Table 1.
Study characteristics for the primary outcome – indicators of dopaminergic neurotransmission.
| Study | Rodent | PD model | GLP-1 receptor agonist intervention | Outcome (unit of measurement) | Included/not included in meta-analysis with rationale |
|---|---|---|---|---|---|
| Zhang et al. 2019 | Mouse | MPTP (20 mg/kg/day i.p. for 30 days) | Simultaneous to PD-model induction:Semaglutide (25 nmol/kg every two days i.p. for 30 days);Liraglutide (25 nmol/kg/day i.p. for 30 days) | TH + neurons in the SNpc (cell count) | Yes – primary outcome within the study |
| Badawi et al. 2019 | Rat | Rotenone (3 mg/kg/day, s.c. for 10 days) | Following PD-model induction:Liraglutide (50 μg/kg/day s.c. for 16 days) | Striatal dopamine content (ng/mg of protein) | Yes – primary outcome within the study |
| Zhang et al. 2018 | Mouse | MPTP (20 mg/kg/day i.p. for 7 days) | Following PD-model induction:Semaglutide (25 nmol/kg every two days i.p. for 30 days);Liraglutide (25 nmol/kg/day i.p. for 30 days) | TH + neurons in the SNpc (% of non-PD vehicle control) | Yes – PD symptoms primarily caused by degeneration of dopaminergic neurons in the SNpc |
| TH + striatal optical density (% of non-PD vehicle control) | No – non-independent secondary study outcome | ||||
| Aksoy et al. 2017 | Rat | Rotenone (stereotaxical infusion of 3ug/ul in the left SNpc and the ventral tegmental area) | Following PD-model induction:Exenatide (30 ug/kg/day i.p. for 28 days) | No relevant outcomes | No – no relevant outcomes |
| Badawi et al. 2017 | Rat | Rotenone (3 mg/kg/day s.c. for 10 days) | Following PD-model induction:Liraglutide (50 μg/kg/day s.c. for 16 days) | Striatal dopamine content (ng/mg of protein) | No – non-independent secondary study outcome |
| TH + neurons in the SNpc (% of non-PD vehicle control) | Yes – PD symptoms primarily caused by degeneration of dopaminergic neurons in the SNpc | ||||
| Hansen et al. 2016 | Rat | 6-OHDA (stereotaxical infusion of 13.5 ug in the right medial forebrain bundle) | Following PD-model induction:Liraglutide (500 ug/kg/day s.c for 6 weeks) | TH + neurons in the SNpc (cell count) | Yes – primary outcome within the study |
| Harkavyi et al. 2008 | Rat | 6-OHDA (stereotaxical infusion of 8ug/4ul in the right medial forebrain bundle) | Following PD-model induction:Exendin-4 (0.5 ug/kg twice daily i.p. for 7 days) | Striatal dopamine content (pg/g of protein) | Yes – primary outcome within the study |
| Zhang et al. 2020 | Rat | 6-OHDA (stereotaxical infusion of 5uL in the right medial forebrain bundle) | Following PD-model induction:Exendin-4 (10 nmol/kg/day i.p. for 30 days) | Striatal dopamine content (pg/mg of protein) | No – non-independent secondary study outcome |
| TH + neurons in the SNpc (cell count) | Yes – PD symptoms primarily caused by degeneration of dopaminergic neurons in the SNpc | ||||
| Feng et al. 2018 | Mouse | MPTP (25 mg/kg/2h i.p. for 8 h) | Following PD-model induction:Liraglutide (25 nmol/kg/day i.p. for 6 days) | TH + density in the SNpc (optical density) | Yes – primary outcome within the study |
| Yuan et al. 2017 | Mouse | MPTP (25 mg/kg/day i.p. for 7 days) | Following PD-model induction:Liraglutide (25 nmol/kg/day i.p. for 7 days) | TH + density in the SNpc (optical density) | Yes – PD symptoms primarily caused by degeneration of dopaminergic neurons in the SNpc |
| TH + density in the striatum (optical density) | No – non-independent secondary study outcome | ||||
| Liu et al. 2015 | Mouse | MPTP (20 mg/kg/day i.p. for 7 days) | Simultaneous to PD-model induction:Liraglutide (25 nmol/kg/day i.p. for 14 days);Lixisenatide (10 nmol/kg/day i.p. for 14 days);Exendin-4 (10 nmol/kg/day i.p. for 14 days) | TH + neurons in the SNpc (cell count) | Yes – PD symptoms primarily caused by degeneration of dopaminergic neurons in the SNpc |
| TH + density in the striatum (optical density) | No – non-independent secondary study outcome |