scholarly journals Glucagon resistance and decreased susceptibility to diabetes in a model of chronic hyperglucagonemia

2020 ◽  
Author(s):  
Ada Admin ◽  
Nadejda Bozadjieva Kramer ◽  
Camila Lubaczeuski ◽  
Manuel Blandino-Rosano ◽  
Grant Barker ◽  
...  
Keyword(s):  
Glucose Homeostasis ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Cell Mass ◽  
Glucagon Secretion ◽  
Glucagon Receptor ◽  
Glucose Levels ◽  
Conditional Deletion ◽  
Mtorc1 Signaling ◽  
Nutrient Signaling ◽  
A Cell

Elevation of glucagon levels and increase in a-cell mass are associated with states of hyperglycemia in diabetes. Our previous studies have highlighted the role of nutrient signaling via mTOR Complex 1 (mTORC1) regulation that controls glucagon secretion and a-cell mass. The current studies investigated the effects of activation of nutrient signaling by conditional deletion of the mTORC1 inhibitor, TSC2, in a-cells (aTSC2<sup>KO</sup>). We showed that activation of mTORC1 signaling is sufficient to induce chronic hyperglucagonemia as a result of a-cell proliferation, cell size and mass expansion. Hyperglucagonemia in aTSC2<sup>KO</sup> was associated with an increase in glucagon content and enhanced glucagon secretion. This model allowed us to identify the effects of chronic hyperglucagonemia on glucose homeostasis by inducing insulin secretion and resistance to glucagon in the liver. Liver glucagon resistance in aTSC2<sup>KO</sup> mice were characterized by reduced expression of the glucagon receptor (GCGR), phosphoenolpyruvate carboxykinase (PEPCK) and genes involved in amino acid metabolism and urea production. Glucagon resistance in aTSC2<sup>KO</sup> mice was associated with improved glucose levels in Streptozotocin (STZ)-induced β-cell destruction and HFD-induced glucose intolerance. These studies demonstrate that chronic hyperglucagonemia can improve glucose homeostasis by inducing glucagon resistance in the liver.

scholarly journals Glucagon resistance and decreased susceptibility to diabetes in a model of chronic hyperglucagonemia

2020 ◽  
Author(s):  
Nadejda Bozadjieva Kramer ◽  
Camila Lubaczeuski ◽  
Manuel Blandino-Rosano ◽  
Grant Barker ◽  
George K. Gittes ◽  
...  
Keyword(s):  
Glucose Homeostasis ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Cell Mass ◽  
Glucagon Secretion ◽  
Glucagon Receptor ◽  
Glucose Levels ◽  
Conditional Deletion ◽  
Mtorc1 Signaling ◽  
Nutrient Signaling ◽  
A Cell

Elevation of glucagon levels and increase in a-cell mass are associated with states of hyperglycemia in diabetes. Our previous studies have highlighted the role of nutrient signaling via mTOR Complex 1 (mTORC1) regulation that controls glucagon secretion and a-cell mass. The current studies investigated the effects of activation of nutrient signaling by conditional deletion of the mTORC1 inhibitor, TSC2, in a-cells (aTSC2<sup>KO</sup>). We showed that activation of mTORC1 signaling is sufficient to induce chronic hyperglucagonemia as a result of a-cell proliferation, cell size and mass expansion. Hyperglucagonemia in aTSC2<sup>KO</sup> was associated with an increase in glucagon content and enhanced glucagon secretion. This model allowed us to identify the effects of chronic hyperglucagonemia on glucose homeostasis by inducing insulin secretion and resistance to glucagon in the liver. Liver glucagon resistance in aTSC2<sup>KO</sup> mice were characterized by reduced expression of the glucagon receptor (GCGR), phosphoenolpyruvate carboxykinase (PEPCK) and genes involved in amino acid metabolism and urea production. Glucagon resistance in aTSC2<sup>KO</sup> mice was associated with improved glucose levels in Streptozotocin (STZ)-induced β-cell destruction and HFD-induced glucose intolerance. These studies demonstrate that chronic hyperglucagonemia can improve glucose homeostasis by inducing glucagon resistance in the liver.

scholarly journals Glucagon resistance and decreased susceptibility to diabetes in a model of chronic hyperglucagonemia

