Effects of acute caloric restriction compared to caloric balance on the temporal response of the IGF-I system

Influence of smoking status on acute biomarker responses to successive days of arduous military training

INTRODUCTION

Habitual smoking is highly prevalent in military populations despite its association with poorer training outcomes. Smoking imposes challenges on the immune and endocrine systems which could alter how smokers acutely respond to, and recover from, intensive exercise particularly over multiple days of training.

METHODS

Over a two-day period, 35 male British Army recruits (age 22±3 years; mass 76.9±8.0 kg; height 1.78±0.06 m; 15 smokers) completed a 16.1 km loaded march (19.1 kg additional mass) on the first morning and a best-effort 3.2 km 'log race' (carrying a 60 kg log between six and eight people) on the subsequent morning. Blood samples were obtained on waking and immediately postexercise on both days and analysed for C reactive protein (CRP), interleukin 6 (IL-6), testosterone to cortisol ratio and insulin-like growth factor 1 (IGF-1).

RESULTS

Independent of smoking group, the exercise bouts on both days evoked significant increases in IL-6 (p<0.001) and decreases in testosterone to cortisol ratio (p<0.05). CRP concentrations on day 2 were significantly higher than both time points on day 1 (p<0.001), and a 9% decline in IGF-1 occurred over the two-day period, but was not significant (p=0.063). No significant differences were observed between smokers and non-smokers (p>0.05).

CONCLUSIONS

Military-specific tasks elicited inflammatory and endocrine responses, with systemic CRP and IGF-1 indicating that the physiological stress generated during the first training day was still evident on the second day. Despite the well-established impacts of smoking on resting levels of the markers examined, responses to two days of arduous military-specific training did not differ by smoking status.

Association of Daily Eating Duration and Day-To-Day Variability in the Timing of Eating With Fatal Cancer Risk in Older Men

Meal timing has significant effects on health. However, whether meal timing is associated with the risk of developing and dying of cancer is not well-researched in humans. In the present study, we used data from 941 community-dwelling men aged 71 years who participated in the Uppsala Longitudinal Study of Adult Men to examine the association of meal timing with cancer morbidity and fatal cancer. The following meal timing variables were derived from 7-day food diaries: (i) daily eating duration, i.e., the time between the first and last eating episode of an arbitrary day; (ii) the calorically weighted midpoint of the daily eating interval, a proxy of when the eating window typically occurs during an arbitrary day; and (iii) the day-to-day variability in the timing of eating. We also assessed the reported daily energy intake reliability using the Goldberg method. During a mean observational period of 13.4 years, 277 men (29.4%) were diagnosed with cancer. Furthermore, 191 men (20%) died from cancer during 14.7 years of follow-up. As shown by Cox regression adjusted for potential confounders (e.g., smoking status and daily energy intake), men with reliable dietary reports whose daily eating intervals were on average 13 h long had a 2.3-fold greater fatal cancer risk than men whose daily eating windows were on average about 11 h long. We also found that men with an average day-to-day variability in the timing of eating of 48 to 74 min had a 2- to 2.2-fold higher fatal cancer risk than those with the lowest average day-to-day variability in the timing of eating (i.e., 23 min). No clear associations were found in men with inadequate dietary reports, emphasizing the need to consider the reliability of dietary records in nutritional epidemiology. To fully unlock its potential, studies are needed to test whether recommendations to time-restrict the 24-h eating interval and reduce day-to-day variability in the timing of eating can meaningfully alter the risk of death due to cancer.

Fasting reduces the incidence of vincristine-associated adverse events in dogs

Fasting has been shown to decrease chemotherapy‐associated adverse events (AEs), in part through insulin‐like growth factor (IGF‐1) reduction, and may induce a protective effect on normal cells during chemotherapy treatment in mice and people. The purpose of this study was to evaluate the effect of fasting on constitutional, bone marrow and gastrointestinal (GI) AEs, and serum glucose, IGF‐1 and insulin levels in dogs receiving vincristine. The study was a prospective, crossover clinical trial in tumour‐bearing dogs. Dogs were randomized to be fasted for 24 to 28 hours prior to and 6 hours following their first or second vincristine treatment, and fed normally for the alternate dose. A significant reduction in nausea, anorexia, lethargy and serum insulin was observed when dogs were fasted; however, no significant differences were found in other GI symptoms, neutrophil count, serum glucose or IGF‐1. Fasting prior to vincristine therapy is a safe and effective treatment modality that helped mitigate constitutional and GI AEs in tumour‐bearing dogs.

