Prenatal treatment with preimplantation factor improves early postnatal neurogenesis and cognitive impairments in a mouse model of Down syndrome.

Down syndrome (DS) is a genetic disease characterized by a supernumerary chromosome 21. Intellectual deficiency (ID) is one of the most prominent features of DS. Central nervous system defects lead to learning disabilities, motor and language delays, and memory impairments. At present, a prenatal treatment for the ID in DS is lacking. Subcutaneous administration of synthetic preimplantation factor (sPIF, a peptide with a range of biological functions) in a model of severe brain damage has shown neuroprotective and anti-inflammatory properties by directly targeting neurons and microglia. Here, we evaluated the effect of PIF administration during gestation and until weaning on Dp(16)1Yey mice (a mouse model of DS). Possible effects at the juvenile stage were assessed using behavioral tests and molecular and histological analyses of the brain. To test the influence of perinatal sPIF treatment at the adult stage, hippocampus-dependent memory was evaluated on postnatal day 90. Dp(16)1Yey pups showed significant behavioral impairment, with impaired neurogenesis, microglial cell activation and a low microglial cell count, and the deregulated expression of genes linked to neuroinflammation and cell cycle regulation. Treatment with sPIF restored early postnatal hippocampal neurogenesis, with beneficial effects on astrocytes, microglia, inflammation, and cell cycle markers. Moreover, treatment with sPIF restored the level of DYRK1A, a protein that is involved in cognitive impairments in DS. In line with the beneficial effects on neurogenesis, perinatal treatment with sPIF was associated with an improvement in working memory in adult Dp(16)1Yey mice. Perinatal treatment with sPIF might be an option for mitigating cognitive impairments in people with DS.

Exploring the link between hedonic overeating and prefrontal cortex dysfunction in the Ts65Dn trisomic mouse model.

Individuals with Down syndrome (DS) have a higher prevalence of obesity compared to the general population. Conventionally, this has been attributed to endocrine issues and lack of exercise. However, deficits in neural reward responses and dopaminergic disturbances in DS may be contributing factors. To investigate this, we focused on a mouse model (Ts65Dn) bearing some triplicated genes homologous to trisomy 21. Through detailed meal pattern analysis in male Ts65Dn mice, we observed an increased preference for energy-dense food, pointing towards a potential "hedonic" overeating behavior. Moreover, trisomic mice exhibited higher scores in compulsivity and inflexibility tests when limited access to energy-dense food and quinine hydrochloride adulteration were introduced, compared to euploid controls. Interestingly, when we activated prelimbic-to-nucleus accumbens projections in Ts65Dn male mice using a chemogenetic approach, impulsive and compulsive behaviors significantly decreased, shedding light on a promising intervention avenue. Our findings uncover a novel mechanism behind the vulnerability to overeating and offer potential new pathways for tackling obesity through innovative interventions.

Over-expression of Dyrk1A affects bleeding by modulating plasma fibronectin and fibrinogen level in mice.

Down syndrome is the most common chromosomal abnormality in humans. Patients with Down syndrome have hematologic disorders, including mild to moderate thrombocytopenia. In case of Down syndrome, thrombocytopenia is not associated with bleeding, and it remains poorly characterized regarding molecular mechanisms. We investigated the effects of overexpression of Dyrk1A, an important factor contributing to some major Down syndrome phenotypes, on platelet number and bleeding in mice. Mice overexpressing Dyrk1A have a decrease in platelet number by 20%. However, bleeding time was found to be reduced by 50%. The thrombocytopenia and the decreased bleeding time observed were not associated to an abnormal platelet receptors expression, to a defect of platelet activation by ADP, thrombin or convulxin, to the presence of activated platelets in the circulation or to an abnormal half-life of the platelets. To propose molecular mechanisms explaining this discrepancy, we performed a network analysis of Dyrk1A interactome and demonstrated that Dyrk1A, fibronectin and fibrinogen interact indirectly through two distinct clusters of proteins. Moreover, in mice overexpressing Dyrk1A, increased plasma fibronectin and fibrinogen levels were found, linked to an increase of the hepatic fibrinogen production. Our results indicate that overexpression of Dyrk1A in mice induces decreased bleeding consistent with increased plasma fibronectin and fibrinogen levels, revealing a new role of Dyrk1A depending on its indirect interaction with these two proteins.

