Anti-Obesity Effects of Isorhamnetin and Isorhamnetin Conjugates.

Isorhamnetin is a plant-derived secondary metabolite which belongs to the family of flavonoids. This review summarises the main outcomes described in the literature to date, regarding the effects of isorhamnetin on obesity from in vitro and in vivo studies. The studies carried out in pre-adipocytes show that isorhamnetin is able to reduce adipogenesis at 10 µM or higher doses and that these effects are mediated by Pparγ and by Wnt signalling pathway. Very few studies addressed in rodents are available so far. It seems that treatment periods longer than two weeks are needed by isorhamnetin and its glycosides to be effective as anti-obesity agents. Nevertheless, improvements in glycaemic control can be observed even in short treatments. Regarding the underlying mechanisms of action, although some contradictory results have been found, reductions in de novo lipogenesis and fatty acid uptake could be proposed. Further research is needed to increase the scientific evidence referring to this topic; studies in animal models are essential, as well as randomised clinical trials to determine whether the positive results observed in animals could also be found in humans, in order to determine if isorhamnetin and its glycosides can represent a real tool against obesity.

Anti-Obesity Effects of Microalgae.

In recent years, microalgae have attracted great interest for their potential applications in nutraceutical and pharmaceutical industry as an interesting source of bioactive medicinal products and food ingredients with anti-oxidant, anti-inflammatory, anti-cancer, and anti-microbial properties. One potential application for bioactive microalgae compounds is obesity treatment. This review gathers together in vitro and in vivo studies which address the anti-obesity effects of microalgae extracts. The scientific literature supplies evidence supporting an anti-obesity effect of several microalgae: Euglena gracilis, Phaeodactylum tricornutum, Spirulina maxima, Spirulina platensis, or Nitzschia laevis. Regarding the mechanisms of action, microalgae can inhibit pre-adipocyte differentiation and reduce de novo lipogenesis and triglyceride (TG) assembly, thus limiting TG accumulation. Increased lipolysis and fatty acid oxidation can also be observed. Finally, microalgae can induce increased energy expenditure via thermogenesis activation in brown adipose tissue, and browning in white adipose tissue. Along with the reduction in body fat accumulation, other hallmarks of individuals with obesity, such as enhanced plasma lipid levels, insulin resistance, diabetes, or systemic low-grade inflammation are also improved by microalgae treatment. Not only the anti-obesity effect of microalgae but also the improvement of several comorbidities, previously observed in preclinical studies, has been confirmed in clinical trials.

Effect of Gracilaria vermiculophylla Macroalga on Non-Alcoholic Fatty Liver Disease in Obese Rats.

Marine algae are valuable sources of bioactive compounds that have the potential to be used in the management of various pathologies. Despite the increasing prevalence of NAFLD, the absence of an approved effective pharmacological treatment with demonstrable effectiveness persists. In this context, the aim of the present study is to assess the effect of Gracilaria vermiculophylla red seaweed dietary supplementation on hepatic lipid accumulation, as well as on oxidative stress, inflammation and fibrosis- related markers on obese fa/fa Zucker rats fed with a standard diet, supplemented or not with 2.5% or 5% dehydrated Gracilaria vermiculophylla. After a six-week supplementation with the macroalga, no significant reduction in hepatic total lipid content or hepatic triglyceride content was observed. However, both doses were able to diminish hepatic NEFA concentration by reducing de novo lipogenesis and increasing mitochondrial biogenesis. Moreover, supplementation with the dose of 2.5% improved some oxidative stress and inflammation-related markers. Supplementation with the dose of 5% did not exert these clear beneficial effects. Thus, this study demonstrates that while Gracilaria vermiculophylla may not mitigate hepatic steatosis, it could exert protective effects on the liver by reducing NEFA content and enhancing oxidative stress and inflammation parameters.

Anti-Steatotic Effects of Chlorella vulgaris, Nannochloropsis gaditana and Gracilaria vermiculophylla Algae Extracts in AML-12 Hepatocytes.

Non-alcoholic fatty liver disease (NAFLD) is considered the most common chronic liver alteration whose prevalence is increasing in Western countries. Microalgae and macroalgae have attracted great interest due to the high content in bioactive compounds with beneficial effects on health. The aim of the present study is to assess the potential interest of extracts rich in proteins obtained from the microalgae Chlorella vulgaris and Nannochloropsis gaditana and the macroalga Gracilaria vermiculophylla in the prevention of lipid accumulation in AML-12 hepatocytes. Toxicity was not observed at any of the tested doses. Both microalgae and the macroalga were effective in preventing triglyceride accumulation, with Nannochloropsis gaditana being the most effective one. Although the three algae extracts were able to increase different catabolic pathways involved in triglyceride metabolism, the mechanisms underlying the anti-steatotic effect were different in each algae extract. In conclusion, the present study demonstrates that Chlorella vulgaris, Nannochloropsis gaditana and Gracilaria vermiculophylla extracts are able to partially prevent the accumulation of triglycerides induced by palmitic acid in cultured hepatocytes, a model used to mimic the steatosis induced in liver by dietary patterns rich in saturated fat.

Effect of Microalgae and Macroalgae Extracts on Non-Alcoholic Fatty Liver Disease.

