Association of insulin-like growth factor-I with body composition, weight history, and past health behaviors in the very old: the Framingham Heart Study

Association of a Blood-Based Aging Biomarker Index With Death and Chronic Disease: Cardiovascular Health Study

BACKGROUND

A goal of gerontology is to discover phenotypes that reflect biological aging distinct from disease pathogenesis. Biomarkers that are strongly associated with mortality could be used to define such a phenotype. However, the relation of such an index with multiple chronic conditions warrants further exploration.

METHODS

A biomarker index (BI) was constructed in the Cardiovascular Health Study (N = 3 197), with a mean age of 74 years. The BI incorporated circulating levels of new biomarkers, including insulin-like growth factor-1, interleukin-6, amino-terminal pro-B-type natriuretic peptide, cystatin-C, C-reactive protein, tumor necrosis factor-alpha soluble receptor 1, fasting insulin, and fasting glucose, and was built based on their relationships with mortality. Cox proportional hazards models predicting a composite of death and chronic disease involving cardiovascular disease, dementia, and cancer were calculated with 6 years of follow-up.

RESULTS

The hazard ratio (HR, 95% CI) for the composite outcome of death or chronic disease per category of BI was 1.65 (1.52, 1.80) and 1.75 (1.58, 1.94) in women and men, respectively. The HR (95% CI) per 5 years of age was 1.57 (1.48, 1.67) and 1.55 (1.44, 1.67) in women and men, respectively. Moreover, BI could attenuate the effect of age on the composite outcome by 16.7% and 22.0% in women and men, respectively.

CONCLUSIONS

Biomarker index was significantly and independently associated with a composite outcome of death and chronic disease, and attenuated the effect of age. The BI that is composed of plasma biomarkers may be a practical intermediate phenotype for interventions aiming to modify the course of aging.

To Be Frail or Not to Be Frail: This Is the Question-A Critical Narrative Review of Frailty

Many factors have contributed to rendering frailty an emerging, relevant, and very popular concept. First, many pandemics that have affected humanity in history, including COVID-19, most recently, have had more severe effects on frail people compared to non-frail ones. Second, the increase in human life expectancy observed in many developed countries, including Italy has led to a rise in the percentage of the older population that is more likely to be frail, which is why frailty is much a more common concern among geriatricians compared to other the various health-care professionals. Third, the stratification of people according to the occurrence and the degree of frailty allows healthcare decision makers to adequately plan for the allocation of available human professional and economic resources. Since frailty is considered to be fully preventable, there are relevant consequences in terms of potential benefits both in terms of the clinical outcome and healthcare costs. Frailty is becoming a popular, pervasive, and almost omnipresent concept in many different contexts, including clinical medicine, physical health, lifestyle behavior, mental health, health policy, and socio-economic planning sciences. The emergence of the new "science of frailty" has been recently acknowledged. However, there is still debate on the exact definition of frailty, the pathogenic mechanisms involved, the most appropriate method to assess frailty, and consequently, who should be considered frail. This narrative review aims to analyze frailty from many different aspects and points of view, with a special focus on the proposed pathogenic mechanisms, the various factors that have been considered in the assessment of frailty, and the emerging role of biomarkers in the early recognition of frailty, particularly on the role of mitochondria. According to the extensive literature on this topic, it is clear that frailty is a very complex syndrome, involving many different domains and affecting multiple physiological systems. Therefore, its management should be directed towards a comprehensive and multifaceted holistic approach and a personalized intervention strategy to slow down its progression or even to completely reverse the course of this condition.

Association of Biomarker and Physiologic Indices With Mortality in Older Adults: Cardiovascular Health Study

Background

A goal of gerontology is discovering aging phenotypes that reflect biological aging distinct from disease pathogenesis. Biomarkers that strongly and independently associated with mortality and that statistically attenuated chronologic age could be used to define such a phenotype. We determined the association of a Biomarker Index (BI) with mortality and compared it with a validated Physiologic Index (PI) in older adults.

Methods

The indices were constructed in the Cardiovascular Health Study, mean (SD) age 74.5 (5.1) years. The BI incorporated circulating levels of new biomarkers, including insulin-like growth factor-1, insulin-like growth factor-binding protein 3, amino-terminal pro-B-type natriuretic peptide, dehydroepiandrosterone sulfate, and interleukin-6, and was built in test (N = 2,197) and validation (N = 1,124) samples. The PI included carotid intima-media thickness, pulmonary capacity, brain white matter grade, cystatin-C, and fasting glucose. Multivariable Cox proportional hazards models predicting death were calculated with 10 years of follow-up.

Results

In separate age-adjusted models, the hazard ratio for mortality per point of the BI was 1.30 (95% confidence interval 1.25, 1.34) and the BI attenuated age by 25%. The hazard ratio for the PI was 1.28 (1.24, 1.33; 29% age attenuation). In the same model, the hazard ratio for the BI was 1.23 (1.18, 1.28) and for the PI was 1.22 (1.17, 1.26), and age was attenuated 42.5%. Associations persisted after further adjustment.

Conclusions

The BI and PI were significantly and independently associated with mortality. Both attenuated the age effect on mortality substantially. The indices may be feasible phenotypes for developing interventions hoping to alter the trajectory of aging.

Self-Reported Physical Activity and Relations to Growth and Neurotrophic Factors in Diabetes Mellitus: The Framingham Offspring Study

AIMS

Circulating insulin-like growth factor- (IGF-) 1, vascular endothelial growth factor (VEGF), and brain-derived neurotrophic factor (BDNF) levels are often lower in individuals with diabetes mellitus (DM) and are important for repairing vascular and neuronal dysfunction. The purpose of this investigation was to determine the cross-sectional relations of physical activity to circulating concentrations of IGF-1, VEGF, and BDNF in individuals with and without DM.

METHODS

In 1730 participants from the Framingham Offspring Study examination cycle 7, including those with DM (n = 179, mean age 64 years, 39% women) and without DM (n = 1551, mean age 60 years, 46% women), we related self-reported physical activity variables to circulating concentrations of IGF-1, VEGF, and BDNF using linear multivariable regression models. We also tested for interactions by age. Participants with prevalent cardiovascular disease, stroke, and dementia or taking hormone replacement therapy were excluded.

RESULTS

In participants with DM, more ambulatory physical activity was associated with higher IGF-1 levels (β ± standard error (SE) = 0.22 ± 0.08, p = 0.009), and more total physical activity was related to higher BDNF levels (β ± SE = 0.18 ± 0.08, p = 0.035), but physical activity was not significantly related to circulating VEGF. In participants without DM, no associations were observed. Moreover, in the examination of interactions by age, the association of ambulatory physical activity with IGF-1 levels was only observed in older adults with DM (age ≥ 60 years, β ± SE = 0.23 ± 0.11, p = 0.042) but not in middle-aged adults with DM (age < 60 years, β ± SE = 0.06 ± 0.13, p = 0.645).

CONCLUSION

Our results suggest that more physical activity is associated with higher circulating IGF-1 and BDNF in participants with DM. These results, dissecting interactions by both age and DM status, may also help to explain some of the inconsistent results in studies relating physical activity to growth and neurotrophic factors.

Serum Myostatin and IGF-1 as Gender-Specific Biomarkers of Frailty and Low Muscle Mass in Community-Dwelling Older Adults

OBJECTIVES

(i) To investigate serum myostatin (absolute and normalized for total body lean mass (TBLM)) and IGF-1 as biomarkers of frailty and low relative appendicular skeletal muscle mass (RASM) in older adults, and; (ii) to examine gender differences in the association of serum myostatin and IGF-1 levels with frailty and low RASM.

DESIGN

Cross-sectional study.

SETTING

The "Longitudinal Assessment of Biomarkers for characterization of early Sarcopenia and predicting frailty and functional decline in community-dwelling Asian older adults Study" (GERI-LABS) study in Singapore.

PARTICIPANTS

200 subjects aged 50 years and older residing in the community.

MEASUREMENTS

Frailty was assessed using the modified Fried criteria. Low RASM was defined using cutoffs for height-adjusted appendicular skeletal muscle mass measured by dual-energy X-ray absorptiometry as recommended by the Asian Working Group for Sarcopenia. Comorbidities, cognitive and functional performance, physical activity and nutritional status were assessed. Blood samples collected included serum myostatin, insulin-like growth factor 1 (IGF-1) and markers of inflammation (total white cell count, CRP, IL-6 and TNFaR1). Subjects were classified into 4 groups: Frail/Prefrail with low RASM (Frail/Low RASM), Frail/Prefrail with normal RASM (Frail/Normal RASM), Robust with low RASM (Robust/Low RASM) and Robust with normal RASM (Robust/Normal RASM).

