Development of a human mitochondria-focused cDNA microarray (hMitChip) and validation in skeletal muscle cells: implications for pharmaco- and mitogenomics

Mitochondrial research has influenced our understanding of human evolution, physiology and pathophysiology. Mitochondria, intracellular organelles widely known as 'energy factories' of the cell, also play fundamental roles in intermediary metabolism, steroid hormone and heme biosyntheses, calcium signaling, generation of radical oxygen species, and apoptosis. Mitochondria possess a distinct DNA (mitochondrial DNA); yet, the vast majority of mitochondrial proteins are encoded by the nuclear DNA. Mitochondria-related genetic defects have been described in a variety of mostly rare, often fatal, primary mitochondrial disorders; furthermore, they are increasingly reported in association with many common morbid conditions, such as cancer, obesity, diabetes and neurodegenerative disorders, although their role remains unclear. This study describes the creation of a human mitochondria-focused cDNA microarray (hMitChip) and its validation in human skeletal muscle cells treated with glucocorticoids. We suggest that hMitChip is a reliable and novel tool that will prove useful for systematically studying the contribution of mitochondrial genomics to human health and disease.

Free testosterone and risk for Alzheimer disease in older men

OBJECTIVE

To investigate the relationships between age-associated decreases in endogenous serum total testosterone (T) and a free T index (FTI) in men and the subsequent development of Alzheimer disease (AD).

METHOD

The authors used a prospective, longitudinal design with follow-up in men since 1958. Participants were from the Baltimore Longitudinal Study of Aging, a community-dwelling volunteer sample with baseline ages of 32 to 87 years. All subjects were free of AD at baseline T assessment. Five hundred seventy-four men assessed at multiple time points were followed for a mean of 19.1 years (range, 4 to 37 years). Diagnoses of AD were based on biennial physical, neurologic, and neuropsychological evaluations.

RESULTS

Diagnosis of AD was associated inversely with FTI by itself and after adjustments for age, education, smoking status, body mass index, diabetes, any cancer diagnoses, and hormone supplements. In separate analyses, total T and sex hormone binding globulin were not significant predictors after adjustment with covariates. Increases in the FTI were associated with decreased risk of AD (hazard ratio = 0.74; 95% CI = 0.57 to 0.96), a 26% decrease for each 10-nmol/nmol FTI increase.

CONCLUSIONS

Calculated free testosterone concentrations were lower in men who developed Alzheimer disease, and this difference occurred before diagnosis. Future research may determine whether higher endogenous free testosterone levels offer protection against a diagnosis of Alzheimer disease in older men.

Comparison of GH, IGF-I, and testosterone with mRNA of receptors and myostatin in skeletal muscle in older men

Growth hormone (GH), insulin-like growth factor I (IGF-I), and testosterone (T) are important mediators of muscle protein synthesis, and thus muscle mass, all of which decline with age. We hypothesized that circulating hormones would be related to the transcriptional levels of their respective receptors and that this expression would be negatively related to expression of the myostatin gene. We therefore determined content of mRNA transcripts (by RT-PCR) for GH receptor (GHR), IGF-I, androgen receptor (AR), and myostatin in skeletal muscle biopsy samples from 27 healthy men >65 yr of age. There were no significant relationships between age, lean body mass, or percent body fat and transcript levels of GHR, IGF-I, AR, or myostatin. Moreover, there were no significant correlations of serum GH, IGF-I, or T with their corresponding target mRNA levels (GHR, intramuscular IGF-I, or AR) in skeletal muscle. However, GHR was negatively correlated (r = -0.60, P = 0.001) with myostatin mRNA levels. The lack of apparent relationships of muscle transcripts with their respective ligands in healthy older adults suggests that age-related deficits in both GH and T may lead to an increase in myostatin expression and a disassociation in autocrine IGF-I effects on muscle protein synthesis, both of which could contribute to age-related sarcopenia.

Effects of GH and/or sex steroid administration on abdominal subcutaneous and visceral fat in healthy aged women and men

Aging is associated with reduced GH, IGF-I, and sex steroid axis activity and with increased abdominal fat. We employed a randomized, double-masked, placebo-controlled, noncross-over design to study the effects of 6 months of administration of GH alone (20 microg/kg BW), sex hormone alone (hormone replacement therapy in women, testosterone enanthate in men), or GH + sex hormone on total abdominal area, abdominal sc fat, and visceral fat in 110 healthy women (n = 46) and men (n = 64), 65-88 yr old (mean, 72 yr). GH administration increased IGF-I levels in women (P = 0.05) and men (P = 0.0001), with the increment in IGF-I levels being higher in men (P = 0.05). Sex steroid administration increased levels of estrogen and testosterone in women and men, respectively (P = 0.05). In women, neither GH, hormone replacement therapy, nor GH + hormone replacement therapy altered total abdominal area, sc fat, or visceral fat significantly. In contrast, in men, administration of GH and GH + testosterone enanthate decreased total abdominal area by 3.9% and 3.8%, respectively, within group and vs. placebo (P = 0.05). Within-group comparisons revealed that sc fat decreased by 10% (P = 0.01) after GH, and by 14% (P = 0.0005) after GH + testosterone enanthate. Compared with placebo, sc fat decreased by 14% (P = 0.05) after GH, by 7% (P = 0.05) after testosterone enanthate, and by 16% (P = 0.0005) after GH + testosterone enanthate. Compared with placebo, visceral fat did not decrease significantly after administration of GH, testosterone enanthate, or GH + testosterone enanthate. These data suggest that in healthy older individuals, GH and/or sex hormone administration elicits a sexually dimorphic response on sc abdominal fat. The generally proportionate reductions we observed in sc and visceral fat, after 6 months of GH administration in healthy aged men, contrast with the disproportionate reduction of visceral fat reported after a similar period of GH treatment of nonelderly GH deficient men and women. Whether longer term administration of GH or testosterone enanthate, alone or in combination, will reduce abdominal fat distribution-related cardiovascular risk in healthy older men remains to be elucidated.

Cortisol and GH secretory dynamics, and their interrelationships, in healthy aged women and men

We studied 130 healthy aged women (n = 57) and men (n = 73), age 65-88 yr, with age-related reductions in insulin-like growth factor I and gonadal steroid levels to assess the interrelationships between cortisol and growth hormone (GH) secretion and whether these relationships differ by sex. Blood was sampled every 20 min from 8:00 PM to 8:00 AM; cortisol was measured by RIA and GH by immunoradiometric assay, followed by deconvolution analyses of hormone secretory parameters and assessment of approximate entropy (ApEn) and cross-ApEn. Cortisol mass/burst, cortisol production rate, and mean and integrated serum cortisol concentrations (P < 0.0005), and overnight basal GH secretion (P < 0.05), were elevated in women vs. men. Integrated cortisol concentrations were directly related to most measures of GH secretion in women (P < 0.01) and with mean and integrated GH concentrations in men (P < 0.05). Integrated GH concentrations were directly related to mean and integrated cortisol levels in women (P < 0.005) and men (P < 0.05), with no sex differences. There were no sex differences in cortisol or GH ApEn values; however, the cross-ApEn score was greater in women (P < 0.05), indicating reduced GH-cortisol pattern synchrony in aged women vs. men. There were no significant relationships of integrated cortisol secretion with GH ApEn, or vice versa, in either sex. Thus postmenopausal women appear to maintain elevated cortisol production in patterns that are relatively uncoupled from those of GH, whereas mean hormone outputs remain correlated.

Longitudinal effects of aging on serum total and free testosterone levels in healthy men. Baltimore Longitudinal Study of Aging

Many studies have shown cross-sectional (and two small studies, longitudinal) declines in total and/or free testosterone (T) levels, with age, in men. The extent to which decline in T is the result of the aging process per se, as opposed to chronic illness, medication use, and other age-related factors, remains controversial. The frequency with which aging leads to T levels consistent with hypogonadism has also not been defined. These issues bear on the potential use of T replacement in aging men, because aging and hypogonadism have, in common, reduced bone and lean body mass and muscle strength and increased total and abdominal fat. We measured T and sex hormone-binding globulin (SHBG), by RIA, in stored samples from 890 men in the Baltimore Longitudinal Study on Aging. Using a mixed-effects model, we found independent effects of age and date of sampling to reduce T levels. After compensating for date effects, which investigation suggested was artifactual, we observed significant, independent, age-invariant, longitudinal effects of age on both T and free T index (free T index = T/SHBG), with an average change of -0.124 nmol/L.yr and -0.0049 nmol T/nmol SHBG.yr. T, but not free T index, also decreased with increasing body mass index. Use of beta-blocking drugs was associated with higher T and higher free T index levels. Using total T criteria, incidence of hypogonadal T levels increased to about 20% of men over 60, 30% over 70 and 50% over 80 yr of age, and even greater percentages when free T index criteria were employed. Our observations of health factor independent, age-related longitudinal decreases in T and free T, resulting in a high frequency of hypogonadal values, suggest that further investigation of T replacement in aged men, perhaps targeted to those with the lowest serum T concentrations, are justified.

