Exploring the Therapeutic Potential of Benfotiamine in a Sporadic Alzheimer's-Like Disease Rat Model: Insights into Insulin Signaling and Cognitive function

Abstract

Alzheimer's disease (AD) is a complex neurodegenerative process, also considered a metabolic condition due to alterations in glucose metabolism and insulin signaling pathways in the brain, which share similarities with diabetes. This study aimed to investigate the therapeutic effects of benfotiamine (BFT), a vitamin B1 analog, in the early stages of the neurodegenerative process in a sporadic model of Alzheimer's-like disease induced by intracerebroventricular injection of streptozotocin (STZ). Supplementation with 150 mg/kg of BFT for 7 days reversed the cognitive impairment in short- and long-term memories caused by STZ in rodents. We attribute these effects to BFT's ability to modulate glucose transporters type 1 and 3 (GLUT1 and GLUT3) in the hippocampus, inhibit GSK3 activity in the hippocampus, and modulate the insulin signaling in the hippocampus and entorhinal cortex, as well as reduce the activation of apoptotic pathways (BAX) in the hippocampus. Therefore, BFT emerges as a promising and accessible intervention in the initial treatment of conditions similar to AD.

Keywords: cognitive decline; neurodegeneration; neuroprotection; streptozotocin; thiamine; vitamin B1.

Figure 1

Effect of 7-day-BFT treatment in the anxiety-like behavior of rats in 5 min of the open field test (OF). (A) Fecal boli count. (B) Groomings. (C) Time in the center (s). Results are presented as mean ± SD (n = 9–14).*p < 0.05.

Figure 2

Effect of 7 day-BFT treatment in the anxiety-like behavior of rat in 5 min of the elevated plus maze. (A) Open arm entries (%). (B) Time on open arms (%). (C) Fecal boli count. (D) Head dippings. (E) Time in the center (s). Results are presented as mean ± SD (n = 5–10). *p < 0.05.

Figure 3

Novel object recognition test. Recognition index (RI) for (A) short-term memory (STM) and (B) long-term memory (LTM). Discrimination ratio (DR) for (C) STM and (D) LTM. Results are presented as mean ± SD (n = 8–13). *p < 0.05; **p < 0.01; ***p < 0.001.

Figure 4

Effect of 7-day-BFT treatment in the levels of GluN2B detected by immunoblotting in the (A) hippocampus and (B) entorhinal cortex. Results are presented as mean ± SD (n = 5–7) *p < 0.05; **p < 0.01.

Figure 5

Effect of 7-day-BFT treatment in mRNA levels of brain-derived neurotrophic factor (BDNF) and TRKβ receptors in the (A and C) hippocampus and (B and D) entorhinal cortex. Results are presented as mean ± SD (n = 5–6). *p < 0.05; **p < 0.01.

Figure 6

Effect of BFT (50 μM, 24h) and STZ (5 mM, 29h) treatments on mitochondrial activity of neuroblastoma 2a (Neuro2a) cell line. (A) Routine respiration. (B) Leak respiration. (C) Electron transfer (ET)—Capacity is maximum respiratory capacity after addition of FCCP and (D) ROX and respiratory rate after electron transfer inhibition by antimycin. (E) The oxygen consumption rate linked to ATP production (OCR). Results are presented as mean ± SD (n = 8–9). *p < 0.05.

Figure 7

Effect of 7 day-BFT treatment in the levels of thiamine receptor (THTR-1) detected by immunoblotting in the (A) hippocampus and (B) entorhinal cortex. mRNA levels of THTR-1 in the (C) hippocampus and (D) entorhinal cortex. mRNA levels of mitochondrial THTR (mTPPTR) in the (E) hippocampus and (F) entorhinal cortex. Results are presented as mean ± SD (n = 5–11). *p < 0.05; **p < 0.01.

Figure 8

Effect of 7 day-BFT treatment in type 1 glucose transporters (GLUT1). (A) GLUT1 in the hippocampus detected by immunoblotting. (B) GLUT1 in the entorhinal cortex detected by immunoblotting. (C) mRNA levels of GLUT1 in the hippocampus. (D) mRNA levels of GLUT1 in the entorhinal cortex. Results are presented as mean ± SD (n = 4–7). *p < 0.05; **p < 0,0.1; **p < 0.001.

Figure 9

Effect of 7 day-BFT treatment in type 3 glucose transporters (GLUT3). (A) GLUT3 in the hippocampus detected by immunoblotting. (B) GLUT3 in the entorhinal cortex detected by immunoblotting. (C) mRNA levels of GLUT3 in the hippocampus. (D) mRNA levels of GLUT3 in the entorhinal cortex. Results are presented as mean ± SD (n = 4–7). *p < 0.05; **p < 0,0.1.

Figure 10

Effect of 7-day-BFT treatment in the protein levels of the insulin signaling pathway detected by immunoblotting. (A) Insulin receptor β subunit (IRβ) in the hippocampus and (B) in the entorhinal cortex. (C) p-IRS1_Ser636/639 in the hippocampus and (D) in the entorhinal cortex. (E) pAKT_Ser473/AKT in the hippocampus and (F) in the entorhinal cortex. (G) pGSK3_Ser21/9/GSK3 in the hippocampus and (H) in the entorhinal cortex. (I) pERK1/2_{Trh202/Tyr204}/ERK in the hippocampus and (J) in the entorhinal cortex. Results are presented as mean ± SD (n = 3–14). *p < 0.05; **p < 0,.1; ***p < 0.001; ****p < 0.0001.

Figure 11

Effect of 7-day-BFT treatment in the protein levels of the apoptotic pathway detected by immunoblotting. (A) Bcl-2 levels and (B) Bcl-2 mRNA in the hippocampus. (C) Bcl-2 levels and (D) mRNA in the entorhinal cortex. (E) BAX levels and (F) BAX mRNA in the hippocampus. (G) BAX levels and (H) mRNA in the entorhinal cortex. Results are presented as mean ± SD (n = 5–6). *p < 0.05; **p < 0.01; ***p < 0.001.

Figure 12

Experimental design. CMC = carboxymethylcellulose, BFT = benfotiamine, CTL = Control, STZ = streptozotocin, STZB = streptozotocin animals treated with benfotiamine, STM= short-term memory, LTM= long-term memory.