SLC6A8 and hyperinsulinemic hypoglycemia, familial, 4: By contrast, in patients with SLC6A8 deficiency, supplementations with creatine and its precursors arginine or glycine, though improving muscular signs, were found to be without substantial benefit on cognitive and psychiatric signs, and failed to modify the creatine signal in 1H-MRS imaging of the brain [48], suggesting the inefficacy of these supplementations in improving brain as stated by other studies [4,19,30,49-52].