Geraniol, a natural monoterpene, ameliorates hyperglycemia by attenuating the key enzymes of carbohydrate metabolism in streptozotocin-induced diabetic rats

Cymbopogon schoenanthus (L) extract ameliorates high fat diet-induced obesity and dyslipidemia via reducing expression of lipogenic and thermogenic proteins

Globally, obesity has become one of the major health problems. This study was conducted to evaluate the anti-obesity potential of Cymbopogon schoenanthus methanolic extract (CS) in rats. Fifty male Wistar rats of six to eight weeks old, 100-120 g body weight (BW) were randomly assigned into 5 groups (n = 10): The control group was fed a basal diet. CS-group was supplied with basal diet and orally given CS (200 mg/kg BW) for 12 weeks. HFD-group was fed a high-fat diet (HFD) for 18 weeks. HFD + CS-group was fed on HFD and CS HFD then CS-group was fed HFD for 12 weeks then shifted to basal diet and CS for another 6 weeks. Phytochemical analysis of CS indicated the presence of various terpenes and flavonoid compounds. Among the compounds characterized are quercetin, apigenin, luteolin, orientin, eudesmene, cymbopogonol, caffeic acid, coumaric acid, and linolenic acid. Supplementation of HFD significantly increased the body weight, levels of serum triacylglycerol, total cholesterol, very low-density lipoprotein, low-density lipo-protein (HDL), glucose, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. In addition, HFD up-regulated the protein expression of uncoupling protein (UCP)-1 in both brown and white adipose tissue; and the expression of hepatic mRNA of sterol regulatory element-binding protein (SREBP)-1c and SREBP-2. However, it decreased the serum level of HDL, and protein expression level of UCP-1 in both brown and white adipose tissue. Treatment of HFD-fed animals with CS extract either concurrently (HFD + CS-group), or after obesity induction (HFD then CS-group) significantly reversed all HFD-induced alterations in body weight; food intake; serum biochemical profile (including hyperglycemia, dyslipidemia); and tissue gene expressions. These results indicate that CS methanolic extract ameliorated HFD-induced obesity, serum biochemical, hepatic, and adipose tissue gene expression alterations. CS extract accomplished these effects mostly through its various identified bioactive compounds which have been proven to have anti-obesity and anti-diabetic activities.

The Anticancer Activities of Natural Terpenoids That Inhibit Both Melanoma and Non-Melanoma Skin Cancers

The prevalence of two major types of skin cancer, melanoma and non-melanoma skin cancer, has been increasing worldwide. Skin cancer incidence is estimated to rise continuously over the next 20 years due to ozone depletion and an increased life expectancy. Chemotherapeutic agents could affect healthy cells, and thus may be toxic to them and cause numerous side effects or drug resistance. Phytochemicals that are naturally occurring in fruits, plants, and herbs are known to possess various bioactive properties, including anticancer properties. Although the effects of phytochemicals are relatively milder than chemotherapeutic agents, the long-term intake of phytochemicals may be effective and safe in preventing tumor development in humans. Diverse phytochemicals have shown anti-tumorigenic activities for either melanoma or non-melanoma skin cancer. In this review, we focused on summarizing recent research findings of the natural and dietary terpenoids (eucalyptol, eugenol, geraniol, linalool, and ursolic acid) that have anticancer activities for both melanoma and non-melanoma skin cancers. These terpenoids may be helpful to protect skin collectively to prevent tumorigenesis of both melanoma and nonmelanoma skin cancers.

Characterization of the gut bacterial and viral microbiota in latent autoimmune diabetes in adults

Latent autoimmune diabetes in adults (LADA) is a heterogeneous disease characterized by autoantibodies against insulin producing pancreatic beta cells and initial lack of need for insulin treatment. The aim of the present study was to investigate if individuals with LADA have an altered gut microbiota relative to non-diabetic control subjects, individuals with type 1 diabetes (T1D), and individuals with type 2 diabetes (T2D). Bacterial community profiling was performed with primers targeting the variable region 4 of the 16S rRNA gene and sequenced. Amplicon sequence variants (ASVs) were generated with DADA2 and annotated to the SILVA database. The gut virome was sequenced, using a viral particle enrichment and metagenomics approach, assembled, and quantified to describe the composition of the viral community. Comparison of the bacterial alpha- and beta-diversity measures revealed that the gut bacteriome of individuals with LADA resembled that of individuals with T2D. Yet, specific genera were found to differ in abundance in individuals with LADA compared with T1D and T2D, indicating that LADA has unique taxonomical features. The virome composition reflected the stability of the most dominant order Caudovirales and the families Siphoviridae, Podoviridae, and Inoviridae, and the dominant family Microviridae. Further studies are needed to confirm these findings.

Geraniol reverses obesity by improving conversion of WAT to BAT in high fat diet induced obese rats by inhibiting HMGCoA reductase

OBJECTIVES

Present report evaluates the protective effect of geraniol on high fat diet (HFD) induced obesity in rats and also determines the molecular mechanism of it.

METHODS

Rats were induced with obesity with administration of HFD for four weeks and geraniol 200 and 400 mg/kg p.o. was administered for the next four week in the respective groups. Blood glucose and oral glucose tolerance test (OGTT), lipid profile was estimated in the geraniol treated HFD induced obesity in rats. Moreover, docking study was performed to determine the specific mechanism of geraniol by targeting HMG-CoE A reductase (in silico).

RESULTS

There was significant increase in body weight and amelioration in altered serum glucose and lipid profile were observed in the geraniol treated group than negative control group. Weight of organs and adipose tissue isolated from different regions of the body was reduced in geraniol treated group than negative control. Moreover, geraniol interact with HMG-CoA reductase having binding energy -5.13.

CONCLUSIONS

In conclusion, data of the report reveals that geraniol reduces obesity by promoting the conversion of white adipose tissue (WAT) to brown adipose tissue (BAT), as it interacts with HMG-CoA reductase in HFD induced obesity in rats.

Use of Monoterpenes as Potential Therapeutics in Diabetes Mellitus: A Prospective Review

Monoterpenes are secondary metabolites of plants belonging to the terpenoid class of natural products. They are the most abundant components of essential oils that are generally considered to have various pharmacological properties. These compounds are reported to have antidiabetic effects in recent years. Due to nature's complex biosynthetic machinery, they also exhibit a reasonable degree of structural complexity/diversity for further analysis in structure-activity studies. Therefore, monoterpenes as antidiabetic agents have been investigated by recent in vitro and in vivo studies extensively reported in the scientific literature and claimed by patent documents. The purpose of this survey is to provide a comprehensive and prospective review concerning the potential applications of monoterpenes in the treatment of diabetes. The data for this research were collected through the specialized databases PubMed, Scopus, Web of Science, and ScienceDirect between the years 2014 and 2022, as well as the patent databases EPO, WIPO, and USPTO. The research used 76 articles published in the leading journals in the field. The main effect observed was the antidiabetic activity of monoterpenes. This review showed that monoterpenes can be considered promising agents for prevention and/or treatment of diabetes as well as have a marked pharmaceutical potential for the development of bioproducts for therapeutics applications.

