Thyroid hormone deprival and TSH/TSHR signaling deficiency lead to central hypothyroidism-associated intestinal dysplasia

BACKGROUND

Central hypothyroidism (CH) is characterized by low T4 levels and reduced levels or bioactivity of circulating TSH. However, there is a lack of studies on CH-related intestinal maldevelopment. In particular, the roles of TH and TSH/TSHR signaling in CH-related intestinal maldevelopment are poorly understood. Herein, we utilized Tshr-/- mice as a congenital hypothyroidism model with TH deprival and absence of TSHR signaling.

METHODS

The morphological characteristics of intestines were determined by HE staining, periodic acid-shiff staining, and immunohistochemical staining. T4 was administrated into the offspring of homozygous mice from the fourth postnatal day through weaning or administrated after weaning. RT-PCR was used to evaluate the expression of markers of goblet cells and intestinal digestive enzymes. Single-cell RNA-sequencing analysis was used to explore the cell types and gene profiles of metabolic alternations in early-T4-injected Tshr-/- mice.

KEY FINDINGS

Tshr deletion caused significant growth retardation and intestinal maldevelopment, manifested as smaller and more slender small intestines due to reduced numbers of stem cells and differentiated epithelial cells. Thyroxin supplementation from the fourth postnatal day, but not from weaning, significantly rescued the abnormal intestinal structure and restored the decreased number of proliferating intestinal cells in crypts of Tshr-/- mice. Tshr-/- mice with early-life T4 injections had more early goblet cells and impaired metabolism compared to Tshr+/+ mice.

SIGNIFICANCE

TH deprival leads to major defects of CH-associated intestinal dysplasia while TSH/TSHR signaling deficiency promotes the differentiation of goblet cells and impairs nutrition metabolism.

TSHR signaling promotes hippocampal dependent memory formation through modulating Wnt5a/β-catenin mediated neurogenesis

Subclinical hyperthyroidism is defined biochemically as a low or undetectable thyroid-stimulating hormone (TSH) with normal thyroid hormone levels. Low TSHR signaling is considered to associate with cognitive impairment. However, the underlying molecular mechanism by which TSHR signaling modulates memory is poorly understood. In this study, we found that Tshr-deficient in the hippocampal neurons impairs the learning and memory abilities of mice, accompanying by a decline in the number of newborn neurons. Notably, Tshr ablation in the hippocampus decreases the expression of Wnt5a, thereby inactivating the β-catenin signaling pathway to reduce the neurogenesis. Conversely, activating of the Wnt/β-catenin pathway by the agonist SKL2001 results in an increase in hippocampal neurogenesis, resulting in the amelioration in the deficits of memory caused by Tshr deletion. Understanding how TSHR signaling in the hippocampus regulates memory provides insights into subclinical hyperthyroidism affecting cognitive function and will suggest ways to rationally design interventions for neurocognitive disorders.

Superior predictive value of estimated pulse wave velocity for all-cause and cardiovascular disease mortality risk in U.S. general adults

BACKGROUND

Estimated pulse wave velocity (ePWV) has been proposed as a potential approach to estimate carotid-femoral pulse wave velocity. However, the potential of ePWV in predicting all-cause mortality (ACM) and cardiovascular disease mortality (CVM) in the general population is unclear.

METHODS

We conducted a prospective cohort study using the data of 33,930 adults (age ≥ 20 years) from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2014 until the end of December 2019. The study outcomes included ACM and CVM. Survey-weighted Cox proportional hazards models were used to assess hazard ratios (HRs) and 95% confidence intervals (CIs) to determine the association between ePWV and ACM and CVM. To further investigate whether ePWV was superior to traditional risk factors in predicting ACM and CVM, comparisons between ePWV and the Framingham Risk Score (FRS) and Pooled Cohort Equations (PCE) models were performed. Integrated Discriminant Improvement (IDI) and Net Reclassification Improvement (NRI) were employed to analyze differences in predictive ability between models.

RESULTS

The weighted mean age of the 33,930 adults included was 45.2 years, and 50.28% of all participants were men. In the fully adjusted Cox regression model, each 1 m/s increase in ePWV was associated with 50% and 49% increases in the risk of ACM (HR 1.50; 95% CI, 1.45-1.54) and CVM (HR 1.49; 95% CI, 1.41-1.57), respectively. After adjusting for FRS, each 1 m/s increase in ePWV was still associated with 29% (HR 1.29; 95% CI, 1.24-1.34) and 34% (HR 1.34; 95% CI, 1.23-1.45) increases in the risk of ACM and CVM, respectively. The area under the curve (AUC) predicted by ePWV for 10-year ACM and CVM were 0.822 and 0.835, respectively. Compared with the FRS model, the ePWV model improved the predictive value of ACM and CVM by 5.1% and 3.8%, respectively, with no further improvement in event classification. In comparison with the PCE model, the ePWV model's ability to predict 10-year ACM and CVM was improved by 5.1% and 3.5%, and event classification improvement was improved by 34.5% and 37.4%.

