Substrate source utilization during moderate intensity exercise with glucose ingestion in Type 1 diabetic patients

Abstract

Substrate oxidation and the respective contributions of exogenous glucose, glucose released from the liver, and muscle glycogen oxidation were measured by indirect respiratory calorimetry combined with tracer technique in eight control subjects and eight diabetic patients (5 men and 3 women in both groups) of similar age, height, body mass, and maximal oxygen uptake, over a 60-min exercise period on cycle ergometer at 50.8% (SD 4.0) maximal oxygen uptake [131.0 W (SD 38.2)]. The subjects and patients ingested a breakfast (containing approximately 80 g of carbohydrates) 3 h before and 30 g of glucose (labeled with 13C) 15 min before the beginning of exercise. The diabetic patients also received their usual insulin dose [Humalog = 9.1 U (SD 0.9); Humulin N = 13.9 U (SD 4.4)] immediately before the breakfast. Over the last 30 min of exercise, the oxidation of carbohydrate [1.32 g/min (SD 0.48) and 1.42 g/min (SD 0.63)] and fat [0.33 g/min (SD 0.10) and 0.30 g/min (SD 0.10)] and their contribution to the energy yield were not significantly different in the control subjects and diabetic patients. Exogenous glucose oxidation was also not significantly different in the control subjects and diabetic patients [6.3 g/30 min (SD 1.3) and 5.2 g/30 min (SD 1.6), respectively]. In contrast, the oxidation of plasma glucose and oxidation of glucose released from the liver were significantly lower in the diabetic patients than in control subjects [14.5 g/30 min (SD 4.3) and 9.3 g/30 min (SD 2.8) vs. 27.9 g/30 min (SD 13.3) and 21.6 g/30 min (SD 12.8), respectively], whereas that of muscle glycogen was significantly higher [28.1 g/30 min (SD 15.5) vs. 11.6 g/30 min (SD 8.1)]. These data indicate that, compared with control subjects, in diabetic patients fed glucose before exercise, substrate oxidation and exogenous glucose oxidation overall are similar but plasma glucose oxidation is lower; this is associated with a compensatory higher utilization of muscle glycogen.

Whole-body glucose oxidation rate during prolonged exercise in type 1 diabetic patients under usual life conditions

“…Despite the administration of fruit fudge required by T1DM patients to avoid an excessive fall of glycemia, a very similar timedependent decrease in GLUox was observed in the two groups, which is in agreement with previous studies [64,65]. Similar GLUox values (and the contribution to total energy yield) were also observed between the controls and diabetic patients during shorter aerobic exercises (≤ 1-h duration) [31,41]. Indeed, increased extracellular glucose availability, does not translate into increased intracellular GLUox [37,40].…”

“…Undoubtedly, these experimental protocols allow to carefully control several parameters that are likely to affect metabolism. However, exercise metabolism under patients' usual life conditions (i.e., insulin doses and orally administered CHO) is less studied [36,41], particularly during prolonged exercises. In addition, although a time-dependent decrease in the wholebody CHO oxidation rate has been observed in healthy people [42][43][44][45][46][47][48][49][50], no mathematical equations have ever been proposed to describe this behavior.…”

Metabolic and hormonal response to intermittent high-intensity and continuous moderate intensity exercise in individuals with type 1 diabetes: a randomised crossover study

“…Glycogen consumption in the present study was comparable in IHE and CONT both in the muscle and the liver. As supported by previous studies [41,42], muscle glycogen was the most relevant fuel source in both exercise conditions (>50% of total energy yield, data not shown), independently of the prevailing insulin levels.…”

Sélection des substrats lors de l’exercice prolongé avec ingestion de glucides : études par traçage au 13C

“…De façon surprenante, alors que l'on sait ou que l'on soupçonne que la sélection des substrats et l'oxydation des glucides exogènes à l'exercice pourraient être modifiées chez des sujets dont la tolérance au glucose est compromise, peu d'études ont été conduites chez le su-jet obèse (Ravussin et al, 1980) et chez le sujet diabétique (Krzentowski et al, 1981;Riddell et al, 2000a;Robitaille et al, 2007). Il existe également peu de données systématiques sur l'effet du mode d'administration des glucides exogènes [bolus vs doses (Massicotte et al, 1996a) ; ingestion avant vs pendant l'exercice Caron et al, 2004;Krzentowski et al, 1984a) ; effet de la concentration de la solution ingérée (Jandrain et al, 1989;Jentjens et al, 2004bJentjens et al, , 2006Moodley et al, 1992)] sur leur oxydation.…”