Spermatogonial depletion and a spermatogenesis defect in the Dp(16)1Yey mouse model of Down syndrome.

Down syndrome (DS), or Trisomy 21, is the most common chromosomal disorder in humans. Men with DS are infertile. The DYRK1A gene on Hsa21 is involved in several features of DS. Overexpression of the homolog dyrk1A disrupts primordial germ cell migration in zebrafish, and overexpression of Dyrk1A impairs gonadotropic axis function and the early stages of spermatogenesis in the mouse. Other genes on Hsa21 might be involved in the pathogenesis of infertility in DS. We investigated the Dp(16)1Yey mouse model of DS, which features segmental duplication of chromosome Mmu16 (orthologous to a large part of Hsa21 and carrying Dyrk1A and 112 other genes). Using an immunohistochemical assay for the spermatogonial marker STRA8, we observed spermatogonial depletion in the Dp(16)1Yey mouse. This was correlated with low mRNA expression of GFR1 (a marker of the self-renewal stem cell pool) in an RT-qPCR assay and low protein expression of PLZF (a marker of differentiating stem cells) in a slot-blot assay. Spermatogenesis was present but impaired, with a low sperm count, low protamine-1 expression, a low testis weight, and a low seminiferous tubule diameter. Low circulating luteinizing hormone and follicle-stimulating hormone levels and an elevated testis anti-Müllerian hormone level (as measured in ELISAs) revealed the presence of hypogonadotropic hypogonadism. The Dp(16)1Yey mouse model of DS recapitulates observations made in zebrafish and mice overexpressing DYRK1A homologs. The presence of an excess of Mmu16 material perturbs spermatogenesis and the gonadotropic axis. More generally, DYRK1A's role in human infertility (outside DS) remains to be characterized.

Safety and preliminary efficacy on cognitive performance and adaptive functionality of epigallocatechin gallate (EGCG) in children with Down syndrome. A randomized phase Ib clinical trial (PERSEUS study).

PURPOSE: Although some caregivers are using epigallocatechin gallate (EGCG) off label in hopes of improving cognition in young adults with Down syndrome (DS), nothing is known about its safety, tolerability, and efficacy in the DS pediatric population. We aimed to evaluate safety and tolerability of a dietary supplement containing EGCG and if EGCG improves cognitive and functional performance. METHODS: A total of 73 children with DS (aged 6-12 years) were randomized. Participants received 0.5% EGCG (10 mg/kg daily dose) or placebo for 6 months with 3 months follow up after treatment discontinuation. RESULTS: In total, 72 children were treated and 66 completed the study. A total of 38 participants were included in the EGCG group and 35 in the placebo group. Of 72 treated participants, 62 (86%) had 229 treatment-emergent adverse events (AEs). Of 37 participants in the EGCG group, 13 (35%) had 18 drug-related treatment-emergent AEs and 12 of 35 (34%) from the placebo group had 22 events. In the EGCG group, neither severe AEs nor increase in the incidence of AEs related to safety biomarkers were observed. Cognition and functionality were not improved compared with placebo. Secondary efficacy outcomes in girls point to a need for future work. CONCLUSION: The use of EGCG is safe and well-tolerated in children with DS, but efficacy results do not support its use in this population.

Exploring the Structural Rearrangements of the Human Insulin-Degrading Enzyme through Molecular Dynamics Simulations.

Insulin-degrading enzyme (IDE) is a ubiquitously expressed metallopeptidase that degrades insulin and a large panel of amyloidogenic peptides. IDE is thought to be a potential therapeutic target for type-2 diabetes and neurodegenerative diseases, such as Alzheimer's disease. IDE catalytic chamber, known as a crypt, is formed, so that peptides can be enclosed and degraded. However, the molecular mechanism of the IDE function and peptide recognition, as well as its conformation changes, remains elusive. Our study elucidates IDE structural changes and explains how IDE conformational dynamics is important to modulate the catalytic cycle of IDE. In this aim, a free-substrate IDE crystallographic structure (PDB ID: 2JG4) was used to model a complete structure of IDE. IDE stability and flexibility were studied through molecular dynamics (MD) simulations to witness IDE conformational dynamics switching from a closed to an open state. The description of IDE structural changes was achieved by analysis of the cavity and its expansion over time. Moreover, the quasi-harmonic analysis of the hinge connecting IDE domains and the angles formed over the simulations gave more insights into IDE shifts. Overall, our results could guide toward the use of different approaches to study IDE with different substrates and inhibitors, while taking into account the conformational states resolved in our study.

