Ghrelin suppresses glucose-stimulated insulin secretion and deteriorates glucose tolerance in healthy humans.

OBJECTIVE: The orexigenic gut hormone ghrelin and its receptor are present in pancreatic islets. Although ghrelin reduces insulin secretion in rodents, its effect on insulin secretion in humans has not been established. The goal of this study was to test the hypothesis that circulating ghrelin suppresses glucose-stimulated insulin secretion in healthy subjects. RESEARCH DESIGN AND METHODS: Ghrelin (0.3, 0.9 and 1.5 nmol/kg/h) or saline was infused for more than 65 min in 12 healthy patients (8 male/4 female) on 4 separate occasions in a counterbalanced fashion. An intravenous glucose tolerance test was performed during steady state plasma ghrelin levels. The acute insulin response to intravenous glucose (AIRg) was calculated from plasma insulin concentrations between 2 and 10 min after the glucose bolus. Intravenous glucose tolerance was measured as the glucose disappearance constant (Kg) from 10 to 30 min. RESULTS: The three ghrelin infusions raised plasma total ghrelin concentrations to 4-, 15-, and 23-fold above the fasting level, respectively. Ghrelin infusion did not alter fasting plasma insulin or glucose, but compared with saline, the 0.3, 0.9, and 1.5 nmol/kg/h doses decreased AIRg (2,152 +/- 448 vs. 1,478 +/- 2,889, 1,419 +/- 275, and 1,120 +/- 174 pmol/l) and Kg (0.3 and 1.5 nmol/kg/h doses only) significantly (P < 0.05 for all). Ghrelin infusion raised plasma growth hormone and serum cortisol concentrations significantly (P < 0.001 for both), but had no effect on glucagon, epinephrine, or norepinephrine levels (P = 0.44, 0.74, and 0.48, respectively). CONCLUSIONS: This is a robust proof-of-concept study showing that exogenous ghrelin reduces glucose-stimulated insulin secretion and glucose disappearance in healthy humans. Our findings raise the possibility that endogenous ghrelin has a role in physiologic insulin secretion, and that ghrelin antagonists could improve beta-cell function.

Acute administration of unacylated ghrelin has no effect on Basal or stimulated insulin secretion in healthy humans.

Unacylated ghrelin (UAG) is the predominant ghrelin isoform in the circulation. Despite its inability to activate the classical ghrelin receptor, preclinical studies suggest that UAG may promote β-cell function. We hypothesized that UAG would oppose the effects of acylated ghrelin (AG) on insulin secretion and glucose tolerance. AG (1 µg/kg/h), UAG (4 µg/kg/h), combined AG+UAG, or saline were infused to 17 healthy subjects (9 men and 8 women) on four occasions in randomized order. Ghrelin was infused for 30 min to achieve steady-state levels and continued through a 3-h intravenous glucose tolerance test. The acute insulin response to glucose (AIRg), insulin sensitivity index (SI), disposition index (DI), and intravenous glucose tolerance (kg) were compared for each subject during the four infusions. AG infusion raised fasting glucose levels but had no effect on fasting plasma insulin. Compared with the saline control, AG and AG+UAG both decreased AIRg, but UAG alone had no effect. SI did not differ among the treatments. AG, but not UAG, reduced DI and kg and increased plasma growth hormone. UAG did not alter growth hormone, cortisol, glucagon, or free fatty acid levels. UAG selectively decreased glucose and fructose consumption compared with the other treatments. In contrast to previous reports, acute administration of UAG does not have independent effects on glucose tolerance or β-cell function and neither augments nor antagonizes the effects of AG.

A novel non-peptidic agonist of the ghrelin receptor with orexigenic activity in vivo

Loss of appetite in the medically ill and ageing populations is a major health problem and a significant symptom in cachexia syndromes, which is the loss of muscle and fat mass. Ghrelin is a gut-derived hormone which can stimulate appetite. Herein we describe a novel, simple, non-peptidic, 2-pyridone which acts as a selective agonist for the ghrelin receptor (GHS-R1a). The small 2-pyridone demonstrated clear agonistic activity in both transfected human cells and mouse hypothalamic cells with endogenous GHS-R1a receptor expression. In vivo tests with the hit compound showed significant increased food intake following peripheral administration, which highlights the potent orexigenic effect of this novel GHS-R1a receptor ligand.

