FoxO1 target Gpr17 activates AgRP neurons to regulate food intake.

Hypothalamic neurons expressing Agouti-related peptide (AgRP) are critical for initiating food intake, but druggable biochemical pathways that control this response remain elusive. Thus, genetic ablation of insulin or leptin signaling in AgRP neurons is predicted to reduce satiety but fails to do so. FoxO1 is a shared mediator of both pathways, and its inhibition is required to induce satiety. Accordingly, FoxO1 ablation in AgRP neurons of mice results in reduced food intake, leanness, improved glucose homeostasis, and increased sensitivity to insulin and leptin. Expression profiling of flow-sorted FoxO1-deficient AgRP neurons identifies G-protein-coupled receptor Gpr17 as a FoxO1 target whose expression is regulated by nutritional status. Intracerebroventricular injection of Gpr17 agonists induces food intake, whereas Gpr17 antagonist cangrelor curtails it. These effects are absent in Agrp-Foxo1 knockouts, suggesting that pharmacological modulation of this pathway has therapeutic potential to treat obesity.

α-Melanocyte-stimulating hormone alleviates pathological cardiac remodeling via melanocortin 5 receptor.

α-Melanocyte-stimulating hormone (α-MSH) regulates diverse physiological functions by activating melanocortin receptors (MC-R). However, the role of α-MSH and its possible target receptors in the heart remain completely unknown. Here we investigate whether α-MSH could be involved in pathological cardiac remodeling. We found that α-MSH was highly expressed in the mouse heart with reduced ventricular levels after transverse aortic constriction (TAC). Administration of a stable α-MSH analog protected mice against TAC-induced cardiac hypertrophy and systolic dysfunction. In vitro experiments revealed that MC5-R in cardiomyocytes mediates the anti-hypertrophic signaling of α-MSH. Silencing of MC5-R in cardiomyocytes induced hypertrophy and fibrosis markers in vitro and aggravated TAC-induced cardiac hypertrophy and fibrosis in vivo. Conversely, pharmacological activation of MC5-R improved systolic function and reduced cardiac fibrosis in TAC-operated mice. In conclusion, α-MSH is expressed in the heart and protects against pathological cardiac remodeling by activating MC5-R in cardiomyocytes. These results suggest that analogs of naturally occurring α-MSH, that have been recently approved for clinical use and have agonistic activity at MC5-R, may be of benefit in treating heart failure.

Genome-wide loss of heterozygosity predicts aggressive, treatment-refractory behavior in pituitary neuroendocrine tumors.

Pituitary neuroendocrine tumors (PitNETs) exhibiting aggressive, treatment-refractory behavior are the rare subset that progress after surgery, conventional medical therapies, and an initial course of radiation and are characterized by unrelenting growth and/or metastatic dissemination. Two groups of patients with PitNETs were sequenced: a prospective group of patients (n = 66) who consented to sequencing prior to surgery and a retrospective group (n = 26) comprised of aggressive/higher risk PitNETs. A higher mutational burden and fraction of loss of heterozygosity (LOH) was found in the aggressive, treatment-refractory PitNETs compared to the benign tumors (p = 1.3 × 10-10 and p = 8.5 × 10-9, respectively). Within the corticotroph lineage, a characteristic pattern of recurrent chromosomal LOH in 12 specific chromosomes was associated with treatment-refractoriness (occurring in 11 of 14 treatment-refractory versus 1 of 14 benign corticotroph PitNETs, p = 1.7 × 10-4). Across the cohort, a higher fraction of LOH was identified in tumors with TP53 mutations (p = 3.3 × 10-8). A machine learning approach identified loss of heterozygosity as the most predictive variable for aggressive, treatment-refractory behavior, outperforming the most common gene-level alteration, TP53, with an accuracy of 0.88 (95% CI: 0.70-0.96). Aggressive, treatment-refractory PitNETs are characterized by significant aneuploidy due to widespread chromosomal LOH, most prominently in the corticotroph tumors. This LOH predicts treatment-refractoriness with high accuracy and represents a novel biomarker for this poorly defined PitNET category.