Type 2 Diabetes Mellitus and Alzheimer's Disease: Shared Molecular Mechanisms and Potential Common Therapeutic Targets.

The global prevalence of diabetes mellitus and Alzheimer's disease is increasing alarmingly with the aging of the population. Numerous epidemiological data suggest that there is a strong association between type 2 diabetes and an increased risk of dementia. These diseases are both degenerative and progressive and share common risk factors. The amyloid cascade plays a key role in the pathophysiology of Alzheimer's disease. The accumulation of amyloid beta peptides gradually leads to the hyperphosphorylation of tau proteins, which then form neurofibrillary tangles, resulting in neurodegeneration and cerebral atrophy. In Alzheimer's disease, apart from these processes, the alteration of glucose metabolism and insulin signaling in the brain seems to induce early neuronal loss and the impairment of synaptic plasticity, years before the clinical manifestation of the disease. The large amount of evidence on the existence of insulin resistance in the brain during Alzheimer's disease has led to the description of this disease as "type 3 diabetes". Available animal models have been valuable in the understanding of the relationships between type 2 diabetes and Alzheimer's disease, but to date, the mechanistical links are poorly understood. In this non-exhaustive review, we describe the main molecular mechanisms that may link these two diseases, with an emphasis on impaired insulin and IGF-1 signaling. We also focus on GSK3ß and DYRK1A, markers of Alzheimer's disease, which are also closely associated with pancreatic ß-cell dysfunction and type 2 diabetes, and thus may represent common therapeutic targets for both diseases.

Molecular Rescue of Dyrk1A Overexpression Alterations in Mice with Fontup® Dietary Supplement: Role of Green Tea Catechins.

Epigallocatechin gallate (EGCG) is an inhibitor of DYRK1A, a serine/threonine kinase considered to be a major contributor of cognitive dysfunctions in Down syndrome (DS). Two clinical trials in adult patients with DS have shown the safety and efficacy to improve cognitive phenotypes using commercial green tea extract containing EGCG (45% content). In the present study, we performed a preclinical study using FontUp®, a new nutritional supplement with a chocolate taste specifically formulated for the nutritional needs of patients with DS and enriched with a standardized amount of EGCG in young mice overexpressing Dyrk1A (TgBACDyrk1A). This preparation is differential with previous one used, because its green tea extract has been purified to up 94% EGCG of total catechins. We analyzed the in vitro effect of green tea catechins not only for EGCG, but for others residually contained in FontUp®, on DYRK1A kinase activity. Like EGCG, epicatechin gallate was a noncompetitive inhibitor against ATP, molecular docking computations confirming these results. Oral FontUp® normalized brain and plasma biomarkers deregulated in TgBACDyrk1A, without negative effect on liver and cardiac functions. We compared the bioavailability of EGCG in plasma and brain of mice and have demonstrated that EGCG had well crossed the blood-brain barrier.

Down syndrome and infertility: what support should we provide?

Down syndrome (DS) is the most common genetic disease at birth; on average, it affects 1 in 700 newborns. The syndrome features cognitive impairment, susceptibility to certain diseases, and (in some cases) congenital malformations. Improvements in medical care for people with DS have led to an increase in life expectancy. Furthermore, the systematic provision of specific support during childhood improves cognitive function and autonomy in adulthood. Consequently, patients and their families are now seeking the same rights as healthy people. Access to procreation is an emerging debate. The presumption of infertility in DS is based on a few old studies. Down syndrome appears to cause spermatogenesis defects in men and premature menopause in women. When assisted reproductive technology makes it possible to solve these problems, the question of fertility in DS must be addressed. Without entering into highly controversial ethical considerations related to parenthood for people with DS, we reviewed the literature on fertility in DS and tried to specify the associated genetic risk.

Impact of Dyrk1A level on alcohol metabolism.

