Neurovascular Coupling Mechanism and Cognitive Function

This 12-week, double-blind, placebo-controlled trial will examine whether daily supplementation with the Lab4P probiotic can improve cognitive performance and metabolic health in overweight adults aged 18 to 40 with impaired glucose tolerance, a preclinical condition where blood glucose regulation is mildly disrupted. Seventy participants will be randomly assigned to receive either Lab4P or a placebo. The study will assess changes in memory, executive function, and processing speed, along with blood glucose control, cardiovascular function, cholesterol levels, body composition, and markers of inflammation. The study will also analyse changes in the gut microbiome and evaluate the safety and tolerability of the probiotic.

The goal of this pilot clinical trial is to test whether transcranial photobiomodulation (tPBM), a non-invasive brain stimulation technique using near-infrared light, can improve brain blood flow regulation (neurovascular coupling) and cognitive function in older adults. The main questions it aims to answer are: * Does tPBM enhance neurovascular coupling responses during memory and finger tapping tasks? * Are these improvements linked to better cognitive performance and lower levels of brain inflammation and oxidative stress? Researchers will compare an active tPBM treatment arm to a sham treatment arm to see if tPBM leads to measurable improvements in brain activity and cognitive function compared to no active stimulation. Participants will: * Receive either active tPBM or sham stimulation sessions for 4 weeks, every other day using a portable intervention device. * Complete questionnaires and an iPAD-based cognitive testing protocol * Complete memory and motor tasks while their brain activity is measured using non-invasive techniques: simultaneous functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG), transcranial doppler (TCD) flowmetry. * Retinal vessel reactivity will be measured during flickering light stimulus using a special camera (dynamic vessel analysis, DVA). * Provide blood samples to test for biomarkers of inflammation, oxidative stress and brain cell damage.