Partially redundant enhancers cooperatively maintain Mammalian pomc expression above a critical functional threshold.

Cell-specific expression of many genes is conveyed by multiple enhancers, with each individual enhancer controlling a particular expression domain. In contrast, multiple enhancers drive similar expression patterns of some genes involved in embryonic development, suggesting regulatory redundancy. Work in Drosophila has indicated that functionally overlapping enhancers canalize development by buffering gene expression against environmental and genetic disturbances. However, little is known about regulatory redundancy in vertebrates and in genes mainly expressed during adulthood. Here we study nPE1 and nPE2, two phylogenetically conserved mammalian enhancers that drive expression of the proopiomelanocortin gene (Pomc) to the same set of hypothalamic neurons. The simultaneous deletion of both enhancers abolished Pomc expression at all ages and induced a profound metabolic dysfunction including early-onset extreme obesity. Targeted inactivation of either nPE1 or nPE2 led to very low levels of Pomc expression during early embryonic development indicating that both enhancers function synergistically. In adult mice, however, Pomc expression is controlled additively by both enhancers, with nPE1 being responsible for ∼80% and nPE2 for ∼20% of Pomc transcription. Consequently, nPE1 knockout mice exhibit mild obesity whereas nPE2-deficient mice maintain a normal body weight. These results suggest that nPE2-driven Pomc expression is compensated by nPE1 at later stages of development, essentially rescuing the earlier phenotype of nPE2 deficiency. Together, these results reveal that cooperative interactions between the enhancers confer robustness of Pomc expression against gene regulatory disturbances and preclude deleterious metabolic phenotypes caused by Pomc deficiency in adulthood. Thus, our study demonstrates that enhancer redundancy can be used by genes that control adult physiology in mammals and underlines the potential significance of regulatory sequence mutations in common diseases.

Evaluation of CSF and plasma biomarkers of brain melanocortin activity in response to caloric restriction in humans.

The melanocortin neuronal system, which consists of hypothalamic proopiomelanocortin (POMC) and agouti-related protein (AgRP) neurons, is a leptin target that regulates energy balance and metabolism, but studies in humans are limited by a lack of reliable biomarkers to assess brain melanocortin activity. The objective of this study was to measure the POMC prohormone and its processed peptide, ß-endorphin (ß-EP), in cerebrospinal fluid (CSF) and AgRP in CSF and plasma after calorie restriction to validate their utility as biomarkers of brain melanocortin activity. CSF and plasma were obtained from 10 lean and obese subjects after fasting (40 h) and refeeding (24 h), and from 8 obese subjects before and after 6 wk of dieting (800 kcal/day) to assess changes in neuropeptide and hormone levels. After fasting, plasma leptin decreased to 35%, and AgRP increased to 153% of baseline. During refeeding, AgRP declined as leptin increased; CSF ß-EP increased, but POMC did not change. Relative changes in plasma and CSF leptin were blunted in obese subjects. After dieting, plasma and CSF leptin decreased to 46% and 70% of baseline, CSF POMC and ß-EP decreased, and plasma AgRP increased. At baseline, AgRP correlated negatively with insulin and homeostasis model assessment (HOMA-IR), and positively with the Matsuda index. Thus, following chronic calorie restriction, POMC and ß-EP declined in CSF, whereas acutely, only ß-EP changed. Plasma AgRP, however, increased after both acute and chronic calorie restriction. These results support the use of CSF POMC and plasma AgRP as biomarkers of hypothalamic melanocortin activity and provide evidence linking AgRP to insulin sensitivity.

Childhood acromegaly due to X-linked acrogigantism: long term follow-up.

