The effects of overnight nutrient intake on hypothalamic inflammation in a free-choice diet-induced obesity rat model.

Consumption of fat and sugar induces hyperphagia and increases the prevalence of obesity and diabetes type 2. Low-grade inflammation in the hypothalamus, a key brain area involved in the regulation of energy homeostasis is shown to blunt signals of satiety after long term high fat diet. The fact that this mechanism can be activated after a few days of hyperphagia before apparent obesity is present led to our hypothesis that hypothalamic inflammation is induced with fat and sugar consumption. Here, we used a free-choice high-fat high-sugar (fcHFHS) diet-induced obesity model and tested the effects of differential overnight nutrient intake during the final experimental night on markers of hypothalamic inflammation. Male Wistar rats were fed a control diet or fcHFHS diet for one week, and assigned to three different feeding conditions during the final experimental night: 1) fcHFHS-fed, 2) fed a controlled amount of chow diet, or 3) fasted. RT-qPCR and Western blot were utilized to measure hypothalamic gene and protein expression, of cytokines and intermediates of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. Lastly, we investigated the effects of acute fat intake on markers of hypothalamic inflammation in fat-naïve rats. fcHFHS-fed rats consumed more calories, increased adipose tissue, and showed elevated expression of hypothalamic inflammation markers (increased phosphorylation of NF-κB protein, Nfkbia and Il6 gene expression) compared to chow-fed rats. These effects were evident in rats consuming relative high amounts of fat. Removal of the fat and sugar, or fasting, during the final experimental night ameliorated hypothalamic inflammation. Finally, a positive correlation was observed between overnight acute fat consumption and hypothalamic NF-κB phosphorylation in fat-naïve rats. Our data indicate that one week of fcHFHS diet, and especially the fat component, promotes hypothalamic inflammation, and removal of the fat and sugar component reverses these detrimental effects.

Functional neuroanatomy of thyroid hormone feedback in the human hypothalamus and pituitary gland.

A major change in thyroid setpoint regulation occurs in various clinical conditions such as critical illness and psychiatric disorders. As a first step towards identifying determinants of these setpoint changes, we have studied the distribution and expression of thyroid hormone receptor (TR) isoforms, type 2 and type 3 deiodinase (D2 and D3), and the thyroid hormone transporter monocarboxylate transporter 8 (MCT8) in the human hypothalamus and anterior pituitary. Although the post-mortem specimens used for these studies originated from patients who had died from many different pathologies, the anatomical distribution of these proteins was similar in all patients. D2 enzyme activity was detectable in the infundibular nucleus/median eminence (IFN/ME) region coinciding with local D2 immunoreactivity in glial cells. Additional D2 immunostaining was present in tanycytes lining the third ventricle. Thyrotropin-releasing hormone (TRH) containing neurons in the paraventricular nucleus (PVN) expressed MCT8, TRs as well as D3. These findings suggest that the prohormone thyroxine (T4) is taken up in hypothalamic glial cells that convert T4 into the biologically active triiodothyronine (T3) via the enzyme D2, and that T3 is subsequently transported to TRH producing neurons in the PVN. In these neurons, T3 may either bind to TRs or be metabolized into inactive iodothyronines by D3. By inference, local changes in thyroid hormone metabolism resulting from altered hypothalamic deiodinase or MCT8 expression may underlie the decrease in TRH mRNA reported earlier in the PVN of patients with critical illness and depression. In the anterior pituitary, D2 and MCT8 immunoreactivity occurred exclusively in folliculostellate (FS) cells. Both TR and D3 immunoreactivity was observed in gonadotropes and to a lesser extent in thyrotropes and other hormone producing cell types. Based upon these neuroanatomical findings, we propose a novel model for central thyroid hormone feedback in humans, with a pivotal role for hypothalamic glial cells and pituitary FS cells in processing and activation of T4. Production and action of T3 appear to occur in separate cell types of the human hypothalamus and anterior pituitary.

Glucocorticoids suppress vasopressin gene expression in human suprachiasmatic nucleus.

