BACKGROUND: Few natural products have demonstrated the range of protective and therapeutic promise as have turmeric and its principal bioactive components: curcumin, demethoxycurcumin, and bisdemethoxycurcumin. Success in translating this potential into tangible benefits has been limited by inherently poor intestinal absorption, rapid metabolism, and limited systemic bioavailability. Seeking to overcome these limitations, food ingredient formulators have begun to employ a variety of approaches to enhance absorption and bioactivity. Many of these strategies improve upon the age-old practice of consuming turmeric in fat-based sauces, such as in a fat-rich yellow curry. However, there exists uncertainty as to how the various commercially available offerings compare to each other in terms of either uptake or efficacy, and this uncertainty leaves physicians and nutritionists with a dearth of data for making recommendations to interested patients and consumers. Further complicating the issue are recent data suggesting that formulation strategies may not equally enhance the absorption of individual curcuminoids, a significant issue in that these curcuminoids exhibit somewhat different physiologic properties. OBJECTIVE: This review introduces needed order to the curcumin marketplace by examining bioavailability studies on a number of commercial curcumin ingredients and evaluating them on a level playing field. METHODS: The comparative analysis includes standard pharmacokinetic parameters and a new metric, relative mass efficiency (E). Relative mass efficiency allows for the comparison of different formulations even in cases in which the weight percentage of curcuminoids is vastly different. RESULTS: A hydrophilic carrier dispersed curcuminoid formula exhibits 45.9 times the bioavailability of the standard purified 95 percent curcuminoid preparation and, based on relative mass efficiency, 1.5 times the bioavailability of the next best commercial ingredient, a cyclodextrin complex. CONCLUSIONS: Delivery strategies can significantly improve the bioavailability of curcuminoids. Total formula mass is important for making practical formulation decisions about dosing, cost and space.
Garcinia cambogia extract (GC) with its active component consisting of hydroxycitric acid (HCA) is widely utilized for weight loss. Various HCA salts are available, including calcium, magnesium, potassium and mixtures of these. Experimentally, these salts exhibit different properties with some, but not all, improving glucose tolerance and blood pressure. Recently, obesity-prone C57BL/6J mice were fed a high-fat diet (HFD, 45 kcal% fat) with or without GC (1%, w/w) for 16 wk. The active arm reduced visceral fat, adipocyte size and serum glucose, yet purportedly also exhibited hepatic collagen accumulation, lipid peroxidation and increased mRNA levels of genes related to oxidative stress. The latter findings are at odds with a large body of animal and human studies that have been conducted on the safety and efficacy of HCA. This literature shows HCA to be protective against the liver toxicity associated with ethanol and dexamethasone administration, and to maintain serum aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase at near normal levels. In both animal and clinical literature, elevated intakes of HCA per se have not led to signs of inflammation or hepatotoxicity. The compound has been found to reduce markers of inflammation in brain, intestines, kidney and serum.
Bitter melon (BM) was tested in normal and streptozotocin (STZ)-induced diabetic rats. First, normal and diabetic Wistar rats were given four test extracts (EX-1-EX-4) of a wild-genotype BM or metformin by intubation. Second, normal Sprague-Dawley rats were divided into control and three test groups given for 52 days one of three BM preparations in food: Chinese or Indian commercial preparations or EX-4 from experiment I. In experiment I, extracts of BM administered at 50 mg/kg of body weight in normal rats reduced blood sugar for 4 hours without, unlike metformin, inducing hypoglycemia. In STZ-induced diabetic rats, two extracts administered at 250 mg/kg decreased glucose levels to values comparable to metformin at 150 mg/kg. At 4 hours, EX-1 and EX-4 significantly reduced blood glucose 67% and 63%, respectively, compared with metformin's 54%. In experiment II, all test groups had lowered systolic, but not diastolic, blood pressure. The China and EX-4 arms had significantly lowered serum glucose levels compared with the control. In the glucose tolerance test, only EX-4 had significantly lowered glucose levels. Only EX-4 had significantly lowered angiotensin converting enzyme (ACE) activity. All active arms showed significance in the losartan challenge (the renin-angiotensin system [RAS]), with the greatest effect in the EX-4 group. In the N(ω)-nitro-l-arginine-methyl ester challenge, only EX-4 exhibited a significant impact on the nitric oxide system, suggesting higher activity in this group. In the STZ-induced diabetic rat model, wild-type BM powerfully lowered glucose levels, and, in healthy adult rats, wild-type BM exhibited beneficial effects in the regulation of blood glucose, in RAS and ACE inhibition, and in nitric oxide generation.
The findings here suggest that both NAFLD and the MS very early in development have a common inciting mechanism(s)-most likely IR. Accordingly, the early concurrent temporal results are consistent with the concept that NAFLD is a hepatic manifestation of the IR associated with the MS. They do not exclude the possibility that once some liver functional adjustments take place, several aspects of the MS are bolstered further, perhaps via intensified heightening of IR.
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