Long-term disruption of maternal glucose homeostasis induced by prenatal glucocorticoid treatment correlates with miR-29 upregulation

Appraising the Preclinical Evidence of the Role of the Renin-Angiotensin-Aldosterone System in Antenatal Programming of Maternal and Offspring Cardiovascular Health Across the Life Course: Moving the Field Forward: A Scientific Statement From the American Heart Association

There is increasing interest in the long-term cardiovascular health of women with complicated pregnancies and their affected offspring. Emerging antenatal risk factors such as preeclampsia appear to increase the risk of hypertension and cardiovascular disease across the life course in both the offspring and women after pregnancy. However, the antenatal programming mechanisms responsible are complex and incompletely understood, with roots in alterations in the development, structure, and function of the kidney, heart, vasculature, and brain. The renin-angiotensin-aldosterone system is a major regulator of maternal-fetal health through the placental interface, as well as kidney and cardiovascular tissue development and function. Renin-angiotensin-aldosterone system dysregulation plays a critical role in the development of pregnancy complications such as preeclampsia and programming of long-term adverse cardiovascular health in both the mother and the offspring. An improved understanding of antenatal renin-angiotensin-aldosterone system programming is crucial to identify at-risk individuals and to facilitate development of novel therapies to prevent and treat disease across the life course. Given the inherent complexities of the renin-angiotensin-aldosterone system, it is imperative that preclinical and translational research studies adhere to best practices to accurately and rigorously measure components of the renin-angiotensin-aldosterone system. This comprehensive synthesis of preclinical and translational scientific evidence of the mechanistic role of the renin-angiotensin-aldosterone system in antenatal programming of hypertension and cardiovascular disease will help (1) to ensure that future research uses best research practices, (2) to identify pressing needs, and (3) to guide future investigations to maximize potential outcomes. This will facilitate more rapid and efficient translation to clinical care and improve health outcomes.

Glycemia-Induced miRNA Changes: A Review

Diabetes is a rapidly increasing global health concern that significantly strains the health system due to its downstream complications. Dysregulation in glycemia represents one of the fundamental obstacles to achieving glycemic control in diabetic patients. Frequent hyperglycemia and/or hypoglycemia events contribute to pathologies that disrupt cellular and metabolic processes, which may contribute to the development of macrovascular and microvascular complications, worsening the disease burden and mortality. miRNAs are small single-stranded non-coding RNAs that regulate cellular protein expression and have been linked to various diseases, including diabetes mellitus. miRNAs have proven useful in the diagnosis, treatment, and prognosis of diabetes and its complications. There is a vast body of literature examining the role of miRNA biomarkers in diabetes, aiming for earlier diagnoses and improved treatment for diabetic patients. This article reviews the most recent literature discussing the role of specific miRNAs in glycemic control, platelet activity, and macrovascular and microvascular complications. Our review examines the different miRNAs involved in the pathological processes leading to the development of type 2 diabetes mellitus, such as endothelial dysfunction, pancreatic beta-cell dysfunction, and insulin resistance. Furthermore, we discuss the potential applications of miRNAs as next-generation biomarkers in diabetes with the aim of preventing, treating, and reversing diabetes.

Tumor-suppressor p53 specifically binds to miR-29c-3p and reduces ADAM12 expression in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is an extremely aggressive malignant tumor associated with high migratory and invasive potential. The present study intends to explore regulatory mechanism of p53/microRNA (miR)-29c-3p/A disintegrin and metalloproteinase 12 (ADAM12) axis in HCC based on clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology.

METHODS

Putative miR-29c-3p binding sites on ADAM12 3'UTR were verified by a luciferase assay. The binding affinity of p53 to miR-29c-3p was assessed based on CRISPR/Cas9 technology to construct a p53 knockout (p53^-/-) HCCLM3 cell line. Furthermore, the effect of p53/miR-29c-3p/ADAM12 was assessed on maligant phenotypes in vitro and tumor formation and metastasis in nude mice.

