Amelioration of Both Central and Peripheral Neuropathy in Mouse Models of Type 1 and Type 2 Diabetes by the Neurogenic Molecule NSI-189

Abstract

While peripheral neuropathy is the most common complication of long-term diabetes, cognitive deficits associated with encephalopathy and myelopathy also occur. Diabetes is a risk factor for Alzheimer disease (AD) and increases the risk of progression from mild cognitive impairment to AD. The only current recommendation for preventing or slowing the progression of peripheral neuropathy is to maintain close glycemic control, while there is no recommendation for central nervous system disorders. NSI-189 is a new chemical entity that when orally administered promotes neurogenesis in the adult hippocampus, increases hippocampal volume, enhances synaptic plasticity, and reduces cognitive dysfunction. To establish the potential for impact on peripheral neuropathy, we first showed that NSI-189 enhances neurite outgrowth and mitochondrial functions in cultured adult rat primary sensory neurons. Oral delivery of NSI-189 to murine models of type 1 (female) and type 2 (male) diabetes prevented multiple functional and structural indices of small and large fiber peripheral neuropathy, increased hippocampal neurogenesis, synaptic markers and volume, and protected long-term memory. NSI-189 also halted progression of established peripheral and central neuropathy. NSI-189, which is currently in clinical trials for treatment of major depressive disorder, offers the opportunity for the development of a single therapeutic agent against multiple indices of central and peripheral neuropathy.

Figure 1

NSI-189 augments neurite outgrowth and mitochondrial function in adult rat DRG sensory neurons. A and B: Effect of NSI-189 on neurite outgrowth from normal neurons (n = 5–7 replicate cultures). C: Effect of NSI-189 on DRG neurons derived from a 3- to 4-month STZ-induced diabetic rat (n = 6–10 replicate cultures). D: Seahorse XF24 trace showing oxygen consumption rate (OCR) of neurons from diabetic rats treated for 24 h with 1.0 or 3.0 μmol/L NSI-189. The following drugs were added: oligomycin (oligo), carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone (FCCP), and rotenone + antimycin A (Rot+AA) . Basal respiration (E), maximal respiration (F), and spare respiratory capacity (G) derived from D (n = 6–7 replicate cultures). Data are mean ± SD. *P < 0.05, **P < 0.01 by one-way ANOVA, followed by the Dunnett post hoc test.

Figure 2

NSI-189 prevents PNS and CNS neuropathy in type 1 diabetic mice. A: Acquisition phase in the Barnes maze (day 5 of training, week 11 of diabetes and treatment). B: Memory retention (week 15 of diabetes and treatment). C: Short-term memory using the object recognition test after 16 weeks of diabetes. CA1 volume (D), CA3 volume (E), DG volume (F), MNCV (G), paw tactile 50% PWT (H), paw thermal response latency (I), paw IENF density (J), and nerve density in the corneal subbasal plexus (K) after 16 weeks of diabetes and treatment. C, control mice treated daily with vehicle; S, STZ mice treated daily with vehicle; SI, STZ mice with insulin pellet; SNSI, STZ mice treated daily with oral NSI-189. Data are mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001 by one-way ANOVA, followed by the Dunnett post hoc test (n = 8–10/group).

Figure 3

NSI-189 ameliorates CNS and PNS neuropathy in type 1 diabetic mice. A: Acquisition phase in the Barnes maze (day 5 of training, week 10 of diabetes, week 2 of treatment). B: Memory retention in the Barnes maze (week 16 of diabetes, week 8 of treatment). C: Short-term memory using the object recognition test after 16 weeks of diabetes. CA1 (D), CA3 (E), and DG (F) volume after 16 weeks of diabetes, 8 weeks of treatment. MNCV (G), paw tactile 50% PWT (H), paw thermal response latency (I), paw IENF density (J), and nerve density of the corneal subbasal plexus (K) after 16 weeks of diabetes, 8 weeks of treatment. C, control mice treated daily with vehicle; S, STZ mice treated daily with vehicle; SNSI, STZ mice treated daily with oral NSI-189. Data are mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001 by one-way ANOVA, followed by the Dunnett post hoc test, for panels A–F, J, and K. *P < 0.05, **P < 0.01, ***P < 0.001 vs. STZ + vehicle mice by repeated-measures ANOVA, followed by the Dunnett post hoc test, for panels G–I (n = 9–10/group).

Figure 4

Oral glucose tolerance test in db/db mice after 8 weeks of diabetes (A) and after 25 weeks of diabetes and treatment (B). C: Blood glucose levels for db/db mice with NSI-189 treatment starting at onset of diabetes. CA1 (D) and CA3 (E) volume and BrdU-positive cells (F) counted in the hippocampus after 26 weeks of diabetes and treatment. C, control mice treated daily with vehicle; CNSI, control mice treated daily with NSI-189; D, db/db mice treated daily with vehicle; DNSI, db/db mice treated daily with oral NSI-189. Data are mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001 against db/db + vehicle by repeated-measures ANOVA, followed by the Dunnett post hoc test, for panels A–C (n = 8–10/group). *P < 0.05, **P < 0.01, ***P < 0.001 by one-way ANOVA, followed by the Dunnett post hoc test, for panels D–F (n = 5–10/group).

Figure 5

NSI-189 prevents peripheral neuropathy in db/db mice. MNCV (A), paw tactile 50% PWT (B), paw thermal response latency (C), paw IENF density (D), and corneal subbasal nerve plexus density (E) after 26 weeks of diabetes and treatment. C, control mice treated daily with vehicle; CNSI, control mice treated daily with NSI-189; D, db/db mice treated daily with vehicle; DNSI: db/db mice treated daily with oral NSI-189. Data are mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001 by one-way ANOVA, followed by the Dunnett post hoc test (n = 8–10/group).

Figure 6

NSI-189 ameliorates CNS and PNS neuropathy in db/db mice. Hippocampal NeuN (A), PSD95 (B), synaptophysin (C), and BDNF (D) protein levels, and MNCV (E), paw tactile 50% PWT (F), and corneal subbasal plexus nerve length (G) after 24 weeks of diabetes, with NSI treatment for the last 16 weeks. C, control mice treated daily with vehicle; D, db/db mice treated daily with vehicle; DNSI, db/db mice treated daily with oral NSI-189. Data are mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001 by one-way ANOVA, followed by the Dunnett post hoc test (n = 8–10/group).