Macrophages in human visceral adipose tissue: increased accumulation in obesity and a source of resistin and visfatin

http://www.springerlink.com/content/l04607w14751u12r/fulltext.html

Introduction: Increased white adipose tissue accumulation can be seen as an indicator of adverse health effects from obesity. WAT is known for both the storage of energy along with secretion of adipokines. Adipokines control leptin and glucose levels but also contain proinflammatory factors and chemokines, which are higher in obese people. This leads to an accumulation of macrophages, and the study aimed to characterize the relationship of macrophage population and obesity

Subject and methods: The study took white adipose tissue from 33 men and 17 women who underwent abdominal surgery. Immunoselection was used to extract CD14+ and adipocytes from SVF, and FACS to analyze the SVF and CD14+ cells. Concentration of visfatin and resistin was determined with ELISA.
RNA was then extracted via real-time PCR, using primers targeting the genes of interest.
Human Caucasian hepatocyte carcinoma cells were then lysed and incubated with antibodies. The resulting immune complexes were viewed under chemiluminescence.

Results: There was a trend between the increase of CD14+ cells percentage in WAT, as can be seen in figure a. Figure b shows the fold increase of the chemokines, cytokines, and adipokines after real-time PCR was done on the isolated CD14+ and adipocyte cells. Resistin was predominantly in CD14+, and visfatin was also found in CD14+.
Visfatin and resistin were established to be the main product of adipocytes and CD14+ cells




Discussion: The adipose tissue that come with obesity may be the source of proinflammatory factors, and this study showed that there was, in fact, an increase of CD14+ cells that was proportion to BMI. The CD14 cell marker was narrowed down to adipose derived macrophages, as opposed to the usual CD68 cell marker, since CD68 would also be expressed by human preadipose cells. Both vistafin and resistin were predominantly produced by the WAT derived macrophages. However, resistin's effect in humans is still unknown, but there has been a higher expression of it in cases of atherosclerosis. Visfatin is a cytokine for neutrophils, and these two are probably the result of the proinflammatory response in obese people. WAT-derived macrophages also led to stimulation of Akt in hepatocytes, though adipose products did not. This leads to the conclusion that the increase of visceral WAT leads the accumulation of vistafin and resistin, and this increase of macrophages is the reason behind the increase of proinflammatory cytokine production.

Critique: This article aimed to find the connection between the increase of macrophages and that of obesity and adipokine expression. Since rats have already been shown to have this relation, this study was done in order to establish the connection when expressed in humans. Obesity is a health condition that leads to many adverse effects, and by learning more about it we can find ways to help against it. The paper is able to conclude that there is, indeed, a connection between the two.
Though the study does seem to have a varied sample size, it does not mention the use of a group from which they considered to be the control group for the experiments. This would have been useful had there been any sort of possible errors that may have occurred during the protocol, just to make sure that the standards were done correctly. The results, too, though they suggest a general trend, the r for the trendline is rather low at 0.37 and 0.35 for men and women, respectively. Figure 1b is also rather unclear as to the data, and could use better labels to allow readers to understand it at a glance instead of having to read the caption in detail. On the other hand, the graphs in Figure 2 are much clearer, and allow for easy understanding and viewing. The conclusions themselves, do follow the data presented, but to establish a stronger correlation still will need more experimentation before a clear conclusion can be made, limitations of which the article does address.
As a side note, this article is pretty cool, yo. Totally thumbs up, dudes.