Adiporon, an adiponectin receptor agonist acts as an antidepressant and metabolic regulator in a mouse model of depression

Abstract

Major depression is a psychiatric disorder with complex etiology. About 30% of depressive patients are resistant to antidepressants that are currently available, likely because they only target the monoaminergic systems. Thus, identification of novel antidepressants with a larger action spectrum is urgently required. Epidemiological data indicate high comorbidity between metabolic and psychiatric disorders, particularly obesity and depression. We used a well-characterized anxiety/depressive-like mouse model consisting of continuous input of corticosterone for seven consecutive weeks. A panel of reliable behavioral tests were conducted to assessing numerous facets of the depression-like state, including anxiety, resignation, reduced motivation, loss of pleasure, and social withdrawal. Furthermore, metabolic features including weight, adiposity, and plasma biological parameters (lipids, adipokines, and cytokines) were investigated in corticosterone-treated mice. Our data show that chronic administration of corticosterone induced the parallel onset of metabolic and behavioral dysfunctions in mice. AdipoRon, a potent adiponectin receptor agonist, prevented the corticosterone-induced early onset of moderate obesity and metabolic syndromes. Moreover, in all the behavioral tests, daily treatment with AdipoRon successfully reversed the corticosterone-induced depression-like state in mice. AdipoRon exerted its pleiotropic actions on various systems including hippocampal neurogenesis, serotonergic neurotransmission, neuroinflammation, and the tryptophan metabolic pathway, which can explain its antidepressant properties. Our study highlights the pivotal role of the adiponergic system in the development of both metabolic and psychiatric disorders. AdipoRon may constitute a promising novel antidepressant.

Fig. 1. AdipoRon prevents excess weight gain, adiposity, and dyslipidemia in long-term corticosterone-treated mice.

a Schematic representation of the experimental protocol. b Gain of weight expressed as percent of weight values at the onset of the AdipoRon or vehicle treatment from the four groups of mice: vehicle (light gray symbols), corticosterone (cortico, dark gray symbols), cortico with AdipoRon (1 mg/kg, squares) or cortico without AdipoRon (vehicle, circles). Values plotted are mean ± sem. A Friedman statistical analysis was followed by a Dunn’s post hoc test; *P < 0.05 (N = 10 per group). c Weights of epididymal adipose tissue from control (light gray) and cortico-treated (dark gray) mice chronically treated with vehicle (−) or 1 mg/kg of AdipoRon (+). d Representative images of eosin-hematoxylin-stained epididymal adipose tissue from control (water) and cortico-treated (cortico) mice with or without AdipoRon administration for 3 consecutive weeks. Scale bar, 50 µm. e Quantification of the surface area of adipocytes expressed in mm², cells from five random fields containing about 100 cells/field were counted from four slices per mouse per group. Values plotted are mean ± sem; each symbol represents the mean of one mouse. f Concentrations of proinflammatory cytokines IL1β, TNFα, and chemokine MCP1 in epididymal fat tissue (expressed in pg/mg of total proteins) from control and cortico-treated mice ± AdipoRon administration. g–i Histograms showing the plasma concentrations of lipids (g; cholesterol, left; TG, right expressed in mM), adipokines (h; ApN, left, expressed in μg/ml; leptin, center, expressed in ng/ml; ratio leptin/ApN, right), and cytokines (i; IL1β, TNFα, and chemokine MCP1, expressed in pg/ml) from long-term cortico-treated mice ± AdipoRon administration. j Schematic representation of the Trp/Kyn pathway. k Histograms representing the relative plasma content of 5-HT, Trp, L-Lyn, KynA and the ratio KynA/L-Kyn and L-Kyn/Trp from control and cortico-treated mice ± AdipoRon administration. Experiments were conducted as described in SI-MM6. Means of data from vehicle-treated control mice were taken as 1. Values plotted are expressed as mean ± sem; N = 8–10 per group; Kruskal–Wallis statistical analysis was followed by a Dunn’s statistical test for comparison with the vehicle control group. ns non-significant; *P < 0.05, **P < 0.001, ***P < 0.001

