Higher concentration in serum of insulin autoantibodies in patients with schizophrenia or related psychosis, compared to in control subjects

OBJECTIVES

In a recent study, we found increased antibody reactivity against the insulin receptor-A and insulin-like growth factor 1 receptor and their ligands in patients with schizophrenia or related psychosis, indicating that an autoimmune-mediated process may underlie development of schizophrenia. The aim of this study was to supplement our previous study with analysing additional neuronal- and diabetes-associated autoantibodies of potential interest for schizophrenia in the same patients and controls as in the foregoing study.

MATERIAL AND METHODS

Analyses of neuronal (NMDAR, VGKC, AMPAR, GABABR, DPPX, GAD)- and voltage-gated calcium channel (VGCC) autoantibodies in cerebrospinal fluid (12 patients, 11 controls) and of diabetes-associated (GAD, IA-2, ZnT8, insulin)- and VGCC autoantibodies in serum (17 patients, 11 controls) were done by standard methods. Additionally, patients (n = 16) were accessed for clinical symptoms with the Positive and Negative Syndrome Scale (PANSS) for schizophrenia.

RESULTS

Concentrations in cerebrospinal fluid of NMDAR-, VGKC-, AMPAR-, GABABR-, DPPX-, GAD- and VGCC autoantibodies were below detection limits in all patients and controls. Concentration in serum of insulin autoantibodies was significantly higher in patients than in controls (p = 0.001), whereas no significant differences were found in concentrations in serum of GAD-, IA-2-, ZnT8- or VGCC autoantibodies between patients and controls. Patients' serum concentrations of insulin autoantibodies tended to inversely correlate to their PANSS scores.

CONCLUSION

In this study, we show higher concentration in serum of insulin autoantibodies in patients with schizophrenia. This finding is of importance since autoantibodies against insulin may be implicated in the autoimmune-mediated process underlying development of schizophrenia.

Associations between heredity, height, BMI, diabetes mellitus type 1 or 2 and gene variants in the insulin receptor (INSR) gene in patients with schizophrenia

OBJECTIVES

Schizophrenia is a psychotic disorder with high heritability. There are also indications that an autoimmune-mediated process in the brain underlies development of schizophrenia, and that the insulin receptor A may constitute a main antigen target. Therefore, as the insulin receptor gene hitherto has been little studied in schizophrenia, this study was undertaken to investigate this gene in schizophrenia susceptibility.

MATERIALS AND METHODS

To identify gene variants of possible interest, the whole insulin receptor gene was first DNA-sequenced in all or subgroups of patients with schizophrenia and controls, using the Sanger method and the SOLiD technology. Then, association analyses of total 50 identified gene variants were carried out in the whole study population, consisting of 94 patients and 60 controls.

RESULTS

No significant differences in genotype- and allele frequencies for the 50 gene variants were found between all patients and controls. However, in subgroup analyses, rs2229431 and rs747721248 tended to associate with heredity for schizophrenia, rs2229431 associated with height, rs41505247 with body mass index, rs59765738 and rs57476618 with diabetes mellitus (DM) type 1 and/ or heredity for DM type 1, and rs2962, rs2352954, rs2352955 and rs2252673 with DM type 2 and/ or heredity for DM type 2 in patients.

CONCLUSIONS

In this study, we show associations between heredity, height, body mass index, DM type 1, or DM type 2 and gene variants in the insulin receptor gene in patients with schizophrenia. Taken together, these findings clearly point to that the insulin receptor gene is involved in schizophrenia susceptibility.

Association between single nucleotide polymorphisms in non-coding regions of the insulin (INS) gene and schizophrenia

OBJECTIVES

Schizophrenia is a psychotic disorder with high heritability. There are also indications that impaired cellular signalling via the insulin receptor-A and the insulin-like growth factor 1 receptor may play a role in its pathogenesis. Insulin, and possibly also C-peptide, are ligands to these receptors. The insulin gene, coding both insulin and C-peptide, has however not been genetically studied in schizophrenia. Therefore, this study was undertaken to investigate the involvement of this gene in schizophrenia susceptibility.

MATERIAL AND METHODS

For identification of single nucleotide polymorphisms (SNPs) of interest, the whole insulin gene and parts of its promoter region were first DNA sequenced in two subgroups of the study population (37 schizophrenia patients with heredity for schizophrenia or related psychosis, and 25 controls), and mapped to the reference sequence. Then, 7 identified SNPs of potential interest were typed by TaqMan® SNP Genotyping Assays in the whole study population, consisting of 94 patients with schizophrenia and 60 controls.

RESULTS

Allele frequencies tended to differ between patients and controls for two of the 7 SNPs, rs5505 and rs3842749 (p=0.077 and p=0.078, respectively), whereas subgroup analyses of diabetes mellitus (type 1 or 2) and/ or heredity for diabetes mellitus (type 1 or 2) in patients and controls showed overall significant differences in genotype/ allele frequencies solely for rs5505 (p=0.021/ 0.023).

