Sarcopenia and Aging

Question 1

Fried Frality Criteria

Answer 1

Considered frail if 3/5 of the following:
Weight loss (especially unintentional)
Exhaustion
Physical activity
Walk time
Grip strength

Question 2

Sarcopenia

Answer 2

Decline in lean body mass is very significant in contributing to frailty
As we get older we lose muscle mass
Balance between protein synthesis and protein degradation determine if building, losing, or muscle mass is staying the same
Many factors cause the reduction of muscle mass: reduction of physical activity (no access to side walks, pain, etc.), disorder that causes muscle wasting, etc.
Adult muscle is still responsive to activity, but not as much as younger people
Taste also shifts as we get older from protein sources to carbohydrates and sweets

Question 3

Muscle Weakness

Answer 3

Losing muscle strength is a strong risk factor for disability development

Muscle weakness is a critical factor for determining both physical disability and mortality in older adults

Question 4

Sarcopenia vs. Dynapenia

Answer 4

Dynapenia: age related reduction of strength or power
Sarcopenia: age related reduction of muscle mass

Study: measured muscle mass compared to muscle strength and found that no matter if people gained weight or not, they still lost strength over time
Therefore, there are other factors that cause muscle weakness other than muscle mass

The age-related loss of muscle strength (dynapenia) is only partially explained by the reduction in muscle mass (sarcopenia), and these two conditions need to be defined independent of one another
The loss of muscle strength associated with both disuse and aging is weakly associated with the loss of lean body mass.

Question 5

Cognitive Function and Muscle

Answer 5

When gait speed slows down, then that is indicative of risk for cognitive function decline as well
Therefore, how much is mobility driven by the brain vs. just muscle mass
This figure shows the contributions of muscle strength decline
Movement of type II to type I fibers cause loss of strength

Question 6

Stronger Adults vs. Young Adults

Answer 6

Stronger older adults were just as good as the young adults, but weaker older adults had a more significant impairment
If had neurological intervention to target NS, study showed that could increase strength output by 20% independent of skeletal muscle

Question 7

Brain Stimulation Study

Answer 7

Muscle response to brain stimulation, but have contraction during stimulation the brain (period of inhibition) does not respond to it and leads to excitability
Older adults have a longer silent period which means that they have more inhibition and cannot excite as easily

Question 8

Motor Unit Re-Innervation

Answer 8

Motor units drive the response of the muscle and can reinnervate themselves
Develop new sprouts to replace motor unit that has died via pathology or injury; not 100% efficiency … if lost 10, you may or may not get all 10 back
From older cadavers have less functional motor units than younger cadavers

Question 9

Stimulation of PNS to Bypass CNS

Answer 9

Stimulate peripheral nerve (no brain involved) and see relationship to muscle mass and how much force is produced in relation to mass
Excitation coupling process is what is changing the relationship
Amount of force produced in older adults is significantly less than mass compared to younger adults = tells excitation coupling is what makes the difference
Ca release and transient Ca presence is significantly less in older vs younger adults
Ca release is less and Ca absorption is quicker in older adults

Question 10

Physiologic Mechanisms of Muscle Weakness

Answer 10

The physiologic mechanisms of muscle weakness are multifactorial and arise from deficits in neural activation (including degenerative changes in the motor cortex), reductions in the intrinsic force-generating capacity of muscle, as well as muscle wasting.

Question 11

Myostatin Mutation

Answer 11

Gene that encodes a certain protein that exists that if you have a lot of it, it will impede muscle hypertrophy and if you can block the protein than you can get high amounts of muscle hypertrophy
No myostatin = high muscle hypertrophy

REGN1033 Drug: This drug shows that increase in mass is significant at 12 weeks compared to testosterone treatments that take 12 months to get the same increase. Although, because placebo group increased in muscle mass with just exercise, it shows that exercise is the key