Endocrinology in aging

Endocrine and metabolic changes in human aging

Numerous alterations in hormonal secretion occur with aging. In general, these tend towards a disintegration of the normal cyclic secretory patterns resulting in lower total circulating levels. In addition, declines in receptors and postreceptor function further decreases the ability of the hormonal orchestra to maintain coordinated function throughout the organism. Clues to some of these age-related changes in humans may come from the study of simpler organisms where regulatory systems are known to modulate the aging process. In particular, the interactions among the environment, hormones, and insulin receptor genes have led to new insights into the genetic control of longevity and the development of syndrome X.

1,25-Dihydroxyvitamin D fluctuations in cardiac surgery are related to age and clinical outcome*

OBJECTIVE

To investigate the interrelationship between cardiac surgery, age, circulating concentrations of the vitamin D hormone 1,25-dihydroxyvitamin D, and clinical outcome.

DESIGN

Prospective, monocentric, two-arm parallel study.

SETTING

Tertiary Heart and Diabetes Center in the Federal State of North Rhine-Westphalia, Germany.

PATIENTS

Twenty-nine cardiac surgical patients aged ≤ 65 yrs and 30 patients ≥ 75 yrs.

MEASUREMENTS

We assessed 1,25-dihydroxyvitamin D and other biochemical parameters of mineral metabolism (calcium, phosphate, 25-hydroxyvitamin D, and parathyroid hormone), various inflammatory markers (C-reactive protein, interleukin-6 and 8), and different immunological parameters (CD4 and CD8 cells, monocyte HLA-DR expression). We collected blood samples preoperatively, immediately after surgery, and on postoperative days 1, 5, and 30. In addition, we assessed adverse outcome until discharge as a composite of myocardial infarction, low cardiac output syndrome, infection, stroke, or in-hospital death.

RESULTS

There were significant transient cardiac surgery-related fluctuations in 1,25-dihydroxyvitamin D and the aforementioned parameters of mineral metabolism, inflammation, and immune status. Compared to younger patients, older patients had consistently lower 1,25-dihydroxyvitamin D and phosphate levels (p = .013 and p = .036, respectively) and significantly higher interleukin 6 and 8 levels (p = .008 and p < .001, respectively). Circulating 1,25-dihydroxyvitamin D was directly related to glomerular filtration rate (R(2) = .227; p < .001) and inversely related to interleukin 6 (R(2) = .105; p = .012). The rate of adverse outcome tended to be higher in older than in younger patients (20.0% vs. 3.5%; p = .081). In risk score-adjusted logistic regression analysis, adverse outcome risk decreased by 7.7% (SE: 3.7%) for each pmol/L increment in 1,25-dihydroxyvitamin D (p = .037).

CONCLUSIONS

Circulating 1,25-dihydroxyvitamin D levels fluctuate in relation to cardiac surgery. Low 1,25-dihydroxyvitamin D levels are associated with inflammatory processes and age-related differences in clinical outcome. Future studies should determine whether therapies aimed at treating low 1,25-dihydroxyvitamin D levels can improve the outcome in older cardiac surgery patients.

Clinical analysis of 103 elderly patients with pituitary adenomas: transsphenoidal surgery and follow-up

Our objective was to study the single-center clinical diagnosis and surgical treatment of pituitary adenomas in elderly patients. A retrospective single-center study was performed on 103 patients aged 65 years and over with a diagnosis of pituitary adenoma and with a mean follow-up duration of 6.1+/-1.3 years. All cases were macroadenomas. The clinical course was dominated by visual disturbance and headache, and hypopituitarism was also not uncommon. Despite the majority of patients (81.6%) having coexisting medical conditions, transsphenoidal surgery (TSS) was performed and well tolerated in all patients. Before 2000, conventional post operative radiotherapy was performed in 32 patients with radiological evidence of tumor remnants. Long-term follow-up revealed no tumor regrowth. However, progressive hypopituitarism was found in a number of patients. After 2000, gamma knife surgery was used for selected cases with documented tumor regrowth. All the remnant tumors treated using this approach appeared to either stabilize or regress without side-effects during the study period. The findings of this analysis support the use of TSS as a feasible treatment for pituitary adenomas in elderly patients. Age alone is no longer considered a contra-indication for treatment with TSS. With appropriate perioperative management, the technique is associated with minimal morbidity and is tolerated well by patients regardless of age. Additional follow-up, especially neuroradiological follow-up is needed to monitor tumor recurrence. However, the indications for post operative radiotherapy should be better defined.