The relationship between subjective appetite sensations, markers of inflammation and appetite in dialysis patients

Background: Poor appetite is a marker of morbidity and mortality in hemodialysis patients, making it an important area for research. Visual analog scales (VAS) can capture a range of subjective sensations related to appetite (such as hunger, desire to eat or fullness), but have not been commonly used to measure appetite in dialysis patients. The aim of this study was to explore the association between retrospective ratings of appetite using VAS and a range of clinical variables as well as biomarkers of appetite in hemodialysis patients.----- Methods: 28 hemodialysis patients (mean age 61±17y, 50% male, median dialysis vintage 19.5(4-101) months) rated their appetite using VAS for hunger, fullness and desire to eat and a 5-point categorical scale measuring general appetite. Blood levels of the appetite peptides leptin, ghrelin and peptide YY were also measured.----- Results: Hunger ratings measured by VAS were significantly (p<0.05) correlated with a range of clinical, nutritional and inflammatory markers: age (r=-0.376), co-morbidities, (r=-0.380) PG-SGA score (r=-0.451), weight (r=-0.375), fat-free mass (r=-0.435), C-Reactive Protein (CRP) (r=-0.383) and Intercellular adhesion molecule (sICAM-1) (r=-0.387). There was a consistent relationship between VAS and appetite on a 5-point categorical scale for questions of hunger, and a similar trend for desire to eat, but not for fullness. Neither method of measuring subjective appetite correlated with appetite peptides.----- Conclusions: Retrospective ratings of hunger on a VAS are associated with a range of clinical variables and further studies are warranted to support their use as a method of measuring appetite in dialysis patients.

New insights into appetite, inflammation and the use of fish oil in hemodialysis patients