2020 ◽  
Author(s):  
Nadejda Bozadjieva Kramer ◽  
Camila Lubaczeuski ◽  
Manuel Blandino-Rosano ◽  
Grant Barker ◽  
George K. Gittes ◽  
...  
Keyword(s):  
Glucose Homeostasis ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Cell Mass ◽  
Glucagon Secretion ◽  
Glucagon Receptor ◽  
Glucose Levels ◽  
Conditional Deletion ◽  
Mtorc1 Signaling ◽  
Nutrient Signaling ◽  
A Cell

Elevation of glucagon levels and increase in a-cell mass are associated with states of hyperglycemia in diabetes. Our previous studies have highlighted the role of nutrient signaling via mTOR Complex 1 (mTORC1) regulation that controls glucagon secretion and a-cell mass. The current studies investigated the effects of activation of nutrient signaling by conditional deletion of the mTORC1 inhibitor, TSC2, in a-cells (aTSC2<sup>KO</sup>). We showed that activation of mTORC1 signaling is sufficient to induce chronic hyperglucagonemia as a result of a-cell proliferation, cell size and mass expansion. Hyperglucagonemia in aTSC2<sup>KO</sup> was associated with an increase in glucagon content and enhanced glucagon secretion. This model allowed us to identify the effects of chronic hyperglucagonemia on glucose homeostasis by inducing insulin secretion and resistance to glucagon in the liver. Liver glucagon resistance in aTSC2<sup>KO</sup> mice were characterized by reduced expression of the glucagon receptor (GCGR), phosphoenolpyruvate carboxykinase (PEPCK) and genes involved in amino acid metabolism and urea production. Glucagon resistance in aTSC2<sup>KO</sup> mice was associated with improved glucose levels in Streptozotocin (STZ)-induced β-cell destruction and HFD-induced glucose intolerance. These studies demonstrate that chronic hyperglucagonemia can improve glucose homeostasis by inducing glucagon resistance in the liver.

scholarly journals Functional and Structural Adaptations in the Pancreatic α-Cell and Changes in Glucagon Signaling During Protein Malnutrition

Endocrinology ◽  
2012 ◽  
Vol 153 (4) ◽  
pp. 1663-1672 ◽  
Author(s):  
Laura Marroquí ◽  
Thiago M. Batista ◽  
Alejandro Gonzalez ◽  
Elaine Vieira ◽  
Alex Rafacho ◽  
...  
Keyword(s):  
Gene Expression ◽  
Glucose Homeostasis ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Cell Function ◽  
Cell Mass ◽  
Protein Malnutrition ◽  
Peroxisome Proliferator ◽  
Glucagon Receptor ◽  
Peroxisome Proliferator Activated Receptor ◽  
Regulated Gene Expression

Chronic malnutrition leads to multiple changes in β-cell function and peripheral insulin actions to adapt glucose homeostasis to these restricted conditions. However, despite glucose homeostasis also depends on glucagon effects, the role of α-cells in malnutrition is largely unknown. Here, we studied α-cell function and hepatic glucagon signaling in mice fed with low-protein (LP) or normal-protein diet for 8 wk after weaning. Using confocal microscopy, we found that inhibition of Ca2+ signaling by glucose was impaired in α-cells of LP mice. Consistent with these findings, the ability of glucose to inhibit glucagon release in isolated islets was also diminished in LP mice. This altered secretion was not related with changes in either glucagon gene expression or glucagon content. A morphometric analysis showed that α-cell mass was significantly increased in malnourished animals, aspect that was probably related with their enhanced plasma glucagon levels. When we analyzed the hepatic function, we observed that the phosphorylation of protein kinase A and cAMP response-binding element protein in response to fasting or exogenous glucagon was impaired in LP mice. Additionally, the up-regulated gene expression in response to fasting observed in the hepatic glucagon receptor as well as several key hepatic enzymes, such as peroxisome proliferator-activated receptor γ, glucose-6-phosphatase, and phosphoenolpyruvate carboxykinase, was altered in malnourished animals. Finally, liver glycogen mobilization in response to fasting and the ability of exogenous glucagon to raise plasma glucose levels were lower in LP mice. Therefore, chronic protein malnutrition leads to several alterations in both the α-cell function and hepatic glucagon signaling.

scholarly journals Impacts of pre- and postnatal nutrition on glucagon regulation and hepatic signalling in sheep

