Anti-diabetic activity of PUFAs-rich extracts of Chlorella pyrenoidosa and Spirulina platensis in rats

Algae-derived compounds: Bioactivity, allergenicity and technologies enhancing their values

As a rapidly growing source of human nutrients, algae biosynthesize diverse metabolites which have promising bioactivities. However, the potential allergenicity of algal components hinder their widespread adoption. This review provides a comprehensive review of various macro and micronutrients derived from algal biomass, with particular focus on bioactive compounds, including peptides, polyphenols, carotenoids, omega-3 fatty acids and phycocyanins. The approaches used to produce algal bioactive compounds and their health benefits (antioxidant, antidiabetic, cardioprotective, anti-inflammatory and immunomodulatory) are summarised. This review particularly focuses on the state-of-the-art of precision fermentation, encapsulation, cold plasma, high-pressure processing, pulsed electric field, and subcritical water to reduce the allergenicity of algal compounds while increasing their bioactivity and bioavailability. By providing insights into current challenges of algae-derived compounds and opportunities for advancement, this review contributes to the ongoing discourse on maximizing their application potential in the food nutraceuticals, and pharmaceuticals industries.

XQZ3, a Chlorella pyrenoidosa polysaccharide suppresses cancer progression by restraining mitochondrial bioenergetics via HSP90/AKT signaling pathway

The mitochondria are known to exert significant influence on various aspects of cancer cell physiology. The suppression of mitochondrial function represents a novel avenue for the advancement of anti-cancer pharmaceuticals. The heat shock protein HSP90 functions as a versatile regulator of mitochondrial metabolism in cancer cells, rendering as a promising target for anticancer interventions. In this work, a novel acid polysaccharide named as XQZ3 was extracted from Chlorella pyrenoidosa and purified by DEAE-cellulose and gel-filtration chromatography. The structural characteristic of XQZ3 was evaluated by monosaccharides composition, methylation analysis, TEM, FT-IR, and 2D-NMR. It was found that XQZ3 with a molecular weight of 29.13 kDa was a complex branched polysaccharide with a backbone mainly composed of galactose and mannose. It exhibited good antitumor activity in vitro and in vivo by patient-derived 3D organoid models and patient-derived xenografts models. The mechanistic investigations revealed that XQZ3 specifically interacted with HSP90, impeding the activation of the HSP90/AKT/mTOR signaling cascade. This, in turn, led to the induction of mitochondrial dysfunction, autophagy, and apoptosis, ultimately resulting in the demise of cancer cells due to nutrient deprivation. This study offers a comprehensive theoretical foundation for the advancement of XQZ3, a novel polysaccharide inhibitor targeting HSP90, with potential as an effective therapeutic agent against cancer.

Innovative Bioactive Products with Medicinal Value from Microalgae and Their Overall Process Optimization through the Implementation of Life Cycle Analysis-An Overview

Microalgae are being recognized as valuable sources of bioactive chemicals with important medical properties, attracting interest from multiple industries, such as food, feed, cosmetics, and medicines. This review study explores the extensive research on identifying important bioactive chemicals from microalgae, and choosing the best strains for nutraceutical manufacturing. It explores the most recent developments in recovery and formulation strategies for creating stable, high-purity, and quality end products for various industrial uses. This paper stresses the significance of using Life Cycle Analysis (LCA) as a strategic tool with which to improve the entire process. By incorporating LCA into decision-making processes, researchers and industry stakeholders can assess the environmental impact, cost-effectiveness, and sustainability of raw materials of several approaches. This comprehensive strategy will allow for the choosing of the most effective techniques, which in turn will promote sustainable practices for developing microalgae-based products. This review offers a detailed analysis of the bioactive compounds, strain selection methods, advanced processing techniques, and the incorporation of LCA. It will serve as a valuable resource for researchers and industry experts interested in utilizing microalgae for producing bioactive products with medicinal properties.

Alistipes indistinctus-derived hippuric acid promotes intestinal urate excretion to alleviate hyperuricemia

Hyperuricemia induces inflammatory arthritis and accelerates the progression of renal and cardiovascular diseases. Gut microbiota has been linked to the development of hyperuricemia through unclear mechanisms. Here, we show that the abundance and centrality of Alistipes indistinctus are depleted in subjects with hyperuricemia. Integrative metagenomic and metabolomic analysis identified hippuric acid as the key microbial effector that mediates the uric-acid-lowering effect of A. indistinctus. Mechanistically, A. indistinctus-derived hippuric acid enhances the binding of peroxisome-proliferator-activated receptor γ (PPARγ) to the promoter of ATP-binding cassette subfamily G member 2 (ABCG2), which in turn boosts intestinal urate excretion. To facilitate this enhanced excretion, hippuric acid also promotes ABCG2 localization to the brush border membranes in a PDZ-domain-containing 1 (PDZK1)-dependent manner. These findings indicate that A. indistinctus and hippuric acid promote intestinal urate excretion and offer insights into microbiota-host crosstalk in the maintenance of uric acid homeostasis.

Assessment of heavy metals and environmental stress conditions on the production potential of polyunsaturated fatty acids (PUFAs) in indigenous microalgae isolated from the Gulf of Mannar coastal waters

The present study evaluated the effects of heavy metals, viz., lead, mercury, and cadmium, on growth, chlorophyll a, b, c, carotenoids, and PUFA content of marine microalgae Chlorella sp. and Cylindrotheca fusiformis. At 96-h exposure, the IC50 values for Hg2+, Pb2+, and Cd2+ were 0.85 mg/L, 2.4 mg/L, and 5.3 mg/L respectively, in Chlorella sp. In C. fusiformis, IC50 values for Hg2+, Pb2+, and Cd2+ were 0.5 mg/L, 1.2 mg/L, and 3 mg/L respectively. The pigment contents of both microalgae were significantly affected upon heavy metal exposure. In Chlorella sp. and C. fusiformis, the exposed concentrations of Hg2+ averagely decreased the PUFA content by 76.34% and 78.68%, respectively. Similarly, Pb2+-exposed concentrations resulted in 54.50% and 82.64% average reductions in PUFA content of Chlorella sp. and C. fusiformis, respectively. Cd2+-exposed concentrations showed 32.58% and 40.54% average reduction in PUFA content of Chlorella sp. and C. fusiformis, respectively. Among the environmental stress conditions, the dark treatment has increased total PUFA content by 6.63% in Chlorella sp. and 3.92% in C. fusiformis. It was observed that the 50% nitrogen starvation (two-stage) significantly improved the PUFA production from 26.47 ± 6.55% to 40.92 ± 10.74% in Chlorella sp. and from 11.23 ± 5.01 to 32.8 ± 14.17% in C. fusiformis. The toxicity for both microalgae was followed in the order Hg2+ > Pb2+ > Cd2+. Among the two species, Chlorella sp. has shown a high tolerance to heavy metals and can be effectively utilized in PUFA production.

