Type 2 diabetes can be a 'devastating diagnosis' says expert
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Both type 2 diabetes and osteoarthritis are common medical conditions, with type 2 diabetes impacting 12 percent of over 25s (26 percent of those over 65) and osteoarthritis impacting 14 percent of over 25s (and 34 percent of over 65s). Both conditions become more common with advancing age, lead to serious disability, and have a large negative impact on quality of life. However, people with type 2 diabetes (T2DM) appear to be more likely to develop osteoarthritis (OA) than the general population. So why do so many people with T2DM suffer from OA? Is this a coincidence, or could there be a causative link? Express.co.uk chatted to Dr Deborah Lee from Dr Fox Online Pharmacy to find out.
The onset of osteoarthritis in people with type two diabetes happens gradually over a period of many years.
The link between the two doesn’t seem to be a coincidence.
There are many possible theories and explanations as to why people with type two diabetes may be more at risk of developing osteoarthritis.
Six of these include:
- The natural ageing process
- Being overweight or obese
- High blood pressure
- Raised cholesterol
- Chronic inflammation
- The pathological effects of hyperglycaemia (raised blood glucose levels)
Dr Lee explains how each of these factors can increase your risk of developing OA if you’ve got type two diabetes.
The natural ageing process
As we age, the natural ageing process increases the risk of diabetes because pancreatic beta-cell function declines with age.
Dr Lee explained: “Pancreatic beta cells are the cells in the pancreas that produce the hormone, insulin.
“Ageing also reduces the ability of chondrocytes – the cells in the joints which produce cartilage – to produce cartilage.
“As we live longer and become more obese, our joints, especially our knees, are exposed to higher amounts of wear and tear.
“Ageing also leads to a decline in mitochondrial function – mitochondria are the powerhouses that provide cellular energy – which also increases the risk of the development of both type 2 diabetes and osteoarthritis.”
Being overweight or obese
Bodyweight plays a crucial role in the development of both osteoarthritis and type two diabetes.
Dr Lee noted: “In obesity, the excess load bearing on the joints, such as the hips and knees, results in the degradation of cartilage.
“There is considerably increased stress on the muscles and ligaments in and around the joints, and sometimes a joint can even be pulled out of alignment.”
However, even non-weight bearing joints such as those in the fingers and hands, show osteoarthritic changes, meaning that some of the joint damage due to OA is caused by inflammatory mediators (cell signalling molecules), for example, interleukin-6 (IL-6), interleukin 1 (IL-1) and tumour necrosis factor-alpha (TNF-α).
The doctor added: “Adipocytes (fat cells) produce cell-signalling molecules called adipokines which mediate local joint inflammation.
“High levels of the appetite-suppressing hormone, leptin, have been found in osteoarthritic joints – but whether this has a causal effect on the development of OA, is not known.
“This may sound paradoxical, but people suffering from obesity often have high levels of leptin and suffer from leptin resistance.”
High blood pressure
High blood pressure is a recognised risk factor for OA, but the reasons for this association are unclear.
Dr Lee explained: “It has been suggested that high blood pressure can cause narrowing of blood vessels and that this may mean that the cartilage or bone surface is depleted of oxygen.
“This might stimulate the development of the osteoarthritic process.”
Raised cholesterol
A link between raised cholesterol and osteoarthritis has also been noted.
Dr Lee said: “However, again, the reasons for the association are uncertain.
“Chondrocytes in patients with raised cholesterol levels contain more lipid droplets.
“Excessive intake of polyunsaturated fats has also been linked to the development of osteoarthritis.”
Chronic inflammation
The main underlying cause of osteoarthritis is likely to be due to high levels of chronic systemic inflammation (CSI).
Dr Lee said: “This is a harmful metabolic condition in which the inflammatory process is ‘switched on’ by a variety of triggers – these include local tissue damage, high blood pressure, obesity, and raised blood glucose levels.
“A poor diet, for example, lacking in fruit and vegetables, which contain large quantities of antioxidants, is another major contributory factor.”
The pathological effects of hyperglycaemia (raised blood glucose)
High blood sugars – hyperglycaemia – may themselves be responsible for joint damage in osteoarthritis.
Dr Lee explained: “In one research study in a laboratory setting, chondrocytes taken from the joints of OA sufferers, when placed in a hyperglycaemic environment, were unable to lower levels of blood glucose, as compared to chondrocytes exposed to normal blood glucose levels.
“In addition, greater numbers of reactive oxygen species (ROS) (dangerous, electrically charged molecules), were found in those with OA, than in healthy controls. OA sufferers were also found to have greater numbers of metalloproteinase enzymes – which are known to degrade cartilage.
“Overall, it may be that high blood glucose levels have a harmful effect on articular cartilage.”
OA sufferers have also been found to have higher levels of advanced glycation end products (AEGs) in their articular cartilage, Dr Lee said.
The doctor added: “AEGs are proteins that have become stuck to fat or sugar molecules.
“The accumulation of AEGs in joints has been reported as part of the ageing process and seems to be associated with an increase in the stiffness and breakdown of articular cartilage.
“High glucose levels that occur in diabetes stimulate the production of AEGs.
“AEGs may also play a role in the pathogenesis of diabetic neuropathy – a condition that commonly affects diabetics, meaning they lose awareness of the position and/or sensation of their distal joints and extremities.
“Once diabetic neuropathy is present, sufferers lose their normal cues from any excessive mechanical workload on the joint, and this makes them more susceptible to further joint damage.”
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