RESULTS

63 (32%) subjects were classified as Frail/Low RASM, 53 (27%) Frail/Normal RASM, 28 (14%) Robust/Low RASM and 56 (28%) Robust/Normal RASM respectively. Frail/Low RASM subjects were older and had lower BMI compared to Frail/Normal RASM and robust subjects. Mean (SE) normalized myostatin levels were higher in Frail/Low RASM compared to Frail/Normal RASM subjects (1.0 (0.04) versus 0.84 (0.05) ng/ml/kg, P=0.01). Median (IQR) IGF-1 level was lower amongst Frail/Low RASM subjects compared to Frail/Normal RASM subjects (102.3, (77.7, 102.5) vs 119.7 (82.7, 146.0) ng/ml, P=0.046). No differences in myostatin or IGF-1 were observed among robust individuals with or without low muscle mass. In adjusted multinomial logistic regression models with Robust/Normal RASM as the reference group, myostatin (P=0.05) and IGF-1 (P=0.043) were associated with Frail/Low RASM status in the whole cohort. When stratified by gender, myostatin was significantly associated with Frail/Low RASM status in men only (P=0.03). In women, serum IGF-1 was associated with Frail/Low RASM status (P=0.046), but not myostatin (P=0.53).

CONCLUSION

Serum myostatin, normalized for TBLM in men and IGF-1 in women are potential biomarkers for frail individuals with low RASM, and may identify a target group for intervention.

The relationship between serum IGF-1, handgrip strength, physical performance and falls in elderly men and women

OBJECTIVE

Human aging is accompanied by a decrease in growth hormone secretion and serum insulin-like growth factor (IGF)-1 levels. Also, loss of muscle mass and strength and impairment of physical performance, ending in a state of frailty, are seen in elderly. We aimed to investigate whether handgrip strength, physical performance and recurrent falls are related to serum IGF-1 levels in community-dwelling elderly.

DESIGN

Observational cohort study (cross-sectional and prospective).

METHODS

We studied the association between IGF-1 and handgrip strength, physical performance and falls in participants of the Longitudinal Aging Study Amsterdam. A total of 1292 participants were included (633 men, 659 women). Serum IGF-1 levels were divided into quartiles (IGF-1-Q1 to IGF-1-Q4). Data on falls were collected prospectively for a period of 3 years. All analyses were stratified for age and physical activity and adjusted for relevant confounders.

RESULTS

Men with a low physical activity score in IGF-1-Q1 and IGF-1-Q2 of the younger age group had a lower handgrip strength compared to IGF-1-Q4. In younger more active males in IGF-1-Q2 physical performance was worse. Recurrent fallers were less prevalent in older, low active males with low IGF-1 levels. In females, recurrent fallers were more prevalent in older, more active females in IGF-1-Q2. IGF-1 quartile may predict changes in handgrip strength and physical performance in men and women.

CONCLUSIONS

Our results indicate that lower IGF-1 levels are associated with lower handgrip strength and worse physical performance, but less recurrent fallers especially in men. Associations were often more robust in IGF-1-Q2. Future studies on this topic are desirable.

Trajectories of IGF-I Predict Mortality in Older Adults: The Cardiovascular Health Study

Background

Disruption of insulin-like growth factor-I (IGF-I) increases health and life span in animal models, though this is unconfirmed in humans. If IGF-I stability indicates homeostasis, the absolute level of IGF-I may be less clinically relevant than maintaining an IGF-I setpoint.

Methods

Participants were 945 U.S. community-dwelling individuals aged ≥65 years enrolled in the Cardiovascular Health Study with IGF-I levels at 3-6 timepoints. We examined the association of baseline IGF-I level, trajectory slope, and variability around the trajectory with mortality.

Results

There were 633 deaths over median 11.3 years of follow-up. Lower IGF-I levels, declining or increasing slope, and increasing variability were each individually associated with higher mortality (all p < .001). In an adjusted model including all three trajectory parameters, baseline IGF-I levels <70 ng/mL (hazard ratio [HR] 1.58, 95% CI 1.28-1.96 relative to IGF-I levels of 170 ng/mL), steep declines and steep increases in trajectory slope (HR 2.22, 1.30-3.80 for a 15% decline; HR 1.40, 1.07-1.84 for a 10% decline; HR 1.80, 1.12-2.89 for a 15% increase; HR 1.31, 1.00-1.72 for a 10% increase, each vs no change), and variability ≥10% (HR 1.59, 1.09-2.32 for ≥ 30%; HR 1.36, 1.06-1.75 for 20%; and HR 1.17, 1.03-1.32 for 10% variability, each vs 0%) in IGF-I levels were independently associated with mortality.

Conclusions

In contrast to data from animal models, low IGF-I levels are associated with higher mortality in older humans. Irrespective of the actual IGF-I level, older individuals with stability of IGF-I levels have lower mortality than those whose IGF-I levels fluctuate over time.

Update on mitochondria and muscle aging: all wrong roads lead to sarcopenia

Sarcopenia is a well-known geriatric syndrome that has been endorsed over the years as a biomarker allowing for the discrimination, at a clinical level, of biological from chronological age. Multiple candidate mechanisms have been linked to muscle degeneration during sarcopenia. Among them, there is wide consensus on the central role played by the loss of mitochondrial integrity in myocytes, secondary to dysfunctional quality control mechanisms. Indeed, mitochondria establish direct or indirect contacts with other cellular components (e.g. endoplasmic reticulum, peroxisomes, lysosomes/vacuoles) as well as the extracellular environment through the release of several biomolecules. The functional implications of these interactions in the context of muscle physiology and sarcopenia are not yet fully appreciated and represent a promising area of investigation. Here, we present an overview of recent findings concerning the interrelation between mitochondrial quality control processes, inflammation and the metabolic regulation of muscle mass in the pathogenesis of sarcopenia highlighting those pathways that may be exploited for developing preventive and therapeutic interventions against muscle aging.

Reference ranges for serum insulin-like growth factor I (IGF-I) in healthy Chinese adults

Purpose

To determine serum insulin-like growth factor 1 (IGF-I) levels in healthy Chinese adults, establish reference ranges for serum IGF-I levels and observe the effects of age, sex, body mass index (BMI) and geographical region on serum IGF-I levels.

Methods

In total, 2791 healthy adults (1339 males and 1452 females) from the north (Beijing) and south (Guizhou Province) of China were recruited following a questionnaire survey, physical examination and laboratory examination. Both sexes were divided into 13 groups according to age (18, 19, 20–24, 25–29, 30–34, 35–39, 40–44, 45–49, 50–54, 55–59, 60–64, 65–69 and ≥70 years). The serum IGF-I levels were measured by performing a chemiluminescent assay (Immulite 2000®), and the LMS (Lambda-Mu-Sigma) method was applied to construct smooth centile curves of age-specific IGF-I levels.

Results

Serum IGF-I levels in the adults gradually decreased with increasing age from 18 to 70 years in both the male and female participants. Although the decrease in the level of IGF-1 was more pronounced in females than in males, no significant difference was observed between the sexes, except in the 60- to 64-year-old age group (P = 0.0329). The multiple linear regression model showed that there was an inverse relationship between the serum IGF-I level and BMI (P<0.001), and the serum IGF-I level in the Guizhou population was higher than that in the Beijing population (P<0.05).

Conclusion

The normal reference ranges for age- and sex-specific serum IGF-I levels were established for the first time in a large sample of Chinese adults. The serum IGF-I levels were significantly influenced by age, BMI and geographical region.

