Pro-opiomelanocortin peptides in the human hypothalamus: comparative study between normal subjects and Parkinson patients

Morphological MRI investigations of the hypothalamus in 232 individuals with Parkinson's disease

BACKGROUND

The pathophysiology of the hypothalamic involvement in Parkinson's disease (PD) is not well understood. The objective of this study was the quantification of hypothalamic volumes in vivo in PD.

METHODS

High-resolution T₁ -weighted magnetic resonance imaging (MRI) data from 232 individuals with PD and 130 healthy non-PD individuals were used for quantification of the hypothalamic volumes.

RESULTS

The hypothalamus in PD was not atrophied, as indicated by volumetric analyses in the prospectively collected subcohort (30 PD, V = 921 ± 78 mm³ vs 30 non-PD, V = 917 ± 67 mm³ ; P = 0.850) and validated in a large cohort (202 PD, V = 925 ± 88 mm³ vs 100 non-PD, V = 932 ± 114 mm³ ; P = 0.602).

CONCLUSIONS

Hypothalamic involvement in PD as shown by a large body of histopathological evidence does not appear to be detectable by MRI-based volumetric quantification. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Dopamine: A Modulator of Circadian Rhythms in the Central Nervous System

Circadian rhythms are daily rhythms that regulate many biological processes – from gene transcription to behavior – and a disruption of these rhythms can lead to a myriad of health risks. Circadian rhythms are entrained by light, and their 24-h oscillation is maintained by a core molecular feedback loop composed of canonical circadian (“clock”) genes and proteins. Different modulators help to maintain the proper rhythmicity of these genes and proteins, and one emerging modulator is dopamine. Dopamine has been shown to have circadian-like activities in the retina, olfactory bulb, striatum, midbrain, and hypothalamus, where it regulates, and is regulated by, clock genes in some of these areas. Thus, it is likely that dopamine is essential to mechanisms that maintain proper rhythmicity of these five brain areas. This review discusses studies that showcase different dopaminergic mechanisms that may be involved with the regulation of these brain areas’ circadian rhythms. Mechanisms include how dopamine and dopamine receptor activity directly and indirectly influence clock genes and proteins, how dopamine’s interactions with gap junctions influence daily neuronal excitability, and how dopamine’s release and effects are gated by low- and high-pass filters. Because the dopamine neurons described in this review also release the inhibitory neurotransmitter GABA which influences clock protein expression in the retina, we discuss articles that explore how GABA may contribute to the actions of dopamine neurons on circadian rhythms. Finally, to understand how the loss of function of dopamine neurons could influence circadian rhythms, we review studies linking the neurodegenerative disease Parkinson’s Disease to disruptions of circadian rhythms in these five brain areas. The purpose of this review is to summarize growing evidence that dopamine is involved in regulating circadian rhythms, either directly or indirectly, in the brain areas discussed here. An appreciation of the growing evidence of dopamine’s influence on circadian rhythms may lead to new treatments including pharmacological agents directed at alleviating the various symptoms of circadian rhythm disruption.

Diurnal secretion profiles of growth hormone, thyrotrophin and prolactin in Parkinson's disease

Recently, a massive loss of both hypocretin and melanin-concentrating hormone (MCH) neurones was found in the hypothalamus of Parkinson's disease (PD) patients. Because both hypocretin and MCH play a key role in the regulation of sleep, energy homeostasis and autonomic function, partly by modulation of the somatotrophic, thyrotrophic and lactotrophic axes, neuroendocrine dysregulation may contribute to some of the non-motor features of PD. In eight de novo, medication-free PD patients and eight age-, sex- and body mass index-matched controls, we measured serum levels of growth hormone (GH), thyroid-stimulating hormone (TSH) and prolactin every 10 min for 24 h. Auto-deconvolution, cosinor and approximate entropy analysis were applied to quantify GH, TSH and prolactin secretion rates, diurnal rhythmicity, as well as regularity of hormone release. Sleep was polygraphically-recorded throughout the night. Total 24-h secretion of GH (191 ± 31 versus 130 ± 39 mU/l/24 h), TSH (38 ± 9 versus 36 ± 2 mU/l/24 h) and prolactin (102 ± 14 versus 116 ± 17 μg/l/24 h), as well as their diurnal rhythmicity and regularity of release, were not significantly different between PD patients and controls (all P ≥ 0.12). Fasting levels of insulin-like growth factor-1 were also unaltered in PD patients. However, free thyroxine (T(4) ) levels were significantly higher in PD patients compared to controls (16.19 ± 0.80 versus 13.88 ± 0.40 pmol/l; P = 0.031). In PD patients, prolactin levels were related to disease duration (r = 0.76, P = 0.028), whereas both GH (r = -0.91, P = 0.002) and free T(4) (r = -0.71, P = 0.050) levels correlated inversely with body fat content. Apart from a mild increase in free T(4) levels, we found no indications for altered somatotrophic, thyrotrophic and lactotrophic axes activity in early-stage PD patients.

