Phloridzin, an Apple Polyphenol, Exerted Unfavorable Effects on Bone and Muscle in an Experimental Model of Type 2 Diabetes in Rats

Unfavorable effects of memantine on the skeletal system in female rats

Memantine is an N-methyl-D-aspartate (NMDA) receptor antagonist used in the treatment of Alzheimer's disease (AD). NMDA receptors are expressed on bone cells. The aim of the present study was to investigate the effects of memantine on the rat musculoskeletal system. Taking into account that most of female AD patients are postmenopausal, the study was carried out on intact and ovariectomized (estrogen-deficient) rats. Mature Wistar rats were divided into following groups: non-ovariectomized (NOVX) control rats, NOVX rats treated with memantine, ovariectomized (OVX) control rats, and OVX rats treated with memantine. Memantine (2 mg/kg p.o.) was administered once daily for four weeks, starting one week after ovariectomy. The serum bone turnover marker and cytokine levels, bone density, mass, mineralization, mechanical properties, histomorphometric parameters of compact and cancellous bone, skeletal muscle mass and grip strength were determined. In NOVX rats, memantine slightly decreased the strength of compact bone of the femoral diaphysis (parameters in the yield point) and unfavorably affected histomorphometric parameters of cancellous bone (the femoral epiphysis and metaphysis). In OVX rats, in which estrogen deficiency induced osteoporotic changes, memantine increased the phosphorus content in the femoral bone mineral. No other effects on bone were observed in the memantine-treated OVX rats. In conclusion, the results of the present study indicated slight damaging skeletal effects of memantine in rats with normal estrogen levels.

Effects of Donepezil on the Musculoskeletal System in Female Rats

The extension of human life makes it more and more important to prevent and treat diseases of the elderly, including Alzheimer's disease (AD) and osteoporosis. Little is known about the effects of drugs used in the treatment of AD on the musculoskeletal system. The aim of the present study was to investigate the effects of donepezil, an acetylcholinesterase inhibitor, on the musculoskeletal system in rats with normal and reduced estrogen levels. The study was carried out on four groups of mature female rats: non-ovariectomized (NOVX) control rats, NOVX rats treated with donepezil, ovariectomized (OVX) control rats and OVX rats treated with donepezil. Donepezil (1 mg/kg p.o.) was administered for four weeks, starting one week after the ovariectomy. The serum concentrations of CTX-I, osteocalcin and other biochemical parameters, bone mass, density, mineralization, histomorphometric parameters and mechanical properties, and skeletal muscle mass and strength were examined. Estrogen deficiency increased bone resorption and formation and worsened cancellous bone mechanical properties and histomorphometric parameters. In NOVX rats, donepezil decreased bone volume to tissue volume ratio in the distal femoral metaphysis, increased the serum phosphorus concentration and tended to decrease skeletal muscle strength. No significant bone effects of donepezil were observed in OVX rats. The results of the present study indicate slightly unfavorable effects of donepezil on the musculoskeletal system in rats with normal estrogen levels.

Early-life metabolic dysfunction impairs cognition and mitochondrial function in mice

The impact of overnutrition early in life is not restricted to the onset of cardiovascular and metabolic diseases, but also affects critical brain functions related to cognition. This study aimed to evaluate the relationship between peripheral metabolic and bioenergetic changes induced by a two-hit protocol and their impact on cognitive function in juvenile mice. Three-week-old male C57BL/6 mice received a high-fat diet (HFD) or control diet for 7 weeks, associated with 2 low doses of streptozotocin (STZ) or vehicle. Despite the absence of obesity, HFD+STZ impaired glucose metabolism and induced a trend towards cholesterol increase. The two-hit protocol impaired recognition and spatial memories in juvenile mice, without inducing a depressive-like behavior. HFD+STZ mice presented increased immunoreactivity for GFAP and a trend towards a decrease in NeuN in the hippocampus. The treatment caused a bioenergetic impairment in the hippocampus, characterized by a decrease in both O₂ consumption related to ATP production and in the maximum respiratory capacity. The thermogenic capacity of brown adipose tissue was impaired by the two-hit protocol, here verified through the absence of a decrease in O₂ consumption after uncoupled protein-1 inhibition and an increase in the reserve respiratory capacity. Impaired mitochondrial function was also observed in the liver of HFD+STZ juvenile mice, but not in their heart. These results indicate that exposure to HFD+STZ early in life has a detrimental impact on the bioenergetic and mitochondrial function of tissues with metabolic and thermogenic activities, which is likely related to hippocampal metabolic changes and cognitive impairment.

The Effect of the Sodium—Glucose Cotransporter Inhibitor on Cognition and Metabolic Parameters in a Rat Model of Sporadic Alzheimer’s Disease

Type 2 diabetes mellitus increases the risk of sporadic Alzheimer’s disease (sAD), and antidiabetic drugs, including the sodium–glucose cotransporter inhibitors (SGLTI), are being studied as possible sAD therapy. We have explored whether the SGLTI phloridzin may influence metabolic and cognitive parameters in a rat model of sAD. Adult male Wistar rats were randomized to a control (CTR), an sAD-model group induced by intracerebroventricular streptozotocin (STZ-icv; 3 mg/kg), a CTR+SGLTI, or an STZ-icv+SGLTI group. Two-month-long oral (gavage) SGLTI treatment (10 mg/kg) was initiated 1 month after STZ-icv and cognitive performance tested prior to sacrifice. SGLTI treatment significantly decreased plasma glucose levels only in the CTR group and failed to correct STZ-icv-induced cognitive deficit. In both the CTR and STZ-icv groups, SGLTI treatment diminished weight gain, decreased amyloid beta (Aβ) 1-42 in duodenum, and decreased the plasma levels of total glucagon-like peptide 1 (GLP-1), while the levels of active GLP-1, as well as both total and active glucose-dependent insulinotropic polypeptide, remained unchanged, compared to their respective controls. The increment in GLP-1 levels in the cerebrospinal fluid and its effect on Aβ 1-42 in duodenum could be one of the molecular mechanisms by which SGLTIs indirectly induce pleiotropic beneficial effects.

