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.     

Insulin-like Growth Factor-I et dénutrition aiguë ou chronique

Malnutrition is a common problem affecting many patients with both acute and chronic illnesses. Nutrient delivery via parenteral or enteral routes has alleviated some of the problems that arise from well defined nutritional deficiencies. However, it has made a much smaller impact on wasting associated with illness. Modulation of metabolism with exogenous agents is attractive as a means to improve outcomes in patients that are susceptible to wasting. Insulin-like Growth Factor-I (IGF-I) and Growth Hormone (GH) are hormones that can be used for this purpose, and may have widespread clinical utility to improve wound healing, maintain lean body mass, and preserve organ function. Studies are ongoing to elucidate the possible benefits of these agents.     

IGF-I, marqueur nutritionnel

Many of the anabolic effects of growth hormone (GH) are mediated by insulin-like growth factor-I (IGF-I), which is a mitogenic polypeptide with structural similarities to insulin. Plasma levels of IGF-I are modulated by nutritional and metabolic factors and disease status. Although the liver is the principal source of circulating IGF-I, the ubiquity of the sites of secretion and action led to the concept that IGF-I may function as autocrine/paracrine growth factor as well as a classic endocrine hormone. In humans, the majority of the IGFs circulate bound to IGF binding proteins (IGFBPs), particularly IGFBP-3, and less than 5% is free. This binding prolongs the metabolic half-life of IGF-I in the circulation and serves as a metabolic reserve of IGFs. Evidences are accumulating to support a model of the GH/IGF-I/IGFBP-3 axis that is closely regulated by the metabolic and nutritional status of the individual, which thereby controls bioavailability of IGF-I. The regulation of IGF-I by nutrients connects diet intake and growth, brings an interface between nutrients and hormones acting in concert to stimulate growth, and illustrates the significant role of the nutrients in the control of gene expression. Understanding the mechanisms linking nutrient intake and IGF-I synthesis and action to stimulate growth, should permit the formulation of strategies for treatment of catabolic disorders and wiser uses of anabolic agents.     

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.     

Dénutrition et affections neuromusculaires de l''adulte et de l''adolescent

Patients with neuromuscular diseases have protein malnutrition related to the muscle mass decrease. When associated with a decrease in food intake below requirements, patients become cachectic. Respiratory complications are then frequent and severe. In case of respiratory distress, the acute stress might aggravate the protein loss which will be particularly difficult to restore if the muscular activity is reduced. Although there are no curative therapies for neuromuscular diseases but all symptomatic treatments are useful in maintaining function and quality of life; therefore the prevention of malnutrition is essential. Nutritional care is difficult because of the lack of norms for body composition and protein and energy requirements. The nutritional support must take into account the swallowing difficulties, the digestive and polyvisceral involvement and the natural history of the disease. The nutritional support is usually enteral. Feeding through a gastrostomy tube, feasable at home, has improved the quality of life of the patient. Parenteral nutrition is prescribed for limited periods for surgery or acute respiratory failure.     

Traitement diététique et médicamenteux du syndrome du grêle court

The principles of the dietary and drug treatment of short bowel syndrome depend mainly on the presence or absence of the colon in continuity. In patients with a jejunostomy, the major problem is sodium and magnesium losses with corresponding fluid depletion, and a high-energy diet with added salt as in the WHO solution, Vichy water or NaCl capsules must be advised. The drugs used to reduce jejunostomy output include loperamide and codeine, gastric anti-secretory (proton pump inhibitors) and somatostatin analogs. In patients with a colon in continuity, bacterial fermentation of unabsorbed carbohydrates in the colon results in energy salvage; these patients are advised to eat a high-energy diet rich in carbohydrates and low in oxalates and can benefit from cholestyramine. Lactose, notably as milk, must be restricted; a low-fiber regimen is not justified in most cases. Oral or parenteral supplements of liposoluble vitamins (vitamin B12) and trace-elements (zinc) are needed in a majority of patients. The correction of magnesium deficiency is sometimes difficult, even after prolonged weaning of parenteral nutrition, by the oral route. The efficacy of these various measures as well as the status in micronutrients must be reevaluated regularly.     

Thérapeutique nutritionnelle du patient en dialyse péritonéale

Protein-caloric malnutrition is common in peritoneal dialysis patients. Prevention and treatment of this malnutrition can only be achieved by sufficient oral protein and energy intakes, associated with enteral supplementation, in addition to regular follow-up of dialysis adequacy.Modifications of peritoneal dialysis dose to achieve higher Kt/V and creatinine clearance, utilisation of the new osmotic solutions recently made available offer new therapeutic strategies. These various interventions should decrease mortality and morbidity linked to nutrition problems.     

