Is diffuse energy distribution considered in the galaxy rotation curve explanations?
You appear to be asking whether gravitational potential energy acts as a significant contributor to the total mass-energy of a galaxy - a question that is only relevant within the context of General Relativity, where indeed other forms of energy besides the rest-mass energy contribute to the gravitational effects.

It turns out that GR is not required to interpret galaxy rotation curves because the influence of the other forms of mass-energy (or more formally, other contributors to the stress-energy tensor) are very small. 

The contribution of gravitational potential energy can be assessed using the ratio $GM/rc^2$, which is approximately the ratio of gravitational potential energy to rest mass energy. For example, if $10^{12}$ solar masses exists within a 100 kpc radius (reasonable numbers for the Milky Way); then the ratio is $5\times 10^{-7}$. Of course, if there is no dark matter then this would be even smaller.

I should also add that this tiny correction, like the gravitational potential energy, is negative. That is, it reduces the gravitational influence of the mass/energy in a galaxy. The (positive) total kinetic energy of the Galactic components (also tiny) would also need to be added, but since bound systems have a total energy (kinetic plus gravitational potential) $&lt;0$, there is still a net reduction in the gravitational mass.