Modulation of Glucose Production by Central Insulin Requires IGF-1 Receptors in AgRP Neurons

Similar to insulin, central administration of insulin-like Growth Factor-1 (IGF-1) can suppress hepatic glucose production (HGP), but it is unclear if this effect is mediated via insulin receptors (InsRs) or IGF-1 receptors (IGF-1Rs) in the brain. To this end, we utilized pharmacologic and genetic approaches in combination with hyperinsulinemic-euglycemic clamps to decipher the role of these receptors in mediating central effects of IGF-1 and insulin on HGP. In rats, we observed that intracerebroventricular (ICV) administration of IGF-1 or insulin markedly increased the glucose infusion rate (GIR) by >50% and suppressed HGP (<i>P</i><0.001). However, these effects were completely prevented by preemptive ICV infusion with an IGF-1R and InsR/IGF-1R Hybrid (HybridRs) blocking antibody.<a> Likewise, ICV infusion of the InsR antagonist, S961, which also can bind HybridRs, interfered with the ability of central insulin, but not IGF-1 to increase the GIR. </a>Furthermore, hyperinsulinemic clamps in mice lacking IGF-1Rs in AgRP neurons revealed ~30% reduction in the GIR in KO animals, which was explained by an impaired ability of peripheral insulin to completely suppress HGP (<i>P</i><0.05). Signaling studies further revealed an impaired ability of peripheral insulin to trigger ribosomal S6 phosphorylation or PIP3 production in AgRP neurons lacking IGF-1Rs. In summary, these data suggest that attenuation of IGF-1Rs signaling in the MBH, and specifically in AgRP neurons, can phenocopy impaired regulation of HGP as previously demonstrated in mice lacking InsRs in these cells, suggesting a previously unappreciated role for IGF-1Rs and/or HybridRs in the regulation of central insulin/IGF-1 signaling on glucose metabolism.

Modulation of Glucose Production by Central Insulin Requires IGF-1 Receptors in AgRP Neurons

Similar to insulin, central administration of insulin-like Growth Factor-1 (IGF-1) can suppress hepatic glucose production (HGP), but it is unclear if this effect is mediated via insulin receptors (InsRs) or IGF-1 receptors (IGF-1Rs) in the brain. To this end, we utilized pharmacologic and genetic approaches in combination with hyperinsulinemic-euglycemic clamps to decipher the role of these receptors in mediating central effects of IGF-1 and insulin on HGP. In rats, we observed that intracerebroventricular (ICV) administration of IGF-1 or insulin markedly increased the glucose infusion rate (GIR) by >50% and suppressed HGP (<i>P</i><0.001). However, these effects were completely prevented by preemptive ICV infusion with an IGF-1R and InsR/IGF-1R Hybrid (HybridRs) blocking antibody.<a> Likewise, ICV infusion of the InsR antagonist, S961, which also can bind HybridRs, interfered with the ability of central insulin, but not IGF-1 to increase the GIR. </a>Furthermore, hyperinsulinemic clamps in mice lacking IGF-1Rs in AgRP neurons revealed ~30% reduction in the GIR in KO animals, which was explained by an impaired ability of peripheral insulin to completely suppress HGP (<i>P</i><0.05). Signaling studies further revealed an impaired ability of peripheral insulin to trigger ribosomal S6 phosphorylation or PIP3 production in AgRP neurons lacking IGF-1Rs. In summary, these data suggest that attenuation of IGF-1Rs signaling in the MBH, and specifically in AgRP neurons, can phenocopy impaired regulation of HGP as previously demonstrated in mice lacking InsRs in these cells, suggesting a previously unappreciated role for IGF-1Rs and/or HybridRs in the regulation of central insulin/IGF-1 signaling on glucose metabolism.

Correction: Paszkiewicz et al. A Peripheral CB1R Antagonist Increases Lipolysis, Oxygen Consumption Rate, and Markers of Beiging in 3T3-L1 Adipocytes Similar to RIM, Suggesting That Central Effects Can Be Avoided. Int. J. Mol. Sci. 2020, 21, 6639

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The neuropharmacological preclinical effects of Nigella Sativa: A review

Background: Many researches papers have demonstrated that Nigella has neurotropic properties, and it has also been shown that Nigella seeds have several activities, such as analgesic, antiepileptic, anxiolytic, antidepressant, and psychostimulant activities. Methods: Databases such as PubMed, Science Direct, Scopus, and Google Scholar were used. Results : The orientation towards this type of research has become more and more accentuated to enhance and detail the pharmacological properties of medicinal aromatic plants. Conclusion : The present review consists in revealing and combining the experimental research studies carried out to demonstrate the central effects of nigella.