Association analysis between polymorphisms in the myo-inositol monophosphatase 2 (IMPA2) gene and bipolar disorder

Myo-inositol rescued insulin resistance and dyslipidemia in db/db mice

Myo-inositol (MI), present in a variety of foods, is essential in several important processes of cell physiology. In this study, we explored the protective effects of MI against hyperglycemia and dyslipidemia in db/db mice, a typical animal model of type 2 diabetes mellitus (T2DM). MI supplement effectively suppressed the high plasma glucose and insulin levels and markedly relieved the insulin resistance (IR) in the db/db mice, comparable to metformin's effects. In MIN6 pancreatic β cells, MI also restrained the upsurge of insulin secretion stimulated by high-concentration glucose but had no impact on the promoted cell proliferation. Moreover, MI abated the enhanced plasma triglyceride and total cholesterol levels in the db/db mice. Notably, the lipid droplet formation of mesenchymal stem cells (MSCs) from db/db mice was significantly diminished after the treatment of MI, indicating that MI could effectively inhibit the differentiation of db/db mouse MSCs into adipocytes. However, MI regretfully failed to control obesity in db/db mice. This work proved that MI significantly helped db/db mice's metabolic disorders, indicating that MI has potential as an effective adjunctive treatment for hyperglycemia and dyslipidemia in T2DM patients.

Comparative transcriptome and methylome of polar bears, giant and red pandas reveal diet-driven adaptive evolution

Epigenetic regulation plays an important role in the evolution of species adaptations, yet little information is available on the epigenetic mechanisms underlying the adaptive evolution of bamboo-eating in both giant pandas (Ailuropoda melanoleuca) and red pandas (Ailurus fulgens). To investigate the potential contribution of epigenetic to the adaptive evolution of bamboo-eating in giant and red pandas, we performed hepatic comparative transcriptome and methylome analyses between bamboo-eating pandas and carnivorous polar bears (Ursus maritimus). We found that genes involved in carbohydrate, lipid, amino acid, and protein metabolism showed significant differences in methylation and expression levels between the two panda species and polar bears. Clustering analysis of gene expression revealed that giant pandas did not form a sister group with the more closely related polar bears, suggesting that the expression pattern of genes in livers of giant pandas and red pandas have evolved convergently driven by their similar diets. Compared to polar bears, some key genes involved in carbohydrate metabolism and biological oxidation and cholesterol synthesis showed hypomethylation and higher expression in giant and red pandas, while genes involved in fat digestion and absorption, fatty acid metabolism, lysine degradation, resistance to lipid peroxidation and detoxification showed hypermethylation and low expression. Our study elucidates the special nutrient utilization mechanism of giant pandas and red pandas and provides some insights into the molecular mechanism of their adaptive evolution of bamboo feeding. This has important implications for the breeding and conservation of giant pandas and red pandas.

IMPA2 blocks cervical cancer cell apoptosis and induces paclitaxel resistance through p53-mediated AIFM2 regulation

Cervical cancer continues to be a concern, and the prognosis of locally advanced cervical cancer remains poor. IMPA2 was previously identified as a potential oncogene and regulator of tumor apoptosis. In this study, we aim to further elucidate the underlying mechanisms of IMPA2 gene in the regulation of cervical cancer apoptosis. First, we identify AIFM2 as an upregulated gene in IMPA2-silenced cervical cancer cells, and inhibition of AIFM2 reverses IMPA2 knockdown-induced apoptosis. Further study reveals that AIFM2 regulates cell apoptosis in a mitochondrial-dependent manner with a redistribution of mitochondrial membrane potential and intracellular Ca2 ⁺ levels. However, the analysis of the STRING database and our experimental results show that AIFM2 has little effect on cervical cancer progression and survival. Further mechanistic study demonstrates that IMPA2 and AIFM2 silencing inhibits apoptosis by activating p53. Meanwhile, the knockdown of IMPA2 enhances the chemosensitivity of cervical cancer cells by strengthening paclitaxel-induced apoptosis. Based on the above results, the IMPA2/AIFM2/p53 pathway may be a new molecular mechanism for paclitaxel treatment of cervical cancer and an effective strategy to enhance the sensitivity of cervical cancer cells to paclitaxel. Our findings display a novel function of IMPA2 in regulating cell apoptosis and paclitaxel resistance mediated by a disturbance of AIFM2 and p53 expression, potentially making it a novel therapeutic target for cervical cancer treatment.

