Alican Uludag has been awarded several prizes for his reporting on corruption and Turkey's judiciary.
He was arrested at his home in Ankara in February. The charges, which also include spreading disinformation, are based on X posts.
"I criticized the relationship between the judiciary and politics," Uludag testified on Thursday.
"I would like to know what in that is criminal?"
After the interrogation, Uludag was granted conditional release.
Germany has dismissed the allegations as “baseless” and Reporters Without Borders described the arrest as “scandalous”.
Insulting the president was one of the criminal categories used in last year's trial of Swedish journalist Joakim Medin.