A review of nutrition and dietary interventions in oncology

The complex cellular mechanisms and inter-related pathways of cancer proliferation, evasion, and metastasis remain an emerging field of research. Over the last several decades, nutritional research has prominent role in identifying emerging adjuvant therapies in our fight against cancer. Nutritional and dietary interventions are being explored to improve the morbidity and mortality for cancer patients worldwide. In this review, we examine several dietary interventions and their proposed mechanisms against cancer as well as identifying limitations in the currently available literature. This review provides a comprehensive review of the cancer metabolism, dietary interventions used during cancer treatment, anti metabolic drugs, and their impact on nutritional deficiencies along with a critical review of the following diets: caloric restriction, intermittent fasting, ketogenic diet, Mediterranean diet, Japanese diet, and vegan diet.

Effects of Dietary Protein Quantity on Bone Quantity following Weight Loss: A Systematic Review and Meta-analysis

Research supports the hypothesis that higher total protein intake during weight loss promotes retention of lean soft tissue, but the effect of dietary protein quantity on bone mass, a lean hard tissue, is inconsistent. The purpose of this systematic review and meta-analysis was to assess the effect of dietary protein quantity [higher protein (HP): ≥25% of energy from protein or ≥1.0 g · kg body wt-1 · d-1; normal protein (NP): <25% of energy from protein or <1.0 g · kg body wt-1 · d-1] on changes in bone mineral density (BMD) and content (BMC; total body, lumbar spine, total hip, femoral neck) following a prescribed energy restriction. We hypothesized that an HP diet would attenuate the loss of BMD/BMC following weight loss in comparison to an NP diet. Two researchers systematically and independently screened 2366 publications from PubMed, Cochrane, Scopus, CINAHL, and Web of Science Core Collection and extracted data from 34 qualified publications. Inclusion criteria included the following: 1) healthy subjects ≥19 y; 2) a prescribed energy restriction; 3) measurements of total protein intake, BMD, and BMC; and 4) an intervention duration of ≥3 mo. Data from 10 of the 34 publications with 2 groups of different total protein intakes were extracted and used to conduct a random-effects model meta-analysis. A majority of publications (59%) showed a decrease in bone quantity following active weight loss, regardless of total protein intake. Statistically, the loss of total BMD (P = 0.016; weighted mean difference: +0.006 g/cm2; 95% CI: 0, 0.011 g/cm2) and lumbar spine BMD (P = 0.019; weighted mean difference: +0.017 g/cm2; 95% CI: 0.001, 0.033 g/cm2) was attenuated with an HP versus an NP weight-loss diet. However, the clinical significance is questionable given the modest weighted mean difference and study duration. Higher total protein intake does not exacerbate but may attenuate the loss of bone quantity following weight loss.

Circulating levels of the components of the GH/IGF-1/IGFBPs axis total and intact IGF-binding proteins (IGFBP) 3 and IGFBP 4 and total IGFBP 5, as well as PAPPA, PAPPA2 and Stanniocalcin-2 levels are not altered in response to energy deprivation and/or metreleptin administration in humans

OBJECTIVE

It remains unclear whether food deprivation induces changes in components of the GH/IGF-1/IGFBPs axis and if yes, which ones are mediated by leptin, an adipocyte secreted hormone regulating neuroendocrine response to energy deprivation in animals and humans. We aimed to investigate components of the axis that have not been studied to date, i.e. IGF-binding proteins (IGFBPs) and related proteases (total and intact IGFBP 3 and IGFBP 4, total IGFBP 5, PAPPA, PAPPA2 and Stanniocalcin-2), during acute (short-term fasting in healthy subjects) and chronic (women with hypothalamic amenorrhea [HA] due to excessive exercise) energy deprivation and whether metreleptin administration, in replacement, supraphysiologic or pharmacologic levels, may mediate any changes of circulating levels of the above molecules in healthy individuals and in women with hypothalamic amenorrhea.

