Oxytocin-MCH circuit regulates monosynaptic inputs to MCH neurons and modulates social recognition memory.

Oxytocin regulates social behaviors and has been linked to the etiology of autism and schizophrenia. Oxytocin and another hypothalamic neuropeptide, melanin concentrating hormone (MCH), share several physiological actions such as emotion, social behavior and recognition, maternal care, sexual behavior and stress, which suggests that these two systems may interact, however, how they would do it is not known. Here, we study the interactions between the oxytocin and MCH systems in behaviors related to autism and schizophrenia. Specifically, we examined the synaptic inputs of the oxytocin-to the MCH neurons. We selectively deleted oxytocin receptors (OXTR) from MCH neurons (OXTR-cKO mice) using a Cre/loxP recombinase-technology, and used rabies-mediated circuit mapping technique to reveal the changes in the direct monosynaptic inputs to MCH neurons. We examined the behavioral responses of OXTR-cKO mice. Deletion of OXTR from MCH neurons induced a significant decrease in the primary inputs received by MCH neurons from the paraventricular nucleus and the lateral hypothalamus, and from the nucleus accumbens and ventral tegmental area. While OXTR-cKO mice exhibited similar social interactions as control mice, they displayed significantly impaired social recognition memory and increased stereotypic behavior. Our study identifies a selective role for the oxytocin-MCH pathway in social recognition memory and stereotyped behavior that are relevant to psychiatric disorders such as schizophrenia and autism, and warrant further investigation of this circuit to uncover potential benefit of targeting the oxytocin-MCH circuit as a novel therapeutic target for treatment of social recognition deficits in these two disorders.

Novel analgesic effects of melanin-concentrating hormone on persistent neuropathic and inflammatory pain in mice.

The melanin-concentrating hormone (MCH) is a peptidergic neuromodulator synthesized by neurons in the lateral hypothalamus and zona incerta. MCHergic neurons project throughout the central nervous system, indicating the involvements of many physiological functions, but the role in pain has yet to be determined. In this study, we found that pMCH-/- mice showed lower baseline pain thresholds to mechanical and thermal stimuli than did pMCH+/+ mice, and the time to reach the maximum hyperalgesic response was also significantly earlier in both inflammatory and neuropathic pain. To examine its pharmacological properties, MCH was administered intranasally into mice, and results indicated that MCH treatment significantly increased mechanical and thermal pain thresholds in both pain models. Antagonist challenges with naltrexone (opioid receptor antagonist) and AM251 (cannabinoid 1 receptor antagonist) reversed the analgesic effects of MCH in both pain models, suggesting the involvement of opioid and cannabinoid systems. MCH treatment also increased the expression and activation of CB1R in the medial prefrontal cortex and dorsolateral- and ventrolateral periaqueductal grey. The MCH1R antagonist abolished the effects induced by MCH. This is the first study to suggest novel analgesic actions of MCH, which holds great promise for the application of MCH in the therapy of pain-related diseases.

Meta-analysis of melanin-concentrating hormone signaling-deficient mice on behavioral and metabolic phenotypes.

