Bone metabolic and hormonal characteristics of Australian Antarctic expeditioners

Summary: Serum 25(OH)D levels decline without sunlight exposure. We studied 120 expeditioners to Antarctica to determine the skeletal and hormonal responses to sunlight deprivation. With emerging vitamin D insufficiency, serum calcium decreased, PTH increased, and bone loss at the proximal femur was observed. Baseline serum 25(OH)D levels >100 nmol/L prevented vitamin D insufficiency. Introduction: Vitamin D stores deplete without adequate sunlight exposure unless supplementation is provided. We studied 120 healthy adults who spent a year in Antarctica as a model for sunlight deprivation to define the timing and magnitude of the skeletal and hormonal responses to emerging vitamin D insufficiency. Methods: Fasting blood samples were assessed at baseline, 6 and 12 months for serum 25-hydroxyvitamin D (25(OH)D), osteocalcin (OC), bone formation (P1NP) and resorption (CTx), PTH and calcium. Lumbar spine and proximal femur BMD was measured using DXA. Differences over time were determined using repeated measures ANOVA. Percent changes were expressed as (Delta value/(value A +value B)/2)x100. Relationships between outcome measures were determined using Spearman's correlations. Results: Vitamin D insufficiency (<50 nmol/L) was observed in 85% of expeditioners by 6 months when serum calcium decreased and PTH increased (p<0.01). By 12 months, OC increased by 7.4±3.0% (p<0.05), and BMD decreased by 1.0±2.0% at the total proximal femur (p<0.05). For those with vitamin D sufficiency at baseline (>50 nmol/L), sunlight deprivation produced vitamin D insufficiency within 4 months unless baseline values were >100 nmol/L. Conclusion: Supplementation may be necessary for expeditioners with limited access to UV light.

Glucose intolerance caused by a defect in the entero-insular axis: A study in gastric inhibitory polypeptide receptor knockout mice

Mice with a targeted mutation of the gastric inhibitory polypeptide (GIP) receptor gene (GIPR) were generated to determine the role of GIP as a mediator of signals from the gut to pancreatic β cells. GIPR−/− mice have higher blood glucose levels with impaired initial insulin response after oral glucose load. Although blood glucose levels after meal ingestion are not increased by high-fat diet in GIPR+/+ mice because of compensatory higher insulin secretion, they are significantly increased in GIPR−/− mice because of the lack of such enhancement. Accordingly, early insulin secretion mediated by GIP determines glucose tolerance after oral glucose load in vivo, and because GIP plays an important role in the compensatory enhancement of insulin secretion produced by a high insulin demand, a defect in this entero-insular axis may contribute to the pathogenesis of diabetes.

Regulation of sterol regulatory element binding proteins in livers of fasted and refed mice

Hepatic lipid synthesis is known to be regulated by food consumption. In rodents fasting decreases the synthesis of cholesterol as well as fatty acids. Refeeding a high carbohydrate/low fat diet enhances fatty acid synthesis by 5- to 20-fold above the fed state, whereas cholesterol synthesis returns only to the prefasted level. Sterol regulatory element binding proteins (SREBPs) are transcription factors that regulate genes involved in cholesterol and fatty acid synthesis. Here, we show that fasting markedly reduces the amounts of SREBP-1 and -2 in mouse liver nuclei, with corresponding decreases in the mRNAs for SREBP-activated target genes. Refeeding a high carbohydrate/low fat diet resulted in a 4- to 5-fold increase of nuclear SREBP-1 above nonfasted levels, whereas nuclear SREBP-2 protein returned only to the nonfasted level. The hepatic mRNAs for fatty acid biosynthetic enzymes increased 5- to 10-fold above nonfasted levels, a pattern that paralleled the changes in nuclear SREBP-1. The hepatic mRNAs for enzymes involved in cholesterol synthesis returned to the nonfasted level, closely following the pattern of nuclear SREBP-2 regulation. Transgenic mice that overproduce nuclear SREBP-1c failed to show the normal decrease in hepatic mRNA levels for cholesterol and fatty acid synthetic enzymes upon fasting. We conclude that SREBPs are regulated by food consumption in the mouse liver and that the decline in nuclear SREBP-1c upon fasting may explain in part the decrease in mRNAs encoding enzymes of the fatty acid biosynthetic pathway.

