Long-Term Impact of Neonatal Intake of Oleanolic Acid on the Expression of AMP-Activated Protein Kinase, Adiponectin and Inflammatory Cytokines in Rats Fed with a High Fructose Diet

Abstract: AMP-activated protein kinase (AMPK) is known to regulate both glucose and lipid metabolism, which play vital roles in the development of metabolic syndrome. One way of regulating AMPK is through hormonal activation using adiponectin. Patients diagnosed with type-2 diabetes (T2D) and obesity exhibit low adiponectin concentration levels in their blood. Moreover, studies have also shown that inflammatory processes play a significant role in the etiology of these metabolic diseases. In this study, the long-term effects of neonatal intake of oleanolic acid (OA) on the AMPK gene, genes associated with glucose transport and lipid metabolism, adiponectin levels, and inflammatory biomarkers in rats fed with a high fructose diet were investigated. Seven day old pups were randomly divided into five groups and treated as follows; 0.5% dimethylsulphoxide v/v in distilled water vehicle control (CON), oleanolic acid (OA, 60 mg/kg), high fructose diet (HF, 20% w/v), high fructose diet combined with oleanolic acid (HF+OA), and high fructose diet combined with metformin (HF+MET, 500 mg/kg)..

Adiponectin regulation of AMPK on oleanolic acid treated insulin resistance Sprague Dawley rats

MSc (Biology), North-West University, Mahikeng CampusAMPK is the principal regulator of both glucose and lipid metabolic pathways, both critical in the etiology of type-2 diabetes (T2D). Various studies have dermnstrated that AMPK can be activated by the adiponectin Individuals suffering from T2D are known to have low adiponectin levels in their blood plasma. This study was aimed at assessing the effect of the anti-diabetic compound oleanolic acid (OA) on adiponectin levels and the subsequent regulation of AMPK. In addition, the study also assessed the influence of OA on the inflammatory cytokines, biormlecules that also play role in the development of T2D. In this study, Sprague Dawley rats were fed with a high fructose diet (HFD) to induce metabolic disturbance as a rmdel for T2D. The rats that developed metabolic disturbances were considered as diseased, and were consequentially treated with OA. Analysis of adiponectin concentration in blood plasma, AMPK gene expression and subsequent genes that play vital roles in glucose and lipid metabolism (GLUT-4 & CPT-1) were studied using rat skeletal muscle. Lastly, inflammatory cytokine gene expression (IL_6 & IL_10) and inflammatory cytokine concentration levels (1NF-a, IlL-6,IL-10, MCP-1 & VEGF) were also assessed. The results from these studies show a significant increase in blood plasma adiponectin concentration in OA treated rats compared to the untreated rats. Furthermore, OA significantly up-regulated AMPK gene expression with ~4-fold increase and GLUT-4 gene expression with ~1.5-fold. On the other hand, the CTP-1 gene expression was not significantly expressed. All inflammatory cytokines were significantly down-regulated by treatment with OA. However, when a HFD (high fructose diet) was fed to these rats, these cytokines were up-regulated. These results clearly indicate that OA produced desired effects in ameliorating insulin resistance or metabolic disturbance. In conclusion, this study further confirms that OA can be used as an effective therapeutic agent to ameliorate the symptoms of T2D. Furthermore, this study also suggest that OA's mechanism of action could be through AMPK pathway.Master

The influence of neonatal intake of curcumin on lipid metabolism : implication on obesity model

