Abstract
Separately, polyphenols and exercise are known to prevent insulin resistance (IR) but their combined curative effects on established obesity and IR require further investigation. Therefore, we compared the metabolic effects of a combination of exercise and grape polyphenols supplementation in obese IR rats with high-fat diet (EXOPP) to the effect of high-fat diet alone (HF) or with a nutritional supplementation of grape polyphenols (PP) or with endurance exercise (EXO) during 8 wks. We observed an improvement of systemic and skeletal muscle insulin sensitivity in EXO and EXOPP rats. EXOPP rats compared to HF rats presented a lower insulinemia and HOMA-IR with higher liver and muscle glycogen contents. Interestingly, EXOPP rats had a 68% enhanced endurance capacity compared to EXO rats with also a higher activation of AMPK compared to sedentary and EXO rats with increased lipid oxidation. Together, our results suggest that grape polyphenols supplementation combined with exercise has a synergistic effect by increasing muscle lipid oxidation and sparing glycogen utilization which thus enhances endurance capacity. Our data highlight that in cases of established obesity and IR, the combination of nutritional grape polyphenols supplementation and exercise heighten and intensify their individual metabolic effects.
Highlights
During the past decade, obesity has become an alarming worldwide epidemic mainly due to a preventable lifestyle of energy imbalance where the calories consumed outweigh energy expenditure
After four weeks of high-fat diet (HF), rats presented an increase in both body weight (250.6 g ± 1.7 to 422.2 g ± 4.8, p < 0.001) and glycaemia during glucose tolerance test compared to baseline (Fig. 1a,b), as expected[21,22]
During the eight following weeks, the animals were subjected to high-fat diet alone (HF) or HF with a supplementation of grape polyphenols extract at nutritional dose (PP) or to endurance exercise (EXO) or to the combination of exercise and polyphenols supplementation (EXOPP) (Fig. 2)
Summary
Obesity has become an alarming worldwide epidemic mainly due to a preventable lifestyle of energy imbalance where the calories consumed outweigh energy expenditure. Exercise alone or in combination with diet management is more effective in reducing T2D than metformin[2], even after a 10-year follow-up[3] It is well-established that exercise training stimulates insulin sensitivity and alters glucose/lipid metabolism in skeletal muscle, liver and adipose tissue, favoring lipid oxidation[4,5]. Some studies have already investigated the beneficial effect of a combination of polyphenols (mostly from green tea) with exercise in healthy humans[15] and rodents concomitantly subjected to a high-fat diet[16,17], their results were contradictory. The aim of our study was to investigate the potential curative effects on IR and skeletal muscle metabolism of a nutritional supplementation of grape polyphenols in combination with exercise compared to exercise and grape polyphenols individually, in high-fat diet obese and IR rats. Since it has been demonstrated that some polyphenols can mimic exercise, we sought to investigate whether this combination could promote endurance capacity in established obese rats
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