Cellular Stress, Excessive Apoptosis, and the Effect of Metformin in a Mouse Model of Type 2 Diabetic Embryopathy

Diabetes and Early Development: Epigenetics, Biological Stress, and Aging

Pregestational diabetes, either type 1 or type 2 diabetes, induces structural birth defects including neural tube defects and congenital heart defects in human fetuses. Rodent models of type 1 and type 2 diabetic embryopathy have been established and faithfully mimic human conditions. Hyperglycemia of maternal diabetes triggers oxidative stress in the developing neuroepithelium and the embryonic heart leading to the activation of proapoptotic kinases and excessive cell death. Oxidative stress also activates the unfolded protein response and endoplasmic reticulum stress. Hyperglycemia alters epigenetic landscapes by suppressing histone deacetylation, perturbing microRNA (miRNA) expression, and increasing DNA methylation. At cellular levels, besides the induction of cell apoptosis, hyperglycemia suppresses cell proliferation and induces premature senescence. Stress signaling elicited by maternal diabetes disrupts cellular organelle homeostasis leading to mitochondrial dysfunction, mitochondrial dynamic alteration, and autophagy impairment. Blocking oxidative stress, kinase activation, and cellular senescence ameliorates diabetic embryopathy. Deleting the mir200c gene or restoring mir322 expression abolishes maternal diabetes hyperglycemia-induced senescence and cellular stress, respectively. Both the autophagy activator trehalose and the senomorphic rapamycin can alleviate diabetic embryopathy. Thus, targeting cellular stress, miRNAs, senescence, or restoring autophagy or mitochondrial fusion is a promising approach to prevent poorly controlled maternal diabetes-induced structural birth defects. In this review, we summarize the causal events in diabetic embryopathy and propose preventions for this pathological condition. KEY POINTS: · Maternal diabetes induces structural birth defects.. · Kinase signaling and cellular organelle stress are critically involved in neural tube defects.. · Maternal diabetes increases DNA methylation and suppresses developmental gene expression.. · Cellular apoptosis and senescence are induced by maternal diabetes in the neuroepithelium.. · microRNAs disrupt mitochondrial fusion leading to congenital heart diseases in diabetic pregnancy..

New insights into the anti-apoptotic mechanism of natural polyphenols in complex with Bax protein

Excessive apoptosis can kill normal cells and lead to liver damage, heart failure and neurodegenerative diseases. Polyphenols are secondary metabolites of plants that can interact with proteins to inhibit toxins and disease-related apoptosis. Bax is the major pro-apoptotic protein that disrupts the outer mitochondrial membrane to induce apoptosis, but limited studies have focused on the interaction between polyphenols and Bax and the associated anti-apoptotic mechanisms, especially at the atomic level. In this article, we collected 69 common polyphenols for active ingredient screening targeting Bax. Polyphenols with better and worse molecular docking scores were selected, and their anti-apoptosis effects were compared using the H2O2-induced HepG2 cell model. The interactions between the selected polyphenols and Bax protein were analyzed using molecular dynamics simulation to explore the molecular mechanism underlying the anti-apoptosis effect. Secoisolariciresinol diglucoside (SDG) and Epigallocatechin-3-gallate (EGCG) with the best affinity for Bax (-6.76 and -6.52 kcal/mol) reduced the expression of cytochrome c and caspase 3, decreasing the apoptosis rate from 52 to 11% and 12%. Molecular dynamics simulation results showed that Bim unfolded the α1-α2 loop of Bax, and disrupted the non-bond interactions between the loop (Pro-43, Glu-44 and Leu-45) and surface (Ile-133, Arg-134 and Met-137) residues, with binding free energy changed from -15.0 to 0 kJ/mol. The hydrogen bonds and van der Waals interactions formed between polyphenols and Bax prevented the unfolding of the loop. Taken together, our results proved that polyphenols can inhibit apoptosis by maintaining the unactivated conformation of Bax to reduce outer mitochondrial membrane damage.Communicated by Ramaswamy H. Sarma.

Maternal Pre-Existing Diabetes: A Non-Inherited Risk Factor for Congenital Cardiopathies

Congenital heart defects (CHDs) are the most common form of birth defects in humans. They occur in 9 out of 1000 live births and are defined as structural abnormalities of the heart. Understanding CHDs is difficult due to the heterogeneity of the disease and its multifactorial etiology. Advances in genomic sequencing have made it possible to identify the genetic factors involved in CHDs. However, genetic origins have only been found in a minority of CHD cases, suggesting the contribution of non-inherited (environmental) risk factors to the etiology of CHDs. Maternal pregestational diabetes is associated with a three- to five-fold increased risk of congenital cardiopathies, but the underlying molecular mechanisms are incompletely understood. According to current hypotheses, hyperglycemia is the main teratogenic agent in diabetic pregnancies. It is thought to induce cell damage, directly through genetic and epigenetic dysregulations and/or indirectly through production of reactive oxygen species (ROS). The purpose of this review is to summarize key findings on the molecular mechanisms altered in cardiac development during exposure to hyperglycemic conditions in utero. It also presents the various in vivo and in vitro techniques used to experimentally model pregestational diabetes. Finally, new approaches are suggested to broaden our understanding of the subject and develop new prevention strategies.

Is metformin neuroprotective against diabetes mellitus-induced neurodegeneration? An updated graphical review of molecular basis

Diabetes mellitus (DM) is a metabolic disease that activates several molecular pathways involved in neurodegenerative disorders. Metformin, an anti-hyperglycemic drug used for treating DM, has the potential to exert a significant neuroprotective role against the detrimental effects of DM. This review discusses recent clinical and laboratory studies investigating the neuroprotective properties of metformin against DM-induced neurodegeneration and the roles of various molecular pathways, including mitochondrial dysfunction, oxidative stress, inflammation, apoptosis, and its related cascades. A literature search was conducted from January 2000 to December 2022 using multiple databases including Web of Science, Wiley, Springer, PubMed, Elsevier Science Direct, Google Scholar, the Core Collection, Scopus, and the Cochrane Library to collect and evaluate peer-reviewed literature regarding the neuroprotective role of metformin against DM-induced neurodegenerative events. The literature search supports the conclusion that metformin is neuroprotective against DM-induced neuronal cell degeneration in both peripheral and central nervous systems, and this effect is likely mediated via modulation of oxidative stress, inflammation, and cell death pathways.

High glucose causes developmental abnormalities in neuroepithelial cysts with actin and HK1 distribution changes

It has been reported that the offspring of diabetic pregnant women have an increased risk for neural tube defects. Previous studies in animal models suggested that high glucose induces cell apoptosis and epigenetic changes in the developing neural tube. However, effects on other cellular aspects such as the cell shape changes were not fully investigated. Actin dynamics plays essential roles in cell shape change. Disruption on actin dynamics is known to cause neural tube defects. In the present study, we used a 3D neuroepithelial cyst model and a rosette model, both cultured from human embryonic stem cells, to study the cellular effects caused by high glucose. By using these models, we observed couple of new changes besides increased apoptosis. First, we observed that high glucose disturbed the distribution of pH3 positive cells in the neuroepithelial cysts. Secondly, we found that high glucose exposure caused a relatively smaller actin inner boundary enclosed area, which was unlikely due to osmolarity changes. We further investigated key glucose metabolic enzymes in our models and the results showed that the distribution of hexokinase1 (HK1) was affected by high glucose. We observed that hexokinase1 has an apical-basal polarized distribution and is highest next to actin at the boundaries. hexokinase1 was more diffused and distributed less polarized under high glucose condition. Together, our observations broadened the cellular effects that may be caused by high glucose in the developing neural tube, especially in the secondary neurulation process.

"Adjust Zang and arouse spirit" electroacupuncture ameliorates cognitive impairment by reducing endoplasmic reticulum stress in db/db mice

Introduction

Diabetic cognitive impairment (DCI) is a chronic complication of the central nervous system (CNS) caused by diabetes that affects learning and memory capacities over time. Recently, acupuncture has been shown to improve cognitive impairment in streptozotocin-induced diabetic rats. However, the effects of electroacupuncture on DCI and its underlying mechanism have not yet been elucidated in detail.

Methods

In this study, we used db/db mice as DCI animal models which showed low cognitive, learning and memory functions. Electroacupuncture significantly ameliorated DCI, which is reflected by better spatial learning and memory function using behavioral tests. The db/db mice with cognitive impairment were randomly divided into a model group (Mod) and an electroacupuncture treatment group (Acup), while db/m mice were used as a normal control group (Con). First, the mice were subjected to behavioural tests using the Morris water maze (MWM), and body weight, blood glucose, insulin, triglycerides (TG) and total cholesterol (TC) were observed; HE, Nissl, and TUNEL staining were used to observe the morphological changes and neuronal apoptosis in the mice hippocampus; Finally, Western blot and rt-PCR were applied to detect the essential proteins and mRNA of ERS and insulin signalling pathway, as well as the expression levels of Tau and Aβ.