Potential Effects of Geraniol on Cancer and Inflammation-Related Diseases: A Review of the Recent Research Findings

Geraniol (GNL), a natural monoterpene, is found in many essential oils of fruits, vegetables, and herbs, including lavender, citronella, lemongrass, and other medicinal and aromatic plants. GNL is commonly used by the cosmetic and food industries and has shown a wide spectrum of pharmacological activities including anti-inflammatory, anticancer, antimicrobial, antioxidant, and neuroprotective activities. It represents a potential anti-inflammatory agent and a promising cancer chemopreventive agent, as it has been found to be effective against a broad range of cancers, including colon, prostate, breast, lung, skin, kidney, liver, and pancreatic cancer. Moreover, GNL scavenges free radicals and preserves the activity of antioxidant enzymes. In addition, GNL induces apoptosis and cell cycle arrest, modulates multiple molecular targets, including p53 and STAT3, activates caspases, and modulates inflammation via transcriptional regulation. In the present study, different modes of action are described for GNL's activity against cancer and inflammatory diseases. This compound protects various antioxidant enzymes, such as catalase, glutathione-S-transferase, and glutathione peroxidase. Experiments using allergic encephalomyelitis, diabetes, asthma, and carcinogenesis models showed that GNL treatment had beneficial effects with low toxicity. GNL has been shown to be effective in animal models and tumor cell lines, but there have not been any clinical studies carried out for it. The aim of the present review is to provide updated data on the potential effects of GNL on cancer and inflammation, and to enhance our understanding of molecular targets, involved pathways, and the possible use of GNL for clinical studies and therapeutic purposes in the treatment of cancer and inflammation-related diseases.

A systematic review on anti-diabetic plant essential oil compounds: Dietary sources, effects, molecular mechanisms, and safety

Type 2 diabetes mellitus (T2DM) is a multifaceted metabolic syndrome defined through the dysfunction of pancreatic β-cells driven by a confluence of genetic and environmental elements. Insulin resistance, mediated by interleukins and other inflammatory elements, is one of the key factors contributing to the progression of T2DM. Many essential oils derived from dietary plants are beneficial against various chronic diseases. We reviewed the anti-diabetic properties of dietary plant-derived essential oil compounds, with a focus on their molecular mechanisms by modulating specific signaling pathways and other critical inflammatory mediators involved in insulin resistance. High-quality literature published in the last 12 years, from 2010 to 2022, was collected from the Scopus, Web of Science, PubMed, and Embase databases using the search terms "dietary plants," "essential oils," "anti-diabetic," "insulin resistance," "antihyperglycemic," "T2DM," "anti-diabetic essential oils," and anti-diabetic mechanism." According to the results, the essential oil compounds, including cinnamaldehyde, carvacrol, zingerone, sclareol, zerumbone, myrtenol, thujone, geraniol, citral, eugenol, thymoquinone, thymol, citronellol, α-terpineol, and linalool have been demonstrated to contain strong anti-diabetic effects via modulating various signal transduction pathways linked to glucose metabolism. Additionally, in diabetes-related animal models, they can also considerably reduce the expression of TNF-α, IL-1β, IL-4, IL-6, iNOS, and COX-2. The main signaling molecules regulated by these compounds include AMPK, GLUT4, Caspase-3, PPARγ, PPARα, NF-κB, p-IκBα, MyD88, MCP-1, SREBP-1c, AGEs, RAGE, VEGF, Nrf2/HO-1, and SIRT-1. They can also significantly inhibit the generation of TBARS and MDA, reduce oxidative stress, increase insulin levels, adiponectin, and glycoprotein enzymes, boost antioxidant enzymes like SOD, CAT, and GPx, as well as reduce glutathione and vital glycolytic enzymes. Besides, they can significantly lower the levels of liver enzymes and lipid profile markers. Moreover, most essential oil compounds are generally safe based on animal studies. In conclusion, dietary plant-derived essential oil compounds have potential anti-diabetic effects by influencing different signaling pathways and molecular targets linked to glucose metabolism, and should be safe and beneficial against diabetes and related complications.

The Study of Hypoglycemic Activity of 7-Terpenylcoumarins

Natural and synthetic coumarins are often considered privileged scaffolds for obtaining pharmacological agents with hypoglycemic activity. Chemical modification of coumarins often leads to antidiabetic agents with greater efficacy. In the present work, twenty monoterpene-substituted 7-hydroxycoumarins were synthesized. A new approach using the Mitsunobu reaction was shown to be effective for the synthesis of target compounds. All of the synthesized compounds were evaluated in an oral glucose tolerance test, and two of them containing geranyl and (-)-myrtenyl substituents showed in vivo hypoglycemic action. A possible mechanism of action of these compounds may include inhibition of DPP IV, which was proved in an in vitro test.

Cannabinoids and terpenes for diabetes mellitus and its complications: from mechanisms to new therapies

The number of people diagnosed with diabetes mellitus and its complications is markedly increasing worldwide, leading to a worldwide epidemic across all age groups, from children to older adults. Diabetes is associated with premature aging. In recent years, it has been found that peripheral overactivation of the endocannabinoid system (ECS), and in particular cannabinoid receptor 1 (CB1R) signaling, plays a crucial role in the progression of insulin resistance, diabetes (especially type 2), and its aging-related comorbidities such as atherosclerosis, nephropathy, neuropathy, and retinopathy. Therefore, it is suggested that peripheral blockade of CB1R may ameliorate diabetes and diabetes-related comorbidities. The use of synthetic CB1R antagonists such as rimonabant has been prohibited because of their psychiatric side effects. In contrast, phytocannabinoids such as cannabidiol (CBD) and tetrahydrocannabivarin (THCV), produced by cannabis, exhibit antagonistic activity on CB1R signaling and do not show any adverse side effects such as psychoactive effects, depression, or anxiety, thereby serving as potential candidates for the treatment of diabetes and its complications. In addition to these phytocannabinoids, cannabis also produces a substantial number of other phytocannabinoids, terpenes, and flavonoids with therapeutic potential against insulin resistance, diabetes, and its complications. In this review, the pathogenesis of diabetes, its complications, and the potential to use cannabinoids, terpenes, and flavonoids for its treatment are discussed.