CONCLUSION

These findings are of interest, as the two SNPs - rs5505 and rs3842749 - may have regulatory function on the coding of insulin and C-peptide, against which increased antibody reactivity has been previously reported in schizophrenia.

Increased antibody reactivity against insulin receptor-A and insulin like growth factor 1 receptor and their ligands in cerebrospinal fluid and serum of patients with schizophrenia or related psychosis

OBJECTIVES

Evidence has accumulated that an autoimmune-mediated process in the central nervous system may underlie the development of schizophrenia. Various antibodies have also previously been detected in serum of patients with schizophrenia. Therefore, the aim of this study was to analyze antibody reactivity against proteins, selected based on potential schizophrenia disease relevance, in both cerebrospinal fluid and serum of patients with schizophrenia.

MATERIAL AND METHODS

Cerebrospinal fluid and serum from 17 patients with schizophrenia or related psychosis and 12 controls were analyzed regarding antibody reactivity, using bead-based antigen arrays of protein fragments or peptides of 21 selected proteins. Additionally, the patients were accessed for clinical symptoms with the Positive and Negative Syndrome Scale (PANSS) for schizophrenia.

RESULTS

Increased antibody reactivity was found in patients compared to controls against the insulin receptor (INSR), PAGE2B;2;5 and heat shock proteins (HSPs) in both cerebrospinal fluid and serum, and against the insulin like growth factor 1 receptor (IGF1R), insulin (INS), insulin like growth factor 1 (IGF1), cadherin 5 (CDH5), nerve growth factor (NGF) and vascular endothelial growth factor A (VEGFA) in serum alone. Moreover, patients' antibody reactivity in serum against PAGE2B;2;5, IGF1R or NGF correlated positively to their PANSS scores.

CONCLUSIONS

Taken together, these results point to that an autoimmune-mediated process underlies the development of a core group of schizophrenia cases and that the INSR and IGF1R, their ligands (INS and IGF1) and related inter- and intracellular proteins (CDH5, PAGE2B;2;5, HSPs, NGF and VEGFA) may constitute antigen targets.

Schizophrenia- or schizoaffective disorder diagnosis and the risk for subsequent type 1- or type 2 diabetes mellitus: a Swedish nationwide register-based cohort study

OBJECTIVES

The aim of this study was to examine the effect of schizophrenia or schizoaffective disorder on the risk of developing subsequent type 1 (T1)- or type 2 (T2) diabetes mellitus (DM), by carrying out a Swedish register study.

MATERIAL & METHODS

Data from the Total Population- and Medical Birth- Registers were used to create a cohort of all individuals born in Sweden 1987-2004. The cohort individuals were linked with the Inpatient- and Outpatient-Registers and followed from birth to 2018 to identify onset of schizophrenia, schizoaffective disorder and DM. Cox proportional hazard models were applied to assess the associations between schizophrenia or schizoaffective disorder and risk for T1DM or T2DM during a follow-up from age 13.

RESULTS

The study population included 1 736 281 individuals and the length of follow-up was maximally 19.0 (median 10.6) years. The risk of developing T1DM was significantly higher among individuals with, than without, schizophrenia [adjusted hazard ratio (HR) (95% confidence interval (CI)): 2.84 (1.18-6.82), p=0.0195], whereas among individuals with or without schizoaffective disorder, the risk of developing T1DM did not differ [adjusted HR (95% CI): 1.23 (0.17-8.74), p=0.8377]. The risk of developing T2DM was significantly higher both among individuals with schizophrenia and schizoaffective disorder, than among those without such diagnoses [adjusted HR (95% CI): 13.98 (8.70-22.46), p<0.0001 and 14.27 (7.36-27.70), p<0.0001, respectively].

CONCLUSIONS

This study shows that schizophrenia is associated with increased risk for subsequent T1DM. It also shows that both schizophrenia and schizoaffective disorder are associated with increased risk for subsequent T2DM.

Type 1 diabetes mellitus and the risk for schizophrenia or schizoaffective disorder: a Swedish nationwide register-based cohort study

OBJECTIVES

Type 1 diabetes mellitus (T1DM), resulting from an immune-associated destruction of insulin-secreting pancreatic β-cells, has been reported in a few earlier studies to be inversely associated with schizophrenia, but not with schizophrenia-like psychoses. The aim of this study was to verify this finding by carrying out a Swedish register study.

METHODS

Data from the Total Population- and Medical Birth-Registers were used to create a cohort of all individuals born in Sweden 1987-2004. The cohort individuals were linked with the Inpatient- and Outpatient-Registers and followed from birth to 2017 to identify onset of T1DM, schizophrenia and schizoaffective disorder. Cox proportional hazard regression models were used to assess the association between T1DM and risk of developing schizophrenia or schizoaffective disorder during a follow-up from age 13.