Protein-energy wasting (PEW) is commonly seen in patients with chronic kidney disease (CKD). The condition is characterised by chronic, systemic low-grade inflammation which affects nutritional status by a variety of mechanisms including reducing appetite and food intake and increasing muscle catabolism. PEW is linked with co-morbidities such as cardiovascular disease, and is associated with lower quality of life, increased hospitalisations and a 6-fold increase in risk of death1. Significant gender differences have been found in the severity and effects of several markers of PEW. There have been limited studies testing the ability of anti-inflammatory agents or nutritional interventions to reduce the effects of PEW in dialysis patients. This thesis makes a significant contribution to the understanding of PEW in dialysis patients. It advances understanding of measurement techniques for two of the key components, appetite and inflammation, and explores the effect of fish oil, an anti-inflammatory agent, on markers of PEW in dialysis patients. The first part of the thesis consists of two methodological studies conducted using baseline data. The first study aims to validate retrospective ratings of hunger, desire to eat and fullness on visual analog scales (VAS) (paper and pen and electronic) as a new method of measuring appetite in dialysis patients. The second methodological study aims to assess the ability of a variety of methods available in routine practice to detect the presence of inflammation. The second part of the thesis aims to explore the effect of 12 weeks supplementation with 2g per day of Eicosapentaenoic Acid (EPA), a longchain fatty acid found in fish oil, on markers of PEW. A combination of biomarkers and psychomarkers of appetite and inflammation are the main outcomes being explored, with nutritional status, dietary intake and quality of life included as secondary outcomes. A lead in phase of 3 months prior to baseline was used so that each person acts as their own historical control. The study also examines whether there are gender differences in response to the treatment. Being an exploratory study, an important part of the work is to test the feasibility of the intervention, thus the level of adherence and factors associated with adherence are also presented. The studies were conducted at the hemodialysis unit of the Wesley Hospital. Participants met the following criteria: adult, stage 5 CKD on hemodialysis for at least 3 months, not expected to receive a transplant or switch to another dialysis modality during the study, absence of intellectual impairment or mental illness impairing ability to follow instructions or complete the intervention. A range of intermediate, clinical and patient-centred outcome measures were collected at baseline and 12 weeks. Inflammation was measured using five biomarkers: c-reactive protein (CRP), interleukin-6 (IL6), intercellular adhesion molecule (sICAM-1), vascular cell adhesion molecule (sVCAM-1) and white cell count (WCC). Subjective appetite was measured using the first question from the Appetite and Dietary Assessment (ADAT) tool and VAS for measurements of hunger, desire to eat and fullness. A novel feature of the study was the assessment of the appetite peptides leptin, ghrelin and peptide YY as biomarkers of appetite. Nutritional status/inflammation was assessed using the Malnutrition-Inflammation Score (MIS) and the Patient-Generated Subjective Global Assessment (PG-SGA). Dietary intake was measured using 3-day records. Quality of life was measured using the Kidney Disease Quality of Life Short Form version 1.3 (KDQOL-SF™ v1.3 © RAND University), which combines the Short-Form 36 (SF36) with a kidney-disease specific module2. A smaller range of these variables was available for analysis during the control phase (CRP, ADAT, dietary intake and nutritional status). Statistical analysis was carried out using SPSS version 14 (SPSS Inc, Chicago IL, USA). Analysis of the first part of the thesis involved descriptive and bivariate statistics, as well as Bland-Altman plots to assess agreement between methods, and sensitivity analysis/ROC curves to test the ability of methods to predict the presence of inflammation. The unadjusted (paired ttests) and adjusted (linear mixed model) change over time is presented for the main outcome variables of inflammation and appetite. Results are shown for the whole group followed by analyses according to gender and adherence to treatment. Due to the exploratory nature of the study, trends and clinical significance were considered as important as statistical significance. Twenty-eight patients (mean age 61±17y, 50% male, dialysis vintage 19.5 (4- 101) months) underwent baseline assessment. Seven out of 28 patients (25%) reported sub-optimal appetite (self-reported as fair, poor or very poor) despite all being well nourished (100% SGA A). Using the VAS, ratings of hunger, but not desire to eat or fullness, were significantly (p<0.05) associated with a range of relevant clinical variables including age (r=-0.376), comorbidities (r=-0.380) nutritional status (PG-SGA score, r=-0.451), inflammatory markers (CRP r=-0.383; sICAM-1 r=-0.387) and seven domains of quality of life. Patients expressed a preference for the paper and pen method of administering VAS. None of the tools (appetite, MIS, PG-SGA, albumin or iron) showed an acceptable ability to detect patients who are inflamed. It is recommended that CRP should be tested more frequently as a matter of course rather than seeking alternative methods of measuring inflammation. 27 patients completed the 12 week intervention. 20 patients were considered adherent based on changes in % plasma EPA, which rose from 1.3 (0.94)% to 5.2 (1.1)%, p<0.001, in this group. The major barriers to adherence were forgetting to take the tablets as well as their size. At 12 weeks, inflammatory markers remained steady apart from the white cell count which decreased (7.6(2.5) vs 7.0(2.2) x109/L, p=0.058) and sVCAM-1 which increased (1685(654) vs 2249(925) ng/mL, p=0.001). Subjective appetite using VAS increased (51mm to 57mm, +12%) and there was a trend towards reduction in peptide YY (660(31) vs 600(30) pg/mL, p=0.078). There were some gender differences apparent, with the following adjusted change between baseline and week 12: CRP (males -3% vs females +17%, p=0.19), IL6 (males +17% vs females +48%, p=0.77), sICAM-1 (males -5% vs females +11%, p=0.07), sVCAM-1 (males +54% vs females +19%, p=0.08) and hunger ratings (males 20% vs females -5%, p=0.18). On balance, males experienced a maintainence or reduction in three inflammatory markers and an improvement in hunger ratings, and therefore appeared to have responded better to the intervention. Compared to those who didn’t adhere, adherent patients maintained weight (mean(SE) change: +0.5(1.6) vs - 0.8(1.2) kg, p=0.052) and fat-free mass (-0.1 (1.6) vs -1.8 (1.8) kg, p=0.045). There was no difference in change between the intervention and control phase for CRP, appetite, nutritional status or dietary intake. The thesis makes a significant contribution to the evidence base for understanding of PEW in dialysis patients. It has advanced knowledge of methods of assessing inflammation and appetite. Retrospective ratings of hunger on a VAS appear to be a valid method of assessing appetite although samples which include patients with very poor appetite are required to confirm this. Supplementation with fish oil appeared to improve subjective appetite and dampen the inflammatory response. The effectiveness of the intervention is influenced by gender and adherence. Males appear to be more responsive to the primary outcome variables than females, and the quality of response is improved with better adherence. These results provide evidence to support future interventions aimed at reducing the effects of PEW in dialysis patients.

