In this thesis it is demonstrated that leptin and insulin hyperpolarise hypothalamic glucose responsive neurones via the activation of the large conductance ATP-sensitive (K_APT) channel. This channel was potassium selective, had a single channel conductance of 150 pS and channel activity was inhibited by micromolar tolbutamide and millimolar internal ATP. Brain cortical cell bodies and nerve terminals possess a large-conductance calcium-activated potassium (BK) channel. The nerve terminal BK channel switched from high to low activity modes, whereas cell body BK channel activity inactivates during depolarisation. Furthermore, BK channel inactivation was abolished by internal trypsin treatment, suggesting an inactivating particle was associated with the channel. Internal application of alkaline phosphatase irreversibly removed mode switching and inactivation of cortical BK channels. Blocking the cell body BK channel pore with 100 mM intracellular tetraethylammonium (TEA) prevented alkaline phosphatase removal of inactivation, indicating that the phosphatase site of action was located close to the pore. Finally, protein kinase A (PKA) increased the occurrence of the high BK channel activity mode whereas PKA retarded the full recovery of BK inactivation induced by hyperpolarisation. In a separate study it was demonstrated that stably expressed human brain BK (<I>hSlo</I>) channels inactivate in a trypsin-insensitive manner. This inactivation was not due to barium contamination, since 5 μM internal barium blocked <I>hSlo</I> channels only during strong depolarisations, yet inactivation was observed at less positive potentials. Furthermore co-expression of either <I>hSlo</I>β-1, or voltage-gated potassium (Kv) β1.1 or β2.1 subunits with the <I>hSlo</I> α-subunit did not affect the extent or rate of channel inactivation. Finally, the Kvβ-subunits moved the calcium and voltage curves of <I>hSlo</I> to more negative voltages and altered the activation and deactivation kinetics in a manner almost identical to that observed on co-expression of <I>hSlo</I>β-1 subunit with <I>hSlo</I> or by increasing the internal calcium concentration.

Metabolic homeostasis is orchestrated by the hypothalamus through the neuroendocrine and the autonomic nervous systems. The hypothalamic nuclei respond to the peptide leptin secreted from adipose tissue to suppress feeding and increase energy expenditure by promoting fat metabolism via sympathetic activity. Another important, but perhaps less appreciated function of central leptin signaling is to elevate peripheral insulin sensitivity. Environmental and genetic risk factors that affect hypothalamic leptin signaling can lead to obesity and type 2 diabetes mellitus (T2DM). Here, we discovered that LIM domain only 4, LMO4, is a novel protein participating in central leptin signaling. In a process strikingly similar to T2DM in humans, CaMKIIα-Cre;LMO4flox/flox mice, which have LMO4 knocked out in the postnatal brain including the hypothalamus, develop visceral adiposity, reduced insulin sensitivity, obesity and diabetes when fed with regular chow. Central leptin signaling was significantly lost in key hypothalamic nuclei of mutant mice. Caloric restriction prevents obesity but not insulin resistance in these mice. Taken together, our results suggest that LMO4 function in the brain is required for central leptin signaling to control fat metabolism and peripheral insulin sensitivity.

Dietary flaxseed has cardioprotective effects that may be achieved through its rich content of the omega-3 fatty acid, alpha linolenic acid (ALA). We investigated the effects of dietary flaxseed both with and without an atherogenic cholesterol-enriched diet to determine the effects of dietary flaxseed on the expression of the adipose cytokines leptin and adiponectin. Rabbits were fed one of four diets: a regular (RG) diet, or a regular diet with added 0.5% cholesterol (CH), or 10% ground flaxseed (FX), or both (CF) for 8 weeks. Levels of leptin and adiponectin expression were assessed by RT-PCR in visceral adipose tissue. Consumption of flaxseed significantly increased plasma and adipose levels of ALA. Leptin, but not adiponectin, mRNA expression was lower in CH animals and was elevated in CF animals. Changes in leptin expression were strongly and positively correlated with adipose ALA levels and inversely correlated with levels of en face atherosclerosis. Our data demonstrate that the type of fat in the diet as well as its caloric content can specifically influence leptin expression. The findings support the hypothesis that the beneficial cardiovascular effects associated with flaxseed consumption may be related to a change in leptin expression.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available in print.

Thesis (Ph.D.)--University of Wollongong, 2004. / Includes appendices. Typescript. Includes bibliographical references: leaf 154-184.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 148-168).

Thesis (Ph. D.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M. Med. Sc.)--University of Hong Kong, 2006.

The current trend in beef production is quality improvement. Meat quality is influen-ced by many factors, eg. genetic background, age, nutrition, sex, breed, environment, housing type, etc. One of these factors is the quality of beef and storage of intramuscular fat and marbling. Marbling has an effect on juiciness, tenderness and flavor of the meat. This paper describes the influence of UASMS2 polymorphism in the gene leptin to the quality of beef meat, storage of intramuscular fat and marbling. The study was conducted on 174 bulls of Czech pied cattle breed. For the determination of genotypes were used sequencing method. Based on the association analysis was detected significant effect on the quality of the meat and intramuscular fat deposition. The results of association analy-sis were compared with previously published scientific articles by other authors. The work includes a literature review for topic of candidate genes, the current state of the problem, significance and methods for studying genes and storing fat in cattle.

