Physiological characteristics and hormonal profile of young normotensive men with exaggerated blood pressure response to exercise.

Exaggerated blood pressure (BP) response to exercise in normotensive subjects is considered as a predictor of future hypertension. The aim of the study was to find out whether elevated BP response to exercise is associated with any other haemodynamic, metabolic or hormonal abnormalities. Abnormal BP response to exercise, i.e. systolic BP (SBP) > 200 mmHg at 150 W or lower workload, was found in 37 out of 180 normotensive, male students, aged 20-24 years. Fifteen students with elevated exercise BP (group E) volunteered for further examinations. Their resting and ambulatory BP showed high normal values. Eight of them had a family history of hypertension. Four subjects met the criteria of cardiac hypertrophy. Significant correlations were found between exercise SBP and left ventricular mass index, average 24 h and daytime SBP recordings. In comparison with normal subjects of the same age (group N, n = 13), those from group E did not differ in body mass index, plasma lipid profile, fasting glucose, insulin and catecholamine (CA) concentrations, but had increased erythrocyte sodium content, slightly elevated plasma renin activity and cortisol level. During exercise, E subjects showed greater cardiac output (CO) increases with normal heart rate, total peripheral resistance (TPR) and plasma CA. There were no significant differences between groups in haemodynamic and plasma CA responses to posture change from supine to standing. Glucose ingestion (75 g) caused smaller increases in CO and smaller decreases in TPR in E than in N subjects without differences in BP, blood glucose plasma insulin and CA. It is concluded that young normotensive men with exaggerated BP response to exercise show some other characteristics that may be considered as markers of predisposition to hypertension or factors promoting the development of hypertension.

Effects of three day bed-rest on circulatory, metabolic and hormonal responses to oral glucose load in endurance trained athletes and untrained subjects.

NASA: Endurance trained long distance runners and untrained individuals underwent three days of bed rest and oral glucose loading. Before and after bed rest, individuals were given glucose tolerance tests, and their heart rates, blood pressure, blood glucose levels, insulin levels, and catecholamine interactions were measured. Results indicated that glucose tolerance is more affected by bed rest-induced deconditioning in untrained individuals than in trained individuals.^ieng

Phosphate supplementation prevents a decrease of triiodothyronine and increases resting metabolic rate during low energy diet.

Thirty overweight women participated in 8 week slimming program consisting of a self-controlled low-energy diet (4.2 MJ/day) supplemented with highly viscous fibres and mineral tablets containing calcium, potassium and sodium phosphates (Redusan Combi, Biokraft Pharma AB, Sweden). Half of the patients received in double blind manner mineral tablets during first 4 weeks and placebo (without phosphates) during next 4 weeks (group 1) while the remaining patients were treated (cross-over) with placebo first and mineral tablets in the final period (group 2). The rate of weight loss was similar in groups 1 and 2 (4.7 vs 5.2 kg during the first 4 weeks and 2.7 vs 3.0 kg in the further 4 weeks). During periods of phosphate supplementation, the resting metabolic rate (RMR) increased by approx. 12% (p < 0.05) in group 1 and 19% (p < 0.05) in group 2. Phosphate supplementation ameliorated also a decrease in plasma triiodothyronine level and a decrease in thyroxine to triiodothyronine ratio. There were no differences between groups in the plasma insulin, catecholamine, growth hormone, cortisol and testosterone levels. Phosphate supplementation did not affect plasma lipids or blood glucose concentration. It is concluded that phosphate supplementation in obese patients on a low-energy diet enhances RMR irrespectively of the rate of weight loss. This effect seems to be, at least partly, due to an influence of phosphates on peripheral metabolism of thyroid hormones.

Effect of mild psychological stress on physiological responses to exercise in men.

