Regulation Of Hepatic Glucose Production Research Articles

Phytochemical analysis and antihyperglycemic activity of Castilleja arvensis

Castilleja genus comprises approximately 211 species, some of them exhibiting potential in treating various diseases. Remarkably, despite its abundance, there is a significant lack of scientific studies that explore the chemical composition and/or therapeutic activity of this genus.In this work, the chemical composition of Castilleja arvensis was determined, and its antihyperglycemic activity was evaluated in vivo, in vitro, and ex vivo. Hydroalcoholic extract of C. arvensis (HECa) was obtained from the maceration of aerial parts. HECa was fractionated by liquid–liquid extractions to obtain the CH2Cl2 fraction (DF), EtOAc fraction (EF), n-BuOH fraction (BF) and aqueous residue (AR). The antihyperglycemic activity was determined in vivo through oral glucose and sucrose tolerance tests in normoglycemic CD-1 mice. Ex vivo assays were performed to determine intestinal glucose absorption, muscular glucose uptake and hepatic glucose production. α-glucosidase inhibitory activity was evaluated in vitro. Phytochemical screening was carried out through conventional chromatography techniques. Structure elucidation of the isolated compounds was performed by GC–MS and NMR experiments.HECa, its fractions and AR showed significant antihyperglycemic activity in vivo. According to the in vitro and ex vivo assays, this effect can be attributed to different mechanisms of action, including a delay in intestinal glucose absorption, an improvement in insulin sensitivity, and the regulation of hepatic glucose production. These effects may be due to different metabolites identified in fractions from the HECa, including genkwanin, acacetin, verbascoside and ipolamiide. Thus, current research shows that C. arvensis is an important source of bioactive compounds for the management of glycemia.

Effect of C-reactive protein deficiency on insulin resistance reversal in rats with polycystic ovary syndrome through augmented leptin action

BackgroundC-reactive protein(CRP), is an inflammatory marker that weaken leptin bioavailability and insulin sensitivity to disturb energy and glucose metabolism. Polycystic ovary syndrome (PCOS) exhibit a metabolic component consisting of higher plasma CRP levels, hyperinsulinemic and hyperleptinemia. The ability of leptin to regulation of hepatic glucose production (HGP) in the absence of CRP in PCOS remain unknown.MethodsDehydroepiandrosterone (DHEA) was used to induce PCOS in rats. We assessed the effects of CRP gene knockout in PCOS model rats on body weight, energy expenditure glucose metabolism and insulin sensitivity. We conducted experiments involving the administration of leptin to both the peripheral and central systems in PCOS model rats with CRP knockout, and studied the effects on changes in glucose kinetics during hyperinsulinemic-euglycemic clamps.ResultsIn female PCOS rats, the lack of CRP resulted in decreased leptin resistance and weight gain, increased energy expenditure, and improved insulin sensitivity. Additionally, the deletion of the CRP gene strengthened the HGP-lowering effects of leptin when administered peripherally or centrally. This effect was accompanied by a decrease in the expression of hepatic gluconeogenic enzymes and an increase in hepatic insulin signaling. Finally, inhibition of glucose production was also enhanced for central leptin administration during lipid infusion in PCOS rats.ConclusionsOur findings highlight the therapeutic potential of targeting CRP to restore glucose homeostasis and insulin sensitivity for leptin in PCOS.