Involvement of specific macrophage-lineage cells surrounding arterioles in barrier and scavenger function in brain cortex.

The transport of solutes between blood and brain is regulated by a specific barrier. Capillary endothelial cells of brain are known to mediate barrier function and facilitate transport. Here we report that specific cells surrounding arterioles, known as Mato's fluorescent granular perithelial (FGP) cells or perivascular microglial cells, contribute to the barrier function. Immunohistochemical and in situ hybridization studies indicate that, in normal brain cortex, type I and type II macrophage scavenger receptors are expressed only in FGP/perivascular microglial cells, and surface markers of macrophage lineage are also detected on them. These cells mediate the uptake of macromolecules, including modified low density lipoprotein, horseradish peroxidase, and ferritin injected either into the blood or into the cerebral ventricles. Accumulation of scavenged materials with aging or after the administration of a high-fat diet results in the formation of honeycomb-like foam cells and the narrowing of the lumen of arterioles in the brain cortex. These results indicate involvement of FGP/perivascular microglial cells in the barrier and scavenger functions in the central nervous system.

Efeitos de dois modelos experimentais de dietas hipercalóricas sobre parâmetros comportamentais e biológicos em ratos da linhagem Wistar

O objetivo deste estudo foi investigar os efeitos de dois modelos experimentais de dietas hipercalóricas em comportamentos de ansiedade, processos de aprendizagem e memória e alterações metabólicas. Os animais foram divididos em seis grupos experimentais, de acordo com a condição nutricional. 1) Controle (C); 2) Dieta de Cafeteria (DC); 3) Dieta Hiperlipídica (DH); 4) Controle AIN-93 (C/AIN-93); 5) Dieta de Cafeteria AIN-93 (DC/AIN-93), e 6) Dieta Hiperlipídica AIN-93 (DH/AIN-93). Posteriormente, os grupos foram subdivididos em dois grupos independentes, conforme a tarefa à qual foram submetidos. Pesagens foram realizadas semanalmente até os 98 dias de vida; foram verificados os pesos do fígado, do coração e o peso de tecido adiposo retroperitoneal e epididimal e foram realizadas dosagens de glicose, triglicérides, TGO e TGP no soro e gordura total, colesterol total e triglicérides no fígado. Os testes utilizados: Labirinto em T Elevado (LTE), Caixa Claro/Escuro e Labirinto Aquático de Morris (LAM). Os resultados de peso corporal, os dados comportamentais do LAM, do LTE e os dados de peso dos tecidos extraídos no dia do sacrifício e as análises bioquímicas foram submetidos a uma Análise de Variância (ANOVA). Quando apropriado, foi utilizado o teste de comparações múltiplas de Newman-Keuls (p< 0,05). Os dados comportamentais do teste claro/escuro foram submetidos ao teste t-Student (p< 0,05). Animais tratados com dieta hiperlipídica apresentaram maiores medidas de peso e ganho de peso comparados aos animais controle e dieta de cafeteria, tratados com pellet e com dieta AIN-93. Animais DH1, DC1, DH1 AIN-93, DH2 AIN-93 e DH2 apresentaram maior peso no dia do sacrifício. Animais DH1, DH1 AIN-93, DH2 e DH2 AIN-93 apresentaram maior acúmulo dos tecidos adiposos retroperitoneal e epididimal. Animais DH1 AIN-93 e DC2 AIN-93 apresentaram maiores níveis de glicose. Animais C2, DH2 e DC2 apresentaram maiores níveis de triglicérides. Animais DH1 e C1 apresentaram menores valores de TGO. Animais C2 e C2 AIN-93 apresentaram maiores níveis de TGO. Animais C1, DH1, C2 e DH2 apresentaram maiores níveis de TGP. Animais DH1 AIN-93, DH1, DH2 e DH2 AIN-93 apresentaram maiores valores de gordura total no fígado. Animais DH1 AIN-93 e DH2 apresentaram maiores níveis de colesterol no fígado. Animais DH1, DC1, DH2 e DH2 AIN-93 apresentaram maiores níveis de triglicérides no fígado. Com relação ao consumo alimentar, animais DH apresentaram maior consumo calórico e maior consumo lipídico quando comparados aos animais C e DC, com ração em pellet ou dieta AIN-93. Com relação ao LTE, não foram verificadas diferenças nas esquivas e na fuga. Animais DC1, DH1 e DH1 AIN-93 apresentaram menores níveis de ansiedade verificados a partir dos dados do teste da caixa claro-escuro. Animais DC2 AIN-93 apresentaram pior desempenho em tarefa de memória. Os dados obtidos a partir deste estudo demonstraram que as dietas utilizadas foram capazes de acarretar ganho de peso, acúmulo de tecido adiposo, alterações metabólicas, diminuição da ansiedade nos animais e pior desempenho em uma tarefa de memória em um dos grupos nutricionais.

