Genistein promotes insulin action through adenosine monophosphate-activated protein kinase activation and p70 ribosomal protein S6 kinase 1 inhibition in the skeletal muscle of mice fed a high energy diet

Bioactive Peptides from Meretrix lusoria Enzymatic Hydrolysate as a Potential Treatment for Obesity in db/db Mice

Obesity is acknowledged as a significant risk factor for cardiovascular disease, often accompanied by increased inflammation and diabetes. Bioactive peptides derived from marine animal proteins show promise as safe and effective anti-obesity agents by regulating adipocyte differentiation through the AMPK signaling pathway. Therefore, this study aims to investigate the anti-obesity and anti-diabetic effects of bioactive compounds derived from a Meretrix lusoria Protamex enzymatic hydrolysate (MLP) fraction (≤1 kDa) through a 6-week treatment (150 mg/kg or 300 mg/kg, administered once daily) in leptin receptor-deficient db/db mice. The MLP treatment significantly decreased the body weight, serum total cholesterol, triglycerides, and LDL-cholesterol levels while also exhibiting a beneficial effect on hepatic and serum marker parameters in db/db mice. A histological analysis revealed a reduction in hepatic steatosis and epididymal fat following MLP treatment. Furthermore, poor glucose tolerance was improved, and hepatic antioxidant enzyme activities were elevated in MLP-treated mice compared to db/db control mice. Western blot analysis showed an increased expression of the AMPK protein after MLP treatment. In addition, the expression of lipogenic genes decreased in db/db mice. These findings indicate that bioactive peptides, which are known to regulate blood glucose levels, lipid metabolism, and adipogenesis, could be beneficial functional food additives and pharmaceuticals.

Anti-obesity effects of Camellia (Camellia oleifera Abel) oil treatment on high-fat diet-induced obesity in C57BL/6J mice

PURPOSE

In the current study, we investigated the effects of camellia oil and camellia oil infused with herbs (Camellia oleifera Abel) on obesity in obese mice fed a high-fat diet (HFD).

METHODS

The antioxidant activity of camellia oil in scavenging free radicals was investigated. Additionally, body and organ weight changes, serum and liver marker parameters, antioxidant enzyme activities, liver and epididymal fat histology, protein and gene expression associated with lipogenesis and hyperglycemia effect on adenosine monophosphate-activated protein kinase (AMPK) phosphorylation, were examined in HFD-induced obese mice.

RESULTS

The hepatic steatosis and epididymal fat were significantly reduced by the oral administration of camellia oil and herb-infused camellia oil. Moreover, hepatic and serum marker parameters such as total cholesterol, insulin, triglycerides, tumor necrosis factor-α, adiponectin, thiobarbituric acid reactive substances, aspartate aminotransferase, and alanine transaminase were beneficially impacted. Additionally, the activity of antioxidant enzymes also increased. Camellia oil and herb-infused camellia oil treatments reduced the expression of genes linked to hyperglycemia and lipogenesis via activation of AMPK phosphorylation.

CONCLUSION

For many people, exercise poses an obstacle in the daily routine due to lack of ease, difficulty in maintaining consistency, and hard work. Camellia oil combined with herbs has anti-obesity and antihyperglycemic effects. These findings indicate that treatment with herb-infused camellia oil is most beneficial for elderly individuals who do not prefer frequent exercise.

Role of flavonoids in controlling obesity: molecular targets and mechanisms

Obesity presents a major health challenge that increases the risk of several non-communicable illnesses, such as but not limited to diabetes, hypertension, cardiovascular diseases, musculoskeletal and neurological disorders, sleep disorders, and cancers. Accounting for nearly 8% of global deaths (4.7 million) in 2017, obesity leads to diminishing quality of life and a higher premature mortality rate among affected individuals. Although essentially dubbed as a modifiable and preventable health concern, prevention, and treatment strategies against obesity, such as calorie intake restriction and increasing calorie burning, have gained little long-term success. In this manuscript, we detail the pathophysiology of obesity as a multifactorial, oxidative stress-dependent inflammatory disease. Current anti-obesity treatment strategies, and the effect of flavonoid-based therapeutic interventions on digestion and absorption, macronutrient metabolism, inflammation and oxidative stress and gut microbiota has been evaluated. The use of several naturally occurring flavonoids to prevent and treat obesity with a long-term efficacy, is also described.

