Alterations in vasopressin regulation in Alzheimer's disease

c-Rel orchestrates energy-dependent epithelial and macrophage reprogramming in fibrosis

Fibrosis is a common pathological feature of chronic disease. Deletion of the NF-κB subunit c-Rel limits fibrosis in multiple organs, although the mechanistic nature of this protection is unresolved. Using cell-specific gene-targeting manipulations in mice undergoing liver damage, we elucidate a critical role for c-Rel in controlling metabolic changes required for inflammatory and fibrogenic activities of hepatocytes and macrophages and identify Pfkfb3 as the key downstream metabolic mediator of this response. Independent deletions of Rel in hepatocytes or macrophages suppressed liver fibrosis induced by carbon tetrachloride, while combined deletion had an additive anti-fibrogenic effect. In transforming growth factor-β1-induced hepatocytes, c-Rel regulates expression of a pro-fibrogenic secretome comprising inflammatory molecules and connective tissue growth factor, the latter promoting collagen secretion from HMs. Macrophages lacking c-Rel fail to polarize to M1 or M2 states, explaining reduced fibrosis in RelΔLysM mice. Pharmacological inhibition of c-Rel attenuated multi-organ fibrosis in both murine and human fibrosis. In conclusion, activation of c-Rel/Pfkfb3 in damaged tissue instigates a paracrine signalling network among epithelial, myeloid and mesenchymal cells to stimulate fibrogenesis. Targeting the c-Rel-Pfkfb3 axis has potential for therapeutic applications in fibrotic disease.

Proposed biochemistry of Parkinson's and Alzheimer's diseases

The formation of brain compounds linked to Parkinson's and Alzheimer's brain diseases are described. Metabolic mechanisms involved in the control of reacting biochemicals are detailed. Relationships are established between the biochemical reactions, biochemical control mechanisms and the onset of Parkinson's, Alzheimer's. Treatments based on these relationships are proposed.

Hip fracture post-operation dysnatremia and Na+-courses in different cognitive and functional patient groups

The aim of the study was to investigate Na(+)-course of hip fracture patients in relation to demographic and clinical parameters. Data on 155 older hip fracture patients were analyzed retrospectively. Clinical parameters and serum Na(+) on admission (Na1), during 24h pre-op. (Na2), during 24h post-op. (Na3), and pre-discharge (Na4) were recorded. Hyponatremia and hypernatremia rates pre- and post-operation were 26.5%, 2.6%, 24.5% and 5.8%. Higher Na3 (138.76 ± 4.4 mEq/l) vs. Na1 (137.69 ± 4.5 mEq/l) (p = 0.004) and correlation between age and Na3 (p = 0.021) was found. Mean serum Na(+) of impaired mental status (IMS) vs. normal patients and of partially/independent vs. dependent patients were higher (p < 0.05). More complications occurred in IMS patients tending to higher Na3 in patients with complications. No differences in Na(+)-courses were found according to sex or co-morbidities. Dysnatremia is highly prevalent in older hip fracture patients. A distinct post-operative increase in serum Na(+) was found, higher in the cognitively and functionally impaired patients. It seems that the Na(+) increase characterizes more IMS patients who suffer more complications, but does not necessarily indicate complications. We recommend surveillance of serum Na(+), particularly in cognitively and functionally impaired older patients in whom the risk of hypernatremia and complications is higher.

Diabetic hyperosmolarity: a consequence of loss of autonomy

Diabetic hyperosmolarity is a serious acute metabolic disorder mainly occurring in the frail elderly subject presenting age-related favoring factors (reduced sensation of thirst, altered endocrine regulation), disease-related favoring factors (cognitive impairment, poor nutritional status and/or loss of autonomy), and a triggering factor, generally infection. Diabetic hyperosmolarity can occur in a previously non-diabetic patient. Intense dehydration dominants the clinical picture. The prognosis depends largely on the underlying chronic disease.