RESULTS

ADAM12 was highly expressed but miR-29c-3p was poorly expressed in HCC. miR-29c-3p inhibited migratory and invasive abilities of HCC cells by targeting ADAM12 expression. p53 was found to target and upregulate miR-29c-3p, thus downregulating ADAM12 and conferring inhibitory effect on HCC cell activities. Moreover, ADAM12 knockout or p53 overexpression reduced HCC tumor formation and metastasis, which were reversed by further silencing of miR-29c-3p.

CONCLUSION

The identification of the p53/miR-29c-3p/ADAM12 axis in migration and invasion of HCC may potentially further our understanding of mechanisms underpinning HCC, and also bear translational value as novel molecular targets.

The Relationship between Serum Adipokines, miR-222-3p, miR-103a-3p and Glucose Regulation in Pregnancy and Two to Three Years Post-Delivery in Women with Gestational Diabetes Mellitus Adhering to Mediterranean Diet Recommendations

The San Carlos Gestational Diabetes Mellitus (GDM) prevention study, a nutritional intervention RCT based on a Mediterranean Diet (MedDiet), has been shown to reduce the incidence of GDM. The objective of this study is to investigate the relationship of leptin, adiponectin, interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α), insulin and HOMA-IRand circulating miRNAs (miR-29a-3p, miR-103a-3p, miR-132-3p, miR-222-3p) with the appearance of GDM and with MedDiet-based nutritional intervention, at 24−28 gestational weeks (GW), and in glucose regulation 2−3 years post-delivery (PD). A total of 313 pregnant women, 77 with GDM vs. 236 with normal glucose tolerance (NGT), 141 from the control group (CG, MedDiet restricting the consumption of dietary fat including EVOO and nuts during pregnancy) vs. 172 from the intervention group (IG, MedDiet supplemented with extra virgin olive oil (EVOO) and pistachios during pregnancy) were compared at Visit 1 (8−12 GW), Visit 2 (24−28 GW) and Visit 3 (2−3 years PD). Expression of miRNAs was determined by the Exiqon miRCURY LNA RT-PCR system. Leptin, adiponectin, IL-6 and TNF-α, were measured by Milliplex® immunoassays on Luminex 200 and insulin by RIA. Women with GDM vs. NTG had significantly higher leptin median (Q1−Q3) levels (14.6 (9.2−19.4) vs. 9.6 (6.0−15.1) ng/mL; p < 0.05) and insulin levels (11.4 (8.6−16.5) vs. 9.4 (7.0−12.8) µUI/mL; p < 0.001) and lower adiponectin (12.9 (9.8−17.2) vs. 17.0 (13.3−22.4) µg/mL; p < 0.001) at Visit 2. These findings persisted in Visit 3, with overexpression of miR-222-3p (1.45 (0.76−2.21) vs. 0.99 (0.21−1.70); p < 0.05)) and higher levels of Il-6 and TNF-α. When the IG is compared with the CG lower levels of insulin, HOMA-IR-IR, IL-6 levels at Visit 2 and 3 and leptin levels only at Visit 2 were observed. An overexpression of miR-222-3p and miR-103a-3p were also observed in IG at Visit 2 and 3. The miR-222-3p and miR103a-3p expression correlated with insulin levels, HOMA-IR, IL-6 and TNF-α at Visit 2 (all p < 0.05). These data support the association of leptin, adiponectin and insulin/HOMA-IR with GDM, as well as the association of insulin/HOMA-IR and IL-6 and miR-222-3p and miR-103a-3p expression with a MedDiet-based nutritional intervention.

