Plasma leptin concentrations are independently associated with insulin sensitivity in lean and overweight cats

Abstract

This study investigated relationships between plasma leptin, insulin concentrations, insulin sensitivity and glucose tolerance in lean and overweight cats. Leptin concentrations were measured in 16 cats during glucose tolerance tests before and after gaining weight, and after feeding a test meal in overweight cats. An important finding of this study is that in both lean (r=-0.79) and overweight (r=-0.89) cats, the higher the leptin concentrations, the more insulin resistant the cat, independent of the degree of adiposity. Leptin concentrations at baseline and after consuming a meal tended to be higher in overweight cats with glucose intolerance, compared to overweight cats with normal glucose tolerance, although the difference was not significant. After feeding the test meal to overweight cats in the early morning, plasma leptin concentrations initially decreased before subsequently rising to peak 15 h later, which coincided with late evening. The leptin peak occurred 9 h after the insulin peak following ingestion of the test meal. Importantly, this study suggests that increased leptin concentrations may contribute to the diminished insulin sensitivity seen in overweight cats. Alternatively, the compensatory hyperinsulinaemia found with insulin resistance in overweight cats could stimulate leptin production.

Fig 1.

Mean and standard deviation of plasma leptin (A), glucose (B) and insulin (C) concentrations during a glucose tolerance test in 16 cats before and after gaining an average of 44% body weight. Significantly (*P<0.05. **P<0.001) different from baseline concentration. Lean cats, —♦—; obese cats —□—.

Fig 2.

Linear regression between baseline plasma leptin concentrations and the insulin sensitivity index (S_I) in 15 cats after the removal of one inconsistant data point. The correlation coefficient was −0.77 (P<0.001) prior to controlling for the effect of body fat percent.

Fig 3.

Mean and standard deviation of plasma leptin (A), glucose (B) and insulin (C) concentrations during a meal response test in 16 obese cats. Significantly (*P<0.05, **P<0.001) different from baseline concentration.

Fig 4.

Mean and standard deviation of plasma leptin concentrations over 18 h during a meal response test in nine obese cats with normal glucose intolerance (NGT, —♦—) and in seven obese cats with impaired glucose tolerance (IGT, —□—). *Significantly different from baseline concentrations.