Neurohypophyseal peptides in aging and Alzheimer's disease

The neurohypophyseal hormones arginine-vasopressin (AVP) and oxytocin (OT) are produced in the neurons of the hypothalamic supraoptic (SON) and paraventricular (PVN) nucleus and in the much smaller cells of the suprachiasmatic (SCN) nucleus. The SON is the main source of plasma AVP. Part of the AVP and OT neurons of the PVN join the hypothalamo-neurohypophyseal tract, whereas others send projections to the median eminence or various brain areas, where AVP and OT are involved in a number of central functions as neurotransmitters/neuromodulators. AVP and OT from the PVN can also regulate via the autonomous innervation endocrine glands and fat tissue. OT is produced for a major part in the PVN but some OT neurons are present in the SON. Moreover, both AVP and OT containing neurons are observed in the "accessory nuclei", i.e. islands situated between the SON and PVN. The SCN is the biological clock, and the number of AVP expressing neurons in the SCN shows both diurnal and seasonal rhythms. In addition to these hypothalamic areas, AVP and OT may be found to a lesser extent in some other brain areas, such as the bed nucleus of the stria terminalis, diagonal band of Broca, nucleus basalis of Meynert, lateral septal nucleus, globus pallidus and the anterior amygdaloid nucleus, as well as in the peripheral tissues. The AVP and OT containing neurons should not be considered as one system. Prominent functional differences exist between the different nuclei. The heterogeneity also becomes clear from the marked differences in the neurohypophyseal peptides containing neurons of the SON, PVN and SCN during aging, and in the most prevalent age-related neurodegenerative diseases, i.e. Alzheimer's disease (AD). For those reasons, we will discuss the SON, PVN and SCN separately.

Vasopressin and thirst in patients with posterior pituitary ectopia and hypopituitarism

OBJECTIVE

Partial diabetes insipidus has been documented in patients with congenital hypopituitarism and posterior pituitary ectopia, some cases being clinically silent except for enuresis. The objective of our study was to evaluate vasopressin (AVP) secretion and thirst appreciation in hypopituitary patients with posterior pituitary ectopia.

PATIENTS

Twelve males and three females, aged between 13 and 38 years (median 19 years). Eleven had multiple pituitary deficiencies, adequately replaced at the time of the study, and four were only growth hormone deficient. None of the patients suffered from polyuria, polydipsia or nocturnal enuresis. We tested the patients with a 5% NaCl infusion. Five patients with abnormal vasopressin production were also tested with nitroprusside, which affects baroceptor vasopressin secretion.

RESULTS

We found that only two out of 12 patients had normal AVP secretion. Thirst assessment showed severe hypodipsia in one patient, hyperdipsia in three out of 15 and more subtle abnormalities in two out of 15 patients. Concordance was found between osmotically and baroceptor-stimulated vasopressin.

CONCLUSIONS

Patients with posterior pituitary ectopia showed a high prevalence of subclinical subnormal vasopressin response to the osmolar stimulus and moreover an impairment of thirst appreciation. Our data on nonosmotically stimulated AVP release suggest the existence of a damage in the hypothalamic vasopressin secreting centres.

Hyponatremia in a nursing home population

OBJECTIVE

To determine the prevalence of hyponatremia in a nursing home population and to identify clinical factors that increase the risk for development of hyponatremia.

DESIGN

Retrospective and prospective record review.

SETTING

A Veterans Affairs nursing home care unit.

PATIENTS

One hundred nineteen residents, who ranged in age from 60 to 103 years. Sixty ambulatory patients, 62 to 91 years of age, who attended a geriatric medicine outpatient clinic served as a reference population.

MEASUREMENTS

Most recent serum sodium, creatinine, BUN, and all serum sodium determinations during the preceding 12 months; clinical diagnoses, diet, medications, and significant events at the time of recorded hyponatremic episodes; response to acute water loading in a subset of patients; number of deaths in the 12 months following entry into the study.

