Genetic variants of increased waist circumference in psychosis.

OBJECTIVE: We examined whether established metabolic risk genetic variants in the population confer a risk for increased waist circumference in patients with schizophrenia spectrum disorders and also an association with schizophrenia spectrum disorders irrespective of waist circumference. PATIENTS AND METHODS: We analyzed the association in (i) a case-case model in which patients with schizophrenia spectrum disorder with increased waist circumference (≥80 cm for women and ≥94 cm for men) (n=534) were compared with patients with normal waist circumference (<80 cm for women; <94 cm for men) (n=124), and in (ii) a case-control model in which schizophrenia spectrum disorder patients with increased waist circumference or irrespective of waist circumference were compared with population-derived controls (n=494) adjusted for age, sex, fasting glucose, smoking, and family history of diabetes. RESULTS: Genetic variants in five genes (MIA3, MRAS, P2RX7, CAMKK2, and SMAD3) were associated with increased waist circumference in patients with schizophrenia spectrum disorder (P<0.046). Genetic variants in three other genes (PPARD, MNTR1B, and NOTCH2) were associated with increased waist circumference in patients when compared with control individuals (P<0.037). Genetic variants in the PPARD, MNTR1B, NOTCH2, and HNF1B were nominally associated with schizophrenia spectrum disorder irrespective of waist circumference (P<0.027). No differences in waist circumference between specific psychosis diagnoses were detected. CONCLUSION: Increased waist circumference in patients with schizophrenia spectrum disorder may be explained, in part, by increased metabolic risk gene burden, and it indicates a shared genetic susceptibility to metabolic disorder and psychosis per se. Along these lines, common metabolic risk genetic variants confer a risk for increased waist circumference in patients with schizophrenia spectrum disorders.

Melatonin receptor 1B gene associated with hyperglycemia in bipolar disorder.

Bipolar patients are at a higher risk of developing metabolic disorders. Cardiovascular morbidity and mortality is twice the rate reported in the population. Antipsychotic medication increases the risk of metabolic abnormalities. However, bipolar disorder and schizophrenia have a similarly increased mortality from cardiovascular causes of death, although bipolar patients medicate with antipsychotic drugs to a much smaller extent than schizophrenic patients. Bipolar disorder and schizophrenia share substantial genetic risk components; thus, increased metabolic abnormalities is hypothesized to be an effect of specific sets of metabolic risk genes, which might overlap with the metabolic risk genes in schizophrenia. This study reports that a functional genetic variant of MTNR1B, previously implicated in the impairment of glucose-stimulated insulin release also in schizophrenia, was associated with elevated fasting glucose levels in bipolar patients and controls. This finding suggests that the MTNR1B-dependent vulnerability for elevated fasting plasma glucose levels is shared between bipolar disorder and schizophrenia.