Flaxseed enhances the beneficial effect of low-dose estrogen therapy at reducing bone turnover and preserving bone microarchitecture in ovariectomized rats

A comprehensive review on recent novel food and industrial applications of flaxseed: 2014 onwards

Flaxseed or linseed is an oilseed obtained from a plant, known as the flax (Linum usitatissimum). It is a valuable source of various bioactive components such as omega-3 polyunsaturated fatty acids, proteins, lignans, dietary fibres and phytochemicals. The in-vivo, in-vitro studies and research on human subjects and in animal models, conducted throughout the globe, on health benefits associated with the consumption of various forms of flaxseed are discussed in this review. It provides an insight into recent developments and potential applications of flaxseeds in the form of whole seeds, meals, flour or oil in an array of food and feed products and non-food industrial applications. The details about novel health benefits associated with flaxseeds and information related to commercially available flaxseed-based i.e. enriched products are also the salient feature of the review. Here, we have provided the state of the art of most recent comprehensive information post the first detailed review on flaxseed as a modern food released in 2014.

A comprehensive review on recent novel food and industrial applications of flaxseed: 2014 onwards

Flaxseed or linseed is an oilseed obtained from a plant, known as the flax (Linum usitatissimum). It is a valuable source of various bioactive components such as omega-3 polyunsaturated fatty acids, proteins, lignans, dietary fibres and phytochemicals. The in-vivo, in-vitro studies and research on human subjects and in animal models, conducted throughout the globe, on health benefits associated with the consumption of various forms of flaxseed are discussed in this review. It provides an insight into recent developments and potential applications of flaxseeds in the form of whole seeds, meals, flour or oil in an array of food and feed products and non-food industrial applications. The details about novel health benefits associated with flaxseeds and information related to commercially available flaxseed-based i.e. enriched products are also the salient feature of the review. Here, we have provided the state of the art of most recent comprehensive information post the first detailed review on flaxseed as a modern food released in 2014.

Bioaccessibility and bioavailability of calcium in sprouted brown and golden flaxseed

BACKGROUND

Germination promotes changes in the composition of seeds by providing potential nutritional and health benefits compared with unsprouted seeds. This study investigated the influence of germination on the bioaccessibility and bioavailability of calcium in brown flaxseed (BF) and golden flaxseed (GF).

RESULTS

Germination did not influence the calcium levels of BF or GF, but the sprouted GF (SGF, 265.6 ± 12.9 mg) presented higher levels of calcium than the sprouted BF (SBF, 211.6 ± 3.20 mg). Tannin levels were similar among the groups (GF = 79.97 ± 3.49 mg; SGF = 78.81 ± 0.77 mg; BF = 81.82 ± 2.61 mg; SBF = 79.24 ± 4.58 mg), whereas phytate and oxalate levels decreased after germination. Germination reduced the phytate:calcium and oxalate:calcium molar ratios. In the in vitro study, germination increased calcium bioaccessibility (GF = 35.60 mg versus SGF = 41.45 mg; BF = 31.01 mg versus SBF = 38.84 mg). In the in vivo study, all groups present similar levels of urinary calcium (GF = 1.04 mg versus SGF = 2.06 mg; BF = 1.68 mg versus SBF = 1.35 mg) and fecal calcium (GF = 5.06 mg versus SGF = 6.14 mg; BF = 6.47 mg versus SBF = 8.40 mg). The calcium balance/day of the SBF group (37.97 mg) was smaller than the control group (47.22 mg). The germination maintained the plasma levels of calcium, phosphorus, creatinine, and alkaline phosphatase similar among the groups. No changes were observed in morphology and calcium levels of animal femurs.

CONCLUSION

The germination reduced the antinutritional factor in both flaxseed varieties. Although there was an improvement in the in vitro bioaccessibility of calcium, the germination did not increase calcium absorption and balance in the animals, which may be due to the interaction with other compounds in the organism. © 2020 Society of Chemical Industry.