In Vitro Anti-Oxidant, In Vivo Anti-Hyperglycemic, and Untargeted Metabolomics-Aided-In Silico Screening of Macroalgae Lipophilic Extracts for Anti-Diabetes Mellitus and Anti-COVID-19 Potential Metabolites

COVID-19 patients with comorbid DM face more severe outcomes, indicating that hyperglycemic conditions exacerbate SARS-CoV-2 infection. Negative side effects from existing hyperglycemia treatments have urged the need for safer compounds. Therefore, sourcing potential compounds from marine resources becomes a new potential approach. Algal lipids are known to possess beneficial activities for human health. However, due to limitations in analyzing large amounts of potential anti-hyperglycemic and anti-COVID-19-related marine metabolites, there is an increasing need for new approaches to reduce risks and costs. Therefore, the main aim of this study was to identify potential compounds in macroalgae Sargassum cristaefolium, Tricleocarpa cylindrica, and Ulva lactuca lipophilic extracts for treating DM and COVID-19 by an integrated approach utilizing in vitro anti-oxidant, in vivo anti-hyperglycemic, and metabolomic-integrated in silico approaches. Among them, S. cristaefolium and T. cylindrica showed potential anti-hyperglycemic activity, with S. cristaefolium showing the highest anti-oxidant activity. A GC-MS-based untargeted metabolomic analysis was used to profile the lipophilic compounds in the extracts followed by an in silico molecular docking analysis to examine the binding affinity of the compounds to anti-DM and anti-COVID-19 targets, e.g., α-amylase, α-glucosidase, ACE2, and TMPRSS2. Notably, this study reveals for the first time that steroid-derived compounds in the macroalgae T. cylindrica had higher binding activity than known ligands for all the targets mentioned. Studies on drug likeliness indicate that these compounds possess favorable drug properties. These findings suggest the potential for these compounds to be further developed to treat COVID-19 patients with comorbid DM. The information in this study would be a basis for further in vitro and in vivo analysis. It would also be useful for the development of these candidate compounds into drug formulations.

Study on the effect of licochalcone A on intestinal flora in type 2 diabetes mellitus mice based on 16S rRNA technology

Licorice, has a long history in China where it has various uses, including as a medicine, and is often widely consumed as a food ingredient. Licorice is rich in various active components, including polysaccharides, triterpenoids, alkaloids, and nucleosides, among which licochalcone A (LicA) is an active component with multiple physiological effects. Previous studies from our research group have shown that LicA can significantly improve glucose and lipid metabolism and related complications in Type 2 diabetes mellitus (T2DM) mice. However, research on the mechanism of LicA in T2DM mice based on intestinal flora has not been carried out in depth. Therefore, in this study, LicA was taken as the research object and the effects of LicA on glucose and lipid metabolism and intestinal flora in T2DM mice induced by streptozotocin (STZ)/high-fat feed (HFD) were explored. The results indicated that LicA could reduce serum TC, TG, and LDL-C levels, increase HDL-C levels, reduce blood glucose, and improve insulin resistance and glucose tolerance. LicA also alleviated pathological damage to the liver. The results also showed that LicA significantly affected the intestinal microbiota composition and increased the α diversity index. β Diversity analysis showed that after the intervention of LicA, the composition of intestinal flora was significantly different from that in the T2DM model group. Correlation analysis showed that the changes in glucose and lipid metabolism parameters in mice were significantly correlated with the relative abundance of Firmicutes, Bacteroidetes, Helicobacter, and Lachnospiraceae (p < 0.01). Analysis of key bacteria showed that LicA could significantly promote the growth of beneficial bacteria, such as Bifidobacterium, Turicibacter, Blautia, and Faecococcus, and inhibit the growth of harmful bacteria, such as Enterococcus, Dorea, and Arachnococcus. In conclusion, it was confirmed that LicA reversed the imbalanced intestinal flora, and increased the richness and diversity of the species in T2DM mice.

Potential benefits of microalgae intake against metabolic diseases: beyond spirulina-a systematic review of animal studies

CONTEXT

Microalgae are a diverse source of bioactive molecules, such as polyphenols, carotenoids, and omega-3 fatty acids, with beneficial properties in biomarkers of metabolic diseases. Unlike the rest of the microalgae genera, Arthrospira sp., commonly called spirulina, has been widely studied.

OBJECTIVE

This review aims to describe the current knowledge about microalgae, besides spirulina, focusing on their beneficial properties against metabolic diseases.

DATA SOURCES

A systematic research of MEDLINE (via PubMed), Cochrane, and Scopus databases was conducted to identify relevant studies published after January 2012. In vivo animal studies including microalgae consumption, except for spirulina, that significantly improved altered biomarkers related to metabolic diseases were included. These biomarkers included body weight/composition, glucose metabolism, lipid metabolism, oxidative damage, inflammation markers, and gut microbiota.

DATA EXTRACTION

After the literature search and the implementation of inclusion and exclusion criteria, 37 studies were included in the revision out of the 132 results originally obtained after the application of the equation on the different databases.

DATA ANALYSIS

Data containing 15 microalgae genera were included reporting on a wide range of beneficial results at different levels, including a decrease in body weight and changes in plasma levels of glucose and lipoproteins due to molecular alterations such as those related to gene expression regulation. The most reported beneficial effects were related to gut microbiota and inflammation followed by lipid and glucose metabolism and body weight/composition.

