[The role of GSK3ß in adipose tissue inflammation induced by bisphenol-A in high fat diet fed mice].

OBJECTIVE: To study the effect of glycogen synthase kinase 3ß(GSK3ß) in BPA-induced adipose tissue inflammation in high fat diet(HFD) fed mice. METHODS: Four-week-old male C57 BL/6 mice were randomly divided into normal diet(ND) group, HFD group, HFD + GSK3ß inhibitor group, HFD + 1000 nmol/L BPA group, HFD+1000 nmol/L BPA+GSK3ß inhibitor group. The mice were exposed to BPA via drinking water. From the 14 th week of BPA exposure to the end of 16 weeks, the GSK3ß inhibitor group was intraperitoneally injected with 21. 5 mg/kg lithium chloride(Li Cl) every two days for a total of 10 times. At the end of 16 weeks, the mice were sacrificed after anesthesia, and the epididymal fat tissue was taken aseptically. The pathological changes were observed by H&E staining. The expressions of interleukin-1ß(IL-1ß) and tumor necrosis factor-α(TNF-α) were detected by immunohistochemistry(IHC). The expression of GSK3ß protein and its S9 serine(GSK3ß-S9) phosphorylation were detected by western blot. RESULTS: Compared with the ND group, the body weight [(34. 97±1. 91) g]and epididymal fat pad coefficient [(3. 25±0. 39) %]of HFD group was significantly up-regulated(P < 0. 05), the adipose tissue inflammatory cell infiltration was increased, the expression of TNF-α(F = 73. 157, P < 0. 05) and IL-1ß(F = 42. 788, P < 0. 05) was significantly enhanced, and the phosphorylation degree of GSK3ß-S9(F = 57. 991, P < 0. 05) was decreased. The inflammatory cell infiltration of adipose tissue in the HFD+1000 nmol/L BPA group was significantly increased, the body weight [(38. 49±1. 34) g]and epididymal fat pad coefficient [(4. 41±0. 33) %] of the mice were significantly increased, the phosphorylation of GSK3ß-S9(F = 57. 991, P <0. 05) was significantly down-regulated, and the expression of TNF-α(F = 73. 157, P <0. 05) and IL-1ß(F = 42. 788, P <0. 05) was significantly enhanced compared with that in the HFD group. Compared with the HFD + 1000 nmol/L BPA group, the HFD + 1000 nmol/L BPA+GSK3 inhibitor group was decreased inflammatory cell infiltration in adipose tissue, significantly decreased body weight [(32. 61 ± 3. 34) g] and epididymal fat pad coefficient [(3. 33±0. 66) %], significantly increased GSK3-S9(F = 57. 991, P < 0. 05)phosphorylation, and significantly decreased TNF-α(F = 73. 157, P < 0. 05) and IL-1ß(F = 42. 788, P<0. 05) expression. CONCLUSION: GSK3ß inhibitor can down-regulate BPA-induced adipose tissue inflammation, inflammatory cytokine expression and upregulate GSK3ß-S9 phosphorylation in HFD-fed mice, suggesting that BPA exposure may regulate the expression of inflammatory cytokines mediating adipose tissue inflammation by affecting the degree of phosphorylation of GSK3ß-S9.

Enhancing de novo ceramide synthesis induced by bisphenol A exposure aggravates metabolic derangement during obesity.

OBJECTIVE: Exposure to bisphenol A (BPA) has been shown to increase the prevalence of obesity and its related insulin resistance (IR). Ceramide is a sphingolipid known to facilitate the production of proinflammatory cytokines and subsequently exacerbate inflammation and IR during the progression of obesity. Here, we investigated the effects of BPA exposure on ceramide de novo synthesis and whether increased ceramides aggravate adipose tissue (AT) inflammation and obesity-related IR. METHODS: A population-based case-control study was conducted to explore the relationship between BPA exposure and IR and the potential role of ceramide in AT in obesity. Next, we used mice reared on a normal chow diet (NCD) or a high-fat diet (HFD) to verify the results from the population study and then investigated the role of ceramides in low-level BPA exposure with HFD-induced IR and AT inflammation in mice treated with or without myriocin (an inhibitor of the rate-limiting enzyme in de novo ceramide synthesis). RESULTS: BPA levels are higher in obese individuals and are significantly associated with AT inflammation and IR. Specific subtypes of ceramides mediated the associations between BPA and obesity, obesity-related IR and AT inflammation in the obesity group. In animal experiments, BPA exposure facilitated ceramide accumulation in AT, activated PKCζ, promoted AT inflammation, increased the expression and secretion of proinflammatory cytokines via the JNK/NF-κB pathway, and lowered insulin sensitivity by disrupting IRS1-PI3K-AKT signaling in mice fed a HFD. Myriocin suppressed BPA-induced AT inflammation and IR. CONCLUSION: These findings indicate that BPA aggravates obesity-induced IR, which is partly via increased de novo synthesis of ceramides and subsequent promotion of AT inflammation. Ceramide synthesis could be a potential target for the prevention of environmental BPA exposure-related metabolic diseases.