Serotonin 2C receptors (5-HT
2CRs) expressed by pro-opiomelanocortin (POMC) neurons of hypothalamic arcuate nucleus regulate food intake, energy homeostasis and glucose metabolism. However, the ...cellular mechanisms underlying the effects of 5-HT to regulate POMC neuronal activity via 5-HT
2CRs have not yet been identified. In the present study, we found the putative transient receptor potential C (TRPC) channels mediate the activation of a subpopulation of POMC neurons by mCPP (a 5-HT
2CR agonist). Interestingly, mCPP-activated POMC neurons were found to be a distinct population from those activated by leptin. Together, our data suggest that 5-HT
2CR and leptin receptors are expressed by distinct subpopulations of arcuate POMC neurons and that both 5-HT and leptin exert their actions in POMC neurons via TRPC channels.
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► 5-HT2CRs excite arcuate POMC neurons independent of altering GIRK channel activity ► Arcuate POMC 5-HT2CRs activate a Na
+/Ca
2+ permeable mixed-cation conductance ► 5-HT2CR-induced excitation of arcuate POMC neurons requires a putative TRPC channel ► 5-HT2CR- and LepR-activated arcuate POMC neurons are anatomically segregated
The physiologic importance of GABAergic neurotransmission in hypothalamic neurocircuits is unknown. To examine the importance of GABA release from agouti-related protein (AgRP) neurons (which also ...release AgRP and neuropeptide Y), we generated mice with an AgRP neuron-specific deletion of vesicular GABA transporter. These mice are lean, resistant to obesity and have an attenuated hyperphagic response to ghrelin. Thus, GABA release from AgRP neurons is important in regulating energy balance.
Neuroendocrinology of nutritional infertility Wade, George N; Jones, Juli E
American journal of physiology. Regulatory, integrative and comparative physiology
287, Številka:
6
Journal Article
Recenzirano
Natural selection has linked the physiological controls of energy balance and fertility such that reproduction is deferred during lean times, particularly in female mammals. In this way, an ...energetically costly process is confined to periods when sufficient food is available to support pregnancy and lactation. Even in the face of abundance, nutritional infertility ensues if energy intake fails to keep pace with expenditure. A working hypothesis is proposed in which any activity or condition that limits the availability of oxidizable fuels (e.g., undereating, excessive energy expenditure, diabetes mellitus) can inhibit both gonadotropin-releasing hormone (GnRH)/luteinizing hormone secretion and female copulatory behaviors. Decreases in metabolic fuel availability appear to be detected by cells in the caudal hindbrain. Hindbrain neurons producing neuropeptide Y (NPY) and catecholamines (CA) then project to the forebrain where they contact GnRH neurons both directly and also indirectly via corticotropin-releasing hormone (CRH) neurons to inhibit GnRH secretion. In the case of estrous behavior, the best available evidence suggests that the inhibitory NPY/CA system acts primarily via CRH or urocortin projections to various forebrain loci that control sexual receptivity. Disruption of these signaling processes allows normal reproduction to proceed in the face of energetic deficits, indicating that the circuitry responds to energy deficits and that no signal is necessary to indicate that there is an adequate energy supply. While there is a large body of evidence to support this hypothesis, the data do not exclude nutritional inhibition of reproduction by other pathways and processes, and the full story will undoubtedly be more complex than this.
The age-related effects of GDF11 have been a subject of controversy. Here, we find that elevated GDF11 causes signs of cachexia in mice: reduced food intake, body weight, and muscle mass. GDF11 also ...elicited a significant elevation in plasma Activin A, previously shown to contribute to the loss of skeletal muscle. The effects of GDF11 on skeletal muscle could be reversed by administration of antibodies to the Activin type II receptors. In addition to the effects on muscle, GDF11 increased plasma GDF15, an anorectic agent. The anorexia, but not the muscle loss, could be reversed with a GDF15-neutralizing antibody. GDF15 upregulation is due to GDF11-induced recruitment of SMAD2/3 to the GDF15 promoter. Inhibition of GDF15 can restore appetite but cannot restore the GDF11-induced loss of muscle mass, which requires blockade of ActRII signaling. These findings are relevant for treatment of cachexia.
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•Increased levels of GDF11 cause increased circulating Activin A and GDF15 in mice•Supraphysiologic levels of GDF11 induce cachexia, anorexia, and muscle loss•Blockade of GDF15 spares anorexia, but not muscle loss•Blockade of the GDF11 receptor ActRII spares muscle loss and decreases anorexia
Jones et al. find that high levels of GDF11 in mice induce symptoms of cachexia: skeletal muscle loss and anorexia. The anorexia is due to GDF11-dependent upregulation of GDF15. Downregulation of GDF11 in settings in which it exists at high levels is predicted to be beneficial.
