Gut microbiota-derived propionate reduces cancer cell proliferation in the liver

Peer reviewedPublisher PD

Antihypertensive Properties of Plant-Based Prebiotics

Hypertension is one of the major risk factors for cardiovascular disease. Although various drugs for its treatment have been synthesized, the occurring side effects have generated the need for natural interventions for the treatment and prevention of hypertension. Dietary intervention such as the administration of prebiotics has been seen as a highly acceptable approach. Prebiotics are indigestible food ingredients that bypass digestion and reach the lower gut as substrates for indigenous microflora. Most of the prebiotics used as food adjuncts, such as inulin, fructooligosaccharides, dietary fiber and gums, are derived from plants. Experimental evidence from recent studies has suggested that prebiotics are capable of reducing and preventing hypertension. This paper will discuss some of the mechanisms involved, the evidence generated from both in-vitro experiments and in-vivo trials and some controversial findings that are raised

Influence de l'oligofructose sur le métabolisme glucidique et lipidique

Les fructanes sont des glucides, naturellement présents dans certains aliments, qui, de part leur structure chimique échappent à l'hydrolyse par les enzymes digestives mais sont largement fermentés dans le caeco-colon. L'oligofructose (OFS) est un fructane obtenu par hydrolyse enzymatique de l'inuline, extraite à partir de racines de chicorée. De précédentes études ont permis de démontrer un effet hypotriglycéridémiant de l'OFS, résultant d'une moindre capacité de synthèse et d'estérification des acides gras dans le foie de rats Wistar. Au cours de ce travail, nous avons progressé dans la connaissance des effets physiologiques et/ou thérapeutiques de l'OFS, en nous focalisant sur son impact sur le métabolisme glucidique et lipidique. Les études ont été réalisées sur différents modèles de rats présentants ou non des altérations du métabolisme glucidique et lipidique, mais également chez l'homme. Nous avons tenté d'élucider, chez le rat, la nature des médiateurs permettant à ces glucides non digérés d'exercer des effets systémiques. Les résultats obtenus chez le rat contrôle Wistar normoglycémique et chez le rat Zucker fa/fa insulino-résistant, présentant une hyperglycémie modérée,ne nous permettent pas de soupçonner un éventuel effet de l'OFS sur la sensibilité à l'insuline, et suggèrent que l'OFS doit être présent dans le repas pour permettre une diminution de la glycémie. Par ailleurs, chez les rats traités à la streptozotocine, hyperglycémiques et hyperphagiques, l'OFS réduit la prise alimentaire, la glycémie, et restaure partiellement la teneur en insuline pancréatique. Les concentrations en GLP-1, hormone intestinale sécrétée en réponse à l'ingestion de nutriments, sont augmentées suite à l'addition d'OFS dans le régime du rat. Le GLP-1, via son effet sur la satiété et sur la prolifération des cellules B pancréatiques pourrait constituer un médiateur des effets observés chez le rat traité à la streptozotocine. Chez le rat obèse, l'ajout de fructane dans la nourriture permet d'améliorer la stéatose hépatique, un phénomène qui serait majoritairement dépendant d'une réduction de l'apport calorique et du poids corporel engendré par le traitement. La fermentation et plus particulièrement le propionate issu de cette dernière, serait également impliqué dans cet effet anti-stéatogène de l'OFS. Une étude clinique a été réalisée en vue de tester l'influence d'une supplémentation en OFS chez des patients présentants une stéatose hépatique d'origine non alcoolique. Nous avons mis en évidence une diminution significative des taux en AST, reflet d'une moindre altération du tissu hépatique. Toutefois, aucune modification significative de la triglycéridémie, ni de la glycémie n'a pu être observée chez ces patients.Thèse de doctorat en sciences biomédicales (nutrition humaine) (SBIM 3) -- UCL, 200

Dietary fructans and lipid metabolism : building a bridge from the colon to the liver