Sex-specific differences in risk factors for sarcopenia amongst community-dwelling older adults

With considerable variation including potential sex-specific differential rate of skeletal muscle loss, identifying modifiable factors for sarcopenia will be pivotal to guide targeted interventions. This study seeks to identify clinical and biological correlates of sarcopenia in community-dwelling older adults, with emphasis on the role of anabolic and catabolic stimuli, and special reference to gender specificity. In this cross-sectional study involving 200 community-dwelling and functionally independent older adults aged ≥50 years, sarcopenia was defined using the Asian Working Group for Sarcopenia criteria. Comorbidities, cognitive and functional performance, physical activity and nutritional status were routinely assessed. Biochemical parameters included haematological indices, lipid panel, vitamin D level, anabolic hormones [insulin-like growth factor-1 (IGF-1), free testosterone (males only)] and catabolic markers [inflammatory markers (interleukin-6, C-reactive protein) and myostatin]. Multiple logistic regression was performed to identify independent predictors for sarcopenia. Age was associated with sarcopenia in both genders. Malnutrition conferred significantly higher odds for sarcopenia in women (OR = 5.71, 95% CI 1.13-28.84.44, p = 0.035) while higher but acceptable range serum triglyceride was protective in men (OR = 0.05, 95% CI 0.00-0.52, p = 0.012). Higher serum myostatin independently associated with higher odds for sarcopenia in men (OR = 1.11, 95% CI 1.00-1.24, p = 0.041). Serum IGF-1 was significantly lower amongst female sarcopenic subjects, with demonstrable trend for protective effect against sarcopenia in multiple regression models, such that each 1 ng/ml increase in IGF-1 was associated with 1% decline in odds of sarcopenia in women (p = 0.095). Our findings support differential pathophysiological mechanisms for sarcopenia that, if corroborated, may have clinical utility in guiding sex-specific targeted interventions for community-dwelling older adults.

Beneficial effects of exercise on age-related mitochondrial dysfunction and oxidative stress in skeletal muscle

Mitochondria are negatively affected by ageing leading to their inability to adapt to higher levels of oxidative stress and this ultimately contributes to the systemic loss of muscle mass and function termed sarcopenia. Since mitochondria are central mediators of muscle health, they have become highly sought-after targets of physiological and pharmacological interventions. Exercise is the only known strategy to combat sarcopenia and this is largely mediated through improvements in mitochondrial plasticity. More recently a critical role for mitochondrial turnover in preserving muscle has been postulated. Specifically, cellular pathways responsible for the regulation of mitochondrial turnover including biogenesis, dynamics and autophagy may become dysregulated during ageing resulting in the reduced clearance and accumulation of damaged organelles within the cell. When mitochondrial quality is compromised and homeostasis is not re-established, myonuclear cell death is activated and muscle atrophy ensues. In contrast, acute and chronic exercise attenuates these deficits, restoring mitochondrial turnover and promoting a healthier mitochondrial pool that leads to the preservation of muscle. Additionally, the magnitude of these exercise-induced mitochondrial adaptations is currently debated with several studies reporting a lower adaptability of old muscle relative to young, but the processes responsible for this diminished training response are unclear. Based on these observations, understanding the molecular details of how advancing age and exercise influence mitochondria in older muscle will provide invaluable insight into the development of exercise protocols that will maximize beneficial adaptations in the elderly. This information will also be imperative for future research exploring pharmacological targets of mitochondrial plasticity.

Changes in insulin-like growth factor-I and -II associated with fat but not lean mass in early old age

OBJECTIVE

To test the hypothesis that insulin-like growth factors-I and II (IGF-I and II) decline during late midlife and that greater declines are related to higher fat mass and lower lean mass.

METHODS

A total of 1,542 men and women in a British birth cohort study had IGF-I and II measured by immunoassay of blood samples at age 53 and/or 60-64 years. Fat mass, android:gynoid fat ratio, and appendicular lean mass were measured at 60-64 years using dual-energy X-ray absorptiometry (DXA). Associations between changes in IGF-I or II and body composition outcomes were examined using conditional change linear regression models.

RESULTS

Mean IGF-I and IGF-II concentrations were lower at 60-64 than at 53 years, by 12.8% for IGF-I and by 12.5% for IGF-II. Larger declines in either IGF-I or II were associated with higher fat mass at 60-64 years. Although higher IGF-I at 53 years was associated with higher lean mass, there was little evidence linking changes in IGF-I or II to lean mass.

CONCLUSIONS

The findings suggest that IGF-I and II concentrations decline with age, and greater declines are associated with higher fat mass levels. These results provide some evidence for the suggested roles of IGF-I and II in regulating fat mass but not lean mass in older age.

Multiple hormonal dysregulation as determinant of low physical performance and mobility in older persons

Mobility-disability is a common condition in older individuals. Many factors, including the age-related hormonal dysregulation, may concur to the development of disability in the elderly. In fact, during the aging process it is observed an imbalance between anabolic hormones that decrease (testosterone, dehydroepiandrosterone sulphate (DHEAS), estradiol, insulin like growth factor-1 (IGF-1) and Vitamin D) and catabolic hormones (cortisol, thyroid hormones) that increase. We start this review focusing on the mechanisms by which anabolic and catabolic hormones may affect physical performance and mobility. To address the role of the hormonal dysregulation to mobility-disability, we start to discuss the contribution of the single hormonal derangement. The studies used in this review were selected according to the period of time of publication, ranging from 2002 to 2013, and the age of the participants (≥65 years). We devoted particular attention to the effects of anabolic hormones (DHEAS, testosterone, estradiol, Vitamin D and IGF-1) on both skeletal muscle mass and strength, as well as other objective indicators of physical performance. We also analyzed the reasons beyond the inconclusive data coming from RCTs using sex hormones, thyroid hormones, and vitamin D (dosage, duration of treatment, baseline hormonal values and reached hormonal levels). We finally hypothesized that the parallel decline of anabolic hormones has a higher impact than a single hormonal derangement on adverse mobility outcomes in older population. Given the multifactorial origin of low mobility, we underlined the need of future synergistic optional treatments (micronutrients and exercise) to improve the effectiveness of hormonal treatment and to safely ameliorate the anabolic hormonal status and mobility in older individuals.

Hormone replacement therapy and physical function in healthy older men. Time to talk hormones?

Improving physical function and mobility in a continuously expanding elderly population emerges as a high priority of medicine today. Muscle mass, strength/power, and maximal exercise capacity are major determinants of physical function, and all decline with aging. This contributes to the incidence of frailty and disability observed in older men. Furthermore, it facilitates the accumulation of body fat and development of insulin resistance. Muscle adaptation to exercise is strongly influenced by anabolic endocrine hormones and local load-sensitive autocrine/paracrine growth factors. GH, IGF-I, and testosterone (T) are directly involved in muscle adaptation to exercise because they promote muscle protein synthesis, whereas T and locally expressed IGF-I have been reported to activate muscle stem cells. Although exercise programs improve physical function, in the long-term most older men fail to comply. The GH/IGF-I axis and T levels decline markedly with aging, whereas accumulating evidence supports their indispensable role in maintaining physical function integrity. Several studies have reported that the administration of T improves lean body mass and maximal voluntary strength in healthy older men. On the other hand, most studies have shown that administration of GH alone failed to improve muscle strength despite amelioration of the detrimental somatic changes of aging. Both GH and T are anabolic agents that promote muscle protein synthesis and hypertrophy but work through separate mechanisms, and the combined administration of GH and T, albeit in only a few studies, has resulted in greater efficacy than either hormone alone. Although it is clear that this combined approach is effective, this review concludes that further studies are needed to assess the long-term efficacy and safety of combined hormone replacement therapy in older men before the medical rationale of prescribing hormone replacement therapy for combating the sarcopenia of aging can be established.

The longitudinal relation between smoking and muscle strength in healthy adults

AIM

To assess longitudinally whether smoking tobacco is related to muscle strength in healthy adults and to assess the influence of lifestyle covariates on this relation.

METHODS

Data were obtained from the observational Amsterdam Growth and Health Longitudinal Study, with four repeated measurements at the ages of 21 (n = 181), 27 (n = 144), 32 (n = 426) and 36 (n = 373) years. Knee muscle strength (KMS) was measured at an angle of 300° per second. Smoking and the covariates physical activity and dietary intake were assessed with a questionnaire. Other covariates included physical fitness and body fat percentage. Cardiopulmonary fitness was assessed with a maximal running test and body fatness with skinfold measurements. Sex-specific longitudinal analyses were carried out using generalized estimating equations.

RESULTS

In men and women, an inverse relationship between smoking tobacco and KMS was found. Smoking 100 g of tobacco a week resulted in a reduction of 2.9% in KMS in men and a reduction of 5.0% in women. This relation existed largely independently of lifestyle covariates.

CONCLUSION

This study indicates that smoking is inversely related to skeletal muscle strength in healthy adults.

