Except as to the rights of a member, retirant, or beneficiary, no trustee and no officer or employee of the board of any state retirement system shall have any interest, directly or indirectly, in the gains or profits of any investment made by the respective board. Nor shall any retirement system trustee, officer, or employee, directly or indirectly for himself or herself or as an agent, in any manner use the assets of the systems except to make such current and necessary payments as are authorized by the respective boards, nor shall any of them become an endorser or surety or, in any manner, an obligor for moneys loaned by or borrowed from any of the respective systems.