Sarcopenia from Pathophysiology to Clinical : Literature Review

https://doi.org/10.32539/BJI.v7i1.11 A B S T R A C T The causes of sarcopenia are thought to be multifactorial including: environmental factors, illness, activation of inflammatory pathways, mitochondrial dysfunction, loss of neuromuscular junctions, reduced number of satellite cells and changes in the quality of hormonal function. The mechanism of sarcopenia occurs because the aging process coupled with reduced physical activity can cause the formation of cytokines to increase so that inflammation is easy, insulin resistant, anabolic resistance and neuromuscular impairments.


Introduction
Physiological and muscle morphological changes that appear with increasing age include a decrease in the number and size of muscle fibers, especially in type 2 (fast-twitch muscle) muscles, accompanied by infiltration of fatty tissue and fibrous tissue into muscle mass. 1-4 Besides, there is a degenerative change of the satellite and myoblast cells and become inactive. reported that the prevalence of sarcopenia was 4.6% in men and 7.9% of women in adults living in communities with a mean age of 67 in Great Britain. 7-8

Inflammation and Nutrition
The  27 In chronic disease subjects with higher levels of "basal" inflammation, this mechanism is enhanced which can lead to cachexia.
Reduced physical activity also contributes to "anabolic resistance", which causes a vicious cycle to be very difficult to break. [28][29][30] Nutritional interventions can help inhibit "anabolic resistance". There are two pathways that contribute to restoring normal protein synthesis, namely increasing the intake of protein / amino acids that can overcome the increased anabolic threshold, and / or increasing the intake of nutrients that have anti-inflammatory properties. The first approach in several observational studies and clinical trials investigating the role of nutritional interventions in sarcopenia. Surprisingly, most of the evidence claims that protein or amino acid supplements are unable to increase muscle mass, muscle strength and physical performance in parallel. 31 The second approach focuses on key nutrients that are able to reduce inflammatory status as an actor of endocrine nutritional networks. The pathway linking nutrition to inflammation is insulin growth factor-1 (IGF-1), which is positively modulated by diet and the PUFAs and whey protein. [34][35] The 1989 definition At the molecular level, sarcopenia is caused by a disproportionate decrease in muscle protein synthesis rate and / or an increase in muscle protein breakdown.
The neuropathic process is most influential because it is responsible for the degeneration of the alpha motor nerves that supply the muscle fibers and cause loss of motor units. 37 The aging process causes structural and functional changes in skeletal muscles, especially in the first 40 years.

Definition of Sarcopenia 2010
In contributions that vary and develop over time. Figure   2. shows the basic mechanism of sarcopenia. 32 Based on the mechanism of sarcopenia as depicted in Figure 2, the categories of sarcopenia are categorized into primary sarcopenia and secondary sarcopenia. The supporting examinations to determine the diagnosis of sarcopenia are as follows: The  • Sarcopenia malnutrition The sarcopenia phenotype is also associated with malnutrition, regardless of whether the malnutrition is rooted in low food intake (hunger, inability to eat), reduced bioavailability of nutrients (e.g. with diarrhea, vomiting) or high nutritional requirements (e.g. with inflammatory diseases such as cancer or organ failure with cachexia). 9

Degree of sarcopenia
Assessment of the degree of sarcopenia can be seen in Table 2 Several studies on body fat measurement have been conducted before, one of which is the measurement of body fat using the two-electrode hand-to-hand method. 45 In other studies, there are also four electrodes used. Also research was conducted using four electrodes, but what was measured was the impedance between the right and left feet (foot-to-foot). 40 In another study, measurements of body fat using four electrodes were also developed using the whole body measurement method but the user had to move the electrode connector manually according to the body part to be measured. 33 The composition of the human body can be modeled in the form of two compartments, namely the non-fat mass (fat free mass) and the fat mass (fat mass).