Metabolic syndrome and insulin resistance in schizophrenia patients receiving antipsychotics genotyped for the methylenetetrahydrofolate reductase (MTHFR) 677C/T and 1298A/C variants

Introduction

The metabolic syndrome and insulin resistance represent growing concerns related to atypical antipsychotic (AAP) use as their incidence in the schizophrenia population is two-to-four-fold higher than the general population.

Reduced methylenetetrahydrofolate reductase (MTHFR) activity, resulting in aberrant folate metabolism and hyperhomocysteinemia, has been linked to cardiovascular disease and is unstudied in relation to AAP associated metabolic complications.

Purpose

To examine the relationship between MTHFR, metabolic syndrome, and insulin resistance in schizophrenia subjects receiving AAPs for ≥12 months.

Methods

Fifty-eight subjects were included in this cross-sectional analysis and screened for the metabolic syndrome, insulin resistance and MTHFR 677C/T and 1298A/C genotype.

Results

Overall, 23 subjects (40%) met metabolic syndrome criteria. There were no differences in age, gender, race, or AAP exposure between genotype groups. For the 677 T allele carriers, 53% met metabolic syndrome criteria, compared to 23% in the CC genotype group, giving an OR=3.7, (95% CI=1.24–12.66, p=0.02). Thus, for T allele subjects, the risk was almost four times greater, despite similar antipsychotic exposure. Both waist circumference and MTHFR genotype significantly predicted insulin resistance (F=8.35, df=5, 51, p<0.0001), with these two terms interacting (F=8.6, df=2, p=0.0006) suggesting that TT subjects are at greater risk for insulin resistance with increasing central adiposity, which is independent of age, gender, BMI, or metabolic syndrome diagnosis.

Conclusion

Results should be taken cautiously due to the small sample size, but suggest the MTHFR 677C/T variant may predispose patients to AAP metabolic complications.