To conclude, we were able to demonstrate that in a NAFLD mouse model produced by STZ/HFD-32—and thus having a diabetic background—treatment with the R-Tf-D-LP4 peptide reduced blood glucose levels, increased the insulin content of islets, improved their quantity and size, and restored their morphology. The gene discussed is DLGAP4; the disease is metabolic dysfunction-associated steatotic liver disease.