Significant Benefits of AIP Testing and Clinical Screening in Familial Isolated and Young-onset Pituitary Tumors.

CONTEXT: Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene are responsible for a subset of familial isolated pituitary adenoma (FIPA) cases and sporadic pituitary neuroendocrine tumors (PitNETs). OBJECTIVE: To compare prospectively diagnosed AIP mutation-positive (AIPmut) PitNET patients with clinically presenting patients and to compare the clinical characteristics of AIPmut and AIPneg PitNET patients. DESIGN: 12-year prospective, observational study. PARTICIPANTS & SETTING: We studied probands and family members of FIPA kindreds and sporadic patients with disease onset ≤18 years or macroadenomas with onset ≤30 years (n = 1477). This was a collaborative study conducted at referral centers for pituitary diseases. INTERVENTIONS & OUTCOME: AIP testing and clinical screening for pituitary disease. Comparison of characteristics of prospectively diagnosed (n = 22) vs clinically presenting AIPmut PitNET patients (n = 145), and AIPmut (n = 167) vs AIPneg PitNET patients (n = 1310). RESULTS: Prospectively diagnosed AIPmut PitNET patients had smaller lesions with less suprasellar extension or cavernous sinus invasion and required fewer treatments with fewer operations and no radiotherapy compared with clinically presenting cases; there were fewer cases with active disease and hypopituitarism at last follow-up. When comparing AIPmut and AIPneg cases, AIPmut patients were more often males, younger, more often had GH excess, pituitary apoplexy, suprasellar extension, and more patients required multimodal therapy, including radiotherapy. AIPmut patients (n = 136) with GH excess were taller than AIPneg counterparts (n = 650). CONCLUSIONS: Prospectively diagnosed AIPmut patients show better outcomes than clinically presenting cases, demonstrating the benefits of genetic and clinical screening. AIP-related pituitary disease has a wide spectrum ranging from aggressively growing lesions to stable or indolent disease course.

UPDATE ON THE CLINICOPATHOLOGY OF PITUITARY ADENOMAS.

OBJECTIVE: Pituitary adenomas are the third most common central nervous system tumors and arise from the anterior pituitary within the pituitary fossa. METHODS: Literature review and discussion. RESULTS: The signs and symptoms of patients with pituitary adenomas vary from 'mass effects' caused by a large adenoma to features secondary to excess pituitary hormones produced by the functioning pituitary adenoma. Detailed histopathologic assessment, based on novel classifications and the latest World Health Organization guidelines, helps to categorize pituitary adenomas into different subtypes and identify features that, in some cases, help to predict their behavior. Most of the pituitary tumors occur sporadically without known genetic predisposition, but in a significant minority of cases, somatic mutations can be identified in the GNAS and USP8 genes. A small proportion of the cases have germline genetic defects or embryonic mutations leading to mosaicism. Genes with germ-line mutations predisposing to pituitary adenomas include AIP, GPR101, MEN1, CDKN1B, PRKAR1A, PRKAR2A, DICER1, NF1, and SDHx, whereas more recently, CABLES1 has also been implicated. CONCLUSION: Understanding the pathogenesis of pituitary adenomas will allow clinicians to correlate the pathologic and genetic features with clinical data, helping decisions on the best management of these tumors. ABBREVIATIONS: ACTH = adrenocorticotropic hormone; AIP = aryl hydrocarbon receptor-interacting protein; αSU = alpha-subunit; EGFR = epithelial growth factor receptor; ER = estrogen receptor; FSH = follicle-stimulating hormone; GH = growth hormone; GHRH = growth hormone-releasing hormone; IGF-1 = insulin-like growth factor 1; LH = luteinizing hormone; MEN1 = multiple endocrine neoplasia 1; MRI = magnetic resonance imaging; NFPA = nonfunctioning pituitary adenoma; PRL = prolactin; TSH = thyroid-stimulating hormone; USP8 = ubiquitin-specific peptidase 8; WHO = World Health Organization.

The McKittrick-Wheelock syndrome: a rare cause of curable diabetes.

