Inhibitory Effects of Toll-Like Receptor 4, NLRP3 Inflammasome, and Interleukin-1β on White Adipocyte Browning.
Meshail OklaWalid ZaherMusaad AlfayezSoonkyu ChungPublished in: Inflammation (2018)
Adipose tissue expansion is accompanied by infiltration and accumulation of pro-inflammatory macrophages, which links obesity to pathologic conditions such as type 2 diabetes. However, little is known regarding the role of pro-inflammatory adipose tissue remodeling in the thermogenic activation of brown/beige fat. Here, we investigated the effect of pattern recognition receptors (PRR) activation in macrophages, especially the toll-like receptor 4 (TLR4) and Nod-like receptor 3 (NLRP3), on white adipocyte browning. We report that TLR4 activation by lipopolysaccharide repressed white adipocyte browning in response to β3-adrenergic receptor activation and caused ROS production and mitochondrial dysfunction, while genetic deletion of TLR4 protected mitochondrial function and thermogenesis. In addition, activation of NLRP3 inflammasome in macrophages attenuated UCP1 induction and mitochondrial respiration in cultures of primary adipocytes, while the absence of NLRP3 protected UCP1 in adipocytes. The effect of NLRP3 inflammasome activation on browning was mediated by IL-1β signaling, as blocking IL-1 receptor in adipocytes protected thermogenesis. We also report that IL-1β interferes with thermogenesis via oxidative stress stimulation and mitochondrial dysfunction as we observed a statistically significant increase in ROS production, decrease in SOD enzyme activity, and increase in mitochondrial depolarization in adipocytes treated with IL-1β. Collectively, we demonstrated that inflammatory response to obesity, such as TLR4 and NLRP3 inflammasome activation as well as IL-1β secretion, attenuates β3-adrenoreceptor-induced beige adipocyte formation via oxidative stress and mitochondrial dysfunction. Our findings provide insights into targeting innate inflammatory system for enhancement of the adaptive thermogenesis against obesity.
Keyphrases
- adipose tissue
- nlrp inflammasome
- toll like receptor
- insulin resistance
- oxidative stress
- high fat diet induced
- inflammatory response
- immune response
- high fat diet
- type diabetes
- nuclear factor
- dna damage
- metabolic syndrome
- ischemia reperfusion injury
- cell death
- diabetic rats
- weight gain
- skeletal muscle
- reactive oxygen species
- endothelial cells
- squamous cell carcinoma
- radiation therapy
- cardiovascular disease
- binding protein
- rectal cancer
- body mass index
- dna methylation
- fatty acid
- physical activity