PURPOSE: Acromegaly in infancy is extremely rare. We describe a 32 year old woman who presented at 6 months of age with isolated macrocephaly, followed by accelerated linear growth. At 21 months of age, her head circumference was 55 cm (+5.5 SD), height was 97.6 cm (+4.4 SD) and weight was 20.6 kg (+6.2 SD). She had markedly elevated levels of growth hormone (GH) (135 ng/ml), IGF-1 (1540 ng/ml) and prolactin (370 ng/ml). A pituitary macroadenoma was surgically resected. Immunohistochemical staining was positive for GH. Post-operatively, she developed ACTH and TSH deficiency and diabetes insipidus. METHODS: Long term clinical follow-up and genetic testing with chromosomal microarray analysis. RESULTS: Despite GH deficiency, she grew well until 7 ½ years old, with subsequent decline in growth velocity, and received GH therapy for 5 years. Puberty was initiated with estrogen therapy. As an adult, she has no stigmata of acromegaly, with a height of 164.5 cm and non-acromegalic features. IGF-1 has remained in the low normal range. Prolactin has been mildly elevated. Serial MRIs have shown no evidence of tumor recurrence. She receives replacement therapy with hydrocortisone, levothyroxine and DDAVP. Chromosomal microarray analysis revealed that she has X-linked acrogigantism (X-LAG) due to a de novo duplication of Xq26.3 (516 kb). She recently became pregnant following ovarian stimulation and chorionic villus sampling revealed that she is carrying a male with the same duplication. CONCLUSION: This report provides detailed long term clinical follow-up of a patient with X-LAG syndrome.

Proopiomelanocortin, agouti-related protein, and leptin in human cerebrospinal fluid: correlations with body weight and adiposity.

Leptin and its neuronal targets, which produce proopiomelanocortin (POMC) and agouti-related protein (AgRP), regulate energy balance. This study characterized leptin, POMC, and AgRP in the cerebrospinal fluid (CSF) of 47 healthy human subjects, 23 lean and 24 overweight/obese (OW/OB), as related to BMI, adiposity, plasma leptin, soluble leptin receptor (s-OB-R), and insulin. POMC was measured since the POMC prohormone is the predominant POMC peptide in CSF and correlates with hypothalamic POMC in rodents. Plasma AgRP was similarly characterized. CSF leptin was 83-fold lower than in plasma and correlated strongly with BMI, body fat, and insulin. The relative amount of leptin transported into CSF declined with increasing BMI, ranging from 4.5 to 0.52%, consistent with a saturable transport mechanism. CSF sOB-R was 78-fold lower than in plasma and correlated negatively with plasma and CSF leptin. CSF POMC was higher in lean vs. OW/OB subjects (P < 0.001) and correlated negatively with CSF leptin (r = -0.60, P < 0.001) and with plasma leptin, insulin, BMI, and adiposity. CSF AgRP was not different in lean vs. OW/OB; however, plasma AgRP was higher in lean subjects (P = 0.001) and correlated negatively with BMI, adiposity, leptin, insulin, and HOMA (P < 0.005). Thus, CSF measurements may provide useful biomarkers for brain leptin and POMC activity. The striking negative correlation between CSF leptin and POMC could be secondary to leptin resistance and/or neuronal changes associated with obesity but may also indicate that POMC plays a primary role in regulating body weight and adiposity. The role of plasma AgRP as a neuroendocrine biomarker deserves further study.

Defining Predictors of Weight Loss Response to Lorcaserin.