Results

Electroacupuncture significantly ameliorated DCI, which is reflected by better spatial learning and memory function using behavioral tests. Moreover, electroacupuncture attenuated diabetes-induced morphological structure change, neuronal apoptosis in the hippocampus of db/db mice. Our results revealed that electroacupuncture could regulate the expression levels of Tau and Aβ by improving hippocampal ERS levels in db/db mice, inhibiting JNK activation, attenuating IRS1 serine phosphorylation, and restoring normal transduction of the insulin signaling pathway.

Discussion

In summary, ERS and insulin signaling pathway paly causal roles in DCI development. Electroacupuncture can significantly alleviate the pathogenesis of DCI, improve mice's learning and memory ability, and improve cognitive dysfunction. This study adds to our understanding of the effect of acupuncture on DCI and opens the door to further research on DCI.

Advances in Anti-Diabetic Cognitive Dysfunction Effect of Erigeron Breviscapus (Vaniot) Hand-Mazz

Diabetic cognitive dysfunction (DCD) is the decline in memory, learning, and executive function caused by diabetes. Although its pathogenesis is unclear, molecular biologists have proposed various hypotheses, including insulin resistance, amyloid β hypothesis, tau protein hyperphosphorylation hypothesis, oxidative stress and neuroinflammation. DCD patients have no particular treatment options and current pharmacological regimens are suboptimal. In recent years, Chinese medicine research has shown that herbs with multi-component, multi-pathway and multi-target synergistic activities can prevent and treat DCD. Yunnan is home to the medicinal herb Erigeron breviscapus (Vant.) Hand-Mazz. (EBHM). Studies have shown that EBHM and its active components have a wide range of pharmacological effects and applications in cognitive disorders. EBHM's anti-DCD properties have been seldom reviewed. Through a literature study, we were able to evaluate the likely pathophysiology of DCD, prescribe anti-DCD medication and better grasp EBHM's therapeutic potential. EBHM's pharmacological mechanism and active components for DCD treatment were also summarized.

Tripeptide Leu-Pro-Phe from Corn Protein Hydrolysates Attenuates Hyperglycemia-Induced Neural Tube Defect in Chicken Embryos

Neural tube defect (NTD) is the most common and severe embryopathy causing embryonic malformation and even death associated with gestational diabetes mellitus (GDM). Leu-Pro-Phe (LPF) is an antioxidative tripeptide isolated from hydrolysates of corn protein. However, the biological activity of LPF in vivo and in vitro remains unclear. This study is aimed at investigating the protective effects of tripeptide LPF against NTD in the high glucose exposure condition and delineate the underlying biological mechanism. We found that LPF alleviated NTD in the high glucose-exposed chicken embryo model. In addition, DF-1 chicken embryo fibroblast was loaded with high glucose for induction of oxidative stress and abnormal O-GlcNAcylation in vitro. LPF significantly decreased accumulation of reactive oxygen species and content of malondialdehyde in DF-1 cells but increased the ratio of reduced glutathione and oxidized glutathione in chick embryo. Oxygen radical absorbance capacity results showed that LPF itself had good free radical scavenging capacity and could enhance antioxidant activity of the cell content. Mechanistic studies suggested that the resistance of LPF to oxidative damage may be related to promotion of NRF2 expression and nuclear translocation. LPF alleviated the overall O-GlcNAcylation level of cellular proteins under high glucose conditions and restored the level of Pax3 protein. Collectively, our findings indicate that LPF peptide could act as a nutritional supplement for the protection of development of embryonic neural tube affected by GDM.

Deciphering metformin action in obese mice: A critical re-evaluation of established protocols

BACKGROUND AND PURPOSE

Despite extensive efforts and a plethora of suggested targets and pathways, the mechanism via which metformin lowers blood glucose remains obscure. Obstacles that hamper progress in understanding metformin action include unexplained discrepancies between preclinical models and patients.

PROCEDURES

We treated obese male C57BL/6J mice fed high fat diet with metformin provided in the form of a single dose, daily intraperitoneal injections, admixture to drinking water, or continuous infusion via intraperitoneal minipumps.

RESULTS

The results suggest several superimposed components, via which metformin acts on blood glucose. These include (i) marked glucose lowering shortly after dosing, which fades rapidly with the decrease in metformin concentrations in plasma and liver, but could, at least to a major extent, rely on the mechanism also accounting for metformin's therapeutic action in humans; (ii) indirect action via reduced weight gain, which might be responsible for glucose lowering observed in many previous rodent studies; and (iii) deterioration of glucose homeostasis by prolonged treatment that can be unmasked by avoidance of dosing shortly before measuring blood glucose in combination with exclusion of weight-related actions via restricted feeding of the control mice.

CONCLUSIONS

Our work raises the question whether elucidation of metformin's anti-diabetic mechanism(s) in rodent experiments may in the past have been hampered by failure to mimic clinical circumstances, as caused by insufficient consideration of pharmacokinetics and multiplicity of involved actions.

Preconception hemoglobin A1c in healthy women is not associated with fecundability or pregnancy loss

Objective

To examine the relationship of preconception hemoglobin A1c, a marker of cumulative exposure to glucose over the preceding 2–3 months, with time to pregnancy, pregnancy loss, and live birth among fecund women without diagnosed diabetes or other medical diseases.

Design

A secondary analysis of a prospective cohort of women participating in the Effects of Aspirin in Gestation and Reproduction (EAGeR) trial.

Setting

Four US academic medical centers.

Patient(s)

A total of 1,194 healthy women aged 18–40 years with a history of one or two pregnancy losses attempting spontaneous conception were observed for up to six cycles while attempting pregnancy and throughout pregnancy if they conceived.

Intervention(s)

Not applicable.

Main Outcome Measure(s)

Time to pregnancy, human chorionic gonadotropin pregnancy, clinical pregnancy, pregnancy loss, and live birth.

Result(s)

Although increasing preconception A1c level was associated with reduced fecundability (fecundability odds ratio [FOR] per unit increase in A1c 0.74; 95% confidence interval [CI] 0.57, 0.96) in unadjusted models and models adjusted for age, race, smoking and treatment arm (FOR 0.79; 95% CI 0.60, 1.04), results were attenuated after further adjustment for body mass index (FOR 0.91; 95% CI 0.68, 1.21). Preconception A1c levels among women without diagnosed diabetes were not associated with live birth or pregnancy loss.

Conclusions(s)

Among healthy women without diagnosed diabetes, we observed no association of A1c with live birth or pregnancy loss. The association between A1c and fecundability was influenced by body mass index, a strong risk factor for both diabetes and infertility. These data support current recommendations that preconception A1c screening should be reserved for patients with risk factors for diabetes.

Clinical Trial Registration Number

ClinicalTrials.gov: NCT00467363.

Impact of maternal hyperglycemia on cardiac development: Insights from animal models

Congenital heart disease (CHD) is the leading cause of birth defect-related death in infants and is a global pediatric health concern. While the genetic causes of CHD have become increasingly recognized with advances in genome sequencing technologies, the etiology for the majority of cases of CHD is unknown. The maternal environment during embryogenesis has a profound impact on cardiac development, and numerous environmental factors are associated with an elevated risk of CHD. Maternal diabetes mellitus (matDM) is associated with up to a fivefold increased risk of having an infant with CHD. The rising prevalence of diabetes mellitus has led to a growing interest in the use of experimental diabetic models to elucidate mechanisms underlying this associated risk for CHD. The purpose of this review is to provide a comprehensive summary of rodent models that are being used to investigate alterations in cardiac developmental pathways when exposed to a maternal diabetic setting and to summarize the key findings from these models. The majority of studies in the field have utilized the chemically induced model of matDM, but recent advances have also been made using diet based and genetic models. Each model provides an opportunity to investigate unique aspects of matDM and is invaluable for a comprehensive understanding of the molecular and cellular mechanisms underlying matDM-associated CHD.

Metformin Targets Foxo1 to Control Glucose Homeostasis

Metformin is the first-line pharmacotherapy for type 2 diabetes mellitus (T2D). Metformin exerts its glucose-lowering effect primarily through decreasing hepatic glucose production (HGP). However, the precise molecular mechanisms of metformin remain unclear due to supra-pharmacological concentration of metformin used in the study. Here, we investigated the role of Foxo1 in metformin action in control of glucose homeostasis and its mechanism via the transcription factor Foxo1 in mice, as well as the clinical relevance with co-treatment of aspirin. We showed that metformin inhibits HGP and blood glucose in a Foxo1-dependent manner. Furthermore, we identified that metformin suppresses glucagon-induced HGP through inhibiting the PKA→Foxo1 signaling pathway. In both cells and mice, Foxo1-S273D or A mutation abolished the suppressive effect of metformin on glucagon or fasting-induced HGP. We further showed that metformin attenuates PKA activity, decreases Foxo1-S273 phosphorylation, and improves glucose homeostasis in diet-induced obese mice. We also provided evidence that salicylate suppresses HGP and blood glucose through the PKA→Foxo1 signaling pathway, but it has no further additive improvement with metformin in control of glucose homeostasis. Our study demonstrates that metformin inhibits HGP through PKA-regulated transcription factor Foxo1 and its S273 phosphorylation.

