Search

Background: Inflammation in adipose tissue (AT) during obesity causes impaired AT function. Although multiple extracellular matrix (ECM) proteins are expressed in AT their potential role in adipose tissue inflammation is unclear. Biglycan, a pro-inflammatory ECM gene, is highly enriched in adipose tissue. However, whether it is correlated with adipose tissue inflammation is unknown. We provide evidence in support of a strong association between biglycan expression and inflammatory status of adipose tissue., Methods: C57BL6 mice were fed either a control (10% fat calories) or a high fat diet (HFD) (60% fat calories) for 8 weeks. Adipose tissue was analyzed for the expression of biglycan, IL-6 and TNFα. Biglycan knockout or wild type were also fed a high fat diet for 8 weeks and the expression of inflammatory genes in the mesenteric adipose tissue was examined. To test anti-inflammatory treatment on biglycan expression, a group of mice were fed either the low fat or high fat diet for eight weeks supplemented with either saline or sodium salicylate @ 25mg/100ml in their drinking water., Results: Mice on HFD had an increase in ECM genes (BGN and COL1A1), inflammatory genes (IL-6 and TNFα) in both the subcutaneous and epididymal depots. However, correlation analysis only shows a positive correlation between biglycan, IL-6 and TNFα expression. In addition, lower expression of IL-6 and CD68 was found in the mesenteric adipose tissue of biglycan knockout mice compared to the wild type. Sodium salicylate treatment reduced subcutaneous adipose tissue expression of BGN, COL1A1, and COL6A1 and a concurrent downregulation of TNFα and IL-6 and TLR4 expression. Salicylate also lowered the serum TGFβ1 levels., Conclusion: Biglycan expression correlates with adipose tissue inflammation, especially in the subcutaneous depot compared to the epididymal depot. This is supported by the greater effect of sodium salicylate in attenuating both inflammatory and ECM gene expression the subcutaneous adipose depot compared to the epididymal depot. These results show that inflammatory state may explain the induction of biglycan, and perhaps, other ECM genes in adipose tissue.

Background: Secretory leucocyte protease inhibitor (SLPI) is an anti-inflammatory protein that is constitutively expressed in multiple cell types where it functions to counteract localized tissue inflammation by its anti-inflammatory, antimicrobial and anti-protease properties. Little is known about the expression and implication of SLPI in the regulation of adipose tissue inflammation. Therefore, we tested the hypothesis that obesity induces expression of SLPI in adipose tissue where it functions to counteract adipocyte inflammation., Methods: Male C57BL6 mice were fed a high fat (60% fat calories) or a control diet (10% fat calories) diet for 12 weeks. Adipose tissue expression of SLPI was determined by western blotting and PCR. Fully differentiated adipocytes (3T3-L1) were treated with lipopolysaccharide (LPS, 100 ng/ml) or peptidoglycan (10 μg/ml) for 24 hours in the presence or absence of SLPI. Media was collected for interleukin 6 (IL-6) analysis by enzyme-linked immune absorbent assay (ELISA). RNA was isolated for gene expression analysis by real-time polymerase chain reaction (RT-PCR)., Results: Visceral fat (mesenteric and epididymal) express a higher level of SLPI than subcutaneous fat. The expression of SLPI is mostly in the stromal vascular fraction compared to adipocytes. We also confirmed in vitro that activation of TLR2 and 4 with peptidoglycan and LPS respectively leads to induction of SLPI. Finally, we confirmed that SLPI exerted an anti-inflammatory effect in adipocytes treated with LPS by causing a reduction in expression of IL-6 via a mechanism that included stabilization of cellular IKBα expression., Conclusion: Our results show that SLPI is also expressed in adipocytes and adipose tissue where it could play an important feedback role in the resolution of inflammation.

Background: Inflammation is a major component of obesity and diabetes, and toll-like receptors (TLRs) play critical roles in the regulation of inflammation and response to pathogen associated molecular patterns (PAMPs) and fatty acids in. Although immune cells such as macrophages are primarily responsible for recognition and clearance of pathogens, adipocytes are also closely involved in the regulation of innate immunity and inflammation. Whereas it has been demonstrated that adipocytes respond to TLR4 stimulation with lipopolysacccharide, very little is known about their response to the TLR2 agonist, peptidoglycan., Methods: We investigated the response to peptidoglycan from Staphylococcus aureus in differentiated 3T3-L1 adipocytes. Real-time PCR analysis was used to quantify the expression of interleukin 6 (IL6), adiponectin receptors (adipoR1 and adipoR2), toll-like receptor 2 (TLR2) and 4 (TLR2 4). Media level of IL6 was determined with ELISA., Results: Adipocyte stimulation peptidoglycan induces IL6 expression (P < 0.01). Both siRNA mediated suppression of TLR2 and immunoneutralization of TLR2 with a TLR2 specific antibody inhibited response to peptidoglycan (P < 0.05). We also examined the regulation of TLR2 and TLR4 mRNA in peptidoglycan treated cells. Both peptidoglycan and lipopolysaccharide (LPS) robustly induce TLR2 mRNA expression, whereas TLR4 mRNA is weakly induced by LPS only (P < 0.05). Additionally, peptidoglycan downregulates the mRNA expression of adiponectin receptors, adipoR1 and adipoR2 (P < 0.05)., Conclusion: Obesity and type 2 diabetes are associated with increased expression of TLR2, this receptor could play a significant but previously unrecognized role in the establishment of chronic inflammation in adipose tissue in obesity.