Background: The aim of the present study was to investigate the relationship between speed during maximum exercise test (ET) and oxygen consumption (VO₂) in control and STZ-diabetic rats, in order to provide a useful method to determine exercise capacity and prescription in researches involving STZ-diabetic rats. Methods: Male Wistar rats were divided into two groups: control (CG, n = 10) and diabetic (DG, n = 8). The animals were submitted to ET on treadmill with simultaneous gas analysis through open respirometry system. ET and VO₂ were assessed 60 days after diabetes induction (STZ, 50 mg/Kg). Results: VO₂ maximum was reduced in STZ-diabetic rats (72.5 ± 1 mL/Kg/min^-1) compared to CG rats (81.1 ± 1 mL/Kg/min^-1). There were positive correlations between ET speed and VO₂ (r = 0.87 for CG and r = 0.8 for DG), as well as between ET speed and VO₂ reserve (r = 0.77 for CG and r = 0.7 for DG). Positive correlations were also obtained between measured VO₂ and VO₂ predicted values (r = 0.81 for CG and r = 0.75 for DG) by linear regression equations to CG (VO₂ = 1.54 * ET speed + 52.34) and DG (VO₂ = 1.16 * ET speed + 51.99). Moreover, we observed that 60% of ET speed corresponded to 72 and 75% of VO₂ reserve for CG and DG, respectively. The maximum ET speed was also correlated with VO₂ maximum for both groups (CG: r = 0.7 and DG: r = 0.7). Conclusion: These results suggest that: a) VO₂ and VO₂ reserve can be estimated using linear regression equations obtained from correlations with ET speed for each studied group; b) exercise training can be prescribed based on ET in control and diabetic-STZ rats; c) physical capacity can be determined by ET. Therefore, ET, which involves a relatively simple methodology and low cost, can be used as an indicator of cardio-respiratory capacity in future studies that investigate the physiological effect of acute or chronic exercise in control and STZ-diabetic male rats.

Introduction: Fluid overload is a clinical problem frequently related to cardiac and renal dysfunction. The aim of this study was to evaluate fluid overload and changes in serum creatinine as predictors of cardiovascular mortality and morbidity after cardiac surgery. Methods: Patients submitted to heart surgery were prospectively enrolled in this study from September 2010 through August 2011. Clinical and laboratory data were collected from each patient at preoperative and trans-operative moments and fluid overload and creatinine levels were recorded daily after cardiac surgery during their ICU stay. Fluid overload was calculated according to the following formula: (Sum of daily fluid received (L) - total amount of fluid eliminated (L)/preoperative weight (kg) × 100). Preoperative demographic and risk indicators, intra-operative parameters and postoperative information were obtained from medical records. Patients were monitored from surgery until death or discharge from the ICU. We also evaluated the survival status at discharge from the ICU and the length of ICU stay (days) of each patient. Results: A total of 502 patients were enrolled in this study. Both fluid overload and changes in serum creatinine correlated with mortality (odds ratio (OR) 1.59; confidence interval (CI): 95% 1.18 to 2.14, P = 0.002 and OR 2.91; CI: 95% 1.92 to 4.40, P <0.001, respectively). Fluid overload played a more important role in the length of intensive care stay than changes in serum creatinine. Fluid overload (%): b coefficient = 0.17; beta coefficient = 0.55, P <0.001); change in creatinine (mg/dL): b coefficient = 0.01; beta coefficient = 0.11, P = 0.003). Conclusions: Although both fluid overload and changes in serum creatinine are prognostic markers after cardiac surgery, it seems that progressive fluid overload may be an earlier and more sensitive marker of renal dysfunction affecting heart function and, as such, it would allow earlier intervention and more effective control in post cardiac surgery patients.

