The regulation of endogeneous energy stores during starvation and refeeding in the somatic tissues of the golden perch

Adult golden perch Macquaria ambigua were fed to satiety, starved for up to 210 days, or starved for 150 days then fed to satiety for 60 days to investigate the utilization of energy stores in response to food deprivation and re-feeding. Golden perch sequentially mobilize energy from hepatic tissue, extra-hepatic lipid, and finally muscle components in response to food deprivation. The relative size of the liver was significantly reduced by 30 days after the onset of food deprivation due to the simultaneous mobilization of lipid, protein and glycogen reserves. These stores were renewed rapidly within 30 days by satiety feeding. Mobilization of lipid stores in perivisceral fat bodies occurred between 30 and 60 days of food deprivation. These deposits were also renewed upon re-feeding, although not as rapidly as liver reserves. The glycogen content of the epaxial muscle was reduced by the 60th day of food deprivation but subsequently increased indicating the mobilization of other energy reserves. The concentration of muscle lipid decreased after 90 days of food deprivation. The only significant response in body composition observed in the fish fed to satiety throughout the study was an increase in the relative size of the perivisceral fat bodies. The results of this study suggest that golden perch are well adapted to cope with extended periods of food deprivation, storing energy as perivisceral fat when food is readily available and having a clearly sequential process for mobilizing energy when food is scarce which largely protects the integrity of the musculature.     

Physiological and metabolic adjustments of Hoplosternum littorale (Teleostei,Callichthyidae) during starvation

All animals face the possibility of limitations in food resources that could ultimately lead to mortality caused by starvation. The primary goal of this study was to characterize the various physiological strategies that allow fish to survive starvation. A multiparametric approach, including morphological biomarkers, blood plasma metabolites, oxidative stress and energy reserves, was used to assess starvation effects on the fish Hoplosternum littorale. Adult specimens were maintained at four experimental groups: control (fed ad libitum), and starved (not fed) fish for 7 and 28 days. Significant changes were observed not only after 28 days, but also after 7 days of starvation. In the shorter period, the hepatosomatic index as well as plasma triglycerides and glucose were significantly lower in starved fish than in the control ones. These results were accompanied by reduced lipid, glycogen and protein reserves in liver and diminished glycogen content in muscle, suggesting the need of these macromolecules as fuel sources. In addition, increased antioxidant enzyme activities were observed in gills, without evidence of oxidative stress in any of the evaluated tissues. Most significant differences were found in 28-days starved fish: total body weight together with the hepatosomatic index was lower when compared to control fish. The plasmatic metabolites tested (glucose, triglyceride, cholesterol and protein), all energy reserves in liver and glycogen content in muscle decreased in 28-days starved fish. Lipid oxidative damage was reported in liver, kidney and brain, and antioxidant enzymes (GST, GR, GPx and CAT) were activated in gills. According to the multivariate analysis, oxidative stress markers and metabolic parameters were key biomarkers that contributed in separating starved from fed fish. Our study allowed an integrated assessment of the fish response to this particular condition.     

Effect of starvation and a protein diet on the amino acid metabolism enzyme activities of the organs of domestic fowl hatchlings

The activities of alanine and aspartate transaminases, adenylate deaminase, glutamine synthetase and glutamate and xanthine dehydrogenases have been measured in liver, yolk sac membrane, intestine and breast and leg muscle of domestic fowl hatchlings receiving for 3 or 5 days either a standard diet or hard boiled eggwhite as well as in 3 or 5 days starved animals. The patterns of activation of amino acid metabolism enzymes were fully comparable in protein-fed and starved groups with respect to fed controls; the differences with respect to the latter became more marked in 5- than in 3-days old chicks. In 5-days old chicks intestine alanine transaminase activity increased in parallel to that of liver in protein-fed animals but not in those starved, in agreement with an enhanced alanine transfer between both organs under this situation. Both, starvation and protein-feeding, induced a general decrease in the amino acid metabolizing ability of muscle. Glutamine (but not alanine) synthetizing capabilities were enhanced.     

