Wednesday, December 21, 2016
Although taurine deficiency is rare in neonates, it is perhaps inevitable with advancing age. Healthy elderly patients ages 61 to 81 have up to a 49% decrease in plasma taurine concentration compared with healthy individuals ages 27 to 57.124 While reduced renal retention125 and taurine intake126 can account for depressed taurine levels, Eppler and Dawson127 found that tissue and circulating taurine concentrations decrease over the human life span primarily due to an age-dependent depletion of CSD activity in the liver. This effectively impairs the biosynthesis of endogenous taurine from cysteine or methionine or both, forcing a greater reliance on exogenous sources.
While specific mechanisms have not been fully elucidated, taurine deficiency has also been identified in patients suffering from diseases including but not limited to disorders of bone (osteogenesis imperfecta, osteoporosis),128 blood (acute myelogenous leukemia),129 central nervous system (schizophrenia, Friedreich ataxia-spinocerebellar degeneration),130,131 retina (retinitis pigmentosa),132 circulatory system and heart (essential hypertension, atherosclerosis),133 digestion (Gaucher disease),134 absorption (short-bowel syndrome),135 cellular proliferation (cancer),136 and membrane channels (cystic fibrosis),137 as well as in patients restricted to long-term parenteral nutrition.138 However, the apparent correlation between taurine deficiency and these conditions does not necessarily mean causation; more study is needed to elucidate a direct connection.
POTENTIAL THERAPEUTIC APPLICATIONS
Correction of late-life taurine decline in humans could be beneficial for cognitive performance, energy metabolism, sexual function, and vision, but clinical studies remain to be performed. While a decline in taurine with age may intensify the stress caused by reactive oxygen species, taurine supplementation has been shown to decrease the presence of oxidative markers127 and to serve a neuroprotective role in rodents.145,146 Taurine levels increase in the hippocampus after experimentally induced gliosis147 and are neuroprotective against glutamate excitotoxicity.148,149 Furthermore, data in Alzheimer disease, Huntington disease, and brain ischemia experimental models show that taurine inhibits neuronal death (apoptosis).13,150,151 Taurine has even been proposed as a potential preventive treatment for Alzheimer dementia, as it stabilizes protein conformations to prevent their aggregation and subsequent dysfunction.152 Although improvement in memory and cognitive performance has been linked to taurine supplementation in old mice,145,153 similar results have not been found in adult mice whose taurine levels are within normal limits. Taurine also has transient anticonvulsant effects in some epileptic humans.154
Within the male reproductive organs, the age-related decline in taurine may or may not have implications regarding sexuality, as only very limited rat data are available.89–91
In cats, taurine supplementation has been found to prevent the progressive degeneration of retinal photoreceptors seen in retinitis pigmentosa, a genetic disease that causes the loss of vision.155
While several energy drink companies have advertised that taurine plays a role in improving cognitive and physical performance, there are few human studies that examine this contention in the absence of confounding factors such as caffeine or glucose.36,37,95 Taurine supplementation in patients with heart failure has been shown to increase exercise capacity vs placebo.156 This supports the idea that in cases of taurine deficiency, such as those seen in cardiomyopathy,157 taurine supplementation could have restorative effects. However, we are not aware of any double-blind, placebo-controlled clinical trial of taurine alone in healthy patients that measured energy parameters as clinical outcomes.