Phosphorus-31 magnetic resonance spectroscopy and ventricular enlargement in bipolar disorder

Neurobiology and Applications of Inositol in Psychiatry: A Narrative Review

Inositol is a natural sugar-like compound, commonly present in many plants and foods. It is involved in several biochemical pathways, most of them controlling vital cellular mechanisms, such as cell development, signaling and nuclear processes, metabolic and endocrine modulation, cell growth, signal transduction, etc. In this narrative review, we focused on the role of inositol in human brain physiology and pathology, with the aim of providing an update on both potential applications and current limits in its use in psychiatric disorders. Overall, imaging and biomolecular studies have shown the role of inositol levels in the pathogenesis of mood disorders. However, when administered as monotherapy or in addition to conventional drugs, inositol did not seem to influence clinical outcomes in both mood and psychotic disorders. Conversely, more encouraging results have emerged for the treatment of panic disorders. We concluded that, despite its multifaceted neurobiological activities and some positive findings, to date, data on the efficacy of inositol in the treatment of psychiatric disorders are still controversial, partly due to the heterogeneity of supporting studies. Therefore, systematic use of inositol in routine clinical practice cannot be recommended yet, although further basic and translational research should be encouraged.

Neurobiology of bipolar disorders: a review of genetic components, signaling pathways, biochemical changes, and neuroimaging findings

Bipolar disorder (BD) is a chronic mental illness characterized by changes in mood that alternate between mania and hypomania or between depression and mixed states, often associated with functional impairment. Although effective pharmacological and non-pharmacological treatments are available, several patients with BD remain symptomatic. The advance in the understanding of the neurobiology underlying BD could help in the identification of new therapeutic targets as well as biomarkers for early detection, prognosis, and response to treatment in BD. In this review, we discuss genetic, epigenetic, molecular, physiological and neuroimaging findings associated with the neurobiology of BD. Despite the advances in the pathophysiological knowledge of BD, the diagnosis and management of the disease are still essentially clinical. Given the complexity of the brain and the close relationship between environmental exposure and brain function, initiatives that incorporate genetic, epigenetic, molecular, physiological, clinical, environmental data, and brain imaging are necessary to produce information that can be translated into prevention and better outcomes for patients with BD.

Regulation of Inositol Biosynthesis: Balancing Health and Pathophysiology

Inositol is the precursor for all inositol compounds and is essential for viability of eukaryotic cells. Numerous cellular processes and signaling functions are dependent on inositol compounds, and perturbation of their synthesis leads to a wide range of human diseases. Although considerable research has been directed at understanding the function of inositol compounds, especially phosphoinositides and inositol phosphates, a focus on regulatory and homeostatic mechanisms controlling inositol biosynthesis has been largely neglected. Consequently, little is known about how synthesis of inositol is regulated in human cells. Identifying physiological regulators of inositol synthesis and elucidating the molecular mechanisms that regulate inositol synthesis will contribute fundamental insight into cellular processes that are mediated by inositol compounds and will provide a foundation to understand numerous disease processes that result from perturbation of inositol homeostasis. In addition, elucidating the mechanisms of action of inositol-depleting drugs may suggest new strategies for the design of second-generation pharmaceuticals to treat psychiatric disorders and other illnesses.

Phosphocreatine Levels in the Left Thalamus Decline during Wakefulness and Increase after a Nap

Scientists have hypothesized that the availability of phosphocreatine (PCr) and its ratio to inorganic phosphate (Pi) in cerebral tissue form a substrate of wakefulness. It follows then, according to this hypothesis, that the exhaustion of PCr and the decline in the ratio of PCr to Pi form a substrate of fatigue. We used 31P-magnetic resonance spectroscopy (31P-MRS) to investigate quantitative levels of PCr, the γ-signal of ATP, and Pi in 30 healthy humans (18 female) in the morning, in the afternoon, and while napping (n = 15) versus awake controls (n = 10). Levels of PCr (2.40 mM at 9 A.M.) decreased by 7.0 ± 0.8% (p = 7.1 × 10-6, t = -5.5) in the left thalamus between 9 A.M. and 5 P.M. Inversely, Pi (0.74 mM at 9 A.M.) increased by 17.1 ± 5% (p = 0.005, t = 3.1) and pH levels dropped by 0.14 ± 0.07 (p = 0.002; t = 3.6). Following a 20 min nap after 5 P.M., local PCr, Pi, and pH were restored to morning levels. We did not find respective significant changes in the contralateral thalamus or in other investigated brain regions. Left hemispheric PCr was signficantly lower than right hemispheric PCr only at 5 P.M. in the thalamus and at all conditions in the temporal region. Thus, cerebral daytime-related and sleep-related molecular changes are accessible in vivo Prominent changes were identified in the thalamus. This region is heavily relied on for a series of energy-consuming tasks, such as the relay of sensory information to the cortex. Furthermore, our data confirm that lateralization of brain function is regionally dynamic and includes PCr.SIGNIFICANCE STATEMENT The metabolites phosphocreatine (PCr) and inorganic phosphate (Pi) are assumed to inversely reflect the cellular energy load. This study detected a diurnal decrease of intracellular PCr and a nap-associated reincrease in the left thalamus. Pi behaved inversely. This outcome corroborates the role of the thalamus as a region of high energy consumption in agreement with its function as a gateway that relays and modulates information flow. Conversely to the dynamic lateralization of thalamic PCr, a constantly significant lateralization was observed in other regions. Increasing fatigue over the course of the day may also be a matter of cerebral energy supply. Comparatively fast restoration of that supply may be part of the biological basis for the recreational value of "power napping."

Lithium-associated anterior cingulate neurometabolic profile in euthymic Bipolar I disorder: A 1H-MRS study

OBJECTIVE

In the treatment of Bipolar disorder (BD), achieving euthymia is highly complex and usually requires a combination of mood stabilizers. The mechanism of action in stabilizing mood has not been fully elucidated, but alterations in N-Acetylaspartate (NAA), Myo-Inositol (mI) and Choline (Cho) have been implicated. Proton magnetic resonance spectroscopy (¹H-MRS) is the gold standard technique for measuring brain NAA, Cho and mI in vivo. The objective of this study was to investigate the association of lithium use in BD type I and brain levels of NAA, mI and Cho in the (anterior cingulate cortex) ACC.

METHODS

129 BD type I subjects and 79 healthy controls (HC) were submitted to a 3-Tesla brain magnetic resonance imaging scan (¹H-MRS) using a PRESS ACC single voxel (8cm³) sequence.

RESULTS

BD patients exhibited higher NAA and Cho levels compared to HC. Lithium prescription was associated with lower mI (combination + monotherapy) and higher NAA levels (monotherapy).

CONCLUSION

The results observed add to the knowledge about the mechanisms of action of mood stabilizers on brain metabolites during euthymia. Additionally, the observed decrease in mI levels associated with lithium monotherapy is an in vivo finding that supports the inositol-depletion hypothesis of lithium pharmacodynamics.

Brain lactate and pH in schizophrenia and bipolar disorder: a systematic review of findings from magnetic resonance studies

Converging evidence from molecular to neuroimaging studies suggests brain energy metabolism abnormalities in both schizophrenia and bipolar disorder. One emerging hypothesis is: decreased oxidative phosphorylation leading to accumulation of lactic acid from glycolysis and subsequent acidification of tissue. In this regard, integrating lactate and pH data from magnetic resonance spectroscopy (MRS) studies in both diseases may help us understand underlying neurobiological mechanisms. In order to achieve this goal, we performed a systematic search of case-control studies examining brain lactate or pH among schizophrenia and/or bipolar patients by using MRS. Medline/Pubmed and EBSCO databases were searched separately for both diseases and outcomes. Our search yielded 33 studies in total composed of 7 lactate and 26 pH studies. In bipolar disorder, 5 out of 6 studies have found elevated lactate levels especially in the cingulate cortex and 4 out of 13 studies reported reduced pH in the frontal lobe. In contrast, in schizophrenia a single study has examined lactate and reported elevation, while only 2 out of 13 studies examining pH have reported reduction in this measure. There were no consistent patterns for the relationship between lactate or pH levels and medication use, disease type, mood state, and other clinical variables. We highlight the need for future studies combining 1H-MRS and 31P-MRS approaches, using longitudinal designs to examine lactate and pH in disease progression across both schizophrenia and bipolar disorders.

