Harvard stem cell researcher Doug Melton got a lot of press last year for research on a hormone he named betatrophin, after its supposed ability to increase production of beta cells, which regulate insulin.
Now, the conclusions from that paper, which has been cited 59 times, according to Thomson Scientific’s Web of Knowledge, have been called into question by research from an independent group, as well as follow-up work from the original team.
The interest was driven by the hormone’s potential as a new treatment for diabetes. In 2013, Melton told the Harvard Gazette that betatrophin could be in clinical trials within three to five years. Here’s Kerry Grens in The Scientist:
A study published in Cell last year offered evidence that a hormone called betatrophin, or Angiopoietin-like protein 8 (ANGPTL8), could ramp up pancreatic β cell proliferation in a mouse model of insulin resistance. The results made quite a splash; the study’s authors—led by Doug Melton at Harvard University—even wrote that betatrophin treatment “could augment or replace insulin injections by increasing the number of endogenous insulin-producing cells in diabetics.”
However, a new paper in Cell from researchers at Regeneron Pharmaceuticals and elsewhere has found that betatrophin has no effect on beta cell growth. From a blog post by Paul Knoepfler, a UC Davis stem cell biologist:
…the authors report that Betatrophin, which now should probably go by the more objective name ANGPTL8, does not substantially impact beta cell growth, but rather seems to have a notable role in mouse triglyceride metabolism. ANGPTL8 is probably a very interesting molecule, but it is not what it seemed to be.
It’s now unclear what the fate of the 2013 Betatrophin paper will be moving forward given that its central argument is incorrect and even the naming of the molecule “Betatrophin” is indeed perhaps not appropriate any more.
Melton and his team wrote a Perspectives article, also in Cell, including some of their own research:
Our own follow-up experiments using an independent knockout of ANGPTL8 produced the same result. Taken together, these new data contradict our previous conclusion ( Yi et al., 2013) that betatrophin is the sole agent responsible for beta cell proliferation following S961 treatment. Furthermore, these new results cast doubt on the finding that beta cell proliferation can be induced by overexpression of ANGPTL8/betatrophin.
We spoke with Melton for more details:
We reported in the first Cell paper that an insulin antagonist called S961 results in robust beta cell replication. And then we attributed that activity to a member of the angiopoietin-like protein family which we named betatrophin. We showed in that paper that when we injected betatrophin via tail vein injection, it increased beta cell replication and beta cell mass by a significant amount.
This implied that betatrophin would be responsible for the S961 activity. Then the recent paper by Gusarova did an experiment, which we agree with and confirmed, that a knock-out of betatrophin does not prevent the amplification or replication of beta cells by the insulin antagonist.
There are two possibilities: one is that betatrophin doesn’t have that activity. The other is that when you knockout one member of the family, there’s compensation by the others.
If you look at [the new research] you see considerable variation in both beta cell replication and beta cell mass…we said, that’s an unsatisfactory variation. If I had to do those experiments again, I would not use tail vein injection as a method to provide the protein. So now you have a highly variable result, and you ask the question, should you believe those cases where there’s significant replication, or would you say the whole thing is an artifact of how you presented the protein?
That’s how science progresses sometimes. You make a claim, based on evidence. You then reinterpret it, you do more experiements, and you’re wiser for it in the end.
When they got word of the Regeneron paper, Melton’s team was already in the process of writing an article with the new data that they later used in their Perspective:
We were just in the process of submitting a paper showing that the betatrophin knockout was inconsistent with our original proposal…when I was then asked to review the Gusarova paper, I said, it’s a really good paper, they’ve beat us to the punch, and I think it should be published. It shows things aren’t as simple and straightforward as we thought they were in 2013. I may be old fashioned, but I think that’s the point of making things public.
