Szomatotípus dominancia és szexuális érés

The purposes of the study were 1) to examine indices of sexual maturation in athlete girls having predominantly endo-, meso- and ectomorph physique; 2) to demonstrate alterations in somatotype by breast maturation. 813 pubertal athlete girls (aged between 10 and 17 years) belonging to different sports events were studied. Somatotype was determined by the Heath–Carter method. Somatotype dominance was decided arbitrarily: the cut-off point was 4.75 unit for the dominant component. The other two components were minimum 1.5 unit below the dominant one. Breast development was rated according to Tanner’s suggestions. Data for menarche were collected by “status-quo” method. The age medians of maturation indices were calculated. Athletes with endomorph dominance matured the earliest. Mesomorphs started to develop their sexual characteristic later than endomorphs and had the latest completion of breast maturation. Girls with ectomorph predominance matured the latest and the fastest. Meso- and ectomorphs preserved their dominant component during breast maturation. Similarly to normal pubescent girls, they increased their relative fatness, but in a different rate. Staying in the mesomorphic endomorph field, endomorphs did not change their body form as maturation proceeded

Preventive Impact of Long-Term Ingestion of Chestnut Honey on Glucose Disorders and Neurodegeneration in Obese Mice

The purpose of the present study was to evaluate the impact of long-term honey ingestion on metabolic disorders and neurodegeneration in mice fed a high-fat diet (HFD). Three groups of mice were fed with a standard diet (STD), HFD or HFD supplemented with honey (HFD-H) for 16 weeks. Biochemical, histological, Western blotting, RT-PCR and Profiler PCR array were performed to assess metabolic parameters, peripheral and central insulin resistance and neurodegeneration. Daily honey intake prevented the HFD-induced glucose dysmetabolism. In fact, it reduced plasma fasting glucose, insulin and leptin concentrations and increased adiponectin levels. It improved glucose tolerance, insulin sensitivity and HOMA index without affecting plasma lipid concentration. HFD mice showed a significantly higher number of apoptotic nuclei in the superficial and deep cerebral cortex, upregulation of Fas-L, Bim and P27 (neuronal pro-apoptotic markers) and downregulation of Bcl-2 and BDNF (anti-apoptotic factors) in comparison with STD- and HFD-H mice, providing evidence for honey neuroprotective effects. PCR-array analysis showed that long-term honey intake increased the expression of genes involved in insulin sensitivity and decreased genes involved in neuroinflammation or lipogenesis, suggesting improvement of central insulin resistance. The expressions of p-AKT and p-GSK3 in HFD-H mice, which were decreased and increased, respectively, in HFD mouse brain, index of central insulin resistance, were similar to STD animals supporting the ability of regular honey intake to protect brain neurons from insulin resistance. In conclusion, the present results provide evidence for the beneficial preventative impact of regular honey ingestion on neuronal damage caused by HFD

Mechanisms of agouti-induced obesity : effects on adipocyte metabolism and interaction with insulin