The adaptation of maternal energy metabolism to lactation and its underlying mechanisms

Maternal energy metabolism undergoes a singular adaptation during lactation that allows for the caloric enrichment of milk. Changes in the mammary gland, changes in the white adipose tissue, brown adipose tissue, liver, skeletal muscles and endocrine pancreas are pivotal for this adaptation. The present review details the landmark studies describing the enzymatic modulation and the endocrine signals behind these metabolic changes. We will also update this perspective with data from recent studies showing transcriptional and post-transcriptional mechanisms that mediate the adaptation of the maternal metabolism to lactation. The present text will also bring experimental and observational data that describe the long-term consequences that short periods of lactation impose to maternal metabolism.

The microRNA-29 family - role in metabolism and metabolic disease

The microRNA-29a family members miR-29a-3p, miR-29b-3p and miR-29c-3p are ubiquitously expressed and consistently increased in various tissues and cell types in conditions of metabolic disease; obesity, insulin resistance and type 2 diabetes. In pancreatic beta cells, miR-29a is required for normal exocytosis, but increased levels are associated with impaired beta cell function. Similarly, in liver miR-29 species are higher in models of insulin resistance and type 2 diabetes, and either knock-out or depletion using a microRNA inhibitor improves hepatic insulin resistance. In skeletal muscle, miR-29 upregulation is associated with insulin resistance and altered substrate oxidation, and similarly, in adipocytes over-expression of miR-29a leads to insulin resistance. Blocking miR-29a using nucleic acid antisense therapeutics show promising results in preclinical animal models of obesity and type 2 diabetes, although the widespread expression pattern of miR-29 family members complicates the exploration of single target tissues. However, in fibrotic diseases, such as in late complications of diabetes and metabolic disease (diabetic kidney disease, non-alcoholic steatohepatitis), miR-29 expression is suppressed by TGFβ allowing increased extracellular matrix collagen to form. In the clinical setting circulating levels of miR-29a and miR-29b are consistently increased in type 2 diabetes and in gestational diabetes, and are also possible prognostic markers for deterioration of glucose tolerance. In conclusion, miR-29 plays an essential role in various organs relevant to intermediary metabolism and its upregulation contribute to impaired glucose metabolism, while it suppresses fibrosis development. Thus, a correct balance of miR-29a levels seems important for cellular and organ homeostasis in metabolism.

Changes in PGC-1α-Dependent Mitochondrial Biogenesis Are Associated with Inflexible Hepatic Energy Metabolism in the Offspring Born to Dexamethasone-Treated Mothers

In the present study we investigated the participation of hepatic peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) in the metabolic programming of newborn rats exposed in utero to dexamethasone (DEX). On the 21st day of life, fasted offspring born to DEX-treated mothers displayed increased conversion of pyruvate into glucose with simultaneous upregulation of PEPCK (phosphoenolpyruvate carboxykinase) and G6Pase (glucose-6-phosphatase). Increased oxidative phosphorylation, higher ATP/ADP ratio and mitochondrial biogenesis and lower pyruvate levels were also found in the progeny of DEX-treated mothers. On the other hand, the 21-day-old progeny of DEX-treated mothers had increased hepatic triglycerides (TAG) and lower CPT-1 activity when subjected to short-term fasting. At the mechanistic level, rats exposed in utero to DEX exhibited increased hepatic PGC-1α protein content with lower miR-29a-c expression. Increased PGC-1α content was concurrent with increased association to HNF-4α and NRF1 and reduced PPARα expression. The data presented herein reveal that changes in the transcription machinery in neonatal liver of rats born to DEX-treated mothers leads to an inflexible metabolic response to fasting. Such programming is hallmarked by increased oxidative phosphorylation of pyruvate with impaired FFA oxidation and hepatic TAG accumulation.