UNLABELLED: To find out whether a negative shift in subject's mood alters cardio-respiratory and endocrine responses to exercise, 20 young men performed a graded bicycle ergometer test (50, 100, 150 W): 1) when they experienced a mixed emotional and cognitive stress before exercise (1st session), 2) when they were familiarized with the laboratory and rested quietly before exercise (2nd session). The subjects' mood was assessed by the Profile of Mood State (POMS) questionnaire. In the 1st session the subjects started exercise with significantly higher scores of tension, anger, depression, confusion and global mood in comparison with the 2-nd session. They also had slightly elevated systolic blood pressure, blood lactate, plasma cortisol and noradrenaline concentrations. During exercise performed in the 1st session only plasma free and total noradrenaline and cortisol levels were higher than those in the 2nd session. IN CONCLUSION: a mild psychological stress, causing the mood worsening before standard exercise test, does not evoke pronounced alterations in cardio-respiratory responses to exercise in healthy men, but it does affect the magnitude of exercise-induced changes in both plasma free and total noradrenaline concentrations.

Incidence of type I diabetes in people under 30 years of age in Barbados, West Indies, 1982-1991.

OBJECTIVE: To determine the incidence of type I diabetes among individuals < 30 years of age on the island of Barbados in the Caribbean. The population is predominantly African in origin but exhibits a relatively westernized lifestyle. RESEARCH DESIGN AND METHODS: Cases occurring during the years 1982-1991 were drawn from records at Queen Elizabeth Hospital and from physicians treating insulin-dependent diabetes mellitus (IDDM) patients. Patients using insulin and < 30 years of age at onset were included. Ascertainment was estimated at 94%. RESULTS: The average annual incidence of type I diabetes among Barbadians was 4.1/100,000 when age-adjusted to the world's population. There were 59 incident cases during this 10-year interval. The risk for males was 4.4 and for females 4.0/100,000. Among those 0-14 years of age, the risk was 5.0/100,000. Mean age at onset (+/- SD) was 14.7 +/- 6.9 for males and 12.5 +/- 5.7 for females. Males showed marked seasonal variation in risk and a more than threefold increase in annual incidence during 1984-1985. In contrast, females exhibited a stable pattern of IDDM risk during the 10-year interval. CONCLUSIONS: The incidence rate in Barbados falls near the lower limits of rates reported for Caribbean populations. There was a marked seasonal effect among males, even though the climate varies little throughout the year. This observation, and the incidence peak during 1984-1985, provide support for the role of environmental factors in the etiology of IDDM.

Effect of phosphate supplementation on metabolic and neuroendocrine responses to exercise and oral glucose load in obese women during weight reduction.

Thirty six obese women (BMI 29.5 to 44.0 kg m-2, aged 27 to 45 yrs) participated in the 4- week weight reducing program. All of them have prescribed low fat diet of approx. 4.2 MJ (1000 kcal per day) with high viscous fibre capsules as a basic supplement. In addition 18 women (group 1) received Redusan mineral tablets containing mainly calcium and potassium phosphates while the remaining subjects (group 2) were given Placebo instead of mineral tablets. Before energy restriction and after 4 weeks on the diet, half of the women from each group performed 30 min--bicycle ergometer exercise (30-50 W; HR approx. 110 beats.min-1). The remaining subjects were submitted to oral glucose (75 g) tolerance test (OGTT). Weight loss during energy restriction was not affected by phosphate supplementation (4.6 +/- 0.4 and 5.2 +/- 0.5 kg in group 1 and 2, respectively). Phosphates caused a significant increase (p < 0.05) in the resting metabolic rate (RMR). Net energy cost of work, resting and post-exercise blood glucose, lactate, plasma FFA, adrenalin, cortisol, growth hormone, insulin and testosterone did not differ between the groups receiving phosphates and placebo while respiratory exchange ratio was slightly higher (p < 0.05), and the plasma beta-hydroxybutyrate concentration lower (p < 0.05) than without phosphate supplementation. Post-exercise plasma noradrenaline was significantly lowered after 4 weeks of energy restriction in group 2 (on Placebo). Neither blood glucose, plasma insulin and noradrenaline responses to oral glucose ingestion nor the glucose induced thermogenesis were significantly affected by phosphate supplementation, whilst blood pressure increases following glucose load were reduced (p < 0.05). In conclusion, the present study confirmed a potential usefulness of phosphate supplementation during energy restriction in obese patients due to its effect on resting metabolic rate. The results did not, however, reveal any major alterations in the metabolic and hormonal responses to exercise or to glucose ingestion in comparison with placebo treatment.

