Effect of theophylline on thyroid status in the rat

Evaluation of theophylline-stimulated changes in carnitine palmitoyltransferase activity in skeletal muscle and liver of rats

The effect of theophylline treatments on the activity of carnitine palmitoyltransferase (CPT) in skeletal muscle and the liver of rats was investigated. Theophylline was administered at 100 mg/kg bw/day and effects were monitored after a treatment period that lasted between a week and five weeks. Results showed that a significant increase in the activity of CPT was observed in skeletal muscle of theophylline-treated groups as compared to either control or placebo groups. However, there was no significant change in the activity of CPT in the hepatic tissues of theophylline-treated groups. The observed discrepancies in activity of CPT might be due to the presence of two isoenzymes, the muscle type (M-CPT) and liver type (L-CPT); it is possible that theophylline affects only M-CPT activity.

Oral theophylline changes renal carnitine palmitoyltransferase activity in rats

BACKGROUND

Carnitine plays a critical role in lipid metabolism. Carnitine deficiency may adversely affect the oxidation of fatty acids and further aggravate abnormal lipid metabolism. Our objective was to investigate the effect of theophylline on the activity of carnitine palmitoyltransferase (CPT) in renal tissues of rats for 5-week-interval treatments.

METHODS

The study was a randomized, controlled animal study. Theophylline was given at 100 mg/kg body weight (b.w.)/day and effects were monitored after a treatment period of between 1 and 5 weeks.

RESULTS

Theophylline treatment caused a significant increase in renal CPT activity as compared to either control or placebo groups. Moreover, the results showed positive correlations between the renal concentration of long-chain acylcarnitine (LC), activity of CPT, urinary excretion of acylcarnitine (AC), and plasma concentration of LC (p <0.01), respectively.

CONCLUSIONS

The observed changes in activity of renal CPT might be due to the result from theophylline-enhanced mobilization of lipid from adipose tissues that consequently stimulated an increased carnitine transport into the renal tissues to form palmitoylcarnitine groups for subsequent beta-oxidation inside the mitochondria. Thus, these accumulations of palmitoylcarnitine groups in mitochondria may increase the catalytic action of CPT.

Theophylline-induced changes in the activity of carnitine palmitoyltransferase in rat cardiac tissues

This study is conducted to investigate the influence of oral theophylline administration (100 mg/kg bw per day) on the activity of carnitine palmitoyltransferase (CPT) in cardiac tissues of rats for 5-week interval treatments. Results showed significant increase in the activity of CPT was observed in cardiac tissues of theophylline-treated groups as compared to either control or placebo groups. Moreover, the results showed positive correlations between the cardiac concentrations of long-chain acylcarnitine (LC) and the activity of CPT and between plasma concentrations of LC and the cardiac concentrations of LC (P<0.01), respectively. The observed changes in activity of cardiac CPT might be due to the result from theophylline- enhanced decrease the sensitivity of CPT to inhibition by malonyl-CoA and/or from theophylline-enhanced mobilization of lipid from adipose tissues which consequently stimulated an increased carnitine transport into the tissues to form palmitoylcarnitine groups for subsequent beta-oxidation inside the mitochondria. Thus, these accumulations of acylcarnitine groups in mitochondria may increase the catalytic action of CPT.

Investigation of the effect of theophylline administration on total, free, short-chain acyl and long-chain acyl carnitine distributions in rat renal tissues

This study is conducted to investigate the effect of oral theophylline administration on total (TC), free (FC), short-(SC), long-chain acyl (LC), acyl (AC) carnitine distributions as well as the ratio of acyl to free carnitine (AC/FC) in rat renal tissues. Theophylline was administrated at 100 mg kg-1 body weight day-1, and effects were monitored after a treatment period that lasted between 1 week and 5 weeks. The results indicated that theophylline administration leads to significantly higher concentrations of TC, FC, SC, L and AC in renal tissues as compared to those of control and placebo groups (P < 0.001). Moreover, the ratio of AC/FC was significantly increased (P < 0.001) as compared to either control or placebo groups. These changes may result from theophylline-enhanced mobilization of lipids from adipose tissues, which consequently stimulates an increased carnitine transport into the renal tissues to form acylcarnitines for subsequent beta-oxidation inside the renal mitochondria.

Investigations of the effects of theophylline administration on carnitine acetyltransferase activity of rat heart

The effects of oral theophylline administration (100 mg/kg b.w./day) on the activity of carnitine acetyltransferase (CAT) of rat heart for five-week interval treatment were studied. The result indicated that the body weights of placebo groups were not significantly changed as compared to control groups (P < 0.1), but theophylline treatment caused a significant decrease in the body weights of rat (P < 0.01) as compared to either control or placebo groups throughout the five-week interval treatments. Daily administration of theophylline to rats did not significantly affect heart weights as compared to either control or placebo groups (P < 0.1) for the five week-interval treatments. Our data indicated that the activity of CAT was not significantly changed in placebo groups as compared to control groups (P < 0.1), however, there was a significant increase in the activity of CAT in heart of theophylline-treated groups (P < 0.01) as compared to either control or placebo groups. The increase in the activity of CAT was noticed in the first three weeks of theophylline treatments followed by a gradual return toward normal activity by the fourth and fifth weeks of continued treatment. The observed changes in activity of CAT of heart might be due to theophylline-enhanced mobilization of lipid from adipose tissues which consequently stimulated increased L-carnitine transport into the heart tissues to form fatty acyl-carnitine groups for subsequent beta-oxidation inside the heart mitochondria. Accumulations of acyl-carnitine groups in heart mitochondria may increase the catalytic action of CAT and possible mechanisms are discussed.

Study of the effects of theophylline-related changes in total, free, short- chain acyl and long-chain acyl carnitine concentrations in rat heart

This study is conducted to investigate the effect of oral theophylline administration on total (TC), free (FC), short-(SC), long-chain acyl (LC), acyl (AC) carnitine concentrations and acyl to free carnitine (AC/FC) ratio in rat heart. Theophylline was administrated at 100 mg/kg wt/day, and effects were monitored after a treatment period that lasted between a week and five weeks. The results indicated that theophylline feeding leads to significantly higher concentrations of TC, FC, SC, LC and AC in heart tissue as compared to those of control and placebo groups (P < 0.001). Moreover, the ratio of AC/FC was significantly increased (P < 0.001) as compared to either control or placebo groups. These changes may result from theophylline-enhanced mobilization of lipids from adipose tissues, which consequently stimulates an increased carnitine transport into the heart tissues to form fatty acylcarnitines for subsequent beta-oxidation inside the heart mitochondria.