Attenuation of insulin resistance in rats by agmatine: role of SREBP-1c, mTOR and GLUT-2

Metabolic disparities between obese and non-obese patients with polycystic ovary syndrome: implications for endometrial receptivity indicators

OBJECTIVE

To investigate the differences in the metabolic indicators and sex hormones between obese and non-obese patients with polycystic ovary syndrome (PCOS), and their impacts on endometrial receptivity (ER).

METHODS

We selected 255 individuals with PCOS, and categorized them into the obese groups, including the OP group (obese patients with PCOS) and the ON group (obese patients without PCOS), and selected 64 individuals who were categorized in the non-obese groups, namely, the control groups, which comprise the NP group (non-obese patients with PCOS) and the NN group(non-obese patients without PCOS). The one-way analysis of variance (ANOVA) and Mann-Whitney U tests were used to compare the metabolic indicators, and sex hormone-associated and ER-associated indicators between the groups. The correlation between the aforementioned clinical markers and ER was analyzed using the Pearson's correlation coefficient.

RESULTS

(1) In comparison with the NP group, the OP group exhibited higher levels (p < .01) of free androgen index (FAI), anti-müllerian hormone (AMH), fasting insulin (FINS), insulin level within 60 min, 120 min, and 180 min-60minINS, 120minINS, and 180minINS, respectively, fasting blood glucose (FBG), blood glucose level within two hours (2hGlu), homeostatic model assessment for insulin resistance (HOMA-IR), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), waist-to-hip ratio (WHR), waist circumference, hip circumference, the ratio of the maximum blood flow velocity of the uterine artery during systole to the blood flow velocity of the uterine artery at the end of diastole (uterine artery S/D), and blood flow resistance index (RI) of the uterine artery. In comparison with the NP group, the OP group exhibited lower levels (p < .01) of sex hormone binding globulin (SHBG), dehydroepiandrosterone (DHEA), high molecular weight adiponectin (HMWA), and high-density lipoprotein cholesterol (HDL-C). (2) In the PCOS group, RI was significantly positively correlated with FAI, FINS, 120minINS, HOMA-IR, and WHR (p < .01), and significantly negatively correlated with SHBG, HDL-C, and HMWA (p < .01); uterine artery S/D was significantly positively correlated with FAI, FINS, 2hGlu, HOMA-IR, LDL-C, and WHR (p < .01), significantly positively correlated with 120minINS and FBG (p < .05), and significantly negatively correlated with SHBG and HMWA (p < .01).

CONCLUSION

(1) The OP group exhibited obvious metabolic disorders and poor ER, which was manifested as low levels of SHBG and HMWA, and high levels of FAI, HOMA-IR, WHR, uterine artery S/D, and RI. (2) In patients with PCOS, there was a substantial correlation between ER-associated indicators RI and uterine artery S/D and FAI, FINS, 120minINS, HOMA-IR, WHR, SHBG, and HMWA.

Long-term Bisphenol S exposure induced gut microbiota dysbiosis, obesity, hepatic lipid accumulation, intestinal lesions and dyslipidemia in mice

Bisphenol S (BPS) is a commonly detected chemical raw material in water, which poses significant threats to both the ecological environment and human health. Despite being recognized as a typical endocrine disruptor and a substitute for Bisphenol A, the toxicological effects of BPS remain nonnegligible. In order to comprehensively understand the health impacts of BPS, a long-term (154 days) exposure experiment was conducted on mice, during which the physiological indicators of the liver, intestine, and blood were observed. The findings revealed that exposure to BPS resulted in dysbiosis of the gut microbiota, obesity, hepatic lipid accumulation, intestinal lesions, and dyslipidemia. Furthermore, there exists a significant correlation between gut microbiota and indicators of host health. Consequently, the identification of specific gut microbiota can be considered as potential biomarkers for the evaluation of risk associated with BPS. This study will effectively address the deficiency in toxicological data pertaining to BPS. The novel BPS data obtained from this research can serve as a valuable reference for professionals in the field.

The effect of maternal separation stress-induced depression on ovarian reserve in Sprague Dawley Rats: The possible role of imipramine and agmatine through a mTOR signal pathway

PURPOSE

To examine the possible role of impramine and agmatine through a mTOR signal pathway on rat ovary after maternal separation stress-induced depression.

