Protective effect of Psidium guajava leaf extract on altered carbohydrate metabolism in streptozotocin-induced diabetic rats

Natural products for the treatment and management of diabetes mellitus in Zimbabwe-a review

Use of medicinal plants and herbs in the treatment and management of diseases, including diabetes mellitus and its complications remains an integral part of African tradition. In Zimbabwe, nearly one million people are living with diabetes mellitus. The prevalence of diabetes mellitus in Zimbabwe is increasing every year due to lifestyle changes, and has accelerated the use of traditional medicines for its treatment and management in urban areas. In addition, the high cost of modern medicine has led many people in rural parts of Zimbabwe to rely on herbal plant medicine for the treatment of diabetes mellitus and its complications. This review highlights a number of studies carried out to evaluate the antidiabetic properties of indigenous plants found in Zimbabwe with the goal of treating diabetes mellitus. Further, we discuss the mechanism of action of various plant extracts in the treatment and management of diabetes mellitus. Together, this review article can open pathways leading to discovery of new plant derived medicines and regularization of use of crude plant remedies to treat diabetes mellitus by the Zimbabwean government and others across Africa.

Protective effect of sinomenine against inflammation and oxidative stress in gestational diabetes mellitus in female rats via TLR4/MyD88/NF-κB signaling pathway

Gestational diabetes mellitus (GDM) is a dangerous complication of pregnancy which is induced via dysfunction in glucose metabolism during pregnancy. Sinomenine (SM) has already proved an antidiabetic effect against streptozotocin (STZ)-induced diabetes mellitus (DM) in rats. In this protocol, we examined the protective effect of SM against STZ-induced GDM in rats. Wistar rats were divided into three groups and STZ (40 mg/kg) was used to induce GDM. At the end of the experimental protocol, bodyweight, pub weight, and survival rate were estimated. Blood glucose level (BGL), fasting insulin (FINS), free fatty acid (FFA), Hemoglobin A1C (HbA1c), and C-peptide were measured. Lipid, antioxidant, inflammatory cytokines, and inflammatory mediators were also determined. RT-PCR was used for estimation of the role of TLR4/MyD88/NF-κB signaling pathway. SM treatment significantly (p < .001) reduced BGL, hepatic glycogen, and improved the levels of FINS, C-peptide, FFA, and HbA1c. SM significantly (p < .001) suppressed the levels of total cholesterol (TC), low-density lipoprotein (LDL), triglycerides (TG), coronary artery index (CAI), very low-density lipoprotein (VLDL), atherogenic index (AI), and boosted high-density lipoprotein (HDL) levels. SM significantly (p < .001) decreased the lipid peroxidation (LPO) level and enhanced glutathione peroxidase (GPx), total antioxidant capacity (TAC), glutathione S-transferase (GST), superoxide dismutase (SOD), respectively. It reduced the levels of inflammatory cytokines including interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and inflammatory mediators viz., nuclear kappa B factors (NF-κB). SM significantly (p < .001) reduced the mRNA expression of Myd88, NLRP3, TLR4, and NF-κB, which were boosted in the GDM group rats. These findings suggest that SM could be a probable drug to be used for treating GDM via inhibition of the TLR4 signaling pathway. PRACTICAL APPLICATIONS: It is well known that gestational diabetes mellitus (GDM) is a dangerous health problem during the pregnancy. SM reduced the glucose level; boosted the level of fasting insulin (FINS) and bodyweight. SM significantly improved the number of pubs and their survival rates. SM suppressed oxidative stress and inflammation via activation of TLR4/MyD88/NF-κB signaling pathway. According to our research, SM can be used as a preventive drug in the treatment of GDM during pregnancy.

Psidium guajava L. leaf extract inhibits adipocyte differentiation and improves insulin sensitivity in 3T3-L1 cells

BACKGROUND/OBJECTIVES

Psidium guajava L. (guava) leaves have been shown to exhibit hypoglycemic and antidiabetic effects in rodents. This study investigated the effects of guava leaf extract on adipogenesis, glucose uptake, and lipolysis of adipocytes to examine whether the antidiabetic properties are mediated through direct effects on adipocytes.

MATERIALS/METHODS

3T3-L1 cells were treated with 25, 50, 100 µg/mL of methanol extract from guava leaf extract (GLE) or 0.1% dimethyl sulfoxide as a control. Lipid accumulation was evaluated with Oil Red O Staining and AdipoRed assay. Immunoblotting was performed to measure the expression of adipogenic transcription factors, fatty acid synthase (FAS), and AMP-activated protein kinase (AMPK). Glucose uptake under basal or insulin-stimulated condition was measured using a glucose analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-D-glucose. Lipolysis from fully differentiated adipocytes was measured by free fatty acids release into the culture medium in the presence or absence of epinephrine.