CONTEXT: Individual responses to weight loss (WL) medications vary widely and prediction of response remains elusive. OBJECTIVE: We investigated biomarkers associated with use of lorcaserin (LOR), a 5HT2cR agonist that targets proopiomelanocortin (POMC) neurons that regulate energy and glucose homeostasis, to identify predictors of clinical efficacy. METHODS: Thirty individuals with obesity were treated with 7 days of placebo and LOR in a randomized crossover study. Nineteen participants continued on LOR for 6 months. Cerebrospinal fluid (CSF) POMC peptide measurements were used to identify potential biomarkers that predict WL. Insulin, leptin, and food intake during a meal were also studied. RESULTS: LOR induced a significant decrease in CSF levels of the POMC prohormone and an increase in its processed peptide ß-endorphin after 7 days; ß-endorphin/POMC increased by 30% (P < .001). This was accompanied by a substantial decrease in insulin, glucose, and homeostasis model assessment of insulin resistance before WL. Changes in CSF POMC peptides persisted after WL (6.9%) at 6 months that were distinct from prior reports after diet alone. Changes in POMC, food intake, or other hormones did not predict WL. However, baseline CSF POMC correlated negatively with WL (P = .07) and a cutoff level of CSF POMC was identified that predicted more than 10% WL. CONCLUSION: Our results provide evidence that LOR affects the brain melanocortin system in humans and that effectiveness is increased in individuals with lower melanocortin activity. Furthermore, early changes in CSF POMC parallel WL-independent improvements in glycemic indexes. Thus, assessment of melanocortin activity could provide a way to personalize pharmacotherapy of obesity with 5HT2cR agonists.

Hypothalamic obesity in patients with craniopharyngioma: treatment approaches and the emerging role of gastric bypass surgery.

Hypothalamic obesity is a potential sequela of craniopharyngioma, arising from hypothalamic damage inflicted by either the tumor and/or its treatment. The marked weight gain that characterizes this disorder appears to result from impaired sympathoadrenal activation, parasympathetic dysregulation, and other hormonal and hypothalamic disturbances that upset the balance between energy intake and expenditure. Given hypopituitarism is commonly present, careful management of hormonal deficits is important for weight control in these patients. In addition, diet, exercise, and pharmacotherapy aimed at augmenting sympathetic output, controlling hyperinsulinism, and promoting weight loss have been used to treat this disease, but these measures rarely lead to sustained weight loss. While surgical interventions have not routinely been pursued, emerging data suggests that surgical weight loss interventions including Roux-en-Y gastric bypass can be safely and effectively used for the management of hypothalamic obesity in patients with craniopharyngioma.

Functional heterogeneity of POMC neurons relies on mTORC1 signaling.

Hypothalamic pro-opiomelanocortin (POMC) neurons are known to trigger satiety. However, these neuronal cells encompass heterogeneous subpopulations that release γ-aminobutyric acid (GABA), glutamate, or both neurotransmitters, whose functions are poorly defined. Using conditional mutagenesis and chemogenetics, we show that blockade of the energy sensor mechanistic target of rapamycin complex 1 (mTORC1) in POMC neurons causes hyperphagia by mimicking a cellular negative energy state. This is associated with decreased POMC-derived anorexigenic α-melanocyte-stimulating hormone and recruitment of POMC/GABAergic neurotransmission, which is restrained by cannabinoid type 1 receptor signaling. Electrophysiology and optogenetic studies further reveal that pharmacological blockade of mTORC1 simultaneously activates POMC/GABAergic neurons and inhibits POMC/glutamatergic ones, implying that the functional specificity of these subpopulations relies on mTORC1 activity. Finally, POMC neurons with different neurotransmitter profiles possess specific molecular signatures and spatial distribution. Altogether, these findings suggest that mTORC1 orchestrates the activity of distinct POMC neurons subpopulations to regulate feeding behavior.

Approach to the Treatment of a Patient with an Aggressive Pituitary Tumor.

A small subset of pituitary adenomas grows despite maximal treatment with standard therapies; namely, surgery and radiotherapy. These aggressive tumors demonstrate 2 patterns of growth: they may be locally aggressive or metastasize distantly, either hematogenously or through the spinal fluid. Further surgery and radiotherapy may be helpful for palliation of symptoms, but they are rarely definitive in the management of these malignant tumors. The only chemotherapy with established activity in the treatment of pituitary tumors is the alkylating agent temozolomide. At most, 50% of patients exhibit an objective response to temozolomide and the median time to progression is short; thus, there remains a significant unmet need for effective treatments within this patient population. Several targeted agents have reported activity in this tumor type-including small molecule inhibitors, checkpoint inhibitors, and other biologics-but remain investigational at this time.