Hypohydration increases the plasma catecholamine response to moderate exercise in the dog (Canis)

1. The effects of hypohydration produced by 48 hr water deprivation were examined in dogs during moderate treadmill exercise at an ambient temperature (Ta) of 21 degrees C. 2. Hypohydration caused a significant elevation in plasma levels of adrenaline (A), proteins (pp) and osmolality (pOsm). 3. During 1 hr of running, plasma concentrations of adrenaline (A) and noradrenaline (NA) rose significantly, whilst no change in these hormones occurred in dogs hydrated ad libitum. 4. The results suggest that hypovolemia in the dog may be a sufficient stimulus to intensify the sympatho-adrenal response to moderate exercise performed at a room Ta.

Thermal effect of glucose in women with normal carbohydrate tolerance: relationship to body mass index, blood insulin and noradrenaline.

UNLABELLED: Relationships between energy expenditure, body mass index (BMI), blood glucose (BG) responses to glucose ingestion were studied in 35 women aged 22-55 yrs with normal carbohydrate tolerance. In 13 of them plasma insulin (IRI) and catecholamine concentrations were also determined. Thirty seven per cent of patients did not respond to glucose load with an increased energy expenditure. In the remaining women the average thermogenic effect amounted to approx. 10% of their initial metabolic rate. A significant negative correlation (r = -0.415, n = 35, P(0.02) was found between BMI and the overall thermal effect of glucose (sigma TEG) calculated as a sum of the post-glucose energy expenditure measured every 15 min during 2 h minus the baseline value. Neither the fasting nor the post glucose BG concentrations correlated with sigma TEG. Significant correlations were ascertained between sigma TEG and the fasting IRI (r = -0.568), the sigma post-glucose IRI (r = -0.723), the ratio of sigma BG/sigma IRI (r = 0.845) and the post-glucose plasma noradrenaline concentration (r = 0.837). IN CONCLUSION: in women with normal carbohydrate tolerance the thermogenic effect of glucose depends to a large extent on insulin sensitivity and the glucose-induced activation of the sympathetic nervous system.

Metabolic, body temperature and hormonal responses to repeated periods of prolonged cycle-ergometer exercise in men.

This study was designed to find out whether rest intervals and prevention of dehydration during prolonged exercise inhibit a drift in metabolic rate, body temperature and hormonal response typically occurring during continuous work. For this purpose in ten healthy men the heart rate (fc), rectal temperature (Tre), oxygen uptake (VO2), as well as blood metabolite and some hormone concentrations were measured during 2-h exercise at approximately 50% maximal oxygen uptake split into four equal parts by 30-min rest intervals during which body water losses were replaced. During each 30-min exercise period there was a rapid change in Tre and fc superimposed on which, these values increased progressively in consecutive exercise periods (slow drift). The VO2 showed similar changes but there were no significant differences in the respiratory exchange ratio, pulmonary ventilation, mechanical efficiency and plasma osmolality between successive periods of exercise. Blood glucose, insulin and C-peptide concentrations decreased in consecutive exercise periods, whereas plasma free fatty acid, glycerol, catecholamine, growth hormone and glucagon concentrations increased. Blood lactate concentrations did not show any regular drift and the plasma cortisol concentration decreased during the first two exercise periods and then increased. In conclusion, in spite of the relatively long rest intervals between the periods of prolonged exercise and the prevention of dehydration several physiological and hormonal variables showed a distinct drift with time. It is suggested that the slow drift in metabolic rate could have been attributable in the main to the increased concentrations of heat liberating hormones.

Suppressive effect of beta-endorphin and naloxone on the secretion of cortisol under stress conditions in sheep.

The effect of an infusion of beta-endorphin and naloxone into the 3rd cerebral ventricle on the blood serum concentration of cortisol in non-stressed and stressed anoestrous sheep was studied. The infusion of naloxone alone did not alter the secretion of cortisol in non-stressed animals but the response to footshock was inhibited in that the cortisol values were significantly lower (P less than 0.05) when compared with those during the infusion of saline and footshocking. This opiate antagonist also suppressed the cortisol response to an infusion of beta-endorphin (P less than 0.001 and P less than 0.05). When the sheep infused with beta-endorphin were additionally exposed to footshock there was less enhancement of the secretion of cortisol (P less than 0.001 and P less than 0.05). The depressive action of beta-endorphin upon cortisol secretion in stressed sheep is matched by corresponding observations on man and it seems that endogenous opioids may inhibit or attenuate some hormonal responses to stress.