2018 ◽  
Vol 238 (1) ◽  
pp. 1-12
Author(s):  
Bishnu Adhikari ◽  
Prabhat Khanal ◽  
Mette Olaf Nielsen
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Glucagon Secretion ◽  
Late Gestation ◽  
Plasma Glucagon ◽  
Glucagon Receptor ◽  
Protein Requirements ◽  
Daily Energy ◽  
Obesogenic Diet ◽  
Prenatal Undernutrition

To evaluate the long-term impacts of early-life nutritional manipulations on glucagon secretion and hepatic signalling, thirty-six twin-pregnant ewes during their last trimester were exposed to NORM (fulfilling 100% of daily energy/protein requirements), HIGH (fulfilling 150/110% of daily energy/protein requirements) or LOW (50% of NORM) diets. Twin lambs were assigned after birth to a moderate (CONV) or high-carbohydrate high-fat (HCHF) diet until 6 months. Then, responses in plasma glucagon concentrations and glucagon ratios relative to previously reported values for insulin, glucose and lactate were determined after intravenous bolus injections of glucose or propionate (fed and 2-day fasting state). Hepatic mRNA expressions of glucagon receptor (GCGR), glucose-6-phosphatase (G6PC), phosphoenolpyruvate carboxykinase (PEPCK) and fructose 1,6-biphosphatase (FBP) were also determined in a sub group of autopsied lambs. Expression of GCGR and all three enzymes were supressed by prenatal LOW compared to NORM (except PEPCK) and HIGH (except FBP) nutrition. The postnatal HCHF diet reduced plasma glucagon responses to propionate and hepatic mRNA expression of all genes. In response to propionate, insulin/glucagon ratio was decreased (fasted state), but lactate/glucagon and glucose/glucagon increased in HCHF compared to CONV lambs. In conclusion, prenatal undernutrition and postnatal overnutrition had similar long-term implications and reduced hepatic glucagon signalling. Glucagon secretory responses to propionate were, however, not related to the prenatal nutrition history, but negatively affected by the postnatal obesogenic diet. The pancreatic α-cell compared to β-cells may thus be less sensitive towards late gestation malnutrition, whereas hepatic glucagon signalling appears to be a target of prenatal programming.

Antibiotic-induced microbiome depletion alters renal glucose metabolism and exacerbates renal injury after ischemia-reperfusion injury in mice

2021 ◽  
Author(s):  
Yuika Osada ◽  
Shunsaku Nakagawa ◽  
Kanako Ishibe ◽  
Shota Takao ◽  
Aimi Shimazaki ◽  
...  
Keyword(s):  
Glucose Metabolism ◽  
Glucose Homeostasis ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Critical Role ◽  
Kidney Injury ◽  
Short Chain Fatty Acids ◽  
Glucose Levels ◽  
The Impact

Recent studies have revealed the impact of antibiotic-induced microbiome depletion (AIMD) on host glucose homeostasis. The kidney has a critical role in systemic glucose homeostasis; however, information regarding the association between AIMD and renal glucose metabolism remains limited. Hence, we aimed to determine the effects of AIMD on renal glucose metabolism by inducing gut microbiome depletion using an antibiotic cocktail (ABX) composed of ampicillin, vancomycin, and levofloxacin in mice. The results showed that the bacterial 16s rRNA expression, luminal concentrations of short-chain fatty acids and bile acids, and plasma glucose levels were significantly lower in ABX-treated mice than in vehicle-treated mice. In addition, ABX treatment significantly reduced renal glucose and pyruvate levels. The mRNA expression levels of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase in the renal cortex were significantly higher in ABX-treated mice than in vehicle-treated mice. We further examined the impact of AIMD on the altered metabolic status in mice after ischemia-induced kidney injury. After exposure to ischemia for 60 min, the renal pyruvate concentrations were significantly lower in ABX-treated mice than in vehicle-treated mice. ABX treatment caused a more severe tubular injury after ischemia-reperfusion (IR). Our findings confirm that AIMD is associated with decreased pyruvate levels in the kidney, which may have been caused by the activation of renal gluconeogenesis. Thus, we hypothesized that AIMD would increase the vulnerability of the kidney to IR injury.

scholarly journals Glucagon Deficiency Reduces Hepatic Glucose Production and Improves Glucose Tolerance In Adult Mice