Improvement of body image perception in Parkinson's disease by treatment with weak electromagnetic fields

Neuropsychological studies have demonstrated that Parkinson's disease (PD) is associated with various cognitive deficits ultimately leading in about 30% of patients to the development of dementia. These studies have demonstrated also a greater decrement of right hemispheric functions which are manifested by visuospatial deficits occurring in up to 90% of PD patients. The Human Figure Drawing Test has been employed in the assessment of generalized intellectual deterioration and specifically in the evaluation of visuperceptive, visuospatial and visuoconstructional abilities in brain injured patients. I have demonstrated recently, on the basis of various drawing tests, that external application of electromagnetic fields (EMFs) in the picotesla (pT) range intensity improved visuoperceptive and visuospatial functions in Parkinsonian patients. In the present communication I present 4 fully medicated nondemented Parkinsonian patients who were administered the Human Figure Drawing Test before and after a series of treatments with EMFs. The Human Figure Drawing Test was selected for the study specifically since it was shown to be sensitive to the effects of surgery to the basal ganglia in Parkinsonian patients. Prior to application of EMFs these patients' drawings showed distortion, poor perspective, impoverished facial expression, and lack of attention to details suggested poor body image perception related to right posterior hemispheric dysfunction. In response to the administration of EMFs the group demonstrated a striking improvement in the drawings particularly the depiction of the face the perception of which is localized to the right parietal lobe. These findings demonstrate that treatment with pT EMFs improves body image perception in Parkinsonian patients, a deficit which may remain unaffected by treatment with standard dopaminergic pharmacotherapy.

Reversal of visuospatial deficit on the Clock Drawing Test in Parkinson's disease by treatment with weak electromagnetic fields

Visuospatial deficits are among the most frequently encountered abnormalities in neuropsychological testing of patients with Parkinson's disease, being present in up to 90% of cases. Clinically, impairment of visuospatial functions may not be noted by Parkinsonian patients but may contribute to various functional disabilities including frequent falls, difficulties operating a vehicle, ambulating, and dressing. I have reported recently that treatment with external electromagnetic fields (EMFs) in the picotesla (pT) range intensity is an effective nonpharmacological modality in the management of the motor and various cognitive deficits of Parkinsonism including visuoperceptive and visuospatial functions. The present communication concerns four fully medicated Parkinsonian patients who, in response to treatment with EMFs, exhibited reversal of visuospatial impairments as demonstrated on the Clock Drawing Test. Specifically, prior to treatment with EMFs these patients demonstrated a visuospatial deficit which was evident by the placement of the numbers on the clock distant from the periphery. Following a series of treatments with EMFs this visuospatial deficit was corrected. The report supports prior observations demonstrating that externally applied pT range intensity EMFs may bring about reversal of visuospatial deficits in Parkinsonian patients which usually are not improved by treatment with dopaminergic or anticholinergic drugs.

Weak electromagnetic fields reverse visuospatial hemi-inattention in Parkinson's disease

Drawing tasks, both free and copied, have achieved a central position in neuropsychological testing of patients with unilateral cerebral dysfunction by virtue of their sensitivity to different kinds of organic brain disorders and their ability to provide information on lateralized brain damage. In the drawings of patients with right hemispheric damage, visuospatial neglect is revealed by the omission of details on the side of the drawing contralateral to the hemispheric lesion. Patients with unilateral cerebral damage, particularly those with left hemispheric damage, also demonstrate a tendency to place their drawings on the side of the page ipsilateral to the cerebral lesion, a phenomenon which has been termed visuospatial hemi-inattention. It has been reported previously that brief external application of alternating pulsed electromagnetic fields (EMFs) in the picotesla (pT) range intensity improved visuoperceptive and visuospatial functions and reversed neglect in Parkinsonian patients. The present communication concerns four fully medicated elderly nondemented Parkinsonian patients (mean age: 74.7 +/- 4.6 yrs; mean duration of illness: 7.7 +/- 5.2 yrs) in whom application of these EMFs produced reversal of visuospatial hemi-inattention related to left hemispheric dysfunction. These findings support prior observations demonstrating that pT EMFs may bring about reversal of certain cognitive deficits in Parkinsonian patients.