Cardiovascular and sympatho-adrenal responses to static handgrip performed with one and two hands.

12 healthy men aged 21-25 years performed, in the sitting position, a sustained handgrip at 25% of their maximum voluntary contraction, first with each hand separately and then with both hands simultaneously. Heart rate (HR), systolic blood pressure (SBP), stroke volume (determined reographically) and plasma catecholamine concentration were measured during each handgrip test. The HR and SBP increased consistently during each handgrip test while stroke volume decreased by approximately 20% of the initial value. Cardiac output did not change significantly. There were no significant differences in the magnitude and dynamics of the cardiovascular responses between the tests with one and with both hands. Plasma noradrenaline and adrenaline levels showed similar elevations in response to handgrip performed with the right hand and with both hands, while during the exercise performed with the left hand the increase in the plasma catecholamine concentration was less pronounced. It was concluded that: (1) during sustained handgrip, performed in the sitting position by young healthy subjects, the stroke volume markedly decreases and cardiac output does not change significantly in spite of the increased HR; (2) the cardiovascular and sympatho-adrenal responses to static handgrip do not depend on the mass of contracting muscle when the same relative tension is developed.

The effect of 6-hydroxydopamine infused into the third cerebral ventricle on the plasma cortisol concentration in sheep subjected to repeated and prolonged stress stimuli.

It has previously been observed that sheep subjected to repeated and prolonged stress stimuli showed biphasic cortisol responses. On the first and second day of stimulation an elevation was observed, while on the subsequent days and on the day after the stimulation a marked suppression of plasma cortisol level and a disappearance of its circadian rhythm was noted. It was hypothesized that these changes in the secretion of the hormone were caused by the alteration of catecholaminergic systems in the CNS. To verify this suggestion chemical lesions of the catecholergic systems of the diencephalon were carried out by the infusion of 6-hydroxydopamine (6-OHDA) into the third cerebral ventricle and animals treated in this fashion were subjected to repeated and prolonged electrical mild footshocking (applied during 3 days). The pretreated animals lost the circadian rhythm in cortisol secretion on the days before as well as during and after the electrical stimulation. The animals pretreated with 6-OHDA showed a significant rise of the plasma cortisol level during stimulation. This rise, as the highest daily concentration, occurring within about 1 h after the beginning of footshocking, was significantly accelerated in time with respect to the physiological acrophase, occurring in the early morning hours at the end of prestimulatory days. On the other hand, the pretreated animals did not show the decrease of plasma cortisol levels on the day after the stimulation, observed in normal non-pretreated ones.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in circadian rhythm and suppression of the plasma cortisol level after prolonged stress in the sheep.

Diurnal variations in the plasma cortisol level were studied in anoestrous, pro-oestrous and pregnant ewes subjected to weak electric stimulation of the fore-limbs 9 h daily for 3 consecutive days. In non-pregnant ewes the cortisol level rose on each of the 3 days when the stimulation was applied and then decreased on the day following the stimulation. A similar decrease in plasma cortisol concentrations in pregnant ewes appeared on the second day of footshocking. The acrophase of the circadian rhythm on electrostimulation days was synchronous with the time of application of footshocks; therefore, in stimulated ewes it was significantly accelerated compared to the prestimulatory day. A decrease in the plasma cortisol level in pro-oestrous and pregnant ewes was accompanied by disappearance of its normal rhythmicity. Since a normal plasma cortisol response to exogenous corticotrophin was noted after 3 days of footshocking it seems unlikely that the decrease in the cortisol level after prolonged stress was caused by exhaustion of the adrenal cortex. Some central mechanisms which could account for the biphasic changes in the plasma cortisol level and for disturbances of the hormone diurnal rhythmicity under conditions of prolonged stress are discussed.