Phlorizin: a review

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.

Improving oxidative stability of foods with apple-derived polyphenols

Consumers demand healthy and natural food products. Thus, naturally derived antioxidants are emerging as a promising alternative to the use of present ingredients. Apples and apple derivative products (e.g., apple juice, apple cider, apple sauce, and others) are widely consumed throughout the world for a variety of different reasons and supply a large quantity of polyphenolic compounds. The extraction of polyphenolic compounds from apples and their incorporation into processed foods as naturally sourced ingredients could be a preferred alternative to commonly used commercial antioxidants that are used in many foods. In addition, they could have a positive impact on the environment and on the economy due to the utilization of byproducts generated during processing of apples, like apple pomace. In terms of the extraction procedures for the antioxidant compounds found in apples, the most efficient processes are methods that use ultrasound as the extraction tool. With this technique, greater yields are achieved, and less extraction time is required when compared with other, more conventional, extraction methods. However, parameters such as the extraction solvent, temperature during extraction, and extraction time must be suitably optimized in order to obtain the best performance and the highest antioxidant capacity. From an application standpoint, the use of apple-derived polyphenol extracts as a naturally derived food additive has documented applications for bread, meat, fish, cookies, and juices and there is evidence of increased antioxidant capacity, reduced rate of lipid oxidation, and increased storage time without compromising on sensory properties.

Two Birds One Stone: The Neuroprotective Effect of Antidiabetic Agents on Parkinson Disease-Focus on Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitors

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease affecting more than 1% of the population over 65 years old. The etiology of the disease is unknown and there are only symptomatic managements available with no known disease-modifying treatment. Aging, genes, and environmental factors contribute to PD development and key players involved in the pathophysiology of the disease include oxidative stress, mitochondrial dysfunction, autophagic-lysosomal imbalance, and neuroinflammation. Recent epidemiology studies have shown that type-2 diabetes (T2DM) not only increased the risk for PD, but also is associated with PD clinical severity. A higher rate of insulin resistance has been reported in PD patients and is suggested to be a pathologic driver in this disease. Oral diabetic drugs including sodium-glucose cotransporter 2 (SGLT2) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, and dipeptidyl peptidase-4 (DPP-4) inhibitors have been shown to provide neuroprotective effects in both PD patients and experimental models; additionally, antidiabetic drugs have been demonstrated to lower incidence rates of PD in DM patients. Among these, the most recently developed drugs, SGLT2 inhibitors may provide neuroprotective effects through improving mitochondrial function and antioxidative effects. In this article, we will discuss the involvement of mitochondrial-related oxidative stress in the development of PD and potential benefits provided by antidiabetic agents especially focusing on sglt2 inhibitors.

Normoglycemic diabetic ketoacidosis in a type 2 diabetes patient on dapagliflozin: A case report

A 48-year-old male patient with Type 2 diabetes mellitus(T2D), on insulin replacement therapy, glipizide, and dapagliflozin presented with generalized weakness with weight loss of 40 pounds in 6 months ever since he was started on dapagliflozin. He was hemodynamically stable on arrival with a finger stick glucose of 121 gm%. Physical examination was unremarkable except for dry mucus membranes. His laboratory results on arrival are shown in Table 1. His serum osmolar gap was within the normal range. He was treated insulin drip per DKA protocol and gap was closed, the patient was clinically and biochemically back to baseline, and he was discharged home. Delayed diagnosis of normoglycemic diabetic ketoacidosis (DKA) in adults with diabetes treated with multiple antidiabetic drugs (eg, sodium-glucose cotransporter-2 [SGLT-2] inhibitors) can potentially increase morbidity and mortality. Patient education in terms of symptoms and signs, physician awareness of early recognition of ketoacidosis in the setting of paradoxically normal or near-normal blood glucose levels in these patients is the primary focus of this case study. This is paradoxical DKA because theoretically patient is not meeting one of the criteria for DKA which include triad of hyperglycemia, Ketoacidosis with widened anion gap, Ketonemia. This is a short case report of presumed SGLT-2 inhibitor euglycemic diabetic ketoacidosis. The main teaching point is recognition and early diagnosis of this issue when multiple diabetic medications are present with the absence of hyperglycemia. This is, by current definition, not DKA because theoretically, the patient does not meet one of the criteria for DKA as the patient was apparently not hyperglycemic, albeit with, ketoacidosis and widened anion gap. (ketonemia).

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.

Cardiovascular benefit of SGLT2 inhibitors

Patients with type 2 diabetes mellitus (T2D) are at increased risk of cardiovascular (CV) disease. Sodium glucose cotransporter 2 (SGLT2) inhibitors, also known as gliflozins, are a class of medications used to treat T2D by preventing the reabsorption of glucose filtered through the kidney and thereby facilitating glucose excretion in the urine. Over the past 5 years, many cardiovascular outcome trials (CVOTs) have evaluated the safety and efficacy of SGLT2 inhibitors in preventing CV events. The results of 7 CVOTs have provided solid evidence that the use of SGLT2 in patients with T2D and at high CV risk significantly reduced the risk of death from CV causes. Moreover, in patient with heart failure with reduced ejection fraction, regardless of the presence or absence of T2D, SGLT2 inhibitors use significantly reduced the risk of worsening heart failure and death from CV causes. Although the exact mechanism of the cardiorenal benefit of SGLT2 inhibitors is still unknown, studies have shown that the beneficial effect of these drugs cannot be exclusively explained by their glucose lowering effect, and several possible mechanisms have been proposed. This review will explore the changing role of SGLT2 inhibitors from a diabetes drug to clinical practice guideline-supported therapy for the prevention and treatment of CV diseases, including heart failure.

Sodium Glucose Transporter, Type 2 (SGLT2) Inhibitors (SGLT2i) and Glucagon-Like Peptide 1-Receptor Agonists: Newer Therapies in Whole-Body Glucose Stabilization

Diabetes is a worldwide epidemic that is increasing rapidly to become the seventh leading cause of death in the world. The increased incidence of this disease mirrors a similar uptick in obesity and metabolic syndrome, and, collectively, these conditions can cause deleterious effects on a number of organ systems including the renal and cardiovascular systems. Historically, treatment of type 2 diabetes has focused on decreasing hyperglycemia and glycated hemoglobin levels. However, it now is appreciated that there is more to the puzzle. Emerging evidence has indicated that newer classes of diabetes drugs, sodium-glucose co-transporter 2 inhibitors and glucagon-like peptide 1-receptor agonists, improve cardiovascular and renal function, while appropriately managing hyperglycemia. In this review, we highlight the recent clinical and preclinical studies that have shed light on sodium-glucose co-transporter 2 inhibitors and glucagon-like peptide 1-receptor agonists and their ability to stabilize blood glucose levels while offering whole-body protection in diabetic and nondiabetic patient populations.