Alcoholic liver diseases arise from complex phenotypes involving many genetic factors. It is quite common to find hyperhomocysteinemia in chronic alcoholic liver diseases, mainly due to deregulation of hepatic homocysteine metabolism. Dyrk1A, involved in homocysteine metabolism at different crossroads, is decreased in liver of hyperhomocysteinemic mice. Here, we hypothesized that Dyrk1A contributes to alcohol-induced hepatic impairment in mice. Control, hyperhomocysteinemic and mice overexpressing Dyrk1A were fed using a Lieber-DeCarli liquid diet with or without ethanol (5% v/v ethanol) for one month, and liver histological examination and liver biochemical function tests were performed. Plasma alanine aminotransferase and homocysteine levels were significantly decreased in mice overexpressing Dyrk1A compared to control mice with or without alcohol administration. On the contrary, the mean plasma alanine aminotransferase and homocysteine levels were significantly higher in hyperhomocysteinemic mice than that of control mice after alcohol administration. Paraoxonase 1 and CYP2E1, two phase I xenobiotic metabolizing enzymes, were found increased in the three groups of mice after alcohol administration. However, NQO1, a phase II enzyme, was only found increased in hyperhomocysteinemic mice after alcohol exposure, suggesting a greater effect of alcohol in liver of hyperhomocysteinemic mice. We observed positive correlations between hepatic alcohol dehydrogenase activity, Dyrk1A and ADH4 protein levels. Importantly, a deleterious effect of alcohol consumption on hepatic Dyrk1A protein level was found. Our study reveals on the one hand a role of Dyrk1A in ethanol metabolism and on the other hand a deleterious effect of alcohol administration on hepatic Dyrk1A level.

Prefrontal deficits in a murine model overexpressing the down syndrome candidate gene dyrk1a.

The gene Dyrk1a is the mammalian ortholog of Drosophila minibrain. Dyrk1a localizes in the Down syndrome (DS) critical region of chromosome 21q22.2 and is a major candidate for the behavioral and neuronal abnormalities associated with DS. PFC malfunctions are a common denominator in several neuropsychiatric diseases, including DS, but the contribution of DYRK1A in PFC dysfunctions, in particular the synaptic basis for impairments of executive functions reported in DS patients, remains obscure. We quantified synaptic plasticity, biochemical synaptic markers, and dendritic morphology of deep layer pyramidal PFC neurons in adult mBACtgDyrk1a transgenic mice that overexpress Dyrk1a under the control of its own regulatory sequences. We found that overexpression of Dyrk1a largely increased the number of spines on oblique dendrites of pyramidal neurons, as evidenced by augmented spine density, higher PSD95 protein levels, and larger miniature EPSCs. The dendritic alterations were associated with anomalous NMDAR-mediated long-term potentiation and accompanied by a marked reduction in the pCaMKII/CaMKII ratio in mBACtgDyrk1a mice. Retrograde endocannabinoid-mediated long-term depression (eCB-LTD) was ablated in mBACtgDyrk1a mice. Administration of green tea extracts containing epigallocatechin 3-gallate, a potent DYRK1A inhibitor, to adult mBACtgDyrk1a mice normalized long-term potentiation and spine anomalies but not eCB-LTD. However, inhibition of the eCB deactivating enzyme monoacylglycerol lipase normalized eCB-LTD in mBACtgDyrk1a mice. These data shed light on previously undisclosed participation of DYRK1A in adult PFC dendritic structures and synaptic plasticity. Furthermore, they suggest its involvement in DS-related endophenotypes and identify new potential therapeutic strategies.

Dyrk1a haploinsufficiency induces diabetes in mice through decreased pancreatic beta cell mass.

AIMS/HYPOTHESIS: Growth factors and nutrients are important regulators of pancreatic beta cell mass and function. However, the signalling pathways by which these factors modulate these processes have not yet been fully elucidated. DYRK1A (also named minibrain/MNB) is a member of the dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) family that has been conserved across evolution. A significant amount of data implicates DYRK1A in brain growth and function, as well as in neurodegenerative processes in Alzheimer's disease and Down's syndrome. We investigated here whether DYRK1A would be an attractive candidate for beta cell growth modulation. METHODS: To study the role of DYRK1A in beta cell growth, we used Dyrk1a-deficient mice. RESULTS: We show that DYRK1A is expressed in pancreatic islets and provide evidence that changes in Dyrk1a gene dosage in mice strongly modulate glycaemia and circulating insulin levels. Specifically, Dyrk1a-haploinsufficient mice show severe glucose intolerance, reduced beta cell mass and decreased beta cell proliferation. CONCLUSIONS/INTERPRETATION: Taken together, our data indicate that DYRK1A is a critical kinase for beta cell growth as Dyrk1a-haploinsufficient mice show a diabetic profile.