Anti-Obesity and Anti-Hyperglycemic Effects of Meretrix lusoria Protamex Hydrolysate in ob/ob Mice

Meretrix lusoria (M. lusoria) is an economically important shellfish which is widely distributed in South Eastern Asia that contains bioactive peptides, proteins, and enzymes. In the present study, the extracted meat content of M. lusoria was enzymatic hydrolyzed using four different commercial proteases (neutrase, protamex, alcalase, and flavourzyme). Among the enzymatic hydrolysates, M. lusoria protamex hydrolysate (MLPH) fraction with MW ≤ 1 kDa exhibited the highest free radical scavenging ability. The MLPH fraction was further purified and an amino acid sequence (KDLEL, 617.35 Da) was identified by LC-MS/MS analysis. The purpose of this study was to investigate the anti-obesity and anti-hyperglycemic effects of MLPH containing antioxidant peptides using ob/ob mice. Treatment with MLPH for 6 weeks reduced body and organ weight and ameliorated the effects of hepatic steatosis and epididymal fat, including a constructive effect on hepatic and serum marker parameters. Moreover, hepatic antioxidant enzyme activities were upregulated and impaired glucose tolerance was improved in obese control mice. In addition, MLPH treatment markedly suppressed mRNA expression related to lipogenesis and hyperglycemia through activation of AMPK phosphorylation. These findings suggest that MLPH has anti-obesity and anti-hyperglycemic potential and could be effectively applied as a functional food ingredient or pharmaceutical.

Intraperitoneal injection of genistein affects the distribution and metabolism of cholesterol in female yellow catfish Tachysurus fulvidraco

Genistein is an abundant phytoestrogen in soybean. This study aimed to determine the effects of genistein on cholesterol distribution and metabolism in female yellow catfish. Three hundred fish (49.2 ± 1.4 g) were randomly divided into five treatments and received intraperitoneal injections as follows: (1) blank, no injection; (2) control, vehicle only; (3) E2, 17β-estradiol at 10 μg·g^-1 body weight; (4) low genistein doses, genistein at 10 μg·g^-1 body weight; (5) high genistein doses, genistein at 100 μg·g^-1 body weight. Both high and low genistein doses significantly reduced (p < 0.05) serum TC and LDL-C 24 h after injection. Moreover, the high genistein doses significantly reduced (p < 0.05) serum HDL-C. Both high and low doses of genistein significantly increased (p < 0.05) hepatic TC. Only high genistein doses significantly increased (p < 0.05) ovary TC. In the liver, both high and low genistein doses significantly increased (p < 0.05) protein and mRNA expression of ldlr. Meanwhile, high genistein doses significantly decreased (p < 0.05) mRNA expression of hmgcr. In ovary tissue, high genistein doses significantly decreased (p < 0.05) mRNA expression of cyp11a1. These results suggested that genistein affected the cholesterol distribution in female yellow catfish. Both high and low doses of genistein reduced cholesterol content in blood and increased its content in the liver by increasing the uptake of blood cholesterol. Meanwhile, high genistein doses may inhibit hepatic cholesterol synthesis. Additionally, high genistein doses could increase cholesterol transfer from serum into the ovary and disturb cholesterol conversion to pregnenolone.

Dietary Flavonoids and Insulin Signaling in Diabetes and Obesity

Type 2 diabetes (T2D) and obesity are relevant worldwide chronic diseases. A common complication in both pathologies is the dysregulation of the insulin-signaling pathway that is crucial to maintain an accurate glucose homeostasis. Flavonoids are naturally occurring phenolic compounds abundant in fruits, vegetables and seeds. Rising evidence supports a role for the flavonoids against T2D and obesity, and at present, these compounds are considered as important potential chemopreventive agents. This review summarizes in vitro and in vivo studies providing data related to the effects of flavonoids and flavonoid-rich foods on the modulation of the insulin route during T2D and obesity. Notably, few human studies have evaluated the regulatory effect of these phenolic compounds at molecular level on the insulin pathway. In this context, it is also important to note that the mechanism of action for the flavonoids is not fully characterized and that a proper dosage to obtain a beneficial effect on health has not been defined yet. Further investigations will contribute to solve all these critical challenges and will enable the use of flavonoids to prevent, delay or support the treatment of T2D and obesity.

