Abstract
Schizophrenia is a major public health problem, affecting 1% of the population and accruing over $60 billion in healthcare costs annually for the United States. The physical and mental comorbidities associated with schizophrenia are extensive and pervasive, and contribute to the high rate of hospitalization, readmission, morbidity and mortality. Pharmacotherapy in the form of second generation antipsychotic drugs (SGAs), including quetiapine, is the primary treatment for schizophrenia; however, the growth in utilization of these medications has led to a simultaneous rise in the occurrence of weight gain and metabolic syndrome in this patient population. Vitamin D is essential in the normal functioning of the musculoskeletal system. However, its deficiency is prevalent. Vitamin D is involved in the pathology of mental illness, including schizophrenia. Furthermore, in recent years, it has also been suggested that an insufficient vitamin D status may be a risk factor for the development of metabolic syndrome. Increasingly, epidemiological studies have linked vitamin D status with various components of metabolic syndrome. The aim of this study was to examine the levels of the major circulating metabolite of vitamin D, serum 25(OH)D, as well as the mRNA transcripts of the vitamin D receptor (VDR), and the vitamin D metabolizing enzymes CYP24A and CYP27B in schizophrenic and bipolar patients that either gain weight or do not gain weight on the SGA, quetiapine. These findings were also correlated with basal metabolic index (BMI) and other metabolic risk factors. A high rate of vitamin D deficiency was found among this patient population. There was a significant negative correlation between serum 25(OH)D and both BMI and fasting glucose levels. There were no statistically significant differences between the relative levels of the mRNA transcripts for VDR, CYP24A and CYP27B; however, decreased relative expression of each transcript predicted a more favorable vitamin D outcome in each case. In conclusion, the results from this study demonstrate that patients who gain weight on the SGA quetiapine have significantly lower vitamin D levels compared to those who do not gain weight on the drug. A high incidence of vitamin D deficiency occurs in this patient population, which is already at an increased risk for morbidity and mortality. Vitamin D supplementation is not currently included in the standard care for mentally ill patients, but has the potential to be both an effective and inexpensive treatment for weight gain associated with the use of SGAs, including quetiapine.