Secoisolariciresinol diglucoside in high-fat diet and streptozotocin-induced diabetic nephropathy in rats: a possible renoprotective effect

Distribution, biosynthesis and therapeutic potential of lignans

Lignans have long been known for their abundant therapeutic properties due to their polyphenolic structure. Linseed is the richest plant source of lignans and has been studied widely for their properties. The most prevalent lignan, secoisolariciresinol diglucoside (SDG), is consumed with linseed and converted into mammalian lignans, enterodiol (END) and enterolactone (ENL), by the gut microbiota. SDG can easily be assessed using HPLC and its deglycosylated form viz secoisolariciresinol can be asses using GC-MS techniques. Variety of extraction and analysis methods has been reported for plant lignans. SDG is known to have therapeutic properties including anti-oxidant, anti-cancerous, anti-inflammatory, modulation of gene expression, anti-diabetic, estrogenic and anti-estrogenic. Despite a large number of bioactivities, strong evidences for the underlying mechanisms for most of the properties are still unknown. SDG is most studied for its anti-cancerous properties. But the use of lignans as anti-carcinogenic agent is limited and commercially not reported due to challenges of purification at commercial level, rapid metabolism, untargeted delivery and toxic compounds associated with lignans. Exploration of more prominent and active derivatives of SDG and their targeted drug delivery should be an important research toward the use of bioactive lignans of linseed.

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

Atherosclerosis Development and Aortic Contractility in Hypercholesterolemic Rabbits Supplemented with Two Different Flaxseed Varieties

Alpha-linolenic acid (ALA) is widely regarded as the main beneficial component of flax for the prevention of cardiovascular disease. We evaluated the effect of the transgenic flaxseed W86-which is rich in ALA-on the lipid profile, atherosclerosis progression, and vascular reactivity in hypercholesterolemic rabbits compared to the parental cultivar Linola with a very low ALA content. Rabbits were fed a basal diet (control) or a basal diet supplemented with 1% cholesterol, 1% cholesterol and 10% flaxseed W86, or 1% cholesterol and 10% Linola flaxseed. A high-cholesterol diet resulted in an elevated plasma cholesterol and triglyceride levels compared to the control animals. Aortic sections from rabbits fed Linola had lower deposits of foamy cells than those from rabbits fed W86. A potassium-induced and phenylephrine-induced contractile response was enhanced by a high-cholesterol diet and not influenced by the W86 or Linola flaxseed. Pretreatment of the aortic rings with nitro-L-arginine methyl ester resulted in a concentration-dependent tendency to increase the reaction amplitude in the control and high-cholesterol diet groups but not the flaxseed groups. Linola flaxseed with a low ALA content more effectively reduced the atherosclerosis progression compared with the W86 flaxseed with a high concentration of stable ALA. Aorta contractility studies suggested that flaxseed ameliorated an increased contractility in hypercholesterolemia but had little or no impact on NO synthesis in the vascular wall.

C1q/Tumor Necrosis Factor-Related Protein-9 Attenuates Diabetic Nephropathy and Kidney Fibrosis in db/db Mice

Diabetic nephropathy (DN) is characterized by excessive accumulation of extracellular matrix leading to early thickening of glomerular and tubular basement membrane. C1q/tumor necrosis factor (TNF)-related protein-9 (CTRP9) was recently identified as an adiponectin paralog of superior prominence. CTRP9 is an anti-inflammatory, antioxidant, vasodilation and atheroprotective adipose cytokine that share a similar metabolic regulatory function as adiponectin. Additionally, CTRP9 inhibits apoptosis of endothelial cells, decreases blood glucose level, and increases insulin sensitivity. However, the renoprotective effects of CTRP9 and the underlying molecular mechanisms in DN have not been explored. This study examined the effects of CTRP9 on DN in diabetic db/db mice through adenovirus-mediated overexpression. From the results, CTRP9 ameliorated renal dysfunction and injury at the structural and functional level in diabetic db/db mice. Additionally, CTRP9 inhibited glomerular and tubular glycogen accumulation, fibrosis, relieved hyperglycemia-mediated oxidative stress, and apoptosis. This is the first study to report on therapeutic effects of CTRP9 on DN, presenting a potentially effective clinical treatment method for DN patients.