Participação da conexina 32 na fisiopatogênese da doença hepática gordurosa não alcoólica em camundongos

A doença hepática gordurosa não alcoólica (DHGNA) abrange alterações desde esteatose até esteato-hepatite não alcoólica (EHNA), podendo evoluir para fibrose, cirrose e carcinoma hepatocelular. A DHGNA é considerada a doença hepática mais comum na atualidade e com prevalência mundial alarmante. Esta doença caracteriza-se, basicamente, pela deposição de triglicérides nos hepatócitos, podendo evoluir com inflamação e fibrose, e está intimamente associada com resistência à insulina (RI), diabetes mellitus tipo 2 e obesidade. Os hepatócitos representam as principais células hepáticas e se comunicam através de junções do tipo gap, formadas principalmente por conexina 32 (Cx32). Esta proteína apresenta importante função no controle da homeostase tecidual, regulando processos fisiológicos e tem sido associada como agente protetor na hepatocarcinogênese e outros processos patológicos, porem pouco se sabe sobre sua participação na DHGNA. Sendo assim, o objetivo deste trabalho foi avaliar a participação da Cx32 na fisiopatogênese da DHGNA, utilizando camundongos knockout para Cx32 (Cx32-KO) submetidos a uma dieta hiperlipídica deficiente em colina. Foram analisados dados biométricos, histopatológicos, função hepática, RI, citocinas inflamatórias, adipocinas, estresse oxidativo, peroxidação lipídica e a expressão de genes envolvidos na DHGNA. Os animais Cx32-KO apresentaram maior acumulo de triglicérides hepáticos em relação aos animais selvagens e, consequentemente, maior peso absoluto e relativo do fígado. Adicionalmente, apresentaram maior inflamação hepática demonstrado pela exacerbação da citocina TNF-α e supressão da IL-10, maior dano hepatocelular indicado pelo aumento das enzimas AST e ALT, aumento da peroxidação lipídica e alterações na expressão de genes chaves na fisiopatogênese da DHGNA, como SREBP1c. No entanto, não houve diferença nos marcadores histopatológicos, RI e estresse oxidativo hepático. Por fim, os animais Cx32-KO apresentaram maior produção de leptina e adiponectina no tecido adiposo. Todos esses resultados revelam que a Cx32 pode atuar como um agente protetor ao desenvolvimento da DHGNA, sugerindo seu potencial como novo alvo terapêutico

