Preischemic administration of ribose to delay the onset of irreversible ischemic injury and improve function: studies in normal and hypertrophied hearts

D-ribose: Potential clinical applications in congestive heart failure and diabetes, and its complications (Review)

The quality of life of patients with certain diseases may be improved through the development of technologies and advancements in pharmacology, with the aim of prolonging their life. However, congestive heart failure (CHF), as well their complications, continue to be the leading cause of disease-associated death. The mechanisms underlying the development and progression of diabetes and CHF have been uncovered in a stepwise manner and the understanding of these mechanisms has improved the management of these diseases, resulting in reduced mortality and morbidity rates; however, CHF remains the leading cause of death worldwide, particularly in developed countries. In the past decades, research has indicated that several supplements and naturally occurring compounds may be used to treat muscle weakness, for cardiac failure management, rehabilitation following myocardial ischemia-reperfusion and various complications of diabetes. D-ribose is an essential component of the respiratory, skeletal and nervous systems and is a popular compound, as its supplementation may have beneficial effects. In the present review, the physiological roles, toxic reactions and the potential use of D-ribose in the management of clinical diseases are summarized.

The Role of 17β-Estradiol in Myocardial Hypertrophy in Females in the Presence and Absence of Hypertension

PURPOSE

There are gender-differences in the development of cardiac hypertrophy, which appear to be related, in part, to sex hormones. This report gives an overview of this relationship and reports on original data assessing how varying levels of plasma 17β-estradiol determine relative heart size, in vivo function, in hypertensive versus normotensive rats.

METHODS

Female spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were either surgically neutered or sham operated at 21 days of age. A subgroup of neutered females received 17β-estradiol replacement. At 6 months, in vivo heart function was measured, the heart/body weight ratio (mg/g) was assessed as a measure of hypertrophy and correlated with plasma 17β-estradiol.

RESULTS

There was a significant positive relationship between plasma 17β-estradiol and heart/body weight ratio in both WKY (R = 0.509, P = 0.011) and SHR females (R = 0.359, P = 0.032). Interestingly, the slope of this relationship was 2-fold steeper in the WKY females, suggesting a blunted effect in the SHR, whose hearts also had 35 % lower ERβ content. With increasing plasma estradiol levels, WKY females showed improved LV function while SHR females showed impaired LV relaxation.

CONCLUSIONS

Plasma estradiol modulates relative heart mass in both normotensive and hypertensive female rats. With any increase in plasma 17β-estradiol, hypertensive females show a blunted response compared with the normotensive females, which may be related to a reduced estrogen receptor expression in the presence of hypertension. In contrast to normotensive females, hypertensive females showed impaired function with increases in plasma 17β-estradiol.

Impact of female sex hormones on liver tissue lactic acidosis during ischemia

BACKGROUND

Lower liver transplant success is observed when the donor is female. Intracellular acidosis during ischemia is proposed to contribute to the injury sustained by the transplanted organ and its role in livers obtained from nonheartbeating donors is unclear. Research has shown that livers of female rats develop a greater degree of intracellular acidosis during ischemia than males. This work explores the role of sex hormones in mediating this sex difference.

METHODS

Subgroups of neutered female rats were given 17 beta-estradiol (E), progesterone (P), or combination (E+P). To compare the effects of female sex hormones in males, subgroups of intact and castrated males received 17 beta-estradiol. In vivo and ischemic liver biopsies were taken and analyzed for lactate and H.

RESULTS

Although there was no effect of hormone therapy on baseline metabolic parameters, during ischemia compared to neutered females, livers from E females significantly (P<0.01) increased lactate by 56% and H+ by 71%, while E+P significantly increased only lactate (39%; P<0.05). Livers from neutered males given 17 beta-estradiol showed significantly greater (P<0.001) accumulation of lactate (80%) and H+ (79%). This was even shown in intact males, where despite a blunted response, 17 beta-estradiol, significantly (P<0.05) increased lactate by 39% and H+ by 25%.

CONCLUSION

This study illustrates the mechanisms for the sex difference in the liver's metabolic response to ischemia are estrogen mediated, which is seen even in the presence of male hormones, thus offering one explanation for the lower liver transplant success when the donor is female.

Preservation of diastolic function in monocrotaline-induced right ventricular hypertrophy in rats

During ischemic heart diseases and when heart failure progresses depletion of myocardial energy stores occurs. D-Ribose (R) has been shown to improve cardiac function and energy status after ischemia. Folic acid (FA) is an essential cofactor in the formation of adenine nucleotides. Therefore, we assessed whether chronic R-FA administration during the development of hypertrophy resulted in an improved cardiac function and energy status. In Wistar rats (n = 40) compensatory right ventricular (RV) hypertrophy was induced by monocrotaline (30 mg/kg; MCT), whereas saline served as control. Both groups received a daily oral dose of either 150 mg.kg(-1).day(-1) dextrose (placebo) or R-FA (150 and 40 mg.kg(-1).day(-1), respectively). In Langendorff-perfused hearts, RV and left ventricular (LV) pressure development and collagen content as well as total RV adenine nucleotides (TAN), creatine content, and RV and LV collagen content were determined. In the control group R-FA had no effect. In the MCT-placebo group, TAN and creatine content were reduced, RV and LV diastolic pressure-volume relations were steeper, RV systolic pressures were elevated, RV and LV collagen content was increased, and RV-LV diastolic interaction was altered compared with controls. In the MCT-R-FA group, TAN, RV and LV diastolic stiffness, RV and LV collagen content, and RV-LV diastolic interaction were normalized to the values in the control group while creatine content remained depressed and RV systolic function remained elevated. In conclusion, the depression of energy status in compensated hypertrophic myocardium observed was partly prevented by chronic R-FA administration and accompanied by a preservation of diastolic function and collagen deposition.

Lower liver transplant success in females: gender differences in metabolic response to global ischemia

BACKGROUND

Research has shown that gender plays a significant role in the metabolic processes of different organs and that transplanting livers of females into male or female recipients has significantly higher failure rates. To understand why, this study examined whether gender differences exist in various metabolic responses of livers to ischemia.

METHODS

The following metabolic liver parameters in Sprague-Dawley rats (male, n = 14; and female, n = 18) were examined; adenosine triphosphate (ATP) and lactate expressed as micromoles/g dry weight, and hydrogen ion content [H+] expressed as 10(-8) mol/L. In vivo liver biopsy specimens were compared with ischemic biopsy specimens at 3, 10, 15, 30, and 45 minutes (37 degrees C).

RESULTS

In vivo female ATP values (9.9 +/- 0.8) were similar to males (9.8 +/- 0.9) and both had early, rapid decline during ischemia reaching 20% of baseline by 10 minutes of ischemia. In contrast, male liver lactate accumulation peaked by 3 minutes and at much lower levels (35 +/- 13), whereas female liver lactate peaked by 10 minutes at 71 +/- 11. For the rest of the ischemic period, female livers exhibited significantly (P < .05) greater lactate accumulation. Female liver H+ levels also increased to higher levels (55 +/- 10) than the male livers (37 +/- 7) and this pattern was significantly (P < .05) different from 10 minutes onward.

CONCLUSIONS

Although livers of females ultimately have similar ATP profiles to livers of males, they experienced more rapid and greater degree of tissue lactate and H+ accumulation during ischemia. Therefore, female livers have increased acidosis during ischemia, which could adversely affect transplant outcome.