RESULTS

In the 119 nursing home patients, ages 60 years or older, the most recent serum sodium identified 18% who were hyponatremic, compared with a prevalence of 8% in similarly aged ambulatory patients. When all serum sodium determinations for the previous 12 months were examined, 53% of the nursing home patients had at least one episode of hyponatremia during this time period. There was a high incidence of central nervous system (CNS) and spinal cord disease in the total nursing home population. Episodes of hyponatremia were frequently associated with an increased intake of fluids, given either orally or intravenously, and with tube feeding. Water load testing revealed abnormal water handling consistent with the syndrome of inappropriate antidiuretic hormone (ADH) secretion in 18 of 23 patients who had a history of hyponatremia. Seventeen percent of the patients with hyponatremia died over the following 12 months, compared to a death rate of 21% in the normonatremic patients.

CONCLUSIONS

Hyponatremia is a common occurrence in nursing home residents and may be a consequence of abnormal ADH secretion resulting from CNS disease. Exposure to increased fluid intake, or to a low sodium tube-feeding diet, can lead to the onset of hyponatremia or to a worsening of an already present low-serum sodium concentration.

No vasopressin cell loss in the human hypothalamus in aging and Alzheimer's disease

The total number of immunocytochemically identified vasopressin (AVP) cells was determined morphometrically in the paraventricular (PVN) and dorsolateral part of the supraoptic nucleus (dl-SON) of the human hypothalamus in 30 subjects ranging in age from 15 to 97 years, including 10 Alzheimer's disease (AD) patients. The aim of the present study was to test the hypothesis that the increased activity of AVP neurons reported earlier is accompanied by an absence of cell loss in these nuclei in senescence and AD. The results show that numbers of immunoreactive AVP cells in the PVN and dl-SON do not decline during aging or in AD. During aging, the number of neurons expressing AVP even increased in the PVN of control subjects. The nuclear diameter of the AVP cells in the PVN and dl-SON showed an increase in old AD patients. It is concluded that no cell loss occurs in the AVP cell population in the PVN and dl-SON during aging and in AD, and that AVP expression increases in the PVN during normal aging, but not in AD.

Lack of cholinergic regulation of vasopressin and norepinephrine responses to hypertonic saline in humans

In vitro studies in hypothalamic-pituitary explants in the rat have suggested cholinergic mediation of arginine vasopressin (AVP) osmoregulation. In this study we attempted to demonstrate, in humans, cholinergic mediation of AVP osmoregulation. Specifically, we tested the hypothesis that the plasma AVP response to an osmolar stimulus would be attenuated by pharmacologic blockade of central nervous system muscarinic or nicotinic receptors in humans. We also evaluated the effects of cholinergic blockade on the norepinephrine (NE) response to an osmolar stimulus. Young normal males underwent hypertonic saline infusion following administration of the centrally active muscarinic antagonist scopolamine or the centrally active nicotinic antagonist mecamylamine. Neither mecamylamine nor scopolamine affected the AVP response to hypertonic saline infusion. Mecamylamine reduced NE concentrations in a dose-dependent manner, but did not affect the slope of the NE increase during hypertonic saline infusion. In a second experiment, we evaluated the effects of scopolamine and mecamylamine on the AVP and NE responses to physostigmine, a cholinesterase inhibitor which stimulates AVP release into plasma through a non-osmolar central nervous system cholinergic mechanism. Scopolamine eliminated the AVP response to physostigmine. Mecamylamine reduced NE concentrations both before and after scopolamine administration but did not affect the slope of the AVP response. These results fail to support cholinergic regulation of the AVP response to osmolar stimulation in humans.

Hypouricemia, abnormal renal tubular urate transport, and plasma natriuretic factor(s) in patients with Alzheimer's disease

OBJECTIVE

To study tubular urate transport in Alzheimer's disease (AD) and measure sodium and lithium transport rates in rats exposed to AD plasma.

DESIGN

Cross-sectional study in three comparison groups.

SETTING

Referral private institution involving outpatient and hospitalized patients.

