Beta-cell Function and Metabolic Clearance Rate of Glucose in Patients with Major Mental Health Disorders on Antipsychotic Drug Treatment.

BACKGROUND

Insulin resistance and metabolic alteration continue to be essential features of major mental health disorders (MMHD) with poorly understood and multifaceted mechanisms. This study was carried out to provide information on insulin resistance, beta-cell function, metabolic clearance rate of glucose and their possible interplay with duration of antipsychotic use in patients with major mental health disorders.

METHODOLOGY

Plasma levels of glucose and insulin were determined in 124 patients with MMHD after an overnight fast and at 30 and 120 min of standard Oral Glucose Tolerance Test. Thereafter, indices of insulin resistance, beta-cell function and estimated metabolic clearance rate of glucose (eMCR) were calculated appropriately. Statistical analysis was done using ANOVA, Kruskal Wallis, independent Student's t-test and Mann-Whitney U. P-values less than 0.05 were considered as statistically significant.

RESULTS

Metabolic factors (fasting and postprandial glucose and insulin), indices of insulin sensitivity and β-cell function were not significantly different when patients with schizophrenia, bipolar and depression were compared with one another. Postprandial insulin level at 30 min (30 min PPI), estimated First and Second Phases of Insulin Release (eFPIR, eSPIR) were significantly lower in patients on atypical antipsychotic drugs [18.15 (3.57-40.35) μIU/ml), 617.63 (320.06-911.31) pmol/l, 180.30 (114.82-249.39) pmol/l] compared with patients on typical antipsychotic drugs [27.48 (13.33-47.68) μIU/ml, 767.69 (530.58-1198.35) pmol/l, 209.89 (154.01-310.97) pmol/l]. Furthermore, the mean waist circumference and body mass index were significantly higher in patients who have been on anti-psychotic drug for more than 10 years compared with patients with less than 5 years history of anti-psychotic use. eMCR of glucose progressively declined with increasing duration of antipsychotic use and it was significantly lower in patients who have been on antipsychotic drugs for more than 10 years [8.09 (5.90-9.44) ml.kg.min] compared with patients who have been on the drugs for less than 5 years [9.03 (7.47-10.04) ml.kg.min].

CONCLUSION

Patients on atypical antipsychotics seem to have insulin secretion phases consistent with β-cell dysfunction. Also, chronicity of antipsychotic treatment predisposes patients with major mental health disorders to central adiposity and low metabolic clearance rate of glucose, a forerunner of glucose intolerance.