Background: A growing number of observational and epidemiological studies have suggested that mental illness, in particular mood disorders, is associated with reduced dietary intake and/or cellular abundance of omega-3 polyunsaturated fatty acids (PUFA). This has prompted researchers to test the efficacy of omega-3 PUFA in a range of different psychiatric disorders. We have critically reviewed the double blind placebo controlled clinical trials published prior to April 2007 to determine whether omega-3 PUFA are likely to be efficacious in these disorders.

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Asthma is a chronic inflammatory disease, with hyper-responsive bronchoconstriction and airway remodelling, leading to extensive airway narrowing. The regulation of airway responsiveness and inflammation by endogenous hydrogen sulfide (H 2 S) during the pathogenic development of asthma has been suggested. Hydrogen sulfide can be produced in the lung and airway tissues via the actions of two H 2 S-generating enzymes, cystathionine β-synthase (CBS) and/or cystathionine γ-lyase (CSE). The abnormal metabolism and function of H 2 S have been reported in experimental animals with asthma, especially ovalbumin-induced rat or mouse models. In patients with asthma, serum H 2 S levels are significantly reduced. Supplementation with exogenous H 2 S has been shown to mitigate the severity of asthma in experimental animals. It is hypothesized that decreased H 2 S production in the lung and airway tissues may be used as an early detection biomarker, and H 2 S-based therapy would represent a new treatment strategy for asthma. Major challenges for establishing the diagnostic and treatment values of H 2 S include the differential expression of CSE and CBS along the airway and their changes during asthma, the effects of H 2 S on bronchoconstriction and airway remodelling, as well as the underlying mechanisms, and the detection of the changes in H 2 S levels in airway tissues and in exhaled air.

Damage to brain membrane phospholipids may play an important role in the pathogenesis of Alzheimer's disease (AD); however, the critical metabolic processes responsible for the generation and repair of membrane phospholipids affected by the disease are unknown. We measured the activity of key phospholipid catabolic and anabolic enzymes in morphologically affected and spared areas of autopsied brain of patients with AD and in matched control subjects. The activity of the major catabolic enzyme phospholipase A2 (PLA2), measured in both the presence and absence of Ca

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Attention deficit hyperactivity disorder (ADHD) comprises a range of behavioural problems including inattention, hyperactivity and impulsivity. Diagnosis and treatment of the disorder is made difficult due to its unknown biological basis. Several studies have identified abnormalities in membrane fatty acids in some subjects with ADHD, and some success has been reported using lipid therapies. We have measured exhalant ethane levels, a non-invasive measure of oxidative damage to n-3 fatty acids, to probe biochemical alterations in ADHD. Patients with ADHD (N = 10) had higher levels of ethane in exhalant than in healthy volunteers (N = 12) with approximately 50% of ADHD cases being above the control range. In contrast, levels of butane, a marker of protein oxidation, were unaltered. Our data, although preliminary, suggests that some patients with ADHD have higher rates of oxidative breakdown of n-3 polyunsaturated fatty acids (PUFAs). Such a biochemical abnormality may underlie the previously observed fatty acid deficiencies, as well as providing further rationale for the use of anti-oxidant and/or lipid supplementation therapy in the treatment of ADHD. Larger studies of ADHD using this non-invasive assessment of oxidative stress appear warranted.

Growing evidence suggests an involvement of brain membrane phospholipid metabolism in a variety of neurodegenerative and psychiatric conditions. This has prompted the use of drugs (e.g., CDPcholine) aimed at elevating the rate of neural membrane synthesis. However, no information is available regarding the human brain enzymes of phospholipid synthesis which these drugs affect. Thus, the objective of our study was to characterize the enzymes involved, in particular, whether differences existed in the relative affinity of substrates for the enzymes of phosphatidylethanolamine (PE) compared to those of phosphatidylcholine (PC) synthesis. The concentration of choline in rapidly frozen human brain biopsies ranged from 32-186 nmol/g tissue, a concentration similar to that determined previously for ethanolamine. Since human brain ethanolamine kinase possessed a much lower affinity for ethanolamine (Km = 460 microM) than choline kinase did for choline (Km = 17 microM), the activity of ethanolamine kinase in vivo may be more dependent on substrate availability than that of choline kinase. In addition, whereas ethanolamine kinase was inhibited by choline, and to a lesser extent by phosphocholine, choline kinase activity was unaffected by the presence of ethanolamine, or phosphoethanolamine, and only weakly inhibited by phosphocholine. Phosphoethanolamine cytidylyltransferase (PECT) and phosphocholine cytidylyltransferase (PCCT) also displayed dissimilar characteristics, with PECT and PCCT being located predominantly in the cytosolic and particulate fractions, respectively. Both PECT and PCCT exhibited a low affinity for CTP (Km approximately 1.2 mM), suggesting that the activities of these enzymes, and by implication, the rate of phospholipid synthesis, are highly dependent upon the cellular concentration of CTP. In conclusion our data indicate different regulatory properties of PE and PC synthesis in human brain, and suggest that the rate of PE synthesis may be more dependent upon substrate (ethanolamine) availability than that of PC synthesis.

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