The effects of exercise-induced weight loss on appetite-related peptides and motivation to eat

Context: The magnitude of exercise-induced weight loss depends on the extent of compensatory responses. An increase in energy intake is likely to result from changes in the appetite control system toward an orexigenic environment; however, few studies have measured how exercise impacts on both orexigenic and anorexigenic peptides. ---------- Objective: The aim of the study was to investigate the effects of medium-term exercise on fasting/postprandial levels of appetite-related hormones and subjective appetite sensations in overweight/obese individuals. ---------- Design and Setting: We conducted a longitudinal study in a university research center. ---------- Participants and Intervention: Twenty-two sedentary overweight/obese individuals (age, 36.9 ± 8.3 yr; body mass index, 31.3 ± 3.3 kg/m2) took part in a 12-wk supervised exercise programme (five times per week, 75% maximal heart rate) and were requested not to change their food intake during the study. ---------- Main Outcome Measures: We measured changes in body weight and fasting/postprandial plasma levels of glucose, insulin, total ghrelin, acylated ghrelin (AG), peptide YY, and glucagon-like peptide-1 and feelings of appetite. ---------- Results: Exercise resulted in a significant reduction in body weight and fasting insulin and an increase in AG plasma levels and fasting hunger sensations. A significant reduction in postprandial insulin plasma levels and a tendency toward an increase in the delayed release of glucagon-like peptide-1 (90–180 min) were also observed after exercise, as well as a significant increase (127%) in the suppression of AG postprandially. ---------- Conclusions: Exercise-induced weight loss is associated with physiological and biopsychological changes toward an increased drive to eat in the fasting state. However, this seems to be balanced by an improved satiety response to a meal and improved sensitivity of the appetite control system.

Foreword

Ghrelin was first identified in 1999 by Kojima and colleagues (Kojima et al. 1999) as the natural ligand of an orphan G-protein coupled receptor, the Growth Hormone (GH) secretagogue receptor (GHS-R), which had been identified several years earlier through the actions of a growing number of synthetic growth hormone releasing peptides (GHRPs) and non-peptidyl GH secretagogues (Howard et al. 1996). Early studies, therefore, focussed on the actions of ghrelin as an important regulator of GH secretion. As a result Kojima et al (1999) designated this GH-releasing peptide, ghrelin (ghre is the Proto-Indo-European root of the word 'grow'). We now recognise that the functions of ghrelin extend well beyond its GH releasing actions and that it is a multi-functional peptide with both endocrine and autocrine/paracrine modes of action.

Identification of a long non-coding RNA gene, GHSROS (growth hormone secretagogue receptor opposite strand), which stimulates cell migration in non-small cell lung cancer cell lines

