Two opposite extremes of adiposity similarly reduce inflammatory response of antigen-induced acute joint inflammation

Abstract

Objective: Acute inflammation is a normal response of tissue to an injury. During this process, inflammatory mediators are produced and metabolic alterations occur. Adipose tissue is metabolically activated, and upon food consumption, it disrupts the inflammatory response. However, little is known about the acute inflammatory response in joints that results from diet-induced adipose tissue remodeling. The objective of this study was to determine whether alterations in adipose tissue mass arising from food consumption modify the inflammatory response of antigen-induced joint inflammation in mice.

Methods: Male BALB/c mice were fed a chow diet, a highly refined carbohydrate-containing (HC) diet for 8 wk. They were then immunized and, after 2 wk, received a knee injection of methylated bovine serum albumin (mBSA). They were sacrificed at 6, 24, and 48 h after injection. The effect of the cafeteria diet for 8 wk, which also increases adipose tissue, or conjugated linoleic acid (CLA) supplementation for 4 wk, a model of lipodystrophy, was evaluated 24 h after knee challenge with mBSA.

Results: Cellular influx, predominantly neutrophils, in synovial fluid was attenuated in the HC diet group, as were levels of myeloperoxidase and IL-1β in periarticular tissue and histopathological analysis. These responses were associated with reduced adiponectin and increased leptin in serum, which was pronounced in mice fed the HC diet. Cafeteria diet and CLA supplementation induced a profile similar to that seen with the HC diet in terms of inflammation, disease response, and metabolic alteration. Interestingly, after the injection of mBSA, the area of adipocytes in the infrapatellar fat pad increased in mice fed with chow diet similar to those fed the HC and cafeteria diet.

Conclusions: We demonstrated that attenuation of joint response induced by diet was independent of adipose tissue remodeling but could be associated with metabolic alterations.

Keywords: Adipocytes; Arthritis; Diet; Inflammation; Metabolism.