Molecular Mechanisms of Bipolar Disorder: Progress Made and Future Challenges

Bipolar disorder (BD) is a chronic and progressive psychiatric illness characterized by mood oscillations, with episodes of mania and depression. The impact of BD on patients can be devastating, with up to 15% of patients committing suicide. This disorder is associated with psychiatric and medical comorbidities and patients with a high risk of drug abuse, metabolic and endocrine disorders and vascular disease. Current knowledge of the pathophysiology and molecular mechanisms causing BD is still modest. With no clear biological markers available, early diagnosis is a great challenge to clinicians without previous knowledge of the longitudinal progress of illness. Moreover, despite recommendations from evidence-based guidelines, polypharmacy is still common in clinical treatment of BD, reflecting the gap between research and clinical practice. A major challenge in BD is the development of effective drugs with low toxicity for the patients. In this review article, we focus on the progress made and future challenges we face in determining the pathophysiology and molecular pathways involved in BD, such as circadian and metabolic perturbations, mitochondrial and endoplasmic reticulum (ER) dysfunction, autophagy and glutamatergic neurotransmission; which may lead to the development of new drugs.

Mitochondrial dysfunction in bipolar disorder: Evidence, pathophysiology and translational implications

Bipolar disorder (BD) is a chronic psychiatric illness characterized by severe and biphasic changes in mood. Several pathophysiological mechanisms have been hypothesized to underpin the neurobiology of BD, including the presence of mitochondrial dysfunction. A confluence of evidence points to an underlying dysfunction of mitochondria, including decreases in mitochondrial respiration, high-energy phosphates and pH; changes in mitochondrial morphology; increases in mitochondrial DNA polymorphisms; and downregulation of nuclear mRNA molecules and proteins involved in mitochondrial respiration. Mitochondria play a pivotal role in neuronal cell survival or death as regulators of both energy metabolism and cell survival and death pathways. Thus, in this review, we discuss the genetic and physiological components of mitochondria and the evidence for mitochondrial abnormalities in BD. The final part of this review discusses mitochondria as a potential target of therapeutic interventions in BD.

Inositol depletion, GSK3 inhibition and bipolar disorder

Valproic acid and lithium are widely used to treat bipolar disorder, a severe illness characterized by cycles of mania and depression. However, their efficacy is limited, and treatment is often accompanied by serious side effects. The therapeutic mechanisms of these drugs are not understood, hampering the development of more effective treatments. Among the plethora of biochemical effects of the drugs, those that are common to both may be more related to therapeutic efficacy. Two common outcomes include inositol depletion and GSK3 inhibition, which have been proposed to explain the efficacy of both valproic acid and lithium. Here, we discuss the inositol depletion and GSK3 inhibition hypotheses, and introduce a unified model suggesting that inositol depletion and GSK3 inhibition are inter-related.

Decreased brain PME/PDE ratio in bipolar disorder: a preliminary (31) P magnetic resonance spectroscopy study

OBJECTIVES

The aim of the present study was to measure brain phosphorus-31 magnetic resonance spectroscopy ((31) P MRS) metabolite levels and the creatine kinase reaction forward rate constant (kf ) in subjects with bipolar disorder (BD).

METHODS

Subjects with bipolar euthymia (n = 14) or depression (n = 11) were recruited. Healthy comparison subjects (HC) (n = 23) were recruited and matched to subjects with BD on age, gender, and educational level. All studies were performed on a 3-Tesla clinical magnetic resonance imaging system using a (31) P/(1) H double-tuned volume head coil. (31) P spectra were acquired without (1) H-decoupling using magnetization-transfer image-selected in vivo spectroscopy. Metabolite ratios from a brain region that includes the frontal lobe, corpus callosum, thalamus, and occipital lobe are expressed as a percentage of the total phosphorus (TP) signal. Brain pH was also investigated.

RESULTS

Beta-nucleoside-triphosphate (β-NTP/TP) in subjects with bipolar depression was positively correlated with kf (p = 0.039, r(2) = 0.39); similar correlations were not observed in bipolar euthymia or HC. In addition, no differences in kf and brain pH were observed among the three diagnostic groups. A decrease in the ratio of phosphomonoesters to phosphodiesters (PME/PDE) was observed in subjects with bipolar depression relative to HC (p = 0.032). We also observed a trend toward an inverse correlation in bipolar depression characterized by decreased phosphocreatine and increased depression severity.

CONCLUSIONS

In our sample, kf was not altered in the euthymic or depressed mood state in BD. However, decreased PME/PDE in subjects with bipolar depression was consistent with differences in membrane turnover. These data provide preliminary support for alterations in phospholipid metabolism and mitochondrial function in bipolar depression.

Abnormal high-energy phosphate molecule metabolism during regional brain activation in patients with bipolar disorder

Converging evidence suggests bioenergetic abnormalities in bipolar disorder (BD). In the brain, phosphocreatine (PCr) acts a reservoir of high-energy phosphate (HEP) bonds, and creatine kinases (CK) catalyze the transfer of HEP from adenosine triphosphate (ATP) to PCr and from PCr back to ATP, at times of increased need. This study examined the activity of this mechanism in BD by measuring the levels of HEP molecules during a stimulus paradigm that increased local energy demand. Twenty-three patients diagnosed with BD-I and 22 healthy controls (HC) were included. Levels of phosphorus metabolites were measured at baseline and during visual stimulation in the occipital lobe using (31)P magnetic resonance spectroscopy at 4T. Changes in metabolite levels showed different patterns between the groups. During stimulation, HC had significant reductions in PCr but not in ATP, as expected. In contrast, BD patients had significant reductions in ATP but not in PCr. In addition, PCr/ATP ratio was lower at baseline in patients, and there was a higher change in this measure during stimulation. This pattern suggests a disease-related failure to replenish ATP from PCr through CK enzyme catalysis during tissue activation. Further studies measuring the CK flux in BD are required to confirm and extend this finding.

A pilot study of alterations in high energy phosphoryl compounds and intracellular pH in unmedicated adolescents with bipolar disorder

BACKGROUND

Several lines of evidence suggest that mitochondrial dysfunction underlies the pathophysiology of bipolar disorder, including prior studies indicating abnormalities in phosphometabolites. We examined abnormalities in biomarkers of cellular metabolism including adenosine triphosphate and adenosine diphosphate as well as the pH levels in the anterior cingulate (ACC) and left ventrolateral prefrontal cortices (VLPFC) of adolescents with bipolar disorder.

METHOD

Nineteen unmedicated manic and 14 unmedicated euthymic bipolar adolescents as well as 20 healthy adolescents underwent (1)H and (31)P magnetic resonance spectroscopy scans. Intracellular pH levels and concentrations of phosphometabolites were compared among groups.

RESULTS

A significant reduction in pHi was found in the ACC of manic adolescents compared to healthy subjects (p=0.03) but not in the left VLPFC. There was no difference in concentration of adenosine triphosphate in the ACC or the left VLPFC among groups. However, compared to healthy subjects, adenosine diphosphate was significantly lower in manic subjects in the ACC (p=0.01) and in euthymic subjects in the left VLPFC (p=0.02).

LIMITATIONS

This was a cross-sectional study with a modest sample size. A longitudinal study of a larger number of bipolar adolescents who are treatment naïve would clarify the impact of mood state on metabolic function.

CONCLUSION

These results are suggestive of abnormal cellular metabolism and mitochondrial dysfunction in the pathophysiology of bipolar disorder.