PATIENTS

AD, multi-infarct dementia (MID) and non-demented controls (C) were selected and evaluated by a geriatrician and a psychiatrist according to availability and willingness to participate in the study. Demented patients had brain imaging, categorized according to NINCDS-DSM III criteria, and had Mini-mental status examination (MMSE) scores determined.

INTERVENTIONS

Injection of 0.5 mL of plasma I.P. followed 120 minutes later by an IV plasma injection of 0.2 mL priming dose and infusion of 1.8 mL of plasma at 0.01 mL/min in Sprague Dawley rats.

MEASUREMENTS

Renal clearance studies were performed in subjects and in rats exposed to the plasma of study subjects. We measured serum urate concentration and fractional excretion (FE) of urate in subjects and FE sodium and FE lithium in rats.

RESULTS

Serum urate was lower and FE urate higher in 18 AD patients compared with six patients with MID, P < 0.05 and P < 0.005, and 11 C, P < 0.02 and P < 0.005, respectively. Higher FE sodium and FE lithium were noted in rats given plasma from 19 AD patients compared with 12 with MID, P < 0.005 and P < 0.0025, and 14 C, P < 0.0025 and P < 0.0005, respectively. FE sodium and FE lithium decreased progressively after serial dilutions of three AD plasmas and FE lithium was negatively correlated with MMSE scores only in AD, r = -0.71 and P < 0.0005.

CONCLUSIONS

In AD there is defective tubular urate transport and a plasma natriuretic factor(s). FE sodium and/or FE lithium in rats exposed to plasma of demented patients may differentiate AD from MID and estimate the severity of AD.

Altered vasopressin response to metoclopramide in multiple system atrophy: evidence of a cholinergic defect in the hypothalamus

Multiple system atrophy (MSA) is a heterogeneous group of central neurological degenerations often associated with diffuse deterioration of the hypothalamic cholinergic neurons. In the hypothesis of an altered cholinergic regulation of vasopressin release, we evaluated vasopressin response to metoclopramide (20 mg i.v.), a cholinomimetic agonist, in 12 MSA patients. In the same patients the hemodynamic and osmolal control of vasopressin was also evaluated. We found that MSA patients had significantly lower basal plasma vasopressin values and higher plasma osmolality than control subjects. However, they displayed a normal vasopressin response to osmotic stimulation. During head-up tilting, orthostatic hypotension occurred in all patients, and the vasopressin response to hypotension was severely blunted in 5 of 12 patients, thus demonstrating the presence of a lesion of the afferent noradrenergic pathways. Metoclopramide increased vasopressin in control subjects, whereas MSA patients did not display any increase in vasopressin. These results clearly indicate that cholinergic neurons that regulate vasopressin release are damaged in MSA. Such an alteration may be dissociated from the lesion of the afferent noradrenergic pathways. As a consequence of the altered vasopressin release, MSA patients show lower plasma vasopressin levels with consequent propensity to dehydration and hypovolemia, which may further aggravate their hypotension.

Molecular features of hypothalamic plaques in Alzheimer's disease

The pathology of Alzheimer's disease (AD) involves subcortical as well as cortical structures. The authors have used immunohistochemical methods to study the molecular composition of AD plaques in the hypothalamus. In contrast to previous studies using histochemical methods, the authors observed large numbers of diffuse plaques in the AD hypothalamus labeled with an antiserum to the beta-amyloid, or A4 peptide, of the beta-amyloid precursor proteins (beta APPs), whereas A4-immunoreactive plaques were uncommon in the hypothalamus of patients without AD. Unlike plaques in the cortex and hippocampus of AD patients, hypothalamic plaques did not contain epitopes corresponding to other regions of the beta APPs, nor did they contain tau-, neurofilament-, or microtubule-associated protein-reactive epitopes, and did not disrupt the neuropil or produce astrogliosis. These findings demonstrate that there are substantial molecular and cellular differences in the pathologic features of AD in the hypothalamus compared with those observed in hippocampal and cortical structures, which may provide insight into the pathogenetic mechanisms of AD.

