Increased expression of GAPDH protein is not indicative of nitrosative stress or apoptosis in liver of starved rainbow trout (Oncorhynchus mykiss)

The health and condition responses of Delta Smelt to fasting: A time series experiment

There is an extensive literature establishing, validating, and quantifying a wide range of responses of fishes to fasting. Our study complements this work by comparing fed and unfed treatments of hatchery-raised Delta Smelt (Hypomesus transpacificus)-an imperiled fish that is endemic to the San Francisco Estuary and its tributaries in California, USA-across a diverse suite of endpoints over a two-month time series. The experiment was conducted at 15.9°C, and individuals were sampled at 12 time points as starvation became increasingly severe. We found that hepatosomatic index and condition factor were relatively sensitive to starvation, becoming significantly depressed at Day 4 and 7, respectively. Histological analysis of liver showed elevated cytoplasmic inclusion bodies at Day 7, followed by increased glycogen depletion, single cell necrosis, and hydropic vacuolar degeneration at Day 14, 21, and 28, respectively. Of four antioxidants measured, glutathione decreased at Day 4, superoxide dismutase increased at Day 14, catalase increased at Day 56, and glutathione peroxidase was not affected by starvation. The net result was a ~2-fold increase in lipid peroxidation (malondialdehyde) in fasted fish that was highly inconsistent through time. RNA to DNA ratio and triglycerides in muscle were relatively insensitive to starvation, only consistently decreasing with fasting after mortality began increasing in the 'No Feeding' treatment, at Day 21. Together, these results suggest that Delta Smelt mobilize hepatic energy stores far more rapidly than lipids in muscle when subjected to fasting, leading to rapid atrophy of liver and the development of cytoplasmic inclusion bodies-possibly autophagosomes-in hepatocytes.

Antistarvation Strategies of E. Sinensis: Regulatory Networks under Hepatopancreas Consumption

Crustaceans have a more persistent starvation tolerance than mammals, birds, reptiles, and even fish. This study is aimed at assessing the survival strategy and regulatory mechanism of crustaceans in response to starvation through an animal model using Eriocheir sinensis. In the 42-day starvation experiment, the hepatopancreas was found to become the target organ, which was characterized by atrophy of the thin wall in the hepatic tubules and expansion of the lumen. During short-term starvation, E. sinensis activates lipid and glycogen metabolism in the hepatopancreas with lipid metabolism dominating. In lipid metabolism, there was a significant decline in triglyceride, whereas cholesterol did not change significantly. Meanwhile, the fatty acid metabolism pathway was inhibited, but autophagy increased in the hepatopancreas, which may be the selective pathway for the decomposition of intracellular substances. However, under long-term starvation, the stored energy in the hepatopancreas was depleted, and E. sinensis selects to consume hepatopancreatic cells and maintain energy metabolism through apoptosis, which was triggered by both the death receptor pathway and the mitochondrial pathway. In addition, cell proliferation was blocked to reduce unnecessary energy consumption.

Dietary Effect on the Proteome of the Common Octopus (Octopus vulgaris) Paralarvae

Nowadays, the common octopus (Octopus vulgaris) culture is hampered by massive mortalities occurring during early life-cycle stages (paralarvae). Despite the causes of the high paralarvae mortality are not yet well-defined and understood, the nutritional stress caused by inadequate diets is pointed out as one of the main factors. In this study, the effects of diet on paralarvae is analyzed through a proteomic approach, to search for novel biomarkers of nutritional stress. A total of 43 proteins showing differential expression in the different conditions studied have been identified. The analysis highlights proteins related with the carbohydrate metabolism: glyceraldehyde-3-phosphate-dedydrogenase (GAPDH), triosephosphate isomerase; other ways of energetic metabolism: NADP⁺-specific isocitrate dehydrogenase, arginine kinase; detoxification: glutathione-S-transferase (GST); stress: heat shock proteins (HSP70); structural constituent of eye lens: S-crystallin 3; and cytoskeleton: actin, actin-beta/gamma1, beta actin. These results allow defining characteristic proteomes of paralarvae depending on the diet; as well as the use of several of these proteins as novel biomarkers to evaluate their welfare linked to nutritional stress. Notably, the changes of proteins like S-crystallin 3, arginine kinase and NAD⁺ specific isocitrate dehydrogenase, may be related to fed vs. starving paralarvae, particularly in the first 4 days of development.

