Alanylglutamine

Adults aged >65 face a higher risk of both Clostridioides difficile infection (CDI) and dementia. CDI in the elderly may exacerbate functional and cognitive impairments. Current CDI treatment options are limited. Alanyl-glutamine (AQ) is a dipeptide shown to decrease C. difficile toxin effects in vitro and in vivo.

We tested the potential benefits of AQ on the clinical outcomes and cognitive impairment in the aged mouse model of CDI treated at various timings of AQ and vancomycin treatment.

C57BL/6 retired breeder (9 mo) and aged (18 mo) mice were treated with AQ-supplemented water as a 2-wk pretreatment or continuously. The mice underwent a standard CDI protocol (VPI10463) and were treated, or not, with vancomycin. Disease severity was tracked for 14 d, then novel object recognition (NOR) tests for acute memory were performed. Hippocampal tissues were assayed for molecular markers.

NOR testing confirmed CDI-induced cognitive impairment (P = 0.0352). AQ pretreatment had mild neuroprotective effects during CDI. Mice treated with vancomycin and continuous AQ had better clinical scores and better memory performance than vancomycin controls (P = 0.0286). Continuous AQ treatment, when used alone or paired with vancomycin, offered protection against CDI-induced cognitive impairment. The mechanism of CDI-induced memory impairment remains unclear, but infected mice had elevated synaptobrevin-2 (P = 0.0396) and neural cell adhesion molecule (P = 0.008) compared with uninfected controls on day 14 post infection.

Our findings suggest that neuroinflammation and memory loss occur during CDI, which may be ameliorated by AQ supplementation. AQ supplementation may have both neurological and intestinal protective effects during CDI treatment.

Glutamine availability may be reduced in chronic diseases, such as type 2 diabetes mellitus (T2DM)-induced by obesity. Herein, the antioxidant, anti-inflammatory and lipid metabolism effects of chronic oral glutamine supplementation in its free and dipeptide form were assessed in ob/ob mice. Adult male C57BL/6J ob/ob mice were supplemented with L-alanyl-L-glutamine (DIP) or free L-glutamine (GLN) in the drinking water for 40 days, whilst C57BL/6J Wild-type lean (WT) and control ob/ob mice (CTRL) received fresh water only. Plasma and tissue (skeletal muscle and liver) glutamine levels, and insulin resistance parameters (e.g., GTT, ITT, insulin) were determined. Oxidative stress (e.g., GSH system, Nrf2 translocation), inflammatory (e.g., NFkB translocation, TNF-α gene expression) and lipid metabolism parameters (e.g., plasma and liver triglyceride levels, SRBP-1, FAS, ACC, and ChRBP gene expression) were also analyzed. CTRL ob/ob mice showed lower glutamine levels in plasma and tissue, as well as increased insulin resistance and fat in the liver. Conversely, chronic DIP supplementation restored glutamine levels in plasma and tissues, improved glucose homeostasis and reduced plasma and liver lipid levels. Also, Nrf2 restoration, reduced NFkB translocation, and lower TNF-α gene expression was observed in the DIP group. Interestingly, chronic free GLN only increased muscle glutamine stores but reduced overall insulin resistance, and attenuated plasma and liver lipid metabolic biomarkers. The results presented herein indicate that restoration of body glutamine levels reduces oxidative stress and inflammation in obese and T2DM ob/ob mice. This effect attenuated hepatic lipid metabolic changes observed in obesity.