UNLABELLED: McKittrick-Wheelock syndrome (MWS) is a rare consequence of severe dehydration and electrolyte depletion due to mucinous diarrhoea secondary to a rectosigmoid villous adenoma. Reported cases of MWS commonly describe hypersecretion of mucinous diarrhoea in association with dehydration, hypokalaemia, hyponatraemia, hypochloraemia and pre-renal azotemia. Hyperglycaemia and diabetes are rarely reported manifestations of MWS. Herein we describe the case of a 59-year-old woman who presented with new-onset diabetes and severe electrolyte derangement due to a giant rectal villous adenoma. Subsequent endoscopic resection of the tumour cured her diabetes and normalised electrolytes. This case describes a rare cause of 'curable diabetes' and indicates hyperaldosteronism and/or whole-body potassium stores as important regulators of insulin secretion and glucose homeostasis. LEARNING POINTS: McKittrick-Wheelock syndrome (MWS) is typically characterised by the triad of pre-renal failure, electrolyte derangement and chronic diarrhoea resulting from a secretory colonic neoplasm.Hyperglycaemia and new-onset diabetes are rare clinical manifestations of MWS.Hyperaldosteronism and/or hypokalaemia may worsen glucose tolerance in MWS.Aggressive replacement of fluid and electrolytes is the mainstay of acute management, with definitive treatment and complete reversal of the metabolic abnormalities being achieved by endoscopic or surgical resection of the neoplasm.

Genetic aspects of human obesity.

Obesity and its related metabolic consequences represent a major public health problem. Huge changes within the environment have undoubtedly contributed to the increased prevalence of obesity but genetic factors are also critical in determining an individual's predisposition to gain weight. The last two decades have seen a huge increase in the understanding of the mechanisms controlling appetitive behavior, body composition, and energy expenditure. Many regions throughout the central nervous system play critical roles in these processes but the hypothalamus, in particular, receives and orchestrates a variety of signals to bring about coordinated changes in energy balance. Reviewing data from human genetic and model organism studies, we consider how disruptions of hypothalamic pathways evolved to maintain energy homeostasis and go on to cause obesity. We highlight ongoing technological developments which continue to lead to novel insights and discuss how this increased knowledge may lead to effective therapeutic interventions in the future.

Invasive medical procedure skills amongst Foundation Year Doctors - a questionnaire study.

OBJECTIVES: Competency in practical skills is an important aspect of training for medical doctors. This questionnaire survey aimed to investigate if the current Foundation Year trainees have performed several practical procedures of importance and their level of confidence in carrying them out unsupervised. DESIGN: Questionnaire study. SETTING: Five National Health Service hospitals in England. PARTICIPANTS: A total of 103 Foundation Year trainees responded to the survey (73 FY1s; 30 FY2s). MAIN OUTCOME MEASURES: Percentage of trainees who have performed these skills and their average level of confidence. RESULTS: The percentage of trainees who have performed these skills and their average level of confidence (scale of 1 to 5) are as follows: intubation (32%, 1); chest drain (33%, 1); central line (26%, 1); femoral line (23%, 1); peripheral line (28%, 1); lumbar puncture (64%, 3); ascitic tap (57%, 3). Only 25% of the trainees have attended certified training courses on these skills during their Foundation Year training. More than half of these trainees (73%) found the courses very useful. Ninety-two per cent of trainees who did not attend practical skill courses are very interested to attend them. All the trainees agreed that these courses should be available for all the Foundation Year doctors, and 92% believe that these courses are most beneficial during the Foundation Year 1 training. CONCLUSION: Most Foundation Year trainees have low confidence and exposure to these important practical skills. Certified practical skills courses should be made available to the Foundation Year doctors for the benefit of their training. This will also increase the quality of patient care.

Coinfusion of low-dose GLP-1 and glucagon in man results in a reduction in food intake.

