**3.3 Vitamin E**

*Background and Management of Muscular Atrophy*

**3.2 Hormones and sarcopenia**

declines in aged population.

of IGF-I level [75].

the synthesis of vitamin D [76, 77].

metabolism [68].

cytokines such as tissue necrosis factor (TNF)-α and IL-1, 6, and 8 that trigger a cytokine cascade of the inflammatory cytokines that worsen the insulin resistance

A variety of other hormones appear to play roles in the age-related altera-

Testosterone appears to be the central hormone involved in the development of sarcopenia. Testosterone is an important physiologic steroid hormone in muscle mass maintenance. Endogenous testosterone which naturally produced within the endocrine system in both men and women decline gradually with age, correlating with decreased muscle strength it increases both muscle mass and activates adult

Normal growth hormone (GH) level is associated with notable protection from age-related disease in general, and more specifically against sarcopenia. The levels of GH and GH binding proteins declines upon aging. Growth hormone deficiency

Skeletal muscle is the major organ in which the insulin-mediated glucose uptake by glucose transporter 4 (GLUT4) takes place. Lack of insulin, or IGF-1, or insulin resistance leads to accelerated development of sarcopenia. The muscle IGF-I level

The primary action of insulin in skeletal muscle is to stimulate glucose uptake and metabolism. In physiological condition as insulin resistance, there is a gradual muscle wasting by several mechanisms such as the following: (a) suppression of PI3K/Akt signaling leading to the activation of caspase-3 and the ubiquitinproteasome proteolytic pathway causing muscle protein degradation; (b) betaadrenergic stimulation increases the lipolysis of the cell membrane, breaking down G-proteins that lead to interfering with growth hormone/insulin growth factor-1 receptor bind and diminished muscle regeneration; (c) advancement of gluconeogenesis metabolic pathway; (d) upregulation of sterol regulatory element-binding protein 1c (SREBP-1c); and (e) altering triglyceride and cholesteryl esters transport in the core of plasma lipoproteins, which causes triglycerides to accumulate in skeletal muscle [71, 72]. It has been reported that IGF-I drops 1.88 ng/ml/year in men and 2.13 ng/ml/year in women [73]. Circulating IGF-I level was found to be significantly reduced in sarcopenia patients [74]. mTOR signaling is a significant factor in sarcopenia, and mTOR signaling is altered by the change

Various medical problems and health conditions such as muscle weakness reduced the muscle mass that is predominantly a type II muscle fiber, bone pain, and systematic oxidative stress linked to 1,25-dihydroxyvitamin D [1,25(OH)2D]/ vitamin D deficiency. The vitamin D deficiency expands the sarcomeres space that allows the infiltration of irregular connective tissue and fat tissue. As such, the vitamin D deficiency resulting in reducing physical performance such as gait speed and cognitive performance (such as sustained attention and speed of information processing), mental well-being (e.g., depression), falls and leading to bone deformities. The vitamin D deficiency is a serious medical condition that drastically affects the quality of life of older adults. There are a number of reasons that play a role in vitamin D deficiencies in older adults. Since the majority of the time they spend indoors, they get minimal exposure to sunlight, lacking resistance exercise which is well known to preserve muscle function, and their skin is less exposed to

tions in muscle mass, strength function, and in the regulation of muscle

stem cells (i.e., satellite cells) leading to improved muscle function [69].

leads to the loss of muscle mass but not muscle strength [69, 70].

in skeletal muscle, resulting in the decrease of aerobic capacity [67].

**58**

Vitamin E, which is a group of eight fat soluble compounds, four tocopherols (α, β, γ, and δ) and four tocotrienols (α, β, γ, and δ), is a lipid soluble vitamin, with potent antioxidant properties and has a role in the modulation of signaling pathways. The vitamin E molecules deficiency, due to malabsorption or malnutrition, worsens age-associated skeletal dysfunction and enhances muscle degeneration, thus increasing sarcopenia [78, 79].