RESULTS

The study population included 1 745 977 individuals and the length of follow-up was maximally 18.0 (median 9.7) years. During the follow-up, 1 280 individuals developed schizophrenia and 649 individuals schizoaffective disorder. The risk of developing schizophrenia was significantly lower among individuals with, than among individuals without, a diagnosis of T1DM, whereas the risk of developing schizoaffective disorder did not differ among individuals with or without a T1DM diagnosis [adjusted hazard ratio (95% confidence interval); schizophrenia: 0.29 (0.09-0.91), p=0.0338, schizoaffective disorder: 1.50 (0.71-3.16), p=0.2909].

CONCLUSIONS

This study, in line with previous studies, shows that a diagnosis of T1DM is associated with a decreased risk of schizophrenia. This finding of an inverse association between T1DM and schizophrenia may bring an interesting piece, related to autoimmunity, into the schizophrenia-aetiology puzzle.

Sequencing of the insulin receptor (INSR) gene reveals association between gene variants in exon and intron 13 and schizoaffective disorder

OBJECTIVES

From the hypothesis that an impaired insulin and insulin-like growth factor cellular signalling in brain and body might result in the development of schizophrenia or related psychoses, I in this study chose to thoroughly investigate the insulin receptor gene in patients with schizophrenia or schizoaffective disorder and controls.

METHODS

For identification of single nucleotide polymorphisms (SNPs) of interest in the insulin receptor gene, targeted whole gene sequencing of DNA using the SOLiD technology was first carried out in two subgroups of the study population: 1) 49 schizophrenia or schizoaffective disorder patients with heredity for schizophrenia or related psychoses, and 2) 25 controls. Ten possible SNPs of interest were identified and these were then typed by standard methods in the whole study population consisting of 105 patients with schizophrenia or schizoaffective disorder and 60 controls.

RESULTS

In comparisons between schizophrenia patients, schizoaffective disorder patients and controls, overall significant differences were found in genotype distribution and allele frequency for SNP rs2229431 in exon 13, and tendencies towards overall significant differences were found for SNP rs12610022 in intron 13, but not for the other 8 possible SNPs investigated. It was the patients with schizoaffective disorder who differed in genotype distributions and allele frequencies compared to both the patients with schizophrenia and the controls, whereas between the patients with schizophrenia and the controls, no significant differences were found.

CONCLUSION

The results of this study show that two gene variants in exon and intron 13 of the insulin receptor gene confer risk specifically for schizoaffective disorder.

Signs of impaired blood-brain barrier function and lower IgG synthesis within the central nervous system in patients with schizophrenia or related psychosis, compared to that in controls

OBJECTIVES

Evidence has accumulated that an inflammatory, possibly autoimmune-mediated, process in the central nervous system (CNS), and by way of an aberrant immune system, may underlie the development of schizophrenia. Therefore, the aim of this study was to evaluate patients with schizophrenia or related psychosis for blood-brain barrier (BBB) function and immunoglobulin (Ig)G synthesis within the CNS.

METHODS

Fifteen patients with schizophrenia or schizoaffective disorder and 12 controls were investigated using lumbar puncture and blood sampling. Cerebrospinal fluid (CSF) and serum/plasma (S/P) were analysed for albumin and IgG by standard laboratory methods, and the ratio of CSF-albumin to P-albumin (marker of BBB function) and the IgG index (marker of CNS IgG synthesis) were calculated. Additionally, the patients were assessed for clinical symptoms with the Positive and Negative Syndrome Scale for schizophrenia.

RESULTS

The ratio of CSF-albumin to P-albumin was higher and the IgG index was lower in patients than in controls (p=0.045 and p=0.001, respectively). Moreover, subgroup analyses showed that patients in partial symptom remission had higher ratios of CSF-albumin to P-albumin than patients in full symptom remission, and that patients with heredity for schizophrenia or related psychosis had lower IgG indices than patients without heredity.

CONCLUSIONS

In this study we show that patients with schizophrenia or related psychosis have impaired BBB function and lower IgG synthesis within the CNS, compared to controls. These findings support the view that a pathological process within the CNS, combined with an aberrant immune system, may underlie the development of schizophrenia.

Early-onset inguinal hernia as risk factor for schizophrenia or related psychosis: a nationwide register-based cohort study

OBJECTIVES

In an earlier interview study, we found that more men with familial schizophrenia had undergone inguinal hernia operation, than men with sporadic schizophrenia. However, there are no other studies published specifically on inguinal hernia and schizophrenia. Therefore, the aim of this study was to carry out a Swedish register-based cohort study on the association between inguinal hernia and schizophrenia or related psychosis.

METHODS

Data from the Total Population- and Medical Birth-Registers were used to create a cohort of all individuals born in Sweden 1987-1999 (n=1 406 168). The cohort individuals were linked with the In- and Out-patient Registers and followed from birth to 2015 to identify onset of schizophrenia, schizoaffective disorder and inguinal hernia. Cox proportional hazards regression models were used to assess the association between inguinal hernia before age 13 and risk of developing schizophrenia or schizoaffective disorder during a follow-up from age 13.

