T.P. Mommsen

Bio: T.P. Mommsen is an academic researcher from University of Victoria. The author has contributed to research in topics: Protein sparing & Nutrient. The author has an hindex of 2, co-authored 2 publications receiving 1100 citations.

Carbohydrates in fish nutrition: effects on growth, glucose metabolism and hepatic enzymes

Abstract: The utilisation of dietary carbohydrates and their effects on fish metabolism are reviewed. Details on how dietary carbohydrates affect growth, feed utilisation and deposition of nutrients are discussed. Variations in plasma glucose concentrations emphasizing results from glucose tolerance tests, and the impact of adaptation diets are interpreted in the context of secondary carbohydrate metabolism. Our focus then shifts to selected aspects of hormonal regulation of carbohydrate metabolism and dietary carbohydrates and their variable effects on glycogen and glucose turnover. We analyse the interaction of carbohydrates with other nutrients, especially protein and protein sparing, and de novo synthesis of lipids, and finish by discussing the correlation of dietary carbohydrates with fish health.

Carbohydrates in fish nutrition: digestion and absorption in postlarval stages

Abstract: This review summarizes information regarding digestion and absorption of carbohydrates in cultivated fish Relevant results of studies of digestive enzymes, eg amylase, chitinase, cellulase and brush border disaccharidases are presented Fish amylases appear to be molecularly closely related and to have characteristics comparable to mammalian amylases Whether chitinases and cellulases are endogenous enzymes of some fish species is still a matter of speculation, although recent molecular evidence, at least for chitinase seems to settle the issue in favour of endogenous sources Feed and intestinal microbes may be the source of polysaccharidases in fish feeding on nutrients-containing non-starch polysaccharides Knowledge regarding monosaccharide transport in fish intestine as interpreted from studies of brush border membrane vesicles, everted sleeves of fish intestinal sections and molecular biology is discussed Glucose transporters of the intestinal brush border show characteristics similar to those found in mammals A tabulatory presentation of experimental details and results reported in the literature regarding starch digestibility is included as a basis for discussion Although numerous investigations on digestion of starch and other carbohydrates in fish have been published, the existing information is highly fragmentary As yet, it is impossible to derive a cohesive picture on the integrated process of carbohydrate hydrolysis and absorption and interaction with diet composition for any of the fish species under cultivation The physiological mechanisms behind the species differences are not known

Glucose metabolism in fish: a review

Abstract: Teleost fishes represent a highly diverse group consisting of more than 20,000 species living across all aquatic environments. This group has significant economical, societal and environmental impacts, yet research efforts have concentrated primarily on salmonid and cyprinid species. This review examines carbohydrate/glucose metabolism and its regulation in these model species including the role of hormones and diet. Over the past decade, molecular tools have been used to address some of the downstream components of these processes and these are incorporated to better understand the roles played by carbohydrates and their regulatory paths. Glucose metabolism remains a contentious area as many fish species are traditionally considered glucose intolerant and, therefore, one might expect that the use and storage of glucose would be considered of minor importance. However, the actual picture is not so clear since the apparent intolerance of fish to carbohydrates is not evident in herbivorous and omnivorous species and even in carnivorous species, glucose is important for specific tissues and/or for specific activities. Thus, our aim is to up-date carbohydrate metabolism in fish, placing it to the context of these new experimental tools and its relationship to dietary intake. Finally, we suggest that new research directions ultimately will lead to a better understanding of these processes.

Carbohydrates in fish nutrition: digestion and absorption in postlarval stages

Abstract: This review summarizes information regarding digestion and absorption of carbohydrates in cultivated fish Relevant results of studies of digestive enzymes, eg amylase, chitinase, cellulase and brush border disaccharidases are presented Fish amylases appear to be molecularly closely related and to have characteristics comparable to mammalian amylases Whether chitinases and cellulases are endogenous enzymes of some fish species is still a matter of speculation, although recent molecular evidence, at least for chitinase seems to settle the issue in favour of endogenous sources Feed and intestinal microbes may be the source of polysaccharidases in fish feeding on nutrients-containing non-starch polysaccharides Knowledge regarding monosaccharide transport in fish intestine as interpreted from studies of brush border membrane vesicles, everted sleeves of fish intestinal sections and molecular biology is discussed Glucose transporters of the intestinal brush border show characteristics similar to those found in mammals A tabulatory presentation of experimental details and results reported in the literature regarding starch digestibility is included as a basis for discussion Although numerous investigations on digestion of starch and other carbohydrates in fish have been published, the existing information is highly fragmentary As yet, it is impossible to derive a cohesive picture on the integrated process of carbohydrate hydrolysis and absorption and interaction with diet composition for any of the fish species under cultivation The physiological mechanisms behind the species differences are not known