RESULTS

Oil Red O staining and AdipoRed assay have shown that GLE treatment reduced lipid accumulation during adipocyte differentiation. Mitotic clonal expansion, an early essential event for adipocyte differentiation, was inhibited by GLE treatment. GLE inhibited the expression of transcription factors involved in adipocyte differentiation, such as peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα), and sterol regulatory element-binding protein-1c (SREBP-1c). FAS expression was also decreased while the phosphorylation of AMPK was increased by GLE treatment. In addition, GLE increased insulin-induced glucose uptake into adipocytes. In lipid-filled mature adipocytes, GLE enhanced epinephrine-induced lipolysis but reduced basal lipolysis dose-dependently.

CONCLUSIONS

The results show that GLE inhibits adipogenesis and improves adipocyte function by reducing basal lipolysis and increasing insulin-stimulated glucose uptake in adipocytes, which can be partly associated with antidiabetic effects of guava leaves.

AMPK Activation of Flavonoids from Psidium guajava Leaves in L6 Rat Myoblast Cells and L02 Human Hepatic Cells

Objective

To isolate the hypoglycemic bioactive components from leaves of Psidium guajava and evaluate their AMP-activated protein kinase (AMPK) activities.

Methods

A variety of column chromatography was used for the isolation of compounds, and nuclear magnetic resonance (NMR) and mass spectrum (MS) were used for the structure identification of compounds. AMP-activated protein kinase (AMPK) activity of compounds obtained from leaves of Psidium guajava was evaluated in L6 rat myoblast cells and L02 human hepatic cells by western blot.

Results

Six principal flavonoids largely present in the leaves of Psidium guajava, quercetin (1), quercetin-3-O-α-L-arabinofuranoside (2), quercetin-3-O-α-L-arabinopyranoside (3), quercetin-3-O-β-D-galactopyranoside (4), quercetin-3-O-β-D-glucopyranoside (5), and quercetin-3-O-β-D-xylopyranoside (6), were obtained and compound 1-6 exhibited significant activity on AMPK activation both in L6 cells and L02 cells (p < 0.01) compared with Control. In particular, the effects of quercetin on AMPK activation were extremely significant compared with Control (p < 0.001).

Conclusions

These findings demonstrated that these flavonoids had potential for the activation of AMPK and hypoglycemic activity.

Capability of polygonum cuspidatum extract in inhibiting AGEs and preventing diabetes

Diabetes is a metabolic disorder disease associated with advanced glycation end products (AGEs) and protein glycation. The effect of polygonum cuspidatum extract (PE) on AGEs and Nε-(Carboxymethyl)-L-lysine formation, protein glycation, and diabetes was investigated. Six primary phenolics in a range of 12.36 mg/g for ellagic acid to 0.01 mg/g for piceid were determined in PE. In an intermediate-moisture-foods model, inhibition rate of PE was as high as 54.2% for AGEs and 78.9% for CML under aw 0.75. The protein glycation was also inhibited by PE. In a diabetic rat model, the levels of blood glucose, serum malondialdehyde, cholesterol, triglycerides, and low-density lipoproteins were effectively reduced by PE treatment. The antioxidation capacity (T-AOC) and superoxide dismutase (SOD) activity were also mediated by PE. Additionally, the activates of liver function-related enzymes including alkaline phosphatase (ALP), glutamate pyruvate transaminase (GPT), and glutamate oxaloacetate transaminase (GOT) in diabetic rat were improved by PE.

The effect of Psidium guajava aqueous leaf extract on liver glycogen enzymes, hormone sensitive lipase and serum lipid profile in diabetic rats

Diabetes mellitus is characterized by hyperglycaemia that results from defects in insulin secretion or insulin action and is accompanied by general disturbances metabolism. Psidium guajava (PG) leaf is known to have antidiabetic effects that include lowering of blood glucose. The aim of the study was to investigate the effect of PG leaf extract on tissue activity of glycogen synthase (GS) and glycogen phosphorylase (GP); tissue activity of hormone sensitive lipase (HSL); serum lipid profile; and serum enzyme biomarkers of tissue damage. Diabetes was induced in male Sprague-Dawley rats with a single dose of 40 mg/kg body weight streptozotocin. The aqueous extract of PG leaves was used to treat both normal and diabetic animals (400 mg/kg body weight) for 2 weeks while control animals were treated with the vehicle. At the end of the treatment period, blood, liver and adipose tissue samples were collected from the euthanized animals. The results show that PG extract significantly decreased (P < 0.05) HSL activity in adipose tissue and liver of diabetic animals which was accompanied by increased glycogen levels, reduced serum triglycerides, total cholesterol, LDL-cholesterol and increased HDL-cholesterol. This study demonstrates that P. guajava has significant anti-diabetic effects that include increased glycogen storage and reduced HSL activity in the liver and adipose tissue with an improved serum lipid profile.