Enhancing synaptic plasticity and cellular resilience to develop novel, improved treatments for mood disorders

There is mounting evidence that recurrent mood disorders - once considered “good prognosis diseases”- are, in fact, often very severe and life-threatening illnesses. Furthermore, although mood disorders have traditionally been conceptualized as neurochemical disorders, there is now evidence from a variety of sources demonstrating regional reductions in central nervous system (CNS) volume, as well as reductions in the numbers and/or sizes ofglia and neurons in discrete brain areas. Although the precise cellular mechanisms underlying these morphometric changes remain to be fully elucidated, the data suggest that mood disorders are associated with impairments of synaptic plasticity and cellular resilience. In this context, it is noteworthy that there is increasing preclinical evidence that antidepressants regulate the function of the glutamatergic system. Moreover, although clearly preliminary, the available clinical data suggest that attenuation of N-methyl-D-aspartate (NMDA) function has antidepressant effects. Recent preclinical and clinical studies have shown that signaling pathways involved in regulating cell survival and cell death are long-term targets for the actions of antidepressant agents. Antidepressants and mood stabilizers indirectly regulate a number of factors involved in cell survival pathways, including cyclic adenosine monophosphate (cAMP) response element binding protein (CREB), brain-derived neurotrophic factor (BDNF), the antiapoptotic protein bcl-2, and mitogen-activated protein (MAP) kinases, and may thus bring about some of their delayed long-term beneficial effects via underappreciated neurotrophic effects. There is much promise for the future development of treatments that more directly target molecules in critical CNS signaling pathways regulating synaptic plasticity and cellular resilience. These will represent improved long-term treatments for mood disorders.

pH as a biomarker of neurodegeneration in Huntington's disease: a translational rodent-human MRS study

Early diagnosis and follow-up of neurodegenerative diseases are often hampered by the lack of reliable biomarkers. Neuroimaging techniques like magnetic resonance spectroscopy (MRS) offer promising tools to detect biochemical alterations at early stages of degeneration. Intracellular pH, which can be measured noninvasively by (31)P-MRS, has shown variations in several brain diseases. Our purpose has been to evaluate the potential of MRS-measured pH as a relevant biomarker of early degeneration in Huntington's disease (HD). We used a translational approach starting with a preclinical validation of our hypothesis before adapting the method to HD patients. (31)P-MRS-derived cerebral pH was first measured in rodents during chronic intoxication with 3-nitropropionic acid (3NP). A significant pH increase was observed early into the intoxication protocol (pH=7.17±0.02 after 3 days) as compared with preintoxication (pH=7.08±0.03). Furthermore, pH changes correlated with the 3NP-induced inhibition of succinate dehydrogenase and preceded striatum lesions. Using a similar MRS approach implemented on a clinical MRI, we then showed that cerebral pH was significantly higher in HD patients (n=7) than in healthy controls (n=6) (7.05±0.03 versus 7.02±0.01, respectively, P=0.026). Altogether, both preclinical and human data strongly argue in favor of MRS-measured pH being a promising biomarker for diagnosis and follow-up of HD.

Lithium and valproate and their possible effects on themyo-inositol second messenger system in healthy volunteers and bipolar patients

Over 25 years ago it was suggested that the mechanism by which lithium was clinically effective may be due to a stabilizing effect on the phosphoinositol second messenger system (PI-cycle), which has multiple effects within cells. It was proposed that lithium, which is an inhibitor of one of the key enzymes in the PI-cycle, acted to lower myo-inositol concentrations; termed the 'inositol-depletion hypothesis'. Initial animal evidence supported this hypothesis, and also suggested that it was possible that sodium valproate could affect the PI-cycle. Since the first magnetic resonance studies in this area in the early 1990s many studies have examined various aspects of this hypothesis in both healthy volunteers and patients utilizing magnetic resonance spectroscopy (MRS). The present review considers research in this area and concludes that, despite initial promise, current evidence suggests that it is unlikely that either lithium or valproate produce clinically relevant changes in myo-inositol concentrations or the PI-cycle. These findings do not suggest that lithium-induced changes in the PI-cycle are the primary mechanism by which lithium or valproate exert their beneficial clinical effects in bipolar disorder. Nonetheless, given the current technical and clinical limitations of the literature to date, this conclusion cannot be considered completely definitive.

Cellular plasticity cascades in the pathophysiology and treatment of bipolar disorder

Bipolar disorder (BPD) is characterized by recurrent episodes of disturbed affect including mania and depression as well as changes in psychovegetative function, cognitive performance, and general health. A growing body of data suggests that BPD arises from abnormalities in synaptic and neuronal plasticity cascades, leading to aberrant information processing in critical synapses and circuits. Thus, these illnesses can best be conceptualized as genetically influenced disorders of synapses and circuits rather than simply as deficits or excesses in individual neurotransmitters. In addition, commonly used mood-stabilizing drugs that are effective in treating BPD have been shown to target intracellular signaling pathways that control synaptic plasticity and cellular resilience. In this article we draw on clinical, preclinical, neuroimaging, and post-mortem data to discuss the neurobiology of BPD within a conceptual framework while highlighting the role of neuroplasticity in the pathophysiology and treatment of this disorder.

Rational approaches to the neurobiologic study of youth at risk for bipolar disorder and suicide

OBJECTIVES

The aims of this paper are to provide an overview of neuroimaging findings specific to bipolar disorder and suicide, and to consider rational approaches to the design of future in vivo studies in youth at risk.

METHODS

Neuroimaging and related neurobiological literature pertaining to bipolar disorder and suicide in adult and pediatric samples was reviewed in a non-quantitative manner.

RESULTS

Specific structural and functional brain findings in bipolar disorder are described, where possible in the context of relevant current neurobiological theories of etiology. Diagnostic and prognostic implications are discussed.

CONCLUSIONS

The simultaneous use of complementary neurobiological approaches may be a powerful way of identifying and validating factors reliably associated with bipolar disorder and suicide. A profile of neurobiological markers with which to screen for bipolar disorder and suicide risk may provide for earlier and more accurate diagnosis, perhaps even in the pre- or subsyndromal stages in high-risk youth.

Mitochondrial-related gene expression changes are sensitive to agonal-pH state: implications for brain disorders

Mitochondrial defects in gene expression have been implicated in the pathophysiology of bipolar disorder and schizophrenia. We have now contrasted control brains with low pH versus high pH and showed that 28% of genes in mitochondrial-related pathways meet criteria for differential expression. A majority of genes in the mitochondrial, chaperone and proteasome pathways of nuclear DNA-encoded gene expression were decreased with decreased brain pH, whereas a majority of genes in the apoptotic and reactive oxygen stress pathways showed an increased gene expression with a decreased brain pH. There was a significant increase in mitochondrial DNA copy number and mitochondrial DNA gene expression with increased agonal duration. To minimize effects of agonal-pH state on mood disorder comparisons, two classic approaches were used, removing all subjects with low pH and agonal factors from analysis, or grouping low and high pH as a separate variable. Three groups of potential candidate genes emerged that may be mood disorder related: (a) genes that showed no sensitivity to pH but were differentially expressed in bipolar disorder or major depressive disorder; (b) genes that were altered by agonal-pH in one direction but altered in mood disorder in the opposite direction to agonal-pH and (c) genes with agonal-pH sensitivity that displayed the same direction of changes in mood disorder. Genes from these categories such as NR4A1 and HSPA2 were confirmed with Q-PCR. The interpretation of postmortem brain studies involving broad mitochondrial gene expression and related pathway alterations must be monitored against the strong effect of agonal-pH state. Genes with the least sensitivity to agonal-pH could present a starting point for candidate gene search in neuropsychiatric disorders.

Protective effect of the apo epsilon2 allele in major depressive disorder in Taiwanese

OBJECTIVE

Major depression is an important comorbidity in Alzheimer's disease, which is definitely associated with the apolipoprotein E (apo E) polymorphism. The aim of this study was to explore the role of the different apo E polymorphisms in major depressive disorder (MDD) in a Taiwanese population.

METHOD

We examined apo E genotypes in 273 Taiwanese patients with MDD and 429 healthy community controls, and compared their polymorphism distribution.

RESULTS

The allelic frequency of apo epsilon2 was significantly lower in patients with MDD than in the controls, whereas no significant difference in apo epsilon4 allelic frequency between these two groups was found.