RESULTS

Inguinal hernia before age 13 was identified in 21 095 individuals, and during the follow-up in total 1314 individuals developed schizophrenia or schizoaffective disorder. The risk of schizophrenia or schizoaffective disorder was higher among individuals with inguinal hernia before age 13, than among individuals without such a diagnosis, especially among the men [adjusted hazard ratio (95% confidence interval); all: 1.44 (1.01-2.06), p=0.0452, men: 1.46 (1.01-2.12), p=0.0460, women: 0.56 (0.14-2.27), p=0.4173].

CONCLUSIONS

This study shows that early-onset inguinal hernia is associated with increased risk of developing schizophrenia or schizoaffective disorder, especially in men. Such an association may point to a common biological basis for the development of inguinal hernia and schizophrenia or related psychosis.

Higher serum concentrations of tyrosine and glutamate in schizophrenia patients treated with clozapine, compared to in those treated with conventional antipsychotics

RATIONALE

The effect of long-term treatment with the atypical antipsychotic clozapine on the serum amino acid profile in schizophrenia patients has not previously been studied.

OBJECTIVES

The aim of this study was to compare serum amino acid patterns in patients on long-term clozapine treatment with long-term conventional antipsychotic treatment, and their relationships to insulin resistance and antipsychotic serum concentrations.

METHODS

Thirty-three patients with schizophrenia or schizoaffective disorder on long-term treatment (mean 8.3 years) with clozapine (n=20) or conventional antipsychotics (n=13) were studied. Amino acids were quantified in fasting serum samples by ion exchange chromatography and markers of insulin resistance and antipsychotic drug concentrations were determined by standard methods.

RESULTS

Several amino acids, most notably tyrosine and glutamic acid, were elevated above the reference range in several patients receiving clozapine. Additionally, significantly higher mean values of tyrosine (1.5-fold, p=0.001), glutamic acid (2-fold, p=0.0005) and six other amino acids were observed in the clozapine group than in the conventional antipsychotic group. Several amino acids were related to insulin resistance in both treatment groups.

CONCLUSIONS

In this study, we show that serum tyrosine and glutamic acid concentrations are markedly elevated in patients on long-term clozapine treatment, compared to patients on long-term conventional antipsychotic treatment. These findings are of importance since these two amino acids have been implicated in the pathophysiology of schizophrenia.

Case report of a patient with schizophrenia and a mutation in the insulin receptor substrate-4 gene

This report deals with a female patient with schizophrenia who was found to have a mutation in the insulin receptor substrate-4 gene that is located on chromosome Xq22.3. Since this mutation is expected to change amino acid coding from histidine to tyrosine and cause an altered insulin receptor substrate-4 protein, and the insulin receptor substrate-4 protein may be involved in neuronal growth and function in the brain, it is possible that it is this insulin receptor substrate-4 gene mutation that underlies this patient's schizophrenia development.

Evidence for a negative association between schizophrenia and a polymorphism in the insulin receptor substrate-3 (IRS-3) gene

OBJECTIVES

Since there are clear indications that schizophrenia is a systemic disorder, we sought for a common molecular basis for schizophrenia abnormalities in brain and body. Our hypothesis was that an impaired insulin and insulin-like growth factor signalling in cells might underlie changes in both brain and body in schizophrenia. In this regard, the insulin receptor substrates 1-4, linking both the insulin and insulin-like growth factor-1 receptors with intracellular pathways, might be of interest to study genetically. In the present study, we chose to study the insulin receptor substrate-3 (IRS-3) gene as a candidate gene in schizophrenia.

METHODS

The IRS-3 gene of 93 patients with the diagnosis of schizophrenia according to DSM-IV criteria and 57 healthy control subjects was screened for DNA sequence variations, followed by case-control analyses of total 10 detected polymorphisms.

RESULTS

The A/G genotype of the single nucleotide polymorphism (SNP) rs117078492 in the IRS-3 gene occurred in 5.3% of the control subjects compared with in 0% of the patients (p=0.05). Similarly, the haplotypes 5 and 3X, constructed from polymorphisms in the IRS-3 gene and including the A allele of this A/G SNP, occurred only in the control subjects and not in the patients (5.3% vs 0%, p=0.05).

CONCLUSION

Our findings suggest that individuals carrying the A allele of this A/G SNP in the IRS-3 gene as well as the estimated haplotypes 5 or 3X including this A allele, have a protection against schizophrenia development.

Metabolic parameters and long-term antipsychotic treatment: a comparison between patients treated with clozapine or olanzapine

OBJECTIVES

This study was undertaken to examine if patients exhibit more pronounced metabolic abnormalities after 8-year treatment with clozapine or olanzapine than before, and also to investigate whether there exist any differences between long-term clozapine and olanzapine therapies regarding metabolic side- effects.