Transcription Factor Forkhead Box O1 Mediates Transforming Growth Factor-β1–Induced Apoptosis in Hepatocytes

Dysregulation of hepatocyte apoptosis is associated with several types of chronic liver diseases. Transforming growth factor-β1 (TGF-β1) is a well-known pro-apoptotic factor in the liver, which is constituted by a receptor complex composed of TGF-β receptor I and II, along with transcription factor Smad proteins. As a member of the forkhead box O (Foxo) class of transcription factors, Foxo1 is a predominant regulator of hepatic glucose production and apoptosis. In this study, we investigated the potential relationship between TGF-β1 signaling and Foxo1 in control of apoptosis in hepatocytes. By using hepatocytes isolated from both wild-type and liver-specific Foxo1 knockout mice, we found that TGF-β1 induces hepatocyte apoptosis in a Foxo1-dependent manner. We further demonstrated that TGF-β1 activates protein kinase A through TGF-β receptor I-Smad3, followed by phosphorylation of Foxo1 at Ser273 in promotion of apoptosis in hepatocytes. Moreover, Smad3 overexpression in the liver of mice promoted the levels of phosphorylated Foxo1-S273, total Foxo1, and a Foxo1-target pro-apoptotic gene Bim, which eventually resulted in hepatocyte apoptosis. We further demonstrated a crucial role of Foxo1-S273 phosphorylation in the pro-apoptotic effect of TGF-β1 by using hepatocytes isolated from Foxo1-S273A/A knock-in mice, in which the phosphorylation of Foxo1-S273 is disrupted. Taken together, we established a novel role of TGF-β1→protein kinase A→Foxo1 signaling cascades in control of hepatocyte survival.

Hepatocyte Rap1a contributes to obesity- and statin-associated hyperglycemia.

SUMMARYExcessive hepatic glucose production contributes to the development of hyperglycemia and is a key feature of type 2 diabetes. Here, we report that activation of hepatocyte Rap1a suppresses gluconeogenic gene expression and glucose production, whereas Rap1a silencing stimulates them. Rap1a activation is suppressed in obese mouse liver, and restoring its activity improves glucose intolerance. As Rap1a′s membrane localization and activation depends on its geranylgeranylation, which is inhibited by statins, we show that statin-treated hepatocytes and the human liver have lower active-Rap1a levels. Similar to Rap1a inhibition, statins stimulate hepatic gluconeogenesis and increase fasting blood glucose in obese mice. Geranylgeraniol treatment, which acts as the precursor for geranylgeranyl isoprenoids, restores Rap1a activity and improves statin-mediated glucose intolerance. Mechanistically, Rap1a activation induces actin polymerization, which suppresses gluconeogenesis by Akt-mediated FoxO1 inhibition. Thus, Rap1a regulates hepatic glucose homeostasis, and blocking its activity, via lowering geranylgeranyl isoprenoids, contributes to statin-induced glucose intolerance.

NSAID-Induced Enteropathy Affects Regulation of Hepatic Glucose Production by Decreasing GLP-1 Secretion.

Background/Aim: Given their widespread use and their notorious effects on the lining of gut cells, including the enteroendocrine cells, we explored if chronic exposure to non-steroidal anti-inflammatory drugs (NSAIDs) affects metabolic balance in a mouse model of NSAID-induced enteropathy. Method: We administered variable NSAIDs to C57Blk/6J mice through intragastric gavage and measured their energy balance, glucose hemostasis, and GLP-1 levels. We treated them with Exendin-9 and Exendin-4 and ran a euglycemic-hyperinsulinemic clamp. Results: Chronic administration of multiple NSAIDs to C57Blk/6J mice induces ileal ulcerations and weight loss in animals consuming a high-fat diet. Despite losing weight, NSAID-treated mice exhibit no improvement in their glucose tolerance. Furthermore, glucose-stimulated (glucagon-like peptide -1) GLP-1 is significantly attenuated in the NSAID-treated groups. In addition, Exendin-9—a GLP-1 receptor antagonist—worsens glucose tolerance in the control group but not in the NSAID-treated group. Finally, the hyper-insulinemic euglycemic clamp study shows that endogenous glucose production, total glucose disposal, and their associated insulin levels were similar among an ibuprofen-treated group and its control. Exendin-4, a GLP-1 receptor agonist, reduces insulin levels in the ibuprofen group compared to their controls for the same glucose exchange rates. Conclusions: Chronic NSAID use can induce small intestinal ulcerations, which can affect intestinal GLP-1 production, hepatic insulin sensitivity, and consequently, hepatic glucose production.