PGC-1 alfa como regulador inflamatório na esteato-hepatite não-alcoólica

A doença hepática gordurosa não-alcoólica (NAFLD, do inglês) é a manifestação clínica hepática da síndrome metabólica, cuja incidência aumenta consideravelmente em todo o mundo. A NAFLD pode progredir para um estado de esteatohepatite não-alcoólica (NASH, do inglês), caracterizado por inflamação hepatocelular, com ou sem fibrose. Dados na literatura mostram que o coativador-1 alfa do receptor ativado por proliferadores de peroxissoma gama (PGC-1alfa), além de estar envolvido em diversos processos metabólicos, representa uma estratégia terapêutica promissora na modulação da inflamação. Neste projeto investigamos as alterações inflamatórias no fígado induzida por dieta hiperlipídica e o papel do PGC-1alfa nesse processo. Camundongos C57black/6 receberam dieta hiperlipídica contendo 30% de gordura por 10 semanas. O peso dos animais foi avaliado semanalmente. Após a eutanásia, o tecido adiposo intra-abdominal (retroperitoneal e periepididimal) foi coletado e pesado. Analisamos o perfil glicêmico e lipídico sérico e expressão de genes envolvidos no metabolismo glicêmico e lipídico. Avaliou-se também o aspecto histológico e a inflamação do tecido hepático por quantificação das citocinas IL-6, TNF-alfa e IL-1beta. A dieta rica em gordura conduziu a um aumento dos depósitos de gordura intra-abdominal, hiperglicemia e hiperlipidemia. Os animais também apresentavam esteatohepatite, com aumento de citocinas pró-inflamatórias e diminuição na expressão de PGC-1alfa no tecido hepático. O envolvimento do PGC-1alfa na produção de mediadores inflamatórios por hepatócitos foi avaliado em células HepG2 utilizando RNA de interferência (RNAi). O knockdown da expressão de PGC-1alfa causou aumento na expressão e liberação de IL-6 em hepatócitos via aumento na fosforilação de IkBalfa e consequente ativação do NFkB. Portanto, nossos dados mostram que o PGC-1alfa inibe a produção de mediadores inflamatórios (IL-6) em hepatócitos, e fornecem novas evidências das conexões existentes entre as vias metabólicas e imunes

Efeito das gorduras interesterificadas sobre o desenvolvimento da lesão aterosclerótica em camundongos knockout para o receptor de LDL

Nas últimas décadas, diversos estudos têm demonstrado os efeitos nocivos dos ácidos graxos trans à saúde. Consequentemente, diversas agências reguladoras de saúde e sociedades responsáveis pela elaboração de diretrizes nutricionais recomendaram a redução do consumo desses ácidos graxos. Deste modo, a indústria de alimentos vem adequando seus produtos a fim de substituir os ácidos graxos trans por gorduras interesterificadas, porém seus efeitos sobre o desenvolvimento da aterosclerose não foram ainda totalmente elucidados. Portanto, o objetivo deste estudo foi avaliar o efeito de gorduras interesterificadas contendo principalmente ácido graxo palmítico ou esteárico sobre o desenvolvimento da aterosclerose. Desta forma, camundongos knockout para o receptor de LDL (LDLr-KO) recém-desmamados foram alimentados por 16 semanas com dietas hiperlipídicas (40% do valor calórico total sob forma de gordura) contendo principalmente ácidos graxos poli-insaturados (POLI), trans (TRANS), palmítico (PALM), palmítico interesterificado (PALM INTER), esteárico (ESTEAR) ou esteárico interesterificado (ESTEAR INTER) para determinação de concentrações plasmáticas de colesterol total e triglicérides; perfil de lipoproteínas; conteúdo de lípides (Oil Red O) e colágeno (Picrosirius Red) e infiltrado de macrófagos (imuno-histoquímica) na área de lesão aterosclerótica; expressão e conteúdo proteico de citocinas na aorta; dosagem das citocinas secretadas por macrófagos de peritônio estimulados ou não com lipopolissacarídeo (LPS); efluxo celular de colesterol mediado pela apo-AI e HDL2. Os resultados mostraram que os animais que consumiram a gordura interesterificada contendo ácido palmítico (PALM INTER) desenvolveram importante lesão aterosclerótica em comparação aos grupos PALM, ESTEAR, ESTEAR INTER e POLI, resultados confirmados pelo conteúdo de colágeno na lesão. Apesar do processo de interesterificação não ter alterado as concentrações plasmáticas de lípides, conforme verificado entre os grupos PALM vs PALM INTER e ESTEAR vs ESTEAR INTER, o acúmulo de colesterol na partícula de LDL foi similar entre os grupos PALM INTER e TRANS. Além desse efeito sobre o perfil de lipoproteínas, macrófagos do peritônio de camundongos que consumiram PALM INTER secretaram significativamente mais IL-1beta, IL-6 e MCP-1 em comparação aos demais grupos. Esse efeito pró-inflamatório foi confirmado na aorta, onde se observou maior expressão de TNF-alfa e IL-1beta para o grupo PALM INTER em comparação a PALM. Tal insulto inflamatório foi similar ao provocado por TRANS. Esses efeitos deletérios do PALM INTER podem ser parcialmente atribuídos ao acúmulo de colesterol nos macrófagos, promovido pelo prejuízo no efluxo de colesterol mediado pela apo-AI e HDL2, bem como aumento da expressão de receptores envolvidos na captação de LDL modificada (Olr-1) e diminuição daqueles envolvidos na remoção intracelular de colesterol (Abca1 e Nr1h3) na parede arterial. Como conclusão, as gorduras interesterificadas contendo ácido palmítico favorecem o acúmulo de colesterol nas partículas de LDL e em macrófagos, ativando o processo inflamatório, o que conjuntamente contribuiu para maior desenvolvimento de lesão aterosclerótica