Diabetes: discovery of insulin, genetic, epigenetic and viral infection mediated regulation

Diabetes mellitus, commonly referred to as diabetes, is a combination of many metabolic diseases. Insulin deficiency in our body is the main cause of diabetes. Insulin is one of the most well studied proteins, yet the genesis of its discovery was not getting much attention so far. Nevertheless, the history of the discovery of insulin is an exemplary of solving observational and scientific riddles, drudgery, patience and even professional turmoil. It is an inspiration for all medical personnel and scientists who are practising in the field of molecular medicine. Additionally, the genetic and epigenetic regulation of different types of diabetes needs to be addressed because of the widespread nature of the disease. Diabetes not only involves genetic predisposition but environmental factors, lifestyle etc. can be the major contributor for its inception. Nonetheless, viral infections at an early age are also found to trigger the onset of type I diabetes. In this review article, the history of the discovery of insulin is detailed along with the justification for the genetic and epigenetic regulatory mechanisms of diabetes and explained how viral infections can also trigger the onset of diabetes.

The Predominant microRNAs in β-cell Clusters for Insulin Regulation and Diabetic Control

micro (mi)-RNAs are vital regulators of multiple processes including insulin signaling pathways and glucose metabolism. Pancreatic β-cells function is dependent on some miRNAs and their target mRNA, which together form a complex regulative network. Several miRNAs are known to be directly involved in β-cells functions such as insulin expression and secretion. These small RNAs may also play significant roles in the fate of β-cells such as proliferation, differentiation, survival and apoptosis. Among the miRNAs, miR-7, miR-9, miR-375, miR-130 and miR-124 are of particular interest due to being highly expressed in these cells. Under diabetic conditions, although no specific miRNA profile has been noticed, the expression of some miRNAs and their target mRNAs are altered by posttranscriptional mechanisms, exerting diverse signs in the pathobiology of various diabetic complications. The aim of this review article is to discuss miRNAs involved in the process of stem cells differentiation into β-cells, resulting in enhanced β-cell functions with respect to diabetic disorders. This paper will also look into the impact of miRNA expression patterns on in vitro proliferation and differentiation of β-cells. The efficacy of the computational genomics and biochemical analysis to link the changes in miRNA expression profiles of stem cell-derived β-cells to therapeutically relevant outputs will be discussed as well.

Insulin resistance and depressed cardiac G6PD activity induced by glucocorticoid exposure during pregnancy are attenuated by maternal estrogen-progestin therapy

This study aimed to investigate the effects of maternal combined oral contraceptive (COC) on dams that were exposed to late gestational glucocorticoids (GC). Twenty-four pregnant female rats were randomly allotted into 4 groups of 6 dams each. Dams received COC (combination of 1.0 μg ethinylestradiol and 5.0 μg levonorgestrel p.o.) between 3rd and 11^th week after delivery with or without prior exposure to GC (dexamethasone; 0.2 mg/kg p.o.) that was administered between gestational days 14-19. Data showed that late-gestational GC exposure led to insulin resistance (IR), increased cardiac adenosine deaminase (ADA), xanthine oxidase (XO), lactate, lactate dehydrogenase (LDH), and disrupted cardiac glucose-6-phosphate dehydrogenase (G6PD)-dependent antioxidant defenses. On the other hand, maternal COC treatment in dams not exposed to gestational GC led to IR, increased cardiac XO, LDH and defective cardiac G6PD-dependent antioxidant defenses. However, maternal COC with prior gestational GC exposure led to attenuated IR, cardiac ADA, UA, LDH, and improved cardiac G6PD-dependent antioxidant defenses but worsened cardiac triglyceride (TG) accumulation when compared with dam with gestational GC exposure without maternal COC. Taken together, the findings of this study provide evidence that maternal COC treatment improves late gestational GC-programmed effects. This is however accompanied with enhanced cardiac TG accumulation.

Dexamethasone increases renal free fatty acids and xanthine oxidase activity in female rats: could there be any gestational impact?

