Comparison of indices of islet B-cell function in type 2 diabetes in relation to insulin effectiveness and clinical outcome

Pathogenesis of feline diabetes mellitus

Cats are one of the few species that develop a form of diabetes mellitus that is clinically and histologically analogous to human type 2 diabetes mellitus. Figure 9 summarizes the etiologic factors thought to be involved in the development of feline and human type 2 diabetes. The main metabolic characteristics of type 2 diabetes mellitus are impaired insulin secretion and resistance to the action of insulin in its target tissues. Impaired beta cell function occurs before histologic changes become evident. The characteristic histologic finding in cats with type 2 diabetes is deposition of amyloid in pancreatic islets. Amyloid deposition occurs before the onset of clinical signs, but does not seem to be the primary defect. Pancreatic amyloid is derived form the recently discovered pancreatic hormone amylin. Amylin is synthesized in pancreatic beta cells, and is co-stored and co-secreted with insulin. Amylin has been postulated to be involved in the pathogenesis of feline diabetes mellitus both through its metabolic effects, which include inhibition of insulin secretion and induction of insulin resistance, and via progressive amyloid deposition and beta cell degeneration. Increased amylin concentration has been documented intracellularly in cats with impaired glucose tolerance and in the plasma of diabetic cats, and supports the hypothesis that amylin is involved in the pathogenesis of type 2 diabetes. Obesity is a common finding in diabetic felines and is a contributing factor to the insulin resistance present in type 2 diabetes. Clinical signs of diabetes develop once total insulin secretion decreases to 20% to 25% of normal levels. Many diabetic cats have been treated successfully with oral hypoglycemics, but 50% to 70% of diabetic cats are insulin dependent. Based on histologic evidence, this is the result of extensive amyloid deposition and subsequent beta cell degeneration, rather than autoimmune destruction of pancreatic beta cells associated with type 1 diabetes. Alternative ways of treating type 2 diabetes currently are being investigated. Amylin antagonists recently have been proposed as a novel treatment to reverse the deleterious effects of excessive amylin concentrations. The gastrointestinal hormone glucagon-like peptide-1 may also prove useful in treating diabetic cats, because of its stimulatory effect on insulin secretion and synthesis, and the absence of significant hypoglycemic effect.

First-phase insulin response to intravenous glucose in cystic fibrosis patients with different degrees of glucose tolerance

The aim of our study was to determine whether first-phase insulin response to intravenous (i.v.) glucose could be used as a simple and rapid test to identify cystic fibrosis (CF) patients at risk to develop diabetes mellitus. Forty consecutive CF patients with normal fasting blood glucose values but with different degrees of glucose tolerance on the standard oral glucose tolerance test (22 with normal glucose tolerance, 16 with impaired glucose tolerance, 2 with diabetes mellitus) and 12 normal subjects, matched for age and body mass index, underwent an i.v. glucose bolus to evaluate early phase insulin release. When compared to the normal subjects, CF patients had significantly reduced basal (76 +/- 50 vs 108 +/- 30 pM/l, 2 p < 0.02) and glucose stimulated insulin levels (1 + 3 min insulin = 456 +/- 275 vs 951 +/- 170 pM/l, 2 p < 0.01). Early phase insulin release, however, did not differentiate between CF patients with normal and impaired glucose tolerance; also in the two diabetic patients insulin levels did not clearly differ from those observed in the other groups of CF subjects. In conclusion, first-phase insulin response may identify an impairment of B-cell function in CF subjects; however, it does not discriminate between different degrees of glucose tolerance, as determined by the oral glucose tolerance test and, therefore, it does not reliably identify those patients who will eventually develop overt diabetes mellitus.

A review of new developments in type 2 diabetes in human beings and cats

Cats appear to be one of the few non-human species that develop a type of diabetes mellitus analogous to human Type 2, or non-insulin-dependent diabetes mellitus (NIDDM). In this review, some current theories on diabetogenesis are discussed. In both cats and human beings, Type 2 diabetes is characterized by impaired insulin secretion due to a functional defect in pancreatic beta-cells, and insulin resistance. In both species, amyloid deposition occurs in pancreatic islets and is derived from the newly discovered pancreatic hormone islet amyloid polypeptide (IAPP), or amylin. Amylin also reduces insulin secretion and induces insulin resistance. Thus, the hypothesis of amylin being intimately involved in the pathogenesis of human and feline Type 2 diabetes appears justified. Obesity is a frequent concomitant problem in feline and human Type 2 diabetes and contributes to the insulin resistance characteristic of the disease.