Orientador: Mario Jose Abdalla Saad / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-24T20:19:32Z (GMT). No. of bitstreams: 1 Silva_CarlaGrazielleBueno_M.pdf: 6872753 bytes, checksum: db709bf5644b03a8beed89ed9769f29c (MD5) Previous issue date: 2014 / Resumo: A leptina é um polipeptídeo derivado do tecido adiposo e tem como principal função informar o estado nutricional do indivíduo a centros hipotalâmicos, que por sua vez regulam a ingestão e o gasto energético. Tais ações são orquestradas pela fosforilação do receptor ObRb em tyr 985 e 1138, sendo esta última relacionada ao metabolismo e à via da Stat3. Recentemente foi demonstrado que os altos níveis séricos de leptina, presentes na obesidade induzida por dieta hiperlipídica (DH), correlacionam-se fortemente com hipertensão arterial. Por outro lado, indivíduos obesos possuem resistência às ações metabólicas da leptina (saciedade e termogênese). Para investigar as vias moleculares hipotalâmicas que caracterizam a atividade seletiva da leptina sobre o efeito de aumento da pressão arterial, ratos Sprague Dawley adultos foram alimentados com ração padrão (RP) ou DH por três meses e submetidos à injeção crônica intracerebroventricular de leptina (2?g/dia) ou salina (2?l) por 10 dias. Pressão Arterial Sistêmica (PAS) , ingestão e gasto energético foram avaliados antes e depois do tratamento. O grupo RP+leptina teve redução de ingestão de 109,48±8,48 para 57,3±7,04 kcal/dia, aumento do gasto energético de 85,6±1,87 para 94,4±0,58 kcal/dia/kg^0,75 e consequente redução de peso de 15,25±3,54 g (P<0,0001 todos os dados), o que não ocorreu no grupo DH+leptina. Porém, tanto no grupo RP como em DH, a leptina causou aumento da PAS de 10,44±0,12% e 14,22±1,9%, respectivamente. Como esperado, animais obesos apresentaram valores aumentados de leptina sérica, quando comparados ao grupo RP (RP: 2,24±0,38 ng/dl e DH: 9,88±1,82 ng/dl, p<0,05). Adicionalmente, foram avaliadas as principais vias de sinalização ativadas por leptina no hipotálamo. No grupo RP+leptina houve aumento significativo da atividade das proteínas Stat3, Akt e expressão de MAPK 1 e 2 (MAPK). No entanto, no grupo DH+leptina, foi observado apenas aumento da expressão da via da MAPK. Ambos os grupos DH e RP tratados com leptina apresentaram maior fosforilação de ObRb tyr985 de maneira semelhante, o que não foi observado em relação à ObRb tyr1138 É possível notar que a via dependente de ObRb tyr985 encontra-se responsiva à leptina em DH e RP e que ObRb tyr1138 bem como a proteína relacionada Stat3 e Akt estão reduzidas em animais obesos. Desta forma, pode-se sugerir que na obesidade induzida por DH, a via hipotalâmica ObRb tyr985 / MAPK, diferentemente das outras vias, não fica resistente e pode estar relacionada às ações cardiovasculares da leptina / Abstract: Leptin is an adipose tissue-derivated polypeptide and its main function is to inform the individual's nutritional status to hypothalamic centers, which in turn regulate food intake and energy expenditure. Such actions are orchestrated by phosphorylation of ObRb receptor on tyrosine 985 and 1138, the latter is related to metabolism and Stat3 pathway. Recently it was demonstrated that high serum levels of leptin, which is seen in diet-induced-obesity, correlates strongly with hypertension. On the other hand, obese individuals have resistance to metabolic actions of leptin (satiety and thermogenesis). To investigate the molecular hypothalamic pathways that characterize the selective activity of leptin on the effect of blood pressure increase, adults Sprague Dawley rats were fed with standard diet (SD) ou high fat diet (HFD) for three months and were submitted to chronic intracerebroventricular injection of leptin (2?g/dia) or saline (2?l) for 10 days. Blood pressure (BP), food intake and energy expenditure were assessed before and after treatment. SD + leptin group had reduced food intake from 109,48±8,48 to 57,3±7,04 kcal / day, increased energy expenditure from 85,6±1,87 to 94,4±0,58 kcal/day/kg^0,75 and consequently weight reduction of 15,25±3,54 g (P <0.0001 all) which did not occur in HFD + leptin. However, both SD and HFD group, leptin increased BP of 10.44 ± 0.12 % and 14.22 ± 1.9%, respectively. As expected, obese animals had elevated levels of serum leptin when compared to SD group (SD: 2,24±0,38 ng/dl and HFD: 9,88±1,82 ng/dl, p<0,05). Additionally, we evaluate the main activated signal pathways by leptin in hypothalamus. SD + leptin group showed a significant increase in activity of Stat3, Akt and in MAPK expression. However, DH + leptin manifested an increase only on the expression of MAPK pathway. Both SD and HFD leptin-treated groups had higher ObRb tyr985 phosphorylation, which was not observed with the ObRb tyr1138. It was possible to see that ObRb tyr985 dependent pathway is responsive to leptin in SD and HFD, and ObRb tyr1138 as well as the related protein Stat3 and Akt are reduced in obese animals. Therefore, it may be suggested that in HFD-induced obesity, hypothalamic pathway ObRb tyr985 / MAPK, unlike the other pathways, is not resistent and can be related to cardiovascular actions of leptin / Mestrado / Fisiopatologia Médica / Mestra em Ciências