TOX4, an insulin receptor-independent regulator of hepatic glucose production, is activated in diabetic liver

Increased hepatic glucose production (HGP) contributes to hyperglycemia in type 2 diabetes. Hormonal regulation of this process is primarily, but not exclusively, mediated by the AKT-FoxO1 pathway. Here, we show that cAMP and dexamethasone regulate the high-mobility group superfamily member TOX4 to mediate HGP, independent of the insulin receptor/FoxO1 pathway. TOX4 inhibition decreases glucose production in primary hepatocytes and liver and increases glucose tolerance. Combined genetic ablation of TOX4 and FoxO1 in liver has additive effects on glucose tolerance and gluconeogenesis. Moreover, TOX4 ablation fails to reverse the metabolic derangement brought by insulin receptor knockout. TOX4 expression is increased in livers of patients with steatosis and diabetes and in diet-induced obese and db/db mice. In the latter two murine models, knockdown Tox4 decreases glycemia and improves glucose tolerance. We conclude that TOX4 is an insulin receptor-independent regulator of HGP and a candidate contributor to the pathophysiology of diabetes.

The adipokine FABP4 is a key regulator of neonatal glucose homeostasis.

During pregnancy, fetal glucose production is suppressed, with rapid activation immediately postpartum. Fatty acid–binding protein 4 (FABP4) was recently demonstrated as a regulator of hepatic glucose production and systemic metabolism in animal models. Here, we studied the role of FABP4 in regulating neonatal glucose hemostasis. Serum samples were collected from pregnant women with normoglycemia or gestational diabetes at term, from the umbilical circulation, and from the newborns within 6 hours of life. The level of FABP4 was higher in the fetal versus maternal circulation, with a further rise in neonates after birth of approximately 3-fold. Neonatal FABP4 inversely correlated with blood glucose, with an approximately 10-fold increase of FABP4 in hypoglycemic neonates. When studied in mice, blood glucose of 12-hour-old WT, Fabp4–/+, and Fabp4–/– littermate mice was 59 ± 13 mg/dL, 50 ± 11 mg/dL, and 43 ± 11 mg/dL, respectively. Similar to our observations in humans, FABP4 levels in WT mouse neonates were approximately 8-fold higher compared with those in adult mice. RNA sequencing of the neonatal liver suggested altered expression of multiple glucagon-regulated pathways in Fabp4–/– mice. Indeed, Fabp4–/– liver glycogen was inappropriately intact, despite a marked hypoglycemia, with rapid restoration of normoglycemia upon injection of recombinant FABP4. Our data suggest an important biological role for the adipokine FABP4 in the orchestrated regulation of postnatal glucose metabolism.

Glucoregulatory and Anti-Inflammatory Activities of Peptide Fractions Separated by Electrodialysis with Ultrafiltration Membranes from Salmon Protein Hydrolysate and Identification of Four Novel Glucoregulatory Peptides.