CONCLUSION

The apo epsilon4 allele was not associated with MDD in this study. However, the finding of a lower frequency of the apo epsilon2 allele in MDD could lead to the conclusion that the apo epsilon2 allele likely provides a protective effect against MDD in the Taiwanese population.

Mitochondrial dysfunction in bipolar disorder: evidence from magnetic resonance spectroscopy research

Magnetic resonance spectroscopy (MRS) affords a noninvasive window on in vivo brain chemistry and, as such, provides a unique opportunity to gain insight into the biochemical pathology of bipolar disorder. Studies utilizing proton ((1)H) MRS have identified changes in cerebral concentrations of N-acetyl aspartate, glutamate/glutamine, choline-containing compounds, myo-inositol, and lactate in bipolar subjects compared to normal controls, while studies using phosphorus ((31)P) MRS have examined additional alterations in levels of phosphocreatine, phosphomonoesters, and intracellular pH. We hypothesize that the majority of MRS findings in bipolar subjects can be fit into a more cohesive bioenergetic and neurochemical model of bipolar illness that is both novel and yet in concordance with findings from complementary methodological approaches. In this review, we propose a hypothesis of mitochondrial dysfunction in bipolar disorder that involves impaired oxidative phosphorylation, a resultant shift toward glycolytic energy production, a decrease in total energy production and/or substrate availability, and altered phospholipid metabolism.

A review of the possible relevance of inositol and the phosphatidylinositol second messenger system (PI-cycle) to psychiatric disorders--focus on magnetic resonance spectroscopy (MRS) studies

Myo-inositol is an important part of the phosphatidylinositol second messenger system (PI-cycle). Abnormalities in nerve cell myo-inositol levels and/or PI-cycle regulation has been suggested as being involved in the pathophysiology and/or treatment of many psychiatric disorders including bipolar disorder, major depressive disorder, panic disorder, obsessive-compulsive disorder, eating disorders and schizophrenia. This review examines the metabolism and biochemical importance of myo-inositol and the PI-cycle. It relates this to the current in vivo evidence for myo-inositol and PI-cycle involvement in these psychiatric disorders, particularly focusing upon the magnetic resonance spectroscopy (MRS) findings in patient studies to date. From this review it is concluded that while the evidence suggests probable relevance to the pathophysiology and/or treatment of bipolar disorder, there is much less support for a significant role for the PI-cycle or myo-inositol in any other psychiatric disorder. More definitive investigation is required before PI-cycle dysfunction can be considered specific to bipolar disorder.

Neuropsychological dysfunction in bipolar affective disorder: a critical opinion

Data from the imaging literature have led to suggestions that permanent structural brain changes may be associated with bipolar disorder. Individuals diagnosed with bipolar disorder display deficits on a range of neuropsychological tasks in both the acute and euthymic phases of illness, and correlations between experienced number of affective episodes and task performance are commonly reported. These findings have renewed interest in the neuropsychological profile of individuals with bipolar disorder, with deficits of attention, learning and memory, and executive function, asserted to be present. This paper critically reviews five different potential causes of neurocognitive dysfunction in bipolar disorder: (i) iatrogenic, (ii) acute functional changes associated with depression or mania, (iii) permanent structural lesions of a neurodegenerative origin, (iv) permanent structural lesions that are neurodevelopmental in origin, and (v) permanent functional changes that are most likely genetic in origin. Although the potential cognitive effects of residual symptomatology and long-term medication use cannot be entirely excluded, we conclude that functional changes associated with genetically driven population variation in critical neural networks underpin both the neurocognitive and affective symptoms of bipolar disorder. The philosophical implications of this conclusion for neuropsychology are briefly discussed.

Magnetic resonance findings in bipolar disorder

The MR findings reviewed in this article suggest structural, chemical, and functional abnormalities in specific brain regions participating in mood and cognitive regulation, such as the DLPFC, anterior cingulate, amygdala,STG, and corpus callosum in subjects with bipolar disorder. These abnormalities would represent an altered anterior-limbic network disrupting inter- and intrahemispheric communication and underlying the expression of bipolar disorder. Available studies are limited by several confounding variables, such as small and heterogeneous patient samples, differences in clinical and medication status, and cross-sectional design. It is still unclear whether abnormalities in neurodevelopment or neurodegeneration play a major role in the pathophysiology of bipolar disorder. These processes could act together in a unitary model of the disease, with excessive neuronal pruning/apoptosis during childhood and adolescence being responsible for the onset of the disorder and subsequent neurotoxic mechanisms and impaired neuroplasticity and cellular resilience being responsible for further disease progression. Future MR studies should investigate larger samples of first-episode drug-free patients, pediatric patients, subjects at high risk for bipolar disorder, and unaffected family members longitudinally. Such a study population is crucial to examine systematically whether brain changes are present before the appearance of symptoms (eg, maldevelopment) or whether they develop afterwards, as a result of illness course (eg, neurodegeneration). These studies will also be instrumental in minimizing potentially confounding factors commonly found in adult samples, such as the effects of long-term medication, chronicity, and hospitalizations. Juvenile bipolar patients often have a strong family history of bipolar disorder. Future studies could help elucidate the relevance of brain abnormalities as reflections of genetic susceptibility to the disorder. MR studies associated with genetic, post-mortem, and neuropsychologic studies will be valuable in separating state from trait brain abnormalities and in further characterizing the genetic determinants, the neuropathologic underpinnings, and the cognitive disturbances of bipolar disorder.

Anatomical MRI abnormalities in bipolar disorder: do they exist and do they progress?

AIM

Morphometric brain imaging studies have revealed regional brain abnormalities in patients with bipolar disorder, which may play a role in illness pathophysiology. It is not known whether such changes are of neurodevelopmental, neurodegenerative, or combined origin. We reviewed the anatomical brain imaging literature in bipolar disorder, in an attempt to determine whether there is evidence to suggest that such abnormalities are progressive.

METHOD

Literature searches were conducted using MEDLINE for the period from 1966 to June 2004, using specific key words; bipolar disorder and the names of the individual brain structures. Papers were selected according to their salience in relation to whether reported changes are progressive.

RESULTS

Available findings suggest reduced grey matter in prefrontal brain regions such as anterior cingulate and subgenual prefrontal cortex, and abnormalities in amygdala size in adult and paediatric bipolar patients. White matter hyperintensities, which are non-specific abnormalities, are also common in bipolar patients. Bipolar patients may lose more brain grey matter by ageing. There is also evidence for impaired myelination of the corpus callosum in bipolar disorder. Lithium may reverse or prevent grey matter prefrontal cortex abnormalities in bipolar patients by its neuroprotective effects.

CONCLUSIONS

Both early developmental and later neurodegenerative processes may play a role in the pathophysiology of bipolar disorder. Findings from anatomical brain imaging studies implicate key regions involved in mood regulation. The evidence for the progressive nature of this illness is tentative, as no follow-up study with bipolar patients has been reported to this date.

Increased calcium-independent phospholipase A2 activity in first but not in multiepisode chronic schizophrenia

BACKGROUND

Increased activity of calcium independent phospholipase A2 (iPLA2) has repeatedly been found in the serum of unmedicated first-episode schizophrenia patients and assumed to reflect a pertubation of phospholipid metabolism. Previous studies in chronic schizophrenia were less conclusive. To explore whether iPLA2 changes are stage dependent, we investigated serum iPLA2 activity in various stages of schizophrenia.

METHODS

iPLA2 activity was assessed in the serum of 30 first-episode and 23 multiepisode schizophrenia patients and 53 healthy control subjects matched for age and gender. A fluorimetric assay was applied using the PLA2 specific substrate NBDC6-HPC, thin-layer chromatography of reaction products, and digital image scanning for signal detection.

RESULTS

Group comparison between first-episode and multiepisode patients and corresponding control groups revealed significantly increased iPLA2 activity only in first-episode patients. Enzyme activity in first-episode patients was also markedly increased, compared with chronic patients. iPLA2 changes observed were irrespective of neuroleptic medication, age, or gender.