The demand for meta-analyses in basic biomedical research has been increasing because the phenotyping of genetically modified mice does not always produce consistent results. Melanin-concentrating hormone (MCH) has been reported to be involved in a variety of behaviors that include feeding, body-weight regulation, anxiety, sleep, and reward behavior. However, the reported behavioral and metabolic characteristics of MCH signaling-deficient mice, such as MCH-deficient mice and MCH receptor 1 (MCHR1)-deficient mice, are not consistent with each other. In the present study, we performed a meta-analysis of the published data related to MCH-deficient and MCHR1-deficient mice to obtain robust conclusions about the role of MCH signaling. Overall, the meta-analysis revealed that the deletion of MCH signaling enhanced wakefulness, locomotor activity, aggression, and male sexual behavior and that MCH signaling deficiency suppressed non-REM sleep, anxiety, responses to novelty, startle responses, and conditioned place preferences. In contrast to the acute orexigenic effect of MCH, MCH signaling deficiency significantly increased food intake. Overall, the meta-analysis also revealed that the deletion of MCH signaling suppressed the body weight, fat mass, and plasma leptin, while MCH signaling deficiency increased the body temperature, oxygen consumption, heart rate, and mean arterial pressure. The lean phenotype of the MCH signaling-deficient mice was also confirmed in separate meta-analyses that were specific to sex and background strain (i.e., C57BL/6 and 129Sv). MCH signaling deficiency caused a weak anxiolytic effect as assessed with the elevated plus maze and the open field test but also caused a weak anxiogenic effect as assessed with the emergence test. MCH signaling-deficient mice also exhibited increased plasma corticosterone under non-stressed conditions, which suggests enhanced activity of the hypothalamic-pituitary-adrenal axis. To the best of our knowledge, the present work is the first study to systematically compare the effects of MCH signaling on behavioral and metabolic phenotypes.

Melanin-concentrating hormone regulates beat frequency of ependymal cilia and ventricular volume.

Ependymal cell cilia help move cerebrospinal fluid through the cerebral ventricles, but the regulation of their beat frequency remains unclear. Using in vitro, high-speed video microscopy and in vivo magnetic resonance imaging in mice, we found that the metabolic peptide melanin-concentrating hormone (MCH) positively controlled cilia beat frequency, specifically in the ventral third ventricle, whereas a lack of MCH receptor provoked a ventricular size increase.

Pmch-deficiency in rats is associated with normal adipocyte differentiation and lower sympathetic adipose drive.

The orexigenic neuropeptide melanin-concentrating hormone (MCH), a product of Pmch, is an important mediator of energy homeostasis. Pmch-deficient rodents are lean and smaller, characterized by lower food intake, body-, and fat mass. Pmch is expressed in hypothalamic neurons that ultimately are components in the sympathetic nervous system (SNS) drive to white and interscapular brown adipose tissue (WAT, iBAT, respectively). MCH binds to MCH receptor 1 (MCH1R), which is present on adipocytes. Currently it is unknown if Pmch-ablation changes adipocyte differentiation or sympathetic adipose drive. Using Pmch-deficient and wild-type rats on a standard low-fat diet, we analyzed dorsal subcutaneous and perirenal WAT mass and adipocyte morphology (size and number) throughout development, and indices of sympathetic activation in WAT and iBAT during adulthood. Moreover, using an in vitro approach we investigated the ability of MCH to modulate 3T3-L1 adipocyte differentiation. Pmch-deficiency decreased dorsal subcutaneous and perirenal WAT mass by reducing adipocyte size, but not number. In line with this, in vitro 3T3-L1 adipocyte differentiation was unaffected by MCH. Finally, adult Pmch-deficient rats had lower norepinephrine turnover (an index of sympathetic adipose drive) in WAT and iBAT than wild-type rats. Collectively, our data indicate that MCH/MCH1R-pathway does not modify adipocyte differentiation, whereas Pmch-deficiency in laboratory rats lowers adiposity throughout development and sympathetic adipose drive during adulthood.

Reduced intestinal tumorigenesis in APCmin mice lacking melanin-concentrating hormone.