METHODS

We studied: 1) 11 healthy men and women during three four day admissions i.e. a baseline admission in the fed isocaloric state and two admissions in the complete food deprivation state for 72-h with either placebo (resulting in a hypoleptinemic state) or metreleptin administration in doses designed to normalize circulating leptin levels for the duration of the study, 2) 15 healthy men and women during three 72-hour long admissions in a complete food deprivation state receiving three escalating doses of metreleptin designed to bring circulating leptin levels to physiologic, supraphysiologic, or pharmacologic levels, and 3) 18 women with HA randomized to either metreleptin treatment in replacement doses or placebo for nine months.

RESULTS

There were no significant changes in the circulating profiles of the above molecules in the fasting vs. fed state and/or with metreleptin administration during acute and chronic energy deprivation.

CONCLUSIONS

The studied components of the GH/IGF-1/IGFBPs axis are not affected by energy deprivation, leptin deficiency associated with energy deprivation, or by metreleptin administration in physiologic, supraphysiologic or pharmacologic doses.

Effects of short-term fasting on cancer treatment

Growing preclinical evidence shows that short-term fasting (STF) protects from toxicity while enhancing the efficacy of a variety of chemotherapeutic agents in the treatment of various tumour types. STF reinforces stress resistance of healthy cells, while tumor cells become even more sensitive to toxins, perhaps through shortage of nutrients to satisfy their needs in the context of high proliferation rates and/or loss of flexibility to respond to extreme circumstances. In humans, STF may be a feasible approach to enhance the efficacy and tolerability of chemotherapy. Clinical research evaluating the potential of STF is in its infancy. This review focuses on the molecular background, current knowledge and clinical trials evaluating the effects of STF in cancer treatment. Preliminary data show that STF is safe, but challenging in cancer patients receiving chemotherapy. Ongoing clinical trials need to unravel if STF can also diminish toxicity and increase efficacy of chemotherapeutic regimes in daily practice.

Role of IGF-binding proteins in regulating IGF responses to changes in metabolism

The IGF-binding protein family contains six members that share significant structural homology. Their principal function is to regulate the actions of IGF1 and IGF2. These proteins are present in plasma and extracellular fluids and regulate access of both IGF1 and II to the type I IGF receptor. Additionally, they have functions that are independent of their ability to bind IGFs. Each protein is regulated independently of IGF1 and IGF2, and this provides an important mechanism by which other hormones and physiologic variables can regulate IGF actions indirectly. Several members of the family are sensitive to changes in intermediary metabolism. Specifically the presence of obesity/insulin resistance can significantly alter the expression of these proteins. Similarly changes in nutrition or catabolism can alter their synthesis and degradation. Multiple hormones such as glucocorticoids, androgens, estrogen and insulin regulate IGFBP synthesis and bioavailability. In addition to their ability to regulate IGF access to receptors these proteins can bind to distinct cell surface proteins or proteins in extracellular matrix and several cellular functions are influenced by these interactions. IGFBPs can be transported intracellularly and interact with nuclear proteins to alter cellular physiology. In pathophysiologic states, there is significant dysregulation between the changes in IGFBP synthesis and bioavailability and changes in IGF1 and IGF2. These discordant changes can lead to marked alterations in IGF action. Although binding protein physiology and pathophysiology are complex, experimental results have provided an important avenue for understanding how IGF actions are regulated in a variety of physiologic and pathophysiologic conditions.

