Introduction to Feline Diabetes Mellitus

5. Introduction to Feline Diabetes Mellitus

Major Defects in Feline Diabetes Mellitus

Feline diabetes and human 2DM are pathophysiologically comparable endocrinopathies. When necessary for the understanding of underlying disturbances, reference to data from experimental models, mostly from rodents, will be made in this chapter.

The major defects in diabetic cats and 2DM humans are:

• Insulin resistance resulting in disturbed utilization of nutrients in insulin-sensitive tissues.
• Disturbed pancreatic beta-cell function, resulting in the abnormal release and lack of insulin and amylin.
• Deposition of pancreatic islet amyloid resulting from precipitation of amylin (islet amyloid polypeptide) (Figure 5).

Further defects will also be discussed in this paragraph. It is still debated whether the primary defect in 2DM or feline diabetes is disturbed beta-cell function or impaired insulin action. However, at the time of diagnosis both defects are usually present and contribute to the deterioration of the metabolic situation. Due to glucotoxicity, both defects also contribute to the self-perpetuation of the disease that usually can be observed.

Figure 5. Major physiological disturbances in feline diabetes mellitus.

Genetics and Feline Diabetes Mellitus

In human 2DM, genetics determining the predisposition of individuals to the development of 2DM are an area of intensive research. Several mutations and gene polymorphisms have been identified which are linked to an increased risk to develop 2DM in certain diabetic patients (for review, see e.g., Barroso, 2005; Malecki, 2005). However, it is clear that the massive increase in the occurrence of human 2DM is not the result of a major change in the genetic background but rather the result of life style changes such as abundance of food and lack of physical activity that make us more vulnerable to the development of obesity and subsequently 2DM. Hence, a previously beneficial genetic background may have deleterious effects in today’s life.

Studies on a possible role of genetic factors in the development of feline diabetes are far less advanced than in humans. Some cats may have an underlying predisposition for glucose intolerance because it was found that baseline insulin levels were higher while first phase insulin response and insulin sensitivity were lower in cats that developed a more severe reduction in insulin sensitivity when gaining body weight (Appleton et al., 2001b). Similar findings were reported by Wilkins et al. (2004). Further, at least some studies suggest a breed disposition for the development of feline DM with Burmese cats being at higher risk (Rand et al., 1997). Despite these indications for a possible role of genetic factors, nothing is known about the mode of inheritance and about the nature of the genes that could possibly be affected.