Sarcopenia and diabetes: pathogenesis and consequences

Sarcopenia, loss of muscle mass with age, is considered as a major cause of frailty and decreased independence in the elderly population. On the other hand, ageing is associated with an increase in prevalence of diabetes. In this review, we discuss the pathophysiological basis of sarcopenia and its relationship to oxidative stress and insulin resistance state, which contribute to development of glucose intolerance and type 2 diabetes. We will also discuss some ideas on the consequences and treatment of sarcopenia.

Insulin-like growth factor I and the pathogenesis of delirium: a review of current evidence

Delirium is a frequent complication in medically ill elderly patients that is associated with serious adverse outcomes including increased mortality. Delirium risk is linked to older age, dementia, and illness that involves activation of inflammatory responses. IGF-I is increasingly postulated as a key link between environmental influences on body metabolism with a range of neuronal activities and has been described as the master regulator of the connection between brain and bodily well-being. The relationships between IGF-I and ageing, cognitive impairment and inflammatory illness further support a possible role in delirium pathogenesis. Five studies of IGF-I in delirium were identified by a systematic review. These conflicting findings, with three of the five studies indicating an association between IGF-1 and delirium occurrence, may relate to the considerable methodological differences in these studies. The relevance of IGF-I and related factors to delirium pathogenesis can be clarified by future studies which account for these issues and other confounding factors. Such work can inform therapeutic trials of IGF-I and/or growth hormone administration.

Total and cause-specific mortality in the cardiovascular health study

BACKGROUND

Few cohort studies have adequate numbers of carefully reviewed deaths to allow an analysis of unique and shared risk factors for cause-specific mortality. Shared risk factors could be targeted for prevention of premature death and the study of longevity.

METHODS

A total of 5,888 community-dwelling persons aged 65 years or older living in four communities in the United States participated in the Cardiovascular Health Study cohort. Participants were initially recruited from 1989 to 1990; an additional 687 black participants were recruited in 1992-1993. The average length of follow-up was 16 years. Total and cause-specific mortality, including cardiovascular disease, stroke, cancer, dementia, pulmonary disease, infection, and other cause, were examined as outcomes. Variables previously associated with total mortality were examined for each cause of death using Cox proportional hazard models.

RESULTS

Multiple risk factors were related to total mortality. When examining specific causes, many factors were related to cardiovascular death, whereas fewer were related to other causes. For most causes, risk factors were specific for that cause. For example, apolipoprotein E epsilon4 was strongly associated for dementia death and forced vital capacity with pulmonary death. Age, male sex, markers of inflammation, and cognitive function were related to multiple causes of death.

CONCLUSIONS

In these older adults, associations of risk factors with a given cause of death were related to specific deficits in that same organ system. Inflammation may represent a common pathway to all causes of death.

Inflammation, coagulation, and the pathway to frailty

There are inevitable physiologic changes associated with advancing age, yet for some people these changes are exaggerated, and as a result a phenotype emerges recognized as "frailty." Why some people become frail and others do not remains incompletely understood. Although chronic illnesses are common among frail elderly persons, some will develop all of the phenotypic features without a diagnosed underlying disease. It has been recognized that certain proinflammatory cytokines and coagulation factors are elevated to a greater extent in those who are frail than in age-matched nonfrail individuals. In this review, we provide an overview of current research in the biology of frailty with particular emphasis on the role of inflammatory pathways and disordered coagulation in its pathogenesis.

IGF-I and IGFBP-3 polymorphisms in relation to circulating levels among African American and Caucasian women

Circulating insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) levels have been associated with common diseases. Although family-based studies suggest that genetic variation contributes to circulating IGF-I and IGFBP-3 levels, analyses of associations with multiple IGF-I and IGFBP-3 single nucleotide polymorphisms (SNP) have been limited, especially among African Americans. We evaluated 30 IGF-I and 15 IGFBP-3 SNPs and estimated diplotypes in association with plasma IGF-I and IGFBP-3 among 984 premenopausal African American and Caucasian women. In both races, IGFBP-3 rs2854746 (Ala32Gly) was positively associated with plasma IGFBP-3 (CC versus GG mean difference among Caucasians, 631 ng/mL; 95% confidence interval, 398-864; African Americans, 897 ng/mL; 95% confidence interval, 656-1,138), and IGFBP-3 diplotypes with the rs2854746 GG genotype had lower mean IGFBP-3 levels than reference diplotypes with the CG genotype, whereas IGFBP-3 diplotypes with the CC genotype had higher mean IGFBP-3 levels. IGFBP-3 rs2854744 (-202 A/C) was in strong linkage disequilibrium with rs2854746 in Caucasians only, but was associated with plasma IGFBP-3 in both races. Eight additional IGFBP-3 SNPs were associated with >or=5% differences in mean IGFBP-3 levels, with generally consistent associations between races. Twelve IGF-I SNPs were associated with >or=10% differences in mean IGF-I levels, but associations were generally discordant between races. Diplotype associations with plasma IGF-I did not parallel IGF-I SNP associations. Our study supports that common IGFBP-3 SNPs, especially rs2854746, influence plasma IGFBP-3 levels among African Americans and Caucasians but provides less evidence that IGF-I SNPs affect plasma IGF-I levels.

The effect of intravitreal bevacizumab (avastin) administration on systemic hypertension

AIMS

To determine the short-term effect of intravitreal bevacizumab administration on systemic blood pressure levels of patients and to evaluate the safety of the drug in these patients.

METHODS

Study population was divided into two groups: group A comprised patients who had hypertension and were under medication with antihypertensive drugs; group B comprised patients with normal blood pressure and were not under medication with antihypertensive drugs. All patients were graded according to their blood pressure levels before single dose of bevacizumab (0.05 ml; 1.25 mg) injection, and at day 1 and weeks 1, 3, and 6 thereafter. The blood pressure levels were analysed using repeated measures of analysis of variance (ANOVA). A P-value of <0.05 was considered significant.

RESULTS

The study population included 82 patients with a mean age of 67.2+/-5.2 years. In group A, the systolic blood pressure levels showed significant increases at weeks 1, 3, and 6 (P=0.001, P<0.001, and P=0.003, respectively) compared with baseline. Similarly, diastolic blood pressure levels were significantly higher at weeks 3 (P<0.001) and 6 (P=0.016). In group B, the mean systolic and diastolic blood pressure levels showed significant elevations only at week 3 (P=0.004 and P<0.001, respectively). The percentages of both group A and B patients with normal blood pressure decreased at week 3 compared with baseline (P<0.001 and P=0.012 for groups A and B, respectively).

CONCLUSIONS

The findings of this study show that there is a risk of disregulation of blood pressure levels or persistence of hypertension in hypertensive patients after intravitreal bevacizumab injections.

Physical activity, inflammation, and muscle loss

Sarcopenia is the degenerative loss of skeletal muscle that occurs naturally in individuals as they age. Although many factors underlie sarcopenia, epidemiological and experimental evidence suggests that low-grade chronic inflammation is an important contributor to its progression. Still, few healthcare professionals have a clear understanding of the profound effects of cytokines on sarcopenia, or how these effects may be counteracted. Interestingly, mounting evidence suggests that along with good diet and vitamin supplementation, this muscle damage can be mitigated with regular physical activity. Without a doubt, exercise is an intervention that reliably counteracts the loss of muscle mass, strength, and power common in our increasingly aged, and pervasively sedentary, population.

Alterations in IGF-I affect elderly: role of physical activity

The growth hormone–insulin-like growth factor I (IGF-I) axis is an important physiological regulator muscle for development. Although there is evidence that aging muscle retains the ability to synthesize IGF-I, there is also evidence that aging may be associated with attenuation of the ability of exercise to induce an isoform of IGF-I that promotes satellite cell proliferation. However, it is clear that overexpression of IGF-I in the muscle can protect against age-related sarcopenia. Strength training appears to be the intervention of choice for the prevention and treatment of sarcopenia. IGF-I has been implicated in the loss of the muscle with age, and IGF-I expression levels change as a consequence of strength training in older adults. However, it seems that advancing age, rather than declining serum levels of IGF-I, appears to be a major determinant of life-time changes in body composition in women and men. We concluded that resistive exercise is a significant determinant of muscle mass and function. Elevated levels of IGF-I have been found in physically active compared to sedentary individuals. Recent work suggests that IGF-I as a mediator plays an important role in muscle hypertrophy and angiogenesis, both of which characterize the anabolic adaptation of muscles to exercise.