The molecular mechanisms involved in non‑small cell lung cancer tumourigenesis are largely unknown; however, recent studies have suggested that long non-coding RNAs (lncRNAs) are likely to play a role. In this study, we used public databases to identify an mRNA-like, candidate long non-coding RNA, GHSROS (GHSR opposite strand), transcribed from the antisense strand of the ghrelin receptor gene, growth hormone secretagogue receptor (GHSR). Quantitative real-time RT-PCR revealed higher expression of GHSROS in lung cancer tissue compared to adjacent, non-tumour lung tissue. In common with many long non-coding RNAs, GHSROS is 5' capped and 3' polyadenylated (mRNA-like), lacks an extensive open reading frame and harbours a transposable element. Engineered overexpression of GHSROS stimulated cell migration in the A549 and NCI-H1299 non-small cell lung cancer cell lines, but suppressed cell migration in the Beas-2B normal lung-derived bronchoepithelial cell line. This suggests that GHSROS function may be dependent on the oncogenic context. The identification of GHSROS, which is expressed in lung cancer and stimulates cell migration in lung cancer cell lines, contributes to the growing number of non-coding RNAs that play a role in the regulation of tumourigenesis and metastatic cancer progression.

Tandem B1 SINE retro-elements may provide a basis for natural antisense transcription in the Magi1 locus of the mouse (Mus musculus)

Transposable elements, which are DNA sequences that can move between different sites in genomes, comprise approximately 40% of the genome of mammals and are emerging as important contributors to biological diversity. Here we report a transcription unit lying within intron 1 of the murine Magi1 (membrane associated guanylate kinase inverted 1) gene that codes for a cell-cell junction scaffolding protein. The transcription unit, termed Magi1OS (Magi1 Opposite Strand), originates from a region with tandem B1 short interspersed nuclear elements (SINEs) and is an antisense gene to Magi1. Mag1OS transcription initiates in a proximal B1 element that shows only 4% divergence from the consensus sequence, indicating that it has been recently inserted into the mouse genome and could be replication competent. Moreover, a chimaeric transcript may result from intra-chromosomal interaction and trans-splicing of the Magi1 antisense transcript (Magi1OS) and Ghrl, which codes for the multifunctional peptide hormone ghrelin. These two genes are 20 megabases apart on chromosome 6 and are transcribed in opposite directions. We propose that the Magi1OS locus may serve as a useful model system to study exaptation and retrotransposition of B1 SINEs, as well as to examine the mechanisms of intra-chromosomal trans-splicing.

Effect of moderate- and high-intensity acute exercise on appetite in obese individuals

Purpose The effect of acute exercise, and exercise intensity, on appetite control in obese individuals requires further study. The aim of this study was to compare the effects of acute isocaloric bouts (250 kcal) of high-intensity intermittent cycling (HIIC) and moderate-intensity continuous cycling (MICC) or short-duration HIIC (S-HIIC) (125 kcal) and a resting control condition on the appetite hormone responses, subjective feelings of appetite, energy intake (EI), and food reward in overweight/obese individuals. Methods This study is a randomized crossover study on 12 overweight/obese volunteers. Participants were assigned to the control, MICC, HIIC, and S-HIIC conditions, 1 wk apart, in a counterbalanced order. Exercise was performed 1 h after a standard breakfast. An ad libitum test lunch was served 3 h after breakfast. Fasting/postprandial plasma samples of insulin, acylated ghrelin, polypeptide YY3–36, and glucagon-like peptide 1 and subjective feelings of appetite were measured every 30 min for 3 h. Nutrient and taste preferences were measured at the beginning and end of each condition using the Leeds Food Preference Questionnaire. Results Insulin levels were significantly reduced, and glucagon-like peptide 1 levels significantly increased during all exercise bouts compared with those during rest. Acylated ghrelin plasma levels were lower in the MICC and HIIC, but not in S-HIIC, compared with those in control. There were no significant differences for polypeptide YY3–36 plasma levels, hunger or fullness ratings, EI, or food reward. Conclusions Our findings suggest that, in overweight/obese individuals, isocaloric bouts of moderate- or high-intensity exercise lead to a similar appetite response. This strengthens previous findings in normal-weight individuals that acute exercise, even at high intensity, does not induce any known physiological adaptation that would lead to increased EI.

