Slanted Science

Scientists report that a swollen ankle will make you less happy than you were before. Sounds like one for the “Favoured sites of defecation in animals of the genus Ursus“ file.

No, no, no. We’re being facetious. It’s a serious paper, it’s in the Journal of Immunology, and it highlights important research pertaining to the effects of chronic inflammation on people’s general happiness. So great news for those suffering from such horrible diseases as arthritis.

Or a stubbed toe.

Sorry, we just can’t help ourselves. Seriously, this is good stuff. Kelley and pals used a mouse model of chronic inflammation – the little furballs receive an injection of the BCG vaccine – to show that, in this system, inflammation was accompanied by increasing amounts of a particular enzyme in the brain.

The enzyme, indoleamine 2,3 dioxygenase (IDO), breaks down tryptophan, an essential amino acid (‘essential’ meaning your body cannot make it itself, but relies on a constant dietary supply). One of its metabolites is the famous 5-HT (5-hydroxytryptophan, or serotonin), now well-established as one of the brain’s key proteins in mood balance.

So, this is the pattern they predict: chronic inflammation in the body–>increased IDO in the brain–>increased breakdown of serotonin–>decreased levels of serotonin–>decreased happiness.

Of huge interest to us all is their further finding that blocking the activity of the induced IDO enzyme, with a drug, cured the depressive symptoms without affecting the immune response. If you’re thinking it would be better if it also interfered with the inflammation, then please don’t forget that this immune response is not always bad (rheumatoid arthritis), but is mostly extremely useful (fighting off bacteria around a small skin wound).

So, the upshot is this: we have data suggesting that chronic inflammation (as often present in the obese, those undergoing cancer treatments, and those with rheumatoid arthritis, amongst many others) leads to a pharmacologically reversible lowering of mood (depression).

As a side note, we once convinced ourselves that a two inch increase in trouser size in one month was due to inflammation. And not the fortnight spent in Italy, eating nothing but pasta, cheese, and sausage. Our treatment schedule did nothing for weight loss, but spiked the price of Ibuprofen by 30%.

Don’t Hold Your Breath, But This May Lead To: patients with inflammatory conditions and associated depression being given a pill which eases the depression without interfering with the treatments for inflammation.

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