CONCLUSIONS

Our results suggest increased lipid turnover in the acute early phase of schizophrenia that is less obvious in chronic stages. Future longitudinal studies involving iPLA2 activity and phosphorous magnetic resonance spectroscopy need to address the relation between perturbed brain lipid metabolism and iPLA2 increment in the course of schizophrenia.

Bipolar disorder and myo-inositol: a review of the magnetic resonance spectroscopy findings

OBJECTIVES

Myo-inositol is an important component of the phosphatidylinositol second messenger system (PI-cycle). Alterations in PI-cycle activity have been suggested to be involved in the pathophysiology and/or treatment of bipolar disorder. More specifically, lithium has been suggested to act primarily by lowering myo-inositol concentrations, the so-called inositol-depletion hypothesis. myo-Inositol concentrations can be measured in vivo with magnetic resonance spectroscopy (MRS).

METHODS

The current review primarily examines animal and human MRS studies that evaluated the role of myo-inositol in bipolar illness and treatment.

RESULTS

Studies have been carried out in patients who are manic, depressed, and euthymic, both on and off treatment. However, there are several limitations of these studies.

CONCLUSIONS

The preclinical and clinical MRS findings were generally supportive of the involvement of myo-inositol in bipolar disorder and its treatment. Overall, in bipolar patients who are manic or depressed there are abnormalities in brain myo-inositol concentrations, with changes in frontal and temporal lobes, as well as the cingulate gyrus and basal ganglia. These abnormalities are not seen in either euthymic patients or healthy controls, possibly due to a normalizing effect of treatment with either lithium or sodium valproate. There is also increasing evidence that sodium valproate may also act upon the PI-cycle. Nonetheless, it remains uncertain if these changes in myo-inositol concentration are primary or secondary. Findings regarding the specific inositol-depletion hypothesis are also generally supportive in acutely ill patients, although it is not yet possible to definitively confirm or refute this hypothesis based on the current MRS evidence.

[Changes in brain structure in bipolar affective disorders]

The neurobiological basis of bipolar affective disorders is unknown. However, neuroanatomic circuits of mood regulation have been hypothesized. Neuroimaging revealed volumetric changes of specific brain structures in these circuits. The most prominent abnormality is enlargement of the amygdala. In addition there might be structural changes in the frontal lobe, cerebellum, and pituitary. The findings in bipolar disorder differ from those in unipolar depression and schizophrenia. For further identification of the neurobiological basis of bipolar disorders, structural neuroimaging combined with functional neuroimaging such as magnetic resonance spectroscopy, neuroendocrinological studies, and genetical analyses are required to subgroup patients with bipolar disorder by diagnostic, prognostic, and therapeutic criteria.

New insights help define the pathophysiology of bipolar affective disorder: neuroimaging and neuropathology findings

Bipolar affective disorder (BD) is a severe mental illness, characterized by episodes of mania and depression. With the development of Magnetic Resonance Imaging (MRI), neuroimaging methods are now allowing investigation of the neurocircuitry involved in this disorder. This in turn has aided further neuropathological exploration of the brain. Structural MRI and Magnetic Resonance Spectroscopy studies suggest that brain abnormalities in BD are mostly regional, as global measures (cerebral, white and gray matter and ventricular volumes) do not seem to be affected in the majority of patients. The prefrontal and anterior cingulate cortices, and amygdalae are consistently implicated in BD, whilst the evidence for hippocampal involvement is less convincing. Functional studies have found that the activity of the dorsal prefrontal cortex and the anterior cingulate are closely associated with mood symptoms. Activity in the ventral and orbital prefrontal cortex appears reduced both during episodes and in remission. In contrast, amygdala activity shows a persistent increase. We suggest that abnormal interaction between the amygdala and the ventral/orbitofrontal cortex may be a central feature of the pathophysiology of BD.

Mitochondrial DNA polymorphisms and extraversion

Mitochondria is the major site of energy production in cells, therefore, mitochondrial abnormality may affect functions of organs including the brain, which constantly requires high levels of energy consumption. Previous studies have suggested a role of mitochondria and their DNA polymorphisms in neuro-psychiatric disorders, including Alzheimer's disease, Parkinson's disease, schizophrenia and bipolar mood disorder. Thus, we hypothesized that mitochondrial DNA polymorphisms might be related with the development of personality. The present study investigated a role of two mitochondrial DNA polymorphisms, the C5178A and A10398G, in personality traits evaluated using the NEO PI-R scores in 238 healthy Japanese volunteers. Subjects with the 5178A genotype showed significantly higher extraversion score than those with the 5178C genotype (P = 0.027), while no significant association was observed between the C5178A polymorphism and other scores. No significant association was found between the A10398G polymorphism and any scores. Regarding the 5178-10398 haplotype, the score of extraversion, not other scores, was significantly associated with the A-G haplotype (P = 0.042). Although further studies are recommended for the confirmation, the result may suggest a role of the mitochondrial DNA polymorphism in the personality trait.

Reduced intracellular pH in the basal ganglia and whole brain measured by 31P-MRS in bipolar disorder

The authors have previously reported that intracellular pH measured by phosphorus-31 magnetic resonance spectroscopy (31P-MRS) was decreased in the frontal lobes of patients with bipolar disorder. In the present study, phosphorus metabolism in the basal ganglia was examined in 13 patients with bipolar disorder and 10 matched controls by localized 31P-MRS. While no significant alteration of peak area ratios was found for all phosphorus metabolites, intracellular pH was significantly reduced in the basal ganglia in patients with bipolar disorder (7.014 +/- 0.045) compared with control subjects (7.066 +/- 0.047, P < 0.05). Unexpectedly, non-localized 31P-MR spectra also showed significantly lower levels of intracellular pH (6.970 +/- 0.025) than controls (6.986 +/- 0.024, P < 0.05). These results suggest that decreased intracellular pH in the brain of patients with bipolar disorder is not caused by dysfunction of the frontal lobes but reflect altered metabolism at the cellular level.

Mood disorders - review of structural MRI studies

BACKGROUND

Mood disorders are related to considerable morbidity and mortality, and although there is little doubt that they are brain-based disorders, their neural correlates still remain elusive. A neuro-anatomic model of mood regulation comprising the prefrontal cortex, amygdala-hippocampus complex, thalamus, basal ganglia, and connections among these areas has been proposed.

OBJECTIVE

We reviewed the evidence for regional brain abnormalities in bipolar disorder, and attempted to integrate available findings into a comprehensive pathophysiological model of illness.

METHODS

A computerized Medline Ovid search was conducted for the period 1966-2002, and complemented by a manual search of bibliographical references from recent reviews. Articles meeting specified criteria were included.

RESULTS

Hyperintense lesions in cortical and subcortical regions are the most consistently reported and widely studied structural abnormalities. Smaller prefrontal cortical volume is a common finding in bipolar disorder and unipolar depression. Enlarged amygdala (in bipolar disorder) and smaller hippocampus (in unipolar depression) have been reported by several groups. Decreased volumes (in unipolar depression) and increased or unaltered volumes (in bipolar disorder) of striatal structures have been reported.

CONCLUSIONS

Bipolar and unipolar mood disorders are associated with detectable structural brain abnormalities. The histopathology underlying such anatomical changes remains to be elucidated. To reach more definitive conclusions about neuroanatomical changes that take place during the course of mood disorders, prospective longitudinal studies are needed. Also, integration with functional imaging is necessary in order to elucidate the relevance of identified structural abnormalities.