Selected Phytochemicals and Culinary Plant Extracts Inhibit Fructose Uptake in Caco-2 Cells

This study compared the ability of nine culinary plant extracts containing a wide array of phytochemicals to inhibit fructose uptake and then explored the involvement of intestinal fructose transporters and phytochemicals for selected samples. The chemical signature was characterized by high performance liquid chromatography with mass spectrometry. Inhibition of [(14)C]-fructose uptake was tested by using human intestinal Caco-2 cells. Then, the relative contribution of the two apical-facing intestinal fructose transporters, GLUT2 and GLUT5, and the signature components for fructose uptake inhibition was confirmed in naive, phloretin-treated and forskolin-treated Caco-2 cells. HPLC/MS analysis of the chemical signature revealed that guava leaf contained quercetin and catechin, and turmeric contained curcumin, bisdemethoxycurcumin and dimethoxycurcumin. Similar inhibition of fructose uptake (by ~50%) was observed with guava leaf and turmeric in Caco-2 cells, but with a higher contribution of GLUT2 for turmeric and that of GLUT5 for guava leaf. The data suggested that, in turmeric, demethoxycurcumin specifically contributed to GLUT2-mediated fructose uptake inhibition, and curcumin did the same to GLUT5-mediated fructose uptake inhibition, but GLUT2 inhibition was more potent. By contrast, in guava leaf, catechin specifically contributed to GLUT5-mediated fructose uptake inhibition, and quercetin affected both GLUT5- and GLUT2-mediated fructose uptake inhibition, resulting in the higher contribution of GLUT5. These results suggest that demethoxycurcumin is an important contributor to GLUT2-mediated fructose uptake inhibition for turmeric extract, and catechin is the same to GLUT5-mediated fructose uptake inhibition for guava leaf extract. Quercetin, curcumin and bisdemethoxycurcumin contributed to both GLUT5- and GLUT2-mediated fructose uptake inhibition, but the contribution to GLUT5 inhibition was higher than the contribution to GLUT2 inhibition.

Ethnopharmacological field study of the plants used to treat type 2 diabetes among the Cakchiquels in Guatemala

ETHNOPHARMACOLOGICAL RELEVANCE

Type 2 diabetes is characterized by tissue resistance to the action of insulin, combined with a relative deficiency in insulin secretion. In Guatemala, type 2 diabetes results in significant mortality rates. The low incomes of the indigenous population results in the use of alternative therapies such as medicinal plants to treat the illness. We could not find any previous study related to the use of medicinal plants to treat diabetes in Guatemala. The aim of this work is to determine the most effective plant species used in traditional medicine to treat type 2 diabetes.

MATERIALS AND METHODS

We performed an ethnopharmacological field study among the Cakchiquels of Chimaltenango to select the most prominent plants used to treat the disease. Type 2 diabetic patients from their community health centers were interviewed using structured questionnaires. Two mathematical tools were used to identify potential plant species: the Disease Consensus Index and the Use Value. International databases, including SCOPUS, PubMed, and Google Scholar, were used to identify whether the plants with the highest scores were known to elicit hypoglycemic effects.

RESULTS

After analyzing the data, we can propose the following plants as the most prominent among the Cakchiquels of Chimaltenango to treat type 2 diabetes: Hamelia patens Jacq., Neurolaena lobata (L.) R.Br.ex Cass., Solanum americanum Mill., Croton guatemalensis Lotsy, and Quercus peduncularis Née.

CONCLUSIONS

The Cakchiquel patients interviewed did not understand type 2 diabetes; however, they associated the onset of their disease with a negative emotion, such as shock, sadness or anger. Despite changes in lifestyle, influences of advertising, the availability of innovative treatments and the use of oral hypoglycemic treatments provided by health facilities serving indigenous communities, the Cakchiquel continue to use medicinal plants as adjunctive treatment. While they are unaware whether the plants can cause additional harm, they consider their consumption beneficial because they feel better. There were 11 plants identified with UVs greater than 0.5 and high DCIs; from these 64% of the plants have been identified as having hypoglycemic effects; this finding supports the traditional selection by the Cakchiquels of medicinal plants to treat T2D.