Sleep impairment is one of the major side effects of glucocorticoid therapy. The mechanism responsible for this circadian disorder is unknown, but alterations in the suprachiasmatic nucleus (SCN), the biological clock of the human brain, are presumed to play a major role. In the present study, the amount of vasopressin mRNA (AVP mRNA) expression in the SCN was investigated in 10 glucocorticoid-exposed patients and 10 glucocorticoid free, age- and clock time of death-matched controls. The total amount of AVP mRNA, expressed as masked silver grains in the SCN, was two times lower in glucocorticoid-exposed patients (n = 10; 5115 +/- 1314 microm(2)) than that in controls (n = 10; 11,021 +/- 1408 microm(2)) (P = 0.006). There was also a 53% decrease in the total number of profiles in the SCN that expressed AVP mRNA in glucocorticoid-exposed patients (16,759 +/- 3110) compared with those in controls (31,490 +/- 3816) (P = 0.01). In conclusion, glucocorticoids have an inhibitory effect on AVP mRNA expression in the human SCN, which may be the biological basis of the circadian rhythm disturbances during glucocorticoid therapy.

Neuroanatomical pathways for thyroid hormone feedback in the human hypothalamus.

CONTEXT: Recent findings point to an increasing number of hypothalamic proteins involved in the central regulation of thyroid hormone feedback. The functional neuroanatomy of these proteins in the human hypothalamus is largely unknown at present. OBJECTIVE: The aim of this study was to report the distribution of type II and type III deiodinase (D2 and D3) as well as the recently identified T(3) transporter, monocarboxylate transporter 8 (MCT8), in the human hypothalamus. DESIGN: The study included enzyme activity assays, immunocytochemical studies, and mRNA in situ hybridizations in postmortem human hypothalamus (n = 9). RESULTS: D2 immunoreactivity is prominent in glial cells of the infundibular nucleus/median eminence, blood vessels, and cells lining the third ventricle. By contrast, both D3 and MCT8 are expressed by neurons of the paraventricular (PVN), supraoptic, and infundibular nucleus (IFN). In support of these immunocytochemical data, D2 and D3 enzyme activities are detectable in the mediobasal human hypothalamus. Combined D2, D3, MCT8, and thyroid hormone receptor immunohistochemistry and TRH mRNA in situ hybridization clearly showed that D3, MCT8, and thyroid hormone receptor isoforms are all expressed in TRH neurons of the PVN, whereas D2 is not. CONCLUSIONS AND IMPLICATIONS: Based on these findings, we propose three possible routes for thyroid hormone feedback on TRH neurons in the human PVN: 1) local thyroid hormone uptake from the vascular compartment within the PVN, 2) thyroid hormone uptake from the cerebrospinal fluid in the third ventricle followed by transport to TRH neurons in the PVN or IFN neurons projecting to TRH neurons in the PVN, and 3) thyroid hormone sensing in the IFN of the mediobasal hypothalamus by neurons projecting to TRH neurons in the PVN.

Increased melanin concentrating hormone receptor type I in the human hypothalamic infundibular nucleus in cachexia.

Melanin-concentrating hormone (MCH) exerts a positive regulation on appetite and binds to the G protein-coupled receptors, MCH1R and MCH2R. In rodents, MCH is produced by neurons in the lateral hypothalamus with projections to various hypothalamic and other brain sites. In the present study, MCH1R was shown, by immunocytochemistry, to be present in the human infundibular nucleus/median eminence, paraventricular nucleus, lateral hypothalamic area, and perifornical area, although in the latter two regions, only a few MCH1R-containing cells were found. In addition, MCH1R staining was found in nerve fibers in the periventricular nucleus, dorsomedial and ventromedial nucleus, suprachiasmatic nucleus, and tuberomammillary nucleus. A significant 1.6 times increase in the number of MCH1R cell body staining was found in the infundibular nucleus in postmortem brain material of cachectic patients, compared with matched controls, supporting a role for this receptor in energy homeostasis in the human.

Diminished aromatase immunoreactivity in the hypothalamus, but not in the basal forebrain nuclei in Alzheimer's disease.

In previous studies we have shown in Alzheimer's disease (AD) an enhanced nuclear estrogen receptor (ER) alpha expression in the cholinergic basal forebrain nuclei, i.e. the vertical limb of the diagonal band of Broca (VDB) and the nucleus basalis of Meynert (NBM), and in a number of hypothalamic nuclei, i.e. the supraoptic nucleus (SON), the infundibular nucleus (INF), the medial mamillary nucleus (MMN). We aimed at determining whether the increase in nuclear ERalpha seen in AD patients was related to a rise in local production of estrogens by aromatase (P-450arom), which is a key enzyme that catalyzes the biosynthesis of estrogens from precursor aromatizable androgens. We confirmed for the first time the presence of aromatase mRNA in neurons and glial cells in the human NBM and the tuberomamillary nucleus by RT-QPCR using laser microdissection. Enhanced aromatase immunoreactivity (ir) was indeed observed in the NBM in AD. However, in contrast a decreased aromatase-ir was found in the SON, INF and MMN of AD patients. In addition, P-450arom-ir was clearly diminished in ependymal and choroid plexus cells in AD. While an increase in aromatase-ir was found in the NBM and SON during normal aging, a decrease in staining was observed in the MMN. No sex differences in young control, elderly control or AD patients were present in any of the nuclei studied. In conclusion, brain P-450arom-ir and the relationship of its regulation with plasma sex steroid levels, estrogen and androgen receptors in the human hypothalamus and basal forebrain are region-specific.

