Oral Galactose Provides a Different Approach to Incretin-Based Therapy of Alzheimer's Disease

Abstract

Incretin-based drugs originally developed for the treatment of type 2 diabetes mellitus are currently under investigation for their therapeutic potential in sporadic Alzheimer's disease (AD). Two major incretin hormones are glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP), which both additionally have neuroprotective, neurotrophic and neurogenesis-promoting effects upon the stimulation of GLP-1 and GIP receptors in the brain. This review points out another approach to the incretin-related sAD therapy based on the therapeutic potential of oral galactose in a streptozotocin-induced rat model of sporadic AD (STZ-icv model). Chronic oral galactose treatment prevents the development and ameliorates already developed cognitive deficits in the early stage of sAD-like pathology in STZ-icv rat model. The underlying mechanism(s) of these beneficial effects might be related to stimulation of endogenous GLP-1-mediated central effects and normalization of cerebral glucose hypometabolism as well as other oral galactose-induced effects along the oro-gastro-intestinal tract. The beneficial effects on cognitive impairment seem to depend on galactose exposure, presence and stage of sAD-like pathology. Further research is needed to clarify therapeutic potential and safety profile of oral galactose treatment as well as its possible advantages over or synergistic activity with the GLP-1 analogues and inhibitors of dipeptidyl peptidase-4.