O câncer é uma doença que aflige pessoas no mundo todo, e mata muitas todos os anos. Muitos estudos são desenvolvidos para sintetizar novos compostos com atividade antitumoral cada vez melhor. O maior número de compostos possibilita um maior número de possibilidades de cura, já que alguns tumores podem adquirir resistência ao medicamento, sendo necessária a troca por outro.<br /> Para que não seja feita uma síntese aleatória de compostos, desperdiçando tempo, reagentes e dinheiro sintetizando compostos inativos, um estudo teórico prévio para orientar a síntese é válido. Um estudo QSAR pode orientar a síntese indicando quais compostos são mais interessantes de serem sintetizados e quais são menos interessantes. Assim, há o desenvolvimento de mais compostos ativos em um menor tempo, do que se fosse realizada sínteses e testes para todos os compostos possíveis.<br /> O presente estudo tem esse foco, avaliar a relação quantitativa entre a estrutura molecular e a atividade antitumoral de compostos &beta;-carbolínicos substituídos nas posições 1 e 3. Nesse estudo será possível elucidar quais características são relevantes para que os compostos sejam ativos no tratamento de câncer de pulmão e melanoma. / Cancer is a disease that afflicts people worldwide and kills many every year. Many studies are developed to synthesize new compounds with better antitumor activity. The largest number of compounds allows a greater number of curability, because some tumors may acquire used drug resistance and are necessary different drugs.<br /> To avoid a random synthesis of compounds, wasting time, money and reagents in synthesizing inactive compounds, a previous theoretical study as guide of synthesis is valid. A QSAR study can guide the synthesis indicating which compounds are most interesting to be synthesized and which are less interesting. Thus, more compounds active are developed in a shorter time.<br /> The present study has this focus, assess the quantitative relationship between molecular structure and antitumor activity of &beta;-carboline compounds substituted in positions 1 and 3. In this study will be possible to elucidate characteristics that are relevant to the compounds under study be active in the treatment of lung cancer and melanoma.

Cognitive impairment after stroke or transient ischemic attack (TIA) is a prototype of vascular cognitive impairment (VCI). 30% of subjects with poststroke cognitive impairment are detected Alzheimer’s disease (AD)-like amyloid-beta (Aβ) retention with reference to ¹¹C-Pittsburgh compound B (PiB) positron emission tomography (PET). Therefore, poststroke cognitive impairment provides a good clinical context for the study about contribution of comorbid Alzheimer’s and cerebrovascular disease (CVD) pathologies to cognition. In this thesis, there are four studies addressing the effect of Aβ on poststroke cognitive impairment. / The first study investigated the accuracy