BACKGROUND: Melanin-concentrating hormone (MCH) is an evolutionary conserved hypothalamic neuropeptide that in mammals primarily regulates appetite and energy balance. We have recently identified a novel role for MCH in intestinal inflammation by demonstrating attenuated experimental colitis in MCH deficient mice or wild type mice treated with an anti-MCH antibody. Therefore, targeting MCH has been proposed for the treatment of inflammatory bowel disease. Given the link between chronic intestinal inflammation and colorectal cancer, in the present study we sought to investigate whether blocking MCH might have effects on intestinal tumorigenesis that are independent of inflammation. METHODOLOGY: Tumor development was evaluated in MCH-deficient mice crossed to the APCmin mice which develop spontaneously intestinal adenomas. A different cohort of MCH-/- and MCH+/+ mice in the APCmin background was treated with dextran sodium sulphate (DSS) to induce inflammation-dependent colorectal tumors. In Caco2 human colorectal adenocarcinoma cells, the role of MCH on cell survival, proliferation and apoptosis was investigated. RESULTS: APCmin mice lacking MCH developed fewer, smaller and less dysplastic tumors in the intestine and colon which at the molecular level are characterized by attenuated activation of the wnt/beta-catenin signaling pathway and increased apoptotic indices. Form a mechanistic point of view, MCH increased the survival of colonic adenocarcinoma Caco2 cells via inhibiting apoptosis, consistent with the mouse studies. CONCLUSION: In addition to modulating inflammation, MCH was found to promote intestinal tumorigenesis at least in part by inhibiting epithelial cell apoptosis. Thereby, blocking MCH as a therapeutic approach is expected to decrease the risk for colorectal cancer.

Ablation of the hypothalamic neuropeptide melanin concentrating hormone is associated with behavioral abnormalities that reflect impaired olfactory integration.

Melanin-concentrating hormone (MCH) is an orexigenic hypothalamic neuropeptide. At least one receptor, MCH receptor 1 (MCHR1), is present in all mammals and is expressed widely throughout the brain, including cortex, striatum and structures implicated in the integration of olfactory cues such as the piriform cortex and olfactory bulb. Consistent with a potential role for MCH in mediating olfactory function, MCH knockout mice demonstrate abnormal olfactory behaviors. These behaviors include impaired food seeking by both genders in the context of normal levels of exploratory behavior, suggesting impaired olfaction. Males also exhibit increased aggression while females show defects in several olfactory mediated behaviors including mating, estrous cycle synchronization and maternal behavior. These findings suggest that hypothalamic inputs through MCH play an important role in regulating sensory integration from olfactory pathways.

Chronic loss of melanin-concentrating hormone affects motivational aspects of feeding in the rat.

Current epidemic obesity levels apply great medical and financial pressure to the strenuous economy of obesity-prone cultures, and neuropeptides involved in body weight regulation are regarded as attractive targets for a possible treatment of obesity in humans. The lateral hypothalamus and the nucleus accumbens shell (AcbSh) form a hypothalamic-limbic neuropeptide feeding circuit mediated by Melanin-Concentrating Hormone (MCH). MCH promotes feeding behavior via MCH receptor-1 (MCH1R) in the AcbSh, although this relationship has not been fully characterized. Given the AcbSh mediates reinforcing properties of food, we hypothesized that MCH modulates motivational aspects of feeding.Here we show that chronic loss of the rat MCH-precursor Pmch decreased food intake predominantly via a reduction in meal size during rat development and reduced high-fat food-reinforced operant responding in adult rats. Moreover, acute AcbSh administration of Neuropeptide-GE and Neuropeptide-EI (NEI), both additional neuropeptides derived from Pmch, or chronic intracerebroventricular infusion of NEI, did not affect feeding behavior in adult pmch(+/+) or pmch(-/-) rats. However, acute administration of MCH to the AcbSh of adult pmch(-/-) rats elevated feeding behavior towards wild type levels. Finally, adult pmch(-/-) rats showed increased ex vivo electrically evoked dopamine release and increased limbic dopamine transporter levels, indicating that chronic loss of Pmch in the rat affects the limbic dopamine system.Our findings support the MCH-MCH1R system as an amplifier of consummatory behavior, confirming this system as a possible target for the treatment of obesity. We propose that MCH-mediated signaling in the AcbSh positively mediates motivational aspects of feeding behavior. Thereby it provides a crucial signal by which hypothalamic neural circuits control energy balance and guide limbic brain areas to enhance motivational or incentive-related aspects of food consumption.

You deserve what you eat: lessons learned from the study of the melanin-concentrating hormone (MCH)-deficient mice.

