Acquired hypothalamic obesity: A clinical overview and update.

Hypothalamic obesity (HO) is a rare and complex disorder that confers substantial morbidity and excess mortality. HO is a unique subtype of obesity characterized by impairment in the key brain pathways that regulate energy intake and expenditure, autonomic nervous system function, and peripheral hormonal signalling. HO often occurs in the context of hypothalamic syndrome, a constellation of symptoms that follow from disruption of hypothalamic functions, for example, temperature regulation, sleep-wake circadian control, and energy balance. Genetic forms of HO, including the monogenic obesity syndromes, often impact central leptin-melanocortin pathways. Acquired forms of HO occur as a result of tumours impacting the hypothalamus, such as craniopharyngioma, surgery or radiation to treat those tumours, or other forms of hypothalamic damage, such as brain injury impacting the region. Risk for severe obesity following hypothalamic injury is increased with larger extent of hypothalamic damage or lesions that contain the medial and posterior hypothalamic nuclei that support melanocortin signalling pathways. Structural damage in these hypothalamic nuclei often leads to hyperphagia, central insulin and leptin resistance, decreased sympathetic activity, low energy expenditure, and increased energy storage in adipose tissue, the collective effect of which is rapid weight gain. Individuals with hyperphagia are perpetually hungry. They do not experience fullness at the end of a meal, nor do they feel satiated after meals, leading them to consume larger and more frequent meals. To date, most efforts to treat HO have been disappointing and met with limited, if any, long-term success. However, new treatments based on the distinct pathophysiology of disturbed energy homeostasis in acquired HO may hold promise for the future.

Treatment of hypothalamic obesity in people with hypothalamic injury: new drugs are on the horizon.

Hypothalamic obesity (HO) is a complex and rare disorder affecting multiple regulatory pathways of energy intake and expenditure in the brain as well as the regulation of the autonomic nervous system and peripheral hormonal signaling. It can be related to monogenic obesity syndromes which often affect the central leptin-melanocortin pathways or due to injury of the hypothalamus from pituitary and hypothalamic tumors, such as craniopharyngioma, surgery, trauma, or radiation to the hypothalamus. Traditional treatments of obesity, such as lifestyle intervention and specific diets, are still a therapeutic cornerstone, but often fail to result in meaningful and sustained reduction of body mass index. This review will give an update on pharmacotherapies of HO related to hypothalamic injury. Recent obesity drug developments are promising for successful obesity intervention outcomes.

STEAM-DWI as a robust alternative to EPI-DWI: Evaluation in pediatric brain MRI.

PURPOSE: Diffusion-weighted imaging (DWI) is an essential element of almost every brain MRI examination. The most widely applied DWI technique, a single-shot echo-planar imaging DWI (EPI-DWI) sequence, suffers from a high sensitivity to magnetic field inhomogeneities. As an alternative, a single-shot stimulated echo acquisition mode diffusion-weighted MRI (STEAM-DWI) has recently been re-introduced after it became significantly faster. The aim of the study was to investigate the applicability of STEAM-DWI as a substitute to EPI-DWI in a daily routine of pediatric radiology. METHODS: Retrospectively, brain MRI examinations of 208 children with both EPI-DWI and STEAM-DWI were assessed. Visual resolution and diagnostic confidence were evaluated, the extent of susceptibility artifacts was quantified, and contrast-to-noise ratio was calculated in case of diffusion restriction. Furthermore, the correlation of apparent diffusion coefficient values between STEAM-DWI and EPI-DWI was tested. RESULTS: STEAM-DWI was inferior to EPI-DWI in visual resolution but with higher diagnostic confidence and lower artifact size. The apparent diffusion coefficient values of both sequences demonstrated excellent correlation. The contrast-to-noise ratio of STEAM-DWI was only half of that of EPI-DWI (58% resp. 112%). CONCLUSION: STEAM-DWI is a robust alternative to EPI-DWI when increased susceptibility artifacts are to be expected. Drawbacks are a lower contrast-to-noise ratio and poorer visual resolution.

