Métabolisme des nutriments au cours de l'insuffisance rénale chronique

The suppression of renal metabolic function is responsible of metabolic acidosis, uremic toxicity and endocrine disturbances. Subsequent abnormalities of protein metabolism are:

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  an increase in muscle proteolysis related to acidosis and hypercortisolemia;

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  a decrease in hepatosplanchnic amino acid utilization which is responsible for reduced protein synthesis and ureagenesis as well as abnormal amino acid release in the absorptive phase.

Main abnormalities in energy substrate metabolism are: insulin resistance, impaired blood glucose regulation, and reduced triglyceride clearance. Energy metabolism is also characterized by an increase in energy expenditure and an accelerated fasting behaviour. Hypermetabolism together with increased protein turnover are responsible for an increase in nutritional requirements: 35–40 kcal/kg.day and, in dialysis patients, 1,2–1,4 g protein/kg.day.     

Nutrition et insuffisance rénale chronique de l'enfant

The nutritional management of the uremic child depends on the residual glomerular filtration rate. When it has dropped to 25% of the normal range, one can observe decreased growth velocity, anemia, hyperparathyroidism, poor tolerance to changes in water and sodium intake and anorexia. The assessment of the nutritional status is based on anthropometric measurements by using standard deviation scores — i.e. body weight, height, growth velocity, head circumference and skinfold thickness —, on some biochemical parameter — i.e. serum proteins, calcium, phosphorus, parathyroid hormone and urea: creatinine ratio — and sometimes on biophysical methods (dual energy X ray absorptiometry). The current nutritional practices of the uremic child are less restrictive than in adults due to energy and protein requirements for both cerebral maturation and statural growth. Such uremic children should therefore be fed according to recommended dietary allowances, that often require tube feeding in infants. In addition to diet, some other treatments have a nutritional impact, like recombinant human growth hormone and erythropoietin. Such strategies should be adapted to the type of treatment — i.e. conservative, transplantation, haemodialysis, peritoneal dialysis.     

Régulation du métabolisme protéique intestinal par les nutriments

The gut plays a central role in some pathophysiological conditions and the preservation or restoration of gut function, such as gut barrier, is a major issue. Cellular removal and protein turnover are high. Indeed, approximately 50% of proteins are synthesized every day in the human duodenal mucosa. During catabolic or inflammatory states, intestinal protein metabolism seems to be deregulated that could be involved in gut barrier dysfunction. Gut protein metabolism can also be affected by nutrients according to the type or the amount. An increasing number of studies focus on this topic but data are still limited and remain controversial. This paper aims to review the available data on the regulation of intestinal protein metabolism during pathophysiologic conditions and the influence of nutrients.     

Les effets métaboliques de l'hormone de croissance

Human growth hormone (GH) metabolism and the roles of this hormone in the body are becoming increasingly understood. Numerous factors regulate GH release by the pituitary gland in humans, including nutritional status, age, drugs and activity level. GH action in tissues is modulated by production of insulin-like growth factor-I (IGF-I), IGF binding proteins (IGFBPs), which may act as endocrine, paracrine or autocrine regulators, and other as yet poorly understood molecular events. GH has well described effects on carbohydrate, fat and protein metabolism: GH causes insulin resistance, enhances lipolysis and induces protein anabolism. In addition to routine use in children with GH deficiency, recombinant GH has been recently approved for use in many countries to enhance somatic growth in pediatric renal failure, to improve body composition and physical/mental function in adults with GH deficiency and to counteract wasting in AIDS patients. The anabolic effects of GH are also being studied in other catabolic states, including patients requiring specialized feeding in the hospital and home setting.     

Mécanismes de la dénutrition au cours de l'insuffisance respiratoire chronique

The study of the mechanisms of denutrition during chronic obstructive pulmonary disease is useful because this common evolutive complication has severe functional consequences and is associated with a poor prognosis, irrespective of respiratory functional status. Conversely, renutrition improves the prognosis in these patients. Adaptation to hypoxia, the basis of which is oxygen conformance, is described. Denutrition during chronic obstructive pulmonary disease is linked to the imbalance arising from increased energy expenditure and inadequate food intake. The origins of the imbalance are discussed. The clinical implications of knowing the mechanisms of denutrition are set out and perspectives for both experimental and applied research are proposed.     

Prévalence et conséquences de la dénutrition dans l'insuffisance respiratoire chronique

From large series of patients with COPD, the prevalence of malnutrition can be estimated at 25% taking a cut-off value for Body Mass Index (BMI) less than 20 kg/m², and 35% for a body weight less than 90% of the ideal body weight. Data are very scarce for the other causes of respiratory failure. Malnutrition is a feature of emphysema. There is a well established correlation between height related body weight and FEV1, and TCO: it is not possible to assert that malnutrition is lither a cause or a consequence of the altered respiratory function. Nutritional status is a predictor for the capacity of exercise, independently of the alteration of respiratory function. There is probably a link between malnutrition and the performance of respiratory muscles. The prognostic influence of malnutrition in chronic respiratory failure is well established, with the best survival rates for overweight patients.     

