Silencing of ANGPTL 3 (angiopoietin-like protein 3) in human hepatocytes results in decreased expression of gluconeogenic genes and reduced triacylglycerol-rich VLDL secretion upon insulin stimulation

We show that silencing of ANGPTL3 in human hepatocytes in addition to reducing secretion of TAG-enriched VLDL upon insulin stimulation enhances glucose uptake and improves insulin response. Thus, our data provide insight into the lower insulin and glucose levels observed in humans with ANGPTL3 loss-of-function mutation.

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Abstract 13133: Silencing of Angiopoietin-like Protein 3 ( ANGPTL3 ) in IHH- Hepatocytes Results in Increased Insulin Sensitivity and Reduced Triglyceride-rich VLDL Secretion

Circulation ◽

10.1161/circ.130.suppl_2.13133 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Anna M Tikka ◽

Pirkka-Pekka Laurila ◽

Jarkko Soronen ◽

Jari Metso ◽

Christian Ehnholm ◽

...

Keyword(s):

Insulin Sensitivity ◽

Glucose Uptake ◽

Secretory Protein ◽

Whole Body ◽

Dependent Manner ◽

Loss Of Function ◽

Insulin Stimulation ◽

Vldl Secretion ◽

Immortalized Hepatocytes ◽

Pkb Phosphorylation

AIMS: Homozygosity of loss-of-function mutations in ANGPTL3 -gene results in familial combined hypolipidemia (FHBL2,OMIM #605019) characterized by reduction of all major plasma lipoprotein classes VLDL, LDL, HDL and low circulating free fatty acids, glucose and insulin levels. Thus complete lack of ANGPTL3 in humans not only affects lipid metabolism but also whole-body insulin and glucose balance. Our aim was to investigate the function of ANGPTL3, a hepatic secretory protein, in promoting hypolipidemia and hepatic insulin sensitivity. METHODS: We used wild type and ANGPTL3-silenced human immortalized hepatocytes (IHH) to investigate the effect of ANGPTL3-silencing on hepatic VLDL secretion and glucose uptake. RESULTS: We demonstrate that insulin downregulates hepatic secretion of ANGPTL3 and triglyceride-enriched VLDL1-type particles in a dose dependent manner. Similar effect on VLDL secretion was demonstrated with a treatment of PPAR[[Unable to Display Character: ƴ]] agonist rosiglitazone. We further show that ANGPTL3-silenced cells display a more pronounced shift from the secretion of TG-enriched VLDL1-type particles to a secretion of lipid poor VLDL2-type particles during insulin stimulation. Silencing of ANGPTL3 improved hepatic glucose uptake by 20-50 % depending on the glucose and insulin concentration, resulted in a trend towards increased AKT/PKB phosphorylation upon insulin stimulation and downregulated fasting induced transcription factor PGC1α and its downstream targets. CONCLUSION: Our results indicate a similar function of both insulin and rosiglitazone regarding regulation of ANGPTL3 and VLDL secretion in hepatocytes, and suggest that insulin and PPAR[[Unable to Display Character: ƴ]] might mediate some of their functions via ANGPTL3. Our results give more insight into the liver specific role of ANGPTL3 and links silencing of ANGPTL3 with Insulin sensitivity. Since humans with elevated levels of ANGPTL3 display hyperlipidemia and insulin resistance it might be beneficial to target ANGPTL3 silencing in the liver, the major site of ANGPTL3 expression, to balance lipid and glucose homeostasis and lower risk for cardiovascular diseases.

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Muscle glucose uptake during and after exercise is normal in insulin-resistant rats

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1993.264.2.e167 ◽

1993 ◽

Vol 264 (2) ◽

pp. E167-E172 ◽

Cited By ~ 2

Author(s):

M. Kusunoki ◽

L. H. Storlien ◽

J. MacDessi ◽

N. D. Oakes ◽

C. Kennedy ◽

...

