Disvitaminosi. In Trattato di Medicina Interna

Il capitolo prende in esame i diversi aspetti delle vitamine e ha l\u2019obiettivo di rivedere, alla luce della pi\uf9 recente letteratura, le modalit\ue0 di classificazione, il metabolismo, le funzioni, i fabbisogni, in condizioni fisiologiche , nelle diverse et\ue0 e nei due sessi, e nelle situazioni di disvitaminosi, oggi spesso subcliniche, ma comunque presenti e talora di difficile definizione, i quadri clinici di carenza, le pi\uf9 aggiornate indagini diagnostiche, le principali sorgenti alimentari e le interazioni tra farmaci e nutrienti. Le funzioni svolte delle vitamine si sono rivelate pi\uf9 complesse rispetto al passato, intervenendo nella regolazione della crescita dei tessuti, nella differenziazione cellulare, nella regolazione epigenetica dell\u2019espressione genica, come antiossidanti, antiinfiammatori e regolatori del sistema immunitario, e nella patogenesi di diverse patologie. Il testo comprende anche una descrizione della tossicit\ue0 di vitamine assunte in sovradosaggio, sostenuta da un diffuso e frequente ricorso a supplementi e integratori alimentari di vario tipo, assunti talora in modo indiscriminato o per funzioni non ancora confermate sul piano sperimentale

Mechanisms of altered protein turnover in chronic diseases: a review of human kinetic studies.

PURPOSE OF REVIEW: Changes in hormone secretion, tissue perfusion, oxygen availability, energy-protein intake, free amino acid pattern, hydration state, acid-base balance as well as activation of the systemic inflammatory response may affect protein synthesis and degradation. The overall purpose of this review is to describe how these factors may interact to change protein turnover in the different directions seen in kinetic studies in humans. RECENT FINDINGS: Evidence indicates that, in vivo, changes of protein synthesis and degradation are strictly related. When protein synthesis is primarily suppressed, protein degradation is found to be unchanged or even slightly decreased. When protein degradation is primarily accelerated, the rate of synthesis is unchanged or even increased. Chronic disease states can, therefore, be characterized either by decreased or accelerated protein turnover. Apparent discrepancies among various studies in chronic uraemia, liver cirrhosis, chronic obstructive pulmonary disease and cancer may stem from the fact that the pathogenesis of protein metabolism abnormalities is multifactorial. When the effects of inflammatory mediators and stress hormones start overwhelming factors that tend to decrease protein synthesis and turnover (decreased protein-energy intake, physical activity, tissue oxygen delivery, leucine levels, etc.), the rate of protein degradation and turnover may increase. SUMMARY: Low-protein turnover conditions are usually associated with the adequate sparing of body proteins, whereas in high-protein turnover conditions protein loss may proceed at a faster rate. Nonetheless, impaired recovery from acute complications and the reduced renewal of damaged and toxic proteins are potential undesired consequences of low-protein turnover