Preparation and characterization of geraniol nanoemulsions and its antibacterial activity

Geraniol nanoemulsions (G-NE) based on Tween 80 and medium chain triglyceride (MCT) as surfactant and co-surfactant, respectively, has been prepared by the spontaneous emulsification method. Its physical and chemical properties such as mean particle size, zeta potential, PDI, pH, viscosity, contact angle, appearance morphology, and stability (storage stability, thermal stability, centrifugal properties, acid-base stability, and freeze-thaw properties) of the droplet were analyzed. The results showed that the mean particle size of G-NE was 90.33 ± 5.23 nm, the PDI was 0.058 ± 0.0007, the zeta potential was -17.95 ± 5.85 mV and the encapsulation efficiency was >90%. The produced G-NE has been demonstrated to be fairly stable in long-term storage at 4°C, pH = 5 and high-speed centrifuges. Moreover, G-NE had a significant inhibition effect on Staphylococcus aureus, Escherichia coli, Salmonella typhimurium and Listeria monocytogenes (p < 0.05). The bacterial inhibition rates of G-NE at a concentration of 1 MIC were 48, 99, 71.73, and 99% after 12 h of action against these four foodborne pathogenic bacteria, respectively. Therefore, the results obtained indicated that nanoemulsification enhanced the stability and antibacterial activity of geraniol to some extent, which will promote the utilization of geraniol in food preservation.

Amelioration of Age-Related Multiple Neuronal Impairments and Inflammation in High-Fat Diet-Fed Rats: The Prospective Multitargets of Geraniol

Neuroinflammation is documented to alter brain function as a consequence of metabolic changes linked with a high-fat diet (HFD). The primary target of this study is to see how geraniol is effective in manipulating age- and diet-associated multiple toxicity and neuroinflammation in HFD-fed rats. Sixty-four adult male Wistar rats were partitioned into two groups: Group 1 (untreated normal young and aged rats) and Group 2 (HFD-fed young and aged rats) that received HFD for 16 weeks before being orally treated with geraniol or chromax for eight weeks. The results revealed a dropping in proinflammatory cytokines (TNF-α and IL-6) and leptin while boosting adiponectin in geraniol-supplemented rats. The liver, kidney, and lipid profiles were improved in geraniol-HFD-treated groups. HFD-induced brain insulin resistance decreased insulin clearance and insulin-degrading enzyme (IDE) levels significantly after geraniol supplementation. Geraniol suppressed acetylcholinesterase (AChE) activity and alleviated oxidative stress by boosting neuronal reduced glutathione (GSH), catalase (CAT), glutathione-S-transferase (GST), and superoxide dismutase (SOD) activities. It lowered malondialdehyde concentration (TBARS), nitric oxide (NO), and xanthine oxidase (XO) and restored the structural damage to the brain tissue caused by HFD. Compared with model rats, geraniol boosted learning and memory function and ameliorated the inflammation status in the brain by lowering the protein levels of IL-1β, iNOS, NF-κBp65, and COX-2. In addition, the expression levels of inflammation-related genes (MCP-1, TNF-α, IL-6, IL-1β, and IDO-1) were lessened significantly. Remarkably, the supplementation of geraniol reversed the oxidative and inflammation changes associated with aging. It affected the redox status of young rats. In conclusion, our results exhibit the effectiveness of dietary geraniol supplementation in modifying age-related neuroinflammation and oxidative stress in rats and triggering off the use of geraniol as a noninvasive natural compound for controlling age- and diet-associated neuronal impairments and toxicity.

The promising role of hypoxia-resistant insulin-producing cells in ameliorating diabetes mellitus in vivo

Aim:

This study aimed to evaluate the efficacy of hypoxia-persistent insulin-producing cells (IPCs) against diabetes in vivo.

Materials & methods:

Mesenchymal stem cells (MSCs) differentiation into IPCs in the presence of Se/Ti (III) or CeO₂ nanomaterials. IPCs were subjected to hypoxia and hypoxia genes were analyzed. PKH-26-labeled IPCs were infused in diabetic rats to evaluate their anti-diabetic potential.

Results:

MSCs were differentiated into functional IPCs. IPCs exhibited overexpression of anti-apoptotic genes and down-expression of hypoxia and apoptotic genes. IPCs implantation elicited glucose depletion and elevated insulin, HK and G6PD levels. They provoked VEGF and PDX-1 upregulation and HIF-1α and Caspase-3 down-regulation. IPCs transplantation ameliorated the destabilization of pancreatic tissue architecture.

Conclusion:

The chosen nanomaterials were impressive in generating hypoxia-resistant IPCs that could be an inspirational strategy for curing diabetes.

Transplantation of cells that can release insulin have been reported as an alternate method to islet transfer for curing diabetes; however, the main difficulty facing the quality of the pancreatic cells is the deficiency of oxygen. Thus, this study was done to discover a new curing method for diabetes by producing cells that can release insulin and could survive under low oxygen circumstances, and assessing their healing ability against diabetes in rats.

The Genus Alternanthera: Phytochemical and Ethnopharmacological Perspectives

Ethnopharmacological relevance: The genus Alternanthera (Amaranthaceae) comprises 139 species including 14 species used traditionally for the treatment of various ailments such as hypertension, pain, inflammation, diabetes, cancer, microbial and mental disorders.

Aim of the review: To search research gaps through critical assessment of pharmacological activities not performed to validate traditional claims of various species of Alternanthera. This review will aid natural product researchers in identifying Alternanthera species with therapeutic potential for future investigation.

Materials and methods: Scattered raw data on ethnopharmacological, morphological, phytochemical, pharmacological, toxicological, and clinical studies of various species of the genus Alternanthera have been compiled utilizing search engines like SciFinder, Google Scholar, PubMed, Science Direct, and Open J-Gate for 100 years up to April 2021.

Results: Few species of Alternanthera genus have been exhaustively investigated phytochemically, and about 129 chemical constituents related to different classes such as flavonoids, steroids, saponins, alkaloids, triterpenoids, glycosides, and phenolic compounds have been isolated from 9 species. Anticancer, antioxidant, antibacterial, CNS depressive, antidiabetic, analgesic, anti-inflammatory, and immunomodulator effects have been explored in the twelve species of the genus. A toxicity study has been conducted on 3 species and a clinical study on 2 species.

Conclusions: The available literature on pharmacological studies of Alternanthera species reveals that few species have been selected based on ethnobotanical surveys for scientific validation of their traditional claims. But most of these studies have been conducted on uncharacterized and non-standardized crude extracts. A roadmap of research needs to be developed for the isolation of new bioactive compounds from Alternanthera species, which can emerge out as clinically potential medicines.