Lack of ACTH/cortisol and GH responses to intravenously-infused substance P in Parkinson's disease

In order to test possible changes in the stimulating effect of intravenously-infused substance P (SP) on ACTH/cortisol and GH secretion in Parkinson's disease, 10 male parkinsonian patients and 10 age-matched normal controls were infused intravenously for 60 min with SP (1.0 or 1.5 pmol/kg-1/min-1 SP) or normal saline. The circulating levels of ACTH, cortisol and GH were measured during and for 20 min after SP or saline infusion. No untoward side effects or changes in blood pressure were observed during SP infusion in any subjects. In basal conditions and during saline infusion, plasma ACTH and cortisol levels were similar in normal and parkinsonian patients. During SP infusions, ACTH/cortisol concentrations in normal controls rose significantly vs baseline and saline test in a dose-dependent fashion. In contrast, at both SP infused amounts, parkinsonian patients showed ACTH/cortisol levels similar to those observed in the saline test. All subjects showed similar basal concentrations of GH. GH levels rose significantly in the normal controls when the higher dose of SP was infused, but they were not modified by the infusion of the lower dose of SP or saline. At both tested amounts of SP and during saline infusion, GH levels remained unchanged in the parkinsonian subjects. In agreement with previous observations in the literature showing SP abnormalities in the parkinsonian brain, these data fail to show significant effects of plasma SP on the ACTH/cortisol and GH secretory systems in Parkinson's disease.

Nocturnal plasma melatonin and alpha-melanocyte stimulating hormone levels during exacerbation of multiple sclerosis

The pineal gland has been implicated recently in the pathogenesis of multiple sclerosis (MS). To investigate this hypothesis further, we studied nocturnal plasma melatonin levels and the presence or absence of pineal calcification (PC) on CT scan in a cohort of 25 patients (5 men, 20 women; mean age: 41.1 years; SD = 11.1; range: 27-72) who were admitted to a hospital Neurology service for exacerbation of symptoms. Plasma alpha-melanocyte stimulating hormone (alpha-MSH) estimations were included in the study since there is evidence for a feedback inhibition between alpha-MSH and melatonin secretion. Abnormal melatonin levels were found in 13 patients (52.0%), 11 of whom had nocturnal levels which were below the daytime values (i.e., < 25 pg/ml). Although melatonin levels were unrelated to the patient's age and sex, there was a positive correlation with age of onset of symptoms (p < .0001) and an inverse correlation with the duration of illness (p < .05). PC was noted in 24 of 25 patients (96%) underscoring the pathogenetic relationship between MS and the pineal gland. Alpha-MSH levels were undetectable in 15 patients (60.0%), low in two patients (8.0%), normal in seven patients (28.0%), and elevated in one patient (4.0%). Collectively, abnormal alpha-MSH levels were found in over 70% of patients. These findings support the hypothesis that MS may be associated with pineal failure and suggest, furthermore, that alterations in the secretion of alpha-MSH also occur during exacerbation of symptoms. The relevance of these findings to the pathogenesis of MS are discussed.

Amine accumulation: a possible precursor of Lewy body formation in Parkinson's disease

It is now well recognized that the hypothalamus is an important site of neuropathology in Parkinson's disease (PD). Lewy bodies, a marker of nerve cell degeneration and a pathological hallmark of PD, have been observed frequently in the hypothalamus of PD patients by Lewy (1923) and other investigators and confirmed by more recent systematic studies by Langston & Forno (1978). Both Lewy and Langston & Forno found a predilection of Lewy body formation in specific hypothalamic nuclei with the tuberomammillary, lateral, and posterior areas containing by far the highest average counts per nucleus. Selective vulnerability of the tuberomammillary, lateral, and posterior hypothalamic cell groups to degeneration has been observed also in aging, postencephalitic Parkinsonism, Alzheimer's disease, and schizophrenia. The susceptibility of these particular nuclei to degenerative changes including Lewy body formation is not presently understood nor are the mechanisms by which Lewy bodies are formed in PD and other CNS disorders. Accumulation of amines, a pathological process which follows degeneration of catecholamine-containing neurons in experimental animals, also occurs most frequently in the lateral and posterior hypothalamic areas. In the present communication we propose that in PD, amine accumulation may be a precursor to Lewy body formation and that the susceptibility of certain hypothalamic areas to Lewy body formation may be related to their propensity to accumulate amines. Furthermore, the frequent co-existence of Lewy bodies and Alzheimer's neurofibrillary tangles in the lateral and posterior hypothalamic nuclei suggest that they may share a common pathogenetic etiology. If confirmed, this hypothesis may provide an experimental model by which the formation of Lewy bodies and neurofibrillary tangles may be investigated.