CONCLUSIONS

In the U.S. adults, ePWV is an independent risk factor for ACM and CVM and is independent of traditional risk factors. In the general population aged 20 to 85 years, ePWV has a robust predictive value for the risk of ACM and CVM, superior to the FRS and PCE models. The predictive power of ePWV likely originates from the traditional risk factors incorporated into its calculation, rather than from an indirect association with measured pulse wave velocity.

Predictive value of estimated pulse wave velocity with all-cause and cause-specific mortality in the hypertensive population: the National Health and Nutrition Examination Surveys 1999-2014

BACKGROUND

Estimated pulse wave velocity (ePWV) has been proposed as a potential approach to assess carotid-femoral pulse wave velocity (cfPWV). However, the potential ability of ePWV to predict all-cause and cause-specific mortality in the population group with hypertension remains unresolved.

METHODS

We conducted a prospective cohort study using the data of 14 044 adults (age ≥18 years) from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2014, and followed this cohort until the end of December 2019. ePWV was calculated by using a regression equation for age and mean blood pressure (MBP), derived by the Arterial Stiffness Collaborative Group.

RESULTS

The weighted mean age of the 14 044 adults included was 54.79 years; 49.42% of all participants were men. During the median follow-up period of 11 years, 3795 deaths were recorded. In the fully adjusted cox regression model, each 1 m/s increase in ePWV was associated with an increased risk of 56% [hazard ratio 1.61; 95% confidence interval (CI) 1.49-1.64] risk for all-cause mortality. Every 1 m/s increase in ePWV resulted in an increased risk of mortality from cardiovascular disease, cerebrovascular disease, respiratory disease, Alzheimer's disease, accidents, cancer, influenza and pneumonia by 60, 70, 47, 118, 73, 41 and 103%, respectively. ePWV has a robust predictive value for 5- and 10-year all-cause mortality in the hypertensive population with AUCs of 0.749 and 0.741, respectively.

CONCLUSION

Elevated ePWV is positively correlated with all-cause mortality and most cause-specific mortalities, independent of traditional risk factors. Moreover, ePWV demonstrates high accuracy in predicting 5-year and 10-year all-cause mortality, outperforming Framingham Risk Score.

Impact of glucagon-like peptide 1 analogs on cognitive function among patients with type 2 diabetes mellitus: A systematic review and meta-analysis

BACKGROUND

Diabetes is an independent risk factor for cognitive impairment. However, little is known about the neuroprotective effects of glucagon-like peptide 1 (GLP-1) analogs on type 2 diabetes mellitus (T2DM). Herein, we assessed the impact of GLP-1 analogs on the general cognitive functioning among patients with T2DM.

METHODS

Relevant studies were retrieved from PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov databases from their inception till June 30, 2022, without any language restrictions. For continuous variables, the mean and standard deviation (SD) were extracted. Considering the heterogeneity in general cognitive functioning assessments among the pooled studies, the standardized mean differences (SMDs) with corresponding 95% confidence intervals (CIs), were calculated.

RESULTS

Five studies including 7,732 individuals with T2DM were selected for the meta-analysis. The use of GLP-1 analogs exerted no significant effects on the general cognitive functioning in self-controlled studies (SMD 0.33, 95% CI -0.03 to 0.69). Subgroup analyses among the self-controlled studies based on age and history of cardio-cerebrovascular disease showed that GLP-1 analogs significantly improved the general cognitive functioning in T2DM patients younger than 65 years (SMD 0.69, 95% CI 0.31 to 1.08) or those without cardio-cerebrovascular diseases (SMD 0.69, 95% CI 0.31 to 1.08). Similarly, differences in the general cognitive functioning for GLP-1 analogs between treated and non-treated patients with T2DM were significant in subgroups with patients younger than 65 years (SMD 1.04, 95% CI 0.61 to 1.47) or those with no history of cardio-cerebrovascular diseases (SMD 1.04, 95% CI 0.61 to 1.47).