Natural Products & Bioactivity Inspired Synthetic Pursuits Interfacing with Carbohydrates: Ongoing Journey with C-Glycosides

Natural products, remains the most important source for the discovery of new drugs for the treatment of human diseases. This has inspired the synthetic community to design and develop mimics of natural products either to answer important questions in biology or to explore their therapeutic potentials. Glycosides present themselves abundantly in nature, right from the cell surface receptors to natural products of any origin. The O-Glycosides are hydrolytically less stable compared to C-glycosides and this feature has presented a great opportunity for drug discovery. The discovery of Dapagliflozin, an SGLT inhibitor and C-glucoside, for the treatment of diabetes is one such example. Aryl acyl-anion chemistry has been explored for the synthesis of 2-deoxy-C-aryl furanoside/pyranoside/septanosides. Besides success, the studies have provided valuable insight into the natural propensities of the architectural framework for the cascade to furan derivatives. The aryl acyl-anion chemistry has also enabled the synthesis of biologically active diaryl heptanoids. Inspired from sucesss of Dapagliflozin, new analogues have been synthesized with pyridine and isocoumarin heterocycle as the proximal ring. C-glucosides of isoliquiritigenin have been synthesized for the first time and evaluated as an efficient aldose reductase inhibitor. The synthesis and evaluation of acyl-C-β-D-glucosides and benzyl-C-β-D-glucoside as glucose-uptake promoters has revealed promise in small molecules. The concept of building blocks has been used to obtain natural oxylipins, D-xylo and L-xylo-configured alkane tetrols and novel lipophilic ketones with erythro/threo configured trihydroxy polar head-group as possible anti-mycobacterial agents.

Evidence that human oral glucose detection involves a sweet taste pathway and a glucose transporter pathway

The taste stimulus glucose comprises approximately half of the commercial sugar sweeteners used today, whether in the form of the di-saccharide sucrose (glucose-fructose) or half of high-fructose corn syrup (HFCS). Therefore, oral glucose has been presumed to contribute to the sweet taste of foods when combined with fructose. In light of recent rodent data on the role of oral metabolic glucose signaling, we examined psychopharmacologically whether oral glucose detection may also involve an additional pathway in humans to the traditional sweet taste transduction via the class 1 taste receptors T1R2/T1R3. In a series of experiments, we first compared oral glucose detection thresholds to sucralose thresholds without and with addition of the T1R receptor inhibitor Na-lactisole. Next, we compared oral detection thresholds of glucose to sucralose and to the non-metabolizable glucose analog, α-methyl-D-glucopyranoside (MDG) without and with the addition of the glucose co-transport component sodium (NaCl). Finally, we compared oral detection thresholds for glucose, MDG, fructose, and sucralose without and with the sodium-glucose co-transporter (SGLT) inhibitor phlorizin. In each experiment, psychopharmacological data were consistent with glucose engaging an additional signaling pathway to the sweet taste receptor T1R2/T1R3 pathway. Na-lactisole addition impaired detection of the non-caloric sweetener sucralose much more than it did glucose, consistent with glucose using an additional signaling pathway. The addition of NaCl had a beneficial impact on the detection of glucose and its analog MDG and impaired sucralose detection, consistent with glucose utilizing a sodium-glucose co-transporter. The addition of the SGLT inhibitor phlorizin impaired detection of glucose and MDG more than it did sucralose, and had no effect on fructose, further evidence consistent with glucose utilizing a sodium-glucose co-transporter. Together, these results support the idea that oral detection of glucose engages two signaling pathways: one that is comprised of the T1R2/T1R3 sweet taste receptor and the other that utilizes an SGLT glucose transporter.

Diabetic proximal tubulopathy: Can we mimic the disease for in vitro screening of SGLT inhibitors?

Diabetic kidney disease (DKD) is the foremost cause of renal failure. While the glomeruli are severely affected in the course of the disease, the main determinant for disease progression is the tubulointerstitial compartment. DKD does not develop in the absence of hyperglycemia. Since the proximal tubule is the major player in glucose reabsorption, it has been widely studied as a therapeutic target for the development of new therapies. Currently, there are several proximal tubule cell lines available, being the human kidney-2 (HK-2) and human kidney clone-8 (HKC-8) cell lines the ones widely used for studying mechanisms of DKD. Studies in these models have pushed forward the understanding on how DKD unravels, however, these cell culture models possess limitations that hamper research, including lack of transporters and dedifferentiation. The sodium-glucose cotransporters (SGLT) are identified as key players in glucose reabsorption and pharmacological inhibitors have shown to be beneficial for the long-term clinical outcome in DKD. However, their mechanism of action has, as of yet, not been fully elucidated. To comprehend the protective effects of SGLT inhibitors, it is essential to understand the complete functional, structural, and molecular features of the disease, which until now have been difficult to recapitulate. This review addresses the molecular events of diabetic proximal tubulopathy. In addition, we evaluate the protective role of SGLT inhibitors in cardiovascular and renal outcomes, and provide an overview of various in vitro models mimicking diabetic proximal tubulopathy used so far. Finally, new insights on advanced in vitro systems to surpass past limitations are postulated.

Underutilized Northern plant sources and technological aspects for recovering their polyphenols

Consumers worldwide are increasingly interested in the authenticity and naturalness of products. At the same time, the food, agricultural and forest industries generate large quantities of sidestreams that are not effectively utilized. However, these raw materials are rich and inexpensive sources of bioactive compounds such as polyphenols. The exploitation of these raw materials increases income for producers and processors, while reducing transportation and waste management costs. Many Northern sidestreams and other underutilized raw materials are good sources of polyphenols. These include berry, apple, vegetable, softwood, and rapeseed sidestreams, as well as underutilized algae species. Berry sidestreams are especially good sources of various phenolic compounds. This chapter presents the properties of these raw materials, providing an overview of the techniques for refining these materials into functional polyphenol-rich ingredients. The focus is on economically and environmentally sound technologies suitable for the pre-treatment of the raw materials, the modification and recovery of the polyphenols, as well as the formulation and stabilization of the ingredients. For example, sprouting, fermentation, and enzyme technologies, as well as various traditional and novel extraction methods are discussed. Regarding the extraction technologies, this chapter focuses on safe and green technologies that do not use organic solvents. In addition, formulation and stabilization that aim to protect isolated polyphenols during storage and extend shelflife are reviewed. The formulated polyphenol-rich ingredients produced from underutilized renewable resources could be used as sustainable, active ingredients--for example, in food and nutraceutical industries.

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.

QSAR analysis of sodium glucose co-transporter 2 (SGLT2) inhibitors for anti-hyperglycaemic lead development

QSAR (Quantitative Structure Activity Relationship) modelling was performed on a dataset of 90 sodium-dependent glucose cotransporter 2 (SGLT2) inhibitors. The quantitative and explicative evaluations revealed some of the subtle and distinguished structural features that are responsible for the inhibitory potency of these compounds against SGLT2, such as less possible number of ring carbons at 8 Å from the lipophilic atoms in the molecule (fringClipo8A) and more possible value for the sum of the partial charges of the lipophilic atoms present within seven bonds from the donor atoms (lipo_don_7Bc). Multivariate GA-MLR (genetic algorithm-multi linear regression) and thorough validation methodology out-turned a statistically robust QSAR model with a very high predictability shown from various statistical parameters. A QSAR model with r² = 0.83, F = 51.54, Q²_LOO = 0.79, Q²_LMO = 0.79, CCC_cv = 0.88, Q²Fⁿ = 0.76-0.81, r²_ext = 0.77, CCC_ext = 0.85, and with RMSE_tr < RMSE_cv was proposed. This QSAR model will assist synthetic chemists in the development of the SGLT2 inhibitors as the antidiabetic leads.