Keyword(s):

Glucose Uptake ◽

Glucose Transporter ◽

Treadmill Exercise ◽

Glycogen Synthesis ◽

Insulin Stimulation ◽

Adult Rats ◽

Insulin Resistant ◽

Glucose Levels ◽

Hindlimb Muscles ◽

Postexercise Recovery

It is not generally known whether impaired stimulation of muscle glucose metabolism in insulin-resistant states is specific to insulin stimulation. Our aim was to examine whether glucose uptake responded normally to exercise and postexercise recovery in insulin-resistant high-fat-fed (HFF) rats. Three-week HFF or Chow-fed [control (Con)] adult rats were studied 5 days after cannulation. Before, during, or immediately after (recovery) 50 min of treadmill exercise, bolus 2-deoxy-[3H]glucose and [14C]glucose were administered to estimate muscle glucose uptake (R'g) and glycogen incorporation rates. Mean exercise and recovery plasma glucose levels were similar in HFF and Con rats. In hindlimb muscles sampled, exercise and recovery R'g were similar in HFF and Con (e.g., red quadriceps exercise 104 +/- 13 vs. 113 +/- 8, recovery 45.3 +/- 3.9 vs. 47.7 +/- 4.5 mumol.100 g-1.min-1, respectively). Moreover, muscle glucose transporter (GLUT-4) content was not reduced in HFF rats. Glycogen resynthesis accounted almost entirely for R'g during recovery and was equivalent between groups. We conclude that impaired muscle glucose uptake and glycogen synthesis in HFF rats are characteristic of insulin but not of exercise or postexercise stimulation.

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DAG accumulation from saturated fatty acids desensitizes insulin stimulation of glucose uptake in muscle cells

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2001.280.2.e229 ◽

2001 ◽

Vol 280 (2) ◽

pp. E229-E237 ◽

Cited By ~ 162

Author(s):

Eulàlia Montell ◽

Marco Turini ◽

Mario Marotta ◽

Matthew Roberts ◽

Véronique Noé ◽

...

Keyword(s):

Insulin Resistance ◽

Fatty Acids ◽

Protein Kinase C ◽

Protein Kinase ◽

Glucose Uptake ◽

Insulin Response ◽

Insulin Stimulation ◽

Kinase C ◽

Basal Glucose Uptake ◽

Stimulation Of

The increased availability of saturated lipids has been correlated with development of insulin resistance, although the basis for this impairment is not defined. This work examined the interaction of saturated and unsaturated fatty acids (FA) with insulin stimulation of glucose uptake and its relation to the FA incorporation into different lipid pools in cultured human muscle. It is shown that basal or insulin-stimulated 2-deoxyglucose uptake was unaltered in cells preincubated with oleate, whereas basal glucose uptake was increased and insulin response was impaired in palmitate- and stearate-loaded cells. Analysis of the incorporation of FA into different lipid pools showed that palmitate, stearate, and oleate were similarly incorporated into phospholipids (PL) and did not modify the FA profile. In contrast, differences were observed in the total incorporation of FA into triacylglycerides (TAG): unsaturated FA were readily diverted toward TAG, whereas saturated FA could accumulate as diacylglycerol (DAG). Treatment with palmitate increased the activity of membrane-associated protein kinase C, whereas oleate had no effect. Mixture of palmitate with oleate diverted the saturated FA toward TAG and abolished its effect on glucose uptake. In conclusion, our data indicate that saturated FA-promoted changes in basal glucose uptake and insulin response were not correlated to a modification of the FA profile in PL or TAG accumulation. In contrast, these changes were related to saturated FA being accumulated as DAG and activating protein kinase C. Therefore, our results suggest that accumulation of DAG may be a molecular link between an increased availability of saturated FA and the induction of insulin resistance.

