Safety, tolerability, and efficacy of a glucose-insulin-potassium-magnesium-carnitine solution in acute myocardial infarction

PROTECTIVE ROLE OF CARNITINE SYNERGIZED WITH VITAMIN E AGAINST ISOPROTERENOL INDUCED CARDIAC INFARCTION IN RATS

Background:

The current study aimed to evaluate the role of carnitine in combination with vitamin E in protection against myocardial infarction induced by isoproterenol (ISO) in rats.

Materials and Methods:

Rats were grouped into 5 (each 10 rats): Group I. Control fed a standard diet. Group III: Rats were injected with vitamin E (100 IU/kg bw, i.p) daily. Group IV: Rats were given carnitine (20 mg/kg bw, i.p) daily. Group V: Rats were injected with both vitamin E (100 IU/kg bw, i.p) and carnitine (20 mg/kg bw, i.p) daily. On 7^th, 8^th, and 9^th day, rats in groups (II-V) were injection i.p with ISO (55mg/kg b.w for successive three days). The treatment with carnitine and vitamin E were continuous for 21 days.

Results:

Canirine combined with vitamin E significantly increased coronary flow (CF) (P<0.001) in rats injected with ISO. The recovery of rate pressure product (RPP) and left ventricular developed pressure (LVDP) were significantly improved in treated rats in comparison to untreated. The rats administrated with ISO resulted in a significant elevation of serum enzymes (CK-MB and LDH) compared with control group (p<0.001). However, it returned to about normal. ISO administration resulted in a significant elevation in the levels of malondialdehyde (MDA) and nitric oxide (NO) as compared with control (p<0.001) and a significant reduction in the activities of GSPxase and GSRase (p<0.001) compared with control group. The levels of cardiac inflammatory markers interleukine-6 (IL-6) and tumor necrosis factor (TNF-α) were markedly elevated in rats injected with ISO compared with control group. Vitamin E combined with carnitine reversed these effects. However, pretreatment with vitamin E or carnitine or combined together showed a significant reduction in MDA and NO (p<0.001) and a significant elevation in the activities of GSPxase and GSRase (p<0.001) as compared to ISO injected group. The combined effect was more significant than individual ones.

Conclusion:

Vitamin E combined with carnitine exerts potential protective effect against MI through suppression of inflammatory mediators and enhancement of antioxidant activity.

Role of carnitine in cancer chemotherapy-induced multiple organ toxicity

In the last few years, cancer chemotherapy has been successfully employed in the treatment of different types of human tumours. Unfortunately, the optimal clinical usefulness of this important treatment modality is usually limited secondary to the development of life-threatening multiple organ toxicity. Cancer chemotherapy may cause these toxic effects by mechanisms not involved in their anticancer activity that can severely affect the life of patients and represent a direct cause of death. Several experimental and clinical studies have demonstrated that some important anticancer drugs interfere with the absorption, synthesis, and excretion of carnitine in non-tumour tissues, resulting in a secondary carnitine deficiency which is reversed by carnitine treatment without affecting anticancer therapeutic efficacy. Prototypes of anticancer drugs that alter carnitine system are doxorubicin, cisplatin, carboplatin, oxaliplatin, cyclophosphamide and ifosfamide. Furthermore, cachectic cancer patients are especially at risk for carnitine deficiency due to decreased oral intake and/or increased renal losses. Altered serum and urine carnitine levels have been reported in cancer patients with various forms of malignant diseases. Recent studies in our laboratory have demonstrated that carnitine deficiency constitute a risk factor and should be viewed as a mechanism during development of oxazaphosphorines-induced cardiotoxicity in rats. Similarly, inhibition of gene expression of heart fatty acid-binding protein and organic cation/carnitine transporter in doxorubicin cardiomyopathic rat model has been reported. In view of these facts and in view of irreplaceability of these important anticancer drugs, this review aimed to highlight the role of carnitine depletion and supplementation during development of chemotherapy-induced multiple organ toxicity.

Effects of glucose-insulin-potassium infusion on QT dispersion in patients with acute myocardial infarction

BACKGROUND

Increased QT dispersion during acute myocardial infarction (AMI) has been associated with the occurrence of ventricular arrhythmias. Also, serum potassium levels have been shown to be relevant to the arrhythmic risk in this group of patients. The aim of the present study was to assess changes in QT dispersion during infusion of glucose-insulin-potassium (GIK) during AMI.

METHODS

Patients from the Pol-GIK study were analyzed retrospectively. The patients were selected from the placebo (1000 mL of 0.89% NaCl) and the GIK (1000 mL of 10% dextrose, 20-32 units of insulin, 80 mEq K(+)) groups (18 and 24 patients, respectively). QT interval duration and dispersion (the difference between the longest and shortest QT intervals) were measured at baseline, 18-24 hours into placebo/GIK infusion and 24 hours after the end of infusion.

RESULTS

In the placebo group, plasma potassium levels changed from 4.1 +/- 0.5 mmol/L at baseline to 4.6 +/- 0.8 mmol/L during infusion (P < 0.05) and 4.6 +/- 0.4 mmol/L after infusion, whereas in the GIK group the respective values were 4.0 +/- 0.4, 4.6 +/- 0.3 (P < 0.0001), and 4.5 +/- 0.5 mmol/L. QT interval duration was stable throughout the study and there was no difference between the groups. The two groups did not differ in respect to QT dispersion at any time point, the respective values were 79 +/- 28, 65 +/- 25, and 77 +/- 27 ms in the placebo group, and 61 +/- 35, 60 +/- 26, and 76 +/- 43 ms in the GIK group. The incidence of arrhythmias was also similar in both groups.

CONCLUSIONS

GIK, at the dose used, is unlikely to affect heterogeneity of ventricular repolarization during AMI.

Increased glycolytic substrate protection improves ischemic cardiac dysfunction and reduces injury

Early clinical trials of glucose-insulin-potassium for acute myocardial infarction were inconclusive. However, several recent placebo-controlled, prospective, randomized clinical trials of glucose-insulin-potassium for acute myocardial infarction or metabolic support during and after cardiac surgery have demonstrated its efficacy. These clinical results are supported by experimental studies that have shown a strong protective effect of increased glycolytic substrate on ischemic myocardium in concert with an improved bioenergetic status.

[Therapy with glucose-insulin-potassium reduces the complications in the acute phase of myocardial infarct. Arguments against]

Glucose-insulin-potassium therapy has shown its efficacy in diminishing the myocardial damage under ischemia-reperfusion conditions in experimental models. This effect appears to be mainly due to the increase of anaerobic glycolysis in ischemic cells with a consequent reduction in the use of fatty acids. On the other hand, clinical studies in the acute phase of myocardial infarction are out-dated and almost non-existent in the thrombolytic era. The absence of current consistent data makes it difficult to draw conclusions concerning the real utility of this therapy in the clinical practice.

Carnitine and its derivatives in cardiovascular disease

Carnitine and its derivative propionyl-L-carnitine are endogenous cofactors which enhance carbohydrate metabolism and reduce the intracellular buildup of toxic metabolites in ischemic conditions. The carnitines have been, and are being used in a spectrum of diseases including multiple cardiovascular conditions. These include angina, acute myocardial infarction, postmyocardial infarction, congestive heart failure, peripheral vascular disease, dyslipidemia, and diabetes. Most published data on carnitine, propionyl-L-carnitine, and other carnitine congeners are favorable but the clinical trials have been relatively small. In currently used doses, these substances are virtually devoid of significant side effects.