Thinned young apple polyphenols may prevent neuronal apoptosis by up-regulating 5-hydroxymethylcytosine in the cerebral cortex of high-fat diet-induced diabetic mice

Apple polyphenols exert neuroprotective effects by improving the mitochondrial tricarboxylic acid (TCA) cycle function, but the details of their mechanisms are still not fully understood. TCA cycle metabolites regulate the level of 5-hydroxymethylcytosine (5hmC) by affecting the ten-eleven translocation (TET) enzyme activity. Therefore, we hypothesized that thinned young apple polyphenols (TYAPs) inhibit neuronal apoptosis by up-regulating the level of 5hmC in the cerebral cortex of high-fat diet-induced diabetic mice. C57BL/6J mice were randomly divided into 5 groups (n = 10 each group): the control (CON) group, the high-fat diet (HFD, negative control) group, the lovastatin (LOV, positive drug control) group, the resveratrol (RES, positive polyphenol control) group and the TYAP group during an eight-week intervention. The presented results verified that in the HFD group, the level of 5hmC and the expression of TET2 in the cerebral cortex were significantly lower, and the ratio of (succinic acid + fumaric acid)/α-ketoglutarate and the neuronal apoptosis rate were significantly higher than those in the CON group. However, TYAP intervention effectively restored the level of 5hmC through up-regulating the expression and activity of TET2, so as to improve diabetes symptoms and prevent diabetes-induced neuronal apoptosis.

Dihydrochalcones in Sweet Tea: Biosynthesis, Distribution and Neuroprotection Function

Sweet tea is a popular herbal drink in southwest China, and it is usually made from the shoots and tender leaves of Lithocarpus litseifolius. The sweet taste is mainly attributed to its high concentration of dihydrochalcones. The distribution and biosynthesis of dihydrochaldones in sweet tea, as well as neuroprotective effects in vitro and in vivo tests, are reviewed in this paper. Dihydrochalones are mainly composed of phloretin and its glycosides, namely, trilobatin and phloridzin, and enriched in tender leaves with significant geographical specificity. Biosynthesis of the dihydrochalones follows part of the phenylpropanoid and a branch of flavonoid metabolic pathways and is regulated by expression of the genes, including phenylalanine ammonia-lyase, 4-coumarate: coenzyme A ligase, trans-cinnamic acid-4-hydroxylase and hydroxycinnamoyl-CoA double bond reductase. The dihydrochalones have been proven to exert a significant neuroprotective effect through their regulation against Aβ deposition, tau protein hyperphosphorylation, oxidative stress, inflammation and apoptosis.

Effects of UVA disappearance and presence on the acylated anthocyanins formation in grape berries

•

UVA block inhibited acylated anthocyanin formation.

•

UVA presence promoted acylated anthocyanin formation.

•

Peonidin for acetylation and p-coumaroylation primarily respond to UVA.

•

A total of 3962 DEGs and 136 DAMs were identified.

•

VvMYBA1 played a key role in co-expression network.

Ultraviolet A (UVA), the major component of the UV, plays a crucial role in formatting the characteristics of color in wine grapes by influencing its anthocyanin composition and contents. Results showed that anthocyanin biosynthesis was suppressed by UVA screening and enhanced by irradiation. The acetylation and p-coumaroylation of anthocyanins were more pronounced and showed positive correlation with a* and negative correlation with L*, b*, C*, and h, thereby leading to changes in color. Weighted gene co-expression network analysis showed that two modules (red and turquoise) were significantly related to the acetylation and p-coumaroylation of peonidin. In addition, relative gene expression assays and correlation analysis also indicated that VvMYBA1 might influence anthocyanin accumulation by directly regulating VvOMT expression and increasing the flux to the vacuole through VvGST4. In conclusion, the results helped in improving our understanding of the role of UVA in skin color formation.

Unfavorable effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors on the skeletal system of nondiabetic rats

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a new class of antidiabetic drugs, acting by inhibiting the reabsorption of glucose in the kidneys. They turned out to improve cardiovascular and renal outcomes not only in patients with type 2 diabetes but also in nondiabetic patients. At present, they are more and more widely used in patients without diabetes. Since there were concerns that SGLT2 inhibitors may increase fracture risk in diabetes, the aim of the study was to examine the effect of dapagliflozin and canagliflozin on the musculoskeletal system of nondiabetic, healthy rats. The experiments were carried out on mature female rats, divided into the control rats and rats treated with dapagliflozin (1.4 mg/kg p.o.) or canagliflozin (4.2 mg/kg p.o.) for 4 weeks. Serum bone turnover markers, skeletal muscle strength and mass, bone mass, density, histomorphometric parameters and mechanical properties were determined. Administration of the drugs did not affect the skeletal muscle mass and strength. There was no effect on serum bone turnover markers, and bone mass and composition. However, administration of both drugs resulted in disorders of cancellous bone microarchitecture and worsening of bone mechanical properties. In conclusion, both SGLT2 inhibitors unfavorably affected the skeletal system of healthy rats.