Soy diet for nonalcoholic fatty liver disease: A meta-analysis of randomized controlled trials

INTRODUCTION

The efficacy of soy diet for nonalcoholic fatty liver disease remains controversial. We conduct a systematic review and meta-analysis to explore the influence of soy diet vs placebo on the treatment of non-alcoholic fatty liver disease.

METHODS

We search PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through October 2020 for randomized controlled trials assessing the efficacy of soy diet vs placebo for nonalcoholic fatty liver disease. This meta-analysis is performed using the random-effect model.

RESULTS

Five randomized controlled trials are included in the meta-analysis. Overall, compared with control group for nonalcoholic fatty liver disease, soy diet is associated with significantly reduced HOMA-IR (standard mean difference [SMD] = -0.42; 95% confidence interval [CI] = -0.76 to -0.08; P = .01), increased insulin (SMD = -0.64; 95% CI = -0.98 to -0.30; P = .0002) and decreased malondialdehyde (SMD = -0.43; 95% CI = -0.74 to -0.13; P = .005), but demonstrated no substantial impact on body mass index (SMD = 0.17; 95% CI = -0.20 to 0.53; P = .37), alanine aminotransferase (SMD = -0.01; 95% CI = -0.61 to 0.60; P = .98), aspartate-aminotransferase (SMD = 0.01; 95% CI = -0.47 to 0.49; P = .97), total cholesterol (SMD = 0.05; 95% CI = -0.25 to 0.35; P = .73) or low density lipoprotein (SMD = 0; 95% CI = -0.30 to 0.30; P = .99).

CONCLUSIONS

Soy diet may benefit to alleviate insulin resistance for nonalcoholic fatty liver disease.

Medicinal Potential of Isoflavonoids: Polyphenols That May Cure Diabetes

In recent years, there is emerging evidence that isoflavonoids, either dietary or obtained from traditional medicinal plants, could play an important role as a supplementary drug in the management of type 2 diabetes mellitus (T2DM) due to their reported pronounced biological effects in relation to multiple metabolic factors associated with diabetes. Hence, in this regard, we have comprehensively reviewed the potential biological effects of isoflavonoids, particularly biochanin A, genistein, daidzein, glycitein, and formononetin on metabolic disorders and long-term complications induced by T2DM in order to understand whether they can be future candidates as a safe antidiabetic agent. Based on in-depth in vitro and in vivo studies evaluations, isoflavonoids have been found to activate gene expression through the stimulation of peroxisome proliferator-activated receptors (PPARs) (α, γ), modulate carbohydrate metabolism, regulate hyperglycemia, induce dyslipidemia, lessen insulin resistance, and modify adipocyte differentiation and tissue metabolism. Moreover, these natural compounds have also been found to attenuate oxidative stress through the oxidative signaling process and inflammatory mechanism. Hence, isoflavonoids have been envisioned to be able to prevent and slow down the progression of long-term diabetes complications including cardiovascular disease, nephropathy, neuropathy, and retinopathy. Further thoroughgoing investigations in human clinical studies are strongly recommended to obtain the optimum and specific dose and regimen required for supplementation with isoflavonoids and derivatives in diabetic patients.

Antioxidant Effects and Mechanisms of Medicinal Plants and Their Bioactive Compounds for the Prevention and Treatment of Type 2 Diabetes: An Updated Review

Diabetes mellitus is a metabolic disorder that majorly affects the endocrine gland, and it is symbolized by hyperglycemia and glucose intolerance owing to deficient insulin secretory responses and beta cell dysfunction. This ailment affects as many as 451 million people worldwide, and it is also one of the leading causes of death. In spite of the immense advances made in the development of orthodox antidiabetic drugs, these drugs are often considered not successful for the management and treatment of T2DM due to the myriad side effects associated with them. Thus, the exploration of medicinal herbs and natural products as therapeutic sources for the treatment of T2DM is promoted because they have little or no side effects. Bioactive molecules isolated from natural sources have been proven to lower blood glucose levels via regulating one or more of the following mechanisms: improvement of beta cell function, insulin resistance, glucose (re)absorption, and glucagon-like peptide-1 homeostasis. In recent times, the mechanisms of action of different bioactive molecules with antidiabetic properties and phytochemistry are gaining a lot of attention in the area of drug discovery. This review article presents an update of the findings from clinical research into medicinal plant therapy for T2DM.