Dexamethasone (DEX) is used for various conditions in female and even during pregnancy. We tested the hypothesis that DEX exposure in female rats would lead to renal free fatty acid (FFA) accumulation with elevated xanthine oxidase (XO) activity that would be aggravated by pregnancy. Twenty-four female rats (n = 6/group) were randomly assigned to non-pregnant (NPR), DEX-exposed non-pregnant (NPR + DEX), pregnant (PRE) and DEX-exposed pregnant (PRE + DEX), respectively. NPR and PRE rats received vehicle (po) while NPR + DEX and PRE + DEX groups received DEX (0.2 mg/kg; po), between gestational days 14 and 19. Data showed that DEX exposure caused increased plasma creatinine, urea, renal FFA accumulation, lipid peroxidation, aminotranferases, depressed glutathione, increased activity of XO, and elevated uric acid in both pregnant and non-pregnant rats. The findings of this study indicate that DEX exposure would cause renal FFA accumulation and glutathione depletion that are accompanied by increased activity of XO/uric acid independently of gestation. The study also implies that DEX-induced renal damage could be worsened by gestation.

Dexamethasone causes defective glucose-6-phosphate dehydrogenase dependent antioxidant barrier through endoglin in pregnant and nonpregnant rats

Glucocorticoid therapy has been associated with adverse cardiometabolic effects during pregnancy. Inflammation-mediated cardiac dysfunction, an independent risk factor for morbidity and mortality, has been linked to defective glucose-6-phosphate dehydrogenase (G6PD) dependent antioxidant defenses and increased endoglin expression. We therefore sought to investigate the effects of dexamethasone (DEX) on cardiac endoglin and G6PD-dependent antioxidant defense. Twenty-four rats were randomly assigned to nonpregnant (PRE(-)), DEX-exposed nonpregnant (PRE(-) + DEX), pregnant (PRE(+)), and DEX-exposed pregnant (PRE(+) + DEX) rats, respectively (n = 6 per group). PRE(-) and PRE(+) rats received vehicle (per oral (po)), while PRE(-) + DEX and PRE(+) + DEX groups were administered DEX (0.2 mg/kg po) between gestational days 14 and 19, respectively. Results showed that DEX caused increased cardiac pro-inflammatory markers (adenosine deaminase (ADA) activity, endoglin, vascular cell adhesion molecule-1 (VCAM-1), tissue injury markers (LDH, GGT, AST, ALT, and ALP), metabolic disturbances (elevated fasting plasma glucose, free fatty acid (FFA), lactate, cardiac FFA, and lactate) and depressed G6PD-dependent antioxidant defenses (G6PD activity, reduced glutathione/oxidized glutathione ratio, and nitric oxide) in pregnant and nonpregnant rats. The present study demonstrates that DEX led to increased cardiac endoglin and VCAM-1 that is accompanied by defective G6PD-dependent antioxidant defenses but not cardiac lipid accumulation in both pregnant and nonpregnant rats.

Glucocorticoid exposure causes disrupted glucoregulation, cardiac inflammation and elevated dipeptidyl peptidase-4 activity independent of glycogen synthase kinase-3 in female rats

Objective: We tested the hypothesis that glucocorticoid (GC) exposure in female rats would lead to glucose dysregulation and elevated cardiac inflammatory biomarkers, which are dipeptidyl peptidase-4 (DPP-4)- and glycogen synthase kinase-3 (GSK-3)-dependent. Methods: Female Wistar rats received vehicle (control; n = 6) or GC (dexamethasone; n = 6; 0.2 mg/kg; p.o.) for six days. Insulin resistance was determined by HOMA-IR. DPP-4 activity was determined by fluorescence method, whereas vascular cell adhesion molecule-1 (VCAM-1), uric acid, malondialdehyde (MDA), lactate dehydrogenase (LDH) and nitric oxide (NO) from plasma and cardiac homogenate were estimated as cardiac pro-inflammatory biomarkers. Results: Results showed that GC exposure resulted in glucose dysregulation and increased plasma and cardiac pro-inflammatory markers which are associated with elevated DPP-4 activity but reduced GSK-3. Conclusions: The present results demonstrate that GC exposure would cause glucose dysregulation, increased DPP-4 activity and cardiac inflammation that is independent of GSK-3.

