Physical Exercise and Stress
Health benefits of regular physical exercise are undebatable. Both resting and contracting skeletal muscles produce reactive oxygen and nitrogen species (ROS, RNS). Low physiological levels of ROS are generated in the muscles to maintain the normal tone and contractility, but the excessive generation of ROS promotes contractile dysfunction resulting in muscle weakness and fatigue. This is perhaps the reason why intense and prolonged exercise results in oxidative damage to both proteins and lipids in the contracting muscle fibers. The magnitude of exercise-mediated changes in superoxide dismutase (SOD) activity of skeletal muscle increases as a function of the intensity and duration of the exercise. Adaption to exercise is the key to prolonged regulation of an oxidant/antioxidant “balance”. Here we have to distinguish several levels.
Pre-conditioning. The first generation of promotion of oxidation for energy. ROS/RNS is up
Rest and recuperation. ROS / RNS is down
Conditioning. Regular training intervals depending on age and achievement. ROS/RNS up
Rest and recuperation. ROS / RNS is down but needs a shorter time to come down
Specialism. High level of training with a maximum production of ROS/RNS
Rest and recuperation. ROS / RNS is down but needs a shorter time to come down
Aging sets in. Unstable ROS / RNS levels and changing recuperation times. More bad/good days interchange.
Aging becomes apparent. Different levels of ROS / RNS throughout the body. Fall out occur but recuperation is high.
Aging only becomes a hazard when the actual damage overrules the recuperation and decline is complete.
Physiological Role of Stress
The physiological role of ROS is associated with almost all the body processes.
With reproductive processes, since under physiological conditions, a certain level of free radicals and reactive metabolites is required, complete suppression of FR (free radical) formation would not be beneficial. One further beneficial example of ROS seen at low/moderate concentrations is the induction of a mitogenic response. Mitogenesis is the induction (triggering) of mitosis, typically via a mitogen. A mitogen is usually some form of a protein
Stress leads to activation of the hypothalamic-pituitary-adrenal axis. The increased endogenous catecholamine release has been observed in cold environmental conditions. The activity of succinate dehydrogenase gets elevated indicating the influence of ROS as evident in cold environmental conditions. Coronary blood flow is reduced and an altered basophil activity in the myocardium is observed.
Free radicals play an irreplaceable role in phagocytosis as one of the significant microbicidal systems, or in several biochemical reactions, for example, hydroxylating, carboxylating, or peroxidation reactions, or in the reduction of ribonucleotides. At present, free radicals and their metabolites are assumed to have important biomodulating activities and a regulatory ability in signal transduction process during the transduction of intercellular information.
In the presence of metals such as iron or copper, H2O2 can form the reactive and toxic hydroxyl radical (HO•). Increasing evidence indicates that H2O2 is a particularly intriguing candidate as an intracellular and intercellular signaling molecule because it is neutral and membrane permeable. Specifically, H2O2 can oxidize thiol (–SH) of cysteine residues and form a sulphenic acid (–SOH), which can get glutathionylated (–SSG), form a disulfide bond (–SS–) with adjacent thiols, or form a sulfenyl amide (–SN–) with amides. Each of these modifications modifies the activity of the target protein and thus its function in a signaling pathway. Phosphatases appear to be susceptible to regulation by ROS in this manner, as they possess a reactive cysteine moiety in their catalytic domain that can be reversibly oxidized, which inhibits their dephosphorylation activity. Specific examples of phosphatases known to be regulated in this manner are PTP1b, PTEN, and MAPK phosphatases.
Hydrogen peroxide (H2O2) production due to oxidative stress is also associated with apoptosis and melanogenesis in melanocytes.
Nutrition is one of the most important external factors for oxidative stress if not the most important. Food and drinks come in all combinations. Ingredients interact, react, and deliver reactive parts into the body. Oxidants and antioxidants are just a few of them. The amount delivered through the digestive tracks all depends on the diet, amount of product, a combination of particles, time and place of delivery, and conditions under which it is delivered. There is more than one food regime. To name a few:
Regular eater, 3 meals a day. Standard local combination.
Irregular eater. Eat when feels like doing so or when the time is available
Regulated eater =
Vegetarian also lacto-vegetarian
Hindu, Jewish, or Muslim food regime
Another Religious dieting
Driven eater. Emotional eating.
All food intake supposed to be climate-controlled, which is no longer the case. This has positive and negative effects. New products at the wrong time of the year can deliver a negative instead of a positive physical reaction of the body.
Food regimes have a local, environmental, traditional, or religious background. Going back in time there were times of lavishly overproduction or availability of food and times of limitation or not the availability of products. This periodical change strengthened the body and soul. Only recently it has been discovered that it also can make us stronger.
Fasting induces an increase in total leukocytes counts, eosinophils, and metamyelocytes in the blood profile, accompanied by a decrease in the basophils and monocytes, a typical “stress leukogram” produced in the animal body due to the increased endogenous production of cortisol from the adrenal glands during oxidative stress. The leukocytosis with neutrophilia associated with fasting may be a consequence of an inflammatory reaction, caused by the direct action of ammonia on the rumen wall. The monocytopenia may be a result of adaptation and defense mechanism undergoing in the body and leads to higher susceptibility to pathogens.
Nutritional stress causes adrenal gland hyperfunction and, thus, an increased release of catecholamines in the blood, with simultaneous inhibition of the production of insulin in the pancreas. The process of glycogenolysis is observed in the first 24 hours of fasting. Thereafter, gluconeogenesis from amino acid precursors and lipolysis from glycerol, as well as from lactate through the Cori cycle, maintain a regular supply of glucose. Lactate gets transformed into pyruvate and participates in the gluconeogenesis along with the deaminated amino acids. The increased production of catecholamines (epinephrine and dopamine) owing to fasting results in peripheral vasoconstriction and redistribution in the blood which is expressed as erythrocytosis, leukocytosis, and neutrophilia
Unlike innate antioxidant defensive enzyme systems, nutritional antioxidants are non-enzymatic, meaning that they are not enzymes that catalyze redox reactions directly affecting pro-oxidant substrates. For the most part, they work by breaking oxidative chains, either by accepting (or donating) electrons, thereby eliminating the unpaired electron. They are inferior to the body’s natural enzymatic antioxidants because they cannot be activated selectively in response to the continually changing redox status of specific cellular compartments. Their activity is indiscriminate. Since ROS serve many important functions, neutralizing them is not always beneficial. Furthermore, by interfering with the normal signaling pathways that activate the body’s natural enzymatic defenses, in many cases, exogenous antioxidants can increase oxidative stress (OS).
Certain botanical phenolic compounds appear to work indirectly. Rather than interrupt oxidative chains by directly reducing pro-oxidants, they appear to decrease OS through a variety of signaling pathways, some of which may result in upregulation of the body’s innate enzymatic antioxidants. This is true for the so-called “hormetic” botanicals including catechins, quercetin, and curcumin which are actually mild pro-oxidants, even though they indirectly decrease OS.