Therapeutic Potential and Pharmaceutical Development of a Multitargeted Flavonoid Phloretin

Phloretin is a flavonoid of the dihydrogen chalcone class, present abundantly in apples and strawberries. The beneficial effects of phloretin are mainly associated with its potent antioxidant properties. Phloretin modulates several signaling pathways and molecular mechanisms to exhibit therapeutic benefits against various diseases including cancers, diabetes, liver injury, kidney injury, encephalomyelitis, ulcerative colitis, asthma, arthritis, and cognitive impairment. It ameliorates the complications associated with diabetes such as cardiomyopathy, hypertension, depression, memory impairment, delayed wound healing, and peripheral neuropathy. It is effective against various microbial infections including Salmonella typhimurium, Listeria monocytogenes, Mycobacterium tuberculosis, Escherichia coli, Candida albicans and methicillin-resistant Staphylococcus aureus. Considering the therapeutic benefits, it generated interest for the pharmaceutical development. However, poor oral bioavailability is the major drawback. Therefore, efforts have been undertaken to enhance its bioavailability by modifying physicochemical properties and molecular structure, and developing nanoformulations. In the present review, we discussed the pharmacological actions, underlying mechanisms and molecular targets of phloretin. Moreover, the review provides insights into physicochemical and pharmacokinetic characteristics, and approaches to promote the pharmaceutical development of phloretin for its therapeutic applications in the future. Although convincing experimental data are reported, human studies are not available. In order to ascertain its safety, further preclinical studies are needed to encourage its pharmaceutical and clinical development.

Effect of Administration of Azithromycin and/or Probiotic Bacteria on Bones of Estrogen-Deficient Rats

The gut microbiota plays an important role in maintaining homeostasis, including that of the skeletal system. Antibiotics may affect the skeletal system directly or indirectly by influencing the microbiota. Probiotic bacteria have been reported to favorably affect bones in conditions of estrogen deficiency. The aim of this study was to investigate the effects of azithromycin (AZM) administered alone or with probiotic bacteria (Lactobacillus rhamnosus; LR) on bones in estrogen-deficient rats. The experiments were carried out on mature rats divided into five groups: non-ovariectomized (NOVX) control rats, ovariectomized (OVX) control rats, and OVX rats treated with: LR, AZM, or AZM with LR. The drugs were administered for 4 weeks. Serum biochemical parameters, bone mineralization, histomorphometric parameters, and mechanical properties were examined. Estrogen deficiency increased bone turnover and worsened cancellous bone microarchitecture and mechanical properties. The administration of LR or AZM slightly favorably affected some skeletal parameters of estrogen-deficient rats. The administration of AZM with LR did not lead to the addition of the effects observed for the separate treatments, indicating that the effects could be microbiota-mediated.

Quality Assessment of Apple and Grape Juices from Serbian and German Markets by Planar Chromatography-Chemometrics

The high consumption of plant-based foods on a global scale has increased the number of adulterations in the food industry. Along with this, analytical approaches to fraud detection need to be further developed. A nontargeted effect-directed profiling by high-performance thin-layer chromatography hyphenated with five effect-directed assays (free radical scavenging assay, Aliivibrio fischeri bioassay, and acetylcholinesterase, butyrylcholinesterase, and tyrosinase inhibition assays) and multi-imaging provided additional information on the antioxidative, antimicrobial, and enzyme inhibition activities for 18 apple and 18 grape juices from markets in Serbia and Germany. Bioactive zones of interest were eluted using an elution head-based interface and further characterized by electrospray ionization high-resolution mass spectrometry. The different profiles were evaluated chemometrically, and several compounds, which were characteristic of samples from different markets located in Serbia and Germany, were identified in apple juice (such as chlorogenic acid, phloridzin, epicatechin, and caffeic acid) and grape juice (such as chlorogenic acid, epicatechin, and quercetin). The developed rapid and simple method for the quality assessment of fruit juices coming from different (geographic) markets showed clear quality differences. Thus, it could be used to learn more about quality differences, to detect fraud in fruit juice production, and to verify the authenticity of the origin.

Effects of natural dihydrochalcones in sweet tea (Lithocarpus polystachyus) on diabetes: a systematical review and meta-analysis of animal studies

Sweet tea (Lithocarpus polystachyus Rehd.), a natural functional food highly rich in dihydrochalcones including trilobatin, phlorizin and phloretin, is reported to possess numerous biological activities especially for treating diabetes. Here, the aim of this systematical review and meta-analysis is to assess the effect of dihydrochalcones in sweet tea (DST) on diabetes and summarize their possible mechanisms. We searched in eight databases including Embase, PubMed, Cochrane, Web of Science, WanFang database, VIP database, China National Knowledge Infrastructure and China Biology Medicine from Jan 2000 to Nov 2021 and ultimately included 21 animal studies in this review. A total of 10 outcome measurements including blood lipid indexes, blood glucose, insulin resistance indicators and oxidative stress biomarkers were extracted for meta-analysis using RevMan 5.4 software. DST significantly decreased the levels of triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), blood glucose (BG), homeostasis model assessment of insulin resistance (HOMA-IR) and malondialdehyde (MDA), and increased high-density lipoprotein cholesterol (HDL-c), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity in diabetic animal models. In summary, DST could treat diabetes by regulation of blood glucose/lipid metabolism, oxidative/carbonyl stress, inflammatory response etc.

