A fibre cocktail of fenugreek, guar gum and wheat bran reduces oxidative modification of LDL induced by an atherogenic diet in rats

Dietary natural products as emerging lipoprotein(a)-lowering agents

Elevated plasma lipoprotein(a) (Lp(a)) levels are associated with an increased risk of cardiovascular disease (CVD). Hitherto, niacin has been the drug of choice to reduce elevated Lp(a) levels in hyperlipidemic patients but its efficacy in reducing CVD outcomes has been seriously questioned by recent clinical trials. Additional drugs may reduce to some extent plasma Lp(a) levels but the lack of a specific therapeutic indication for Lp(a)-lowering limits profoundly reduce their use. An attractive therapeutic option is natural products. In several preclinical and clinical studies as well as meta-analyses, natural products, including l-carnitine, coenzyme Q ₁₀ , and xuezhikang were shown to significantly decrease Lp(a) levels in patients with Lp(a) hyperlipoproteinemia. Other natural products, such as pectin, Ginkgo biloba, flaxseed, red wine, resveratrol and curcuminoids can also reduce elevated Lp(a) concentrations but to a lesser degree. In conclusion, aforementioned natural products may represent promising therapeutic agents for Lp(a) lowering.

Food Ingredients That Inhibit Cholesterol Absorption

Cholesterol is a vital component of the human body. It stabilizes cell membranes and is the precursor of bile acids, vitamin D and steroid hormones. However, cholesterol accumulation in the bloodstream (hypercholesterolemia) can cause atherosclerotic plaques within artery walls, leading to heart attacks and strokes. The efficiency of cholesterol absorption in the small intestine is of great interest because human and animal studies have linked cholesterol absorption with plasma concentration of total and low density lipoprotein cholesterol. Cholesterol absorption is highly regulated and influenced by particular compounds in the food supply. Therefore, it is desirable to learn more about natural food components that inhibit cholesterol absorption so that food ingredients and dietary supplements can be developed for consumers who wish to manage their plasma cholesterol levels by non-pharmacological means. Food components thus far identified as inhibitors of cholesterol absorption include phytosterols, soluble fibers, phospholipids, and stearic acid.

Diosgenin, 4-hydroxyisoleucine, and fiber from fenugreek: mechanisms of actions and potential effects on metabolic syndrome

Metabolic syndrome and its complications continue to rise in prevalence and show no signs of abating in the immediate future. Therefore, the search for effective treatments is a high priority in biomedical research. Products derived from botanicals have a time-honored history of use in the treatment of metabolic diseases including type 2 diabetes. Trigonella foenum-graecum, commonly known as fenugreek, is an annual herbaceous plant that has been a staple of traditional herbal medicine in many cultures. Although fenugreek has been studied in both clinical and basic research settings, questions remain about its efficacy and biologic mechanisms of action. Diosgenin, 4-hydroxyisoleucine, and the fiber component of the plant are the most intensively studied bioactive constituents present in fenugreek. These compounds have been demonstrated to exert beneficial effects on several physiologic markers including glucose tolerance, inflammation, insulin action, liver function, blood lipids, and cardiovascular health. Although insights into the molecular mechanisms underlying the favorable effects of fenugreek have been gained, we still do not have definitive evidence establishing its role as a therapeutic agent in metabolic disease. This review aims to summarize the currently available evidence on the physiologic effects of the 3 best-characterized bioactive compounds of fenugreek, with particular emphasis on biologic mechanisms of action relevant in the context of metabolic syndrome.

Protective effect of dietary tender cluster beans (Cyamopsis tetragonoloba) in the gastrointestinal tract of experimental rats

In this study, the gastrointestinal protective effect of soluble, dietary fiber-rich tender cluster beans, with respect to the activities of antioxidant enzymes and the concentration of antioxidant molecules, was examined in Wistar rats. Dietary intervention with tender cluster beans (15% freeze-dried powder in the diet for 8 weeks) significantly enhanced the activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase, glutathione-S-transferase, and GPX) and the concentrations of antioxidant molecules in both gastric and intestinal mucosa. Further, in combination with capsaicin (0.01%), the beneficial effect was even higher. There is a strong indication that tender cluster beans offer a significant gastroprotective effect, and a much greater effect when combined with capsaicin in terms of increased antioxidant status. In a separate study, these dietary components were found to alleviate the diminished activities of antioxidant enzymes and antioxidant molecules in gastric and intestinal mucosa under conditions of ethanol-induced oxidative stress. The gastroprotective effect of the cluster bean was also reflected in its positive effect on gastric mucosal glycoproteins, resulting in a lowering of mucosal injury. Incidentally, the serum and liver also showed an elevated antioxidant status, thus suggesting desirable lowered oxidative stress results when tender cluster beans are consumed.

Guar gum and similar soluble fibers in the regulation of cholesterol metabolism: current understandings and future research priorities

The hypocholesterolemic effects associated with soluble fiber consumption are clear from animal model and human clinical investigations. Moreover, the modulation of whole-body cholesterol metabolism in response to dietary fiber consumption, including intestinal cholesterol absorption and fecal sterol and bile acid loss, has been the subject of many published reports. However, our understanding of how dietary fibers regulate molecular events at the gene/protein level and alter cellular cholesterol metabolism is limited. The modern emphasis on molecular nutrition and rapid progress in 'high-dimensional' biological techniques will permit further explorations of the role of genetic polymorphisms in determining the variable interindividual responses to soluble fibers. Furthermore, with traditional molecular biology tools and the application of 'omic' technology, specific insight into how fibers modulate the expression of genes and proteins that regulate intestinal cholesterol absorption and alter hepatic sterol balance will be gained. Detailed knowledge of the molecular mechanisms by which soluble fibers reduce plasma cholesterol concentrations is paramount to developing novel fiber-based "cocktails" that target specific metabolic pathways to gain maximal cholesterol reductions.

