Summary Objective In recent years great advances have been made in our understanding of the peripheral signals produced within the gastrointestinal tract that regulate appetite, such as ghrelin and peptide YY (PYY). While ghrelin elicites hunger signals, PYY elicites satiety. Therefore, alterations in hormone physiology may play a role in the pathogenesis of bulimia nervosa (BN). In this study, we investigated the postprandial profile of ghrelin and PYY levels in patients with BN. Design and patients Postprandial plasma ghrelin and PYY levels and insulin and glucose responses were measured in 10 patients with BN and 12 control patients in response to a standard 400 kcal meal. Results Basal ghrelin levels present in BN subjects (265·0 ± 25·5 pmol/l) were significantly higher than those in healthy controls (199·3 ± 18·4 pmol/l, P < 0·05), while basal PYY levels were equivalent in BN (14·6 ± 1·3 pmol/l) and control (12·8 ± 1·1 pmol/l, P = 0·30) subjects. Postprandial ghrelin suppression (decremental ghrelin area under the curve) was significantly attenuated in BN patients, compared to controls (−96·3 ± 26·8 pmol/l × 3 h vs . −178·2 ± 25·7 pmol/l × 3 h, P < 0·05). After a meal, the incremental PYY area under the curve in BN patients was significantly blunted from that observed in controls (9·2 ± 2·6 pmol/l × 3 h vs. 26·8 ± 3·2 pmol/l × 3 h, P < 0·01).Glucose and insulin responses to meals were similar between the two groups. Conclusions BN patients exhibit elevated ghrelin levels before meals with reduced ghrelin suppression after eating. In bulimia nervosa subjects, the rise in PYY levels after meals is also blunted. A gut–hypothalamic pathway involving peripheral signals, such as ghrelin and PYY, may be involved in the pathophysiology of BN.
A high-fat diet (HFD) induces inflammation in systemic organs including the hypothalamus, resulting in obesity and diabetes. The vagus nerve connects the visceral organs and central nervous system, and the gastric-derived orexigenic peptide ghrelin transmits its starvation signals to the hypothalamus via the vagal afferent nerve. Here we investigated the inflammatory response in vagal afferent neurons and the hypothalamus in mice following one day of HFD feeding. This treatment increased the number of macrophages/microglia in the nodose ganglion and hypothalamus. Furthermore, one-day HFD induced expression of Toll-like receptor 4 in the goblet cells of the colon and upregulated mRNA expressions of the proinflammatory biomarkers Emr1, Iba1, Il6, and Tnfα in the nodose ganglion and hypothalamus. Both subcutaneous administration of ghrelin and celiac vagotomy reduced HFD-induced inflammation in these tissues. HFD intake triggered inflammatory responses in the gut, nodose ganglion, and subsequently in the hypothalamus within 24 h. These findings suggest that the vagal afferent nerve may transfer gut-derived inflammatory signals to the hypothalamus via the nodose ganglion, and that ghrelin may protect against HFD-induced inflammation.
Serum levels of cholesterol absorption and synthesis markers have been associated with cardiovascular risk in the United States and European countries. In this study, we examined the relevance of these biomarkers and the presence of cardiovascular disease (CVD) in Japanese individuals.The CACHE consortium, comprising of 13 research groups in Japan possessing data on campesterol, an absorption marker, and lathosterol, a synthesis marker measured by gas chromatography, compiled the clinical data using the REDCap system.Among the 2,944 individuals in the CACHE population, those with missing campesterol or lathosterol data were excluded. This cross-sectional study was able to analyze data from 2,895 individuals, including 339 coronary artery disease (CAD) patients, 108 cerebrovascular disease (CeVD) patients, and 88 peripheral artery disease (PAD) patients. The median age was 57 years, 43% were female, and the median low-density lipoprotein cholesterol and triglyceride levels were 118 mg/dL and 98 mg/dL, respectively. We assessed the associations of campesterol, lathosterol, and the ratio of campesterol to lathosterol (Campe/Latho ratio) with the odds of CVD using multivariable-adjusted nonlinear regression models. The prevalence of CVD, especially CAD, showed positive, inverse, and positive associations with campesterol, lathosterol, and the Campe/Latho ratio, respectively. These associations remained significant even after excluding individuals using statins and/or ezetimibe. The associations of the cholesterol biomarkers with PAD were determined weaker than those with CAD. Contrarily, no significant association was noted between cholesterol metabolism biomarkers and CeVD.This study showed that both high cholesterol absorption and low cholesterol synthesis biomarker levels were associated with high odds of CVD, especially CAD.
Neuropeptide W (NPW) is an anorectic peptide produced in the brain. Here, we showed that NPW was present in several hypothalamic nuclei, including the paraventricular hypothalamic nucleus, ventromedial hypothalamic nucleus, lateral hypothalamus, and hypothalamic arcuate nucleus. NPW expression was significantly up-regulated in leptin-deficient ob/ob and leptin receptor-deficient db/db mice. The increase in NPW expression in ob/ob mice was abrogated to control levels after leptin replacement. Leptin induced suppressors of cytokine signaling-3 after phosphorylation of signal transducer and activator of transcription-3 in NPW-expressing neurons. In addition, we demonstrated that NPW reduces feeding via the melanocortin-4-receptor signaling pathway. We also showed that NPW activates proopiomelanocortin and inhibits neuropeptide Y neurons using loose-patch extracellular recording of these neurons identified by promoter-driven green fluorescent protein expression. This study indicates that NPW may play an important role in the regulation of feeding and energy metabolism under the conditions of leptin insufficiency.