In Vitro and In Vivo Antidiabetic Potential of Monoterpenoids: An Update

Diabetes mellitus (DM) is a chronic metabolic condition characterized by persistent hyperglycemia due to insufficient insulin levels or insulin resistance. Despite the availability of several oral and injectable hypoglycemic agents, their use is associated with a wide range of side effects. Monoterpenes are compounds extracted from different plants including herbs, vegetables, and fruits and they contribute to their aroma and flavor. Based on their chemical structure, monoterpenes are classified into acyclic, monocyclic, and bicyclic monoterpenes. They have been found to exhibit numerous biological and medicinal effects such as antipruritic, antioxidant, anti-inflammatory, and analgesic activities. Therefore, monoterpenes emerged as promising molecules that can be used therapeutically to treat a vast range of diseases. Additionally, monoterpenes were found to modulate enzymes and proteins that contribute to insulin resistance and other pathological events caused by DM. In this review, we highlight the different mechanisms by which monoterpenes can be used in the pharmacological intervention of DM via the alteration of certain enzymes, proteins, and pathways involved in the pathophysiology of DM. Based on the fact that monoterpenes have multiple mechanisms of action on different targets in in vitro and in vivo studies, they can be considered as lead compounds for developing effective hypoglycemic agents. Incorporating these compounds in clinical trials is needed to investigate their actions in diabetic patients in order to confirm their ability in controlling hyperglycemia.

Monoterpenes: current knowledge on food source, metabolism, and health effects

Monoterpenes, volatile metabolites produced by plants, are involved in the taste and aroma perception of fruits and vegetables and have been used for centuries in gastronomy, as food preservatives and for therapeutic purposes. Biological activities such as antimicrobial, analgesic and anti-inflammatory are well-established for some of these molecules. More recently, the ability of monoterpenes to regulate energy metabolism, and exert antidiabetic, anti-obesity and gut microbiota modulation activities have been described. Despite their promising health effects, the lack of reliable quantification of monoterpenes in food, hindered the investigation of their role as dietary bioactive compounds in epidemiological studies. Moreover, only few studies have documented the biotransformation of these compounds and identified the monoterpene metabolites with biological activity. This review presents up-to-date knowledge about the occurrence of monoterpenes in food, their bioavailability and potential role in the modulation of intermediate metabolism and inflammation, focusing on novel findings of molecular mechanisms, underlining research gaps and new avenues to be explored.

Characterization of the chemical profile and the effects of ethanolic extracts of Maytenus ilicifolia Mart. ex Reissek on glucose metabolism in normal hyperglycemic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Maytenus ilicifolia Mart. ex Reissek, Celastraceae, is popularly known as "espinheira-santa" and used to treat pathologies related to the stomach. However, in popular culture, this species has also been used to treat other disorders such as diabetes, but without scientific evidence, requiring more phytochemical and pharmacological studies on the plant.

AIM OF THE STUDY

This work aims to investigate the anti-hyperglycemic potential of ethanolic extracts obtained from leaves from two different accessions of Maytenus ilicifolia (MIA and MIB) in normal hyperglycemic rats.

MATERIALS AND METHODS

The animals were divided into different experimental groups: normal hyperglycemic (negative control); MIA (treatment of Maytenus ilicifolia extract from access 116); MIB (treatment with Maytenus ilicifolia extract from access 122; and glipizide (positive control). At 30 min after treatment, all animals received glucose overload orally. Blood collection occurred at different periods for the assessment of blood glucose (0, 60, 90 and 210 min after treatment) and at the end of the experiment blood was collected through cardiac puncture and the liver, muscle, pancreas and intestine were dissected for further analysis.

RESULTS

Chromatographic analysis identified oleic and palmitic acid as the most common constituents, and both extracts of Maytenus ilicifolia caused a reduction in blood glucose levels within 60 min after administration of glucose overload when compared to the normal hyperglycemic group. No significant changes were observed in hepatic and muscular glycogen levels, plasma insulin concentration and disaccharidases activity with none of the extracts in the model employed. However, hyperglycemic rats treated with the extracts showed a marked increase in triglyceride and HDL cholesterol levels.

CONCLUSIONS

Our data suggest that Maytenus ilicifolia extracts from different locations showed differences in chemical composition which did not reflect significant differences in the results of biological tests. In addition, it was possible to conclude that the treatment with Maytenus ilicifolia had a discreet anti-hyperglycemic effect; however, it was not possible to identify the responsible mechanism, being necessary, therefore, new studies using different technologies in order to determine the possible mechanisms of action of the extract.

Piperlongumine attenuates oxidative stress, inflammatory, and apoptosis through modulating the GLUT-2/4 and AKT signaling pathway in streptozotocin-induced diabetic rats

The current study was done to measure the role of piperlongumine (PL) on hyperglycemia interrelated oxidative stress-mediated inflammation and apoptosis, inflammatory stress, and the diabetic insulin receptor substrate 2 (IRS2), protein kinase B (AKT), and glucose transporter 2 (GLUT-2)/4 signaling pathway in streptozotocin (STZ)-persuaded diabetic animals. Diabetes was initiated in experimental animals via a single dose intraperitoneal inoculation of STZ. Diabetic rats revealed an augmented blood-glucose level with drastically diminished plasma-insulin status. The functions of antioxidants were diminished with enhanced lipid peroxidation, conjugated dienes, and protein carbonyls noticed in diabetic rats'  plasma and pancreatic tissues. An elevation of nuclear factor-κB (NF-κB), tumor necrosis factor-α, and interleukin-6 proteins was noticed in pancreatic tissues as well as IRS2, AKT, GLUT-2, and GLUT-4 marker expressions were quantified in the hepatic tissue of control and diabetic rats. Oral administration of PL for 30 days drastically lowered glucose and higher insulin status in STZ-induced diabetic rats. Impressively, PL oral supplementation considerably restored the antioxidant levels and reduced inflammation and diabetic marker expressions in STZ-diabetic rats. These results were supported through a histological study. Moreover, PL also augmented the level of B-cell lymphoma 2 and diminished the level of Bcl-2-associated X protein in STZ-treated rat's hepatic tissues. Thus, we concluded that PL excellently rescued pancreatic β cells through mitigating hyperglycemia via dynamic insulin secretion, activating antioxidants, and inhibiting inflammation and apoptosis in the pancreatic and hepatic tissue of diabetic rats.

