Metabolism and Oxidative stress

quiz

How does maximal oxidative capacity (VO2max) change with age in sedentary adults?

Maximal oxidative capacity declines by about 9% per decade in sedentary adults after the age of 25

How does maximal oxidative capacity change with age in older adults who remain active?

Maximal oxidative capacity declines by about 5% per decade in older adults who remain active

What are some age-related changes in aerobic capacity?

Older adults exhibit lower aerobic enzyme activity compared to middle-aged adults, have lower walking economy (using more oxygen when walking at the same speed as younger adults), and have reduced leg blood flow/oxygen delivery due to lower skeletal muscle capillarization

How can regular exercise affect the declines in submaximal aerobic capacity that come with age?

Regular aerobic and resistance training can improve walking economy by improving enzyme activity, mechanical efficiency, and blood flow, as well as reducing body mass/fat3. The effects of exercise depend on intensity, with older runners having better walking economies than older walkers, and similar walking economies as younger sedentary individuals.

How does anaerobic performance change with age?

Anaerobic performance declines with age, with men slowing by about 7% per decade and women slowing by about 9% per decade. There is a greater reliance on aerobic energy systems with older age.

What are some age-related changes in intramuscular phosphocreatine (PCr)?

Intramuscular PCr levels are 5% lower in older adults (52-79 years) compared to younger adults (18-36 years), and older adults have lower total intramuscular creatine and a lower PCr resynthesis rate.

How can exercise training affect PCr in older adults?

Increase intramuscular PCr levels in older adults, decrease intramuscular creatine, increase the PCr/total creatine ratio, and increase the ATP/ADP ratio. Creatine supplementation combined with high-intensity or resistance training appears to be safe and beneficial.

How do muscle glycogen levels change with age?

Muscle glycogen levels are 61% lower in sedentary older adults compared to younger adults, which may contribute to age-related declines in anaerobic performance

How does anaerobic enzyme activity change with age?

Non-weight-bearing muscles exhibit lower anaerobic enzyme activity, specifically lactate dehydrogenase (LDH), in older versus middle-aged adults

How does activity of Krebs cycle enzymes change with age?

The activity of Krebs cycle enzymes, such as succinate dehydrogenase (SDH) and citrate synthase, decreases with age. Oxidative enzyme activity is about 10-15% lower in older versus younger endurance-trained adults. Aerobic exercise training (AEX) can maintain oxidative capacity

How do peak blood lactate levels change with age?

Peak blood lactate levels are lower in older adults. This is partly because older adults rely less on anaerobic metabolism. Furthermore, older adults experience delayed and diminished lactate shuttling, which is related to a reduced ability to oxidize lactate.

How does exercise affect anaerobic capacity in older adults?

Anaerobic training interventions to improve anaerobic capacity in older adults are limited, though some studies show that resistance training can improve sprint performance.

How do glycolytic enzymes change with age?

Such as phosphofructokinase (PFK)a glycolytic, predominate in Type II muscle fibers. With older age, there is a shift towards a more oxidative (Type I) muscle profile. There are currently mixed findings on the declines in glycolytic enzymes with aging, which may depend on physical activity.

What training interventions can be taken into consideration for older adults?

• Eight weeks of hypertrophy resistance training improved strength, thigh girth, and 100- and 300-m sprint performance in older sprinters.

• Twenty weeks of sprint and resistance training increased strength outcomes, power outcomes, and sprint velocity.

  Training effectiveness may be affected by a more significant proportion of Type 1 muscle fibers in older adults, which may be less responsive to supplementation.

What is oxidative stress?

Oxidative stress is caused by a buildup of free radicals in the body1. It occurs when there is an imbalance between the production of free radicals and the body's ability to neutralize them with antioxidants2.

What are free radicals?

Free radicals are atoms with one or more unpaired electrons2. This makes them highly reactive2. They are also known as reactive oxygen species (ROS)

How are free radicals formed?

Free radicals can form through the "leaking" of electrons to oxygen during mitochondrial respiration in the electron transport chain (ETC)3.... They can also be formed when oxygen splits during oxidative metabolism3.

What damage can free radicals cause?

Free radicals can cause damage to cell membranes, DNA, and tissues2. They can also alter enzyme reactions2. This damage can lead to a variety of pathological conditions and aging

What are antioxidants?

Antioxidants are molecules that neutralize free radicals by donating an extra electron6. They are also referred to as free radical scavengers1....

What are the sources of antioxidants?

• Endogenous antioxidants are produced naturally by the body. Examples include superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPX)7.

• Exogenous antioxidants come from foods. Examples include vitamins, quercetin, resveratrol, coco flavonoids, and curcumin7.

How does exercise relate to oxidative stress?

Exercise increases cellular respiration, which can lead to an increased production of ROS8. However, it also triggers the upregulation of the endogenous antioxidant system, which can result in greater protection from oxidative stress over time8. Aerobic training improves resistance to oxidative stress

How does aging relate to oxidative stress?

Older adults tend to have greater systemic oxidative stress compared to younger adults5. Oxidative stress in specific tissues is related to disease burden5. Older adults with better fitness levels exhibit lower levels of oxidative stress

How does the electron transport chain (ETC) relate to free radical production?

The mitochondrial ETC is a major source of reactive oxygen species (ROS), due to electrons "leaking" to oxygen during cellular respiration3.... A small percentage (0.1% to 4%) of oxygen used by actively respiring mitochondria forms free radicals

What is the relationship between fitness and oxidative stress?

Improved fitness levels, as measured by VO2 max, are associated with a greater resistance to oxidative stress9. Exercise training can improve the body's anti-oxidative defense system11.