Effects of exercise on l-carnitine and lipid metabolism in African catfish (Clarias gariepinus) fed different dietary l-carnitine and lipid levels

African catfish (Clarias gariepinus) were fed four isonitrogenous diets (34 % crude protein), each containing one of two lipid (100 or 180 g/kg) and two l-carnitine (15 or 1000 mg/kg) levels. After 81 d of feeding, thirty-two fish (body weight 32 g) from each dietary group were randomly selected, sixteen fish were induced to a 3-h swim (speed of 1.5 body length (BL)/s), while the other sixteen fish were kept under resting condition. Fish fed 1000 mg l-carnitine accumulated 3.5 and 5 times more l-carnitine in plasma and muscle, respectively, than fish fed the 15 mg l-carnitine. Muscle l-carnitine content was significantly lower in exercised fish than in rested fish. High dietary lipid level (fish oil) led to an increase in muscle n-3 PUFA content and a decrease in SFA and MUFA content. In liver, the increase in dietary lipid level resulted in an increased levels of both n-6 and n-3 PUFA. l-carnitine supplementation significantly decreased n-3 PUFA content. Exercise decreased n-3 PUFA in both muscle and liver. Plasma lactate and lactate dehydrogenase, normally associated with increased glycolytic processes, were positively correlated with exercise and inversely correlated with dietary l-carnitine level. l-carnitine supplementation reduced significantly the RQ from 0.72 to 0.63, and an interaction between dietary l-carnitine and lipid was observed (P <0.03). Our results indicate that an increase in fatty acids (FA) intake may promote FA oxidation, and both carnitine and exercise might influence the regulation of FA oxidation selectivity

Bedreigen virussen de palingpopulatie?

Resultaten van een onderzoek naar het voorkomen van virussen (EVEX, Eel Virus European X; HVA, Herpes Virus Anguillea; EVE, Eel Virus European) bij palingen afkomstig uit diverse landen (zowel wilde paling als paling van kwekerijen) en van een zwemexperiment met geïnfecteerde en niet-geïnfecteerde palingen. Na voltooiing van de zwemreis werd in beide groepen het bloedbeeld onderzocht op diverse parameters (o.a. op hematocriet, het aantal rode bloedcellen). De resultaten zijn zeer verontrustend, omdat ze een aanwijzing vormen dat virus-infectie ertoe leidt dat palingen hun migratie naar de paaigronden niet kunnen voltooien door bloedarmoede, een beschadigde lever en een tekort aan eiwitten. Dit kan mede een oorzaak zijn voor het wereldwijd teruglopen van de palingstan

Dietary Carnitine maintains energy reserves and delays fatigue of exercised African catfish (Clarias Gariepinus) fed high fat diets

Lipids, together with proteins, are traditionally considered as primary fuels during aerobic swimming. The effects of dietary fat and carnitine supplements and exercise on the energy metabolism of juvenile fish were investigated. One hundred African catfish (Clarias gariepinus) were fed four isonitrogenous diets containing a fat level of 100 or 190 g kg-1 diet and one of the two levels of carnitine (15 and 1000 mg kg-1). Fish grew from 61 to 162 g in 10 wk. Thereafter, 6 fish per group swam vigorously for 3 h and the results were compared with unexercised groups. Fish receiving 1,000 mg carnitine accumulated 2- to 3-fold more carnitine than fish receiving 15 mg carnitine. Plasma acyl-carnitine level was affected by an interaction between dietary treatment and exercise (P <0.05). Adenosine triphosphate and phosphocreatine concentrations were higher in the white muscle (WM) of exercised fish fed the high-carnitine supplements, compared with the low-carnitine fed fish (P <0.05). Adenilate energy charge indexes were higher and ammonia concentrations were lower in WM of fish fed high-carnitine and high-fat diets. Dietary carnitine supplements may be needed in growing fish when dietary lipid level is high. In that case extra dietary carnitine can maintain the body energy reserves at adequate level when fish is exposed to a short-term, exhaustive exercise, a physiologic stress common both in nature and in intensive aquaculture systems