METHODS

Sprague Dawley neonatal female rats were divided into control, maternal separation (MS), MS+imipramine, and MS+agmatine groups. Rats were subjected to MS for 4 hours daily from postnatal day (PND) 2 to PND 21 and pups were exposed to social isolation (SI) on PND23 for 37 days for model establishment treated with imipramine (30 mg/kg; ip) or agmatine (40 mg/kg; ip) for 15 days. In order to examine behavioral changes rats were all subjected to locomotor activity and forced swimming tests (FST). Ovaries were isolated for morphological evaluation, follicle counting and mTOR signal pathway protein expression levels were detected.

RESULTS

Increased number of primordial follicles and diminished ovarian reserve in the MS groups were detected. Imipramine treatment caused diminished ovarian reserve and atretic follicle; however, agmatine treatment provided the maintenance of ovarian follicular reserve after MS. mTOR signal pathway may have an important role during rat ovarian follicular development in model of MS.

CONCLUSIONS

Our findings suggest that agmatine may help to protect ovarian reserve during follicular development by controlling cell growth.

Inhibition of Atherosclerosis and Liver Steatosis by Agmatine in Western Diet-Fed apoE-Knockout Mice Is Associated with Decrease in Hepatic De Novo Lipogenesis and Reduction in Plasma Triglyceride/High-Density Lipoprotein Cholesterol Ratio

Atherosclerosis and NAFLD are the leading causes of death worldwide. The hallmark of NAFLD is triglyceride accumulation caused by an imbalance between lipogenesis de novo and fatty acid oxidation. Agmatine, an endogenous metabolite of arginine, exerts a protective effect on mitochondria and can modulate fatty acid metabolism. In the present study, we investigate the influence of agmatine on the progression of atherosclerotic lesions and the development of hepatic steatosis in apoE^−/− mice fed with a Western high-fat diet, with a particular focus on its effects on the DNL pathway in the liver. We have proved that treatment of agmatine inhibits the progression of atherosclerosis and attenuates hepatic steatosis in apoE^−/− mice on a Western diet. Such effects are associated with decreased total macrophage content in atherosclerotic plaque as well as a decrease in the TG levels and the TG/HDL ratio in plasma. Agmatine also reduced TG accumulation in the liver and decreased the expression of hepatic genes and proteins involved in lipogenesis de novo such as SREBP-1c, FASN and SCD1. In conclusion, agmatine may present therapeutic potential for the treatment of atherosclerosis and fatty liver disease. However, an exact understanding of the mechanisms of the advantageous actions of agmatine requires further study.

Possible involvement of agmatine in neuropharmacological actions of metformin in diabetic mice

The risk of psychiatric and neurological disorders is significantly higher in patients with diabetes mellitus. Diabetic patients are more susceptible to depression, anxiety and memory impairment as compared with non-diabetic individuals. Metformin, a biguanide used for the management of type 2 diabetes mellitus (T2DM), promotes neurogenesis, enhances spatial memory function and protects the brain against oxidative imbalance beyond its effect on glucose metabolism. However, the exact mechanism of its neuropharmacological actions in T2DM is not known. We investigated the role of the agmatinergic system in neuropharmacological actions of metformin in diabetic mice. Diabetes was induced by the streptozotocin (STZ) injection and confirmed by high blood glucose levels. After 28 days, STZ treated mice exhibited memory impairment in radial arm maze, depression-like behavior in forced swim test and anxiety-like behavior in elevated plus maze along with increased expression of pro-inflammatory cytokines like TNF-α, IL-1β, IL-6, IL-10 also, reduced agmatine and BDNF levels in the hippocampus and prefrontal cortex compared to the control animals. Metformin and agmatine alone or in combination, by once-daily administration during 14-27 day of the protocol significantly reversed the STZ induced high blood glucose levels, memory impairment, depression and anxiety-like behaviors. It also reduced neuro-inflammatory markers and increased agmatine and BDNF levels in the hippocampus and prefrontal cortex. The present study suggests the importance of endogenous agmatine in the neuropharmacological action of metformin in diabetic mice. The data projects agmatine and metformin combination as a potential therapeutic strategy for diabetes associated memory impairment, depression, anxiety, and other comorbidities.

