Immunologic Effects of Metformin and Pioglitazone Treatment on Metabolic Syndrome and Multiple Sclerosis

Metabolic syndrome (MetS) is thought to influence several autoimmune diseases, including multiple sclerosis (MS). Anti-inflammatory effects of treatments used for MetS, such as metformin hydrochloride and pioglitazone hydrochloride, have been demonstrated, although clinical evidence supporting use of these treatments in MS is lacking.

To determine whether metformin and/or pioglitazone are associated with a reduction in disease activity as measured by brain magnetic resonance imaging in patients with MS and MetS and to evaluate the potential mechanisms underlying this anti-inflammatory effect.

A prospective cohort study was conducted from March 1, 2012, to December 30, 2014, at a private MS referral center among 50 obese patients with MS who also developed MetS. Twenty patients received metformin hydrochloride, 850 to 1500 mg/d, and 10 patients received pioglitazone hydrochloride, 15 to 30 mg/d; 20 untreated patients served as controls. Groups were comparable in terms of sex, age, body mass index, Expanded Disability Status Scale score, disease duration, annual relapse rate, and treatment status. Patients were followed up for a mean (SD) of 26.7 (2.7) months (range, 24-33 months).

Magnetic resonance imaging of the brain was performed at 6-month intervals, and the presence of new or enlarging T2 lesions or gadolinium-enhancing lesions was registered. Serum leptin and adiponectin levels were measured. The production of cytokines by peripheral blood mononuclear cells was assayed, as were regulatory T-cell numbers and function.

Of 50 patients, after 6 months of treatment, 20 patients with MS who were treated with metformin and 10 who received pioglitazone showed a significant decrease in the number of new or enlarging T2 lesions (metformin, 2.5 at study entry to 0.5 at month 24; pioglitazone, 2.3 at study entry to 0.6 at month 24), as well as of gadolinium-enhancing lesions (metformin, 1.8 at study entry to 0.1 at month 24; pioglitazone, 2.2 at study entry to 0.3 at month 24). Compared with controls, both treatments led to a decrease in mean (SD) leptin levels (metformin, 5.5 [2.4] vs 10.5 [3.4] ng/mL, P < .001; pioglitazone, 4.1 [0.8] vs 11.0 [2.6] ng/mL, P < .001) and increase in mean (SD) adiponectin serum levels (metformin, 15.4 [5.5] vs 4.5 [2.4] μg/mL, P < .001; pioglitazone, 12.6 [3.6] vs 4.8 [0.6] μg/mL, P < .001). Mean (SD) number of myelin basic protein peptide-specific cells secreting interferon γ and interleukin (IL)-17 were significantly reduced in patients receiving metformin compared with controls (interferon γ, 30.3 [11.5] vs 82.8 [18.8], P < .001; IL-17, 212.4 [85.5] vs 553.8 [125.9], P < .001). Patients treated with pioglitazone showed significant decreases in the mean (SD) number of myelin basic protein peptide-specific cells secreting IL-6 and tumor necrosis factor compared with controls (IL-6, 361.6 [80.5] vs 1130.7 [149.21], P < .001; tumor necrosis factor, 189.9 [53.4] vs 341.0 [106.0], P < .001). Both metformin and pioglitazone resulted in a significant increase in the number and regulatory functions of CD4+CD25+FoxP3+ regulatory T cells compared with controls (metformin, 6.7 [1.5] vs 2.1 [1.0], P = .001; pioglitazone, 6.9 [0.8] vs 3.0 [0.8], P = .001).

Treatment with metformin and pioglitazone has beneficial anti-inflammatory effects in patients with MS and MetS and should be further explored.