Measurement of postprandial incremental glucose and insulin changes in healthy dogs: influence of food adaptation and length of time of blood sampling

Variations in the blood glucose and insulin responses to different foods have been studied in dogs (Holste et al. 1989, Nguyen et al. 1994), and different trends in postprandial concentrations have been observed. These differences arose in the extent of the variations (areas under the curves and maximal increments) and the time from meal to peak increases. The main purpose of these studies was to rank foods on the basis of the incremental glucose responses that they produced and to relate these responses to foods characteristics. It is known that methodologic variables can markedly modify the interpretation of the glycemic response. In particular, this concerns the length of time of blood sampling (Gannon and Nuttall 1987), short-term (Wolever and al. 1988) and long-term (Cannon and al. 1980) remnant effects of the previous meal, blood sampling (Jackson and al. 1983) and fasting blood glucose values (Nielsen and Nielsen 1989). 
In dogs, the variations of the glycemic response have been evaluated with (Holste et al. 1989) or without (Nguyen et al. 1994) an adaptation period to the tested meals. As in human beings, the plasma concentrations were measured over a period of 3 or 4 h even though the gastrointestinal transit time is shorter in dogs than in humans. 
The purpose of our study was to examine whether an adaptation time (inducing digestive changes and modifications in basal insulin secretion and glucose tolerance) modifies the postprandial response to meal feeding in normal dogs. We also studied the effect of length of time of blood sampling on the consistency of the response value expressed by the areas under the glycemic and insulin curves, the peak incremental values and the times from meal to peaks.