Mechanisms of Herbal Nephroprotection in diabetes mellitus

Diabetic nephropathy (DN) is a leading cause of kidney morbidity. Despite the multilayered complexity of the mechanisms involved in the pathogenesis of DN, the conventional treatment is limited to just a few drug classes fraught with the risk of adverse events, including the progression of renal dysfunction. Phytoceuticals offer a promising alternative as they act on the many-sidedness of DN pathophysiology, multitargeting its intricacies. This paper offers a review of the mechanisms underlying the protective action of these phytoagents, including boosting the antioxidant capabilities, suppression of inflammation, averting the proliferative and sclerosing/fibrosing events. The pathogenesis of DN is viewed as a continuum going from the original offense, high glucose, through the noxious products it generates (advanced glycation end-products, products of oxidative and nitrosative stress) and the signaling chains consequently brought into action, to the harmful mediators of inflammation, sclerosis, and proliferation that eventually lead to DN, despite the countervailing attempts of the protective mechanisms. Special attention was given to the various pathways involved, pointing out the ability of the phytoagents to hinder the deleterious ones (especially those leading to, driven by, or associated with TGF-β activation, SREBP, Smad, MAPK, PKC, NF-κB, NLRP3 inflammasome, and caspase), to promote the protective ones (PPAR-α, PPAR-γ, EP4/Gs/AC/cAMP, Nrf2, AMPK, and SIRT1), and to favorably modulate those with potentially dual effect (PI3K/Akt). Many phytomedicines have emerged as potentially useful out of in vitro and in vivo studies, but the scarcity of human trials seriously undermines their usage in the current clinical practice-an issue that stringently needs to be addressed.

Mangosteen Vinegar Rind from Garcinia mangostana Prevents High-Fat Diet and Streptozotocin-Induced Type II Diabetes Nephropathy and Apoptosis

Type II diabetes (T2D) nephropathy, a major cause of end-stage kidney disease, progresses and develops from oxidative stress. Natural polyphenols can protect the kidney from diabetic nephropathy exerting antioxidant activities. The present approach enumerates the reno-protective and anti-apoptotic effects of mangosteen vinegar rind (MVR, a phenolic aqueous extract) against high-fat diet (5 g/day up to five weeks)-/streptozotocin (single ip, dose 30 mg/kgBW)-induced T2D nephropathy of albino mice. In vitro total phenolic content, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) activity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant capacity, and α-amylase inhibition activity as antidiabetic assay of MVR were performed. In vivo mice body weight, oral glucose, and maltose tolerance test, metabolic parameters (plasma glucose, insulin level, omeostasis model assessment-estimated insulin resistance), biochemical parameters (kidney hypertrophy, blood urea nitrogen, creatinine), oxidative stress parameters (malondialdehyde, superoxide dismutase, catalase) were estimated in an intervention study. Additionally, renal morphology and early apoptosis were observed following the H & E staining and TUNEL assay of the tissue frozen section. We found that the aqueous extract of MVR possesses potent in vitro antioxidative and antidiabetic activities. Animal intervention results showed that MVR 100, 200 mg/kgBW, and Glibenclamide 60 mg/kgBW treatments significantly improved (P < 0.05) the abovementioned parameters compared to the diabetic control group. Furthermore, treatments also significantly restored (P < 0.05) kidney histological alterations and reduced cellular apoptosis compared to the diabetic control group. These findings concluded that MVR treatments significantly modulated the glucose intolerance, metabolic alterations, and oxidative stress-induced pathological alterations and cellular apoptosis of diabetic kidney. PRACTICAL APPLICATION: Garcinia mangostana, a polyphenol rich natural product, is obtained from the tropical rain forest area of Southeast Asian countries and processes diverse biological activities including antioxidant, anti-proliferative, anti-inflammatory, anti-carcinogenic, and so on. This research first time focuses on the nephro-protective and anti-apoptotic effects of mangosteen vinegar rind (MVR) from the mangosteen fruit pericarp. Our study provides the efficient data to prove the beneficial effect of MVR as a dietary supplement for the prevention and management of diabetic nephropathy.

Inducible nitric oxide synthase-derived nitric oxide reduces vagal satiety signalling in obese mice

KEY POINTS

Obesity is associated with disrupted satiety regulation. Mice with diet-induced obesity have reduced vagal afferent neuronal excitability and a decreased afferent response to satiety signals. A low grade inflammation occurs in obesity with increased expression of inducible nitric oxide synthase (iNOS). Inhibition of iNOS in diet-induced obese mice restored vagal afferent neuronal excitability, increased the afferent response to satiety mediators and distention of the gut, and reduced short-term energy intake. A prolonged inhibition of iNOS reduced energy intake and body weight gain during the first week, and reduced amounts of epididymal fat after 3 weeks. We identified a novel pathway underlying disrupted satiety regulation in obesity. Blocking of this pathway might be clinically useful for the management of obesity.