CONCLUSIONS

Microalgae intake improved different altered biomarkers due to metabolic diseases and seem to have potential in the design of enriched foodstuffs or novel nutraceuticals. Nevertheless, to advance to clinical trials, more thorough/detailed studies should be performed on some of the microalgae genera included in this review to collect more information on their molecular mechanisms of action.

Therapeutic Potentials of Microalgae and Their Bioactive Compounds on Diabetes Mellitus

Diabetes mellitus is a metabolic disorder characterized by hyperglycemia due to impaired insulin secretion, insulin resistance, or both. Oxidative stress and chronic low-grade inflammation play crucial roles in the pathophysiology of diabetes mellitus. There has been a growing interest in applying natural products to improve metabolic derangements without the side effects of anti-diabetic drugs. Microalgae biomass or extract and their bioactive compounds have been applied as nutraceuticals or additives in food products and health supplements. Several studies have demonstrated the therapeutic effects of microalgae and their bioactive compounds in improving insulin sensitivity attributed to their antioxidant, anti-inflammatory, and pancreatic β-cell protective properties. However, a review summarizing the progression in this topic is lacking despite the increasing number of studies reporting their anti-diabetic potential. In this review, we gathered the findings from in vitro, in vivo, and human studies to discuss the effects of microalgae and their bioactive compounds on diabetes mellitus and the mechanisms involved. Additionally, we discuss the limitations and future perspectives of developing microalgae-based compounds as a health supplement for diabetes mellitus. In conclusion, microalgae-based supplementation has the potential to improve diabetes mellitus and be applied in more clinical studies in the future.

Regulatory mechanisms of the edible alga Ulva lactuca polysaccharide via modulation of gut microbiota in diabetic mice

In this study, Ulva lactuca polysaccharide (ULP) antihyperglycemic effect was assessed by monitoring changes in the gut microbiota of aging diabetic mice. The results showed that ULP alleviated type 2 diabetes by improving insulin tolerance, increasing SOD and CAT activities, and thus lowering blood glucose level. Moreover, ULP regulated the expressions of INSR and AMPK concurrent with inhibition the expression of JNK, JAK, STAT3, p16 and p38 to improve glucose metabolism dysfunction. Interestingly, the abundance of Alloprevotella and Pediococcus change might the key factor for ULP antihyperglycemic effectiveness in aging-related diabetes. These results suggest that ULP can exert a mechanism of blood glucose regulation by improving intestinal diversity composition asides from direct insulin mimetic actions.

Oral Palatability and Owners' Perception of the Effect of Increasing Amounts of Spirulina (Arthrospira platensis) in the Diet of a Cohort of Healthy Dogs and Cats

The nutraceutical supplementation of Spirulina (Arthrospira platensis) in dogs and cats has not yet been investigated. The aim of this study was to evaluate if the dietary supplementation of increasing amounts of Spirulina for 6 weeks is palatable to pets and to assess the owner's perception of such supplementation. The owners of the 60 dogs and 30 cats that participated in this study were instructed to daily provide Spirulina tablets starting with a daily amount of 0.4 g, 0.8 g, and 1.2 g for cats as well as small dogs, medium dogs, and large dogs, respectively, and allowing a dose escalation of 2× and 3× every 2 weeks. The daily amount (g/kg BW) of Spirulina ranged from 0.08 to 0.25 for cats, from 0.06 to 0.19 for small-sized dogs, from 0.05 to 0.15 for medium-sized dogs, and from 0.04 to 0.12 for large-sized dogs. Each owner completed a questionnaire at the time of recruitment and the end of each 2-week period. No significant effect on the fecal score, defecation frequency, vomiting, scratching, lacrimation, general health status, and behavioral attitudes was detected by the owners' reported evaluations. Most animals accepted Spirulina tablets either administrated alone or mixed with food in the bowl. Daily supplementation of Spirulina for 6 weeks in the amounts provided in this study is therefore palatable and well tolerated by dogs and cats.

Bioprocessing to Preserve and Improve Microalgae Nutritional and Functional Potential: Novel Insight and Perspectives

Microalgae are aquatic unicellular microorganisms and, although various species are approved for human consumption, Arthrospira and Chlorella are the most widespread. Several nutritional and functional properties have been bestowed to microalgae principal micro- and macro-nutrients, with antioxidant, immunomodulatory and anticancer being the most common. The many references to their potential as a food of the future is mainly ascribed to the high protein and essential amino acid content, but they are also a source of pigments, lipids, sterols, polysaccharides, vitamins, and phenolic compounds with positive effects on human health. Nevertheless, microalgae use is often hindered by unpleasant color and flavor and several strategies have been sought to minimize such challenges. This review provides an overview of the strategies so far proposed and the main nutritional and functional characteristic of microalgae and the foods made thereof. Processing treatments have been used to enrich microalgae-derived substrates in compounds with antioxidant, antimicrobial, and anti-hypertensive properties. Extraction, microencapsulation, enzymatic treatments, and fermentation are the most common, each with their own pros and cons. Yet, for microalgae to be the food of the future, more effort should be put into finding the right pre-treatments that can allow the use of the whole biomass and be cost-effective while bringing about features that go beyond the mere increase of proteins.

Effects of Spirulina maxima on a Model of Sexual Dysfunction in Streptozotocin-Induced Diabetic Male Rats

Arthrospira (Spirulina) maxima (SM) is a cyanobacterium that has a long history of being used as human food. In recent years, several investigations have shown its beneficial biological effects, among which its antioxidant capacity has been highlighted. The purpose of this study was to evaluate the effects of SM on body weight, glycemia, sexual behavior, sperm quality, testosterone levels, sex organ weights, and the activity of antioxidant enzymes in diabetic male rats (a disease characterized by an increase in reactive oxygen species). The experiment consisted of six groups of sexually expert adult males (n = 6): (1) control (vehicle); (2) streptozotocin (STZ)-65 mg/kg; (3) SM-400 mg/kg; (4) STZ + SM-100 mg/kg; (5) STZ + SM-200 mg/kg; and (6) STZ + SM-400 mg/kg. Sexual behavior tests were performed during the first 3 h of the dark period under dim red illumination. Our results showed that SM significantly improved sexual behavior and sperm quality vs. diabetic animals. Likewise, while the enzymatic activities of SOD and GPx increased, TBARS lipoperoxidation decreased and testosterone levels increased. In view of the findings, it is suggested that SM may potentially be used as a nutraceutical for the treatment of diabetic male sexual dysfunction due to its antioxidant property.