METHODS

Fifty psychiatric outpatients diagnosed with schizophrenia or schizoaffective disorder and on treatment with clozapine or olanzapine were studied during 8 years. Fasting blood or serum samples for glucose, lipids, prolactin and antipsychotic drug concentrations were analyzed. In addition, body mass index was calculated.

RESULTS

More patients treated with olanzapine compared with those treated with clozapine ended with their medication, in most cases because of diabetes mellitus and/or hyperlipidemia, during the 8-year follow-up. Also more patients treated with olanzapine compared with those treated with clozapine developed manifest diabetes mellitus during the 8-year period. Prolactin levels were higher in the patients treated with olanzapine compared with in those treated with clozapine at study start, but there were no differences in the other parameters between the treatment groups at study start. In the patients remaining on their medication all 8 years, the glucose level increased over time in the clozapine group, but not in the olanzapine group, whereas body mass index and lipids were unchanged over time in both treatment groups.

CONCLUSIONS

Our findings point to that both olanzapine and clozapine long-term treatments cause development of hyperglycemia and/or hyperlipidemia. Furthermore, olanzapine long-term treatment seems to more often lead to development of manifest diabetes mellitus than long-term treatment with clozapine.

The insulin receptor substrate-4 (IRS-4) gene and schizophrenia: no evidence for a main genetic factor, however one report of a single schizophrenia patient with a mutation

OBJECTIVES

Since there are clear indications that schizophrenia is a systemic disorder, we sought for a common molecular basis for schizophrenia abnormalities in brain and body. Our hypothesis was that an impaired insulin/ insulin-like growth factor signalling in cells might underlie both structural and functional brain changes and peripheral abnormalities in schizophrenia. No associations between polymorphisms in the genes for insulin-like growth factor 1 or its receptor and schizophrenia have been reported. However, the insulin receptor substrates 1-4 linking both the insulin and insulin-like growth factor 1 receptors with intracellular pathways have not been extensively studied in schizophrenia. In this study, we therefore chose to study the insulin receptor substrate-4 (IRS-4) gene as a candidate gene in schizophrenia.

METHODS

The IRS-4 gene of 93 patients and 59 control subjects was screened for DNA sequence variations, followed by case-control analyses of 10 detected single nucleotide polymorphisms.

RESULTS

No significant genotype, allele or haplotype associations were found with the schizophrenia illness. However, one female patient with paranoid schizophrenia had an IRS-4 gene mutation at position 107863596, resulting in a change in amino acid coding from histidine to tyrosine at position 879.

CONCLUSIONS

Although this study supports the view that the IRS-4 gene is not of major importance for the aetiology of the vast majority of schizophrenia cases, our finding of this single patient with schizophrenia and a mutation in the IRS-4 gene may point to that the insulin/ insulin-like growth factor signalling system in cells is still of interest in the future search for schizophrenia genes.

Association between body mass index and insulin receptor substrate-4 (IRS-4) gene polymorphisms in patients with schizophrenia

OBJECTIVES

The insulin receptor substrate-4 (IRS-4) protein is highly expressed in the hypothalamus that plays a main role in the regulation of body weight. Therefore, as overweight and obesity are more frequent in patients with schizophrenia compared to the general population, this study was undertaken to investigate potential associations between body mass index (BMI) or height and polymorphisms in the IRS-4 gene in schizophrenia patients and healthy controls.

METHODS

The IRS-4 gene of 93 patients and 59 controls was screened for DNA sequence variations, and then 10 detected single nucleotide polymorphisms (SNPs) were investigated in relation to BMI and height of patients and controls.

RESULTS

Mean BMI was higher in patients than in controls, whereas there was no difference regarding height. Significant associations were found between patients' BMI and genotypes of six SNPs (rs1801164, rs80131334, rs41307415, rs73253702, rs1801162, rs2073114) or a haplotype including these six SNPs. In contrast, no associations were found between BMI or height of controls, or height of patients, and the genotypes or haplotypes.

CONCLUSION

This study clearly demonstrates associations between BMI and IRS-4 variants in schizophrenia patients, but not in healthy controls, pointing to a possible involvement of IRS-4 in the control of body weight in schizophrenia.

Effect of antipsychotic-induced hyperprolactinemia on anthropometric measures, insulin sensitivity and lipid profile in patients with schizophrenia or related psychoses

OBJECTIVES

This study consisting of two subprojects was undertaken to evaluate the effects of hyperprolactinemia on cardiovascular disease (CVD) risk parameters such as anthropometric measures, insulin sensitivity and blood lipids in patients with schizophrenia or related psychoses on long term treatment with antipsychotics.

