Implicaciones de la hormona de crecimiento, hormonas gastrointestinales, irisina y "microARNs" en la obesidad

[Resumo]A obesidade é unha das principais preocupacións relacionadas coa saúde pública. Na obesidade prodúcense diferentes alteracións hormonais, como o aumento da leptina e a dlminución da hormona de crecemento (GH) e a ghrelina. Entre os estímulos secretorios de GH que se conserva na obesidad e é destacable o que se presenta de forma tardía tras a sobrecarga oral de glucosa (SOG). A ghrelina ten unha potente acción como factor oresixénico e poderla ser un sinal fundamental relacionando a inxestión co desenvolvemento da obesidade. Existen outras hormonas importantes na regulación da inxestión, entre elas o péptido Y (PYV). Ademais o descubrimento recente dunha nova hormona segregada polo músculo esquelético (irisina) abre o abano no estudo das alteracions hormonais na obesidade. Por outra parte, os microARNs (mIARNs) postuláronse como posibles reguladores dunha serie de procesos biolóxicos, incluida a adipoxénese. Neste contexto, o obxectivo global desta tese é avanzar na caracterización do papel da GH, PYV, irisina e ghrelina en pacientes normais, obesos e hipopituitarios e por outra parte estudar o papel dos miARNs hipotalámicos nun modelo animal na regulaci6n de diversos problemas metabóicos asociados coa obesidade como a resistencia á insulina e á leptina. Podemos concluir que tras a SOG os niveis de GH e ghrelina total están diminuidos nos pacientes obesos con respecto aos controis, ademais en mulleres encontramos que a ghrellna circulante é un importante regulador da secreción da GH, que os valores de irisina son superiores en obesos e que existen varias familias de miARNs relacionados coas rutas de sinalizaci6n da leptina e a insulina que se atopan alterados a nivel hipotalámico en ratas obesas, anoréxicas e/ou tratadas con leptina.[Resumen]La obesidad es una de las principales preocupaciones relacionadas con la salud pública. En la obesidad se producen diferentes alteraciones hormonales, como el aumento de la leptina y la disminución de la hormona de crecimiento (GH) y la ghrellna. Entre los estlmulos secretorios de GH que se conservan en la obesidad es destacable el que se presenta de forma tardla tras la sobrecarga oral de glucosa (SOG). La ghrelina tiene una potente acción como factor orexigénico y podrfa ser una seílal fundamental relacionando la ingesta con el desarrollo de la obesidad. Existen otras hormonas importantes en la regulación de la ingesta, entre ellas el péptido Y (PVY). Además el descubrimiento reciente de una nueva hormona secretada por el músculo esquelético (irisina) abre el abanico en el estudio de las alteraciones hormonales en la obesidad. Por otra parte, los microARNs (miARNs) se postularon como posibles reguladores de una serie de procesos biológicos, incluida la adipogénesis. En este contexto, el objetivo global de esta tesis es avanzar en la caracterización del papel de la GH, PVY, irisina y ghrelina en pacientes normales, obesos e hipopituitarios y por otra parte estudiar el papel de los miARNs hlpotalámlcos en un modelo animal en la regulación de diversos problemas metabólicos asociados con la obesidad como la resistencia a la insulina ya la leptina. Podemos concluir que tras la SOG los niveles de GH V ghrelina total están disminuidos en los pacientes obesos con respecto a los controles, además en mujeres encontramos que la ghrelina circulante es un importante regulador de la secreción de la GH, que los valores de irisina son superiores en obesos V que existen varias familias de miARNs relacionados con las rutas de seílalización de la leptina V la insulina que se encuentran alterados a nivel hipotalámico en ratas obesas, anoréxicas V/o tratadas con leptina[Abstract]Obesity is one of the main concerns related to the public health. In the obesity different hormonal alteratlons, as the increase of leptin and the decrease of growth hormone (GH) and ghrelin, take place. Among the GH secretory stimuli that are preserved in the obesity is noteworthy which occurs at a late stage after the oral glucose overload (OGO). Ghrelin has a powerful action as orexlgenic factor and could be a basic signal relating the food intake to the development of the obesity. There are other important hormones in the regulation of the ingestion, among them the peptide Y (PYY). Besides the recent discovery of a new hormone secreted by the skeletal muscle (irlsin) opens the range in the study of the hormonal alterations in the obesity. On the other hand, the microRNAs (miRNAs) were postulated as possible regulators of a series of biological processes, included adipogenesis. In thls context, the global goal of thls thesis is to advance in the characterization of role the GH, PYY, irisin and ghrelin in normal, obese and hypopituitary patients and on the other hand, to study the role of hypothalamic miRNAs in an animal model in the regulation of different metabolic problems related with the obesity like insulin and leptin resistance. We can conclude that after the OGO GH and total ghrelin levels are decreased in the obese patients with regard to the controls, besides in women we find that circulating ghrelin levels are an important regulator of GH secretion, that blood irisin levels are superior In obese and moreover several famlies of miRNAs related with leptin and insulin signaling pathways show hypothalamic expression levels altered in obese, anorexic and/or with leptin treatment