2021 Consensus Pathway of the Taiwan Society of Cardiology on Novel Therapy for Type 2 Diabetes

Type 2 diabetes is a major threat to human health in the 21st century. More than half a billion people may suffer from this pandemic disease in 2030, leading to a huge burden of cardiovascular complications. Recently, 2 novel antidiabetic agents, glucagon-like peptide 1 receptor agonists and sodium-glucose cotransporter 2 inhibitors, reduced cardiovascular complications in a number of randomized control trials. To integrate new information and to achieve a streamlined process for better patient care, a working group was appointed by the Taiwan Society of Cardiology to formulate a stepwise consensus pathway for these therapies to reduce cardiovascular events in patients with type 2 diabetes. This consensus pathway is complementary to clinical guidelines, acting as a reference to improve patient care.

Do sodium-glucose co-transporter-2 inhibitors increase plasma glucagon by direct actions on the alpha cell? And does the increase matter for the associated increase in endogenous glucose production?

Sodium-glucose co-transporter-2 inhibitors (SGLT2is) lower blood glucose and are used for treatment of type 2 diabetes. However, SGLT2is have been associated with increases in endogenous glucose production (EGP) by mechanisms that have been proposed to result from SGLT2i-mediated increases in circulating glucagon concentrations, but the relative importance of this effect is debated, and mechanisms possibly coupling SGLT2is to increased plasma glucagon are unclear. A direct effect on alpha-cell activity has been proposed, but data on alpha-cell SGLT2 expression are inconsistent, and studies investigating the direct effects of SGLT2 inhibition on glucagon secretion are conflicting. By contrast, alpha-cell sodium-glucose co-transporter-1 (SGLT1) expression has been found more consistently and appears to be more prominent, pointing to an underappreciated role for this transporter. Nevertheless, the selectivity of most SGLT2is does not support interference with SGLT1 during therapy. Paracrine effects mediated by secretion of glucagonotropic/static molecules from beta and/or delta cells have also been suggested to be involved in SGLT2i-induced increase in plasma glucagon, but studies are few and arrive at different conclusions. It is also possible that the effect on glucagon is secondary to drug-induced increases in urinary glucose excretion and lowering of blood glucose, as shown in experiments with glucose clamping where SGLT2i-associated increases in plasma glucagon are prevented. However, regardless of the mechanisms involved, the current balance of evidence does not support that SGLT2 plays a crucial role for alpha-cell physiology or that SGLT2i-induced glucagon secretion is important for the associated increased EGP, particularly because the increase in EGP occurs before any rise in plasma glucagon.

Expression of SGLT1 in the Mouse Endometrial Epithelium and its Role in Early Embryonic Development and Implantation

Many functional activities of endometrium epithelium are energy consuming which are very important for maintaining intrauterine environment needed by early embryonic development and establishment of implantation window. Glucose is a main energy supplier and one of the main components of intrauterine fluid. Obviously, glucose transports in endometrium epithelium involve in for these activities but their functions have not been elucidated. In this research, we observed a spatiotemporal pattern of sodium glucose transporter 1 (SGLT1) expression in the mouse endometrium. We also determined that progesterone can promote the expression of SGLT1 in the mouse endometrial epithelium in response to the action of oestrogen. Treatment with the SGLT1 inhibitor phlorizin or small interfering RNA specific for SGLT1 (SGLT1-siRNA) altered glucose uptake in primary cultured endometrial epithelial cells, which exhibited reduced ATP levels and AMPK activation. The injection of phlorizin or SGLT1-siRNA into one uterine horn of each mouse on day 2 of pregnancy led to an increased glucose concentration in the uterine fluid and decreased number of harvested normal blastocysts and decreased expression of integrin αVβ3 in endometrial epithelium and increased expression of mucin 1 and lactoferrin in endometrial epithelium and the uterine homogenates exhibited activated AMPK, a decreased ATP level on day 4, and a decreased number of implantation sites on day 5. In embryo transfer experiments, pre-treatment of the uterine horn with phlorizin or SGLT1-siRNA during the implantation window led to a decreased embryo implantation rate on day 5 of pregnancy, even when embryos from normal donor mice were used. In conclusion, SGLT1, which participates in glucose transport in the mouse endometrial epithelium, inhibition and/or reduced expression of SGLT1 affects early embryo development by altering the glucose concentration in the uterine fluid. Inhibition and/or reduced expression of SGLT1 also affects embryo implantation by influencing energy metabolism in epithelial cells, which consequently influences implantation-related functional activities.

Enzymatic Production of 3-OH Phlorizin, a Possible Bioactive Polyphenol from Apples, by Bacillus megaterium CYP102A1 via Regioselective Hydroxylation

Phlorizin is the most abundant glucoside of phloretin from the apple tree and its products. Phlorizin and its aglycone phloretin are currently considered health-beneficial polyphenols from apples useful in treating hyperglycemia and obesity. Recently, we showed that phloretin could be regioselectively hydroxylated to make 3-OH phloretin by Bacillus megaterium CYP102A1 and human P450 enzymes. The 3-OH phloretin has a potent inhibitory effect on differentiating 3T3-L1 preadipocytes into adipocytes and lipid accumulation. The glucoside of 3-OH phloretin would be a promising agent with increased bioavailability and water solubility compared with its aglycone. However, procedures to make 3-OH phlorizin, a glucoside of 3-OH phloretin, using chemical methods, are not currently available. Here, a biocatalytic strategy for the efficient synthesis of a possibly valuable hydroxylated product, 3-OH phlorizin, was developed via CYP102A1-catalyzed regioselective hydroxylation. The production of 3-OH phlorizin by CYP102A1 was confirmed by HPLC and LC–MS spectroscopy in addition to enzymatic removal of its glucose moiety for comparison to 3-OH phloretin. Taken together, in this study, we found a panel of mutants from B. megaterium CYP102A1 could catalyze regioselective hydroxylation of phlorizin to produce 3-OH phlorizin, a catechol product.

Safety evaluation and hypolipidemic effect of aqueous-ethanol and hot-water extracts from E Se tea in rats

E Se tea, processed by the fresh leaves of Malus toringoides (Rehd.) Hughes, is a traditional herbal tea with various human benefits. The present study was aimed to evaluate the toxicity and hypolipidemic effect of aqueous-ethanol extract (EE) and hot-water extract (WE) from E Se tea. Eight main chemical constituents in EE and WE were respectively identified and quantified by UHPLC-HRMS/MS. EE is rich in TPC and TFC, while WE had higher TPS content. Both EE and WE exhibited strong antioxidant activity with no significant difference. The acute toxicity study revealed that the LD₅₀ values were higher than 5000 mg/kg, while both WE and EE had no significant adverse effect in rats by subacute toxicity assay. However, the triglyceride (TG) content in experiment groups (male) and highest doses groups (female) significantly decreased. Furthermore, the hypolipidemic effect of WE and EE were performed on high fat diet induced hyperlipidemic rats. The result exhibited that either WE or EE could effectively regulate lipid droplet accumulation in liver, and reduce the adipocyte size. These results demonstrated that these two extracts from E Se tea could be regarded as a potential functional dietary supplement in preventing and treating diet induced metabolic diseases.

Recent Advances in the Development of Type 2 Sodium-Glucose Cotransporter Inhibitors for the Treatment of Type 2 Diabetes Mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is one of the most serious and prevalent diseases worldwide. In the last decade, type 2 sodium-glucose cotransporter inhibitors (iSGLT2) were approved as alternative drugs for the pharmacological treatment of T2DM. The anti-hyperglycemic mechanism of action of these drugs involves glycosuria. In addition, SGLT2 inhibitors cause beneficial effects such as weight loss, a decrease in blood pressure, and others.