Serum levels of insulin-like growth factor I (IGF-I), IGF-II, IGF-binding protein-3, and prostate-specific antigen as predictors of clinical prostate cancer

Insulin-like growth factors (IGFs) may play a role in prostate growth, hyperplasia, and malignancy. High plasma IGF-I has been associated with increased prostate cancer risk. In a prospective, cohort, case-control study in the Baltimore Longitudinal Study on Aging population, we examined prostate volume by magnetic resonance imaging, and prostate-specific antigen (PSA), IGF-I, IGF-II, and IGF-binding protein-3 (IGFBP-3) in sera obtained approximately 9 yr before diagnosis of prostate cancer in cases (n = 72) or age-matched controls (n = 127) and in 76 additional Baltimore Longitudinal Study on Aging men (normal subjects) with measured prostate volumes and no prostate cancer. We calculated adjusted odds ratios (OR) by logistic regression, relative risks for significant ORs, and receiver operator curves for prostate cancer, using serum measures alone and in combination. Adjusted ORs for the high vs. low tertile were: for IGF-I, 3.1 [confidence interval (CI), 1.1-8.7]; for IGF-II, 0.2 (CI, 0.07-0.6); for IGFBP-3, 0.71 (CI, 0.3-1.7); and for PSA, 12.5 (CI, 3.8-40.9). For significant ORs, relative risk estimates remained significant at 2.0 for IGF-I, 0.3 for IGF-II, and 5.5 for PSA. Receiver operator curves showed PSA to be the most powerful predictor of prostate cancer. Adding IGF-II to PSA improved prediction. IGF-II was significantly and inversely related (r = -0.219; P < 0.01) and PSA was directly and significantly related (r = 0.461; P < 0.0001) to prostate volume, whereas IGF-I and IBFBP-3 were not. High IGF-I and low IGF-II are independently associated with increased risk of prostate cancer, but PSA level is a much stronger predictor of prostate cancer in the ensuing 10 yr than either IGF-I or IGF-II. The absence of a relationship of IGF-I to prostate size is inconsistent with increased ascertainment in men with large prostates as the source of greater prostate cancer risk associated with IGF-I. Our data suggest that IGF-II may inhibit both prostate growth and development of prostate cancer.

The relationship between longitudinal declines in dehydroepiandrosterone sulfate concentrations and cognitive performance in older men

BACKGROUND

The observation that dehydroepiandrosterone (DHEA) concentrations decrease markedly with age has led to the hypothesis that declining DHEA concentrations may contribute to age-related changes in cognition. In the United States, DHEA is widely available as an over-the-counter supplement that individuals are using in an effort to ameliorate age-related cognitive and physical changes.

OBJECTIVE

To investigate the relationship between age-associated decreases in endogenous DHEA sulfate (DHEA-S) concentrations and declines in neuropsychological performance in a prospective, longitudinal study.

METHODS

The subjects were 883 men from a community-dwelling volunteer sample in the Baltimore Longitudinal Study of Aging. The men were aged 22 to 91 years at the initial visit, and they were followed up for as long as 31 years (mean, 11. 55 years), with biennial reassessments of multiple cognitive domains and contemporaneous measurement of serum DHEA-S concentrations. Outcome measures were the results of cognitive tests of verbal and visual memory, 2 tests of mental status, phonemic and semantic word fluency tests, and measures of visuomotor scanning and attention. Serum DHEA-S concentrations were determined by standard radioimmunoassay.

RESULTS

Neither the rates of decline in mean DHEA-S concentrations nor the mean DHEA-S concentrations within individuals were related to cognitive status or cognitive decline. A comparison between the highest and lowest DHEA-S quartiles revealed no cognitive differences, despite the fact that these groups differed in endogenous DHEA-S concentration by more than a factor of 4 for a mean duration of 12 years.

CONCLUSION

Our longitudinal results augment those of previous prospective studies by suggesting that the decline in endogenous DHEA-S concentration is independent of cognitive status and cognitive decline in healthy aging men.

The relationship between aerobic exercise capacity and circulating IGF-1 levels in healthy men and women

OBJECTIVES

To determine whether aerobic capacity is associated independently with insulin-like growth factor-I (IGF-1) levels in healthy community-dwelling men and women.

SETTING

The Baltimore Longitudinal Study on Aging (BLSA).

DESIGN

A cross-sectional analysis of data from the population-based cohort of the Baltimore Longitudinal Study of Aging (BLSA).

PARTICIPANTS

We studied 181 men and 92 women aged 20 to 93 years, volunteers in the Baltimore Longitudinal Study on Aging (BLSA). Subjects were free of endocrine, renal, hepatic, gastrointestinal, or cardiac diseases, and they were taking no medications known to interfere with the growth hormone-IGF-1 axis.

MEASUREMENTS

All subjects underwent a single measurement of serum IGF-1 in the fasting state, as well as peak VO2 determinations during maximal treadmill exercise testing performed within one visit of the IGF-1 determination. Dual energy X-ray absorptiometry (DEXA) scans were performed in a subset of 171 subjects (64 women and 107 men) for determination of fat free mass (FFM).

RESULTS

In the pooled group of women and men, univariate regression analysis revealed that age was correlated strongly with decreasing IGF-1 levels (r = -0.53, P < .001) and with peak VO2r = -0.56, P < .001). IGF-1 levels were also significantly correlated with peak VO2 (r = 0.29, P < .001). There were no significant gender-related differences in these relationships. On multivariate analysis, age (beta = -0.54, P < .001), but not peak VO2 (P = -0.01, P = .840), remained strongly associated with IGF-1 levels. After adjustment of peak VO2 for FFM in subjects with DEXA scans, results were similar.

CONCLUSIONS

These findings indicate that although both peak aerobic capacity and circulating IGF-1 levels decline with age, aerobic capacity is not independently related to circulating IGF-1 in healthy men and women across the adult life span.

Enhanced endothelial vasoreactivity in endurance-trained older men

Using external vascular ultrasound, we measured brachial artery diameter (Diam) at rest, after release of 4 min of limb ischemia, i. e., endothelium-dependent dilation (EDD), and after sublingual nitroglycerin, i.e., non-endothelium-dependent dilation (NonEDD), in 35 healthy men aged 61-83 yr: 12 endurance athletes (A) and 23 controls (C). As anticipated, treadmill exercise maximal oxygen consumption (VO(2 max)) was significantly higher in A than in C (40. 2 +/- 6.6 vs. 27.9 +/- 3.8 ml. kg(-1). min(-1); respectively, P < 0. 0001). With regard to arterial physiology, A had greater EDD (8.9 +/- 4.2 vs. 5.7 +/- 3.5%; P = 0.02) and a tendency for higher NonEDD (13.9 +/- 6.7 vs. 9.7 +/- 4.2%; P = 0.07) compared with C. By multiple linear regression analysis in the combined sample of older men, only baseline Diam (beta = -2.0, where beta is the regression coefficient; P = 0.005) and VO(2 max) (beta = 0.23; P = 0.003) were independent predictors of EDD; similarly, only Diam (beta = -4.0; P = 0.003) and VO(2 max) (beta = 0.27; P = 0.01) predicted NonEDD. Thus endurance-trained older men demonstrate both augmented EDD and NonEDD, consistent with a generalized enhanced vasodilator responsiveness, compared with their sedentary age peers.