Drugs activating 5-hydroxytryptamine 2C receptors (5-HT2CRs) potently suppress appetite, but the underlying mechanisms for these effects are not fully understood. To tackle this issue, we generated ...mice with global 5-HT2CR deficiency (2C null) and mice with 5-HT2CRs re-expression only in pro-opiomelanocortin (POMC) neurons (2C/POMC mice). We show that 2C null mice predictably developed hyperphagia, hyperactivity, and obesity and showed attenuated responses to anorexigenic 5-HT drugs. Remarkably, all these deficiencies were normalized in 2C/POMC mice. These results demonstrate that 5-HT2CR expression solely in POMC neurons is sufficient to mediate effects of serotoninergic compounds on food intake. The findings also highlight the physiological relevance of the 5-HT2CR-melanocortin circuitry in the long-term regulation of energy balance.
Background: Praliciguat (IW-1973) is an sGC stimulator in clinical development as a potential treatment for diabetic kidney disease. In animal models, praliciguat distributes broadly to tissues and ...elicits hemodynamic, anti-inflammatory, anti-fibrotic, and metabolic effects. Here, we assessed the metabolic effects of praliciguat in diabetic TALLYHO mice housed at thermoneutrality in order to minimize any confounding contribution of brown fat thermogenesis on metabolism, which is rare in humans but common in mice.
Methods: Six- to eight-week-old male TALLYHO/JngJ mice were maintained on low-fat diet (10% kcal from fat, LFD). Due to incomplete penetrance of the diabetic phenotype in this model, diabetic mice were identified prior to study initiation using HbA1c and urinary glucose/creatinine ratio as criteria. At 10-12 weeks of age, a diabetic control group (n=6) was maintained on LFD, while another group (n=6) was switched to LFD formulated with praliciguat to achieve a Cmax drug exposure similar to a 20 mg oral clinical dose. Plasma was collected at baseline and after 4 weeks of treatment. Oral glucose tolerance tests (OGTT) and oral lipid tolerance tests (LTT) were performed after 5 and 6 weeks of treatment, respectively.
Results: At week 4, praliciguat treatment attenuated the HbA1c increase in TALLYHO diabetic mice (+0.40 vs. +0.95%, in praliciguat and control groups, respectively P<0.05). At week 5, fasting glucose (561 ± 33 vs. 650 ± 46 mg/dl; -14%, P<0.01) and OGTT glucose AUC (-12%, P<0.01) were lower in praliciguat-treated mice than in untreated controls. At week 6, fasting plasma triglycerides (721 ± 97 vs. 1134 ± 190 mg/dl; -36%, P<0.05) and LTT triglyceride AUC (-23%, P<0.01) were lower in praliciguat-treated mice than in untreated controls. Body weight loss and food intake were lower in praliciguat-treated mice than in untreated mice.
Conclusion: Praliciguat improved nutrient handling in diabetic TALLYHO mice.
Disclosure
C. Schwartzkopf: None. A. Carvalho: Stock/Shareholder; Self; Cyclerion Therapeutics. J. Hadcock: None. M. Currie: Employee; Self; Cyclerion Therapeutics. Stock/Shareholder; Self; Cyclerion Therapeutics. J.E. Jones: None.
Inflammation in the central nervous system (CNS) is observed in many neurological disorders. Nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate (NO-sGC-cGMP) signaling plays an ...essential role in modulating neuroinflammation. CYR119 is a CNS-penetrant sGC stimulator that amplifies endogenous NO-sGC-cGMP signaling. We evaluated target engagement and the effects of CYR119 on markers of neuroinflammation in vitro in mouse microglial cells and in vivo in quinolinic acid (QA)-induced and high-fat diet-induced rodent neuroinflammation models.
Target engagement was verified in human embryonic kidney (HEK) cells, rat primary neurons, mouse SIM-A9 cells, and in rats by measuring changes in cGMP and downstream targets of sGC signaling phosphorylated vasodilator-stimulated phosphoprotein (pVASP), phosphorylated cAMP-response element binding (pCREB). In SIM-A9 cells stimulated with lipopolysaccharides (LPS), markers of inflammation were measured when cells were treated with or without CYR119. In rats, microinjections of QA and vehicle were administered into the right and left hemispheres of striatum, respectively, and then rats were dosed daily with either CYR119 (10 mg/kg) or vehicle for 7 days. The activation of microglia ionized calcium binding adaptor molecule 1 (Iba1) and astrocytes glial fibrillary acidic protein (GFAP) was measured by immunohistochemistry. Diet-induced obese (DIO) mice were treated daily with CYR119 (10 mg/kg) for 6 weeks, after which inflammatory genetic markers were analyzed in the prefrontal cortex.