OBJECTIVE

This review aimed to describe the origin of SGLT2 inhibitors and analyze their recent development in preclinical and clinical trials.

RESULTS

In 2013, the FDA approved SGLT2 inhibitors as a new alternative for the treatment of T2DM. These drugs have shown good tolerance with few adverse effects in clinical trials. Additionally, new potential anti-T2DM agents based on iSGLT2 (O-, C-, and N-glucosides) have exhibited a favorable profile in preclinical evaluations, making them candidates for advanced clinical trials.

CONCLUSION

The clinical results of SGLT2 inhibitors show the importance of this drug class as new anti-T2DM agents with a potential dual effect. Additionally, the preclinical results of SGLT2 inhibitors favor the design and development of more selective new agents. However, several adverse effects could be a potential risk for patients.

Mechanisms of Glucose Absorption in the Small Intestine in Health and Metabolic Diseases and Their Role in Appetite Regulation

The worldwide prevalence of metabolic diseases such as obesity, metabolic syndrome and type 2 diabetes shows an upward trend in recent decades. A characteristic feature of these diseases is hyperglycemia which can be associated with hyperphagia. Absorption of glucose in the small intestine physiologically contributes to the regulation of blood glucose levels, and hence, appears as a putative target for treatment of hyperglycemia. In fact, recent progress in understanding the molecular and cellular mechanisms of glucose absorption in the gut and its reabsorption in the kidney helped to develop a new strategy of diabetes treatment. Changes in blood glucose levels are also involved in regulation of appetite, suggesting that glucose absorption may be relevant to hyperphagia in metabolic diseases. In this review we discuss the mechanisms of glucose absorption in the small intestine in physiological conditions and their alterations in metabolic diseases as well as their relevance to the regulation of appetite. The key role of SGLT1 transporter in intestinal glucose absorption in both physiological conditions and in diabetes was clearly established. We conclude that although inhibition of small intestinal glucose absorption represents a valuable target for the treatment of hyperglycemia, it is not always suitable for the treatment of hyperphagia. In fact, independent regulation of glucose absorption and appetite requires a more complex approach for the treatment of metabolic diseases.

Plants Secondary Metabolites as Blood Glucose-Lowering Molecules

Recently, significant advances in modern medicine and therapeutic agents have been achieved. However, the search for effective antidiabetic drugs is continuous and challenging. Over the past decades, there has been an increasing body of literature related to the effects of secondary metabolites from botanical sources on diabetes. Plants-derived metabolites including alkaloids, phenols, anthocyanins, flavonoids, stilbenoids, saponins, tannins, polysaccharides, coumarins, and terpenes can target cellular and molecular mechanisms involved in carbohydrate metabolism. In addition, they can grant protection to pancreatic beta cells from damage, repairing abnormal insulin signaling, minimizing oxidative stress and inflammation, activating AMP-activated protein kinase (AMPK), and inhibiting carbohydrate digestion and absorption. Studies have highlighted many bioactive naturally occurring plants' secondary metabolites as candidates against diabetes. This review summarizes the current knowledge compiled from the latest studies published during the past decade on the mechanism-based action of plants-derived secondary metabolites that can target various metabolic pathways in humans against diabetes. It is worth mentioning that the compiled data in this review will provide a guide for researchers in the field, to develop candidates into environment-friendly effective, yet safe antidiabetics.

Medical management of resistant hypertension: the role of sodium-glucose cotransporter 2 inhibitors (SGLT2i)

PURPOSE OF REVIEW

Controlling hypertension to the desired target is commonly unsuccessful and requires multi-drug regimen, which can lead to undesirable side effects. Resistant hypertension (RH) is more cumbersome to deal with and has robust morbidity and mortality burden even with current multiple medical options. Herein, we review the literature for the potential role of sodium-glucose cotransporter 2 inhibitors (SGLT2i) as a treatment option for hypertension and RH.

RECENT FINDINGS

With more recent randomized controlled trials (RCTs), SGLT2i have gained more recognition for their renal and cardiovascular protection as well as mortality benefit that are believed to be medication class-related effects. Multiple RCTs have evaluated blood pressure (BP) lowering properties of SGLT2i, as a primary or secondary end point, in diabetic and nondiabetic patients, yet trials are scarce in studying SGLT2i as first-line antihypertensives, or as add-on agents for treating RH.

SUMMARY

Finding the right medical therapy in treating hypertension, especially RH, is commonly onerous when it comes to achieving BP targets, avoiding medication side effects, and aiming for the best outcomes. Utilizing existing drugs like SGLT2i or exploring other novel agents with more RCTs for these purposes will be beneficial. The addition of SGLT2i to the therapeutic armamentarium in patients with RH should be considered as a target for upcoming RCTs.

Dynamics of Phloridzin and Related Compounds in Four Cultivars of Apple Trees during the Vegetation Period

Apple trees (Malus domestica Borgh) are a rich source of dihydrochalcones, phenolic acids and flavonoids. Considering the increasing demand for these phytochemicals with health-benefitting properties, the objective of this study was to evaluate the profile of the main bioactive compounds—phloridzin, phloretin, chlorogenic acid and rutin—in apple tree bark, leaves, flower buds and twigs. The variety in the phenolic profiles of four apple tree cultivars was monitored during the vegetation period from March to September using chromatography analysis. Phloridzin, the major glycoside of interest, reached the highest values in the bark of all the tested cultivars in May (up to 91.7 ± 4.4 mg g⁻¹ of the dried weight (DW), cv. ‘Opal’). In the leaves, the highest levels of phloridzin were found in cv. ‘Opal’ in May (82.5 ± 22.0 mg g⁻¹ of DW); in twigs, the highest levels were found in cv. ‘Rozela’ in September (52.4 ± 12.1 mg g⁻¹ of DW). In the flower buds, the content of phloridzin was similar to that in the twigs. Aglycone phloretin was found only in the leaves in relatively low concentrations (max. value 2.8 ± 1.4 mg g⁻¹ of DW). The highest values of rutin were found in the leaves of all the tested cultivars (10.5 ± 2.9 mg g⁻¹ of DW, cv. ‘Opal’ in September); the concentrations in the bark and twigs were much lower. The highest content of chlorogenic acid was found in flower buds (3.3 ± 1.0 mg g⁻¹ of DW, cv. ‘Rozela’). Whole apple fruits harvested in September were rich in chlorogenic acid and phloridzin. The statistical evaluation by Scheffe’s test confirmed the significant difference of cv. ‘Rozela’ from the other tested cultivars. In conclusion, apple tree bark, twigs, and leaves were found to be important renewable resources of bioactive phenolics, especially phloridzin and rutin. The simple availability of waste plant material can therefore be used as a rich source of phenolic compounds for cosmetics, nutraceuticals, and food supplement preparation.