Thyroid hormone receptor expression in the human hypothalamus and anterior pituitary.

In the present study, we describe for the first time the distribution of thyroid hormone receptor (TR) isoforms in the human postmortem hypothalamus and anterior pituitary using immunocytochemistry. We used a set of polyclonal antisera raised against the specific isoforms of the human TR. The distribution of TR alpha 1, alpha 2, beta 1, and beta 2 was studied in consecutive sections of six hypothalami and pituitaries. Staining intensity showed strong interindividual variation but was consistently present in the infundibular nucleus, paraventricular nucleus, and supraoptic nucleus. In addition, strong TR immunoreactivity was observed in the anterior pituitary. Neuropeptide Y and proopiomelanocortin mRNA-positive cells in the infundibular nucleus, which were studied in three other hypothalami, appeared not to express TRs, and thus, the neurons expressing TRs in the human mediobasal hypothalamus remain to be characterized.

Estrogen-receptor-beta distribution in the human hypothalamus: similarities and differences with ER alpha distribution.

This study reports the first systematic rostrocaudal distribution of estrogen receptor beta immunoreactivity (ER beta-ir) in the human hypothalamus and adjacent areas in five males and five females between 20-39 years of age and compares its distribution to previously reported ER alpha in the same patients. ER beta-ir was generally observed more frequently in the cytoplasm than in the nucleus and appeared to be stronger in women. Basket-like fiber stainings, suggestive for ER beta-ir in synaptic terminals, were additionally observed in various areas. Men showed more robust nuclear ER beta-ir than women in the medial part of the bed nucleus of the stria terminalis, paraventricular and paratenial nucleus of the thalamus, while less intense, but more nuclear, ER beta-ir appeared to be present in, e.g., the BSTc, sexually dimorphic nucleus of the medial preoptic area, diagonal band of Broca and ventromedial nucleus. Women revealed more nuclear ER beta-ir than men of a low to intermediate level, e.g., in the suprachiasmatic, supraoptic, paraventricular, infundibular, and medial mamillary nucleus. These data indicate potential sex differences in ER beta expression. ER beta-ir expression patterns in subjects with abnormal hormone levels suggests that there may be sex differences in ER beta-ir that are "activational" rather than "organizational" in nature. Similarities, differences, potential functional, and clinical implications of the observed ER alpha and ER beta distributions are discussed in relation to reproduction, autonomic-function, mood, cognition, and neuroprotection in health and disease.

Estrogen receptor-alpha distribution in the human hypothalamus in relation to sex and endocrine status.

The present study reports the first systematic rostrocaudal distribution of estrogen receptor-alpha immunoreactivity (ERalpha-ir) in the human hypothalamus and its adjacent areas in young adults. Postmortem material taken from 10 subjects (five male and five female), between 20 and 39 years of age, was investigated. In addition, three age-matched subjects with abnormal levels of estrogens were studied: a castrated, estrogen-treated 50-year-old male-to-female transsexual (T1), a 31-year-old man with an estrogen-producing tumor (S2), and an ovariectomized 46-year-old woman (S8). A strong sex difference, with more nuclear ERalpha-ir in women, was observed rostrally in the diagonal band of Broca and caudally in the medial mamillary nucleus. Less robust sex differences were observed in other brain areas, with more intense nuclear ERalpha-ir in men, e.g., in the sexually dimorphic nucleus of the medial preoptic area, paraventricular nucleus, and lateral hypothalamic area, whereas women had more nuclear ERalpha-ir in the suprachiasmatic nucleus and ventromedial nucleus. No nuclear sex differences in ERalpha were found, e.g., in the central part of the bed nucleus of the stria terminalis. In addition to nuclear staining, ERalpha-ir appeared to be sex-dependently present in the cytoplasm of neurons and was observed in astrocytes, plexus choroideus, and other non-neuronal cells. ERalpha-ir in T1, S2, and S8 suggested that most of the observed sex differences in ERalpha-ir are "activational" (e.g., ventromedial nucleus/medial mamillary nucleus) rather than "organizational." Species similarities and differences in ERalpha-ir distribution and possible functional implications are discussed.