Identification of IMPA2 as the hub gene associated with colorectal cancer and liver metastasis by integrated bioinformatics analysis

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IMPA2 was selected as the hub gene associated with CRC and liver metastasis by integrated bioinformatics analysis.

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The expression of IMPA2 was significantly decreased in CRC and liver metastasis samples, and low IMPA2 expression was correlated with poor prognosis.

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The potential mechanisms of IMPA2-mediated CRC and metastasis may be associated with lipid metabolism and epithelial mesenchymal transition (EMT).

Background and Objectives

Colorectal cancer (CRC) is one of the most common malignant tumors worldwide with high incidence and mortality rate, while colorectal liver metastasis (CRLM) is one of the major causes of cancer-related deaths. Therefore, the present study aims to identify the hub gene associated with CRC carcinogenesis and liver metastasis, and then explore its diagnostic and prognostic value as well as the potential regulation mechanism.

Methods

The overlapping differential co-expression genes among CRC, CRLM, and normal tissues were explored on the GSE49355 and GSE81582 datasets from the Gene Expression Omnibus (GEO) database by integrated bioinformatics analysis. Then, the hub prognostic genes were selected from the overlapping genes by univariate Cox proportional hazard analysis and online database Gene Expression Profiling Interactive Analysis 2 (GEPIA2). Subsequently, the clinical value of the hub genes was evaluated in the TCGA and GSE39582 cohorts. Finally, the underlying mechanisms of the hub gene regulating CRC carcinogenesis and metastasis were explored by Gene function annotation and DNA methylation analysis.

Results

Inositol mono-phosphatase 2 (IMPA2) was identified as the hub gene associated with CRC carcinogenesis and liver metastasis. IMPA2 had an excellent diagnostic efficiency, and its expression was significantly decreased in CRC and liver metastasis samples, being positively correlated with poor prognosis. Moreover, its low expression was associated with AJCC stage III+IV, T4, N1+2, and M1. In addition, our results revealed that the potential mechanisms used by IMPA2 to mediate CRC carcinogenesis and metastasis could be associated with lipid metabolism and epithelial mesenchymal transition (EMT). Finally, IMPA2 expression could be regulated by DNA methylation.

Conclusions

IMPA2 was identified and reported for the first time as a hub gene biomarker in the diagnosis and prognosis of CRC, which could regulate CRC carcinogenesis and liver metastasis through the regulation of lipid metabolism, EMT, and DNA methylation.

Dysregulation of the miR-25-IMPA2 axis promotes metastatic progression in clear cell renal cell carcinoma

Background

The molecular mechanism underlying clear cell renal cell carcinoma (ccRCC) metastasis remains unclear. We therefore aimed to elucidate the role of IMPA2 in ccRCC metastatic progression.

Methods

Using the Cancer Genome Atlas (TCGA) database and immunohistochemistry (IHC) staining, we investigated differences in IMPA2 mRNA and protein expression, as well as their clinical relevance, in ccRCC. To investigate the function of IMPA2 in ccRCC metastasis, we performed in vitro migration and in vivo lung colony-forming assays. We further explored the effect of microRNA (miR)-25 on IMPA2 expression by performing a luciferase reporter assay.

