Table 2.

Advantages and disadvantages of different categories of type 2 diabetic animal models*.

Model category	Advantages	Disadvantages
(I) Spontaneous diabetic animals	Development of type 2 diabetes is of spontaneous origin involving genetic factors, and the features resemble human type 2 diabetes	Highly inbred, homogenous and mostly monogenic. Inheritance and development is genetically determined, unlike heterogeneity of humans
	Most inbred animal models are homogeneous and environmentally controlled, that allows easy genetic dissection	Limited availability and expensive. Mortality due to ketosis is high in animals with brittle pancreas (db/db, ZDF rat P. obesus, etc.), and it requires insulin in later stage for survival
	Variability of results is minimum and require small sample size	Require sophisticated maintenance
(II) Diet/nutrition induced diabetics	Develop diabetes with obesity due to over nutrition like diabesity syndrome of human	Mostly require long dietary treatment
	Toxicity of chemicals on other vital organs can be avoided	No frank hyperglycaemia develops upon dietary treatment in normal animals and hence unsuitable for screening antidiabetic agents on circulating glucose parameters
(III) Chemical induced diabetic animals	Selective loss of pancreatic beta cells (alloxan/STZ) leaving alpha and delta cells intact	Hyperglycaemia develops by cytotoxic action on the beta cells, leads to insulin deficiency rather than insulin resistance
	Residual insulin secretion help animals to live long without insulin treatment	Diabetes induced by chemicals is less stable and is reversible due to spontaneous regeneration of beta cells. Thus, care is required to assess beta cell function in long-term experiments
	Ketosis and mortality is relatively less	Chemically induced toxicity on other organs along with its cytotoxic action on beta cells
	Comparatively cheaper, easier to develop and maintain	Variability of results on development of hyperglycaemia is high
(IV) Surgical diabetic animals	Avoids cytotoxic effects of chemical diabetogenes on other organes	Involvement of cumbersome technical and post operative procedures
	Resembles human type 2 diabetes due to reduced islet beta cell mass	Occurrence of some digestive problems, due to excision of exocrine portion leads to the deficiency of amylase
		Dissection of alpha cells (secreting glucagon) along with beta cells leads to the counter regulatory response to hypoglycaemia
		Mortality is comparatively higher
(V) Transgenic/knock out diabetic animals	In vivo effect of single gene or mutation on diabetes can be investigated	Highly sophisticated and costly for production and maintenance
	Dissection of complex genetics of type 2 diabetes is easier	Expensive for regular screening experiments

*After [40].