Interrelationships of spontaneous growth hormone axis activity, body fat, and serum lipids in healthy elderly women and men

Aging is associated with decreased growth hormone (GH) secretion and plasma insulin-like growth factor-I (IGF-I) levels, increased total and abdominal fat, total and low-density lipoprotein (LDL) cholesterol, and triglycerides, and reduced high-density lipoprotein (HDL) cholesterol. Similar changes in lipids and body composition occur in nonelderly GH-deficient adults and are reversed with GH administration. To examine whether GH/IGF-I axis function in the elderly is related to the lipid profile independently of body fat, we evaluated GH secretion, serum IGF-I and IGF binding protein-3 (IGFBP-3) levels, adiposity via the body mass index (BMI), waist to hip ratio (WHR), dual-energy x-ray absorptiometry (DEXA), and magnetic resonance imaging (MRI), and circulating lipids in 101 healthy subjects older than 65 years. Integrated nocturnal GH secretion (log IAUPGH) was inversely related (P < .005) to DEXA total and abdominal fat and MRI visceral fat in both genders. Log IAUPGH was inversely related to visceral fat in women (P < .005) and men (P < .0001), but was not significantly related to total fat in either gender. In women, log IAUPGH was related inversely to total and LDL cholesterol and positively to HDL cholesterol (P < .008). In men, log IAUPGH was inversely related to total cholesterol and triglycerides (P < .005). In women, HDL cholesterol was inversely related to the WHR (P < .005). In men, triglycerides were positively related (P < .001) to the WHR and DEXA abdominal and MRI visceral fat. Multivariate regression revealed log IAUPGH, but not DEXA total body fat, to be an independent determinant of total (P < .001 for women and P = .01 for men) and LDL (P < .007 and P = .05) cholesterol in both sexes and of HDL cholesterol (P < .005) and triglycerides (P < .03) in women. Log IAUPGH, but not DEXA abdominal fat, was related to total (P < .005 and P < .03) and LDL (P < .03 and P = .05) cholesterol in both genders and to HDL in women (P < .05). Log IAUPGH, but not MRI visceral fat, was related to total cholesterol (P < .03 and P = .05) in women and men. Age, IGF-I, and IGFBP-3 were not significantly related to any body fat or lipid measures, except for a positive correlation of IGF-I with triglycerides in men. Thus, endogenous nocturnal GH secretion predicts total, LDL, and HDL cholesterol levels independently of total or abdominal fat, suggesting that it is an independent cardiometabolic risk factor in healthy elderly people.

Neuroendocrine responses to intravenous infusion of physostigmine in patients with Alzheimer disease

We have reported that physostigmine, a reversible cholinesterase inhibitor, enhances verbal memory in patients with Alzheimer disease (AD). To elucidate the mechanism of cognition enhancement, plasma hormones were measured during high-dose acute and low-dose chronic steady-state intravenous infusions of physostigmine in nine subjects with AD. High-dose hormone responses were measured during and for 24 h after the infusion of physostigmine 1-1.5 mg over 45-60 min. Chronic responses were measured during continuous intravenous infusions of physostigmine at doses (0.5-25 mg/day) that escalated over 2 weeks, and then during 1 week infusion of the dose that optimized cognition (2-12 mg/day) or placebo administered in a randomized, double-blind, cross-over design. A replicable improvement in verbal memory was found in five subjects. High-dose physostigmine infusion that produced noxious side effects resulted in significant elevation above baseline in plasma levels of adrenocorticotrophic hormone (ACTH) (p = 0.0001), cortisol (p = 0.0001), and beta-endorphin (p = 0.0001). Chronic physostigmine administration, in the absence of adverse effects, produced no significant elevation in ACTH (p = 0.08), cortisol (p = 0.70), or beta-endorphin (p = 0.82). These results indicate that high-dose physostigmine activates the hypothalamic-pituitary-adrenal (HPA) axis, likely representing a "stress response." In contrast, cognition-enhancing doses do not produce a peripheral corticosteroid response. Thus, physostigmine-induced memory improvement is independent of the activation of the HPA axis.

Age-related changes in human oestrogen receptor alpha function and levels in osteoblasts

Oestrogen receptors (ERs) are present in human osteoblasts and mediate anti-resorptive effects on bone. Human osteoblast-like cells derived from different aged healthy female donors not on hormone replacement therapy were utilized under well-defined conditions in vitro to investigate ER function and levels. Treatment with 0.1 nM oestradiol-17beta of cell strains derived from eight young women (less than 50 years of age) increased hydroxyproline levels significantly [an average (2.2+/-0.1 S.E.M.)-fold increase], whereas cells derived from nine older women (more than 50 years of age) were not significantly affected. Similarly, cell strains, derived from younger women, transfected with a consensus oestrogen-responsive element linked to chloramphenicol acetyltransferase exhibited a greater response to oestrogen than strains derived from older women. When basal ERalpha levels were measured by enzyme immunoassay and normalized on a per cell basis, osteoblast-like strains derived from younger women (n=24) had a mean value of 2.54+/-0.16 fmol of ERalpha per 10(6) cells. In contrast, strains derived from older women (n=20) had a mean value of 5.44+/-0.48 fmol of ERalpha per 10(6) cells. An age-related increase in ERalpha number was also observed in human skin-derived fibroblasts and directly in dermal biopsies from women not on hormone replacement therapy. The results demonstrate ligand concentration-dependent ERalpha induction and indicate a loss of receptor regulation and diminution of ligand-receptor signal transduction with increasing donor age.

Serum levels of insulin-like growth factor-I are related to age and not to body composition in healthy women and men

BACKGROUND

Aging is accompanied by decreased bone and lean body mass, increased fat mass, and reduced growth hormone (GH) axis function, reflected in diminished levels of insulin-like growth factor-I (IGF-I). Similar changes in body composition occur in nonelderly, GH-deficient adults and are reversible with GH administration, suggesting that diminished GH/IGF-I axis activity may contribute to such age-related changes. To determine the precise pattern of IGF-I decline with age, and to test the hypothesis that this decline is related to concomitant changes in body composition and bone metabolism independent of age, we conducted a cross-sectional survey in 351 healthy participants in the Baltimore Longitudinal Study of Aging.

METHODS

We evaluated relationships among IGF-I, age, and total and regional adiposity, as assessed by body mass index (BMI) and waist-to-hip ratio (WHR); lean body mass, as estimated from urinary creatinine excretion (Crex/ht); bone mineral density (BMD), as assessed by single and dual photon absorptiometry scanning; and circulating levels of parathyroid hormone (PTH), 1,25-(OH)2 D3, 25-OHD, and osteocalcin.

RESULTS

Serum IGF-I levels declined with age (p < .0001) in both men (r = -.51) and women (r = -.67). In men, the decline was linear, whereas IGF-I levels decreased faster in women < 45 years of age than in older women (p < .01) or in men (p < .001). IGF-I was inversely related to BMI (p < .005), WHR (p < .001), and PTH (p < .01) in women. IGF-I was positively related to BMD of the hip and radius in both genders (p < .0003) and to Crex/ht (p < .0005) and osteocalcin (p < .0001) in men. With increasing age, Crex/ht and BMD decreased (p < .0001) and WHR, PTH, and osteocalcin increased (p < .005) in both genders, whereas BMI increased only in women (p < .005). After adjustment for age, IGF-I was not significantly related to BMI, WHR, Crex/ht, or BMD in either gender. IGF-I was positively related to 1,25-(OH)2 D3 (p < .01) independently of age in women.

CONCLUSIONS

Advancing age, rather than declining serum levels of IGF-I, appears to be a major determinant of life-time changes in body composition and BMD in women and men.