Inhibiting the JNK/ERK signaling pathway with geraniol for attenuating the proliferation of human gastric adenocarcinoma AGS cells

Geraniol, a natural compound found in the essential oils of various aromatic plants, has attracted attention for its probable anticancer effects. The molecular mechanisms of the cell proliferation suppression and apoptosis induction via geraniol in gastric cancer cells (AGS), however, remain unclear. Gastric cancer cells were treated with geraniol, and it was found that the IC₅₀ values were 25 μM/ml, as determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Results showed that 20 and 25 μM geraniol-induced reactive oxygen species (ROS) production (2'-7'dichlorofluorescin diacetate staining) and decreased mitochondrial membrane potential (rhodamine 123 staining) in AGS cells. Then, it effectively inhibited cell growth and induced apoptosis, confirmed through acridine orange/ethidium bromide, 4',6-diamidino-2-phenylindole, and propidium iodide staining and molecular marker analysis in AGS cells. Also, geraniol potently diminished caspase-9, Bax, Bcl-2, and caspase-3 expression in AGS cells. We also evaluated the essential mechanism of the cytotoxic effect of geraniol. Moreover, the present study depicted that geraniol-induced cell death through mitochondrial ROS production and inhibited the phosphorylation form of mitogen-activated protein kinase (p38, MAPK, JNK, and ERK1/2) signaling pathway. Taken together, these results concluded that geraniol has a novel therapeutic property against human stomach cancer.

Ethnopharmacological perspectives of glucokinase activators in the treatment of diabetes mellitus

Traditional medicinal plants have wide-reaching utilisation in the treatment of diabetes especially in developing countries where medical resources are meagre. Traditionally used anti-diabetic plants act by numerous mechanisms, however, only a few of them act through activation of the glucokinase enzyme. Glucokinase is a key regulatory enzyme in glucose metabolism thereby controls glucose homeostasis and insulin secretion. The present review significantly analyses the knowledge about various plant-based glucokinase activators including numerous phytochemicals which modulate the activity and gene expression of glucokinase and would provide data support and perspective regarding future research in the discovery and development of different plant-derived glucokinase activators.

Isoprenoid Derivatives of Lysophosphatidylcholines Enhance Insulin and GLP-1 Secretion through Lipid-Binding GPCRs

Insulin plays a significant role in carbohydrate homeostasis as the blood glucose lowering hormone. Glucose-induced insulin secretion (GSIS) is augmented by glucagon-like peptide (GLP-1), a gastrointestinal peptide released in response to ingesting nutriments. The secretion of insulin and GLP-1 is mediated by the binding of nutrients to G protein-coupled receptors (GPCRs) expressed by pancreatic β-cells and enteroendocrine cells, respectively. Therefore, insulin secretagogues and incretin mimetics currently serve as antidiabetic treatments. This study demonstrates the potency of synthetic isoprenoid derivatives of lysophosphatidylcholines (LPCs) to stimulate GSIS and GLP-1 release. Murine insulinoma cell line (MIN6) and enteroendocrinal L cells (GLUTag) were incubated with LPCs bearing geranic acid (1-GA-LPC), citronellic acid (1-CA-LPC), 3,7-dimethyl-3-vinyloct-6-enoic acid (GERA-LPC), and (E)-3,7,11-trimethyl- 3-vinyldodeca-6,10-dienoic acid (1-FARA-LPC). Respective free terpene acids were also tested for comparison. Besides their insulin- and GLP-1-secreting capabilities, we also investigated the cytotoxicity of tested compounds, the ability to intracellular calcium ion mobilization, and targeted GPCRs involved in maintaining lipid and carbohydrate homeostasis. We observed the high cytotoxicity of 1-GERA-LPC and 1-FARA-LPC in contrast 1-CA-LPC and 1-GA-LPC. Moreover, 1-CA-LPC and 1-GA-LPC demonstrated the stimulatory effect on GSIS and 1-CA-LPC augmented GLP-1 secretion. Insulin and GLP-1 release appeared to be GPR40-, GPR55-, GPR119- and GPR120-dependent.

Association of metabolites with obesity based on two gene variants, MC4R rs17782313 and BDNF rs6265

Previous genome-wide association analyses for obesity related genes demonstrated the association of BDNF gene variant rs6265 and MC4R gene variant rs17782313 with body mass index (BMI). However, the associated metabolite pathways are still behind the curtain. The aim of the current study is to investigate the associations of metabolic changes in obesity with MC4R gene variant rs17782313 and BDNF variant rs6265. Gas chromatography-mass spectrometry based untargeted metabolomics approach was used and 42 identified serum metabolites were selected for statistical analyses. Significant association of seven metabolites with MC4R gene variant rs17782313 based on obesity and thirty metabolites with obesity dependent BDNF variant rs6265 using additive model (adjusted p < 0.05) was observed. This study highlights the importance of alteration of fatty acid biosynthesis, probably due to high consumption of fats may cause to develop obesity. But obesity is a complex disorder and the full clarification of this complex machinery is still distant. To understand the obesity in a better way, more studies are required to identify remaining metabolites and also mechanism of these metabolic entities.

Medicinal plants utilized in Thai Traditional Medicine for diabetes treatment: Ethnobotanical surveys, scientific evidence and phytochemicals

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes mellitus remains the most lethal metabolic disease of contemporaneous times and despite the therapeutic arsenal currently available, research on new antidiabetic agents remains a priority. In recent years, the revitalization of Thai Traditional Medicine (TTM) became a clear priority for the Thai government, and many efforts have been undertaken to accelerate research on herbal medicines and their use in medical services in various hospitals. Additionally, and particularly in rural areas, treatment of diabetes and associated symptomatology frequently relies on herbal preparations recommended by practitioners of TTM. In the current work, medicinal plants used in Thailand for treating diabetes, as well as their hypoglycaemic pharmacological evidences and potential therapeutic use for diabetes-related complications were reviewed.

MATERIALS AND METHODS

Ethnopharmacological information on the plant materials used in TTM for diabetes treatment was collected through literature search in a range of scientific databases using the search terms: diabetes, folk medicine, Thailand medicinal plants, traditional medicine. Information regarding scientific evidence on the antidiabetic effects of surveyed species was obtained considering not only the most common taxonomic designation, but also taxonomic synonyms, and including the keywords 'diabetes' and 'hypoglycaemic effect'.

RESULTS

A total of 183 species known to be used for diabetes management in TTM were reviewed, with 30% of them still lacking experimental evidences to support claims regarding the mechanisms and phytochemicals underlying their antidiabetic properties. Moreover, a total of 46 bioactives displaying effective antidiabetic effects have been isolated from 24 species, their underlying mechanism(s) of action being fully or partially disclosed.

CONCLUSIONS

We deliver the most extensive survey dealing with the ethnomedicinal knowledge of Thai medicinal plants utilized on diabetes management. We are certain that the current review will spark further research on Thai plants for the development of new standardized phytomedicines through drug discovery programmes.