Dexamethasone during pregnancy impairs maternal pancreatic β-cell renewal during lactation

Pancreatic islets from pregnant rats develop a transitory increase in the pancreatic β-cell proliferation rate and mass. Increased apoptosis during early lactation contributes to the rapid reversal of those morphological changes. Exposure to synthetic glucocorticoids during pregnancy has been previously reported to impair insulin secretion, but its impacts on pancreatic islet morphological changes during pregnancy and lactation have not been described. To address this issue, we assessed the morphological and molecular characteristics of pancreatic islets from rats that underwent undisturbed pregnancy (CTL) or were treated with dexamethasone between the 14th and 19th days of pregnancy (DEX). Pancreatic islets were analyzed on the 20th day of pregnancy (P20) and on the 3rd, 8th, 14th and 21st days of lactation (L3, L8, L14 and L21, respectively). Pancreatic islets from CTL rats exhibited transitory increases in cellular proliferation and pancreatic β-cell mass at P20, which were reversed at L3, when a transitory increase in apoptosis was observed. This was followed by the appearance of morphological features of pancreatic islet neogenesis at L8. Islets from DEX rats did not demonstrate an increase in apoptosis at L3, which coincided with an increase in the expression of M2 macrophage markers relative to M1 macrophage and T lymphocyte markers. Islets from DEX rats also did not exhibit the morphological characteristics of pancreatic islet neogenesis at L8. Our data demonstrate that maternal pancreatic islets undergo a renewal process during lactation that is impaired by exposure to DEX during pregnancy.

Insight into miRNAs related with glucometabolic disorder

A microRNA (miRNA) is a single-stranded, small and non-coding RNA molecule that contains 20-25 nucleotides. More than 2000 miRNAs have been identified in human genes since the first miRNA was discovered in Caenorhabditis elegans in the early 1990s. miRNAs play a crucial role in various biological processes by regulating gene expression through post-transcriptional mechanisms. The alterations of their levels are associated with various diseases, such as glucometabolic disorder and lipid metabolism disorder. In recent years, miRNAs have been proved to be involved in regulating the functions of pancreatic β-cells, insulin resistance and other biological behaviors related to glucometabolic disorder and the pathogenesis of diabetes mellitus (DM). This review summarized specific miRNAs, including miRNA-375 (miR-375), miRNA-155 (miR-155), miRNA-21 (miR-21), miRNA-33 (miR-33), the let-7 family and some other miRNAs related to glucometabolic regulation, introduced the obstacles and challenges in miRNA therapy, and discussed the prospect of new treatment methods for glucometabolic disorder.

Dexamethasone Administration During Late Gestation Has No Major Impact on Lipid Metabolism, but Reduces Newborn Survival Rate in Wistar Rats

A rise in plasma triacylglycerol levels is a common physiological occurrence during late gestation and excess of glucocorticoids (GCs) has been shown to impair lipid metabolism. Based on those observations, we investigated whether the administration of dexamethasone during the late gestational period could exacerbate this pregnancy associated hypertriacylglycerolemia in rats. For this, female Wistar rats were treated with dexamethasone (0.2 mg/kg of body mass in the drinking water on days 14-19 of pregnancy; DP group) or equivalent days in the virgin rats (DV group). Untreated pregnant rats (control pregnant group) and age-matched virgin rats (control virgin group) were used as controls. Functional, biochemical, and molecular analyses were carried out after treatment with GC and in the control groups. Euthanasia was performed on day 20 of pregnancy. The metabolic parameters of the mothers (dams) at the time of weaning and 6 months later, as well as newborn survival, were evaluated. We observed that neither dexamethasone nor pregnancy affected blood glucose or glucose tolerance. Hypertriacylglycerolemia associated with lipid intolerance or reduced hepatic triacylglycerol clearance was observed during the late gestational period. GC treatment caused a further increase in basal plasma triacylglycerol levels, but did not have a significant effect on lipid tolerance and hepatic triacylglycerol clearance in pregnant rats. GC, but not pregnancy, caused few significant changes in mRNA expression of proteins involved in lipid metabolism. Dexamethasone during pregnancy had no impact on lipid metabolism later in the dams' life; however, it led to intra-uterine growth restriction and reduced pup survival rate. In conclusion, GC exposure during the late gestational period in rats has no major impact on maternal lipid homeostasis, soon after parturition at weaning, or later in the dams' life, but GC exposure is deleterious to the newborn when high doses are administered at late gestation. These data highlight the importance of performing an individualized and rigorous control of a GC treatment during late pregnancy considering its harmful impact on the fetuses' health.

