Diet-induced hyperhomocysteinemia causes sex-dependent deficiencies in offspring musculature and brain function

Hyperhomocysteinemia (HHcy), characterized by elevated homocysteine (Hcy) levels, is a known risk factor for cardiovascular, renal, and neurological diseases, as well as pregnancy complications. Our study aimed to investigate whether HHcy induced by a high-methionine (high-Met) diet exacerbates cognitive and behavioral deficits in offspring and leads to other breeding problems. Dietary HHcy was induced four weeks before mating and continued throughout gestation and post-delivery. A battery of behavioral tests was conducted on offspring between postnatal days (PNDs) 5 and 30 to assess motor function/activity and cognition. The results were correlated with brain morphometric measurements and quantitative analysis of mammalian target of rapamycin (mTOR)/autophagy markers. The high-Met diet significantly increased parental and offspring urinary tHcy levels and influenced offspring behavior in a sex-dependent manner. Female offspring exhibited impaired cognition, potentially related to morphometric changes observed exclusively in HHcy females. Male HHcy pups demonstrated muscle weakness, evidenced by slower surface righting, reduced hind limb suspension (HLS) hanging time, weaker grip strength, and decreased activity in the beaker test. Western blot analyses indicated the downregulation of autophagy and the upregulation of mTOR activity in HHcy cortexes. HHcy also led to breeding impairments, including reduced breeding rate, in-utero fetal death, lower pups' body weight, and increased mortality, likely attributed to placental dysfunction associated with HHcy. In conclusion, a high-Met diet impairs memory and cognition in female juveniles and weakens muscle strength in male pups. These effects may stem from abnormal placental function affecting early neurogenesis, the dysregulation of autophagy-related pathways in the cortex, or epigenetic mechanisms of gene regulation triggered by HHcy during embryonic development.

Deletion of the Homocysteine Thiolactone Detoxifying Enzyme Bleomycin Hydrolase, in Mice, Causes Memory and Neurological Deficits and Worsens Alzheimer's Disease-Related Behavioral and Biochemical Traits in the 5xFAD Model of Alzheimer's Disease

BACKGROUND

Bleomycin hydrolase (BLMH), a homocysteine (Hcy)-thiolactone detoxifying enzyme, is attenuated in Alzheimer's disease (AD) brains. Blmh loss causes astrogliosis in mice while the loss of histone demethylase Phf8, which controls mTOR signaling, causes neuropathy in mice and humans.

OBJECTIVE

To examine how Blmh gene deletion affects the Phf8/H4K20me1/mTOR/autophagy pathway, amyloid-β (Aβ) accumulation, and cognitive/neuromotor performance in mice.

METHODS

We generated a new mouse model of AD, the Blmh-/-5xFAD mouse. Behavioral assessments were conducted by cognitive/neuromotor testing. Blmh and Phf8 genes were silenced in mouse neuroblastoma N2a-APPswe cells by RNA interference. mTOR- and autophagy-related proteins, and AβPP were quantified by western blotting and the corresponding mRNAs by RT-qPCR. Aβ was quantified by western blotting (brains) and by confocal microscopy (cells).

RESULTS

Behavioral testing showed cognitive/neuromotor deficits in Blmh-/- and Blmh-/-5xFAD mice. Phf8 was transcriptionally downregulated in Blmh-/- and Blmh-/-5xFAD brains. H4K20me1, mTOR, phospho-mTOR, and AβPP were upregulated while autophagy markers Becn1, Atg5, and Atg7 were downregulated in Blmh-/- and Blmh-/-5xFAD brains. Aβ was elevated in Blmh-/-5xFAD brains. These biochemical changes were recapitulated in Blmh-silenced N2a-APPswe cells, which also showed increased H4K20me1-mTOR promoter binding and impaired autophagy flux (Lc3-I, Lc3-II, p62). Phf8-silencing or treatments with Hcy-thiolactone or N-Hcy-protein, metabolites elevated in Blmh-/- mice, induced biochemical changes in N2a-APPswe cells like those induced by the Blmh-silencing. However, Phf8-silencing elevated Aβ without affecting AβPP.

CONCLUSIONS

Our findings show that Blmh interacts with AβPP and the Phf8/H4K20me1/mTOR/autophagy pathway, and that disruption of those interactions causes Aβ accumulation and cognitive/neuromotor deficits.

