Sarcopenia (muscle loss) is a condition characterized by loss of skeletal muscle mass and function resulting in weakness and loss of balance. Virtually all old dogs suffer from sarcopenia, which is a major cause of morbidity and mortality. Dogs with advanced sarcopenia have poor quality of life and are often euthanized when their rear legs can no longer support them. Sarcopenia is often viewed as a component of arthritis and not treated directly.
Sarcopenia is not a simple condition. Many dysfunctions contribute to the development of sarcopenia. The complexity of sarcopenia is a major factor contributing to the neglect of and failure to treat this common condition. The causes of sarcopenia which have been identified are : mitochondrial dysfunction, increased apoptosis (cell death), abnormal autophagy (dead cell removal), decline in satellite cell function, increased generation of reactive oxygen species, alterations of signaling and stress response pathways, inadequate diet, and hypothyroidism.
Mitochondrial dysfunction is a major contributor to aging, so it is not surprising that it is involved with sarcopenia. There are many mitochondrial support products available. Unfortunately, supplement manufacturers do not include ribose in their mitochondrial support products. Perhaps, the most important mitochondrial function is the production of cellular energy. The rate limiting step in the generation of cellular energy is the conversion of glucose to ribose. Ribose is a component of ATP, which is the source of cellular energy. Without adequate energy, nothing works correctly.
Impaired apoptosis and autophagy result in the production of “zombie” cells. These are cells that are alive but not functional. When enough zombie cells accumulate, muscle physiology is impaired. Fortunately, there is a supplement which destroys zombie cells. Fisetin is derived from strawberries and is effective in removing zombie cells.
When muscle cells are damaged, stem cells ( satellite cells) replace cells that are damaged beyond repair. Resveratrol, nicotinamide riboside, ECGC (green tea extract), and beta-hydroxy-beta-methylbutarate are all effective in optimizing stem cell function.
Diet is extremely important in preventing and reversing sarcopenia. Older dogs require more and better quality protein. The easiest way to provide this type of diet is by feeding home prepared food. The diet should be grain free since older dogs do not metabolize carbohydrates effectively. Crae should be taken to ensure the diet is hypoallergenic in order to reduce inflammation and resulting reactive oxygen species. Given the toxic nature of the environment, a multiple vitamin supplement will improve the elimination of toxins. If inflammation is a problem, supplements such as vitamin c, vitamin e, alpha lipoic acid, cucumin, etc. are helpful.
Hypothyroidism is a well known cause of myopathy. Myopathy results in inflammation which further impairs muscle function. Thyroid hormone determines the metabolic rate of all cells. Reduced metabolic rate further impairs muscle function.
One of the major factors contributing to muscle loss is impairment of signaling pathways. Cells must receive messages that instruct them to take metabolic actions. These messages are carried by hormones. Without the proper instructions, muscle cells become atrophied and non-functional. Muscle growth and strength are controlled by myostatin, which inhibits muscle growth, and follestatin, which inhibits myostatin. One of the consequences of age is the production of excessive myostatin. Fortunately, supplemental follestatin has become commercially available.
When sarcopenia is viewed holistically, all the factors contributing to this debilitating condition are recognized and can be treated. Effective treatment of muscle loss in older dogs will greatly improve quality of life and will result in increased longevity.