Fig. 2. Antidepressant-like effects of AdipoRon assessed through behavioral tests on corticosterone-induced depressive-like mice.

a Schematic representation of the experimental protocol (SI-MM1). Five-week-old male mice were randomly distributed to the following groups for a 7-week period, i.e., vehicle (light gray symbols), cortico (dark gray symbols), cortico + AdipoRon (1 mg/kg, squares) or cortico – AdipoRon (vehicle alone, circles). As described in the SI-MM1 and SI-MM2, during the seventh week of treatment, mice were submitted to behavioral testing: the light and dark test (b), the sucrose preference test (c), the FST (d), the NSF test (e), the social interaction test (f) and the learned helplessness test from which latency data were extracted (g, h) and the number of failures to escape the aversive box (i). Values plotted were mean ± sem; each symbol represents a mouse (N = 10–12 per group); Kruskal–Wallis statistical analysis was followed by a Dunn’s statistical test for comparison between groups. ns non-significant; *P < 0.05; **P < 0.01; ***P < 0.001

Fig. 3. AdipoRon alleviates depression-related neuroinflammation and the Trp/L-Kyn pathway.

a Proinflammatory cytokines IL1β, IL6, TNFα, and INFγ were measured from the hypothalamus, the hippocampus and the prefrontal cortex using a multiarray assay from control (light gray) and cortico-treated mice (dark gray) chronically treated by vehicle (−) or 1 mg/kg AdipoRon (+). b The expression of genes that encode enzymes involved in the Trp/L-Kyn pathway, i.e., IDO1, IDO2, KAT1, KAT2, and KAT3 was assessed by quantitative PCR in the hypothalamus, the hippocampus and the prefrontal cortex from control and cortico-treated mice ± AdipoRon administration. Data are expressed as relative amount (means data from control vehicle-treated mice taken as 1) are expressed as mean ± sem. c Concentration of 5-HT and its metabolite 5-HIAA assessed using HPLC analysis from the dorsal raphe of control (light) and cortico-treated mice (dark) ± 1 mg/kg of AdipoRon as described in SI-MM7. Histograms are means ± sem of 5-HT (left) and 5-HIAA (center) concentrations expressed in pmol/mg of total protein and the ratio 5-HIAA/5-HT (right). N = 8 per group; Kruskal–Wallis statistical analysis was followed by a Dunn’s statistical test for comparison with the vehicle control group. ns non-significant; *P < 0.05; **P < 0.01; ***P < 0.001

Fig. 4. AdipoRon rescues neurogenesis in the dentate gyrus of the hippocampus of depressive-like mice.

a Representative immunohistochemical images depicting co-staining BrdU-labeled nuclei (green) and DCX- (left, red) or NeuN-positive neurons (right, red). Upper panel: ×10 magnification bar, 100 μm; Lower panel: ×60 magnification bar, 10 μm. b Representative immunohistochemical images depicting BrdU-labeled nuclei (black, insert) of dentate gyrus slices from brains of vehicle-treated (upper) or chronically cortico-treated (lower) mice treated with AdipoRon (right) or vehicle (left). c BrdU (50 mg/kg of body weight) was injected three times, 3-h apart one day before sacrifice to examine the effects on neuronal proliferation after 7 weeks of cortico treatment ± AdipoRon (1 mg/kg/day). d BrdU was administered daily during the cortico treatment for 5 consecutive days prior the initiation of a 3-week period of treatment ± AdipoRon to assess for neuronal survival. Experiments were conducted as described in SI-MM3. Data represent the number of BrdU-positive nuclei counted in the dentate gyrus from the four groups of mice. Values plotted are mean ± sem; each symbol represents a mouse. e Dentate gyri were micro-dissected from hippocampus from long-term cortico-treated mice ± AdipoRon administration. The level of expression for genes involved in synaptic maturation, i.e., BDNF, VEGFα, IGF1, and NGF was determined by quantitative PCR. Histograms are means ± sem expressed as fold-change compared to vehicle control group. N = 8/group; Kruskal–Wallis followed by a Dunn’s post hoc test for comparison with the vehicle control group; ns non-significant, *P < 0.05, **P < 0.01