Metabolic depression in fish measured by direct calorimetry: A review

In nature under adverse conditions like low oxygen conditions or starvation fish often lower their metabolism: `metabolic depression¿. This strategy of lowering the metabolic rate is a survival strategy and is used to save energy stores and diminish end-product accumulation. The overall metabolic rate of animals can be deduced by measuring metabolic processes such as oxygen consumption, but the ultimate method is measuring heat flow. In this review, we will summarise the available data about metabolic depression measuring heat flow, i.e. by direct calorimetry in fishes, which were carried out almost exclusively with a 1-l flow through calorimeter. Using deconvolution techniques the time constant of this calorimeter was measured that allowed to estimate the time course of metabolic depression, which was found to take place on a time scale of 20-30 min. We demonstrated that metabolic depression is species dependent. Goldfish, eel and tilapia show metabolic depression under low oxygen conditions while this is not the case for common carp. In addition it is shown that metabolic depression is flexible and increases with decreasing oxygen availability. Furthermore using a video analysing system we demonstrated that metabolic depression is not caused by a reduction of external activity. As heart rate falls dramatically during metabolic depression as shown by small wireless transmitters, we hypothesise that blood flow reduction might be the proximate cause for metabolic depressio

“Infectobesity: viral infections (especially with human adenovirus-36: Ad-36) may be a cause of obesity

In recent years viral infections have been recognized as possible cause of obesity, alongside the traditionally recognized causes (genetic inheritance, and behaviour/environmental causes such as diet exercise, cultural practices and stress). Although four viruses have been reported to induce obesity (infectoobesity) in animal models (chickens, mice, sheep, goat, dogs, rats and hamsters), until recently the viral etiology of human obesity has not received sufficient attention, possibly because the four viruses are not able to infect humans. In a series of papers over the last ten years, however, the group of Prof. Dhurandhar (Pennington Biomedical Research Center, LA, USA) demonstrated that a human adenovirus, adenovirus-36 (Ad-36), is capable of inducing adiposity in experimentally infected chickens, mice and non-human primates (marmosets). Ad-36 is known to increase the replication, differentiation, lipid accumulation and insulin sensitivity in fat cells and reduces those cells’ leptin secretion and expression. It also affects human primary preadipocytes. In rats increased adiposity was observed due to Ad-36 infection. Recent studies have shown that, in the USA, antibodies to Ad-36 were more prevalent in obese subjects (30%) than in non-obese subjects (11%). We postulate that Ad-36 may be a contributing factor to the worldwide rising problem of obesity. We suggest the extension of comparative virological studies between North America and Europe, and studies between discordant twins (both dizygous and monozygous

Tilapia are able to withstand long-term exposure to low environmental pH, judged by their energy status, ionic balance and plasma cortisol

Contains fulltext : 28548___.PDF (publisher's version ) (Open Access

Bedreigen virussen de palingpopulatie?

Resultaten van een onderzoek naar het voorkomen van virussen (EVEX, Eel Virus European X; HVA, Herpes Virus Anguillea; EVE, Eel Virus European) bij palingen afkomstig uit diverse landen (zowel wilde paling als paling van kwekerijen) en van een zwemexperiment met geïnfecteerde en niet-geïnfecteerde palingen. Na voltooiing van de zwemreis werd in beide groepen het bloedbeeld onderzocht op diverse parameters (o.a. op hematocriet, het aantal rode bloedcellen). De resultaten zijn zeer verontrustend, omdat ze een aanwijzing vormen dat virus-infectie ertoe leidt dat palingen hun migratie naar de paaigronden niet kunnen voltooien door bloedarmoede, een beschadigde lever en een tekort aan eiwitten. Dit kan mede een oorzaak zijn voor het wereldwijd teruglopen van de palingstan