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Obstacles in the Application of Microencapsulation in Islet Transplantation

The International Journal of Artificial Organs ◽

10.1177/039139889301600407 ◽

1993 ◽

Vol 16 (4) ◽

pp. 205-212 ◽

Cited By ~ 59

Author(s):

P. De Vos ◽

G.H.J. Wolters ◽

W.M. Fritschy ◽

R. Van Schilfgaarde

Keyword(s):

Islet Transplantation ◽

Insulin Response ◽

Limiting Factors ◽

Survival Times ◽

Glucose Levels ◽

Blood Glucose Levels ◽

Functional Aspects ◽

Second Category ◽

Transplantation Site ◽

Insight Into

Several factors stand in the way of successful clinical transplantation of alginate-polylysine-alginate microencapsulated pancreatic islets. These obstacles can be classified into three categories. The first regards the technical aspects of the production process. Limiting factors are the insufficient ability to produce small capsules with an adequate production rate, and insufficient insight into the factors determining the optimal chemical and mechanical properties of the capsules. The second category regards the functional aspects of the microencapsulated islets, such as the limitations of the transplantation site and the absence of a physiologic insulin response of the encapsulated islets to elevated blood glucose levels. The third category regards the fact that survival times of encapsulated islet grafts are still limited to several weeks or months, which is mainly explained by a pericapsular fibrotic overgrowth reaction as a consequence of the bioincom-patibility of the capsule membrane. This study describes these obstacles, and thereby summarizes the requirements needed for successful clinical application of encapsulated islet transplantation.

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New Insight into Diabetes Management: From Glycemic Index to Dietary Insulin Index

Current Diabetes Reviews ◽

10.2174/1573399815666190614122626 ◽

2020 ◽

Vol 16 (4) ◽

pp. 293-300 ◽

Cited By ~ 1

Author(s):

Zahra Yari ◽

Vahideh Behrouz ◽

Hamid Zand ◽

Katayoun Pourvali

Keyword(s):

Glycemic Index ◽

Diabetes Management ◽

Glycemic Load ◽

Insulin Response ◽

Diet Therapy ◽

Current Data ◽

Diabetic Patients ◽

Carbohydrate Counting ◽

Insulin Requirements ◽

Insight Into

Background: Despite efforts to control hyperglycemia, diabetes management is still challenging. This may be due to focusing on reducing hyperglycemia and neglecting the importance of hyperinsulinemia; while insulin resistance and resultant hyperinsulinemia preceded diabetes onset and may contribute to disease pathogenesis. Objective: The present narrative review attempts to provide a new insight into the management of diabetes by exploring different aspects of glycemic index and dietary insulin index. Results: The current data available on this topic is limited and heterogeneous. Conventional diet therapy for diabetes management is based on reducing postprandial glycemia through carbohydrate counting, choosing foods with low-glycemic index and low-glycemic load. Since these indicators are only reliant on the carbohydrate content of foods and do not consider the effects of protein and fat on the stimulation of insulin secretion, they cannot provide a comprehensive approach to determine the insulin requirements. Conclusion: Selecting foods based on carbohydrate counting, glycemic index or glycemic load are common guides to control glycemia in diabetic patients, but neglect the insulin response, thus leading to failure in diabetes management. Therefore, paying attention to insulinemic response along with glycemic response seems to be more effective in managing diabetes.

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High glucose and insulin in combination cause insulin receptor substrate-1 and -2 depletion and protein kinase B desensitisation in primary cultured rat adipocytes: possible implications for insulin resistance in type 2 diabetes

Acta Endocrinologica ◽

10.1530/eje.0.1480157 ◽

2003 ◽

Vol 148 (1) ◽

pp. 157-167 ◽

Cited By ~ 43

Author(s):

J Buren ◽

HX Liu ◽

J Lauritz ◽

JW Eriksson

Keyword(s):

