Well this is no good-scientists have found an interesting connection between fat cells and cancerous tumours, at least in mice that is.
"In obese and lean mice that ate the same diet, tumors grew much faster
in obese mice than they did in lean mice. The researchers also observed
that there were far more white adipose tissue cells (called adipose
stromal cells) in obese mice than in lean mice and thus turned their
focus on the role of these cells.
Detailed analyses indicated
cancer induced mobilization of adipose stromal cells into the
circulation. Once in the tumors, some of these cells developed into fat
cells, while others were incorporated into tumor-associated blood
vessels.
Tumor-associated blood vessels support tumor growth by bringing in
oxygen and nutrients vital for cancer cell survival and proliferation.
Kolonin noted that the ability of adipose stromal cells to contribute to
the formation of tumor-associated blood vessels is likely one of the
main reasons that the excess of these cells in tumors was associated
with increased malignant cell proliferation and tumor growth."
It looks like fat cells are being taken by tumours and used to promote growth. I don't know how they do this, I'm not a doctor, but that sounds bad to me. Anything that helps cancer growth is bad, right? When I went to the online home of the research journal and looked for the abstract, I couldn't figure out which one I wanted. Can someone help me out with this? Someone with a background in health or biology? I'd like to learn more.
I do not have my degree yet, but I have studied biology and some biochemistry and that is my intended major.
What they are basically saying that that tumors need nutrition to survive. Fat is energy dense and is stored in our bodies so we can live off of it if need be. Unfortunately, that seems to promote cancer growth, but on the other hand, it is those same reserves that keep us alive when chemo is keeping us from eating, etc. There are two sides to this coin.
I would not worry too much about this study, or any other study about cancer in rodents because mice and rats are extremely vulnerable to cancer and tumors. In fact, female rats will almost always develop tumors by 18 months old if they are not spayed. This is why is why they are used so extensively in cancer research.
Keep in mind that mice and rats are small, fragile animals with shorter lifespans to begin with and that any disease progression will be very accelerated in such animals, more so than in humans.
Not having an abstract, and not being as well educated or trained as these researchers are, I could be wrong, but there you go. My two cents.:)
Well, I am finishing up a PhD in biochemistry looking at stem cell recruitment and survival in a slightly different model (ionizing radiation combined with injury). I skimmed this article, "White adipose tissue cells are recruited by experimental tumors..." Out of the UT Health Science Center and MD Anderson. I am currently doing my research in the UT system as well, and the research in general out of MD Anderson is quite good, and Paul Simmons is known for his work with progenitor (stem) cells.
In summary, the article is slated towards obesity mainly because it is sexy and gets funding right now. Especially in the cancer fields where it is extraordinarily difficult to get grants funded. However, what they are looking at is just stem cell recruitment into the tumor, which is known to come from bone marrow as well. So skinny people have bone marrow with stem cells, fat people do as well, and it seems that obese people with more white adipose have an additional repository of stem cells. The authors state that this needs to be shown in humans. The experiment I was really looking for was where they compared bone marrow stromal cell recruitment to the adipose recruitment. The graph shows one point of significance at 5 weeks that doesn't remain significant at 6 weeks, so not too convincing. They are definitely showing recruitment of the adipose stem cells to the tumor in this study, but no real difference between bone marrow or adipose derived stem cells.
Also these are not obese mouse models. It would be interesting to see if the same happens in obese mouse models that have comorbidities like type II diabetes, etc. They mention briefly in the article the metabolic syndrome. In humans it is known that in people with this syndrome (central obesity, raised triglycerides, elevated blood pressure, raised fasting glucose) that as it progresses there is impairment of stem cell recruitment. Especially in diabetics and those with peripheral vascular disease they have problems healing due in part to poor stem cell recruitment. So to be taken with a grain of salt in mice that do not have metabolic comorbidities. Also mice are known to be a rather poor model of human cancer; unfortunately, they are the best model we really have.
I think there is nothing to raise an alarmist flag about at this point. Especially unless the added reserves of stem cells somehow made the patient less sensitive to radiation or chemotherapy used to kill the tumor. In such a case added weight may actually serve to help the patient withstand the harsh treatments to kill the cancer.
Again I am not in the cancer field so I unfortunately don't know whether or not obese patients have worse outcomes than non obese. In other words do they present with more advanced stages of cancer, harder to treat forms of cancer, have higher mortality? As with most research it raises more questions than it answers, but the study definitely does not show that fat=cancer=death.
Also an interesting note, when fat people that have heart attacks and various other things, they are known to have better outcomes than skinny patients. Maybe due to the extra repository of stem cells? Stem cell therapies are currently being tested in heart attack and other models to reduce death of tissue and promote some limited healing, so having more stem cells would be good in these instances. Everything is pretty much a trade-off with cancer. If we all lived long enough we would all end up with cancer, it is simply a metabolic byproduct of life.
Thanks so much, Joanna! I appreciate your insight. That's the obesity paradox in a nutshell, isn't it? In some ways being obese does seem to have negative AND positive affects on health, at the same time.
Wow, thanks for all that, Kim! Yeah, I know not to put too much stock in mouse studies, but its' all we have because there are some pretty strong feelings about testing on humans. :P I appreciate you taking the time to comment and stop by.
I believe this is the full article - http://cancerres.aacrjournals.org/content/72/20/5198.full?sid=13da1d75-1eae-42d4-8565-291d427cb578
I haven't read the whole thing, but I've got to give the researchers credit for at least proposing an actual mechanism and then testing it, rather than merely relying on correlations drawn from epidemiological surveys.
There are always risks and benefits to everything, and being fat is no different. The question is, are those risks changeable? What can we do about them while still preserving quality of life?
Thanks for finding the original, Michelle!
With the caveat that I am not a professional scientist....
It looks like they took mice and fed them different diets to get some of them to gain fat, then switched them all to the same diet so that they could look at the effect of body fat separately from the effect of the diet the mice were on while the cancer was developing. (Switching the fat mice to the skinny mice's diet caused them to lose some weight, but they hadn't lost much by the time they were given tumors.) The fat mice's tumors grew faster than the lean mice's tumors. Note that they're only talking about how fast tumors grew in mice that already had cancer (because the researchers grafted the cancer into them), NOT the initial development of cancer. The researchers noted that the fat mice's tumors had more blood vessels and better blood supply than the lean mice's. They also found that more stem cells from fat were circulating in fat mice than lean mice. These stem cells sometimes develop into fat cells and sometimes develop into cells supporting blood vessels. (As Kim said, cells from the bone marrow develop into blood vessel cells.) At first I thought that the fat stem cells were developing into blood vessels, but it looks like they're saying that when they reach the tumor, the fat stem cells can develop into either fat cells or some type of cell that helps support blood vessels. The blood vessels supply the tumor with more blood and thus more nutrients, and allow it to grow faster.
As Joanna and Michelle said, there are both benefits and risks to being fat. Since this study shows that tumors grow faster in fat mice, if it applies to humans it may be an indication that catching a tumor early is more important in fat people than thin people, or that the window for catching it is smaller.