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Human physiology, hazards and health risks
Published in Stephen Battersby, Clay's Handbook of Environmental Health, 2023
Revati Phalkey, Naima Bradley, Alec Dobney, Virginia Murray, John O’Hagan, Mutahir Ahmad, Darren Addison, Tracy Gooding, Timothy W Gant, Emma L Marczylo, Caryn L Cox
The inner two layers of the adrenal cortex, the zona fasciculata and the zona reticularis, produce hormones collectively known as corticosteroids. The main corticosteroid secreted is cortisol (hydrocortisone). The corticosteroids have several actions which are as follows: Promoting the utilisation of proteins for the production of heat and energy in preference to the use of carbohydrates;Anti-allergy;Anti-inflammatory;Aldosterone-like effects, causing retention of sodium and of water and loss of potassium. The salt and water retention may lead to oedema and/or high blood pressure (hypertension). Cortisol reduces the utilisation of carbohydrates for energy; thus they increase the blood glucose level (a diabetogenic effect). When body proteins are broken down, wound healing is impaired and the effect on suppression of immune or inflammatory response can lead to ‘masking’ of infections (which may cause delays in diagnosis) and also an increased susceptibility to infections.
Human physiology, hazards and health risks
Published in Stephen Battersby, Clay's Handbook of Environmental Health, 2016
David J. Baker, Naima Bradley, Alec Dobney, Virginia Murray, Jill R. Meara, John O’Hagan, Neil P. McColl, Caryn L. Cox
The inner two layers of the adrenal cortex, the zona fasciculata and the zona reticularis, produce hormones collectively known as corticosteroids. The main corticosteroid secreted is cortisol (hydrocortisone). The corticosteroids have several actions:promoting the utilisation of proteins for the production of heat and energy in preference to the use of carbohydrates;anti-allergy;anti-inflammatory;aldosterone-like effects, causing retention of sodium and of water and loss of potassium. The salt and water retention may lead to oedema and/or high blood pressure (hypertension).
Correlation between biomarkers of creatine metabolism and serum indicators of peripheral muscle fatigue during exhaustive exercise in active men
Published in Research in Sports Medicine, 2020
Valdemar Stajer, Milan Vranes, Sergej M. Ostojic
Serum GAA and creatine poorly correlated with exercise-provoked responses in blood lactate, muscle-specific creatine kinase and interleukin-6 levels, or with rated perceived exertion. A non-significant negative trend (r = −0.68) was found between serum GAA and creatine kinase, suggesting a possible low-to-moderate inverse relationship between these two variables. Taken together, the results show a limited applicability of serum indicators of creatine metabolism as biomarkers of running-to-exhaustion at iRSAT in active men. However, we reported significant positive correlations between circulating GAA and creatine, and serum cortisol stress response. An increase in GAA (also creatine) was accompanied by an increase in serum cortisol levels, suggesting a link between GAA-creatine availability and cortisol. Since cortisol acts as a modulator of amino acid uptake by high-energy output tissues (Christiansen et al., 2007), an exercise-induced cortisol release might inhibit uptake of GAA and creatine (both amino acid derivatives) into the skeletal muscle, with more compounds available in the circulation. On the other hand, creatine might regulate cortisol response during high-intensity exercise (Dobgenski, Santos, Campbell, & Kreider, 2014), suggesting a rather complex metabolic relationship between two variables. Additional studies are needed to evaluate possible effects of circulating cortisol on the creatine transporter (SLC6A8) expression and activity, along with potential impact of GAA and creatine on the cholesterol-originated synthesis of cortisol in the zona fasciculata of the adrenal cortex. Concerning other limitations of the present study, we evaluated only a narrow panel of biomarkers for creatine metabolism during exhaustive exercise. Using advanced variables (e.g. blood amino acid profiles, creatinine elimination assays) may help to better understand GAA-to-creatine dynamics throughout heavy exertion. Our study only evaluated the acute effects from a single session of heavy exercise, while the response may change with repeated bouts of exhaustive exercise. Hypothetically, chronic exhaustive exercise could deplete GAA-creatine pool that negatively influences muscular performance (also brain function), which requires further investigation. In addition, the training status of participants should be accounted as another factor that may influence creatine bioenergetics response to exhaustive exercise, since the previous study have shown differences in creatine utilization machinery between trained and untrained individuals (Vincent & Vincent, 1997). Here, we recruited a cohort of relatively active and well-trained man (weekly exercise ~ 10 h; VO2max ~ 50 ml/kg/min) so the responses may change with different training status or levels of habitual physical activity. Finally, age- and sex-specific differences in creatine metabolites responses to heavy exercise need to be addressed in the future studies due to possible variations in muscle phosphocreatine kinetics during high-intensity exercise in male and female adolescents and adults (Willcocks, Williams, Barker, Fulford, & Armstrong, 2010).