A novel cobiotic containing a prebiotic and an antioxidant augments the glucose control and gastrointestinal tolerability of metformin: a case report.

The gut microbiome plays an important role in regulation of metabolic processes, including digestion, absorption, and synthesis of bioactive molecules that signal physiological host mechanisms. Changes in the human gut microbiome are associated with type 2 diabetes and insulin resistance. Water-soluble dietary fibres like inulin and beta-glucan are fermented in the colon, and beta-glucan increases viscosity. Blueberries improve insulin sensitivity through an antioxidant effect. A cobiotic, consisting of purified inulin, sugar-free blueberry pomace extract, and an oat preparation of purified beta-glucan was developed for twice a day (bid) consumption as a smoothie drink to repair the gastrointestinal dysbiosis in type 2 diabetes. A 30-year-old man presented with new onset type 2 diabetes and a fasting glucose (FBS) of 375 mg/dl. Metformin 500 mg bid was initiated and increased to 1 g bid after 1 week. During the first 9 days of metformin treatment, he developed diarrhoea, but his FBS only dropped to 325 mg/dl. The cobiotic bid was added on the 9th day of metformin treatment, and after 2 days, his FBS dropped to 175 mg/dl. After 8 weeks on metformin and the cobiotic, his blood sugar was 100 mg/dl and he lost 5.5 kg. His stools became soft and formed on the cobiotic, reverted to diarrhoea when off of it for 2 days, and returned to normal on resuming the cobiotic formulation. Metformin is a safe, effective and inexpensive generic medication favouring weight loss, recommended as initial treatment of type 2 diabetes by the American Diabetes Association. However, a 20% incidence of diarrhoea limits its tolerability. A safe food supplement that can increase the efficacy of metformin and its tolerability, as occurred in this case report, would have significant positive public health consequences. A controlled clinical trial of the cobiotic with metformin is planned.