Phytochemicals affect T helper 17 and T regulatory cells and gut integrity: implications on the gut-bone axis

The pathology of osteoporosis is multifactorial, but a growing body of evidence supports an important role of the gut-bone axis, especially in bone loss associated with menopause, rheumatoid arthritis, and periodontal disease. Aberrant T cell responses favoring an increase in the ratio of T helper 17 cells to T regulatory cells play a critical role in the underlying etiology of this bone loss. Many of the dietary phytochemicals known to have osteoprotective activity such as flavonoids, organosulfur compounds, phenolic acids, as well as the oligosaccharides also improve gut barrier function and affect T cell differentiation and activation within gut-associated lymphoid tissues and at distal sites. Here, we examine the potential of these phytochemicals to act as prebiotics and immunomodulating agents, in part targeting the gut to mediate their effects on bone.

Flaxseed Lignans as Important Dietary Polyphenols for Cancer Prevention and Treatment: Chemistry, Pharmacokinetics, and Molecular Targets

Cancer causes considerable morbidity and mortality across the world. Socioeconomic, environmental, and lifestyle factors contribute to the increasing cancer prevalence, bespeaking a need for effective prevention and treatment strategies. Phytochemicals like plant polyphenols are generally considered to have anticancer, anti-inflammatory, antiviral, antimicrobial, and immunomodulatory effects, which explain their promotion for human health. The past several decades have contributed to a growing evidence base in the literature that demonstrate ability of polyphenols to modulate multiple targets of carcinogenesis linking models of cancer characteristics (i.e., hallmarks and nutraceutical-based targeting of cancer) via direct or indirect interaction or modulation of cellular and molecular targets. This evidence is particularly relevant for the lignans, an ubiquitous, important class of dietary polyphenols present in high levels in food sources such as flaxseed. Literature evidence on lignans suggests potential benefit in cancer prevention and treatment. This review summarizes the relevant chemical and pharmacokinetic properties of dietary polyphenols and specifically focuses on the biological targets of flaxseed lignans. The consolidation of the considerable body of data on the diverse targets of the lignans will aid continued research into their potential for use in combination with other cancer chemotherapies, utilizing flaxseed lignan-enriched natural products.

Synergistic attenuation of ovariectomy-induced bone loss by combined use of fish oil and 17β-oestradiol

Oestrogen and n-3 PUFA, especially EPA and DHA, have been reported to have beneficial effects on bone loss. Thus, the purpose of the present study was to investigate the synergistic bone-protective mechanism of combined treatments of EPA+DHA supplementation and oestrogen injection in ovariectomised rats. Rats were fed a modified American Institute of Nutrition-93G diet with 0 %, 1 % or 2 % n-3 PUFA (EPA+DHA) relative to the total energy intake for 12 weeks. Rats were surgically ovariectomised at week 8, and after a 1-week recovery period rats were injected with either 17β-oestradiol-3-benzoate (E2) or maize oil for the last 3 weeks. Combined use of n-3 PUFA and E2 synergistically increased femoral cortical bone volume, bone mineral content and the bone expression of runt-related transcription factor 2 (RUNX2), but decreased the bone expression of IL-1β. Both n-3 PUFA and E2 decreased the bone expressions of IL-7, TNF-α and PPAR-γ, and increased the bone expression of oestrogen receptor-α. n-3 PUFA in the presence of E2 and E2 alone significantly decreased the bone expressions of IL-1β and IL-6 and increased the bone expression of RUNX2. E2 significantly decreased the serum levels of bone turnover markers and the bone expression of receptor activator of NF-κB ligand, but decreased the bone expression of osteoprotegerin. The combined use of n-3 PUFA and E2 exerted synergistic bone-protective efficacy through up-regulation of RUNX2, an essential transcription factor for bone formation, as well as the suppression of bone-resorbing cytokine IL-1β.

Lifelong intake of flaxseed or menhaden oil to provide varying n-6 to n-3 PUFA ratios modulate bone microarchitecture during growth, but not after OVX in Sprague-Dawley rats

SCOPE

Skeletal health is a lifelong process impacted by environmental factors, including nutrient intake. The n-3 source and PUFA ratio affect bone health in growing rats, or following ovariectomy (OVX), but no study has investigated the longitudinal effect of PUFA-supplementation throughout these periods of bone development.

METHODS AND RESULTS

One-month-old, Sprague-Dawley rats (n = 98) were randomized to receive one of four diets from 1 through 6 months of age. Diets were modified from AIN-93G to contain a varying amount and source of n-3 (flaxseed versus menhaden oil) to provide an n-6 to n-3 ratio of 10:1 or 5:1. At 3 (prior to SHAM or OVX) and 6 months of age, bone microarchitecture of the tibia was quantified using in vivo micro-computed tomography (SkyScan 1176, Bruker microCT). Providing 5:1 (flaxseed) resulted in lower trabecular thickness and medullary area and greater cortical area fraction during growth compared to diets with a 10:1 PUFA ratio, but many of these differences were not apparent following OVX.

