Plasma Transthyretin Indicates the Direction of both Nitrogen Balance and Retinoid Status in Health and Disease

Abstract

Whatever the nutritional status and the disease condition, the actual transthyretin (TTR) plasma level is deter- mined by opposing influences between anabolic and catabolic alterations. Rising TTR values indicate that synthetic proc- esses prevail over tissue breakdown with a nitrogen balance (NB) turning positive as a result of efficient nutritional sup- port and / or anti-inflammatory therapy. Declining TTR values point to the failure of sustaining NB as an effect of malad- justed dietetic management and / or further worsening of the morbid condition. Serial measurement of TTR thus appears as a dynamic index defining the direction of NB in acute and chronic disorders, serving as a guide to alert the physician on the validity of his therapeutic strategy. The level of TTR production by the liver also works as a limiting factor for the cel- lular bioavailability of retinol and retinoid derivatives which play major roles in the brain ageing process. Optimal protein nutritional status, as assessed by TTR values within the normal range, prevents the occurrence of vascular and cerebral damages while maintaining the retinoid-mediated memory, cognitive and behavioral activities of elderly persons.