Dominant mutations at the agouti locus such as viable yellow (Avy) cause a syndrome of marked obesity and diabetes in addition to a characteristic yellow coat color. Recent studies indicate that agouti acts both centrally and peripherally to induce obesity.We hypothesized that agouti modulation of adipocyte metabolism may account for part of the yellow mouse obesity. Studies from our laboratory indicated that agouti increases adipocyte de novo lipogenesis and triglyceride levels in a calcium (Ca2+)-dependent manner. However, the precise molecular mechanisms that are involved in agouti regulation of adipocyte metabolism, have not been determined. The objective of this work is to determine the mechanisms of agouti action on adipocyte metabolism using two specific markers of adiposity: (1) leptin, the product of the obesity gene, ob which is secreted by fat cells in amounts that are positively correlated with adiposity, and (2) fatty acid synthase (FAS), a key de novo lipogenic enzyme which is highly responsive to hormonal and nutritional changes. We investigated effects of agouti and its interaction with insulin on leptin synthesis and secretion in cultured adipocytes as well as in transgenic mice overexpressing agouti in adipose tissue (under the control of adipocyte specific promoter aP2). We also investigated whether transcription rate of the FAS gene in cultured adipocytes is altered via agouti specific response elements in the FAS promoter. Results from this study demonstrated that agouti significantly increase intracellular and plasma leptin levels in aP2 transgenic mice relative to control mice. Further,administration of insulin (1 unit/day) increased intracellular leptin levels without any significant effect on plasma leptin. The lack of insulin effect on plasma leptin levels were further confirmed by in vitro assays; media collected from 3T3-L1 adipocytes that were treated with 100 nM insulin showed no effect on leptin secreted into the culture media. These results suggest that agouti increases leptin synthesis and secretion while insulin only modulates leptin synthesis. Agouti may increase leptin levels as a result of its effect on triglyceride storage. Alternatively, agouti may directly regulate leptin synthesis and secretion by altering ob gene expression. However, further studies are required to determine mechanisms of agouti and insulin regulation of leptin. In addition to agouti regulation of leptin, our study demonstrate that both agouti and insulin upregulate FAS gene transcription. Furthermore, agouti and insulin exert additive effects on FAS gene transcription. Using transfection assays, we demonstrated that transcriptional regulation of the FAS gene by agouti was mediated by novel agouti response elements within the FAS promoter. This agouti responsive region mapped to a region distinct from the previously identified insulin responsive region. We confirmed the specificity of adipocyte nuclear factor(s) binding to this response region by electrophoretic gel mobility-shift assays. Interestingly, agouti response elements appeared to be also responsive to intracellular calcium.In summary, the results from this study indicate that agouti effects on adipocyte may contribute to yellow mouse obesity. We demonstrated that agouti effects adipocyte metabolism by (1) inducing synthesis and secretion of leptin levels, and (2) by increasingFAS transcription rate via novel agouti responsive elements that are distinct from the previously mapped insulin response element. Results from this investigation are relevant to human obesity. Unlike mice, humans normally express agouti in adipose tissue. As shown in aP2 transgenic mice, high levels of insulin (especially in hyperinsulinemic type II diabetic patients) combined with agouti expression in adipose tissue may contribute to increased adiposity. Therefore, modulation of agouti expression/action may be a potential target in therapeutic intervention to treat obesity and diabetes

The Effect of Gut Hormones on Metabolism and Energy Homeostasis

The increasing prevalence of obesity, and its associated morbidity and mortality, together with limited treatment options, underscores an urgent need for investigation into effective therapeutic interventions. Gut hormones have been identified as integral factors in the regulation of appetite. This thesis examines two signalling systems involved in the gastrointestinal regulation of energy homeostasis: Peptide YY (PYY) and Proglucagon-derived peptides. PYY is a gut hormone released from the L cells of the intestine after the ingestion of food and elicits its effects via the Y2 receptor. The predominant circulating form of PYY, PYY3-36, has been shown to acutely reduce food intake when administered peripherally at physiological concentrations in both lean and obese rodents and humans. However, several groups have shown that continuous administration of PYY3-36 via osmotic mini-pumps results in a transient reduction in food intake. It has been suggested that an apparent desensitisation to the anorectic effects of PYY3-36 may be due to the physiological defence of body weight and counter regulatory mechanisms; however tolerance due to receptor downregulation may also occur. In this thesis, I aimed to elucidate if the transient anorectic effect of PYY3-36 is a result of direct tolerance to the peptide itself or if this is indirect, due to the homeostatic defence of body weight. I have shown that the anorectic effect of PYY3-36 is attenuated following prior exposure to a low dose, suggesting tolerance at the receptor level. In addition, animals which were food restricted preceding an infusion of PYY3-36 remained sensitive to the anorectic effects, suggesting that body weight change alone cannot result in the hyperphagic response. However, no change in Y2 mRNA receptor expression following PYY3-36 infusion was detected. The proglucagon peptide family includes the hormones Glucagon like peptide-1 (GLP-1) and Glucagon (GCG). GLP-1 is release from the L-cells of the intestine in response to food intake and has known actions as a satiety factor and incretin hormone. GCG is released under fasting conditions and in response to adrenergic stimulation to stimulate gluconeogenesis and glycogenolysis, as well as to increase energy expenditure. Recent evidence suggests that simultaneous co-agonism of the GLP-1 and GCG receptors may be beneficial to the treatment of obesity and diabetes. In this thesis, I explore the development of a GLP-1R and GCGR co-agonist which reduces food intake and increases energy expenditure in rodents. Furthermore, to investigate the mechanism of GCG agonism on energy expenditure, I evaluate the effect of the specific dual agonist, GX6, on metabolic gene expression in brown adipose tissue and the liver. Overall, this thesis evaluates the potential roles of PYY, GLP-1 and GCG receptor agonism as novel therapies for obesity

