You have two regression models:
Yi​=β0​+β1​Xi​+ui​

And
Yi∗​=α0​+α1​Xi∗​+ui

In the first model Y and X are in the original variables. In the second model Y is demeaned value of Y and X∗ is the demeaned value of X. How beta 0 is related to alpha 0? How beta1 is related to alpha1?