scholarly journals Insulin effects on apolipoprotein B production by normal, diabetic and treated-diabetic rat liver and cultured rat hepatocytes

1989 ◽  
Vol 261 (1) ◽  
pp. 83-88 ◽  
Author(s):  
J D Sparks ◽  
C E Sparks ◽  
L L Miller
Keyword(s):  
Primary Cultures ◽  
Rat Hepatocytes ◽  
Insulin Injection ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Apo B ◽  
Hormone Effect ◽  
Daily Insulin Injection ◽  
The Media ◽  
Rat Livers

1. The effect of insulin on apolipoprotein (apo B) secretion was studied in 24 h recirculating liver perfusions of isolated normal, diabetic and insulin-treated diabetic rats. In single perfusions from each group apo B accumulated in the media in a linear fashion. 2 In perfusions of normal rat livers, when the medium contained insulin plus cortisol, apo B production was significantly inhibited (by 35.8%), demonstrating a hormone effect on apo B secretion. 3. In perfusions of diabetic-rat livers, apo B production was decreased to 11.8% of normal when the medium contained no hormones, and was not significantly changed by the addition of insulin plus cortisol to the medium, suggesting that the hormone effect on apo B secretion is missing in long-term hypoinsulinaemic states. 4. Treatment of diabetic rats with daily insulin injection restored apo B production and restored the effect of insulin plus cortisol in the medium to inhibit apo B secretion during perfusion. 5. Parallel studies of apo B secretion with insulin alone, cortisol alone and insulin plus cortisol in the medium were performed in primary cultures of hepatocytes to compare results from liver perfusions. 6. Apo B secretion by hepatocytes from normal, diabetic and treated-diabetic rats was inhibited (by 36.8%, 57.1% and 57.9% respectively) when insulin alone was added to the medium. 7. Insulin plus cortisol inhibited apo B secretion by hepatocytes from normal and treated diabetic rats (by 30.2% and 47.2% respectively), but failed to inhibit apo B secretion by hepatocytes from diabetic rats.

Studies on regulatory mechanisms of heme biosynthesis in hepatocytes from normal and experimental-diabetic rats. Role of insulin

1990 ◽  
Vol 68 (6) ◽  
pp. 914-921 ◽  
Author(s):  
Eduardo T. Cánepa ◽  
Elena B. C. Llambías ◽  
Moisés Grinstein
Keyword(s):  
Aminolevulinic Acid ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Inhibitory Effect ◽  
Diabetic Rats ◽  
Significant Inhibition ◽  
Diabetic Rat ◽  
Experimental Conditions ◽  
Cytochrome P 450

In the present work we demonstrate that insulin decreases the phenobarbital-induced activities of δ-aminolevulinic acid synthase and ferrochelatase in isolated hepatocytes from normal and experimental-diabetic rats. Insulin concentrations required to produce significant inhibition in diabetic hepatocytes were higher than in normal cells. Under similar experimental conditions, insulin decreased the basal activities of δ-aminolevulinic acid synthase and ferrochelatase in hepatocytes from normal rats; no inhibitory effect was observed on the basal activity of δ-aminolevulinic acid synthase in hepatocytes from diabetic rats. Cytochrome P-450 content of both normal and diabetic cells was not affected by insulin in absence or presence of phenobarbital. The inhibitory action of insulin was exerted even when effective concentrations of glucagon, dexamethasone, or 8-(p-chlorophenylthio)-cAMP were present.Key words: δ-aminolevulinic acid synthase, ferrochelatase, cAMP, insulin, diabetic rat hepatocytes.

scholarly journals Synchronized synthesis and intracellular transport of serum albumin and apolipoprotein B in cultured rat hepatocytes as studied by double immunofluorescence.

1986 ◽  
Vol 34 (9) ◽  
pp. 1223-1230 ◽  
Author(s):  
G A Keller ◽  
C Glass ◽  
D Louvard ◽  
D Steinberg ◽  
S J Singer
Keyword(s):  
Serum Albumin ◽  
Apolipoprotein B ◽  
Intracellular Transport ◽  
Primary Cultures ◽  
Rat Hepatocytes ◽  
Cell System ◽  
Secretory Proteins ◽  
Transport Pathway ◽  
Apo B ◽  
Normal Rat