Gestational glucocorticoid exposure disrupts glucose homeostasis that is accompanied by increased endoglin and DPP-4 activity instead of GSK-3 in rats

Gestational glucocorticoid (GC) treatment has been associated with cardiometabolic disorder (CMD) in offspring's in later life. Elevated dipeptidyl peptidase-4 (DPP-4) activity, endoglin and glycogen synthase kinase-3 (GSK-3) has also been implicated in the development of insulin resistance (IR) and/or vascular inflammation. We aimed to investigate the impact of GC exposure on glucose metabolism and the circulating levels of inflammatory biomarkers, DPP-4 activity and GSK-3 in pregnant rats. Pregnant Wistar rats received either vehicle or dexamethasone (DEX; 0.2 mg/kg; po) between gestational days 14 and 19. Gestational GC exposure resulted in impaired glucose homeostasis that is accompanied with elevated circulating levels of inflammatory biomarkers (endoglin, uric acid, and platelet/lymphocyte ratio), oxidative stress (malondialdehyde), blood viscosity, reduced NO level and increased DPP-4 activity. However, these effects were associated with atherogenic dyslipidemia and reduced GSK-3.We conclude that plasma endoglin, a marker of vascular inflammation, and plasma DPP-4 activity are increased in pregnant rats treated with GC during late gestation. Therefore, glucose deregulation associated with gestational GC exposure is through endoglin-/DPP-4-dependent but GSK-3-independent pathway.

Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men

The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.

Prolonged fasting elicits increased hepatic triglyceride accumulation in rats born to dexamethasone-treated mothers

We investigated the effect of dexamethasone during the last week of pregnancy on glucose and lipid metabolism in male offspring. Twelve-week old offspring were evaluated after fasting for 12-hours (physiological) and 60-hours (prolonged). Physiological fasting resulted in glucose intolerance, decreased glucose clearance after pyruvate load and increased PEPCK expression in rats born to dexamethasone-treated mothers (DEX). Prolonged fasting resulted in increased glucose tolerance and increased glucose clearance after pyruvate load in DEX. These modulations were accompanied by accumulation of hepatic triglycerides (TG). Sixty-hour fasted DEX also showed increased citrate synthase (CS) activity, ATP citrate lyase (ACLY) content, and pyruvate kinase 2 (pkm2), glucose transporter 1 (slc2a1) and lactate dehydrogenase-a (ldha) expressions. Hepatic AKT2 was increased in 60-hour fasted DEX, in parallel with reduced miRNAs targeting the AKT2 gene. Altogether, we show that metabolic programming by prenatal dexamethasone is characterized by an unexpected hepatic TG accumulation during prolonged fasting. The underlying mechanism may depend on increased hepatic glycolytic flux due to increased pkm2 expression and consequent conversion of pyruvate to non-esterified fatty acid synthesis due to increased CS activity and ACLY levels. Upregulation of AKT2 due to reduced miRNAs may serve as a permanent mechanism leading to increased pkm2 expression.