Pilot multi-site and reproducibility study of hypothalamic gliosis in children.

OBJECTIVE: Quantitative magnetic resonance imaging (MRI) evidence of mediobasal hypothalamic (MBH) gliosis positively correlates with body mass index (BMI) in adults. This has neither been well explored in children nor have other brain regions involved in appetitive processing been tested for evidence of gliosis. METHODS: Multi-site cross-sectional study in children to test for differences in quantitative T2 signal (measure of gliosis) by region and to assess relationships with age and BMI. Participants underwent brain MRI using the same equipment and protocol to quantify T2 relaxation time in six bilateral regions of interest (ROIs): putamen, caudate, ventral striatum, amygdala, hippocampus and MBH, and three control regions: white matter, motor cortex and dorsal hypothalamus. RESULTS: Thirty-one participants (61% female) were included in a combined sample from the University of Washington (N = 9) and John Hopkins University (N = 22). Mean age was 14 ± 3 years, and BMI z-score was 0.7 ± 1.1 (26% with obesity). No study site-related differences were seen in T2 relaxation time across all nine regions (chi2 (8): 9.46, P = .30). Regional differences in T2 relaxation time were present (P < .001). MBH presented longer T2 relaxation time, suggestive of gliosis, when compared to all regions (P < .001), including an intra-hypothalamic control. Physiological age-related declines in T2 relaxation times were found in grey matter ROIs, but not in the MBH (r = -0.14, P = .46). MBH was the only region with a positive correlation between T2 relaxation time and BMI z-score (r = 0.38, P = .03). CONCLUSIONS: In a multi-site study, pilot data suggest that quantitative MRI detected normal maturation-related brain variation as well as evidence that MBH gliosis is associated with increased adiposity in children.

Robust Reductions of Excess Weight and Hyperphagia by Beloranib in Rat Models of Genetic and Hypothalamic Obesity.

Hypothalamic lesions or deficient melanocortin (MC) signaling via MC4 receptor (MC4r) mutations often lead to hyperphagia and severe treatment-resistant obesity. We tested the methionine aminopeptidase 2-inhibitor beloranib (ZGN-440) in 2 male rat models of obesity, one modeling hypothalamic obesity with a combined medial hypothalamic lesion (CMHL) and the other modeling a monogenic form of obesity with MC4r mutations (MC4r knockout [MC4rKO]). In CMHL rats (age 3 months), postsurgery excess weight gain was significantly inhibited (ZGN-440, 0.2 ± 0.7 g/d; vehicle, 3.8 ± 0.6 g/d; P < 0.001) during 12 days of ZGN-440 treatment (0.1 mg/kg daily subcutaneously) together with a 30% reduction of daily food intake vs vehicle injection. In addition, ZGN-440 treatment improved glucose tolerance and reduced plasma insulin, and circulating levels of α-melanocyte stimulating hormone were increased. Serum lipid levels did not differ significantly in ZGN-440-treated vs vehicle-treated rats. Similar results were found in MC4rKO rats: ZGN-440 treatment (14-21 d) was associated with significant reductions of body weight gain (MC4rKO, -1.7 ± 0.6 vs 2.8 ± 0.4 g/d; lean wild-type controls, -0.7 ± 0.2 vs 1.7 ± 0.7 g/d; ZGN-440 vs vehicle, respectively), reduction of food intake (MC4rKO, -28%; lean controls, -7.5%), and insulin resistance, whereas circulating levels of interleukin-1ß did not change. In both obesity models, body temperature and locomotor activity were not affected by ZGN-440 treatment. In conclusion, the robust reduction of body weight in response to ZGN-440 observed in rats with severe obesity is related to a strong reduction of food intake that is likely related to changes in the central regulation of feeding.

Semiquantitative analysis of hypothalamic damage on MRI predicts risk for hypothalamic obesity.

