Role of age-related decrease of renal organic cation transporter 2 in the effect of atenolol on renal excretion of metformin in rats

Many diabetes patients, especially the elder ones, suffered from hypertension simultaneously. Therefore, it is very likely that a large number of diabetes patients receiving metformin hydrochloride may simultaneously be given beta-blockers. Knowing that both metformin and atenolol are eliminated by organic cation transporter 2 (OCT2/SLC22A2) expressed in the renal basolateral membrane, it is not clear whether there is a competitive effect on the renal excretion of metformin and/or atenolol when metformin and atenolol were co-administered, and whether age was involved in this drug-drug interaction. In this present study, both young rats (aged 3 months) and aged rats (aged 12 months) were used, rats were divided into metformin-treated group and metformin and atenolol co-administrated group, respectively. Either metformin (2.5 mg/kg) alone or metformin (2.5 mg/kg) in combination with atenolol (8 mg/kg) was administered to rats by tail vein injection. Then, urine was collected and the metformin concentration in urine was determined by HPLC. The localization and expression of rOCT2 in kidney were also investigated by Western blotting and immunohistochemistry. Significant differences of t 1/2, K e, CLtot and the accumulated metformin excretion in urine were founded in aged rats, but not in young rats, between metformin-treated group (2.002 ± 0.51 h, 0.346 ± 0.07/h, 57.161 ± 18.59 %, 4,287.087 ± 458.08 μg) and metformin plus atenolol-treated group (3.03 ± 0.67 h, 0.228 ± 0.05/h, 43.199 ± 10.28 %, 3,239.972 ± 446.61 μg). Moreover, a significant age-related decrease in rOCT2 protein expression was observed in the aged rats (P < 0.01), which may be responsible for the effect of atenolol on the renal excretion of metformin in the aged rats. In conclusion, there is a drug-drug interaction between atenolol and metformin, and more attention should be paid when atenolol and metformin were co-administered to the aged people inclinical.

Suppression subtractive hybridization analysis of low-protein diet- and vitamin D-induced gene expression from rat kidney inner medullary base

Protein restriction and hypercalcemia result in a urinary concentrating defect in rats and humans. Previous tubular perfusion studies show that there is an increased active urea transport activity in the initial inner medullary (IM) collecting duct in low-protein diet (LPD) and vitamin D (Vit D) animal models. To investigate the possible mechanisms that cause the urinary concentrating defect and to clone the new active urea transporter, we employed a modified two-tester suppression subtractive hybridization (ttSSH) approach and examined gene expression induced by LPD and Vit D in kidney IM base. Approximately 600 clones from the subtracted library were randomly selected; 150 clones were further confirmed to be the true positive genes by slot blot hybridization with subtracted probes from LPD and Vit D and sent for DNA sequencing. We identified 10 channel/transporter genes that were upregulated in IM base in LPD and Vit D animal models; 8 were confirmed by real-time PCR. These genes include aquaporin 2 (AQP2), two-pore calcium channel protein 2, brain-specific organic cation transporter, Na(+)- and H(+)-coupled glutamine transporter, and solute carrier family 25. Nine genes are totally new, and twelve are uncharacterized hypothetical proteins. Among them, four genes were shown to be new transmembrane proteins as judged by Kyte-Doolittle hydrophobic plot analysis. ttSSH provides a useful method to identify new genes from two conditioned populations.

Evidence-based and potential benefits of metformin in the polycystic ovary syndrome: a comprehensive review

Metformin is an insulin sensitizer widely used for the treatment of patients affected by type 2 diabetes mellitus. Because many women with polycystic ovary syndrome (PCOS) are insulin resistant, metformin was introduced in clinical practice to treat these patients also. Moreover, metformin's effect has other targets beside its insulin-sensitizing action. The present review was aimed at describing all evidence-based and potential uses of metformin in PCOS patients. In particular, we will analyze the uses of metformin not only for the treatment of all PCOS-related disturbances such as menstrual disorders, anovulatory infertility, increased abortion, or complicated pregnancy risk, hyperandrogenism, endometrial, metabolic and cardiovascular abnormalities, but also for the prevention of the syndrome.