Sodium-Glucose Co-transporter-2 Inhibitors and Nephroprotection in Diabetic Patients: More Than a Challenge

Diabetic nephropathy is the most common cause of end-stage renal disease worldwide. Control of blood glucose and blood pressure (BP) reduces the risk of developing this complication, but once diabetic nephropathy is established, it is then only possible to slow its progression. Sodium-glucose cotransporter-2 inhibitors (SGLT2is) are a novel class of oral hypoglycemic agents that increase urinary glucose excretion by suppressing glucose reabsorption at the renal proximal tubule. SGLT2is lower glycated hemoglobin (HbA1c) without increasing the risk of hypoglycemia, induce weight loss and improve various metabolic parameters including BP, lipid profile, albuminuria and uric acid. Several clinical trials have shown that SGLT2is (empagliflozin, dapagliflozin canagliflozin, and ertugliflozin) improve cardiovascular and renal outcomes and mortality in patients with type 2 diabetes. Effects of SGLT2is on the kidney can be explained by multiple pathways. SGLT2is may improve renal oxygenation and intra-renal inflammation thereby slowing the progression of kidney function decline. Additionally, SGLT2is are associated with a reduction in glomerular hyperfiltration, an effect which is mediated by the increase in natriuresis, the re-activation of tubule-glomerular feedback and independent of glycemic control. In this review, we will focus on renal results of major cardiovascular and renal outcome trials and we will describe direct and indirect mechanisms through which SGLT2is confer renal protection.

Phlorizin from sweet tea inhibits the progress of esophageal cancer by antagonizing the JAK2/STAT3 signaling pathway

Phlorizin, an important member of the dihydrochalcone family, has been widely used as a Chinese Traditional Medicine for treatment of numerous diseases. The present study aimed to investigate the potential therapeutic effects of phlorizin on esophageal cancer. Phlorizin, extracted from sweet tea, was used to treat esophageal cancer cells. Cell proliferation, migration and invasion were determined using Cell Counting Kit-8 and colony formation assays, and wound healing and Transwell assays, respectively. RNA sequencing and bioinformatics analysis was used to investigate the potential mechanism of phlorizin in the development of esophageal cancer. Fluorescent staining and flow cytometry was used to measure the level of apoptosis. The expression level of the proteins, P62/SQSTM1 and LC3 І/II, and the effect of phlorizin on the JAK2/STAT3 signaling pathway was detected using western blot analysis. The results demonstrated that phlorizin could inhibit cell proliferation, migration and invasion. Bioinformatics analysis showed that phlorizin might be involved in pleiotropic effects, such as the ‘JAK/STAT signaling pathway’ (hsa04630), ‘MAPK signaling pathway’(hsa04010) and ‘apoptosis’ (hsa04210). It was also confirmed that phlorizin promoted apoptosis and inhibited autophagy in the esophageal cancer cells. Notably, phlorizin might inhibit the proteins in the JAK/STAT signaling pathway, which would affect cancer cells. Taken together, the present data showed that phlorizin inhibited the progression of esophageal cancer by antagonizing the JAK2/STAT3 signaling pathway.

Phlorizin attenuates visceral hypersensitivity and colonic hyperpermeability in a rat model of irritable bowel syndrome

Visceral hypersensitivity and impaired gut barrier are crucial contributors to the pathophysiology of irritable bowel syndrome (IBS), and those are mediated via corticotropin-releasing factor (CRF)-Toll like receptor 4-pro-inflammatory cytokine signaling. Phlorizin is an inhibitor of sodium-linked glucose transporters (SGLTs), and known to have anti-cytokine properties. Thus, we hypothesized that phlorizin may improve these gastrointestinal changes in IBS, and tested this hypothesis in rat IBS models, i.e., lipopolysaccharide (LPS) or CRF-induced visceral hypersensitivity and colonic hyperpermeability. The visceral pain threshold in response to colonic balloon distention was estimated by abdominal muscle contractions by electromyogram, and colonic permeability was measured by quantifying the absorbed Evans blue in colonic tissue. Subcutaneous (s.c.) injection of phlorizin inhibited visceral hypersensitivity and colonic hyperpermeability induced by LPS in a dose-dependent manner. Phlorizin also blocked CRF-induced these gastrointestinal changes. Phlorizin is known to inhibit both SGLT1 and SGLT2, but intragastric administration of phlorizin may only inhibit SGLT1 because gut mainly expresses SGLT1. We found that intragastric phlorizin did not display any effects, but ipragliflozin, an orally active and selective SGLT2 inhibitor improved the gastrointestinal changes in the LPS model. Compound C, an adenosine monophosphate-activated protein kinase (AMPK) inhibitor, N^G-nitro-L-arginine methyl ester, a nitric oxide (NO) synthesis inhibitor and naloxone, an opioid receptor antagonist reversed the effects of phlorizin. In conclusions, phlorizin improved visceral hypersensitivity and colonic hyperpermeability in IBS models. These effects may result from inhibition of SGLT2, and were mediated via AMPK, NO and opioid pathways. Phlorizin may be effective for the treatment of IBS.

Sodium-glucose transporter inhibition in heart failure: from an unexpected side effect to a novel treatment possibility

Sodium-glucose transporter-2 inhibitors (SGLT2i), originally launched as glucose-lowering drugs, have been studied in large cardiovascular outcome trials to ascertain safety. Surprisingly, these compounds reduced the risk of cardiovascular events (cardiovascular death, non-fatal myocardial and non-fatal stroke) and total mortality. The mechanisms behind this benefit are only partly understood, but a major contributor is the reduction of heart failure hospitalisations, evident already within weeks after the initiation of the SGLT2i. SGLT2 inhibition increases urinary glucose excretion, thereby improving glycaemic control in an insulin-independent manner. Moreover, SGLT2i potentially impact the cardiovascular system both indirectly via weight loss and blood pressure lowering and directly through osmotic diuresis and increased sodium excretion and presumably by improving myocardial energetics. The aim of this review is to summarise evidence from all major outcome trials investigating SGLT2i in patients with diabetes, as well as recent evidence from trials in heart failure patients without glucose perturbations, which pave the way for novel treatment of large groups of patients. The results of these studies have been taken into account in recently issued guidelines for the management of diabetes and cardiovascular disease. An important task for diabetologists, cardiologists and general practitioners is to incorporate them into clinical practice to the benefit of many patients.

Dual-Target Compounds against Type 2 Diabetes Mellitus: Proof of Concept for Sodium Dependent Glucose Transporter (SGLT) and Glycogen Phosphorylase (GP) Inhibitors

A current trend in the quest for new therapies for complex, multifactorial diseases, such as diabetes mellitus (DM), is to find dual or even multi-target inhibitors. In DM, the sodium dependent glucose cotransporter 2 (SGLT2) in the kidneys and the glycogen phosphorylase (GP) in the liver are validated targets. Several (β-D-glucopyranosylaryl)methyl (het)arene type compounds, called gliflozins, are marketed drugs that target SGLT2. For GP, low nanomolar glucose analogue inhibitors exist. The purpose of this study was to identify dual acting compounds which inhibit both SGLTs and GP. To this end, we have extended the structure-activity relationships of SGLT2 and GP inhibitors to scarcely known (C-β-D-glucopyranosylhetaryl)methyl arene type compounds and studied several (C-β-D-glucopyranosylhetaryl)arene type GP inhibitors against SGLT. New compounds, such as 5-arylmethyl-3-(β-D-glucopyranosyl)-1,2,4-oxadiazoles, 5-arylmethyl-2-(β-D-glucopyranosyl)-1,3,4-oxadiazoles, 4-arylmethyl-2-(β-D-glucopyranosyl)pyrimidines and 4(5)-benzyl-2-(β-D-glucopyranosyl)imidazole were prepared by adapting our previous synthetic methods. None of the studied compounds exhibited cytotoxicity and all of them were assayed for their SGLT1 and 2 inhibitory potentials in a SGLT-overexpressing TSA201 cell system. GP inhibition was also determined by known methods. Several newly synthesized (C-β-D-glucopyranosylhetaryl)methyl arene derivatives had low micromolar SGLT2 inhibitory activity; however, none of these compounds inhibited GP. On the other hand, several (C-β-D-glucopyranosylhetaryl)arene type GP inhibitor compounds with low micromolar efficacy against SGLT2 were identified. The best dual inhibitor, 2-(β-D-glucopyranosyl)-4(5)-(2-naphthyl)-imidazole, had a K_i of 31 nM for GP and IC₅₀ of 3.5 μM for SGLT2. This first example of an SGLT-GP dual inhibitor can prospectively be developed into even more efficient dual-target compounds with potential applications in future antidiabetic therapy.