Proteome-Wide Analysis of Protein Lysine N-Homocysteinylation in Saccharomyces cerevisiae

Protein N-homocysteinylation by a homocysteine (Hcy) metabolite, Hcy-thiolactone, is an emerging post-translational modification (PTM) that occurs in all tested organisms and has been linked to human diseases. The yeast Saccharomyces cerevisiae is widely used as a model eukaryotic organism in biomedical research, including studies of protein PTMs. However, patterns of global protein N-homocysteinylation in yeast are not known. Here, we identified 68 in vivo and 197 in vitro N-homocysteinylation sites at protein lysine residues (N-Hcy-Lys). Some of the N-homocysteinylation sites overlap with other previously identified PTM sites. Protein N-homocysteinylation in vivo, induced by supplementation of yeast cultures with Hcy, which elevates Hcy-thiolactone levels, was accompanied by significant changes in the levels of 70 yeast proteins (38 up-regulated and 32 down-regulated) involved in the ribosomal structure, amino acid biosynthesis, and basic cellular pathways. Our study provides the first global survey of N-homocysteinylation and accompanying changes in the yeast proteome caused by elevated Hcy level. These findings suggest that protein N-homocysteinylation and dysregulation of cellular proteostasis may contribute to the toxicity of Hcy in yeast. Homologous proteins and N-homocysteinylation sites are likely to be involved in Hcy-related pathophysiology in humans and experimental animals. Data are available via ProteomeXchange with identifier PXD020821.

iTRAQ-based proteomic analysis of plasma reveals abnormalities in lipid metabolism proteins in chronic kidney disease-related atherosclerosis

Patients with chronic kidney disease (CKD) have a considerably higher risk of death due to cardiovascular causes. Using an iTRAQ MS/MS approach, we investigated the alterations in plasma protein accumulation in patients with CKD and classical cardiovascular disease (CVD) without CKD. The proteomic analysis led to the identification of 130 differentially expressed proteins among CVD and CKD patients and healthy volunteers. Bioinformatics analysis revealed that 29 differentially expressed proteins were involved in lipid metabolism and atherosclerosis, 20 of which were apolipoproteins and constituents of high-density lipoprotein (HDL) and low-density lipoprotein (LDL). Although dyslipidemia is common in CKD patients, we found that significant changes in apolipoproteins were not strictly associated with changes in plasma lipid levels. A lack of correlation between apoB and LDL concentration and an inverse relationship of some proteins with the HDL level were revealed. An increased level of apolipoprotein AIV, adiponectin, or apolipoprotein C, despite their anti-atherogenic properties, was not associated with a decrease in cardiovascular event risk in CKD patients. The presence of the distinctive pattern of apolipoproteins demonstrated in this study may suggest that lipid abnormalities in CKD are characterized by more qualitative abnormalities and may be related to HDL function rather than HDL deficiency.

Inactivation of the paraoxonase 1 gene affects the expression of mouse brain proteins involved in neurodegeneration

Homocysteine (Hcy) is a risk factor for Alzheimer's disease (AD). Paraoxonase 1 (Pon1) participates in Hcy metabolism and is also linked to AD. The inactivation of the Pon1 gene in mice causes the accumulation of Hcy-thiolactone in the brain and increases the susceptibility to Hcy-thiolactone-induced seizures. To gain insight into the brain-related Pon1 function, we used two-dimensional IEF/SDS-PAGE gel electrophoresis and MALDI-TOF/TOF mass spectrometry to study brain proteomes of Pon1-/- and Pon1+/+ mice fed with a hyperhomocysteinemic high-methionine (Met) or a control diet. We found that: 1) proteins involved in brain-specific function (Nrgn), antioxidant defenses (Sod1, DJ-1), and cytoskeleton assembly (Tbcb, CapZa2) were differentially expressed in brains of Pon1-null mice; 2) proteins involved in brain-specific function (Ncald, Nrgn, Stmn1), antioxidant defenses (Prdx2, DJ-1), energy metabolism (Ak1), cell cycle (GDI1, Ran), cytoskeleton assembly (Tbcb), and unknown function (Hdhd2) showed differential expression in brains of Pon1-null fed with a hyperhomocysteinemic high-Met diet; 3) most proteins regulated by the Pon1-/- genotype were also regulated by the high-Met diet; 4) the proteins differentially expressed in Pon1-null mouse brains play important roles in neural development, learning, plasticity, and aging and are linked to neurodegenerative diseases, including AD. Taken together, our findings suggest that Pon1 interacts with diverse cellular processes from energy metabolism and anti-oxidative defenses to cell cycle, cytoskeleton dynamics, and synaptic plasticity essential for normal brain homeostasis and that these interactions are modulated by hyperhomocysteinemia and account for the involvement of Hcy and Pon1 in AD.

