Age‐related analysis of insulin resistance, body weight and arterial pressure in the Zucker fatty rat

Abstract

The evolution with ageing of insulin resistance, body weight (BW) and mean arterial pressure (MAP) was studied in a group of Zucker fatty rats (ZFRs, n = 22), between 7 and 16 weeks of age, compared with an age-matched control group of Zucker lean rats (ZLRs, n = 22). The minimal model of glucose kinetics was applied to estimate glucose effectiveness, S G , and insulin sensitivity, S I , from insulinaemia and glycaemia measured during a 70 min intravenous glucose tolerance test. No correlation was found between S G and age in both ZFR and ZLR groups. No significant changes in mean S G between the two groups indicated no alteration of glucose-mediated glucose disposal. Estimates of S I from individual ZFRs were independent of age and, on average, showed 83% reduction (P < 0.001) compared with the ZLR group. Despite the lack of alteration of S I with age, the ZFR group showed an age-related increase of MAP, which correlated with increasing BW (r = 0.71 and P < 0.001). These results support the hypothesis that in our ZFRs, as a suitable genetic model of obesity and hypertension, insulin resistance is fully established at the age of 7 weeks and remains practically unaltered until at least the sixteenth week. An age-related increase in arterial pressure, observed in this strain, relates more properly to increasing BW, rather than insulin resistance. Development of hypertension with increasing age and BW may result from an enhanced insulin-mediated activity of the sympathetic nervous system, as observed in our previously reported study.

Exercise Training Prevents Age-induced Insulin Resistance in Rats: Effect on Circulating Catecholamines, Inflammatory Cytokines and Skeletal Muscle Glut4 Transporters

“…To understand the mechanisms underlying the impact of exercise on age-induced insulin resistance, serum levels of catecholamines, pro-inflammatory cytokines and TAC together with Glut4 mRNA expression level in skeletal muscles were assessed. The present data showed increased level of circulating catecholamines in aged animals, an effect that is supported by a previous report of Di Nardo's group [47] . The elevated levels of catecholamines could be explained by a significant reduction in catecholamines clearance from plasma [48] .…”

Carotid body function in aged rats: responses to hypoxia, ischemia, dopamine, and adenosine

“…The cardiovascular effects associated with aging are: a striking attenuation in the cardiac frequency in humans (Kronenberg and Drage 1973); no significant effect of age on resting HR of rats (Gordon 2008); and increase in blood pressure in both rats (Di Nardo et al 2009) and humans (Fleg et al 1995). In the present work, mean arterial blood pressure was lower in 24 months old rats than in young adults.…”

VO(dmpp)2 normalizes pre-diabetic parameters as assessed by in vivo magnetic resonance imaging and spectroscopy

“…Their mutation in the leptin receptor promotes the development of different pathological features such as obesity, steatosis, hyperinsulinemia, hyperlipoproteinemia, hyperphagia and a glucose intolerant profile [34,41]. This animal model was carefully chosen according to its pre-diabetic features, being very suitable to assess the therapeutic properties of the VO(dmpp) 2 compound under study.…”