Low IGF-1 levels are associated with cardiovascular risk factors in haemodialysis patients

Cardiovascular diseases (CVD) constitute a significant risk and may, in part, explain the high morbidity and mortality rates among haemodialysis (HD) patients. Several studies have implicated reduced insulin like growth factor (IGF-1) levels in the development of CVD. However, it is not clear whether IGF-1, and its relationship with other hormones such as leptin, insulin, and growth hormone (GH), as well as anthropometric variables may explain the high incidence of vascular complications in chronic kidney disease (CKD) patients. This study was designed to measure total serum IGF-1, leptin, insulin and GH levels in CKD patients and in age-matched control subjects and to elucidate the relationship between IGF-1 and GH, leptin, and insulin as well as other known aetiological risk factors for CVD including blood pressure, body mass index (BMI), and age. The study consisted of 50 CKD patients [36 M and 14 F; mean age; 41.8 +/- 10.3 years) on maintenance haemodialysis and 50 healthy control subjects (36 M and 14 F; mean age 41.6 +/- 10.2 years) matched for age and sex. None of the subject among patients and controls reported either smoking or history of diabetes mellitus. The circulating levels of IGF-1 were significantly lower (P < 0.001) in both male and female patients compared to the control subjects. Moreover, IGF-1 was strongly and inversely correlated with both systolic blood pressure (SBP) (r = -0.360; P < 0.01) and diastolic blood pressure (DBP) (r = -0.512; P < 0.001) in the CKD group, and when the two groups were combined SBP (r = -0.396; P < 0.001) and DBP (r = -0.296; P < 0.01). When adjusted for age, the correlation was more significant, however, when adjusted for BMI no significant correlation was observed between IGF-1 and blood pressure. IGF-1 was inversely correlated with age (r = -0.367; P < 0.01) and BMI (r = -0.310; P < 0.05) in the control group, but not the patient group. In controls and patients, respectively, a positive correlation between leptin and BMI (r = 0.358; P < 0.01; r = 0.640, P < 0.001) was observed. The results show that circulating levels of IGF-1 were significantly lower in CKD patients as compared to healthy normal subjects and were inversely correlated with SBP and DBP independent of age, but not BMI indicative of a strong relationship between cardiovascular risk factors and low IGF-1 levels. Although, the data do not clearly indicate low IGF-1 levels as a cause or an effect of these cardiovascular risk factors, they do point to an interesting relationship between low IGF-1 levels and increased cardiovascular risk factors among CKD patients as compared to age-matched healthy control subjects.

Body mass index, waist circumference and waist–hip ratio and serum levels of IGF-I and IGFBP-3 in European women

OBJECTIVE

To examine the relationship between body mass index (BMI) and waist-hip ratio (WHR) with serum levels of insulin-like growth factor-I (IGF-I), and its binding protein (IGFBP)-3.

DESIGN

Cross-sectional study on 2139 women participating in a case-control study on breast cancer and endogenous hormones. Data on lifestyle and reproductive factors were collected by means of questionnaires. Body height, weight, waist and hip circumferences were measured. Serum levels of IGF-I and insulin-like binding protein (IGFBP)-3 were measured by enzyme-linked immunosorbent assays. Adjusted mean levels of IGF-I and IGFBP-3 across quintiles of BMI, waist circumference, and WHR were calculated by linear regression. Results were adjusted for potential confounders associated with IGF-I and IGFBP-3.

RESULTS

Adjusted mean serum IGF-I values were lower in women with BMI<22.5 kg/m(2) or BMI>29.2 kg/m(2) compared to women with BMI within this range (P(heterogeneity)<0.0001, P(trend)=0.35). Insulin-like growth factor-I was not related to WHR after adjustment for BMI. IGF-binding protein-3 was linearly positively related to waist and WHR after mutual adjustment. The molar ratio IGF-I/IGFBP-3 had a non-linear relation with BMI and a linear inverse relationship with WHR (P (trend)=0.005).

CONCLUSIONS

Our data confirm the nonlinear relationship of circulating IGF-I to total adiposity in women. Serum IGFBP-3 was positively related to central adiposity. These suggest that bioavailable IGF-I levels could be lower in obese compared to non-obese women and inversely related to central adiposity.

Possible acceleration of aging by adjuvant chemotherapy: a cause of early onset frailty?

Cancer chemotherapy has three main applications. It is curative for a small number of malignancies including childhood leukemia, Hodgkin's and non-Hodgkin's lymphoma, and germ cell malignancies. It has a palliative role for most metastatic epithelial malignancies. Finally, it has an adjuvant role in several types of resected epithelial malignancies particularly breast cancer. First successfully employed in the mid 1970s, adjuvant chemotherapy is associated with up to a 30% relative improvement in long-term overall survival in high risk breast cancer but demonstrates significantly less absolute improvement. Now that adjuvant chemotherapy is being used in lower risk disease, both the relative and absolute improvement in overall survival is even less impressive. With a growing number of long-term survivors, we are only now able to define the delayed implications of adjuvant chemotherapy. These long-term side effects include acceleration of neurocognitive decline, musculoskeletal complications such as early onset osteoporosis, premature skin and ocular changes and the most common long-term complaint; mild to profound fatigue. This complex of problems is suggestive of early onset frailty. This paper explores various potential mechanisms of aging including accumulation of free-radical damage, accumulation of DNA damage, telomere shortening with accompanying decline in telomerase activity and finally a decline in neuroendocrine/immune function. The impact of chemotherapy, particularly those agents used in the adjuvant setting, in relationship to these aging mechanisms is explored. There is good evidence that chemotherapy can effect all these aging mechanisms leading to early onset frailty. The implications of this hypothesis are quite profound. Whereas short-term toxicity of chemotherapy can usually be considered acceptable even for a small improvement in survival, long-term toxicity such as early onset frailty can have an impact on quality of life that could last for years. This possible effect on aging could have implications on the decision to take adjuvant chemo, what agents to use, means to minimize the aging effect and the need to monitor for early onset frailty.

Variation in plasma insulin-like growth factor-1 and insulin-like growth factor binding protein-3: personal and lifestyle factors (United States)

Insulin-like growth factors (IGFs) play an important role in cell proliferation and apoptosis, and recent epidemiologic studies have suggested that circulating IGF-1 and IGF binding protein-3 (IGFBP-3) may be related to colorectal, breast, and prostate cancer risk. The purpose of this analysis was to investigate the role of various personal and lifestyle factors in the inter-individual variation of circulating IGF-1 and IGFPB-3. We measured plasma levels of IGF-1 and IGFBP-3 in a sequential sample of 333 population-based control subjects enrolled in the Seattle Colorectal Cancer Family Registry from August 1999 through December 2001, who had provided a blood sample. Total IGF-1 and IGFBP-3 were measured from plasma samples using ELISA assays. Interviewer-administered questionnaires collected data on various personal and lifestyle factors. Multivariate-adjusted linear regression was used to assess the associations between specific personal and lifestyle factors with IGF-1 and IGFBP-3 levels. Age, body mass index, and postmenopausal hormone use were statistically significantly inversely related to IGF-1 concentrations, and milk consumption was significantly positively related to IGF-1 levels. Only age was significantly related to circulating IGFBP-3. Although the sources of inter-individual variation of IGF-1 and IGFB-3 are not yet fully understood, this analysis provides some insights into factors that may contribute.

Strength, But Not Muscle Mass, Is Associated With Mortality in the Health, Aging and Body Composition Study Cohort

BACKGROUND

Although muscle strength and mass are highly correlated, the relationship between direct measures of low muscle mass (sarcopenia) and strength in association with mortality has not been examined.

METHODS

Total mortality rates were examined in the Health, Aging and Body Composition (Health ABC) Study in 2292 participants (aged 70-79 years, 51.6% women, and 38.8% black). Knee extension strength was measured with isokinetic dynamometry, grip strength with isometric dynamometry. Thigh muscle area was measured by computed tomography (CT) scan, and leg and arm lean soft tissue mass were determined by dual energy x-ray absorptiometry (DXA). Both strength and muscle size were assessed as in gender-specific Cox proportional hazards models, with age, race, comorbidities, smoking status, level of physical activity, fat area by CT or fat mass by DXA, height, and markers of inflammation, including interleukin-6, C-reactive protein, and tumor necrosis factor-alpha considered as potential confounders.