Paraoxonase 1 deficiency and hyperhomocysteinemia alter the expression of mouse kidney proteins involved in renal disease

SCOPE

Hyperhomocysteinemia (HHcy) is associated with kidney disease and leads to atherosclerosis and thrombosis. Paraoxonase 1 (Pon1), a hydrolase that participates in homocysteine (Hcy) metabolism and is carried in the circulation on high-density lipoprotein, has also been linked to kidney disease and atherothrombosis. Pon1-knockout mice are susceptible to atherosclerosis and exhibit a kidney-associated phenotype, polyuria or urine dilution. We hypothesize that HHcy and Pon1 deficiency are toxic to kidney function because they impair metabolic pathways important for normal kidney homeostasis.

METHODS AND RESULTS

We examined changes in the mouse kidney proteome induced by Pon1 gene deletion and dietary HHcy, using 2D IEF/SDS-PAGE gel electrophoresis and MALDI-TOF mass spectrometry. We found that the expression of ten mouse kidney proteins was altered by the Pon1(-/-) genotype or HHcy. Proteins involved in metabolism of lipid (ApoA-I), protein (Hspd1), carbohydrate (Pdhb, Fbp1-isoform2, Eno1), and energy (Ndufs8, Ldhd) were down-regulated. Proteins involved in lipid transport (Pebp1), oxidative stress response (Prdx2), and cellular detoxification (Glo1) were up-regulated. The kidney proteins altered by HHcy or Pon1 are also altered in renal disease.

CONCLUSION

Our findings suggest that excess Hcy is toxic because it deregulates the expression of proteins involved in diverse cellular processes-from lipid, protein, carbohydrate, and energy metabolisms to detoxification and antioxidant defenses-that are essential for normal kidney homeostasis. Dysregulation of these processes can account for the involvement of HHcy and reduced Pon1 in kidney disease. Our findings also show that Pon1 plays an important role in maintaining normal kidney homeostasis.

Paraoxonase 1 and dietary hyperhomocysteinemia modulate the expression of mouse proteins involved in liver homeostasis

Homocysteine (Hcy), a product of methionine metabolism, is elevated by the consumption of a high-methionine diet that can cause fatty liver disease. Paraoxonase 1 (Pon1), a hydrolase expressed mainly in the liver and carried in the circulation on high-density lipoprotein, participates in Hcy metabolism. Low Pon1 activity is linked to fatty liver disease. We hypothesize that hyperhomocysteinemia and low Pon1 induce changes in gene expression that could impair liver homeostasis. To test this hypothesis, we analyzed the liver proteome of Pon1(-/-) and Pon1(+/+) mice fed a high methionine diet (1% methionine in the drinking water) for 8 weeks using 2D IEF/SDS-PAGE gel electrophoresis and MALDI-TOF mass spectrometry. We identified seven liver proteins whose expression was significantly altered in Pon1(-/-) mice. In animals fed with a control diet, the expression of three liver proteins involved in lipoprotein metabolism (ApoE), iron metabolism (Ftl), and regulation of nitric oxide generation (Ddah1) was up-regulated by the Pon1(-/-) genotype. In mice fed with a high-methionine diet, expression of four liver proteins was up-regulated and of three proteins was down-regulated by the Pon1(-/-) genotype. The up-regulated proteins are involved in lipoprotein metabolism (ApoE), energy metabolism (Atp5h), oxidative stress response (Prdx2), and nitric oxide regulation (Ddah1). The down-regulated proteins are involved in energy metabolism (Gamt), iron metabolism (Ftl), and catechol metabolism (Comt). Expression of one protein (Ftl) was up-regulated both by the Pon1(-/-) genotype and a high-methionine diet. Our findings suggest that Pon1 interacts with diverse cellular processes - from lipoprotein metabolism, nitric oxide regulation, and energy metabolism to iron transport and antioxidant defenses - that are essential for normal liver homeostasis and modulation of these interactions by a high-methionine diet may contribute to fatty liver disease.

Paraoxonase 1 and dietary hyperhomocysteinemia modulate the expression of mouse proteins involved in liver homeostasis

