Concurrent Akt, ERK1/2 and AMPK Activation by Obestatin Inhibits Apoptotic Signaling Cascades on Nutrient-Deprived PC12 Cells

This work was supported by grants from Instituto de Salud Carlos III in co-financing with Fondo Europeo de Desarrollo Regional [ISCIII-FEDER; Ministerio de Asuntos Económicos y Transformación Digital (MINECO), Spain; PI17/01707 and PI18/00760], Axencia de Coñecemento en Saúde (ACIS), Servicio Galego de Saúde (SERGAS; Xunta de Galicia; PRIS Program), and Axencia Galega de Innovación (GAIN; Xunta de Galicia; IN607B2019/06)S

Obestatin as a regulator of adipocyte metabolism and adipogenesis

The role of obestatin, a 23-amino-acid peptide encoded by the ghrelin gene, on the control of the metabolism of pre-adipocyte and adipocytes as well as on adipogenesis was determined. For in vitro assays, pre-adipocyte and adipocyte 3T3-L1 cells were used to assess the obestatin effect on cell metabolism and adipogenesis based on the regulation of the key enzymatic nodes, Akt and AMPK and their downstream targets. For in vivo assays, white adipose tissue (WAT) was obtained from male rats under continuous subcutaneous infusion of obestatin. Obestatin activated Akt and its downstream targets, GSK3alpha/beta, mTOR and S6K1, in 3T3-L1 adipocyte cells. Simultaneously, obestatin inactivated AMPK in this cell model. In keeping with this, ACC phosphorylation was also decreased. This fact was confirmed in vivo in white adipose tissue (omental, subcutaneous and gonadal) obtained from male rats under continuous sc infusion of obestatin (24 and 72 hrs). The relevance of obestatin as regulator of adipocyte metabolism was supported by AS160 phosphorylation, GLUT4 translocation and augment of glucose uptake in 3T3-L1 adipocyte cells. In contrast, obestatin failed to modify translocation of fatty acid transporters, FATP1, FATP4 and FAT/CD36, to plasma membrane. Obestatin treatment in combination with IBMX and DEX showed to regulate the expression of C/EBPalpha, C/EBPbeta, C/EBPdelta and PPARgamma promoting adipogenesis. Remarkable, preproghrelin expression, and thus obestatin expression, increased during adipogenesis being sustained throughout terminal differentiation. Neutralization of endogenous obestatin secreted by 3T3-L1 cells by anti-obestatin antibody decreased adipocyte differentiation. Furthermore, knockdown experiments by preproghrelin siRNA supported that obestatin contributes to adipogenesis. In summary, obestatin promotes adipogenesis in an autocrine/paracrine manner, being a regulator of adipocyte metabolism. These data point to a putative role in the pathogenesis of metabolic syndrome

Preproghrelin expression is a key target for insulin action on adipogenesis.

This study aimed to investigate the role of preproghrelin-derived peptides in adipogenesis. Immunocytochemical analysis of 3T3-L1 adipocyte cells showed stronger preproghrelin expression compared with that observed in 3T3-L1 preadipocyte cells. Insulin promoted this expression throughout adipogenesis identifying mTORC1 as a critical downstream substrate for this profile. The role of preproghrelin-derived peptides on the differentiation process was supported by preproghrelin knockdown experiments, which revealed its contribution to adipogenesis. Neutralization of endogenous O-acyl ghrelin (acylated ghrelin), unacylated ghrelin, and obestatin by specific antibodies supported their adipogenic potential. Furthermore, a parallel increase in the expression of ghrelin-associated enzymatic machinery, prohormone convertase 1/3 (PC1/3) and membrane-bound O-acyltransferase 4 (MBOAT4), was dependent on the expression of preproghrelin in the course of insulin-induced adipogenesis. The coexpression of preproghrelin system and their receptors, GHSR1a and GPR39, during adipogenesis supports an autocrine/paracrine role for these peptides. Preproghrelin, PC1/3, and MBOAT4 exhibited dissimilar expression depending on the white fat depot, revealing their regulation in a positive energy balance situation in mice. The results underscore a key role for preproghrelin-derived peptides on adipogenesis through an autocrine/paracrine mechanism

The Obestatin/GPR39 System Is Up-regulated by Muscle Injury and Functions as an Autocrine Regenerative System

Background: Satellite cell activation is orchestrated by several signals, which induce their differentiation into skeletal muscle fibers. Results: Obestatin and the GPR39 receptor exert an autocrine role on the control of myogenesis. Conclusion: Our data indicate that obestatin/GPR39 is an injury-regulated signal that functions as a myogenic regenerative system. Significance: Strategies to enhance obestatin-mediated signaling could be useful in treating trauma-induced muscle injuries and skeletal muscle myopathies

New retinoid chemotypes: 9-cis-retinoic acid analogs with hydrophobic rings derived from terpenes as selective RAR agonists.

International audienceA series of 9-cis-retinoic acid analogs modified at the hydrophobic ring with a (bi)cyclohexenyl moiety derived from natural terpenes has been stereoselectively prepared using a Suzuki cross-coupling as key step. Transient transactivation studies indicate that modification of the hydrophobic ring impacts dramatically on RXR-binding and transactivation, with most retinoids being inactive on RXRbeta, while preserving their RAR pan-agonist profile. Furthermore, only the RARgamma subtype was capable of enantiomeric discrimination with some pairs of enantiomeric terpene-retinoids