OBJECTIVE: Excessive weight gain frequently occurs in patients with hypothalamic tumors and lesions leading to hypothalamic obesity (HO). METHODS: Digital brain magnetic resonance imaging (MRI) and clinical outcomes were studied retrospectively in a single center, including 45 children with postoperative lesions in the sellar region (41 craniopharyngiomas, 4 with Rathke's cleft cysts), ∼5 years post-surgery, mean age 13.9 years. Four standard sections covering hypothalamic areas critical to energy homeostasis were used to assess lesions and calculate a hypothalamic lesion score (HLS); the association with HO was examined. RESULTS: Compared to subjects who did not develop HO (n = 23), subjects with HO (n = 22) showed more frequently lesions affecting the third ventricular floor, mammillary bodies, and anterior, medial (all P < 0.05), and most importantly posterior hypothalamus (P < 0.01). The HLS correlated significantly with BMI z-score changes 12 and 30 months post-surgery, even after adjusting for potential confounders of gender, age at surgery, surgery date, surgery BMI z-score, hydrocephalus, and residual hypothalamic tumor (r = 0.34, P = 0.03; r = 0.40, P = 0.02, respectively). Diabetes insipidus was found to be an endocrine marker for HO risk. CONCLUSIONS: The extent of damage following surgery in the sellar region can be assessed by MRI using a novel scoring system for early HO risk assessment.

Evidence for small RNAs homologous to effector-encoding genes and transposable elements in the oomycete Phytophthora infestans.

Phytophthora infestans is the oomycete pathogen responsible for the devastating late blight disease on potato and tomato. There is presently an intense research focus on the role(s) of effectors in promoting late blight disease development. However, little is known about how they are regulated, or how diversity in their expression may be generated among different isolates. Here we present data from investigation of RNA silencing processes, characterized by non-coding small RNA molecules (sRNA) of 19-40 nt. From deep sequencing of sRNAs we have identified sRNAs matching numerous RxLR and Crinkler (CRN) effector protein genes in two isolates differing in pathogenicity. Effector gene-derived sRNAs were present in both isolates, but exhibited marked differences in abundance, especially for CRN effectors. Small RNAs in P. infestans grouped into three clear size classes of 21, 25/26 and 32 nt. Small RNAs from all size classes mapped to RxLR effector genes, but notably 21 nt sRNAs were the predominant size class mapping to CRN effector genes. Some effector genes, such as PiAvr3a, to which sRNAs were found, also exhibited differences in transcript accumulation between the two isolates. The P. infestans genome is rich in transposable elements, and the majority of sRNAs of all size classes mapped to these sequences, predominantly to long terminal repeat (LTR) retrotransposons. RNA silencing of Dicer and Argonaute genes provided evidence that generation of 21 nt sRNAs is Dicer-dependent, while accumulation of longer sRNAs was impacted by silencing of Argonaute genes. Additionally, we identified six microRNA (miRNA) candidates from our sequencing data, their precursor sequences from the genome sequence, and target mRNAs. These miRNA candidates have features characteristic of both plant and metazoan miRNAs.

Glucagon-like peptide-1 agonist exendin-4 leads to reduction of weight and caloric intake in a rat model of hypothalamic obesity.

BACKGROUND: Hypothalamic obesity caused by damage of medial hypothalamic nuclei presents a therapeutic challenge. Glucagon-like peptide-1 agonist exenatide (synthetic version of exendin-4 (Ex4)), used for treatment of diabetes, causes weight loss via hindbrain signaling. METHODS: We tested Ex4 in an established rat model of medial hypothalamic lesions. Lesion and control animals were administered either daily intraperitoneal injections of 1 µg·kg(-1) Ex4 or saline for 9 days. RESULTS: In our rat model, a significant difference in percent baseline food intake (lesion -20.8%, control -13.6%; p < 0.001) and percent change in body weight (lesion -4.9%/9 days, control -3.2%/9 days; p < 0.05) was observed during Ex4 treatment compared with saline. CONCLUSION: Ex4 resulted in reduction of food intake and body weight. Follow-up studies are required to further elucidate its effects on energy homeostasis and to establish Ex4 as a potential drug for treatment of hypothalamic obesity.