Dénutrition au stade pré-dialytique de l''insuffisance rénale chronique

Protein-caloric malnutrition is not uncommon in pre-dialysis patients at an advanced stage of evolution. Malnutrition is associated with a poor prognosis during the first months of dialysis.The decline of spontaneous alimentary intake with the progression of renal failure results from the retention of anorexigenic substances. Metabolic acidosis and abnormalities in nutrient metabolism may also contribute to malnutrition. A sufficient protein-caloric intake must be offered to the pre-dialysis patients, adapted to the degree of CRF. Persistent malnutrition despite regular medical and dietetic follow-up is a valuable criterion for initiating of dialysis.     

Obésité sarcopénique et altérations du métabolisme protéique musculaire

The increasing prevalence of obesity among elderly people has led to the definition of the concept of sarcopenic obesity. This concept is defined as the potential to combine muscle metabolic changes associated with both aging and obesity. Several definitions have been proposed, but the absence of a consensus led to great variability in the prevalence of this phenomenon in literature. However, the proportion of the older obese population is not negligible, representing 5 to 15% of elderly people. The study of metabolic abnormalities associated with sarcopenic obesity is of importance, since these subjects are at increased risk of developing functional disability. However, very few studies evaluated the mechanisms involved in the cumulating and aggravating effect of obesity in the elderly, particularly at muscle level. Of note, significant alterations of muscle protein anabolism were observed in elderly people but also in obese subjects. Impairment in muscle protein metabolism, including protein synthesis rate, could be involved in the loss of functional capacity during sarcopenic obesity.     

La perception des messages de santé par les populations défavorisées

In a context of diffusion of nutritional recommendations and of the PNNS program, this contribution analyses the perception of the recommendations in the lower social strata, compared to the upper one. It underlines the existence of significant social inequalities. Thus, in the lower strata, the injunction, for health reasons, of a higher consumption of fruits and vegetables, and of a lower one of fat and sweet foodstuffs, and the incentive for regular physical activity are not compatible with the financial constraints of these deprived strata, with the representation of a “proper meal” and with the representations of an ideal body shared by these social categories. Consequently, these poorer strata, in a broad meaning, constitute a real issue, because they perceive more often the recommendations as external injunctions. In order to be more effective, the public health policy should take in account the constraints, daily practices and representations of this social category.     

Place des facteurs de croissance dans le traitement de la dénutrition des patients dialysés

Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are two endogenous growth factors necessary for growth in children and maintenance of normal body composition in adults. The anabolic effects of these substances have been confirmed in vitro and in vivo since they are now available from recombinant synthesis. Chronic renal failure is associated with an impaired GH/IGF-1 axis responsible for abnormal growth in children and potentially involved in the frequent loss of muscle mass that occurs in adults undergoing chronic dialysis. Treatments with recombinant GH and/or IGF-1 induce strong anabolic responses in both adult and children suffering from renal failure. These encouraging results support the future use of these substances in the treatment of malnutrition in chronic renal failure patients.     

Effets physiopathologiques des mélanges de pesticides

Pesticides are considered as risk factors for human health. Indeed, epidemiological studies often show a positive correlation between occupational exposure and the risk of developing diseases for users and/or their descendants. The exposure of the general population is different from the exposure of professionals. Indeed, the consumer is exposed through the diet to mixtures of pesticides at low doses and during a long-term period. Now the question raised is what may be the impact of such an exposure on the health of consumers or their descendants. The hypothesis that compounds at doses corresponding to their No Observable Adverse Effect Level (NOAEL), which act via different mechanisms of action, could not exert an effect even when they are present in combination is today rebutted. Studies on endocrine disrupters or on pesticides mixture in general, as we develop in our laboratory, show that the effects of mixtures cannot be predicted from the effect of the single molecule. The effects of mixtures can be cumulative, antagonistic, additive or synergistic depending on the function or the parameter of the studied physiological function. Even if it is difficult to evaluate experimentally all possible combinations to which consumers may be exposed, it is essential to evaluate the effects of representative mixtures for a better understanding of the risk assessment of consumers.     