miR-222 is involved in the regulation of genistein on skeletal muscle fiber type

In skeletal muscle, the composition of the fiber types has a profound impact on athletic performance, such as endurance or strength output. The proportions of muscle fiber types have also been associated with certain diseases, including dyskinesia, obesity and insulin resistance. Genistein, a natural estrogen, has been demonstrated to regulate fatty acid oxidation and insulin sensitivity in skeletal muscle. However, it is unknown whether genistein can regulate skeletal muscle fiber types. Furthermore, the mechanism of its effect on skeletal muscle energy metabolism is not entirely clear. In this study, in vivo and in vitro experiments were used to explore the effect of genistein on the muscle fiber-type transitions and muscle metabolism. The results indicated that genistein not only promotes skeletal muscle development but increases the expression of slow muscle fibers in mice as well. It was also demonstrated that genistein altered the ratios of fiber type and promoted mitochondrial biogenesis in C2C12 myoblasts. Interestingly, the expression of miR-222 was decreased by genistein, and it was demonstrated that this microRNA targets the PGC1α gene. In C2C12 myoblasts, miR-222 appears to regulate fiber type conversion and mitochondrial biogenesis. However, this function was significantly reduced following genistein treatment. These results suggest that miR-222 may be involved in the regulation of genistein on skeletal muscle fiber and muscle metabolism, and genistein may be used to improve muscle health.

Protective effect of genistein on nonalcoholic fatty liver disease (NAFLD)

NAFLD is a vital health problem worldwide; however, no effective treatment is currently available for NAFLD. Intensive studies have indicated the efficacy of genistein (GE), a bioactive isoflavone extracted from soy, in treating NAFLD. In addition to its oestrogen-like effects, GE is known to have multiple molecular effects, for instance, lipid and glucose metabolism-promoting effects and activities against lipid peroxidation, inflammation, fibrosis, and NAFLD-related tumours. Here, this review summarizes the potential role of GE in the treatment and prevention of NAFLD and some of the currently known targets and signalling pathways of GE in NAFLD.

Dietary soya protein improves intra-myocardial lipid deposition and altered glucose metabolism in a hypertensive, dyslipidaemic, insulin-resistant rat model

This study investigates the effects of replacing dietary casein by soya protein on the underlying mechanisms involved in the impaired metabolic fate of glucose and lipid metabolisms in the heart of dyslipidaemic rats chronically fed (8 months) a sucrose-rich (62·5 %) diet (SRD). To test this hypothesis, Wistar rats were fed an SRD for 4 months. From months 4 to 8, half the animals continued with the SRD and the other half were fed an SRD in which casein was substituted by soya. The control group received a diet with maize starch as the carbohydrate source. Compared with the SRD-fed group, the following results were obtained. First, soya protein significantly (P<0·001) reduced the plasma NEFA levels and normalised dyslipidaemia and glucose homoeostasis, improving insulin resistance. The protein levels of fatty acid translocase at basal state and under insulin stimulation and the protein levels and activity of muscle-type carnitine palmitoyltransferase 1 were normalised. Second, a significant (P<0·001) reduction of TAG, long-chain acyl CoA and diacylglycerol levels was observed in the heart muscle. Third, soya protein significantly increased (P<0·01) GLUT4 protein level under insulin stimulation and normalised glucose phosphorylation and oxidation. A reduction of phosphorylated AMP protein kinase protein level was recorded without changes in uncoupling protein 2 and PPARα. Fourth, hydroxyproline concentration decreased in the left ventricle and hypertension was normalised. The new information provided shows the beneficial effects of soya protein upon the altered pathways of glucose and lipid metabolism in the heart muscle of this rat model.