Arginine reverses growth hormone resistance through the inhibition of toll-like receptor 4-mediated inflammatory pathway

OBJECTIVE

Growth hormone stimulates growth by increasing insulin-like growth factor 1 expression and secretion. In the presence of insufficient nutrients, GH increases, whereas IGF-1 expression becomes severely suppressed, leading to GH resistance. This study aimed to explore the effect of arginine (Arg) on GH resistance during malnutrition and to describe its underlying mechanism.

METHODS

C57BL/6J mice were injected intraperitoneally with Arg for 1h or subjected to caloric restriction with Arg supplement in drinking water for 18days. HepG2 cells were exposed to different Arg concentrations for 24h. Signaling pathway agonists/inhibitors, siRNA, and overexpression plasmids were used to investigate the underlying molecular mechanism. Liver-specific toll-like receptor (TLR4) knockout mice were utilized to clarify the role of TLR4 in Arg-induced IGF-I expression and secretion.

RESULTS

Arg inhibited the TLR4 downstream pathway by binding to TLR4 and consequently activated Janus kinase 2/signal transducer and activator of transcription 5 signaling pathway. As a result, IGF-1 transcription and secretion increased. Arg activity was absent in liver-specific TLR4 knockout mice and was greatly suppressed in liver with overexpressed TLR4, suggesting that hepatic TLR4 was required and sufficient to induce GH resistance. By contrast, the mammalian target of rapamycin pathway was unnecessary for Arg activity. Arg not only significantly increased IGF-1 expression and secretion under acute fasting and chronic CR conditions but also attenuated body weight loss.

CONCLUSIONS

Our results demonstrate a previously unappreciated pathway involving Arg that reverses GH resistance and alleviates malnutrition-induced growth restriction through the inhibition of TLR4-mediated inflammatory pathway.

Resistance training during a 12-week protein supplemented VLCD treatment enhances weight-loss outcomes in obese patients

BACKGROUND

This investigation evaluated the efficacy by which resistance training enhances body composition, metabolic, and functional outcomes for obese patients undergoing a 12-week medically supervised hypocaloric treatment.

METHODS

This was a single-blind, randomized, parallel-group prospective trial. Morbidly obese patients were prescribed a 12-week proprietary very low calorie diet (VLCD) treatment (Optifast^®) with supplemental protein (1120 kcals/day) and were placed in one of two groups for 14 weeks: 1) Standard Treatment Control (CON) (n = 5) or 2) Resistance Training (RT) (n = 6). Both groups underwent a pedometer-based walking program; however only RT performed resistance training 3 days/week for 12 weeks. Body composition, resting energy expenditure (REE), neuromuscular function, and serum biomarkers were measured at weeks 0, 6, and 13.

RESULTS

Both groups exhibited a significant loss of total body mass (TBM) (CON: -19.4 ± 2.3 kg, p = 0.0009 vs. RT: -15.8 ± 1.5 kg, p = 0.0002) and fat mass (FM) (CON: -14.7 ± 1.8 kg, p = 0.0002 vs. RT: -15.1 ± 2.1 kg, p = 0.0002) with no group differences. CON lost 4.6 ± 0.8 kg (p = 0.004) of lean mass (LM) while RT demonstrated no changes. Group differences were found for the relative proportion of total weight-loss due to FM-loss (CON: 75.6 ± 3.4% vs. RT: 96.0 ± 6.0%, p = 0.03) and LM-loss (CON: 24.4 ± 3.2% vs. RT: 4.0 ± 6.5%, p = 0.03). CON demonstrated a 328.6 ± 72.7 kcal/day (-14.3 ± 2.4%) (p = 0.02) decrease in REE while RT exhibited a non-significant decrease of 4.6 ± 1.6% (p = 0.78). RT demonstrated greater improvements in all measures of contractile function and strength when compared to CON (p < 0.05). At post-treatment, RT exhibited greater serum free fatty acids (p = 0.01), glycerol (p = 0.003), and β-hydroxybutyrate (p = 0.005) than CON.

CONCLUSION

Resistance training was advantageous for weight-loss composition by preservation of LM without compromising overall weight- or fat-loss in morbidly obese men and women undergoing a protein supplemented VLCD. These changes accompanied positive adaptations for resting metabolism and muscular function.