In vitro, CYR119 synergized with exogenous NO to increase the production of cGMP in HEK cells and in primary rat neuronal cell cultures. In primary neurons, CYR119 stimulated sGC, resulting in accumulation of cGMP and phosphorylation of CREB, likely through the activation of protein kinase G (PKG). CYR119 attenuated LPS-induced elevation of interleukin 6 (IL-6) and tumor necrosis factor (TNF) in mouse microglial cells. Following oral dosing in rats, CYR119 crossed the blood-brain barrier (BBB) and stimulated an increase in cGMP levels in the cerebral spinal fluid (CSF). In addition, levels of proinflammatory markers associated with QA administration or high-fat diet feeding were lower in rodents treated with CYR119 than in those treated with vehicle.
These data suggest that sGC stimulation could provide neuroprotective effects by attenuating inflammatory responses in nonclinical models of neuroinflammation.
Praliciguat is a soluble guanylate cyclase stimulator that elicits hemodynamic, anti-inflammatory, and antifibrotic effects in preclinical models of metabolic dysfunction. We assessed the metabolic ...effects of praliciguat in a mouse diet-induced obesity (DIO) model housed at thermoneutrality. At 6 weeks old, male C57BL/6N mice were either maintained on low-fat diet (LFD, lean mice) or placed on 60% high-fat diet (HFD, DIO mice). At 14 weeks old, the DIO mice were either maintained on HFD or switched to HFD with praliciguat (6-mg/kg). Day 28 samples were collected for biomarker analysis. In a second study under the same paradigm, indirect calorimetry was performed on days 8, 9, 20, 21, 32, and 33 and an oral lipid tolerance test (LTT) on day 38. Mice treated 28 days with praliciguat had lower levels of fasting plasma insulin, C-peptide, triglycerides, and HOMA-IR (homeostatic model assessment for insulin resistance) than DIO controls. In addition, energy expenditure was higher in praliciguat-treated than in DIO control mice on days 9, 20, 32, and 33; and day-38 triglycerides were lower. HFD-induced increases in gene expression of liver TNF-ɑ, lipoprotein lipase (
), and patatin-like phospholipase domain-containing protein 3 (
) in control DIO mice were attenuated in praliciguat-treated DIO mice. The positive metabolic effects observed in praliciguat-treated mice were associated with the restoration of liver PI3K (pAKT-Thr308) signaling, but not MAPK (pERK). In conclusion, praliciguat-treated DIO mice had increased energy utilization, improved insulin sensitivity, and lower plasma triglycerides. These results illustrate metabolic effects associated with praliciguat treatment in DIO mice.
Background and Purpose
Reduced bioavailability of NO, a hallmark of sickle cell disease (SCD), contributes to intravascular inflammation, vasoconstriction, vaso‐occlusion and organ damage observed in ...SCD patients. Soluble guanylyl cyclase (sGC) catalyses synthesis of cGMP in response to NO. cGMP‐amplifying agents, including NO donors and phosphodiesterase 9 inhibitors, alleviate TNFα‐induced inflammation in wild‐type C57BL/6 mice and in ‘humanised’ mouse models of SCD.
Experimental Approach
Effects of the sGC stimulator olinciguat on intravascular inflammation and renal injury were studied in acute (C57BL6 and Berkeley mice) and chronic (Townes mice) mouse models of TNFα‐induced and systemic inflammation associated with SCD.
Key Results
Acute treatment with olinciguat attenuated increases in plasma biomarkers of endothelial cell activation and leukocyte‐endothelial cell interactions in TNFα‐challenged mice. Co‐treatment with hydroxyurea, an FDA‐approved SCD therapeutic agent, further augmented the anti‐inflammatory effect of olinciguat. In the Berkeley mouse model of TNFα‐induced vaso‐occlusive crisis, a single dose of olinciguat attenuated leukocyte‐endothelial cell interactions, improved blood flow and prolonged survival time compared to vehicle‐treated mice. In Townes SCD mice, plasma biomarkers of inflammation and endothelial cell activation were lower in olinciguat‐ than in vehicle‐treated mice. In addition, kidney mass, water consumption, 24‐h urine excretion, plasma levels of cystatin C and urinary excretion of N‐acetyl‐β‐d‐glucosaminidase and neutrophil gelatinase‐associated lipocalin were lower in Townes mice treated with olinciguat than in vehicle‐treated mice.
Conclusion and Implications
Our results suggest that the sGC stimulator olinciguat attenuates inflammation, vaso‐occlusion and kidney injury in mouse models of SCD and systemic inflammation.
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