2010 ◽  
Vol 31 (4) ◽  
pp. 606-606
Author(s):  
Aidan S. Hancock ◽  
Aiping Du ◽  
Jingxuan Liu ◽  
Mayumi Miller ◽  
Catherine L. May
Keyword(s):  
Glucose Homeostasis ◽  
Hepatic Glucose Production ◽  
Glucose Production ◽  
Postprandial Glucose ◽  
Glucagon Receptor ◽  
Glucose Levels ◽  
Adult Mice ◽  
Hepatic Glucose ◽  
Knockout Animals

Abstract The major role of glucagon is to promote hepatic gluconeogenesis and glycogenolysis to raise blood glucose levels during hypoglycemic conditions. Several animal models have been established to examine the in vivo function of glucagon in the liver through attenuation of glucagon via glucagon receptor knockout animals and pharmacological interventions. To investigate the consequences of glucagon loss to hepatic glucose production and glucose homeostasis, we derived mice with a pancreas specific ablation of the α-cell transcription factor, Arx, resulting in a complete loss of the glucagon-producing pancreatic α-cell. Using this model, we found that glucagon is not required for the general health of mice but is essential for total hepatic glucose production. Our data clarifies the importance of glucagon during the regulation of fasting and postprandial glucose homeostasis.

scholarly journals An AlphaScreen Assay for the Discovery of Synthetic Chemical Inhibitors of Glucagon Production

2015 ◽  
Vol 21 (4) ◽  
pp. 325-332 ◽  
Author(s):  
Matthew R. Evans ◽  
Shuguang Wei ◽  
Bruce A. Posner ◽  
Roger H. Unger ◽  
Michael G. Roth
Keyword(s):  
Cell Culture ◽  
Small Molecules ◽  
Culture Media ◽  
Glucagon Secretion ◽  
Cell Culture Media ◽  
Glucagon Receptor ◽  
Synthetic Compounds ◽  
Glucose Levels ◽  
Blood Glucose Levels ◽  
Chemical Inhibitors

Glucose homeostasis is primarily controlled by two opposing hormones, insulin and glucagon, and diabetes results when insulin fails to inhibit glucagon action. Recent efforts to control glucagon in diabetes have focused on antagonizing the glucagon receptor, which is effective in lowering blood glucose levels but leads to hyperglucogonemia in rodents. An alternative strategy would be to control glucagon production with small molecules. In pursuit of this goal, we developed a homogeneous AlphaScreen assay for measuring glucagon in cell culture media and used this in a high-throughput screen to discover synthetic compounds that inhibited glucagon secretion from an alpha cell–like cell line. Some of these compounds inhibited transcription of the glucagon gene.

scholarly journals Prevention of Diabetes in db/db Mice by Dietary Soy Is Independent of Isoflavone Levels

Endocrinology ◽  
2012 ◽  
Vol 153 (11) ◽  
pp. 5200-5211 ◽  
Author(s):  
Céline Zimmermann ◽  
Christopher R. Cederroth ◽  
Lucie Bourgoin ◽  
Michelangelo Foti ◽  
Serge Nef
Keyword(s):  
Glucose Homeostasis ◽  
Cell Function ◽  
Hepatic Glucose Production ◽  
Cell Mass ◽  
Glucose Production ◽  
Metabolic Effects ◽  
Pancreatic Β Cell ◽  
Β Cell ◽  
Glucose Levels ◽  
Hepatic Glucose

Abstract Recent evidence points towards the beneficial use of soy proteins and isoflavones to improve glucose control and slow the progression of type 2 diabetes. Here, we used diabetic db/db mice fed a high soy-containing diet (SD) or a casein soy-free diet to investigate the metabolic effects of soy and isoflavones consumption on glucose homeostasis, hepatic glucose production, and pancreatic islet function. Male db/db mice fed with a SD exhibited a robust reduction in hyperglycemia (50%), correlating with a reduction in hepatic glucose production and preserved pancreatic β-cell function. The rapid decrease in fasting glucose levels resulted from an inhibition of gluconeogenesis and an increase in glycolysis in the liver of db/db mice. Soy consumption also prevented the loss of pancreatic β-cell mass and thus improved glucose-stimulated insulin secretion (3-fold), which partly accounted for the overall improvements in glucose homeostasis. Comparison of SD effects on hyperglycemia with differing levels of isoflavones or with purified isoflavones indicate that the beneficial physiological effects of soy are not related to differences in their isoflavone content. Overall, these findings suggest that consumption of soy is beneficial for improving glucose homeostasis and delaying the progression of diabetes in the db/db mice but act independently of isoflavone concentration.