Caloric restriction stabilizes body weight and accelerates behavioral recovery in aged rats after focal ischemia

Obesity and hyperinsulinemia are risk factors for stroke. We tested the hypothesis that caloric restriction, which reduces the incidence of age‐related obesity and metabolic syndrome, may represent an efficient and cost‐effective strategy for preventing stroke and its devastating consequences. To this end, we placed aged, obese Sprague‐Dawley aged rats on a calorie‐restricted diet for 8 weeks prior to the experimental infarction. Stroke in this animal model caused a progressive decrease in weight that reached a minimum at day 6 for the young rats, and at day 10 for the aged, ad libitum‐fed rats. However, in aged animals that were calorie‐restricted prior to stroke, body weight did not decrease after stroke, but we noted accelerated body weight gain shortly thereafter starting at day 5 poststroke. Moreover, calorie‐restricted aged animals showed improved behavioral recovery in tasks requiring complex sensorimotor skills, or in tasks requiring cutaneous sensitivity and sensorimotor integration or spatial memory. Likewise, calorie‐restricted aged rats showed significant poststroke increases in serum glucose, insulin, and IGF1 levels, as well as CR‐specific changes in the expression of gene transcripts involved in glycogen metabolism, IGF signaling, apoptosis, arteriogenesis, and hypoxia. In conclusion, our study shows that recovery from stroke is enhanced in aged rats by a dietary regimen that reduces body weight prior to infarct.

Physiological parameters regulating circulating levels of the IGFBP-4/Stanniocalcin-2/PAPP-A axis

BACKGROUND

Insulin Growth Factor Binding Protein 4 (IGFBP-4), Stanniocalcin-2 (STC-2) and Pregnancy-Associated Plasma Protein-A (PAPP-A) have a well-documented involvement in several physiological functions in humans but predictors of their circulating levels remain largely unknown. We aimed to identify anthropometric and biochemical parameters associated with circulating levels of IGFBP-4/STC-2/PAPP-A axis (ISPa) cross-sectionally and to study their day-night variation and their regulation in response to mixed meal and exercise.

METHODS

One hundred twenty two healthy individuals were evaluated cross-sectionally. Subgroups were subjected to standardized mixed meal ingestion in increasing quantities of 125mL or 250mL, or aerobic exercise for 30min, or day-night rhythm study. Main outcome measurements were circulating IGFBP-4 (total and intact), STC-2 and PAPP-A levels.

RESULTS

In multivariate models, the main predictors of serum total IGFBP-4 were PAPP-A and female gender. Intact IGFBP-4 was positively associated with serum creatinine. Height was inversely and female gender and % of total body fat were positively correlated with STC-2. PAPP-A decreased after ingesting both the 125mL (p=0.03) and 250mL quantities (p=0.001), while total IGFBP-4 was reduced after the 250mL quantity (p=0.001). Exercise increased STC-2 and PAPP-A levels (p<0.001 for both). Intact, and to a lesser extent total, IGFBP-4 displayed a cortisol-like day/night variation.

CONCLUSIONS

We report for the first time anthropometric and physiological modulators of ISPa serum levels in healthy humans.

High insulin-like growth factor-binding protein-1 (IGFBP-1) is associated with low relative muscle mass in older women

OBJECTIVE

Skeletal muscles serve several important roles in maintaining good health. Insulin-like growth factor-1 (IGF-1) is a promoter of protein synthesis in skeletal muscle. Its binding protein, Insulin-like growth factor-binding protein-1 (IGFBP-1) can be one determinant of IGF-1 activity. In the present study we investigate the association between serum IGFBP-1 and muscle mass.

DESIGN

Cross-sectional analysis of 4908 women, between 55 and 85years old, participating in the Swedish Mammography Cohort-Clinical.