Synthesis and intracellular transport of two secretory proteins, serum albumin (SA) and apolipoprotein B (apo B) have been synchronized in primary cultures of normal rat hepatocytes to make possible immunocytochemical study of the transport pathway. Under appropriate conditions of cycloheximide treatment, synthesis of new protein was inhibited and, by double immunofluorescent labeling, the cells were found to be largely depleted of the SA and apo B previously synthesized. Re-initiation of protein synthesis led to sequential appearance of SA and apo B, first in the endoplasmic reticulum, then in the Golgi complex, and finally at the cell surface. These results indicate that it should be feasible to use this cell system for high-resolution investigation of the sequence of structures involved in intracellular transport of SA and apo B by corresponding immunolabeling experiments as observed by electron microscopy.

scholarly journals Insulin-mediated inhibition of apolipoprotein B secretion requires an intracellular trafficking event and phosphatidylinositol 3-kinase activation: studies with brefeldin A and wortmannin in primary cultures of rat hepatocytes

1996 ◽  
Vol 313 (2) ◽  
pp. 567-574 ◽  
Author(s):  
Janet D. SPARKS ◽  
Thuy L. PHUNG ◽  
Mary BOLOGNINO ◽  
Charles E. SPARKS
Keyword(s):  
Apolipoprotein B ◽  
Enzyme Inhibitor ◽  
Primary Cultures ◽  
Brefeldin A ◽  
Rat Hepatocytes ◽  
Phosphatidylinositol 3 Kinase ◽  
Apo B ◽  
Insulin Effect ◽  
Insulin Inhibition ◽  
Phosphatidylinositol 3

Insulin inhibition of the secretion of apolipoprotein B (apo B) was studied in primary cultures of rat hepatocytes by using brefeldin A (BFA), an inhibitor of protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus, and by using the phosphatidylinositol 3-kinase (PI 3-K) inhibitor wortmannin. Incubation of hepatocytes with BFA (10 μg/ml) for 1 h inhibited the subsequent secretion of apo B, albumin and transferrin for up to 3 h. BFA treatment resulted in the time-dependent accumulation in cells of [14C]leucine-labelled proteins and apo B. Under conditions where insulin decreased total apo B (cell plus secreted), BFA blocked the insulin-dependent effect. These results suggest that export of apo B from the ER is a prerequisite for the observed insulin effect. Treatment of hepatocytes with wortmannin for 20 min abolished insulin inhibition of apo B secretion, suggesting that the insulin effect on the apo B pathway involves activation of PI 3-K. Enzyme inhibitor studies indicate that chymostatin and (+)-(2S,3S)-3-[(S)-methyl-1-(3-m e t h y l b u t y l c a r b a m o y l) - b u t y l c a r b a m o y l] - 2-oxiranecarboxylate (E-64-c) partially block insulin effects on apo B compared with leupeptin, which had no discernible effect. The cell-permeable derivative of E-64-c, EST, and N-Ac-Leu-Leu-norleucinal (ALLN) were most effective in blocking insulin effects on apo B. These results suggest that insulin action on apo B in primary rat hepatocytes involves (1) vesicular movement of apo B from the ER; (2) activation of PI 3-K and (3) a cellular protease that is either a cysteine- or calcium-activated neutral protease.

Sorghum (Sorghum bicolor) Extract Affects Plasma Lipid Metabolism and Hepatic Macrophage Infiltration in Diabetic Rats

2020 ◽  
Vol 16 (5) ◽  
pp. 824-832 ◽  
Author(s):  
Yuuka Mukai ◽  
Saori Kataoka ◽  
Shin Sato
Keyword(s):  
Lipid Metabolism ◽  
Sorghum Bicolor ◽  
Plasma Lipid ◽  
Diabetic Rats ◽  
Macrophage Infiltration ◽  
Diabetic Rat ◽  
Hepatic Expression ◽  
Protein Levels ◽  
Chronic Hyperglycemia ◽  
Rat Livers

Background: Chronic hyperglycemia is known to be a high-risk factor for progressive chronic liver diseases, such as abnormal lipid metabolism. The activation of AMP-activated protein kinase (AMPK) has a beneficial effect on dyslipidemia. Polyphenols derived from various plants are involved in AMPK activation. Objective: We investigated the effects of polyphenol-containing sorghum (Sorghum bicolor) extract (SE) on plasma lipid metabolism and macrophage infiltration, and measured the expression and phosphorylation of AMPK and acetyl-CoA carboxylase (ACC) in diabetic rat livers. Methods: Streptozotocin-induced diabetic rats received 0, 50, or 250 mg/kg of SE orally for 4 weeks. Blood chemistry, total and phosphorylated protein levels of AMPK and ACC, sterol regulatory element- binding protein-1c (SREBP-1c) mRNA and protein levels, and macrophage infiltration in the livers were examined. Results: Plasma glucose and triacylglycerol levels, which were increased in the untreated diabetic rats, were significantly lower in the 250 mg/kg SE-treated diabetic rats. AMPK and ACC phosphorylation levels were significantly increased in the 250 mg/kg SE-treated diabetic rats compared with those in the untreated rats. There was no difference in the hepatic expression of SREBP-1c between the diabetic rat groups. Macrophage infiltration in the liver was suppressed by 250 mg/kg of SEtreatment. Conclusion: These data suggest that SE treatment may affect plasma lipid metabolism and chronic inflammation by upregulating phosphorylation of AMPK and ACC in diabetic rat livers.