Impact of eel viruses on recruitment of European eel

Eels have an uncommon catadromic life cycle with exceptional migratory patterns to their spawning grounds several thousand kilometres away: the European eel (Anguilla anguilla) travels over 5,500 km to the Sargasso Sea (Schmidt 1923; McCleave and Kleckner 1987; Tesch 1982; Tesch and Wegner 1990); the American eel (A. rostrata) migrates over 4,000 km also to the Sargasso Sea (Castonguay and McCleave 1987; McCleave and Kleckner 1987; Tesch and Wegner 1990); the Australian eel (A. aus-tralis) travels over 5,000 km into the Pacific Ocean to spawn (Jellyman 1987); and the Japanese eel (A. japonica) travels over 4,000 km to an area near the Marianna Islands in the Philippines to spawn (Tsukamoto 1992). Evidently such long distance swimming will place those fishes under extra stress caused by the long starvation period, the high energy cost of the journey, and the many changes in the environment such as salt water, darkness, high pressure, and low temperatures, among other stress factors. Stress is often a basis for disease in eel, especially in intensive eel culture (Haenen and Engelsma, 2005 unpublished finding). Nowadays, global transport of live fishes for aquaculture has facilitated the global spread of pathogens from diseased to healthy stocks. Within the last few decades, aquaculture has become an important production branch in our society. Its global production has more than doubled between 1986 and 1996 in tonnage and value, and over one quarter of human fish consumption at world scale is now produced in aquaculture (Naylor et al. 2000). The Netherlands is one of the leading eel producing & trading countries (Heinsbroek and Kamstra 1995). Blanc (1997) showed that nearly 100 pathogens have been introduced into European water bodies since the introduction of aquaculture. Worldwide many diseases are known in both wild and cultured eel. Parasites, for example trematodes, Anguillicola crassus(nematode), and Myxidium giardi (myxosporean)occur naturally in wild eel populations, mostly in low numbers, without causing mortality (Køie 1988; Van Banning and Haenen 1990; Borgsteede et al. 1999). However, under culture conditions, with eels kept in high densities, they may be harmful. Eel pathogenic bacteria like Vibrio vulnificus, Vibrio anguillarum, Pseudomonas anguillisepticaand Edwardsiella tardamay also cause disease, especially when a stress factor is involved or when the eel is injured (Veenstra et al. 1993; Austin and Austin 1999; Haenen and Davidse 2001). As far as we know, the clinical signs are often more severe under culture conditions compared to in the wild

Are dioxin-like contaminants responsible for the eel (Anguilla anguilla) drama?

Eel populations worldwide are dangerously close to collapsing. Our study is the first to show that current levels of dioxin-like contaminants are strong candidates because of their devastating effects on development and survival of eel embryos. Female and male silver eels were artificially stimulated to maturation and reproduction by treatment with carp pituitary extracts and hCG, respectively. During maturation of female European silver eels, about 60 g fat per kg eel is incorporated in the oocytes. Together with the fat, however, persistent organic pollutants such as dioxin-like polychlorinated biphenyls (PCBs) are incorporated too. The total dioxin-like toxic potency of the individual gonad batches was determined as 2,3,7,8-tetrachlorodibenzo-p-dioxine equivalents (TEQs), using an in vitro reporter gene assay. The observed differences in development and survival showed a significant negative correlation with the TEQ levels in the gonads, already at levels far below the maximal allowable level for fish consumption, i.e., 4 ng TEQ/kg fish. The clear inverse relationship between the TEQ level and the survival period of the fertilised eggs strongly suggests that the current levels of dioxin-like compounds seriously impair the reproduction of the European eel. The peak of the environmental levels of dioxin-like PCBs and the decline of eel coincide worldwide, further suggesting that, in addition to other threats, these contaminants contributed significantly to the current collapse in eel populations