Sunday, March 3, 2013

Inflammation

“Inflammation is one of those words that people use without really thinking about its actual meaning” 
-          Mark Sisson 

Which is the whole point of the next two posts. 

The Role of Inflammation in Chronic Disease 

Inflammation is a major cause of chronic diseases such as obesity, osteoporosis, autoimmune diseases, depression, cancer and cardiovascular disease. 

  • Several pro-inflammatory cytokines increase SOCS3 and TNF-α increases PTP1B.  SOCS3 and PTP1B and increase leptin resistance, therefore obesity [1].
  • Several pro-inflammatory cytokines increase osteoclast synthesis and activity and induce osteoblast apoptosis, leading to a higher rate of bone resorption and a lower rate of bone formation, which contributes towards osteoporosis [2].
  • Some pro-inflammatory cytokines are required for Th17 cell development and IL-17 production, which can lead to an elevated Th17:Treg cell (and IL-17:IL10) ratio, which is an immune profile that promotes autoimmune disease [3]
  • Elevated levels of pro-inflammatory cytokines inhibit neurogenesis and initiate apoptosis, which contributes to the hippocampal atrophy seen in depression [4]
  • Pro-inflammatory cytokines promote angiogenesis, growth and proliferation of tumour cells and inhibit apoptosis of tumour cells and NFκB also promotes tumour survival, metastasis and inhibits the adaptive immune system, which promotes cancer [5] 
  • Pro-inflammatory cytokines promote monocyte adhesion to endothelial cells, endothelial dysfunction, oxidative stress and apoptosis of endothelial cells, all of which lead to the development of atherosclerosis and CVD [6]. 

Acute vs. Chronic Inflammation 

But inflammation can also be a good thing: 

  • Inflammation is a response by the innate immune system to pathogens, damaged cells or irritants
  • Inflammation initiates the healing response
  • Inflammation is necessary to get the physiological adaptations from exercise 

The inflammation from bruises, cuts, burns, exercise, etc, is acute inflammation, which only lasts a short time and is a normal and adaptive physiological response.  The inflammation from something like metabolic endotoxemia and autoimmune diseases, etc, is chronic inflammation, which generally lasts a long time (until the cause is resolved) and may not necessarily be adaptive.  It’s the chronic inflammation* that promotes disease** and should concern us. 

* When I say ‘inflammation’ that’s usually just shorthand for ‘chronic inflammation’.  It would be silly to suggest exercise or a few bruises promote chronic disease. 

** While acute inflammation can be a trigger for chronic disease, it’s likely that this will only the case for people who don’t resolve inflammation well, which could be due to them having low Treg cells/IL-10 or glucocorticoid resistance, etc. 

If you want to read about the basics of inflammation see What is Inflammation? and What’s All This Talk About Inflammation?.  Mark Sisson explains it well and there’s no need for me to repeat what he says.  You can also read the Wikipedia article on inflammation 

Rather than finish up with ‘chronic inflammation is bad’, the next post will be a list of some causes of chronic inflammation and what to do about it.

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