Maternal diabetes induces senescence and neural tube defects sensitive to the senomorphic rapamycin

Neural tube defects (NTDs) are the second most common structural birth defect. Senescence, a state of permanent cell cycle arrest, occurs only after neural tube closure. Maternal diabetes-induced NTDs are severe diabetic complications that lead to infant mortality or lifelong morbidity and may be linked to premature senescence. Here, we report that premature senescence occurs in the mouse neuroepithelium and disrupts neurulation, leading to NTDs in diabetic pregnancy. Premature senescence and NTDs were abolished by knockout of the transcription factor Foxo3a, the miR-200c gene, and the cell cycle inhibitors p21 and p27; transgenic expression of the dominant-negative FoxO3a mutant; or the senomorphic rapamycin. Double transgenic expression of p21 and p27 mimicked maternal diabetes in inducing premature neuroepithelium senescence and NTDs. These findings integrate transcription- and epigenome-regulated miRNAs and cell cycle regulators in premature neuroepithelium senescence and provide a mechanistic basis for targeting premature senescence and NTDs using senomorphics.

The effect of gestational diabetes on identification of key genes and pathways in human umbilical vein endothelial cell by integrated bioinformatics analysis

Maternal diabetes may lead to long-term risks for the offspring. The study aims at identifying the potential crucial genes and pathways associated with foetal metabolism and malformation of gestational diabetes mellitus (GDM). Gene Expression Series 49524 and 87295 were downloaded from Gene Expression Omnibus database, including eight from GDM and eight from non-GDM. A total of 35 differentially expressed genes were identified. Gene ontology functional annotation and signalling pathway analyses were performed. Four hub genes were identified by protein-protein interaction network: SHH, E2F1, STAT1, and HOXA9. The four hub genes were assessed by western blot and real-time quantitative PCR in clinical samples. The results of this data mining and integration help to reveal the pathophysiologic and molecular mechanism imprinted in primary umbilical cord-derived cells from GDM offspring. These genes and pathways identified are potential stratification biomarkers and provide further insight for developing therapeutic intervention for the offspring of diabetic mothers.Impact statementWhat is already known on this subject? Maternal diabetes may lead to long-term risks for the offspring. A high glucose environment might change the umbilical cord expression of genes implicated in foetal metabolism and development. However, underlying molecular mechanisms have not been investigated thoroughly.What do the results of this study add? GO functional annotation showed that the biological functions of differentially expressed genes mainly involved in metanephros development, salivary gland morphogenesis, fat cell differentiation, vasculogenesis, muscle cell proliferation, heart morphogenesis and Wnt signalling pathway. Signalling pathway analyses found that these differentially expressed genes mainly implicated in the apoptosis, cell cycle, Hedgehog, P53, and NOTCH signalling pathway. Four hub genes were identified by protein-protein interaction network: SHH, E2F1, STAT1 and HOXA9.What are the implications of these findings for clinical practice and/or further research? The genes and pathways identified in the present study are potential stratification biomarkers and provide further insight for developing therapeutic intervention for the offspring of diabetic mothers.

Human embryonic stem cells as an in vitro model for studying developmental origins of type 2 diabetes

The developmental origins of health and diseases (DOHaD) is a concept stating that adverse intrauterine environments contribute to the health risks of offspring. Since the theory emerged more than 30 years ago, many epidemiological and animal studies have confirmed that in utero exposure to environmental insults, including hyperglycemia and chemicals, increased the risk of developing noncommunicable diseases (NCDs). These NCDs include metabolic syndrome, type 2 diabetes, and complications such as diabetic cardiomyopathy. Studying the effects of different environmental insults on early embryo development would aid in understanding the underlying mechanisms by which these insults promote NCD development. Embryonic stem cells (ESCs) have also been utilized by researchers to study the DOHaD. ESCs have pluripotent characteristics and can be differentiated into almost every cell lineage; therefore, they are excellent in vitro models for studying early developmental events. More importantly, human ESCs (hESCs) are the best alternative to human embryos for research because of ethical concerns. In this review, we will discuss different maternal conditions associated with DOHaD, focusing on the complications of maternal diabetes. Next, we will review the differentiation protocols developed to generate different cell lineages from hESCs. Additionally, we will review how hESCs are utilized as a model for research into the DOHaD. The effects of environmental insults on hESC differentiation and the possible involvement of epigenetic regulation will be discussed.

The Reciprocal Causation of the ASK1-JNK1/2 Pathway and Endoplasmic Reticulum Stress in Diabetes-Induced Cognitive Decline

Diabetes significantly induces cognitive dysfunction. Neuronal apoptosis is the main cause of diabetes-induced cognitive decline (DICD). Apoptosis signal-regulating kinase 1 (ASK1) and endoplasmic reticulum (ER) stress are remarkably activated by diabetes. The role and relationship of ASK1-JNK1/2 signaling and ER stress in DICD have not yet been elucidated. In this study, we used db/db mice as the DICD animal model and confirmed that db/db mice displayed cognitive decline with inferior learning and memory function. Diabetes significantly induced morphological and structural changes, excessive neuronal apoptosis, Aβ_{1 - 42} large deposition, and synaptic dysfunction in the hippocampus. Mechanistic studies found that diabetes significantly triggered ASK1-JNK1/2 signaling activation and increased ER stress in the hippocampus. Moreover, diabetes enhanced the formation of the IRE1α-TRAF2-ASK1 complex, which promotes the crosstalk of ER stress and the ASK1-JNK1/2 pathway during DICD. Furthermore, 4-PBA treatment blocked high glucose (HG)-induced ASK1-JNK1/2 signaling activation, and excessive apoptosis in vitro. Inhibiting ASK1 via siRNA remarkably ameliorated the HG-induced increase in p-IRE1α and associated apoptosis in SH-SY5Y cells, suggesting that ASK1 is essential for the assembly and function of the proapoptotic kinase activity of the IRE1α signalosome. In summary, ER stress and ASK1-JNK1/2 signaling play causal roles in DICD development, which has crosstalk through the formation of the IRE1α-TRAF2-ASK1 complex.

Identification of histone malonylation in the human fetal brain and implications for diabetes-induced neural tube defects

BACKGROUND

Neural tube defects (NTDs) are severe congenital malformations. Diabetes during pregnancy is a risk factor for NTDs, but its mechanism remains elusive. Emerging evidence suggests that protein malonylation is involved in diabetes. Here, we report the correlation between histone lysine malonylation in diabetes-induced NTDs.

METHODS

Nano-HPLC/MS/MS was used to screen the histone malonylation profile in human embryonic brain tissue. Then, the histone malonylation level was compared between the brains of normal control mice and mice with diabetes-induced NTDs. Finally, the histone malonylation level was compared under high glucose exposure in an E9 neuroepithelial cell line (NE4C).

RESULTS

A total of 30 histone malonylation sites were identified in human embryonic brain tissue, including 18 novel sites. Furthermore, we found an increased histone malonylation level in brain tissues from mice with diabetes-induced NTDs. Finally, both the histone malonylation modified sites and the modified levels were proved to be increased in the NE4C treated with high glucose.

CONCLUSION

Our results present a comprehensive map of histone malonylation in the human fetal brain. Furthermore, we provide experimental evidence supporting a relationship between histone malonylation and NTDs caused by high glucose-induced diabetes. These findings offer new insights into the pathological role of histone modifications in human NTDs.

Fibroblast growth factor 1 ameliorates diabetes-induced splenomegaly via suppressing inflammation and oxidative stress

Type-2 diabetes (T2D) is a common metabolic disorder, which causes several physiological and pathological complications. Spleen is regarded as an important organ, which regulates immune system and iron metabolism in the body. Precious few studies have been conducted to explore the pathological and deleterious roles of diabetes on spleen. In our current study, we have explored and confirmed the pathological effects of diabetes on spleen in db/db experimental mice model. In our current study, 0.5 mg/kg fibroblast growth factor 1 (FGF1) dose was intraperitoneally administrated to db/db mice. We found that diabetes evidently induced spleen enlargement and fibrosis progression in the db/db mice. Additionally, our studies demonstrate that iron has hugely deposited in the spleen in db/db mice. Several studies have documented that diabetes largely disrupts the inflammatory cells distribution, immune homeostasis, proliferation and oxidative stress with the down-regulation of anti-inflammatory cytokines and antioxidant activities. Moreover, we have observed that FGF1 administration significantly reversed the deleterious effect of diabetes on spleen enlargement and dysfunction. In summary, these substantial findings clearly demonstrate that diabetes plays deleterious roles in maintaining the spleen structure and functions. Therefore, our investigations suggest that FGF1 can effectively prevent diabetes-mediated splenomegaly progression.

Exogenous fibroblast growth factor 1 ameliorates diabetes-induced cognitive decline via coordinately regulating PI3K/AKT signaling and PERK signaling

BACKGROUND

Diabetes induces central nervous system damage, leading to cognitive decline. Fibroblast growth factor 1 (FGF1) has dual function of neuroprotection and normalizing hyperglycemia. To date, the precise mechanisms and potential treating strategies of FGF1 for diabetes-induced cognitive decline (DICD) hasn't been fully elucidated.

