Sarcopenia’s Dual Threat: Physical and Metabolic Consequences

In the realm of aging and health, sarcopenia stands out as a significant yet often overlooked condition. Defined as an age-associated loss of muscle mass and strength, sarcopenia affects a substantial portion of the elderly. However, this condition is not confined to the elderly as young individuals can also be susceptible to the risks of sarcopenia due to various factors, including low muscle mass, physical inactivity, poor nutrition, and specific medical conditions.

Early signs of sarcopenia include weaker muscles and persistent fatigue, which can make everyday activities such as climbing stairs, lifting objects, or walking more challenging. For younger adults, this can result in decreased physical performance and reduced productivity, affecting their ability to engage in sports, exercise, and daily tasks effectively. As muscle strength declines, individuals may experience difficulties with balance and coordination, increasing the risk of falls and injuries. This is particularly concerning for the elderly, as it impacts their ability to perform essential activities of daily living, such as bathing, dressing, and cooking, potentially leading to a significant decline in quality of life.

But did you know sarcopenia leads to more than just physical decline? In fact, the condition can lead to various metabolic consequences, including obesity, diabetes, hypertension, and osteoporosis.

In this blog post, we will delve deeper into how sarcopenia can lead to these health issues and why early screening and intervention are crucial. By understanding the broader impact of sarcopenia, we can better appreciate the importance of maintaining muscle health at all stages of life.

Beyond Physical Decline: The Metabolic Consequences of Sarcopenia

Sarcopenia and Obesity

Sarcopenia can significantly influence the development of obesity, resulting in a challenging condition known as sarcopenic obesity, which is the loss of muscle mass is coupled with an increase in fat mass. This dual burden occurs because as sarcopenia progresses, there is a natural decline in physical activity due to loss of muscle mass and strength.

This decrease in physical activity may lead to weight gain, characterized mainly by the accumulation of abdominal fat. Moreover, inflammation, a key mechanism in sarcopenia, can induce insulin resistance. This inflammation-induced insulin resistance disrupts the body’s ability to properly use insulin, causing glucose to be stored as fat, thereby further contributing to obesity.

In fact, research on the association of muscle strength and obesity has shown that muscle strength is negatively correlated with Percent Body Fat (PBF) and Visceral Fat Area (VFA). This means that lower muscle strength is linked to higher body fat percentage and higher level of visceral fat.

Sarcopenia and Diabetes

Skeletal muscle is the largest insulin-sensitive tissue in the body and accounts for 80% of glucose uptake. Thus, reduced skeletal muscle mass impairs glucose metabolism, significantly increasing the risk of developing type 2 diabetes.

This relationship was underscored by a cohort study showing that lower relative muscle mass (RMM) is inversely associated with the incidence of type 2 diabetes in healthy individuals. Simply put, having low muscle mass increases the likelihood of developing type 2 diabetes.

Additionally, there is also a national study that has found that higher muscle mass is associated with better insulin sensitivity and a lower risk of prediabetes. Specifically, for every 10% increase in skeletal muscle index, there is a 12% decrease in the incidence of prediabetes.

Furthermore, among all the muscle groups, leg muscles being the largest muscle group in the body, play a crucial role in glucose uptake. Low leg muscle mass is associated with an increased risk of insulin resistance, where the muscles cells become less responsive to insulin. This insulin resistance leads to elevated blood glucose levels over time, which is a significant factor in the development of type 2 diabetes. Research supports this relationship, showing that leg muscle mass, strength, and functional performance are significantly lower in older patients with type 2 diabetes compared to healthy individuals.

 

Sarcopenia and Hypertension

Hypertension, or high blood pressure, is another metabolic consequence of sarcopenia. Specifically, sarcopenia has been linked to the development of hypertension through several potential mechanisms.

• Chronic inflammation: Chronic inflammation is characterized by the production of catabolic cytokines, is a well-studied mechanism in sarcopenia. These cytokines are produced as part of the inflammatory response and can affect the sympathetic nervous system and the renin-angiotensin-aldosterone system that regulates blood pressure, potentially leading to elevated blood pressure levels.
• Insulin resistance: Sarcopenia leads to insulin resistance because the reduced muscle mass decreases glucose uptake. Insulin resistance then increases the risk of hypertension through various mechanisms, including enhanced activity of angiotensin II and aldosterone, elevated sympathetic nervous system activity, and oxidative stress, all of which contribute to elevated blood pressure.
• Oxidative stress: Oxidative stress arises when the body produces more reactive oxygen species (ROS) than it can effectively neutralize with antioxidants. In sarcopenia, the elevated oxidative stress can lead to hypertension due to the elevated levels of ROS in the body, which induce vasoconstriction and contribute to the development of arterial hypertension.