Natural bioactive peptides are suitable candidates for preventing the development of Type 2 diabetes (T2D), by reducing the various risk factors. The aim of this study was to concentrate glucoregulatory and anti-inflammatory peptides, from salmon by-products, by electrodialysis with ultrafiltration membrane (EDUF), and to identify peptides responsible for these bioactivities. Two EDUF configurations (1 and 2) were used to concentrate anionic and cationic peptides, respectively. After EDUF separation, two fractions demonstrated interesting properties: the initial fraction of the EDUF configuration 1 and the final fraction of the EDUF configuration 2 both showed biological activities to (1) increase glucose uptake in L6 muscle cells in insulin condition at 1 ng/mL (by 12% and 21%, respectively), (2) decrease hepatic glucose production in hepatic cells at 1 ng/mL in basal (17% and 16%, respectively), and insulin (25% and 34%, respectively) conditions, and (3) decrease LPS-induced inflammation in macrophages at 1 g/mL (45% and 30%, respectively). More impressive, the initial fraction of the EDUF configuration 1 (45% reduction) showed the same effect as the phenformin at 10 μM (40%), a drug used to treat T2D. Thirteen peptides were identified, chemically synthesized, and tested in-vitro for these three bioactivities. Thus, four new bioactive peptides were identified: IPVE increased glucose uptake by muscle cells, IVDI and IEGTL decreased hepatic glucose production (HGP) of insulin, whereas VAPEEHPTL decreased HGP under both basal condition and in the presence of insulin. To the best of our knowledge, this is the first time that (1) bioactive peptide fractions generated after separation by EDUF were demonstrated to be bioactive on three different criteria; all involved in the T2D, and (2) potential sequences involved in the improvement of glucose uptake and/or in the regulation of HGP were identified from a salmon protein hydrolysate.

Inhibition of Alpha‐glucosidase by guava (Psidium guajava)

Diabetes mellitus is a disorder of carbohydrate regulation related to either of the following: reduced pancreatic insulin production, peripheral insulin resistance, or an impaired regulation of hepatic glucose production. Due to their insulin disorder, patients diagnosed with diabetes mellitus are unable to properly conduct cellular uptake and utilization of glucose as an energy source which ultimately leads to hyperglycemia. Several categories of pharmacological treatments exist today to treat diabetes mellitus. However, they all have adverse effects. Our screening program aims at finding alternative local herbs that can treat diabetes. The herb that will be used in this study is guava (Psidium guajava L., Myrtaceae) leaves. Guava leaf extracts are said to be helpful for people with diabetes. A previous study conducted on guava leaves and its antidiabetic effect indicated that guava leaf polysaccharides (GLP) demonstrated antidiabetic capabilities. The anti-diabetic effects of GLP was shown to be related to a decrease in fasting blood sugar while also improving kidney, liver, and pancreas damage related to diabetes. Using guava extracts as a herbal alternative to manage diabetes will remarkably decrease the expense and complications associated with present medications used for diabetes management. The purpose of this study was to examine the mechanism of action of guava fruit as an inhibitor of alpha-glucosidase. The IC50 of Guava was compared with acarbose which is a proven antidiabetic agent known for lowering post-prandial hyperglycemic level by inhibiting α-glucosidase. In this study, we investigated the mechanism of action of guava fruit by in vitro method. The inhibition study was carried out in a 96 well plate using PNPG as the substrate and measured with Thermo Scientific® Multiskan Spectrometer. The EC50 was obtained and compared with that of acarbose. The result showed that guava fruit has some inhibitory activity on α-glucosidase. However, more studies are to be carried out.

Dysregulation of CRY1 Promotes Hyperglycemia in Diabetic Mice

Abnormally activated hepatic glucose production (HGP) is one of major factors contributing to hyperglycemia in diabetes. Recently, we have reported that cryptochrome (CRY1) plays a key role in hepatic glucose production. Although decreased hepatic CRY1 is closely associated with type 2 diabetes, the underlying mechanisms of dysregulated protein stability of hepatic CRY1 are largely unknown. Here, we demonstrate that upon overnutrition, elevated phosphorylation of CRY1 plays a role in the regulation of hepatic glucose production through proteasomal degradation in liver. Also, we uncover crucial signaling pathways involved in phosphorylation-mediated degradation of hepatic CRY1 protein in diabetic animals. In diabetic animals, increased CRY1 protein by suppressing CRY1 phosphorylation improved upregulated HGP in a CRY1-FOXO1 dependent manner. Collectively, our data suggest that protein stability of CRY1 would be critical to maintain systemic glucose homeostasis.