Beneficial Effects of Flavonoids on Skeletal Muscle Health: A Systematic Review and Meta-Analysis

Skeletal muscle (SkM) is a highly dynamic tissue that responds to physiological adaptations or pathological conditions, and SkM mitochondria play a major role in bioenergetics, regulation of intracellular calcium homeostasis, pro-oxidant/antioxidant balance, and apoptosis. Flavonoids are polyphenolic compounds with the ability to modulate molecular pathways implicated in the development of mitochondrial myopathy. Therefore, it is pertinent to explore its potential application in conditions such as aging, disuse, denervation, diabetes, obesity, and cancer. To evaluate preclinical and clinical effects of flavonoids on SkM structure and function. We performed a systematic review of published studies, with no date restrictions applied, using PubMed and Scopus. The following search terms were used: "flavonoids" OR "flavanols" OR "flavones" OR "anthocyanidins" OR "flavanones" OR "flavan-3-ols" OR "catechins" OR "epicatechin" OR "(-)-epicatechin" AND "skeletal muscle." The studies included in this review were preclinical studies, clinical trials, controlled clinical trials, and randomized-controlled trials that investigated the influence of flavonoids on SkM health. Three authors, independently, assessed trials for the review. Any disagreement was resolved by consensus. The use of flavonoids could be a potential tool for the prevention of muscle loss. Their effects on metabolism and on mitochondria function suggest their use as muscle regulators.

Ameliorative potential of phloridzin in type 2 diabetes-induced memory deficits in rats

Diabetes associated oxidative stress and impaired cholinergic neurotransmission causes cognitive deficits. Although phloridzin shows antioxidant- and insulin sensitizing-activities, its ameliorative potential in diabetes-induced memory dysfunction remains unexplored. In the present study, type 2 diabetes (T2D) was induced by streptozotocin (35 mg/kg, intraperitoneal) in rats on ad libitum high-fat diet. Diabetic animals were treated orally with phloridzin (10 and 20 mg/kg) for four weeks. Memory functions were evaluated by passive avoidance test (PAT) and novel object recognition (NOR) test. Brains of rats were subjected to biochemical analysis of glutathione (GSH), brain-derived neurotrophic factor (BDNF), malonaldehyde (MDA) and acetylcholinesterase (AChE). Role of cholinergic system in the effects of phloridzin was evaluated by scopolamine pre-treatment in behavioral studies. While diabetic rats showed a significant decrease in step through latency in PAT, and exploration time and discrimination index in NOR test; a substantial increase in all parameters was observed following phloridzin treatment. Phloridzin reversed abnormal levels of GSH, BDNF, MDA and AChE in the brain of diabetic animals. Moreover, in silico molecular docking study revealed that phloridzin acts as a potent agonist at M1 receptor as compared to acetylcholine. Viewed collectively, reversal of T2D-induced memory impairment by phloridzin might be attributed to upregulation of neurotrophic factors, reduced oxidative stress and increased cholinergic signaling in the brain. Therefore, phloridzin may be a promising molecule in the management of cognitive impairment comorbid with T2D.

Omnifarious fruit polyphenols: an omnipotent strategy to prevent and intervene diabetes and related complication?

Diabetes mellitus is a metabolic syndrome which cannot be cured. Recently, considerable interest has been focused on food ingredients to prevent and intervene in complications of diabetes. Polyphenolic compounds are one of the bioactive phytochemical constituents with various biological activities, which have drawn increasing interest in human health. Fruits are part of the polyphenol sources in daily food consumption. Fruit-derived polyphenols possess the anti-diabetic activity that has already been proved either from in vitro studies or in vivo studies. The mechanisms of fruit polyphenols in treating diabetes and related complications are under discussion. This is a comprehensive review on polyphenols from the edible parts of fruits, including those from citrus, berries, apples, cherries, mangoes, mangosteens, pomegranates, and other fruits regarding their potential benefits in preventing and treating diabetes mellitus. The signal pathways of characteristic polyphenols derived from fruits in reducing high blood glucose and intervening hyperglycemia-induced diabetic complications were summarized.

New Glycosylated Dihydrochalcones Obtained by Biotransformation of 2'-Hydroxy-2-methylchalcone in Cultures of Entomopathogenic Filamentous Fungi

Flavonoids, including chalcones, are more stable and bioavailable in the form of glycosylated and methylated derivatives. The combined chemical and biotechnological methods can be applied to obtain such compounds. In the present study, 2'-hydroxy-2-methylchalcone was synthesized and biotransformed in the cultures of entomopathogenic filamentous fungi Beauveria bassiana KCH J1.5, Isaria fumosorosea KCH J2 and Isaria farinosa KCH J2.6, which have been known for their extensive enzymatic system and ability to perform glycosylation of flavonoids. As a result, five new glycosylated dihydrochalcones were obtained. Biotransformation of 2'-hydroxy-2-methylchalcone by B. bassiana KCH J1.5 resulted in four glycosylated dihydrochalcones: 2'-hydroxy-2-methyldihydrochalcone 3'-O-β-d-(4″-O-methyl)-glucopyranoside, 2',3-dihydroxy-2-methyldihydrochalcone 3'-O-β-d-(4″-O-methyl)-glucopyranoside, 2'-hydroxy-2-hydroxymethyldihydrochalcone 3'-O-β-d-(4″-O-methyl)-glucopyranoside, and 2',4-dihydroxy-2-methyldihydrochalcone 3'-O-β-d-(4″-O-methyl)-glucopyranoside. In the culture of I. fumosorosea KCH J2 only one product was formed-3-hydroxy-2-methyldihydrochalcone 2'-O-β-d-(4″-O-methyl)-glucopyranoside. Biotransformation performed by I. farinosa KCH J2.6 resulted in the formation of two products: 2'-hydroxy-2-methyldihydrochalcone 3'-O-β-d-(4″-O-methyl)-glucopyranoside and 2',3-dihydroxy-2-methyldihydrochalcone 3'-O-β-d-(4″-O-methyl)-glucopyranoside. The structures of all obtained products were established based on the NMR spectroscopy. All products mentioned above may be used in further studies as potentially bioactive compounds with improved stability and bioavailability. These compounds can be considered as flavor enhancers and potential sweeteners.

