A unique role of monocyte chemoattractant protein 1 among chemokines in adipose tissue of obese subjects.
BACKGROUND
Low-grade inflammation in adipose tissue may contribute to insulin resistance in obesity. However, the roles of individual inflammatory mediators in adipose tissue are poorly understood.


OBJECTIVE
The objective of this study was to determine which inflammation markers are most overexpressed at the gene level in adipose tissue in human obesity and how this relates to corresponding protein secretion.


METHODS
We examined gene expression profiles in 17 lean and 20 obese subjects. The secretory pattern of relevant corresponding proteins was examined in human s.c. adipose tissue or isolated fat cells in vitro and in vivo in several obese or lean cohorts.


RESULTS
In ranking gene expression, defined pathways associated with obesity and immune and defense responses scored high. Among seven markedly overexpressed chemokines, only monocyte chemoattractant protein 1 (MCP1) was released from adipose tissue and isolated fat cells in vitro. In obesity, the secretion and expression of MCP1 in adipose tissue pieces were more than 6- and 2-fold increased, respectively, but there was no change in circulating MCP1 levels. There was no net release of MCP1, but there was a net release of leptin, in vivo from adipose tissue into the circulation.


CONCLUSIONS
Obesity is associated with the increased expression of several chemokine genes in adipose tissue. However, only MCP1 is secreted into the extracellular space, where it primarily acts as a local factor, because little or no spillover into the circulation occurs. MCP1 influences the function of adipocytes, is a recruitment factor for macrophages, and may be a crucial link among chemokines between adipose tissue inflammation and insulin resistance.
Dahlman
Ingrid
I
Department of Medicine, Huddinge, Karolinska Institute, Stockholm, Sweden.
Kaaman
Maria
M
Olsson
Tommy
T
Tan
Garry D
GD
Bickerton
Alex S T
AS
Wåhlén
Kerstin
K
Andersson
Jonas
J
Nordström
Elisabet Arvidsson
EA
Blomqvist
Lennart
L
Sjögren
Annelie
A
Forsgren
Margaretha
M
Attersand
Anneli
A
Arner
Peter
P
D000273:Adipose Tissue / Q000503:physiopathology*; D000328:Adult; D015992:Body Mass Index; D018932:Chemokine CCL2 / Q000096:biosynthesis / Q000502:physiology*; D018925:Chemokines / Q000096:biosynthesis / Q000502:physiology*; D005260:Female; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007109:Immunity / Q000502:physiology; D018836:Inflammation Mediators / Q000502:physiology; D007333:Insulin Resistance; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D020411:Oligonucleotide Array Sequence Analysis; D011506:Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
C111835:CCL2 protein, human; D018932:Chemokine CCL2; D018925:Chemokines; D018836:Inflammation Mediators; D011506:Proteins