Predicting Conversion to Insulin Sensitivity With Metformin: A Promising Tool for Clinicians in Addressing Insulin Resistance and Improving Outcomes in Patients With Treatment Resistant Bipolar Depression.

BACKGROUND: Insulin resistance (IR) changes the trajectory of responsive bipolar disorder to a treatment-resistant course. A clinical trial conducted by our group demonstrated that IR reversal by metformin improved clinical and functional outcomes in treatment-resistant bipolar depression (TRBD). To aid clinicians identify which metformin-treated TRBD patients might reverse IR, and given strong external evidence for their association with IR, we developed a predictive tool using body mass index (BMI) and homeostatic model assessment-insulin resistance (HOMA-IR). METHODS: The predictive performance of baseline BMI and HOMA-IR was tested with a logistic regression model using known metrics: area under the receiver operating curve, sensitivity, and specificity. In view of the high benefit to low risk of metformin in reversing IR, high sensitivity was favored over specificity. RESULTS: In this BMI and HOMA-IR model for IR reversal, the area under the receiver operating curve is 0.79. At a cutoff probability of conversion of 0.17, the model's sensitivity is 91% (95% confidence interval [CI], 57%-99%), and the specificity is 56% (95% CI, 36%-73%). For each unit increase in BMI or HOMA-IR, there is a 15% (OR, 0.85; 95% CI, 0.71-0.99) or 43% (OR, 0.57; CI, 0.18-1.36) decrease in the odds of conversion, respectively. CONCLUSIONS: In individuals with TRBD, this tool using BMI and HOMA-IR predicts IR reversal with metformin with high sensitivity. Furthermore, these data suggest early intervention with metformin at lower BMI, and HOMA-IR would likely reverse IR in TRBD.

Treating Insulin Resistance With Metformin as a Strategy to Improve Clinical Outcomes in Treatment-Resistant Bipolar Depression (the TRIO-BD Study): A Randomized, Quadruple-Masked, Placebo-Controlled Clinical Trial.

Objective: Therapeutic options are limited for treatment-resistant bipolar depression (TRBD). Insulin resistance (IR) confers increased risk for TRBD. We investigated metformin, an insulin sensitizer, to reverse IR and improve clinical outcomes in TRBD.Methods: Using a random-assignment (1:1), intent-to-treat, 2-site, quadruple-masked, parallel-group (metformin to 2,000 mg/d or placebo) clinical trial design, patients with DSM-5 bipolar disorder (BD) type I or II and IR received study medication for 26 weeks (February 2016 to October 2019). The primary outcome was the change in depression rating scores (Montgomery-Asberg Depression Rating Scale [MADRS]) at 14 weeks between those who no longer met IR criteria (converters) and those who still did (non-converters). Additional outcomes included scores on the Global Assessment of Functioning (GAF); the Clinical Global Impressions Scale, Bipolar Disorders version (CGI-BP); and the Hamilton Anxiety Rating Scale (HAM-A) and maintenance of improved outcomes up to 26 weeks.Results: Forty-five BD patients were randomized to metformin (n = 20) or placebo (n = 25), and at 14 weeks or later, 11 subjects no longer met IR criteria (n = 10 with metformin, n = 1 with placebo; P = .0009). These converters experienced significant improvements in MADRS (P values ranged from .031 to .008) and GAF (P values ranged from .045 to .008) scores compared to non-converters beginning at week 6, sustained to week 26. HAM-A (P = .022 at week 14 and .019 at week 26) and CGI-BP change scores (P = .046 at 26 weeks) significantly favored converters over non-converters. Effect sizes were large for the MADRS and GAF (Cohen d > 1 at 14 and 26 weeks) and large for the HAM-A and CGI-BP at 26 weeks. Transient gastrointestinal side effects occurred under both treatment conditions.Conclusions: Pending replication, this early study suggests that reversal of IR by metformin offers a path out of TRBD. Further characterization of metformin converters with TRBD will prove informative.Trial Registration: ClinicalTrials.gov identifier: NCT02519543.