Modulation of the Cardiovascular Risk in Type 1 Diabetic Rats by Endurance Training in Combination with the Prebiotic Xylooligosaccharide

Abstract

Diabetic cardiomyopathy is a major etiological factor in heart failure in diabetic patients, characterized by mitochondrial oxidative metabolism dysfunction, myocardial fibrosis, and marked glycogen elevation. The aim of the present study is to evaluate the effect of endurance training and prebiotic xylooligosaccharide (XOS) on the activity of key oxidative enzymes, myocardial collagen, and glycogen distribution as well as some serum biochemical risk markers in streptozotocin-induced type 1 diabetic rats. Male Wistar rats (n = 36) were divided into four diabetic groups (n = 9): sedentary diabetic rats on a normal diet (SDN), trained diabetic rats on a normal diet (TDN), trained diabetic rats on a normal diet with an XOS supplement (TD-XOS), and sedentary diabetic rats with an XOS supplement (SD-XOS). The results show that aerobic training managed to increase the enzyme activity of respiratory Complex I and II and the lactate dehydrogenase in the cardiomyocytes of the diabetic rats. Furthermore, the combination of exercise and XOS significantly decreased the collagen and glycogen content. No significant effects on blood pressure, heart rate or markers of inflammation were detected. These results demonstrate the beneficial effects of exercise, alone or in combination with XOS, on the cardiac mitochondrial enzymology and histopathology of diabetic rats.

Keywords: diabetic cardiomyopathy; endurance training; glycogen content; mitochondrial function; myocardial fibrosis; type 1 diabetes; xylooligosaccharides.

Figure 1

Effects of aerobic training and XOS on the biochemical parameters. (a) Serum T-AOC; (b) Serum levels of IL-6; (c) Serum levels of hsCRP. The graphs present the raw data (n = 9) as well as mean ± SD values. SDN—Sedentary type 1 diabetic rats on a normal diet; TDN—Trained type 1 diabetic rats on a normal diet; TD-XOS—Trained type 1 diabetic rats on a normal diet with an XOS supplement; SD-XOS—Sedentary type 1 diabetic rats on a normal diet with an XOS supplement.

Figure 2

Effects of aerobic training and XOS on the enzyme activity of SDH, NADH + H⁺-CoQ oxidoreductase and LDH in the myocardium of animals from the experimental groups (n = 6). (a) Microphotographs of the myocardium used for the enzyme histochemical assessment (magnification ×200). Enzyme activities of SDH (b), NADH + H⁺-CoQ oxidoreductase (c) and LDH (d) (AU) in cardiomyocytes of hearts of the experimental animals at the end of the experiment. The graphs present the raw data as well as mean ± SD values. *—p < 0.05 vs. SDN; **—p < 0.01 vs. SDN, ##—p < 0.01 vs. TD-XOS; &&—p < 0.01 vs. SD-XOS; &&&—p < 0.001 vs. SD-XOS. SDN—Sedentary type 1 diabetic rats on a normal diet; TDN—Trained type 1 diabetic rats on a normal diet; TD-XOS—Trained type 1 diabetic rats on a normal diet with an XOS supplement; SD-XOS—Sedentary type 1 diabetic rats on a normal diet with an XOS supplement. Note: Photographs of group SD-XOS were not included due to a lack of significant differences from the diabetic control group (SDN).

Figure 3

Effects of endurance training and XOS on the distribution of collagen fibers and glycogen in the myocardium of animals from the experimental groups (n = 6). (a) Upper row: Collagen fibers (in blue), AZAN staining. Bottom row: Glycogen content, PAS reaction (magnification ×200). (b) Percentage of collagen fiber distribution and (c) glycogen content, AU (raw data and mean ± SD values) in the cardiomyocytes of the LV of the heart. ***—p < 0.001 vs. SDN, §§—p < 0.01 vs. TDN, &&&—p < 0.001 vs. SD-XOS. SDN—Sedentary type 1 diabetic rats on a normal diet; TDN—Trained type 1 diabetic rats on a normal diet; TD-XOS—Trained type 1 diabetic rats on a normal diet with an XOS supplement; SD-XOS—Sedentary type 1 diabetic rats on a normal diet with an XOS supplement. Note: Photographs of group SD-XOS were not included due to a lack of significant differences from the diabetic control group (SDN).

Figure 4

Study design. BP—blood pressure, HR—heart rate, MTE—maximum time to exhaustion, AC—abdominal circumference, T-AOC—total antioxidant capacity, Il-6—interleukin-6, hsCRP—high-sensitive C-reactive protein, NADH + H+—nicotinamide adenine dinucleotide hydride, CoQ—coenzyme Q, LDH—lactate dehydrogenase, SDH—succinate dehydrogenase.