Geraniol ameliorates diabetic nephropathy via interference with miRNA-21/PTEN/Akt/mTORC1 pathway in rats

Deregulated activity of protein kinase B/mammalian target of rapamycin complex-1 (Akt/mTORC1) incites crucial pathological characteristics of diabetic nephropathy. The acyclic monoterpene geraniol has been recently reported to possess antidiabetic effects; however, its potential renoprotective effect in diabetes has not yet been elucidated. This study aimed to assess the possible modulatory effect of geraniol on the Akt/mTORC1 pathway in diabetes-induced nephropathy in rats compared to the standard antidiabetic drug gliclazide. Geraniol and gliclazide was administered daily to diabetic rats for 6 weeks starting on the 3rd-day post diabetes induction by streptozotocin (STZ). Geraniol amended the deteriorated renal function (serum creatinine; blood urea nitrogen). It exerted a remarkable antihyperglycemic effect that is comparable to that of gliclazide and suppressed the fibrotic marker, transforming growth factor-β. Geraniol restored redox balance and inhibited lipid peroxidation by reducing nicotine amide adenine dinucleotide phosphate oxidase and enhancing the antioxidant enzyme, superoxide dismutase. These beneficial effects were associated with a robust downregulation of miRNA-21 and consequently, reversion of tumor suppressor protein phosphatase and tension homolog (PTEN)/Akt/mTORC1 cue and its downstream proteins required for mesangial cell proliferation and matrix protein synthesis. The current study indicates that geraniol interfered with miRNA-21/ PTEN/AKT/mTORC1 pathway signaling that contributes largely to the progression of mesangial expansion and extracellular matrix deposition in diabetic nephropathy.

Protective and therapeutic effects of natural products against diabetes mellitus via regenerating pancreatic β-cells and restoring their dysfunction

Diabetes mellitus is a growing public health concern and an increasing interest has been raised to search for new compounds with therapeutic effects on β-cells. There are chronic insulin resistance and loss of β-cell mass in the case of type-2 diabetes which covers about 90% of total diabetic patients. This work aims to critically review the protective and regenerative effects of various antidiabetic natural products on pancreatic β-cells. A thorough literature survey was conducted on the natural molecules and extracts having a protective, regenerative, and repairing effect on β-cells. The primary source of the literature was online scientific databases such as PubMed, Scopus, and Google Scholar. Besides, selected relevant textbooks were also consulted. Various natural molecules including berberine, curcumin, mangiferin, stevioside and capsaicin, and extracts obtained from the plants like Capsicum annum, Gymnema sylvestre, Stevia rebaudiana and Nymphaea stellate, were found to produce regenerative and anti-apoptosis effects on β-cells. These natural products were also found to increase insulin secretion by stimulating β-cells. The present review concluded that a large number of molecules and extracts, abundantly found in nature, possess antidiabetic effect via targeting β-cells. Further research is warranted to use these agents as a drug against diabetes.

Essential Oil-Bearing Plants From Balkan Peninsula: Promising Sources for New Drug Candidates for the Prevention and Treatment of Diabetes Mellitus and Dyslipidemia

Metabolic diseases like diabetes mellitus or dyslipidemia have a complex etiology characterized by the interference of genetic predisposition and environmental factors like diet or lifestyle. Over time they can cause significant vascular complications, leading to dysfunction or failure of key organs (brain, heart), with possible fatal consequences or a severe reduction of life quality. Although current authorized drugs may successfully control blood glucose or cholesterol level, their use is often associated with severe side effects, therefore the development of new drug candidates is necessary for a better management of metabolic diseases. Among potential new drug sources, aromatic plants rich in essential oils like Melissa officinalis L., Mentha x piperita L., Cuminum cyminum L. or Pistacia lentiscus L. var. chia are very promising due to their diverse chemical composition and multiple mechanisms of action. This review describes a series of recent experimental studies investigating antidiabetic and hypolipemic effects of essential oils extracted from several aromatic plant species with an ethnopharmacological relevance in the Balkan peninsula. The pharmacological models used in the studies together with the putative mechanisms of action of the main constituents are also detailed. The presented data clearly sustain a potential administration of the studied essential oils for the prevention and treatment of metabolic diseases. Further research is needed in order to ascertain the therapeutic importance of these findings.

Natural Products Derived from the Mediterranean Diet with Antidiabetic Activity: from Insulin Mimetic Hypoglycemic to Nutriepigenetic Modulator Compounds

BACKGROUND

The Mediterranean diet is a healthy eating pattern that protects against the development of Type 2 diabetes mellitus (T2DM), a metabolic disease characterized by elevated blood sugar levels due to pancreatic beta-cell functional impairment and insulin resistance in various tissues. Inspired by the ancient communities, this diet emphasizes eating primarily plant-based foods, including vegetables, legumes, fruits, cereals, and nuts. Importantly, virgin olive oil is used as the principal source of fat. Red meat is consumed in low amounts while wine and fish are consumed moderately.

OBJECTIVE

Here, we review the most beneficial components of the Mediterranean Diet and tentative mechanisms of action for prevention and/or management of T2DM, based on research conducted within the last decade.

METHODS

The references over the last five years have been reviewed and they have been selected properly according to inclusion/ exclusion criteria.

RESULTS

Several bioactive diet components were evaluated to prevent inflammation and cytokine-induced oxidative damage, reduce glucose concentration, carbohydrate absorption and increase insulin sensitivity and related gene expression.

CONCLUSION

The adherence to a healthy lifestyle, including diet, exercise and habits remains the best approach for the prevention of diabetes as well as frequent check-ups and education. Though diabetes has a strong genetic component, in recent years many reports strongly point to the critical role of lifestyle specific epigenetic modifications in the development of T2DM. It remains to be established how different components of the Mediterranean Diet interact and influence the epigenetic landscape to prevent or treat the disease.

Monoterpenes modulating autophagy: A review study

From the beginning of the 21st century, much attention has been made towards the medicinal herbs due to their low side effects and valuable biological activities. Among them, terpenes comprise a large group of naturally occurring chemical compounds that are considered as main components of flavours, antifeedants and pheromones. Monoterpenes have demonstrated a favourable profile as compounds that have antioxidant, anti-inflammatory, anti-diabetic, hepatoprotective and anti-tumour activities. On the other hand, autophagy is a 'self-digestion' mechanism which plays a remarkable role in a number of pathological conditions such as cancer, ageing, metabolic disorders and infection. Also, autophagy is considered as a stress adaptor that may lead to apoptotic cell death under severe and sustained stress. Autophagy modulation is a promising strategy in cancer treatment, and a variety of drugs have been designed in line with this strategy. In the present MiniReview, we discuss the effects of monoterpenes on autophagy and its relationship with therapeutic impacts of monoterpenes.