Hormone-dependent aging problems in women

One of the major social issues nowadays is the aging society. Korea is already an aging society, and 63 cities and districts are ultra-aged societies where the rate of people older than 65 yr exceeds 20%. Among them, more than 67% are women. These statistics reveal the importance of healthcare for older women. Disease and disability of older women are very closely related to the loss of female sex hormones after menopause. Major hormone-dependent aging problems in women such as osteoporosis, Alzheimer's disease (AD), urinary incontinence, and coronary atherosclerosis were surveyed in this review, and the key role of hormones in those diseases and hormone replacement therapy (HRT) were summarized. We expect that this review would provide some understanding of factors that must be considered to give optimal care to older women for healthy lives.

Management of nutritional problems in subacute care

Poor nutritional status is one of the major factors associated with functional decline and mortality in older persons. Older persons are at increased risk for malnutrition because of the physiologic anorexia of aging. During a stay in a subacute care facility, attention to nutrition is a major component of the rehabilitative process. The pathophysiology of malnutrition, diagnostic techniques available to diagnose malnutrition, causes and management of protein energy malnutrition, specific nutritional problems caused by vitamin and trace element deficiency, and nutritional management of specific diseases (e.g., hip fracture and diabetes mellitus) are reviewed.

Psychosocial stress and HPA functioning: no evidence for a reduced resilience in healthy elderly men

In order to investigate if HPA functioning is altered with age, the present study was conducted. Fifteen healthy elderly men (60-76 years; mean age 66.5 +/- 1.48 yrs.) and 12 younger adults (20-29 years; mean age 25.6 +/- 0.77 yrs.) collected salivary free cortisol profiles after awakening for basal HPA activity. Then, all subjects were exposed to the "Trier Social Stress Test" (TSST). This psychosocial stress protocol consists of a free speech and a mental arithmetic task of 13 minutes duration performed in front of an audience. Beside the assessment of endocrine and cardiovascular responses to the stressful task ratings of depression, mood and perceived stressfulness were obtained. Results show that younger and elderly men had similar morning cortisol profiles after awakening with both groups showing the expected rise after awakening (P=0.004). The TSST induced significant increases in ACTH, total plasma cortisol, saliva free cortisol, and heart rates (all P<0.0001). Regardless of age, both age groups showed comparable endocrine response patterns when confronted with the stressor. However, cardiovascular responses were significantly higher in younger men compared to elderly men (P=0.03). Catecholamine data revealed significant norepinephrine and epinephrine increases due to the stressor (both P<0.0001) with a trend toward elevated norepinephrine levels in elderly men (P=0.058). In sum, the investigated basal and response parameters of HPA functioning neither support the idea of a reduced resilience in healthy aged humans nor do they appear to strengthen assumptions derived from the so called "glucocorticoid cascade hypothesis".

Mapping of cocaine and amphetamine regulated transcript (CART) mRNA expression in the hypothalamus of elderly human

The expression of cocaine and amphetamine regulated transcript (CART) in the hypothalamus of aged humans was studied by in situ hybridization histochemistry. Formalin fixed coronal sections through the hypothalamus were hybridized with [35S]dATP 3' end-labeled deoxyoligonucleotide probes complementary to sequences of the CART encoding gene. Large populations of cells expressing CART messenger RNA were mainly detected in the paraventricular nucleus of the hypothalamus. Other hypothalamic subdivisions displaying numerous radiolabeled cells were the dorsomedial, ventromedial, infundibular and tuberomammillary nuclei, and the dorsal hypothalamic area. Additionally, a few labeled cells were observed in the perifornical and lateral hypothalamic areas. Hybridizing cells were occasionally seen in the supraoptic nucleus. Overall, the pattern of distribution of CART expressing cells observed throughout the human hypothalamus, with few exception, e.g. the supraoptic nucleus, is comparable to that previously reported in the rat brain. These anatomical results suggest that in human, hypothalamic CART expression could be involved a variety of neuroendocrine functions including food-intake.

