Enhanced Coupling Within Gonadotropic and Adrenocorticotropic Axes by Moderate Exercise in Healthy Men

Effects of Normobaric Hypoxia of Varying Severity on Metabolic and Hormonal Responses Following Resistance Exercise in Men and Women

Background/Objectives: Resistance exercise under hypoxic conditions induces various metabolic and hormonal responses, yet the relationship between hypoxia severity and anabolic hormone responses remains unclear. This study aimed to assess the effects of a single bout of resistance exercise on metabolic and hormonal responses in normoxia and three levels of hypoxia in both men and women. Methods: The study involved 16 physically active individuals with at least two years of experience in recreational resistance training. The participants completed resistance exercise sessions in normoxia and normobaric hypoxia at simulated altitudes of 3000 m (H3000), 4000 m (H4000), and 5000 m (H5000). Blood levels of total testosterone (T), cortisol (C), growth hormone (GH), and metabolic variables were measured before and after exercise. Results: In women, severe hypoxia (H4000 and H5000) was found to significantly enhance post-exercise increases in T and GH compared to H3000 (p < 0.05), without affecting C levels. In men, hypoxia (regardless of intensity) did not significantly augment post-exercise changes in T and GH compared to normoxia. In H4000 conditions, an increase in C levels was observed (p < 0.05), leading to an unfavorable reduction in the T/C ratio. Additionally, a reduction in the total number of repetitions performed during the training session and a weakened metabolic response (lactate and creatine kinase) were observed in men at H5000. Conclusions: In women, severe hypoxia (H5000) was found to induce a pronounced hormonal response, particularly in GH levels. The use of severe hypoxia during resistance exercise appears unfavorable in men due to a reduced metabolic response, and diminished exercise capacity, coupled with a failure to induce more favorable changes in the secretion of anabolic hormones than in normoxic conditions.

Interleukin-2 drives cortisol secretion in an age-, dose-, and body composition-dependent way

BACKGROUND

Interleukin-2 (IL-2), one of the proinflammatory cytokines, is used in the treatment of certain malignancies. In some studies, transient increases in cortisol and ACTH secretion occurred. Thus, this agent may be used as an experimental probe of adrenal cortisol secretion.

OBJECTIVE

This study quantifies the effects of low and moderate doses of IL-2 on cortisol secretion and assesses the modulation by age, dose and body composition.

SITE

Mayo Clinical Translational Research Unit.

SUBJECTS

Study comprised 35 healthy men, 17 young and 18 older.

METHODS

Randomized prospective double-blind saline-controlled study of IL-2 administration in two doses with concurrent 10-min blood sampling for 24 h.

OUTCOME MEASURES

Deconvolution analysis and approximate entropy of cortisol secretion.

RESULTS

Low-dose IL-2 administration increased nocturnal pulsatile cortisol secretion from 1460 ± 160 to 2120 ± 220 nmol/L/8 h in young subjects and from 1680 ± 105 to 1960 ± 125 nmol/L/8 h (treatment P < 0.0001, but more in young than older, P = 0.02). Comparable results were obtained for total cortisol secretion (P treatment <0.0001, age effect P = 0.005). The higher IL-2 dose caused a large increase in young (P < 0.0001), but not in older (P = 0.90) subjects. This dose also increased approximate entropy from 0.877 ± 0.041 to 1.024 ± 0.049 (P = 0.008), pointing to reduced secretory orderliness. Incremental cortisol (nocturnal) secretion correlated negatively with visceral fat mass (R = -0.41, P = 0.019).

CONCLUSION

In healthy men, IL-2 injection drives pulsatile cortisol secretion in a dose-dependent way in young, but not older, individuals and erodes cortisol secretory orderliness at a higher dose in young subjects. Cortisol responses are diminished with increasing abdominal visceral fat mass.

Enkephalins and ACTH in the mammalian nervous system

The pentapeptides methionine-enkephalin and leucine-enkephalin belong to the opioid family of peptides, and the non-opiate peptide adrenocorticotropin hormone (ACTH) to the melanocortin peptide family. Enkephalins/ACTH are derived from pro-enkephalin, pro-dynorphin or pro-opiomelanocortin precursors and, via opioid and melanocortin receptors, are responsible for many biological activities. Enkephalins exhibit the highest affinity for the δ receptor, followed by the μ and κ receptors, whereas ACTH binds to the five subtypes of melanocortin receptor, and is the only member of the melanocortin family of peptides that binds to the melanocortin-receptor 2 (ACTH receptor). Enkephalins/ACTH and their receptors exhibit a widespread anatomical distribution. Enkephalins are involved in analgesia, angiogenesis, blood pressure, embryonic development, emotional behavior, feeding, hypoxia, limbic system modulation, neuroprotection, peristalsis, and wound repair; as well as in hepatoprotective, motor, neuroendocrine and respiratory mechanisms. ACTH plays a role in acetylcholine release, aggressive behavior, blood pressure, bone maintenance, hyperalgesia, feeding, fever, grooming, learning, lipolysis, memory, nerve injury repair, neuroprotection, sexual behavior, sleep, social behavior, tissue growth and stimulates the synthesis and secretion of glucocorticoids. Enkephalins/ACTH are also involved in many pathologies. Enkephalins are implicated in alcoholism, cancer, colitis, depression, heart failure, Huntington's disease, influenza A virus infection, ischemia, multiple sclerosis, and stress. ACTH plays a role in Addison's disease, alcoholism, cancer, Cushing's disease, dermatitis, encephalitis, epilepsy, Graves' disease, Guillain-Barré syndrome, multiple sclerosis, podocytopathies, and stress. In this review, we provide an updated description of the enkephalinergic and ACTH systems.