of diagnosing cognitive impairment subtype in subjects with stroke/TIA using current clinical diagnostic criteria with reference to ¹¹C-PiB PET. We found the agreement between the pre and the post-PET diagnoses was poor (Kappa=0.194). The overall accuracy of clinical diagnosis of pure VCI (pVCI) was 66.7%, while that of mixed (i.e., AD with CVD) VCI (mVCI) was 68.0%. / Dementia may occur after stroke/TIA within 3-6 months (early poststroke dementia [PSD]) or from 3-6 months onward (delayed PSD). In the second study, apart from age and history of diabetes mellitus, chronic small vessel disease (SVD) lesions including lacunes and white matter changes (WMC) predicted delayed PSD as they did for early PSD. With comparable levels of SVD, the presence of acute infarcts and AD-like Aβ retention were associated with the early dementia after stroke/ TIA. / So far, there is a lack of research on the long-term effect of Alzheimer’s pathology on cognitive impairment in the context of stroke/TIA. We hypothesized that comorbid AD-like Aβ deposition played a key role in progressive cognitive decline after stroke/TIA. To test this hypothesis, we conducted a 3-year longitudinal study as study 3. Over 3 years, there was significant difference between mVCI and pVCI on the changes of the Mini-Mental State Examination (MMSE) score over time. We observed a significant decline in MMSE in the mVCI group but not the pVCI group. The annual rates of decline in MMSE and Montreal Cognitive Assessment (MoCA) score were greater in the mVCI group compared to the pVCI group. Of all MoCA domains measured, memory, executive and visuospatial functions were related to Aβ deposition. / In study 4, we investigated the relative contribution of Aβ deposition and CVD lesions to neuropsychological profiles in subjects with cognitive impairment after stroke/TIA. We found that in mVCI, Aβ retention in deep region or parietal lobe was predominantly associated with memory or executive function, respectively. In pVCI, frontal WMC and global large acute infarcts could affect memory or executive function via brain atrophy. / The conclusion of these studies reported herein can be summarized as follows: First, the overall accuracy of clinical diagnosis for cognitive impairment subtypes after stroke/TIA was low. Second, subjects with AD-like Aβ deposition tended to have dementia early after stroke/TIA, and they were more likely to experience a continuous and more severe cognitive decline 3 years later. Finally, Aβ deposition could affect both memory and executive function directly as a predominant factor in subjects with mixed Alzheimer’s and CVD pathologies. / 中風或短暫性腦缺血發作後的認知障礙被普遍視為血管性認知障礙的一種原型。通過澱粉樣蛋白正電子發射計算機斷層掃描技術（¹¹C-PiB PET），30%的中風或短暫性腦缺血發作後認知障礙患者具有阿爾茲海默氏病型的澱粉樣蛋白(Aβ)沈積。因此，中風或短暫性腦缺血發作後認知障礙是一種研究共存的阿爾茲海默氏病和腦血管疾病對認知功能的影響的良好模型。該論文通過四個研究，闡述了Aβ對中風或短暫性腦缺血發作後認知功能的影響。 / 第一個研究通過藉助¹¹C-PiB PET,調查了臨床診斷中對中風或短暫性腦缺血發作後認知障礙的分型的準確性。