Kursi Wufarikun Ziyabit Improves the Physiological Changes by Regulating Endoplasmic Reticulum Stress in the Type 2 Diabetes db/db Mice

Kursi Wufarikun Ziyabit (KWZ) is a classic traditional medicine used for the prevention treatment of diabetes in China. It was widely used as healthcare tea in folk and can prevent and treat type 2 diabetes. However, the underlying mechanism of KWZ in type 2 diabetes has not been investigated extensively. Here, the weekly body weight and blood glucose level of KWZ in type 2 diabetes db/db male mice were observed. After 4 weeks of treatment, the physiological changes and pharmacological effects of KWZ were investigated. The results showed that KWZ can significantly decrease fasting blood glucose and improve glucose tolerance and insulin sensitivity in db/db mice. The serum/liver lipid profiles such as LDL-C, TC, TG, and serum-free fatty acid/Fructosamine levels were decreased, and the serum/liver HDL-C levels were increased. In addition, significant improvement in glucose metabolism enzymes and antioxidant enzymes in experimental mice's livers was observed. Moreover, the expression of GRP78, p-IRE1α/IRE1α, p-eIF2α/eIF2α, and XBP1s was decreased. The expression of p-PERK/PERK, p-Akt/Akt, and p-GSK-3β/GSK-3β was markedly increased. These results suggested that KWZ is effective for type 2 diabetes by improving endoplasmic reticulum (ER) stress in the liver of db/db mice, and it might prevent the damage of insulin Beta cells and alleviate insulin resistance.

Transplantation of neuregulin 4-overexpressing adipose-derived mesenchymal stem cells ameliorates insulin resistance by attenuating hepatic steatosis

IMPACT STATEMENT

Due to high-fat and high-sugar diets accompanied by sedentary lifestyles, diabetes has become a global epidemic. Literature findings suggest a potential therapeutic effect of Nrg4 on treating obesity-related metabolic disorders including type 2 diabetes (T2D). Adipose tissue-derived MSCs (ADSCs) were used in our study as they are abundant and can be harvested with minimally invasive procedures. In the end, our study reveals that ADSC transplantation improves glucose tolerance and metabolic balance in HFD-fed mice by multiple mechanisms, including upregulating GLUT4 expression and suppressing inflammation. More importantly, our study shows that Nrg4 overexpression could improve the efficacy of ADSCs in ameliorating insulin resistance (IR) and other obesity-related metabolic disorders, given the function of Nrg4 in attenuating hepatic lipogenesis. It would provide a new therapeutic strategy for the treatment of obesity, IR, and T2D.

Molecular aspects of pancreatic β-cell dysfunction: Oxidative stress, microRNA, and long noncoding RNA

Metabolic syndrome is known as a frequent precursor of type 2 diabetes mellitus (T2D). This disease could affect 8% of the people worldwide. Given that pancreatic β-cell dysfunction and loss have central roles in the initiation and progression of the disease, the understanding of cellular and molecular pathways associated with pancreatic β-cell dysfunction can provide more information about the underlying pathways involved in T2D. Multiple lines evidence indicated that oxidative stress, microRNA, and long noncoding RNA play significant roles in various steps of diseases. Oxidative stress is one of the important factors involved in T2D pathogenesis. This could affect the function and survival of the β cell via activation or inhibition of several processes and targets, such as receptor-signal transduction, enzyme activity, gene expression, ion channel transport, and apoptosis. Besides oxidative stress, microRNAs and noncoding RNAs have emerged as epigenetic regulators that could affect pancreatic β-cell dysfunction. These molecules exert their effects via targeting a variety of cellular and molecular pathways involved in T2D pathogenesis. Here, we summarized the molecular aspects of pancreatic β-cell dysfunction. Moreover, we highlighted the roles of oxidative stress, microRNAs, and noncoding RNAs in pancreatic β-cell dysfunction.

The inhibition of inducible nitric oxide synthase and oxidative stress by agmatine attenuates vascular dysfunction in rat acute endotoxemic model

