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Abstract

We report upon the effects of a cycle of long-term starvation followed by re-feeding on the liver-protein turnover rates and nature of protein growth in the rainbow trout (Oncorhynchus mykiss). We determined the protein-turnover rate and its relationship with the nucleic-acid concentrations in the livers of juvenile trout starved for 70 days and then re-fed for 9 days. During starvation the total hepatic-protein and RNA contents decreased significantly and the absolute protein-synthesis rate (A(S)) also fell, whilst the fractional protein-synthesis rate (K(S)) remained unchanged and the fractional protein-degradation rate (K(D)) increased significantly. Total DNA content, an indicator of hyperplasia, and the protein:DNA ratio, an indicator of hypertrophy, both fell considerably. After re-feeding for 9 days the protein-accumulation rates (K(G), A(G)) rose sharply, as did K(S), A(S), K(D)), protein-synthesis efficiency (K(RNA)) and the protein-synthesis rate/DNA unit (K(DNA)). The total hepatic protein and RNA contents increased but still remained below the control values. The protein:DNA and RNA:DNA ratios increased significantly compared to starved fish. These changes demonstrate the high response capacity of the protein-turnover rates in trout liver upon re-feeding after long-term starvation. Upon re-feeding hypertrophic growth increased considerably whilst hyperplasia remained at starvation levels.

Starvation alters the liver transcriptome of the innate immune response in Atlantic salmon (Salmo salar)

“…In mammals [19,20] and fish [30] protein synthesis is depressed following reduction in protein intake which appears to be a conserved response. Although both synthesis and degradation are decreased during starvation, the balance between synthesis and degradation shifts towards greater relative degradation [25,42,43], and in turn the reduced protein synthesis levels are reflected in the lower quantities of serum proteins synthesised and secreted [44]. Protein degradation, similar to protein synthesis is a tightly controlled process [45], with two key pathways of protein degradation down regulated in the starved fish, namely genes relating to the ubiquitin proteasome pathway of degradation [46] and lysosomal pathway enzymes including cathepsin D. Although the ubiquitin proteasome pathway in mammals is most often viewed as important in muscle tissue [47] clearly the general decreased transcription of genes in liver in the present study show it is an important pathway in liver tissue in fish.…”

Antiproliferative and Pro-Apoptotic Effect of Uvaol in Human Hepatocarcinoma HepG2 Cells by Affecting G0/G1 Cell Cycle Arrest, ROS Production and AKT/PI3K Signaling Pathway

“…Therefore, the participation of NADPH in both metabolic aspects makes it especially important for growth and cell differentiation [ 12 ]. For these reasons, the regulation of NADPH levels is essential to understand the behavior of numerous physiological processes and, in this sense, nutritional conditions [ 13 , 14 , 15 , 16 ]; the presence of triterpenes [ 17 , 18 ]; and the redox state [ 19 ] modify significantly the levels of those reduction equivalents.…”

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

“…Condition factor reflects nutritional status because body mass responds more quickly to food limitation than body length (e.g., [ 13 ]). Similarly, hepatosomatic index is responsive to food limitation because liver weight declines more rapidly than body weight as hepatic energy stores are rapidly mobilized (i.e, glycogen, lipid, and protein; [ 14 – 16 ]). The ratio of RNA to DNA in muscle is an indicator of recent growth, and therefore fasting, because RNA concentration in cells correlates with protein synthesis, whereas DNA concentration remains constant (e.g., [ 17 , 18 ]).…”