OBJECTIVES: Diet plays a crucial role in the development of obesity and insulin resistance via multiple mechanisms. Saturated fatty acids can directly trigger tissue specific proinflammatory pathways via Toll-like receptor-4 (TLR4)-dependent mechanisms. Moreover, diet can change the gut microbiome and increase gut permeability. However, very few studies have addressed the obesity-independent role of diet. Dissecting the effects of diet from those of obesity per se will enhance our understanding of the underlying pathogenesis, and, at the translational level, advance our treatment approaches for obesity and its co-morbidities. METHODS: Melanin-concentrating hormone (MCH) is an important regulator of appetite and energy balance. MCH-deficient mice are resistant to diet-induced obesity, primarily due to increased locomotor activity. We took advantage of the unique phenotype of these mice to examine the metabolic and inflammatory consequences of a 15-week consumption of a diet high in saturated fat. RESULTS: MCH-deficient mice chronically exposed to a high-fat diet gain less weight compared to their wild-type littermates, despite similar food intake, and are protected from hepatosteatosis. They also lack obesity-associated upregulation of serum leptin and insulin levels and have improved total body insulin sensitivity. Nevertheless, we found indistinguishable liver-specific innate immune responses in both genotypes associated with high-fat feeding, which involved activation of TLR4 and its downstream effectors, MyD88, p38 MAP kinase and STAT-3. CONCLUSIONS: Our findings indicate that high-fat feeding is deleterious to the liver, independently of the obesity status. They also suggest that MCH is not necessary for the TLR4-dependent immune response triggered by the high-fat diet.

Incomplete deficiency of hypothalamic hormones in hypothalamic hypopituitarism associated with an old traumatic brain injury.

A 62 year-old man was admitted to determine the pathogenesis of his hypoglycemia. He was unconscious and his plasma glucose level was 26 mg/dL. When he was 31 years old, he had a traffic accident and was unconscious for several days. Physical findings on admittance showed that the patient's BMI was 17.8 and blood pressure, 114/70 mmHg. He was alert. He had a hypogonadal face with a lack of beard, and he had an atrophic testis with a volume of 1 to 2 ml. Laboratory findings showed that his fasting plasma glucose was 73 mg/dL; serum sodium, 133 mmol/l; potassium, 4.1 mmol/l; serum insulin, less than 1.0 muU/ml.; plasma ACTH, 45.8 pg/ml; serum cortisol, 5.2 microg/dL; and free cortisol urinary excretion, less than 4.5 microg/day; serum LH, 0.8 mIU/ml; serum testosterone, less than 0.05 ng/ml; serum TSH, 2.0 uIU/ml; free T(4), 0.7 ng/dL; free T(3), 1.5 pg/ml; and serum prolactin, 29.0 ng/ml. The levels of all the pituitary hormones were elevated in response to a mixture of exogenous corticotrophin-releasing hormone (CRH), luteinizing hormone-releasing hormone (LH-RH), thyrotropin-releasing hormone (TRH), and growth hormone-releasing hormone (GRH). However, there was no increased secretion of adrenocorticotropic hormone (ACTH) in response to hypoglycemia (induced by the administration of insulin) and there was no increased secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH) in response to the administration of clomiphene. Magnetic resonance imaging revealed an atrophied pituitary gland with an empty sella, but there were no abnormal findings of the hypothalamus. Hydrocortisone replacement at a dosage of 20 mg/day increased the patient's plasma glucose from 73 to 100 mg/dL and his serum sodium from 133 to 138 mmol/l. These findings therefore indicate a partial impairment in hypothalamic hormone release, resulting from a traumatic brain injury that the patient had received 31 years ago.

Abnormal response of melanin-concentrating hormone deficient mice to fasting: hyperactivity and rapid eye movement sleep suppression.

