Beneficial Effect of Moderate Exercise in Kidney of Rat after Chronic Consumption of Cola Drinks

Abstract

Aim: The purpose of this study was to investigate the effect of moderate intensity exercise on kidney in an animal model of high consumption of cola soft drinks.

Methods: Forty-eight Wistar Kyoto rats (age: 16 weeks; weight: 350-400 g) were assigned to the following groups: WR (water runners) drank water and submitted to aerobic exercise; CR (cola runners) drank cola and submitted to aerobic exercise; WS (water sedentary) and CS (cola sedentary), not exercised groups. The aerobic exercise was performed for 5 days per week throughout the study (24 weeks) and the exercise intensity was gradually increased during the first 8 weeks until it reached 20 meters / minute for 30 minutes. Body weight, lipid profile, glycemia, plasma creatinine levels, atherogenic index of plasma (AIP) and systolic blood pressure (SBP) were determined. After 6 months all rats were sacrificed. A kidney histopathological score was obtained using a semiquantitative scale. Glomerular size and glomerulosclerosis were estimated by point-counting. The oxidative stress and pro-inflammatory status were explored by immunohistochemistry. A one way analysis of variance (ANOVA) with Tukey-Kramer post-hoc test or the Kruskal-Wallis test with Dunn's post-hoc test was used for statistics. A value of p < 0.05 was considered significant.

Results: At 6 months, an increased consumption of cola soft drink was shown in CS and CR compared with water consumers (p<0.0001). Chronic cola consumption was associated with increased plasma triglycerides, AIP, heart rate, histopathological score, glomerulosclerosis, oxidative stress and pro-inflammatory status. On the other hand, moderate exercise prevented these findings. No difference was observed in the body weight, SBP, glycemia, cholesterol and plasma creatinine levels across experimental groups.

Conclusions: This study warns about the consequences of chronic consumption of cola drinks on lipid metabolism, especially regarding renal health. Additionally, these findings emphasize the protective role of exercise training on renal damage.

Fig 1. Representative microphotographs of kidney stained with hematoxylinand eosin.

In sedentary rats that consume cola soft drink (A) were observed glomerular hypertrophy, glomerulosclerosis, tubular atrophy and dilatation, tubular casts, interstitial fibrosis and chronic inflammatory infiltrates (black arrows). The moderate exercise regimen partially protects against chronic consumption of cola drinks (B). These lesions were less apparent in rats that consume water (C and D). Magnification: 100X, scale bar 500 microns.

Fig 2. Representative microphotographs of glomeruli stained with periodic acid-Schiff.

Sedentary rats that consume cola soft drink (A) showed segmental scarring and obliteration of glomerular capillaries with increased mesangial cellularity, mesangial matrix expansion and adhesion formation between the tuft and Bowmans’ capsule (black arrow). These pathological changes, corresponding to glomerulosclerosis, werelower in CR (B), WS (C) and WR (D) groups. Magnification: 400X, scale bar 100 microns.

Fig 3. Immunohistochemical expression for trx1 at tubular level.

Sedentary animals that consume cola soft drink (A) or water (C) showed lowest cytoplasmic staining that was partially reverted by aerobic training in CR (B) in comparison with WR (D). Magnification: 400X, scale bar 100 microns.

Fig 4. Immunohistochemical expression for prx1.

The immunohistochemical profile for prx1 was similar than trx1 at the proximal tubule epithelia in CS (A), CR (B), WS (C) and WR (D) constituting a sensor for oxidative stress, favoring a protective effect in oxidative aggression. Magnification: 400X, scale bar 100 microns.

Fig 5. Immunohistochemical expression for IL6 at tubular level.

Sedentary animals that consume cola soft drink (A) showed high cytoplasmic staining for IL6, that was reduced with aerobic exercise practice (B). The expression for this proinflammatory cytokine was lowest in experimental groups that drank water, both, sedentary (C) and runners’ (D). Magnification: 400X, scale bar 100 microns.

Fig 6. Immunohistochemical expression for TNFα.

The immunohistochemical profile for this proinflammatory cytokine was similar than IL6 at tubular level in CS (A), CR (B), WS (C) and WR (D) groups. Magnification: 400X, scale bar 100 microns.