Natural products: A lead for drug discovery and development

Natural products are used since ancient times in folklore for the treatment of various ailments. Plant-derived products have been recognized for many years as a source of therapeutic agents and structural diversity. A literature survey has been carried out to determine the utility of natural molecules and their modified analogs or derivatives as pharmacological active entities. This review presents a study on the importance of natural products in terms of drug discovery and development. It describes how the natural components can be utilized after small modifications in new perspectives. Various new modifications in structure offer a unique opportunity to establish a new molecular entity with better pharmacological potential. It was concluded that in this current era, new attempts are taken to utilize the compounds derived from natural sources as novel drug candidates, with a focus to find and discover new effective molecules that were referred to as "new entities of natural product drug discovery."

Enzymatic synthesis of phlorizin fructosides

Phlorizin is a low soluble dihydrochalcone with relevant pharmacological properties. In this study, enzymatic fructosylation was approached to enhance the water solubility of phlorizin, and consequently its bioavailability. Three enzymes were assayed for phlorizin fructosylation in aqueous reactions using sucrose as fructosyl donor. Levansucrase (EC 2.4.1.10) from Gluconacetobacter diazotrophicus (Gd_LsdA) was 6.5-fold more efficient than invertase (EC 3.2.1.26) from Rhodotorula mucilaginosa (Rh_Inv), while sucrose:sucrose 1-fructosyltransferase (EC 2.4.1.99) from Schedonorus arundinaceus (Sa_1-SST) failed to modify the non-sugar acceptor. Gd_LsdA synthesized series of phlorizin mono- di- and tri-fructosides with maximal conversion efficiency of 73 %. The three most abundant products were identified by ESI-MS and NMR analysis as β-D-fructofuranosyl-(2→6)-phlorizin (P1a), phlorizin-4'-O-β-D-fructofuranosyl-(2→6)-D-fructofuranoside (P2c) and phlorizin-4-O-monofructofuranoside (P1b), respectively. Purified P1a was 16 times (30.57 g L^-1 at 25 °C) more soluble in water than natural phlorizin (1.93 g L^-1 at 25 °C) and exhibited 44.56 % free radical scavenging activity. Gd_LsdA is an attractive candidate enzyme for the scaled synthesis of phlorizin fructosides in the absence of co-solvent.

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.

Biotransformation of Phlorizin by Eurotium cristatum to Increase the Antioxidant and Antibacterial Activity of Docynia indica Leaves

Docynia indica is used as a plant resource for both medicine and food in minority areas of southwestern China and Southeast of Asia, especially Docynia indica leaves, which are often used as a kind of functional tea in daily life. In our previous research, it has found that D. indica is rich in polyphenols (mainly phlorizin (PHZ)). Although PHZ is the first polyphenolic competitive inhibitor of sodium-dependent glucose transporters (SGLTs) to be discovered, the promotion and application of PHZ are limited due to its extremely low bioavailability. As a kind of aglycons, phloretin (PHT) possesses a better bioavailability and bioactivity than PHZ. Therefore, the conversion of PHZ to PHT in D. indica leaves by the method of biotransformation can be applied to solve the above issue. In this study, Aspergillus niger and Eurotium cristatum were used to transform PHZ to PHT in D. indica. Compared with Aspergillus niger, Eurotium cristatum can cause the equimolar conversion of PHZ to PHT. However, Aspergillus niger resulted in the complete degradation of PHZ. In the process of deep fermentation, PHZ in D. indica leaves was gradually biotransformed into PHT, and its content was as high as ~ 12% after fermentation. With the increase of PHT content, the antioxidant and antibacterial activity of Docynia indica leaves increased. By the acute toxicity evaluation, it was confirmed that Docynia indica leaves and Eurotium cristatum fermented leaves were much safer. These results indicate that Eurotium cristatum fermentation has the ability to transform the functional compounds in Docynia indica leaves and increase the antioxidant and antibacterial activity of Docynia indica, thus making it a substitute for PHT and functional tea.

Impact of sodium glucose cotransporter 2 (SGLT2) inhibitors on atherosclerosis: from pharmacology to pre-clinical and clinical therapeutics

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are new oral drugs for the therapy of patients with type 2 diabetes mellitus (T2DM). Research in the past decade has shown that drugs of the SGLT2i class, such as empagliflozin, canagliflozin, and dapagliflozin, have pleiotropic effects in preventing cardiovascular diseases beyond their favorable impact on hyperglycemia. Of clinical relevance, recent landmark cardiovascular outcome trials have demonstrated that SGLT2i reduce major adverse cardiovascular events, hospitalization for heart failure, and cardiovascular death in T2DM patients with/without cardiovascular diseases (including atherosclerotic cardiovascular diseases and various types of heart failure). The major pharmacological action of SGLT2i is through inhibiting glucose re-absorption in the kidney and thus promoting glucose excretion. Studies in experimental models of atherosclerosis have shown that SGLT2i ameliorate the progression of atherosclerosis by mechanisms including inhibition of vascular inflammation, reduction in oxidative stress, reversing endothelial dysfunction, reducing foam cell formation and preventing platelet activation. Here, we summarize the anti-atherosclerotic actions and mechanisms of action of SGLT2i, with an aim to emphasize the clinical utility of this class of agents in preventing the insidious cardiovascular complications accompanying diabetes.

Glucose-Lowering Medications and Cardiovascular Outcomes

PURPOSE OF THE REVIEW

The purpose of this review is to examine recent evidence supporting CV safety profile and improvement of CV outcomes of some of the newer classes of diabetic medications.

RECENT FINDINGS

Diabetes mellitus (DM) is associated with increased risk of cardiovascular disease (CVD). Thus, CVD management is critical in diabetic patients. Since 2008, the US Food and Drug Administration (FDA) has mandated that all newer diabetic medications should establish cardiovascular safety before it is approved for use. Diabetic medications that also lower CV risk would be a significant advancement as shown in recent studies. There are 3 new class of diabetic medications: Dipeptidyl peptidase-4 inhibitors (DPP-4), glucagon-like peptide receptor agonists (GLP-1 RA), and sodium-glucose cotransporter type 2 (SGLT 2) inhibitors which have established both CV safety and improvement in CV outcomes with some drugs. In patients with type 2 diabetes and established atherosclerotic cardiovascular disease, multiple atherosclerotic cardiovascular disease risk factors, or diabetic kidney disease, a sodium-glucose cotransporter 2 inhibitor, or a glucagon-like peptide 1 receptor agonist with demonstrated cardiovascular benefit is recommended to reduce the risk of major adverse cardiovascular events.