Melanin-concentrating hormone (MCH) is a hypothalamic neuropeptide that has been implicated in energy homeostasis. Pharmacological studies with MCH and its receptor antagonists have suggested additional behavioral roles for the neuropeptide in the control of mood and vigilance states. These suggestions have been supported by a report of modified sleep in the MCH-1 receptor knockout mouse. Here we found that MCH knockout (MCH(-)(/)(-)) mice slept less during both the light and dark phases under baseline conditions. In response to fasting, MCH(-)(/)(-) mice exhibited marked hyperactivity, accelerated weight loss and an exaggerated decrease in rapid eye movement (REM) sleep. Following a 6-h period of sleep deprivation, however, the sleep rebound in MCH(-)(/)(-) mice was normal. Thus MCH(-)(/)(-) mice adapt poorly to fasting, and their loss of bodyweight under this condition is associated with behavioral hyperactivity and abnormal expression of REM sleep. These results support a role for MCH in vigilance state regulation in response to changes in energy homeostasis and may relate to a recent report of initial clinical trials with a novel MCH-1 receptor antagonist. When combined with caloric restriction, the treatment of healthy, obese subjects with this compound resulted in some subjects experiencing vivid dreams and sleep disturbances.

Melanin-concentrating hormone projections to areas involved in somatomotor responses.

The lateral hypothalamic area (LHA) participates in the integration of sensory information and somatomotor responses associated with hunger and thirst. Although the LHA is neurochemically heterogeneous, a particularly high number of cells express melanin-concentrating hormone (MCH), which has been reported to play a role in energy homeostasis. Treatment with MCH increases food intake, and MCH mRNA is overexpressed in leptin-deficient (ob/ob) mice. Mice lacking both MCH and leptin present reduced body fat, mainly due to increased resting energy expenditure and locomotor activity. Dense MCH innervation of the cerebral motor cortex (MCx) and the pedunculopontine tegmental nucleus (PPT), both related to motor function, has been reported. Therefore, we postulated that a specific group of MCH neurons project to these areas. To investigate our hypothesis, we injected retrograde tracers into the MCx and the PPT of rats, combined with immunohistochemistry. We found that 25% of the LHA neurons projecting to the PPT were immunoreactive for MCH, and that 75% of the LHA neurons projecting to the MCx also contained MCH. Few MCH neurons were found to send collaterals to both areas. We also found that 15% of the incerto-hypothalamic neurons projecting to the PPT expressed MCH immunoreactivity. Those neurons preferentially innervated the rostral PPT. In addition, we observed that the MCH neurons express glutamic acid decarboxylase mRNA, a gamma-aminobutyric acid (GABA) synthesizing enzyme. We postulate that MCH/GABA neurons are involved in the inhibitory modulation of the innervated areas, decreasing motor activity in states of negative energy balance.

MCH-/- mice are resistant to aging-associated increases in body weight and insulin resistance.

Ablation of the hypothalamic peptide, melanin-concentrating hormone (MCH), leads to a lean phenotype and resistance to diet-induced obesity. Observation of MCH(-/-) mice at older ages suggested that these effects persist in mice >1 year old. Leanness secondary to caloric restriction is known to be associated with improved glucose tolerance as well as an overall increase in life span. Because the MCH(-/-) model represents leanness secondary to increased energy expenditure rather than caloric restriction, we were interested in determining whether this model of leanness would be associated with beneficial metabolic effects at older ages. To assess the effects of MCH ablation over a more prolonged period, we monitored male and female MCH(-/-) mice up to 19 months. The lean phenotype of MCH(-/-) mice persisted over the duration of the study. At 19 months, MCH(-/-) male and female mice weighed 23.4 and 30.8% less than their wild-type counterparts, a result of reduced fat mass in MCH(-/-) mice. Aged MCH(-/-) mice exhibited better glucose tolerance and were more insulin sensitive compared with wild-type controls. Aging-associated decreases in locomotor activity were also attenuated in MCH(-/-) mice. We also evaluated two molecules implicated in the pathophysiology of aging, p53 and silent inflammatory regulator 2 (Sir2). We found that expression of the tumor suppressor protein p53 was higher in MCH(-/-) mice at 9 and 19 months of age. In contrast, expression of Sir2 was unchanged. In aggregate, these findings suggest that MCH ablation improves the long-term outcome for several indicators of the aging process.