Genistein represses PEPCK-C expression in an insulin-independent manner in HepG2 cells and in alloxan-induced diabetic mice

Genistein has been reported to exert beneficial effects on type 2 diabetes mellitus (T2DM); however, the underlying molecular mechanisms involved therein have not been clearly elucidated. To address this question, the effect of genistein on the expression of phosphoenolpyruvate carboxykinase (PEPCK), and glucose production in HepG2 cells and in alloxan-induced diabetic mice was investigated. HepG2 cells were exposed to different concentration of genistein in presence or absence of modulators, and the expression of cytosolic PEPCK (PEPCK-C) and the signaling pathways was studied. Further, the biological relevance of the in vitro study was tested in alloxan-induced diabetic mice. Genistein lowered PEPCK-C expression and glucose production in HepG2 cells accompanied with increased in phosphorylation states of AMPK, MEK½, ERK½, and CRTC2. Treatment with the AMPK inhibitor (compound C) enhanced genistein-induced MEK½ and ERK½ activity indicating a potential cross-talk between the two signaling pathways. In vivo, genistein also reduced fasting glucose levels accompanied with reduced PEPCK-C expression and increased in AMPK and ERK½ phosphorylation states in the liver of genistein-treated alloxan-induced diabetic mice. Genistein fulfills the criteria of a suitable anti-diabetic agent by reducing glucose production and inhibiting PEPCK-C expression in HepG2 cells and also in alloxan-induced diabetic mice. These results indicate that genistein is an effective candidate for preventing T2DM through the modulation of AMPK-CRTC2 and MEK/ERK signaling pathways, which may allow a novel approach to modulate dysfunction in hepatic gluconeogenesis in T2DM.

Genistein supplementation improves insulin resistance and inflammatory state in non-alcoholic fatty liver patients: A randomized, controlled trial

BACKGROUND & AIMS

The beneficial effect of genistein has indicated on metabolic disorders and inflammatory state. The aim of this study was to investigate the effect of genistein supplementation on non-alcoholic fatty liver disease (NAFLD) as the hepatic manifest of metabolic syndrome.

METHODS

In the present randomized double-blind controlled trial, patients with NAFLD were daily supplemented with either 250 mg genistein (n = 41) or placebo (n = 41) for 8-weeks. Both groups were instructed to follow an energy-balanced diet and physical activity recommendations. And their anthropometric and biochemical indices were assessed before and after the intervention.

RESULTS

At the end of the study, the genistein group had lower level of serum insulin (p = 0.001) and homeostasis model assessment for insulin resistance (HOMA-IR) (p = 0.041) compare to the placebo group. In addition serum malondialdehyde (MDA) (p = 0.004), tumor necrosis factor-α (TNF-α) (p = 0.045) and interleukin (IL)-6 (p = 0.018) also were lower in the genistein group. Compare with placebo, genistein supplementation significantly reduced waist to hip ratio (p = 0.021), body fat percentage (p = 0.015) and triglyceride (p = 0.018). However, there were no significant changes in BMI, fasting blood glucose (p = 0.122), alanine aminotransferase (ALT) (p = 0.536), aspartate aminotransferase (AST) (p = 0.265) between the two groups.

CONCLUSIONS

Oral supplementation with 250 mg genistein for 8-weeks can reduce insulin resistance, oxidative and inflammatory indices along with improvement in fat metabolism in patients with NAFLD. Studies with longer duration and larger samples might be needed to reveal other beneficial effects of genistein.

Inflammation and intracellular metabolism: new targets in OA

Articular cartilage degeneration is hallmark of osteoarthritis (OA). Low-grade chronic inflammation in the joint can promote OA progression. Emerging evidence indicates that bioenergy sensors couple metabolism with inflammation to switch physiological and clinical phenotypes. Changes in cellular bioenergy metabolism can reprogram inflammatory responses, and inflammation can disturb cellular energy balance and increase cell stress. AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1) are two critical bioenergy sensors that regulate energy balance at both cellular and whole-body levels. Dysregulation of AMPK and SIRT1 has been implicated in diverse human diseases and aging. This review reveals recent findings on the role of AMPK and SIRT1 in joint tissue homeostasis and OA, with a focus on how AMPK and SIRT1 in articular chondrocytes modulate intracellular energy metabolism during stress responses (e.g., inflammatory responses) and how these changes dictate specific effector functions, and discusses translational significance of AMPK and SIRT1 as new therapeutic targets for OA.