METHODS

In this study, db/db mice were used as DICD animal model. We found that diabetes remarkably suppressed FGF1 expression in hippocampus. Thus, exogenous FGF1 had been treated for db/db mice and SH-SY5Y cells.

RESULTS

FGF1 significantly ameliorates DICD with better spatial learning and memory function. Moreover, FGF1 blocked diabetes-induced morphological structure change, neuronal apoptosis and Aβ1-42 deposition and synaptic dysfunction in hippocampus. But normalizing glucose may not the only contributed factor for FGF1 treating DICD with evidencing that metformin-treated db/db mice has a inferior cognitive function than that in FGF1 group. Current mechanistic study had found that diabetes inhibits cAMP-response element binding protein (CREB) activity and subsequently suppresses brain derived neurotrophic factor (BDNF) level via coordinately regulating PERK signaling and PI3K/AKT signaling in hippocampus, which were reversed by FGF1.

CONCLUSION

We conclude that FGF1 exerts its neuroprotective role and normalizing hyperglycemia effect, consequently ameliorates DICD, implying FGF1 holds a great promise to develop a new treatment for DICD. Video abstract.

Fibroblast Growth Factor 1 Ameliorates Diabetes-Induced Liver Injury by Reducing Cellular Stress and Restoring Autophagy

Background

Type 2 diabetes (T2D) is a metabolic dysfunction disease that causes several complications. Liver injury is one of these that severely affects patients with diabetes. Fibroblast growth factor 1 (FGF1) has glucose-lowering activity and plays a role in modulation of several liver injuries. Nevertheless, the effects and potential mechanisms of FGF1 against diabetes-induced liver injury are unknown.

Methods

To further investigate the effect of FGF1 on diabetic liver injury, we divided db/db mice into two groups and intraperitoneally (i.p.) injected either with FGF1 at 0.5 mg/kg body weight or saline every other day for 4 weeks. Then body weights were measured. Serum and liver tissues were collected for biochemical and molecular analyses.

Results

FGF1 significantly reduced blood glucose and ameliorated diabetes-induced liver steatosis, fibrosis, and apoptosis. FGF1 also restored defective hepatic autophagy in db/db mice. Mechanistic investigations showed that diabetes markedly induced oxidative stress and endoplasmic reticulum stress and that FGF1 treatment significantly attenuated these effects.

Conclusions

FGF1-associated glucose level reduction and amelioration of cellular stress are potential protective effects of FGF1 against diabetes-induced liver injury.

Metformin attenuates cartilage degeneration in an experimental osteoarthritis model by regulating AMPK/mTOR

Background: It is generally thought that the occurrence and progression of osteoarthritis (OA) results from multiple causes, including degradation and destruction of the cartilage matrix and aging of chondrocytes. Metformin is a first-line drug for the treatment of diabetes, and has great potential for the treatment of other disorders. However, the role of metformin in OA is unknown.

Results: Metformin displayed a protective effect against OA. There were lower OARSI scores and fewer MMP-13-positive cells in DMM mice and cartilage explants after treatment with metformin. In addition, metformin treatment decreased p16^INK4a levels in OA chondrocytes, and enhanced polarization of AMPK and inhibition of mTORC1 in OA mice and chondrocytes in a dose-dependent manner.

Conclusions: Metformin effectively alleviated cartilage degradation and aging through regulation of the AMPK/mTOR signaling pathways, suggesting that it could be an effective treatment for OA.

Methods: The effects of metformin on cartilage degradation and chondrocyte aging was determined in a destabilization of the medial meniscus (DMM)-induced OA mouse model and in IL-1β-treated mouse chondrocytes and cartilage explants. Articular cartilage degeneration was graded using the Osteoarthritis Research Society International (OARSI) criteria. Immunostaining, RT-PCR, and western blot analyses were conducted to detect the relative expressions of protein and RNA.

High Glucose Inhibits Neural Stem Cell Differentiation Through Oxidative Stress and Endoplasmic Reticulum Stress

Maternal diabetes induces neural tube defects by suppressing neurogenesis in the developing neuroepithelium. Our recent study further revealed that high glucose inhibited embryonic stem cell differentiation into neural lineage cells. However, the mechanism whereby high glucose suppresses neural differentiation is unclear. To investigate whether high glucose-induced oxidative stress and endoplasmic reticulum (ER) stress lead to the inhibition of neural differentiation, the effect of high glucose on neural stem cell (the C17.2 cell line) differentiation was examined. Neural stem cells were cultured in normal glucose (5 mM) or high glucose (25 mM) differentiation medium for 3, 5, and 7 days. High glucose suppressed neural stem cell differentiation by significantly decreasing the expression of the neuron marker Tuj1 and the glial cell marker GFAP and the numbers of Tuj1⁺ and GFAP⁺ cells. The antioxidant enzyme superoxide dismutase mimetic Tempol reversed high glucose-decreased Tuj1 and GFAP expression and restored the numbers of neurons and glial cells differentiated from neural stem cells. Hydrogen peroxide treatment imitated the inhibitory effect of high glucose on neural stem cell differentiation. Both high glucose and hydrogen peroxide triggered ER stress, whereas Tempol blocked high glucose-induced ER stress. The ER stress inhibitor, 4-phenylbutyrate, abolished the inhibition of high glucose or hydrogen peroxide on neural stem cell differentiation. Thus, oxidative stress and its resultant ER stress mediate the inhibitory effect of high glucose on neural stem cell differentiation.

Metformin Improves Fertility in Obese Males by Alleviating Oxidative Stress-Induced Blood-Testis Barrier Damage

Background/Aims

Obesity, which is related to increased oxidative stress in various tissues, is a risk factor for male infertility. Metformin is reported to have an antioxidant effect; however, the precise role of metformin in obesity-induced male infertility remains unknown. The current study is aimed at exploring the effects of metformin and characterizing its underlying mechanism in the fertility of obese males.

Methods

An obese male mouse model was generated by feeding mice with a high-fat diet; then, the mice were administered metformin in water for 8 weeks. Reproductive ability, metabolic parameters, and follicle-stimulating hormone (FSH) were assessed by cohabitation, enzymatic methods, and ELISA, respectively. Damage to the integrity of the blood-testis barrier (BTB), which ensures spermatogenesis, was assessed by transmission electron microscopy and immunofluorescence with a biotin tracer. Malondialdehyde (MDA), superoxide dismutase (SOD), and reactive oxygen species (ROS) were employed for the assessments of oxidative stress. BTB-related proteins were measured by immunoblotting. Nuclear factor κB (NF-κB) was assessed by immunofluorescence.

Results

High-fat-diet-fed mice presented evident lipid metabolic disturbances, disrupted BTB integrity, and decreased reproductive function. Metformin alleviated the decrease in male fertility, decreased ectopic lipid deposition in the testis, and increased serum FSH levels. A further mechanistic analysis revealed that metformin ameliorated the high-fat-diet-induced injury to the BTB structure and permeability and restored the disordered BTB-related proteins, which might be associated with an improvement in oxidative stress and a recovery of NF-κB activity in Sertoli cells (SCs).

Conclusion

Metformin improves obese male fertility by alleviating oxidative stress-induced BTB damage. These findings provide new insights into the effect of metformin on various diseases and suggest future possibilities in the treatment of male infertility.

Comparative effects of glibenclamide, metformin and insulin on fetal pancreatic histology and maternal blood glucose in pregnant streptozotocin-induced diabetic rats

BACKGROUND

Oral hypoglycemic agents use during pregnancy was assumed to cause fetal macrosomia and skeletal deformities, and maternal complications due to significant transfer across placenta or ineffective control of blood glucose.

OBJECTIVE

This study investigated effects of insulin, metformin and glibenclamide on maternal blood glucose; and fetal crown-rump length, gross malformation and pancreatic histology in pregnant streptozotocin-induced diabetic rats.

METHODS

Twenty-five pregnant rats of groups 1 to 5 as normal and diabetic controls; and diabetic treated with insulin, metformin and glibenclamide were used. Experimental GDM was induced using 45 and 35mg/Kgbw of intraperitoneal streptozotocin.

RESULTS

Metformin, Insulin and Glibenclamide significantly reduced maternal glucose by 140.6mg/dL, 103.2mg/dL and 98.54mg/dl; respectively and showed islets with regular interlobular ducts, islets with some irregular interlobular ducts, and islets with many irregular interlobular ducts in histological fetal pancreatic photomicrographs respectively. This depicts metformin having highest ameliorative effect. There were no significant differences in maternal and fetal body weights, maternal blood glucose between diabetic groups, and fetal gross examination.

CONCLUSION

At the doses used in this research, metformin and glibenclamide showed no adverse effects on maternal and fetal features in the treatment of GDM. Thus, they can be used as safe and inexpensive alternatives to insulin.

