The possible implication of the gasotransmitters NO and CO for the development of diabetes remains unresolved. Our previous investigations in rodents suggested NO being inhibitory, and CO stimulatory, to glucose-stimulated insulin secretion (GSIS). Here we studied the possible role of these gasotransmitters in both murine and human type 2 diabetes (T2D) by mapping the expression pattern of neural nitric oxide synthase (nNOS), inducible NOS (iNOS), constitutive heme oxygenase (HO-2), and inducible HO (HO-1) in isolated pancreatic islets. Two variants of obese murine diabetes with distinct phenotype, the db/db and the ob/ob mouse, were studied at the initiation of the diabetic condition. Plasma glucose and plasma insulin were recorded and β-cell expression levels of the different enzymes were measured with confocal microscopy and fluorescence intensity recordings. In human islets taken from nondiabetic controls (ND) and type 2 diabetes (T2D) the expression of the enzymes was analyzed by RNA-sequencing and qPCR. At the initiation of murine diabetes plasma glucose was slightly increased, whereas plasma insulin was extremely enhanced in both db/db and ob/ob mice. The β-cell expression of nNOS and iNOS was markedly increased over controls in db/db mice, known to develop severe diabetes, while it was very low in ob/ob mice, known to develop mild diabetes. HO-2 expression was unaffected in db/db and modestly decreased in ob/ob mice. HO-1 expression was slightly enhanced in ob/ob, but, in contrast, extremely enhanced in db/db mice, suggesting a counteracting, antidiabetic action by CO. Moreover, the diabetic pattern of highly increased nNOS, iNOS and HO-1 expression seen in db/db mice was also fully recognized in human T2D islets. These results suggest that increased expression of the NOS-enzymes, especially an early upregulation of nNOS, could be involved in the initial development of the severe diabetes of db/db mice as well as in human T2D. Hence, nNOS, iNOS and HO-1 might be regarded as interesting targets to take into consideration in the early treatment of a diabetic condition in different variants of T2D.