Although the following info came in a commercial publication selling supplements, it may have real substance to it (tho I have not checked the references). The supplements mentioned have been addressed on this site before. And tho the article concerns "diabesity" (and therefore, insulin), this forum seems the most appropriate.
Nutrition Science Review
Chromium improves glucose tolerance by taking 200 to 1,000 mcg of this essential trace mineral every day.
Chromium, Glucose Intolerance and ...