RESULTS

There were 286 deaths over an average of 4.9 (standard deviation = 0.9) years of follow-up. Both quadriceps and grip strength were strongly related to mortality. For quadriceps strength (per standard deviation of 38 Nm), the crude hazard ratio for men was 1.51 (95% confidence interval, 1.28-1.79) and 1.65 (95% confidence interval, 1.19-2.30) for women. Muscle size, determined by either CT area or DXA regional lean mass, was not strongly related to mortality. In the models of quadriceps strength and mortality, adjustment for muscle area or regional lean mass only slightly attenuated the associations. Further adjustment for other factors also had minimal effect on the association of quadriceps strength with mortality. Associations of grip strength with mortality were similar.

CONCLUSION

Low muscle mass did not explain the strong association of strength with mortality, demonstrating that muscle strength as a marker of muscle quality is more important than quantity in estimating mortality risk. Grip strength provided risk estimates similar to those of quadriceps strength.

Racial and anthropometric differences in plasma levels of insulin-like growth factor I and insulin-like growth factor binding protein-3

OBJECTIVES

To analyze the differences in the plasma levels of insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP-3), and their ratio between black and white men while controlling for factors that could confound the relationship between IGF levels and race. Furthermore, we analyzed the association between age, height, prostate-specific antigen level, digital rectal examination status, and current smoking status on IGF levels separately in black and white men. Greater levels of IGF-I and lower levels of IGFBP-3 have been associated with an increased risk of prostate cancer in many studies.

METHODS

A cross-sectional analysis was performed on 171 white and 130 black men aged 40 to 80 years. Multiple linear regression analysis was used to model the data separately for blacks and whites. A chi-square global test was used to test for racial differences in regression curves.

RESULTS

Our results indicated that black men have lower levels of IGFBP-3 and IGF-I and a greater IGF-I/IGFBP-3 ratio than white men across all ages younger than 70, with and without an adjustment for height. We found racial differences in the effect of age and height on levels of IGF-I, IGFBP-3, and the molar ratio. Age had an inverse correlation with IGF-I and IGFBP-3 levels in whites, but no such relationship in blacks.

CONCLUSIONS

The differences in IGF levels between blacks and whites may explain some of the racial disparity in prostate cancer risk. Because age and height affect IGF levels differently in black and white men, future analysis exploring the determinants of IGF levels may need to be stratified by race.

Variation in plasma insulin-like growth factor-1 and insulin-like growth factor binding protein-3: genetic factors

Insulin-like growth factors (IGFs) play key roles in cell proliferation and apoptosis. Whereas relatively stable within individuals, IGFs vary substantially between individuals, and a large component of this variation may be determined by genetic factors. Several polymorphisms in IGF genes have been identified, although their functional significance is not clear. We evaluated the association of polymorphisms in IGF-1 and IGFBP-3 and circulating levels of IGF-1 and IGFBP-3 in 323 population-based control subjects enrolled in a case-control study of colorectal cancer from September 1999 through February 2002. Total IGF-1 and IGFBP-3 levels were measured using ELISA assays, and all subjects were genotyped for a microsatellite polymorphism in IGF-1 and a single nucleotide polymorphism in IGFBP-3. Multiple linear regression was used to assess the association of genotype with circulating IGFs. IGF-1 levels were unrelated to either polymorphism. IGFBP-3 was significantly associated with IGFBP-3 genotype, with IGFBP-3 levels increasing from CC (1,895 ng/mL) --> GC (2,029 ng/mL) --> GG (2,182 ng/mL), (p-trend < 0.001). Having an IGF-1 genotype other than homozygous for the 19-repeat allele was associated with higher IGFBP-3 levels (1,945 versus 2,052 ng/mL). Furthermore, both IGF-1 and IGFBP-3 genotypes modified the relationship between postmenopausal hormone use and IGFs. This analysis provides evidence that common variation in IGF genes may contribute to the variation in circulating levels observed between individuals.

Effects of 9-cis-retinoic acid on the insulin-like growth factor axis in former smokers

PURPOSE

Insulin-like growth factor (IGF) axis has been associated with the risk of lung cancer. 9-cis-retinoic acid (9-cis-RA) has shown potential chemopreventive activities in former smokers. This study was designed to evaluate the effects of 9-cis-RA on IGF axis in former smokers to identify any benefit the retinoid may have in preventing lung cancer.

PATIENTS AND METHODS

Serum concentrations of IGF-I, IGF binding protein (IGFBP)-3, and their molar ratio (IGF-I/IGFBP-3) were measured with radioimmunoassay kits in stored blood samples from the participants of an original chemoprevention trial. The participants had ceased smoking for at least 12 months and were randomly assigned to receive 3 months of daily oral 9-cis-RA (100 mg) or placebo. All statistical tests were two-sided.

RESULTS

A total of 111 samples from the study's baseline and 84 samples from the 3 months treatment were analyzed. The serum concentrations of IGF-I and IGF-I/IGFBP-3 at baseline were significantly lower in female than in male participants. After 3 months of treatment, the serum level of IGF-I and IGF-I/IGFBP-3 were significantly lower in the 9-cis-RA group than in the placebo group (P = .03 and P < .01, respectively), but the IGFBP-3 level was significantly higher (P = .03).

CONCLUSION

9-cis-RA treatment modulated the IGF axis in former smokers, suggesting that the IGF axis is a potential target for the chemopreventive activities of 9-cis-RA and that the serum concentrations of IGF, IGFBP-3, and IGF-I/IGFBP-3 could serve as surrogate end point biomarkers of 9-cis-RA treatment.

Genetic regulation of the variation of circulating insulin-like growth factors and leptin in human pedigrees

Recent literature has shown that circulating levels of insulin-like growth factor I (IGF-I) and/or IGF binding proteins (IGF-BPs) may be of importance in the risk assessment of several chronic diseases including cancer, cardiovascular disease, diabetes mellitus and so on. The present study examined the extent of genetic and environmental influences on the populational variation of circulating IGF-I and IGF-BP-1 in apparently healthy and ethnically homogeneous white families. The plasma levels of each of the studied biochemical indices were determined by enzyme-linked immunoassay in 563 individuals aged 18 to 80 years. Quantitative genetic analysis showed that the IGF-I variation was appreciably attributable to genetic effects (47.1% +/- 9.0%), whereas for IGF-BP-1, only 23.3% +/- 7.8% of the interindividual variation was explained by genetic determinants. Common familial environment factors contributed significantly only to IGF-BP-1 variation (23.3% +/- 7.8%). In addition, we examined the covariations between these molecules and between them and IGF-BP-3 and leptin that were previously studied in the same sample. The analysis revealed that the pleiotropic genetic effects were significant for 2 pairs of traits, namely for IGF-I and IGF-BP-3, and for IGF-BP-1 and leptin. The bivariate heritability estimates were 0.21 +/- 0.04 and 0.15 +/- 0.05. The common environmental factors were consistently a significant source of correlation between all pairs (barring IGF-I and leptin) of the studied molecules; they were the sole predictors of correlation between IGF-I and IGF-BP-1, and between IGF-BP-1 and IGF-BP-3. Our results affirm the existence of specific and common genetic pathways that in combination determine a substantial proportion of the circulating variation of these molecules.

Angiogenic growth factors and hypertension

Emerging evidence supports a novel view of hypertension as a disease of inadequate or aberrant responses to angiogenic growth factors (AGF). Patients with hypertension have reduced microvascular density, with some evidence supporting a primary role for rarefaction in causing hypertension. Two clinical models have demonstrated a link between inhibition of AGF activity and hypertension. A major side effect of bevacizumab, a monoclonal antibody to vascular endothelial growth factor (VEGF), is hypertension. Pre-eclampsia is accompanied by high circulating levels of soluble VEGF receptor-1, which forms inactive complexes with VEGF and placental growth factor (PlGF). Paradoxically, early studies have demonstrated high circulating levels of AGF in hypertension. Several mechanisms may account for this finding including increased vascular stretch, tissue ischemia, compensatory responses, decreased clearance or a combination of these mechanisms. High AGF in hypertension could contribute to clinical sequelae such as peripheral and pulmonary edema, microalbuminuria, and progression of atherosclerosis. However, a role for altered angiogenesis in the pathogenesis of hypertension or its sequelae has not been established. Novel studies to understand the roles of AGF in hypertensive patients are warranted.