Lysosomal enzyme activities in muscle following starvation and refeeding in the saithe Pollachius virens L

Saithe (Pollachius virens L.) were starved for 66 days at 10 degrees C and activities of aryl sulfatase, acid proteinase, beta-glucuronidase, RNAase and acid phosphatase measured in homogenates prepared from fast and slow myotomal muscles. In fed fish, hydrolase activities were generally higher in slow than fast muscles. With the exception of acid proteinase activity in slow muscle, the activities of all the lysosomal enzymes increased by 70 to 100% during starvation. In general, there was a proportionally larger increase in the hydrolase activities in fast than in slow muscle. In a second experiment, fish were starved for 74 days, and refed for up to 52 days. The increases in aryl sulfatase and acid proteinase activity produced in fast muscle with starvation were found to be rapidly reversed by refeeding. Lysosomal enzyme activities in fish sampled after 10 days refeeding were not significantly different from fed controls. Membrane fractions enriched in aryl sulfatase activity were prepared from the fast muscle of 66-day starved fish. These were capable of degrading both myosin heavy chains and actin to lower molecular weight peptides at acid (pH 5.0), but not at neutral pH. The results suggest a role for lysosomal enzymes in the breakdown of myofibrillar proteins during starvation.     

The role of food availability in regulating reproductive development in female golden perch

At a time of the year when female golden perch Macquaria ambigua are not normally reproductively active, they were either fed daily to satiety (Fed), starved for 150 days (S150), or starved for 150 days then fed to satiety for 30 or 60 days (S150/F30 or S150/F60). Fish showed rapid growth and increased food conversion efficiency upon re-feeding relative to Fed animals. The hepatosomatic indices were not significantly different between Fed, S150/F30 and S150/F60 groups, but were significantly reduced in S150 animals. The gonadosomatic indices ( I _G) for both Fed and S150 animals were not significantly different. However, the I _G values for S150/F30 and S150/F60 animals of 6·74±1·22 and 7·84±1·12 were significantly elevated relative to Fed animals and approach those described for wild mature M. ambigua . Oocyte development in Fed and S150 animals did not proceed past the cortical alveoli or perinucleolar stages, respectively, but oocytes in both S150/F30 and S150/F60 animals had undergone vitellogenesis and were close to being mature. The concentration of oestradiol and testosterone in the plasma of S150/F30 and S150/F60 animals increased in accordance with the proposed role of these hormones in teleost reproductive cycles. The reproductive response of M. ambigua to starvation and re-feeding is well suited to reproductive success in temperate Australian rivers where food availability is unpredictable.     

Metabolic changes in the African fruit beetle,Pachnoda sinuata,during starvation

Specimens of the fruit beetle Pachnoda sinuata were starved for up to 30 days. The weight of the beetles declined consistently throughout the starvation period. Concentrations of carbohydrates and alanine in flight muscles, fat body and haemolymph decreased rapidly after onset of starvation, while the concentration of proline remained high. Whereas the lipid concentrations in the haemolymph did not change significantly upon starvation, the lipid content in flight muscles and fat body decreased significantly.Beetles that had been starved for 14 days responded to injection of Mem-CC, the endogenous neuropeptide from its corpora cardiaca, with hyperprolinaemia and a decrease in the alanine level, but no such effect was monitored after prolonged starvation of 28 days. Regardless of the period of starvation, Mem-CC injection could not cause hypertrehalosaemia or hyperlipaemia, although carbohydrates were increased in fed beetles after injection.Flight ability of beetles that had been starved for 15 or 30 days was apparently not impaired. During such periods, beetles used proline exclusively as fuel for flight as evidenced by the increase in the level of alanine in the haemolymph and decrease of the level of proline; the concentrations of carbohydrates and lipids remained unchanged.Activities of malic enzyme and alanine aminotransferase (enzymes involved in transamination in proline metabolism), glyceraldehyde-3-phosphate dehydrogenase (enzyme of glycolysis), 3-hydroxyacyl-CoA dehydrogenase (enzyme of beta-oxidation of fatty acids) and of malate dehydrogenase (enzyme of Krebs cycle) were measured in fat body and flight muscles. In flight muscle tissue the maximum activity of NAD(+)-dependent malic enzyme increased, while that of glyceraldehyde-3-phosphate dehydrogenase decreased during starvation, and malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase and alanine aminotransferase were unchanged. In fat body tissue, activities of NADP(+)-dependent malic enzyme and 3-hydroxyacyl-CoA dehydrogenase increased during food deprivation and activities of glyceraldehyde-3-phosphate dehydrogenase, malate dehydrogenase and alanine aminotransferase remained unchanged.     