Perturbation of hypothalamic MicroRNA expression patterns in male rats after metabolic distress: impact of obesity and conditions of negative energy balance

[Abstract] The hypothalamus plays a crucial role in body weight homeostasis through an intricate network of neuronal circuits that are under the precise regulation of peripheral hormones and central transmitters. Although deregulated function of such circuits might be a major contributing factor in obesity, the molecular mechanisms responsible for the hypothalamic control of energy balance remain partially unknown. MicroRNAs (miRNAs) have been recognized as key regulators of different biological processes, including insulin sensitivity and glucose metabolism. However, the roles of miRNA pathways in the control of metabolism have been mostly addressed in peripheral tissues, whereas the potential deregulation of miRNA expression in the hypothalamus in conditions of metabolic distress remains as yet unexplored. In this work, we used high-throughput screening to define to what extent the hypothalamic profiles of miRNA expression are perturbed in two extreme conditions of nutritional stress in male rats, namely chronic caloric restriction and high-fat diet–induced obesity. Our analyses allowed the identification of sets of miRNAs, including let-7a, mir-9*, mir-30e, mir-132, mir-145, mir-200a, and mir-218, whose expression patterns in the hypothalamus were jointly altered by caloric restriction and/or a high-fat diet. The predicted targets of these miRNAs include several elements of key inflammatory and metabolic pathways, including insulin and leptin. Our study is the first to disclose the impact of nutritional challenges on the hypothalamic miRNA expression profiles. These data will help to characterize the molecular miRNA signature of the hypothalamus in extreme metabolic conditions and pave the way for targeted mechanistic analyses of the involvement of deregulated central miRNAs pathways in the pathogenesis of obesity and related disorders.Instituto de Salud Carlos III; PI10/00088Ministerio de Economia y Competitividad; IN845B-2010/187Instituto de Salud Carlos III; PI13/00322FISXunta de Galicia; 10CSA916014PRXunta de Galicia; EM2013/011Ministerio de Ciencia e Innovación; BFU 2011-2502

La expresión génica de FNDC5 en distintos tejidos, y los niveles circulantes de irisina, están modificados por la dieta y las condiciones hormonales

ResumenXunta de Galicia; EM2013/011Instituto de Salud Carlos III; PI13/0032

Alteración de la expresión génica de Sor1 y RB1 en distintos modelos de estrés metabólico

AbstractXunta de Galicia; EM2013/011Instituto de Salud Carlos III; PI13/0032

FNDC5 expression and circulating irisin levels are modified by diet and hormonal conditions in hypothalamus, adipose tissue and muscle