Factors associated with circulating levels of insulin-like growth factor-I and insulin-like growth factor binding protein-3 in 740 women at risk for breast cancer

Prospective studies have shown an association between elevated plasma levels of insulin-like growth factor-I (IGF-I) and/or decreased levels of its major circulating carrier protein insulin-like growth factor binding protein-3 (IGFBP-3) and increased risk of major cancers. Identifying the factors which affect these biomarkers is of particular interest as subjects at increased risk could benefit from lifestyle changes, and/or chemoprevention intervention. We evaluated the association between constitutional, hormonal and clinical factors and IGF-I and IGFBP-3 in 740 women, including 376 unaffected women and 364 women with intraepithelial neoplasia (IEN) or early invasive breast cancer enrolled in breast cancer chemoprevention trials, conducted at a single institution. Age, body mass index (BMI), height, waist to hip girth ratio (WHR), parity, menopausal status, age at menarche, number of affected first degree relatives, number of biopsies and breast cancer status were considered in the analysis. Women with early breast cancer had 21% higher IGF-I levels (p = 0.033) and 19% higher IGF-I/IGFBP-3 molar ratio (p = 0.047) than unaffected women. In unaffected women, age was negatively associated with IGF-I (p = 0.002) and IGF-I/IGFBP-3 (p = 0.001), while age at menarche was negatively associated with IGFBP-3 levels (p = 0.043). In women with IEN or early breast cancer, IGF-I levels were negatively associated with age (p < 0.001), and positively associated with prior biopsies for benign disease (p = 0.013), while age, parity and menopausal status were significant predictors of IGF-I/IGFBP-3 molar ratio. We conclude that circulating IGF-I levels are higher in women with prior breast cancer compared to unaffected women, and that IGF-I and/or IGFBP-3 levels are influenced by age and by reproductive and hormonal factors. These findings support their putative role as breast cancer risk biomarker.

Effects of aging on muscle fibre type and size

Aging has been associated with a loss of muscle mass that is referred to as 'sarcopenia'. This decrease in muscle tissue begins around the age of 50 years, but becomes more dramatic beyond the 60th year of life. Loss of muscle mass among the aged directly results in diminished muscle function. Decreased strength and power contribute to the high incidence of accidental falls observed among the elderly and can compromise quality of life. Moreover, sarcopenia has been linked to several chronic afflictions that are common among the aged, including osteoporosis, insulin resistance and arthritis. Loss of muscle fibre number is the principal cause of sarcopenia, although fibre atrophy--particularly among type II fibres--is also involved. Several physiological mechanisms have been implicated in the development of sarcopenia. Denervation results in the loss of motor units and thus, muscle fibres. A decrease in the production of anabolic hormones such as testosterone, growth hormone and insulin-like growth factor-1 impairs the capacity of skeletal muscle to incorporate amino acids and synthesise proteins. An increase in the release of catabolic agents, specifically interleukin-6, amplifies the rate of muscle wasting among the elderly. Given the demographic trends evident in most western societies, i.e. increased number of those considered aged, management interventions for sarcopenia must become a major goal of the healthcare profession.

IGF-I and testosterone levels as predictors of bone mineral density in healthy, community-dwelling men

OBJECTIVE

Age-related decline in IGF-I and gonadal hormones have been postulated to play an important role in the pathogenesis of age-related bone loss in men. In this cross-sectional study, the relation between serum IGF-I and gonadal hormones with bone mineral density (BMD) was examined in community-dwelling men.

DESIGN AND SUBJECTS

Serum IGF-I, testosterone and BMD were examined in 61 community-dwelling men over the age of 27, who were randomly selected from the Calgary cohort of 1000 subjects in the Canadian Multicentre Osteoporosis Study. In the present study, IGF-I, serum testosterone, SHBG, free androgen index (FAI), parathyroid hormone (PTH), 25-hydroxy-vitamin D [25(OH)D] and other markers of bone turnover were measured. BMD was measured at the spine and hip (HOLOGIC 4500). Simple linear regression was used to assess the linear relation between IGF-I, testosterone, BMD and other biochemical markers of bone metabolism and potential confounding variables and subsequent multivariate regression models were constructed separately for each BMD measurement to assess the importance of IGF-I and testosterone in the presence of potential confounding variables.

RESULTS

Serum IGF-I, FAI and SHBG significantly decreased as a function of age, whereas serum levels of PTH increased. Only 25(OH)D, total testosterone and FAI were positively associated with serum IGF-I after adjusting for age and BMI. Multiple linear regression models revealed that IGF-I was a significant predictor of BMD at the total hip, femoral neck and femoral trochanter neck (P < or = 0.001). In contrast, the FAI was a significant predictor of BMD at the lumbar spine and wards area (P < or = 0.011), and SHBG was a significant predictor at the total hip and femoral trochanter (P < or = 0.045).

CONCLUSION

These data support the hypothesis that the age-related decline in bone mass in men is associated with declining levels of IGF-I and testosterone.

Frailty and the biochemical effects of recombinant human growth hormone in women after surgery for hip fracture

We report a randomised double blind controlled trial investigating the short-term biochemical and adverse clinical responses to recombinant human growth hormone (r-hGH) after surgery for hip fracture. Hip fractures are common, dangerous and expensive, typically affecting frail women with osteoporosis and reduced muscle mass and strength, factors also associated with poor clinical outcomes. Growth hormone therapy increases IGF-I levels, promotes anabolism and increases muscle strength in well older people and selected patient groups and therefore has therapeutic potential to assist recovery of frail patients.Thirty-one women, mean age 86 years, received 14 nightly subcutaneous injections of r-hGH 0.05 mg/kg/day (high dose) or 0.025 mg/kg/day (low dose), or placebo from the 4th post-operative day. There were several serious adverse clinical events but no excess number of adverse events in the r-hGH treatment groups. The r-hGH treatment groups had similar serum IGF-I and IGFBP-3 responses, both significantly different from placebo. The large inter-individual variation of IGF-I responses were inversely correlated with pre-treatment indicators of frailty (body composition and functional abilities).

Cytokines, insulin-like growth factor 1, sarcopenia, and mortality in very old community-dwelling men and women: the Framingham Heart Study

BACKGROUND

Aging is associated with increased production of catabolic cytokines, reduced circulating levels of insulin-like growth factor 1 (IGF-1), and acceleration of sarcopenia (loss of muscle with age). We hypothesized that these factors are independently linked to mortality in community-dwelling older persons.

METHODS

We examined the relation of all-cause mortality to peripheral blood mononuclear cell production of inflammatory cytokines (tumor necrosis factor alpha [TNF-alpha], interleukin 1 beta, interleukin 6), serum interleukin 6 and IGF-1, and fat-free mass and clinical status in 525 ambulatory, free-living participants in the Framingham Heart Study.

RESULTS

Of the 525 subjects (aged 72 to 92 years at baseline), 122 (23%) died during 4 years of follow-up. After adjusting for age, sex, comorbid conditions, smoking, and body mass index, mortality was associated with greater cellular production of TNF-alpha (hazard ratio [HR] = 1.27 per log(10) difference in ng/mL; 95% confidence interval [CI]: 1.00 to 1.61; P = 0.05) and higher serum interleukin 6 levels (HR = 1.30 per log(10) difference in pg/mL; 95% CI: 1.04 to 1.63]; P = 0.02), but not with higher serum IGF-1 levels (HR = 0.70 per log(10) difference in pg/mL; 95% CI: 0.49 to 0.99; P = 0.04). In a subset of 398 subjects (55 deaths) in whom change in fat-free mass index during the first 2 years was measured, less loss of fat-free mass and greater IGF-1 levels were associated with reduced mortality during the next 2 years.

CONCLUSION

Greater levels or production of the catabolic cytokines TNF-alpha and interleukin 6 are associated with increased mortality in community-dwelling elderly adults, whereas IGF-1 levels had the opposite effect.

