Diabetes is a disease related to the body’s inability to effectively regulate glycaemia (blood sugar levels), ultimately leading to chronic hyperglycemia. Diabetes is undoubtedly one of the most common non-communicable diseases in the world today. It is estimated to affect over 500 million people (more accurately 537 million), making it the number one non-communicable disease pandemic. Did you know that diabetes is much more common in older people? That it can itself be an aggravating risk factor for certain diseases? Indeed, in France, it is considered that nearly a quarter of people suffering from diabetes are over 75 years of age and that the disease can lead to or worsen sarcopenia, a geriatric syndrome characterized by a reduction in muscular capacity and a deterioration in physical performance. But what is the relationship between diabetes mellitus and sarcopenia? Let’s take a closer look.
What is sarcopenia?
While it is perfectly normal to suffer from muscle loss with age (it is estimated that humans lose between 3 and 8% of their muscle mass every 10 years from the age of 30), the accelerated loss of muscle mass is not. This specific phenomenon is called sarcopenia.
This is a geriatric syndrome that most often affects people over 60 years of age. This syndrome is characterized by a decrease in the patient’s muscular capacities, resulting in a deterioration in muscular strength and physical performance.
Like diabetes, sarcopenia has both endogenous and exogenous causes. Indeed, it is attributable to the normal ageing of an organism, but can also be accelerated by certain behavioral factors, such as poor diet, reduced physical activity or a sedentary lifestyle.
What are the links between diabetes and sarcopenia?
The link between diabetes mellitus and sarcopenia has long been established by various scientific studies in the United States and Europe.
For example, in several studies, individuals with type 2 diabetes have been shown to have significantly lower muscle mass than those without diabetes.
Similarly, it has been shown that diabetes has an incremental influence relative to age on the reduction of muscle strength. Various studies have shown that people aged 70-79 years with diabetes have less leg strength than people of the same age without diabetes.
These various links between sarcopenia and diabetes mellitus have led some researchers to suggest that sarcopenia – induced by the development of diabetes – is undoubtedly one of the main explanations for the loss and reduction of functional muscle capacity and mobility often seen in elderly patients with type 2 diabetes.
How does diabetes contribute to sarcopenia?
Although diabetes has been shown to accelerate the process by which muscles lose mass, the causal mechanisms are not yet fully understood. However, several mechanisms appear to explain how diabetes influences and worsens sarcopenia.
Firstly, it seems that the main feature of type 2 diabetes, insulin resistance, is also the main cause of sarcopenia. Indeed, one of the main roles of insulin is to influence the transport of nutrients (including glucose) in the blood to the body’s muscle tissue and to stimulate protein synthesis. Under normal circumstances, insulin fulfils its role and enables the body – and in particular the muscles – to synthesize new proteins. However, in patients with type 2 diabetes, the function of insulin is impaired, and it cannot effectively deliver glucose to the muscle tissue. As a result, the muscle cannot synthesize new proteins quickly enough to compensate for the natural breakdown of muscle tissue.
Furthermore, muscle loss in diabetes is also caused by mitochondrial dysfunction. As a matter of fact, patients with diabetes mellitus often suffer from a decrease in mitochondrial function, which then contributes to the decrease in muscle function. As a reminder, mitochondria are structures that convert energy from food into a form that cells can use.
Peripheral neuropathy could also be the cause of sarcopenia. As a matter of fact, just under half of all people with diabetes mellitus suffer from peripheral neuropathy. And healthy nerves are essential to help muscles contract properly. Thus, diabetes followed by peripheral neuropathy can lead to sarcopenia.
Other factors that are often mentioned to explain the influence of diabetes on sarcopenia include hyperthyroidism (from which many diabetics suffer), and its influence on leg muscle mass. In any case, a large number of mechanisms have been identified to explain the influence of diabetes on sarcopenia.
Can sarcopenia lead to diabetes?
Until very recently, the scientific literature has focused more on diabetes as a cause of sarcopenia. It is widely accepted that people with diabetes suffer accelerated muscle loss with age. However, the reverse may also be true. Muscle loss and sarcopenia could also be the cause of diabetes.
Indeed, a scientific study has shown that men with high muscle mass have a lower risk of developing diabetes. The same study also showed that individuals in the low muscle mass quartile were twice as likely to develop diabetes as those in the high muscle mass quartile.
This is because muscles consume the most glucose in the body (apart from the brain). In other words, if an individual does not have enough muscle mass to assimilate ingested glucose, the glucose will remain in the bloodstream, leading to hyperglycemia, then insulin resistance and eventually the development of type 2 diabetes.
Other studies point to sarcopenia as a cause of decreased physical activity and a sedentary lifestyle. This sedentary lifestyle and lack of physical activity are then themselves the cause of the development of insulin resistance.
Thus, it is now clearly established that sarcopenia is both a cause and consequence of diabetes.
How to regulate blood sugar to prevent sarcopenia?
If it is clearly demonstrated that blood glucose levels can have an impact on muscle mass, it would follow that regulating blood glucose levels would also help to maintain muscle health.
It has been shown that some diabetes treatments that regulate blood glucose levels also influence the rate of muscle loss in older people. A treatment that regulates blood sugar levels can therefore improve the body’s insulin resistance and provide nutrients to muscle tissue.
However, scientific research on the subject has not yielded reliable results, the main reason being that the population affected by both diabetes and sarcopenia is extremely heterogeneous, making it difficult to draw reliable conclusions.
Prevention of diabetes and sarcopenia
While there are treatments for diabetes and sarcopenia, the best thing we can do today is to prevent them and avoid altogether the emergence of the disease.
In the case of diabetes, it is possible to monitor for the early signs of the disease. This is called pre-diabetes, a buffer zone between a so-called “normal” blood sugar level and a characteristic “diabetic” blood sugar level. The symptoms of pre-diabetes are similar to diabetes, with one difference: the former is reversible. It is then possible to turn the tide and avoid, or at least delay, diabetes. This can be done by following a specific diet, exercising, or by reducing tobacco and alcohol consumption.
Sarcopenia can also be prevented by a balanced and varied diet and by regulating blood sugar levels.
In both cases, regular physical activity is essential. It helps to reduce certain risk factors linked to the onset of type 2 diabetes and builds up muscle mass, thus alleviating sarcopenia.
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