Phloridzin Ameliorates Lipid Deposition in High-Fat-Diet-Fed Mice with Nonalcoholic Fatty Liver Disease via Inhibiting the mTORC1/SREBP-1c Pathway

We aimed to investigate whether phloridzin could alleviate nonalcoholic fatty liver disease (NAFLD) in mice, which was induced by feeding a high-fat diet (HFD). We initially analyzed the effect of phloridzin on alleviating HFD-induced NAFLD in C57BL/6J mice and oleic acid (OA)-stimulated human normal liver L-02 cells (L02). Then, we investigated the mechanism of phloridzin on the mTORC1/sterol-regulatory element-binding protein-1c (SREBP-1c) signaling pathway by siRNA analysis, qRT-PCR, flow cytometry, and western blot analysis in vivo and in vitro. The results revealed that phloridzin significantly inhibited the increase in body weight, alleviated abnormal lipid metabolism, and decreased lipid biosynthesis and insulin resistance. Moreover, phloridzin augmented the number of CD8⁺CD122⁺PD-1⁺ Tregs and CD4⁺FoxP3⁺ Tregs in HFD-fed C57BL/6J mice and HFD-fed aP2-SREBF1c mice and downregulated the mTORC1/SREBP-1c signaling pathway-related protein expressions in vivo and in vitro. Furthermore, phloridzin reduced the expression of SREBP-1c in SREBP-1c-RNAi-lentivirus-transfected L02 cells and reversed the SREBP-1c expression in HFD-fed aP2-SREBF1c transgenic mice. Phloridzin ameliorates lipid accumulation and insulin resistance via inhibiting the mTORC1/SREBP-1c pathways. These results indicated that phloridzin may actively ameliorate NAFLD.

Phloridzin ameliorates type 2 diabetes-induced depression in mice by mitigating oxidative stress and modulating brain-derived neurotrophic factor

PURPOSE

Type 2 diabetes (T2D) is linked with depression due to insulin resistance, oxidative stress and disruption of neurotrophic factors. We evaluated potential benefits of phloridzin in ameliorating depressive symptoms in T2D.

METHODS

Adult male Swiss-albino mice (25-30 g) on high-fat-diet (HFD) for 2 weeks were administered with streptozotocin (STZ; 35 mg/kg, intraperitoneal) to induce T2D. Seven days after STZ administration, diabetic mice on HFD were distributed into different groups. Animals were subjected daily to oral treatment of saline (0.25 ml), fluoxetine (10-20 mg/kg) or phloridzin (10-20 mg/kg) for a period of 4 weeks. One hour after last dose, the immobility time of animals was evaluated in forced swim test (FST) and tail suspension test (TST). To further confirm the mechanisms involved in antidepressant effect of phloridzin, biochemical parameters like brain derived neurotropic factor (BDNF), glutathione (GSH), extracellular signal-regulated kinase (ERK), tyrosine receptor kinase B (TrkB) and cAMP-response element binding protein (CREB) were estimated in the brain.

RESULTS

Animals with T2D showed a significant increase in immobility as compared to control in FST and TST. However, 4 weeks administration of fluoxetine or phloridzin attenuated this effect. A significant decline in GSH, BDNF, TrkB, CREB and ERK levels were noticed in the brain of mice with T2D. These changes were also attenuated by administration of phloridzin.

CONCLUSIONS

Phloridzin may ameliorates T2D-induced depression by mitigating the oxidative stress, and up-regulation of neurotrophins in the brain. Therefore, phloridzin can be used as a therapeutic intervention for the management of depression co-morbid with T2D.

Phloridzin Acts as an Inhibitor of Protein-Tyrosine Phosphatase MEG2 Relevant to Insulin Resistance

Inhibition of the megakaryocyte protein tyrosine phosphatase 2 (PTP-MEG2, also named PTPN9) activity has been shown to be a potential therapeutic strategy for the treatment of type 2 diabetes. Previously, we reported that PTP-MEG2 knockdown enhances adenosine monophosphate activated protein kinase (AMPK) phosphorylation, suggesting that PTP-MEG2 may be a potential antidiabetic target. In this study, we found that phloridzin, isolated from Ulmus davidiana var. japonica, inhibits the catalytic activity of PTP-MEG2 (half-inhibitory concentration, IC₅₀ = 32 ± 1.06 μM) in vitro, indicating that it could be a potential antidiabetic drug candidate. Importantly, phloridzin stimulated glucose uptake by differentiated 3T3-L1 adipocytes and C2C12 muscle cells compared to that by the control cells. Moreover, phloridzin led to the enhanced phosphorylation of AMPK and Akt relevant to increased insulin sensitivity. Importantly, phloridzin attenuated palmitate-induced insulin resistance in C2C12 muscle cells. We also found that phloridzin did not accelerate adipocyte differentiation, suggesting that phloridzin improves insulin sensitivity without significant lipid accumulation. Taken together, our results demonstrate that phloridzin, an inhibitor of PTP-MEG2, stimulates glucose uptake through the activation of both AMPK and Akt signaling pathways. These results strongly suggest that phloridzin could be used as a potential therapeutic candidate for the treatment of type 2 diabetes.