[Abstract] Irisin is processed from fibronectin type III domain-containing protein 5 (FNDC5). However, a controversy exists concerning irisin origin, regulation and function. To elucidate the relationship between serum irisin and FNDC5 mRNA expression levels, we evaluated plasma irisin levels and FNDC5 gene expression in the hypothalamus, gastrocnemius muscle and different depots of adipose tissue in models of altered metabolism. In normal rats, blood irisin levels diminished after 48-h fast and with leptin, insulin and alloxan treatments, and serum irisin concentrations increased in diabetic rats after insulin treatment and acute treatments of irisin increased blood insulin levels. No changes were observed during long-term experiments with different diets. We suggested that levels of circulating irisin are the result of the sum of the irisin produced by different depots of adipose tissue and skeletal muscle. This study shows for the first time that there are differences in FNDC5 expression depending on white adipose tissue depots. Moreover, a considerable decrease in visceral and epididymal adipose tissue depots correlated with increased FNDC5 mRNA expression levels, probably in an attempt to compensate the decrease that occurs in their mass. Hypothalamic FNDC5 expression did not change for any of the tested diets but increased with leptin, insulin and metformin treatments suggesting that the regulation of central and peripheral FNDC5/irisin expression and functions are different.Galicia. Consellería de Cultura, Educación e Ordenación Universitaria; EM2013/011Instituto de Salud Carlos III; PI13/0032

Niveles séricos de la adipomioquina irisina en pacientes con enfermedad renal crónica

[Abstract] Background. Irisin is an adipomyokine with claimed anti-obesity and anti-diabetic effects. This hormone has been insufficiently studied in patients with advanced chronic kidney disease (CKD). Objective. To perform an exploratory analysis of serum irisin levels in patients undergoing different CKD treatments. Method. Following a cross-sectional design, we estimated serum levels of irisin in 95 patients with CKD managed conservatively (advanced CKD), with peritoneal dialysis (PD) or with haemodialysis, and compared our findings with a control group of 40 healthy individuals. We investigated the correlations between serum irisin and demographic, clinical, body composition and metabolic variables. Results. Irisin levels were lower in all the CKD groups than in the control group. The univariate analysis revealed limited correlations between irisin, on the one hand, and fat (but not lean) mass, glomerular filtration rate (GFR) and plasma albumin and bicarbonate, on the other. The multivariate analysis confirmed that advanced CKD patients managed conservatively (difference 111.1 ng/mL), with PD (25.9 ng/mL) or haemodialysis (61.4 ng/mL) (all p < .0005) presented lower irisin levels than the control group. Furthermore, PD patients presented higher serum levels of irisin than those on haemodialysis (difference 39.4 ng/mL, p = .002) or those managed conservatively (24.4 ng/mL, p = .036). The multivariate analysis also identified plasma bicarbonate (B = 3.90 per mM/l, p = .001) and GFR (B = 1.89 per mL/min, p = .003) as independent predictors of irisin levels. Conversely, no adjusted correlation between irisin and body composition markers was found. Conclusions. Serum irisin levels are low in patients with CKD and show a consistent correlation with GFR and plasma bicarbonate levels. PD patients present higher levels of irisin than those managed conservatively or with haemodialysis. Our study confirms a general inconsistency of the association between serum irisin levels, on the one hand, and body composition and metabolic markers, on the other.[Resumen] Antecedentes. La irisina es una adipomioquina con posibles efectos antiobesidad y antidiabéticos. Esta hormona ha sido insuficientemente estudiada en pacientes con enfermedad renal crónica (ERC) avanzada. Objetivo. Realizar un análisis exploratorio de los niveles séricos de irisina en pacientes con diferentes modalidades de tratamiento de la ERC. Método. Según diseño transversal, estimamos niveles de irisina en 95 pacientes con ERC manejados conservadoramente (ERCA), con diálisis peritoneal (DP) o con hemodiálisis, comparándolos con un grupo control de 40 individuos sanos. También investigamos las correlaciones entre irisina sérica y variables demográficas, clínicas, metabólicas y de composición corporal. Resultados. Los niveles de irisina fueron más bajos en cualquier grupo de pacientes que en los controles. El análisis univariante desveló correlaciones moderadas entre irisina, por un lado, y masa grasa (pero no magra), filtrado glomerular (GFR) y albúmina y bicarbonato plasmático, por otro. El análisis multivariante confirmó que los pacientes con ERCA (diferencia 111,1 ng/mL), en DP (25,9 ng/mL) o hemodiálisis (61,4 ng/mL) (todos p < 0,0005) presentaban niveles ajustados más bajos de irisina que los controles. Asimismo, los pacientes en DP presentaban niveles más altos de la hormona que los de hemodiálisis (diferencia 39,4 ng/mL; p = 0,002) o ERCA (24,4 ng/mL; p = 0,036). El análisis multivariante también identificó bicarbonato plasmático (B = 3,90 por mM/L; p = 0,001) y GFR (B = 1,89 por mL/min; p = 0,003) como predictores independientes de los niveles de irisina. Por el contrario, no observamos correlación ajustada entre irisina y marcadores de composición corporal. Conclusiones. Los niveles de irisina son bajos en pacientes con ERC, y muestran correlación consistente con GFR y bicarbonato plasmático. Los pacientes en DP presentan niveles más altos de irisina que los manejados conservadoramente o con hemodiálisis. Nuestro estudio confirma una inconsistencia general en los análisis de asociación entre irisina sérica, por un lado, y marcadores metabólicos y de composición corporal, por otro.Instituto de Salud Carlos III; PI10/00088Instituto de Salud Carlos III; PI13/00322Xunta de Galicia; IN845B-2010/187Xunta de Galicia; 10CSA916014PRXunta de Galciia; CN2012/31

