Accessibility of 3H-Secoisolariciresinol Diglycoside Lignan Metabolites in Skeletal Tissue of Ovariectomized Rats

Targeting the gut microbiota-related metabolites for osteoporosis: The inextricable connection of gut-bone axis

Osteoporosis is a systemic skeletal disease characterized by decreased bone mass, destruction of bone microstructure, raised bone fragility, and enhanced risk of fractures. The correlation between gut microbiota and bone metabolism has gradually become a widespread research hotspot in recent years, and successive studies have revealed that the alterations of gut microbiota and its-related metabolites are related to the occurrence and progression of osteoporosis. Moreover, several emerging studies on the relationship between gut microbiota-related metabolites and bone metabolism are also underway, and extensive research evidence has indicated an inseparable connection between them. Combined with latest literatures and based on inextricable connection of gut-bone axis, this review is aimed to summarize the relation, potential mechanisms, application strategies, clinical application prospects, and existing challenges of gut microbiota and its-related metabolites on osteoporosis, thus updating the knowledge in this research field and providing certain reference for future researches.

Secoisolariciresinol diglucoside regulates estrogen receptor expression to ameliorate OVX-induced osteoporosis

OBJECTIVE

Secoisolariciresinol diglucoside (SDG) is a phytoestrogen that has been reported to improve postmenopausal osteoporosis (PMOP) caused by estrogen deficiency. In our work, we aimed to investigate the mechanism of SDG in regulating the expressions of ERs on PMOP model rats.

METHODS

Ovariectomization (OVX) was used to establish PMOP model in rats. The experiment was allocated to Sham, OVX, SDG and raloxifene (RLX) groups. After 12-week treatment, micro-CT was used to detect the transverse section of bone. Hematoxylin and Eosin staining and Safranine O-Fast Green staining were supplied to detect the femur pathological morphology of rats. Estradiol (E2), interleukin-6 (IL-6), bone formation and bone catabolism indexes in serum were detected using ELISA. Alkaline phosphatase (ALP) staining was used to detect the osteogenic ability of chondrocytes. Immunohistochemistry and Western blot were applied to detect the protein expressions of estrogen receptors (ERs) in the femur of rats.

RESULTS

Compared with the OVX group, micro-CT results showed SDG could lessen the injury of bone and improve femoral parameters, including bone mineral content (BMC) and bone mineral density (BMD). Pathological results showed SDG could reduce pathological injury of femur in OVX rats. Meanwhile, SDG decreased the level of IL-6 and regulated bone formation and bone catabolism indexes. Besides, SDG increased the level of E2 and conversed OVX-induced decreased the expression of ERα and ERβ.

CONCLUSION

The treatment elicited by SDG in OVX rats was due to the reduction of injury and inflammation and improvement of bone formation index, via regulating the expression of E2 and ERs.

High-yield production of secoisolariciresinol diglucoside from flaxseed hull by extraction with alcoholic ammonium hydroxide and chromatography on microporous resin

This study used alcoholic ammonium hydroxide to directly hydrolyze and extract secoisolariciresinol diglucoside (SDG) from flaxseed hull in a one pot reaction. The optimal extraction conditions, including the concentration of ammonium hydroxide, extraction time, and temperature, were examined in single factor experiments, followed by response surface methodology (RSM) with 3-level, 3-factor Box-Behnken experiments. As a result, the optimal extraction conditions were determined as follows: material-liquid ratio 1:20, percentage of reagent ammonium hydroxide (25–28% of NH3 in water) in ethanol 33.7% (pH = 12.9), extraction time 4.9 h, and extraction temperature 75.3 °C. Under these conditions, the yield of SDG, as measured by ultra-high-performance liquid chromatography-mass spectrometry, was 23.3 mg/g, consistent with the predicted content of SDG in flaxseed hull (23.0 mg/g). Further, 30.0 g of pulverized flaxseed hull was extracted under the optimal conditions, and the extract was subjected to a single run of macroporous resin chromatography to obtain 772.1 mg of a fraction with an SDG content exceeding 76.1%. Subsequent chromatography on Sephadex LH20, yielded 602.8 mg SDG of 98.0% purity, and the yield was 20.1 mg/g (2.0%) from flaxseed hulls. Thus, one-pot hydrolysis and extraction of SDG using alcoholic ammonium hydroxide is simple, and of high-yield.

Graphical abstract

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.