Effects of exercise training on autonomic and myocardial dysfunction in streptozotocin-diabetic rats

Angelis, Kátia De; Oliveira, Álvaro Reischak de; Dall’Ago, Pedro; Peixoto, Luisa; Gadonski, Giovani; Lacchini, Sílvia; Fernandes, Tania Regina Gattelli; Irigoyen, Maria Cláudia

doi:10.1590/s0100-879x2000000600004

Cited by 90 publications

(158 citation statements)

References 26 publications

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“…Studies from our laboratory have shown reduction in vagal tonus and maintenance of sympathetic tonus to the heart evaluated by pharmacological blockade with propranolol and methylatropine, respectively (14,16) (Figure 1), as previously demonstrated by Wegner et al (17), suggesting the presence of cardiac vagal neuropathy. Resting bradycardia in STZ-diabetic rats has been attributed to changes in the sinoatrial node with a consequent reduction in intrinsic HR (14,16,18), although functional alterations in the cholinergic mechanism cannot be excluded as a causal factor.…”

Section: Autonomic Control Of Heart Rate In Experimental Diabetessupporting

confidence: 78%

“…The mechanisms involved in these alterations are not completely understood. Some investigators have associated bradycardia and hypotension with reduction in intrinsic HR, in vagal tonus and in cardiovascular reflex control (10,(14)(15)(16), suggesting early autonomic dysfunction. Furthermore, impairment of heart contractility and vascular responsiveness, as well as changes in blood volume caused by osmotic diuresis could be involved in the pathogenesis of these alterations.…”

Section: Introductionmentioning

confidence: 99%

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Cardiovascular control in experimental diabetes

Angelis

Schaan

Maeda

et al. 2002

Braz J Med Biol Res

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Several studies have reported impairment in cardiovascular function and control in diabetes. The studies cited in this review were carried out from a few days up to 3 months after streptozotocin administration and were concerned with the control of the circulation. We observed that early changes (5 days) in blood pressure control by different peripheral receptors were maintained for several months. Moreover, the impairment of reflex responses observed after baroreceptor and chemoreceptor stimulation was probably related to changes in the efferent limb of the reflex arc (sympathetic and parasympathetic), but changes also in the central nervous system could not be excluded. Changes in renal sympathetic nerve activity during volume expansion were blunted in streptozotocin-treated rats, indicating an adaptive natriuretic and diuretic response in the diabetic state. The improvement of diabetic cardiovascular dysfunction induced by exercise training seems to be related to changes in the autonomic nervous system. Complementary studies about the complex interaction between circulation control systems are clearly needed to adequately address the management of pathophysiological changes associated with diabetes.

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Section: Autonomic Control Of Heart Rate In Experimental Diabetessupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Cardiovascular control in experimental diabetes

Angelis

Schaan

Maeda

et al. 2002

Braz J Med Biol Res

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“…The female fructose-fed rats presented reduced vagal tonus, without changes in sympathetic tonus and in intrinsic HR. We previously reported that male and female ovariectomized streptozotocin-induced diabetic rats presented reduced vagal tonus and unchanged sympathetic tonus to the heart compared to control male rats (10,15). Moreover, a recent study reported increased sympathetic modulation of the circulation during the dark (active) period that was demonstrated by the increase in low frequency component of systolic AP; however, no changes in autonomic modulation to the heart were observed in those male mice submitted to fructose overload (5).…”

mentioning

confidence: 96%

“…During the experiment the rats were conscious and allowed to move freely. The recorded data were analyzed on a beat-to-beat basis to quantify changes in mean AP and heart rate (HR) (10).…”

mentioning

confidence: 99%

“…Intrinsic HR was evaluated after simultaneous blockade with propranolol and methylatropine, and sympathetic tonus was determined as the difference between maximum HR after methylatropine injection and intrinsic HR. Vagal tonus was obtained by the difference between the lowest HR after propranolol injection and intrinsic HR (10). All metabolic and cardiovascular evaluations were performed in the non-ovulatory phases of estrous cycle.…”

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confidence: 99%

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Parasympathetic dysfunction is associated with insulin resistance in fructose-fed female rats

Brito

Ponciano

Figueroa

et al. 2008

Braz J Med Biol Res

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The objective of the present study was to identify metabolic, cardiovascular and autonomic changes induced by fructose overload administered in the drinking water of rats for 8 weeks. Female Wistar rats (200-220 g) were divided into 2 groups: control (N = 8) and fructose-fed rats (N = 5; 100 mg/L fructose in drinking water for 8 weeks). The autonomic control of heart rate was evaluated by pharmacological blockade using atropine (3 mg/kg) and propranolol (4 mg/kg). The animals were submitted to an intravenous insulin tolerance test (ITT) and to blood glucose measurement. The fructose overload induced a significant increase in body weight (~10%) and in fasting glycemia (~28%). The rate constant of glucose disappearance (KITT) during ITT was lower in fructose-fed rats (3.25 ± 0.7%/min) compared with controls (4.95 ± 0.3%/min, P < 0.05) indicating insulin resistance. The fructose-fed group presented increased arterial pressure compared to controls (122 ± 3 vs 108 ± 1 mmHg, P < 0.05) and a reduction in vagal tonus (31 ± 9 vs 55 ± 5 bpm in controls, P < 0.05). No changes in sympathetic tonus were observed. A positive correlation, tested by the Pearson correlation, was demonstrable between cardiac vagal tonus and KITT (r = 0.8, P = 0.02). These data provided new information regarding the role of parasympathetic dysfunction associated with insulin resistance in the development of early metabolic and cardiovascular alterations induced by a high fructose diet.

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Low‐intensity treadmill exercise‐related changes in the rat stellate ganglion neurons

Cavalcanti¹,

Pureza²,

Melo³

et al. 2008

J of Neuroscience Research

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Stellate ganglion (SG) represents the main sympathetic input to the heart. This study aimed at investigating physical exercise-related changes in the quantitative aspects of SG neurons in treadmill-exercised Wistar rats. By applying state-of-the-art design-based stereology, the SG volume, total number of SG neurons, mean perikaryal volume of SG neurons, and the total volume of neurons in the whole SG have been examined. Arterial pressure and heart rate were also measured at the end of the exercise period. The present study showed that a low-intensity exercise training program caused a 12% decrease in the heart rate of trained rats. In contrast, there were no effects on systolic pressure, diastolic pressure, or mean arterial pressure. As to quantitative changes related to physical exercise, the main findings were a 21% increase in the fractional volume occupied by neurons in the SG, and an 83% increase in the mean perikaryal volume of SG neurons in treadmill-trained rats, which shows a remarkable neuron hypertrophy. It seems reasonable to infer that neuron hypertrophy may have been the result of a functional overload imposed on the SG neurons by initial posttraining sympathetic activation. From the novel stereological data we provide, further investigations are needed to shed light on the mechanistic aspect of neuron hypertrophy: what role does neuron hypertrophy play? Could neuron hypertrophy be assigned to the functional overload induced by physical exercise?

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Effects of exercise training on autonomic and myocardial dysfunction in streptozotocin-diabetic rats

Cited by 90 publications

References 26 publications

Cardiovascular control in experimental diabetes

Cardiovascular control in experimental diabetes

Parasympathetic dysfunction is associated with insulin resistance in fructose-fed female rats

Low‐intensity treadmill exercise‐related changes in the rat stellate ganglion neurons

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