A novel rodent model that mimics the metabolic sequelae of obese craniopharyngioma patients.

Patients with craniopharyngioma (CP), a tumor located in the pituitary and/or hypothalamus, are susceptible to developing obesity and many metabolic complications. The study aim was to create a rodent model that mimics the complex neuroanatomical and metabolic disturbances commonly seen in obese CP patients. We compared the metabolic phenotype of animals with three distinct types of hypothalamic lesions: 1) destruction of the arcuate nucleus (ARC) induced by monosodium glutamate (MSG), 2) electrolytic lesion of the adjacent ventromedial nucleus (VMN) alone, 3) both the VMN and dorsomedial nucleus (DMN), or a 4) combined medial hypothalamic lesion (CMHL) affecting the VMN, DMN, and the ARC. Only the CMHL model exhibited all key features observed in patients with hypothalamic obesity induced by CP. These features included excessive weight gain due to increased adiposity, increased food intake, and pronounced hyperinsulinemia and hyperleptinemia. Similar to characteristics of patients with CP, CMHL animals exhibited reduced plasma levels of alpha-melanocyte stimulating hormone and reduced ambulatory activity compared with weight-matched controls. Therefore, the CMHL model best mimics the complex metabolic abnormalities observed in obese CP patients compared with lesions to other hypothalamic areas and provides a foundation for future pharmacological approaches to treat obesity in children with hypothalamic damage.

Roles of gastrointestinal and adipose tissue peptides in childhood obesity and changes after weight loss due to lifestyle intervention.

Childhood obesity is a global epidemic and associated with an increased risk of hypertension, diabetes mellitus, and coronary heart disease, in addition to psychological disorders. Interventions such as bariatric surgery are highly invasive and lifestyle modifications are often unsuccessful because of disturbed perceptions of satiety. New signaling peptides discovered in recent years that are produced in peripheral tissues such as the gut, adipose tissue, and pancreas communicate with brain centers of energy homeostasis, such as the hypothalamus and hindbrain. This review discusses the major known gut- and adipose tissue-derived hormones involved in the regulation of food intake and energy homeostasis and their serum levels in childhood obesity before and after weight loss as well as their relationship to consequences of obesity. Since most of the changes of gastrointestinal hormones and adipokines normalize in weight loss, pharmacological interventions based on these hormones will likely not solve the obesity epidemic in childhood. However, a better understanding of the pathways of body weight- and food intake-regulating gut- and adipose tissue-derived hormones will help to find new strategies to treat obesity and its consequences.

Expression of a tumor-related gene network increases in the mammalian hypothalamus at the time of female puberty.

Much has been learned in recent years about the central mechanisms controlling the initiation of mammalian puberty. It is now clear that this process requires the interactive participation of several genes. Using a combination of high throughput, molecular, and bioinformatics strategies, in combination with a system biology approach, we singled out from the hypothalamus of nonhuman primates and rats a group of related genes whose expression increases at the time of female puberty. Although these genes [henceforth termed tumor-related genes (TRGs)] have diverse cellular functions, they share the common feature of having been earlier identified as involved in tumor suppression/tumor formation. A prominent member of this group is KiSS1, a gene recently shown to be essential for the occurrence of puberty. Cis-regulatory analysis revealed the presence of a hierarchically arranged gene set containing five major hubs (CDP/CUTL1, MAF, p53, YY1, and USF2) controlling the network at the transcriptional level. In turn, these hubs are heavily connected to non-TRGs involved in the transcriptional regulation of the pubertal process. TRGs may be expressed in the mammalian hypothalamus as components of a regulatory gene network that facilitates and integrates cellular and cell-cell communication programs required for the acquisition of female reproductive competence.

Quantitative proteomics identifies a change in glial glutamate metabolism at the time of female puberty.