Regulation of insulin signalling by exercise in skeletal muscle

Regular physical activity improves insulin action and is an effective therapy for the treatment and prevention of type 2 diabetes. However, little is known of the mechanisms by which exercise improves insulin action in muscle. These studies investigate the actions of a single bout of exercise and short-term endurance training on insulin signalling. Twenty-four hours following the completion of a single bout of endurance exercise insulin action improved, although greater enhancement of insulin action was demonstrated following the completion of endurance training, implying that cumulative bouts of exercise substantially increase insulin action above that seen from the residual effects of an acute bout of prior exercise. No alteration in the abundance and phosphorylation of proximal members of the insulin-signalling cascade in skeletal muscle, including the insulin receptor and IRS-1 were found. A major finding however, was the significant increase in the serine phosphorylation of a known downstream signalling protein, Akt (1.5 fold, p ≤0.05) following an acute bout of exercise and exercise training. This was matched by the observed increase in protein abundance of SHPTP2 (1.6 fold, p ≤0.05) a protein tyrosine phosphatase, in the cytosolic fraction of skeletal muscle following endurance exercise. These data suggest a small positive role for SHPTP2 on insulin stimulated glucose transport consistent with transgenic mice models. Further studies were aimed at examining the gene expression following a single bout of either resistance or endurance exercise. There were significant transient increases in IRS-2 mRNA concentration in the few hours following a single bout of both endurance and resistance exercise. IRS-2 protein abundance was also observed to significantly increase 24-hours following a single bout of endurance exercise indicating transcriptional regulation of IRS-2 following muscular contraction. One final component of this PhD project was to examine a second novel insulin-signalling pathway via c-Cbl tyrosine phosphorylation that has recently been shown to be essential for insulin stimulated glucose uptake in adipocytes. No evidence was found for the tyrosine phosphorylation of c-Cbl in the skeletal muscle of Zucker rats despite demonstrating significant phosphorylation of the insulin receptor and Akt by insulin treatment and successfully immunoprecipitating c-Cbl protein. Surprisingly, there was a small but significant increase in c-Cbl protein expression following insulin-stimulation, however c-Cbl tyrosine phosphorylation does not appear to be associated with insulin or exercise-mediated glucose transport in skeletal muscle

La deleción de Ptpn1 protege a las células ovales frente a la lipoapoptosis mediante la regulación de la formación y dinamismo de las gotas lipídicas