Nur77 regulates lipolysis in skeletal muscle cells - Evidence for cross-talk between the beta-adrenergic and an orphan nuclear hormone receptor pathway

Skeletal muscle is a major mass peripheral tissue that accounts for similar to 40% of total body weight and 50% of energy expenditure and is a primary site of glucose disposal and fatty acid oxidation. Consequently, muscle has a significant role in insulin sensitivity, obesity, and the blood-lipid profile. Excessive caloric intake is sensed by the brain and induces beta-adrenergic receptor (beta-AR)- mediated adaptive thermogenesis. beta-AR null mice develop severe obesity on a high fat diet. However, the target gene(s), target tissues(s), and molecular mechanism involved remain obscure. We observed that 30 - 60 min of beta-AR agonist ( isoprenaline) treatment of C2C12 skeletal muscle cells strikingly activated (> 100-fold) the expression of the mRNA encoding the nuclear hormone receptor, Nur77. In contrast, the expression of other nuclear receptors that regulate lipid and carbohydrate metabolism was not induced. Stable transfection of Nur77-specific small interfering RNAs (siNur77) into skeletal muscle cells repressed endogenous Nur77 mRNA expression. Moreover, we observed attenuation of gene and protein expression associated with the regulation of energy expenditure and lipid homeostasis, for example AMP-activated protein kinase gamma 3, UCP3, CD36,adiponectin receptor 2, GLUT4, and caveolin-3. Attenuation of Nur77 expression resulted in decreased lipolysis. Finally, in concordance with the cell culture model, injection and electrotransfer of siNur77 into mouse tibialis cranialis muscle resulted in the repression of UCP3 mRNA expression. This study demonstrates regulatory cross-talk between the nuclear hormone receptor and beta-AR signaling pathways. Moreover, it suggests Nur77 modulates the expression of genes that are key regulators of skeletal muscle lipid and energy homeostasis. In conclusion, we speculate that Nur77 agonists would stimulate lipolysis and increase energy expenditure in skeletal muscle and suggest selective activators of Nur77 may have therapeutic utility in the treatment of obesity.