Effects of single nightly injections of growth hormone-releasing hormone (GHRH 1-29) in healthy elderly men

Age-related reductions in growth hormone (GH) and insulin-like growth factor-I (IGF-I) may contribute to decreased muscle mass and strength in older persons. The relationship of this phenomenon to skeletal muscle bioenergetics has not been reported. We sought to determine whether administration of GH-releasing hormone (GHRH) would sustain increases in GH and IGF-I and improve skeletal muscle function and selected measures of body composition and metabolism. We measured GH secretion, muscle strength, muscle histology, and muscle energy metabolism by phosphorus nuclear magnetic resonance spectroscopy (31P-NMRS), body composition, and endocrine-metabolic functions before and after 6 weeks of treatment. Eleven healthy, ambulatory, non-obese men aged 64 to 76 years with low baseline IGF-I levels were treated at home as outpatients by nightly subcutaneous self-injections of 2 mg GHRH for 6 weeks. We measured GH levels in blood samples obtained every 20 minutes from 8:00 PM to 8:00 AM; AM serum levels of IGF-I, IGF binding protein-3 (IGFBP-3), and GH binding protein (GHBP); muscle strength; muscle histology; the normalized phosphocreatine abundance, PCr/[PCr + Pi], and intracellular pH in forearm muscle by NMRS during both sustained and ramped exercise; body composition by dual-energy x-ray absorptiometry (DEXA); lipid levels; and glucose, insulin, and GH levels during an oral glucose tolerance test (OGTT). GHRH treatment increased mean nocturnal GH release (P < .02), the area under the GH peak ([AUPGH] P < .006), and GH peak amplitude (P < .05), with no change in GH pulse frequency or in levels of IGF-I, IGFBP-3, or GHBP Two of six measures of muscle strength, upright row (P < .02) and shoulder press (P < .04), and a test of muscle endurance, abdominal crunch (P < .03), improved. GHRH treatment did not alter exercise-mediated changes in PCr/[PCr + Pi] or intracellular pH, but decreased or abolished significant relationships between changes in PCr/[PCr + Pi] or pH and indices of muscle strength. GHRH treatment did not change weight, body mass index, waist to hip ratio, DEXA measures of muscle and fat, muscle histology, glucose, insulin, or GH responses to OGTT, or lipids. No significant adverse effects were observed. These data suggest that single nightly doses of GHRH are less effective than multiple daily doses of GHRH in eliciting GH- and/or IGF-I-mediated effects. GHRH treatment may increase muscle strength, and it alters baseline relationships between muscle strength and muscle bioenergetics in a manner consistent with a reduced need for anaerobic metabolism during exercise. Thus, an optimized regimen of GHRH administration might attenuate some of the effects of aging on skeletal muscle function in older persons.

Age and gender influence basal and stress-modulated hypothalamic-pituitary-thyroidal function in Fischer 344/N rats

To investigate possible gender- and age-associated changes of the hypothalamic-pituitary-thyroid (HPT) axis at baseline and during stress, we studied healthy young (3-month) and old (23-month) female 344/N Fischer rats at the basal state and after 2 h of immobilization (IMMO), in parallel to age-matched male rats. At baseline, there were no major differences on HPT axis functions between young female and male animals. Old age was associated with impaired central thyroid function in both genders, albeit to a much lesser extent in females than in males. Plasma prolactin (PRL) levels were similar in young females and males but were higher in old females than males. IMMO inhibited HPT axis functions in both genders in young, but not old animals. Thus, plasma TSH and hypothalamic TRH mRNA levels were decreased by IMMO in young, but not in old rats of both genders. IMMO increased plasma PRL in young and old males, but did not have any effect in young and old females. In summary, these data indicate that age and gender exert diverse effects on HPT axis functions at baseline and after stress.

Serum hormones in men with human immunodeficiency virus-associated wasting

Weight loss is commonly associated with increased morbidity and mortality in individuals with human immunodeficiency virus (HIV) infection. We performed a nested case-control study of 26 HIV-infected subjects recruited from a cohort of gay men enrolled in the Multicenter Acquired Immunodeficiency Syndrome Cohort Study. To test the hypothesis that hormonal changes precede and may induce the wasting syndrome, we performed a nested case-control study and analyzed serum gonadal steroids and GH in samples of HIV-infected men with or without weight loss, uncomplicated by diarrhea or ever having an opportunistic infection. We studied 13 cases (mean age +/- SD, 45 +/- 7.2 yr) with a mean weight loss of 13 +/- 3.6%, considered to have the wasting syndrome by Centers for Disease Control criteria (weight loss of > 10%) and 13 controls matched for age and duration of follow-up. Serum bioavailable testosterone (T) levels decreased in the case group (P < 0.05) before the definition of wasting was attained, although weight loss had already begun. More impressive declines occurred in serum T (P = 0.012), free T (P = 0.0025), and bioavailable T (P < 0.0001) during the 6 months immediately before documentation of wasting. These changes were concurrent with an increase in serum FSH (P = 0.0135) without a change in serum LH. We conclude that a decline in bioavailable T occurs early in the course of events leading to wasting, suggesting that changes in gonadal hormones may contribute to the multifactorial etiology of the wasting syndrome.

Effects of oral versus transdermal estrogen on the growth hormone/insulin-like growth factor I axis in younger and older postmenopausal women: a clinical research center study

To compare the effects of oral vs. transdermal estrogens on GH secretion and levels of circulating insulin-like growth factor I (IGF-I) and IGF-binding protein-3 (IGFBP-3) in younger vs. older postmenopausal women, we conducted a placebo-controlled, cross-over trial of 6 weeks of oral conjugated estrogen (1.25 mg daily) or transdermal estradiol (100 micrograms/day) administered in random order and separated by an 8-week, treatment-free interval. Sixteen healthy postmenopausal women, ages 49-75 yr, were studied on an NIH-funded General Clinical Research Center grant. Data were analyzed for the combined group as well as in the younger ( <or= 62 yr, n = 8) and older women ( > 62 yr, n = 8). Spontaneous GH secretion, as assessed by 12-h overnight blood sampling at 20-min intervals; GH responsiveness to i.v. bolus injection of GHRH; and levels of serum IGF-I and IGFBP-3, before and after GHRH stimulation, were measured at enrollment and after 6 weeks of each estrogen treatment. Before estrogen treatment, spontaneous nocturnal GH secretion and morning IGF-I levels tended to be lower, IGFBP-3 levels did not differ, and GHRH-stimulated GH levels were significantly reduced in older vs. younger postmenopausal women. Oral estrogens increased spontaneous GH secretion, decreased serum IGF-I levels, and did not alter IGFBP-3 levels, whereas transdermal estrogens did not alter nocturnal GH secretion or morning IGF-I levels and decreased IGFBP-3 levels only in the older women. GHRH-stimulated GH levels were similar before and after oral or transdermal estrogen treatment. In contrast, after, GHRH administration, IGF-I levels were decreased only with oral estrogens, whereas IGFBP-3 levels were decreased with both oral (younger women only) and transdermal (younger and older women) estrogens. We conclude that, in postmenopausal women, oral and transdermal estrogens exert differing effects on the GH/IGF-I axis, but neither form of estrogen completely reverses the known age-related reductions in spontaneous or GHRH-stimulated GH and IGF-I.

Stress-induced inhibition of the hypothalamic-pituitary-thyroid axis is attenuated in the aged Fischer 344/N male rat

Aging is associated with a progressive decrement in the basal activity of the hypothalamic-pituitary-thyroid axis in male Fischer 344/N rats. The aim of this study was to determine whether stress influences the activity of this axis in young and old rats. As prolactin and growth hormone share some regulatory mechanisms with thyrotropin-releasing and thyroid-stimulating hormones, which are influenced by stress, the plasma levels of these two hormones were also determined during immobilization (Immo). To accomplish this, young (3-month-old) and old (23-month-old) male 344/N Fischer rats were immobilized for 2 h; blood was collected by cannulation from the tail artery at different intervals during Immo (0, 5, 30, 60, and 120 min), and brains were removed at the end of Immo. The basal plasma levels of thyroid-stimulating hormone were similar in both groups, but were significantly and progressively inhibited by Immo in young, but not in old rats. The baseline plasma levels of total triiodothyronine were slightly lower in old than in young rats; Immo caused a significant decrease of total triiodothyronine levels only in the young animals. The baseline plasma levels of free triiodothyronine were similar and were not altered by Immo in either age group. The paraventricular nucleus thyrotropin-releasing hormone mRNA levels were lower in old than in young rats under basal conditions; under stress they were significantly inhibited in young, but remained unchanged in old rats. The basal thyroid-stimulating hormone beta mRNA levels in the anterior pituitary were significantly lower in old than in young rats, but were not affected by Immo in either age group. The plasma prolactin levels were similar at baseline and were significantly increased by Immo in both age groups, but significantly more in old than in young rats. The plasma growth hormone levels were also similar at baseline; they were significantly decreased by Immo to a similar extent in both age groups. In summary, these data indicate that the stress-induced decrease in plasma thyroid-stimulating hormone is in part mediated at the level of the hypothalamic thyrotrophin-releasing hormone neuron and that this phenomenon is attenuated in the aged rat.