Sexual dimorphism on growth hormone secretion after oral glucose administration

[Abstract] Sexual dimorphism of GH secretion is unclear in humans. There is evidence that oral glucose (OG) administration initially decreases and subsequently stimulates GH secretion. Our aim was to study fasting GH concentrations and their response to OG administration in obese and healthy women and men, in order to elucidate the mechanism of sexual dimorphism of GH secretion and the possible contribution of ghrelin. We selected 33 women and 11 men as obese and healthy subjects. After an overnight fast, 75 g of oral glucose were administered; glucose, insulin, ghrelin, and PYY1-36 were obtained at baseline and during 300 min. Fasting GH (μg/l) was higher in women than men; 1.3 ± 0.3 vs. 0.2 ± 0.1, p=0.009, for women and men, respectively. The area under the curve between 0 and 150 min (AUC) of GH (μg/l · min) was higher in women than men; 98.2 ± 25.9 vs. 41.5 ± 28.6, p=0.002, for women and men, respectively. The AUC of total ghrelin (pg/ml · min, mean ± SEM) between 0 and 150 min was borderline and significantly higher in women than men; 128 562.3 ± 8 335.9 vs. 98 839.1 ± 7 668.6, p=0.069, for women and men, respectively. Several initial time points were higher in women than men. Glucose, insulin, and PYY1-36 were similar in women and men after OG. There were significant correlations between indices of post-oral glucose GH and ghrelin secretion. Fasting and initial GH secretion is higher in women than men, in contrast to peak and late GH secretion, which is similar in both cases. Sexual dimorphism in the regulation of GH secretion probably involves ghrelin.Instituto de Salud Carlos III; PI070413Instituto de Salud Carlos III; PI10/00088Xunta de Galicia; PS07/12Xunta de Galicia; INCITE08ENA916110ESXunta de Galicia; INCITE09E1R91634ESXunta de Galicia; IN845B-2010/187Xunta de Galicia; 10CSA916014P

Oral glucose-stimulated growth hormone (GH) test in adult GH deficiency patients and controls: potential utility of a novel test

[Abstract] Context. The diagnosis of adult GH deficiency requires confirmation with a GH stimulation test. Oral glucose (OG) administration affects GH secretion, initially decreasing and subsequently stimulating GH secretion. Objective. The aim of this study was to investigate the diagnostic efficacy and safety of a long OG test (LOGT) as a stimulus of GH secretion for the diagnosis of adult GH deficiency (AGHD). Design. Prospective experimental cross-sectional study. Settings. The study was conducted at the Endocrinology department of the University Hospital of a Coruña, Spain. Participants and methods. We included 60 (40 women) AGHD patients (15) and controls (45) paired 1:3, of similar age, sex and BMI. The area under the curve (AUC) and peak were calculated for GH. The Mann-Whitney test was used to compare the different groups. ROC curve analyses were used. p-Values < 0.05 were considered as statistically significant. Interventions. The intervention consisted of orally administering 75 g oral glucose administration; GH was obtained every 30 min for a total of 300 min. Main outcome measurement. Peak GH area under receiver operating characteristic curve (ROC-AUC) following LOGT. Results. Peak GH (μg/L) levels were lower in the AGHD patients (0.26 ± 0.09) than in the controls (4.00 ± 0.45), p < 0.001. After LOGT, with the ROC plot analysis the best peak GH cut-point was 1.0 μg/L, with 100% sensitivity, 78% specificity, ROC-AUC of 0.9089 and 81.82% accuracy. There were no relevant adverse events during any of the LOGT. Conclusions. The LOGT could be a cheap, safe, convenient and effective test for the diagnosis of AGHD.Instituto de Salud Carlos III; PI13/00322Instituto de Salud Carlos III; PI16/00884Xunta de Galicia; 10CSA916014P