Maternal hyperglycemia and fetal cardiac development: Clinical impact and underlying mechanisms

Congenital heart disease (CHD) is the most common type of birth defect and is both a significant pediatric and adult health problem, in light of a growing population of survivors. The etiology of CHD has been considered to be multifactorial with genetic and environmental factors playing important roles. The combination of advances in cardiac developmental biology, which have resulted in the elucidation of molecular pathways regulating normal cardiac morphogenesis, and genome sequencing technology have allowed the discovery of numerous genetic contributors of CHD ranging from chromosomal abnormalities to single gene variants. Conversely, mechanistic details of the contribution of environmental factors to CHD remain unknown. Maternal diabetes mellitus (matDM) is a well-established and increasingly prevalent environmental risk factor for CHD, but the underlying etiologic mechanisms by which pregestational matDM increases the vulnerability of embryos to cardiac malformations remains largely elusive. Here, we will briefly discuss the multifactorial etiology of CHD with a focus on the epidemiologic link between matDM and CHD. We will describe the animal models used to study the underlying mechanisms between matDM and CHD and review the numerous cellular and molecular pathways affected by maternal hyperglycemia in the developing heart. Last, we discuss how this increased understanding may open the door for the development of novel prevention strategies to reduce the incidence of CHD in this high-risk population.

A Model for Apoptotic-Cell-Mediated Adaptive Immune Evasion via CD80-CTLA-4 Signaling

Apoptotic cells carry a plethora of self-antigens but they suppress eliciting of innate and adaptive immune responses to them. How apoptotic cells evade and subvert adaptive immune responses has been elusive. Here, we propose a novel model to understand how apoptotic cells regulate T cell activation in different contexts, leading mostly to tolerogenic responses, mainly via taking control of the CD80-CTLA-4 coinhibitory signal delivered to T cells. This model may facilitate understanding of the molecular mechanisms of autoimmune diseases associated with dysregulation of apoptosis or apoptotic cell clearance, and it highlights potential therapeutic targets or strategies for treatment of multiple immunological disorders.

Trehalose restores functional autophagy suppressed by high glucose

Autophagy is required for neurulation, and autophagy activators with minimal toxicity, such as the natural compound trehalose, a nonreducing disaccharide, possess high therapeutic value. To determine whether trehalose directly induces autophagy, FITC-labeled trehalose was used for tracing its presence in autophagosome complexes. Trehalose was as potent as rapamycin and starvation in inducing de novo autophagosome formation and increasing autophagosome flux in GFP-LC3 reporter cells and C17.2 neural stem cells. Trehalose effectively reversed high glucose-suppressed autophagy and reduced p62 protein expression. Trehalose abolished the disruption of autophagosome complexes under high glucose conditions in vitro and maternal diabetes in vivo. Autophagosomes induced by trehalose were functionally active, forming mitophagy and reticulophagy in removing damaged cellular organelles in neuroepithelial cells exposed to maternal diabetes. Thus, trehalose directly participated in functional autophagosome generation by incorporating itself into autophagosomes. These findings provide the mechanistic basis for the use of trehalose in preventing disruptive autophagy-associated pathogenesis.

Direct toxicity of insulin on the human placenta and protection by metformin

OBJECTIVE

To study the effects of insulin and metformin on primary trophoblasts from early pregnancies.

DESIGN

Experimental in vitro study.

SETTING

Academic research institute.

PATIENT(S)

Trophoblasts from healthy patients undergoing first trimester elective termination of pregnancy and primary lung fibroblasts (IMR-90).

INTERVENTION(S)

Culture and treatment with insulin and metformin of primary trophoblasts and primary lung fibroblasts (IMR-90).

MAIN OUTCOME MEASURE(S)

DNA damage measured by expression of γ-H2AX with immunofluorescence and Western blot. Apoptosis measured by expression of cleaved caspase-3 by Western blot. Cell survival measured by cell proliferation assay.

RESULT(S)

Culture of purified primary trophoblast cells in the presence of insulin at levels as low as 1 nM resulted in a 386% increase in the number of cell with elevated γ-H2AX expression, a 66% reduction in cell survival and a marked increase of cleaved caspase-3 expression. Pretreatment of trophoblasts with therapeutic doses of metformin prevented the detrimental effects of insulin. Treatment with insulin and/or metformin had no effects on primary fibroblasts.

CONCLUSION(S)

Elevated insulin levels are directly toxic to first trimester trophoblasts and result in increased DNA damage, apoptosis, and decreased cell survival. These effects are prevented by metformin. Trophoblast cells from early pregnancy are uniquely vulnerable to elevated levels of insulin. These findings, if confirmed in vivo, suggest that there may be a role for insulin resistance screening before attempting pregnancy and for focusing on prevention of hyperinsulinemia during early pregnancy.

Prenatal metformin exposure or organic cation transporter 3 knock-out curbs social interaction preference in male mice

Poorly managed gestational diabetes can lead to severe complications for mother and child including fetal overgrowth, neonatal hypoglycemia and increased autism risk. Use of metformin to control it is relatively new and promising. Yet safety concerns regarding gestational metformin use remain, as its long-term effects in offspring are unclear. In light of beneficial findings with metformin for adult mouse social behavior, we hypothesized gestational metformin treatment might also promote offspring sociability. To test this, metformin was administered to non-diabetic, lean C57BL/6 J female mice at mating, with treatment discontinued at birth or wean. Male offspring exposed to metformin through birth lost social interaction preference relative to controls by time in chambers, but not by sniffing measures. Further, prenatal metformin exposure appeared to enhance social novelty preference only in females. However due to unbalanced litters and lack of statistical power, firm establishment of any sex-dependency of metformin's effects on sociability was not possible. Since organic cation transporter 3 (OCT3) transports metformin and is dense in placenta, social preferences of OCT3 knock-out males were measured. Relative to wild-type, OCT3 knock-outs had reduced interaction preference. Our data indicate gestational metformin exposure under non-diabetic conditions, or lack of OCT3, can impair social behavior in male C57BL6/J mice. Since OCT3 transports serotonin and tryptophan, impaired placental OCT3 function is one common mechanism that could persistently impact central serotonin systems and social behavior. Yet no gross alterations in serotonergic function were evident by measure of serotonin transporter density in OCT3, or serotonin turnover in metformin-exposed offspring brains. Mechanisms underlying the behavioral outcomes, and if with gestational diabetes the same would occur, remain unclear. Metformin's impacts on placental transporters and serotonin metabolism or AMPK activity in fetal brain need further investigation to clarify benefits and risks to offspring sociability from use of metformin to treat gestational diabetes.

Reduction of cellular stress is essential for Fibroblast growth factor 1 treatment for diabetic nephropathy

Diabetic nephropathy (DN) is one of general and common complication of diabetes, which severely affects the physical and mental health of diabetic patients. Fibroblast growth factor 1 (FGF1), an effective control agent of blood glucose, plays an effective treatment role on diabetes-induced renal injury. But the specific molecule mechanism underlying it is still unclear. Since induction of cellular stress is the main and common mechanism of diabetes-induced complication, we hypothesized that reduction of cellular stress is also the molecular mechanism of FGF1 treatment for DN. Here, we have further confirmed that FGF1 significantly ameliorated the diabetes-induced renal interstitial fibrosis and glomerular damage. The expression levels of collagen and α-smooth muscle actin (α-SMA) also dramatically induced in kidney from db/db mice, but these effects were blocked by FGF1 administration. Our mechanistic investigation had further revealed that diabetes significantly induced oxidative stress, nitrosative stress, and endoplasmic reticulum (ER) stress with upregulation of malondialdehyde (MDA), nitrotyrosine level, ER stress makers and downregulation of antioxidant capacity (AOC). FGF1 treatment significantly attenuated the effect of diabetes on cellular stress. We conclude that FGF1-associated glucose decreases and subsequent reduction of cellular stress is the another potential molecule mechanism underlying FGF1 treatment for DN.

Metformin from mother to unborn child - Are there unwarranted effects?

For more than 40 years, metformin has been used before and during pregnancy. However, it is important to note that metformin can cross the placenta and circulate in the developing foetus. Recent studies reported that the concentration of metformin in foetal cord blood ranges from half to nearly the same concentration as in the maternal plasma. Since metformin has anti-cell growth and pro-apoptotic effects, there are persistent concerns over the use of metformin in early pregnancy. Current human studies are limited by sample size, lack of controls or, short follow-up durations. In this review, we examine the settings in which metformin can be passed on from mother to child during pregnancy and address the current controversies relating to the cellular and molecular mechanisms of metformin. Our efforts highlight the need for more data on the effects of metformin on general offspring health as well as further scrutiny into foetal development upon exposure to metformin.

CBP/p300 inhibitor C646 prevents high glucose exposure induced neuroepithelial cell proliferation

BACKGROUND

Maternal diabetes related neural tube defects (NTDs) are a result of oxidative stress and apoptosis. However, the molecular mechanism behind the pathogenesis is not fully understood. Here, we report that high glucose exposure-induced epigenetic changes influence histone H4 acetylation and neuroepithelial cell proliferation. We also show that the acetyltransferase inhibitor C646 can prevent high glucose induced changes in histone H4 acetylation and neuroepithelial cell proliferation.