Testosterone, growth hormone and IGF-I responses to acute and chronic resistive exercise in men aged 55-70 years

We investigated the responses of serum testosterone (T) and human growth hormone (hGH) concentrations to a bout of heavy resistive exercise and the responses of T, hGH, and insulin-like growth factor I (IGF-I) to a 16 wk progressive resistive training program in 13 men (60 +/- 4 yrs). Body composition via hydrostatic weighing and muscle strength using a 3 repetition maximum (3RM) test on 6 variable resistance exercise machines were assessed before and after the training program. Fasting blood samples were drawn on 2 consecutive days prior to training and again on 2 consecutive days after the last day of exercise. Blood was also drawn immediately before and approximately 10 min after a single exercise session during the first wk of training, and after an exercise session of the same relative resistance during the last wk of training. The training program resulted in a 37% increase in upper body strength and a 39% increase in lower body strength (both p < 0.01). Lean body mass increased significantly (61.8 +/- 2.1 vs 63.7 +/- 7.8 kg; p < 0.001) while % fat decreased (26.5 +/- 1.5 vs 24.9 +/- 6.0%; p < 0.01) as a result of training. Serum T concentration was unchanged, but GH increased approximately 18-fold in response to a single bout of resistive exercise before (0.24 +/- 0.08 vs 4.60 +/- 1.35 mg/l) and after (0.26 +/- 0.06 vs 4.66 +/- 1.46 mg/l; p < 0.01) training. Baseline serum concentrations of T, hGH, and IGF-I were unaffected by the training program. We conclude that an acute bout of resistive exercise causes a substantial hGH response in older men, but 16 wks of progressive resistive training does not affect baseline concentrations of the anabolic hormones.

Decreased stress responsivity of central and peripheral catecholaminergic systems in aged 344/N Fischer rats

We investigated the effects of stress on central and peripheral sympatho-adrenal and sympatho-neural functions in healthy, intact young (3-4 mo) and aged (24 mo) male Fischer 344/N rats. Extracellular fluid (ECF) levels of the catecholamines norepinephrine (NE), dihydroxyphenylglycol (DHPG), methoxyhydroxyphenylglycol (MHPG), and dihydroxyphenylacetic acid (DOPAC) were obtained by microdialysis in the paraventricular nucleus (PVN) of the hypothalamus at baseline and during immobilization (IMMO). The baseline levels of these substances were similar in both age groups, and their concentrations increased significantly in response to IMMO. The IMMO-induced increases of NE and MHPG, however, were significantly smaller in old than in young rats. Plasma levels of the catecholamines NE, DHPG, MHPG, DOPAC, dihydroxyphenylalanine (DOPA), epinephrine (EPI), dopamine (DA), and HVA were also determined in young and old rats during IMMO. Basal levels of these substances were significantly higher in old than in young rats. The magnitude of the IMMO-induced increases in the majority of these compounds however, was significantly smaller in old than in young rats. We conclude that, at the basal state, aging in the Fischer rat is associated with normal PVN ECF, but high plasma catecholamine levels; at stress state, however, old rats have substantially lesser activation of their central and peripheral catecholaminergic systems than young rats.

Aging and acute stress decrease corticotropin releasing hormone in the ovary of the Fischer 344/N rat

Corticotropin-releasing hormone (CRH), originally isolated from the hypothalamus, is widely distributed in many extrahypothalamic central nervous system sites, and in the periphery. Immunoreactive (ir)-CRH has been identified in rat and human inflammatory sites, in rat testicular Leydig cells, and in rat thecal and stromal ovarian cells. In the current study, we investigated whether aging and stress are associated with changes in ovarian ir-CRH in the rat. Healthy young (3-4 mo) and old (24 mo) female Fischer 344/N rats (6 per group) were studied in the morning, before and after being stressed by 120 min of immobilization, and were sacrificed by decapitation. Young females were all in proestrous, and old females were in constant anestrous. Pre-immobilization corticosterone (CORT) levels were similar in both age groups; immobilization produced a dramatic increase in CORT in both groups; however, the increase was smaller in the old rats, although this did not reach statistical significance (P < 0.06). Immunoreactive CRH was detected in the ovaries of all rats, and its distribution and intensity were quantified masked to the age and treatment group, in the theca, granulosa, stroma, and corpus luteum. At baseline, ir-CRH was 50% lower in old than in young rats in the theca and stroma by both distribution and intensity. Stress was associated with a decrease of ir-CRH levels in the theca in both age groups, albeit to a significantly lesser extent in old rats (old 35% versus young 70%). These data suggest a functional and, perhaps, developmental role for ovarian CRH.

Neuroendocrine responses to intravenous infusion of arecoline in patients with Alzheimer's disease

We have reported that arecoline, a muscarinic receptor agonist replicably enhanced verbal memory in five of nine subjects with Alzheimer's disease (AD). To investigate the mechanism of cognitive improvement, circulating hormone measurements were made during high-dose acute and low-dose chronic intravenous (i.v.) arecoline administration to AD patients. Acute hormone responses were measured during, and for 6 h after, infusion of arecoline 5 mg i.v. over 30 min. Chronic responses were measured in cognitive responders during continuous i.v. infusion of arecoline escalating over 2 weeks (0.5-40 mg/day) and then during a 1 week infusion of the dose optimizing cognition (4-16 mg/day). Acute arecoline administered to 14 subjects produced unpleasant side-effects (e.g. nausea, vomiting), mean adrenocorticotrophic hormone (p = .0006), cortisol (p = .0001) and beta-endorphin (p = .0001) levels were elevated. During chronic arecoline treatment, no side-effects occurred and plasma cortisol, adrenocorticotrophic hormone and beta-endorphin levels were unchanged in nine subjects overall and in five cognitive responders. Thus, high-dose arecoline activates the hypothalamic-pituitary-adrenal (HPA) axis and may increase other anterior pituitary hormone levels, likely representing a 'stress response', but cognition-enhancing, low doses of arecoline do not produce a glucocorticoid response. Hence, arecoline-induced memory improvement is not due to the induction of 'stress' nor to the elevation of peripheral corticosteroid levels.

Male Fischer 344/N rats show a progressive central impairment of the hypothalamic-pituitary-adrenal axis with advancing age

We investigated the effects of aging on the regulation of hypothalamic-pituitary-adrenal function and hippocampal steroid receptors in a series of in vivo and in vitro studies conducted in healthy intact 2-, 8-, 18-, and 24-month-old male Fischer 344/N rats. Basal plasma ACTH levels were similar among age groups, and basal plasma corticosterone levels showed a significant aging-associated decline. Two i.v. doses (2 and 20 micrograms/kg BW) of rat CRF elicited significantly greater and delayed ACTH and greater corticosterone responses in older rats, consistent with the pattern encountered in hypothalamic CRF deficiency. In contrast, the i.v. injection of a muscarinic agonist, arecoline, elicited similar ACTH and corticosterone responses in all age groups. An i.v. injection of ACTH-(1-24) evoked lower corticosterone responses in the older (18- and 24-month-old) than in the younger (2- and 8-month-old) groups of rats, consistent with an impairment of hypothalamic-pituitary-adrenal axis function in older animals. Steady state mRNA levels of mineralocorticoid and glucocorticoid receptors were significantly decreased in the hippocampus of the 8-, 18-, and 24-month-old rats, compatible with maturational, rather than senescent, changes. CRF mRNA levels in the paraventricular nucleus of the hypothalamus, CRF content, and in vitro secretion by whole explanted hypothalami were progressively and significantly reduced with age, whereas the steady state levels of arginine vasopressin mRNA were significantly increased with age. Steady state levels of POMC mRNA were decreased, and ACTH content and in vitro secretion by corticotrophs were increased with age in the anterior pituitary. We conclude that male Fischer 344/N rats show a progressive hypothalamic CRH deficiency with advancing age, which appears to be associated with elevated production of arginine vasopressin in the hypothalamus.