Findings

We show that ccRCC expresses relatively lower transcript levels of IMPA2 than normal kidney tissue. IMPA2 downregulation was greater in high-grade ccRCC than in low-grade ccRCC and was correlated with a poor prognosis in ccRCC patients. Importantly, we demonstrate that IMPA2 expression is inversely associated with the metastatic potential of ccRCC cells. We found that IMPA2 knockdown promotes, but overexpression suppresses, the cellular migration and lung colony-forming abilities of ccRCC cells. By using in silico and luciferase reporter assays, we found that IMPA2 expression is primarily influenced by miR-25 in ccRCC cells. Significantly, the inhibition of miR-25 function restored IMPA2 expression, thereby diminishing the metastatic potential of ccRCC cells.

Interpretation

We conclude that miR-25-mediated IMPA2 downregulation constitutes a novel signature for cancer metastasis and poor outcomes in ccRCC. We further postulate that the therapeutic targeting of miR-25 can be useful for preventing the metastatic progression of ccRCC associated with IMPA2 downregulation.

Fund

This study was supported by the Ministry of Science and Technology, Taiwan (MOST 107-2314-B-038-094, MOST 106-2314-B-038-069-MY3, MOST 105-2320-B-038-021-MY3 and MOST 107-2320-B-038-056).

Association between genetic variation in the myo-inositol monophosphatase 2 (IMPA2) gene and age at onset of bipolar disorder

INTRODUCTION

The age at onset of bipolar disorder (BD) has significant implications for severity, duration of affective episodes, response to treatment, and psychiatric comorbidities. It has been suggested that early-onset BD (EO-BD) could represent a clinically distinct subtype with probable genetic risk factors different from those of late-onset BD (LO-BD). To date, several genes have been associated with BD risk but few studies have investigated the genetic differences between EO-BD and LO-BD. The aim of this study was to evaluate if variants of the gene coding for myo-inositol monophosphatase (IMPA2) are linked to age at onset of BD.

METHOD

235 bipolar patients were recruited and assessed. The final sample consisting of 192 euthymic individuals, was compared according to the age at onset. Polymorphisms were genotyped in the IMPA2 gene (rs669838, rs1020294, rs1250171, and rs630110). Early-onset was defined by the appearance of a first affective episode before the age of 18.

RESULTS

The analyses showed that in the genotype distribution rs1020294 (p = .01) and rs1250171 (p = .01) were associated with the age at onset. The significant effect remained only in the rs1020294 SNP in which G carriers were more likely to debut later compared to patients presenting the AA genotype (p = .002; OR = 9.57, CI95%[2.37-38.64]). The results also showed that EO-BD tended to experience more alcohol misuse (p = .003; OR = .197, CI95%[.07-.58]) compared to LO-BD.

CONCLUSIONS

Our results provide evidence for genetic differences between EO-BD and LO-BD at the IMPA2 gene as well as clinical differences between subgroups with therapeutic implications.

Molecular actions and clinical pharmacogenetics of lithium therapy

Mood disorders, including bipolar disorder and depression, are relatively common human diseases for which pharmacological treatment options are often not optimal. Among existing pharmacological agents and mood stabilizers used for the treatment of mood disorders, lithium has a unique clinical profile. Lithium has efficacy in the treatment of bipolar disorder generally, and in particular mania, while also being useful in the adjunct treatment of refractory depression. In addition to antimanic and adjunct antidepressant efficacy, lithium is also proven effective in the reduction of suicide and suicidal behaviors. However, only a subset of patients manifests beneficial responses to lithium therapy and the underlying genetic factors of response are not exactly known. Here we discuss preclinical research suggesting mechanisms likely to underlie lithium's therapeutic actions including direct targets inositol monophosphatase and glycogen synthase kinase-3 (GSK-3) among others, as well as indirect actions including modulation of neurotrophic and neurotransmitter systems and circadian function. We follow with a discussion of current knowledge related to the pharmacogenetic underpinnings of effective lithium therapy in patients within this context. Progress in elucidation of genetic factors that may be involved in human response to lithium pharmacology has been slow, and there is still limited conclusive evidence for the role of a particular genetic factor. However, the development of new approaches such as genome-wide association studies (GWAS), and increased use of genetic testing and improved identification of mood disorder patients sub-groups will lead to improved elucidation of relevant genetic factors in the future.