Homocysteine (Hcy), a product of methionine metabolism, is elevated by the consumption of a high-methionine diet that can cause fatty liver disease. Paraoxonase 1 (Pon1), a hydrolase expressed mainly in the liver and carried in the circulation on high-density lipoprotein, participates in Hcy metabolism. Low Pon1 activity is linked to fatty liver disease. We hypothesize that hyperhomocysteinemia and low Pon1 induce changes in gene expression that could impair liver homeostasis. To test this hypothesis, we analyzed the liver proteome of Pon1(-/-) and Pon1(+/+) mice fed a high methionine diet (1% methionine in the drinking water) for 8 weeks using 2D IEF/SDS-PAGE gel electrophoresis and MALDI-TOF mass spectrometry. We identified seven liver proteins whose expression was significantly altered in Pon1(-/-) mice. In animals fed with a control diet, the expression of three liver proteins involved in lipoprotein metabolism (ApoE), iron metabolism (Ftl), and regulation of nitric oxide generation (Ddah1) was up-regulated by the Pon1(-/-) genotype. In mice fed with a high-methionine diet, expression of four liver proteins was up-regulated and of three proteins was down-regulated by the Pon1(-/-) genotype. The up-regulated proteins are involved in lipoprotein metabolism (ApoE), energy metabolism (Atp5h), oxidative stress response (Prdx2), and nitric oxide regulation (Ddah1). The down-regulated proteins are involved in energy metabolism (Gamt), iron metabolism (Ftl), and catechol metabolism (Comt). Expression of one protein (Ftl) was up-regulated both by the Pon1(-/-) genotype and a high-methionine diet. Our findings suggest that Pon1 interacts with diverse cellular processes - from lipoprotein metabolism, nitric oxide regulation, and energy metabolism to iron transport and antioxidant defenses - that are essential for normal liver homeostasis and modulation of these interactions by a high-methionine diet may contribute to fatty liver disease.

Methionine-induced hyperhomocysteinemia and bleomycin hydrolase deficiency alter the expression of mouse kidney proteins involved in renal disease

SCOPE

Hyperhomocysteinemia (HHcy) induced by dietary or genetic factors is linked to kidney disease. Bleomycin hydrolase (Blmh) metabolizes Hcy-thiolactone to Hcy. We aimed to explain the role of dietary HHcy in kidney disease.

METHODS AND RESULTS

We examined kidney proteome in dietary HHcy and Blmh-knockout mouse models using 2D IEF/SDS-PAGE gel electrophoresis and MALDI-TOF mass spectrometry. We found that the kidney proteome was altered by dietary HHcy and the Blmh(-/-) genotype. Proteins involved in metabolism of lipoprotein (ApoA1), amino acid and protein (Acy1, Hspd1), carbohydrate (Pdhb, Fbp1-isoform 1, Eno1), and energy metabolism (Ndufs8, Ldhd) were down-regulated. Proteins involved in carbohydrate metabolism (Fbp1-isoform 2), oxidative stress response (Prdx2), and detoxification (Glod4) were up-regulated. The Blmh(-/-) genotype down-regulated Glod4 isoform 3 mRNA but did not affect isoform 1 mRNA expression in mouse kidneys, suggesting post-transcriptional regulation of the Glod4 protein by the Blmh(+/+) genotype. Responses of ApoA1, Acy1, Hspd1, Ndufs8, Fbp1, Eno1, and Prdx2 to HHcy and/or Blmh deficiency mimic their responses to renal disease.

CONCLUSION

Our findings indicate that Blmh interacts with diverse cellular processes--lipoprotein, amino acid and protein, carbohydrate, and energy metabolisms, detoxification, antioxidant defenses--that are essential for normal kidney homeostasis and that deregulation of these processes can account for the involvement of HHcy in kidney disease.

Bleomycin hydrolase and hyperhomocysteinemia modulate the expression of mouse proteins involved in liver homeostasis

The liver is the major contributor to homocysteine (Hcy) metabolism and fatty liver disease is associated with hyperhomocysteinemia. Bleomycin hydrolase (Blmh) is an aminohydrolase that also participates in Hcy metabolism by hydrolyzing Hcy-thiolactone. To gain insight into hepatic functions of Blmh, we analyzed the liver proteome of Blmh(-/-) and Blmh(+/+) mice in the absence and presence of diet-induced (high methionine) hyperhomocysteinemia using 2D IEF/SDS-PAGE gel electrophoresis and MALDI-TOF mass spectrometry. We identified eleven liver proteins whose expression was significantly altered as a result of the Blmh gene inactivation. The differential expression (Blmh(-/-) vs. Blmh(+/+)) of four liver proteins was lower, of two proteins was higher, and was further modified in mice fed with a hyperhomocysteinemic high-Met diet. The down-regulated proteins are involved in lipoprotein metabolism (ApoA1, ApoE), antigen processing (Psme1), energy metabolism (Atp5h, Gamt), methylglyoxal detoxification (Glo1), oxidative stress response (Sod1), and inactivation of catecholamine neurotransmitters (Comt). The two up-regulated proteins are involved in nitric oxide generation (Ddah1) and xenobiotic detoxification (Sult1c1). We also found that livers of Blmh(-/-) mice expressed a novel variant of glyoxalase domain-containing protein 4 (Glod4) by a post-transcriptional mechanism. Our findings suggest that Blmh interacts with diverse cellular processes-from lipoprotein metabolism, nitric oxide regulation, antigen processing, and energy metabolism to detoxification and antioxidant defenses-that are essential for liver homeostasis and that modulation of these interactions by hyperhomocysteinemia underlies the involvement of Hcy in fatty liver disease.