NMR Structure Implications of Enhanced Efficacy of Obestatin Fragment Analogs

Obestatin is a more recently discovered hormone that is encoded by the ghrelin gene and produced in the stomach and gut. We report NMR analysis on synthetic Obestatin (OB23), a 23 residue peptide, along with three overlapping fragments of the same in methanol solvent as a first step towards structure activity relationship. Selective substitutions on the promising N-terminal and middle fragments of obestatin have been carried out in order to improve the efficacy and potency. In the N-terminal fragment two peptides were obtained by the replacement of Gly (8) with a-aminoisobutyric acid (Aib, U) and Phe (F5) with Cyclohexylalanine (Cha). In case of the middle fragment both Gly (3) and Gly (8) were replaced with Aib residues. The rationale being, these unusual amino acids could provide protection from immediate degradation and aid structure stabilization. Our previous studies showed that the N-terminal and the middle fragment were unstructured and hence this substitution would directly evaluate the effect of structure on the activity of these fragment analogs. Detailed NMR analysis clearly demonstrates formation of helical secondary structure in all the peptide analogues and provides justification for relative activities reported by our group previously (Nagaraj et al. 2009).

Association between dietary phylloquinone intake and peripheral metabolic risk markers related to insulin resistance and diabetes in elderly subjects at high cardiovascular risk

Background: Vitamin K has been related to glucose metabolism, insulin sensitivity and diabetes. Because inflammation underlies all these metabolic conditions, it is plausible that the potential role of vitamin K in glucose metabolism occurs through the modulation of cytokines and related molecules. The purpose of the study was to assess the associations between dietary intake of vitamin K and peripheral adipokines and other metabolic risk markers related to insulin resistance and type 2 diabetes mellitus. Methods: Cross-sectional and longitudinal assessments of these associations in 510 elderly participants recruited in the PREDIMED centers of Reus and Barcelona (Spain). We determined 1-year changes in dietary phylloquinone intake estimated by food frequency questionnaires, serum inflammatory cytokines and other metabolic risk markers. Results: In the cross-sectional analysis at baseline no significant associations were found between dietary phylloquinone intake and the rest of metabolic risk markers evaluated, with exception of a negative association with plasminogen activator inhibitor-1. After 1-year of follow-up, subjects in the upper tertile of changes in dietary phylloquinone intake showed a greater reduction in ghrelin (-15.0%), glucose-dependent insulinotropic peptide (-12.9%), glucagon-like peptide-1 (-17.6%), IL-6 (-27.9%), leptin (-10.3%), TNF (-26.9%) and visfatin (-24.9%) plasma concentrations than those in the lowest tertile (all p<0.05). Conclusion: These results show that dietary phylloquinone intake is associated with an improvement of cytokines and other markers related to insulin resistance and diabetes, thus extending the potential protection by dietary phylloquinone on chronic inflammatory diseases.

Regulação endócrina de curto prazo de hormônios relacionados à fome em mulheres obesas que apresentam episódios de compulsão alimentar

A compulsão alimentar está associada a diversas doenças, entre elas, a obesidade.Com o intuito de pesquisar a diferença hormonal ligada ao controle da fome e da saciedade associada ao episódio de compulsão alimentar (ECA), avaliou-se a concentração sérica dos hormônios que regulam este processo em mulheres adultas. Métodos: O estudo experimental foi composto de 3 grupos (n=23), sendo: grupo Eutrófico (GE;n=8), grupo obeso sem ECA (GO;n=7) e obesas com ECA (ECA;n=8). Todas as mulheres que participaram do estudo freqüentavam os serviços de saúde da Policlínica Piquet Carneiro. Foram dosados os hormônios: Grelina Total, Glucagon, Adiponectina, Amilina, Peptídeo C, GLP-1, Insulina e Leptina séricos nos tempos: jejum, 15 e 60 minutos após a ingestão da refeição fornecida. As refeições ingeridas foram controladas em energia, 55% carboidratos, 15% proteínas, 30% lipídios. Os dados foram analisados como valores médios por grupo em software SAS, considerando p<0,05. Resultados: A idade das mulheres estudadas variou de 32 a 50 anos. A concentração de adiponectina encontrada, que é inversamente proporcional a adiposidade, foi significativamente menor no grupo ECA em relação aos demais grupos (p=0,01). Em relação à leptina, o grupo GO apresentou concentração maior em relação aos demais grupos (p<0,0001). Já, a concentração de grelina encontrada foi significativamente menor no grupo ECA em relação aos demais grupos (p=0,02). Foram encontradas concentrações significativamente maiores de insulina no grupo GO em relação aos demais grupos (p=0,04). A concentração de amilina encontrada foi significativamente maior no grupo GO em relação aos outros grupos (p=0,01). A concentração de GLP-1 encontrada no grupo GO foi maior em média, porém esta diferença não foi estatisticamente significativa entre os grupos (p=0,25). A concentração de Peptídeo C encontrada no grupo GO foi maior em relação aos outros grupos (p=0,003). Apesar da concentração de Glucagon no grupo ECA ser maior em relação aos demais grupos, estes valores não eram diferentes estatisticamente (p=0,13). Nossos achados mostraram que obesas ECA tem perfil hormonal diferente de obesas sem ECA. A baixa concentração de grelina do grupo de obesas ECA e a alta concentração de insulina, peptídeo C e amilina nas obesas com e sem ECA pode estar relacionado com o aumento da ingestão alimentar e com o desequilíbrio energético.