Enhancing neuronal plasticity and cellular resilience to develop novel, improved therapeutics for difficult-to-treat depression

There is growing evidence from neuroimaging and ostmortem studies that severe mood disorders, which have traditionally been conceptualized as neurochemical disorders, are associated with impairments of structural plasticity and cellular resilience. It is thus noteworthy that recent preclinical studies have shown that critical molecules in neurotrophic signaling cascades (most notably cyclic adenosine monophosphate [cAMP] response element binding protein, brain-derived neurotrophic factor, bcl-2, and mitogen activated protein [MAP] kinases) are long-term targets for antidepressant agents and antidepressant potentiating modalities. This suggests that effective treatments provide both trophic and neurochemical support, which serves to enhance and maintainnormal synaptic connectivity, thereby allowing the chemical signal to reinstate the optimal functioning of critical circuits necessary for normal affective functioning. For many refractory patients, drugs mimicking "traditional" strategies, which directly or indirectly alter monoaminergic levels, may be of limited benefit. Newer "plasticity enhancing" strategies that may have utility in the treatment of refractory depression include N-methyl-D-aspartate antagonists, alpha-amino-3-hydroxy-5-methylisoxazole propionate (AMPA) potentiators, cAMP phosphodiesterase inhibitors, and glucocorticoid receptor antagonists. Small-molecule agents that regulate the activity f growth factors, MAP kinases cascades, and the bcl-2 family of proteins are also promising future avenues. The development of novel, nonaminergic-based therapeutics holds much promise for improved treatment of severe, refractory mood disorders.

Chronic treatment with both lithium and sodium valproate may normalize phosphoinositol cycle activity in bipolar patients

BACKGROUND

It has been proposed that lithium may be clinically effective due to its actions on the phosphoinositol second messenger system (PI-cycle). Studies have also suggested that untreated manic patients may have raised myo-inositol and phosphomonoester (PME) concentrations and also that unmedicated euthymic bipolar patients may have lowered PME concentrations. The objective of the present study was to test the hypothesis that chronic treatment with either lithium or sodium valproate in patients with bipolar mood disorder leads to a normalization in the activity of the PI-cycle.

METHODS

This study had two parts each with different MRS methodology. The first part compared healthy controls (n = 19) with euthymic bipolar patients who were taking either lithium (n = 16) or sodium valproate (n = 11) using both (1)H-MRS and (31)P-MRS. In the second part we examined a separate group of euthymic bipolar disorder patients taking sodium valproate (n = 9) and compared these with age and sex-matched healthy controls (n = 11) using (1)H-MRS.

RESULTS

Both studies showed that there were no differences in either myo-inositol or phosphomonoester (PME) concentrations between controls and patients taking either medication.

CONCLUSIONS

These findings examine two key components of the PI-cycle in treated euthymic bipolar (myo-inositol and PME concentrations). The results from this study are consistent with the suggestion that chronic treatment with either lithium or sodium valproate in bipolar patients may normalize PI-cycle functioning.

Can brain-imaging studies provide a 'mood stabilizer signature?'

Brain-imaging investigations have attempted to characterize the neurobiological basis of bipolar disorder. Preliminary studies have also focused on in vivo brain correlates of treatment response with antidepressants, mood stabilizers and other psychotropic medications. A MEDLINE literature search was conducted dating back to 1966. Selected in vivo brain-imaging studies that examined neurobiological correlates of treatment response in mood disorder patients were identified. Discrete anatomical abnormalities in subregions of the prefrontal cortex, medial temporal lobe and cerebellum have been identified in bipolar patients. Functional imaging studies suggested abnormalities in particular brain circuits encompassing these same brain regions and the striatum. However, functional imaging correlates of treatment response with lithium or other mood stabilizers have not yet been characterized. Neurochemical studies suggested a reduction in N-acetyl aspartate levels in prefrontal cortex and abnormalities in membrane phospholipids in frontal and temporal lobes. Preliminary findings suggest that lithium may increase the gray matter content and N-acetyl aspartate levels in various cortical regions, which could reflect its putative neurotrophic effects. Few in vivo receptor-imaging studies have examined brain correlates of treatment response in bipolar patients. The available studies suggest anatomical, neurochemical and functional brain abnormalities in bipolar patients. However, in vivo brain correlates of treatment response with mood stabilizers in bipolar patients have not yet been well characterized.

In vivo magnetic resonance spectroscopy and its application to neuropsychiatric disorders

In vivo magnetic resonance spectroscopy (MRS) is the only noninvasive imaging technique that can directly assess the living biochemistry in localized brain regions. In the past decade, spectroscopy studies have shown biochemical alterations in various neuropsychiatric disorders. These first-generation studies have, in most cases, been exploratory but have provided insightful biochemical information that has furthered our understanding of different brain disorders. This review provides a brief description of spectroscopy, followed by a literature review of key spectroscopy findings in schizophrenia, affective disorders, and autism. In schizophrenia, phosphorus spectroscopy studies have shown altered metabolism of membrane phospholipids (MPL) during the early course of the illness, which is consistent with a neurodevelopmental abnormality around the critical period of adolescence when the illness typically begins. Children and adolescents who are at increased genetic risk for schizophrenia show similar MPL alterations, suggesting that schizophrenia subjects with a genetic predisposition may have a premorbid neurodevelopmental abnormality. Independent of medication status, bipolar subjects in the depressive state tended to have higher MPL precursor levels and a deficit of high-energy phosphate metabolites, which also is consistent with major depression, though these results varied. Further bipolar studies are needed to investigate alterations at the early stage. Lastly, associations between prefrontal metabolism of high-energy phosphate and MPL and neuropsychological performance and reduced N-acetylaspartate in the temporal and cerebellum regions have been reported in individuals with autism. These findings are consistent with developmental alterations in the temporal lobe and in the cerebellum of persons with autism. This paper discusses recent findings of new functions of N-acetylaspartate.

Volumetric MRI studies of mood disorders: do they distinguish unipolar and bipolar disorder?

The authors reviewed magnetic resonance imaging volumetric imaging results in major mood disorders, particularly comparing similarities and differences from studies of bipolar disorder and unipolar major depression. Abnormalities of cerebral brain regions appear inconsistently in mood disorders and, when present, typically consist of decreased frontal or prefrontal cortical volumes in both unipolar depression and bipolar disorder. In contrast, subcortical and medial temporal abnormalities are more commonly observed and are different between these two major classes of affective illness. Specifically, whereas structural enlargement of the basal ganglia and amygdala have been observed in bipolar disorder, in unipolar depression, these structures appear to be smaller in patients than healthy subjects. These findings suggest that affective illnesses may share in common an underdeveloped or atrophied prefrontal region, leading to loss of cortical modulation of limbic emotional networks. The effect of this loss results in unipolar depression or cycling (mania with depression) depending on the abnormalities of the subcortical structures involved. The cerebellum may also play a role in the presentation of mood disorders. This hypothesis remains speculative as much more research is needed to specifically examine how morphometric brain abnormalities translate into the neurophysiologic deficits that produce mood disorders.

The neuropsychology and neuroanatomy of bipolar affective disorder: a critical review

Bearden CE, Hoffman KM, Cannon TD. The neuropsychology and neuroanatomy of bipolar affective disorder: a critical review. Bipolar Disord 2001: 3: 106 150. C Munksgaard, 2001

OBJECTIVES

To present a comprehensive review of the existing neuropsychological and neuroimaging literature on bipolar affective disorder. This review critically evaluates two common conceptions regarding the neuropsychology of bipolar disorder: 1) that, in contrast to schizophrenia, bipolar affective disorder is not associated with general cognitive impairment independent of illness episodes, and 2) relative right hemisphere (RH) dysfunction is implicated in bipolar illness patients, supported by reports of relatively greater impairment in visuospatial functioning, lateralization abnormalities, and mania secondary to RH lesions.

METHODS

The major computerized databases (Medline and PSYCInfo) were consulted in order to conduct a comprehensive, integrated review of the literature on the neuropsychology and neuroanatomy of bipolar disorder. Articles meeting specified criteria were included in this review.

RESULTS

In a critical evaluation of the above notions, this paper determines that: 1) while there is little evidence for selective RH dysfunction, significant cognitive impairment may be present in bipolar illness, particularly in a subgroup of chronic, elderly or multiple-episode patients, suggesting a possible toxic disease process, and 2) the underlying functional correlate of these cognitive deficits may be white matter lesions ('signal hyperintensities') in the frontal lobes and basal ganglia, regions critical for executive function, attention, speeded information processing, learning and memory, and affect regulation. While this hypothesized neural correlate of cognitive impairment in bipolar disorder is speculative, preliminary functional neuroimaging evidence supports the notion of frontal and subcortical hypometabolism in bipolar illness.

