Diabetes mellitus in Burmese cats

Rose Lederer (2010). Diabetes mellitus in Burmese cats PhD Thesis, School of Veterinary Science, The University of Queensland.

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Author Rose Lederer
Thesis Title Diabetes mellitus in Burmese cats
School, Centre or Institute School of Veterinary Science
Institution The University of Queensland
Publication date 2010-03
Thesis type PhD Thesis
Supervisor Dr. Judy E. Seton
Total pages 227
Total colour pages 21
Total black and white pages 206 (including black and white photographs)
Abstract/Summary Abstract The frequency of diabetes mellitus was estimated for cats that received veterinary care from two large feline-only clinics in Brisbane. Frequency was estimated using period prevalences - the proportion of the population at risk that was affected by diabetes at any point during a specified time period. Of the 12,576 study cats, 93 were affected with diabetes during the 5-year study period, resulting in a 5-year period prevalence of 7.4 cats per 1,000 cats. Period prevalence was significantly higher in Burmese cats (22.4 cats per 1,000) than domestic short and longhaired cats (7.6 cats per 1,000) and the mean age at first diagnosis during the study period was significantly higher amongst Burmese cats (13.6 years) compared to domestic short and longhaired cats (10.9 years). The risk factors for the development of diabetes mellitus in Burmese cats were investigated by interviewing the owners of 33 randomly selected diabetic Burmese cats and 33 age and gender matched non-diabetic Burmese cats from South East Queensland, Australia, and examining their medical files. The most consistent effect on the probability of diabetes was the knowledge of a relative affected by diabetes, with an Odd’s ratio (OR) of 57. The prior occurrence of two or more clinical diseases in any cat was also a strong risk factor for the development of diabetes (OR=45). Prior treatment with two or more corticosteroids was a strongly predisposing factor (OR=13). Cats fed on a diet that contained more than 20% of fresh food were much less likely to be diabetic (OR=0.12). These findings are consistent with an underlying genetic predisposition to diabetes mellitus in Burmese cats, and provide evidence that diet, chronic or recurring diseases, and corticosteroids affect the occurrence of diabetes mellitus. Pancreas tissue from Burmese and non-Burmese cats (n=98) with and without a prior diagnosis of diabetes was examined light microscopically for any pathological features that might have an influence on islets, such as pancreatitis, increased incidence or severity of islet amyloidosis, fibrosis, neoplastic processes or decreased islet density. All diabetic as well as most non-diabetic Burmese (9/14, 65%) and non-Burmese (49/54, 91%) cats in this study showed some form of pancreatic pathology. Pancreatitis, although present in 33% of cats (32/98), did not appear to be related to diabetes (P=0.58). The probability of amyloid infiltration in islets was significantly higher (P<0.001) in diabetic cats (26/30, 87%) when compared to non-diabetic cats (31/65, 48%), and increased significantly (P<0.05) with increasing age. The proportion of amyloid showed a significant effect of diabetic status (P<0.001) and of breed (P<0.05), such that diabetic cats had a higher proportion whereas Burmese cats had a lower proportion of amyloid. Vacuolation of islet cells was similarly more likely in diabetic cats (29/30, 97%) than in non-diabetic cats (54/66, 82%; P=0.01). Almost all cases with severe islet vacuolation that were stained with PAS for glycogen did contain glycogen, but none of the small number of samples examined with Oil Red O stained positive for lipids. There was evidence of compensatory islet growth in diabetic cats, average islet size being about 50% greater in diabetic cats (P<0.01). There was no significant effect of diabetic status or breed on the density of islets. The majority of pancreas tissue samples (n=95) examined for pancreas pathology were subsequently examined using immunohistochemical staining for insulin and amylin in order to compare Burmese and non-Burmese cats’ insulin and amylin (IAPP) producing areas. For each cat, the arithmetic mean of the proportion of each of five fields (×200) that was composed of insulin-producing and amylin-producing beta-cells was calculated. Insulin and amylin immunoreactivity was seen in islets as well as in single extrainsular cells. Insulin and amylin producing areas were significantly reduced in diabetic cats compared to non-diabetics. The proportion of insulin and amylin was significantly affected by diabetes (P<0.001), but not by breed. The multiple model predicted that the mean square root-transformed proportions of insulin and amylin would be 49% and 22% respectively higher in non-diabetic cats than in diabetic cats. Insulin and amylin producing areas were not different in Burmese than in cats of other breeds, but were significantly decreased in diabetic cats. The electron microscopic appearance of islet amyloid and associated cell damage in a diabetic Burmese cat was examined and described. Non-branching single-strand amyloid fibers were about 100 nm long, and were often arranged in parallel forming larger fibrils of several m. These fibers were co-localised with areas of pancreatic cell destruction and caused insulation of vessels. Fasting glucose, insulin, baseline glucose to insulin ratio, non-esterified fatty acid (NEFA), total cholesterol and triglyceride levels were examined in 12 clinically healthy, lean, client-owned Burmese and 9 non-Burmese cats. Median plasma glucose concentration was significantly (P<0.05) higher in Burmese cats (6.8 mmol/l) than in non-Burmese cats (4.7 mmol/l). There was no significant effect of gender on plasma glucose concentration (P=0.426). Serum cholesterol concentration differed significantly (Burmese 4.28  1.20 mmol/l SD, non-Burmese 3.14  0.57 mmol/l SD; P = 0.017), as did serum NEFA concentration (Burmese 0.782  0.22 mmol/l SD, non-Burmese 0.574  0.18 mmol/l SD; P=0.034). G0/I0 tended to be higher (P=0.052) in female neutered cats (median = 0.977) than in male neutered cats (median = 0.389). This small study showed that fasting glucose, cholesterol and (NEFA) concentrations were significantly higher in Burmese cats than in domestic shorthaired cats, suggesting that they have distinctive glucose and lipid metabolism. Glucose and lipid metabolism were examined and compared in 8 clinically healthy Burmese and 8 age, gender and body condition score- matched non-Burmese cats using a simplified glucose tolerance test (SGTT). Area under the curve (AUC) was calculated for glucose, insulin, leptin and NEFA. Burmese cats had significantly higher glucose concentrations before and during most of the glucose tolerance test compared to non-Burmese cats (P≤0.05). Six of the eight Burmese cats finished the test at 120 minutes with glucose values greater than the highest glucose value of non-Burmese cats (10.1 mmol/l). Burmese cats also had a tendency for increased baseline insulin (P=0.088) and 120 min insulin concentrations (P=0.059), significantly lower insulin AUC (P=0.042) and significantly higher leptin AUC (P=0.0472). Some changes were more evident in older Burmese, such as greater differences in baseline glucose values between older Burmese cats and their non-Burmese matches (P=0.014) and significantly higher baseline insulin concentrations (P=0.042). It was concluded that Burmese cats in this study had impaired glucose tolerance, and there might be decreased insulin sensitivity in older Burmese cats.
Keyword diabetes mellitus, Burmese cats, pancreas, amyloid, pancreatitis, glucose tolerance, dyslipidaemia
Additional Notes pages xx, 72-76, 80-82, 85, 86, 97-101, 103, 103-107 There are black and white photographs on pages 110-119

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Created: Sat, 30 Apr 2011, 23:13:30 EST by Ms Rose Lederer on behalf of Library - Information Access Service