我們發現，對不同認知障礙類型的臨床診斷準確率較低（Kappa=0.194）。其中，對血管性認知障礙的臨床診斷準確率為66.7％，對混合性(阿爾茲海默氏病和腦血管疾病混合型)認知障礙的臨床診斷準確率為68.0％。 / 通常，我們把於中風或短暫性腦缺血發作後3至6個月內發生的癡呆定義為早髮型中風或短暫性腦缺血發作後癡呆，3至6個月后發生的癡呆定義為晚髮型中風或短暫性腦缺血發作後癡呆。在第二個研究中，我們發現，慢性小血管病（腔隙性梗塞和腦白質病變）不僅可以導致早髮型中風或短暫性腦缺血發作後癡呆，而且和晚髮型中風或短暫性腦缺血發作後癡呆也有關聯。然而，如果在相同程度的小血管病損傷的情況下，具有急性缺血性損傷和阿爾茲海默氏型Aβ沈積的患者更易提早發生中風或短暫性腦缺血發作後癡呆。 / 迄今，尚無關於共存的阿爾茲海默氏病和腦血管疾病對認知功能的長期影響的研究。我們假設合併的阿爾茲海默氏病可以導致患者中風或短暫性腦缺血發作後認知功能持續下降。為了驗證這一假設，我們進行了一個為期3年的長期隨訪研究（研究三）。在三年的隨訪中，混合性認知障礙患者和血管性認知障礙患者的簡短認知檢測（MMSE）評分變化有著顯著不同：混合性認知障礙患者的MMSE評分顯著下降，而血管性認知障礙患者的MMSE評分則無明顯改變。而且，混合性認知障礙患者的MMSE和蒙特利爾認知評估量表（MoCA）評分每年下降的平均速度皆高於血管性認知障礙患者。此外，藉助MoCA，我們發現中風或短暫性腦缺血發作後認知障礙患者的記憶、執行能力和視覺空間能力的損傷都和Aβ沉積有關。 / 在第四個研究中，我們研究了Aβ和腦血管病損傷對中風或短暫性腦缺血發作後患者不同認知功能的影響。我們發現，在混合性認知障礙患者中，腦深部的Aβ沉積和記憶功能損害直接相關，腦頂葉的Aβ沉積則和執行功能損害直接相關。在血管性認知障礙患者中，額葉腦白質病變和全腦大型腦梗病灶則可通過腦萎縮的介導，影響記憶或執行功能。 / 總之，我們的研究發現: 1.目前關於中風或短暫性腦缺血發作後患者認知障礙分型的臨床診斷的準確性較低。2.具有阿爾茲海默氏型Aβ沉積的患者不僅易於在中風或短暫性腦缺血發作後早期發生認知障礙，而且其認知水平在長期隨訪中也會不斷下降。3. Aβ沉積可以作為主導因素直接影響混合性認知障礙患者的記憶和執行功能。 / Liu, Wenyan. / Thesis Ph.D. Chinese University of Hong Kong 2015. / Includes bibliographical references (leaves 164-187). / Abstracts also in Chinese; appendixes in Chinese. / Title from PDF title page (viewed on 12, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

Neste trabalho são apresentados resultados experimentais referentes ao decaimento beta do Nb POT.92, obtidos a partir de medidas da atividade gama residual que segue a reação Nb POT.93 (gamma, n). A alimentação do nível a 2067 keV do Zr POT.92 foi determinada com boa precisão. A não observação de transições gama que envolvem os níveis 0 POT.+ e 4 POT.+ do Zr POT.92 permitiram, a partir de uma analise estatística rigorosa determinar-se limites superiores para a alimentação desses níveis. Os resultados experimentais obtidos, bem como diversos outros disponíveis na bibliografia especializada, foram analisados a luz do modelo de camadas, explorando-se especialmente a contribuição do orbital de nêutrons g IND.7/2 nos primeiros níveis excitados do Zr POT.92. Os cálculos foram feitos usando-se valores publicados para os elementos de matriz da interação residual próton-próton e supondo-se uma interação delta superficial para a interação nêutron-nêutron. / We have investigated the beta decay of Nb POT.92 measuring the residual gamma activities associated with the Nb POT.93 (gamma, n) reaction. The beta branch to the 2067 keV Zr POT.92 level has been determined. Unobserved gamma-rays, with a rigorous statistical analysis, allow the determination of upper limits to beta transitions to the 0 POT.+ and 4 POT.+ levels of Zr POT.92. We have compared ours and other published results with the predictions of shells model, exploring the g IND.7/2 neutron orbit contribution to the levels of Zr POT.92 The shell model calculations have been made using published values for the proton-proton matrix elements. The neutron-neutron matrix elements have been determined assuming a surface delta interaction.