Lipid mobilization during starvation in the rainbow trout, Salmo gairdneri Richardson, with attention to fatty acids

Rainbow trout, Salmo gairdneri , were fed pelleted food ad libitum for 35 and 50 days. Lipid deposits were determined in the viscera, liver and muscle (epaxial and hypaxial). Most of the lipid accumulated in the viscera, but the lipid content of liver and epaxial muscle also increased. Hypaxial muscle lipid content remained the same throughout the feeding period. Upon starving the fish for 27 and 48 days following 50 days of feeding, visceral lipid contributed most to energy metabolism among the depots investigated. Muscle also contributed a considerable share while the absolute amount derived from the liver was much smaller.
Patterns of fatty acid mobilization during starvation were also investigated. Saturated acids were preferentially mobilized from the viscera, resulting in a rise in the percentage of monoenes and polyunsaturates. In liver, the percentage of saturates remained relatively constant whereas the percentage of monoenes declined and polyunsaturates increased. In muscle, a substantial increase in saturates was caused by a decline in monoenes; polyunsaturate content remained constant. As a result of these shifts in relative fatty acid composition the U/S (unsaturates to saturates) ratio rose in viscera and liver and decreased in muscle. The UI (unsaturation index) responded in essentially the same way. Possible explanations for preferential fatty acid utilization are discussed in terms of energetics and structural relationships.     

Effects of starvation on lipid accumulation and antioxidant response in the right and left lobes of liver in large yellow croaker Pseudosciaena crocea

The present study aimed to determine the effects of starvation on lipid content and antioxidant responses in the right and left lobes of liver in large yellow croaker. Fish were divided into three groups: the control fish fed normally and the fish starved for 4 and 12 days. The set of biomarkers were determined, including crude lipid and MDA contents, and mRNA levels and activities of copper and zinc superoxide dismutase (Cu/Zn-SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR). Starvation for 12 days decreased lipid content and increased MDA content and mRNA levels and activities of antioxidant enzyme genes tested in both lobes of liver. No significant difference in these biomarkers between both lobes of liver was observed in fish starved for 12 days. However, there were significant differences between both lobes of liver in lipid and MDA contents, activities of CAT and GR, and expression levels of Cu/Zn-SOD and GR in fish starved for 4 days. These observed differences between starved and fed fish and between both lobes of liver could be important biomarkers that contributed in separating starved from fed fish and short-term starved from long-term starved fish, respectively. Our study emphasized the same lobe of the liver should be sampled when evaluating biomarkers during starvation in fish.     

Radioglucose metabolism by richardson's ground squirrels in the weight-gain and weight-loss phases of the circannual cycle

Summary Captive fed, starved, and refed Richardson's ground squirrels in the weight-gain and weight-loss phases of the circannual cycle were injected with radioglucose and the activity of the label in skeletal muscle proteins and white adipose tissue lipids four hours after injection was used to determine if lean body mass and white adipose tissue would be rapidly restored when starved animals were refed. Starvation for six days reduced carcass mass 27–31% and white adipose tissue mass 23–24% (Table 1). Activity of the label in both tissues of weight-gain and weight-loss animals was reduced by starvation. After four days of refeeding activities retured to levels similar to those in fed animals, with the exception of lower activity in skeletal muscle proteins of weight-gain animals. Furthermore, activity in each tissue fraction of starved and refed weight-gain animals was similar to that in weight-loss animals when expressed as per cent of activity in the respective fed state (Table 2). Radioglucose incorporation indicated that when skeletal muscle and adipose tissue are depleted by starvation, distribution of the label upon refeeding is similar to that in the fed state. Four days after refeeding weight-gain phase ground squirrels had restored 5.5 g of lean body mass and 7.5 g of adipose tissue, including 1.4 g (6 kcal) of protein and 7.0 g (66 kcal) of lipid, respectively. These results are also consistent with the fed state, in which weight-gain animals were depositing more lipid than lean body mass.     