METHODS

In subproject Ι, 45 patients receiving the 2nd generation antipsychotics risperidone, clozapine or olanzapine were compared regarding prolactin (PRL), body mass index (BMI), insulin, homeostasis model assessment of insulin resistance (HOMA-IR) and blood lipids. In subproject Π, 24 patients receiving 1st or 2nd generation antipsychotics were investigated with diurnal profile of PRL and oral glucose tolerance test (OGTT).

RESULTS

Elevated PRL levels were found in about 45% of the patients and occurred more often in patients receiving risperidone or haloperidol, compared to patients receiving clozapine or olanzapine. In contrast, in subproject Ι, insulin and HOMA-IR were higher and high density lipoprotein cholesterol was lower in patients receiving clozapine or olanzapine, compared with patients receiving risperidone. However, PRL levels did not correlate to BMI, insulin, HOMA-IR or lipids in any of these three treatment groups. In subproject Π, OGTT showed impaired glucose tolerance in 25% and new-onset diabetes in 4% of the 24 patients investigated. Additionally, the PRL (median 24 h) levels correlated positively to the 2 h glucose level at OGTT (rs=0.42, p=0.04).

CONCLUSIONS

Our findings point to that hyperprolactinemia due to 1st and 2nd generation antipsychotics may decrease insulin sensitivity, whereas other mechanisms probably underlie insulin resistance induced by PRL-sparing antipsychotics such as clozapine and olanzapine.

Familial and sporadic schizophrenia: a comparison of somatic diseases and abuse in patients and their relatives

OBJECTIVE

Comparing schizophrenia patients on the basis of familial and non-familial forms of the illness provides a promising approach to the identification of genes involved in schizophrenia. The aim of this study was to search for somatic factors that discriminate between patients with and without a family history of schizophrenia and between their relatives.

METHODS

Ninety-five schizophrenia patients were structurally interviewed about mental and physical health and alcohol and substance use in themselves and their families. Besides this, complementary information was obtained from the patients' case records. Patients with (41%) and without (59%) a family history were then compared.

RESULTS

The main differences were found in the patients' relatives. Fewer patients with a family history, compared with patients without a family history, had relatives with cancer (p = 0.002). Conversely, there was a tendency towards that more patients with a family history, compared with patients without a family history, had relatives with cardiac infarction (p = 0.05).

CONCLUSION

The genetic risk associated with schizophrenia seems to cosegregate into a factor(s) that protects against cancer and possibly also increases the risk for cardiac infarction.

Serotonin receptor 2A gene polymorphisms and schizophrenia: association with family history, diagnostic subtype and height in patients

OBJECTIVES

The 102T/C single nucleotide polymorphism (SNP) in the 5-hydroxytryptamine receptor 2A (HTR2A) gene has been reported to be associated with schizophrenia. However, SNPs of the HTR2A gene other than the 102T/C have attracted only limited studies in relation to schizophrenia, and also on the whole SNPs of the HTR2A gene have been little studied in relation to clinical parameters in patients. Therefore, the aim of this study was to evaluate the impact of main functionally characterized SNPs of the HTR2A gene on both the schizophrenia and clinical parameters.

METHODS

Ninety-four patients with schizophrenia and 57 control subjects were genotyped for the -1438A/G, -783A/G, 102T/C and His452Tyr SNPs of the HTR2A gene. The four SNPs were then investigated in relation to the schizophrenia and clinical parameters.

RESULTS

No differences were found in genotype-, allele- or haplotype frequencies between schizophrenia patients and control subjects. However, the 452Tyr variant of the His452Tyr polymorphism occurred more often in patients with a family history of schizophrenia compared with patients without heredity (p=0.028). The 452Tyr variant was also more common in female patients with paranoid schizophrenia than in those with non-paranoid schizophrenia (p=0.018). Moreover, the male patients carrying the A/A or T/T genotypes of the -1438A/G and 102T/C polymorphisms were shorter than those carrying the G/A or C/T genotypes (p=0.007; p=0.006).

CONCLUSION

The present findings bring further support to the view that the -1438A/G, 102T/C and His452Tyr polymorphisms of the HTR2A gene are connected with a constitutive cellular change that causes susceptibility to schizophrenia.

Effects of the atypical antipsychotic clozapine on insulin release in vitro

OBJECTIVES

Treatment with the atypical antipsychotic clozapine is frequently associated with metabolic side-effects such as weight gain, lipid abnormalities and diabetes mellitus. Since insulin is a hormone that is involved in both the regulation of body weight, as well as in lipid metabolism and glucose regulation, an effect of clozapine on insulin secretion and/or on insulin action - at least in part - might explain its capability to induce these side-effects. The aim of this study was therefore to examine the influence of clozapine on insulin release in vitro.

METHODS

The effect of clozapine in three different concentrations, 10(-6), 10(-5) and 10(-4) M, was investigated on both basal (i.e. 3.3 mM glucose) and glucose-stimulated (i.e. 16.7 mM glucose) insulin release, using isolated rat islets of Langerhans.