CONCLUSION

Limited evidence suggests that the use of GLP-1 analogs exerts no significant effects on general cognitive functioning but may be beneficial for patients with T2DM younger than 65 years or those without a history of cardio-cerebrovascular diseases. Further prospective clinical studies with large sample sizes are needed to validate these findings.

SYSTEMATIC REVIEW REGISTRATION

www.inplasy.com, identifier 202260015.

Thyrotropin receptor signaling deficiency impairs spatial learning and memory in mice

Subclinical hyperthyroidism, a condition characterized by decreased thyroid-stimulating hormone (TSH) and normal concentration of thyroid hormone, is associated with an elevated risk for cognitive impairment. TSH is the major endogenous ligand of the TSH receptor (TSHR) and its role is dependent on signal transduction of TSHR. It has not, however, been established whether TSHR signaling is involved in the regulation of cognition. Here, we utilized Tshr knockout mice and found that Tshr deletion led to significantly compromised performance in learning and memory tests. Reduced dendritic spine density and excitatory synaptic density as well as altered synaptic structure in CA1 subfield of the hippocampus were also noted. Furthermore, the synapse-related gene expression was altered in the hippocampus of Tshr -/- mice. These findings suggest that TSHR signaling deficiency impairs spatial learning and memory, which discloses a novel role of TSHR signaling in brain function.

SAT-285 TSH/TSHR Signaling Deficiency Impairs Spatial Learning and Memory

Background: Subclinical hyperthyroidism is associated with cognitive impairment, but the mechanism has remained unclear. As subclinical hyperthyroidism is characterized by significantly decreased TSH levels, this study aimed to investigate whether TSH regulates cognitive function. Methods: The correlation between TSH and cognitive impairment was investigated in a cross-sectional population study. The role of TSH/TSH receptor (TSHR) signaling in spatial learning and memory was further examined by behavior tests in Tshr^-/- mice. Dendritic spine, synaptic density and structure of hippocampal CA1 pyramidal neurons were detected by Golgi’s method and electron microscopy. The mRNA and protein expression levels of learning and memory-related genes were assessed by RNA sequencing, real-time PCR, immunoblotting and immunofluorescence approaches. Results: Serum TSH level correlated negatively with cognitive impairment in the current population. Consistently, Tshr deletion in mice led to significantly compromised performance in hippocampus-dependent tasks, reduced dendritic spine density and excitatory synaptic density as well as altered synaptic structure in CA1 subfield of the hippocampus. Furthermore, the mRNA levels of learning and memory-related genes were altered, and protein levels of CREB-regulated genes were downregulated in the hippocampus of Tshr^-/- mice. Conclusions: These findings reveal that TSH/TSHR signaling ablation impairs spatial learning and memory, indicating a decline in TSH level might contribute to the increased prevalence of cognitive impairment in subclinical hyperthyroidism patients.

Effect of a grain challenge on ruminal, urine, and fecal pH, apparent total-tract starch digestibility, and milk composition of Holstein and Jersey cows

The effects of a grain challenge on ruminal, urine, and fecal pH, apparent total-tract starch digestibility, and milk composition were determined. Six Holstein cows, 6 rumen-cannulated Holstein cows, and 6 Jersey cows were used in a replicated 3 × 3 Latin square design balanced to measure carryover effects. Periods (10 d) were divided into 4 stages (S): S1, d 1 to 3, served as baseline with regular total mixed ration ad libitum; S2, d 4, served as restricted feeding, with cows offered 50% of the total mixed ration fed on S1 (dry matter basis); S3, d 5, a grain challenge was performed, in which cows were fed total mixed ration ad libitum and not fed (CON) or fed an addition of 10% (MG) or 20% (HG) pellet wheat-barley (1:1) top-dressed onto the total mixed ration, based on dry matter intake obtained in S1; S4, d 6 to 10, served as recovery stage with regular total mixed ration fed ad libitum. Overall, cows had a quadratic treatment effect for milk yield where CON (22.6 kg/d) and HG (23.5 kg/d) had lower milk yield than cows in MG (23.7 kg/d). Jersey cows had a quadratic treatment effect for dry matter intake where cows in CON (13.2 kg/d) and HG (12.4 kg/d) had lower dry matter intake than cows in MG (14 kg/d). Holstein cows had a linear treatment effect for dry matter intake (17.7, 18.4, and 18.6 kg/d for CON, MG, and HG, respectively). Rumen pH for the rumen-cannulated cows had a linear treatment effect (6.45, 6.35, and 6.24 for CON, MG, and HG, respectively). Cows in HG spent more time with rumen pH below 5.8 (4.33 h) than MG (2 h) or CON (2.17 h) as shown by the quadratic treatment effect. Holstein cows in HG (8.46) had lower urine pH than MG (8.51) or CON (8.54) as showed by the linear treatment effect for urine pH. Apparent total-tract starch digestibility had a tendency for a linear treatment effect on S3 (97.62 ± 1.5, 97.47 ± 1.5, and 91.84 ± 1.6%, for CON, MG, and HG, respectively). Fecal pH was associated with rumen pH depression as early as 15 h after feeding for Holstein cows. In conclusion, a grain challenge reduced urine pH in Holstein cows but not in Jersey cows. Holstein cows' health were not affected when rumen pH was depressed. A potentially useful link between rumen pH and systemic (urine) pH within 2 h after feeding was quantified in Holstein cows.