Life history response and age-specific tolerance to starvation in Brachionus plicatilis O.F. Müller (Rotifera)

To examine the life history response and age-specific tolerance to starvation in the rotifer Brachionus plicatilis O.F. Müller, we carried out two series of individual culture experiments. In the first experiment, rotifers were fed until each of the ages of 1-4 days, and were then starved during the rest of their lifetimes. The control group was fed throughout their lifespans. Rotifers stopped active reproduction just after the onset of food deprivation, and showed shorter subsequent survival times when they were starved at older ages. The finding that the larger the number of offspring produced before food deprivation, the shorter the subsequent lifetime under starvation, appeared to reflect a trade-off with the cost of reproduction. In the second experiment, newborns were starved until each of the ages of 1-5 days, and were fed thereafter. The lifespans of the rotifers starved up to the age of 3 days were not statistically different from those that were not starved. Although the starved rotifers began to reproduce once fed again, their lifetime fecundity decreased significantly from that of the non-starved group. Based on these results, it was suggested that the reproductive suppression caused by starvation would cause rotifers to have a longer lifespan to allow for future reproduction.     

The effects of long-term food deprivation on respiration and haematology of the neotropical fish Hoplias malabaricus

Growth of adult traíras Hoplias malabaricus ceased and body mass ( M ) decreased during starvation periods of 30, 60, 90, 150, 180 and 240 days. Hepatic reserves were mobilized in fish starved for 30 days, but liver mass of fish starved for longer periods was not significantly different from those starved for 30 days. Perivisceral fat bodies were consumed gradually, being completely exhausted after 240 days of food deprivation. Length of starvation was associated with a significant decrease in the oxygen uptake ( V o₂). In spite of this reduction, the respiratory frequency ( f _R) was kept nearly constant during the starvation periods. The haematocrit and the number of red blood cells decreased after 150 and 240 days of starvation, respectively. These parameters did not recover after refeeding (after 90 and 240 days of starvation). This hypometabolic state in response to food deprivation contributed to energy conservation during these periods. Traíras can survive food deprivation for periods of up to 180 days without reductions in metabolism and when they do become hypometabolic, normal metabolic rates are rapidly restored upon refeeding.     

In vitro degradation of leucine in muscle,adipose tissue,liver, and kidney of fed and starved sheep

In vitro rates of conversion of [1-14C]leucine to 4-methyl-2-oxo[1-14C]pentanoate and of oxidation of [1-14C] and [U-14C]leucine were measured for tissues from fed and starved (5 days) sheep. Slices of liver and kidney and preparations of adipose tissue and of fibre bundles of external intercostal muscle (EIC) were used. Skeletal muscle is likely the major site of leucine catabolism in sheep although adipose tissue is capable of substantial metabolism. Muscle and adipose tissue from fed sheep released 17 and 5% of the [1-14C]leucine transaminated as 4-methyl-2-oxo-[1-14C]pentanoate and upon starvation the proportions were increased (P less than 0.001) to 46 and 32%. Starvation reduced (P less than 0.01) leucine catabolism in all tissues except the kidney. The pattern of leucine catabolism in EIC muscle changed from extensive oxidation in the fed state to being limited essentially to transamination and decarboxylation in the starved state.     

Effects of feeding,starvation, and refeeding on the fatty acid composition of channel catfish,ICtalurus punctatus,tissues

• 1.1. The effects of feeding, food deprivation (14 and 28 days) and refeeding (starved 14 then fed 14 days) on the fatty acid composition of white muscle, liver and brain of pond-raised channel catfish (Ictalurus punctatus) were investigated.
• 2.2. Levels of n-3 fatty acids were significantly higher (P < 0.05) in white muscle of fish starved 28 days (10.7%) than in fish fed throughout the study (8.0%), due primarily to an increase in 22:6(n-3) docosahexaenoic acid or DHA.
• 3.3. Significantly higher levels of 20:5(n-3) (eicosapentaenoic acid or EPA) were found in livers offish starved 28 days (P < 0.05) compared to fish fed throughout the study.
• 4.4. Results suggest that the fatty acid compositions of channel catfish white muscle and liver are subject to only limited perturbation during periods of starvation and refeeding and that the brain is extremely well protected.

     

Metabolic priorities during starvation: enzyme sparing in liver and white muscle of Atlantic cod,Gadus morhua L