Vascular dysfunction leading to hypotension is a major complication in patients with septic shock. Inducible nitric oxide synthase (iNOS) together with oxidative stress play an important role in development of vascular dysfunction in sepsis. Searching for an endogenous, safe and yet effective remedy was the chief goal for this study. The current study investigated the effect of agmatine (AGM), an endogenous metabolite of l-arginine, on sepsis-induced vascular dysfunction induced by lipopolysaccharides (LPS) in rats. AGM pretreatment (10mg/kg, i.v.) 1h before LPS (5mg/kg, i.v.) prevented the LPS-induced mortality and elevations in serum creatine kinase-MB isoenzyme (CK-MB) activity, lactate dehydrogenase (LDH) activity, C-reactive protein (CRP) level and total nitrite/nitrate (NOx) level after 24h from LPS injection. The elevation in aortic lipid peroxidation illustrated by increased malondialdehyde (MDA) content and the decrease in aortic glutathione (GSH) and superoxide dismutase (SOD) were also ameliorated by AGM. Additionally, AGM prevented LPS-induced elevation in mRNA expression of iNOS, while endothelial NOS (eNOS) mRNA was not affected. Furthermore AGM prevented the impaired aortic contraction to KCl and phenylephrine (PE) and endothelium-dependent relaxation to acetylcholine (ACh) without affecting endothelium-independent relaxation to sodium nitroprusside (SNP).

IN CONCLUSION

AGM may represent a potential endogenous therapeutic candidate for sepsis-induced vascular dysfunction through its inhibiting effect on iNOS expression and oxidative stress.

Aegle marmelos impedes onset of insulin resistance syndrome in rats provided with drinking fructose from weaning to adulthood stages of development — a mechanistic study

In this study, we explored the effect of aqueous extract of leaves of Aegle marmelos (AM) on hepatic carbohydrate metabolism and insulin downstream signalling in rats given fructose (15%) in drinking water from weaning to adulthood. Wistar albino rats (4 weeks old) were randomly divided into normal control (NC), fructose control (FC), and treatment (AMT) groups and were fed for a period of 8 weeks the following diets: chow + water, chow + fructose (15%), and chow + fructose (15%) + AM (500 mg/kg per day, p.o.), respectively. Compared with the NC group, the FC group was found to have significantly (p < 0.05) raised levels of fasting blood glucose, lipid, visceral mass, plasma insulin and leptin, glycogen, and gluconeogenesis enzyme but decreased glycolytic enzyme activity. Raised levels of glucose transporter 2 protein but decreased activity of phosphatidylinositol-3-kinase (PI3K/Akt) and Janus kinase – signal transducer and activator of transcription-3 (JAK–STAT3) in hepatic tissue indicate a state of insulin and leptin resistance in the FC group. A significant (p < 0.05) lowering of physical and glycemic parameters, strengthening of the hepatic glycolytic pathway over the gluconeogenic pathway, and upregulation of the PI3K/Akt and JAK–STAT3 pathways was observed in the AMT group, as compared with the FC group. For the first time, the mechanism underlying the development of insulin resistance syndrome is delineated here, along with the potential of A. marmelos to impede it.

Oral arginine supplementation protects female mice from the onset of non-alcoholic steatohepatitis

Dietary arginine (Arg) supplementation has been proposed to have positive effects on the development of liver diseases. In the present study, we investigate if an oral Arg supplementation in diet protects mice fed a fructose, fat and cholesterol enriched Western-style diet (WSD) from the development of non-alcoholic steatohepatitis (NASH). Female C57BL/6J mice were fed a liquid control diet or a liquid WSD ± Arg (2.49 g/kg body weight/day) for 6 weeks. Indices of liver injury, glucose metabolism and intestinal permeability were determined. While Arg supplementation had no effects on body weight gain, fasting blood glucose levels were significantly lower in WSD+Arg-fed mice than in C+Arg-fed animals. WSD-fed mice developed liver steatosis accompanied with inflammation, both being significantly attenuated in WSD+Arg-fed mice. These effects of Arg supplementation went along with a protection against WSD-induced decreased tight junction protein levels in the upper parts of the small intestine, increased levels of bacterial endotoxin in portal plasma as well as increased hepatic toll-like receptor-4 mRNA and 4-hydroxynonenal protein adduct levels. In conclusion, Arg supplementation may protect mice from the development of NASH.

Hypoglycemic effect of the polyphenols rich extract from Rose rugosa Thunb on high fat diet and STZ induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Rosa rugosa Thunb is a traditional Uygur medicine that has been used in the treatment of diabetes in Uygur ancient recipe for hundreds of years. However, the mechanism of Rosa rugosa Thunb activity is still unclear. This study was designed to address this issue by studying the polyphenols enriched extract (RPE) of Rosa rugosa Thunb in diabetic rats.

