Abstract
Background4-Hydroxyisoleucine (4-HIL) is an active ingredient extracted from Trigonella foenum-graecum L., a Chinese traditional herbal medicine, which exerts the efficacy of anti-obesity and anti-diabetes. We previously reported that 4-HIL potentiates anti-inflammatory and anti-insulin resistance effects through down-regulation of TNF-α and TNF-α converting enzyme (TACE) in 3 T3-L1 adipocytes and HepG2 cells. In the present study, we further investigate the effects and mechanisms of 4-HIL on obesity-induced inflammation in RAW264.7 macrophages and 3 T3-L1 adipocytes co-culture system.MethodsRAW264.7 macrophages and 3 T3-L1 adipocytes were co-cultured to mimic the microenvironment of adipose tissue. siRNA-iRhom2 transfection was performed to knockdown iRhom2 expression in RAW264.2 macrophages. The mRNA and protein expression of iRhom2 and TACE were measured by real-time quantitative PCR (RT-qPCR) and western blotting. The production of tumor necrosis factor-α (TNF-α), monocyte chemotactic protein-1 (MCP-1), IL-6 and IL-10 were evaluated by ELISA. The ratio of M2/M1 was detected by flow cytometry.Results4-HIL significantly repressed the mRNA and protein levels of iRhom2 and TACE in RAW264.7 macrophages after LPS stimulated. Meanwhile, the levels of pro-inflammatory cytokines, including TNF-α, MCP-1, and IL-6, were substantially suppressed by 4-HIL in the co-culture system. Moreover, the level of anti-inflammatory cytokine IL-10 was increased significantly by 4-HIL in the co-culture system after LPS stimulation. Additionally, the ratio of M2/M1 was also increased by 4-HIL in the co-culture system after LPS stimulation. Finally, these effects of 4-HIL were largely enhanced by siRNA-iRhom2 transfection.ConclusionTaken together, our results indicated that obesity-induced inflammation was potently relieved by 4-HIL, most likely through the iRhom2-dependent pathway.
Highlights
Obesity is a medical disease that leads to many complications [1], such as diabetes, cardiovascular disease, metabolic disorders and cancer [2,3,4,5]
We aimed to investigate whether the coculture of 3 T3-L1 adipocytes and RAW264.7 macrophages could aggravate inflammation, to observe the effects of 4-HIL on the co-culture system, and to explore the underlying molecular mechanisms
In light of the key role of Inactive rhomboid protein 2 (iRhom2) in TNF-α converting enzyme (TACE)-mediated proteolytic shedding of tumor necrosis factor-α (TNF-α), we hypothesized whether 4-HIL could modulate iRhom2 to reverse obesity-induced inflammation
Summary
Obesity is a medical disease that leads to many complications [1], such as diabetes, cardiovascular disease, metabolic disorders and cancer [2,3,4,5]. A body mass index (BMI) of 25.0 kg/m2 to 30.0 kg/m2 was defined as overweight; and BMI > 30.0 kg/m2 was defined as obesity [6]. According to WHO, worldwide obesity has nearly tripled since 1975, and there were more than 1.9 billion adults who were reported to be overweight. It is of great significance to explore the pathogenesis and therapeutic drugs for obesity, elucidating the pathogenesis of obesity-related metabolic diseases and finding new treatment methods. There is no effective method for the treatment of obesity, and the efficacy of traditional Chinese medicine in obesity has gradually attracted widespread attention
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