Obesity is a growing epidemic, and current medical therapies have proven inadequate. Endogenous satiety hormones provide an attractive target for the development of drugs that aim to cause effective weight loss with minimal side effects. Both glucagon and GLP-1 reduce appetite and cause weight loss. Additionally, glucagon increases energy expenditure. We hypothesized that the combination of both peptides, administered at doses that are individually subanorectic, would reduce appetite, while GLP-1 would protect against the hyperglycemic effect of glucagon. In this double-blind crossover study, subanorectic doses of each peptide alone, both peptides in combination, or placebo was infused into 13 human volunteers for 120 min. An ad libitum meal was provided after 90 min, and calorie intake determined. Resting energy expenditure was measured by indirect calorimetry at baseline and during infusion. Glucagon or GLP-1, given individually at subanorectic doses, did not significantly reduce food intake. Coinfusion at the same doses led to a significant reduction in food intake of 13%. Furthermore, the addition of GLP-1 protected against glucagon-induced hyperglycemia, and an increase in energy expenditure of 53 kcal/day was seen on coinfusion. These observations support the concept of GLP-1 and glucagon dual agonism as a possible treatment for obesity and diabetes.

The CB1 receptor mediates the peripheral effects of ghrelin on AMPK activity but not on growth hormone release.

This study aimed to investigate whether the growth hormone release and metabolic effects of ghrelin on AMPK activity of peripheral tissues are mediated by cannabinoid receptor type 1 (CB1) and the central nervous system. CB1-knockout (KO) and/or wild-type mice were injected peripherally or intracerebroventricularly with ghrelin and CB1 antagonist rimonabant to study tissue AMPK activity and gene expression (transcription factors SREBP1c, transmembrane protein FAS, enzyme PEPCK, and protein HSL). Growth hormone levels were studied both in vivo and in vitro. Peripherally administered ghrelin in liver, heart, and adipose tissue AMPK activity cannot be observed in CB1-KO or CB1 antagonist-treated mice. Intracerebroventricular ghrelin treatment can influence peripheral AMPK activity. This effect is abolished in CB1-KO mice and by intracerebroventricular rimonabant treatment, suggesting that central CB1 receptors also participate in the signaling pathway that mediates the effects of ghrelin on peripheral tissues. Interestingly, in vivo or in vitro growth hormone release is intact in response to ghrelin in CB1-KO animals. Our data suggest that the metabolic effects of ghrelin on AMPK in peripheral tissues are abolished by the lack of functional CB1 receptor via direct peripheral effect and partially through the central nervous system, thus supporting the existence of a possible ghrelin-cannabinoid-CB1-AMPK pathway.

Ghrelin and cannabinoids require the ghrelin receptor to affect cellular energy metabolism.

INTRODUCTION: Ghrelin is a potent orexigenic brain-gut peptide with lipogenic and diabetogenic effects, possibly mediated by growth hormone secretagogue receptor (GHS-R1a). Cannabinoids also have orexigenic and lipogenic effects. AMPK is a regulator of energy homeostasis and we have previously shown that ghrelin and cannabinoids stimulate hypothalamic AMPK activity while inhibiting it in the liver and adipose tissue, suggesting that AMPK mediates both the central appetite-inducing and peripheral effects of ghrelin and cannabinoids. AIMS: Using GHS-R KO mice, we investigated whether the known ghrelin receptor GHS-R1a is required for the tissue-specific effects of ghrelin on AMPK activity, and if an intact ghrelin signalling pathway is necessary for the effects of cannabinoids on AMPK activity. METHODS: Wild-type and GHS-R KO mice were treated intraperitoneally with ghrelin 500 ng/g bodyweight or CB1 agonist HU210 20 ng/g and hypothalamic, hepatic and adipose AMPK activity was studied using a functional kinase assay. RESULTS: Ghrelin and HU210 significantly stimulated hypothalamic AMPK activity in wild-type animals (mean±SEM, 122.5±5.2% and 128±11.6% of control, p<0.05) and inhibited it in liver (55.1±4.8% and 62.2±14.5%, p<0.01) and visceral fat (mesenteric fat (MF): 54.6±16% and 52.0±9.3%, p<0.05; epididymal fat (EF): 47.9±12.1% and 45.6±1.7%, p<0.05). The effects of ghrelin, and interestingly also HU210, on hypothalamic, visceral fat and liver AMPK activity were abolished in the GHS-R KO mice (hypothalamus: 107.9±7.7% and 87.4±13.3%, liver: 100.5±11.6% and 116.7±5.4%, MF: 132.1±29.9% and 107.1±32.7%, EF: 89.8±7.3% and 91.7±18.3%, p>0.05). CONCLUSIONS: Ghrelin requires GHS-R1a for its effect on hypothalamic, liver and adipose tissue AMPK activity. An intact ghrelin signalling pathway is necessary for the effects of cannabinoids on AMPK activity.