Expression analysis of a human hepatic cell line in response to palmitate

Saturated fat plays a role in common debilitating diseases such as obesity, type 2 diabetes, and coronary heart disease. It is also clear that certain fatty acids act as regulators of metabolism via both direct and indirect signalling of target tissues. As the molecular mechanisms of saturated fatty acid signalling in the liver are poorly defined, hepatic gene expression analysis was undertaken in a human hepatocyte cell line after incubation with palmitate. Profiling of mRNA expression using cDNA microarray analysis revealed that 162 of approximately 18,000 genes tested were differentially expressed after incubation with palmitate for 48 h. Altered transcription profiles were observed in a wide variety of genes, including genes involved in lipid and cholesterol transport, cholesterol catabolism, cell growth and proliferation, cell signalling, P-oxidation, and oxidative stress response. While palinitate signalling has been examined in pancreatic beta-cells, this is the first report showing that palmitate regulates expression of numerous genes via direct molecular signalling mechanisms in liver cells. (C) 2005 Elsevier Inc. All rights reserved.

Appetite regulatory mechanisms and food intake in mice are sensitive to mismatch in diets between pregnancy and postnatal periods

Human and animal studies suggest that obesity in adulthood may have its origins partly during prenatal development. One of the underlying causes of obesity is the perturbation of hypothalamic mechanisms controlling appetite. We determined mRNA levels of genes that regulate appetite, namely neuropeptide Y (NPY), pro-opiomelanocortin (POMC) and the leptin receptor isoform Ob-Rb, in the hypothalamus of adult mouse offspring from pregnant dams fed a protein-restricted diet, and examined whether mismatched post-weaning high-fat diet altered further expression of these gene transcripts. Pregnant MF1 mice were fed either normal protein (C, 18% casein) or protein-restricted (PR, 9% casein) diet throughout pregnancy. Weaned offspring were fed to adulthood a high-fat (HF; 45% kcal fat) or standard chow (21% kcal fat) diet to generate the C/HF, C/C, PR/HF and PR/C groups. Food intake and body weight were monitored during this period. Hypothalamic tissues were collected at 16 weeks of age for analysis of gene expression by real time RT-PCR. All HF-fed offspring were observed to be heavier vs. C groups regardless of the maternal diet during pregnancy. In the PR/HF males, but not in females, daily energy intake was reduced by 20% vs. the PR/C group (p <0.001). In PR/HF males, hypothalamic mRNA levels were lower vs. the PR/C group for NPY (p <0.001) and Ob-Rb (p <0.05). POMC levels were similar in all groups. In females, mRNA levels for these transcripts were similar in all groups. Our results suggest that adaptive changes during prenatal development in response to maternal dietary manipulation may have long-term sex-specific consequences on the regulation of appetite and metabolism following post-weaning exposure to an energy-rich nutritional environment. © 2008 Elsevier B.V. All rights reserved.

The hypotensive effect of acute and chronic AMP-activated protein kinase activation in normal and hyperlipidemic mice

AMP-activated protein kinase (AMPK) is present in the arterial wall and is activated in response to cellular stressors that raise AMP relative to ADP/ATP. Activation of AMPK in vivo lowers blood pressure but the influence of hyperlipidemia on this response has not been studied. ApoE-/- mice on high fat diet for 6 weeks and age-matched controls were treated with the AMPK activator, AICAR daily for two weeks. Under anesthesia, the carotid artery was cannulated for blood pressure measurements. Aortic tissue was removed for in vitro functional experiments and AMPK activity was measured in artery homogenates by Western blotting. ApoE-/- mice had significantly raised mean arterial pressure; chronic AICAR treatment normalized this but had no effect in normolipidemic mice, whereas acute administration of AICAR lowered mean arterial pressure in both groups. Chronic AICAR treatment increased phosphorylation of AMPK and its downstream target acetyl-CoA carboxylase in normolipidemic but not ApoE-/- mice. In aortic rings, AMPK activation induced vasodilation and an anticontractile effect, which was attenuated in ApoE-/- mice. This study demonstrates that hyperlipidemia dysregulates the AMPK pathway in the arterial wall but this effect can be reversed by AMPK activation, possibly through improving vessel compliance.