Responses and tolerance mechanisms of microalgae to heavy metal stress: A review

Microalgae, the primary producers in water ecosystems, are the main food of fish and shrimp. Microalgae have a great capacity to absorb heavy metals, and low concentrations of heavy metals can promote the growth of them. But high concentrations have a strong influence on the physiological and biochemical processes in algae, such as growth, photosynthesis, cell ultrastructure, protein content and fatty acid composition. Heavy metals may also induce the formation of reactive oxygen species (ROS), which causes the oxidation damage of protein, lipid and thiol peptides, and activates the antioxidant system. Heavy metals can be removed or converted into another state by biosorption of cell surface, accumulation in cells, combining with antioxidant enzymes and so on. This review summarized the responses of microalgae to heavy metals and comprehensively described the removal and tolerance mechanisms by extracellular adsorption and intracellular accumulation, which are helpful to treat pollution and improve the culture of microalgae.

Inhibitory Effects of Parachlorella Beijerinckii Extracts on the Formation of Advanced Glycation End Products and Glycative Stress-Induced Inflammation in an In Vitro Skin Dermis-Like Model

Advanced glycation end products (AGEs) are formed via a nonenzymatic glycosylation reaction called glycation. The formation and accumulation of AGEs increases in skin with age, contributing to the appearance of facial wrinkles and loss of skin elasticity. Therefore, inhibition of AGEs may delay skin aging. The microalgae Parachlorella beijerinckii has been used as a health food supplement for many years and contains carotenoids and vitamins that have antioxidant and anti-inflammatory effects. The aim of this study was to investigate whether Chlorella extract also has antiglycation activity. Antiglycation activity was measured using fluorescent AGEs, Nε-(carboxymethyl) lysine (CML), and Nε-(carboxymethyl) arginine (CMA) from glycated bovine serum albumin and type I collagen in vitro. A gel with a dermis-like structure consisting of collagen and a live fibroblast cell line was glycated with glyoxal. The content of fluorescent AGE, CML, and CMA, and the gel contraction activity were measured. In addition, to investigate the level of inflammation induced by the glycation of the collagen gel, the expression level of the receptor for AGEs and interleukin-8 were examined. Fat-solubleChlorella extract suppressed the formation of fluorescent AGEs, CML, and CMA in both models. These results indicated that Chlorella extract directly inhibited AGE formation. The collagen gel contracted over time during culturing, whereas contraction was inhibited in the glyoxal-treated collagen gel. Chlorella extract remarkably attenuated the glyoxal-induced gel contraction. Moreover, Chlorella extract substantially decreased the fluorescent AGEs, CML, and CMA in the collagen gels with glyoxal. Glyoxal exposure increased the expression levels of interleukin-8 and receptor for AGE proteins in collagen gels, while Chlorella extract inhibited this increase. This study showed that fat-solubleChlorella extract has a direct inhibitory effect on AGEs and decreases receptor expression for AGE-mediated inflammation by reducing AGEs. Chlorella may delay skin aging by inhibiting the formation and accumulation of AGEs.

Peanut skin procyanidins ameliorate insulin resistance via modulation of gut microbiota and gut barrier in type 2 diabetic mice

BACKGROUND

Peanut skin procyanidins (PSP) have been shown to possess antidiabetic activities. However, the mechanism remains poorly understood due to its low bioavailability. This study aims to investigate the preventive effect of PSP on type 2 diabetes (T2D) in mice through regulating gut microbiota and gut barrier in mice with streptozotocin (STZ)-induced T2D. During the 30 consecutive days of the study, T2D mice were administered PSP intragastrically at 75, 150 and 300 mg kg^-1 body weight d^-1 .

RESULTS

PSP treatment obviously alleviated glucolipid metabolism disorders, decreased the levels of lipopolysaccharide (LPS), interleukin (IL)-6 and myeloperoxidase(MPO), and increased that of IL-10. PSP treatment enhanced the abundance of Lachnospiraceae_NK4A136_group, Alloprevotella, Akkermansia and Faecalibaculum, and reduced that of Muribaculaceae. Some of these were associated with the production of short-chain fatty acids and anti-inflammatory effect, suggesting their important roles in T2D mice. More importantly, PSP improved the gut barrier integrality by restoring gut morphology and enhancing tight junction protein expression including ZO1, claudin1 and occludin in colon. Subsequently, PSP ameliorated insulin resistance by decreasing the LPS/Toll-like receptor 4/c-Jun N-terminal kinase inflammatory response, and enhancing insulin receptor substrate 1/ phosphatidylinositol-3-kinase/protein kinase B insulin signaling pathways in the liver.

CONCLUSION

Peanut skin procyanidins may alleviate the symptoms of T2D by mitigating inflammatory response, modulating gut microbiota and improving intestinal integrity. © 2022 Society of Chemical Industry.

Extraction of lipids from microalgae using classical and innovative approaches

Microalgae, as a photosynthetic autotrophic organism, contain a variety of bioactive compounds, including lipids, proteins, polysaccharides, which have been applied in food, medicine, and fuel industries, among others. Microalgae are considered a good source of marine lipids due to their high content in unsaturated fatty acid (UFA) and can be used as a supplement/replacement for fish-based oil. The high concentration of docosahexaenoic (DHA) and eicosapentaenoic acids (EPA) in microalgae lipids, results in important physiological functions, such as antibacterial, anti-inflammatory, and immune regulation, being also a prerequisite for its development and application. In this paper, a variety of approaches for the extraction of lipids from microalgae were reviewed, including classical and innovative approaches, being the advantages and disadvantages of these methods emphasized. Further, the effects of microalgae lipids as high value bioactive compounds in human health and their use for several applications are dealt with, aiming using green(er) and effective methods to extract lipids from microalgae, as well as develop and extend their application potential.