Inhibition of GLUT2 transporter by geraniol from Cymbopogon martinii: a novel treatment for diabetes mellitus in streptozotocin-induced diabetic rats

Objective

To isolate and identify the bioactive component from Cymbopogon martinii having GLUT2 transporter inhibitory activity – towards development of a novel strategy for treatment of diabetes mellitus.

Method

Isolation of bioactive component was carried out using differential solvent extraction, HPTLC and HPLC, and identification was done by GC-MS. In-vitro studies on intestine, liver, kidney and in-vivo assessment by OGTT and long-term treatment on diabetic rats were carried out.

Key findings

Geraniol was isolated and identified as bioactive component. Intestinal glucose absorption demonstrated 60.28% inhibition of transport at 648.34 μm of geraniol. It was found to inhibit glucose release from liver on adrenaline challenge by 89.82% at 324.17 μm/ml. Kidney glycogen content doubled using 648.34 μm of geraniol as compared to control. Geraniol demonstrated 2.14 times higher renal glucose output than diabetic control. OGTT demonstrated prevention of postprandial spikes. Prolonged treatment for 60 days with 29.37 mm/kg B.W. twice a day of geraniol improved the lipid profile, HbA1C levels and renal parameters. In mRNA studies for 10 days, over expression of GLUT2 was prevented by geraniol.

Conclusions

Inhibition of GLUT2 by geraniol has the potential to reduce hyperglycaemia and prevent secondary complications in diabetes.

Effects of Orally Consumed Rosa damascena Mill. Hydrosol on Hematology, Clinical Chemistry, Lens Enzymatic Activity, and Lens Pathology in Streptozotocin-Induced Diabetic Rats

Diabetes mellitus is a multisystemic metabolic disorder that may affect the eyes, kidneys, vessels, and heart. Chronic hyperglycemia causes non-enzymatic glycation of proteins and elevation of the polyol pathway resulting in oxidative stress that damages organs. The current study aimed to investigate the dose-dependent effects of orally consumed Rosa damascena Mill. hydrosol on hematology, clinical biochemistry, lens enzymatic activity, and lens pathology in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced into male Sprague-Dawley rats by intraperitoneal administration of STZ (40 mg/kg body weight). Rose hydrosols containing 1515 mg/L and 500 mg/L total volatiles (expressed as citronellol) were introduced to rats orally for 45 days. Consumption of 1515 mg/L volatile containing rose hydrosol successfully ameliorated hematologic, hepatic, and renal functions. Hydrosols also attenuated hyperglycemia and decreased the advanced glycation end-product formation in a dose-dependent manner. Rose hydrosol components significantly increased the lens enzymatic activities of glutathione peroxidase and decreased the activity of aldose reductase to prevent cataractogenesis. Histopathological examinations of rat lenses also indicated that increasing the dose of rose hydrosol had a protective effect on lenses in diabetic conditions. Additionally, in silico modeling of aldose reductase inhibition with rose hydrosol volatiles was carried out for extrapolating the current study to humans. The present results suggest that rose hydrosol exerts significant protective properties in diabetes mellitus and has no toxic effect on all studied systems in healthy test groups.

Reversion of down-regulation of intestinal multidrug resistance-associated protein 2 in fructose-fed rats by geraniol and vitamin C: Potential role of inflammatory response and oxidative stress

Intestinal multidrug resistance-associated protein 2 is an ABC transporter that limits the absorption of xenobiotics ingested orally, thus acting as essential component of the intestinal biochemical barrier. Metabolic Syndrome (MetS) is a pathological condition characterized by dyslipidemia, hyperinsulinemia, insulin resistance, chronic inflammation, and oxidative stress (OS). In a previous study we demonstrated that MetS-like conditions induced by fructose in drinking water (10% v/v, during 21 days), significantly reduced the expression and activity of intestinal Mrp2 in rats. We here evaluated the potential beneficial effect of geraniol or vitamin C supplementation, natural compounds with anti-inflammatory and anti-oxidant properties, in reverse fructose-induced Mrp2 alterations. After MetS-like conditions were induced (21 days), animals were cotreated with geraniol or vitamin C or vehicle for another 14 days. Decreased expression of Mrp2 protein and mRNA due to fructose administration was reversed by geraniol and by vitamin C, consistent with restoration of Mrp2 activity evaluated in everted intestinal sacs. Concomitantly, increased intestinal IL-1β and IL-6 levels induced by fructose were totally and partially counterbalanced, respectively, by geraniol administration. The intestinal redox unbalance generated by fructose was improved by geraniol and vitamin C, as evidenced by decreasing lipid peroxidation products and activity of Superoxide Dismutase and by normalizing glutathione reduced/oxidized glutathione ratio. The restoration effects exhibited by geraniol and vitamin C suggest that local inflammatory response and OS generated under MetS-like conditions represent important mediators of the intestinal Mrp2 down-regulation. Additionally, both agents could be considered of potential therapeutic value to preserve Mrp2 function under MetS conditions.

Isoquercetin upregulates antioxidant genes, suppresses inflammatory cytokines and regulates AMPK pathway in streptozotocin-induced diabetic rats

Lifestyle and genetic factors contribute to the initiation of oxidative stress and inflammation in diabetes mellitus (DM). Oxidative stress and lipid peroxidation worked in an orchestrated manner and reported to be strongly associated with the formation of the hyperlipidemic condition in DM patients. Isoquercetin, a bioactive constituent isolated from guava leaves has attracted considerable attention because of its antidiabetic activity. The antidiabetic activity of guava leaves may be due to the presence of isoquercetin at a significant level. However, how isoquercetin regulates different pathways in DM is insufficiently studied. We have selected versatile regulators of oxidative stress and inflammatory pathways to fully analyze if isoquercetin effectively modulated the genes of these pathways. At the end of our experimental duration, rats were dissected and analyzed for the oxidative stress, lipid peroxidation, inflammatory and lipid markers. The nuclear factor erythroid 2-related factor 2 (Nrf2) pathway is believed to be the key regulator of expression of various antioxidant enzyme genes and it is directly or indirectly related to nuclear factor Kappa- B (NF-kB) and AMP-activated protein kinase (AMPK) pathways. Therefore, we tend to study the effects of STZ on Nrf2, NF-kB and AMPK pathway and how the isoquercetin treatment performs at a molecular level to overcome the burden of DM. The results of our study provided convincing evidence of significant pharmacological properties of isoquercetin in context of its ability to inhibit the oxidative stress elicited by the STZ through generation of the free radicals and regulation of the expression of Nrf2 pathway-associated proteins and genes and it also reduced the burden of hyperlipidemia and inflammation. By taking the above results into consideration isoquercetin can be studied further to elucidate its antidiabetic effects at various levels.

