Severe Hyperhomocysteinemia Decreases Creatine Kinase Activity and Causes Memory Impairment: Neuroprotective Role of Creatine.

In the present study, we investigate the effect of severe hyperhomocysteinemia on biochemical (creatine kinase activity), behavioral (memory tests), and histological assessments (hippocampal volume). A possible neuroprotective role of creatine on hyperhomocysteinemia effects was also evaluated. Severe hyperhomocysteinemia was induced in neonate rats (starting at 6 days of age) by treatment with homocysteine (0.3-0.6 µmol/g body weight) for 23 days. Creatine (50 mg/kg body weight) was administered concomitantly with homocysteine. Controls received saline in the same volumes. Twelve hours after the last injection, the rats were submitted to behavioral tests [(recognition task (NOR)] and inhibitory avoidance (IA)]. Following behavioral assessment, the animals were perfused and decapitated, the brain removed for subsequent morphological analysis of the hippocampus. Another group of animals was used to test creatine kinase activity in hippocampus. The results showed that rats treated with homocysteine decreased (44%) the exploration of the novel object in NOR. In the IA task, homocysteine-treated animals presented decreased latencies to step down the platform in short- (32%) and long-term (18%) testings (3 h and 7 days, respectively), evidencing aversive memory impairment. Hippocampal volume was not altered by homocysteine administration. Hyperhomocysteinemia decreased (45%) creatine kinase activity, and creatine was able to prevent such effect probably by creatine kinase/phosphocreatine/creatine homeostasis, which serves as energy circuit within of the cell. This finding may be associated, at least in part, with memory improvement, suggesting that creatine might represent an effective adjuvant to protect against the effects of high homocysteine plasma levels.

Severe Hyperhomocysteinemia Decreases Respiratory Enzyme and Na(+)-K(+) ATPase Activities, and Leads to Mitochondrial Alterations in Rat Amygdala.

Severe hyperhomocysteinemia is caused by increased plasma levels of homocysteine (Hcy), a methionine derivative, and is associated with cerebral disorders. Creatine supplementation has emerged as an adjuvant to protect against neurodegenerative diseases, due to its potential antioxidant role. Here, we examined the effects of severe hyperhomocysteinemia on brain metabolism, and evaluated a possible neuroprotective role of creatine in hyperhomocysteinemia, by concomitant treatment with Hcy and creatine (50 mg/Kg body weight). Hyperhomocysteinemia was induced in young rats (6-day-old) by treatment with homocysteine (0.3-0.6 µmol/g body weight) for 23 days, and then the following parameters of rat amygdala were evaluated: (1) the activity of the respiratory chain complexes succinate dehydrogenase, complex II and cytochrome c oxidase; (2) mitochondrial mass and membrane potential; (3) the levels of necrosis and apoptosis; and (4) the activity and immunocontent of Na(+),K(+)-ATPase. Hcy treatment decreased the activities of succinate dehydrogenase and cytochrome c oxidase, but did not alter complex II activity. Hcy treatment also increased the number of cells with high mitochondrial mass, high mitochondrial membrane potential, and in late apoptosis. Importantly, creatine administration prevented some of the key effects of Hcy administration on the amygdala. We also observed a decrease in the activity and immunocontent of the α1 subunit of the Na(+),K(+)-ATPase in amygdala after Hcy- treatment. Our findings support the notion that Hcy modulates mitochondrial function and bioenergetics in the brain, as well as Na(+),K(+)-ATPase activity, and suggest that creatine might represent an effective adjuvant to protect against the effects of high Hcy plasma levels.

Homocysteine induces energy imbalance in rat skeletal muscle: is creatine a protector?

Homocystinuria is a neurometabolic disease caused by a severe deficiency of cystathionine beta-synthase activity, resulting in severe hyperhomocysteinemia. Affected patients present several symptoms including a variable degree of motor dysfunction. In this study, we investigated the effect of chronic hyperhomocysteinemia on the cell viability of the mitochondrion, as well as on some parameters of energy metabolism, such as glucose oxidation and activities of pyruvate kinase, citrate synthase, isocitrate dehydrogenase, malate dehydrogenase, respiratory chain complexes and creatine kinase in gastrocnemius rat skeletal muscle. We also evaluated the effect of creatine on biochemical alterations elicited by hyperhomocysteinemia. Wistar rats received daily subcutaneous injections of homocysteine (0.3-0.6 µmol/g body weight) and/or creatine (50 mg/kg body weight) from the 6th to the 28th days of age. The animals were decapitated 12 h after the last injection. Homocysteine decreased the cell viability of the mitochondrion and the activities of pyruvate kinase and creatine kinase. Succinate dehydrogenase was increased other evaluated parameters were not changed by this amino acid. Creatine, when combined with homocysteine, prevented or caused a synergistic effect on some changes provoked by this amino acid. Creatine per se or creatine plus homocysteine altered glucose oxidation. These findings provide insights into the mechanisms by which homocysteine exerts its effects on skeletal muscle function, more studies are needed to elucidate them. Although creatine prevents some alterations caused by homocysteine, it should be used with caution, mainly in healthy individuals because it could change the homeostasis of normal physiological functions.