The Bioavailability, Extraction, Biosynthesis and Distribution of Natural Dihydrochalcone: Phloridzin

Phloridzin is an important phytochemical which was first isolated from the bark of apple trees. It is a member of the dihydrochalcones and mainly distributed in the plants of the Malus genus, therefore, the extraction method of phloridzin was similar to those of other phenolic substances. High-speed countercurrent chromatography (HSCCC), resin adsorption technology and preparative high-performance liquid chromatography (HPLC) were used to separate and purify phloridzin. Many studies showed that phloridzin had multiple pharmacological effects, such as antidiabetic, anti-inflammatory, antihyperglycaemic, anticancer and antibacterial activities. Besides, the physiological activities of phloridzin are cardioprotective, neuroprotective, hepatoprotective, immunomodulatory, antiobesity, antioxidant and so on. The present review summarizes the biosynthesis, distribution, extraction and bioavailability of the natural compound phloridzin and discusses its applications in food and medicine.

Phloridzin attenuates lipopolysaccharide-induced cognitive impairment via antioxidant, anti-inflammatory and neuromodulatory activities

BACKGROUND

Lipopolysaccharide (LPS) is known to produce neuroinflammation and memory impairment. Although phloridzin (a phenolic phytoconstituent) shows antioxidant- and anti-inflammatory activities, its ameliorative potential in LPS-mediated neuroinflammation and memory dysfunction remains unexplored.

OBJECTIVES

To investigate the protective effect of phloridzin against LPS-mediated memory impairment and neuroinflammation in mice.

METHODS

Different groups of mice were treated with LPS (250 μg/kg) via intraperitoneal (ip) route to induce cognitive impairments. The animals were administered with phloridzin (10-20 mg/kg, oral) or donepezil (1 mg/kg, intraperitoneal), and memory functions were evaluated by Morris water maze (MWM) and Y-maze. At the end of the behavioral experiments, the animals were sacrificed and different biochemical parameters like acetylcholinesterase (AChE), brain derived neurotropic factor (BDNF), tumor necrosis factor (TNF-α), interleukin-6 (IL-6), superoxide dismutase (SOD) and glutathione (GSH) concentration in the hippocampus and the cerebral cortex were estimated.

RESULTS

While LPS administered animals showed significantly decreased memory retention in both MWM and Y maze, a significant reversal in all the parameters were observed following treatment with phloridzin. LPS-treated animals showed significantly decreased level of antioxidants (SOD and GSH), neurotropic factor (BDNF) and cholinergic transmission (increased AChE) and increased levels of inflammatory/oxidative markers (TNF-α, IL-6 and MDA) in hippocampus and cortex. These changes were alleviated after the treatment with phloridzin.

CONCLUSIONS

Phloridzin may have neuroprotective role against LPS-induced neuroinflammation and memory impairment by virtue of its antioxidant, anti-inflammatory, and enhanced cholinergic signalling activity in the hippocampus and cerebral cortex.

Negligible Effect of Estrogen Deficiency on Development of Skeletal Changes Induced by Type 1 Diabetes in Experimental Rat Models

Although postmenopausal osteoporosis often occurs concurrently with diabetes, little is known about interactions between estrogen deficiency and hyperglycemia in the skeletal system. In the present study, the effects of estrogen deficiency on the development of biochemical, microstructural, and mechanical changes induced by streptozotocin-induced diabetes mellitus (DM) in the rat skeletal system were investigated. The experiments were carried out on nonovariectomized (NOVX) and ovariectomized (OVX) control and diabetic mature female Wistar rats. Serum levels of bone turnover markers (CTX-I and osteocalcin) and 23 cytokines, bone mass and mineralization, histomorphometric parameters, and mechanical properties of cancellous and compact bone were determined. The results were subjected to two-way ANOVA and principal component analysis (PCA). Estrogen deficiency induced osteoporotic changes, with increased bone resorption and formation, and worsening of microstructure (femoral metaphyseal BV/TV decreased by 13.0%) and mechanical properties of cancellous bone (the maximum load in the proximal tibial metaphysis decreased by 34.2%). DM in both the NOVX and OVX rats decreased bone mass, increased bone resorption and decreased bone formation, and worsened cancellous bone microarchitecture (for example, the femoral metaphyseal BV/TV decreased by 17.3% and 18.1%, respectively, in relation to the NOVX controls) and strength (the maximum load in the proximal tibial metaphysis decreased by 35.4% and 48.1%, respectively, in relation to the NOVX controls). Only in the diabetic rats, profound increases in some cytokine levels were noted. In conclusion, the changes induced by DM in female rats were only slightly intensified by estrogen deficiency. Despite similar effects on bone microstructure and strength, the influence of DM on the skeletal system was based on more profound systemic homeostasis changes than those induced by estrogen deficiency.