CONCLUSION

PUFA-supplementation at levels attainable in human diet modulates some bone structure outcomes during periods of growth, but is not an adequate strategy for the prevention of OVX-induced bone loss in rats.

Suppression of NADPH Oxidase Activity May Slow the Expansion of Osteolytic Bone Metastases

Lysophosphatidic acid (LPA), generated in the microenvironment of cancer cells, can drive the proliferation, invasion, and migration of cancer cells by activating G protein-coupled LPA receptors. Moreover, in cancer cells that have metastasized to bone, LPA signaling can promote osteolysis by inducing cancer cell production of cytokines, such as IL-6 and IL-8, which can stimulate osteoblasts to secrete RANKL, a key promoter of osteoclastogenesis. Indeed, in cancers prone to metastasize to bone, LPA appears to be a major driver of the expansion of osteolytic bone metastases. Activation of NADPH oxidase has been shown to play a mediating role in the signaling pathways by which LPA, as well as RANKL, promote osteolysis. In addition, there is reason to suspect that Nox4 activation is a mediator of the feed-forward mechanism whereby release of TGF-beta from bone matrix by osteolysis promotes expression of PTHrP in cancer cells, and thereby induces further osteolysis. Hence, measures which can down-regulate NADPH oxidase activity may have potential for slowing the expansion of osteolytic bone metastases in cancer patients. Phycocyanin and high-dose statins may have utility in this regard, and could be contemplated as complements to bisphosphonates or denosumab for the prevention and control of osteolytic lesions. Ingestion of omega-3-rich flaxseed or fish oil may also have potential for controlling osteolysis in cancer patients.

An 8-O-4' norlignan exerts oestrogen-like actions in osteoblastic cells via rapid nongenomic ER signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Sambucus williamsii Hance (SWH), which belongs to the Caprifoliaceae family distributed in various regions of China, Korea and Japan, has been used as a folk medicine for treatment of bone and joint diseases in China for thousands of years. In previous studies, SWH was shown to possess anti-osteoporosis, healing fracture, anti-inflammatory and analgesic activities. Our previous studies showed that SWH extract effectively suppressed ovariectomy-induced increase in bone turnover and improved bone mineral density and bone biomechanical strength in rats as well as in mice. An 8-O-4' norlignan, (7R,8S)-1-(4-hydroxy-3-methoxyphenyl)-2-[4-(3-hydroxypropyl)-2-methoxyphenoxy]-1,3-propanediol (PPD) was previously isolated and identified as the bioactive ingredient in SWH. The present study aimed to characterize the bone protective effects as well as its mechanism of actions in osteoblasts.

MATERIALS AND METHODS

Bone protective actions of PPD on different cells were determined by proliferation assay, alkaline phosphatase (ALP) activity assay, calcium deposition as well as real-time reverse transcriptase-polymerase chain reaction (RT-PCR). In addition, estrogen receptor (ER) antagonist ICI182,780 and mitogen-activated protein kinase kinase (MEK) inhibitor U0126 blocking assays, competitive ER radioligand binding assay, ERE-dependent luciferase reporter assay and immunoblotting were used to determine if PPD activated ER and if the effects of PPD on osteoblastic functions were ER dependent.

RESULTS

PPD exerted anabolic effects in osteoblasts and its effects were abolished by co-incubation with ICI182,780 or U0126. PPD induced mRNA expressions of Runx2, ALP, osteocalcin, and increased the ratio of osteoprotegerin/receptor activator of nuclear factor κB (OPG/RANKL). PPD failed to bind to either ERα or ERβ and did not activate ERE-luciferase activity via ER. PPD induced the phosphorylation of extracellular regulated kinases (ERK) and its effect was completely abolished by U0126. It also induced the phosphorylation of ERα at serine 118.

CONCLUSION

These data show that PPD is a bioactive compound in SWH that exerts oestrogen-like actions in osteoblast-like cells via ligand-independent, estrogen response element (ERE)-independent and mitogen-activated protein (MAP) Kinase-mediated rapid nongenomic ER signaling pathway.