A celulose é o biopolímero de maior abundância no mundo e tem potencial para se tornar fonte de energia renovável através de sua transformação em açúcares fermentáveis, que por sua vez serão transformados em etanol. A recalcitrância da celulose, principal dificuldade encontrada no processo, pode ser superada com o auxílio de enzimas (celulases). Ao menos três enzimas celulolíticas são necessárias para a degradação total da celulose, incluindo as celobioidrolases, que hidrolisam as ligações glicosídicas das extremidades redutoras e não redutoras da cadeia, as endoglucanases, que clivam a cadeia de celulose amorfa randomicamente, e as beta-glicosidases, que produzem glicose através dos celo-oligômeros. Mas para que esse processo se torne financeiramente viável é necessário conhecer o funcionamento, otimizar a atividade e aumentar a produção dessas celulases. Com o intuito de avançar na compreensão da função e estrutura dessas enzimas, o presente trabalho teve como objetivo o estudo estrutural de beta-glicosidases da família GH1 e endoglucanases da família GH5. Na primeira parte do trabalho, a expressão da endoglucanase II de Trichoderma reesei não foi alcançada, mesmo utilizando diferentes organismos e condições de expressão. Porém, na segunda etapa, foi obtida a expressão, purificação e os primeiros ensaios de cristalização de 11 beta-glicosidases bacterianas da família GH1 e 8 endoglucanases bacterianas da família GH5. Dentre elas, três beta-glicosidases e uma endoglucanase de Bacillus licheniformis foram cristalizadas e tiveram sua estrutura resolvida. As beta-glicosidases, apesar de possuírem o enovelamente similar, apresentaram variações no tamanho e posição das alças formadoras da fenda catalítica e divergem em relação a um dos aminoácidos importantes para a estabilização do substrato. Essas diferenças podem ajudar a explicar o mecanismo dessas enzimas para reconhecer substratos distintos. A endoglucanase da família GH5, possuindo dois módulos acessórios, foi cristalizada tanto na forma apo quanto complexada ao substrato celotetraose. O segundo módulo acessório possivelmente é um domínio de ligação à celulose (CBM) e seus resíduos aromáticos, que são responsáveis pela interação com o substrato, parecem complementar o sítio catalítico, sendo assim um novo mecanismo de auxílio enzimático de um CBM. O primeiro módulo acessório não possui um aparente sítio de interação com carboidratos e provavelmente funciona como um conector entre domínio catalítico e o CBM. O posicionamento do substrato no sítio de ligação é parecido com outras estruturas já determinadas, porém, suscita algumas dúvidas sobre a função dos resíduos catalíticos que é conservada na família. O carbono anomérico do substrato possui uma densidade eletrônica contínua com o glutamato da fita &beta;4 (que deveria ser o ácido/base) e está mais próximo dele que do glutamato da fita &beta;7 (que deveria ser o nucleófilo). / Cellulose is the most abundant biopolymer in the world and can become a renewable energy source through its transformation in fermentable sugars, which will be converted in bioethanol. The cellulose recalcitrance, main difficulty in the process, can be overcome with the aid of enzymes (cellulases). At least three cellulolytic enzymes are required for complete hydrolysis of cellulose, including cellobiohydrolases for hydrolyzing the glycosidic linkages from the reducing and non-reducing chain ends, endoglucanases for randomly cleaving cellulose chains in the amorphous regions, and beta-glucosidases for producing glucose from the solubilized cello-oligomers. But, to become a financially viable process it is necessary to know the mechanism, optimize the activity and improve the production of these cellulases. In order to advance the understanding of the structure and function of these enzymes, the present work intended to study the structure of beta-glucosidases from family GH1 and endoglucanases from family GH5. In the first part of the work, the expression of endoglucanase II from Trichoderma reesei was not achieved, even using different organisms and expression conditions. However, in the second part, the expression, purification and the crystallization first trials of eleven bacterial beta-glucosidases and eight bacterial endoglucanases were achieved. Among them, three beta-glucosidases and one endoglucanase from Bacillus licheniformis were crystallized and had their structures solved. Beta-glucosidases, although having a similar folding, showed variations in the length and position of the loops that form the catalytic cleft and diverge in relation to one of the amino acids that are important in substrate stabilization. These differences may help explain the mechanism of these enzymes to recognize distinct substrates. The endoglucanase, which has two accessory modules, was crystallized in the apo form and complexed with the substrate celotetraose. The second accessory module probably is a cellulose binding domain (CBM) and its aromatic residues, which are responsible for the substrate interaction, seem to complement the catalytic site. Therefore it can be a new mechanism of CBM assistance in the enzymatic activity. The first accessory module has no apparent interaction site with carbohydrates and probably works as a connector between the catalytic domain and CBM. The positioning of the substrate in the binding site is similar to other structures already solved but raises some questions about the role of the catalytic residues, that are conserved in the family. The anomeric carbon of the substrate has a continuous electron density with glutamate from sheet-&beta;4 (which should be the acid/base) and is closer to it than to glutamate from sheet-&beta;7 (which should be the nucleophile).