The hypothalamic neuropeptide melanin-concentrating hormone acts in the nucleus accumbens to modulate feeding behavior and forced-swim performance.

Melanin-concentrating hormone (MCH) is a hypothalamic neuropeptide with a prominent role in feeding and energy homeostasis. The rodent MCH receptor (MCH1R) is highly expressed in the nucleus accumbens shell (AcSh), a region that is important in the regulation of appetitive behavior. Here we establish a role for MCH and MCH1R in mediating a hypothalamic-limbic circuit that regulates feeding and related behaviors. Direct delivery of an MCH1R receptor antagonist to the AcSh blocked feeding and produced an antidepressant-like effect in the forced swim test, whereas intra-AcSh injection of MCH had the opposite effect. Expression studies demonstrated that MCH1R is present in both the enkephalin- and dynorphin-positive medium spiny neurons of the AcSh. Biochemical analysis in AcSh explants showed that MCH signaling blocks dopamine-induced phosphorylation of the AMPA glutamate receptor subunit GluR1 at Ser845. Finally, food deprivation, but not other stressors, stimulated cAMP response element-binding protein-dependent pathways selectively in MCH neurons of the hypothalamus, suggesting that these neurons are responsive to a specific set of physiologically relevant conditions. This work identifies a novel hypothalamic-AcSh circuit that influences appetitive behavior and mediates the antidepressant activity of MCH1R antagonists.

Mice with MCH ablation resist diet-induced obesity through strain-specific mechanisms.

Genetics and environment contribute to the development of obesity, in both humans and rodents. However, the potential interaction between genes important in energy balance, strain background, and dietary environment has been only minimally explored. We investigated the effects of genetic ablation of melanin-concentrating hormone (MCH), a neuropeptide with a key role in energy balance, with chow and a high-fat diet (HFD) in two different mouse strains, one obesity-prone (C57BL/6) and the other obesity-resistant (129). Substantial differences were seen in wild-type (WT) animals of different strains. 129 animals had significantly lower levels of spontaneous locomotor activity than C57BL/6; however, 129 mice gained less weight on both chow and HFD. In both strains, deletion of MCH led to attenuated weight gain compared with WT counterparts, an effect secondary to increased energy expenditure. In both strains, feeding a HFD led to further increases in energy expenditure in both WT and MCH-KO mice; however, this increase was more pronounced in 129 mice. In addition, mice lacking MCH have a phenotype of increased locomotor activity, an effect also seen in both strains. The relative increase in activity in MCH(-/-) mice is modest in animals fed chow but increases substantially when animals are placed on HFD. These studies reinforce the important role of MCH in energy homeostasis and indicate that MCH is a plausible target for antiobesity therapy.

Enhanced running wheel activity of both Mch1r- and Pmch-deficient mice.

Mch1r-deficient (Mch1r(-/-)) mice are hyperphagic, hyperactive, lean, and resistant to diet-induced obesity. To examine whether the MCH1R is involved in regulating activity-based energy expenditure, we investigated voluntary wheel running (WR) activity of wild-type (WT) and Mch1r(-/-) mice basally, in response to diets with different caloric density and with different feeding schedules. We also evaluated WR activity of mice with ablation of the prepro-MCH gene (Pmch(-/-) mice). Dark cycle WR activity of Mch1r(-/-) mice fed low fat (LF) chow was increased significantly relative to WT mice. Transition to moderate high-fat (MHF) diet was associated with an increase in nocturnal WR activity in both genotypes. Both Mch1r(-/-) and WT mice exhibited food anticipatory activity (FAA) before the daily scheduled feeding time, indicating that MCH1R is not required for FAA. Naloxone (3 mg/kg, i.p.) suppressed WR activity of both genotypes, suggesting opioid regulation of locomotor activity. WR increased nocturnal dynorphin mRNA levels in Mch1r(-/-) brain. Importantly, Pmch-deficient mice had significantly enhanced WR activity relative to WT controls. These results suggest that endogenous MCH plays an inhibitory role in regulating locomotor activity. In summary, we demonstrated enhanced WR activities in mice lacking either MCH or its cognate receptor.

