Background: Several cytokines and chemokines are released by adipose tissue and associated with insulin resistance. We investigated the systemic and in vitro release of RANTES(Regulated upon Activation Normal T-cell Expressed and Secreted), MCP-1(Monocyte Chemo-attractant Protein-1), adiponectin, leptin and IL-6 from three human adipose tissue depots and their relationship to insulin sensitivity.
Methods: Fasting blood samples were taken from obese female patients undergoing surgery(n=7, mean age 39 years, mean BMI 46 kg. m2). Glucose, insulin and lipid profiles and circulating adipokines named above were measured. Subcutaneous(Sc), omental(Om) and Gastric Fat Pad(GFP) adipose tissue organ culture were set up for determining in vitro adipokine release. Haemostasis Model Assessment for Resistance(HOMA-R) was calculated. Body fat content was measured using bioelectrical impedance. The study was approved by the hospital ethical committee.
Results: Unlike for leptin no significant correlation was observed between % body fat and other adipokines. Production rates of adipokines in vitro per gram adipose tissue per hr were: RANTES(Sc median=67, Om=29, GFP=62 pg/ml), MCP-1(Sc median=5, Om=6, GFP=4 ng/ml), leptin (Sc median=971, Om=212, GFP=447 pg/ml), adiponectin(Sc median=23, Om=25 ng/ml) and Il-6(Sc median=9, Om=12, GFP=10 ng/ml). Depot specific differences in adipokine release were not apparent except in leptin which was mainly subcutaneous. There was a direct significant correlation between % body fat and Sc leptin production and an inverse relationship with Om adiponectin. GFP release of RANTES had a negative and MCP-1 a positive relationship with % body fat. Obese subjects were significantly more insulin resistant. Serum MCP-1 was elevated in patients with worsening insulin resistance. There was a negative correlation between HOMA-R and serum adiponectin and HDL.
Conclusion: RANTES, MCP-1 and adiponectin were released in vivo from adipose tissue. Local production of adipokines varies between depots. Insulin sensitivity and % body fat can alter local production of the adipokines.