Effects of age and sex on basal and dopamine-inhibited in vitro prolactin release, and dopamine receptor binding, by the rat adenohypophysis

We measured basal and dopamine-inhibited pituitary cell prolactin (PRL) release in vitro, and dopamine receptor binding in pituitary homogenates, from intact male and female Wistar rats of varying ages. During 48-72 hours in culture, the baseline secretion rate of PRL from pituitary cells of old (24 months) male rats was less than one-half that from cells of mature (6 months) male rats, whereas the corresponding basal secretion rate of PRL from cells of old female rats was nearly 3-fold greater than that from cells of mature female rats (p < 0.001). After in vitro exposure to various concentrations of dopamine (10(-10)M to 10(-6)M), PRL secretion decreased from pituitary cells of both mature and old rats (p < 0.001). However, repeated measures analysis of variance revealed an age-related dose-dependent decrease in the magnitude of dopamine-inhibited PRL release from cells of both male and female rats (p < 0.001). Dopamine receptor number did not differ with age (3-25 months), but was 2 to 3-fold greater in female than in male rats (p < 0.01). Receptor affinity was decreased with age only in female rats, and was greater in female than in male rats (p < 0.05). These data suggest that the decrease in dopamine-inhibited PRL release from pituitary cells of old male and female rats is not due to altered pituitary dopamine receptor binding, despite certain sex differences.

Oral arginine-lysine does not increase growth hormone or insulin-like growth factor-I in old men

BACKGROUND

Older adults tend to have reduced growth hormone (GH) secretion and insulin-like growth factor I (IGF-I) levels as well as changes in body composition which are partially reversed by GH injections. Arginine stimulates GH release, and lysine may amplify this response. We investigated whether oral arginine/lysine could be used to increase basal IGF-I and GH levels in non-obese old men (age 69 +/- 5 years; mean +/- SD) to values similar to those of untreated young men (age 26 +/- 4 years).

METHODS

Two groups of 8 healthy old men were treated with 3 g of arginine plus 3 g of lysine or with placebo capsules twice daily for 14 days. Before and on day 14 of each treatment GH levels were determined in blood samples taken at 20-minute intervals from 2000-0800 h, IGF-I was measured at 0800 h, and a 1 microgram/kg GHRH stimulation test was done.

RESULTS

At baseline, mean GH peak amplitude (p < .02) and serum IGF-I (p < .0001) were lower, whereas GHRH responses were similar, in old vs young men. Arginine/lysine did not significantly alter spontaneous or GHRH-stimulated GH levels, or serum IGF-I. Arginine absorption was age-independent. The correlation (p < .005) between measured increments in serum arginine and increases in serum GH after a single dose of arginine/lysine was similar in old and young groups.

CONCLUSIONS

Our data suggest that oral arginine/lysine is not a practical means of chronically enhancing GH secretion in old men.

Human growth hormone and human aging

In humans, both aging and GH deficiency are associated with reduced protein synthesis, decreased lean body and bone mass, and increased percent body fat. In healthy individuals, spontaneous and stimulated GH secretion, as well as circulating IGF-I and IGFBP-3 levels, are significantly decreased with advancing age. The extent to which these age-related changes in GH and IGF-I contribute to alterations in body composition and function remains to be elucidated. GH treatment of GH-deficient adults or old men with reduced IGF-I levels with exogenous GH increases plasma IGF-I, nitrogen retention, and lean body mass, decreases percent body fat, and exerts little effect on bone mineral density. Short-term adverse effects of GH therapy have been minimized by using low-dose regimens, but it is still uncertain whether long-term GH supplementation in adult life increases the risk of metabolic abnormalities or malignancy. Administration of GHRH, which has been shown to maintain the pattern of pulsatile GH secretion in old men, may represent another possible physiological approach to therapy. It may be justifiable initially to limit use of GH to certain elderly patients such as those suffering from catabolic illnesses, malnourishment, burns, cachexia, etc. A great deal more research will be necessary to determine whether normalization of GH and IGF-I levels in healthy older persons will lead to improvements in their physical and psychological functional capacity and quality of life.

Continuous subcutaneous infusions of growth hormone (GH) releasing hormone 1-44 for 14 days increase GH and insulin-like growth factor-I levels in old men

Twice daily sc injections of GHRH increase serum GH and IGF-I levels in healthy old men to values like those of untreated young men by producing high amplitude GH peaks after the injections. In the present study, we measured baseline insulin-like growth factor-I (IGF-I) 24-h profiles of GH release, and responses to GHRH stimulation tests in healthy young and old men. Old men were then given, in random order, 1 and 2 mg continuous sc GHRH 1-44 infusions daily for 14 days with an intervening 14-day treatment-free period. The study protocol was repeated on day 14 of each treatment. At baseline, mean duration of GH peaks (P < 0.005) and IGF-I levels (P < 0.0001) were lower in old men. Both doses increased (vs. old basal) mean 24-h GH, integrated area under the GH curve, and GH peak number (P < 0.05), as well as serum IGF-I (P < 0.001). Interpeak GH levels also increased during low (P < 0.01) and high (P < 0.05) dose treatment. Significant increases in mean GH and integrated area under the GH curve occurred only during the day (0800-2000 h) during both low (P < 0.01) and high (P < 0.05) dose treatment. Treatment also decreased nocturnal peak GH amplitude and duration. GH responses to GHRH stimulation tests did not differ with age at baseline, or in old men after treatment. Thus, continuous, short-term sc administration of GHRH to healthy old men restores subnormal GH secretion and IGF-I levels by increasing GH peak frequency and interpeak secretion, particularly during the day.

Immobilization stress rapidly decreases hypothalamic corticotropin-releasing hormone secretion in vitro in the male 344/N Fischer rat

Corticotropin-Releasing-Hormone (CRH) is the principal secretagogue for plasma ACTH and corticosterone secretion and plays an important role in coordinating a variety of physiological and behavioral responses to stress. To explore whether there is a rapid change in the secretory response of the hypothalamic CRH neuron during acute stress, we report here a study of the effects of KCl and norepinephrine (NE) on CRH release in vitro from rat hypothalami explanted after 5, 30, 60, and 120 minutes of immobilization. We also measured the plasma levels of ACTH, beta-endorphin, corticosterone, prolactin, GH, and TSH at these intervals. As the duration of immobilization increased, KCl and NE-induced CRH release in vitro progressively fell. After reaching a maximal rise after 30 minutes of immobilization, plasma ACTH, beta-endorphin, and prolactin progressively fell in plasma, whereas corticosterone remained elevated up to 120 minutes; TSH and GH secretion rapidly declined and remained suppressed. Taken together, these data suggest that during immobilization stress, the responsiveness of the hypothalamic CRH neuron rapidly falls, owing either to CRH depletion and/or desensitization to NE, and this is paralleled by a concomitant decrease in pituitary-adrenal responsiveness.

Central hypothyroidism is associated with advanced age in male Fischer 344/N rats: in vivo and in vitro studies

We investigated age-related alterations in hypothalamic-pituitary-thyroid function in a series of in vivo and in vitro studies in 2-, 8-, 18-, and 24-month-old male Fischer 344/N (F344/N) rats. Thyroid histology showed progressive follicular loss with advancing age; this was associated with significant and progressive decrements in plasma levels of free T4 and free T3, but not immunoreactive TSH, which remained unchanged with age. This was accompanied by a progressive age-dependent loss in in vivo responsivity of the thyrotroph to synthetic TRH and a paradoxically augmented response of GH to this peptide in the oldest rats. Steady state levels of prepro-TRH mRNA in the hypothalamic paraventricular nucleus were decreased with age, whereas TRH content in and in vitro secretion by whole hypothalami remained unchanged. Both anterior pituitary steady state TSH beta-subunit mRNA levels and TSH content were decreased with age. Taken together, these data suggest that aging in male F344/N rats is associated with a progressive, centrally mediated decrease in thyroid function. The relative contributions to this phenomenon of age-related alterations in supra-hypothalamic and/or hypothalamic vs. pituitary thyrotropic function remain to be determined, as do the relationships between changes in hypothalamic-pituitary-thyroid function and those in aging per se.

