Bhavani Prasad Kota

Pomegranate flower improves cardiac lipid metabolism in a diabetic rat model: role of lowering circulating lipids.

1 Excess triglyceride (TG) accumulation and increased fatty acid (FA) oxidation in the diabetic heart contribute to cardiac dysfunction. Punica granatum flower (PGF) is a traditional antidiabetic medicine. Here, we investigated the effects and mechanisms of action of PGF extract on abnormal cardiac lipid metabolism both in vivo and in vitro. 2 Long‐term oral administration of PGF extract (500 mg kg−1) reduced cardiac TG content, accompanied by a decrease in plasma levels of TG and total cholesterol in Zucker diabetic fatty (ZDF) rats, indicating improvement by PGF extract of abnormal cardiac TG accumulation and hyperlipidemia in this diabetic model. 3 Treatment of ZDF rats with PGF extract lowered plasma FA levels. Furthermore, the treatment suppressed cardiac overexpression of mRNAs encoding for FA transport protein, peroxisome proliferator‐activated receptor (PPAR)‐α, carnitine palmitoyltransferase‐1, acyl‐CoA oxidase and 5′‐AMP‐activated protein kinase α2, and restored downregulated cardiac acetyl‐CoA carboxylase mRNA expression in ZDF rats, whereas it showed little effect in Zucker lean rats. The results suggest that PGF extract inhibits increased cardiac FA uptake and oxidation in the diabetic condition. 4 PGF extract and its component oleanolic acid enhanced PPAR‐α luciferase reporter gene activity in human embryonic kidney 293 cells, and this effect was completely suppressed by a selective PPAR‐α antagonist MK‐886, consistent with the presence of PPAR‐α activator activity in the extract and this component. 5 Our findings suggest that PGF extract improves abnormal cardiac lipid metabolism in ZDF rats by activating PPAR‐α and thereby lowering circulating lipid and inhibiting its cardiac uptake.

Novel PPAR-gamma agonists identified from a natural product library: a virtual screening, induced-fit docking and biological assay study.

Peroxisome proliferator‐activated receptor‐gamma (PPAR‐gamma) plays an essential role in lipid and glucose homeostasis. It is recognized as the receptor of the thiazolidinediones—a synthetic class of anti‐diabetic drugs—and is the target of many drug discovery efforts because of its role in disease states, such as type II diabetes mellitus. In this study, structure‐based virtual screening of the PPAR‐gamma ligand binding domain against a natural product library has revealed 29 potential agonists. In vitro testing of this list identified six flavonoids to have stimulated PPAR‐gamma transcriptional activity in a transcriptional factor assay. Of these, flavonoid—psi‐baptigenin—was classed as the most potent PPAR‐gamma agonist, possessing low micromolar affinity (EC50 = 2.9 μM). Further in vitro testing using quantitative RT‐PCR and immunoblotting experiments demonstrated that psi‐baptigenin activated PPAR‐gamma mRNA (4.1 ± 0.2‐fold) and protein levels (2.9 ± 0.4‐fold) in THP‐1 macrophages. Moreover, psi‐baptigenin’s‐induced PPAR‐gamma enhancement was abolished in the presence of a selective PPAR‐gamma antagonist, GW9662. Induced‐fit docking investigations provide a detailed understanding on the ligands’ mechanism of action, suggesting five of the active flavonoids induce significant conformational change in the receptor upon binding. Overall, these results offer insight into various naturally derived flavonoids as leads/templates for development of novel PPAR‐gamma ligands.

The pathophysiological function of peroxisome proliferator-activated receptor-γ in lung-related diseases

Research into respiratory diseases has reached a critical stage and the introduction of novel therapies is essential in combating these debilitating conditions. With the discovery of the peroxisome proliferator-activated receptor and its involvement in inflammatory responses of cardiovascular disease and diabetes, attention has turned to lung diseases and whether knowledge of this receptor can be applied to therapy of the human airways. In this article, we explore the prospect of peroxisome proliferator-activated receptor-γ as a marker and treatment focal point of lung diseases such as asthma, chronic obstructive pulmonary disorder, lung cancer and cystic fibrosis. It is anticipated that peroxisome proliferator-activated receptor-γ ligands will provide not only useful mechanistic pathway information but also a possible new wave of therapies for sufferers of chronic respiratory diseases.

Characterization of PXR mediated P-glycoprotein regulation in intestinal LS174T cells

Intestinal P-glycoprotein (P-gp) is an important target in drug-drug interactions. Pregnane X receptor (PXR) mediates the induction of intestinal P-gp. The LS174T intestinal cell line has been used in several studies as an in vitro tool to identify the effect of PXR inducers on intestinal P-gp expression. In this study we aimed to further characterize this cell line by focusing on the time dependence of P-gp expression, localization and function in the presence of rifampicin, a P-gp inducer. P-gp protein expression was increased in a time and dose dependent manner following exposure of cells to rifampicin (5-50 μM). The induction of P-gp by rifampicin and its inhibition by ketoconazole (an inhibitor of PXR mediated P-gp induction) confirms the suitability of these cells for PXR induction studies. Confocal microscopy showed that P-gp translocated from intracellular compartments to plasma membrane over 7 days in LS174T cells. P-gp function, as established by rhodamine 123 (Rh123) intracellular accumulation, correlated with increasing P-gp expression and plasma membrane localization over this period. Our data demonstrates that LS174T cells provide a suitable in vitro model to test for the effect of PXR inducers/inhibitors on P-gp induction, localization and function over this culture period. This model also has application for the screening of drug candidates for effects on oral bioavailability via effects on the subcellular distribution and trafficking of P-gp.