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Bioquímica. Fecha de lectura: 27-01-2022Nonalcoholic fatty liver disease (NAFLD), the most common cause of chronic liver disease worldwide, ranges from benign and reversible steatosis that is accompanied by insulin resistance and elevated circulating free fatty acids (FAs), to nonalcoholic steatohepatitis (NASH), cirrhosis and culminates in some cases in hepatocarcinoma. The main drivers of NAFLD-associated lipotoxicity are saturated FAs (SFAs), although the molecular mechanisms involved in liver cell death have not been fully defined. Lipid droplets (LDs) buffer the excess of toxic lipid species, including SFAs. The enzyme stearoyl CoA desaturase 1 (SCD1 (encoded by the Scd1 gene) catalyzes desaturation of SFAs such as palmitic acid (PA) and stearic acid (SA) and plays an essential role in the formation of hepatic triglycerides (TGs) easily stored in the LDs. Of relevance for this Thesis, the LDs emerge from the endoplasmic reticulum (ER) and during their life cycle contact with other organelles, not only the ER and mitochondria, but also autophagosomes, lysosomes and peroxisomes through membrane contact sites. Hepatic progenitor cells in humans (HPCs) or oval cells (OCs) in mice (HPCs/OCs) constitute 1-3% of the cell population in the normal adult liver. They are progenitor hepatic stem cells that, upon liver damage, proliferate and differentiate into hepatocytes or cholangiocytes in a process known as ductular reaction, due to their ability to express markers of both biliary and hepatocyte lineages. Activation of HPCs/OCs has been related to hepatocyte injury during chronic liver diseases including NAFLD. However, whether the lipotoxic milieu of the NAFLD affects HPCs/OCs´s viability has not been addressed. Protein tyrosine phosphatase 1B (PTP1B), encoded by the Ptpn1 gene, plays a fundamental role in modulating signaling cascades triggered by hormones/growth factors including insulin, insulin-like growth factor-1 (IGF-1), epidermal growth factor (EGF) and hepatocyte growth factor (HGF), all relevant for liver regeneration. In this Thesis, we have investigated the molecular and cellular processes involved in the susceptibility of HPCs/OCs expressing or not PTP1B to lipotoxicity. We demonstrated that PA induced apoptotic cell death in wild-type (Ptpn1+/+) HPCs/OCs in parallel to oxidative stress and impaired autophagy. This lipotoxic effect was attenuated in HPCs/OCs lacking Ptpn1 that showed up-regulated antioxidant defences, increased unfolded protein response (UPR) signaling, higher ER content and elevated Scd1 expression/activity. These effects in Ptpn1-/- HPCs/OCs concurred with an active autophagy, higher mitochondrial efficiency and a molecular signature of starvation, favoring LD formation and catabolism. Autophagy blockade in Ptpn1-/- HPCs/OCs reduced Scd1 expression, mitochondrial fitness, LD formation and restored lipoapoptosis, an effect also mimicked by Scd1 silencing. The identification of LDs in HPCs/OCs in the livers from Ptpn1-/- mice with NAFLD that concurred with attenuated disease features opens new therapeutic perspectives to ensure HPCs/OCs viability and plasticity under lipotoxic liver damag

Adipokines 2.0

Once viewed solely as fat storage cells, adipocytes and their adipokines have now been proven to be central for human health. Understanding that overweight and obesity may increase the risk for various diseases requires detailed characterization of adipokine function. Weight gain, weight regain, and fasting affect adipocyte health and accordingly their secretome. Different adipose tissue deposits exist and they vary in cellular composition and function. The evidence is strong of a role of adipokines in cancer, reproductive function, neurological diseases, cardiovascular diseases ,and rheumatoid arthritis. Adipokines are considered useful biomarkers for adipose tissue and metabolic health, and may be used as diagnostic tools in rheumatoid arthritis, cancer, or sepsis. This book contains 10 original articles and 9 review articles focusing on these bioactive peptides. Several articles deal with chemerin, an adipokine discovered more than 20 years ago. Data so far have resulted in promising insights related to its biological function. We are only beginning to understand the multiple roles of chemerin, the mechanisms regulating its activity, and the signaling pathways used by this chemokine. Adipokine receptor agonists and antagonists may result in the formulation of novel drugs and ultimately may lead to new therapeutic targets to be used in clinical practice

Central regulation of energy homeostasis and the reproductive axis

Alarin is a recently discovered splice variant of the galanin-like peptide (GALP) gene. Alarin is a highly conserved 25 amino acid peptide which shares its first 5 amino acids with GALP, but lacks the galanin receptor binding domain, suggesting that it mediates its biological effects through alternative receptors. Alarin has been detected in the rodent hypothalamus. GALP has a well-characterised role in the integration of energy and reproductive homeostasis. Intracerebroventricular (ICV) alarin increases food intake and plasma luteinising hormone (LH) levels in rats. Alarin stimulates the release of the orexigenic neuropeptide Y (NPY) and gonadotrophin releasing hormone (GnRH) from hypothalamic explants, and GnRH release from an immortalised GnRH releasing cell line. Pre-treatment with a GnRH antagonist blocked the alarin-induced increase in plasma LH levels in vivo. These results suggest that ICV alarin activates the HPG axis via hypothalamic GnRH release. My data also suggests that alarin does not bind to the known galanin receptors. The ventral tegmental area (VTA) is the origin of the mesolimbic dopamine pathway, which mediates the rewarding properties of palatable food. Recent work suggests that the VTA reward pathway is regulated by appetite-regulating signals including leptin and ghrelin. I have shown that intra-VTA melanocortin receptor agonist administration inhibits food intake and administration of an antagonist stimulates food intake in rats, suggesting that the melanocortin system may be involved in hedonic regulation of appetite, in addition to its role in homeostatic regulation of appetite. These studies have elucidated the biological effects of alarin in the regulation of appetite and the HPG axis, and identified a role for the melanocortin system in regulating the central reward circuitry modulating food intake. Further work is required to determine the receptor by which alarin mediates its effect and its precise physiological function, and the physiological importance of the VTA melanocortin system