Growth hormone (GH)-releasing hormone-(1-29) twice daily reverses the decreased GH and insulin-like growth factor-I levels in old men

Aging is associated with decreased GH and insulin-like growth factor-I (IGF-I) levels and lean body mass, and increased body fat. Recombinant human GH treatment of old men partially reverses body composition changes. Administration of GH-releasing hormone (GHRH) to GH-deficient children and young adults increases GH and IGF-I levels while preserving physiological GH release. We investigated whether GHRH injections restore GH and IGF-I levels in old men to the levels in young men. Healthy young (n = 9; 26.2 +/- 4.1 yr; mean +/- SD) and old (n = 10; 68.0 +/- 6.2 yr) nonobese men underwent baseline blood sampling for measurements of IGF-I and 24-h profiles of GH release, followed by iv bolus GHRH stimulation tests. Old men then took, randomly, both low (0.5 mg) and high (1 mg) dose GHRH-(1-29) sc injections twice daily for 14 days, with an intervening 14-day nontreatment period. The study protocol was repeated on day 14 of each treatment. At baseline, the mean peak duration of spontaneous GH release (P less than 0.005) and IGF-I levels (P less than 0.0001) were lower in the old men. GHRH treatment evoked dose-related increases in all parameters, with significant differences (vs. old basal values) in mean 24-h GH (P less than 0.001), area under peaks (P less than 0.001), peak amplitude (P less than 0.05), and IGF-I (P less than 0.005) only at the high dose. After high dose treatment, there were no significant differences in these parameters between age groups. Peak and integrated responses to iv GHRH stimulation tests did not differ between young and old men either before or during GHRH treatment. Baseline serum levels of both testosterone (P less than 0.01) and phosphate (P less than 0.05) were lower in the older men. Phosphate levels increased (P less than 0.05) during GHRH treatment. GHRH treatment did not affect fasting glucose, urinary C-peptide, blood pressure, or chemistry and hematology profiles. Thus, short term sc administration of GHRH to healthy old men reverses age-related decreases in GH and IGF-I, suggesting that prolonged treatment could improve age-related alterations in body composition.

Glucose tolerance in women: the effects of age, body composition, and sex hormones

OBJECTIVE

To determine the separate and interactive effects of age, phase of the menstrual cycle, menopausal hormone status, body fat mass, and regional fat distribution on glucose tolerance in healthy women.

DESIGN

Retrospective study.

SETTING

The Baltimore Longitudinal Study of Aging.

PATIENTS

Two hundred sixty healthy women aged 22-89 years.

MEASUREMENTS

Plasma levels of estradiol and progesterone, body mass index (BMI), waist-to-hip ratio (WHR), and plasma glucose values in the fasting state (FPG) as well as 120 minutes after 40 gm/m2 of oral glucose (G120) were measured for each participant.

RESULTS

We found a progressive decline in oral glucose tolerance of 0.4 mM (6.7 mg/dL)/decade at G120) in women from early to late adult years, with no relationship to phase of the menstrual cycle and no abrupt change associated with the menopause. Multiple regression analysis revealed significant, independent effects of BMI and WHR on FPG and G120. The influence of age (P less than 0.01) on G120 was stronger than that of the BMI or WHR (P less than 0.05). There was no significant relationship between the levels of endogenous sex hormones and glucose tolerance after adjustments for age, BMI, and WHR. However, women taking oral contraceptives, but not those receiving postmenopausal replacement therapy, did exhibit mildly elevated G120 values.

CONCLUSIONS

Age per se, and to a lesser extent BMI and WHR, but not levels of endogenous sex steroids, contribute to the physiological decline in glucose tolerance in older women.

Age-related changes in the mechanisms of LHRH-stimulated LH release from pituitary cells in vitro

In vitro release of LH in response to LHRH, phorbol myristate acetate (PMA), the ionophore A23187, and nifedipine was evaluated in primary cultures of anterior pituitary cells from intact mature (6 to 7 month) and old (23 to 24 month) male Wistar rats. LH release from pituitary cells is reduced approximately 30% and 60% after 4 and 48 h of 10(-7) M LHRH stimulation in cells of old rats, respectively. This impairment may be secondary to a loss of LHRH receptors. LHRH-stimulated LH release from cells of mature rats was inhibited 70% by the voltage-gated calcium channel blocker, nifedipine (10(-6) M), whereas LHRH-stimulated LH release from cells of old rats was too low to detect the effects of this drug. Age changes can be partially reversed by A23187 and PMA during 4 h, but not 48 hrs of stimulation. It therefore appears that short- and long-term (4 h and 48 h, respectively) stimulation of LH release may proceed through separate mechanisms that are differentially affected by aging.

Transdermal estradiol with oral progestin: biological and clinical effects in younger and older postmenopausal women

The purpose of this study was to compare the biochemical and clinical effects of transdermal estrogen replacement therapy (tERT) in younger and older postmenopausal women. We treated 15 younger (less than 60 y) and 13 older (greater than or equal to 60 y) healthy postmenopausal women (45-72 y) with four successive 8-week regimens of tERT at doses of 0 to 150 micrograms/day, combined with cyclic oral medroxyprogesterone acetate (MPA). In both age groups, there were similar (p = .0001) dose-responsive increases in plasma estrogen levels and decreases in LH and FSH levels, although LH values were lower in older women both before and after tERT (p less than .02). The addition of MPA further suppressed LH and, to a lesser extent, FSH in both younger and older women. The ratio of estrogenized to nonestrogenized vaginal cells increased with tERT (p less than .007) in both age groups, but significant symptomatic improvement of vaginal irritation was noted only at the highest tERT dose. Adverse effects unrelated to age included short-term nausea in 4/28 women, and skin irritation at the patch sites in 20/28 women. Vaginal bleeding was of shorter duration, but breast tenderness was more common in older women. Further studies of long-term tERT effects in elderly women are indicated.

Spontaneous and glucocorticoid-inhibited adrenocorticotropic hormone and cortisol secretion are similar in healthy young and old men

We investigated the effects of age on pituitary-adrenocortical function in healthy young (21-38 yr, n = 11) vs. old (66-78 yr, n = 11) men by drawing frequent serial basal blood samples from 2000-0800 h for measurement of ACTH and cortisol, followed by an iv ovine CRH (oCRH) stimulation test. Subjects were readmitted at intervals and given increasing doses of oral dexamethasone (0.15, 0.3, 0.6, 1 mg) at midnight, followed by repeat blood sampling from 0400-0800 h and oCRH testing. We compared mean hormone levels for the entire 12-h and three component 4-h periods of the basal visit, and for each 4-h dexamethasone visit using the Mann-Whitney U test and repeated measures analysis of variance. Pulsatile secretion was characterized using the Pulsar computer program. Basal mean 12-h and 4-h ACTH and cortisol values did not differ with age (P greater than 0.1). Pulse analysis revealed no age change in the corresponding values for peak frequency, amplitude, or duration for either hormone examined. Increasing doses of dexamethasone produced progressive inhibition of mean ACTH and cortisol levels (P less than 0.001) as well as decreased (P less than 0.01) pulse frequency, amplitude, and duration with no age differences (P greater than 0.1). ACTH and cortisol responses to oCRH were progressively suppressed by increasing doses of dexamethasone (P less than 0.02) and did not differ between age groups (P greater than 0.3) except for a slightly higher peak cortisol response (P = 0.05) in the older men at the 0.3 mg dexamethasone dose. We conclude that basal and oCRH-stimulated ACTH and cortisol secretion, as well as sensitivity of the ACTH-cortisol axis to glucocorticoid feedback suppression, are essentially unaltered with age in healthy men.

Effects of progestin-opposed transdermal estrogen administration on growth hormone and insulin-like growth factor-I in postmenopausal women of different ages

Prior studies in women have shown a positive correlation of endogenous estrogen levels with spontaneous and stimulated GH secretion and basal insulin-like growth factor-I (IGF-I) levels. In postmenopausal women, estrogen replacement therapy (ERT) by the oral route increases basal and GHRH-stimulated GH secretion but decreases basal IGF-I levels. To assess the corresponding effects of transdermal ERT (tERT) on this axis, we administered four 8-week regimens of transdermal 17 beta-estradiol (Estraderm; 0, 50, 100, or 150 micrograms/day) combined with oral medroxyprogesterone acetate (10 mg each day) during weeks 3-4 and 7-8 of each 8-week regimen (except placebo) to 28 healthy nonobese postmenopausal women, aged 45.3-71.8 yr. Basal levels of estradiol (E2), GH, and IGF-I as well as GH responsivity to bolus iv administration of GH-releasing hormone-(1-44) (1 micrograms/kg), were measured before tERT and at weeks 6 and 8 of each regimen; estrone (E1) levels were measured before tERT and at week 6 of each regimen. Before tERT, age was inversely correlated with both the peak GH response to GHRH (r = -0.43; P less than 0.02) and basal IGF-I levels (r = -0.37; P less than 0.05), but not with basal E2, E1, or GH levels. There were progressive increases in plasma E2 and E1 levels with increasing doses of tERT (P = 0.0001), independent of age (P greater than 0.2) and body mass index (P greater than 0.2). Mean basal GH and IGF-I levels were not altered significantly by tERT or medroxyprogesterone acetate. Peak and integrated GH secretory responses to exogenous GHRH decreased with increasing tERT dose (P less than 0.01) in both younger and older postmenopausal women. Our findings suggest that the known effects of tERT on bone and other tissues are not mediated via increases in circulating levels of immunoreactive GH or IGF-I, but do not preclude the possibility of tERT-induced increases in the biological activity or paracrine action of IGF-I.