Hepatocyte-specific Dyrk1a gene transfer rescues plasma apolipoprotein A-I levels and aortic Akt/GSK3 pathways in hyperhomocysteinemic mice.

Hyperhomocysteinemia, characterized by high plasma homocysteine levels, is recognized as an independent risk factor for cardiovascular diseases. The increased synthesis of homocysteine, a product of methionine metabolism involving B vitamins, and its slower intracellular utilization cause increased flux into the blood. Plasma homocysteine level is an important reflection of hepatic methionine metabolism and the rate of processes modified by B vitamins as well as different enzyme activity. Lowering homocysteine might offer therapeutic benefits. However, approximately 50% of hyperhomocysteinemic patients due to cystathionine-beta-synthase deficiency are biochemically responsive to pharmacological doses of B vitamins. Therefore, effective treatments to reduce homocysteine levels are needed, and gene therapy could provide a novel approach. We recently showed that hepatic expression of DYRK1A, a serine/threonine kinase, is negatively correlated with plasma homocysteine levels in cystathionine-beta-synthase deficient mice, a mouse model of hyperhomocysteinemia. Therefore, Dyrk1a is a good candidate for gene therapy to normalize homocysteine levels. We then used an adenoviral construct designed to restrict expression of DYRK1A to hepatocytes, and found decreased plasma homocysteine levels after hepatocyte-specific Dyrk1a gene transfer in hyperhomocysteinemic mice. The elevation of pyridoxal phosphate was consistent with the increase in cystathionine-beta-synthase activity. Commensurate with the decreased plasma homocysteine levels, targeted hepatic expression of DYRK1A resulted in elevated plasma paraoxonase-1 activity and apolipoprotein A-I levels, and rescued the Akt/GSK3 signaling pathways in aorta of mice, which can prevent homocysteine-induced endothelial dysfunction. These results demonstrate that hepatocyte-restricted Dyrk1a gene transfer can offer a useful therapeutic targets for the development of new selective homocysteine lowering therapy.

Excitation/inhibition balance and learning are modified by Dyrk1a gene dosage.

Cognitive deficits in Down syndrome (DS) have been linked to increased synaptic inhibition, leading to an imbalance of excitation/inhibition (E/I). Various mouse models and studies from human brains have implicated an HSA21 gene, the serine/threonine kinase DYRK1A, as a candidate for inducing cognitive dysfunction. Here, consequences of alterations in Dyrk1a dosage were assessed in mouse models with varying copy numbers of Dyrk1a: mBACtgDyrk1a, Ts65Dn and Dp(16)1Yey (with 3 gene copies) and Dyrk1a(+/-) (one functional copy). Molecular (i.e. immunoblotting/immunohistochemistry) and behavioral analyses (e.g., rotarod, Morris water maze, Y-maze) were performed in mBACtgDyrk1a mice. Increased expression of DYRK1A in mBACtgDyrk1a induced molecular alterations in synaptic plasticity pathways, particularly expression changes in GABAergic and glutaminergic related proteins. Similar alterations were observed in models with partial trisomy of MMU16, Ts65Dn and Dp(16)1Yey, and were reversed in the Dyrk1a(+/-) model. Dyrk1a overexpression produced an increased number and signal intensity of GAD67 positive neurons, indicating enhanced inhibition pathways in three different models: mBACtgDyrk1a, hYACtgDyrk1a and Dp(16)1Yey. Functionally, Dyrk1a overexpression protected mice from PTZ-induced seizures related to GABAergic neuron plasticity. Our study shows that DYRK1A overexpression affects pathways involved in synaptogenesis and synaptic plasticity and influences E/I balance toward inhibition. Inhibition of DYRK1A activity offers a therapeutic target for DS, but its inhibition/activation may also be relevant for other psychiatric diseases with E/I balance alterations.

A high-performance liquid chromatography assay for Dyrk1a, a Down syndrome-associated kinase.

