Know your fat!

A lot of people might think that their fat is just sitting there, keeping them fat. And I’m not saying they’re wrong, but fat (also known as adipose tissue) is far from a one-trick pony. So with the barrage of products out there telling us to “burn,” “shrink,” and “eliminate” fat, isn’t is only fair that we take stock of what fat’s doing in our bodies in the first place?

You may not exactly like the things you learn about fat in today’s post, but fat seems to be society’s public enemy number one lately, and you know what they say — it’s always best to know your enemy.

Here’s a fat cell:

It’s relatively huge as far as cells go. With a diameter of about a tenth of a millimeter, it’s over 100 times the size of a skin cell, and just one fat cell is potentially visible by the naked eye. As you can see, most of a fat cell is a huge pool of fat, with all of the other parts of the cell squished off to the side. If you’re the average adult, you’ve got about 30 billion of these guys. All the more reason to know what they’re capable of, right?

1. Fat cells can pilfer your medications and vitamins. At the most basic level, when you take medicine or vitamins, your body uses what you need and the byproducts or whatever your body doesn’t use are excreted. However, many vitamins (like A, D, E, and K) and medications (including many antidepressants and anesthetics) are fat-soluble, as opposed to water-soluble, meaning that as they circulate your body they can slip out of your blood and into your fat. THC, the active compound in marijuana, is an example of a fat-soluble drug; if an obese person with large amounts of body fat gets high with a skinny person with low levels of body fat, it is likely that the obese person would test positive for a longer stretch of time, because the obese person has more fat cells to trap the THC and release its metabolites more slowly over time.

Sneaky fat cells…

2. Fat cells influence how hungry you are and whether or not you get diabetes and heart disease. As it turns out, fat cells don’t just take stuff out of your blood, they put stuff in it, too. In particular, fat cells make a whole bunch of hormones and inflammatory molecules. One of the most important molecules made by fat is leptin, which signals to the brain and decreases appetite. Mice without receptors for leptin become obese:

Fat tissue also releases inflammatory molecules called cytokines that can decrease the ability of the body to respond to insulin, which can set the stage for diabetes. Some of these inflammatory molecules are also thought to promote systemic inflammation, and research suggests that this can make atherosclerosis (artery blockage due to fat accumulation) all the more dangerous. That’s because inflammatory cells might be able to rupture atherosclerotic buildup, creating clots that induce heart attacks or strokes.

This is a lot of information to take in, and the many roles of fat as a signaling tissue make up a very active area of research right now, especially because fat can often turn on or off production of specific molecules in obese individuals.

3. Fat cells can feed cancer cells. If you weren’t hating fat by now, this might just tip the scales. Very recent research in Nature Medicine suggests that abdominal cancers, like ovarian cancer, are made worse by fat. Ovarian cancers tend to metastasize to fat-dense regions of the abdomen, and fat cells can directly transfer fat to cancer cells, which provides the cancer with energy and allows it to grow in size.The silver lining of these findings is that researchers may now have a new mechanism to target when designing drugs to fight cancers that flourish in fatty areas of the body.

4. Fat cells might be the cure to just about everything. Alright, last but not least, a major redeeming feature of fat: it’s got stem cells in it. In general, stem cells are cells that have the potential to differentiate into multiple other cell types. Scientists have theorized stem cells to be a potential therapy for just about every disease condition (e.g. using stem cell-derived neurons to replace the lost/damaged neurons in neurodegenerative diseases). Although fat stem cells can’t turn into as many cell types as embryonic stem cells can, they have many upsides: fat stem cells circumvent ethical concerns, are readily available thanks to all of the fat-removing surgeries done today, and pose far less risk of immune rejection when re-introducing cells taken from someone’s own fat. Fat stem cells have already been shown to essentially cure a mouse model of lupus.

So maybe you’re not necessarily any happier about your fat now, but I hope you have a new appreciation for it. While you lament your muffin top, you can consider the diverse biology of your muffin top. That might sound nerdy, but…well, that’s the whole point.

Ovchinnikova O, Robertson AK, Wågsäter D, Folco EJ, Hyry M, Myllyharju J, Eriksson P, Libby P, & Hansson GK (2009). T-cell activation leads to reduced collagen maturation in atherosclerotic plaques of Apoe(-/-) mice. The American journal of pathology, 174 (2), 693-700 PMID: 19131590

Nieman KM, Kenny HA, Penicka CV, Ladanyi A, Buell-Gutbrod R, Zillhardt MR, Romero IL, Carey MS, Mills GB, Hotamisligil GS, Yamada SD, Peter ME, Gwin K, & Lengyel E (2011). Adipocytes promote ovarian cancer metastasis and provide energy for rapid tumor growth. Nature medicine, 17 (11), 1498-503 PMID: 22037646

Choi EW, Shin IS, Park SY, Park JH, Kim JS, Yoon EJ, Kang SK, Ra JC, & Hong SH (2011). Reversal of serological, immunological and histological dysfunction in systemic lupus erythematosus mice by long-term serial adipose tissue-derived mesenchymal stem cell transplantation. Arthritis and rheumatism PMID: 21904997