Obestatin is a 23-amino acid peptide, initially isolated from rat stomach as an endogenous ligand for the orphan G-protein-coupled receptor. Obestatin is derived from proteolytic cleavage of a 117-amino acid precursor, preproghrelin. Ghrelin increases food intake, body weight, and gastric emptying, whereas obestatin has the opposite effects. In this study, we characterized obestatin in both rat and human stomach, and investigated the peptide's effect on feeding behavior. Using reversed-phase high-performance liquid chromatography coupled with RIAs specific for rat and human obestatin, we detected a very small amount of obestatin, compared with ghrelin, in the gastric fundi. The ratios of obestatin to ghrelin are 0.0039 and 1.94% respectively in the rat and human gastric fundi. In humans, plasma obestatin accounted for 5.21% of the ghrelin concentration, whereas it was undetectable in rat plasma. Plasma ghrelin concentration decreased after a meal in normal subjects, whereas obestatin concentration did not change. When administered centrally or peripherally, obestatin did not suppress food intake in either free-feeding or fasted rodents. Administration of obestatin did not antagonize ghrelin-induced feeding. These findings indicate that obestatin is present at very low levels compared with ghrelin in both rat and human, and has no acute effect on feeding behavior.
Exploration of the mechanisms of alveolar epithelial cells (AECs) integrity is important for understanding the pathogenesis of acute lung injury. The tight junctions (TJs) of AECs provide intercellular sealing and are integral to the maintenance of the integrity of the alveolar-capillary barrier. However, the mechanisms regulating AEC barrier integrity are not fully understood. We explored the role of epithelial Pten in lung injury by using lung-epithelium specific Pten-deficient (SOPten) mice. We also investigated the function of Pten by using stably introduced lentivirus encoding either wild-type PTEN (lenti-PTEN-WT) or dominant-negative mutant of PTEN (lenti-PTEN-CS) in BEAS-2B. SOPten lungs after bleomycin or lipopolysaccharide injury exhibited extensive intralveolar edema and increased alveolar permeability. SOPten lungs demonstrated loss of TJs morphology and dissociation of cell-cell contacts after injury. Levels of TJs protein were decreased in SOPten lungs after injury. Exogenous expressions of PTEN were observed in the lenti-PTEN-WT and lenti-PTEN-CS transfected cells. Expression of WT PTEN abolished Akt phosphorylation, whereas that of PTEN-CS increased pAkt levels in BEAS-2B cells. After treatment with transforming growth factor (TGF)-beta1, monolayers of the lenti-PTEN-WT cells showed retained transpeithelial electrical resistance (TER) levels compared with those of untreated cells. In contrast, monolayers of the lenti-PTEN-CS cells exhibited a substantial reduction of TER after TGF-beta1 treatment. Levels of TJs protein were severely attenuated in the TGF-beta1-treated lenti-PTEN-CS cells. These findings reveal that epithelial Pten is crucial guardian controlling AECs barrier integrity.
Leptin, the product of the ob gene, plays important roles in the regulation of food intake and body weight through its receptor in the hypothalamus. To identify novel transcripts induced by leptin, we performed cDNA subtraction based on selective suppression of the polymerase chain reaction by using mRNA prepared from the forebrain of leptin-injected ob/ob mice. One of the genes isolated was a mouse homolog of human negative regulatory element-binding protein (NREBP). Its expression was markedly increased by leptin in the growth hormone secretagogue-receptor (GHS-R)-positive neurons of the arcuate nucleus and ventromedial hypothalamic nucleus. The promoter region of GHS-R contains one NREBP binding sequence, suggesting that NREBP regulates GHS-R transcription. Luciferase reporter assays showed that NREBP repressed GHS-R promoter activity in a hypothalamic neuronal cell line, GT1-7, and its repressive activity was abolished by the replacement of negative regulatory element in GHS-R promoter. Overexpression of NREBP reduced the protein expression of endogenous GHS-R without affecting the expression of ob-Rb in GT1-7 cells. To determine the functional importance of NREBP in the hypothalamus, we assessed the effects of NREBP on ghrelin action. Although phosphorylation of AMP-activated protein kinase α (AMPKα) was induced by ghrelin in GT1-7 cells, NREBP repressed ghrelin-induced AMPKα phosphorylation. These results suggest that leptin-induced NREBP is an important regulator of GHS-R expression in the hypothalamus and provides a novel molecular link between leptin and ghrelin signaling.
Ghrelin, a 28 amino acid peptide, has recently been isolated from the rat stomach as an endogenous ligand for the GH secretagogue receptor. The fact that administration of ghrelin, centrally or peripherally, stimulates both food intake and GH secretion suggests that stomach ghrelin has an important role in the growth of rats. We used immunohistochemistry and radioimmunoassay to determine the age at which ghrelin-immunostained cells begin to appear in the rat stomach. Ghrelin-immunoreactive cells were found to be expressed in the fetal stomach from pregnancy day 18. The number of ghrelin-immunoreactive cells in the fetal stomach increased as the stomach grew. The amount of ghrelin in the glandular part of the rat stomach also increased, in an age-dependent manner, from the neonatal stage to adult. Eight hours of milk restriction significantly decreased the ghrelin concentration in the stomachs of 1-week-old rats, and increased the ghrelin concentration in their plasma. Administration of ghrelin to 1- and 3-week-old rats increased plasma GH concentrations. The daily subcutaneous administration of ghrelin to pregnant rats from day 15 to day 21 of pregnancy caused an increase in body weight of newborn rats. In addition, daily subcutaneous administration of ghrelin to neonatal rats from birth advanced the day of vaginal opening from day 30.7+/-0.94 to day 27.9+/-0.05. These results suggest that ghrelin may be involved in neonatal development.