Sinalização da grelina no coração de camundongos obesos após hipernutrição durante a lactação

A grelina é um ligante endógeno do receptor secretagogo do hormônio do crescimento (GHSR), potente estimulador da liberação do hormônio de crescimento (GH), ingestão alimentar, e adiposidade. Além disso, sua ação hormonal inclui regulação do metabolismo energético cardíaco. Entretanto, a hipernutrição no início da vida leva ao desenvolvimento da obesidade, induz hipertrofia cardíaca, compromete a função cardíaca, e gera insuficiência cardíaca na vida adulta. Avaliar proteínas chaves no processo de sinalização da grelina no remodelamento cardíaco no coração de camundongos obesos após a hipernutrição na lactação. A obesidade foi induzida por redução de ninhada e camundongos adultos (180 dias) foram divididos em: grupo hiperalimentado, GH com obesidade decorrente de hipernutrição na lactação e controle, GC. Cardiomiócitos (cmi) do ventrículo esquerdo foram analisados por microscopia de luz e estereologia, o conteúdo e fosforilação de proteínas cardíacas: receptor de grelina (hormônio do crescimento secretagogo receptor 1a, GHSR-1a), proteína quinase-B (AKT e pAKT), phosphatidil inositol 3-quinase (PI3K), proteína quinase ativada por AMP (AMPK e pAMPK), m-TOR, pmTOR, Bax, Bcl2 e actina foram analizados por western blotting. A expressão gênica do GHSR-1a foi analisada por PCR em tempo real. A respirometria de alta resolução dos cardiomiócitos foi analisada por oxígrafo OROBOROS. Significância estatística (P< 0,05) determinada por teste t-Student não-pareado. Nossos dados demonstram que a hipernutrição na lactação induz aumento no peso corporal, iniciado aos 10 dias de idade, persistindo até os 180 dias de idade. A glicemia, peso do fígado, e da gordura visceral foram maiores no grupo GH. Além disso, o grupo GH também apresentou aumento no peso do coração e razão peso do coração/CT (comprimento da tíbia), indicando hipertrofia e remodelamento cardíaco, aumento na expressão e conteúdo de GHSR-1a no coração, associado ao maior conteúdo de PI3K e maior conteúdo e fosforilação de AKT, diminuição no conteúdo de Bcl2. Em contraste, o conteúdo e fosforilação da AMPK e mTOR no coração não foram diferentes entre os grupos. Os níveis de grelina plasmático no GH foram menores. A respiração do GH com grelina foi menor que no GC com grelina. A incubação das fibras cardíacas com grelina resultou em aumento do fluxo respiratório após adição de citocromo c nos grupos com grelina, indicando dano à membrana mitocondrial e extravazamento de citocromo c. Os grupos GC com grelina e GH sem grelina apresentaram RCR menor comparado ao GC sem grelina, indicando desacoplamento mitocondrial. Nossos resultados mostram que a hipernutrição na lactação induz diminuição do nível de grelina plasmática e aumento da expressão do GHS-R1a no cardiomiócito do animal quando adulto. Tal processo determina aumento da sensibilidade a grelina no coração, processo que ocorre independentemente de variações do AMPK e mTOR. Sugerimos uma redução no efeito protetor da ação da grelina na AMPK. Também, demonstramos que o remodelamento do miocárdio nestes animais adultos associa-se a GHSR-1a, PI3K, e fosforilação da AKT, mas não com AMPK e mTOR na vida adulta.

