April 21, 2017

Hormone and Metabolite Levels in Diabetic and Nondiabetic Cats

In a recent study, researchers sought to shed light on the pathophysiology of feline diabetes mellitus by measuring levels of selected circulating hormones and metabolites in diabetic and nondiabetic cats.
By JoAnna Pendergrass, DVM
Diabetic and nondiabetic cats demonstrate similarities and differences in the levels of selected circulating hormones and metabolites, according to a study recently published in BMC Veterinary Research.
 
Feline diabetes mellitus (FDM) is a common endocrine disorder, yet its pathophysiology is not well understood. As in humans, obesity decreases insulin sensitivity in cats, increasing the risk for diabetes. Unlike in human type 2 diabetes, though, the role of other obesity-related changes (dyslipidemia, altered glucagon concentrations) in FDM pathophysiology is not yet clear.
 
Previously, researchers investigated correlations between feline obesity and circulating hormone and metabolite levels; results have been variable. For example, one study reported a positive correlation between leptin levels and feline obesity. Correlations between adiponectin levels and feline obesity, though, have been less consistent.
 
Study Design
Authors grouped 31 client-owned cats into 3 categories:
  • Lean (body condition score [BCS] ≤5/9): n = 10
  • Overweight (BCS ≥6/9): n = 11
  • Newly diagnosed diabetic: n = 10
 
Fasting blood samples were collected at baseline and study week 4 to measure levels of blood glucose, plasma insulin, liver enzymes, and circulating hormones and metabolites.
 
To maintain dietary consistency, all lean and overweight cats ate a standardized commercial diet for 2 weeks before baseline and a diabetic diet (high protein/low carbohydrate) from baseline to week 4. Diabetic cats ate their original diet until baseline; from baseline to week 4, they ate the same diabetic diet as the other cats and received insulin twice daily.
 
Statistical analysis was performed to determine between-group differences at baseline and week 4, within-group differences between baseline and week 4, and correlations between the variables.
 
Results
Weight and BCS
Mean weight and BCS were significantly higher for diabetic and overweight cats than for lean cats at 4 weeks; mean BCS for overweight and diabetic cats was 7/9.
 
Glucose, Insulin, Liver Enzymes
Compared with the other cats, diabetic cats had markedly higher blood glucose levels and markedly lower plasma insulin levels. Liver enzyme levels were generally similar between groups.
 
Triglycerides, Leptin
Triglyceride levels were significantly higher in diabetic cats than in the other cats at baseline, and levels were significantly higher in diabetic and overweight cats than in lean cats at week 4.
 
Leptin levels were significantly higher in diabetic and overweight cats than in lean cats at both time points, and they were positively correlated with BCS and triglyceride levels.
 
Adiponectin, Cholesterol, IL-12
Adiponectin levels were significantly lower in diabetic cats than in the other cats at baseline and week 4, and they were negatively correlated with BCS and triglyceride levels. Interestingly, cholesterol levels increased from baseline to week 4 in all groups, with no significant differences between the groups.
 
Interleukin- 12 (IL-12) levels remained similar between groups from baseline to week 4. Notably, though, diabetic cats demonstrated significantly decreased IL-12 levels from baseline to week 4; it is not known whether insulin therapy or diet caused this decrease.
 
Glucagon, Adropin
Glucagon levels were significantly higher in diabetic than in lean cats at baseline, suggesting glucagon’s role in FDM pathophysiology.
 
Levels of adropin, a newly discovered peptide hormone, were similar between groups at baseline. At week 4, adropin levels were significantly lower in diabetic than in overweight cats; whether this decrease was due to insulin therapy or diet is not known. Adropin levels and BCS were positively correlated.
 
Conclusions
Taken together, study results suggest that hypertriglyceridemia and hyperleptinemia are associated with feline obesity and FDM. Determining why adiponectin and adropin levels were lower in diabetic cats than overweight cats, despite similar body conditions and diets, will require further investigation.
 
 
Dr. JoAnna Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.

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