METHODS

By using LC-MS/MS as an unbiased approach, we screened the histone acetylation profile in an E9 neuroepithelial cell line (NE-4C) under high glucose exposure. We further explored the mechanism in cells in vitro and in maternal diabetes-induced mouse embryos in vivo.

RESULTS

We identified 35 core histone acetylation marks in normal E9 neuroepithelial cells, whereas high glucose exposure resulted in novel acetylation sites on H4K31 and H4K44. Acetylation levels of embryonic development associated H4K5/K8/K12/K16 increased in neuroepithelial cells exposed to high glucose in vitro and in brain tissue from maternal diabetes induced exencephalic embryos in vivo. Further, mRNA level of histone acetyltransferase CBP encoded gene Crebbp was significantly increased both in vitro and in vivo. The addition of C646, a selective inhibitor for CBP/p300, significantly rescued increase of H4K5/K8/K12/K16 acetylation levels and H3S10pi-labeled neuroepithelial cell proliferation induced by high glucose exposure.

CONCLUSION

Our data provide complementary insights for potential mechanisms of maternal diabetes induced NTDs.

Metformin in the management of diabetes during pregnancy and lactation

This review explores the current place of metformin in the management of gestational diabetes (GDM) and type 2 diabetes during pregnancy and lactation. The rationale and basic pharmacology of metformin usage in pregnancy is discussed along with the evidence from observational and randomized controlled trials in women with GDM or overt diabetes. There seems to be adequate evidence of efficacy and short-term safety of metformin in relation to maternal and neonatal outcomes in GDM, with possible benefits related to lower maternal weight gain and lower risk of neonatal hypoglycemia and macrosomia. Additionally, metformin offers the advantages of oral administration, convenience, less cost and greater acceptability. Metformin may, therefore, be considered in milder forms of GDM where glycemic goals are not attained by lifestyle modification. However, failure rate is likely to be higher in those with an earlier diagnosis of GDM, higher blood glucose, higher body mass index (BMI) or previous history of GDM, and insulin remains the cornerstone of pharmacological treatment in such cases. The use of metformin in type 2 diabetes has been assessed in observational and small randomized trials. Metformin monotherapy in women with overt diabetes is highly unlikely to achieve glycemic targets. Hence, the use should be restricted as adjunct to insulin and may be considered in women with high insulin dose requirements or rapid weight gain. There is clearly a need for more clinical trials to assess the effect of combined insulin plus metformin therapy in pregnancy with type 2 diabetes. Additionally, there is a paucity of data on long-term effects in offspring exposed to metformin in utero. It is imperative to further explore its impact on offspring as metformin has significant transplacental transfer and has the potential to impact the programming of the epigenome. Therefore, caution must be exercised when prescribing metformin in pregnant women. More research is clearly needed before metformin can be considered as standard of care in the management of diabetes during pregnancy.

The current status and future of cardiac stem/progenitor cell therapy for congenital heart defects from diabetic pregnancy

Pregestational maternal diabetes induces congenital heart defects (CHDs). Cardiac dysfunction after palliative surgical procedures contributes to the high mortality of CHD patients. Autologous or allogeneic stem cell therapies are effective for improving cardiac function in animal models and clinical trials. c-kit+ cardiac progenitor cells (CPCs), the most recognized CPCs, have the following basic properties of stem cells: self-renewal, multicellular clone formation, and differentiation into multiple cardiac lineages. However, there is ongoing debate regarding whether c-kit+ CPCs can give rise to sufficient cardiomyocytes. A new hypothesis to address the beneficial effect of c-kit+ CPCs is that these cells stimulate endogenous cardiac cells through a paracrine function in producing a robust secretome and exosomes. The values of other cardiac CPCs, including Sca1+ CPCs and cardiosphere-derived cells, are beginning to be revealed. These cells may be better choices than c-kit+ CPCs for generating cardiomyocytes. Adult mesenchymal stem cells are considered immune-incompetent and effective for improving cardiac function. Autologous CPC therapy may be limited by the observation that maternal diabetes adversely affects the biological function of embryonic stem cells and CPCs. Future studies should focus on determining the mechanistic action of these cells, identifying new CPC markers, selecting highly effective CPCs, and engineering cell-free products.

Diabetes Induces Abnormal Ovarian Function via Triggering Apoptosis of Granulosa Cells and Suppressing Ovarian Angiogenesis

Diabetes triggers abnormal ovarian follicular development and consequently leads to infertility. Here, we established a type 2 diabetes mouse model by feeding with high fat diet (HFD) for 15/20 weeks and assessed the effect of diabetes on follicular development and ovarian angiogenesis. After fed with HFD for 15 weeks, mice had the characteristics of type 2 diabetes, which was much more serious after 20 weeks on HFD. After 20 weeks on HFD, the mice had shown abnormal ovarian morphology with hyaline appearance, much less blood vessel, follicular development arrest and less of granulosa cells (GCs) in mature follicles, but not in ovaries from 15 weeks on HFD. Elevated makers of DNA damage, ER stress and apoptosis of GCs were observed in ovaries from HFD for 20 weeks. Additionally, diabetes significantly suppressed ovarian angiogenesis with the evidence of down-regulation of CD31 via inhibiting HIF1α-VEGF signaling pathway in time-dependent. We concluded that diabetes triggers abnormal ovarian function via inducing GCs apoptosis and suppressing ovarian angiogenesis.

Pregestational type 2 diabetes mellitus induces cardiac hypertrophy in the murine embryo through cardiac remodeling and fibrosis

BACKGROUND

Cardiac hypertrophy is highly prevalent in patients with type 2 diabetes mellitus. Experimental evidence has implied that pregnant women with type 2 diabetes mellitus and their children are at an increased risk of cardiovascular diseases. Our previous mouse model study revealed that maternal type 2 diabetes mellitus induces structural heart defects in their offspring.

OBJECTIVE

This study aims to determine whether maternal type 2 diabetes mellitus induces embryonic heart hypertrophy in a murine model of diabetic embryopathy.

STUDY DESIGN

The type 2 diabetes mellitus embryopathy model was established by feeding 4-week-old female C57BL/6J mice with a high-fat diet for 15 weeks. Cardiac hypertrophy in embryos at embryonic day 17.5 was characterized by measuring heart size and thickness of the right and left ventricle walls and the interventricular septum, as well as the expression of β-myosin heavy chain, atrial natriuretic peptide, insulin-like growth factor-1, desmin, and adrenomedullin. Cardiac remodeling was determined by collagen synthesis and fibronectin synthesis. Fibrosis was evaluated by Masson staining and determining the expression of connective tissue growth factor, osteopontin, and galectin-3 genes. Cell apoptosis also was measured in the developing heart.

RESULTS

The thicknesses of the left ventricle walls and the interventricular septum of embryonic hearts exposed to maternal diabetes were significantly thicker than those in the nondiabetic group. Maternal diabetes significantly increased β-myosin heavy chain, atrial natriuretic peptide, insulin-like growth factor-1, and desmin expression, but decreased expression of adrenomedullin. Moreover, collagen synthesis was significantly elevated, whereas fibronectin synthesis was suppressed, in embryonic hearts from diabetic dams, suggesting that cardiac remodeling is a contributing factor to cardiac hypertrophy. The cardiac fibrosis marker, galectin-3, was induced by maternal diabetes. Furthermore, maternal type 2 diabetes mellitus activated the proapoptotic c-Jun-N-terminal kinase 1/2 stress signaling and triggered cell apoptosis by increasing the number of terminal deoxynucleotidyl transferase 2'-deoxyuridine 5'-triphosphate nick end labeling-positive cells (10.4 ± 2.2% of the type 2 diabetes mellitus group vs 3.8 ± 0.7% of the nondiabetic group, P < .05).

CONCLUSION

Maternal type 2 diabetes mellitus induces cardiac hypertrophy in embryonic hearts. Adverse cardiac remodeling, including elevated collagen synthesis, suppressed fibronectin synthesis, profibrosis, and apoptosis, is implicated as the etiology of cardiac hypertrophy.

Protein kinase C-alpha suppresses autophagy and induces neural tube defects via miR-129-2 in diabetic pregnancy

Gene deletion-induced autophagy deficiency leads to neural tube defects (NTDs), similar to those in diabetic pregnancy. Here we report the key autophagy regulators modulated by diabetes in the murine developing neuroepithelium. Diabetes predominantly leads to exencephaly, induces neuroepithelial cell apoptosis and suppresses autophagy in the forebrain and midbrain of NTD embryos. Deleting the Prkca gene, which encodes PKCα, reverses diabetes-induced autophagy impairment, cellular organelle stress and apoptosis, leading to an NTD reduction. PKCα increases the expression of miR-129-2, which is a negative regulator of autophagy. miR-129-2 represses autophagy by directly targeting PGC-1α, a positive regulator for mitochondrial function, which is disturbed by maternal diabetes. PGC-1α supports neurulation by stimulating autophagy in neuroepithelial cells. These findings identify two negative autophagy regulators, PKCα and miR-129-2, which mediate the teratogenicity of hyperglycaemia leading to NTDs. We also reveal a function for PGC-1α in embryonic development through promoting autophagy and ameliorating hyperglycaemia-induced NTDs.