Diurnal Patterns for Cortisol, Cortisone and Agouti-Related Protein in Human Cerebrospinal Fluid and Blood.

CONTEXT: Cortisol in blood has a robust circadian rhythm and exerts potent effects on energy balance that are mediated in part by central mechanisms. These interactions involve orexigenic agouti-related protein (AgRP) neurons that are stimulated by glucocorticoids. However, diurnal changes in brain or cerebrospinal fluid (CSF) cortisol and cortisone, which are interconverted by 11ß-HSD1, have not been characterized in humans. OBJECTIVE: To conduct a secondary analysis of existing samples to characterize diurnal changes in cortisol and cortisone in CSF and examine their relationships to changes in AgRP. METHODS: Stored CSF and plasma samples were obtained from 8 healthy subjects who served as controls for a sleep study. CSF was collected every 2h for 36h via indwelling lumbar catheter; plasma was collected every 2h. RESULTS: There was a diurnal rhythm for cortisol and cortisone in CSF that closely followed the plasma rhythm by 2 h with peak and nadir levels at 0900h and 0100h. The ratio of cortisol (active) to cortisone (inactive) in CSF was 48% higher at the peak versus nadir. There was a diurnal rhythm for AgRP in plasma that was out of phase with the cortisol rhythm. There was a less distinct diurnal rhythm for AgRP in CSF that oscillated with a similar phase as cortisol. CONCLUSIONS: There is a robust diurnal rhythm for cortisol and cortisone in CSF. Diurnal changes were noted for AgRP that are related to the cortisol changes. It remains to be determined if AgRP mediates adverse metabolic effects associated with disruption of the cortisol circadian rhythm.

Presenting Features in 269 Patients With Clinically Nonfunctioning Pituitary Adenomas Enrolled in a Prospective Study.

CONTEXT: Clinically nonfunctioning pituitary adenomas (CNFPAs) typically remain undetected until mass effect symptoms develop. However, currently, head imaging is performed commonly for many other indications, which may increase incidental discovery of CNFPAs. Since current presentation and outcome data are based on older, retrospective series, a prospective characterization of a contemporary CNFPA cohort was needed. OBJECTIVE: To determine the prevalence of incidental presentation and hypopituitarism and its predictors in a CNFPA cohort that spanned 6 to 9 mm micro- to macroadenoma included observational and surgical therapy. METHODS: At enrollment in a prospective, observational study, 269 patients with CNFPAs were studied by history, examination, blood sampling, and pituitary imaging analysis and categorized into incidental or symptoms presentation groups that were compared. RESULTS: Presentation was incidental in 48.7% of patients and due to tumor symptoms in 51.3%. In the symptoms and incidental groups, 58.7% and 27.4% of patients had hypopituitarism, respectively, and 25% of patients with microadenomas had hypopituitarism. Many had unappreciated signs and symptoms of pituitary disease. Most tumors were macroadenomas (87%) and were larger in the symptoms than incidental and hypopituitary groups than in the eupituitary groups. The patients in the incidental group were older, and males were older and had larger tumors in both the incidental and symptoms groups. CONCLUSIONS: Patients with CNFPAs commonly present incidentally and with previously unrecognized hypopituitarism and symptoms that could have prompted earlier diagnosis. Our data support screening all large micro and macro-CNFPAs for hypopituitarism. Most patients with CNFPAs still have mass effect signs at presentation, suggesting the need for more awareness of pituitary disease. Our ongoing, prospective observation of this cohort will assess outcomes of these CNFPA groups.

Increased Cerebrospinal Fluid Amyloid-ß During Sleep Deprivation in Healthy Middle-Aged Adults Is Not Due to Stress or Circadian Disruption.