Measurement of AMP-activated protein kinase activity and expression in response to ghrelin.

Ghrelin is a circulating brain-gut peptide that is known to exert several metabolic effects such as stimulating appetite, inducing adiposity, increasing bone formation, and influencing the cardiovascular functions. AMP-activated protein kinase (AMPK), a highly conserved heterotrimeric protein that plays a key role in energy homeostasis, has been shown to mediate many of these metabolic effects of ghrelin. Ghrelin is shown to stimulate hypothalamic AMPK activity and inhibit liver and adipose tissue AMPK activity. The effects of ghrelin on AMPK activity can be studied using an elegant kinase assay, which involves immunoprecipitating AMPK protein from the tissue of interest followed by quantifying its enzymatic activity using radiolabeled adenosine triphosphate (ATP) in the presence of a suitable substrate. As a surrogate marker of AMPK activity, AMPK Thr(172) phosphorylation can be measured by Western blotting. Information about the AMPK pathway can also be gained by studying the mRNA expression of various AMPK subunits and by Western blotting for phosphorylated acetyl-CoA carboxylase, a key AMPK target. These methods have been widely used and published for investigating the effects of ghrelin on AMPK activity. In this chapter, we look into these experiments' methodology in detail.

Paediatric endocrine aspects of ghrelin.

Ghrelin is a 28 amino-acid brain-gut peptide that is well-known for its orexigenic and metabolic effects leading to an overall positive energy balance. It stimulates appetite and growth hormone release via the GHS-R1a receptors. GOAT has been identified as the enzyme that acylates ghrelin, which is important for its endocrine function. The ghrelin/GHS-R/GOAT system has been studied extensively in view of its association with several endocrine diseases and the potential of developing an effective treatment. These include obesity, Prader-Willi syndrome, anorexia nervosa and diabetes mellitus. Ghrelin system has also been associated with growth and stature. All these conditions can affect children and have a significant impact on the quality of health and life prognosis. In this review, we look into the association of ghrelin with appetite, growth and metabolic disorders in children.

Intravenous fluid prescribing practices by foundation year one doctors - a questionnaire study.

OBJECTIVES: Foundation Year Ones (FY1s) are the most junior doctors in the UK who are often required to prescribe intravenous fluid to patients not under their regular care, during on-call or out-of-hours ward cover. This study aimed to investigate FY1s' practice and decision-making process of intravenous fluid prescribing to these patients. DESIGN: Questionnaire survey. SETTING: Survey on Practices during on-calls and out-of-hours ward covers. PARTICIPANTS: FY1s of five National Health Service (NHS) hospitals in England and Scotland. RESULTS: All 149 FY1s responded to survey. Eighty-six percent have been taught intravenous fluid prescribing during medical school, compared with only 48% in FY1 induction. More than half always/often checked the patient's urea and electrolytes (U&Es) (72%), read the fluid balance (58%) and observation charts (80%), discussed the case with nursing staff (75%), enquired about oral status (82%), identified the main diagnosis/operation (75%) and indication for intravenous fluid (72%) of the patient when prescribing intravenous fluid. However, less than half often/always read the medical notes (43%) or performed clinical examinations on patients (16%). Most FY1s (94%) always/often checked patient's U&Es when prescribing potassium. CONCLUSIONS: The questionnaire study demonstrated variations among FY1s in the practice and decision-making process of intravenous fluid prescribing to patients unknown to them, during on-calls or out-of-hours ward covers. Such variations in practice should be addressed especially by medical and foundation schools, and NHS hospitals to improve patient care.

The expression of ghrelin O-acyltransferase (GOAT) in human tissues.