Comparison Of Glycemic Behavior Between Strength Training, HighIntensity Resistance Training (Hirt), High Intensity Interval Training (Hiit):A Case Study

Type 2 Diabetes Mellitus (DM 2) is generally a defect in insulin action and secretion and in the regulation of hepatic glucose production. Exercise to treat type 2 diabetes has had positive impacts on the lives of diabetics. The aim of this study is to analyze the effects of the glycemic curve in three different types of training: Strength Training (TF), High Intensity Resistance Training (HIRT) and Interval High Intensity Training (HIIT). The participantis a 57yearold, sedentary type 2 diabetic who under went the training method - Strength Training (ST) 60% of repetition maximum (RM), 8 to 12 repetitions, cadence 2010, the 2-minute restinterval. High Intensity Resistance Training (HIRT)protocol consisted of three sets with six repetitions at 80% of 1RM followed by rest for 20 seconds, the individual performs another series with the same load until reaching the point of failure again. The rest of one exercises and another is 2’30” , and High IntensityInterval Training (HIIT) a 5-minute warm-upmoderateload – 4 shots of 30 secondsof high intensity duration separated by 4 minutes of rest, once a week at night. Pre-study anamnesis, pre- and post-exercise glycemia were performed.The overall results were satisfactory presenting HIIT as the most effective method for acute post-exercise blood glucose reduction (reducing 29.62%, 34.25%, 38.89 and 36.11% immediatelyat 10, 20, 30 minutes afterexertionrespectively).It was concluded that physical training positively influenced the reduction of blood glucose as an acute effect, but HIIT was the most effective method.

Plasma glucagon levels are associated with obesity, insulin resistance and metabolic syndrome in a general population cohort

Rationale: Glucagon is a well- and long-recognized key regulator of hepatic glucose production playing a major role in plasma glucose control in both type 1 and type 2 diabetes. Experimental models have recently identified a role of glucagon in the regulation of energy balance and intermediate metabolism but potential associations between plasma glucagon, obesity and obesity-associated metabolic complications insulin resistance and metabolic syndrome in general population cohorts is largely unknown.

SYSTEMATIZATION OF NURSING ASSISTANCE TO PATIENTS WITH DIABETES MELLITUS TYPE 2: EXPERIENCE REPORT

Introduction Type 2 Diabetes Mellitus (DM2) is the form found in 90 to 95% of diabetes cases characterized by defects in the action and secretion of insulin and in the regulation of hepatic glucose production. Insulin resistance and functional defect of beta cells appear early in the preclinical phase of the disease. Obesity is the main risk factor for triggering this pathology, considering that, in these cases, insulin resistance is usually the consequence. From this perspective, Systematization of Nursing Assistance (SNA) is essential for the care of patients with a diagnosis of DM2, as it ensures the promotion of systematic and continuous assistance, thus constituting a basis for selection for care interventions. Objective To analyze the importance of Systematization of Nursing Assistance in health promotion for patients with Diabetes Mellitus Type 2. Methodology Descriptive study of the experience report type, conducted from the academic experience in supervised curricular internship, from the Adult and Elderly Health discipline in Primary Care, with home visits together with the Family Health Strategy Team in municipality of Recife – PE, in June 2019. Results With the practice of care planning from SNA, in DM2, it was possible to reach the following Nursing Process implementations: NANDA: Impaired skin integrity related to injury in the left lower limb evidenced by pain and loss of skin continuity after debridement. Nursing Outcomes Classification (NOC): Will have wound healing in a timely manner without complications. Nursing Interventions Classification (NIC): Check for general weakness associated with chronic disease. NANDA – Risk of falls related to visual impairment and difficulty walking. NOC – Verbalizes that understands the personal risk factors that contribute to the risk of falling. NIC – Assess the general health status of the individual, paying attention to factors that may compromise safety, including chronic disorders. Conclusions/Considerations: In this context, the importance of Nursing Systematization is noteworthy, since it can be applied in various areas of nursing practice, concretizing nursing care through scientific bases, granting greater credibility and autonomy to the professional. It also provides the patient with holistic care through various pathological contexts.