BACKGROUND: Concentrations of soluble amyloid-ß (Aß) oscillate with the sleep-wake cycle in the interstitial fluid of mice and cerebrospinal fluid (CSF) of humans. Further, the concentration of Aß in CSF increases during sleep deprivation. Stress and disruption of the circadian clock are additional mechanisms hypothesized to increase CSF Aß levels. Cortisol is a marker for stress and has an endogenous circadian rhythm. Other factors such as glucose and lactate have been associated with changes in sleep-wake activity and/or Aß. OBJECTIVE: In this exploratory study, we used samples collected in a previous study to examine how sleep deprivation affects Aß, cortisol, lactate, and glucose in plasma and CSF from healthy middle-aged adults (N = 11). METHODS: Eleven cognitively normal participants without evidence of sleep disturbance were randomized to sleep deprivation or normal sleep control. All participants were invited to repeat the study. Cortisol, lactate, glucose, and Aß were measured in 2-h intervals over a 36-h period in both plasma and CSF. All concentrations were normalized to the mean prior to calculating mesor, amplitude, acrophase, and other parameters. RESULTS: One night of sleep deprivation increases the overnight concentration of Aß in CSF approximately 10%, but does not significantly affect cortisol, lactate, or glucose concentrations in plasma or CSF between the sleep-deprived and control conditions. CONCLUSION: These data suggest that sleep deprivation-related changes in CSF Aß are not mediated by stress or circadian disruption as measured by cortisol.

Effects of Naltrexone on Energy Balance and Hypothalamic Melanocortin Peptides in Male Mice Fed a High-Fat Diet.

The hypothalamic melanocortin system composed of proopiomelanocortin (POMC) and agouti-related protein (AgRP) neurons plays a key role in maintaining energy homeostasis. The POMC-derived peptides, α-MSH and ß-EP, have distinct roles in this process. α-MSH inhibits food intake, whereas ß-EP, an endogenous opioid, can inhibit POMC neurons and stimulate food intake. A mouse model was used to examine the effects of opioid antagonism with naltrexone (NTX) on Pomc and Agrp gene expression and POMC peptide processing in the hypothalamus in conjunction with changes in energy balance. There were clear stimulatory effects of NTX on hypothalamic Pomc in mice receiving low- and high-fat diets, yet only transient decreases in food intake and body weight gain were noted. The effects on Pomc expression were accompanied by an increase in POMC prohormone levels and a decrease in levels of the processed peptides α-MSH and ß-EP. Arcuate expression of the POMC processing enzymes Pcsk1, Pcsk2, and Cpe was not altered by NTX, but expression of Prcp, an enzyme that inactivates α-MSH, increased after NTX exposure. NTX exposure also stimulated hypothalamic Agrp expression, but the effects of NTX on energy balance were not enhanced in Agrp-null mice. Despite clear stimulatory effects of NTX on Pomc expression in the hypothalamus, only modest transient decreases in food intake and body weight were seen. Effects of NTX on POMC processing, and possibly α-MSH inactivation, as well as stimulatory effects on AgRP neurons could mitigate the effects of NTX on energy balance.

Plasma Agouti-Related Protein Levels in Acromegaly and Effects of Surgical or Pegvisomant Therapy.