Risk factors for neuroleptic-induced movement disorders

Chronic neuroleptic therapy may be associated with the development of diverse movement disorders including Tardive dyskinesia (TD), Parkinsonism, dystonia, and akathisia in a subset of schizophrenic patients. It is presently unknown why only a proportion of neuroleptic-treated patients develop these movement disorders. In the following communication, we present a series of studies which demonstrate that the development of these movement disorders may be facilitated by certain risk factors including disturbances in pineal melatonin functions, diabetes mellitus, cognitive deficits, suicidal behavior, and disturbances in the functions of the choroid plexus. Recognition of these biological factors may prove useful in: (a) further understanding of the pathophysiology of these disorders, and (b) identifying patients at risk for these movement disorders.

Resistance of beta-endorphin to dexamethasone inhibition in Parkinson's and Alzheimer's diseases

The response of plasma beta-endorphin (beta-EP) to dexamethasone suppression was studied in 14 patients with Alzheimer's disease (AD), 14 patients with Parkinson's disease (PD), and 13 age-matched controls in order to evaluate whether an impairment of the opiate system is present in these neurodegenerative disorders. Basal circulating beta-EP was in normal range in all subjects, although the mean concentration was slightly reduced in the patients compared to controls. After 1 mg dexamethasone given at 11:00 p.m. the night before, plasma beta-EP concentration measured at 08:00 a.m. and 04:00 p.m. was not inhibited in AD and PD patients while it was significantly reduced in controls. Circulating ACTH and cortisol were similar in patients and controls and a normal inhibition of plasma cortisol after dexamethasone was observed in 13/14 AD and 12/14 PD patients. The resistance of beta-EP to dexamethasone inhibition is consistent with previous clinical and experimental data indicating a disorder of the opiate system in brain degenerative diseases.

The relationship of negative schizophrenia to parkinsonism

The positive-negative distinction of schizophrenia has emerged as a valid means of clarifying its heterogeneity. Despite evidence that the two symptom classes may reflect different dimensions of the disease, there is presently no integrated model for understanding of the pathophysiology of these symptoms and their co-occurrence in schizophrenia. We propose that negative phenomena of schizophrenia may be a variant of Parkinsonism. This view is supported by the overlap with Parkinsonism in terms of clinical features, neurochemistry, pharmacology, as well as neuroradiological and neuropathological aspects. As such, negative symptoms may be a manifestation of disease of the basal ganglia and constitute the core pathology in schizophrenia. Positive symptoms, conversely, may reflect an "accessory" process related to a compensatory increase in striatal and limbic dopamine activity following an injury to the dopaminergic system. In the present communication we present a series of studies that support the association of negative schizophrenia and Parkinsonism. Based on this evidence, we suggest that schizophrenic patients with prominent negative symptoms might be managed like patients with Parkinson's disease, namely, with dopaminergic drugs and MAO-B inhibitors. Finally, the association of negative schizophrenia with Parkinsonism raises the possibility that adrenal medullary tissue transplantation, which may benefit a selected group of Parkinsonian patients, may be a future promising therapy for refractory negative schizophrenia.