Full-Spectrum Analysis of Bioactive Compounds in Rosemary (Rosmarinus officinalis L.) as Influenced by Different Extraction Methods

Rosmarinus officinalis is a potent antioxidant herb rich in polyphenols. Ultra-high-performance liquid chromatography, coupled with electrospray ionization and quadrupole-time of flight mass spectrometry (UHPLC-ESI-QTOF-MS), enables an exhaustive, full-spectrum analysis of the molecular constituents of natural products. The study aimed to develop a rapid UHPLC method to contribute new insights into the phytochemical composition of rosemary and to assess the performance of nine different procedures for extraction. These include fresh tissue homogenization, fresh and dry leaf decoction, and their respective fermentation, Soxhlet extraction, and sonication using water and methanol. Different extraction methods were found to recover quite different groups of polyphenols within 11 min during 20 min of analysis. Soxhlet extraction, yielded very high concentrations of rosmarinic acid (33,491.33 ± 86.29 µg/g), luteolin-7-O-glucoside (209.95 ± 8.78 µg/g), carnosic acid (2915.40 ± 33.23 µg/g), carnosol (22,000.67 ± 77.39 µg/g), and ursolic acid (5144.27 ± 28.68 µg/g). UHPLC-ESI-QTOF-MS enabled the detection of more than 50 polyphenols, including phenolic acids, flavonoids, and terpenoids in the various extracts. Of these, sagerinic acid ([M - H]-m/z 719.16), salvianolic acid A ([M - H]-m/z 493.11) and B ([M - H]-m/z 717.15), and a pentacyclic triterpenoid corosolic acid ([M - H]-m/z 471.34) were detected for the first time in rosemary. Soxhlet extraction was found to be the most efficient method, followed by dry leaf decoction. The UHPLC-ESI-QTOF-MS methodology for the analysis proved to be very efficient in the identification and characterization of targeted and untargeted bioactive molecules in the rosemary.

Sodium-glucose co-transporter (SGLT) inhibitor restores lost axonal varicosities of the myenteric plexus in a mouse model of high-fat diet-induced obesity

Diabetes impairs enteric nervous system functions; however, ultrastructural changes underlying the pathophysiology of the myenteric plexus and the effects of sodium-glucose co-transporter (SGLT) inhibitors are poorly understood. This study aimed to investigate three-dimensional ultrastructural changes in axonal varicosities in the myenteric plexus and the effect thereon of the SGLT inhibitor phlorizin in mice fed a high-fat diet (HFD). Three-dimensional ultrastructural analysis using serial block-face imaging revealed that non-treated HFD-fed mice had fewer axonal varicosities and synaptic vesicles in the myenteric plexus than did normal diet-fed control mice. Furthermore, mitochondrial volume was increased and lysosome number decreased in the axons of non-treated HFD-fed mice when compared to those of control mice. Phlorizin treatment restored the axonal varicosities and organelles in HFD-fed mice. Although HFD did not affect the immunolocalisation of PGP9.5, it reduced synaptophysin immunostaining in the myenteric plexus, which was restored by phlorizin treatment. These results suggest that impairment of the axonal varicosities and their synaptic vesicles underlies the damage to the enteric neurons caused by HFD feeding. SGLT inhibitor treatment could restore axonal varicosities and organelles, which may lead to improved gastrointestinal functions in HFD-induced obesity as well as diabetes.

Effects of diosgenin on the skeletal system in rats with experimental type 1 diabetes

There is a great interest in substances of plant origin, which may exert health-promoting activities in diabetes and its complications. Previous studies suggested that diosgenin may favorably affect both glucose metabolism and osteoporosis. The aim of the study was to investigate the effects of diosgenin on the skeletal disorders induced by experimental type 1 diabetes (T1D) in rats. The experiments were performed on 3-month-old female rats, divided into three groups: I - healthy control rats, II - streptozotocin-induced diabetic control rats, III - diabetic rats receiving diosgenin. T1D was induced by a single streptozotocin injection (60 mg/kg i.p.). Diosgenin administration (50 mg/kg/day p.o.) started two weeks later and lasted four weeks. Serum bone turnover markers and other biochemical parameters, bone mass and mineralization, mechanical properties and histomorphometric parameters were examined. Diabetes induced profound metabolic disturbances and disorders of cancellous bone microarchitecture and strength. Diosgenin did not favorably affect the serum bone turnover markers and other biochemical parameters, bone mass, mineralization and mechanical properties in the diabetic rats. However, it counteracted the effect of diabetes on the growth plate and cancellous bone microarchitecture in the distal femur, indicating some limited beneficial influence on the skeleton.

Promotion of Adropin Expression by Hyperglycemia Is Associated with STAT3 Activation in Diabetic Rats

BACKGROUND

Adropin is a secreted polypeptide that has been demonstrated to play an important role in energy homeostasis and lipid metabolism. Signal transducer and activator of transcription 3 (STAT3) may promote the transcription of target genes including adropin. In the current study, we investigated the effect of adropin on glucose metabolism in diabetic rats and the mechanism that governs this effect was subsequently assessed.

MATERIALS AND METHODS

Rats received a single injection of streptozotocin to induce type 1 diabetes. The diabetic rats were treated with insulin or phloridzin, another antidiabetic agent through inhibition of glucose reabsorption, for 7 days. Plasma glucose levels and adropin levels were measured. The interaction between STAT3 and adropin was evaluated using the human hepatoma HepG2 cell line. HepG2 cells were pretreated with the specific antagonist Stattic or with STAT3-specific siRNAs to knockout STAT3. Changes in energy homeostasis-associated gene expression were measured using real-time PCR. The protein expression levels of pSTAT3 and STAT3 were measured using Western blotting.

