Exercise: a behavioral intervention to enhance brain health and plasticity

Exercise builds brain health: key roles of growth factor cascades and inflammation

Context.—Physical inactivity contributes to weight gain in adults, but whether
this relationship is true for children of different ethnic groups is not well
established.Objective.—To assess participation in vigorous activity and television watching
habits and their relationship to body weight and fatness in US children.Design.—Nationally representative cross-sectional survey with an in-person interview
and medical examination.Setting and Participants.—Between 1988 and 1994, 4063 children aged 8 through 16 years were examined
as part of the National Health and Nutrition Examination Survey III. Mexican
Americans and non-Hispanic blacks were oversampled to produce reliable estimates
for these groups.Main Outcome Measures.—Episodes of weekly vigorous activity and daily hours of television watched,
and their relationship to body mass index and body fatness.Results.—Eighty percent of US children reported performing 3 or more bouts of
vigorous activity each week. This rate was lower in non-Hispanic black and
Mexican American girls (69% and 73%, respectively). Twenty percent of US children
participated in 2 or fewer bouts of vigorous activity per week, and the rate
was higher in girls (26%) than in boys (17%). Overall, 26% of US children
watched 4 or more hours of television per day and 67% watched at least 2 hours
per day. Non-Hispanic black children had the highest rates of watching 4 or
more hours of television per day (42%). Boys and girls who watch 4 or more
hours of television each day had greater body fat (P<.001)
and had a greater body mass index (P<.001) than
those who watched less than 2 hours per day.Conclusions.—Many US children watch a great deal of television and are inadequately
vigorously active. Vigorous activity levels are lowest among girls, non-Hispanic
blacks, and Mexican Americans. Intervention strategies to promote lifelong
physical activity among US children are needed to stem the adverse health
consequences of inactivity.

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Relationship of Physical Activity and Television Watching With Body Weight and Level of Fatness Among Children Results From the Third National Health and Nutrition Examination Survey

During the last decade, the GH axis has become the compelling focus of remarkably active and broad-ranging basic and clinical research. Molecular and genetic models, the discovery of human GHRH and its receptor, the cloning of the GHRP receptor, and the clinical availability of recombinant GH and IGF-I have allowed surprisingly rapid advances in our knowledge of the neuroregulation of the GH-IGF-I axis in many pathophysiological contexts. The complexity of the GHRH/somatostatin-GH-IGF-I axis thus commends itself to more formalized modeling (154, 155), since the multivalent feedback-control activities are difficult to assimilate fully on an intuitive scale. Understanding the dynamic neuroendocrine mechanisms that direct the pulsatile secretion of this fundamental growth-promoting and metabolic hormone remains a critical goal, the realization of which is challenged by the exponentially accumulating matrix of experimental and clinical data in this arena. To the above end, we review here the pathophysiology of the GHRH somatostatin-GH-IGF-I feedback axis consisting of corresponding key neurotransmitters, neuromodulators, and metabolic effectors, and their cloned receptors and signaling pathways. We propose that this system is best viewed as a multivalent feedback network that is exquisitely sensitive to an array of neuroregulators and environmental stressors and genetic restraints. Feedback and feedforward mechanisms acting within the intact somatotropic axis mediate homeostatic control throughout the human lifetime and are disrupted in disease. Novel effectors of the GH axis, such as GHRPs, also offer promise as investigative probes and possible therapeutic agents. Further understanding of the mechanisms of GH neuroregulation will likely allow development of progressively more specific molecular and clinical tools for the diagnosis and treatment of various conditions in which GH secretion is regulated abnormally. Thus, we predict that unexpected and enriching insights in the domain of the neuroendocrine pathophysiology of the GH axis are likely be achieved in the succeeding decades of basic and clinical research.

Pathophysiology of the neuroregulation of growth hormone secretion in experimental animals and the human

I. Introduction II. Characteristics of the IGFBPs III. Target Cell Actions of the IGFBPs A. To modulate IGF actions B. To facilitate storage of IGFs in extracellular matrices C. To exert IGF-independent effects IV. IGF-IGFBP Complexes in Biological Fluids A. Serum B. Milk C. Urine D. Cerebrospinal fluid (CSF) E. Follicular fluid F. Amniotic fluid G. Lymph H. Seminal fluid I. Other biological fluids V. Assays for Circulating Levels of IGFBP A. Western ligand blotting B. Western immunoblotting C. RIA D. Immunoradiometric assay (IRMA) VI. Relative Distribution of IGFBPs in Serum VII. Regulation of Serum IGFBPs A. Physiological conditions B. Development and aging C. Hormonal effects: mechanisms D. Pathological conditions VIII. IGFBP Proteases in Circulation A. Proteases under normal conditions B. Pregnancy-associated proteases C. Proteases under catabolic and disease states IX. Endocrine Functions of IGFBPs in Serum A. To prevent insulin-like effects B. To increase the half-lives of IGFs C. To control the tra...

