NUTRITIONAL DETERMINANTS OF METABOLIC DISEASES IN HUMANS

A high fructose intake, mainly consumed with products containing added sugars, is currently suspected to be responsible for an increase in the global prevalence of obesity and related metabolic diseases. This suspicion rests on several short-term studies showing that a high- fructose intake negatively impacts cardio-metabolic risk factors in healthy volunteers. Some studies however report that fructose’s harmful metabolic effects can be partially prevented by other dietary or life-style related factors. Each of the two studies included in this PhD thesis aimed to investigate the effects of a candidate factor. The first of them, bariatric surgery, is considered as the most effective treatment for grade III obesity, and is known to markedly improve obesity-associated metabolic alterations. In the first study, we assessed whether Roux- en-Y gastric bypass surgery altered postprandial fructose kinetics and de novo lipogenesis, with a special focus on intestinal de novo lipogenesis and on blood lipid profiles. Our results indicate that this surgical procedure does not induce any fructose malabsorption, but drastically decreases postprandial hyperlipemia. The latter effect was observed without any decrease in intestinal de novo lipogenesis, however. Second, several studies have also shown that a high- protein intake was associated with beneficial effects on body weight, glucose homeostasis, and, more recently, on intrahepatic fat concentration in obese or in healthy subjects during short- term overfeeding experiments. In the second study, we assessed in healthy volunteers whether the short-term effects of saccharose overfeeding was modulated by the dietary protein and lipid intake. Our results indicate that the same excess saccharose and total energy intake caused a five-fold larger increase in intrahepatic fat content when associated with a low-protein, high- lipid diet than with a high-protein, low-lipid diet. -- Il est soupçonné qu’une consommation excessive de fructose, principalement présent dans notre alimentation sous forme de sucres ajoutés, pourrait être responsable de la récente augmentation de la prévalence mondiale d’obésité et des maladies métaboliques. Ceci repose sur de nombreuses études d’intervention qui montrent qu’une suralimentation en fructose influe négativement sur les marqueurs de risque métabolique et cardiovasculaire. Pourtant, certaines études démontrent aussi que les effets négatifs du fructose peuvent être partiellement atténués par divers facteurs, alimentaires ou liés au mode de vie. Les études effectuées dans le cadre de cette thèse avaient pour but de préciser l’effet de certains de ces facteurs. La chirurgie bariatrique est actuellement considérée comme la méthode le plus efficace pour le traitement de l’obésité de degré III. De surcroit, elle est susceptible d’améliorer les anomalies métaboliques associées à l’obésité. Dans une première étude, nous avons évalué si le bypass gastrique selon Roux-en-Y altérait la cinétique postprandiale du fructose et la lipogenèse de novo. Une attention particulière a été portée à la lipogenèse intestinale de novo et aux éventuelles conséquences de sa modification sur les concentrations sanguines de lipides. Les résultats indiquent que le bypass gastrique n’entraîne pas de malabsorption de fructose, mais diminue l’excursion postprandiale de triglycérides, et ce malgré une lipogenèse intestinale préservée. Il a aussi été rapporté à plusieurs reprises, qu’une augmentation de l’apport protéique pouvait être associé à une perte de poids, une amélioration de l'homéostasie du glucose et, plus récemment, la diminution de la quantité de graisse stockée dans le parenchyme hépatique chez l’obèse ou dans des modèles expérimentaux de suralimentation chez le volontaire sain. Dans une seconde étude, nous avons donc évalué si les effets d’une surcharge de courte durée en saccharose variait en fonction du contenu en protéines et lipides de l’alimentation. Les résultats obtenus démontrent que, à même surcharge en saccharose et en énergie totale, le stockage de lipides intrahépatique est 5 fois plus important en présence d’une alimentation pauvre en protéines et riche en lipide qu’en présence d’une alimentation hyper- protéinée pauvre en lipides

Pathogenesis of Cardiovascular and Metabolic Diseases: Are Fructose-Containing Sugars More Involved Than Other Dietary Calories?

There is increasing concern that sugar consumption may be linked to the development of metabolic and cardiovascular diseases. There is indeed strong evidence that consumption of energy-dense sugary beverages and foods is associated with increased energy intake and body weight gain over time. It is further proposed that the fructose component of sugars may exert specific deleterious effects due to its propension to stimulate hepatic glucose production and de novo lipogenesis. Excess fructose and energy intake may be associated with visceral obesity, intrahepatic fat accumulation, and high fasting and postprandial blood triglyceride concentrations. Additional effects of fructose on blood uric acid and sympathetic nervous system activity have also been reported, but their link with metabolic and cardiovascular diseases remains hypothetical. There is growing evidence that fructose at physiologically consumed doses may exert important effects on kidney function. Whether this is related to the development of high blood pressure and cardiovascular diseases remains to be further assessed

Effect of Recasted Material Addition on the Quality of Metal-Ceramic Bond: A Macro-, Micro-, and Nanostudy

Using the recasted alloys in dental prosthetics could affect the quality of the metal-ceramic bond. However, scientists, alloys producers, and prosthetists are still of different opinions. The purpose of this study was to estimate the influence of recasting of the NiCrMo alloy on the metal-ceramic bond quality. The research was carried out on macro-, micro- and nanoscales using the three-point bending test procedure and hardness tests as well as atomic force microscopy and SEM analyses. The SEM analyses showed good integrity of the metal-ceramic bond. The τb index of all test samples was greater than 45 MPa. The highest values were recorded for the samples made of 50% and 100% of a brand new material. SEM analysis made after the bending test confirmed good metal-ceramic bond and exhibited adhesive-cohesive fracture. The largest hardness of metal plates was found for the samples containing 50% of the recycled material. Atomic force microscopy studies showed that the alloy containing 50% of the recycled material was characterized by the highest values of surface roughness parameters