The Regulation of AMD Pathobiology by Complement Factor H

Complement factor H (CFH) is a major susceptibility gene for age-related macular degeneration (AMD); however, its impact on AMD pathobiology is unresolved. Here, the role of CFH in the development of AMD pathology in vivo was interrogated by analyzing aged Cfh+/- and Cfh-/- mice fed a high fat, cholesterol-enriched diet. Strikingly, decreased levels of CFH led to increased sub-retinal pigmented epithelium (RPE) deposit formation, specifically basal laminar deposits, following high fat diet. Mechanistically, our data show that deposits are due to CFH competition for lipoprotein binding sites in Bruch’s membrane. Interestingly and despite sub-RPE deposit formation occurring in both Cfh+/- and Cfh-/- mice, RPE damage accompanied by loss of vision occurred only in old Cfh+/- mice. We demonstrate that such pathology is a function of excess complement activation and C5a production, associated with monocyte recruitment, in Cfh+/- mice versus complement deficiency in Cfh-/- animals. Due to the CFH dependent increase in sub-RPE deposit height we interrogated the potential of CFH as a novel regulator of Bruch’s membrane lipoprotein binding and show, using human Bruch’s membrane explants, that CFH removes endogenous human lipoproteins in aged donors. Interestingly, although the CFH H402 variant shows altered binding to BrM, this does not affect its ability to remove endogenous lipoproteins. This new understanding of the complicated interactions of CFH in AMD-like pathology provides an improved foundation for the development of targeted therapies for AMD.

Études in vivo et in vitro sur le potentiel néphroprotecteur de plantes médicinales anti-diabétiques de la pharmacopée traditionnelle des Cris de la Baie-James

Notre équipe a identifié le thé Labrador [Rhododendron groenlandicum L. (Ericaceae)] comme une plante potentiellement antidiabétique de la pharmacopée traditionnelle des Cris de la Baie James orientale. Dans la présente étude, nous avons évalué les effets néphroprotecteurs potentiels de la plante. De la microalbuminurie et de la fibrose rénale ont été développées chez des souris alimentées avec une diète grasse (DG). Le R. groenlandicum améliore d’une façon non-significative la microalbuminurie, avec des valeurs de l’aire sous la courbe (ACR) diminuant de 0.69 à 0.53. La valeur de la fibrose rénale qui était, à l’origine, de 4.85 unités arbitraires (UA) dans des souris alimentées à la DG, a chuté à 3.27 UA après avoir reçu un traitement de R. groenlandicum. Le R. groenlandicum a réduit la stéatose rénale de presque la moitié alors que l’expression du facteur de modification Bcl-2 (Bmf) a chuté de 13.96 UA à 9.43 UA. Dans leur ensemble les résultats suggèrent que le traitement avec R. groenlandicum peut améliorer la fonction rénale altérée par DG. Dans l’étude subséquente, notre équipe a identifié 17 espèces de la forêt boréale, de la pharmacopée traditionnelle des Cris de la Baie James orientale, qui ont présenté des activités biologiques prometteuses in vitro et in vivo dans le contexte du DT2. Nous avons maintenant examiné ces 17 extraits afin d’identifier lesquels possèdent un potentiel cytoprotecteur rénale en utilisant des cellules Madin Darby Canine Kidney (MDCK) mises à l’épreuve dans un médium hypertonique. Nous concluons que plusieurs plantes antidiabétiques Cris exercent une activité de protection rénale qui pourrait être pertinente dans le contexte de la néphropathie diabétique (ND) qui affecte une proportion importante des Cris. La G. hispidula et la A. balsamea sont parmi les plantes les plus puissantes dans ce contexte et elles semblent protectrices principalement en inhibant la caspase 9 dans la voie de signalisation apoptotique mitochondriale. Finalement, nous avons utilisé une approche de fractionnement guidée par un test biologique pour identifier les fractions actives et les composés de A. balsamea avec un potentiel de protection rénale in vitro dans des cellules MDCK mises au défi avec un médium hypertonique. La fraction d’hexane (Hex) possède le potentiel le plus élevé parmi toutes les fractions de solvant contre les dommages cellulaires induits par le stress hypertonique. Dans des études précédentes, trois composés purs ont été identifiés à partir de la fraction Hex, à savoir, l’acide abiétique, l’acide déhydroabiétique et le squalène. L’acide abiétique se distinguait par son effet puissant dans le maintien de la viabilité des cellules MDCK (AnnV-/PI-) à un niveau relativement élevé (augmentation de 25.48% relative au stress hypertonique, P<0.0001), ainsi qu’une réduction significative (diminution de 20.20% par rapport au stress hypertonique, P<0.0001) de l’apoptose de stade précoce (AnnV+/PI-). L’acide abiétique peut donc servir à normaliser les préparations traditionnelles d’A. balsamea et à trouver des applications potentielles dans le traitement de la néphropathie diabétique. Les trois études ont été intrinsèquement liées les unes aux autres, par conséquent, nous avons réussi à identifier R. groenlandicum ainsi que A. balsamea comme nouvelles plantes prometteuses contre la néphropathie diabétique. Nous croyons que ces résultats profiteront à la communauté crie pour la gestion des complications diabétiques, en particulier la néphropathie diabétique. En parallèle, nos données pourraient faire avancer l'essai clinique de certaines plantes médicinales de la pharmacopée traditionnelle des Cris de la Baie James orientale du Canada.