Determina la frecuencia de los genes blaIMP, blaVIM y blaNDM productores de Metalo-ß-lactamasas en aislamientos de Pseudomonas aeruginosa no sensibles a carbapenemes. Recolecta 149 aislamientos de Pseudomonas aeruginosa procedentes de muestras clínicas de los siguientes nosocomios: Hospital Nacional Daniel A. Carrión, Hospital Nacional Edgardo Rebagliati Martins – ESSALUD, Hospital Alberto Sabogal Sologuren – ESSALUD, Hospital General Fuerza Aérea Peruana (FAP) y el Hospital Nacional Docente Madre Niño San Bartolomé. Los aislamientos se almacenaron en el cepario del NAMRU-6 desde julio del 2010 hasta julio del 2012. Realiza el perfil de susceptibilidad a antibióticos mediante el método de “Kirby – Bauer” de acuerdo a los lineamientos del CLSI (Clinical Laboratory Standars Institute). La detección fenotípica de MBL se realizó mediante el método de aproximación de discos de EDTA (Ácido etilendiaminotetraacetico) y la detección de los genes blaIMP, blaVIM y blaNDM mediante un PCR multiplex. Encuentra que en 28 aislamientos de Pseudomonas aeruginosa se detecta la presencia del gen blaIMP mediante PCR, siendo la frecuencia de este gen 18.8%. No se detectaron los genes blaVIM y blaNDM. Concluye que la detección de los genes productores de MBL por PCR permitió detectar la frecuencia real de los aislamientos de Pseudomonas aeruginosa productores de MBL. / Tesis

The de novo design of peptides is a central area of research in chemical biology. Although it is now possible to design helical peptide structures from first principle, designing â-sheets remains a challenge. Significant advances in this area have been made by using molecular scaffolds, which stabilize â-sheets through intramolecular H-bonding involving the scaffold or which direct supramolecular assembly of the conjugate. In my thesis, I have made use of novel strategies, using ferrocene (Fc) as a central scaffold for controlling the secondary structure of peptides. This approach has been highly successful. Four major new strategies are introduced and described in this thesis: <p>a) Cyclization of Fc-peptide conjugates of the type Fc[CO-Xxx-CSA]2 (Xxx = Gly, Ala, Val, Leu) and Fc[CO-Gly-Xxx-CSA]2 (Xxx = Val, Ile; CSA = cysteamine) leads to the clean formation of novel cyclic bioorganometallic conjugates, which exhibit strong intramolecular hydrogen bonding interactions that restrict the mobility of the podand peptide chains. In the latter system, this intermolecular hydrogen bonding interaction was exploited for the design of a novel â-barrel-like structure. For Fc[CO-Gly-Val-CSA]2 and Fc[CO-Gly-Ile-CSA]2 discrete cyclic supramolecular assemblies were formed in which the individual molecules assemble along the rims of the molecules, resulting in the formation of tubular peptide superstructures that possess a central cavity and are filled with water molecules. <p>b) Prior to my work, work by Hirao and Metzler-Nolte clearly showed that the two podand peptide chains in Fc-peptide conjugates are pointing away from each other. This would indicate that extended â-sheets cannot be formed by simply extending the podand peptide chains. In my work, I clearly demonstrate that, in contrast to earlier results, it is possible to use the Fc scaffold to stabilize â-sheet-like interactions in longer peptide chains. Two systems are described in this thesis Fc[CO-Gly-Val-Cys(Bz)-OMe]2 and Fc[CO-Gly-Ile-Cys(Bz)-OMe]2. In both the cases, amino acids are employed that have a high propensity for â-sheet formation. Both Fc-peptide conjugates exhibit strong interstrand hydrogen bonding, resembling that found in â-sheets.<p>c) In this work, I have demonstrated the use of ferrocene amino acid (Fca) to control the structure in peptides. In contrast to previous work by Metzler-Nolte, my work is largely focusing on the design of a repetitive Fca-peptide motif. It is proposed that this repetition will enable strong interactions between the peptide portions of the conjugate, resulting in the formation of an extended structure. To this effect, a series of Fca-conjugates of the type Boc-[Fca-Ala]n-OMe (n = 1-4) was synthesized and fully characterized. All systems display the expected interaction between the Ala residues having a 12-membered hydrogen bonded ring. Such a structural motif resembles that found in naturally occurring â-helical structures of the spike-region of some viral proteins. <p>d) I have also demonstrated the use of a novel Fc-derivative, Fc[NH-Boc]2, to control the structure of podand amino acid chains. Fc-diamine was synthesized by the convenient carbazide route giving this useful scaffold in high yield. This material was converted into its peptide conjugate and the resulting conjugate displays the elusive 14-membered hydrogen bonding ring. <p>Thus, in my work, I have provided a new complementary tool for peptide design that will undoubtedly find applications for the design of de novo proteins in the near future.