Effects of Betulinic Acid on the Male Reproductive System of a Streptozotocin-Nicotinamide-Induced Diabetic Mouse Model

Purpose

The present study was conducted to evaluate the favorable or harmful effects of betulinic acid (BA) on a diabetic reproductive system.

Materials and Methods

In this experimental study, 60 male Naval Medical Research Institute mice (20∼25 g) were randomly divided into 6 groups: control, diabetes, diabetes+BA (10, 20, and 40 mg/kg), and diabetes+ metformin (200 mg/kg). A diabetic model was induced by a single dose of streptozotocin (STZ) (65 mg/kg) injection intraperitoneally 15 minutes after an intraperitoneal administration of nicotinamide (NA) (120 mg/kg). BA and metformin were gavaged for 2 weeks after confirmed diabetes induction in the treatment groups. One day after the last treatment, plasma luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone levels were evaluated. The cauda epididymis and testis were removed to analyze the sperm count and testis histopathology.

Results

LH levels increased in diabetic (p<0.001) and diabetic BA-treated mice (p=0.009). Plasma levels of testosterone (p< 0.001) and sperm count (p=0.04) decreased in these groups when compared to the control group. Furthermore, administration of 10 mg/kg (p=0.001), 20 mg/kg (p=0.004), or 40 mg/kg (p<0.001) of BA led to a greater reduction in plasma testosterone levels compared to the diabetes group. Seminiferous tubule vacuole numbers increased in diabetic and diabetic BA-treated mice, but testis morphology and FSH level assessment revealed no significant differences between the groups.

Conclusions

STZ-NA can induce diabetic alterations in the male reproductive system and the administration of BA in diabetic treated mice resulted in a worse outcome.

High glucose suppresses embryonic stem cell differentiation into cardiomyocytes : High glucose inhibits ES cell cardiogenesis

Background

Babies born to mothers with pregestational diabetes have a high risk for congenital heart defects (CHD). Embryonic stem cells (ESCs) are excellent in vitro models for studying the effect of high glucose on cardiac lineage specification because ESCs can be differentiated into cardiomyocytes. ESC maintenance and differentiation are currently performed under high glucose conditions, whose adverse effects have never been clarified.

Method

We investigated the effect of high glucose on cardiomyocyte differentiation from a well-characterized ESC line, E14, derived from mouse blastocysts. E14 cells maintained under high glucose (25 mM) failed to generate any beating cardiomyocytes using the hanging-drop embryonic body method. We created a glucose-responsive E14 cell line (GR-E14) through a graduated low glucose adaptation. The expression of stem cell markers was similar in the parent E14 cells and the GR-E14 cells.

Results

Glucose transporter 2 gene was increased in GR-E14 cells. When GR-E14 cells were differentiated into cardiomyocytes under low (5 mM) or high (25 mM) glucose conditions, high glucose significantly delayed the appearance and reduced the number of TNNT2 (Troponin T Type 2)-positive contracting cardiomyocytes. High glucose suppressed the expression of precardiac mesoderm markers, cardiac transcription factors, mature cardiomyocyte markers, and potassium channel proteins. High glucose impaired the functionality of ESC-derived cardiomyocytes by suppressing the frequencies of Ca²⁺ wave and contraction.

Conclusions

Our findings suggest that high glucose inhibits ESC cardiogenesis by suppressing key developmental genes essential for the cardiac program.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0446-5) contains supplementary material, which is available to authorized users.

The green tea polyphenol EGCG alleviates maternal diabetes-induced neural tube defects by inhibiting DNA hypermethylation

BACKGROUND

Maternal diabetes increases the risk of neural tube defects in offspring. Our previous study demonstrated that the green tea polyphenol, Epigallocatechin gallate, inhibits high glucose-induced neural tube defects in cultured embryos. However, the therapeutic effect of Epigallocatechin gallate on maternal diabetes-induced neural tube defects is still unclear.

OBJECTIVE

We aimed to examine whether Epigallocatechin gallate treatment can reduce maternal diabetes-induced DNA methylation and neural tube defects.

STUDY DESIGN

Nondiabetic and diabetic pregnant mice at embryonic day 5.5 were given drinking water with or without 1 or 10 μM Epigallocatechin gallate. At embryonic day 8.75, embryos were dissected from the visceral yolk sac for the measurement of the levels and activity of DNA methyltransferases, the levels of global DNA methylation, and methylation in the CpG islands of neural tube closure essential gene promoters. embryonic day 10.5 embryos were examined for neural tube defect incidence.

RESULTS

Epigallocatechin gallate treatment did not affect embryonic development because embryos from nondiabetic dams treated with Epigallocatechin gallate did not exhibit any neural tube defects. Treatment with 1 μM Epigallocatechin gallate did not reduce maternal diabetes-induced neural tube defects significantly. Embryos from diabetic dams treated with 10 μM Epigallocatechin gallate had a significantly lower neural tube defect incidence compared with that of embryos without Epigallocatechin gallate treatment. Epigallocatechin gallate reduced neural tube defect rates from 29.5% to 2%, an incidence that is comparable with that of embryos from nondiabetic dams. Ten micromoles of Epigallocatechin gallate treatment blocked maternal diabetes-increased DNA methyltransferases 3a and 3b expression and their activities, leading to the suppression of global DNA hypermethylation. Additionally, 10 μM Epigallocatechin gallate abrogated maternal diabetes-increased DNA methylation in the CpG islands of neural tube closure essential genes, including Grhl3, Pax3, and Tulp3.

CONCLUSION

Epigallocatechin gallate reduces maternal diabetes-induced neural tube defects formation and blocks the enhanced expression and activity of DNA methyltransferases, leading to the suppression of DNA hypermethylation and the restoration of neural tube closure essential gene expression. These observations suggest that Epigallocatechin gallate supplements could mitigate the teratogenic effects of hyperglycemia on the developing embryo and prevent diabetes-induced neural tube defects.

Type 2 diabetes mellitus induces congenital heart defects in murine embryos by increasing oxidative stress, endoplasmic reticulum stress, and apoptosis

BACKGROUND

Maternal type 1 and 2 diabetes mellitus are strongly associated with high rates of severe structural birth defects, including congenital heart defects. Studies in type 1 diabetic embryopathy animal models have demonstrated that cellular stress-induced apoptosis mediates the teratogenicity of maternal diabetes leading to congenital heart defect formation. However, the mechanisms underlying maternal type 2 diabetes mellitus-induced congenital heart defects remain largely unknown.

OBJECTIVE

We aim to determine whether oxidative stress, endoplasmic reticulum stress, and excessive apoptosis are the intracellular molecular mechanisms underlying maternal type 2 diabetes mellitus-induced congenital heart defects.

STUDY DESIGN

A mouse model of maternal type 2 diabetes mellitus was established by feeding female mice a high-fat diet (60% fat). After 15 weeks on the high-fat diet, the mice showed characteristics of maternal type 2 diabetes mellitus. Control dams were either fed a normal diet (10% fat) or the high-fat diet during pregnancy only. Female mice from the high-fat diet group and the 2 control groups were mated with male mice that were fed a normal diet. At E12.5, embryonic hearts were harvested to determine the levels of lipid peroxides and superoxide, endoplasmic reticulum stress markers, cleaved caspase 3 and 8, and apoptosis. E17.5 embryonic hearts were harvested for the detection of congenital heart defect formation using India ink vessel patterning and histological examination.

RESULTS

Maternal type 2 diabetes mellitus significantly induced ventricular septal defects and persistent truncus arteriosus in the developing heart, along with increasing oxidative stress markers, including superoxide and lipid peroxidation; endoplasmic reticulum stress markers, including protein levels of phosphorylated-protein kinase RNA-like endoplasmic reticulum kinase, phosphorylated-IRE1α, phosphorylated-eIF2α, C/EBP homologous protein, and binding immunoglobulin protein; endoplasmic reticulum chaperone gene expression; and XBP1 messenger RNA splicing, as well as increased cleaved caspase 3 and 8 in embryonic hearts. Furthermore, maternal type 2 diabetes mellitus triggered excessive apoptosis in ventricular myocardium, endocardial cushion, and outflow tract of the embryonic heart.

CONCLUSION

Similar to those observations in type 1 diabetic embryopathy, maternal type 2 diabetes mellitus causes heart defects in the developing embryo manifested with oxidative stress, endoplasmic reticulum stress, and excessive apoptosis in heart cells.