Chlorella unsaturated fatty acids suppress high-fat diet-induced obesity in C57/BL6J mice

Chlorella has been identified as a rich source of unsaturated fatty acids. Since the antiobesity effects of unsaturated fatty acids have been well documented; therefore, we explored the antiobesity actions of chlorella unsaturated fatty acids (C.UFAs) in the current study. The obtained results demonstrated C.UFAs, which contain abundant linoleic acid, could retard body weight gain (reducing body weigh by 13.93% after 16 weeks of treatment), improve blood glucose (19.29% lower) and lipid profile (23.45% lower in TG, 8.76% lower in TC) compared to high-fat diet-fed C57BL/6J mice. The possible underlying mechanisms might involve reducing hepatic lipid accumulation via down-regulation of lipogenic genes (PPARγ, C/EBPα, LPL, aP2, FAS, and SREBP-1c) and up-regulation of lipolytic gene (adiponectin). We also demonstrate C.UFAs could reduce HFD-induced adipocyte hypertrophy via activation of AMPK signaling pathway in adipose tissue and liver. In summary, our study highlights the potential of C.UFAs as a functional food for obesity management. PRACTICAL APPLICATION: Chlorella has already been commercialized as a functional food antiobesity function. In the current study, the unsaturated fatty acids isolated from chlorella were found to exert beneficial effects on hyperglycemia, hyperlipidemia, hepatic steatosis, and adipocyte hypertrophy in high-fat diet-fed mice. This may provide theoretical foundation for developing novel chlorella-based functional foods.

Ameliorating Effect on Glycolipid Metabolism of Spirulina Functional Formulation Combination from Traditional Chinese Medicine

Insulin resistance is the major factor involved in the pathogenesis of type 2 diabetes. Although the oral drug metformin (MH) is widely used to reduce hyperglycemia, it is associated with adverse effects. Therefore, there is an urgent need to search for safe and natural foods that do not cause adverse effects as alternatives to commercial drugs. In this study, the active substances from Spirulina platensis, Grifola frondosa, Panax ginseng, and chromium-rich yeast were used to obtain Spirulina functional formulations (SFFs), and its therapeutic effects on mice with glycolipid metabolism disorder (GLD) were investigated. Results showed that SFFs not only improved glycolipid metabolism and reduced inflammation in mice with GLD but also showed good regenerative effects on the liver, jejunum, and cecum tissues. Moreover, SFFs could inhibit the growth of harmful microbes in the intestine and promote the proliferation of beneficial bacteria, thereby promoting the production of short-chain fatty acids and further regulating GLD. Additionally, SFFs significantly increased the expression of INS, INSR, IRS-1, PI3K, AKT-1, and GLUT-4 genes and significantly decreased that of GSK-3β in the INS/PI3K/GLUT-4 signaling pathway. Therefore, the findings of this study suggest that SFFs can be further developed as a new class of therapeutic agents against GLD.

Anti-Diabetic Potential of Chlorella Pyrenoidosa-Based Mixture and its Regulation of Gut Microbiota

The aim of the present study was to investigate the anti-diabetic effect of CGSGCG and its beneficial effects on gut microbiota in type 2 diabetes (T2D) mice induced by streptozotocin and high sucrose and high fat diet. The results showed that treatment with CGSGCG reduced fasting blood glucose, improved oral glucose tolerance test, protected the liver from injury, and reduced inflammation in T2D mice. The contents of acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid and isovaleric acid in CGSGCG group were 2.49-, 1.74-, 3.31-, 1.93-, 1.36- and 1.30-fold than that of the model group. Moreover, administration of CGSGCG up-regulated the expression of INSR/IRS-1/PI3K/AKT/GLUT4 and mTOR but down-regulated the P38MAPK expression. Furthermore, the abundance of beneficial bacteria such as Verrucomicrobia, Proteobacteria, Osillibacter, Dubosiella and Lactococcus in intestinal tract increased, indicating that CGSCGG regulated and improved the bacterial community structure of T2D mice, which were closely related to glycometabolism.

Effect of dendrobium mixture in alleviating diabetic cognitive impairment associated with regulating gut microbiota

Dendrobium mixture (DM) is a patent Chinese herbal formulation consisting of Dendrobii Caulis, Astragali Radix, Rehmanniae Radix as the main ingredients. DM has been shown to alleviate diabetic related symptoms attributed to its anti-hyperglycaemic and anti-inflammatory activities. However, the effect on diabetic induced cognitive dysfunction has not been investigated. This study aims to investigate the effect of DM in improving diabetic cognitive impairment and associated mechanisms. Our study confirmed the anti-hyperglycaemic effect of DM and showed its capacity to restore the cognitive and memory function in high fat/high glucose and streptozotocin-induced diabetic rats. The neuroprotective effect was manifested as improved learning and memory behaviours, restored blood-brain barrier tight junction, and enhanced expressions of neuronal survival related biomarkers. DM protected the colon tight junction, and effectively lowered the circulated proinflammatory mediators including tumour necrosis factor-α, interleukin-6 and lipopolysaccharides. In the gut microbiota, DM corrected the increase in the abundance of Firmicutes, the increase in the ratio of Firmicutes/Bacteroidetes, and the decrease in the abundance of Bacteroidetes in diabetic rats. It also reversed the abundance of Lactobacillus, Ruminococcus and Allobaculum genera. Short chain fatty acids, isobutyric acid and ethylmethylacetic acid, were negatively and significantly correlated to Ruminococcus and Allobaculum. Isovaleric acid was positively and significantly correlated with Lactobacillus, which all contributing to the improvement in glucose level, systemic inflammation and cognitive function in diabetic rats. Our results demonstrated the potential of DM as a promising therapeutic agent in treating diabetic cognitive impairment and the underlying mechanism may be associated with regulating gut microbiota.