Glucose Uptake ◽

High Glucose ◽

Insulin Treatment ◽

Insulin Signalling ◽

Binding Capacity ◽

Insulin Binding ◽

Rat Adipocytes ◽

Glucose Levels ◽

High Insulin ◽

The Right

OBJECTIVE: The purpose of this study was to investigate the cellular effects of long-term exposure to high insulin and glucose levels on glucose transport and insulin signalling proteins. DESIGN AND METHODS: Rat adipocytes were cultured for 24 h in different glucose concentrations with 10(4) microU/ml of insulin or without insulin. After washing, (125)I-insulin binding, basal and acutely insulin-stimulated d-[(14)C]glucose uptake, and insulin signalling proteins and glucose transporter 4 (GLUT4) were assessed. RESULTS: High glucose (15 and 25 mmol/l) for 24 h induced a decrease in basal and insulin-stimulated glucose uptake compared with control cells incubated in low glucose (5 or 10 mmol/l). Twenty-four hours of insulin treatment decreased insulin binding capacity by approximately 40%, and shifted the dose-response curve for insulin's acute effect on glucose uptake 2- to 3-fold to the right. Twenty-four hours of insulin treatment reduced basal and insulin-stimulated glucose uptake only in the presence of high glucose (by approximately 30-50%). At high glucose, insulin receptor substrate-1 (IRS-1) expression was downregulated by approximately 20-50%, whereas IRS-2 was strongly upregulated by glucose levels of 10 mmol/l or more (by 100-400%). Insulin treatment amplified the suppression of IRS-1 when combined with high glucose and also IRS-2 expression was almost abolished. Twenty-four hours of treatment with high glucose or insulin, alone or in combination, shifted the dose-response curve for insulin's effect to acutely phosphorylate protein kinase B (PKB) to the right. Fifteen mmol/l glucose increased GLUT4 in cellular membranes (by approximately 140%) compared with 5 mmol/l but this was prevented by a high insulin concentration. CONCLUSIONS: Long-term exposure to high glucose per se decreases IRS-1 but increases IRS-2 content in rat adipocytes and it impairs glucose transport capacity. Treatment with high insulin downregulates insulin binding capacity and, when combined with high glucose, it produces a marked depletion of IRS-1 and -2 content together with an impaired sensitivity to insulin stimulation of PKB activity. These mechanisms may potentially contribute to insulin resistance in type 2 diabetes.

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Insulin and glucagon in rats with Islet cell tumors Induced by small doses of streptozofoclii

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y81-121 ◽

1981 ◽

Vol 59 (8) ◽

pp. 818-823 ◽

Cited By ~ 2

Author(s):

Gen Yoshino ◽

Tsutomu Kazumi ◽

Soichiro Morita ◽

Shighaki Baba

Keyword(s):

Plasma Glucose ◽

Islet Cell ◽

Insulin Response ◽

Oral Glucose ◽

Islet Cell Tumors ◽

Glucose Levels ◽

Tumor Bearing ◽

Small Doses ◽

Wet Weight ◽

Glucose Plasma

Plasma insulin and glucagon responses to oral glucose loading were examined in rats with islet cell tumors induced by a single intravenous injection of streptozotocin (30 or 40 mg/kg body weight). Twenty-four macroscopic and six microscopic tumors occurred in 21 rats. In 15 of 21 tumor-bearing rats, there was exaggerated insulin release in response to oral glucose. Plasma glucose levels did not rise with the oral glucose load and were comparable to those seen in normal animals. Hence these rats are described as having "responsive tumors." In six rats with "nonresponsive tumors" there was no insulin response and the plasma glucose levels rose. No significant differences in plasma glucagon levels were observed between the two groups. Nonresponsive tumors as well as responsive tumors contained a significant amount of extractable insulin (17.68 ± 8.60 and 35.07 ± 10.05 mg/g wet weight, respectively) and detectable amounts of immunoreactive glucagon (1.47 ± 0.61 and 2.24 ± 0.67 μg/g wet weight, respectively).These results suggest that a small dose of streptozotocin produces two types of islet cell tumors. One is insulin producing and insulin secreting whereas the other is insulin producing but not insulin secreting.

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