CONCLUSIONS

The etiology of the structural brain abnormalities commonly seen in bipolar illness, and their corresponding functional deficits, remains unknown. It is possible that neurodevelopmental anomalies may play a role, and it remains to be determined whether there is also some pathophysiological progression that occurs with repeated illness episodes. More research is needed on first-episode patients, relatives of bipolar probands, and within prospective longitudinal paradigms in order to isolate disease-specific impairments and genetic markers of neurocognitive function in bipolar disorder.

31P Nuclear magnetic resonance spectroscopy findings in bipolar illness: a meta-analysis

Published literature comparing 31P MR brain spectra of bipolar patients to healthy controls was evaluated, focusing on phosphomonoester (PME)/phosphodiester (PDE) resonance areas because these metabolites are related to membrane phospholipids and membrane defects in bipolar disorder have been suggested. Studies comparing PME and/or PDE values of bipolar subjects to values observed in healthy controls were reviewed. Data from the studies meeting our inclusion criteria (8 reports involving 139 bipolar and 189 comparison subjects) were grouped according to the mood state of the subjects. Meta-analyses of data were performed to compare PME and PDE levels of euthymic bipolar patients to healthy controls, as well as comparing PME levels during euthymia in bipolar subjects to values observed during manic and depressed states. The PME values of euthymic bipolar patients were found to be significantly lower than PME values of healthy controls. Depressed bipolar patients had significantly higher PME values in comparison to euthymic bipolar patients. No significant difference could be detected between the PDE values of bipolars and controls. This meta-analysis found support for trait- and possibly state-dependent abnormalities of membrane phospholipid metabolism, which may reflect a dysregulation in brain-signal transduction systems of relevance in bipolar illness.

Mitochondrial DNA polymorphisms in bipolar disorder

BACKGROUND

Previous studies suggested mitochondrial abnormality in bipolar disorder: (1) possible contribution of parent-of-origin effect in transmission of bipolar disorder; (2) abnormal brain phosphorus metabolism detected by phosphorus-31 magnetic resonance spectroscopy; (3) comorbidity of affective disorders in patients with mitochondrial encephalopathy; (4) increased levels of the 4977bp deletion of mitochondrial DNA (mtDNA) in the postmortem brains. We investigated mtDNA polymorphisms in association with bipolar disorder.

METHODS

Twelve PCR fragments including all tRNA genes were examined by the single-strand conformation polymorphism method in 43 bipolar patients. All observed polymorphisms were sequenced. Association of these polymorphisms with bipolar disorder was examined by restriction fragment length polymorphism method in 135 bipolar patients and 187 controls.

RESULTS

In total, we found 28 polymorphisms including 14 polymorphisms that have not been reported previously. The A10398G polymorphism was significantly associated with bipolar disorder (10398A genotype: 33.1% in bipolar, 22.2% in the control, P<0.05). Although this difference was not significant after Bonferroni correction, the CA haplotype of the 5178 and 10398 polymorphisms was still significantly associated with bipolar disorder (CA haplotype: 33.6% in bipolar, 16.8% in control, P<0.001). Three rare mutations substituting evolutionary conserved bases; A5539G in tRNA(Trp) gene, A5747G in the origin of L-strand replication, and A8537G in ATPase subunit-6 and -8 genes, were found in patients with family history in which maternal transmission was suspected.

DISCUSSION

The 5178C/10398A haplotype in mtDNA may be a risk factor of bipolar disorder (odds ratio, 2.4). Pathophysiological significance of rare mtDNA mutations needs to be verified in the future. This finding may imply the pathophysiological significance of mtDNA in bipolar disorder.

Neuroplasticity and cellular resilience in mood disorders

Although mood disorders have traditionally been regarded as good prognosis diseases, a growing body of data suggests that the long-term outcome for many patients is often much less favorable than previously thought. Recent morphometric studies have been investigating potential structural brain changes in mood disorders, and there is now evidence from a variety of sources demonstrating significant reductions in regional CNS volume, as well as regional reductions in the numbers and/or sizes of glia and neurons. Furthermore, results from recent clinical and preclinical studies investigating the molecular and cellular targets of mood stabilizers and antidepressants suggest that a reconceptualization about the pathophysiology and optimal long-term treatment of recurrent mood disorders may be warranted. It is proposed that impairments of neuroplasticity and cellular resilience may underlie the pathophysiology of mood disorders, and further that optimal long-term treatment for these severe illnesses may only be achieved by the early and aggressive use of agents with neurotrophic/neuroprotective effects. It is noteworthy that lithium, valproate and antidepressants indirectly regulate a number of factors involved in cell survival pathways including CREB, BDNF, bcl-2 and MAP kinases, and may thus bring about some of their delayed long-term beneficial effects via underappreciated neurotrophic effects. The development of novel treatments which more directly target molecules involved in critical CNS cell survival and cell death pathways have the potential to enhance neuroplasticity and cellular resilience, and thereby modulate the long-term course and trajectory of these devastating illnesses.

Neuroimaging in bipolar disorder: what have we learned?

New technologies are offering increasingly powerful means to obtain structural, chemical, and functional images of the brain during life, often without the use of ionizing radiation. Bipolar disorder, with its clear physiologic features, would appear to be a prime candidate for the application of current brain imaging; however, only a modest number of studies have been reported to date, and most studies have small sample sizes and heterogeneous subject groups. Nonetheless, there are a few consistent findings among these studies, including the following: 1) Structural imaging studies suggest an increased number of white matter hyperintensities in patients with bipolar disorder. These may be lesions unique to bipolar disorder and its treatment, or related to cardiovascular risk factors, which are more common in bipolar patients. Decreased cerebellar size and anomalies of cerebellar blood volume have also been reported. Increased sulcal prominence and enlargement of the lateral and third ventricles are less consistently observed findings. 2) Spectroscopic imaging suggests abnormalities of metabolism of choline-containing compounds in symptomatically ill bipolar patients and, possibly, treatment-induced changes in choline- and myoinositol-containing compounds. Each of these groups of metabolites serves as a component of membrane phospholipids and cellular second-messenger cycles. 3) Metabolic and blood flow studies provide evidence for decreased activity of the prefrontal cortex (PFC) in bipolar patients during depression. It is not clear if these changes are restricted to particular subregions of the PFC, nor if they are reversed with mania. No single pathophysiologic mechanism yet explains these findings, although all might be due to regional alterations in cellular activity and metabolism or changes in cell membrane composition and turnover. The development of imaging technologies has far outpaced their use in bipolar disorder. The promise of future studies is great, with more powerful magnetic resonance scanners, additional ligands for positron emission tomography and single photon emission computed tomography imaging, and improved image generation and processing already available.

Mitochondrial dysfunction in bipolar disorder

Mitochondrial dysfunction is implicated in bipolar disorder based on the following lines of evidence: 1) Abnormal brain energy metabolism measured by 31P-magnetic resonance spectroscopy, that is, decreased intracellular pH, decreased phosphocreatine (PCr), and enhanced response of PCr to photic stimulation. 2) Possible role of maternal inheritance in the transmission of bipolar disorder. 3) Increased levels of the 4977-bp deletion in mitochondrial DNA (mtDNA) in autopsied brains. 4) Comorbidity of affective disorders in certain types of mitochondrial disorders, such as autosomal inherited chronic progressive external ophthalmoplegia and mitochondrial diabetes mellitus with the 3243 mutation. Based on these findings, we searched for mtDNA mutations/ polymorphisms associated with bipolar disorder and found that 5178C and 10398A polymorphisms in mtDNA were risk factors for bipolar disorder. The 5178C genotype was associated with lower brain intracellular pH. mtDNA variations may play a part in the pathophysiology of bipolar disorder through alteration of intracellular calcium signaling systems. The mitochondrial dysfunction hypothesis, which comprehensively accounts for the pathophysiology of bipolar disorder, is proposed.