Regulatory Roles of MicroRNAs in Diabetes

MicroRNAs (miRNAs), a class of endogenous small noncoding RNAs in eukaryotes, have been recognized as significant regulators of gene expression through post-transcriptional mechanisms. To date, >2000 miRNAs have been identified in the human genome, and they orchestrate a variety of biological and pathological processes. Disruption of miRNA levels correlates with many diseases, including diabetes mellitus, a complex multifactorial metabolic disorder affecting >400 million people worldwide. miRNAs are involved in the pathogenesis of diabetes mellitus by affecting pancreatic β-cell functions, insulin resistance, or both. In this review, we summarize the investigations of the regulatory roles of important miRNAs in diabetes, as well as the potential of circulating miRNAs as diagnostic markers for diabetes mellitus.

Bidirectional communication between the Aryl hydrocarbon Receptor (AhR) and the microbiome tunes host metabolism

The ligand-induced transcription factor, aryl hydrocarbon receptor (AhR) is known for its capacity to tune adaptive immunity and xenobiotic metabolism—biological properties subject to regulation by the indigenous microbiome. The objective of this study was to probe the postulated microbiome-AhR crosstalk and whether such an axis could influence metabolic homeostasis of the host. Utilising a systems-biology approach combining in-depth ¹H-NMR-based metabonomics (plasma, liver and skeletal muscle) with microbiome profiling (small intestine, colon and faeces) of AhR knockout (AhR^−/−) and wild-type (AhR^+/+) mice, we assessed AhR function in host metabolism. Microbiome metabolites such as short-chain fatty acids were found to regulate AhR and its target genes in liver and intestine. The AhR signalling pathway, in turn, was able to influence microbiome composition in the small intestine as evident from microbiota profiling of the AhR^+/+ and AhR^−/− mice fed with diet enriched with a specific AhR ligand or diet depleted of any known AhR ligands. The AhR^−/− mice also displayed increased levels of corticosterol and alanine in serum. In addition, activation of gluconeogenic genes in the AhR^−/− mice was indicative of on-going metabolic stress. Reduced levels of ketone bodies and reduced expression of genes involved in fatty acid metabolism in the liver further underscored this observation. Interestingly, exposing AhR^−/− mice to a high-fat diet showed resilience to glucose intolerance. Our data suggest the existence of a bidirectional AhR-microbiome axis, which influences host metabolic pathways.

Day-restricted feeding during pregnancy and lactation programs glucose intolerance and impaired insulin secretion in male rat offspring

AIM

The maternal environment during pregnancy and lactation plays a determining role in programming energy metabolism in offspring. Among a myriad of maternal factors, disruptions in the light/dark cycle during pregnancy can program glucose intolerance in offspring. Out-of-phase feeding has recently been reported to influence metabolism in adult humans and rodents; however, it is not known whether this environmental factor impacts offspring metabolism when applied during pregnancy and lactation. This study aims to determine whether maternal day-restricted feeding (DF) influences energy metabolism in offspring.

METHODS

Pregnant and lactating Wistar rats were subjected to ad libitum (AL) or DF during pregnancy and lactation. The offspring born to the AL and DF dams were intra- and interfostered, which resulted in 4 group types.

RESULTS

The male offspring born to and breastfed by the DF dams (DF/DF off) were glucose intolerant, but without parallel insulin resistance as adults. Experiments with isolated pancreatic islets demonstrated that the male DF/DF off rats had reduced insulin secretion with no parallel disruption in calcium handling. However, this reduction in insulin secretion was accompanied by increased miRNA-29a and miRNA34a expression and decreased syntaxin 1a protein levels.

CONCLUSION

We conclude that out-of-phase feeding during pregnancy and lactation can lead to glucose intolerance in male offspring, which is caused by a disruption in insulin secretion capacity. This metabolic programming is possibly caused by mechanisms dependent on miRNA modulation of syntaxin 1a.