Nutrition de l'insuffisant respiratoire aigu en réanimation

Energy metabolism requires oxygen intake and carbon dioxide elimination provided by the respiratory system. Acute respiratory distress occurs when pulmonary gas exchanges are not adapted to metabolic demand, leading to hypoxemia and/or hypercapnia. Energy metabolism, nutritional status, caloric intake and ventilation are closely related.Respiratory distress can be secondary to impaired ventilatory drive, inspiratory muscle weakness, or impaired pulmonary parenchyma. The clinical relevance of the nutrition-respiratory system relationship is obvious. Malnutrition reduces the contractile strength of the diaphragm and can cause failure to wean a patient from the ventilator. Severe oxidative stress leading to molecular damage due to lipids occurs during acute respiratory distress syndrome. Hemodynamic and gas exchange alterations are observed during infusion of lipid emulsions containing long-chain fatty acids in patients with acute respiratory distress syndrome. A caloric intake exceeding energy expenditure induces a nutritional CO₂ load which increases the work of breathing and can cause acute hypercapnia or failure to wean a patient from a ventilator.     

Effect de l'hGH sur le métabolisme des protéines et des acides aminés chez l'homme

The increased availability of human Growth Hormone (rhGH) as a result of recombinant molecular biology has provided the opportunity to explore its actions and potential utility in humans. rhGH administration is associated with an increase in the resting energy expenditure of GH-deficient adults, but has little effect on the resting energy expenditure of GH-sufficient individuals. By mechanisms which remain to be elucidated, rhGH increases the oxidation of fat, decreases the oxidation of protein, and has little effect on the oxidation of carbohydrate. The net effect of these changes in substrate oxidation is a reduction in fat mass and an increase in muscle mass in GH-deficient adults, and increased linear growth in GH-deficient children. The primary mechanism of rhGH on whole body protein would appear to increase the whole body rate of protein synthesis with little effect on the rates of proteolysis in both the fasting and intracibal conditions. rhGH appears to increase acutely the rates of protein synthesis in forearm tissues, but has little effect on muscle mass or strength following 3 months of treatment in GH-sufficient adults. The effects of rhGH on two experimental models of protein catabolism in humans (caloric restriction and glucocorticosteroid treatment) are reviewed. Our knowledge of the actions and utility of rhGH as a therapeutic agent has increased tremendously over the last decade. However, a great deal remains to be discovered about the specific genes induced or suppressed as a result of rhGH treatment before we will be knowledgeable in all of its potential clinical applications.     

Prévention et prise en charge de la dénutrition dans les EHPAD

In order to identify best practices for undernutrition prevention and management in the 597 institutions for the dependent elderly in Pays de la Loire, two questionnaires were sent in early 2009. Three-quarters had a nutritional axis in their care project, 25% worked with a Diet and Nutrition Liaison Committee (CLAN), and 67% with dieticians; 70% had less than 25% of their staff recently trained to food-nutrition for the elderly. Two thirds were conducting detection of malnutrition at admission and during follow-up. There was enough time for meals in 60% cases, and 48% had all their residents who underwent a long overnight fast. Among beneficial environmental factors identified, the nutritional axis in the care project seemed to be a major determinant of food-nutrition practices. In conclusion, these results show the real structures involvement in this field in the region, but some practices must be further improved. Nutritional policies seem to be a major way to achieve.     

Impact des allégations nutritionnelles et de santé sur le consommateur

Several consumer studies have shown that consumers are quite sceptical towards the concept of functional foods in general. Consumer acceptance is mainly shaped by subjective determinants, more specifically personal confidence in the alleged nutrition and health claims. Additionally, consumers are hardly willing to compromise on taste for the promise of better health. Strongest hesitation is seen towards disease reduction claims, which are also the most explicit and most difficult to prove claim type, as well as for non-natural and unfamiliar combinations of carrier products and functional ingredients. Higher levels of perceived control over personal health, and stronger perceptions of functional foods as a marketing scam have a strong negative impact on consumer reactions towards foods with nutrition and health claims. Reactions of consumers from specific risk groups, e.g. because of their health status or nutritional needs, have hardly been investigated thus far. The identification of needs and interests of these market segments, as well as the evaluation of consumer understanding of claims constitute a major challenge for future consumer research in this domain.     

Modifications des pratiques d’élevage : conséquences pour la viande de porcs et autres monogastriques

The monogastric meat of today differs from that produced by the animals 50 years ago. The selection of animals according to growth performance has modified the sensorial and nutritional qualities of the meat. The carcass is less fat and the animals are slaughtered younger at the same weight. The lipid content of the meat is thus decreased. However, in the medical world, meat still has a negative image of being a fat meat whereas this is no longer the case. The rearing conditions influence the quality of monogastrics meat. The feeding level and the fat matter in the diet determine the rate and composition of growth (lipids/proteins) and influence the fatty acids composition. The lipid composition of tissues highly depends on the lipid composition of the diet. Therefore, the fatty acid profile of meat (n-3 fatty acid content for example) can be easily modified through feeding, thereby improving the meat quality for the consumer and meeting the nutritionist's requirements.