Gut microbiome responses to dietary intervention with hypocholesterolemic vegetable oils

Hypercholesterolemia is becoming a problem with increasing significance. Dietary vegetable oils may help to improve this condition due to presence of phytonutrients with potentially synergistic cholesterol-lowering effects. The objective of this 8-week double-blinded randomized clinical trial was to investigate the effects of consuming 30 g of two different blended cooking oils, rich in omega-3 alpha-linolenic acid and phytonutrients, or refined olive oil on the intestinal microbiota in 126 volunteers with borderline hypercholesterolemia. Multi-factor analysis of relationships between the gut microbiota composition at various taxonomic ranks and the clinical trial parameters revealed the association between beneficial effects of the dietary intervention on the blood lipid profile with abundance of Clostridia class of the gut microbiota. This microbiota feature was upregulated in the course of the dietary intervention and associated with various plasma markers of metabolic health status, such as Triglycerides, Apolipoprotein B and Total Cholesterol to HDL ratio in a beneficial way. The relative abundance of a single species—Clostridium leptum—highly increased during the dietary intervention in all the three study groups. The oil blend with the highest concentration of omega-3 PUFA is associated with faster and more robust responses of the intestinal microbiota, including elevation of alpha-diversity. Butyrate production is being discussed as a plausible process mediating the observed beneficial influence on the plasma lipid profile. Causal mediation analysis suggested that Clostridium genus rather than the higher rank of the phylogeny—Clostridia class—may be involved in the diet-induced improvements of the blood lipid profile.

Applications of algae to obtain healthier meat products: A critical review on nutrients, acceptability and quality

Meat constitutes one the main protein sources worldwide. However, ethical and health concerns have limited its consumption over the last years. To overcome this negative impact, new ingredients from natural sources are being applied to meat products to obtain healthier proteinaceous meat products. Algae is a good source of unsaturated fatty acids, proteins, essential amino acids, and vitamins, which can nutritionally enrich several foods. On this basis, algae have been applied to meat products as a functional ingredient to obtain healthier meat-based products. This paper mainly reviews the bioactive compounds in algae and their application in meat products. The bioactive ingredients present in algae can give meat products functional properties such as antioxidant, neuroprotective, antigenotoxic, resulting in healthier foods. At the same time, algae addition to foods can also contribute to delay microbial spoilage extending shelf-life. Additionally, other algae-based applications such as for packaging materials for meat products are being explored. However, consumers' acceptance for new products (particularly in Western countries), namely those containing algae, not only depends on their knowledge, but also on their eating habits. Therefore, it is necessary to further explore the nutritional properties of algae-containing meat products to overcome the gap between new meat products and traditional products, so that healthier algae-containing meat can occupy a significant place in the market.

Green Alga Enteromorpha prolifera Oligosaccharide Ameliorates Ageing and Hyperglycemia through Gut-Brain Axis in Age-Matched Diabetic Mice

SCOPE

To investigate the anti-ageing and anti-diabetic effects of Enteromorpha prolifera oligosaccharide (EPO) in age-matched streptozocin-induced diabetic mice.

METHODS AND RESULTS

LC-MS metabolomics and 16S rRNA sequencing is used to identify the brain metabolites and gut microbiota, respectively. EPO could significantly improve glucose metabolism and activity of total superoxide dismutase in serum. It also could regulate the tricarboxylic acid cycle, arginine, and inosine-related metabolic pathways in the brain of aged diabetic mice. Inosine is found to enhance the relative expressions of daf-2, daf-16, and skn-1 in insulin-resistant Caenorhabditis elegans. Additionally, EPO could alter the composition and diversity of gut microbiota in mice. It could upregulate the Signal Transducer and Activator of Transcription 3/Forkhead Box O1 (FOXO1)/B cell lymphoma 6 (Bcl-6) pathways in the brain and the c-Jun N-terminal Kinase (JNK)/FOXO1/Bcl-6 signaling axis in the intestine to regulate glucose metabolite status and ageing in mice. EPO could also improve the levels of glucagon-like peptide type 1 (GLP1) expression in the gut, thereby inducing high expression of GLP1 receptor in the brain to control glucose metabolites through the brain-gut axis. Enterococcus is negatively correlated with AMP in the brain and could be a potential hallmark species in age-related diabetes.

CONCLUSIONS

These results suggest that EPO could be a potential novel natural drug for the treatment of diabetes in the elderly.

Yeast assisted algal flocculation for enhancing nutraceutical potential of Chlorella pyrenoidosa

The present research describes yeast assisted algal flocculation followed by evaluation of algae-yeast flocs for nutritional profile as potent food product. Co-flocculation of Chlorella pyrenoidosa using Saccharomyces cerevisiae showed 58.33 ± 2.37% flocculation efficiency. Nutrient composition of algae-yeast flocs (CP-Y) depicted higher protein content (35.52%) as compared to algae (23.72%) and yeast biomass (33.89). Amino acid profiles of CP-Y biomass depicted increase in essential amino acid content with higher ratio of essential to non-essential amino acid (0.68) as compared to Y (0.57) and CP (0.57) biomass. Lipid and carbohydrate content of CP-Y flocs was estimated as 26.95 ± 0.57% and 21.12 ± 0.83%, respectively. Fatty Acid Methyl Esters (FAME) analysis showed presence of omega rich polyunsaturated fatty acids (PUFAs) like α-linolenic acid (ω-3), Linoleic acid (ω-6), Palmitoleic acid (ω-7) etc in CP-Y biomass. The study provides novel insights on nutrition enriched biomass obtained after algal-yeast flocculation, which can be a better alternative to existing flocculation methods for food applications.

Effect of Microalgae Arthrospira on Biomarkers of Glycemic Control and Glucose Metabolism: A Systematic Review and Meta-analysis