Efeito da hiperalimentação na lactação sobre a regulação da adiposidade corporal e sinalização da grelina no tecido adiposo branco de camundongos jovens e adultos

A obesidade é um dos maiores problemas de saúde pública que cresce em todo o mundo, resultante de um desequilíbrio entre ingestão alimentar e gasto energético. O aumento da adiposidade leva ao desenvolvimento de alterações funcionais. Pode-se dizer que a obesidade é o principal fator de risco para o desenvolvimento de doenças crônicas de maior prevalência como dislipidemias, doenças cardiovasculares e diabetes do tipo 2, acarretando na redução da qualidade e expectativa de vida. A Grelina é um hormônio sintetizado pelo estômago, que atua em diferentes tecidos através de um receptor específico (GHS-R1a), incluindo hipotálamo e tecido adiposo. A grelina tem uma ação direta sobre a regulação hipotalâmica da ingestão alimentar, induzindo um efeito orexígeno. Por outro lado, a grelina também modula o armazenamento de energia nos adipócitos. Esta dupla ação sugere que este hormônio pode atuar como uma ligação entre o sistema nervoso central e mecanismos periféricos. Portanto, considerando que a hiperalimentação neonatal induz obesidade na idade adulta por mecanismos desconhecidos, neste estudo foram pesquisados os efeitos da hiperalimentação no início da vida sobre o desenvolvimento da obesidade e, em particular, a sinalização da grelina no tecido adiposo em ratos jovens e adultos. Foram utilizados camundongos Swiss hiperalimentados através do modelo de redução da ninhada. Para induzir a hiperalimentação as ninhadas foram reduzidas a 3 filhotes machos por lactante no 30 dia de vida pós-natal. As ninhadas controles foram ajustadas em 9 filhotes por lactante. Foram avaliados parâmetros antropométricos como: massa corporal e massa do tecido adiposo visceral. A glicemia de jejum foi avaliada utilizando glicosímetro e fitas teste. A análise do conteúdo das proteínas envolvidas na via de sinalização da grelina foram detectadas pelo método de Western Blotting. Os grupos controle (C) e hiperalimentado (H) foram estudados aos 21 e 180 dias de vida. Os dados demonstram que a hipernutrição no início da vida induz um aumento significativo no peso corporal dos camundongos jovens, começando aos 10 dias, e este aumento de peso persistiu até à idade adulta (180 dias de idade). A glicemia e o peso da gordura visceral foram significativamente maiores no grupo hiperalimentado aos 21 e 180 dias, quando comparado com o grupo controle. Os níveis plasmáticos de grelina acilada apresentaram uma redução de 70% nos animais jovens e 49% adultos obesos. Além disso, no tecido adiposo branco, observamos um maior conteúdo (242%) do receptor de grelina (GHSR1a) nos animais hiperalimentados com 21 dias, e este aumento foi associado à modulação positiva do conteúdo e fosforilação de proteínas envolvidas no estoque e utilização de energia celular, tais como AKT, PI3K, AMPK, GLUT-4, e CPT1. No entanto, ao chegar à idade adulta os animais hiperalimentados não apresentaram diferença significativa no conteúdo de GHS-R1a e das proteínas AKT, PI3K, AMPK, GLUT-4, e CPT1. O conteúdo de PPARɣ foi menor no grupo obeso aos 21e 180 dias. Basicamente, mostramos que o metabolismo do tecido adiposo está alterado na obesidade adquirida no início da vida e, provavelmente, devido a essa modificação, ocorre um novo padrão da via de sinalização da grelina.