The Perspectives article has gotten some very critical comments on PubPeer in the last few days. One of them was regarding this figure from the Perspectives paper:
In this Correspondence, Melton and colleagues continue to claim that ANGPTL8 induced beta-cell replication, just at a lower level than they first claimed. To reach that conclusion, they combine the results from 7 mice presented in their initial publication (http://www.ncbi.nlm.nih.gov/pubmed/23623304 ), with data from 38 additional mice presented in the Correspondence. They claim that when examining the results from their initial publication, the data in the Correspondence, and data from a group at Regeneron that found no effect of ANGPTL8 on beta-cell replication (http://www.cell.com/cell/abstract/S0092-8674(14)01176-3 ), there is still a modest effect of ANGPTL8 on beta-cell replication. However, the group from Regeneron found no effect, not a small effect.…In their original publication, Melton and colleagues plotted the effect of ANGPTL8 on a bar graph, preventing the reader from determining the degree of variability within the group of mice treated with ANGPTL8. In the Correspondence, the original data and the new data are shown as dot plots, with each mouse representing a single data point (Figure 1A, B). The data from the initial publication are shown in Figure 1B, revealing that only 3 out of 7 mice demonstrated a meaningful effect of ANGPTL8 on beta-cell replication. The effect appears to be bimodal, with the remaining 4 mice being very low. Because of the bimodality, it was never proper to plot the data on a bar graph, as if there was a single population…In fact, the only significant variability arises from the 3 mice with extremely high levels of beta-cell replication in the original publication in Cell.It is important to note that Melton and colleagues plotted their new data and the old data using different Y axis scales. In panel A, the maximum value is 5%, while in panel B, the maximum value is 10%. This creates a visual impression that the data in panels A and B are fairly comparable in the extent to which beta-cell replication was stimulated by ANGPTL8. However, if the data from A and B were plotted on the same Y axis, it would be apparent that the three animals with high levels of Ki67 in panel B would be considerably higher than any of the animals done as part of the newly presented experiments. Thus, a misleading impression has been created that the data from the original paper are consistent with what was found in the new experiments, except for the “jackpot effect” in the first experiment, with three mice being at the top of the distribution.
I stand by the commentary we wrote for Cell. I have read these comments on PubPeer. I haven’t read them before, but I must say I find them unprofessional, bordering on ad hominem. They don’t really seemed to be aimed at trying to solve the puzzle, so I’m not encouraged by trying to engage with those annonymous people and answer their questions.
The first comment had one interesting point, but unfortunately that poor person did not read the commentary carefully and has completely misunderstood the statistical argument.
It’s a complicated and evolving science. There are new papers coming out that I think are going to be very interesting to the community, so I’ve decided it’s not really helpful to talk to people who write comments like that, so I won’t be providing any rejoinder.
In an earlier conversation, Melton didn’t have an explanation for why they presented the data this way visually, but he did tell us why he chose not to retract the paper:
For me, retraction is when you’ve done something wrong, or the data has been fraudulently produced, or something like that. That’s not the case here. This is more an example of how science progresses. If you were going to say, everything that’s ever been published which has been reinterpreted should be retracted, it would be well near half of all publications, wouldn’t it.
Here’s one more PubPeer comment on the case:
It was nice of Cell to allow the authors to “retract” their paper by adding another Cell item to their CVs under a neutral heading like “Perspectives”.
We’ve reached out to a number of betatrophin researchers. Many have expressed concerns about the original research, but none will go on the record about it. Several have cited Melton’s influential position as the reason they were declining to comment. He’s certainly a major figure in the field – his research group also got a lot of press for a Cell article earlier this month that might herald a “cure” for diabetes, involving production of beta cells using human embryonic stem cells. We asked Melton about this problem:
People should say whatever they want in analyzing the data. It’s not a matter of commenting on a person, it’s really, what does the data tell us?…Evidence is hardly ever so incontrovertible that you know something with absolute certainty. So you do more and more experiments to build a case for the conclusion you think best supports all the evidence. I don’t think there is a strong conclusion about betatrophin…but I kind of like that about science, because it makes lots of experiments you can design to go about and test it.
So what are the next steps for betatrophin research? Melton again:
If you asked me, what am I most worried about, it’s actually not the mouse work. It’s a paper we didn’t even comment on here, which is the paper by Jiao saying that when they transplant human beta cells into this mouse model, there’s no beta cell replication, even in the presence of this insulin antagonist. And that’s what gives me pause. because if it turns out you can replication mouse beta cells, but not human ones, then I would say it’s sort of interesting to figure out what the mouse is doing, but it’s way down on the priorities for me to try and get to the bottom of.