Diabetes mellitus and insulin resistance are associated with an increased risk of cardiovascular disease (CVD) incidence and a higher rate of CVD-related death. In this study, the effects of Arthrospira (Spirulina) a blue-green algae supplementation on biomarkers of glycemic control and glucose metabolism has been evaluated. PubMed, Scopus, and ISI Web of Science were searched systematically of English human subjects and PubMed for pre-clinical animal studies (rats and mice) from January 2008 until November 2020. The pooled weighted mean difference (MD) and its 95% confidence interval (CI) were calculated and pooled using a random-effect model. Seven clinical and 27 preclinical studies were included. Pooled results of the clinical studies showed that Arthrospira supplementation significantly reduced the fasting blood sugar (FBS): (0.63- 2.90-) 1.77-, total cholesterol (TC): (0.46- ، 4.61-) 2.54-, triglycerides (TG): (0.89- ، 6.54-) 3.71- and increased the high-density lipoprotein cholesterol (HDL-C): (3.86 ، 0.67) 2.27; however, Arthrospira was not significantly effective in terms of reducing the glycated hemoglobin A1c (HbA1C): (1.04 ، 2.23-) 0.59- and low-density lipoprotein cholesterol (LDL-C). Pooled results of preclinical studies showed that Arthrospira supplementation reduced FBS [-10.31 (-12.49, -8.13)] and HbA1C [-5.12 (-8.06, -2.19)] significantly in diabetic animals. Sub-group analysis of clinical studies showed that intervention duration less than 2 months [-2.52 (-4.37, -0.67)] and the dose less than 2 gram [-3.22 (-5.67, -0.76)] showed significant improvement in terms of reducing the FBS in humans. It can be concluded that Arthrospira can be considered as an effective FBS, TG, TC, and HDL-C adjusting nutraceutical agent for diabetes mellitus. Due to the differences in the results of clinical and animal studies in terms of HbA1c, more studies are needed for a definitive conclusion.

An In Vitro Pilot Fermentation Study on the Impact of Chlorella pyrenoidosa on Gut Microbiome Composition and Metabolites in Healthy and Coeliac Subjects

The response of a coeliac and a healthy gut microbiota to the green algae Chlorella pyrenoidosa was evaluated using an in vitro continuous, pH controlled, gut model system, which simulated the human colon. The effect of C. pyrenoidosa on the microbial structure was determined by 16S rRNA gene sequencing and inferred metagenomics, whereas the metabolic activitywas determined by¹H-nuclear magnetic resonancespectroscopic analysis. The addition of C. pyrenoidosa significantly increased the abundance of the genera Prevotella, Ruminococcus and Faecalibacterium in the healthy donor, while an increase in Faecalibacterium, Bifidobacterium and Megasphaera and a decrease in Enterobacteriaceae were observed in the coeliac donor. C. pyrenoidosa also altered several microbial pathways including those involved in short-chain fatty acid (SCFA) production. At the metabolic level, a significant increase from baseline was seen in butyrate and propionate (p < 0.0001) in the healthy donor, especially in vessels 2 and 3. While acetate was significantly higher in the healthy donor at baseline in vessel 3 (p < 0.001) compared to the coeliac donor, this was markedly decreased after in vitro fermentation with C. pyrenoidosa. This is the first in vitro fermentation study of C. pyrenoidosa and human gut microbiota, however, further in vivo studies are needed to prove its efficacy.

Edible Microalgae and Their Bioactive Compounds in the Prevention and Treatment of Metabolic Alterations

Marine and freshwater algae and their products are in growing demand worldwide because of their nutritional and functional properties. Microalgae (unicellular algae) will constitute one of the major foods of the future for nutritional and environmental reasons. They are sources of high-quality protein and bioactive molecules with potential application in the modern epidemics of obesity and diabetes. They may also contribute decisively to sustainability through carbon dioxide fixation and minimization of agricultural land use. This paper reviews current knowledge of the effects of consuming edible microalgae on the metabolic alterations known as metabolic syndrome (MS). These microalgae include Chlorella, Spirulina (Arthrospira) and Tetraselmis as well as Isochrysis and Nannochloropsis as candidates for human consumption. Chlorella biomass has shown antioxidant, antidiabetic, immunomodulatory, antihypertensive, and antihyperlipidemic effects in humans and other mammals. The components of microalgae reviewed suggest that they may be effective against MS at two levels: in the early stages, to work against the development of insulin resistance (IR), and later, when pancreatic -cell function is already compromised. The active components at both stages are antioxidant scavengers and anti-inflammatory lipid mediators such as carotenoids and -3 PUFAs (eicosapentaenoic acid/docosahexaenoic acid; EPA/DHA), prebiotic polysaccharides, phenolics, antihypertensive peptides, several pigments such as phycobilins and phycocyanin, and some vitamins, such as folate. As a source of high-quality protein, including an array of bioactive molecules with potential activity against the modern epidemics of obesity and diabetes, microalgae are proposed as excellent foods for the future. Moreover, their incorporation into the human diet would decisively contribute to a more sustainable world because of their roles in carbon dioxide fixation and reducing the use of land for agricultural purposes.

Microalgae as source of functional ingredients in new-generation foods: challenges, technological effects, biological activity, and regulatory issues

Microalgae feasibility as food ingredients or source of nutrients and/or bioactive compounds and their health effects have been widely studied. This review aims to provide an overview of the use of microalgae biomass in food products, the technological effects of its incorporation, and their use as a source of health-promoting bioactive compounds. In addition, it presents the regulatory aspects of commercialization and consumption, and the main trends and market challenges Microalgae have stood out as sources of nutritional compounds (polysaccharides, proteins, lipids, vitamins, minerals, and dietary fiber) and biologically active compounds (asthaxanthin, β-carotene, omega-3 fatty acids). The consumption of microalgae biomass proved to have several health effects, such as hypoglycemic activity, gastroprotective and anti-steatotic properties, improvements in neurobehavioral and cognitive dysfunction, and hypolipidemic properties. Its addition to food products can improve the nutritional value, aroma profile, and technological properties, with important alterations on the syneresis of yogurts, meltability in cheeses, overrun values and melting point in ice creams, physical properties and mechanical characteristics in crisps, and texture, cooking and color characteristics in pastas. However, more studies are needed to prove the health effects in humans, expand the market size, reduce the cost of production, and tighter constraints related to regulations.

Physicochemical characterization and antioxidant effects of green microalga Chlorella pyrenoidosa polysaccharide by regulation of microRNAs and gut microbiota in Caenorhabditis elegans

A novel polysaccharide from Chlorella pyrenoidosa (CPP) was separated and purified with the average molecular weight 15.8 kDa. It was composed of seven monosaccharides including mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, and arabinose. FT-IR and NMR spectra analysis further revealed that CPP was an acidic polysaccharide consisting of β-L-Arap-(1→, →2)-α-L-Rhap-(1→, β-D-GlcpA-(1→, →4)-α-D-GalpA-(1→, →6)-β-D-Glcp-(1→, →3)-β-D-Manp-(1→, and →3, 6)-β-D-Galp-(1→. The CPP treatment could effectively prolong lifespan of Caenorhabditis elegans under the oxidative stress conditions and inhibit the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) as well as enhancing the level of superoxide dismutase (SOD). It could up-regulate the expressions of Daf-16 and Skn-1 genes via declining miR-48-3p, miR-48-5p, and miR-51-5p translocation. Moreover, 16S rRNA sequencing revealed that the CPP-enriched Faecalibacterium, Haemophilus, Vibrio, and Shewanella were strongly correlated with SOD, MDA, apoptosis, and ROS. These results indicated that CPP may be considered as a desired ingredient on regulating the aging and oxidative diseases.