Physiology of Proglucagon Peptides: Role of Glucagon and GLP-1 in Health and Disease

2015 ◽  
Vol 95 (2) ◽  
pp. 513-548 ◽  
Author(s):  
Darleen A. Sandoval ◽  
David A. D'Alessio
Keyword(s):  
Glucose Homeostasis ◽  
Energy Homeostasis ◽  
Glucose Production ◽  
Glucagon Secretion ◽  
The Body ◽  
Pharmacological Interaction ◽  
Glucose Levels ◽  
Health And Disease ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

The preproglucagon gene ( Gcg) is expressed by specific enteroendocrine cells (L-cells) of the intestinal mucosa, pancreatic islet α-cells, and a discrete set of neurons within the nucleus of the solitary tract. Gcg encodes multiple peptides including glucagon, glucagon-like peptide-1, glucagon-like peptide-2, oxyntomodulin, and glicentin. Of these, glucagon and GLP-1 have received the most attention because of important roles in glucose metabolism, involvement in diabetes and other disorders, and application to therapeutics. The generally accepted model is that GLP-1 improves glucose homeostasis indirectly via stimulation of nutrient-induced insulin release and by reducing glucagon secretion. Yet the body of literature surrounding GLP-1 physiology reveals an incompletely understood and complex system that includes peripheral and central GLP-1 actions to regulate energy and glucose homeostasis. On the other hand, glucagon is established principally as a counterregulatory hormone, increasing in response to physiological challenges that threaten adequate blood glucose levels and driving glucose production to restore euglycemia. However, there also exists a potential role for glucagon in regulating energy expenditure that has recently been suggested in pharmacological studies. It is also becoming apparent that there is cross-talk between the proglucagon derived-peptides, e.g., GLP-1 inhibits glucagon secretion, and some additive or synergistic pharmacological interaction between GLP-1 and glucagon, e.g., dual glucagon/GLP-1 agonists cause more weight loss than single agonists. In this review, we discuss the physiological functions of both glucagon and GLP-1 by comparing and contrasting how these peptides function, variably in concert and opposition, to regulate glucose and energy homeostasis.

scholarly journals CREBH Maintains Circadian Glucose Homeostasis by Regulating Hepatic Glycogenolysis and Gluconeogenesis

2017 ◽  
Vol 37 (14) ◽  
Author(s):  
Hyunbae Kim ◽  
Ze Zheng ◽  
Paul D. Walker ◽  
Gregory Kapatos ◽  
Kezhong Zhang
Keyword(s):  
Blood Glucose ◽  
Glucose Homeostasis ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Liver Glycogen ◽  
Glycogen Storage ◽  
Hepatic Glycogen ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Glucose Levels ◽  
Blood Glucose Levels

ABSTRACT Cyclic AMP-responsive element binding protein, hepatocyte specific (CREBH), is a liver-enriched, endoplasmic reticulum-tethered transcription factor known to regulate the hepatic acute-phase response and lipid homeostasis. In this study, we demonstrate that CREBH functions as a circadian transcriptional regulator that plays major roles in maintaining glucose homeostasis. The proteolytic cleavage and posttranslational acetylation modification of CREBH are regulated by the circadian clock. Functionally, CREBH is required in order to maintain circadian homeostasis of hepatic glycogen storage and blood glucose levels. CREBH regulates the rhythmic expression of the genes encoding the rate-limiting enzymes for glycogenolysis and gluconeogenesis, including liver glycogen phosphorylase (PYGL), phosphoenolpyruvate carboxykinase 1 (PCK1), and the glucose-6-phosphatase catalytic subunit (G6PC). CREBH interacts with peroxisome proliferator-activated receptor α (PPARα) to synergize its transcriptional activities in hepatic gluconeogenesis. The acetylation of CREBH at lysine residue 294 controls CREBH-PPARα interaction and synergy in regulating hepatic glucose metabolism in mice. CREBH deficiency leads to reduced blood glucose levels but increases hepatic glycogen levels during the daytime or upon fasting. In summary, our studies revealed that CREBH functions as a key metabolic regulator that controls glucose homeostasis across the circadian cycle or under metabolic stress.

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