MATERIALS AND METHODS

RPE were tested in the inhibition of α-glucosidase and oxidative stress in vitro. RPE was administrated at dosages of 37.5, 75 and 150mg/kg body weight in the type 2 diabetic rats, which were made by high fat diet feeding plus a low dose of STZ injection (30mg/kg). The therapeutic effect was evaluated four weeks later. Oral glucose tolerance test (OGTT), insulin tolerance test (ITT) and insulin signal pathway (PI3K/AKT) were examined to determine insulin sensitivity. Blood glucose levels and body weight were measured weekly in the study.

RESULTS

In vitro, RPE exhibited an activity in the inhibition of α-glucosidase and had an excellent antioxidant activity in the liver of diabetic rats. RPE significantly decreased the fasting blood glucose, improved insulin sensitivity (HOMA-IR), OGTT, ITT and blood lipid profile. The glycogen synthesis and hexokinase activity were increased together with the improved signaling activity of insulin as indicated by p-IRS, p-IR, p-AKT, and p-GSK-3β.

CONCLUSIONS

The results suggest that RPE reduced blood glucose in type 2 diabetic rats by improvement of insulin sensitivity. The effect is likely achieved by inhibition of oxidative stress and α-glucosidase.

Mice endometrium receptivity in early pregnancy is impaired by maternal hyperinsulinemia

Previous studies have investigated the lower embryo implantation rates in women with polycystic ovary syndrome, obesity and type 2 diabetes, and specifically the association between the abnormal oocyte and embryo and hyperinsulinemia. The importance of hyperinsulinemia on maternal endometrium receptivity remains to be elucidated. The present study used a hyperinsulinemic mouse model to determine whether hyperinsulinemia may affect endometrial receptivity. An insulin intervention mouse model was first established. The serum levels of insulin, progesterone and estradiol were subsequently detected by ELISA assay analysis. The number of implantation sites was recorded using Trypan blue dye and the morphology of mice uteri was investigated using hematoxylin and eosin staining. The expression levels of molecular markers associated with endometrial receptivity were detected by reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemistry analyses. Finally, the importance of mechanistic target of rapamycin (mTOR) expression following insulin treatment was determined. Mice treated with insulin developed insulin resistance and hyperinsulinemia. The number of implantation sites following insulin treatment did not differ between the control and insulin‑treated groups. Additionally, no significant morphological alterations in mice uteri between control and insulin‑treated groups were observed. However, the expression levels of estrogen receptor (Esr) 1, Esr2, progesterone receptor and homeobox A10 associated with endometrial receptivity, were imbalanced during endometrium receptivity when maternal hyperinsulinemia was induced. Western blot analysis revealed that expression levels of endometrial phosphorylated (p)‑mTOR and p‑ribosomal protein S6 kinase β‑1 were significantly greater in the insulin‑treated group. These results demonstrated that although an embryo may implant into endometrium, mice endometrium receptivity in early pregnancy may be impaired by maternal hyperinsulinemia. In addition, mTOR signaling may be involved in this process. The present study provides preliminary results demonstrating that female reproduction may be compromised during hyperinsulinemia, which requires further investigation in future studies.

Agmatine ameliorates type 2 diabetes induced-Alzheimer's disease-like alterations in high-fat diet-fed mice via reactivation of blunted insulin signalling

The risk of Alzheimer's disease (AD) is higher in patients with type 2 diabetes mellitus (T2DM). Previous studies in high-fat diet-induced AD animal models have shown that brain insulin resistance in these animals leads to the accumulation of amyloid beta (Aβ) and the reduction in GSK-3β phosphorylation, which promotes tau phosphorylation to cause AD. No therapeutic treatments that target AD in T2DM patients have yet been discovered. Agmatine, a primary amine derived from l-arginine, has exhibited anti-diabetic effects in diabetic animals. The aim of this study was to investigate the ability of agmatine to treat AD induced by brain insulin resistance. ICR mice were fed a 60% high-fat diet for 12 weeks and received one injection of streptozotocin (100 mg/kg/ip) 4 weeks into the diet. After the 12-week diet, the mice were treated with agmatine (100 mg/kg/ip) for 2 weeks. Behaviour tests were conducted prior to sacrifice. Brain expression levels of the insulin signal molecules p-IRS-1, p-Akt, and p-GSK-3β and the accumulation of Aβ and p-tau were evaluated. Agmatine administration rescued the reduction in insulin signalling, which in turn reduced the accumulation of Aβ and p-tau in the brain. Furthermore, agmatine treatment also reduced cognitive decline. Agmatine attenuated the occurrence of AD in T2DM mice via the activation of the blunted insulin signal.