DOCK5 regulates energy balance and hepatic insulin sensitivity by targeting mTORC1 signaling.

The dedicator of cytokinesis 5 (DOCK5) is associated with obesity. However, the mechanism by which DOCK5 contributes to obesity remains completely unknown. Here, we show that hepatic DOCK5 expression significantly decreases at a state of insulin resistance (IR). Deletion of DOCK5 in mice reduces energy expenditure, promotes obesity, augments IR, dysregulates glucose metabolism, and activates the mTOR (Raptor)/S6K1 pathway under a high-fat diet (HFD). The overexpression of DOCK5 in hepatocytes inhibits gluconeogenic gene expression and increases the level of insulin receptor (InsR) and Akt phosphorylation. DOCK5 overexpression also inhibits mTOR/S6K1 phosphorylation and decreases the level of raptor protein expression. The opposite effects were observed in DOCK5-deficient hepatocytes. Importantly, in liver-specific Raptor knockout mice and associated hepatocytes, the effects of an adeno-associated virus (AAV8)- or adenovirus-mediated DOCK5 knockdown on glucose metabolism and insulin signaling are largely eliminated. Additionally, DOCK5-Raptor interaction is indispensable for the DOCK5-mediated regulation of hepatic glucose production (HGP). Therefore, DOCK5 acts as a regulator of Raptor to control hepatic insulin activity and glucose homeostasis.

Forkhead Domains of FOXO Transcription Factors Differ in both Overall Conformation and Dynamics.

FOXO transcription factors regulate cellular homeostasis, longevity and response to stress. FOXO1 (also known as FKHR) is a key regulator of hepatic glucose production and lipid metabolism, and its specific inhibition may have beneficial effects on diabetic hyperglycemia by reducing hepatic glucose production. Moreover, all FOXO proteins are considered potential drug targets for drug resistance prevention in cancer therapy. However, the development of specific FOXO inhibitors requires a detailed understanding of structural differences between individual FOXO DNA-binding domains. The high-resolution structure of the DNA-binding domain of FOXO1 reported in this study and its comparison with structures of other FOXO proteins revealed differences in both their conformation and flexibility. These differences are encoded by variations in protein sequences and account for the distinct functions of FOXO proteins. In particular, the positions of the helices H1, H2 and H3, whose interface form the hydrophobic core of the Forkhead domain, and the interactions between hydrophobic residues located on the interface between the N-terminal segment, the H2-H3 loop, and the recognition helix H3 differ among apo FOXO1, FOXO3 and FOXO4 proteins. Therefore, the availability of apo structures of DNA-binding domains of all three major FOXO proteins will support the development of FOXO-type-specific inhibitors.

Sex Dependent Dysregulation of Hepatic Glucose Production in Lean Type 2 Diabetic Rats.

We have characterized a lean type 2 diabetic rat model by gestational low protein programming. We aimed to identify if the regulation of hepatic glucose production (HGP) via gluconeogenesis and glycogenolysis is affected and if there are any sex differences. Fasting (6–7 months old) type 2 diabetic rats received 2H2O followed by a primed constant rate infusion of [6,6-2H2] glucose. Blood samples were drawn during steady states after 4 h of fasting and following a euglycemic hyperinsulinemic clamp. HGP and the fraction of glucose derived from gluconeogenesis under fasting and euglycemic states were measured from steady state glucose enrichments after the infusion of [6,6-2H2]glucose and 2H2O tracers. Glycogenolysis was determined by calculating the difference between total HGP and gluconeogenesis rates. Hepatic gene expression of enzymes involved in HGP were quantified using qPCR. HGP rates was similar during fasting in both groups and sexes. However, under simulated fed condition, HGP rate was suppressed in controls but not in type 2 diabetic rats. They also showed inefficient HGP suppression in a simulated fed state. Differential analysis showed that suppression of both gluconeogenesis and glycogenolysis under simulated fed state was affected in these low protein programmed type 2 diabetic rats. These effects were greater in females when compared to males. Further, key genes involved in these processes like G6Pase, Pepck, pyruvate carboxylase, and glycogen phosphorylase in liver were dysregulated. Our data shows impaired suppression of HGP via gluconeogenesis and glycogenolysis in type 2 diabetic rats with greater effects on females.

