Short-Term Detraining does not Change Insulin Sensitivity and RBP4 in Rodents Previously Submitted to Aerobic Exercise

Abstract

Elevated serum retinol binding protein 4 (RBP4) levels were previously described in insulin-resistance states. Exercise training can improve insulin sensitivity and RBP4, but the time-response effect of exercise detraining on RBP4 has not been studied. Thus, we examined the effects of exercise training and short-term detraining on insulin resistance, serum RBP4 levels, and GLUT4 expression in spontaneously hypertensive rats (SHR). Thirty-two male SHR, 4 months old, were submitted to 10-week treadmill training, 5 times/week or kept sedentary, followed by a 2- and 4-day detraining period. Body weight, insulin tolerance test, maximum speed in a maximal exercise test, serum RBP4 (ELISA), and epididymal fat GLUT4 expression (Western blot) were measured. Although all rats gained weight (43%, p=0.004) only the trained group showed a reduction (p<0.001) of epididymal fat weight. Detraining did not change these parameters. Exercise training increased insulin sensitivity (26%, p=0.001) and maximum exercise capacity (80%, p<0.001), benefits not lost after detraining. RBP4 levels were reduced in response to exercise training (45%, p<0.001); detraining did not change these benefits. Trained rats had increased GLUT4 expression (microsomal, ~226%; p<0.001 and plasma membrane, ~55%; p=0.011). A slight reduction in GLUT4 expression in the plasma membrane (~28%, p=0.041), but not in the microsomal fraction, was observed after 4 days of detraining. Exercise training is associated with reduced RBP4 levels, increased insulin sensitivity, and epididymal fat GLUT4 expression. Even short periods of detraining (4 days) were shown to be associated with reversal of higher plasma membrane GLUT4.

Transcriptome analysis of fasting caecotrophy on hepatic lipid metabolism in New Zealand rabbits

“…Studies have shown that RBP4 protein levels are positively correlated with TC and negatively correlated with HDL[50]. It is speculated that RBP4 enhances insulin resistance by regulating hepatic TC synthesis and VLDL release into blood, while RBP4 can affect fatty acid metabolism [51]. Disorders are closely related with insulin resistance.…”

Muscular glucose metabolism in middle-age trained rats

“…This translocation increases the intracellular entry of glucose. Hypertensive animals trained for 10 weeks showed an increased expression of GLUT-4 [37].…”

The effect of moderate endurance training on gastrocnemius retinol-binding protein 4 and insulin resistance in streptozotocin-induced diabetic rats

“…The results of this study showed that endurance exercise training reduces gastrocnemius RBP4 contents in STZ-diabetic rats. Intriguingly, it has been reported that a reduction in insulin resistance and serum RBP4 in spontaneously hypertensive rats following 10 weeks aerobic exercise training [ 19 ]. Besides, 7 weeks running on treadmill improved insulin sensitivity in diabetic rats by reducing RBP4 expression in extensor digitorum longus muscle, visceral and subcutaneous fat tissue [ 2 ].…”

“…Based on the above evidence, RBP4 reduces insulin-dependent glucose uptake in muscle tissue through reducing phosphoinositide-3-kinase activity and subsequent phosphorylation of the insulin receptor substrate-1 [ 12 ]. Apart from this, RBP4 resulted in downregulation of GLUT4 expression [ 19 ]. In this regard, a simultaneous reduction in gene expression of GLUT4 induced by 10 weeks running on treadmill has been attributed to increasing levels of RBP4 [ 19 ].…”

“…Apart from this, RBP4 resulted in downregulation of GLUT4 expression [ 19 ]. In this regard, a simultaneous reduction in gene expression of GLUT4 induced by 10 weeks running on treadmill has been attributed to increasing levels of RBP4 [ 19 ]. Furthermore, Graham et al.…”