It’s well-known that obesity can cause or exacerbate osteoarthritis (OA) through excessive mechanical loading. But another mechanism through which obesity can affect joint health is via inflammation and we now know that our gut microbes play a crucial role.
Recent research by Schott et al. has looked into the link between obesity, gut microbes and OA. They found a difference between the types of gut bacteria in obese mice compared to lean mice. The obese mice had more pro-inflammatory and fewer anti-inflammatory species than lean mice. The imbalance led to accelerated knee OA due to systemic inflammation and macrophage migration to the synovium. Interestingly, they found that oligofructose, a non-digestible prebiotic fibre, can help restore a normal lean gut microbiota in obese mice. The restoration of lean gut microbes was “associated with reduced inflammation in the colon, circulation and knee and protection from OA”.
Obviously one could wonder whether these findings apply to humans. About a year ago Dai et al. published the results of long-term studies on around 6000 people. Their findings consistently showed that higher total fibre intake was related to a lower risk of getting symptoms of knee OA!
It’s been known for a while that smoking decreases blood flow and hence reduces the transport of oxygen and other nutrients to tissues. But recent research by Ava Hosseinzadeh et al from the University of Umea in Sweden has looked into its effects on inflammation. Their findings were published in the Journal of Leucocyte Biology. They found that nicotine induces neutrophils to release neutrophil extracellular traps (NETs). NETs surround and destroy microbial pathogens but they can also lead to excessive inflammation and tissue damage. Obviously, it’s the excessive inflammation and tissue damage that’s of concern and it provides yet another reason to stop smoking.
Vilma Aho et al from the University of Helsinki conducted 2 studies looking into the effects of sleep deprivation. The first study was experimental and consisted of partial sleep restriction to a small group of subjects. The second was an epidemiological study with over 2700 individuals. Blood samples were analysed in both cases.
The analyses revealed decreased circulating High Density Lipoproteins (HDL cholesterol), otherwise known as ‘good cholesterol’, and elevated inflammatory markers. Sleep loss decreased the expression of genes encoding cholesterol transporters and increased expression in pathways involved in inflammatory responses. The findings help to explain why sleep deprivation is a risk factor for cardiometabolic disease.
Poor sleep has been linked to increased inflammation. Inflammation is known to cause or exacerbate musculoskeletal disorders as well as more serious diseases such as heart disease, stroke and cancer. Irwin and his colleagues conducted a randomised controlled trial looking into the effects of cognitive behavioural therapy (CBT) and Tai Chi on the inflammatory markers of subjects with insomnia. The participants were offered 2 hour weekly sessions for 4 months.
CBT was found to reduce systemic inflammation whereas Tai Chi reduced cellular inflammatory responses. Both interventions reduced the expression of genes encoding proinflammatory mediators.
Steven Cole et al. from UCLA have recently shown that having a deep sense of purpose and meaning in life can lead to positive genetic changes such as lowering the levels of inflammatory gene expression and strengthening the expression of antiviral and antibody genes. Theoretically, this could mean that those with a strong sense of purpose and meaning have a more efficient immune system and are less susceptible to inflammatory diseases.
Parallels can be drawn with Viktor Frankl’s influential book ‘Man’s Search For Meaning‘. In it, he relates his experiences of life in concentration camps during WWII. He believed that finding a meaning to life was crucial to survival in those terrible circumstances. After the war, he continued his work as a psychiatrist with logotherapy (a form of existential analysis) and became convinced that happiness was to be attained by finding meaning and purpose in life.
A new study by Zoccola and colleagues found that people that were asked to dwell on a stressful event had higher levels of C-reactive protein (CRP). CRP is produced in the liver and its blood levels rise in response to inflammation e.g. infections, injuries, rheumatic or other inflammatory diseases, etc. Patients with high CRP concentrations are more likely to develop stroke, myocardial infarction and severe peripheral vascular disease.
The fact that rumination increases inflammation means that dwelling on negative thoughts has an adverse impact on pain and recovery from soft tissue injuries. Yet another brilliant example of the mind-body connection at work!
Our diets have changed considerably over time. Today, diets in industrialised countries have a higher composition of saturated fat, trans fatty acids, omega-6 polyunsaturated fatty acids (PUFA) and a lower composition of omega-3 PUFA than ancestral diets. The ratio of omega-6 to omega-3 is around 15:1 and it’s thought that an optimum ratio should be about 1-4:1.
What’s the significance of this? Well, omega-6 PUFA and omega-3 PUFA have opposing effects on our bodies. Put simply, omega-6 PUFA are pro-inflammatory whereas omega-3 PUFA are anti-inflammatory. Omega-3 PUFA inhibit the metabolism of omega-6 PUFA into inflammatory cells. Inflammation is characterised by the cardinal signs: pain, redness, swelling, heat and loss of function. Although it’s a normal response to infection and injury…inappropriate inflammation can cause problems! Scientists have noticed that the change in our diets has coincided with an increase in inflammatory disease such as nonalcoholic fatty liver disease, cardiovascular disease, inflammatory bowel disease, rheumatoid arthritis, Alzheimer’s disease, etc.
Clinical studies have reported beneficial effects of increased omega-3 PUFA consumption in people with rheumatoid arthritis, inflammatory bowel disease and asthma. Less pain, fewer tender joints, a shorter duration of morning stiffness, a decreased use of non-steroidal anti-inflammatory drugs and an improved physical performance has been observed in people with rheumatoid arthritis. It has also been suggested that omega-3 supplements may be beneficial to patients in intensive care or post surgery. The grandmother’s remedy of taking cod-liver oil for arthritis now seems to make sense!
I would recommend eating foods rich in omega-3 PUFA or taking supplements for any musculoskeletal condition with inflammation and pain. What foods are rich in omega-3? Make sure to check in next week for the answer…