ABSTRACT

Vagal afferents regulate feeding by transmitting satiety signals to the brain. Mice with diet-induced obesity have reduced vagal afferent sensitivity to satiety signals. We investigated whether inducible nitric oxide synthase (iNOS)-derived NO contributed to this reduction. C57BL/6J mice were fed a high- or low-fat diet for 6-8 weeks. Nodose ganglia and jejunum were analysed by immunoblotting for iNOS expression; NO production was measured using a fluorometric assay. Nodose neuron excitability and intestinal afferent sensitivity were evaluated by whole-cell patch clamp and in vitro afferent recording, respectively. Expression of iNOS and production of NO were increased in nodose ganglia and the small intestine in obese mice. Inhibition of iNOS in obese mice by pre-treatment with an iNOS inhibitor increased nodose neuron excitability via 2-pore-domain K⁺ channel leak currents, restored afferent sensitivity to satiety signals and reduced short-term energy intake. Obese mice given the iNOS inhibitor daily for 3 weeks had reduced energy intake and decreased body weight gain during the first week, compared to mice given saline, and lower amounts of epididymal fat at the end of 3 weeks. Inhibition of iNOS or blocking the action of iNOS-derived NO on vagal afferent pathways might comprise therapeutic strategies for hyperphagia and obesity.

Age-Dependent Differential Expression of Apoptotic Markers in Rat Oral Mucosa

Objective: This study tests the hypothesis that gingival tissue produces age-dependent activation of apoptotic markers. Methods: To address the hypothesis, a prospective experimental study was conducted on 20 adult male albino rats, which were divided into two groups. Group 1 comprised rats aged six months (weighing 150–200 g), and group 2 included old rats aged one year (weighing 250–300 g). Gingival tissue and buccal mucosa biopsy samples were obtained from both groups. Histological and immunohistochemical (Bax apoptotic protein marker) sections were analyzed for both groups. Results: Our data showed a significant decrease in the proliferative activity of oral mucosa (gingiva and buccal mucosa) in old rats and an increase in the immunoreactivity of Bax apoptotic proteins related to increased susceptibility of cells to apoptosis. The mucosal structures (epithelium and lamina propria) were significantly different between the two groups. Furthermore, immunoreactivity for Bax was different between young and old rats. Conclusions: Aging is associated with changes that lead to progressive, irreversible deterioration of the functional capacities of several tissues and organs. Our study demonstrated the effect of age on the histological and apoptotic behavior of oral mucosa (gingiva and buccal mucosa) cells.

Combined systems pharmacology and fecal metabonomics to study the biomarkers and therapeutic mechanism of type 2 diabetic nephropathy treated with Astragalus and Leech

In our study, systems pharmacology was used to predict the molecular targets of Astragalus and Leech, and explore the therapeutic mechanism of type 2 diabetic nephropathy (T2DN) treated with Astragalus and Leech. Simultaneously, to reveal the systemic metabolic changes and biomarkers associated with T2DN, we performed 1H NMR-based metabonomics and multivariate analysis to analyze fecal samples obtained from model T2DN rats. In addition, ELISA kits and histopathological studies were used to examine biochemical parameters and kidney tissue, respectively. Striking differences in the Pearson's correlation of 22 biomarkers and 9 biochemical parameters were also observed among control, T2DN and treated rats. Results of systems pharmacology analysis revealed that 9 active compounds (3,9-di-O-methylnissolin; (6aR,11aR)-9,10-dimethoxy-6a,11a-dihydro-6H-benzofurano[3,2-c]chromen-3-ol; hirudin; l-isoleucine; phenylalanine; valine; hirudinoidine A-C) and 9 target proteins (l-serine dehydratase; 3-hydroxyacyl-CoA dehydrogenase; tyrosyl-tRNA synthetase; tryptophanyl-tRNA synthetase; branched-chain amino acid aminotransferase; acetyl-CoA C-acetyltransferase; isovaleryl-CoA dehydrogenase; pyruvate dehydrogenase E1 component alpha subunit; hydroxyacylglutathione hydrolase) of Astragalus and Leech were closely associated with the treatment of T2DN. Using fecal metabonomics analysis, 22 biomarkers were eventually found to be closely associated with the occurrence of T2DN. Combined with systems pharmacology and fecal metabonomics, these biomarkers were found to be mainly associated with 6 pathways, involving amino acid metabolism (leucine, valine, isoleucine, alanine, lysine, glutamate, taurine, phenylalanine, tryptophan); energy metabolism (lactate, succinate, creatinine, α-glucose, glycerol); ketone body and fatty acid metabolism (3-hydroxybutyrate, acetate, n-butyrate, propionate); methylamine metabolism (dimethylamine, trimethylamine); and secondary bile acid metabolism and urea cycle (deoxycholate, citrulline). The underlying mechanisms of action included protection of the liver and kidney, enhancement of insulin sensitivity and antioxidant activity, and improvement of mitochondrial function. To the best of our knowledge, this is the first time that systems pharmacology combined with fecal metabonomics has been used to study T2DN. 6 metabolites (n-butyrate, deoxycholate, propionate, tryptophan, taurine and glycerol) associated with T2DN were newly discovered in fecal samples. These 6 metabolites were mainly derived from the intestinal flora, and related to amino acid metabolism, fatty acid metabolism, and secondary bile acid metabolism. We hope the results of this study could be inspirational and helpful for further exploration of T2DN treatment. Meanwhile, our results highlighted that exploring the biomarkers of T2DN and therapeutic mechanisms of Traditional Chinese Medicine (TCM) formulas on T2DN by combining systems pharmacology and fecal metabonomics methods was a promising strategy.

