Except as herein provided, no trustee and no employee of the board of trustees shall have any direct interest in the gains or profits of any investment made by the board, nor as such receive any pay or emolument for the trustee’s and employee’s services. No trustee or employee of the board shall, directly or indirectly, for oneself or as an agent in any manner use the moneys of the system, except to make such current and necessary payments as are authorized by the board; nor shall any trustee or employee of the board become an indorser or surety or become in any manner an obligor for moneys loaned by or borrowed from the board.