Dietary isoflavone daidzein promotes Tfam expression that increases mitochondrial biogenesis in C2C12 muscle cells

Mitochondrial dysfunction in muscles leads to a wide range of metabolic and age-related disorders. Recently, it has been reported that a natural polyphenol, resveratrol, affects mitochondrial biogenesis. This study aimed to identify other natural polyphenolic compounds that regulate mitochondrial biogenesis in muscles. For this purpose, we used the C2C12 murine muscle cell line. Screening involved a reporter assay based on the promoter of mitochondrial transcription factor A (Tfam). We found that several polyphenols exhibited the ability to increase Tfam promoter activity and that the soy isoflavone daidzein was a most potent candidate that regulated mitochondrial biogenesis. When C2C12 myotubes were treated with 25-50 μM daidzein for 24h, there were significant increases in the expression of Tfam and mitochondrial genes such as COX1 and Cytb as well as the mitochondrial content. Using several mutant Tfam promoter fragments, we found that the transcription factor, nuclear respiratory factor (NRF) and its coactivator, PGC1α, were necessary for the effect of daidzein on Tfam expression. Finally, silencing of sirtuin-1 (SIRT1) by shRNA resulted in inhibition of the daidzein effects on mitochondrial gene expression. In conclusion, daidzein regulates mitochondrial biogenesis in muscle cells by regulating transcriptional networks through a SIRT1-associated pathway. These results suggest that daidzein would be beneficial to protect against a wide range of diseases caused by muscle mitochondrial dysfunction.

Effects of phytoestrogens on growth-related and lipogenic genes in rainbow trout (Oncorhynchus mykiss)

This study determined whether estradiol (E2) or the phytoestrogens genistein and daidzein regulate expression of growth-related and lipogenic genes in rainbow trout. Juvenile fish (5 mon, 65.8±1.8 g) received intraperitoneal injections of E2, genistein, or daidzein (5 μg/g body weight) or a higher dose of genistein (50 μg/g body weight). Liver and white muscle were harvested 24h post-injection. In liver, expression of vitellogenin (vtg) and estrogen receptor alpha (era1) increased in all treatments and reflected treatment estrogenicity (E2>genistein (50 μg/g)>genistein (5 μg/g)=daidzein (5 μg/g)). Estradiol and genistein (50 μg/g) reduced components of the growth hormone (GH)/insulin-like growth factor (IGF) axis in liver, including increased expression of IGF binding protein-2b1 (igfbp2b1) and reduced igfbp5b1. In liver E2 and genistein (50 μg/g) affected expression of components of the transforming growth factor beta signaling mechanism, reduced expression of ppar and rxr transcription factors, and increased expression of fatty acid synthesis genes srebp1, acly, fas, scd1, and gpat and lipid binding proteins fabp3 and lpl. In muscle E2 and genistein (50 μg/g) increased era1 and erb1 expression and decreased erb2 expression. Other genes responded to phytoestrogens in a manner that suggested regulation by estrogen receptor-independent mechanisms, including increased ghr2, igfbp2a, igfbp4, and igfbp5b1. Expression of muscle regulatory factors pax7 and myod was increased by E2 and genistein. These data indicate that genistein and daidzein affect expression of genes in rainbow trout that regulate physiological mechanisms central to growth and nutrient retention.

Withdrawal of dietary phytoestrogens in adult male rats affects hypothalamic regulation of food intake, induces obesity and alters glucose metabolism

The absence of phytoestrogens in the diet during pregnancy has been reported to result in obesity later in adulthood. We investigated whether phytoestrogen withdrawal in adult life could alter the hypothalamic signals that regulate food intake and affect body weight and glucose homeostasis. Male Wistar rats fed from conception to adulthood with a high phytoestrogen diet were submitted to phytoestrogen withdrawal by feeding a low phytoestrogen diet, or a high phytoestrogen-high fat diet. Withdrawal of dietary phytoestrogens increased body weight, adiposity and energy intake through an orexigenic hypothalamic response characterized by upregulation of AGRP and downregulation of POMC. This was associated with elevated leptin and T4, reduced TSH, testosterone and estradiol, and diminished hypothalamic ERα expression, concomitant with alterations in glucose tolerance. Removing dietary phytoestrogens caused manifestations of obesity and diabetes that were more pronounced than those induced by the high phytoestrogen-high fat diet intake.