Reduced plasma oestrogen stimulated neurophysin and delayed response to oestrogen challenge in Alzheimer's disease

Plasma concentrations of oestrogen stimulated neurophysin (ESN) were reduced in 28 patients with Alzheimer's disease (AD) compared with 14 age-matched controls, 16 patients with other presenile dementias and 12 patients with major depressive disorder. The ESN response to oestrogen challenge was delayed in 10 AD patients compared with 7 age-matched controls. Reduced basal and oestrogen stimulated plasma ESN may be related to impaired responsiveness of the hypothalamo-neurohypophysial neurons and/or a reduction in the amount of pituitary ESN available for release. Plasma ESN measurements may be of value for excluding the diagnosis of AD in patients with dementia who present before the age of 65.

Evidence that cholinergic receptors of muscarinic type may modulate vasopressin release induced by metoclopramide

Studies were carried out in the rat in order to investigate whether cholinergic mechanisms may be involved in vasopressin (VP) release induced by metoclopramide (MCP). The intravenous injection of MCP induced dose-related increases in plasma VP levels in water-loaded rats. These effects were prevented by atropine sulphate, but not by pirenzepine hydrochloride indicating that activation of cholinergic receptors of M-2 type was possibly required for the biologic response.

Vasopressin, prolactin and growth hormone in Alzheimer's disease: their evaluation after metoclopramide stimulation

Recent studies have shown that there is a relationship between an alteration of central neurotransmitters and the modification of some biohumoral parameters in Alzheimer's Disease (AD). In this study the authors evaluated, after metoclopramide (MTC) stimulation, the concentration curve of vasopressin (AVP), prolactin (PRL) and growth hormone (HGH) in the plasma of 34 subjects (20 males and 14 females, mean age 70.5+/-6.9 years; 17 were AD patients, the others constituted the control group). MTC increased AVP serum concentration in healthy (P <0.001), but not in AD patients. This result seemed to be due to the lack of 'procholinergic' action of the drug in the AD patients probably due to an alteration in their cholinergic pathways. The PRL response to MTC was reduced only in the AD female group (P <0.005), suggesting an alteration in dopaminergic control. Lastly, the HGH response in AD did not differ in the two groups, neither in basal conditions, nor after MTC stimulation. The absence of HGH response both in AD and in healthy subjects, demonstrated the ineffectiveness of MTC stimulation. We can conclude that AVP and PRL responses to MTC stimulation efficiently separated the two groups (AD and controls); the former test showing a higher discriminant power than the latter.

Vasopressin response to dehydration in Alzheimer's disease

Alzheimer's disease is a progressive deterioration of neuropsychological functioning. One of the main neuropathological correlates of the disease is a drop-out of cholinergic neurons within the central nervous system. The neuropeptide that is responsible for water homeostasis and defense against dehydration, vasopressin, is also under direct cholinergic control. Several studies have suggested that in Alzheimer's disease there has been a trend toward lower vasopressin levels than in age-matched controls. In order to improve discrimination of normal from diminished vasopressin levels, nine subjects with Alzheimer's disease (mean age 65 +/- 2 years) and nine age- and sex-matched controls (68 +/- 3 years) underwent a mild provocative challenge of overnight fluid restriction. Individuals with Alzheimer's disease had a greater degree of dehydration, with overnight serum osmolality of 313 +/- 4 vs 300 +/- 3 Mosmol/kg, P = .01, and diminished "thirst" as measured by water ingested in one hour of ad libitum water intake. Eight of the nine with Alzheimer's disease had levels of vasopressin which, by extrapolation, appear to be subnormal for their serum osmolalities, whereas seven of the nine control subjects has vasopressin levels within or above the reference range (P less than .05). Elderly individuals with Alzheimer's disease may be at increased risk of dehydration during periods of fluid restriction due to the loss of normal physiological responses of "thirst" and vasopressin secretion.