Activation of cholinergic basal forebrain neurons improved cognitive functions in adult-onset hypothyroid mice.

Cognitive dysfunction is common in hypothyroid patients, even after undergoing sufficient levothyroxine (LT4) replacement therapy for euthyroid. Our previous studies indicated that cholinergic neurons might contribute to the decline of cognition in adult-onset hypothyroidism. Nevertheless, the role of the cellular and neural control of basal forebrain (BF) cholinergic neurons in hypothyroidism-induced cognitive impairments is unknown. Using transgenic mice that specifically expressed chemogenetic activators in their BF cholinergic neurons, we systematically investigated the role of BF cholinergic neurons in hypothyroidism-induced cognitive dysfunction by the combined approaches of patch clamp electrophysiology, behavioral testing, and immunohistochemistry. The results showed that LT4 treatment in the adult-onset hypothyroid mice reversed only 78 % of the BF cholinergic neurons to their normal values of electrophysiological properties. LT4 monotherapy did not rehabilitate cognitive function in the hypothyroid mice. Chemogenetic selective activation of the BF cholinergic neurons combined with LT4 treatment significantly improved learning and memory functions in the hypothyroid mice. In addition, chemogenetic activation of the cholinergic neurons induced the robust expression of c-Fos protein in the BF, prefrontal cortex (PFC), and hippocampus. This indicated that the BF cholinergic neurons improved learning and memory functions in the hypothyroid mice via the BF-PFC and BF-hippocampus pathways. In the hypothyroid C57BL/6 J mice, combined treatment via LT4 and donepezil, a cholinesterase inhibitor, significantly increased cognitive functions. The results suggested that the BF cholinergic neurons are critical for regulating learning and memory and reveal a novel pathophysiological mechanism for hypothyroidism-induced cognitive impairments.

Synaptic loss in a mouse model of euthyroid Hashimoto's thyroiditis: possible involvement of the microglia.

BACKGROUND: Hashimoto's thyroiditis (HT) is an autoimmune illness that renders individuals vulnerable to neuropsychopathology even in the euthyroid state, the mechanisms involved remain unclear. We hypothesized that activated microglia might disrupt synapses, resulting in cognitive disturbance in the context of euthyroid HT, and designed the present study to test this hypothesis. METHODS: Experimental HT model was induced by immunizing NOD mice with thyroglobulin and adjuvant twice. Morris Water Maze was measured to determine mice spatial learning and memory. The synaptic parameters such as the synaptic density, synaptic ultrastructure and synaptic-markers (SYN and PSD95) as well as the interactions of microglia with synapses were also determined. RESULTS: HT mice had poorer performance in Morris Water Maze than controls. Concurrently, HT resulted in a significant reduction in synapse density and ultrastructure damage, along with decreased synaptic puncta visualized by immunostaining with synaptophysin and PSD-95. In parallel, frontal activated microglia in euthyroid HT mice showed increased engulfment of PSD95 and EM revealed that the synaptic structures were visible within the microglia. These functional alterations in microglia corresponded to structural increases in their attachment to neuronal perikarya and a reduction in presynaptic terminals covering the neurons. CONCLUSION: Our results provide initial evidence that HT can induce synaptic loss in the euthyroid state with deficits might be attributable to activated microglia, which may underlie the deleterious effects of HT on spatial learning and memory.

Effect of Restricted Feeding on Metabolic Health and Sleep-Wake Rhythms in Aging Mice.

Aging, an irreversible and unavoidable physiological process in all organisms, is often accompanied by obesity, diabetes, cardiovascular diseases, sleep disorders, and fatigue. Thus, older adults are more likely to experience metabolic symptoms and sleep disturbances than are younger adults. Restricted feeding (RF) is a dietary regimen aimed at improving metabolic health and extending longevity, as well as reorganizing sleep-wake cycles. However, the potential of RF to improve metabolic health and sleep quality in older adults who are known to show a tendency toward increased weight gain and decreased sleep is unknown. To elucidate this issue, aged mice were assigned to an RF protocol during the active phase for 2 h per day for 2 weeks. Sleep-wake cycles were recorded during the RF regime in RF group and control mice. At the end of this period, body weight and blood biochemistry profiles, including blood glucose, cholesterol, and enzyme activity, in addition to dopamine concentrations in the brain, were measured in the RF group and age-matched controls. RF for 2 weeks improved the metabolic health of aged mice by reducing their body weights and blood glucose and cholesterol levels. At the beginning of the RF regime, sleep decreased in the dark period but not in the light period. After stable food entrainment was achieved (7 days post-RF commencement), the amount of time spent in wakefulness during the light period dramatically increased for 2 h before food availability, thereby increasing the mean duration of awake episodes and decreasing the number of wakefulness episodes. There was no significant difference in the sleep-wake time during the dark period in the RF group, with similar total amounts of wakefulness and sleep in a 24-h period to those of the controls. During the RF regime, dopamine levels in the midbrain increased in the RF group, pointing to its potential as the mechanism mediating metabolic symptoms and sleep-wake regulation during RF. In conclusion, our study suggested that RF during aging might prohibit or delay the onset of age-related diseases by improving metabolic health, without having a severe deleterious effect on sleep.