Caffeine ameliorates high energy diet-induced hepatic steatosis: sirtuin 3 acts as a bridge in the lipid metabolism pathway

We demonstrate that caffeine could improve HED-induced hepatic steatosis by promoting lipid metabolism via the cAMP/CREB/SIRT3/AMPK/ACC pathway. SIRT3 acts as a molecular bridge connecting caffeine and lipid metabolism.

JAK2 and AMP-kinase inhibition in vitro by food extracts, fractions and purified phytochemicals

A study of 49 foods shows that ellagitannin containing foods inhibit JAK2 and AMPK kinases.

Opposite effects of genistein on the regulation of insulin-mediated glucose homeostasis in adipose tissue

BACKGROUND AND PURPOSE

Genistein is an isoflavone phytoestrogen found in a number of plants such as soybeans and there is accumulating evidence that it has beneficial effects on the regulation of glucose homeostasis. In this study we evaluated the effect of genistein on glucose homeostasis and its underlying mechanisms in normal and insulin-resistant conditions.

EXPERIMENTAL APPROACH

To induce insulin resistance, mice or differentiated 3T3-L1 adipocytes were treated with macrophage-derived conditioned medium. A glucose tolerance test was used to investigate the effect of genistein. Insulin signalling activation, glucose transporter-4 (GLUT4) translocation and AMP-activated PK (AMPK) activation were detected by Western blot analysis or elisa.

KEY RESULTS

Genistein impaired glucose tolerance and attenuated insulin sensitivity in normal mice by inhibiting the insulin-induced phosphorylation of insulin receptor substrate-1 (IRS1) at tyrosine residues, leading to inhibition of insulin-mediated GLUT4 translocation in adipocytes. Mac-CM, an inflammatory stimulus induced glucose intolerance accompanied by impaired insulin sensitivity; genistein reversed these changes by restoring the disturbed IRS1 function, leading to an improvement in GLUT4 translocation. In addition, genistein increased AMPK activity under both normal and inflammatory conditions; this was shown to contribute to the anti-inflammatory effect of genistein, which leads to an improvement in insulin signalling and the amelioration of insulin resistance.

CONCLUSION AND IMPLICATIONS

Genistein showed opposite effects on insulin sensitivity under normal and inflammatory conditions in adipose tissue and this action was derived from its negative or positive regulation of IRS1 function. Its up-regulation of AMPK activity contributes to the inhibition of inflammation implicated in insulin resistance.

Soy isoflavone affects the autonomic nervous system in a tissue-specific manner in anesthetized rats

We examined and compared the effects of taste stimulation by soy saponin as well as soy isoflavone and intragastric (IG) injection of both on the autonomic nerve activities and feeding behavior in rats. We found that taste stimulation by soy saponin or soy isoflavone-rich solution (SIRS) did not affect the activity of the sympathetic nerve supplying the adrenal gland in urethane-anesthetized rats; however, IG injection of SIRS, but not soy saponin, stimulated the adrenal sympathetic nerve activity (ASNA) in a dose-dependent manner. Moreover, IG injection of SIRS significantly suppressed the activity of the vagus nerve innervating the stomach, whereas sympathetic nerve outflows to brown or white adipose tissue were not affected by IG injection of SIRS. To test the involvement of the afferent autonomic nerve in the abdominal organs for regulation of the efferent ASNA by SIRS, we examined the response of the adrenal sympathetic innervation to SIRS injection in rats with ablated afferent vagus or afferent sympathetic nerves. The activating effect of SIRS on the ASNA was inhibited in sympathectomized rats but not in vagotomized rats. Thus, our data suggest that soy isoflavone might affect tissue-specific autonomic nerves through the afferent sympathetic nerve pathway.

