Effect of training on age‐related changes in plasma insulin and glucose

Abstract

SummaryThe purpose of the study was to determine whether 12 weeks of exercise training would affect plasma glucose and plasma insulin concentrations in young and older Standardbred mares. Eighteen healthy, unfit mares representing 3 age groups were used: young (Y = 6.8 ± 0.4 years; n = 6), middleaged (MA = 15.2 ± 0.4; n = 6), and old (O = 27.0 ± 0.2; n = 6). Pre-and post-training incremental exercise tests (GXT) were performed to measure plasma glucose and insulin concentration from immediately after, until 120 min postexercise. Training consisted of exercise 3 days/week (weeks 1-8) and 4 days/week (weeks 9-12) at a submaximal intensity (~60% of pretraining HR max ) for~30 min/day. Old mares had lower levels of glucose after the GXT when compared to Y and MA mares (P<0.05). There was also a timeby-age interaction (P = 0.003) in that, at 120 min post-GXT, glucose levels had not returned to pre-exercise values. Plasma glucose concentrations, in response to acute exercise, were not altered by training for any age group (P>0.05). Prior to exercise training, O mares had higher plasma insulin compared to Y and MA mares at 120 min postexercise (P<0.05), and insulin was also elevated in O mares compared to all other time points at 120 min post-GXT (P<0.05). Training resulted in increased plasma insulin concentrations at 120 min post-GXT in all age groups (P<0.05). In conclusion, age affected glucose and insulin responses to acute exercise prior to and after 12 weeks of exercise training. With regards to insulin, 12 weeks of exercise training resulted in a postexercise rebound hyperinsulinaemia, which may be related to an increased need for glycogen repletion in the muscle. These factors are important in considering the ability of an older horse to tolerate exercise.

Trends of hematological and biochemical values in the blood of young race horses during standardized field exercise tests

“…The tendency for a decrease in the plasma Glc concentration in consecutive phases of training was reported previously (Malinowski et al, 2002).…”

Effect of age and dietary carbohydrate profiles on glucose and insulin dynamics in horses

“…bolus of insulin (20 mU/kg bwt) (Humulin R). d Blood samples for glucose and insulin measurement were collected at 1, 2, 3, 4, 5, 6,7,8,10,12,14,16,19,22,23,24,25,27,30,35,40, 50, 60, 70, 80, 100, 120, 150, 180, 210 and 240 min postglucose administration.…”

“…These differences have been demonstrated in studies evaluating insulin responses to i.v. glucose challenge (aged: 22.0 AE 0.7 years; young: 7.3 AE 0.6 years) [7], oral glucose challenge (aged: 14.2 AE 0.5 years; young: 6.8 AE 0.4 years) [8] and to feeding (aged: 14.2 AE 0.5 years; young: 2.0 AE 0.1 years) [9].…”

Training-induced alterations in rump fat thickness and plasma leptin concentration in young mature and old Standardbred mares

“…In conclusion, age and training appear to alter the relationship between body composition and leptin, where leptin is not related to a change in body fat mass but has a more complex signal integration and role in overall energy homeostasis. It is clear from past studies of humans and horses that endocrine, immune and other systemic disruptions of the integrative physiological response to exercise occur with age and exercise training 20,[27][28][29][30] . Those alterations in the integration of multiple systems to meet the challenge of exercise may have implications for how the ageing horse's ability to perform exercise is assessed 20 .…”