CONTEXT: GH activates agouti-related protein (AgRP) neurons, leading to orexigenic responses in mice. The relationship between serum GH and plasma AgRP, which has been shown to reflect hypothalamic AgRP, has not been evaluated in humans. OBJECTIVE: To test the hypothesis that central stimulatory actions of GH on hypothalamic AgRP could be reflected in plasma AgRP in acromegaly. METHODS: We studied 23 patients with active acromegaly before and for ≤2 years after surgical (n = 13) or GH receptor antagonist therapy with pegvisomant (n = 10), and 100 healthy subjects with morning fasting blood samples for AgRP, leptin, GH, and IGF-1 and anthropometric measurements. RESULTS: The plasma AgRP levels were higher in those with active acromegaly than in the matched healthy subjects [median, 100 pg/mL; interquartile range (IQR), 78 to 139 pg/mL vs median, 63 pg/mL; IQR, 58 to 67 pg/mL; P < 0.0001]. Plasma AgRP decreased from before to after surgery (median, 102 pg/mL; IQR, 82 to 124 pg/mL vs median, 63 pg/mL; IQR, 55.6 to 83 pg/mL; P = 0.0024) and from before to during pegvisomant therapy (median, 97 pg/mL; IQR, 77 to 175 pg/mL vs median, 63; IQR, 61 to 109 pg/mL; P = 0.006). The plasma AgRP level correlated with GH (r = 0.319; P = 0.011) and IGF-1 (r = 0.292; P = 0.002). In repeated measure analysis, AgRP was significantly associated with IGF-1. CONCLUSIONS: Our data have provided evidence of a stimulatory effect of GH on plasma AgRP in humans. The levels were greater in active acromegaly and decreased in parallel with GH and IGF-1 decreases with acromegaly treatment. Data from mice suggest that AgRP may mediate some of the known effects of GH on energy metabolism. This warrants further study in patients with acromegaly and other populations.

Gpr17 deficiency in POMC neurons ameliorates the metabolic derangements caused by long-term high-fat diet feeding.

BACKGROUND: Proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARH) control energy homeostasis by sensing hormonal and nutrient cues and activating secondary melanocortin sensing neurons. We identified the expression of a G protein-coupled receptor, Gpr17, in the ARH and hypothesized that it contributes to the regulatory function of POMC neurons on metabolism. METHODS: In order to test this hypothesis, we generated POMC neuron-specific Gpr17 knockout (PGKO) mice and determined their energy and glucose metabolic phenotypes on normal chow diet (NCD) and high-fat diet (HFD). RESULTS: Adult PGKO mice on NCD displayed comparable body composition and metabolic features measured by indirect calorimetry. By contrast, PGKO mice on HFD demonstrated a sexually dimorphic phenotype with female PGKO mice displaying better metabolic homeostasis. Notably, female PGKO mice gained significantly less body weight and adiposity (p < 0.01), which was associated with increased energy expenditure, locomotor activity, and respiratory quotient, while males did not have an overt change in energy homeostasis. Though PGKO mice of both sexes had comparable glucose and insulin tolerance, detailed analyses of liver gene expression and serum metabolites indicate that PGKO mice could have reduced gluconeogenesis and increased lipid utilization on HFD. To elucidate the central-based mechanism(s) underlying the better-preserved energy and glucose homeostasis in PGKO mice on HFD, we examined the electrophysiological properties of POMC neurons and found Gpr17 deficiency led to increased spontaneous action potentials. Moreover, PGKO mice, especially female knockouts, had increased POMC-derived alpha-melanocyte stimulating hormone and beta-endorphin despite a comparable level of prohormone POMC in their hypothalamic extracts. CONCLUSIONS: Gpr17 deficiency in POMC neurons protects metabolic homeostasis in a sex-dependent manner during dietary and aging challenges, suggesting that Gpr17 could be an effective anti-obesity target in specific populations with poor metabolic control.

Plasma Agouti-Related Protein and Cortisol Levels in Cushing Disease: Evidence for the Regulation of Agouti-Related Protein by Glucocorticoids in Humans.