PhD (Science with Biochemistry), North-West University, Mahikeng CampusThe high prevalence of obesity and related metabolic disorders due to increased consumption of fructose-rich diet is a serious global threat to the public’s health among children and adolescents. Obesity is associated with several metabolic disorders including, type-2 diabetes, insulin resistance, inflammation, and oxidative stress. Furthermore, obesity is characterised by impaired lipid metabolism in key tissues such as the liver and adipose tissue. Curcumin, a hydrophobic polyphenol extracted from Curcuma longa (turmeric), possesses anti-obesity, anti-diabetic, anti-inflammatory, and antioxidant effects. Although curcumin has been reported to possess a range of biological activities, molecular targets of curcumin are not fully elucidated. The present study was also motivated by evidence suggesting that curcumin may regulate lipid metabolism, which plays a central role in the development of obesity and its complications. Therefore, the first objective of the present study reported the effect of neonatal intake of curcumin on key molecular biomarkers associated with lipid metabolism in the liver, namely, LKB-1, AMPK, CPT-1, and ACC-1. Likewise, the second objective reported the effect of neonatal intake of curcumin on key molecular biomarkers associated with glucose metabolism in the liver, namely, AKT-1, GLUT-2, GP, and PGM (AKT-1 was also considered as the biomarker for insulin resistance in this study). The third objective reported the effect of neonatal intake of curcumin on inflammatory biomarkers in the liver, viz., TNF-α and IL-6. Furthermore, the fourth objective reported the effect of neonatal intake of curcumin on oxidative stress by determining the antioxidant status of curcumin in the liver using FRAP and TEAC assays, as well as the antioxidant scavenging activity of curcumin using DPPH assay and the antioxidant enzyme activity of the SOD. Finally, the fifth objective reported the effect of neonatal intake of curcumin on levels of liver metabolites as well as the concentration of the lipid-bound fatty acids detected as fatty acid methyl esters in adipose tissues. In this study, forty male Sprague Dawley rats were divided into four groups and administered with either a 0.5% dimethyl sulfoxide (vehicle control), 500 mg.kg-1 body mass of curcumin, fructose (20%, w/v) or a combination of curcumin and fructose. The study was conducted in two phases, the first phase was the pre-weaning which began from postnatal day 6 to day 21, and the second phase was the post-weaning which began from postnatal day 21 to day 63. At the end of the treatments on postnatal day 63, rats were euthanized. Then the liver and visceral fat tissues were collected for further molecular analysis. Gene expression was analysed using real-time quantitative polymerase chain reaction while protein expression was analysed using western blot. The antioxidant status was determined using the FRAP and TEAC assays while the antioxidant scavenging activity was determined using the DPPH radical scavenging and SOD activity assays. The concentration levels of hepatic metabolites and the adipose tissue lipid-bound fatty acids were assessed using gas-chromatography-mass spectrometry. Results showed upregulation in the expression of genes and proteins associated with lipid metabolism when the high fructose diet was administered. These include AMPK and its direct activator LKB-1, as well as subsequent target molecules ACC-1 and CPT-1 in the liver tissues. Treatment with curcumin showed to reverse the adverse effects of high fructose diet by upregulating the expression of genes and proteins analysed in the lipid metabolism. This study found that high fructose diet feeding altered hepatic insulin signalling target molecule AKT-1 by downregulating its gene and protein expression. In comparison, treatment with curcumin upregulated the expression of AKT-1. On the one hand, the upregulation of GP and PGM gene and protein expression in the high fructose diet group suggest that hepatic glucose production was promoted. On the other hand, treatment with curcumin suppressed hepatic glucose production by downregulating the expression of GP and PGM. In this study, it was also noted that the administration of curcumin downregulated the gene and protein expression of TNFα and IL-6 whereas the high fructose diet abnormally upregulated their expression. Furthermore, treatment with curcumin showed to enhance hepatic antioxidant status. This was observed by the increase in FRAP and TEAC values, as well as in DPPH level and SOD activity. Finally, it was noted that hepatic carbohydrate metabolite and hepatic organic acids were reduced in the high fructose diet group compared to the control group, while treatment with curcumin showed no significant difference. In the adipose tissue fatty acids levels analysis, results showed an increase in concentration level in the high fructose diet group of all SFA analysed, whereas the opposite had been observed in some of the MUFA and PUFA. Treatment with curcumin showed a decrease in the elevated concentration level of SFA respectively. Moreover, treatment with curcumin increased the concentration level of omega-3 PUFA (EPA and clupanodonic acid), though with no significant difference. The study concluded that curcumin elicits beneficial effects to ameliorate obesity and its related metabolic disorders by regulating molecular biomarkers associated with lipid metabolism through AMPK activation and its subsequent target molecules such as ACC-1 and CPT-1 in the liver tissues. In glucose metabolism, we concluded that curcumin suppressed hepatic glucose production by regulating GP and PGM which are key hepatic glucose production biomarkers. The regulation of an insulin signalling biomarker (AKT-1) by curcumin could also be an alternative therapeutic target to alleviate obesity and its related metabolic disorders. We further confirmed that curcumin possesses anti-inflammatory potential by reducing key inflammatory biomarkers such as TNF-α and IL-6. Finally, using the FRAP and TEAC assays, we further confirmed that curcumin possesses antioxidant capacity in the liver. Similarly, DPPH and SOD activity assays confirmed the antioxidant scavenging activity of curcumin. Therefore, the present study demonstrated that neonatal intake of curcumin could prevent and protect against high fructose diet-induced obesity and its related metabolic disorders such as type-2 diabetes, inflammation, and oxidative stress.Doctora

Oleanolic Acid and Its Derivatives: Biological Activities and Therapeutic Potential in Chronic Diseases

The increasing demand for natural products as an alternative therapy for chronic diseases has encouraged research into the pharmacological importance of bioactive compounds from plants. Recently, there has been a surge of interest in the therapeutic potential of oleanolic acid (OA) in the prevention and management of chronic diseases. Oleanolic acid is a pentacyclic triterpenoid widely found in plants, including fruits and vegetables with different techniques and chromatography platforms being employed in its extraction and isolation. Several studies have demonstrated the potential therapeutic effects of OA on different diseases and their symptoms. Furthermore, oleanolic acid also serves as a framework for the development of novel semi-synthetic triterpenoids that could prove vital in finding therapeutic modalities for various ailments. There are recent advances in the design and synthesis of chemical derivatives of OA to enhance its solubility, bioavailability and potency. Some of these derivatives have also been therapeutic candidates in a number of clinical trials. This review consolidates and expands on recent reports on the biological effects of oleanolic acid from different plant sources and its synthetic derivatives as well as their mechanisms of action in in vitro and in vivo study models. This review suggests that oleanolic acid and its derivatives are important candidates in the search for alternative therapy in the treatment and management of chronic diseases