productions of nitric oxide (NO) and reactive oxygen species, and examined the actions of EACEE on transcription factors in the macrophages.Results: EACEE reduced NO production and inducible nitric oxide synthase protein levels via the inhibition of the nuclear factor (NF)-κB pathway. Additionally, EACEE suppressed redundant reactive oxygen species production and regulated nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) signaling. Furthermore, EACEE significantly inhibited the phosphorylation of p38 mitogen-activated protein kinase (MAPK). Conclusions: Overall, these results indicate that EACEE exerts anti-inflammatory and antioxidant effects via the activation of Nrf2/HO-1 and inhibition of NF-κB/p38 MAPK signaling.