Exercise Ameliorates Endocrine Pancreas Damage Induced by Chronic Cola Drinking in Rats

Abstract

Purpose: This study evaluates whether the daily practice of an exercise routine might protect from endocrine pancreas damage in cola drinking rats.

Methods: Forty-eight Wistar rats were randomly assigned to 4 groups depending on a) beverage consumption ad libitum, water (W) or cola beverage (C), and b) physical activity, sedentary (S) or treadmill running (R). Accordingly, 4 groups were studied: WS (water sedentary), WR (water runner), CS (cola sedentary) and CR (cola runner). Body weight, nutritional data, plasma levels of glucose, creatinine, total cholesterol and cholesterol fractions, and triglycerides (enzymocolorimetry), and systolic blood pressure (plethysmography) were measured. After 6 months, euthanasia was performed (overdose sodium thiopental). Pancreatic tissue was immediately excised and conventionally processed for morphometrical and immunohistochemical determinations.

Results: The effects of running and chronic cola drinking on pancreas morphology showed interaction (p<0.001) rather than simple summation. Cola drinking (CS vs WS) reduced median pancreatic islet area (-30%, 1.8 10(4) μm2 vs 2.58 10(4) μm2, p<0.0001) and median β-cell mass (-43%, 3.81 mg vs 6.73 mg, p<0.0001), and increased median α/β ratio (+49%, 0.64 vs 0.43, p< 0.001). In water drinking rats (WR vs WS), running reduced median α-cell mass (-48%, 1.48 mg vs 2.82 mg, p<0.001) and α/β ratio (-56%, 0.19 vs 0.43, p<0.0001). Differently, in cola drinking rats (CR vs CS), running partially restored median islet area (+15%, 2.06 10(4) μm2 vs 1.79 10(4) μm2, p<0.05), increased median β-cell mass (+47%, 5.59 mg vs 3.81 mg, p <0.0001) and reduced median α/β ratio (-6%, 0.60 vs 0.64, p<0.05).

Conclusion: This study is likely the first reporting experimental evidence of the beneficial effect of exercise on pancreatic morphology in cola-drinking rats. Presently, the increase of nearly 50% in β cells mass by running in cola drinking rats is by far the most relevant finding. Moderate running, advisably indicated in cola consumers and patients at risk of diabetes, finds here experimental support.

Fig 1. Nutritional data and body weight.

A). Nutritional data in g, mL or Kcal/ kg body weight/ 24 hs. Calories calculation based on 3 Kcal/g of food and 0.42 Kcal/mL of cola drink. B). Body weight in g. Values are mean ± SD. Dotted lines indicate value at the beginning of the study. White bars: water sedentary, white hatched bars: water runner, red bars: cola sedentary, red hatched bars: cola runner. * p<0.05, ** p<0.01, *** p<0.001 vs water sedentary; # p<0.01 vs water runner.

Fig 2. Plasma biochemical profile.

A). Glucose in mg/dL. * p<0.05 vs water sedentary, # p<0.01 vs water runner. B). Triglycerides (TG) in mg/dL. ** p<0.01 vs water sedentary, ## p<0.01 vs water runner. C). Total cholesterol in mg/dL. D). High density lipoproteins (HDL) in mg/dL. E). Low density lipoproteins (LDL). Values are mean ± SD. White bars: water sedentary, white hatched bars: water runner, red bars: cola sedentary, red hatched bars: cola runner.

Fig 3. Quantitative morphology and immunohistochemistry of Langerhans islets.

Boxplots show the median value (horizontal line), box limits indicate the 25^th and 75^th percentiles (box size covers the central 50% of the data), whiskers show extreme values of data distribution (maximal and minimal values within total range) and outliers are represented by °. * p<0.05, ** p<0.01, *** p<0.0001 vs WS; # p<0.05, ## p<0.001, ### p<0.0001 vs CS WS: water sedentary, WR: water runner, CS: cola sedentary, CR: cola runner. Values are expressed as mean ± SD. * p<0.05, ** p<0.01, *** p<0.001 vs WS; # p<0.01 vs WR.

Fig 4. Immunolabeling for insulin and glucagon in Langerhans islets.

Representative photomicrograph showing the effects of either chronic cola-drinking or running respectively or both as a combined treatment, on α- and β-cell area and islet size. Cytoplasmic expression of insulin (β-cells) and glucagon (α-cells) in all experimental groups, showing the usual rodent islet architecture. In WS and WR, the core of the islet is exclusively composed of insulin-immunopositive cells as expected, whereas glucagon immunopositivity is typically localized at the islet periphery. In CS and CR, glucagon-positive immunostaining is observed in the periphery, with focal extension into the center of the islet. Insulin-positive immunostaining is localized in the central portion of the islet, though leaving spots free of immunostaining with focal distribution.