Signalling drought in guard cells

A number of environmental conditions including drought, low humidity, cold and salinity subject plants to osmotic stress. A rapid plant response to such stress conditions is stomatal closure to reduce water loss from plants. From an external stress signal to stomatal closure, many molecular components constitute a signal transduction network that couples the stimulus to the response. Numerous studies have been directed to resolving the framework and molecular details of stress signalling pathways in plants. In guard cells, studies focus on the regulation of ion channels by abscisic acid (ABA), a chemical messenger for osmotic stress. Calcium, protein kinases and phosphatases, and membrane trafficking components have been shown to play a role in ABA signalling process in guard cells. Studies also implicate ABA-independent regulation of ion channels by osmotic stress. In particular, a direct osmosensing pathway for ion channel regulation in guard cells has been identified. These pathways form a complex signalling web that monitors water status in the environment and initiates responses in stomatal movements.

A novel family of magnesium transport genes in Arabidopsis

Magnesium (Mg(2+)) is the most abundant divalent cation in plant cells and plays a critical role in many physiological processes. We describe the identification of a 10-member Arabidopsis gene family (AtMGT) encoding putative Mg(2+) transport proteins. Most members of the AtMGT family are expressed in a range of Arabidopsis tissues. One member of this family, AtMGT1, functionally complemented a bacterial mutant lacking Mg(2+) transport capability. A second member, AtMGT10, complemented a yeast mutant defective in Mg(2+) uptake and increased the cellular Mg(2+) content of starved cells threefold during a 60-min uptake period. (63)Ni tracer studies in bacteria showed that AtMGT1 has highest affinity for Mg(2+) but may also be capable of transporting several other divalent cations, including Ni(2+), Co(2+), Fe(2+), Mn(2+), and Cu(2+). However, the concentrations required for transport of these other cations are beyond normal physiological ranges. Both AtMGT1 and AtMGT10 are highly sensitive to Al(3+) inhibition, providing potential molecular targets for Al(3+) toxicity in plants. Using green fluorescence protein as a reporter, we localized AtMGT1 protein to the plasma membrane in Arabidopsis plants. We suggest that the AtMGT gene family encodes a Mg(2+) transport system in higher plants.

A novel family of magnesium transport genes in Arabidopsis

Magnesium (Mg(2+)) is the most abundant divalent cation in plant cells and plays a critical role in many physiological processes. We describe the identification of a 10-member Arabidopsis gene family (AtMGT) encoding putative Mg(2+) transport proteins. Most members of the AtMGT family are expressed in a range of Arabidopsis tissues. One member of this family, AtMGT1, functionally complemented a bacterial mutant lacking Mg(2+) transport capability. A second member, AtMGT10, complemented a yeast mutant defective in Mg(2+) uptake and increased the cellular Mg(2+) content of starved cells threefold during a 60-min uptake period. (63)Ni tracer studies in bacteria showed that AtMGT1 has highest affinity for Mg(2+) but may also be capable of transporting several other divalent cations, including Ni(2+), Co(2+), Fe(2+), Mn(2+), and Cu(2+). However, the concentrations required for transport of these other cations are beyond normal physiological ranges. Both AtMGT1 and AtMGT10 are highly sensitive to Al(3+) inhibition, providing potential molecular targets for Al(3+) toxicity in plants. Using green fluorescence protein as a reporter, we localized AtMGT1 protein to the plasma membrane in Arabidopsis plants. We suggest that the AtMGT gene family encodes a Mg(2+) transport system in higher plants.