RESULTS

The presence of clozapine in the concentrations of 10(-6), 10(-5) and 10(4 )M significantly increased basal insulin release compared to the control after 4 h (but not after 1 h) of incubation. As regards the glucose-stimulated insulin release, the presence of clozapine in the concentrations of 10(-5) and 10(-4) M, but not in that of 10(-6) M, significantly inhibited the glucose-stimulated insulin release compared to the control after both 1 and 4 h of incubation.

CONCLUSION

This study demonstrates that the atypical antipsychotic clozapine exerts dual effects on insulin release in vitro, through stimulating basal insulin release and inhibiting glucose-stimulated insulin release. Both these effects of clozapine on insulin release may contribute to its disadvantage inducing metabolic side-effects.

The atypical antipsychotics quetiapine, risperidone and ziprasidone do not increase insulin release in vitro

OBJECTIVE

In the light of the recent finding that the atypical antipsychotics clozapine and olanzapine have a stimulatory effect on basal insulin release in vitro, the influence on insulin release of three other atypical agents; quetiapine, risperidone and ziprasidone, was examined.

METHODS

The effect of each atypical antipsychotic in a concentration of 10(-6) M was investigated on both basal and glucose-stimulated insulin release from isolated rat pancreatic islets.

RESULTS

No difference in effect on insulin release was found for any of the three atypical antipsychotic substances compared to controls without antipsychotics, either in basal or in glucose-stimulated insulin release.

CONCLUSION

This study demonstrates that the main compounds of quetiapine, risperidone and ziprasidone do not increase insulin release from isolated pancreatic islets, which stands in clear contrast to what has been found previously for clozapine and olanzapine. Thus, atypical antipsychotics seem to differ in their effect on insulin release in vitro.

Differences in prolactin elevation and related symptoms of atypical antipsychotics in schizophrenic patients

OBJECTIVE

The aim of this cross-sectional study was to investigate the degree and frequency of prolactin (PRL) elevation and related symptoms in patients treated with 3 different atypical antipsychotics: clozapine, olanzapine, and risperidone.

METHOD

Twenty-eight patients receiving clozapine, 29 patients receiving olanzapine, and 18 patients receiving risperidone (all meeting DSM-IV criteria for schizophrenia, schizophreni-form disorder, or schizoaffective disorder) were studied. The median daily dose was 400 mg of clozapine, 10 mg of olanzapine, and 3 mg of risperidone. Fasting morning blood samples were analyzed for PRL, and the occurrence of hyper-prolactinemic symptoms in the patients was evaluated.

RESULTS

Elevated PRL levels were found in 16 (89%) of the patients receiving risperidone and in 7 (24%) of the patients receiving olanzapine, but in none of the patients receiving clozapine. In addition, there was a significant difference in median PRL level among the treatment groups (p < .0001), in that the PRL level was higher both in the patients treated with risperidone and in the patients treated with olanzapine, compared to those treated with clozapine. Moreover, hyperpro-lactinemic symptoms-menstrual disturbances, galactorrhea, impotence, oligospermia, and decreased libido-were reported in 8 (44%) of the risperidone-treated patients and in 1 (3%) of the olanzapine-treated patients, but in none of the clozapine-treated patients.

CONCLUSION

Treatment with risperidone was frequently associated with hyperprolactinemia and related symptoms, whereas the occurrence of PRL elevation and related symptoms was modest in patients receiving olanzapine and nonexistent in those receiving clozapine. Thus, atypical anti-psychotics in therapeutic doses differ with regard to effect on PRL secretion.

Clozapine and olanzapine, but not conventional antipsychotics, increase insulin release in vitro

This study was undertaken to examine the influence of conventional and atypical antipsychotics on insulin release in vitro, using isolated pancreatic islets and insulin-secreting INS-1 cells. The effect of the conventional antipsychotics haloperidol and zuclopenthixol, and the atypical agents clozapine and olanzapine in the concentration of 10(-6) M was investigated on basal and glucose-stimulated insulin release. Both clozapine and olanzapine increased basal insulin release, whereas zuclopenthixol inhibited glucose-stimulated release and haloperidol had no significant effect. In summary, clozapine and olanzapine, in contrast to conventional antipsychotics, increase basal insulin release. Interestingly, this stimulatory effect on insulin release in vitro may be supported by recent clinical findings, showing elevated insulin levels in patients being treated with clozapine or olanzapine.