Genetic Difference of Hypothyroidism-Induced Cognitive Dysfunction in C57BL/6j and 129/Sv Mice.

Adult-onset hypothyroidism induces cognitive impairments in learning and memory. Thyroxin (T4) replacement therapy appears to be effective in biochemically restoring euthyroidism, as evidenced by serum T4 and triiodothyronine concentrations within the normal range, although some the patients still exhibit cognitive dysfunctions. Here, we investigated the cognitive functions of propylthiouracil-induced hypothyroid mice in C57BL/6j and 129/Sv strains using the passive avoidance task and the novel object recognition test. Cognitive dysfunctions in hypothyroid mice were found only in the C57BL/6j strain, not in the 129/Sv strain. Further, we found that cholinergic neurons in the basal forebrain increased the membrane potential and input resistance with decreased capacitance, and that they decreased the amplitude and width of action potential in hypothyroid mice in the C57BL/6j strain but not in those in the 129/Sv strain, compared with the controls for each strain. Additionally, the excitability of cholinergic neurons in the basal forebrain was reduced in the hypothyroid mice in the C57BL/6j strain. These results indicated that transgenic mice with the C57BL/6j genetic background are more suitable for revealing the mechanism underlying hypothyroidism-induced cognitive dysfunction, and that the cholinergic basal forebrain may be the appropriate target for treating cognitive dysfunction in adult-onset hypothyroidism.

Hashimoto's thyroiditis induces neuroinflammation and emotional alterations in euthyroid mice.

BACKGROUND: Although studies have reported an increased risk for mood disorders in Hashimoto's thyroiditis (HT) patients even in the euthyroid state, the mechanisms involved remain unclear. Neuroinflammation may play a key role in the etiology of mood disorders in humans and behavioral disturbances in rodents. Therefore, this study established a euthyroid HT model in mice and investigated whether HT itself was capable of triggering neuroinflammation accompanied by emotional alterations. METHODS: Experimental HT was induced by immunizing NOD mice with thyroglobulin and adjuvant twice. Four weeks after the last challenge, mice were tested for anxiety-like behavior in the open field and elevated plus maze tests and depression-like behavior in the forced swimming and tail suspension tests. Then, animals were sacrificed for thyroid-related parameter measure as well as detection of cellular and molecular events associated with neuroinflammation. The changes in components of central serotonin signaling were also investigated. RESULTS: HT mice showed intrathyroidal monocyte infiltration and rising serum thyroid autoantibody levels accompanied by normal thyroid function, which defines euthyroid HT in humans. These mice displayed more anxiety- and depressive-like behaviors than controls. HT mice further showed microglia and astrocyte activation in the frontal cortex detected by immunohistochemistry, real-time RT-PCR, and transmission electron microscopy (TEM). These observations were also accompanied by enhanced gene expression of proinflammatory cytokines IL-1ß and TNF-α in the frontal cortex. Despite this inflammatory response, no signs of neuronal apoptosis were visible by the TUNEL staining and TEM in the frontal cortex of HT mice. Additionally, IDO1 and SERT, key serotonin-system-related genes activated by proinflammatory cytokines, were upregulated in HT mice, accompanied by reduced frontal cortex serotonin levels. CONCLUSIONS: Our results are the first to suggest that HT induces neuroinflammation and alters related serotonin signaling in the euthyroid state, which may underlie the deleterious effects of HT itself on emotional function.

Impact of maternal thyroid autoantibodies positivity on the risk of early term birth: Ma'anshan Birth Cohort Study.