Estradiol-induced anorexia is independent of leptin and melanin-concentrating hormone.

OBJECTIVE: Treatment of male rodents with estradiol (E2) is associated with anorexia and weight loss by poorly understood mechanisms. We examined the role of the orexigenic hypothalamic peptide melanin-concentrating hormone (MCH) and the appetite-inhibiting, fat-derived hormone leptin in mediating E2-induced anorexia. RESEARCH METHODS AND PROCEDURES: We studied the effect of E2 treatment (implantation of either E2 pellet or matching placebo) in male C57Bl/6J mice, as well as in a lean mouse model (MCH knockout mice) and an obese model (leptin-deficient ob/ob mice). We also studied the effect of E2 treatment in the context of high-fat diet. RESULTS: We confirmed E2 dose-dependent anorexia in male wild type mice fed a normal chow diet. E2 treatment was associated with a significant decrease in body fat, serum leptin levels, and arcuate hypothalamic proopiomelanocortin expression. E2-implanted mice also showed increased hypothalamic neuropeptide Y and MCH expression. As MCH has been implicated in E2-induced hypophagia, we performed E2 pellet implantation in MCH knockout mice and observed hypophagia and weight loss, indicating that MCH is not an essential mediator of E2-induced anorexia. E2-implanted ob/ob mice also had hypophagia and weight loss, indicating that leptin is not essential for E2-induced anorexia. High-fat diet significantly exacerbated the effect of E2 treatment, leading to a 99.6% decrease in food intake at 48 hours and a 30% loss of body weight within 1 week. DISCUSSION: The anorectic effects of E2 were independent of MCH and leptin. Our results suggested that E2 may have effects on nutrient preferences.

Melanin-concentrating hormone is a critical mediator of the leptin-deficient phenotype.

Energy homeostasis is regulated by a complex network involving peripheral and central signals that determine food intake and energy expenditure. Melanin-concentrating hormone (MCH) plays an essential role in this process. Animals treated with MCH develop hyperphagia and obesity. Ablation of the prepro-MCH gene leads to a lean phenotype, as does ablation of the rodent MCH receptor, MCHR-1. MCH is overexpressed in the leptin-deficient ob/ob mouse, and we hypothesized that ablation of MCH in this animal would lead to attenuation of its obese phenotype. Compared with ob/ob animals, mice lacking both leptin and MCH (double null) had a dramatic reduction in body fat. Surprisingly, the hyperphagia of the ob/ob mouse was unaffected. Instead, leanness was secondary to a marked increase in energy expenditure resulting from both increased resting energy expenditure and locomotor activity. Furthermore, double-null mice showed improvements in other parameters impaired in ob/ob mice. Compared with ob/ob mice, double-null animals had increased basal body temperature, improved response to cold exposure, lower plasma glucocorticoid levels, improved glucose tolerance, and reduced expression of stearoyl-CoA desaturase 1 (SCD-1). These results highlight the importance of MCH in integration of energy homeostasis downstream of leptin and, in particular, the role of MCH in regulation of energy expenditure.

Hypothalamic growth hormone deficiency and supplementary GH therapy in two patients with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes.

Two pediatric patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes were diagnosed with growth hormone deficiency with the primary lesion identified as the growth hormone-releasing factor producing cells of the hypothalamus. Stimulation tests with insulin, levodopa and sleep did not overcome the deficient pattern of growth hormone secretion. By comparison, the growth hormone-releasing factor stimulation test generated a normal growth hormone response in these two patients. Growth hormone supplementary therapy was effective in terms of growth gain without adverse effects.