Stratégies de prise en charge nutritionnelle spécifiques : l'enfant et l'adulte jeune atteints d'un handicap

Handicapped children are at high risk for malnutrition. In this situation nutritional assessment becomes difficult to perform due to musculo-skeletal deformities, patient's collaboration. In any case nutritional indices require simple measures: weight and height. Nutritional care must be presented early to parents in order to start as soon as possible when oral intake does not meet nutritional needs. For the handicapped child, surgery is often a major stress that requires nutritional care before, during and after. Obesity often aggravates the burden of the handicap and does not provide protection against malnutrition. Like in non-handicapped persons nutritional care can improve the outcome and well being of handicapped children.     

Évaluation de l'état nutritionnel et des besoins de l'enfant et de l'adolescent

Ten to fifteen percent of hospitalized children suffer from malnutrition. Children suffering from chronic diseases are at particularly high risk for malnutrition. A systematic screening for malnutrition and nutritional risk can improve nutritional care in this population. Simple measures (weight and height at admission) can be used to calculate nutritional indices (weight for height ratio or body mass index). Nutritional risk depends on: 1) the severety of the principal diagnosis, 2) the ability to feed oneself, and 3) the pain intensity. The oral or enteral route is preferred when the gut is functional. In all cases nutritional status must be followed throughout hospitalisation. Furthermore, it is preferable to begin nutritional care before malnutrition sets in. Nutritional care can improve the outcome and well-being of hospitalized children.     

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.     

Prise en charge nutritionnelle et effets respiratoires des apports nutritionnels chez l''insuffisant respiratoire chronique

Pulmonary cachexia is a frequently occurring complication in patients with chronic respiratory disorders and is a determining factor of health-related quality of life and mortality. Nutritional support is indicated for depleted patients with COPD, since it provides not only supportive care, but direct intervention through improvement in respiratory and peripheral skeletal muscle function and in exercise performance. Patients responding to energy supplementation by showing weight gain and improvement in functional performance even demonstrated a decreased mortality. Nutritional therapy has to consider acute and chronic effects on functional performance and ventilatory capacity. A combination of oral nutritional supplements and exercise or anabolic agents as anabolic stimulus appears to be the best treatment approach in order to obtain significant functional improvement. Only limited acute adverse effects on symptoms and exercise capacity have been demonstrated after nutritional support, being related to the immediate post-prandial caloric load, but not to the macro-nutrient composition of the supplements. More studies are needed to evaluate the effects of long-term nutritional therapy in clinically stable patients as well as the effectiveness of nutritional support during acute disease exacerbation.     

Myosite localisée chez un diabétique : penser à l’infarctus musculaire

Diabetic muscle infarction is a rare and often unrecognized complication of diabetes mellitus. It usually occurs in patients with long-term diabetic complications, particularly microangiopathy. It is characterized by sudden muscle pain, most often located in one lower limb. The magnetic resonance imaging (MRI) makes it possible to confirm the diagnosis without the need for muscular biopsy. We report the case of a 21-year-old woman with type 1 diabetes and degenerative complications who presented a muscle infarction. The clinical picture mainly consisted in a painful left thigh. The laboratory test showed an inflammatory syndrome without increase in muscle enzymes. MRI signal abnormalities from the affected muscle area confirmed the diagnosis of diabetic myonecrosis.     

Nutrition et maladie d’Alzheimer

Deterioration of memory function and ultimately establishment of Alzheimer's disease (AD) severely debilitates the affected individual, uncompromisingly decreasing the quality of life of both patients and their caregivers. The global prevalence of cognitive impairment and dementia including Alzheimer's disease is expected to rise significantly in proportion to increased life expectancy. Weight loss is a common problem among patients with AD and is associated with mortality, morbidity, disease progression, and poor quality of life. The aim of this article is: (1) to emphasize the importance of malnutrition in Alzheimer's disease and (2) to review published evidences for the role of nutrition as a risk factor of the disease.     

Les biscuits et gâteaux : toute une diversité

Biscuits and cakes are food of cereal origin, of which flour is the first ingredient. There exists a very wide variety of biscuits and cakes, from traditional recipes, fixed by a code of uses, to more recent recipes with either a voluntarily greedy dimension or specific nutritional assets, without forgetting above all pleasure. The consumption of biscuits and cakes of the French population is moderate with an average of 27 g per day for the consumers of biscuits and cakes. They are mainly consumed within meals, mainly during afternoon break and breakfast. Biscuits and cakes can be nutritionally equivalent to other alternatives such as bread with chocolate, and can thus contribute to consumption of a balanced afternoon break or breakfast when eaten with a fruit and a dairy product. The manufacturers have professional tools to communicate on biscuits and cakes and make continuous efforts to go through the technological constraints and optimize nutritional quality of their products by taking into account expectations of the consumer.     

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.     

Nutrition artificielle : utilité ou futilité chez l'enfant en situation palliative

Palliative care are intended to children with life limiting conditions. In France, for the majority of pediatric team, the idea of continuity of cares is essential for the announcement of the diagnosis to the final state. The author describes here different situations according to the initial disease of these children. In all cases, the choices of artificial feeding depend of pluridisciplinary medical teams and their experience, and of family opinion. Ethical consideration must be present in this decision.     

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.