Overall, sarcopenia shows a significant association with hypertension, as shown by a meta-analysis of 10 studies indicating that older individuals with sarcopenia are 1.39 times more likely to develop hypertension.

Sarcopenia and Osteoporosis

Osteoporosis is defined as a systemic skeletal disorder characterized by low bone mass and deterioration of bone tissue microarchitecture, leading to increased bone fragility and susceptibility to fractures. Generally speaking, it involves a higher rate of bone breakdown compared to bone formation, resulting in porous bones.

Sarcopenia can contribute to osteoporosis through complex mechanical and biochemical interactions between bone and muscle tissues.

• Mechanical loading: Mechanical loading refers to the physical forces applied to a structure, such as bones or muscles, when they are subjected to weight, movement, or resistance. In specific, when muscles exert force on bones during activities like walking or lifting weights, bones respond by adjusting their mass and structure to support these loads. This adjustment occurs through bone remodeling processes, which involve the formation of new bone tissue by osteoblasts and the removal of old or damaged bone tissue by osteoclasts. Consequently, reduced muscle function can lead to decreased bone load, less stimulation of bone remodeling processes, potentially resulting in bone loss over time.
• Reduced secretion of myokines: Muscle-bone interactions involve various signaling molecules such as myokines, which are secreted by myocytes (also known as muscle fibers) in response to muscle contraction. Examples of myokines are interleukin-6 (IL-6), irisin and myostatin. In sarcopenia, when there is reduced muscle mass, the production and secretion of these myokines may decrease. This reduction can disrupt the normal balance of bone remodeling processes, potentially leading to decreased bone density and an increased risk of osteoporosis.

To summarize, research indicates a strong link between sarcopenia and osteoporosis, with a low appendicular skeletal muscle mass index (ASMI) emerging as a potential predictor of osteoporosis in individuals diagnosed with chronic liver disease (CLD).

Step-by-step on How to Diagnose Sarcopenia

Now that we understand the metabolic consequences of sarcopenia, let’s delve into how sarcopenia can be diagnosed!

Step 1: Begin with the SARC-F questionnaire, which evaluates components such as strength, ability to walk, rising from a chair, climbing stairs, and history of falls. This initial assessment provides a broad indication of potential sarcopenia risk.

Step 2: Assess muscle strength using a hand grip strength dynamometer. Individuals whose Hand Grip Strength (HGS) falls below a specified cutoff value may be at risk for sarcopenia.

Step 3: Measure muscle mass using methods like DEXA, BIA, or CT scans. In Asian populations, the cutoff value for skeletal muscle index (SMI) is typically 7.0 kg/m² for males and 5.7 kg/m² for females based on the Asian Working Group of Sarcopenia (AWGS) 2019. In contrast, Western guidelines based on European Working Group on Sarcopenia in Older People (EWGSOP) set the cutoff at 7.0 kg/m² for males and 5.5 kg/m² for females. Falling below these thresholds suggests a potential risk of sarcopenia due to reduced muscle mass.

These steps provide a comprehensive approach to diagnosing sarcopenia, integrating both functional assessments and quantitative measurements to accurately evaluate muscle health and identify individuals at risk.

Conclusion

In conclusion, sarcopenia poses a dual threat to health, impacting both physical function and metabolic health. This condition not only diminishes muscle mass and strength, increasing the risk of falls and fractures, but also contributes to metabolic disorders such as obesity, diabetes, hypertension, and osteoporosis.

Recognizing these interconnected health risks underscores the importance of early screening and intervention strategies. Moreover, by prioritizing muscle health through proactive measures like regular exercise, balanced nutrition, and medical monitoring, we can effectively mitigate the detrimental effects of sarcopenia and promote healthier aging and well-being for individuals of all ages.

Read this Guide and Learn How to Prevent Muscle Loss