we recently published an article (4), which has been commented on by Trayhurn et al. (5), showing that human obesity is characterized by an increase in the fat of inflammation markers associated with a decrease of lipogenic factors. According to previously published work on regulation of inflammation by hypoxia in adipose tissue (6), we were interested in evaluating HIF-1α mRNA levels in our samples. No significant variation of this factor was observed between lean or obese subjects or according to adipose tissue localization (4).
However, a previous study has demonstrated an increase of HIF1-α protein levels in adipose tissue in obese subjects (2). Trayhurn et al. (5) strongly support the interest in studying HIF-1α protein rather than mRNA. We agree that in general, and when possible, the measure of the amount of the active form of the protein should be determined. Nevertheless, our samples were obtained during gastric bypass intervention under general anesthesia, while subcutaneous biopsies, as described by Cancello et al. (2), were performed after local anesthesia, which may make difficult any comparison. If anesthesia influences the HIF-1α mRNA level, it may contribute to conflicting observations. It is noteworthy that many abnormalities other than tissue hypoxia have been implicated in obesity, each of them influenced by the genetic background (1, 3), and our objective was not to evaluate the exact contribution of HIF-1α in comparison to others.
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