The de novo design of peptides is a central area of research in chemical biology. Although it is now possible to design helical peptide structures from first principle, designing â-sheets remains a challenge. Significant advances in this area have been made by using molecular scaffolds, which stabilize â-sheets through intramolecular H-bonding involving the scaffold or which direct supramolecular assembly of the conjugate. In my thesis, I have made use of novel strategies, using ferrocene (Fc) as a central scaffold for controlling the secondary structure of peptides. This approach has been highly successful. Four major new strategies are introduced and described in this thesis: <p>a) Cyclization of Fc-peptide conjugates of the type Fc[CO-Xxx-CSA]2 (Xxx = Gly, Ala, Val, Leu) and Fc[CO-Gly-Xxx-CSA]2 (Xxx = Val, Ile; CSA = cysteamine) leads to the clean formation of novel cyclic bioorganometallic conjugates, which exhibit strong intramolecular hydrogen bonding interactions that restrict the mobility of the podand peptide chains. In the latter system, this intermolecular hydrogen bonding interaction was exploited for the design of a novel â-barrel-like structure. For Fc[CO-Gly-Val-CSA]2 and Fc[CO-Gly-Ile-CSA]2 discrete cyclic supramolecular assemblies were formed in which the individual molecules assemble along the rims of the molecules, resulting in the formation of tubular peptide superstructures that possess a central cavity and are filled with water molecules. <p>b) Prior to my work, work by Hirao and Metzler-Nolte clearly showed that the two podand peptide chains in Fc-peptide conjugates are pointing away from each other. This would indicate that extended â-sheets cannot be formed by simply extending the podand peptide chains. In my work, I clearly demonstrate that, in contrast to earlier results, it is possible to use the Fc scaffold to stabilize â-sheet-like interactions in longer peptide chains. Two systems are described in this thesis Fc[CO-Gly-Val-Cys(Bz)-OMe]2 and Fc[CO-Gly-Ile-Cys(Bz)-OMe]2. In both the cases, amino acids are employed that have a high propensity for â-sheet formation. Both Fc-peptide conjugates exhibit strong interstrand hydrogen bonding, resembling that found in â-sheets.<p>c) In this work, I have demonstrated the use of ferrocene amino acid (Fca) to control the structure in peptides. In contrast to previous work by Metzler-Nolte, my work is largely focusing on the design of a repetitive Fca-peptide motif. It is proposed that this repetition will enable strong interactions between the peptide portions of the conjugate, resulting in the formation of an extended structure. To this effect, a series of Fca-conjugates of the type Boc-[Fca-Ala]n-OMe (n = 1-4) was synthesized and fully characterized. All systems display the expected interaction between the Ala residues having a 12-membered hydrogen bonded ring. Such a structural motif resembles that found in naturally occurring â-helical structures of the spike-region of some viral proteins. <p>d) I have also demonstrated the use of a novel Fc-derivative, Fc[NH-Boc]2, to control the structure of podand amino acid chains. Fc-diamine was synthesized by the convenient carbazide route giving this useful scaffold in high yield. This material was converted into its peptide conjugate and the resulting conjugate displays the elusive 14-membered hydrogen bonding ring. <p>Thus, in my work, I have provided a new complementary tool for peptide design that will undoubtedly find applications for the design of de novo proteins in the near future.