The hypothalamus in MPTP-induced parkinsonism

1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) has been shown to produce a parkinsonian syndrome in humans and other primates. Recent studies have demonstrated that in humans the hypothalamus has the highest binding density for (3H) MPTP, which corresponds to monoamine oxidase type B (MAO-B). There is evidence that the conversion of MPTP to the toxic compound MPP+ takes place in the hypothalamus; subsequently, MPP+ is transported to the striatal system, where destruction of nigrostriatal dopamine neurons occurs. Thus, the hypothalamus appears to be a primary target organ of MPTP toxicity. This assumption is supported by the observation that monkeys exposed to MPTP exhibit extensive pathological lesions in the hypothalamus which are manifested clinically by the development of life-threatening anorexia requiring forced feeding to overcome. We discuss the clinical implications of MPTP-induced hypothalamic damage to the pathophysiology of MPTP-induced parkinsonism and to Parkinson disease. It is suggested that consideration of hypothalamic involvement in MPTP-induced parkinsonism may provide a broader understanding of the pathophysiology of parkinsonism and may, in addition, account for the preliminary observations that MAO-B inhibitors retard the progression of Parkinson disease and possibly prolong life expectancy.

MIF-induced augmentation of melatonin functions: possible relevance to mechanisms of action of MIF-1 in movement disorders

MIF-1, a synthetic tripeptide with MSH-release inhibitory properties, has been reported to improve symptoms of Parkinson's disease, attenuate levodopa-related dyskinesias and diminish the dyskinetic movements of Tardive dyskinesia. More recently, MIF-1 has been reported partially to protect against the nigro-striatal dopamine depleting effects of MPTP in mice, raising the possibility that it may exert protective effects against the development of Parkinson's disease. There is evidence to suggest that MIF-1 increases nigro-striatal dopaminergic activity, but its ability to improve symptoms in patients with Parkinson's disease, levodopa-related dyskinesias and Tardive dyskinesia cannot be explained solely on the basis of the drug's effect on striatal dopaminergic neurons. MIF-1 has been reported to potentiate the melanocyte-lightening effect of melatonin in rats and its effects in patients with Parkinson's disease and Tardive dyskinesia are associated with marked mood elevation. It is, therefore, possible that the effects of MIF-1 in movement disorders are associated with increased melatonin secretion. Thus, hypothalamic MIF may modulate nigro-striatal dopaminergic functions in part via pineal melatonin. Such an interaction represents a novel mechanism by which hypothalamic peptides act to modulate the expression of movement disorders.

Melanocyte-stimulating hormone and persistent tardive dyskinesia: a hypothesis

An increased incidence of abnormal perioral movements has recently been reported in drug-naive pinealectomized rats with further accentuation of these movements following administration of haloperidol. Analysis of the temporal course of the development of the perioral dyskinetic movements revealed that the onset of these movements occurred within 4 days postoperatively and peaked at 3 weeks to plateau over the following 4-6 weeks. Increased pituitary Melanocyte-stimulating hormone (MSH) content has been reported in pinealectomized rats. Elevation of MSH content in the pinealectomized rats occurred within 3 days of surgery and was followed by normalization within 4 weeks. These findings suggest that compensatory mechanisms involving hypothalamic-pituitary MSH release must have been activated to induce normalization of pituitary MSH levels. Moreover, reduction of pituitary MSH levels may have coincided with attenuation in the severity of the perioral dyskinetic movements. It is possible that the development of tardive dyskinesia (TD) may in part be associated with increased brain and plasma MSH levels and that impaired hypothalamic-pituitary regulatory mechanisms of MSH release may be associated with persistent TD. The pineal gland may be implicated in this process as diminished melatonin secretion may be associated with disinhibition of MSH release. Thus, the above hypothesis complements and extends the recently presented "melatonin hypothesis" and suggests that research of pineal-hypothalamic interactions may be crucial to the further understanding of TD.

Seborrhea and persistent tardive dyskinesia

The following communication concerns two schizophrenic patients with Tardive dyskinesia (TD) in whom fluctuations in the severity of the dyskinesias were accompanied by changes in the severity of the seborrheic skin lesions. Since seborrheic dermatitis may be associated with increased plasma melanocyte-stimulating hormone (MSH) level, these observations suggest an association between the severity of TD and increased pituitary MSH release. In addition, TD may be associated with hypothalamic-pituitary dysfunction of MSH autoregulation.

Mechanisms of action of ECT in Parkinson's disease: possible role of pineal melatonin

Recent clinical studies have suggested that electroconvulsive therapy (ECT) may be efficacious in the therapy of Parkinson's disease (PD). However, the mechanisms of action of ECT in PD are largely unknown. PD may be associated with reduction in the secretory activity of pineal melatonin, and the therapeutic efficacy of ECT in PD may be associated with an effect on the secretory activity of pineal melatonin. Further studies involving analysis of plasma melatonin levels and circadian release prior to and following ECT are needed more precisely to determine the role of pineal melatonin in PD and in the therapeutic efficacy of ETC in PD.

