Benzyl isothiocyanate inhibits TNFα-driven lipolysis via suppression of the ERK/PKA/HSL signaling pathway in 3T3-L1 adipocytes.

Tumor necrosis factor α (TNFα), an inflammatory cytokine, induces lipolysis and increases circulating concentrations of free fatty acids. In addition, TNFα is the first adipokine produced by adipose tissue in obesity, contributing to obesity-associated metabolic disease. Given that benzyl isothiocyanate (BITC) is a well-known anti-inflammatory agent, we hypothesized that BITC can ameliorate TNFα-induced lipolysis and investigated the working mechanisms involved. We first challenged 3T3-L1 adipocytes with TNFα to induce lipolysis, which was confirmed by increased glycerol release, decreased protein expression of peroxisome proliferator-activated receptor γ (PPARγ) and perilipin 1 (PLIN1), and increased phosphorylation of ERK, protein kinase A (PKA), and hormone-sensitive lipase (HSL). However, inhibition of ERK or PKA significantly attenuated the lipolytic activity of TNFα. Meanwhile, pretreatment with BITC significantly ameliorated the lipolytic activity of TNFα; the TNFα-induced phosphorylation of ERK, PKA, and HSL; the TNFα-induced ubiquitination of PPARγ; the TNFα-induced decrease in PPARγ nuclear protein binding to PPAR response element; and the TNFα-induced decrease in PLIN1 protein expression. Our results indicate that BITC ameliorates TNFα-induced lipolysis by inhibiting the ERK/PKA/HSL signaling pathway, preventing PPARγ proteasomal degradation, and maintaining PLIN1 protein expression. BITC inhibits TNFα-induced ubiquitination of PPARγ and subsequent proteasomal degradation and PPARγ is a critical transcription factor for PLIN1, which acts as a barrier to the breakdown of storage lipids. In addition, TNFα activates the ERK/PKA/HSL signaling pathway participating in lipolysis, which is suppressed by BITC. Abbreviations: BITC, benzyl isothiocyanate; DG, diglyceride; FFA, free fatty acid; HSL, hormone-sensitive lipase; MG, monoglyceride; PKA, protein kinase A; PLIN1, perilipin 1; PPARγ, peroxisome proliferator-activated receptor γ; TG, triglyceride; TNFα, tumor necrosis factor α. [Display omitted] [ABSTRACT FROM AUTHOR]