METHODS

We defined low relative muscle mass (LRMM) as an appendicular lean mass divided by height squared of less than 5.45 (kg/m²), assessed by dual energy x-ray absorptiometry. IGFBP-1 was measured by radioimmunoassay. Logistic regression was used to calculate odds-ratios of LRMM across quartiles of IGFBP-1.

RESULTS

The odds of LRMM increased across quartiles of IGFBP-1. In the age-adjusted model the odds-ratio (OR) of LRMM was 3.41 (95% CI: 2.55-4.56), comparing the highest to the lowest quartile. This estimate was attenuated in multivariate models (OR: 1.84, 95% CI: 1.34-2.53), mainly due to inclusion of fat mass index.

CONCLUSION

Women with higher IGFBP-1 were more likely to have a low relative muscle mass. High IGFBP-1 may be a marker of a catabolic state.

Dietary restriction improves repopulation but impairs lymphoid differentiation capacity of hematopoietic stem cells in early aging

Dietary restriction (DR) improves health, delays tissue aging, and elongates survival in flies and worms. However, studies on laboratory mice and nonhuman primates revealed ambiguous effects of DR on lifespan despite improvements in health parameters. In this study, we analyzed consequences of adult-onset DR (24 h to 1 yr) on hematopoietic stem cell (HSC) function. DR ameliorated HSC aging phenotypes, such as the increase in number of HSCs and the skewing toward myeloid-biased HSCs during aging. Furthermore, DR increased HSC quiescence and improved the maintenance of the repopulation capacity of HSCs during aging. In contrast to these beneficial effects, DR strongly impaired HSC differentiation into lymphoid lineages and particularly inhibited the proliferation of lymphoid progenitors, resulting in decreased production of peripheral B lymphocytes and impaired immune function. The study shows that DR-dependent suppression of growth factors and interleukins mediates these divergent effects caused by DR. Supplementation of insulin-like growth factor 1 partially reverted the DR-induced quiescence of HSCs, whereas IL-6/IL-7 substitutions rescued the impairment of B lymphopoiesis exposed to DR. Together, these findings delineate positive and negative effects of long-term DR on HSC functionality involving distinct stress and growth signaling pathways.

Nutritionally-induced catch-up growth

Malnutrition is considered a leading cause of growth attenuation in children. When food is replenished, spontaneous catch-up (CU) growth usually occurs, bringing the child back to its original growth trajectory. However, in some cases, the CU growth is not complete, leading to a permanent growth deficit. This review summarizes our current knowledge regarding the mechanism regulating nutrition and growth, including systemic factors, such as insulin, growth hormone, insulin- like growth factor-1, vitamin D, fibroblast growth factor-21, etc., and local mechanisms, including autophagy, as well as regulators of transcription, protein synthesis, miRNAs and epigenetics. Studying the molecular mechanisms regulating CU growth may lead to the establishment of better nutritional and therapeutic regimens for more effective CU growth in children with malnutrition and growth abnormalities. It will be fascinating to follow this research in the coming years and to translate the knowledge gained to clinical benefit.

High protein diets do not attenuate decrements in testosterone and IGF-I during energy deficit

OBJECTIVE

Energy deficit (ED) diminishes fat-free mass (FFM) with concomitant reductions in anabolic hormone secretion. A modest increase in protein to recommended dietary allowance (RDA) levels during ED minimally attenuates decrements in insulin-like growth factor-I (IGF-I). The impact of dietary protein above the RDA on circulating anabolic hormones and their relationships with FFM in response to ED are not well described.

MATERIALS/METHODS

Thirty-three adults were assigned diets providing protein at 0.8 (RDA), 1.6 (2×-RDA), and 2.4 (3×-RDA) g/kg/d for 31days. Testosterone, sex-hormone binding globulin (SHBG) and IGF-I system components were assessed after a 10-day period of weight-maintenance (WM) and after a 21-day period of ED (40%) achieved by an increase in energy expenditure and decreased energy intake. Associations between the change in FFM and anabolic hormone levels were determined.