Dietary and lifestyle factors in relation to plasma insulin-like growth factor I in a general population sample

There is evidence that the insulin-like growth factor system (IGF), particularly IGF-I, is important in human carcinogenesis. We studied in a general, though not strictly random population sample of 620 adults, the relationship of IGF-I to demographic, lifestyle and dietary factors, the latter ascertained through an extensive validated questionnaire. Plasma IGF-I levels declined significantly with age and the decline was more evident among women than among men. Tobacco smoking, body mass index and regular physical activity were unrelated to this hormone and a positive association with height was not statistically significant. Neither protein nor carbohydrate intake was related to plasma IGF-I levels but there was inconsistent evidence that ethanol intake may be inversely associated with plasma IGF-I and saturated and polyunsaturated lipids may be positively associated with it. The findings are evaluated in conjunction with evidence indicating that the incidence of cancer is lower among women than among men, height is a risk factor for several forms of cancer, and saturated and polyunsaturated lipids have been more closely linked to human and animal carcinogenesis than monounsaturated lipids.

Effects of resistance training on insulin-like growth factor and its binding proteins in men and women aged 60 to 85

OBJECTIVES

We have reported that resistance training (RT) elevates insulin-like growth factor (IGF-I) in healthy young adults. Our goals were to determine whether RT produces a similar effect in the healthy older persons and to determine the effects of low- versus high-intensity RT on hormonal status.

SETTING

Center for Exercise Science, University of Florida, Gainesville.

PARTICIPANTS

Sixty-two men and women (mean age = 68.1).

INTERVENTION

A 6-month, 3-day/week program of low-intensity RT (LEX), high-intensity RT (HEX), or no exercise (CON).

MEASUREMENTS

Before and after training, blood was drawn for hormone analysis. IGF-I, IGF binding protein-1 (IGFBP-1), and IGFBP-3 were measured at rest. Testosterone and cortisol were measured at rest and immediately after exercise.

RESULTS

RT caused significant increases in 1-repetition maximum (1RM) strength and peak oxygen consumption (V02peak), which we have reported separately. Currently, we report that RT had no effect on the resting serum concentrations of IGF-I, IGFBP-1, IGFBP-3, testosterone, or cortisol. Acute resistance exercise caused no change in circulating testosterone in men or women but did cause a significant elevation of cortisol in the HEX group. This increase in cortisol was blunted as a result of training.

CONCLUSIONS

We conclude that the increases in strength and endurance caused by RT were not mediated by increases in circulating IGF-I, IGFBPs, or testosterone.

Habitual physical activity, anabolic hormones, and potassium content of fat-free mass in postmenopausal women

BACKGROUND

Total body potassium (TBK) is known to decline throughout adulthood. The relations between physical activity, age, anabolic hormones, and TBK have rarely been considered.

OBJECTIVE

We sought to describe the relation between habitual physical activity, age, serum estradiol, and insulin-like growth factor I (IGF-I) and TBK in postmenopausal women.

DESIGN

TBK, fat-free mass (FFM), moderate-to-vigorous-intensity physical activity (MVPA; assessed with use of a semistructured interview), and serum concentrations of estradiol, IGF-I, and IGF binding protein 3 (IGFBP-3) were quantified in 51 healthy white women aged 54-76 y.

RESULTS

The potassium content of FFM declined curvilinearly with age, indicating an accelerated loss of skeletal muscle after 65 y of age. With the data split into high (n = 25) and low (n = 26) MVPA groups, the active women had 6.5% more potassium per FFM than did their less-active counterparts (P < 0.01). In multiple regression analysis, MVPA was the major determinant of the potassium content of FFM (P = 0.02), such that an active 70-y-old had the potassium content value of a 55-y-old sedentary woman. Serum estradiol, IGF-I, and IGFBP-3 were not significant determinants of the potassium content of FFM.

CONCLUSIONS

These data suggest that 1) habitual physical activity can significantly influence FFM potassium content; 2) physical activity must, therefore, be considered if the effect of aging per se on TBK is to be clarified; and 3) MVPA, such as that pursued by the active women in the present study (eg, walking, dancing, floor exercises, and swimming), can assist in preventing sarcopenia in older women.

A cross-sectional study of IGF-I determinants in women

Evidence is accumulating that elevated circulating insulin-like growth factor I (IGF-I) is related to increased cancer risk. The identification of hormonal, reproductive and lifestyle characteristics influencing its synthesis and bioavailability is of particular interest. Data from 400 women, who served as controls in two case-control studies nested within the same prospective cohort study, were combined. IGF-I, IGF-binding proteins 1, 2 and 3 (IGFBP-1, -2, -3) and insulin were measured in serum samples from all subjects and cotinine in 186 samples. Age appears to be the most important determinant of total IGF-I levels in women. Anthropometric measures, such as body mass index (BMI) or waist-to-hip ratio (WHR) do not seem to influence total IGF-I concentrations in peripheral blood, but may modulate IGF-I bioavailability through insulin-dependent changes in IGFBP-1 and -2 concentrations. Age at menarche, phase of the menstrual cycle at blood draw, parity, menopause, past oral contraceptive or hormone replacement therapy use, and tobacco smoking do not appear to exert an independent effect on IGF-I and its binding proteins. There was some suggestion that regular physical activity may increase total IGF-I and that women with positive family history of breast cancer might have higher IGF-I levels than those without such diagnosis in their relatives.

Association of IGF-I levels with muscle strength and mobility in older women

The functional consequences of the age-associated decline in IGF-I are unknown. We hypothesized that low IGF-I levels in older women would be associated with poor muscle strength and mobility. We assessed this question in a population representative of the full spectrum of health in the community, obtaining serum IGF-I levels from women aged 70-79 yr, enrolled in the Women's Health and Aging Study I or II. Cross-sectional analyses were performed using 617 women with IGF-I levels drawn within 90 d of measurement of outcomes. After adjustment for age, there was an association between IGF-I and knee extensor strength (P = 0.004), but not anthropometry or other strength measures. We found a positive relationship between IGF-I levels and walking speed for IGF-I levels below 50 microg/liter (P < 0.001), but no relationship above this threshold. A decline in IGF-I level was associated with self-reported difficulty in mobility tasks. All findings were attenuated after multivariate adjustment. In summary, in a study population including frail and healthy older women, low IGF-I levels were associated with poor knee extensor muscle strength, slow walking speed, and self-reported difficulty with mobility tasks. These findings suggest a role for IGF-I in disability as well as a potential target population for interventions to raise IGF-I levels.

Utility of insulin-like growth factor-I and its binding protein assays

Insulin-like growth factor-I circulates in serum either in free form or bound to insulin-like growth factor-binding proteins that modulate its bioavailability. Insulin-like growth factor-binding proteins interfere with insulin-like growth factor-I assay, which remains technically difficult. Many assays have been developed, but their results are somewhat discordant. The choice of separation method, standard and tracer considerably influences the results. The circulating concentration of insulin-like growth factor-I, however, is clearly dependent on nutritional status, and total levels are a valuable marker of nutritional status. The clinical utility of free insulin-like growth factor-I assay and simultaneous assay, in the same sample, of total insulin-like growth factor-I and its binding proteins (reflecting the bioavailable insulin-like growth factor-I fraction), remains to be evaluated.

Are dietary influences on the risk of prostate cancer mediated through the insulin-like growth factor system?

OBJECTIVES

To investigate whether dietary factors that appear to affect the risk of prostate cancer may be similarly associated with serum levels of insulin-like growth factor 1 (IGF-1). Patients and methods In the context of a case-control study, 112 men were admitted to three teaching hospitals in Athens, Greece, for disorders other than cancer. Sociodemographic data and detailed histories of smoking, alcohol and coffee consumption were recorded. A validated food-frequency questionnaire was administered by an interviewer and serological measurements of IGF-1 and its binding protein-3 conducted.

RESULTS

IGF-1 declined significantly by almost 25% among men aged >75 years and there was a small reduction in IGF-1 levels with increased alcohol intake, with a mean (95% confidence interval, CI) change of -1.6 (- 2.2 to -0.9)% for an increment of one drink per day. There was no evidence for an effect of either smoking or coffee consumption on IGF-1 level. Among foods, the consumption of cooked tomatoes was substantially and significantly inversely associated with IGF-1 levels, with a mean (95% CI) change of -31.5 (- 49.1 to -7.9)% for an increment of one serving per day.

CONCLUSIONS

The strongest known dietary risk factor for prostate cancer (lycopene deficit, as reflected in a reduced intake of cooked tomatoes) and an important endocrine factor in the aetiology of this disease (IGF-1) seem to be related in a way that suggests that at least one, and perhaps more, exogenous factors in the development of prostate cancer may be mediated through the IGF-1 system.