Learning and memory in the SAMP8 mouse

The SAMP8 (P8) mouse strain develops deficits in learning and memory relatively early in its lifespan. This review provides an overview of the age-related changes that occur in P8 mice. Behavioral studies with P8 mice show impaired acquisition and retention as early as 4 months of age. Deficits in acquisition and retention occur with both aversive and appetitive training tasks. Anatomical studies have detected a number of age-related changes that occur in the central nervous system of P8 mice. The age-related increase in amyloid beta protein is well correlated with the age-related decline in learning and memory. Antibody to amyloid beta protein injected prior to training alleviated impaired acquisition and retention, whereas post-training injections alleviated retention deficits in older P8 mice. Biochemical studies have detected numerous age-related changes with reduced NMDA receptor activity most closely related to impaired learning and memory in P8 mice. Pharmacological studies have found age-related functional changes in the ability of drugs to improve memory processing in P8 mice in the septum and the hippocampus. The specific pattern of pharmacological changes and the inferred change in neurotransmitter activity suggest that age-related impairment in memory processing may be due to impaired septohippocampal interactions. The proposal that P8 mice may be a useful model for studying the early phases of age-related dementia of the Alzheimer type, while still requiring considerable study, seems reasonable.

Nutrition and the older female: a review

Reviewed here are the major nutritional problems of older females, stressing where older female nutrition differs from that of older males. Older females have a higher body mass index and lower waist-to-hip ratio than do older males. Older females reduce their food intake compared to younger females much less than do older males compared to younger males. Total energy expenditure is minimally reduced in older females compared to young females. Resting metabolic rate is reduced by 13% in older females. The major nutritional problem faced by older females, protein energy malnutrition, and its reversible causes are addressed. Inability to recognize the need for fluids is a common problem leading to dehydration in older persons. Older persons are at major risk for ingesting less than two-thirds of the recommended dietary allowance for vitamins. Older women are more likely than men to take vitamin or mineral supplements. Osteopenia is a common problem leading to fractures in older women, and decreased calcium intake and vitamin D deficiency, as well as estrogen deficiency, play a role in the pathogenesis of osteopenia. Total cholesterol levels increase with age in older women, while high-density lipoprotein cholesterol levels decline. However, cholesterol levels that are optimum for survival are higher in older women than in older men. At < 65 years of age, diabetes mellitus (DM) is more common in females, and at > 65 years of age it is more common in males. Over one-half of older persons with DM are undiagnosed. Management of DM in older persons requires a judicious approach to balance the potential problems of hypo- and hyperglycemia.

The interrelationship between physical exercise, muscle strength and body adiposity in a healthy elderly population

OBJECTIVE

To determine the relationship between habitual physical exercise and body adiposity in a healthy elderly population.

RESEARCH DESIGN AND METHODS

Physical exercise was measured by a questionnaire previously adapted for use with the healthy elderly. The level of exercise was converted into calories expended over the previous 14 days and was divided into tertiles. Body adiposity was measured at six sites by anthropometry, and overall percent body fat was measured by bioelectric impedence.

PARTICIPANTS AND SETTING

Two hundred and thirteen healthy ambulatory subjects over the age of 60 (116 females and 97 males) were recruited from a large retirement community in Southern Arizona. The mean age of the subjects was 70.0 years.

RESULTS

Percent body fat was similar in men with different levels of physical activity (27.9% for lowest tertile of activity, 28.1% for middle tertile of activity, and 28.5% for highest tertile of activity). The corresponding values of percent fat in women was 38.0%, 36.0%, and 37%, respectively. There was a statistically significant increase in muscle strength measured in five muscle groups with a hand-held dynamometer with increasing levels of activity.

CONCLUSIONS

These data indicate that level of physical exercise, over the range of 0 to 1,528 Kcal/day, does not predict body adiposity in the healthy elderly population. To decrease body fat without a change in dietary habits would require a more intensive exercise regimen than currently being undertaken by most healthy elderly people.

The hepatic transcellular transport of 3,5,3'-triiodothyronine is reduced in aged rats

