Faculty Bibliography

A clerodane diterpene, 16α-Hydroxycleroda-3, 13 (14) Z-dien-15, 16-olide (compound 1) isolated from Polyalthia longifolia had previously been reported as a new structural class of HMG-CoA reductase inhibitor apart from statins. Statins are known to be anti-adipogenic in nature. The distant structural similarity between compound 1 and lovastatin (polyketide class of compound) prompted us to investigate effects of diterpene compound 1 on adipogenesis and thereby obesity. High content microscopy proved diterpene compound 1 exhibits better anti-adipogenic activity and less toxicity in differentiating adipocytes. Moreover, it reduced expression levels of PPARγ, C/EBPα and GLUT4 during differentiation in a time and concentration dependent manner. Diterpene compound 1 during early differentiation reduced MDI induced-Akt/mTOR phosphorylation and expression of cell cycle proteins, and thereby halted mitotic clonal expansion, the decisive factor in early adipogenesis. Further, its anti-adipogenic activity was validated in murine mesenchymal cell-line C3H10T1/2 and human mesenchymal stem cell models of adipogenic differentiation. When compound 1 was administered along with HFD, for another 8 weeks in 2 month HFD fed overweight mice (with BMI > 30 and impaired glucose tolerance), it attenuated weight gain and epididymal fat accumulation. It improved body glucose tolerance, reduced HFD induced increase in total cholesterol and leptin/adiponectin ratio. All these effects were comparable with standard anti-obesity drug Orlistat with added edge of potently decreasing circulating triglyceride levels comparable with normal chow fed group. Histological analysis shows that compound 1 inhibit adipocyte hypertrophy and decreased steatosis in hepatocytes. Both in vivo and in vitro results demonstrate a potential value of compound 1 as a novel anti-adipogenic and anti-obesity agent.

According to the World Health Organization obesity is defined as the excessive accumulation of fat, which increases risk of other metabolic disorders such as insulin resistance, dyslipidemia, hypertension, cardiovascular diseases, etc. There are two types of adipose tissue, white and brown adipose tissue (BAT) and the latter has recently gathered interest of the scientific community. Discovery of BAT has opened avenues for a new therapeutic strategy for the treatment of obesity and related metabolic syndrome. BAT utilizes accumulated fatty acids for energy expenditure; hence it is seen as one of the possible alternates to the current treatment. Moreover, browning of white adipocyte on exposure to cold, as well as with some of the pharmacological agents presents exciting outcomes and indicates the feasibility of transdifferentiation. A better understanding of molecular pathways and differentiation factors, those that play a key role in transdifferentiation are of extreme importance in designing novel strategies for the treatment of obesity and associated metabolic disorders.

Obesity is a result of adipocyte hypertrophy followed by hyperplasia. It is a risk factor for several metabolic disorders such as dyslipidemia, type-2 diabetes, hypertension, and cardiovascular diseases. Coagulanolides, particularly coagulin-L isolated from W. coagulan has earlier been reported for anti-hyperglycemic activity. In this study, we investigated the effect of coagulin-L on in vitro models of adipocyte differentiation including 3T3-L1 pre-adipocyte, mouse stromal mesenchymal C3H10T1/2 cells and bone marrow derived human mesenchymal stem cells (hMSCs). Our results showed that, coagulin-L reduces the expressions of peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα), the major transcription factors orchestrating adipocyte differentiation. Detailed analysis further proved that early exposure of coagulin-L is sufficient to cause significant inhibition during adipogenesis. Coagulin-L inhibited mitotic clonal expansion (MCE) by delayed entry in G1 to S phase transition and S-phase arrest. This MCE blockade was caused apparently by decreased phosphorylation of C/EBPβ, modulation in expression of cell cycle regulatory proteins, and upregulation of Wnt/β-catenin pathway, the early stage regulatory proteins of adipogenic induction. Taken together all evidences, a known anti-hyperglycemic agent coagulin-L has shown potential to inhibit adipogenesis significantly, which can be therapeutically exploited for treatment of obesity and metabolic syndrome.

Colorectal cancer is the third most common cancer and is associated with significant morbidity and mortality. Epidemiological and animal studies indicate that regular acetylsalicylic acid (aspirin) intake is associated with a reduction in the incidence of colorectal cancer. Acetylsalicylic acid (ASA) has also been shown to inhibit colorectal cancer cell proliferation in vitro. The molecular basis for this specific cytotoxicity is an area of considerable debate. To investigate the toxicity of salicylates, the sensitivity of the DNA mismatch repair proficient SW480 human colorectal cancer cell line to four categories of compounds with varying degrees of structural similarity to acetylsalicylic acid was tested. These compounds were: i) salicylic acid analogues with substituents at the 5-position; ii) ASA analogues with extended chain lengths in the acyl group; iii) vanillin (4-hydroxy-3-methoxybenzaldehyde; and iv) bis(2-carboxyphenyl) succinate (BCS) and structurally similar derivatives thereof. It was found that compounds with amino and acetamido substituents at the salicylate 5-position were less toxic than ASA itself. Modifications to the length of the hydrocarbon chain in the acyl groups of ASA analogues also marginally reduced toxicity. Vanillin exhibited relatively limited toxicity against the SW480 colorectal cancer cell line. Commercially available and in-house synthesised BCS (diaspirin) were notably more inhibitory to cell growth than ASA itself, yet retained substantial specificity against colorectal cancer cell lines vs. non-colorectal cancer cell lines. BCS and ASA were toxic to SW480 cells through initiation of necrotic and apoptotic pathways. Fumaroyldiaspirin and benzoylaspirin exhibited greater toxicity than ASA against the SW480 cell line. A novel method for synthesis of BCS, a compound that has erratic commercial availability, is described. We propose that the anti-inflammatory and anticancer capacity of BCS and the other analogues described herein is worthy of investigation.