Spirulina for the food and functional food industries

Humans are no strangers to the consumption of microalgae as already in the sixteenth century Spirulina was harvested from Lake Texcoco and consumed in markets in Tenochtitlan (today Mexico City). Nowadays, microalgae are being incorporated into many food formulations. Most of these use microalgae as a marketing strategy or as a colouring agent. However, Spirulina (and compounds derived thereof) show potential for being used as ingredients in the development of novel functional foods, which are one of the top trends in the food industry. Several human intervention studies demonstrated the potential of Spirulina for being used in the prevention or treatment of disorders related to metabolic syndrome. The aim of the current paper was to review current and potential applications of this microalga in the food and functional food industries. Health benefits associated with consuming Spirulina and/or some of the most important compounds derived from Spirulina were also discussed.

Ecophysiological Features of Polar Soil Unicellular Microalgae1

Due to their ecological, physiological, and molecular adaptations to low and varying temperatures, as well as varying seasonal irradiances, polar non-marine eukaryotic microalgae could be suitable for low-temperature biotechnology. Adaptations include the synthesis of compounds from different metabolic pathways that protect them against stress. Production of biological compounds and various biotechnological applications, for instance, water treatment technology, are of interest to humans. To select prospective strains for future low-temperature biotechnology in polar regions, temperature and irradiance of growth requirements (Q₁₀ and Ea of 10 polar soil unicellular strains) were evaluated. In terms of temperature, three groups of strains were recognized: (i) cold-preferring where temperature optima ranged between 10.1 and 18.4°C, growth rate 0.252 and 0.344 · d^-1 , (ii) cold- and warm-tolerating with optima above 10°C and growth rate 0.162-0.341 · d^-1 , and (iii) warm-preferring temperatures above 20°C and growth rate 0.249-0.357 · d^-1 . Their light requirements were low. Mean values Q₁₀ for specific growth rate ranged from 0.7 to 3.1. The lowest Ea values were observed on cold-preferring and the highest in the warm-preferring strains. One strain from each temperature group was selected for P_N and R_D measurements. The P_N :R_D ratio of the warm-preferring strains was less affected by temperature similarly as Q₁₀ and Ea. For future biotechnological applications, the strains with broad temperature tolerance (i.e., the group of cold- and warm-tolerating and warm-preferring strains) will be most useful.

Physicochemical Characterization of a Polysaccharide from Green Microalga Chlorella pyrenoidosa and Its Hypolipidemic Activity via Gut Microbiota Regulation in Rats

A bioactive polysaccharide from microalga Chlorella pyrenoidosa (CPP) was successively prepared via DEAE-52 and G-100 columns. Nuclear magnetic resonance analysis showed that the main glycosidic bonds were composed of 1,2-linked-α-l-Fucp, 1,4-linked-α-l-Rhap, 1,4-linked-β-l-Araf, 1-linked-α-d-Glcp, 1,3-linked-β-d-GlcpA, 1,4-linked-β-d-Xylp, and 1,3,6-linked-β-d-Manp. Its molecular weight was 5.63 × 10⁶ Da. The hypolipidemic effect and intestinal flora regulation of CPP on diet-induced rats were evaluated through histopathology and biochemistry analyses. CPP could improve plasma and liver lipid metabolism and accelerate the metabolism of the cecal total bile acids and short-chain fatty acids. CPP has also upregulated the adenosine-monophosphate-activated protein kinase α and downregulated the acetyl-CoA carboxylase, sterol regulatory element-binding protein 1c, and β-hydroxy β-methylglutaryl-CoA expressions. Moreover, with the 16S rRNA gene sequencing, it was revealed that the composition of intestinal flora changed drastically after treatment, such as the bloom of Coprococcus_1, Lactobacillus, and Turicibacter, whereas there was a strong reduction of the [Ruminococcus]_gauvreauii_group. The above results illustrated that CPP might be served as an effective ingredient to ameliorate lipid metabolism disorders and intestinal flora in hyperlipidemia rats.

Rotundic Acid Protects against Metabolic Disturbance and Improves Gut Microbiota in Type 2 Diabetes Rats

Rotundic acid (RA) is a major triterpene constituent in the barks of Ilex rotunda Thunb, which have been widely used to make herbal tea for health care in southern China. RA has a variety of bioactivities such as anti-inflammation and lipid-lowering effect. However, little is known about the effects and mechanisms of RA on metabolic disturbance in type 2 diabetes (T2D) and its effect on gut microbiota. A T2D rat model induced by high fat diet (HFD) feeding and low-dose streptozotocin (STZ) injection was employed and RA showed multipronged effects on T2D and its complications, including improving glucolipid metabolism, lowering blood pressure, protecting against cardiovascular and hepatorenal injuries, and alleviating oxidative stress and inflammation. Furthermore, 16s rRNA gene sequencing was carried out on an Illumina HiSeq 2500 platform and RA treatment could restore the gut microbial dysbiosis in T2D rats to a certain extent. RA treatment significantly enhanced the richness and diversity of gut microbiota. At the genus level, beneficial or commensal bacteria Prevotella, Ruminococcus, Leuconostoc and Streptococcus were significantly increased by RA treatment, while RA-treated rats had a lower abundance of opportunistic pathogen Klebsiella and Proteus. Spearman’s correlation analysis showed that the abundances of these bacteria were strongly correlated with various biochemical parameters, suggesting that the improvement of gut microbiota might help to prevent or attenuate T2D and its complication. In conclusion, our findings support RA as a nutraceutical agent or plant foods rich in this compound might be helpful for the alleviation of T2D and its complications through improving gut microbiota.