Whey protein supplementation, containing large amount of leucine, has been a traditional intervention to maintain net protein balance in the past decades. It has been recognized that leucine alone is able to stimulate protein synthesis by activating mTOR and its related downstream pathway without affecting protein degradation, whereas its metabolite β-hydroxy-β-methylbutyrate (HMB) is known to attenuate protein degradation when provided chronically. However, the mechanism of HMB’s benefit remains unclear. To address how HMB regulates protein synthesis and degradation signaling pathways, we compared one dose of whey protein (187.5mg/kg), HMB (400mg/kg) or leucine (1.4g/kg) by oral gavage. Blood was collected at 0, 45 and 90 min for blood glucose and plasma insulin analysis. Red and white gastrocnemius muscle was taken separately 90 min after gavage. Blood glucose was reduced by leucine at 45 and 90 min post gavage. Plasma insulin was enhanced by leucine at 45 min and then decreased at 90 min post gavage, whereas HMB decreased plasma insulin through 90 min post gavege. Western blot analysis showed that HMB phosphorylated Akt in red gastronemius, and enhanced phosphorylation of mTOR in both types of muscles. Leucine phosphorylated mTOR, p70s6k and 4E-BP1 in both red and white gastronemius. Regarding protein degradation signals, phosphorylation of FOXO3A was enhanced by HMB, but not in the other treatment groups. Whey protein had no effect on those cellular signaling. Our results indicate that both HMB and leucine may stimulate protein synthesis through the mTOR pathway in red and white gastrocnemius muscles by different degrees with leucine more effective than HMB. HMB may have a greater effect than leucine on limiting protein degradation by phosphorylating Akt and FOXO3A in red and white gastrocnemius muscles. A combination of HMB and leucine, as a new interventional strategy, is predicted to maximize protein accretion by increasing protein synthesis as well as inhibiting protein degradation. / text

ABSTRACT Aims/hypothesis: Obesity is associated with a dysregulation of beta-cell and adipocyte function. The molecular interactions between adipose tissue and beta-cells are not yet fully elucidated. We investigated, whether or not the adipocytokine nicotinamide phosphoribosyltransferase (Nampt), which has been associated with obesity and type 2 diabetes mellitus (T2DM) directly influences beta-cell survival and function. Methods: The effect of Nampt on viability of INS-1E cells was assessed by WST-1 assay. Apoptosis was measured by Annexin V/PI and TUNEL assay. Activation of apoptosis signaling pathways was evaluated. Adenylate kinase release was determined to assess cytotoxicity. Chronic and acute effects of the adipocytokine Nampt and its enzymatic product nicotinamide mononucleotide (NMN) on insulin secretion were assessed by glucose stimulated insulin secretion in human islets. Results: While stimulation of beta-cells with the cytokines IL-1β, TNFα and IFN-γ or palmitate significantly decreased viability, Nampt showed no direct effect on viability in INS-1E cells or in human islets, neither alone nor in the presence of pro-diabetic conditions (elevated glucose concentrations and palmitate or cytokines). At chronic conditions over 3 days of culture, Nampt and its product NMN had no effects on insulin secretion. In contrast, both Nampt and NMN potentiated glucose stimulated insulin secretion acutely during 1h incubation of human islets. Conclusion/interpretation: Nampt did influence neither beta-cell viability nor apoptosis but acutely potentiated glucose stimulated insulin secretion.

No description available.