Context: Glucocorticoids regulate energy balance, in part by stimulating the orexigenic neuropeptide agouti-related protein (AgRP). AgRP neurons express glucocorticoid receptors, and glucocorticoids have been shown to stimulate AgRP gene expression in rodents. Objective: We sought to determine whether there is a relationship between plasma AgRP and hypothalamic AgRP in rats and to evaluate the relationship between cortisol and plasma AgRP in humans. Methods: We retrospectively evaluated plasma AgRP levels prior to transsphenoidal surgery in 31 patients with Cushing disease (CD) vs 31 sex- and body mass index-matched controls from a separate study. We then prospectively measured plasma AgRP, before and 6 to 12 months after surgery, in a subgroup of 13 patients with CD. Plasma and hypothalamic AgRP were measured in adrenalectomized rats with and without corticosterone replacement. Results: Plasma AgRP was stimulated by corticosterone in rats and correlated with hypothalamic AgRP expression. Plasma AgRP levels were higher in patients with CD than in controls (139 ± 12.3 vs 54.2 ± 3.1 pg/mL; P < 0.0001). Among patients with CD, mean 24-hour urine free cortisol (UFC) levels were 257 ± 39 µg/24 hours. Strong positive correlations were observed between plasma AgRP and UFC (r = 0.76; P < 0.0001). In 11 of 13 patients demonstrating surgical cure, AgRP decreased from 126 ± 20.6 to 62.5 ± 8.0 pg/mL (P < 0.05) postoperatively, in parallel with a decline in UFC. Conclusions: Plasma AgRP levels are elevated in CD, are tightly correlated with cortisol concentrations, and decline with surgical cure. These data support the regulation of AgRP by glucocorticoids in humans. AgRP's role as a potential biomarker and as a mediator of the adverse metabolic consequences of CD deserves further study.

Familial X-Linked Acrogigantism: Postnatal Outcomes and Tumor Pathology in a Prenatally Diagnosed Infant and His Mother.

CONTEXT: X-linked acrogigantism (X-LAG), a condition of infant-onset acrogigantism marked by elevated GH, IGF-1, and prolactin (PRL), is extremely rare. Thirty-three cases, including three kindreds, have been reported. These patients have pituitary adenomas that are thought to be mixed lactotrophs and somatotrophs. CASE DESCRIPTION: The patient's mother, diagnosed with acrogigantism at 21 months, underwent pituitary tumor excision at 24 months. For more than 30 years, stable PRL, GH, and IGF-1 concentrations and serial imaging studies indicated no tumor recurrence. During preconception planning, X-LAG was diagnosed: single-nucleotide polymorphism microarray showed chromosome Xq26.3 microduplication. After conception, single-nucleotide polymorphism microarray on a chorionic villus sample showed the same microduplication in the fetus, confirming familial X-LAG. The infant grew rapidly with rising PRL, GH, and IGF-1 concentrations and an enlarging suprasellar pituitary mass, despite treatment with bromocriptine. At 15 months, he underwent tumor resection. The pituitary adenoma resembled the mother's pituitary adenoma, with tumor cells arranged in trabeculae and glandular structures. In both cases, many tumor cells expressed PRL, GH, and pituitary-specific transcription factor-1. Furthermore, the tumor expressed other lineage-specific transcription factors, as well as SOX2 and octamer-binding transcription factor 4, demonstrating the multipotentiality of X-LAG tumors. Both showed an elevated Ki-67 proliferation index, 5.6% in the mother and 8.5% in the infant, the highest reported in X-LAG. CONCLUSIONS: This is a prenatally diagnosed case of X-LAG. Clinical follow-up and biochemical evaluation have provided insight into the natural history of this disease. Expression of stem cell markers and several cell lineage-specific transcription factors suggests that these tumors are multipotential.

Effects of selective modulation of the central melanocortin-3-receptor on food intake and hypothalamic POMC expression.

Hypothalamic POMC neurons regulate energy balance via interactions with brain melanocortin receptors (MC-Rs). POMC neurons express the MC3-R which can function as an inhibitory autoreceptor in vitro. We now demonstrate that central activation of MC3-R with ICV infusion of the specific MC3-R agonist, [D-Trp(8)]-gamma-MSH, transiently suppresses hypothalamic Pomc expression and stimulates food intake in rats. Conversely, we also show that ICV infusion of a low dose of a selective MC3-R antagonist causes a transient decrease in feeding and weight gain. These data support a functional inhibitory role for the MC3-R on POMC neurons that leads to changes in food intake.