PURPOSE: We aim to investigate associations of maternal serum anti-thyroperoxidase autoantibody (TPOAb) with duration of gestation. We aim to investigate whether maternal TPOAb positivity is associated with the risk of premature or early term birth. METHODS: This was a prospective birth cohort study performed in an iodine sufficient area of China. Serum samples were collected from 2931 women at both the first and second trimesters of pregnancy. Thyrotropin (TSH), free thyroxine (FT4), and TPOAb levels were measured. Data on gestational age at birth was obtained from delivery records. RESULTS: The prevalence of early term birth was 23.8%, while the prevalence of premature birth was 4.2%. The prevalence of TPOAb positivity was 12.1% in the first trimester and was 7.2% in the second trimester. Gestational age at birth was inversely associated with lgTPOAb both in the first trimester (ß, -0.283, 95% CI -0.408, -0.158; P < 0.001) and in the second trimester (ß, -0.174, 95% CI -0.319, -0.030; P = 0.018), after adjustment for potential confounding factors. There was a positive association of TPOAb positivity with the risk of early term birth both in the first (OR = 1.691, 95% CI 1.302, 2.197) and second trimesters (OR = 1.644, 95% CI 1.193, 2.264), after adjustment for potential confounding factors. TPOAb positivity in the second trimester was associated with a 1.863-fold higher risk of premature birth (OR = 1.863, 95% CI 1.009, 3.441), after adjustment for potential confounding factors. CONCLUSIONS: Our results show that TPOAb is associated with shorter duration of gestation and with higher risk of premature and early term birth.

Thyroid autoantibodies in pregnancy are associated with hypertensive disorders of pregnancy: Ma'anshan Birth Cohort Study.

OBJECTIVE: Hypertensive disorders of pregnancy (HDP) have been associated with adverse health outcomes for both mothers and children. Previous studies examining associations of maternal thyroid autoantibodies with HDP indicate conflicting results. The objective of this study was to examine associations of maternal thyroid autoantibody positivity in the first and the second trimesters with the risk of HDP. DESIGN, PARTICIPANTS AND MEASUREMENTS: In the Ma'anshan Birth Cohort study, a population-based prospective study in China, a total of 3474 pregnant women were enrolled between May 2013 and September 2014. Thyroid autoantibodies, including antithyroperoxidase autoantibody (TPOAb) and antithyroglobulin autoantibody (TgAb), as well as thyroid function tests, were measured in both the first and the second trimesters in 2893 pregnant women. Multivariate logistic regression analyses were conducted to calculate the odds ratio (OR) and 95% confidence interval (CI) for the associations between thyroid autoantibodies and HDP. RESULTS: Multivariate logistic regression analyses showed that TPOAb positivity in the first trimester was associated with a 1.80 (95% CI = 1.17-2.78) increased odds of HDP after adjustment for confounders, which was mainly due to an increased risk of gestational hypertension (OR = 1.93, 95% CI = 1.17-3.18). In addition, TgAb positivity in the first trimester was associated with a higher risk of HDP (OR = 1.78, 95% CI = 1.16-2.73) after adjustment for confounders, which was mainly due to an increased risk of gestational hypertension (OR = 1.89, 95% CI = 1.15-3.11). These associations were also seen among euthyroid women. Women with positive TPOAb in the second trimester seemed to have a higher risk of gestational hypertension (OR = 1.87, 95% CI = 1.02-3.43) after adjustment for confounders. However, among euthyroid women, TPOAb positivity in the second trimester was not associated with HDP. The TgAb status in the second trimester was not associated with HDP. CONCLUSIONS: Our results show that TPOAb positivity and TgAb positivity in the first trimester are associated with an increased risk of HDP. These data demonstrate that these associations are even seen among euthyroid women.

Hyperactivation of working memory-related brain circuits in newly diagnosed middle-aged type 2 diabetics.

