Abstract:Supplementation of standard treatment with high-dose levothyroxine (L-T 4 ) is a novel approach for treatment-refractory bipolar disorders. This study tested for effects on brain function associated with mood alterations in bipolar depressed patients receiving high-dose L-T 4 treatment adjunctive to ongoing medication (antidepressants and mood stabilizers). Regional activity and whole-brain analyses were assessed with positron emission tomography and [ 18 F]fluorodeoxyglucose in 10 euthyroid depressed women wi… Show more
“…2,68 TH treatment is also beneficial in bipolar disorders resistant to other forms of treatment. 69,70 Concerning cognitive functioning, there was no difference among the experimental groups in the long-term object recognition memory. A recent study 71 found that treatment with the antimitotic agent methylazoxymethanol acetate reduces neurogenesis in the hippocampus up to 65% and prevents the long-term memory improvement induced by environmental enrichment, as measured in this object recognition task.…”
Hormonal imbalances are involved in many of the age-related pathologies, as neurodegenerative and psychiatric diseases. Specifically, thyroid state alterations in the adult are related to psychological changes and mood disorders as depression. The dentate gyrus of the hippocampal formation undergoes neurogenesis in adult mammals including humans. Recent evidence suggests that depressive disorders and their treatment are tightly related to the number of newly born neurons in the dentate gyrus. We have studied the effect of thyroid hormones (TH) on hippocampal neurogenesis in adult rats in vivo. A short period of adultonset hypothyroidism impaired normal neurogenesis in the subgranular zone of the dentate gyrus with a 30% reduction in the number of proliferating cells. Hypothyroidism also reduced the number of newborn neuroblasts and immature neurons (doublecortin (DCX) immunopositive cells) which had a severely hypoplastic dendritic arborization. To correlate these changes with hippocampal function, we subjected the rats to the forced swimming and novel object recognition tests. Hypothyroid rats showed normal memory in object recognition, but displayed abnormal behavior in the forced swimming test, indicating a depressive-like disorder. Chronic treatment of hypothyroid rats with TH not only normalized the abnormal behavior but also restored the number of proliferative and DCX-positive cells, and induced growth of their dendritic trees. Therefore, hypothyroidism induced a reversible depressive-like disorder, which correlated to changes in neurogenesis. Our results indicate that TH are essential for adult hippocampal neurogenesis and suggest that mood disorders related to adult-onset hypothyroidism in humans could be due, in part, to impaired neurogenesis.
“…2,68 TH treatment is also beneficial in bipolar disorders resistant to other forms of treatment. 69,70 Concerning cognitive functioning, there was no difference among the experimental groups in the long-term object recognition memory. A recent study 71 found that treatment with the antimitotic agent methylazoxymethanol acetate reduces neurogenesis in the hippocampus up to 65% and prevents the long-term memory improvement induced by environmental enrichment, as measured in this object recognition task.…”
Hormonal imbalances are involved in many of the age-related pathologies, as neurodegenerative and psychiatric diseases. Specifically, thyroid state alterations in the adult are related to psychological changes and mood disorders as depression. The dentate gyrus of the hippocampal formation undergoes neurogenesis in adult mammals including humans. Recent evidence suggests that depressive disorders and their treatment are tightly related to the number of newly born neurons in the dentate gyrus. We have studied the effect of thyroid hormones (TH) on hippocampal neurogenesis in adult rats in vivo. A short period of adultonset hypothyroidism impaired normal neurogenesis in the subgranular zone of the dentate gyrus with a 30% reduction in the number of proliferating cells. Hypothyroidism also reduced the number of newborn neuroblasts and immature neurons (doublecortin (DCX) immunopositive cells) which had a severely hypoplastic dendritic arborization. To correlate these changes with hippocampal function, we subjected the rats to the forced swimming and novel object recognition tests. Hypothyroid rats showed normal memory in object recognition, but displayed abnormal behavior in the forced swimming test, indicating a depressive-like disorder. Chronic treatment of hypothyroid rats with TH not only normalized the abnormal behavior but also restored the number of proliferative and DCX-positive cells, and induced growth of their dendritic trees. Therefore, hypothyroidism induced a reversible depressive-like disorder, which correlated to changes in neurogenesis. Our results indicate that TH are essential for adult hippocampal neurogenesis and suggest that mood disorders related to adult-onset hypothyroidism in humans could be due, in part, to impaired neurogenesis.
“…The functional relevance of this structure in mood disorders has been underlined by different lines of evidence, including deep brain stimulation 9 and pharmacological treatment. 10 Furthermore, a pathmodelling meta-analysis of cerebral blood flow in depressive patients 11 has demonstrated that different effective connectivity patterns between the SC and the amygdalo-hippocampal (AH) complex distinguished treatment responders from nonresponders.…”
Bipolar disorder has been associated with anatomical as well as functional abnormalities in a brain network that mediates normal and impaired emotion regulation. Previous brain imaging studies have highlighted the subgenual cingulate (SC) and the amygdalo-hippocampal (AH) complex as core regions of this network. Thus we investigated white matter (WM) fiber tracts between the SC and the AH region, the uncinate fasciculus, as well as between two control regions (pons and cerebellum), using diffusion tensor imaging tractography in 16 euthymic bipolar patients (BP) and 16 sex-, age-and handedness-matched controls. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of the reconstructed fiber bundle and the number of virtual reconstructed fibers were compared between groups. The tractography results revealed a significantly increased number of reconstructed fibers between the left SC and left AH in BP as compared to healthy controls. FA and ADC of the reconstructed fiber tract did not differ significantly between the groups. Furthermore, no significant group differences were observed neither for reconstructed fiber tracts between the right SC and right AH nor between the control regions. The present results suggest an altered WM pathway between the left SC and AH region and thus extend previous findings of anatomical and functional modifications in these structures in BP.
“…Direct clinical evidence for hippocampal pathology in bipolar illness stems from post-mortem histological analysis, [6][7][8][9] volumetric magnetic resonance imaging 10 and [(18)F]fluorodeoxyglucose-positron emission tomography. 11 Recently, magnetic resonance spectroscopy (MRS) has also provided evidence for hippocampal neurometabolite alterations in bipolar disorder. [12][13][14] After 50 years of clinical use, lithium salts have remained the most effective and widely used longterm preventive treatment for bipolar disorder to date.…”
While an excess of glucocorticoids is associated with hippocampal pathology in mood disorders, lithium exerts robust neuroprotective and neurotrophic effects. Here, 21 stably remitted bipolar I patients who had been on chronic lithium maintenance therapy, on average, for more than a decade, and 19 carefully matched healthy controls were studied using 3 T 1 Hmagnetic resonance spectroscopy of left and right hippocampus. Salivary cortisol samples were obtained to assess activity of the hypothalamus-pituitary-adrenal system. Absolute concentrations of N-acetylaspartate (NAA), choline-containing compounds and total creatine were similar in euthymic bipolar patients and healthy controls. Hippocampal glutamate concentrations were significantly increased as an effect of patient status (patients > controls) and laterality (left hippocampus > right hippocampus). Hippocampal glutamate content (Glu) was strongly correlated with NAA. Across groups and within the patient group, diurnal saliva cortisol levels showed a significant inverse relationship with both Glu and NAA. Taken together, these results add to the concept of bipolar disorder as an illness involving disturbed hippocampal structural plasticity under the opposing influences of lithium and glucocorticoids.
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