Atlantic cod, Gadus morhua, respond to starvation first by mobilising hepatic lipids, then muscle and hepatic glycogen and finally muscle proteins. The dual role of proteins as functional elements and energetic reserves should lead to a temporal hierarchy of mobilisation where the nature of a function dictates its conservation during starvation. We examined (1) whether lysosomal and anti-oxidant enzymes in liver and white muscle are spared during prolonged starvation, (2) whether the responses of these enzymes in muscle vary longitudinally. Hepatic contents of lysosomal proteases decreased with starvation, whereas those of catalase (CAT) increased and lysosomal enzymes of carbohydrate metabolism and glutathione S-transferase (GST) did not change. In white muscle, starvation decreased the specific activity of lysosomal enzymes of carbohydrate degradation and doubled that of cathepsin D (CaD). The activity of anti-oxidant enzymes and acid phosphatase in muscle was unchanged with starvation. In white muscle neither lysosomal enzymes nor anti-oxidant enzymes varied significantly with sampling position. In cod muscle, antioxidant enzymes, CaD and acid phosphatase are spared during a period of starvation that decreases lysosomal enzymes of carbohydrate metabolism and decreases glycolytic enzyme activities. In cod liver, the anti-oxidant enzymes, CAT and GST, were also spared during starvation.     

The effect of starvation and starvation followed by feeding on enzyme activity and the metabolism of [U-14C]glucose in liver from growing chicks

1. The conversion of [U-(14)C]glucose into carbon dioxide, cholesterol and fatty acids in liver slices and the activities of ;malic' enzyme, citrate-cleavage enzyme, NADP-linked isocitrate dehydrogenase and hexose monophosphate-shunt dehydrogenases in the soluble fraction of homogenates of liver were measured in chicks that were starved or starved then fed. 2. In newly hatched chicks the incorporation of [U-(14)C]glucose and the activity of ;malic' enzyme did not increase unless the birds were fed. The response to feeding of [U-(14)C]glucose incorporation into fatty acids increased as the starved chicks grew older. 3. Citrate-cleavage enzyme activity increased slowly even when the newly hatched chicks were unfed. On feeding, citrate-cleavage enzyme activity increased at a much faster rate. 4. In normally fed 20-day-old chicks starvation decreased the incorporation of [U-(14)C]glucose into all three end products and depressed the activities of ;malic' enzyme and citrate-cleavage enzyme. Re-feeding increased all of these processes to normal or higher-than-normal levels. 5. In both newly hatched and 20-day-old chicks starvation increased the activity of isocitrate dehydrogenase and feeding or re-feeding decreased it. 6. Very little change in hexose monophosphate-shunt dehydrogenase activity was observed during the dietary manipulations. 7. The results indicate that increased substrate delivery to the liver is the principal stimulus to the increased rate of glucose metabolism observed in newly hatched chicks. The results also suggest that changes in the activities of ;malic' enzyme and citrate-cleavage enzyme are secondary to an increased flow of metabolites through the glucose-to-fatty acid pathway and that the dehydrogenases of the hexose monophosphate shunt play a minor role in NADPH production for fatty acid synthesis.     

Lack of hepatic enzymatic adaptation to low and high levels of dietary protein in the adult cat.

The activities of three urea cycle enzymes, several nitrogen catabolic, gluconeogenic, and lipogenic enzymes were measured in the liver of adult cats fed: a commercial kibble; a 17.5 or 70% protein purified diet, or starved for 5 days. Except for an increase in tyrosine transaminase (EC 2.6.1.5) after feeding the high protein diet, there were no changes in the activities of the hepatic enzymes as influenced by dietary protein level. Likewise, starvation had a minimal effect on the activities of these enzymes as compared to that found in similar experiments in rats. These results indicate that the cat may have only minimal capabilities for enzyme adaptation as compared to that found in many herbivores and omnivores and may provide an explanation as to why cats have an unusually high protein requirement as compared to many other mammals.     

Increases in hepatic fructose-2,6-bisphosphate level and fructose-6-phosphate,2-kinase activity in rats with ventromedial lesions of the hypothalamus

To investigate altered fructose-2,6-bisphosphate (fructose-2,6-P2) metabolism, we measured fructose-2,6-P2 levels and fructose-6-phosphate,2-kinase (fructose-6-P,2-kinase) activities in various tissues, including liver, kidney, heart, and skeletal muscle, of ventromedial hypothalamus (VMH)-lesioned rats during feeding and starvation. The plasma insulin level was 6 times or more higher in these rats than in the controls. The fructose-2,6-P2 level in liver was much greater in VMH-lesioned rats than in the controls: 15.1 +/- 2.2 nmol/g tissue versus 7.7 +/- 0.7 in the fed state, 5.3 +/- 1.1 versus 1.6 +/- 0.4 in the starved state. In kidney, heart, and skeletal muscle, fructose-2,6-P2 levels were not different between the two animal groups. The activity of hepatic fructose-6-P,2-kinase remained high after 20 h of starvation in VMH-lesioned rats, whereas it was decreased markedly in the controls. The hepatic concentration of fructose-6-phosphate was also high in VMH-lesioned rats. Both fructose-6-P,2-kinase activity and fructose-6-phosphate concentration in the liver of starved VMH-lesioned rats were comparable to those of control rats in fed conditions. These results indicate that the alteration of fructose-2,6-P2 metabolism is characteristic of liver in VMH-lesioned rats, and that the increase in hepatic fructose-2,6-P2 may activate hepatic glycolysis not only during feeding but also during starvation, leading to the enhanced lipogenesis in these obese rats.     

