Papel de la somatostanina, cortistanina y ghrelina en la desregulación celular y molecular del páncreas endocrino en situaciones metabólicas normales y extremas como la obesidad y la diabetes

El adecuado funcionamiento del eje neuroendocrino-metabólico es crucial para el mantenimiento de la homeostasis del organismo, de forma que los defectos de su regulación conducen con frecuencia a graves patologías, tales como la obesidad, anorexia o diabetes. En el complejo proceso de modulación de la homeostasis juega un papel esencial la regulación precisa de la secreción de neuropéptidos y hormonas, pues su disfunción puede provocar una liberación tanto excesiva como deficiente de estos factores que, a su vez, son la causa de desordenes endocrino-metabólicos. Así, la regulación de la homeostasis energética constituye en realidad un complejo proceso en el que están implicados diversos componentes tanto de origen central (hipotálamo), como hipofisario y periférico (tejido adiposo, estómago, hígado, páncreas, gónadas, etc) que, en conjunto, forman un circuito regulador integrado. Además, en los últimos años viene recibiendo una atención muy especial el sistema que regula la ingesta y las patologías asociadas, como la obesidad y anorexia, debido a que estas patologías están aumentando a tasas epidémicas en todo el mundo. La somatostatina (SST), es un péptido de 14 aminoácidos inicialmente aislado del hipotálamo ovino por su capacidad para inhibir la secreción de la hormona del crecimiento. Inmediatamente tras su descubrimiento se encontró que la somatostatina estaba ampliamente distribuida en diferentes órganos y tejidos, especialmente en el páncreas y el tracto gastrointestinal, y que ejerce una gama de acciones y funciones patofisiológicas desde la inhibición de secreciones endocrinas hasta la neurotransmisión, pero también ejerce el control de la motilidad intestinal, la función pancreática, función inmune y crecimiento de las células tumorales. Esta capacidad pleiotrópica de la SST es debida a la amplia distribución en el organismo de una familia de 5 receptores específicos de somatostatina con 7 dominios transmembrana (TMDs), llamados sst1- sst5, que a veces están presentes simultáneamente e interaccionando funcionalmente en la misma célula. Sin embargo, la acción pleiotrópica de la somatostatina también se debe a la existencia de un péptido muy similar de la misma familia, la cortistatina (CORT), descubierta en 1996, que comparte 11 aminoácidos con la SST, posiblemente explicando así la comparable afinidad (nM) con la SST por los 5 sst. Aunque la CORT también fue inicialmente descubierta en el cerebro y es especialmente abundante en el córtex, estudios posteriores han demostrado que este neuropéptido está también ampliamente distribuido en el organismo y puede imitar la mayoría de las acciones endocrinas y no endocrinas de la SST. Realmente, las mayores divergencias entre SST y CORT residen en la capacidad de esta última para controlar la actividad locomotora y ejercer potentes acciones antiinflamatorias. Por otro lado, la ghrelina, un péptido de 28 aminoácidos y acilado en su Ser-3, producido fundamentalmente en el estómago y presente también en el hipotálamo, fue descubierto por su capacidad para estimular la liberación de GH a través del receptor para los secretagogos sintéticos de GH (GHS-R). De forma similar a la SST, e inmediatamente tras su descubrimiento, se demostró que la ghrelina estaba presente en multitud de órganos y tejidos, y ejerce diferentes acciones en condiciones normales y patológicas, desde la motilidad intestinal a la función pancreática, y de manera muy importante, en la regulación de la homeostasis metabólica, el apetito y la ingesta. La regulación del eje neuroendocrino-metabólico es crucial para el correcto mantenimiento de la homeostasis del organismo, y sus defectos pueden producir graves patologías tales como obesidad, anorexia o la diabetes tipo 2. Dada la relevancia clínica y elevada prevalencia de estas patologías neuroendocrino-metabólicas, resulta esencial considerar su naturaleza multifactorial, analizando los diferentes sistemas de regulación implicados, y empleando modelos adecuados para obtener una perspectiva global, conjunta e integrada, que nos aproxime a su naturaleza real. En este contexto, la alteración del sistema regulador integrado por SST, CORT, ghrelina y sus receptores, pueden contribuir de manera relevante en la desregulación celular y molecular del páncreas endocrino en situaciones metabólicas normales y extremas como en la obesidad y el ayuno. Objetivos. El objetivo general de esta Tesis Doctoral es investigar el papel ejercido por los diferentes componentes del sistema SST/CORT/ghrelina y sus receptores (sst1-5, GHS-R1a) en condiciones metabólicas extremas como la obesidad y el ayuno. En particular, estableceremos el perfil de expresión básico, las funciones y la posible relevancia terapéutica de este sistema así como el de nuevos componentes del mismo identificados recientemente por nuestro equipo: los receptores truncados sst5 TMD1, TMD2 y TMD4, y la variante de ghrelina, In2 ghrelina. Para ello, la presente Tesis Doctoral propone los siguientes objetivos específicos: 1.- Establecer y caracterizar el perfil o patrón de expresión básico a nivel pancreático del sistema SST/CORT/ghrelina y sus receptores (sst1-5, GHS-R,) en ratones normales y en ratones sometidos a condiciones relacionadas con alteraciones metabólicas (obesidad y ayuno). 2.- Determinar el papel de la SST y la CORT en alteraciones metabólicas como el ayuno y la obesidad inducida por la dieta en ratones carentes de la expresión de CORT. 3.- Evaluar funcional y molecularmente los componentes concretos del sistema regulador formado por SST, CORT, ghrelina y sus receptores, cuyos niveles se alteren sustancialmente en respuesta a estados metabólicos extremos (obesidad y ayuno). Para ello, emplearemos cultivos...The proper functioning of the neuroendocrine-metabolic axis is crucial for the maintenance of the homeostasis, thus defects on its regulation often lead to serious diseases, such as obesity, anorexia, or diabetes. In the complex homeostasis modulation process, precisely secretion of neuropeptides and hormones regulation play an essential role, since their dysfunction can cause both excessive and inadequate release of these factors which, in turn, are the cause of endocrinemetabolic disorders. Thus, the energy homeostasis regulation is actually a complex process in which various components of the central system (hypothalamus) pituitary and peripheral tissues (adipose tissue, stomach, liver, pancreas, gonads, etc) are implicated, and all together form part of an integrated regulator circuit. In addition, in recent years the system regulating food intake and associated diseases, like obesity and anorexia, comes receiving special attention since these diseases are increasing at epidemic rates worldwide. Somatostatin (SST), is a 14 amino acid peptide originally isolated from sheep hypothalamus by its ability to inhibit the growth hormone secretion. Immediately after its discovery it was found that somatostatin was widely distributed in different organs and tissues, especially in the pancreas and the gastrointestinal tract, and that it exerts a range of actions and pathophysiologic functions, from inhibition of endocrine secretions to neurotransmission, but also carries out the control of intestinal motility, pancreatic function, immune function and growth of tumor cells. Such pleiotropic capacity of SST is due to the wide distribution in the organism of a family of 5 specific SST receptors with 7 transmembrane domains (TMDs), called sst1-sst5, which sometimes are present simultaneously and functionally interacting in the same cell. However, the pleiotropic action of SST is also due to the existence of a very similar peptide of its same family, cortistatin (CORT), discovered in 1996, which shares 11 amino acids with SST, thus explaining their comparable binding affinity (nM) with the 5 receptors of SST. Although CORT was also initially discovered at the brain and is especially abundant in the cortex, subsequent studies have shown that this neuropeptide is also widely distributed in the organism and can imitate most of endocrine and not endocrine SST actions. Effectively, the biggest divergence between SST and CORT reside in the latters capacity to control the locomotive activity and exert powerful anti-inflammatory actions. On the other hand, ghrelin, a peptide 28 amino acids and acilated in its Ser-3, produced primarily in the stomach and present also in the hypothalamus, was discovered by its ability to stimulate the release of GH through the GH synthetic secretagogues receptor (GHS-R). Similarly to SST, and immediately after its discovery, it was showed that ghrelin was present in many organs and tissues, and exerts different actions under normal and pathological conditions from the intestinal motility to the pancreatic function, and very importantly, in the regulation of..

