I'm suprised that this article by Olesen et al has attracted little attention so far. The work is well done, state-of-the-art and comprises studies with gain and loss-of-function of PGC-1alpha. It's a solid in vivo study that shows a novel role of PGC-1alpha in proinflammatory processes in skeletal muscle.

The findings of Olesen et al is backed up by an independent in vitro study from Mormeneo et al (http://www.plosone.org/ar...). Mormeneo et al found increased expression of proinflammatory factors in cultured muscle cells following overexpression of PGC-1alpha.

Recently, a new article has appeared from Eisele et al (http://www.ncbi.nlm.nih.g...) on the same subject. There findings strikingly contrast with the findings of Olesen et al.

What is true?

I critically read all these studies.
The study by Eisele et al is in my opinion pretty dubious. They used adenoviruses to overexpress PGC-1alpha. There is, however, no information about the multiplicity of infection (MOI) used to infect the cells. The virus itself is a strong proinflammatory stimulus. For the study to be interpretable, it's crucial that the control and the PGC-1 viruses are used at exactly the same MOI.

In fact, there are a myriad of inconsistencies in that paper by Eisele et al:

-Figures 1 A, 2 D and 3 A all show IL-6 expression levels. 3 times the same control experiment is shown; i.e. cells infected with GFP or PGC-1alpha under untreated conditions. 3 times they obtain different results. Once IL-6 is about 3.5 times higher in control cells infected with PGC-1alpha compared to GFP. Once there is no difference between PGC-1alpha and GFP infected control cells. Once they get 3 times lower IL-6 levels than GFP infected cells. Within the same study they obtain for the same measurement 3 absolutely different results. And although they are diametrically opposed, showing that the data are absolutely not reproducible, they should be reproducible according to the highly significant p-values.

-Similar differences are observed for other genes. E.g. TNFalpha levels in Figure 1A (PGC-1alpha compared to GFP, controls) are not different. In Figure 3 A, there is suddenly a significant reduction of p<0.05 within the same experimental context. Or Mip-1 levels in Figure 1A are not different between PGC-1alpha compared to GFP, controls, but are suddenly highly significantly reduced (p<0.01) in Figure 3 A. More such examples can be found.

Some western blots seem to have been pasted together. But how can quantification be performed from different blots?

-In Figure 6 there are substantial problems with the western blots: It is claimed that the density of protein blots has been measured. But the blots of tubulin, to which everything has been normalized seem to be completely saturated. No densitometry is possible.
That holds also true for other quantified blots. E.g. p65.

-Independent of that basic quantification problem there are further inconsistencies. In Figure 6 B it's shown that GFP infected cells treated with TNF have about 3 times higher Pp65 than GFP control cells. The difference is highly significant with p<0.01. If we look at the blots then we see the following: Tubulin (although saturated) is at least 2 times more in GFP TNF than GFP control. The Pp65 levels of GFP TNF compared to GFP control are not so denser. If it has really been normalized to that it is impossible that a 3 fold induction came it. If the example shown in the blot was an outlier and not representable, then it is statistically impossible that with 3 independent experiments such p value came out!

-A similar issue if you compare in Figure 6 A PGC-1alpha with TNF to PGC-1beta with TNF. In the quantification there is no difference. In the blots shown in Figure 6 A there is a huge difference.

-The quantification of p65 seems also to be incorrect. If GFP control and GFP TNF shown in the blots (around 2 times different) are really normalized to the corresponding p65 shown (around 2 times different) then there is no difference and the quantification of these blots can not lead to the significant result shown in Figure 6 B.

-Figure 7 A, 2 publications have already demonstrated that PGC-1alpha strongly induced Akt, which is the complete opposite of what In Figure is shown here

-In Figure 7 B in the p65 control blots there are always higher levels of p65 at 5 mins. If Pp65 at 5 mins is normalized to that, then there is no increase in phosphorylation. The results shown in Figure 7 C do not at all fit to the blots shown in Figure 7 B. How is it is impossible that they could find 4 fold increases with that blots?

-In Figure 7 C they claim that at 120 mins TNF induced a more than two fold increase in Pp65 in GFP infected cells, but in Figure 7 D under the exactly same conditions that cannot be seen, although the statistical signifigance was <0.01 before.

Personally, I have enormous doubt on that study. I guess it will be a subject of retraction. At the moment the study of Olesen et al is much more robust and trustworthy.