Role of methylglyoxal in the pathogenesis of insulin resistance

Methylglyoxal (MG) is a reactive metabolite presents in all biological systems. The accumulation of MG in diabetic patients and animals has been long recognized. Recently, studies have shown that MG levels are elevated in hypertensive rats. However, the pathological effects of MG in diabetes and related insulin resistance syndrome such as obesity are currently unknown. In the present study, the role of MG in the pathogenesis of insulin resistance was investigated. First, it was observed that MG induced structural and functional changes of insulin. Incubation of human insulin with MG in vitro yielded MG-insulin adducts, as evidenced by additional peaks observed upon mass spectrometric (MS) analysis. Tandem MS analysis of insulin B-chain adducts confirmed attachment of MG at an arginine residue. [3H]-2-deoxyglucose uptake ([3H]-2-DOG) by 3T3-L1 adipocytes was significantly and concentration-dependently decreased after treatment with MG-insulin adducts, in comparison with the effect of native insulin at the same concentration. A significant decrease of glucose uptake induced by MG-insulin adducts was also observed in L8 skeletal muscle cells. Unlike native insulin, MG-insulin adducts did not inhibit insulin release from pancreatic â-cells. The degradation of MG-insulin by cultured liver cells was also decreased. In conclusion, MG modifies insulin by attaching to internal arginine residue in the â-chain of insulin. The formation of this MG-insulin adduct decreases insulin-mediated glucose uptake, impairs autocrine control of insulin secretion, and decreases insulin clearance. These structural and functional abnormalities of the insulin molecule may contribute to the pathogenesis of insulin resistance. Second, the effects of MG on the insulin signaling pathway were investigated. After 9 weeks of fructose treatment, an insulin resistant state was developed in Sprague-Dawley (SD) rats, demonstrated as increased triglyceride and insulin levels, elevated blood pressure, and decreased insulin-stimulated glucose uptake by adipose tissue. A close correlation between insulin resistance and the elevated MG accumulation in adipose and skeletal muscle tissues was observed. The insulin resistant state and the elevated MG level were reversed by the MG scavenger, N-acetyl cysteine (NAC) and metformin. In cultured adipose cells, MG treatment impaired insulin signaling as measured by decreased tyrosine phosphorylation of insulin-receptor substrate-1 (IRS-1) and the decreased kinase activity of phosphatidylinositol 3-kinase (PI3K). The ability of NAC to block MG-impairment of PI3K activity and IRS-1 phosphorylation further confirmed the role of MG in the development of insulin resistance. In cultured skeletal muscle cells, MG treatment significantly reduced the expression of IRS-1 and PI3K at the mRNA level. Similar to adipose cells, MG also decreased tyrosine phosphorylation of IRS-1 and PI3K activity. We also examined the mechanism of metformin to inhibit AGEs. Using mass spectrometry, stable metformin-MG adducts were identified. In addition, we investigated the causative effect of MG in the pathogenesis of obesity, another form of insulin resistance. This study revealed a previously unrecognized effect of MG in stimulating adipogenesis by up-regulating Akt signaling. In Zucker fatty rats, dramatically increased MG accumulations in serum and different tissues were identified. The serum MG level increased age. In 10 and 12 week-old obese rats, MG was 144±50% and 171±15% of the age-matched control Zucker rats; this value increased to 241±7 % and 329±10% by 14 and 16 weeks (