Maternal adiponectin prevents visceral adiposity and adipocyte hypertrophy in prenatal androgenized female mice

Hyperandrogenism is the main characteristic of polycystic ovary syndrome, which affects placental function and fetal growth, and leads to reproductive and metabolic dysfunction in female offspring. Adiponectin acts on the placenta and may exert endocrine effects on the developing fetus. This study aims to investigate if maternal and/or fetal adiponectin can prevent metabolic and reproductive dysfunction in prenatal androgenized (PNA) female offspring. Adiponectin transgenic (APNtg) and wild-type dams received dihydrotestosterone/vehicle injections between gestational days 16.5-18.5 to induce PNA offspring, which were followed for 4 months. Offspring from APNtg dams were smaller than offspring from wild-type dams, independent of genotype. Insulin sensitivity was higher in wild-type mice from APNtg dams compared to wild-types from wild-type dams, and insulin sensitivity correlated with fat mass and adipocyte size. PNA increased visceral fat% and adipocyte size in wild-type offspring from wild-type dams, while wild-type and APNtg offspring from APNtg dams were protected against this effect. APNtg mice had smaller adipocytes than wild-types and this morphology was associated with an increased expression of genes regulating adipogenesis (Ppard, Pparg, Cebpa, and Cebpb) and metabolism (Chrebp and Lpl). Anogenital distance was increased in all PNA-exposed wild-type offspring, but there was no increase in PNA APNtg offspring, suggesting that adiponectin overexpression protects against this effect. In conclusion, elevated adiponectin levels in utero improve insulin sensitivity, reduce body weight and fat mass gain in the adult offspring and protect against PNA-induced visceral adiposity. In conclusion, these data suggest that PNA offspring benefit from prenatal adiponectin supplementation. CC BY-NC-ND 4.0© 2020 The Authors. The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.</p

