Two clusters of serum midkine levels in drug-naive patients with schizophrenia

Increased serum midkine levels in autism spectrum disorder patients

BACKGROUND

Midkine (MK) is a heparin binding growth factor and is involved in neurogenesis, neural development and neuroprotection. Additionally, MK may contribute to cancer development and pathogenesis of neurodegenerative disorders and schizophrenia. Considering these effects of MK, this study researched whether MK is involved in autism spectrum disorders (ASD) pathogenesis.

METHODS

We evaluated serum MK levels of 38 patients with ASD and 32 healthy control group. MK levels were measured with ELISA, while ASD severity was assessed with Childhood Autism Rating Scale.

RESULTS

Our data showed that the serum MK concentration in ASD patients (mean ± SD, 11.51 ± 8.53 pg/ml) is significantly higher than healthy controls (mean ± SD, 6.19 ± 3.94 pg/ml) (p = 0.007).

CONCLUSIONS

According to these results, MK may play a role in ASD pathogenesis.

Comparative gene expression study of the chronic exposure to clozapine and haloperidol in rat frontal cortex

Antipsychotic drugs (APDs) are effective in treating some of the positive and negative symptoms of schizophrenia. APDs take time to achieve a therapeutic effect which suggests that changes in gene expression are involved in their efficacy. We hypothesized that there would be altered expression of specific genes associated with the etiology or treatment of schizophrenia in frontal cortex of rats that received chronic treatment with a typical APD (haloperidol) vs. an atypical APD (clozapine). Rats were administered clozapine, haloperidol, or sterile saline intraperitoneally daily for 21days. Frontal cortices from clozapine-, haloperidol-, and saline-treated rats were dissected and subjected to microarray analysis. We observed a significant (1.5 fold, p<0.05) downregulation of 278 genes and upregulation of 73 genes in the clozapine-treated brains vs. controls and downregulation of 451 genes and upregulation of 115 genes in the haloperidol-treated brains vs. control. A total of 146 genes (130 downregulated and 16 upregulated) were significantly altered by both clozapine and haloperidol. These genes were classified by functional groups. qRT-PCR (quantitative real-time polymerase chain reaction) analysis verified the direction and magnitude of change for a group of nine genes significantly altered by clozapine and 11 genes significantly altered by haloperidol. Three genes verified by qRT-PCR were altered by both drugs: Bcl2-like 1 (Bcl2l1), catechol-O-methyltransferase (Comt), and opioid-binding protein/cell adhesion molecule-like (Opcml). Our results show that clozapine and haloperidol cause changes in levels of many important genes that may be involved in etiology and treatment of schizophrenia.

Converging evidence of blood-based biomarkers for schizophrenia: an update

This chapter has carried out a review of the literature and combined this with the results of in-house studies to identify candidate blood-based biomarkers for schizophrenia and antipsychotic drug response. Literature searches retrieved 185 publications describing a total of 273 schizophrenia biomarkers identified in serum and/or plasma. Examination of seven in-house multicenter studies resulted in the identification of 137 serum/plasma biomarkers. Taken together, the findings suggested an ongoing immunological and inflammatory process in schizophrenia. This was accompanied by altered cortisol levels which suggested activated stress response and altered hypothalamic-pituitary-adrenal axis function in these patients. The authors conclude that such biomarkers may prove useful as additional parameters for characterizing specific immune and/or metabolic or hormonal subsystems in schizophrenia and might, therefore, facilitate the development of future patient stratification and personalized medicine strategies.

Serum levels of Midkine in children and adolescents without malignant disease

BACKGROUND

Midkine (MK), a heparin-binding growth factor, is a secreted protein and can be detected in a patient's sera.

METHOD

MK was studied in the sera of 215 children and adolescents without malignant disease using an enzyme-linked immunosorbent assay in order to determine the distribution of concentrations in a control population for pediatric oncology patients. Tested subjects either underwent surgical procedures or suffered from endocrinological diseases.

RESULTS

Elevated MK levels were found in patients with short stature, diabetes mellitus, obesity, and cleft lip and palate. These patients were subsequently excluded from the "non-cancer" group. MK serum levels did neither correlate with sex, age, weight or height nor showed a normal distribution (n= 152, range: 0.0-5.58 ng/ml, median: 0.0 ng/ml, mean: 0.26 ng/ml, SD: +/-0.61).

CONCLUSION

MK serum values in children and adolescents are widely spread and not normally distributed. The present results indicate that the MK expression is influenced by many factors apart from cancer, which have not yet been identified.

Dopaminergic hypofunctions and prepulse inhibition deficits in mice lacking midkine

Midkine is a 13-kDa retinoic acid-induced heparin-binding growth factor involved in various biological phenomena such as cell migration, neurogenesis, and tissue repair. We previously demonstrated that midkine-deficient (Mdk(-/-)) mice exhibited a delayed hippocampal development with impaired working memory and increased anxiety only at the age of 4 weeks. To assess whether midkine gene could play important roles in development and maintenance of central nervous system, we investigated biochemical and behavioral parameters in dopamine and glutamate neurotransmission of Mdk(-/-) mice. The Mdk(-/-) mice exhibited a hypodopaminergic state (i.e., decreased levels of dopamine and its receptors in the striatum) with no alterations of glutamatergic system (i.e., normal level of glutamate, glutamine, glycine, d-serine, l-serine, and NMDA receptors in the frontal cortex and hippocampus). We also found prepulse inhibition deficits reversed by clozapine and haloperidol in the Mdk(-/-) mice. Our results suggested that midkine deficiency may be related to neurochemical and behavioral dysfunctions in dopaminergic system.

Possible association between nonsynonymous polymorphisms of the anaplastic lymphoma kinase (ALK) gene and schizophrenia in a Japanese population

We examined, for the first time, the possible association between schizophrenia and the anaplastic lymphoma kinase (ALK) gene which plays an important role in neurodevelopment. When two nonsynonymous polymorphisms (Arg1491Lys and Glu1529Asp) were examined, there were significant differences in genotype and allele distributions between patients and controls. Individuals homozygous for the minor allele (1491Lys-1529Asp) were more common in patients than in controls (p = 0.0064, odds ratio 2.4, 95% CI 1.3-4.6). These results suggest that genetic variations of the ALK gene might confer susceptibility to schizophrenia.

Increased midkine levels in sera from patients with Alzheimer's disease

Midkine (MK) is a heparin binding growth factor and promotes growth, survival and migration of various cells including neurons. It is also known to accumulate in senile plaques of patients with Alzheimer's disease (AD). To investigate the involvement of serum MK in the pathophysiology of AD, serum MK levels were determined in patients with AD (n=36) and age- and sex-matched healthy controls (n=32), using an enzyme-linked immunosorbent assay (ELISA). The serum MK values of the patients with AD (median 560 and interquartile range (500-755) pg/ml) were significantly (U=278.5, P=0.0003, Mann-Whitney U-test) higher than those of the controls (median 500 and interquartile range (385-520) pg/ml). Moreover, 17 patients (47.2%) had abnormally high values of more than 600 pg/ml, but no controls (0%) did. There was no correlation between serum MK level and the mini mental state examination (MMSE) score in the patients. The demonstration of elevated MK levels in sera of patients with AD may contribute toward an understanding the pathophysiology of this disease, and provide a novel potential therapeutic strategy for decreasing neuronal damages in patients with AD. We found that serum MK levels in patients with AD were increased in comparison with those of normal controls.