Mammalian puberty requires activation of luteinizing hormone-releasing hormone (LHRH) neurons. In turn, these neurons are controlled by transsynaptic and glia-to-neuron communication pathways, which employ diverse cellular proteins for proper function. We have now used a high throughput relative quantitative proteomics technique to identify such proteins. We selected the method of two-dimensional liquid chromatography tandem mass spectrometry (2DLC-MS/MS) and cleavable isotope-coded affinity tags (cICAT), to both identify and quantify individual proteins within a complex protein mixture. The proteins used derived from the hypothalamus of juvenile (25-day-old) and peripubertal (first proestrus, LP) female rats, and their identity was established by analyzing their mass spectra via database searching. Five proteins involved in glutamate metabolism were detected and two of them appeared to be differentially expressed. They were selected for further analysis, because of their importance in controlling glutamate synthesis and degradation, and their preferential expression in astroglial cells. One, glutamate dehydrogenase (GDH) catalyzes glutamate synthesis; its hypothalamic content detected by 2DLC-MS/MS increases at first proestrus. The other, glutamine synthetase (GS), catalyzes the metabolism of glutamate to glutamine; its content decreases in proestrus. Western blot analysis verified these results. Because these changes suggested an increased glutamate production at puberty, we measured glutamate release from hypothalamic fragments from juvenile 29-day old rats, and from rats treated with PMSG to induce a premature proestrus surge of luteinizing hormone (LH). To determine the net output of glutamate in the absence of re-uptake we used the excitatory amino acid transporter (EAAT) inhibitor l-trans-pyrrolidine-2,4-dicarboxylic acid (PDC). PDC elicited significantly more glutamate- and LHRH-release from the proestrus hypothalamus. Thus, an increase excitatory drive to the LHRH neuronal network provided by glutamatergic inputs of glial origin, is an event contributing to the pubertal activation of LHRH secretion.

Neuroendocrine mechanisms controlling female puberty: new approaches, new concepts.

Sexual development and mature reproductive function are controlled by a handful of neurones that, located in the basal forebrain, produce the decapeptide luteinizing hormone releasing hormone (LHRH). LHRH is released into the portal system that connects the hypothalamus to the pituitary gland and act on the latter to stimulate the synthesis and release of gonadotrophin hormones. The pubertal activation of LHRH release requires coordinated changes in excitatory and inhibitory inputs to LHRH-secreting neurones. These inputs are provided by both transsynaptic and glia-to-neurone communication pathways. Using cellular and molecular approaches, in combination with transgenic animal models and high-throughput procedures for gene discovery, we are gaining new insight into the basic mechanisms underlying this dual control of LHRH secretion and, hence, the initiation of mammalian puberty. Our results suggest that the initiation of puberty requires reciprocal neurone-glia communication involving excitatory amino acids and growth factors, and the coordinated actions of a group of transcriptional regulators that appear to represent a higher level of control governing the pubertal process.

Minireview: the neuroendocrine regulation of puberty: is the time ripe for a systems biology approach?

The initiation of mammalian puberty requires an increase in pulsatile release of GnRH from the hypothalamus. This increase is brought about by coordinated changes in transsynaptic and glial-neuronal communication. As the neuronal and glial excitatory inputs to the GnRH neuronal network increase, the transsynaptic inhibitory tone decreases, leading to the pubertal activation of GnRH secretion. The excitatory neuronal systems most prevalently involved in this process use glutamate and the peptide kisspeptin for neurotransmission/neuromodulation, whereas the most important inhibitory inputs are provided by gamma-aminobutyric acid (GABA)ergic and opiatergic neurons. Glial cells, on the other hand, facilitate GnRH secretion via growth factor-dependent cell-cell signaling. Coordination of this regulatory neuronal-glial network may require a hierarchical arrangement. One level of coordination appears to be provided by a host of unrelated genes encoding proteins required for cell-cell communication. A second, but overlapping, level might be provided by a second tier of genes engaged in specific cell functions required for productive cell-cell interaction. A third and higher level of control involves the transcriptional regulation of these subordinate genes by a handful of upper echelon genes that, operating within the different neuronal and glial subsets required for the initiation of the pubertal process, sustain the functional integration of the network. The existence of functionally connected genes controlling the pubertal process is consistent with the concept that puberty is under genetic control and that the genetic underpinnings of both normal and deranged puberty are polygenic rather than specified by a single gene. The availability of improved high-throughput techniques and computational methods for global analysis of mRNAs and proteins will allow us to not only initiate the systematic identification of the different components of this neuroendocrine network but also to define their functional interactions.

