Project description:Cholecystokinin (CCK) is a satiety hormone produced by discrete enteroendocrine cells scattered among absorptive cells of the small intestine. CCK is released into blood following a meal; however, the mechanisms inducing hormone secretion are largely unknown. Ingested fat is the major stimulant of CCK secretion. We recently identified a novel member of the lipoprotein remnant receptor family known as immunoglobulin-like domain containing receptor 1 (ILDR1) in intestinal CCK cells and postulated that this receptor conveyed the signal for fat-stimulated CCK secretion. In the intestine, ILDR1 is expressed exclusively in CCK cells. Orogastric administration of fatty acids elevated blood levels of CCK in wild type but not ILDR1-deficient mice, although the CCK secretory response to trypsin inhibitor was retained. The uptake of fluorescently labeled lipoproteins in ILDR1-transfected CHO cells and release of CCK from isolated intestinal cells required a unique combination of fatty acid plus HDL. CCK secretion secondary to ILDR1 activation is associated with increased [Ca2+]i consistent with regulated hormone release. These findings demonstrate that ILDR1 regulates CCK release through a mechanism dependent on fatty acids and lipoproteins and that absorbed fatty acids regulate gastrointestinal hormone secretion. GFP positive cells from CCK-EGFP transgenic mice were isolated by FACS and the expression profile was compared with an equal number of non-fluorescent intestinal cells.
Project description:At high altitude, hypoxic atmosphere decreases the oxygen partial pressure (pO2) in the body, inducing several metabolic changes in tissues and cells. Furthermore, it exerts potent anorectic effects, thus causing energy deficit. Two decades ago, a marked increase in the level of resting plasma cholecystokinin (CCK) was observed at Mt. Kanchenjunga basecamp (BC) located at 5,100 m above the sea level, compared to sea-level control values. Interestingly, acute exercise also raises plasma CCK and exerts potent anorectic effects under normoxic conditions. However, the molecular mechanism underlying these effects has not yet been established. We employed acute electrical pulse stimulation (EPS), followed by a microarray analysis, to discover novel myokines in 3D engineered muscle. Acute EPS efficiently affects the contractile function, inducing a decline of the contractile force. Surprisingly, microarray analysis revealed an EPS-induced activation of the cholecystokinin receptor (CCKR)-mediated signaling. Furthermore, Cck was constitutively expressed in 3D engineered muscle, and was upregulated by hypoxic conditions. Notably, a hypoxia responsive element (HRE) was detected in the Cck promoter of mice and humans. Our results suggested that, under hypoxic conditions, Hif-1a binding to HRE transactivated Cck expression in mice and humans. Furthermore, the plasma CCK elevation after acute exercise or at high altitude might be partly attributed to myogenic cells.
Project description:Cholecystokinin (CCK) is a satiety hormone produced by discrete enteroendocrine cells scattered among absorptive cells of the small intestine. CCK is released into blood following a meal; however, the mechanisms inducing hormone secretion are largely unknown. Ingested fat is the major stimulant of CCK secretion. We recently identified a novel member of the lipoprotein remnant receptor family known as immunoglobulin-like domain containing receptor 1 (ILDR1) in intestinal CCK cells and postulated that this receptor conveyed the signal for fat-stimulated CCK secretion. In the intestine, ILDR1 is expressed exclusively in CCK cells. Orogastric administration of fatty acids elevated blood levels of CCK in wild type but not ILDR1-deficient mice, although the CCK secretory response to trypsin inhibitor was retained. The uptake of fluorescently labeled lipoproteins in ILDR1-transfected CHO cells and release of CCK from isolated intestinal cells required a unique combination of fatty acid plus HDL. CCK secretion secondary to ILDR1 activation is associated with increased [Ca2+]i consistent with regulated hormone release. These findings demonstrate that ILDR1 regulates CCK release through a mechanism dependent on fatty acids and lipoproteins and that absorbed fatty acids regulate gastrointestinal hormone secretion.
Project description:Oxytocin-expressing paraventricular hypothalamic neurons (PVN^OT neurons) integrate afferent signals from the gut including cholecystokinin (CCK) to adjust whole-body energy homeostasis. However, the molecular underpinnings by which PVN^OT neurons orchestrate gut-to-brain feeding control remain unclear. Here, we show that mice undergoing selective ablation of PVNOT neurons fail to reduce food intake in response to CCK and develop hyperphagic obesity on chow diet. Notably, exposing wildtype mice to a high-fat/high-sugar (HFHS) diet recapitulates this insensitivity towards CCK, which is linked to diet-induced transcriptional and electrophysiological aberrations specifically in PVNOT neurons. Restoring OT pathways in DIO mice via chemogenetics or polypharmacology sufficiently re-establishes CCK?s anorexigenic effects. Lastly, by single-cell profiling, we identify a specialized PVN^OT neuronal subpopulation with increased ?-opioid signaling under HFHS diet, which restrains their CCK-evoked activation. In sum, we here document a novel (patho)mechanism by which PVN^OT signaling uncouples a gut-brain satiation pathway under obesogenic conditions.
Project description:Spinocerebellar Ataxias (SCAs) are a group of genetic diseases characterized by progressive ataxia and neurodegeneration, often in cerebellar Purkinje neurons. A SCA1 mouse model, Pcp2-ATXN1[30Q]D776, has severe ataxia in absence of progressive Purkinje neuron degeneration and death. Previous RNA-seq analyses identified cerebellar up-regulation of the peptide hormone Cholecystokinin (Cck) in Pcp2-ATXN1[30Q]D776 mice. Importantly, absence of Cck1 receptor (Cck1R) in Pcp2-ATXN1[30Q]D776 mice confers a progressive disease with Purkinje neuron death. A Cck1R agonist, A71623 administered to Pcp2-ATXN1[30Q]D776;Cck-/- and Pcp2-AXTN1[82Q] mice dampened Purkinje neuron pathology and associated deficits in motor performance. In addition, A71623 administration improved motor performance of Pcp2-ATXN2[127Q] SCA2 mice. Moreover, the Cck1R agonist A71623 corrected mTORC1 signaling and improved expression of calbindin in cerebella of AXTN1[82Q] and ATXN2[127Q] mice. These results indicate that manipulation of the Cck-Cck1R pathway is a potential therapeutic target for treatment of diseases involving Purkinje neuron degeneration.
Project description:Behavioural and neurochemical mechanisms underpinning the synergistic feeding-suppressive effect of GLP-1/CCK combinatorial therapy
Project description:Fundic mucosa gene expression in wildtype vs gastrin knockout, gastrin replaced gastrin KO and gastrin-CCK double knockout mice; Fundic mucosal scraping RNA were isolated from WT, Gastrin Knockout, Gastrin replaced KO and Gastrin-CCK double knockout mice. Targets from three biological replicates of each were generated and the expression profiles were determined using Affymetrix murine 430A arrays. Comparisons between the sample groups allow the identification of genes with gastrin responsiveness and Gastrin-CCK double effect . Experiment Overall Design: 3 WT, 3 Gastrin KO, 3 Gastrin replaced KO and 3 Gastrin-CCK double Knockout fundic RNA replicates were analyzed