Preventative effect of Zingiber officinale on insulin resistance in a high-fat high-carbohydrate diet-fed rat model and its mechanism of action.

Insulin resistance is a core component of metabolic syndrome and usually precedes the development of type 2 diabetes mellitus. We have examined the preventative effect of an ethanol extract of ginger (Zingiber officinale, Zingiberaceae) on insulin resistance in a high‐fat high‐carbohydrate (HFHC) diet‐fed rat model of metabolic syndrome. The HFHC control rats displayed severe insulin resistance, whilst rats treated with ginger extract (200 mg/kg) during HFHC diet feeding showed a significant improvement of insulin sensitivity using the homeostatic model assessment of insulin resistance (HOMA‐IR) after 10 weeks (p < 0.01). An in vitro mechanistic study showed that (S)‐[6]‐gingerol, the major pungent phenolic principle in ginger, dose‐dependently (from 50 to 150 μM) increased AMPK α‐subunit phosphorylation in L6 skeletal muscle cells. This was accompanied by a time‐dependent marked increment of PGC‐1α mRNA expression and mitochondrial content in L6 skeletal muscle cells. These results suggest that the protection from HFHC diet‐induced insulin resistance by ginger is likely associated with the increased capacity of energy metabolism by its major active component (S)‐[6]‐gingerol.

Pharmacology of Traditional Herbal Medicines and Their Active Principles Used in the Treatment of Peptic Ulcer, Diarrhoea and Inflammatory Bowel Disease

The endocrine, exocrine and paracrine secretions of the gastrointestinal (GI) tract play a pivotal role in the digestion and absorption of food and orally administered drugs. The secretion of mucus by mucus-secreting cells protects the erosion of the gastric mucosa from the highly acidic gastric juice. The secretion of hydrochloric acid from parietal cells is regulated by acetylcholine, histamine and gastrin. Disturbances in secretory functions of the gastrointestinal tract can lead to several GI complications. Conventional therapies employ a range of drugs that have been pharmacologically well characterised. While these drug molecules are proven to be beneficial, the adverse effects and drug-drug interactions highlight the need for better treatment modalities for GI tract disorders.

The effect of vitamin D3 and ketoconazole combination on VDR-mediated P-gp expression and function in human colon adenocarcinoma cells : implications in drug disposition and resistance

The vitamin D3 metabolite 1,25-dihydroxycholecalciferol (DHC) and analogues derived from it are being investigated as potential agents for the treatment of cancer. Combining ketoconazole (KTZ) with DHC has been recommended to enhance the anticancer activity of DHC. DHC exerts its biological activities through the vitamin D receptor (VDR). VDR is recognized to be a regulator of P-glycoprotein (P-gp), a member of the ABC transporter family well known for its role in multidrug resistance in cancer chemotherapy. We have investigated the effect of DHC and adding KTZ together with DHC on P-gp and VDR expression and the functional consequences of P-gp induction in intestinal human colonic adenocarcinoma cells LS174T cells. DHC increased P-gp expression by two times, and the addition of KTZ further increased the expression to four times. The combination of DHC + KTZ also significantly increased VDR expression, consistent with the enhanced increase in P-gp expression by this combination. The increase in P-gp expression was accompanied by increased P-gp function, as measured by decreased Rh123 accumulation in the LS174T cells. In addition, DHC significantly decreased colchicine cytotoxicity in a dose-sensitive manner, and the addition of KTZ further decreased the colchicine cytotoxicity, indicating the chemo-protective effect of DHC is enhanced by KTZ, consistent with the enhanced expression of P-gp. The results of this study raise the possibility that DHC and the addition of KTZ to DHC treatment may decrease the effectiveness of cancer chemotherapy by promoting P-gp-mediated drug resistance.

Effect of vitamin D3 supplementation on the pharmacokinetics of digoxin – a pilot study

Emerging evidence from preclinical, clinical and epidemiological studies suggests that vitamin D3 plays vital roles in several diseases in addition to bone disorders. According to new medical evidence, it is being recommended that vitamin D3 intake to be increased for maximal benefits in human health. However, it is necessary to consider potential side effects of increased intake of vitamin D3. Vitamin D3 exerts its actions through the vitamin D receptor, which is known to be an important regulator of P‐glycoprotein (P‐gp). As P‐gp plays a significant role in limiting drug bioavailability, we undertook a study to compare single‐dose digoxin (a P‐gp substrate) pharmacokinetics in eight healthy male subjects before and after vitamin D3 supplementation (1000 IU per day). The geometric mean ratios for AUC0–3h, AUC0–48h and Cmax were 1.06 (90% CI 0.92, 1.21) and 1.02 (90% CI 0.97, 1.08) and 1.03 (95% CI 0.86, 1.24), respectively. The median for digoxin Tmax was 0.75 h before and after vitamin D3 ingestion. The mean plasma 25‐hydroxyvitamin D3 (25(OH)D3) levels remained constant after the intake of vitamin D3 (15.4 ± 3.7 and 14.4 ± 3.6 ng/mL, respectively), while there was a modest but statistically significant increase in plasma calcium levels, from 9.32–9.68 mg/dL (P = 0.0277). These results suggest that vitamin D3 supplementation (1000 IU per day) in human volunteers does not produce a P‐gp‐mediated drug interaction with orally administered digoxin.