Neuroimaging in bipolar disorder

OBJECTIVE

The authors reviewed neuroimaging studies of bipolar disorder in order to evaluate how this literature contributes to the current understanding of the neurophysiology of the illness.

METHOD

Papers were reviewed as identified, using the NIMH PubMed literature search systems that reported results of neuroimaging studies involving a minimum of five bipolar disorder patients compared with healthy comparison subjects.

RESULTS

Structural neuroimaging studies report mixed results for lateral and third ventriculomegaly. Recent studies suggest subcortical structural abnormalities in the striatum and amygdala, as well as the prefrontal cortex. Proton spectroscopic studies suggest that abnormalities in choline metabolism exist in bipolar disorder, particularly in the basal ganglia. Additionally, phosphorous MRS suggests that there may be abnormalities in frontal phospholipid metabolism in bipolar disorder. Functional studies have identified affective state-related changes in cerebral glucose metabolism and blood flow, particularly in the prefrontal cortex during depression, but no clear abnormalities specific to bipolar disorder have been consistently observed.

CONCLUSIONS

The current literature examining the neurophysiology of bipolar disorder using neuroimaging is limited. Nonetheless, abnormalities in specific frontal-subcortical brain circuits seem likely. Additional targeted studies are needed to capitalize on this burgeoning technology to advance our understanding of the neurophysiology of bipolar disorder.

Moclobemide reduces intracellular pH and neuronal activity of CA3 neurones in guinea-pig hippocampal slices-implication for its neuroprotective properties

Mechanisms underlying the neuroprotective properties of the weak MAO-A inhibitor moclobemide are not understood. Increasing evidence suggests that a moderate increase in intracellular free protons may contribute to neuroprotective properties due to a proton-mediated decrease in neuronal activity. Therefore, we studied effects of 10-700 microM moclobemide (i) on the intracellular pH (pH(i)) of BCECF-AM loaded CA3 neurones as well as (ii) on spontaneous action potentials and epileptiform activity (induced by bicuculline-methiodide, caffeine, or 4-aminopyridine) of CA3 neurones in the stratum pyramidale. Moclobemide-concentrations of > or = 300 microM reversibly reduced the steady-state pH(i) by up to 0. 25 pH-units within 5-20 min. Simultaneously, the frequency of spontaneous action potentials and epileptiform discharges became depressed. Moclobemide also abolished 4-aminopyridine-induced GABA-mediated hyperpolarisations suggesting that the inhibitory and acidifying effects of moclobemide do not result from an amplification of the GABA system. The stronger MAO-A inhibitors clorgyline or pargyline (both 10 microM) mimicked the moclobemide-effects. Investigating effects on pH(i)-regulation we found that 700 microM moclobemide impaired the recovery from intracellular acidification elicited by an ammonium prepulse which demonstrates an impairment of transmembrane acid extrusion. We suggest that the latter effect is responsible for the moderate decrease in the steady-state pH(i) which in turn reduced neuronal activity. This mechanism may substantially contribute to the neuroprotective properties of moclobemide.

An MRI study of temporal lobe structures in men with bipolar disorder or schizophrenia

BACKGROUND

Hippocampal atrophy has been described in postmortem and magnetic resonance imaging studies of schizophrenia. The specificity of this finding to schizophrenia remains to be determined. The neuropathology of bipolar disorder is understudied, and temporal lobe structures have only recently been evaluated.

METHODS

Twenty-four bipolar, 20 schizophrenic, and 18 normal comparison subjects were evaluated using magnetic resonance brain imaging. Image data were acquired using a three-dimensional spoiled GRASS sequence, and brain images were reformatted in three planes. Temporal lobe structures including the amygdala, hippocampus, parahippocampus, and total temporal lobe were measured to obtain volumes for each structure in the three subject groups. Severity of symptoms in both patient groups was assessed at the time the magnetic resonance images were obtained.

RESULTS

Hippocampal volumes were significantly smaller in the schizophrenic group than in both bipolar and normal comparison subjects. Further, amygdala volumes were significantly larger in the bipolar group than in both schizophrenic and normal comparison subjects.

CONCLUSIONS

The results suggest differences in affected limbic structures in patients with schizophrenia and bipolar disorder. These specific neuroanatomic abnormalities may shed light on the underlying pathophysiology and presentation of the two disorders.

Psychotropic drug prescription patterns among patients with bipolar I disorder

INTRODUCTION

Combination treatment, rather than monotherapy, is prevalent in the treatment of subjects with bipolar disorder, probably due to the complex and phasic nature of the illness. In general, prescription patterns may be influenced by the demographic characteristics of patients as well. We evaluated prescription patterns and the influence of demographic variables on these patterns in a voluntary registry of subjects with bipolar disorder.

METHODS

A subset of data from a larger voluntary registry was extracted for demographic variables and psychotropic medication use that had been reported in the month prior to registration by ambulatory, non-hospitalized subjects with bipolar I disorder in 1995/96 (n = 457).

RESULTS

Among the thymoleptic agents, lithium was prescribed in over 50% of subjects, valproate in approximately 40%, and carbamazepine in 11% of subjects. Eighteen percent of subjects had no prescription for thymoleptic agents. Nearly one-third of all subjects were receiving antipsychotic agents, of whom two-thirds were receiving the traditional neuroleptic agents. More than half of all subjects were receiving concomitant antidepressants, of whom nearly 50% received the SSRI antidepressants and nearly 25% received buproprion. Approximately 40% of subjects received benzodiazepines. Only 18% of subjects received monotherapy, and nearly 50% received three or more psychotropic agents. In general, no associations were noted between demographic parameters including age, gender, marital or educational status, and psychotropic prescriptions.

CONCLUSION

Consistent with the anecdotal reports, these data confirm that combination treatment is far more common than monotherapy. Demography appears to have a minimal impact on cross-sectional prescription patterns in subjects with bipolar disorder. Given that combination treatments are the rule rather than the exception, we should strive to achieve rational, yet pragmatic, treatment guidelines and algorithms to minimize the risks while maximizing the benefits of these combination treatments for patients with bipolar disorder.

Depression and bipolar disorder: relationships to impaired fatty acid and phospholipid metabolism and to diabetes, cardiovascular disease, immunological abnormalities, cancer, ageing and osteoporosis. Possible candidate genes

Depression and bipolar disorder are two of the commonest illnesses in the developed world. While some patients can be treated effectively with available drugs, many do not respond, especially in the depression related to bipolar disorder. Depression is associated with diabetes, cardiovascular disease, immunological abnormalities, multiple sclerosis, cancer, osteoporosis and ageing: in each case depressed individuals have a worse outcome than non-depressed individuals. In all of these conditions there is now evidence of impaired phospholipid metabolism and impaired fatty acid-related signal transduction processes. Impaired fatty acid and phospholipid metabolism may be a primary cause of depression in many patients and may explain the interactions with other diseases. Several novel gene candidates for involvement in depression and bipolar disorder are proposed.

Age-dependent alteration of metabolic response to photic stimulation in the human brain measured by 31P MR-spectroscopy

Effects of photic stimulation (PS) on energy metabolism were examined in the occipital cortex of 25 healthy volunteers aged 23-69 years old using phosphorus-31 magnetic resonance spectroscopy (31P-MRS). A significant effect of photic stimulation was found only for intracellular pH (p<0.05 by repeated measures analysis of variance) but not for any peak area ratios. An interaction between intracellular pH and age were statistically significant (p<0.005), and the interaction between phosphocreatine and age was close to significance (p=0.06). In subjects aged more than 40 years old, phosphocreatine was significantly decreased during the photic stimulation (p<0.05, multiple comparison by Dunnett's method), and intracellular pH tended to be elevated just after the stimulation (p=0.07). There were no significant changes in these values in younger subjects. These results suggest that no significant effect of photic stimulation on brain energy metabolism was found in younger subjects, and that significant effects of photic stimulation on intracellular pH and phosphocreatine were found in middle-aged subjects. Metabolic response of the human brain to photic stimulation may be dependent on age.