Pineal melatonin functions: possible relevance to Parkinson's disease

Barbeau hypothesized that Parkinson's disease is associated with hypothalamic deficiency of the specialized neuroendocrine cell system (A.P.U.D.) and that the degeneration of brainstem monoaminergic neurons is secondary to progressive functional loss of this cell system in the disease. The pineal gland meets criteria of the A.P.U.D. cell system and it is possible that dysfunction of the pineal gland may be associated with the pathophysiology and clinical manifestations of Parkinson's disease. Since the role of pineal melatonin in humans remains enigamatic, it is currently unclear which of the symptoms of Parkinson's disease may be associated with deregulation of the secretory activity of pineal melatonin. This review summarizes evidence linking possible alterations of pineal melatonin functions with the clinical manifestations of Parkinson's disease.

Pineal melatonin and sensory symptoms in Parkinson disease

Sensory symptoms have been reported in 40-60% of patients with Parkinson's disease, and in at least 10% of patients these symptoms precede the onset of the motor disorder. The pathophysiology of these symptoms remains unknown. Diminished brain serotonin concentration has been reported to be associated with sensory symptoms. Serotonin metabolism is regulated by pineal melatonin. The secretory activity of the pineal gland may be diminished in Parkinson's disease. In experimental animals pineal melatonin has been shown to exert analgesic effects by interacting with opiate receptors. In addition, since opioid peptides mediate the analgesic effects of melatonin, decreased opioid peptide functions in Parkinson's disease may be associated with disruption of the "fine-tuning" pain modulatory functions of melatonin and possibly indirectly facilitate the emergence of sensory symptoms.

Hypothalamic compensatory mechanisms in Parkinson's disease

Parkinson's disease (PD) is associated with loss of dopaminergic neurons of the nigrostriatal bundle and to a lesser extent of the mesolimbic and hypothalamic dopaminergic systems. Frank symptoms of the disease usually emerge when at least 70-80% of striatal dopamine (DA) content have been reduced, raising the possibility that the preclinical phase of the disease might be due to compensatory changes that permit residual dopaminergic neurons to subserve functions previously carried out by the entire projection. These neurochemical compensatory mechanisms are known to occur at a striatal level of the rate limiting enzymes of catecholamine synthesis as well as alterations in the sensitivity of the dopaminergic postsynaptic receptors (Zigmond et al., 1984; Bokobza et al., 1984). Compensatory mechanisms, although generally less well recognized, also occur in the hypothalamus and involve endocrine regulation, abnormal neuropeptide release and the emergence of several autonomic and sensory symptoms manifesting prior to or during the course of the disease. Such neurochemical and clinical adaptation mechanisms of the hypothalamus may help to explain the neurobiological events underlying the preclinical phase of Parkinsonism. Moreover, progressive failure of these hypothalamic adaptive mechanisms may be critical in the transition of the disease into the "malignant phase" (Danielczyk et al., 1980).

beta-Endorphin-like immunoreactivity in cerebrospinal fluid of patients with Alzheimer's disease and Parkinson's disease

beta-Endorphin-like immunoreactivity (beta-EP-LI) in cerebrospinal fluid (CSF) was measured in 42 patients with Alzheimer's disease (AD), 36 patients with Parkinson's disease (PD), and 35 controls. Values for patients with Alzheimer's disease (10.9 +/- 2.8 pmol/l) seemed to be lower than those for controls (12.9 +/- 2.5 pmol/l) (P less than 0.05). In addition, the severely demented patients had lower values than the moderately demented (P less than 0.01). In patients with Parkinson's disease no significant difference in beta-EP-LI values was observed compared to the controls. The data suggest, that processing of pro-opiomelanocortin, precursor of beta-endorphin, and the mechanism of cognitive impairment may differ in Alzheimer's disease and Parkinson's disease.