Daidzein promotes glucose uptake through glucose transporter 4 translocation to plasma membrane in L6 myocytes and improves glucose homeostasis in Type 2 diabetic model mice

Daidzein shows estrogenic, antioxidant and antiandrogenic properties as well as cell cycle regulatory activity. However, the antihyperglycemic effect of daidzein remains to be elucidated. In this study, we investigated the in vitro effect of daidzein on glucose uptake, AMPK phosphorylation and GLUT4 translocation on plasma membrane in L6 myotubes and its in vivo antihyperglycmic effect in obese-diabetic model db/db mice. Daidzein was found to promote glucose uptake, AMPK phosphorylation and GLUT4 translocation by Western blotting analyses in L6 myotubes under a condition of insulin absence. Promotion by daidzein of glucose uptake as well as GLUT4 translocation to plasma membrane by immunocytochemistry was also demonstrated in L6 myoblasts transfected with a GLUT4 cDNA-coding vector. Daidzein (0.1% in the diet) suppressed the rises in the fasting blood glucose, serum total cholesterol levels and homeostasis model assessment index of db/db mice. In addition, daidzein supplementation markedly improved the AMPK phosphorylation in gastrocnemius muscle of db/db mice. Daidzein also suppressed increases in blood glucose levels and urinary glucose excretion in KK-Ay mice, another Type 2 diabetic animal model. These in vitro and in vivo findings suggest that daidzein is preventive for Type 2 diabetes and an antidiabetic phytochemical.

Genistein sensitizes hepatic insulin signaling and modulates lipid regulatory genes through p70 ribosomal S6 kinase-1 inhibition in high-fat-high-fructose diet-fed mice

CONTEXT

Genistein reduces high-calorie diet-induced insulin resistance and fat accumulation in animals, but the mechanism is unresolved.

OBJECTIVE

This study explores whether action of genistein is associated with p70 ribosomal S6 kinase-1 (S6K1) inhibition.

MATERIALS AND METHODS

Adult male mice were fed either normal diet or high-fat-high-fructose diet (HFFD) for 15 days, after which animals in each dietary group were divided into two groups and administered either genistein (1 mg kg(-1) day(-1), p.o.) in 0.5 ml of 30% dimethylsulfoxide (DMSO) or 30% DMSO (0.5 ml) for the next 45 days. At the end of the study, their liver was analyzed for lipid content. Semi-quantitative RT-PCR and western blotting methods were used to analyze lipid regulatory genes and insulin signaling proteins, respectively.

RESULTS

Genistein significantly (p < 0.05) lowered HFFD-induced body and liver weight gain and plasma and hepatic lipid levels. Histology showed a 2.5-fold increase of lipid in HFFD compared to control. Genistein treatment to HFFD-fed animals significantly decreased lipid accumulation (by 40%) compared to HFFD. Insulin-stimulated tyrosine phosphorylation of insulin receptor-β and insulin receptor substrates-1 (IRS-1), IRS-1 associated phospatidylinositol-3kinase (PI3K) and Akt Ser(473) phosphorylation were improved while IRS-1 serine phosphorylation was significantly (p < 0.05) decreased by genistein in HFFD. Significant (p < 0.05) increase in adenosine monophosphate-activated protein kinase (AMPK) Thr(172) phosphorylation and decrease in S6K1 Thr(389) phosphorylation were observed in HFFD-plus genistein compared to HFFD. Genistein downregulated lipogenic genes and upregulated fatty acid oxidative genes in HFFD-fed mice.

CONCLUSION

Genistein improves insulin signaling and attenuates fat accumulation in liver through S6K1 inhibition.

Phytochemicals targeting genes relevant for type 2 diabetes

Nutrigenomic approaches based on ethnopharmacology and phytotherapy concepts have revealed that type 2 diabetes mellitus (T2DM) may be susceptible to dietary intervention. Interaction between bioactive food components and the genome may influence cell processes and modulate the onset and progression of the disease. T2DM, characterized by insulin resistance and beta cell dysfunction, is one of the leading causes of death and disability. Despite the great advances that have been made in the understanding and management of this complex, multifactorial disease, T2DM has become a worldwide epidemic in the 21st century. Population and family studies have revealed a strong genetic component of T2DM, and a number of candidate genes have been identified in humans. Variations in the gene sequences such as single nucleotide polymorphisms, explain the individual differences in traits like disease susceptibility and response to treatment. A clear understanding of how nutrients affect the expression of genes should facilitate the development of individualized intervention and, eventually, treatment strategies for T2DM. Review of the literature identified many phytochemicals/extracts from traditional medicinal plants that can target diabetogenic genes. This review focuses on the genetic aspects of T2DM, nutrient modification of genes relevant for diabetes, and future prospects of nutritional therapy of T2DM.