Effect of high-fat diet-induced obesity on the Akt/FoxO/Smad signaling pathway and the follicular development of the mouse ovary

Obesity has a negative effect on ovarian functions, which is reported to increase the risk of infertility. The mechanism underlying obesity‑induced infertility is not yet clear. The present study established a high‑fat diet (HFD)‑induced obesity mouse model to elucidate the mechanisms underlying the effect of HFD‑induced obesity on follicular development in the mouse ovary. The 4‑week‑old female mice were fed with HFD or normal control (NC) diet for 15 or 20 weeks. Body mass index was used to demonstrate that the mice were obese following HFD treatment. The follicular development of the ovaries from the HFD group mice was retarded in a time‑dependent manner, as demonstrated by morphological and histological examination of the ovaries. Further investigation via western blot analysis demonstrated that the activity of the transcription factor, forkhead box O3a (FoxO3a), was increased by HFD through downregulated FoxO3a phosphorylation, which may contribute to the inhibited development of ovarian follicles. To determine the regulatory mechanism of FoxO3 on the follicular development, the expression levels of FoxO3a target protein, Smad1/5/8, were also determined and there was significant decrease in phosphorylated Smad1/5/8 in the ovaries from the HFD group compared with the NC group, indicating that FoxO3a/Smad1/5/8 may be important in the regulation of follicular development. The expression levels of the upstream regulator of FoxO3a, Akt, were also examined and it was demonstrated that Akt phosphorylation was significantly reduced in the HFD group compared with the NC group, indicating that Akt/FoxO3a may be also involved in follicular development. Together, the experiments demonstrated that HFD‑induced obesity affected the activity of the Akt/FoxO3a/Smad1/5/8 signaling pathway in a time‑dependent manner during the follicular development of the mouse ovary, leading to abnormal follicular development. These findings may provide part of a theoretical basis for the clinical prevention and treatment of obesity-associated female infertility.

Effect of Hyperglycemia on Gene Expression during Early Organogenesis in Mice

Background

Cardiovascular and neural malformations are common sequels of diabetic pregnancies, but the underlying molecular mechanisms remain unknown. We hypothesized that maternal hyperglycemia would affect the embryos most shortly after the glucose-sensitive time window at embryonic day (ED) 7.5 in mice.

Methods

Mice were made diabetic with streptozotocin, treated with slow-release insulin implants and mated. Pregnancy aggravated hyperglycemia. Gene expression profiles were determined in ED8.5 and ED9.5 embryos from diabetic and control mice using Serial Analysis of Gene Expression and deep sequencing.

Results

Maternal hyperglycemia induced differential regulation of 1,024 and 2,148 unique functional genes on ED8.5 and ED9.5, respectively, mostly in downward direction. Pathway analysis showed that ED8.5 embryos suffered mainly from impaired cell proliferation, and ED9.5 embryos from impaired cytoskeletal remodeling and oxidative phosphorylation (all P ≤ E-5). A query of the Mouse Genome Database showed that 20–25% of the differentially expressed genes were caused by cardiovascular and/or neural malformations, if deficient. Despite high glucose levels in embryos with maternal hyperglycemia and a ~150-fold higher rate of ATP production from glycolysis than from oxidative phosphorylation on ED9.5, ATP production from both glycolysis and oxidative phosphorylation was reduced to ~70% of controls, implying a shortage of energy production in hyperglycemic embryos.

Conclusion

Maternal hyperglycemia suppressed cell proliferation during gastrulation and cytoskeletal remodeling during early organogenesis. 20–25% of the genes that were differentially regulated by hyperglycemia were associated with relevant congenital malformations. Unexpectedly, maternal hyperglycemia also endangered the energy supply of the embryo by suppressing its glycolytic capacity.

Superoxide dismutase 2 overexpression alleviates maternal diabetes-induced neural tube defects, restores mitochondrial function and suppresses cellular stress in diabetic embryopathy

Pregestational diabetes disrupts neurulation leading to neural tube defects (NTDs). Oxidative stress resulting from reactive oxygen species (ROS) plays a central role in the induction of NTD formation in diabetic pregnancies. We aimed to determine whether mitochondrial dysfunction increases ROS production leading to oxidative stress and diabetic embryopathy. Overexpression of the mitochondrion-specific antioxidant enzyme superoxide dismutase 2 (SOD2) in a transgenic (Tg) mouse model significantly reduced maternal diabetes-induced NTDs. SOD2 overexpression abrogated maternal diabetes-induced mitochondrial dysfunction by inhibiting mitochondrial translocation of the pro-apoptotic Bcl-2 family members, reducing the number of defective mitochondria in neuroepithelial cells, and decreasing mitochondrial membrane potential. Furthermore, SOD2 overexpression blocked maternal diabetes-increased ROS production by diminishing dihydroethidium staining signals in the developing neuroepithelium, and reducing the levels of nitrotyrosine-modified proteins and lipid hydroperoxide level in neurulation stage embryos. SOD2 overexpression also abolished maternal diabetes-induced endoplasmic reticulum stress. Finally, caspase-dependent neuroepithelial cell apoptosis enhanced by oxidative stress was significantly reduced by SOD2 overexpression. Thus, our findings support the hypothesis that mitochondrial dysfunction in the developing neuroepithelium enhances ROS production, which leads to oxidative stress and endoplasmic reticulum (ER) stress. SOD2 overexpression blocks maternal diabetes-induced oxidative stress and ER stress, and reduces the incidence of NTDs in embryos exposed to maternal diabetes.

High glucose-induced oxidative stress represses sirtuin deacetylase expression and increases histone acetylation leading to neural tube defects

Aberrant epigenetic modifications are implicated in maternal diabetes-induced neural tube defects (NTDs). Because cellular stress plays a causal role in diabetic embryopathy, we investigated the possible role of the stress-resistant sirtuin (SIRT) family histone deacetylases. Among the seven sirtuins (SIRT1-7), pre-gestational maternal diabetes in vivo or high glucose in vitro significantly reduced the expression of SIRT 2 and SIRT6 in the embryo or neural stem cells, respectively. The down-regulation of SIRT2 and SIRT6 was reversed by superoxide dismutase 1 (SOD1) over-expression in the in vivo mouse model of diabetic embryopathy and the SOD mimetic, tempol and cell permeable SOD, PEGSOD in neural stem cell cultures. 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), a superoxide generating agent, mimicked high glucose-suppressed SIRT2 and SIRT6 expression. The acetylation of histone 3 at lysine residues 56 (H3K56), H3K14, H3K9, and H3K27, putative substrates of SIRT2 and SIRT6, was increased by maternal diabetes in vivo or high glucose in vitro, and these increases were blocked by SOD1 over-expression or tempol treatment. SIRT2 or SIRT6 over-expression abrogated high glucose-suppressed SIRT2 or SIRT6 expression, and prevented the increase in acetylation of their histone substrates. The potent sirtuin activator (SRT1720) blocked high glucose-increased histone acetylation and NTD formation, whereas the combination of a pharmacological SIRT2 inhibitor and a pan SIRT inhibitor mimicked the effect of high glucose on increased histone acetylation and NTD induction. Thus, diabetes in vivo or high glucose in vitro suppresses SIRT2 and SIRT6 expression through oxidative stress, and sirtuin down-regulation-induced histone acetylation may be involved in diabetes-induced NTDs. The mechanism underlying pre-gestational diabetes-induced neural tube defects (NTDs) is still elusive. Our study unravels a new epigenetic mechanism in which maternal diabetes-induced oxidative stress represses sirtuin deacetylase 2 (SIRT2) and 6 (SIRT6) expression leading to histone acetylation and gene expression. SIRT down-regulation mediates the teratogenicity of diabetes leading to (NTD) formation. The study provides a mechanistic basis for the development of natural antioxidants and SIRT activators as therapeutics for diabetic embryopathy.

High glucose suppresses embryonic stem cell differentiation into neural lineage cells

Abnormal neurogenesis occurs during embryonic development in human diabetic pregnancies and in animal models of diabetic embryopathy. Our previous studies in a mouse model of diabetic embryopathy have implicated that high glucose of maternal diabetes delays neurogenesis in the developing neuroepithelium leading to neural tube defects. However, the underlying process in high glucose-impaired neurogenesis is uncharacterized. Neurogenesis from embryonic stem (ES) cells provides a valuable model for understanding the abnormal neural lineage development under high glucose conditions. ES cells are commonly generated and maintained in high glucose (approximately 25 mM glucose). Here, the mouse ES cell line, E14, was gradually adapted to and maintained in low glucose (5 mM), and became a glucose responsive E14 (GR-E14) line. High glucose induced the endoplasmic reticulum stress marker, CHOP, in GR-E14 cells. Under low glucose conditions, the GR-E14 cells retained their pluripotency and capability to differentiate into neural lineage cells. GR-E14 cell differentiation into neural stem cells (Sox1 and nestin positive cells) was inhibited by high glucose. Neuron (Tuj1 positive cells) and glia (GFAP positive cells) differentiation from GR-E14 cells was also suppressed by high glucose. In addition, high glucose delayed GR-E14 differentiation into neural crest cells by decreasing neural crest markers, paired box 3 (Pax3) and paired box 7 (Pax7). Thus, high glucose impairs ES cell differentiation into neural lineage cells. The low glucose adapted and high glucose responsive GR-E14 cell line is a useful in vitro model for assessing the adverse effect of high glucose on the development of the central nervous system.