Several non digestible but fermentable dietary carbohydrates, besides their effect on the gastrointestinal tract, are also able to exert systemic effect, namely by modifying the metabolism of lipids. The present review aims at illustrating how specific fermentable carbohydrates, namely dietary fructans, escaping the hydrolysis by amylases or disaccharidases, highly fermented in the caeco-colon by gramnegative bacteria, are susceptible to influence fatty acid metabolism and lipemia in experimental animal models, but also in humans. By focusing on the effect of oligofructose or inulin, which are dietary fructans obtained from chicorey roots, we illustrate here that the hepatic metabolism of fatty acids seems to be a relevant goal of fructans. The panel of the putative mediators of the systemic effects of fructans are presented and discussed, and consist in either 1) modifications in glucose/insulin homeostasis 2) the end-products of colonic fermentation of fructans, reaching the liver by the portal vein and /or 3) intestinal hormones and /or 4) other nutrients availability

Dietary oligofructose lessens hepatic steatosis, but does not prevent hypertriglyceridemia in obese zucker rats

We studied the influence of oligofructose (OFS), a nondigestible fructan, on lipid metabolism in obese fa/fa Zucker rats. The addition of 10 g/100 g OFS to the diet slowed the increase in body weight without modifying serum triglycerides or glucose concentrations after 7 wk of treatment. However, an oral load of 2 g glucose and 5 g corn oil/kg body weight increased triglyceridemia more in OFS-fed rats than in control rats. After 10 wk, OFS decreased the hepatic concentration of triglycerides 57% relative to controls. The less severe steatosis was confirmed by histologic analysis. Among the key enzymes involved in fatty acid synthesis and esterification, only malic enzyme activity was significantly lower in OFS-fed rats than in controls. The epididymal fat mass was significantly lower in OFS-fed rats. In conclusion, dietary enrichment with OFS can counteract both the fat mass development and the hepatic steatosis that occur in obese Zucker rats. Future studies will be designed to clarify in obese animals the influence of dietary OFS on postprandial triglyceridemia, which is an important variable associated with the development of atherosclerosis in humans, and to analyze the biochemical mechanism underlying the "hepatoprotective" effect of OFS

Inulin and oligofructose modulate lipid metabolism in animals : review of biochemical events and future prospects

Inulin and oligofructose, besides their effect on the gastro-intestinal tract, are also able to exert 'systemic' effect, namely by modifying the hepatic metabolism of lipids in several animal models. Feeding male Wistar rats on a carbohydrate-rich diet containing 10 % inulin or oligofructose significantly lowers serum triacylglycerol (TAG) and phospholipid concentrations. A lower hepatic lipogenesis, through a coordinate reduction of the activity and mRNA of lipogenic enzymes is a key event in the reduction of very low-density lipoprotein-TAG secretion by oligofructose. Oligofructose is also able to counteract triglyceride metabolism disorder occurring through dietary manipulation in animals, and sometimes independently on lipogenesis modulation: oligofructose reduces post-prandial triglyceridemia by 50 % and avoids the increase in serum free cholesterol level occurring in rats fed a Western-type high fat diet. Oligofructose protects rats against liver TAG accumulation (steatosis) induced by fructose, or occurring in obese Zucker fa/fa rats. The protective effect of dietary inulin and oligofructose on steatosis in animals, would be interesting, if confirmed in humans, since steatosis is one of the most frequent liver disorders, occurring together with the plurimetabolic syndrome, in overweight people. The panel of putative mediators of the systemic effects of inulin and oligofructose consists in either modifications in glucose/insulin homeostasis, the end-products of their colonic fermentation (i.e. propionate) reaching the liver by the portal vein, incretins and/or the availability of other nutrients. The identification of the key mediators of the systemic effects of inulin and oligofructose is the key to identify target function(s) (or dysfunction(s)), and finally individuals who would take an advantage of increasing their dietary intake