Ghrelin is a circulating growth hormone-releasing and appetite-inducing brain-gut peptide. It needs to be acylated on its serine-3 with octanoate for its endocrine actions. The acyl-transferase that catalyses ghrelin octanoylation has recently been identified and named as GOAT (ghrelin O-acyltransferase); GOAT enzyme is coded by the MBOAT4 gene. This study aimed to investigate GOAT expression in the human. The distribution of GOAT mRNA expression was studied in various human tissues using classical and real-time reverse transcription and polymerase chain reaction. GOAT expression was found in all tissues studied (stomach, adrenal cortex, breast, right and left colon, duodenum, jejunum, ileum, fat, Fallopian tube, gallbladder, lymph node, lymphocyte cell line, kidney, liver, lung, muscle, myocardium, pituitary, oesophagus, pancreas, ovary, placenta, prostate, testis, spleen and thyroid). The widespread expression of GOAT corresponds to the widespread distribution of ghrelin expression. GOAT expression was high in stomach and gut, the major ghrelin-secreting tissues, and in the pituitary, in which ghrelin is known to show autocrine and paracrine effects. Identification of GOAT expression in various tissues support the concept that in addition to the important endocrine effect of acylated ghrelin, the paracrine effects of locally synthetised and acylated ghrelin may be important.

The ghrelin/GOAT/GHS-R system and energy metabolism.

Ghrelin is a brain-gut peptide that was discovered through reverse pharmacology and was first isolated from extracts of porcine stomach. Ghrelin binds to growth hormone secretagogue receptor (GHS-R) and is acylated on its serine 3 residue by ghrelin O-acyltransferase (GOAT). Several important biological functions of ghrelin have been identified, which include its growth hormone-releasing and appetite-inducing effects. Ghrelin exerts its central orexigenic effect mainly by acting on the hypothalamic arcuate nucleus via the activation of the GHS-R. Peripherally ghrelin has multiple metabolic effects which include promoting gluconeogenesis and fat deposition. These effects together with the increased food intake lead to an overall body weight gain. AMP-activated protein kinase, which is a key enzyme in energy homeostasis, has been shown to mediate the central and peripheral metabolic effects of ghrelin. The hypothalamic fatty acid pathway, hypothalamic mitochondrial respiration and uncoupling protein 2 have all been shown to act as the downstream targets of AMPK in mediating the orexigenic effects of ghrelin. Abnormal levels of ghrelin are associated with several metabolic conditions such as obesity, type 2 diabetes, Prader-Willi syndrome and anorexia nervosa. The ghrelin/GOAT/GHS-R system is now recognised as a potential target for the development of anti-obesity treatment.

Ghrelin's role as a major regulator of appetite and its other functions in neuroendocrinology.

Ghrelin is a circulating growth-hormone-releasing and appetite-inducing brain-gut peptide. It is a known natural ligand of the growth hormone secretagogue receptor (GHS-R). Ghrelin is acylated on its serine 3 residue by ghrelin O-acyltransferase (GOAT). The acylation is essential for its orexigenic and adipogenic effects. Ghrelin exerts its central orexigenic effect through activation of various hypothalamic and brain stem neurons. Several new intracellular targets/mediators of the appetite-inducing effect of ghrelin in the hypothalamus have recently been identified, including the AMP-activated protein kinase, its upstream kinase calmodulin kinase kinase 2, components of the fatty acid pathway and the uncoupling protein 2. The ghrelin/GOAT/GHS-R system is now recognised as a potential target for the development of anti-obesity treatment. Ghrelin regulates the function of the anterior pituitary through stimulation of secretion not only of growth hormone, but also of adrenocorticotrophin and prolactin. The implication of ghrelin and its receptor in the pathogenesis of the neuroendocrine tumors will also be discussed in this review.

AMPK as a mediator of hormonal signalling.

AMP-activated protein kinase (AMPK) is a key molecular player in energy homeostasis at both cellular and whole-body levels. AMPK has been shown to mediate the metabolic effects of hormones such as leptin, ghrelin, adiponectin, glucocorticoids and insulin as well as cannabinoids. Generally, activated AMPK stimulates catabolic pathways (glycolysis, fatty acid oxidation and mitochondrial biogenesis) and inhibits anabolic pathways (gluconeogenesis, glycogen, fatty acid and protein synthesis), and has a direct appetite-regulating effect in the hypothalamus. Drugs that activate AMPK, namely metformin and thiazolidinediones, are often used to treat metabolic disorders. Thus, AMPK is now recognised as a potential target for the treatment of obesity and associated co-morbidities.