Acetyl-l-carnitine and oxfenicine on cardiac pumping mechanics in streptozotocin-induced diabetes in male Wistar rats

Methylprednisolone Protects Cardiac Pumping Mechanics from Deteriorating in Lipopolysaccharide-Treated Rats

It has been shown that a prolonged low-dose corticosteroid treatment attenuates the severity of inflammation and the intensity and duration of organ system failure. In the present study, we determined whether low-dose methylprednisolone (a synthetic glucocorticoid) can protect male Wistar rats against cardiac pumping defects caused by lipopolysaccharide-induced chronic inflammation. For the induction of chronic inflammation, a slow-release ALZET osmotic pump was subcutaneously implanted to infuse lipopolysaccharide (1 mg kg(-1) d(-1)) for 2 weeks. The lipopolysaccharide-challenged rats were treated on a daily basis with intraperitoneal injection of methylprednisolone (5 mg kg(-1) d(-1)) for 2 weeks. Under conditions of anesthesia and open chest, we recorded left ventricular (LV) pressure and ascending aortic flow signals to calculate the maximal systolic elastance (E max) and the theoretical maximum flow (Q max), using the elastance-resistance model. Physically, E max reflects the contractility of the myocardium as an intact heart, whereas Q max has an inverse relationship with the LV internal resistance. Compared with the sham rats, the cardiodynamic condition was characterized by a decline in E max associated with the increased Q max in the lipopolysaccharide-treated rats. Methylprednisolone therapy increased E max, which suggests that the drug may have protected the contractile status from deteriorating in the inflamed heart. By contrast, methylprednisolone therapy considerably reduced Q max, indicating that the drug may have normalized the LV internal resistance. In parallel, the benefits of methylprednisolone on the LV systolic pumping mechanics were associated with the reduced cardiac levels of negative inotropic molecules such as peroxynitrite, malondialdehyde, and high-mobility group box 1 protein. Based on these data, we suggested that low-dose methylprednisolone might prevent lipopolysaccharide-induced decline in cardiac intrinsic contractility and LV internal resistance, possibly through its ability to reduce the aforementioned myocardial depressant substances. However, since our results were obtained in anesthetized open-chest rats, extrapolation to what may occur in conscious intact animals should be done with caution.

Systolic aortic pressure-time area is a useful index describing arterial wave properties in rats with diabetes

The accurate measurement of arterial wave properties in terms of arterial wave transit time (τ_w) and wave reflection factor (R_f) requires simultaneous records of aortic pressure and flow signals. However, in clinical practice, it will be helpful to describe the pulsatile ventricular afterload using less-invasive parameters if possible. We investigated the possibility of systolic aortic pressure-time area (PTAs), calculated from the measured aortic pressure alone, acting as systolic workload imposed on the rat diabetic heart. Arterial wave reflections were derived using the impulse response function of the filtered aortic input impedance spectra. The cardiovascular condition in the rats with either type 1 or type 2 diabetes was characterized by (1) an elevation in PTAs; and (2) an increase in R_f and decrease in τ_w. We found that an inverse linear correlation between PTAs and arterial τ_w reached significance (τ_w = 38.5462 − 0.0022 × PTAs; r = 0.7708, P < 0.0001). By contrast, as the PTAs increased, the reflection intensity increased: R_f = –0.5439 + 0.0002 × PTAs; r = 0.8701; P <0 .0001. All these findings suggested that as diabetes stiffened aortas, the augmented aortic PTAs might act as a useful index describing the diabetes-related deterioration in systolic ventricular workload.