Adiponectin stimulates Sca1+CD34−-adipocyte precursor cells associated with hyperplastic expansion and beiging of brown and white adipose tissue

Background: The adipocyte hormone adiponectin improves insulin sensitivity and there is an inverse correlation between adiponectin levels and type-2 diabetes risk. Previous research shows that adiponectin remodels the adipose tissue into a more efficient metabolic sink. For instance, mice that overexpress adiponectin show increased capacity for hyperplastic adipose tissue expansion as evident from smaller and metabolically more active white adipocytes. In contrast, the brown adipose tissue (BAT) of these mice looks “whiter” possibly indicating reduced metabolic activity. Here, we aimed to further establish the effect of adiponectin on adipose tissue expansion and adipocyte mitochondrial function as well as to unravel mechanistic aspects in this area. Methods: Brown and white adipose tissues from adiponectin overexpressing (APN tg) mice and littermate wildtype controls, housed at room and cold temperature, were studied by histological, gene/protein expression and flow cytometry analyses. Metabolic and mitochondrial functions were studied by radiotracers and Seahorse-based technology. In addition, mitochondrial function was assessed in cultured adiponectin deficient adipocytes from APN knockout and heterozygote mice. Results: APN tg BAT displayed increased proliferation prenatally leading to enlarged BAT. Postnatally, APN tg BAT turned whiter than control BAT, confirming previous reports. Furthermore, elevated adiponectin augmented the sympathetic innervation/activation within adipose tissue. APN tg BAT displayed reduced metabolic activity and reduced mitochondrial oxygen consumption rate (OCR). In contrast, APN tg inguinal white adipose tissue (IWAT) displayed enhanced metabolic activity. These metabolic differences between genotypes were apparent also in cultured adipocytes differentiated from BAT and IWAT stroma vascular fraction, and the OCR was reduced in both brown and white APN heterozygote adipocytes. In both APN tg BAT and IWAT, the mesenchymal stem cell-related genes were upregulated along with an increased abundance of Lineage−Sca1+CD34− “beige-like” adipocyte precursor cells. In vitro, the adiponectin receptor agonist Adiporon increased the expression of the proliferation marker Pcna and decreased the expression of Cd34 in Sca1+ mesenchymal stem cells. Conclusions: We propose that the seemingly opposite effect of adiponectin on BAT and IWAT is mediated by a common mechanism; while reduced adiponectin levels are linked to lower adipocyte OCR, elevated adiponectin levels stimulate expansion of adipocyte precursor cells that produce adipocytes with intrinsically higher metabolic rate than classical white but lower metabolic rate than classical brown adipocytes. Moreover, adiponectin can modify the adipocytes' metabolic activity directly and by enhancing the sympathetic innervation within a fat depot. CC BY 4.0 DEED© 2023 The AuthorsCorrespondence Address: I. Wernstedt Asterholm; Department of Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Medicinaregatan 11, PO Box 432, SE-405 30, Sweden; email: [email protected]; CODEN: METAA</p

Adipose Tissue—Breast Cancer Crosstalk Leads to Increased Tumor Lipogenesis Associated with Enhanced Tumor Growth

We sought to identify therapeutic targets for breast cancer by investigating the metabolic symbiosis between breast cancer and adipose tissue. To this end, we compared orthotopic E0771 breast cancer tumors that were in direct contact with adipose tissue with ectopic E0771 tumors in mice. Orthotopic tumors grew faster and displayed increased de novo lipogenesis compared to ectopic tumors. Adipocytes release large amounts of lactate, and we found that both lactate pretreatment and adipose tissue co-culture augmented de novo lipogenesis in E0771 cells. Continuous treatment with the selective FASN inhibitor Fasnall dose-dependently decreased the E0771 viability in vitro. However, daily Fasnall injections were effective only in 50% of the tumors, while the other 50% displayed accelerated growth. These opposing effects of Fasnall in vivo was recapitulated in vitro; intermittent Fasnall treatment increased the E0771 viability at lower concentrations and suppressed the viability at higher concentrations. In conclusion, our data suggest that adipose tissue enhances tumor growth by stimulating lipogenesis. However, targeting lipogenesis alone can be deleterious. To circumvent the tumor’s ability to adapt to treatment, we therefore believe that it is necessary to apply an aggressive treatment, preferably targeting several metabolic pathways simultaneously, together with conventional therapy

Role of endogenous cortistatin in the regulation of ghrelin system expression at pancreatic level under normal and obese conditions.

