Acute Phase Protein Levels and Thymus, Spleen and Plasma Protein Synthesis Rates Differ in Adult and Old Rats

Abstract

Aging induces a dysregulation of immune and inflammation functions that may affect protein synthesis rates in lymphoid tissue and plasma proteins. We quantified in vivo synthesis rates of thymus, spleen and plasma proteins, including albumin and acute phase proteins, in adult (8 mo old) and old (22 mo old) rats using the flooding dose method [L-(1-(13)C) phenylalanine]. Immunosenescence was reflected by thymus atrophy and spleen hypertrophy in old rats but not in adult rats. A low albumin plasma level associated with high concentrations of fibrinogen, alpha(2)-macroglobulin, alpha(1)-acid glycoprotein and proteins other than albumin revealed a low grade inflammation in old rats. Protein fractional synthesis rates (FSR) and protein synthesis efficiencies of thymus were 29 and 26% lower in old than in adult rats, respectively; these variables did not differ in spleen. Protein absolute synthesis rates (ASR) of the thymus and spleen were 76% lower and 67% greater in old than adult rats, respectively. The FSR and ASR of albumin and other plasma proteins were greater in old than in adult rats. Protein synthesis measurement is a valuable nonimmunological tool to assess, in vivo, immune and inflammatory variables. Alterations in secondary lymphoid organs and plasma protein synthesis may contribute to the significant repartitioning of amino acids in old compared with adult rats and may be involved in sarcopenia.

Glutamine metabolism in advanced age

“…43 Moreover, aging is known to induce a dysregulation of immune and inflammation functions that may affect protein synthesis rates in lymphoid tissues and plasma proteins. 110 Aging has been also described as a condition characterized by anabolic resistance to nutrients, especially amino acids, which impairs muscle protein synthesis and contributes to muscle wasting. Table 2 provides an overview of the effect of amino acids on protein turnover in skeletal muscle.…”

Mixed muscle and hepatic derived plasma protein metabolism is differentially regulated in older and younger men following resistance exercise

“…Numerous physiological and pathological conditions, including the process of aging, can alter the response of plasma proteins, with some studies demonstrating a coordinated increase in the fractional synthesis rates (FSR) of albumin and fibrinogen (14,22,26), whereas in others the responses have been shown to be directionally opposite (16,32). For example, total liver protein synthesis is elevated in conditions such as sepsis, trauma, and inflammation, whereas muscle protein synthesis is blunted (26).…”

“…We (31) recently demonstrated that an acute bout of moderate-intensity aerobic exercise induced a significant increase in muscle protein turnover and albumin and fibrinogen synthesis in postabsorptive older and younger men. Additionally, a few studies find that aging induces a proinflammatory state (22,41) that may ultimately affect skeletal muscle protein metabolism by shifting a disproportionate amount of these free amino acids toward the splanchnic bed (7) due to the increased demand for synthesis of plasma proteins (22). Quantification of mixed muscle and hepatically synthesized plasma protein synthetic rates after resistance exercise could provide insight as to how protein metabolism is partitioned between tissues and organs in older persons.…”

Effects of oxidative stress on the virulence profile of Prevotella intermedia during experimental infection in gnotobiotic mice

“…Similarly to human beings, alterations in albumin and alkaline phosphatase levels observed in animals challenged with the aero strain could be the results of inflammatory reactions (Fey & Gauldie, 1990;Cabral et al, 2001). Spleen hypertrophy could be related to the haemorrhagic process as well as to immunosuppression due to degeneration of lymphoid tissue (Casadevall & Pirofski, 1999;Papet et al, 2003). These observations were confirmed by the increase in dissolved haemoglobin and the congestion of red pulp observed in the follicular area of the lymphoid component in the spleen of mice challenged with the aero strain.…”