Down syndrome is the most common aneuploidy. It is caused by the presence of an extra copy of chromosome 21. Several studies indicate that aberrant expression of the kinase Dyrk1a (dual-specificity tyrosine phosphorylation-regulated kinase 1a) is implicated in Down syndrome, in particular in the onset of mental retardation. Moreover, elevated Dyrk1a activity may also be a risk factor for other neurodegenerative disorders such as Alzheimer's disease. Over the past years, Dyrk1a has appeared as a potential drug target. Availability of sensitive and quantitative enzyme assays is of prime importance to understand the role of Dyrk1a and to develop specific inhibitors. Here, we describe a new method to measure Dyrk1a activity based on the separation and quantification of specific fluorescent peptides (substrate and phosphorylated product) by high-performance liquid chromatography (HPLC). Kinetic and mechanistic analyses using well-known inhibitors of Dyrk1a confirmed the reliability of this approach. In addition, this assay was further validated using brain extracts of mice models expressing different copies of the Dyrk1a gene. Our results indicate that this novel Dyrk1a assay is simple, sensitive, and specific. It avoids the use of radioactivity-based approaches that, until now, have been widely employed to measure Dyrk1a activity.

EGCG-like non-competitive inhibitor of DYRK1A rescues cognitive defect in a down syndrome model.

Overexpression of the chromosome 21 DYRK1A gene induces morphological defects and cognitive impairments in individuals with Down syndrome (DS) and in DS mice models. Aging neurons of specific brain regions of patients with Alzheimer's disease, DS and Pick's disease have increased DYRK1A immunoreactivity suggesting a possible association of DYRK1A with neurofibrillary tangle pathology. Epigallocatechin-3-gallate (EGCG) displays appreciable inhibition of DYRK1A activity and, contrary to all other published inhibitors, EGCG is a non-competitive inhibitor of DYRK1A. Prenatal exposure to green tea polyphenols containing EGCG protects from brain defects induced by overexpression of DYRK1A. In order to produce more robust and possibly more active analogues of the natural compound EGCG, here we synthetized new EGCG-like molecules with several structural modifications to the EGCG skeleton. We replaced the ester boun of EGCG with a more resistant amide bond. We also replaced the oxygen ring by a methylene group. And finally, we positioned a nitrogen atom within this ring. The selected compound was shown to maintain the non-competitive property of EGCG and to correct biochemical and behavioral defects present in a DS mouse model. In addition it showed high stability and specificity.

DYRK1A overexpression decreases plasma lecithin:cholesterol acyltransferase activity and apolipoprotein A-I levels.

BACKGROUND AND AIMS: Down syndrome is caused by trisomy of all or part of human chromosome 21. Individuals with Down syndrome present some metabolic abnormalities involving lipoproteins, notably lower high-density lipoprotein levels associated with altered lecithin:cholesterol acyltransferase activity and apolipoprotein A-I levels. DYRK1A is a kinase overexpressed in Down syndrome that can activate the STAT3 pathway, which is involved in lecithin:cholesterol acyltransferase expression. Therefore, we characterized the role of DYRK1A overexpression on lecithin:cholesterol acyltransferase activity and expression in mouse models. METHODS: Effects of Dyrk1a overexpression were examined in mice overexpressing Dyrk1a by ELISA, chemical analyses and Western blotting. RESULTS: Overexpression of DYRK1A decreased plasma lecithin:cholesterol acyltransferase activity and hepatic STAT3 activation, which was associated with activation of SHP2, a tyrosine phosphatase. Although hepatic apolipoprotein E and D levels were increased in mice overexpressing DYRK1A, decreased plasma lecithin:cholesterol acyltransferase activity was associated with decreased hepatic and plasma apolipoprotein A-I levels. High-density lipoprotein-cholesterol levels were also decreased in plasma despite similar total cholesterol and non-high-density lipoprotein-cholesterol levels. CONCLUSIONS: We identified the role of DYRK1A overexpression on altered lipoprotein metabolism.

Effect of catechin/epicatechin dietary intake on endothelial dysfunction biomarkers and proinflammatory cytokines in aorta of hyperhomocysteinemic mice.