Internal aluminum block of plant inward K(+) channels

Aluminum (Al) inhibits inward K(+) channels (K(in)) in both root hair and guard cells, which accounts for at least part of the Al toxicity in plants. To understand the mechanism of Al-induced K(in) inhibition, we performed patch clamp analyses on K(in) in guard cells and on KAT1 channels expressed in Xenopus oocytes. Our results show that Al inhibits plant K(in) by blocking the channels at the cytoplasmic side of the plasma membrane. In guard cells, single-channel recording revealed that Al inhibition of K(in) occurred only upon internal exposure. Using both "giant patch" recording and single-channel analyses, we found that Al reduced KAT1 open probability and changed its activation kinetics through an internal membrane-delimited mechanism. We also provide evidence that a Ca(2)+ channel-like pathway that is sensitive to antagonists verapamil and La(3)+ mediates Al entry across the plasma membrane. We conclude that Al enters plant cells through a Ca(2)+ channel-like pathway and inhibits K(+) uptake by internally blocking K(in).

Interaction specificity of Arabidopsis calcineurin B-like calcium sensors and their target kinases

Calcium is a critical component in a number of plant signal transduction pathways. A new family of calcium sensors called calcineurin B-like proteins (AtCBLs) have been recently identified from Arabidopsis. These calcium sensors have been shown to interact with a family of protein kinases (CIPKs). Here we report that each individual member of AtCBL family specifically interacts with a subset of CIPKs and present structural basis for the interaction and for the specificity underlying these interactions. Although the C-terminal region of CIPKs is responsible for interaction with AtCBLs, the N-terminal region of CIPKs is also involved in determining the specificity of such interaction. We have also shown that all three EF-hand motifs in AtCBL members are required for the interaction with CIPKs. Several AtCBL members failed to interact with any of the CIPKs presented in this study, suggesting that these AtCBL members either have other CIPKs as targets or they target distinct proteins other than CIPKs. These results may provide structural basis for the functional specificity of CBL family of calcium sensors and their targets.

Inward potassium channel in guard cells as a target for polyamine regulation of stomatal movements

A number of studies show that environmental stress conditions such as drought, high salt, and air pollutants increase polyamine levels in plant cells. However, little is understood about the physiological function of elevated polyamine levels. We report here that polyamines regulate the voltage-dependent inward K(+) channel in the plasma membrane of guard cells and modulate stomatal aperture, a plant "sensor" to environmental changes. All natural polyamines, including spermidine, spermine, cadaverine, and putrescine, strongly inhibited opening and induced closure of stomata. Whole-cell patch-clamp analysis showed that intracellular application of polyamines inhibited the inward K(+) current across the plasma membrane of guard cells. Single-channel recording analysis indicated that polyamine regulation of the K(+) channel requires unknown cytoplasmic factors. In an effort to identify the target channel at the molecular level, we found that spermidine inhibited the inward K(+) current carried by KAT1 channel that was functionally expressed in a plant cell model. These findings suggest that polyamines target KAT1-like inward K(+) channels in guard cells and modulate stomatal movements, providing a link between stress conditions, polyamine levels, and stomatal regulation.

ATMPK4, an Arabidopsis homolog of mitogen-activated protein kinase, is activated in vitro by AtMEK1 through threonine phosphorylation

The modulation of mitogen-activated protein kinase (MAPK) activity regulates many intracellular signaling processes. In animal and yeast cells, MAP kinases are activated via phosphorylation by the dual-specificity kinase MEK (MAP kinase kinase). Several plant homologs of MEK and MAPK have been identified, but the biochemical events underlying the activation of plant MAPKs remain unknown. We describe the in vitro activation of an Arabidopsis homolog of MAP kinase, ATMPK4. ATMPK4 was phosphorylated in vitro by an Arabidopsis MEK homolog, AtMEK1. This phosphorylation occurred principally on threonine (Thr) residues and resulted in elevated ATMPK4 kinase activity. A second Arabidopsis MEK isoform, ATMAP2Kalpha, failed to phosphorylate ATMPK4 in vitro. Tyr dephosphorylation by the Arabidopsis Tyr-specific phosphatase AtPTP1 resulted in an almost complete loss of ATMPK4 activity. Immunoprecipitates of Arabidopsis extracts with anti-ATMPK4 antibodies displayed myelin basic protein kinase activity that was sensitive to treatment with AtPTP1. These results demonstrate that a plant MEK can phosphorylate and activate MAPK, and that Tyr phosphorylation is critical for the catalytic activity of MAPK in plants. Surprisingly, in contrast to the animal enzymes, AtMEK1 may not be a dual-specificity kinase but, rather, the required Tyr phosphorylation on ATMPK4 may result from autophosphorylation.