RESULTS

In diabetic rats, the serum concentrations of adropin were increased in the vehicle-treated group and decreased in the insulin- or phloridzin-treated group. In liver tissues, the Enho expression level and the activity of STAT3 also showed similar tendencies. After HepG2 cells were treated with medium containing high glucose, the ratio of p-STAT3 to STAT3, Enho mRNA levels and reactive oxygen species expression levels in HepG2 cells were significantly increased in conjunction with increased glucose levels. The effect was inhibited after pretreatment with Stattic or knockdown with STAT3-specific siRNAs.

CONCLUSION

STAT3 is involved in the genetic regulation of adropin, increasing the levels of circulating adropin and promoting Enho expression in the livers of diabetic rats.

Effect of Rosmarinic Acid and Sinapic Acid on Oxidative Stress Parameters in the Cardiac Tissue and Serum of Type 2 Diabetic Female Rats

Cardiovascular diseases are one of the most common complications of type 2 diabetes. They are considered the leading cause of death among diabetics. One of the mechanisms underlying diabetic cardiovascular complications is oxidative stress. Many phenolic acids are regarded as antioxidants. The aim of the study was to investigate the effect of rosmarinic acid (RA) and sinapic acid (SA) on oxidative stress parameters in the cardiac tissue and serum of type 2 diabetic female rats. Additionally, the effect of these compounds on glucose homeostasis and lipid profile in the serum was evaluated. Type 2 diabetes was induced with high-fat diet and streptozotocin. RA at the doses of 10 and 50 mg/kg and SA at the doses of 5 and 25 mg/kg were administrated orally for 28 days. Untreated diabetic rats exhibited unfavorable changes in glucose metabolism and lipid profile. Changes in the enzymatic and non-enzymatic markers indicated the onset of oxidative stress in these animals. The results showed that the higher doses of the tested phenolic acids-50 mg/kg of RA and 25 mg/kg of SA-revealed beneficial effects on oxidative stress in the cardiac tissue of diabetic rats.

Unraveling the Inhibition of Intestinal Glucose Transport by Dietary Phenolics: A Review

Background:

Glucose transport across the intestinal brush border membrane plays a key role in metabolic regulation. Depending on the luminal glucose concentration, glucose is mainly transported by the sodium- dependent glucose transporter (SGLT1) and the facilitated-transporter glucose transporter (GLUT2). SGLT1 is apical membrane-constitutive and it is active at a low luminal glucose concentration, while at concentrations higher than 50 mM, glucose is mainly transported by GLUT2 (recruited from the basolateral membrane). Dietary phenolic compounds can modulate glucose homeostasis by decreasing the postprandial glucose response through the inhibition of SGLT1 and GLUT2.

Methods:

Phenolic inhibition of intestinal glucose transport has been examined using brush border membrane vesicles from rats, pigs or rabbits, Xenopus oocytes and more recently Caco-2 cells, which are the most promising for harmonizing in vitro experiments.

Results:

Phenolic concentrations above 100 µM has been proved to successfully inhibit the glucose transport. Generally, the aglycones quercetin, myricetin, fisetin or apigenin have been reported to strongly inhibit GLUT2, while quercetin-3-O-glycoside has been demonstrated to be more effective in SGLT1. Additionally, epigallocatechin as well as epicatechin and epigallocatechin gallates were observed to be inhibited on both SGLT1 and GLUT2.

Conclusion:

Although, valuable information regarding the phenolic glucose transport inhibition is known, however, there are some disagreements about which flavonoid glycosides and aglycones exert significant inhibition, and also the inhibition of phenolic acids remains unclear. This review aims to collect, compare and discuss the available information and controversies about the phenolic inhibition of glucose transporters. A detailed discussion on the physicochemical mechanisms involved in phenolics-glucose transporters interactions is also included.

Water Extracts of Hull-less Waxy Barley (Hordeum vulgare L.) Cultivar 'Boseokchal' Inhibit RANKL-induced Osteoclastogenesis

Osteoporosis is a disease that leads to reduced bone mineral density. The increase in patient and medical costs because of global aging is recognized as a problem. Decreased bone mass is a common symptom of bone diseases such as Paget’s disease, rheumatoid arthritis, and multiple myeloma. Osteoclasts, which directly affect bone mass, show a marked increase in differentiation and activation in the aforementioned diseases. Moreover, these multinucleated cells made from monocytes/macrophages under the influence of RANKL and M-CSF, are the only cells capable of resorbing bones. In this study, we found that the water extracts of Boseokchal (BSC-W) inhibited osteoclast differentiation in vitro and investigated its inhibitory mechanism. BSC-W was obtained by extracting flour of Boseokchal using hexane and water. To osteoclast differentiation, bone marrow-derived macrophage cells (BMMs) were cultured with the vehicle (0.1% DMSO) or BSC-W in the presence of M-CSF and RANKL for 4 days. Cytotoxicity was measured by CCK-8. Gene expression of cells was confirmed by real-time PCR. Protein expression of cells was observed by western blot assay. Bone resorption activity of osteoclast evaluated by bone pit formation assay using an Osteo Assay Plate. BSC-W inhibited RANKL-induced osteoclastogenesis in a dose-dependent manner without exerting a cytotoxic effect on BMMs. BSC-W decreased the transcriptional and translational expression of c-Fos and NFATc1, which are regulators of osteoclastogenesis and reduced the mRNA expression level of TRAP, DC-STAMP, and cathepsin K, which are osteoclast differentiation marker. Furthermore, BSC-W reduced the resorption activity of osteoclasts. Taken together, our results indicate that BSC-W is a useful candidate for health functional foods or therapeutic agents that can help treat bone diseases such as osteoporosis.