Type 2 diabetes mellitus (T2DM) is well known for its adverse impacts on brain and cognition, which leads to multidimensional cognitive deficits and wildly spread cerebral structure abnormalities. However, existing literatures are mainly focused on patients with advanced age or extended T2DM duration. Therefore, it remains unclear whether and how brain function would be affected at the initial onset stage of T2DM in relatively younger population. In current study, twelve newly diagnosed middle-aged T2DM patients with no previous diabetic treatment history and twelve matched controls were recruited. Brain activations during a working memory task, the digit n-back paradigm (0-, 1- and 2-back), were obtained with functional magnetic resonance imaging and tested by repeated measures ANOVA. Whereas patients performed the n-back task comparably well as controls, significant load-by-group interactions of brain activation were found in the right dorsolateral prefrontal cortex (DLPFC), left middle/inferior frontal gyrus, and left parietal cortex, where patients exhibited hyperactivation in the 2-back, but not the 0-back or 1-back condition compared to controls. Furthermore, the severity of chronic hyperglycemia, estimated by glycosylated hemoglobin (HbA1c) level, was entered into partial correlational analyses with task-related brain activations, while controlling for the real-time influence of glucose, estimated by instant plasma glucose level measured before scanning. Significant positive correlations were found between HbA1c and brain activations in the anterior cingulate cortex and bilateral DLPFC only in patients. Taken together, these findings suggest there might be a compensatory mechanism due to brain inefficiency related to chronic hyperglycemia at the initial onset stage of T2DM.

Functional magnetic resource imaging assessment of altered brain function in hypothyroidism during working memory processing.

CONTEXT: Hypothyroidism is related to multiple cognitive deficits including working memory dysfunction, of which the underlying neural correlates were rarely studied. In this study, the impact of hypothyroidism on neural circuits involved in working memory processing was explored by functional magnetic resource imaging (fMRI). DESIGN: Using fMRI, we conducted a longitudinal study investigating alterations of brain function during a working memory task, the four-digit backward recall (BR) and forward recall (FR), in hypothyroid patients and controls. METHODS: fMRI scan was used in 13 female patients at two time points: before and after having been treated with levothyroxine (L-T(4)) for ∼6 months, and 12 matched euthyroid controls were also scanned. Wechsler Memory Scale-Chinese Revision was used to assess the memory states of each participant. RESULTS: The hypothyroid patients showed poorer memory states than that in controls. Furthermore, significant differences of task-induced deactivation (TID, task-dependent decreases in neural activity relative to rest) between patients and controls were found in the bilateral medial prefrontal cortices, posterior cingulate cortices, and left inferior partial lobule (P<0.05). These regions were considered as parts of a task-negative network, namely the default mode network (DMN). Concretely, relative to controls, patients showed diminished TID during BR in contrast to FR. After the L-T(4) treatment, neither the poor memory states nor the alteration of TID was detectable in patients. CONCLUSION: Hypothyroidism is related to alterations of TID within DMN regions during working memory processing. These exploratory findings may imply potential neural correlates in hypothyroidism-related cognitive deficits and their recoveries.

fMRI revealed neural substrate for reversible working memory dysfunction in subclinical hypothyroidism.

Cognitive impairments have been found in thyroid hormone-related diseases (e.g. hyperthyroidism and hypothyroidism) for a long time. However, whether and how subclinical hypothyroidism (SCH) causes any deficits in brain functions, and whether a hormone-replacement treatment is necessary for SCH patients, still remain controversial subjects. In the present study, functional MRI (fMRI) was used to measure brain functions by asking euthyroid subjects, hyperthyroid patients and SCH patients to perform the widely used digit n-back working memory task. After having been treated with l-thyroxine for approximately 6 months, the SCH patients were asked to do the same fMRI experiment. The hypothyroid and SCH patients scored significantly lower in the 2-back task than either the hyperthyroid patients or the euthyroid subjects (P < 0.012). The fMRI showed that a common frontoparietal network, including bilateral middle/inferior frontal gyri (M/IFG), bilateral dorsolateral prefrontal cortex (DLPFC), bilateral premotor areas (PreMA), the supplementary motor area/anterior cingulate cortex (SMA/ACC) and bilateral parietal areas (PA), was activated by the n-back task in all the subjects. Further quantitative analysis showed that the load effect of blood oxygen level-dependent (BOLD) response appeared in all the five regions of interest (ROIs) in the euthyroid and hyperthyroid subjects. In the pre-treatment SCH patients, however, the load effect of BOLD response was only found in the PA and PreMA, but not in other frontal cortex ROIs [general linear model (GLM), F < 2.6, P > 0.1]. After an approximately 6 month treatment with LT4, the SCH patients exhibited the same load effects in all five ROIs as the euthyroid subjects (GLM, F > 6, P < 0.05) along with an improvement of performance in n-back task. These results suggest that working memory (but not other memory functions) is impaired in SCH patients, mainly as far as disorders of the frontoparietal network were concerned. Both the memory performance and frontal executive functions were improved after an l-thyroxine-replacement treatment.