RESULTS

As compared to WM and regardless of dietary protein intake, total and free testosterone, total IGF-I, and acid-labile subunit decreased (P<0.05), whereas SHBG and IGF binding proteins-1, -2, and -3 increased (P<0.05) during ED. There were no energy-by-protein interactions on any hormones or IGF-I system components measured. Changes in FFM in response to ED were negatively associated with acid-labile subunit (ALS) (r=-0.62, P<0.05) in 2×-RDA; however, no other relationships were observed.

CONCLUSION

Consuming a high protein diet does not impact the androgenic and IGF-I system response to ED. These data suggest that the protective effects of high protein diets on FFM during ED are likely not influenced by anabolic hormone concentrations.

Recovery of endocrine and inflammatory mediators following an extended energy deficit

CONTEXT

Due to current operational requirements, elite soldiers deploy quickly after completing arduous training courses. Therefore, it is imperative that endocrine and inflammatory mediators have fully recovered.

OBJECTIVE

Our objective was to determine whether a short-term (2-6 wk) recovery period was sufficient to restore endocrine and inflammatory homeostasis after sustained energy deficit.

DESIGN

Before and immediately after the course, serum concentrations of inflammatory and endocrine markers were taken along with anthropometric measures prior to and immediately after the Army Ranger course. In addition, nine soldiers were assessed between 2 and 6 weeks after the course.

SETTING

This research occurred in a field setting during an intensive 8-week military training course characterized by high-energy expenditure, energy restriction, and sleep deprivation (U.S. Army Ranger School).

PARTICIPANTS

Twenty-three male soldiers (23.0 ± 2.8 y; 177.6 ± 7.9 cm; 81.0 ± 9.6 kg, 16.8 ± 3.9% body fat) participated in this study.

INTERVENTIONS

There were no interventions used in this research.

OUTCOME MEASURES AND RESULTS

Significant changes occurred in circulating total testosterone (-70%), brain-derived neurotrophic factor (-33%), total IGF-1 (-38.7%), free IGF-1 (-41%), IGF binding protein (IGFBP-6; -23.4%), sex-hormone binding globulin (+46%), thyroid stimulating hormone (+85%), IGFBP-1 (+534.4%), IGFBP-2 (+98.3%), IGFBP-3 (+14.7%), IL-4 (+135%), IL-6 (+217%), and IL-8 (+101%). Significant changes in body mass (-8%), bicep (-14%), forearm (-5%), thigh (-7%), and calf (-2%) circumferences, sum of skinfolds (-52%), and percentage body fat (-54%). All anthropometric, inflammatory, and hormonal values, except T3, were restored to baseline levels within 2-6 weeks after the course.

CONCLUSIONS

Endocrine markers and anthropometric measures were degraded, and inflammatory mediators increased after an extended energy deficit. A short-term recovery of 2-6 weeks was sufficient to restore these mediators.

Effect of GH/IGF-1 on Bone Metabolism and Osteoporsosis

Background. Growth hormone (GH) and insulin-like growth factor (IGF-1) are fundamental in skeletal growth during puberty and bone health throughout life. GH increases tissue formation by acting directly and indirectly on target cells; IGF-1 is a critical mediator of bone growth. Clinical studies reporting the use of GH and IGF-1 in osteoporosis and fracture healing are outlined. Methods. A Pubmed search revealed 39 clinical studies reporting the effects of GH and IGF-1 administration on bone metabolism in osteopenic and osteoporotic human subjects and on bone healing in operated patients with normal GH secretion. Eighteen clinical studies considered the effect with GH treatment, fourteen studies reported the clinical effects with IGF-1 administration, and seven related to the GH/IGF-1 effect on bone healing. Results. Both GH and IGF-1 administration significantly increased bone resorption and bone formation in the most studies. GH/IGF-1 administration in patients with hip or tibial fractures resulted in increased bone healing, rapid clinical improvements. Some conflicting results were evidenced. Conclusions. GH and IGF-1 therapy has a significant anabolic effect. GH administration for the treatment of osteoporosis and bone fractures may greatly improve clinical outcome. GH interacts with sex steroids in the anabolic process. GH resistance process is considered.