Antioxidant and detoxify genes polymorphisms in colorectal cancer predisposition

Colorectal cancer (CRC) results from histologic and gene alterations can lead to a massive cellular proliferation. Most of the authors assume multifactorial causes to CRC genesis. Low physical activity, a fat diet poor in fibers and smoking habits seems to have an important role in CRC. However, there are also genetic causes associated with CRC risk. It has been described that oxidative stress levels could influence CRC development. Thus, cellular balance reactive species and defense enzymes involved in oxidative stress are crucial to maintain a good tissue function and avoid neoplasic process. Therefore, genome variations on these defense enzymes, such as MNSOD, SOD3, GSTP1, GSTT1 and GSTM1, could be important biomarkers to colorectal adenocarcinomas. We intend to determine frequencies distribution of most common polymorphisms involved on oxidative stress regulation (MNSOD, SOD3, GSTP1, GSTT1 and GSTM1) in patients with sporadic colorectal adenocarcinoma (SCA) and in healthy controls, evaluation their possible correlation with SCA risk. Samples common polymorphisms of antioxidant and detoxify genes (MNSOD T175C, SOD3 R213G, GSTP1 A105G, GSTP1 C114T, GSTT1del and GSTM1del) analysis was done by PCR-SSP techniques. In this study we found a higher prevalence of MNSOD 175CC (55% vs 2%; p<0.0001; OR: 58.5; CI 13.3 to 256.7), SOD3 213GG (31% vs 2%; p<0.0001; OR: 21.89; CI 4.93 to 97.29), GSTP1 105GG (46% vs 12%; p<0.0001; OR: 6.14; CI 2.85 to 13.26), GSTP1 114TT (38% vs 0%; p<0.0001; OR: Infinity) and GSTT1 null (75% vs 28%; p<0.0001; OR: 7.71; CI 3.83 to 15.56) mutated genotypes among SCA patients, while the normal genotypes were associated with SCA absence. Furthermore, we found GSTP1 114TT mutated genotype (52% vs 27%; p=0.003; OR: 2.88; CI: 1.41 to 5.89) and GSTT1 null genotype (87% vs 65%; p=0.003; OR: 3.66; CI 1.51 to 8.84) associated with colon samples. These findings suggest a positive association between most of common polymorphisms involved on oxidative stress regulation and SCA prevalence. Dysregulation of MNSOD, SOD3, GSTP1, GSTT1 and GSTM1 genes could be associated with an increase of ROS in colon and rectum tissue and p53 pathway deregulation, induced by oxidative stress on colonic and rectal cells. The present study also provides preliminary evidence that MNSOD 175C, SOD3 213G, GSTP1 105G, GSTP1 114T and GSTT1 null polymorphisms, may be involved in SCA risk and could be useful to clarify this multifactorial disorder.