Synthesis of hepatic secretory proteins in normal adults consuming a diet marginally adequate in protein.
The plasma concentration and hepatic synthesis rates of albumin, transthyretin, very low-density lipoprotein apolipoprotein B-100 (VLDL-apoB-100), high-density lipoprotein apolipoprotein A-1, fibrinogen, alpha1-antitrypsin, and haptoglobin were measured in six normal adults before and after consuming a protein intake of 0.6 g. kg body wt(-1). day(-1) for 7 days. The synthesis of hepatic proteins was measured from the incorporation of [(2)H(5)]- phenylalanine, following prime/continuous infusion, using plasma VLDL-apoB-100 isotopic enrichment to represent the precursor pool. Synthesis of albumin declined by 50% (P < 0.001) following the lower-protein diet, VLDL-apoB-100 declined by 20% (P < 0.001), and apoA-1 declined by 16% (P < 0.05). By contrast, synthesis increased for fibrinogen (50%, P < 0.05) and haptoglobin (90%, P < 0.001). This pattern of change, with decreased synthesis of nutrient transport proteins and increased formation of acute-phase proteins, suggestive of a low-grade inflammatory response, was accompanied by increased plasma concentration of the inflammatory cytokine interleukin 6 (30%, P < 0.05). The pattern of change in the synthesis of hepatic secretory proteins following 7 days on the low-protein diet may be of functional relevance for lipid transport and the capacity to cope with stress.
Jackson
A A
AA
Institute of Human Nutrition, University of Southampton, Southampton S016 6YD, United Kingdom.
Phillips
G
G
McClelland
I
I
Jahoor
F
F
D000209:Acute-Phase Proteins / Q000378:metabolism; D000328:Adult; D001798:Blood Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D018753:Diet, Protein-Restricted; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D008099:Liver / Q000378:metabolism*; D008297:Male; D009747:Nutritional Physiological Phenomena / Q000502:physiology; D012016:Reference Values
D000209:Acute-Phase Proteins; D001798:Blood Proteins; D002352:Carrier Proteins; D015850:Interleukin-6