CILP-2 is a novel secreted protein and associated with insulin resistance.

Genetic association studies have implicated that cartilage intermediate layer protein 2 (CILP-2) confers the risk susceptibility for type 2 diabetes (T2DM). However, it is still unknown whether CILP-2 is involved in the regulation of glucose homeostasis and insulin resistance (IR). In the current study, we initially observed that CILP-2 as a secreted protein was detected in both conditioned medium and lysates of cells transfected with an overexpressed vector. We then found that circulating CILP-2 levels had a progressive increase from normal to impaired glucose tolerance (a pre-diabetic status) and then to diabetes, which was correlated positively with waist-to-hip ratio, triglyceride, fasting blood glucose, 2-h blood glucose after glucose overload, HbA1c, fasting insulin, 2-h plasma insulin after glucose overload, and homeostasis model assessment of insulin resistance but negatively with HDL-C. CILP-2 expression was increased in the liver and muscle but decreased in adipose tissues of obese mice or T2DM patients. Furthermore, we demonstrated that CILP-2 circulating levels were affected by OGTT and Exenatide. CILP-2 overexpression resulted in impaired glucose tolerance and hepatic IR in vivo and increased PEPCK expression whereas suppressed phosphorylation of insulin receptor and Akt kinase in vitro. Based on these findings, we have identified a direct interaction between CILP-2 and PEPCK and suggested that CILP-2 plays an important role in the regulation of hepatic glucose production.

1853-P: Transforming Growth Factor Beta 1 Acts as a Hepatokine in Control of Glucose and Energy Metabolism

Liver and adipose tissue are crucial for blood glucose and energy homeostasis, while impaired regulation of hepatic glucose production (HGP) and energy expenditure contribute to hyperglycemia and excessive fat storage in type 2 diabetes mellitus. Hepatokines are proteins secreted by hepatocytes, and several hepatokines have been shown to directly affect glucose and energy expenditure. In this study, we investigated the role of transforming growth factor beta 1 (TGF-β1) in hepatocytes in regulating glucose and energy homeostasis. We generated the liver-specific TGF-β1 knockout mice and found that the mice exhibited lower blood glucose, increased hepatic insulin sensitivity compared with wild type (WT) control mice. Using the mouse primary hepatocytes, we found that TGF-β1 deletion impaired HGP and TGF-β1 treatment promoted protein kinase A (PKA) signaling and stimulated the nuclear translocation of FoxO1. Under high fat diet (HFD) treatment, hepatic TGF-β1 deficiency protected mice from HFD-induced obesity and insulin resistance, decreased HGP and improved energy expenditure. Moreover, we used hepatic insulin receptor substrate-1, 2 (IRS1, 2) knockout (DKO) mice and deleted the TGF-β1 gene in the liver of DKO mice. We found that hepatic TGF-β1 ablation prevented hyperglycemia and hyperinsulinemia in DKO mice. Deletion of TGF-β1 or neutralization of TGF-β1 with antibody significantly decreased HGP of DKO hepatocytes. Additionally, hepatic TGF-β1 ablation enhanced thermogenesis and inguinal white adipose tissue (iWAT) browning in DKO mice. These findings underscore an important role of hepatic TGF-β1 in contribution to systemic glucose and energy homeostasis. Thus, hepatic TGF-β1 may serve as a therapeutic target for control of glucose and energy homeostasis in insulin resistance and type 2 diabetes mellitus. Disclosure Q. Pan: None. Y. Chen: None. D. Kim: None. Z. Shen: None. W. Yang: None. X. Li: None. Y. Sun: None. S. Guo: None. Funding American Diabetes Association (1-15-CD-09 to S.G.)