Cost-effectiveness analysis of preoperative treatment of acromegaly with somatostatin analogue on surgical outcome

[Abstract] Context. There is no uniform standard of care for acromegaly. Due to the high costs involved, steps must be taken to ensure the cost-effective delivery of treatment. Objective. Taking the results of an earlier meta-analysis as a starting point, this study aims to determine whether treatment with long-acting somatostatin analogue (SSA) prior to surgery improves the cost-effectiveness of the treatment of acromegaly. Methods. The results are presented as an Incremental Cost Effectiveness Ratio (ICER) immediately after surgery, for the following year and over the next four decades. The cure rates percentage (95% CI) for the three randomized prospective controlled trials were 44.4% (34.2–54.7) and 18.2% (10.1–26.3) for preoperative treated and untreated patients respectively. The cost of pharmacological treatments was based on the number of units prescribed, dose and length of treatment. Results. The mean (95% CI) ICER immediately after surgery was €17,548 (12,007–33,250). In terms of the postoperative SSA treatment, the ICER changes from positive to negative before two years after surgery. One decade after surgery the ICER per patient/year was €− 9973 (− 18,798; − 6752) for postoperative SSA treatment and €− 31,733 (− 59,812; − 21,483) in the case of postoperative pegvisomant treatment. Conclusions. In centres without optimal surgical results, preoperative treatment of GH-secreting pituitary macroadenomas with SSA not only shows a significant improvement in the surgical results, but is also highly cost-effective, with an ICER per patient/year one decade after surgery, of between €− 9973 (− 18,798; − 6752) and €− 31,733 (− 59,812; − 21,483) for SSA and pegvisomant respectively.Instituto de Salud Carlos III; PI10/00088Instituto de Salud Carlos III; PI13/00322Xunta de Galicia; IN845B-2010/187Xunta de Galicia; 10CSA916014PRXunta de Galicia; CN2012/31

Evaluation of Thyroid Hormone Replacement Dosing in Morbidly Obese Hypothyroid Patients after Bariatric Surgery-Induced Weight Loss

[Abstract] The most frequent endocrine disease in obese patients is hypothyroidism. To date, there are no clear data regarding what happens to the dose of levothyroxine (LT4) after bariatric surgery (BS). The objective of the present study was to evaluate thyroid hormone replacement dose in morbidly obese hypothyroid patients after BS-induced weight loss. We explore the best type of measured or estimated body weight for LT4 dosing. We performed an observational study evaluating patients with morbid obesity and hypothyroidism who underwent BS. We included 48 patients (three men). In morbidly obese hypothyroid patients 12 months after BS-induced weight loss, the total LT4 dose or the LT4 dose/kg ideal body weight did not change, while there was a significant increase in LT4 dose/body surface area, LT4 dose/kg weight, LT4 dose/kg adjusted body weight, LT4 dose/kg body fat, and LT4 dose/kg lean body weight. There were no differences in LT4 dose and its variation between sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB). The present study strongly suggests that LT4 dosing in obese hypothyroid patients can be individually adapted more precisely if it is based on ideal body weight.The results of this work have been funded by the Project Nº PI16/00884 to F.C. and S.S-A.; integrated in the National Plan for Scientific Research, Development and Technological Innovation 2013–2016, Spain and funded by the ISCIII (Instituto de Salud Carlos III)-General Subdirection of Assessment and Promotion of the Research–European Regional Development Fund (FEDER) “A way of making Europe