Cats differ from other species in their cytokine and antioxidant enzyme response when developing obesity

Abstract

Objectives: Obese cats show many similarities to obese people, including insulin resistance and an increased diabetes risk. However, atherosclerosis and cardiovascular disease are not seen in cats. In people, they are associated with the development of an inflammatory response, which, we hypothesized, does not occur in cats. Design and Methods: Twenty neutered cats of equal gender distribution were allowed to gain weight by offering food ad libitum and were examined before and at 10, 30, 60, and 100% weight gain. All cats reached 60% of weight gain, 12 cats gained 100 % in 12 months. Results: Fat was equally distributed between subcutaneous and visceral depots. Insulin-independent glucose uptake increased and insulin sensitivity decreased with increasing adiposity. However, baseline glucose concentrations were unchanged suggesting a decrease in EGP. Inflammatory cytokines (Il-1, IL-6, TNFa) and catalase, superoxide dismutase, glutathione peroxidase did not change. Insulin, proinsulin, and leptin were positively and adiponectin negatively correlated with adiposity. Heat production increased with obesity, but became less when body weight gain was > 60 %. Conclusions: This indicates that metabolism adapts more appropriately to the higher intake of calories in the initial phase of obesity but slows at higher body fat content. This likely contributes to the difficulty to lose weight.

Metabolic Effects of Obesity and Its Interaction with Endocrine Diseases

“…In a longitudinal study of feline weight gain, although energy expenditure (measured as heat production during indirect calorimetry) increased with increasing body mass, the increase tapered off as the cats approached 100% gain over their lean body weight. 23 A previous study had also shown decreased energy expenditure per metabolic body size in obese compared with lean cats, 61 although the appropriate method of normalizing energy expenditure in animals with different body composition remains a matter of debate. 62,63 Additionally, a decreased caloric requirement for weight maintenance has been shown after weight loss programs in cats and dogs, suggesting an increase in metabolic efficiency that must be surmounted during the weight maintenance period.…”

“…Additionally, there was a statistically significant increase in glucose area under the curve at 60% weight gain or greater. 23 In an earlier study, expression of the insulin-dependent glucose transporter GLUT-4 in both muscle and fat was found to be lower in obese than in lean cats, 24 suggesting a possible mechanism for decreased glucose uptake.…”

“…1). 23 Traditionally, compensatory hyperinsulinemia has been thought to result from an increase in beta cell mass 31,32 ; however, decreased insulin clearance has been shown in obese, hyperinsulinemic dogs. 33 Of note, pharmacologic doses of glucose used in IVGTT in dogs and cats do not reflect the routine concentrations to which pancreatic beta cells are subjected after a meal.…”

“…This may be owing to the lack of concurrent changes in circulating inflammatory markers and cytokines in obese cats. 23 Adipose tissue in obese humans and rodents is infiltrated by macrophages with a proinflammatory phenotype. 75,76 TNF-a and IL-6 may be released either from these macrophages or from dysfunctional adipocytes, resulting in local and systemic elevations of inflammatory markers 76,77 and promotion of vascular lesions.…”

Translational value of animal models of obesity—Focus on dogs and cats

“…However, the role of inflammation in the development of obesity-induced insulin resistance has been discussed controversially in cats. Some studies, in fact, reported no changes in anti-oxidant enzymes' activity or inflammatory cytokines in obese cats (Hoenig et al, 2013;Jaso-Friedmann et al, 2008). Moreover, assays for the quantification of feline circulating cytokines and chemokines are currently not available or have not been validated appropriately.…”