The structural and functional characterization of Malus domestica double bond reductase MdDBR provides insights towards the identification of its substrates

In this study we describe the crystal structures of the apoform, the binary and the ternary complexes of a double bond reductase from Malus domestica L. (MdDBR) and explore a range of potential substrates. The overall fold of MdDBR is similar to that of the medium chain reductase/dehydrogenase/zinc-dependent alcohol dehydrogenase-like family. Structural comparison of MdDBR with Arabidopsis thaliana DBR (AtDBR), Nicotiana tabacum DBR (NtDBR) and Rubus idaeus DBR (RiDBR) allowed the identification of key amino acids involved in cofactor and ligands binding and shed light on how these residues may guide the orientation of the substrates. The enzyme kinetic for the substrate trans-4-phenylbuten-2-one has been analyzed, and MdDBR activity towards a variety of substrates was tested. This enzyme has been reported to be involved in the phenylpropanoid pathway where it would catalyze the NADPH-dependent reduction of the α, β-unsaturated double bond of carbonyl metabolites. Our study provides new data towards the identification of MdDBR natural substrate and the biosynthetic pathway where it belongs. Furthermore, the originally proposed involvement in dihydrochalcone biosynthesis in apple must be questioned.

mTOR-dependent dysregulation of autophagy contributes to the retinal ganglion cell loss in streptozotocin-induced diabetic retinopathy

BACKGROUND

Neurodegeneration, an early event in the pathogenesis of diabetic retinopathy (DR), precedes clinically detectable microvascular damage. Autophagy dysregulation is considered a potential cause of neuronal cell loss, however underlying mechanisms remain unclear. The mechanistic target of rapamycin (mTOR) integrates diverse environmental signals to coordinate biological processes, including autophagy. Here, we investigated the role of mTOR signaling in neuronal cell death in DR.

METHODS

Diabetes was induced by a single intraperitoneal injection of streptozotocin and tissue samples were harvested at 1, 2, 3, 4, and 6 months of diabetes. Early-stage of DR was investigated in 1-month-diabetic mice treated with phlorizin (two daily subcutaneous injections at a dose of 200 mg/kg of body weight during the last 7 full days of the experiment and the morning of the 8th day, 3 h before sacrifice) or rapamycin (daily intraperitoneal injections, at a dose of 3 mg/kg for the same period as for phlorizin treatment). The effect of autophagy modulation on retinal ganglion cells was investigated in 3-months-diabetic mice treated with phlorizin (two daily subcutaneous injections during the last 10 full days of the experiment and the morning of the 11th day, 3 h before sacrifice) or MHY1485 (daily i.p. injections, at a dose of 10 mg/kg for the same period as for phlorizin treatment). Tissue samples obtained from treated/untreated diabetic mice and age-matched controls were used for Western blot and histologic analysis.

RESULTS

mTOR-related proteins and glucose transporter 1 (GLUT1) was upregulated at 1 month and downregulated in the following period up to 6 months. Diabetes-induced neurodegeneration was characterized by an increase of apoptotic marker-cleaved caspase 3, a decrease of the total number of cells, and NeuN immunoreactivity in the ganglion cell layer, as well as an increase of autophagic protein. Insulin-independent glycemic control restored the mTOR pathway activity and GLUT1 expression, along with a decrease of autophagic and apoptotic proteins in 3-months-diabetic mice neuroretina. However, blockade of autophagy using MHY1485 resulted in a more protective effect on ganglion cells compared with phlorizin treatment.

CONCLUSION

Collectively, our study describes the mechanisms of neurodegeneration through the hyperglycemia/ mTOR/ autophagy/ apoptosis pathway. Video Abstract.

The Safety of Pharmacological and Surgical Treatment of Diabetes in Patients with Diabetic Retinopathy-A Review

BACKGROUND

Diabetes mellitus (DM) is a non-infectious pandemic of the modern world; it is estimated that in 2045 it will affect 10% of the world's population. As the prevalence of diabetes increases, the problem of its complications, including diabetic retinopathy (DR), grows. DR is a highly specific neurovascular complication of diabetes that occurs in more than one third of DM patients and accounts for 80% of complete vision loss cases in the diabetic population. We are currently witnessing many groundbreaking studies on new pharmacological and surgical methods of treating diabetes.

AIM

The aim of the study is to assess the safety of pharmacological and surgical treatment of DM in patients with DR.

MATERIAL AND METHODS

An analysis of the data on diabetes treatment methods currently available in the world literature and their impact on the occurrence and progression of DR.

RESULTS

A rapid decrease in glycaemia leads to an increased occurrence and progression of DR. Its greatest risk accompanies insulin therapy and sulfonylurea therapy. The lowest risk of DR occurs with the use of SGLT2 inhibitors; the use of DPP-4 inhibitors and GLP-1 analogues is also safe. Patients undergoing pancreatic islet transplants or bariatric surgeries require intensive monitoring of the state of the eye, both in the perioperative and postoperative period.

CONCLUSIONS

It is of utmost importance to individualize therapy in diabetic patients, in order to gradually achieve treatment goals with the use of safe methods and minimize the risk of development and progression of DR.

Inhibitory effects of Gymnema inodorum (Lour.) Decne leaf extracts and its triterpene saponin on carbohydrate digestion and intestinal glucose absorption

ETHNOPHARMACOLOGICAL RELEVANCE

Chiang-Da, Gymnema inodorum (Lour.) Decne. (GI), is an ethnomedicinal plant that has been used for diabetic treatment since ancient times. One of the anti-diabetic mechanisms is possibly related to the actions of triterpene glycoside, (3β, 16β)-16,28-dihydroxyolean-12-en-3-yl-O-β-D-glucopyranosyl-β-D-glucopyranosiduronic acid (GIA1) in decreasing carbohydrate digestive enzymes and intestinal glucose absorption in the gut system.

AIMS OF THE STUDY

To observe the amount of GIA1 in GI leaf extracts obtained from different ethanol concentrations and to investigate the anti-hyperglycemic mechanisms of the extracts and GIA1.

MATERIALS AND METHODS

The crude extracts were prepared using 50%v/v to 95%v/v ethanol solutions and used for GIA1 isolation. The anti-hyperglycemic models included in our study examined the inhibitory activities of α-amylase/α-glucosidase and intestinal glucose absorption related to sodium glucose cotransporter type 1 (SGLT1) using Caco-2 cells.

RESULTS

GIA1 was found about 8%w/w to 18%w/w in the GI extract depending on ethanol concentrations. The GI extracts and GIA1 showed less inhibitory activities on α-amylase. The extracts from 75%v/v and 95%v/v ethanol and GIA1 significantly delayed the glycemic absorption by lowering α-glucosidase activity and glucose transportation of SGLT1. However, the 50%v/v ethanolic extract markedly decreased the α-glucosidase activity than the SGLT1 function.

CONCLUSION

Differences in the GIA1 contents and anti-glycemic properties of the GI leaf extract was dependent on ethanol concentrations. Furthermore, the inhibitory effects of the 75%v/v and 95%v/v ethanolic extracts on α-glucosidase and SGLT1 were relevant to GIA1 content.

Pharmacological investigations on efficacy of Phlorizin a sodium-glucose co-transporter (SGLT) inhibitor in mouse model of intracerebroventricular streptozotocin induced dementia of AD type

OBJECTIVES

The study has been commenced to discover the potential of Phlorizin (dual SGLT inhibitor) in streptozotocin induced dementia of Alzheimer's disease (AD) type.