Plasma levels of estradiol, testosterone, and DHEAS do not predict risk of coronary artery disease in men

Prior studies have reported men with coronary artery disease (CAD) to have elevated plasma levels of estrogens and reduced concentrations of dehydroepiandrosterone (DHEA) or DHEA-sulfate (DHEAS). We investigated whether gonadal steroids or DHEAS are risk factors for CAD in men, using a prospective design, in a well characterized population studied at regular intervals. We studied 46 men (Cardiac group) who developed CAD and 124 men (Control group) who remained free of CAD (mean follow-up, 9.5 years). We measured testosterone (T), estradiol (E2), and DHEAS, as well as plasma binding of T and E2, in samples stored before the onset of CAD (Cardiac group) or at matched times (Control group). Body mass index, blood pressure, and total serum cholesterol were measured at each visit. Both systolic blood pressure (SBP; P less than 0.001) and cholesterol (P less than 0.001) were increased in the Cardiac group, but no significant differences were found in total or free T or E2, the ratio of E2/T, or DHEAS between the two groups. The difference in cholesterol was significant only in men less than or equal to 65 years old (P less than 0.001), and SBP only in men greater than 65 years old (P less than 0.005). Cholesterol (P less than 0.05) and E2 (P less than 0.001) appeared to decrease with age in the Cardiac, but not the Control, group. Moreover, total (P less than 0.01) and free E2 (P less than 0.05) were lower only in Cardiac men less than or equal to 55 years old.(ABSTRACT TRUNCATED AT 250 WORDS)

Discordant effects of aging on prolactin and luteinizing hormone-beta messenger ribonucleic acid levels in the female rat

To examine the molecular genetic basis for the age-related increase in PRL secretion and decrease in LH production in the rat, we measured steady state levels of PRL and LH beta mRNA in pituitary homogenates and cell lysates from monolayer adenohypophyseal cultures. These mRNA levels were compared with the corresponding levels of immunoreactive PRL and LH in sera and culture media. Paired groups (n = 4-10/group) of intact and 4-week ovariectomized mature (6-7 months old) and old (23-25 months old) female Wistar rats were studied. Serum PRL levels were 550% higher in intact old vs. mature rats (P less than 0.001), whereas the corresponding pituitary homogenate levels of PRL mRNA were similar (P greater than 0.4). Medium PRL concentrations were 230% greater (P less than 0.006) whereas cell lysate concentrations of PRL mRNA were unaltered (P greater than 0.2) in monolayer cultures from intact old vs. mature rats. Serum PRL levels were 650% higher (P less than 0.003) and pituitary homogenate PRL mRNA levels were slightly increased (P less than 0.04) in ovariectomized old vs. mature rats. Neither serum LH values (P greater than 0.07) nor pituitary homogenate LH beta mRNA levels (P greater than 0.1) differed in intact old and mature rats, whereas the corresponding medium concentrations of LH were reduced (P less than 0.001). Ovariectomized old vs. mature rats exhibited reductions in serum (P less than 0.02) and medium (P less than 0.001) LH concentrations, as well as in pituitary homogenate (P less than 0.002) and cell lysate (P less than 0.006) LH beta mRNA levels. Thus, these data revealed coordinate decreases with age in LH beta mRNA and LH secretion, particularly in ovariectomized rats, suggesting an age-related alteration at or before LH beta gene transcription. These findings parallel observations on other genes whose products change with age. In contrast, the observation that the increased secretion of PRL in old rats is accompanied by little or no increase in PRL mRNA is novel and suggests that age-related alterations in PRL gene expression proceed through a posttranscriptional mechanism.

Thyroid hormone elevations during acute psychiatric illness: relationship to severity and distinction from hyperthyroidism

Acute psychiatric illness may be accompanied by transient hyperthyroxinemia. The mechanism of this phenomenon was examined by determining the role of thyrotropin (TSH) in the genesis of this state. Serial measurements of TSH, thyroxine (T4), free T4 index (FT4I), triiodothyronine (T3), and free T3 index (FT3I) were performed in 45 acutely hospitalized patients with major psychiatric disorders. Twenty-two (49%) patients exhibited significant elevations (greater than or equal to 2 SD above mean value of controls) of one or more thyroid hormone (or index) levels. Among depressed patients with elevated FT4I, TSH was higher (p less than .05) on the day of the peak FT4I than on the day of the FT4I nadir. There were significant positive correlations between psychiatric symptom severity and levels of FT4I among both depressed (p less than .01) and schizophrenic (p less than .025) patients. These data show that elevations of T4, FT4I, T3, and FT3I are common among psychiatric inpatients, especially early in their hospitalization, and that levels of thyroid hormones are correlated with severity of psychiatric symptomatology. TSH is higher early in the acute phase of illness and is not suppressed in the face of elevated thyroid hormone levels, a finding that distinguishes this phenomenon from ordinary hyperthyroidism. Elevations of peripheral thyroid hormone levels, particularly among depressed patients, may result from a centrally-mediated hypersecretion of TSH.

Impaired down-regulation of pituitary dopamine receptors by estradiol in aged rats

Administration of 17 beta-estradiol to mature (6-12 months) rats results in a more than 50% reduction in pituitary dopamine receptor concentrations, without affecting binding affinity. In contrast, when the same manipulation is performed on senescent (24-25 months) rats, negligible change in receptor concentration occurs. These results suggest that age-related increases in estrogen-stimulated prolactin release are not due to decreased dopaminergic inhibition at the receptor level.

Osteoporosis: diagnostic screening and its place in current care

Osteoporosis, or decreased total bone mass, results from a number of factors: accelerated trabecular bone loss in postmenopausal women; age-related loss of trabecular and cortical bone; and multiple chronic diseases and medications. Routine laboratory and radiographic tests are not helpful in assessing bone turnover. However, a ratio of urinary calcium to creatinine exceeding 0.16 on a spot urine sample obtained in the fasted state suggests high bone turnover. Both single and dual photon absorptiometry are useful research tools but are unproved screening tests, especially in light of the more frequent use of preventive measures, such as postmenopausal hormone replacement therapy, calcium supplementation, and weight-bearing exercise.

Comparison of the effects of lung cancer, benign lung disease, and normal aging on pituitary-gonadal function in men

We retrospectively determined serum total testosterone (T), fraction of T bound, free T index, LH, and FSH levels in 122 men with malignant lung disease, 32 men with benign lung disease, and 106 normal men. Men with malignant and, to a lesser extent, benign lung disease had decreased serum total T and free T index values at the 5th percentiles, with elevations of LH and FSH levels at the 95th percentiles. Linear regression analysis showed reductions in total T and free T index and increases in FSH, but not LH, levels with age in each group. Using multivariate analysis, we found stronger independent effects of disease than age on serum total T and fraction of T bound, but a greater influence of age on free T index. Serum LH values differed by diagnosis, whereas FSH differed by age. Relative to values in the normal men, mean serum total T levels were reduced in men with lung cancer; the fraction of T bound was decreased in the men with lung cancer and increased in the men with benign lung disease, the free T index was decreased in the men with both malignant and benign lung disease, and LH was increased in the men with lung cancer. The hormone and hormone binding results were similar in men with different types of lung cancer. Biochemical evidence of primary and secondary (or combined primary and secondary) hypogonadism was present in 50-59% and 28-32%, respectively, of the men with malignant and benign lung disease vs. 10% of the normal men. These data suggest that 1) there is an increased prevalence of both pituitary gonadotropic and testicular dysfunction in men with malignant and, to a lesser extent, benign chronic lung disease, and 2) the effects of illness are independent of, and quantitatively greater than, those due to age.

Pituitary hormones and aging

This article reviews the reported effects of aging on pituitary structure and function in man.