Human beta-melanocyte-stimulating hormone revisited

It is generally accepted that human beta-melanocyte-stimulating hormone (h beta MSH) does not normally exist in humans but was merely an artifactually generated 22-amino acid peptide corresponding to a lipotropin (LPH) fragment (residues 35-56). We examined whether the shorter 18-amino acid peptide h beta MSH-(5-22) could be detected in some human tissues. Normal human pituitaries and hypothalami as well as corticotropin-secreting pituitary and nonpituitary tumors were extracted and chromatographed on Sephadex G-50, and the fractions were measured with two radioimmunoassays using either a COOH-terminal human gamma LPH (h gamma LPH) antiserum that recognized equally h gamma LPH, h beta MSH, and h beta MSH-(5-22) or a mid-portion h gamma LPH antiserum that recognized h gamma LPH and h beta MSH but not h beta MSH-(5-22). Normal pituitaries and pituitary tumors contained a single immunoreactive material coeluting with h gamma LPH. The hypothalami and the nonpituitary tumors all contained h gamma LPH and a smaller molecular weight material that was only detected in the COOH-terminal h gamma LPH radioimmunoassay; its elution volume (Ve/V, 0.75) was identical to that of h beta MSH-(5-22) but different from that of h beta MSH (Ve/V, 0.60); on reversed-phase HPLC, it coeluted with synthetic h beta MSH-(5-22) with a retention time different from that of h beta MSH. It is concluded that h beta MSH-(5-22) that corresponds to the 18-amino acid peptide h beta LPH-(39-56), flanked by two pairs of basic amino acids within the h beta LPH molecule, is a normal maturation product of proopiomelanocortin in human nonpituitary tissues.

Extrahypophyseal distribution of alpha-melanocyte stimulating hormone (alpha-MSH)-like immunoreactivity in postmortem brains from normal subjects and Alzheimer-type dementia patients

Using a sensitive double-antibody solid-phase enzyme immunoassay method alpha-melanocyte stimulating hormone-like immunoreactivity (alpha-MSH-LI) was measured in 21 regions of postmortem brains from 8 normal subjects and 5 patients with Alzheimer-type dementia (ATD). In the brains from the normal subjects, the highest concentration of alpha-MSH-LI was found in the hypothalamus. Relatively high concentration were also measured in the locus coeruleus, substantia innominata, substantia nigra, amygdala and medial nucleus of thalamus. alpha-MSH-LI in other regions was approximately 1/100 of the hypothalamic content. This data is consistent with the existence of alpha-MSH in extrahypophyseal regions and indicates its regional distribution in the human brain. In the Alzheimer brains, although the temporal cortex and hippocampus had normal concentrations of alpha-MSH-LI, the cingulate cortex, caudate and substantia nigra showed significantly lower concentrations of alpha-MSH-LI than those of the control brains. This data suggests that further studies of alpha-MSH content in a larger number of ATD brains would be useful.

Altered proopiomelanocortin gene expression in adrenocorticotropin-producing nonpituitary tumors. Comparative studies with corticotropic adenomas and normal pituitaries

In order to assess the mechanisms of proopiomelanocortin (POMC) gene expression in human ACTH-producing tumors, we performed the simultaneous evaluation of POMC products and messenger RNA (mRNA) in tissue fragments obtained from two corticotropic adenomas, five nonpituitary tumors, and two normal human pituitaries. The POMC products were examined using a combination of gel exclusion chromatography and four different radioimmunoassays directed against gamma 3 melanocyte stimulating hormone (gamma 3MSH), ACTH, gamma-lipotropin (gamma LPH), and beta-endorphin. The POMCmRNA was detected and analyzed by dot and northern blot hybridization using a single-stranded genomic DNA probe corresponding to the coding region of the human POMC gene. Tissue concentrations of POMC products and mRNA showed parallel distributions. Immunoreactive gamma 3MSH and gamma LPH patterns revealed only 16-kD fragment- and gamma LPH-like peptides in normal and tumoral pituitaries; additional gamma 3MSH- and/or beta MSH-like peptides were found in all five nonpituitary tumors. A single POMCmRNA of approximately 1,200 bases (b) was detected in normal and tumoral pituitaries; a single identical POMCmRNA was also found in four nonpituitary tumors. A thymic carcinoid tumor, in addition to the 1,200-b POMCmRNA, contained equal amounts of a second larger POMCmRNA of approximately 1,450 b. It is concluded that POMC gene expression appears qualitatively unaltered in corticotropic adenomas. In nonpituitary tumors, in contrast, abnormal POMC processing is frequent; in addition, an extra POMCmRNA was detected in a thymic tumor with a greater length than the normal mRNA; the mechanisms and pathophysiological implications of these modifications remain to be elucidated.