MATERIAL AND METHODS

Injection of Streptozotocin (STZ) was given via i.c.v. route (3 mg/kg) to induce dementia of Alzheimer's type. In these animals learning and memory was evaluated using Morris water maze (MWM) test. Glutathione (GSH) and thiobarbituric acid reactive species (TBARS) level was quantified to evaluate the oxidative stress; cholinergic activity of brain was estimated in term of acetylcholinesterase (AChE) activity; and the levels of myeloperoxidase (MPO) were measured as inflammation marker.

RESULTS

The mice model had decreased performance in MWM, representing impairment of cognitive functions. Biochemical evaluation showed rise in TBARS level, MPO and AChE activity, and fall in GSH level. The histopathological study revealed severe infiltration of neutrophils. In the study, Phlorizin/Donepezil (serving as positive control) treatment mitigate streptozotocin induced cognitive decline, histopathological changes and biochemical alterations.

CONCLUSIONS

The results suggest that Phlorizin decreased cognitive function via its anticholinesterase, antioxidative, antiinflammatory effects and probably through SGLT inhibitory action. It can be conferred that SGLTs can be an encouraging target for the treatment of dementia of AD.

SGLT2 inhibitors: a focus on cardiac benefits and potential mechanisms

This paper highlights the cardioprotective potential of sodium-glucose cotransporter 2 inhibitors (SLGT2i), as well as several most discussed mechanisms responsible for their cardioprotection. Cardiovascular diseases are considered a primary cause of death in nearly 80% of type 2 diabetes mellitus (T2DM) patients, with a 2-4-fold greater incidence of heart failure (HF) among diabetics. As novel hypoglycemics, SGLT2i showed exceptional cardiovascular benefits, reflected through robust reductions of cardiovascular mortality and hospitalization for HF in T2DM patients. Recently, those effects have been reported even in patients with HF and reduced ejection fraction irrespectively of diabetic status, suggesting that cardioprotective effects of SGLT2i are driven independently of their hypoglycemic actions. SGLT2i exerted hemodynamic and metabolic effects, partially driven by natriuresis and osmotic diuresis. However, those systemic effects are modest, and therefore cannot be completely related to the cardiac benefits of these agents in T2DM patients. Hence, increased circulating ketone levels during SGLT2i administration have brought out another hypothesis of a cardiac metabolic switch. Moreover, SGLT2i influence ion homeostasis and exert anti-inflammatory and antifibrotic effects. Their enviable influence on oxidative stress markers, as well as anti- and pro-apoptotic factors, have also been reported. However, since the main mechanistical contributor of their cardioprotection has not been elucidated yet, a joint action of systemic and molecular mechanisms has been suggested. In the light of ongoing trials evaluating the effects of SGLT2i in patients with HF and preserved ejection fraction, a new chapter of beneficial SGLT2i mechanisms is expected, which might resolve their main underlying action.

Metabolomics Insights of the Immunomodulatory Activities of Phlorizin and Phloretin on Human THP-1 Macrophages

Dihydrochalcones, phlorizin (PZ) and its aglycone phloretin (PT), have evidenced immunomodulatory effects through several mechanisms. However, the differential metabolic signatures that lead to these properties are largely unknown. Since macrophages play an important role in the immune response, our study aimed to characterise human THP-1 macrophages under PZ and PT exposure. A multiplatform-based untargeted metabolomics approach was used to reveal metabolites associated with the anti-inflammatory mechanisms triggered by the dihydrochalcones in LPS-stimulated macrophages, for the first time. Results showed differential phenotypic response in macrophages for all treatments. Dihydrochalcone treatment in LPS-stimulated macrophages mimics the response under normal conditions, suggesting inhibition of LPS response. Antagonistic effects of dihydrochalcones against LPS was mainly observed in glycerophospholipid and sphingolipid metabolism besides promoting amino acid biosynthesis. Moreover, PT showed greater metabolic activity than PZ. Overall, the findings of this study yielded knowledge about the mechanisms of action PZ and PT at metabolic level in modulating inflammatory response in human cells.

NMR Characterization of Ten Apple Cultivars from the Piedmont Region

The metabolite profile of ten traditional apple cultivars grown in the Piedmont region (Italy) was studied by means of nuclear magnetic resonance spectroscopy, identifying an overall number of 36 compounds. A more complete assignment of the proton nuclear magnetic resonance (¹H NMR) resonances from hydroalcoholic and organic apple extracts with respect to literature data was reported, identifying fructose tautomeric forms, galacturonic acid, γ-aminobutyric acid (GABA), p-coumaroyl moiety, phosphatidylcholine, and digalactosyldiacylglycerol. The chemical profile of each apple cultivar was defined by thorough quantitative NMR analysis of four sugars (fructose, glucose, sucrose, and xylose), nine organic acids (acetic, citric, formic, citramalic, lactic, malic, quinic, and galacturonic acids), six amino acids (alanine, asparagine, aspartate, GABA, isoleucine, and valine), rhamnitol, p-coumaroyl derivative, phloretin/phloridzin and choline, as well as β-sitosterol, fatty acid chains, phosphatidylcholine, and digalactosyldiacylglycerol. Finally, the application of PCA analysis allowed us to highlight possible differences/similarities. The Magnana cultivar showed the highest content of sugars, GABA, valine, isoleucine, and alanine. The Runsé cultivar was characterized by high amounts of organic acids, whereas the Gamba Fina cultivar showed a high content of chlorogenic acid. A significant amount of quinic acid was detected in the Carla cultivar. The knowledge of apple chemical profiles can be useful for industries interested in specific compounds for obtaining ingredients of food supplements and functional foods and for promoting apple valorization and preservation.

Mitigation effects of phlorizin immersion on acrylamide formation in fried potato strips

BACKGROUND

Several researches reported that natural polyphenols affected acrylamide formation of fried products. However, the effects of different variety of polyphenols on acrylamide formation were distinct. In this study, we isolated and purified phlorizin from apples and identified the influence of phlorizin immersion on acrylamide formation and sensory properties of fried potato strips with regard to the immersion concentration, time and temperature.

RESULTS

The acrylamide formation of fried samples decreased as the phlorizin concentration increased from 0 to 0.3 g kg^-1 , and 0.14 g kg^-1 could be selected as the suitable immersion concentration to dramatically inhibit acrylamide formation with considering the cost of industrial production. Additionally, the acrylamide formation significantly reduced from 8.71 × 10^-3 to 2.13 × 10^-3 g kg^-1 lyophilized weight (LW) with immersion time from 0 to 120 min, and 60 min could be selected to significantly reduce acrylamide formation in consideration of efficiency of the large-scale industrial processing. However, the effect of phlorizin immersion temperature on acrylamide formation of fried samples was not significant. Compared to the fried samples without immersion, the phlorizin immersion improved the color properties and the change of texture parameters was slight.

CONCLUSION

The fresh potato strips immersed in the phlorizin solution of 0.14 g kg^-1 at 40 °C for 60 min before frying could significantly decrease acrylamide formation of fried samples and retain the majority of fresh sensorial properties. The significant correlations obtained between sensory properties and acrylamide content indicated the sensory properties could be used as the indicator of acrylamide levels during industrial processing. © 2020 Society of Chemical Industry.