Ghrelin-system components [native ghrelin, In1-ghrelin, Ghrelin-O-acyltransferase enzyme (GOAT) and receptors (GHS-Rs)] are expressed in a wide variety of tissues, including the pancreas, where they exert different biological actions including regulation of neuroendocrine secretions, food intake and pancreatic function. The expression of ghrelin system is regulated by metabolic conditions (fasting/obesity) and is associated with the progression of obesity and insulin resistance. Cortistatin (CORT), a neuropeptide able to activate GHS-R, has emerged as an additional link in gut-brain interplay. Indeed, we recently reported that male CORT deficient mice (cort-/-) are insulin-resistant and present a clear dysregulation in the stomach ghrelin-system. The present work was focused at analyzing the expression pattern of ghrelin-system components at pancreas level in cort-/- mice and their control littermates (cort +/+) under low- or high-fat diet. Our data reveal that all the ghrelin-system components are expressed at the mouse pancreatic level, where, interestingly, In1-ghrelin was expressed at higher levels than native-ghrelin. Thus, GOAT mRNA levels were significantly lower in cort-/- mice compared with controls while native ghrelin, In1-ghrelin and GHS-R transcript levels remained unaltered under normal metabolic conditions. Moreover, under obese condition, a significant increase in pancreatic expression of native-ghrelin, In1-ghrelin and GHS-R was observed in obese cort+/+ but not in cort-/- mice. Interestingly, insulin expression and release was elevated in obese cort+/+, while these changes were not observed in obese cort-/- mice. Altogether, our results indicate that the ghrelin-system expression is clearly regulated in the pancreas of cort+/+ and cort -/- under normal and/or obesity conditions suggesting that this system may play relevant roles in the endocrine pancreas. Most importantly, our data demonstrate, for the first time, that endogenous CORT is essential for the obesity-induced changes in insulin expression/secretion observed in mice, suggesting that CORT is a key regulatory component of the pancreatic function

Genetic Disruption of Protein Kinase STK25 Ameliorates Metabolic Defects in a Diet-Induced Type 2 Diabetes Model

Understanding the molecular networks controlling ectopic lipid deposition, glucose tolerance, and insulin sensitivity is essential to identifying new pharmacological approaches to treat type 2 diabetes. We recently identified serine/threonine protein kinase 25 (STK25) as a negative regulator of glucose and insulin homeostasis based on observations in myoblasts with acute depletion of STK25 and in STK25-overexpressing transgenic mice. Here, we challenged Stk25 knockout mice and wild-type littermates with a high-fat diet and showed that STK25 deficiency suppressed development of hyperglycemia and hyperinsulinemia, improved systemic glucose tolerance, reduced hepatic gluconeogenesis, and increased insulin sensitivity. Stk25(−/−) mice were protected from diet-induced liver steatosis accompanied by decreased protein levels of acetyl-CoA carboxylase, a key regulator of both lipid oxidation and synthesis. Lipid accumulation in Stk25(−/−) skeletal muscle was reduced, and expression of enzymes controlling the muscle oxidative capacity (Cpt1, Acox1, Cs, Cycs, Ucp3) and glucose metabolism (Glut1, Glut4, Hk2) was increased. These data are consistent with our previous study of STK25 knockdown in myoblasts and reciprocal to the metabolic phenotype of Stk25 transgenic mice, reinforcing the validity of the results. The findings suggest that STK25 deficiency protects against the metabolic consequences of chronic exposure to dietary lipids and highlight the potential of STK25 antagonists for the treatment of type 2 diabetes

Expression profile of insulin 1 and insulin 2 (panels A and B, respectively) in the whole pancreas of cort+/+ and cort−/− male mice fed a low fat (LF) or high fat diet (HFD).

<p>C, plasma insulin level obtained from cort+/+ and cort−/− animals fed a LF- or HF-diet. Values represent mean ± SEM of copy number adjusted by normalization factor (NF) per 100 ng of cDNA obtained from 4–7 animals per experimental group. (*: p<0,05).</p

Expression level of different ghrelin system components in the whole pancreas of cort+/+ and cort−/− male mice fed a low fat (LF) or high fat diet (HFD).

<p>Values represent mean ± SEM of copy number adjusted by normalization factor (NF) per 100 ng of cDNA obtained from 3–7 animals per experimental group. (*: p<0,05; **: p<0,01; ***: p<0,001).</p