The present review aims to gather scientific evidence regarding the beneficial effects of microalgae and macroalgae extracts on non-alcoholic fatty liver disease (NAFLD). The described data show that both microalgae and macroalgae improved this alteration. The majority of the reported studies analysed the preventive effects because algae were administered to animals concurrent with the diet that induced NAFLD. The positive effects were demonstrated using a wide range of doses, from 7.5 to 300 mg/kg body weight/day or from 1 to 10% in the diet, and experimental periods ranged from 3 to 16 weeks. Two important limitations on the scientific knowledge available to date are that very few studies have researched the mechanisms of action underlying the preventive effects of microalgae on NAFLD and that, for the majority of the algae studied, a single paper has been reported. For these reasons, it is not possible to establish the best conditions in order to know the beneficial effects that these algae could bring. In this scenario, further studies are needed. Moreover, the beneficial effects of algae observed in rodent need to be confirmed in humans before we can start considering these products as new tools in the fight against fatty liver disease.

Scientific Evidence Supporting the Beneficial Effects of Isoflavones on Human Health.

Isoflavones are phenolic compounds with a chemical structure similar to that of estradiol. They are present in several vegetables, mainly in legumes such as soy, white and red clover, alfalfa and beans. The most significant food source of isoflavones in humans is soy-derived products. Isoflavones could be used as an alternative therapy for pathologies dependent on hormonal disorders such as breast and prostate cancer, cardiovascular diseases, as well as to minimize menopausal symptoms. According to the results gathered in the present review, it can be stated that there is scientific evidence showing the beneficial effect of isoflavones on bone health and thus in the prevention and treatment of osteoporosis on postmenopausal women, although the results do not seem entirely conclusive as there are discrepancies among the studies, probably related to their experimental designs. For this reason, the results should be interpreted with caution, and more randomized clinical trials are required. By contrast, it seems that soy isoflavones do not lead to a meaningful protective effect on cardiovascular risk. Regarding cancer, scientific evidence suggests that isoflavones could be useful in reducing the risk of suffering some types of cancer, such as breast and endometrial cancer, but further studies are needed to confirm these results. Finally, isoflavones could be useful in reducing hot flushes associated with menopause. However, a limitation in this field is that there is still a great heterogeneity among studies. Lastly, with regard to isoflavone consumption safety, it seems that they are safe and that the most common adverse effect is mild and occurs at the gastrointestinal level.

Comparative Effects of Pterostilbene and Its Parent Compound Resveratrol on Oxidative Stress and Inflammation in Steatohepatitis Induced by High-Fat High-Fructose Feeding.

Different studies have revealed that oxidative stress and inflammation are crucial in NAFLD (Non-alcoholic fatty liver disease). The aim of this study is to analyze whether pterostilbene and resveratrol are able to either avoid or delay the progression of non-alcoholic liver steatosis towards steatohepatitis. This has been performed by examining their effects on oxidative stress, inflammation, fibrosis and pre-carcinogenic stages. Rats were distributed into five experimental groups and were fed with either a standard diet or a high-fat high-fructose diet, supplemented or not with pterostilbene (15 or 30 mg/kg/d) or resveratrol (30 mg/kg/d), for 8 weeks. Liver histological analysis was carried out by haematoxylin-eosin staining. Serum and hepatic oxidative stress-related parameters were assessed using spectrophotometry, and the expression of genes related to inflammation, fibrosis and cancer by qRT-PCR. The dietary model used in this study led to the development of steatohepatitis, where rats displayed oxidative stress, inflammation and ballooning, although not fibrosis. It also modified the expression of hepatocarcinoma-related genes. The results show, for the first time, that pterostilbene was able to partially prevent these alterations, with the exception of changes in hepatocarcinoma-related genes, mainly at 30 mg/kg/d. Pterostilbene was more effective than its parent compound resveratrol, probably due to its high bioavailability and higher anti-oxidant and anti-inflammatory activities, attributable to its different chemical structure.

Anti-Obesity Effects of Macroalgae.

Macroalgae have attracted great interest for their potential applications in nutraceutical and pharmaceutical industries as source of bioactive medicinal products and food ingredients. This review gathers data from in vitro and in vivo studies addressing the anti-obesity effects of macroalgae. Great consensus exists in all reported in vitro studies concerning the reduction induced by seaweed extracts in the expression of transcriptional factors controlling adipogenesis. In animals, macroalgae reduced body fat accumulation and prevented other obesity features, such as dyslipidemia, insulin resistance and fatty liver. These effects are not due to food intake reduction, since few studies have reported such event. Indeed, the effects on metabolic pathways in target tissues/organs seem to play a more relevant role. Macroalgae can reduce de novo lipogenesis, limiting fatty acid availability for triglyceride synthesis in white adipose tissue. This effect has been observed in both cell cultures and adipose tissue from animals treated with macroalgae extracts. In addition, increased fatty acid oxidation and thermogenic capacity, as well as a shift towards healthier gut microbiota composition may contribute to the body fat-lowering effect of macroalgae. Studies in humans are needed to determine whether macroalgae can represent a feasible tool to prevent and/or manage overweight and obesity.