Catalysis, subcellular localization, expression and evolution of the targeting peptides degrading protease, AtPreP2.

We have previously identified a zinc metalloprotease involved in the degradation of mitochondrial and chloroplast targeting peptides, the presequence protease (PreP). In the Arabidopsis thaliana genomic database, there are two genes that correspond to the protease, the zinc metalloprotease (AAL90904) and the putative zinc metalloprotease (AAG13049). We have named the corresponding proteins AtPreP1 and AtPreP2, respectively. AtPreP1 and AtPreP2 show significant differences in their targeting peptides and the proteins are predicted to be localized in different compartments. AtPreP1 was shown to degrade both mitochondrial and chloroplast targeting peptides and to be dual targeted to both organelles using an ambiguous targeting peptide. Here, we have overexpressed, purified and characterized proteolytic and targeting properties of AtPreP2. AtPreP2 exhibits different proteolytic subsite specificity from AtPreP1 when used for degradation of organellar targeting peptides and their mutants. Interestingly, AtPreP2 precursor protein was also found to be dual targeted to both mitochondria and chloroplasts in a single and dual in vitro import system. Furthermore, targeting peptide of the AtPreP2 dually targeted green fluorescent protein (GFP) to both mitochondria and chloroplasts in tobacco protoplasts and leaves using an in vivo transient expression system. The targeting of both AtPreP1 and AtPreP2 proteases to chloroplasts in A. thaliana in vivo was confirmed via a shotgun mass spectrometric analysis of highly purified chloroplasts. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that AtPreP1 and AtPreP2 are differentially expressed in mature A. thaliana plants. Phylogenetic evidence indicated that AtPreP1 and AtPreP2 are recent gene duplicates that may have diverged through subfunctionalization.

Pituitary and gonadal effects of GnRH (gonadotropin releasing hormone) analogues in two peripubertal female rat models.

Central precocious puberty is commonly treated by gonadotropin releasing hormone (GnRH) agonists. To compare modes of action and effectiveness of GnRH analogues and assess treatment combinations of agonistic (triptorelin) and antagonistic (cetrorelix acetate) GnRH analogues with established treatment, we used prepubertal 31-d-old ovariectomized female rats. Strongest inhibition of LH and FSH occurred after 2-d treatment with antagonist alone (LH 0.08 +/- 0.02 versus 3.2 +/- 0.56 ng/mL in controls; FSH 10.8 +/- 2.8 versus 44.2 +/- 5.0 ng/mL in controls, p < 0.001). Combined agonist/antagonist was second most effective of the treatments (after 5 d treatment, LH 0.52 +/- 0.15 versus 4.9 +/- 1.1 ng/mL in controls; p < 0.01). Pituitary gonadotropin subunit LHbeta mRNA levels were inhibited in all groups except controls, but pituitary GnRH receptor mRNA was stimulated by agonist yet unaffected by combined analogues. Explanted ovaries were incubated with either analogue, both 10-6 M. After 4 h, GnRH receptor mRNA levels were significantly reduced by antagonist but not agonist. To verify puberty-inhibiting effects of GnRH analogues, we used 26-d-old female rats with androgen-induced precocious puberty after injecting subcutaneously single 300 microg danazol on postnatal d 5. Single application of cetrorelix depot (cetrorelix embonate) reduced serum estradiol levels and pituitary LHbeta expression; GnRH receptor mRNA levels were down-regulated in the pituitary and ovary (p < 0.05). In androgen-induced precocious puberty model, single injection of antagonist effectively arrests premature hormonal activation and down-regulates pituitary and ovarian GnRH receptors. We conclude that GnRH analogue combination and especially antagonist alone treatment most directly suppress gonadotropin levels. This implies that early treatment gonadotropin flare-up associated with agonist treatment is avoidable.