Partially hydrolyzed guar gum supplement reduces high-fat diet increased blood lipids and oxidative stress and ameliorates FeCl3-induced acute arterial injury in hamsters

Increased reactive oxygen species (ROS) and hyperlipidemia can promote arterial thrombus. We evaluated the potential of a partially hydrolyzed guar gum (PHGG) as dietary fiber on lipid profiles and FeCl₃-induced arterial thrombosis in the high fat-diet fed hamsters. Our in vitro results found that PHGG is efficient to scavenge O₂^-•, H₂O₂, and HOCl. High fat-diet increased plasma triglyceride, total cholesterol, LDL, VLDL, methylguanidine and dityrosine level and accelerated FeCl₃-induced arterial thrombosis formation (from 463 ± 51 to 303 ± 45 sec). Low dose PHGG supplement significantly decreased the total cholesterol, LDL, methylguanidine and dityrosine level and delayed the time for arterial thrombosis formation (528 ± 75 sec). High dose PHGG supplement decreased the level in triglyceride, total cholesterol, LDL and VLDL and further delayed the time for arterial thrombus (671 ± 36 sec). The increased Bax protein and decreased Bcl-2 and HSP-70 protein expression was found in the carotid and femoral arteries of high fat-diet hamsters. Low and high dose of PHGG supplement decreased Bax expression and increased Bcl-2 and HSP-70 protein expression. We found that FeCl₃ significantly enhanced intercellular adhesion molecule-1 and 4-hydroxynonenal expression in the endothelial site of damaged artery after 150-sec FeCl₃ stimulation. PHGG supplement decreased the endothelial ICAM-1 and 4-hydroxynonenal expression after 150-sec FeCl₃ stimulation. Based on these results, we conclude that PHGG supplement can increase antioxidant protein expression and thus decrease oxidative stress induced arterial injury.

Fenugreek Extract Rich in 4-Hydroxyisoleucine and Trigonelline Activates PPARα and Inhibits LDL Oxidation: Key Mechanisms in Controlling the Metabolic Syndrome

Fenugreek ( Trigonella foenum-graecum L.) has properties which are hypolipidemic, hypocholesterolemic, hypoglycemic, insulinotropic, and antioxidant. These properties are related to the control of the Metabolic Syndrome, a disorder of carbohydrate and lipid metabolism which increases the risk of diabetes and cardiovascular disease. The purpose of this study was to evaluate the effect of fenugreek extract (Hydroxylean®, Naturex) containing 25% of 4-hydroxyisoleucine (4-OH-Ile, isomer 2 S,3 R,4 S) and 15.7% of trigonelline on peroxisome proliferator-activated receptor alpha (PPARα) transcriptional activity and Cu2+-induced low-density lipoprotein (LDL) oxidation in vitro. The activation of PPARα is linked to controlling lipidemia, cholesterolemia and glycemia, all associated with diabetes and cardiovascular disease. Also, the inhibition of LDL oxidation reduces the risk of stroke. 1,000 μg/mL of fenugreek extract showed a 31.2% activation of PPARα as compared with the positive control, 100 μM of fenofibrate. Fenugreek extract also inhibited LDL oxidation induced by Cu2+ at concentrations higher than 5 μg/mL (P<0.01). To our knowledge, this is the first report on PPARα transcriptional activity and Cu2+-induced LDL oxidation in vitro for fenugreek extract rich in 4-OH-Ile and trigonelline. The findings support the current evidence on fenugreek's capacity to control the Metabolic Syndrome.

Oxidation of low-density lipoprotein cholesterol following administration of poloxamer 407 to mice results from an indirect effect

Atherosclerosis is an inflammatory response to accumulation of cholesterol in the artery wall. Low-density lipoproteins (LDL) accumulate and are oxidized to proinflammatory compounds in the arterial intima during hypercholesterolemia, leading to activation of endothelial cells, macrophages, and T cells. We sought to define the role of oxidized LDL (oxLDL) in the poloxamer 407 (P-407)-induced mouse model of dose-dependent hyperlipidemia and atherosclerosis developed in our laboratory. The hyperlipidemic agent P-407 was evaluated for its ability to oxidize native LDL in vitro as determined by measuring the rate of formation of conjugated dienes, as well as malondialdehyde (MDA) production using the thiobarbituric acid reactive substances assay. Additionally, plasma obtained from C57BL/6 mice treated with P-407 for 100 days and maintained on either a normal diet or a diet supplemented with 0.5% w/w cholic acid was assayed for both MDA and lipid hydroperoxide content. Lastly, plasma from these same groups of mice was analyzed for the presence of immunoglobulin (Ig) G and IgM autoantibodies against oxLDL. Our results indicate that P-407 is unable to directly oxidize native LDL in vitro. However, plasma obtained from P-407-treated mice demonstrated a significant (P < 0.05) increase in the content of oxidized lipids, but showed a significant (P < 0.05) decrease in the concentration of lipid hydroperoxides when compared to controls. Both plasma IgG and IgM antibodies to MDA-modified LDL (MDA-LDL) were significantly (P < 0.05) elevated in P-407-treated mice, as was IgG1 anti-MDA-LDL, whereas the titer of IgG2a anti-MDA-LDL was significantly (P < 0.05) reduced. We suggest that P-407 causes oxidation of LDL in vivo by an indirect mechanism and we further conclude that P-407-induced hypercholesterolemia in C57BL/6 mice is associated with T cell-dependent (IgG) and T cell-independent (IgM) B-cell responses to MDA-LDL.