Are the increases in local tumour necrosis factor and lipid peroxidation observed in pre-starved mice infected with Salmonella typhimurium markers of increased liver damage?

Pathogenic microorganisms are known to sense and process signals within their hosts, including those resulting from starvation. Therefore, an attempt was made to evaluate the extent and the possible underlying mechanism of Salmonella typhimurium-induced hepatic damage using pre-starved laboratory mice. The following parameters were analysed, comparing control, fed infected, starved, and starved infected mice: the bacterial load in the liver, fluctuations in liver-derived enzymes alanine-aminotransferase and aspartate-aminotransferase, histopathological changes, lipid peroxidation as well as estimation of reduced glutathione, superoxide dismutase and catalase, along with the TNF content in livers. The number of bacterial cells recovered from starved infected livers at 3 days post-S. typhimurium inoculation was comparable to the number recovered from fed infected livers at 5 days post-Salmonella inoculation, indicating an early increase in the development of the bacteria in starved mice. A marked elevation in liver-derived enzymes in mouse serum and significant histopathological changes are markers of liver damage of higher amplitude in starved infected mice. Analysis of the liver indicated a significant increase in lipid peroxidation in starved infected mice compared to their control counterparts, a process coupled with increased TNF level. Although the reduced glutathione levels showed a marked increase in the starved infected mice, there was a significant decrease in superoxide dismutase and catalase activities in this group.     

Effects of repeated cycles of starvation and refeeding on lungs of growing rats.

Adult male rats were subjected to four cycles of mild starvation (2 wk) and refeeding (1 wk) and were compared with a fed group. Starvation was induced by giving rats one-third of their measured daily food consumption. During each starvation cycle, rats lost approximately 20% of their body weight. Despite catch-up growth and overall weight gain, starved rats had lower final body weight than fed rats. Lung dry weight and lung volumes were also reduced in the starved group. The mechanical properties of air- and saline-filled lungs did not change significantly with repeated cycles of starvation. Mean linear intercept was similar in the two groups, but alveolar surface area was reduced in the starved rats. Total content of crude connective tissue and concentration per lung dry weight of hydroxyproline and crude connective tissue were reduced in starved rats. We conclude that lung growth is retarded in growing rats subjected to repeated cycles of mild starvation and refeeding, as manifested by smaller lung volume and reduced alveolar surface area. Because alveolar size is unchanged, a reduced number of alveoli is most likely responsible for decreased lung volumes.     

The metabolic effects of prolonged starvation and refeeding in sturgeon and rainbow trout

The present study examines the particular metabolic strategies of the sturgeon Acipenser naccarii in facing a period of prolonged starvation (72 days) and subsequent refeeding (60 days) compared to the trout Oncorhynchus mykiss response under similar conditions. Plasma metabolites, endogenous reserves, and the activity of intermediate enzymes in liver and white muscle were evaluated. This study shows the mobilization of tissue reserves during a starvation period in both species with an associated enzymatic response. The sturgeon displayed an early increase in hepatic glycolysis during starvation. The trout preferentially used lactate for gluconeogenesis in liver and white muscle. The sturgeon had higher lipid-degradation capacity and greater synthesis of hepatic ketone bodies than the trout, although this latter species also showed strong synthesis of ketone bodies during starvation. During refeeding, the metabolic activity present before starvation was recovered in both fish, with a reestablishment of tissue reserves, plasmatic parameters (glucemia and cholesterol), and enzymatic activities in the liver and muscle. A compensatory effect in enzymes regarding lipids, ketone bodies, and oxidative metabolism was displayed in the liver of both species. There are metabolic differences between sturgeon and trout that support the contention that the sturgeon has common characteristics with elasmobranchs and teleosts.