Impact of EGCG Supplementation on the Progression of Diabetic Nephropathy in Rats: An Insight into Fibrosis and Apoptosis

Apoptosis is an active response of cells to altered microenvironments, which is characterized by cell shrinkage, chromatin condensation, and DNA fragmentation, in a variety of cell types such as renal epithelial cells, endothelial cells, mesangial cells, and podocytes. Hyperglycemia is among the microenvironmental factors that may facilitate apoptosis, which plays a decisive role in the initiation of diabetic nephropathy. Transforming growth factor-β emerges as a powerful fibrogenic factor in the development of renal hypertrophy. Although, a number of potential treatment strategies exist for diabetic nephropathy, considering the ease of use and bioavailability, phytochemicals stands distinct as the preeminent option. EGCG, a green tea catechin is one such phytochemical which possesses hypoglycemic and antifibrotic activity. The present study aims to explore the potential of EGCG to prevent apoptosis in a high-fat diet and STZ induced diabetic nephropathy rats by assessing renal function, pro-fibrotic marker, and the expression of apoptotic and antiapoptotic proteins. Our results validate EGCG as a potential antiapoptotic agent evidently by improving renal function via down regulating TGF-β, consequently ameliorating diabetic nephropathy. In accordance with this, EGCG might be regarded as a prospective therapeutic candidate in modulating diabetic nephropathy, thus being a promising treatment.

Hemorheological effects of secoisolariciresinol in ovariectomized rats

BACKGROUND

Postmenopausal women often develop hemorheological disorders which may affect the systemic blood circulation and present a cardiovascular risk factor.

OBJECTIVE

We evaluated effects of secoisolariciresinol (SECO), a phytoestrogen, on hemorheological parameters and lipid peroxidation in a model of the age-related and/or surgical menopause induced by ovariectomy in rats.

METHODS

Arterial blood was sampled from sham-operated female rats, ovariectomized rats (OVX), and OVX treated with SECO (OVXSECO) (20 mg/kg/day intragastrically for two weeks). Plasma estrogen concentration and the following hemorheological parameters were measured: RBC aggregation (half-time of aggregation, T1/2; amplitude of aggregation, AMP; aggregation index, AI), RBC deformability (elongation index, EI), whole blood viscosity at the shear rate of 3-300 s-1, plasma viscosity, hematocrit, plasma fibrinogen. Lipid peroxidation was evaluated by measuring conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) in plasma.

RESULTS

Ovariectomy in rats caused a 60% decrease in plasma estrogen level and triggered the development of macro- and microhemorheological abnormalities. Blood viscosity increased by 12-31%, RBC elongation index reduced by 16-28%, and T1/2 and AI increased by 35% and 29% respectively. The increase in blood viscosity correlated predominantly with reduced RBC deformability. Plasma CD and TBARS were elevated by 47% and 104% respectively. SECO therapy for OVX rats reduced blood viscosity by 9-18% and T1/2 by 32%, and increased EI by 4-17%. SECO therapy disrupted the correlation between blood viscosity and RBC deformability. Lipid peroxidation was significantly inhibited, as shown by the reduction in CD and TBARS plasma concentrations by 89% and 70% respectively. SECO did not affect plasma viscosity, estrogen or fibrinogen levels.

CONCLUSIONS

SECO treatment for OVX rats improves blood macro- and microrheological parameters, possibly through antioxidant protection of RBC.