The db/db mice serve as a good model for type 2 diabetes characterized by hyperinsulinaemia and progressive hyperglycaemia. There are limited and conflicting data on the cardiovascular changes in this model. The aim of the present study was to characterize the cardiovascular and autonomic phenotype of male db/db mice and evaluate the role of angiotensin II AT₁ receptors. Radiotelemetry was used to monitor 24 h blood pressure (BP) in mice for 8 weeks. Parameters measured were mean arterial pressure (MAP), heart rate (HR) and their variabilities. In 8‐week‐old db/db mice, the MAP and BP circadian rhythms were not different from age‐matched control mice, while HR and locomotor activity were decreased. With ageing, MAP gradually increased in db/db mice, and the 12 h light values did not dip significantly from the 12 h dark periods. In 14‐week‐old mice, MAP was increased during light (101 ± 1 versus 117 ± 2 mmHg, P < 0.01; control versus db/db mice) and dark phases (110 ± 1.7 versus 121 ± 3.1 mmHg, P < 0.01; control versus db/db mice). This increase in MAP was associated with a significant increase in plasma angiotensin‐converting enzyme activity and angiotensin II levels. Chronic treatment with losartan (10 mg kg⁻¹ day⁻¹) blocked the increase in MAP in db/db mice, with no effect in control animals. Spectral analysis was used to monitor autonomic cardiovascular function. The circadian rhythm observed in systolic arterial pressure variance and its low‐frequency component in control mice was absent in db/db mice. There were no changes in HR variability and spontaneous baroreflex sensitivity between control and db/db mice. The results document an age‐related increase in MAP in db/db mice, which can be reduced by antagonism of angiotensin II AT₁ receptors, and alterations in autonomic balance and components of the renin–angiotensin system.

Background: Because cardiomyopathy is the leading cause of death in diabetic patients, the determination of myocardial function in diabetes mellitus is essential. In the present study, we provide an integrated approach, using noninvasive echocardiography and invasive hemodynamics to assess early changes in myocardial function of diabetic rats. Methods: Diabetes was induced by streptozotocin injection (STZ, 50 mg/kg). After 30 days, echocardiography (noninvasive) at rest and invasive left ventricular (LV) cannulation at rest, during and after volume overload, were performed in diabetic (D, N = 7) and control rats (C, N = 7). The Student t test was performed to compare metabolic and echocardiographic differences between groups at 30 days. ANOVA was used to compare LV invasive measurements, followed by the Student-Newman-Keuls test. Differences were considered significant at P < 0.05 for all tests. Results: Diabetes impaired LV systolic function expressed by reduced fractional shortening, ejection fraction, and velocity of circumferential fiber shortening compared with that in the control group. The diabetic LV diastolic dysfunction was evidenced by diminished E-waves and increased A-waves and isovolumic relaxation time. The myocardial performance index was greater in diabetic compared with control rats, indicating impairment in diastolic and systolic function. The LV systolic pressure was reduced and the LV end-diastolic pressure was increased at rest in diabetic rats. The volume overload increased LVEDP in both groups, while LVEDP remained increased after volume overload only in diabetic rats. Conclusion: These results suggest that STZ-diabetes induces systolic and diastolic dysfunction at rest, and reduces the capacity for cardiac adjustment to volume overload. In addition, it was also demonstrated that rodent echocardiography can be a useful, clinically relevant tool for the study of initial diabetic cardiomyopathy manifestations in asymptomatic patients.

Background: To evaluate the effect of nicotinamide prior to streptozotocin-induced (STZ) diabetes in baroreflex sensitivity and cardiovascular autonomic modulation, and its association with hemodynamics and metabolic parameters. Methods: Methods: Male Wistar rats were divided into control (Cont) and STZ-induced diabetes (Diab). Half of the rats from each group received a single dose of nicotinamide (100 mg/Kg) before STZ injection (Cont+NicA and Diab+NicA). All groups were followed-up for 5 weeks. Results: Body weight loss of more than 40% was observed in Diab throughout the period (Diab: 271.00 ± 12.74 g; Diab+NicA: 344.62 ± 17.82). Increased glycemia was seen in Diab rats (541.28 ± 18.68 mg/dl) while Diab+NicA group had a slight decrease (440.87 ± 20.96 mg/dl). However, insulin resistance was observed only in Diab. In relation to Cont, heart rate, mean blood pressure and diastolic function were reduced when compared to Diab, together with parasympathetic modulation and baroreflex sensitivity. All of these parameters were improved in Diab+NicA when compared to Diab. Improved baroreflex sensitivity and parasympathetic modulation were correlated with glycemia, insulin resistance, and body weight mass. Additionally, Diab+NicA group increased survival rate. Conclusions: Results suggest that the association of nicotinamide in STZ-induced diabetic rats prevents most of the expected derangements mainly by preserving parasympathetic and baroreflex parameters.