Enzyme‐producing bacteria isolated from fish gut: a review

Abstract: Digestion of food depends on three main factors: (i) the ingested food and the extent to which the food is susceptible to the effects of digestive enzymes, (ii) the activity of the digestive enzymes and (iii) the length of time the food is exposed to the action of the digestive enzymes. Each of these factors is affected by a multitude of secondary factors. The present review highlights the experimental results on the secondary factor, enzymatic activity and possible contribution of the fish gut microbiota in nutrition. It has been suggested that fish gut microbiota might have positive effects to the digestive processes of fish, and these studies have isolated and identified the enzyme-producing microbiota. In addition to Bacillus genera, Enterobacteriaceae and Acinetobacter, Aeromonas, Flavobacterium, Photobacterium, Pseudomonas, Vibrio, Microbacterium, Micrococcus, Staphylococcus, unidentified anaerobes and yeast are also suggested to be possible contributors. However, in contrast to endothermic animals, it is difficult to conclude the exact contribution of the gastrointestinal microbiota because of the complexity and variable ecology of the digestive tract of different fish species, the presence of stomach and pyloric caeca and the relative intestinal length. The present review will critically evaluate the results to establish whether or not intestinal microbiota do contribute to fish nutrition.

Nutrition and health of aquaculture fish.

Abstract: Under intensive culture conditions, fish are subject to increased stress owing to environmental (water quality and hypoxia) and health conditions (parasites and infectious diseases). All these factors have negative impacts on fish well-being and overall performance, with consequent economic losses. Though good management practices contribute to reduce stressor effects, stress susceptibility is always high under crowded conditions. Adequate nutrition is essential to avoid deficiency signs, maintain adequate animal performance and sustain normal health. Further, it is becoming evident that diets overfortified with specific nutrients [amino acids, essential fatty acids (FAs), vitamins or minerals] at levels above requirement may improve health condition and disease resistance. Diet supplements are also being evaluated for their antioxidant potential, as fish are potentially at risk of peroxidative attack because of the large quantities of highly unsaturated FAs in both fish tissues and diets. Functional constituents other than essential nutrients (such as probiotics, prebiotics and immunostimulants) are also currently being considered in fish nutrition aiming to improve fish growth and/or feed efficiency, health status, stress tolerance and resistance to diseases. Such products are becoming more and more important for reducing antibiotic utilization in aquafarms, as these have environmental impacts, may accumulate in animal tissues and increase bacterial resistance. This study reviews knowledge of the effect of diet nutrients on health, welfare and improvement of disease resistance in fish.

Nutritional regulation of hepatic glucose metabolism in fish

Abstract: Glucose plays a key role as energy source in the majority of mammals, but its importance in fish appears limited. Until now, the physiological basis for such apparent glucose intolerance in fish has not been fully understood. A distinct regulation of hepatic glucose utilization (glycolysis) and production (gluconeogenesis) may be advanced to explain the relative inability of fish to efficiently utilize dietary glucose. We summarize here information regarding the nutritional regulation of key enzymes involved in glycolysis (hexokinases, 6-phosphofructo-1-kinase and pyruvate kinase) and gluconeogenesis (phosphoenolpyruvate carboxykinase, fructose-1,6-bisphosphatase and glucose-6-phosphatase) pathways as well as that of the bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. The effect of dietary carbohydrate level and source on the activities and gene expression of the mentioned key enzymes is also discussed. Overall, data strongly suggest that the liver of most fish species is apparently capable of regulating glucose storage. The persistent high level of endogenous glucose production independent of carbohydrate intake level may lead to a putative competition between exogenous (dietary) glucose and endogenous glucose as the source of energy, which may explain the poor dietary carbohydrate utilization in fish.