The mechanisms of age-related reduction in tissue-responsiveness to thyroid hormones is not clear. Since the first step in hormone action is the transport of the hormone from plasma to the tissues, tissue uptake of T3 was determined in three groups of male Fischer 344 rats: young (6 months old), aged (24-26 months old) and young rats pair-fed with aged rats. At steady state, total tissue uptake of T3 in the liver, heart and rectus abdominis muscle was reduced in aged rats while T3 uptake by cerebral tissues, femoris and soleus muscles was not altered with age. The subcellular distribution of T3 in the liver was determined and the binding power of cytosol and plasma was measured by equilibrium dialysis. In vitro saturation techniques provided estimates for the affinity (Ka) and binding capacity for L- and D-T3 of isolated hepatic nuclei at 37 degrees C. The plasma concentration of T3 was determined with radioimmunoassay. From these parameters the free cytosolic to plasma T3 ratio (Fc/Fp) and free nuclear to cytosolic ratio (Fn/Fc) were calculated. The Fc/Fp for L-T3 was significantly reduced in aged rats (2.34 +/- 0.15) compared to young rats (4.33 +/- 0.16) and young rats pair-fed with old (3.55 +/- 0.46). The Fc/Fp for D-T3 were 6.2 +/- 0.39, 24.3 +/- 2.3 and 10.1 +/- 1.5, respectively. The affinity constant (Ka) and the maximum binding capacity measured in isolated hepatic nuclei were not different in the three groups of rats. However, the nuclear uptake of L-T3 (T3N/P: percentage of dose per mg DNA per percentage of dose per ml plasma) was significantly reduced in aged rats (0.29 +/- 0.03) and young rats pair-fed with old (0.32 +/- 0.02) compared to young rats fed ad libitum (0.44 +/- 0.02). The corresponding values of D-T3 were 0.09 +/- 0.007, 0.13 +/- 0.006 and 0.22 +/- 0.01, respectively. The Fn/Fc of L- and D-T3 was not altered in aged rats or young rats pair fed with old. The liver uptake index (Ul) of L-[125I]T3 was determined in vivo with single injection tissue sampling technique. The liver uptake index in old rats (73.3 +/- 9.9%) was significantly reduced compared to young rats (107.5 +/- 9.4%). These results indicate that (1) cellular uptake of T3 is reduced in aged rat liver. These changes may be in part secondary to age-related reduction in food intake.(ABSTRACT TRUNCATED AT 400 WORDS)

Lack of an association between the presence of tumor necrosis factor or interleukin-1 alpha in the blood and weight loss among elderly patients

To determine the association between blood cytokine levels and body weight loss in elderly patients, serum levels of cachectin/tumor necrosis factor alpha (TNF) and interleukin-1 alpha (IL-1) were measured with specific and sensitive ELISA systems. Of the 19 healthy young subjects, two (10.5%) had detectable levels of serum TNF and one (5.3%) was positive for IL-1. In the healthy elderly group, two of the 12 subjects (16.7%) had measurable TNF levels and four (33.3%) had elevated IL-1 levels. Of the 61 ambulatory elderly patients, 31.1% had serum that contained TNF and 22.9% had IL-1. Similar proportions were found in 127 nursing home patients. None of the common diseases examined in this study nor any commonly used medications were associated with increased serum cytokine levels. Patients with weight loss of more than 5 lbs were less likely to have elevated serum TNF and IL-1 levels compared to the rest of the group. It is concluded that although elevated levels of TNF or IL-1 may occur more frequently in older groups, there is no evidence for a causal relationship between these circulating cytokines and clinically significant weight loss in the elderly.

Blood-brain transport of triiodothyronine is reduced in aged rats

An age-related decline in blood-brain barrier transport of thyroid hormones may contribute to the central nervous system changes with aging. To test this hypothesis, the brain uptake index (BUI) of levo (L) and dextro (D) triiodothyronine (T3) was determined in male Fischer 344 rats at 6 months of age (young) and 26 months of age (aged). Young rats pair fed with aged were included to control for reduced food intake in aged rats. The L-T3 BUI of aged rats (22.4 +/- 2.1%) was significantly reduced compared to young rats (29.5 +/- 2.0%) or young rats pair fed with aged rats (28.5 +/- 2.5%) (p less than 0.05). This could not be attributed to age-related changes in BBB permeability or to reduced cerebral blood flow. At steady state conditions, the brain uptake of either L-T3 or D-T3 was not altered with aging. There were no significant changes in plasma or brain binding of T3. These results indicate that the reduced BBB transport of T3 in aged rats is counterbalanced by a reduction in T3 clearance from the brain.

Age-related differences in body weight loss in response to altered thyroidal status

To determine whether age-related differences in body weight loss in hyperthyroidism could be related to caloric intake, the body weight and food consumption of Fischer 344 male rats were monitored every other day for four weeks. Six-month-old (young) rats were compared to 16-month-old rats (intermediate age) and 25-month-old (aged) rats. Hypothyroidism was induced with 0.025% methimazole in the drinking water for four weeks. Hyperthyroidism was induced with triiodothyronine (T3) injections (15 micrograms/100 g body weight i.p.) for the last 10 days of observation. A group of young rats pair fed with aged rats was included as a control group. The body weight changes of aged rats were similar to hypothyroid young rats. An index of T3 catabolic effect was calculated based on the net weight loss and food intake. This index was not different in aged rats compared to young rats. The apparent hypersensitivity of aged rats to T3 as evidenced by excessive weight loss could totally be attributed to decreased caloric intake. It is concluded that aged rats compared to the young are not more sensitive to the overall catabolic effects of thyroid hormones.