Complex sentence: More than 500 (45 people per district) were be involved in the Torch Relay as the torchbearer, they came from the sports world: athletes (local, national, and international), coaches, and officials.
Split into simpler sentences: More than 500 people (45 per district) were involved in the Torch Relay as torchbearer. They came from the sports world: athletes (local, national, and international), coaches, and officials.