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Insulin-Like Growth Factor-Binding Proteins in Serum and Other Biological Fluids: Regulation and Functions

We hypothesized that circulating GH would increase only if a threshold of work intensity [corresponding to the anaerobic or lactate threshold (LT)] was exceeded. Ten healthy male volunteers (18-35 yr) first performed ramp-type progressive cycle-ergometer exercise to determine the LT and the maximal oxygen uptake. On subsequent mornings after an overnight fast, each subject performed bouts of 1, 5, and 10 min constant work rate exercise of either high intensity (above LT) or low intensity (below LT). A 1-h interval separated exercise bouts. Gas exchange (breath-by-breath), GH, immunoreactive insulin, glucose, lactate, pyruvate, and epinephrine and norepinephrine were measured at regular intervals. After the 10-min bouts of high compared with low intensity exercise, lactate was 7.2 +/- 3.7 mmol/L vs. 1.4 +/- 1.3, P less than 0.05; epinephrine was 1,113 +/- 519 pmol/L vs. 496 +/- 273, P less than 0.05; and norepinephrine was 7.89 +/- 3.45 nmole/L vs. 2.83 +/- 1.34, P less than 0.05. GH did not increase significantly from preexercise baseline during low intensity exercise (e.g., GH after 10-min low intensity exercise changed from baseline values by 1.5 +/- 2.0 micrograms/L, NS). Although lactate was elevated after 5-min of high intensity exercise, peak GH was significantly elevated (mean increase above baseline of 7.7 +/- 2.4 micrograms/L, P less than 0.05) only after 10 min of high intensity exercise (increases in 9 of 10 subjects). The GH increase occurred despite simultaneous increases in both IRI and glucose. A minimum duration of 10 min, high intensity exercise consistently increased circulating GH in adult males.

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Effect of low and high intensity exercise on circulating growth hormone in men

We measured circulating levels of the GH insulin-like growth factor (IGF) system in response to brief exercise of different intensities. Ten males (mean age 28 +/- 5 yr) were studied on three separate occasions: once under resting conditions (control) and once each performing 10 min of low- or high-intensity exercise. Blood samples were assayed by RIA for GH, IGF-I and -II, IGF-binding protein-3 (IGFBP-3), and IGFBP-3 proteolytic activity. After 10 min of low-intensity exercise, IGF-I and IGFBP-3 had increased over preexercise baseline by 7.7 +/- 2.7% (P < 0.05) and 12.5 +/- 3.3% (P < 0.004), respectively. After 10 min of high-intensity exercise, all measured components of the IGF system were increased: IGF-I by 13.3 +/- 3.2% (P < 0.002), IGF-II by 15.7 +/- 3.1 (P < 0.01), and IGFBP-3 by 23 +/- 6% (P < 0.001). IGFBP-3 proteolytic activity also was increased (44 +/- 14% above baseline, P < 0.05). GH reached its peak 10 min after the cessation of high-intensity exercise, unlike the earlier peaks of IGF-I and II. In summary: 1) brief exercise leads to small but significant increases in circulating IGF-I, IGF-II, IGFBP-3, and IGFBP-3 proteolysis; and 2) these responses may be influenced by exercise intensity. The IGF responses seem to be unrelated to GH. Acute exercise-induced proteolysis of IGFBP-3 may contribute to anabolic effects of physical activity by increasing the bioavailability of IGF-I.

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Acute effect of brief low- and high-intensity exercise on circulating insulin-like growth factor (IGF) I, II, and IGF-binding protein-3 and its proteolysis in young healthy men

https://escholarship.org/content/qt2314s3h1/qt2314s3h1.pdf?t=otndiz

Abnormal dynamic cardiorespiratory responses to exercise in pediatric patients after Fontan procedure

Hornum, Mette, Dan M. Cooper, Jo Anne Brasel, Alina Bueno, and Kathy E. Sietsema. Exercise-induced changes in circulating growth factors and cyclic variation in plasma estradiol in women.J. Appl. P...

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Exercise-induced changes in circulating growth factors with cyclic variation in plasma estradiol in women.

The health promoting, anabolic effects of physical activity may be mediated, in part, by an exercise-associated increase in GH. However, little is known about the acute effects of diet on exercise-induced GH release. We hypothesized that a single meal could attenuate the GH response to exercise by modulating substances like somatostatin, insulin, or glucose. Eleven healthy young adults performed 10 min of high intensity, standardized cycle ergometry in the morning following an overnight fast. On separate days they ingested a noncaloric placebo liquid meal or an isovolemic, isocaloric liquid meal high in either fat or glucose. Venous blood samples were obtained before and for 90 min after exercise began, whereas gas exchange data were measured breath by breath. Peak mean oxygen consumption (VO2) was, on average, 9-fold greater than preexercise levels in all groups. Although there was no difference in preexercise GH levels, mean peak, postexercise GH was 54% lower after the high-fat meal compared with placebo (P < 0.01). Modest decreases in GH response to exercise after the high-glucose meal were not statistically significant. Mean serum somatostatin was significantly higher after the high-fat meal compared with both high glucose and placebo meals. This study demonstrates that exercise-induced GH release can be significantly attenuated by the contents of a single preexercise meal. The high fat meal increased circulating somatostatin and was associated with an inhibition of the GH secretion. The data provide a possible specific mechanism to explain how diet can acutely modulate the anabolic effects of exercise.

Dan M. Cooper

Papers

Effect of low and high intensity exercise on circulating growth hormone in men

Acute effect of brief low- and high-intensity exercise on circulating insulin-like growth factor (IGF) I, II, and IGF-binding protein-3 and its proteolysis in young healthy men

Abnormal dynamic cardiorespiratory responses to exercise in pediatric patients after Fontan procedure

Exercise-induced changes in circulating growth factors with cyclic variation in plasma estradiol in women.

Acute effects of high fat and high glucose meals on the growth hormone response to exercise.