Adverse Metabolic Effects Associated with Atypical Antipsychotics

Adverse metabolic effects, such as diabetes mellitus, lipid abnormalities and weight gain, have increasingly been recognised with the use of the newer, so-called atypical antipsychotic drugs. This article reviews the current literature in the field and attempts to answer the question of whether the atypical antipsychotics differ in their effects on glucose-insulin homeostasis and lipid metabolism. It also addresses how then to manage the use of the atypical antipsychotics that do interfere with these metabolic systems. Differences in effects of atypical antipsychotics on leptin levels are also summarised and put into context; bodyweight gain associated with atypical antipsychotics is reviewed elsewhere. In summary, there are no large controlled trials published quantifying the prevalence of adverse effects on glucose-insulin homeostasis and lipid metabolism in patients receiving atypical antipsychotics. Nevertheless, the published articles and case reports reviewed in this article give a fairly good view of those adverse effects occurring with clozapine, olanzapine and risperidone, whereas little data are available regarding quetiapine, ziprasidone and zotepine, and no data exist for amisulpride and aripiprazole. Estimated rankings of the atypical agents, based on the available literature, show that the relative risk of glucose intolerance/diabetes mellitus, hyperlipidaemia and hyperleptinaemia is highest for clozapine and olanzapine, moderately high for quetiapine, rather low for risperidone and lowest for ziprasidone. Since adverse metabolic effects of atypical antipsychotics may have a negative influence on both the antipsychotic treatment outcome as well as the physical health of the patient, these effects have to be recognised and adequately managed. In this review, recommendations for prevention and treatment of the adverse metabolic effects are outlined.

[Antipsychotic drugs can affect hormone balance. Weight gain, blood lipid disturbances and diabetes are important]

Hormonally related side effects of antipsychotic drugs, e.g. weight gain, hyperlipidemia and diabetes have come to the forefront in that the use of clozapine and new antipsychotics have increased. Hormones involved are prolactin, growth hormone (GH), insulin-like growth factor I (IGF-I), insulin and leptin. Patients treated with clozapine had lower levels of GH-dependent IGF-I than patients receiving classical antipsychotics. Patients treated with olanzapine had higher serum insulin levels than those receiving classical antipsychotics, indicating a probable influence of olanzapine on insulin secretion. In clozapine-treated patients the insulin levels correlated to the clozapine serum concentration, indicating a likely influence also of clozapine on insulin secretion. The gender difference, i.e. that women normally have higher leptin levels than men, was found in patients receiving classical antipsychotics, but not in patients treated with clozapine or olanzapine.

Different effects of antipsychotic drugs on insulin release in vitro

The aim of this study was to examine the influence of antipsychotic drugs on insulin release from pancreatic beta cells in vitro. The effect of seven antipsychotics (i.e. chlorpromazine, haloperidol, perphenazine, zuclopenthixol, clozapine, olanzapine and risperidone) in a concentration of 10(-6) M was investigated on basal and glucose-stimulated insulin release. Clozapine increased basal insulin release, whereas haloperidol inhibited glucose-stimulated release and the other five antipsychotics had no significant effects. A possible stimulatory effect of clozapine on insulin release may explain its ability to increase appetite and induce weight gain.

Hormonal evaluation in schizophrenic patients treated with neuroleptics

The aim of this study was to hormonally evaluate schizophrenic patients on long-term treatment with neuroleptics. Twenty-eight patients (14 men and 14 women) on long-term therapy with different neuroleptics were investigated. Blood samples for prolactin (PRL), growth hormone (GH) and insulin-like growth factor I (IGF-I) were measured, as well as gonadotropins and testosterone in the males. In addition, clinical signs and symptoms of the neuroleptic side effects were evaluated. Seven out of 14 women had elevated PRL and five of the six fertile women in this group had menstrual disturbances. Twelve of the l4 men had normal PRL levels, whereas two had slightly elevated PRL without related symptoms. Four patients had low IGF-I levels, which in one case was combined with elevated PRL. We conclude that PRL levels in schizophrenic patients on long-term therapy with neuroleptics are elevated in about 50% of the women and in 10-20% of the men. Furthermore, irrespective of PRL levels or other hormonal disturbances, some patients on long-term neuroleptic therapy show low IGF-I levels, pointing at a possible interference with neuroleptics on the hypothalamic-pituitary regulation of GH-dependent IGF-I secretion.

Prolactin-secreting pituitary adenoma in neuroleptic treated patients with psychotic disorder

Three patients with psychoses and concomitant prolactin-secreting pituitary tumours are described. Patients A and B had bipolar and schizoaffective disorders, respectively. They had both been treated with neuroleptics for 20 years before the prolactinomas were revealed. Patient C developed a paranoid psychosis after two years of continuous bromocriptine treatment for a pituitary tumour. In patient A the prolactin level was successfully normalized and a good antipsychotic effect was maintained by combined therapy with haloperidol and quinagolide but not bromocriptine. In patient B the prolactinoma was removed by surgery, in view of the serious nature of the psychotic disorder, to avoid psychotic relapse by treatment with a dopamine agonist. In patient C a good result was obtained with the combination of clozapine and bromocriptine. These case reports support the view that neuroleptics being dopamine antagonists and dopamine agonistic agents which are the primary treatment of prolactinomas can cancel out each other's effects. The combination of clozapine and quinagolide is recommended as the treatment of choice for most patients.