The interactive effect of digesting a meal and thermal acclimation on maximal enzyme activities in the gill, kidney, and intestine of goldfish (Carassius auratus)

Surrounding environmental temperatures affect many aspects of ectotherm physiology. Generally, organisms can compensate at one or more biological levels, or allow temperature to dictate processes such as enzyme activities through kinetic effects on reaction rates. As digestion also alters physiological processes such as enzyme activities, this study determined the interacting effect of thermal acclimation (8 and 20 °C) and digesting a single meal on maximal enzyme activities in three tissues of the goldfish (Carrassius auratus). Acclimation to elevated temperatures decreased branchial Na⁺, K⁺, ATPase (NKA) activity. In contrast, acclimation to elevated temperatures had no effect on citrate synthase (CS) or pyruvate kinase (PK) activity in any tissue, nor were renal NKA or glutamine synthetase (GS) activities impacted. Warm water-acclimation exaggerated the positive impact of digestion on intestinal and branchial NKA activities and intestinal GS activity only, but digestion had no effect in the kidney. CS and PK did not display intestinal zonation; however, there was a distinct increase towards the distal intestine in NKA and GS activities. Zonation of NKA was more prominent in warm-acclimated animals, while acclimation temperature did not affect intestinal heterogeneity of GS. Finally, the impact of tissue protein content on enzyme activity was discussed. We conclude that the intestine and gill of warm-acclimated goldfish exhibited an augmented capacity for increasing several enzyme activities in response to digestion while the kidney was unaffected by thermal acclimation or digesting a single meal. However, this amplified capacity was ameliorated by alterations in tissue protein content. Amplified increases in NKA activity may ultimately have implications for ATP demand in these tissues, while increased GS activity may beneficially increase ammonia-detoxifying capacity in the intestine.

Proteomic analysis of rainbow trout (Oncorhynchus mykiss) intestinal epithelia: physiological acclimation to short-term starvation

The intestinal epithelia form the first line of defense against harmful agents in the gut lumen of most monogastric vertebrates, including teleost fishes. Previous investigations into the effect of starvation on the intestinal epithelia of teleost fishes have focused primarily on changes in morphological characteristics and targeted molecular analysis of specific enzymes. The goal of this study was to use a comprehensive approach to help reveal how the intestinal epithelia of carnivorous teleost fishes acclimate to short-term nutrient deprivation. We utilized two-dimensional gel electrophoresis (2-DE) to conduct the proteomic analysis of the mucosal and epithelial layer of the anterior gut intestinal tract (GIT) from satiation fed vs. 4 week starved rainbow trout (Oncorhynchus mykiss). A total of 40 proteins were determined to be differentially expressed and were subsequently picked for in-gel trypsin digestion. Peptide mass fingerprint analysis was conducted using matrix assisted laser desorption time-of-flight/time-of-flight. Nine of the 11 positively identified proteins were directly related to innate immunity. The expression of α-1 proteinase inhibitor decreased in starved vs. fed fish. Also, the concentration of one leukocyte elastase inhibitor (LEI) isomer decreased in starved fish, though the concentration of another LEI isomer increased in due to starvation. In addition, starvation promoted an increased concentration of the important xenobiotic-transporter p-glycoprotein. Finally, starvation resulted in a significant increase in type II keratin E2. Overall, our results indicate that starvation promoted a reduced capacity to inhibit enzymatic stress but increased xenobiotic resistance and paracellular permeability of epithelial cells in the anterior intestine of rainbow trout.