A New Activator of Hepatocyte CaMKII in Fasting and Type 2 Diabetes.

Positive regulation of hepatic glucose production (HGP) and stimulation of glycogenolysis during fasting are critical processes to prevent hypoglycemia. A key hormone that carries out this function is glucagon, which is secreted by pancreatic α-cells in response to fasting and acts on its receptor on hepatocytes to promote HGP and glycogenolysis (1). However, as often happens, processes that are critical in physiology can promote disease processes in nonphysiological settings. As such, glucagon-induced HGP is a major contributor to excessive HGP and hyperglycemia in obesity and type 2 diabetes (T2D) (2). In this issue of Diabetes , Wang et al. (3) provide evidence that another circulating factor that is increased in fasting and obesity/T2D—prostaglandin F2α (PGF2α)—also promotes HGP in both fasting and obese, insulin-resistant mice. Previous work has elucidated a number of pathways through which activation of the hepatocyte glucagon receptor (GcgR), which is a G-protein–coupled receptor (GPCR), promotes HGP and glycogenolysis in both fasting and obesity. Specifically, adenylyl cyclase/cyclic AMP-mediated protein kinase A (PKA) activation by G proteins of the GcgR controls the transcriptional regulation of HGP and glycogenolysis through at least three distinct but complementary processes (Fig. 1): phosphorylation of CREB, which results in recruitment of its coactivators, CBP and p300; deactivation of a kinase called SIK2; and activation of inositol 3-phosphate receptors (IP3Rs), leading to release of endoplasmic reticulum calcium into the cytosol and subsequent activation of the phosphatase calcineurin and the kinase Ca2+/calmodulin-activated protein kinase IIγ …

Regulation of hepatic glucose production and AMPK by AICAR but not by metformin depends on drug uptake through the equilibrative nucleoside transporter 1 (ENT1).

AimRecently we have observed differences in the ability of metformin and AICAR to repress glucose production from hepatocytes using 8CPT‐cAMP. Previous results indicate that, in addition to activating protein kinase A, 8CPT‐modified cAMP analogues suppress the nitrobenzylthioinosine (NBMPR)‐sensitive equilibrative nucleoside transporter ENT1. We aimed to exploit 8CPT‐cAMP, 8CPT‐2‐Methyl‐O‐cAMP and NBMPR, which is highly selective for a high‐affinity binding‐site on ENT1, to investigate the role of ENT1 in the liver‐specific glucose‐lowering properties of AICAR and metformin.MethodsPrimary mouse hepatocytes were incubated with AICAR and metformin in combination with cAMP analogues, glucagon, forskolin and NBMPR. Hepatocyte glucose production (HGP) and AMPK signalling were measured, and a uridine uptake assay with supporting LC‐MS was used to investigate nucleoside depletion from medium by cells.ResultsAICAR and metformin increased AMPK pathway phosphorylation and decreased HGP induced by dibutyryl cAMP and glucagon. HGP was also induced by 8CPT‐cAMP, 8CPT‐2‐Methyl‐O‐cAMP and NBMPR; however, in each case this was resistant to suppression by AICAR but not by metformin. Cross‐validation of tracer and mass spectrometry studies indicates that 8CPT‐cAMP, 8CPT‐2‐Methyl‐O‐cAMP and NBMPR inhibited the effects of AICAR, at least in part, by impeding its uptake into hepatocytes.ConclusionsWe report for the first time that suppression of ENT1 induces HGP. ENT1 inhibition also impedes uptake and the effects of AICAR, but not metformin, on HGP. Further investigation of nucleoside transport may illuminate a better understanding of how metformin and AICAR each regulate HGP.