PURPOSE: Hyperhomocysteinemia is well recognized as an independent risk factor for the development of premature atherosclerosis. Atherosclerosis, however, may be prevented by polyphenols, potent antioxidant compounds with anti-atherogenic properties. Previously, we used cystathionine beta synthase-deficient mice [Cbs (±)] fed a high-methionine diet-a murine model of hyperhomocysteinemia-to show that daily intake of a red wine polyphenolic extract, mainly comprised of catechin and epicatechin, has a beneficial effect on aortic expression of endothelial dysfunction biomarkers and pro-inflammatory cytokines. The aim of the present study was to understand whether catechin and epicatechin, in purified forms, have anti-atherogenic effects in hyperhomocysteinemia. METHODS: Cbs (±) mice received 50 µg of catechin and/or epicatechin daily in drinking water for 1 month. Plasma homocysteine (Hcy) level and aortic expression of several endothelial dysfunction biomarkers (Vcam-1, Icam-1, E-selectin, and Lox-1) and pro-inflammatory cytokines (Tnf-α, Il-6) were assessed. RESULTS: We found that both catechin and epicatechin had a beneficial effect on plasma homocysteine levels and endothelial dysfunction biomarker expression; however, only catechin had a beneficial effect on pro-inflammatory cytokine expression. Further, when both polyphenols were given, a beneficial effect was observed only on pro-inflammatory cytokine expression. CONCLUSIONS: Catechin seems to be a more potent anti-atherogenic compound than epicatechin in hyperhomocysteinemia and should be considered as a novel therapeutic approach against endothelial dysfunction induced by this condition.

Early reduction of circulating homocysteine levels in Goto-Kakizaki rat, a spontaneous nonobese model of type 2 diabetes.

Diabetes mellitus is associated with increased risk for cardiovascular disorders, which are major causes of mortality in this disease. Hyperhomocysteinemia, defined by high plasma homocysteine levels, is an independent risk factor for the development of cardiovascular diseases. Type 2 diabetic patients have higher circulating homocysteine levels than healthy subjects and these levels are even higher in plasma of obese than nonobese diabetic patients. Homocysteine metabolism that has been studied in 2 animal models of type 2 diabetes with obesity led to conflicting data. The aim of the present study was to analyze homocysteine metabolism in a spontaneous nonobese model of type 2 diabetes, the Goto-Kakizaki rats at various successive and well characterized stages of the disease: during early postnatal normoglycemia, at the onset of hyperglycemia (around weaning), and during chronic mild hyperglycemia with progressive insulin resistance. Compared to age-matched Wistar controls, Goto-Kakizaki rats showed lower plasma levels of homocysteine and a falling trend in its major byproduct antioxidant, glutathione, from the prediabetic stage onwards. Concomitantly, Goto-Kakizaki rats exhibited increased liver activity of cystathionine beta synthase, which catalyzes the condensation of homocysteine with serine in the first step of the transsulfuration pathway. These results emphasize a strong association between homocysteine metabolism and insulin via the first step of the hepatic transsulfuration pathway in Goto-Kakizaki rats.

Dyrk1a activates antioxidant NQO1 expression through an ERK1/2-Nrf2 dependent mechanism.

BACKGROUND AND AIMS: Among cardiovascular risk factor, people with Down syndrome have a lower plasma homocysteine level. In a previous study, we have shown that DYRK1A (dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1a), a serine/threonine kinase found on human chromosome 21, is implicated on homocysteine metabolism regulation. Indeed, mice that overexpress in liver this kinase have a lower plasma homocysteine level concomitant with an increased hepatic S-adenosyhomocysteine hydrolase (SAHH) activity, which depends on the activation of NAD(P)H:quinone oxidoreductase-1 (NQO1). Since NQO1 gene transcription is under the control of NRF2 and AhR, the aim of the present study was to analyze the effect of DYRK1A overexpression in mice onto NRF2 and AhR signaling pathways. METHODS: Effects of DYRK1A overexpression were examined in mice overexpressing Dyrk1a treated with an inhibitor, harmine, by real-time quantitative reverse-transcription polymerase reaction and western blotting. RESULTS: We found that overexpression of DYRK1A increases the nuclear NRF2 quantity, concomitant with the activation of ERK1/2. We also show that the overexpression of Dyrk1a has no effect on PI3K/AKT activation, and AhR signaling pathway in liver of mice. CONCLUSIONS: Our results reveal a link between DYRK1A and NRF2 signaling pathway.