Rev-erbα activation down-regulates hepatic Pck1 enzyme to lower plasma glucose in mice

REV-ERBα (NR1D1) is a nuclear heme receptor that controls many cellular processes including cell differentiation, lipid metabolism, and inflammatory responses. Although REV-ERBα has been also implicated in regulation of glucose homeostasis, the mechanism for this regulation remains unclear. Here we investigate a potential role of REV-ERBα in regulation of PCK1 (phosphoenolpyruvate carboxykinase 1), a rate-limiting enzyme in gluconeogenesis. Hepatoma cells (Hepa-1c1c7 and HepG2 cells), wild-type mice and streptozotocin-induced diabetic mice were treated with SR9009, a specific REV-ERBα agonist. The relative mRNA and protein levels of enzymes in the cells or mouse livers were determined by qPCR and Western blotting, respectively. The fasting plasma glucose test was performed to determine the effects of Rev-erbα on glucose homeostasis. Transcriptional regulation of Pck1 by Rev-erbα was investigated using a combination of luciferase reporter, mobility shift, and chromatin immunoprecipitation (ChIP) assays. SR9009 treatment significantly decreased the mRNA level of Pck1 in mouse hepatoma Hepa-1c1c7 cells, whereas other major enzymes involved in gluconeogenesis (pyruvate carboxylase, glucose-6-phosphatase, fructose bisphosphatase and Pck2) and in glycolysis (phosphofructokinase and hexokinase-1) were unaffected. Consistent with the mRNA change, the protein level of Pck1 was down-regulated. Similarly, a repressive action of REV-ERBα on PCK1 expression was observed in human HepG2 hepatoma cells. SR9009 administration to wild-type or diabetic mice significantly reduced the level of fasting plasma glucose. This coincided with decreased mRNA and protein levels of Pck1 in the liver. In addition, the diabetic mice showed an improvement in glucose tolerability after SR9009 treatment. Promoter analysis, mobility shift, and ChIP assays revealed that Rev-erbα trans-repressed Pck1 through direct binding to -325 to -320 bp region (a RevRE site) in the gene promoter. In conclusion, Rev-erbα activation down-regulates hepatic Pck1 to lower plasma glucose.

Medicinal properties of terpenes found in Cannabis sativa and Humulus lupulus

Cannabaceae plants Cannabis sativa L. and Humulus lupulus L. are rich in terpenes - both are typically comprised of terpenes as up to 3-5% of the dry-mass of the female inflorescence. Terpenes of cannabis and hops are typically simple mono- and sesquiterpenes derived from two and three isoprene units, respectively. Some terpenes are relatively well known for their potential in biomedicine and have been used in traditional medicine for centuries, while others are yet to be studied in detail. The current, comprehensive review presents terpenes found in cannabis and hops. Terpenes' medicinal properties are supported by numerous in vitro, animal and clinical trials and show anti-inflammatory, antioxidant, analgesic, anticonvulsive, antidepressant, anxiolytic, anticancer, antitumor, neuroprotective, anti-mutagenic, anti-allergic, antibiotic and anti-diabetic attributes, among others. Because of the very low toxicity, these terpenes are already widely used as food additives and in cosmetic products. Thus, they have been proven safe and well-tolerated.

Natural products for the treatment of type 2 diabetes mellitus: Pharmacology and mechanisms

Epidemiological studies have implied that diabetes mellitus (DM) will become an epidemic accompany with metabolic and endocrine disorders worldwide. Most of DM patients are affected by type 2 diabetes mellitus (T2DM) with insulin resistance and insulin secretion defect. Generally, the strategies to treat T2DM are diet control, moderate exercise, hypoglycemic and lipid-lowing agents. Despite the therapeutic benefits for the treatment of T2DM, most of the drugs can produce some undesirable side effects. Considering the pathogenesis of T2DM, natural products (NPs) have become the important resources of bioactive agents for anti-T2DM drug discovery. Recently, more and more natural components have been elucidated to possess anti-T2DM properties, and many efforts have been carried out to elucidate the possible mechanisms. The aim of this paper was to overview the activities and underlying mechanisms of NPs against T2DM. Developments of anti-T2DM agents will be greatly promoted with the increasing comprehensions of NPs for their multiple regulating effects on various targets and signal pathways.

Synchronous application of antibiotics and essential oils: dual mechanisms of action as a potential solution to antibiotic resistance

Antibiotic resistance has increased dramatically in recent years, yet the antibiotic pipeline has stalled. New therapies are therefore needed to continue treating antibiotic resistant infections. One potential strategy currently being explored is the use of non-antibiotic compounds to potentiate the activity of currently employed antibiotics. Many natural products including Essential Oils (EOs) possess broad spectrum antibacterial activity and so have been investigated for this purpose. This article aims to review recent literature concerning the antibacterial activity of EOs and their interactions with antibiotics, with consideration of dual mechanisms of action of EOs and antibiotics as a potential solution to antibiotic resistance. Synergistic interactions between EOs and their components with antibiotics have been reported, including several instances of antibiotic resensitization in resistant isolates, in support of this strategy to control antibiotic resistance. However, a lack of consistency in methods and interpretation criteria makes drawing conclusions of efficacy of studied combinations difficult. Synergistic effects are often not explored beyond preliminary identification of antibacterial interactions and mechanism of action is rarely defined, despite many hypotheses and recommendations for future study. Much work is needed to fully understand EO-antibiotic associations before they can be further developed into novel antibacterial formulations.

Antidiabetic Potential of Monoterpenes: A Case of Small Molecules Punching above Their Weight

Monoterpenes belong to the terpenoids class of natural products and are bio-synthesized through the mevalonic acid pathway. Their small molecular weight coupled with high non-polar nature make them the most abundant components of essential oils which are often considered to have some general antioxidant and antimicrobial effects at fairly high concentrations. These compounds are however reported to have antidiabetic effects in recent years. Thanks to the ingenious biosynthetic machinery of nature, they also display a fair degree of structural complexity/diversity for further consideration in structure-activity studies. In the present communication, the merit of monoterpenes as antidiabetic agents is scrutinized by assessing recent in vitro and in vivo studies reported in the scientific literature. Both the aglycones and glycosides of these compounds of rather small structural size appear to display antidiabetic along with antiobesity and lipid lowering effects. The diversity of these effects vis-à-vis their structures and mechanisms of actions are discussed. Some key pharmacological targets include the insulin signaling pathways and/or the associated PI3K-AKT (protein kinase B), peroxisome proliferator activated receptor-γ (PPARγ), glucose transporter-4 (GLUT4) and adenosine monophosphate-activated protein kinase (AMPK) pathways; proinflammatory cytokines and the NF-κB pathway; glycogenolysis and gluconeogenesis in the liver; glucagon-like-1 receptor (GLP-1R); among others.