Studies on regulatory mechanisms of heme biosynthesis in hepatocytes from normal and experimental-diabetic rats. Role of cAMP

1989 ◽  
Vol 67 (11-12) ◽  
pp. 751-758 ◽  
Author(s):  
Eduardo T. Cánepa ◽  
Elena B. C. Llambías ◽  
Moisés Grinstein
Keyword(s):  
Aminolevulinic Acid ◽  
Rat Hepatocytes ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Intracellular Camp ◽  
Induction Effect ◽  
Isolated Rat Hepatocytes ◽  
Camp Content ◽  
Cytochrome P 450 ◽  
Phenobarbital Induction

In the present work we have been able to demonstrate the existence of some interrelationship between intracellular level of cAMP content and phenobarbital induction of δ-aminolevulinic acid synthase, ferrochelatase, and cytochrome P-450 biosynthesis in isolated rat hepatocytes. The increase of the level of intracellular cAMP produced by activators of adenylate cyclase, inhibitors of phosphodiesterase, or added cyclic nucleotides is reflected by an increase of the phenobarbital induction effect. The greater induction observed in hepatocytes of diabetic rats may be due to a higher level of the intracellular cAMP. The lack of potentiation of added cAMP in diabetic cells is mainly due to the fact that the maximum induction that could be attained is already achieved by the effect of the preexisting high level of the endogenous cAMP.Key words: δ-aminolevulinic acid synthase, ferrochelatase, cytochrome P-450, cAMP, diabetic rat hepatocytes.

scholarly journals Role of Hyperketonemia in Inducing Oxidative Stress and Cellular Damage in Cultured Hepatocytes and Type 1 Diabetic Rat Liver

2015 ◽  
Vol 37 (6) ◽  
pp. 2160-2170 ◽  
Author(s):  
Preeti Kanikarla-Marie ◽  
Sushil K. Jain
Keyword(s):  
Oxidative Stress ◽  
Liver Damage ◽  
Diabetic Control ◽  
Diabetic Rats ◽  
Cellular Damage ◽  
Diabetic Rat ◽  
Blood Levels ◽  
Per Se ◽  
Rat Livers

Background/Aims: Type 1 diabetic (T1D) patients have a higher incidence of liver disease. T1D patients frequently experience elevated plasma ketone levels along with hyperglycemia. However, no study has examined whether hyperketonemia per se has any role in excess liver damage in T1D. This study investigates the hypothesis that hyperketonemia can induce oxidative stress and cellular dysfunction. Methods: STZ treated diabetic rats, FL83B hepatocytes, and GCLC knocked down (GSH deficient) hepatocytes were used. Results: The blood levels of ALT and AST, biomarkers of liver damage, and ketones were elevated in T1D rats. An increase in NOX4 and ROS along with a reduction in GSH and GCLC levels was observed in T1D rat livers in comparison to those seen in non-diabetic control or type 2 diabetic rats. MCP-1 and ICAM-1 were also elevated in T1D rat livers and ketone treated hepatocytes. Macrophage markers CCR2 and CD11A that interact with MCP-1, and ICAM-1 respectively, were also elevated in the T1D liver, indicating macrophage infiltration. Additionally, activated macrophages increased hepatocyte damage with ketone treatment, which was similar to that seen in GCLC knockdown hepatocytes without ketones. Conclusion: Hyperketonemia per se can induce macrophage mediated damage to hepatocytes and the liver, caused by GSH depletion and oxidative stress up regulation in T1D.

cAMP regulation of phenobarbital-mediated induction of δ-aminolevulinate synthase mRNA in hepatocytes from normal and experimental diabetic rats

1994 ◽  
Vol 72 (9-10) ◽  
pp. 381-390 ◽  
Author(s):  
Cecilia L. Varone ◽  
Eduardo T. Canépa ◽  
Elena B. C. Llambías ◽  
Moisés Grinstein
Keyword(s):  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Dibutyryl Camp ◽  
Dependent Protein Kinase ◽  
Normal Cells ◽  
Aminolevulinate Synthase ◽  
Maximum Activation ◽  
Dependent Protein

We examined the mechanism underlying the effect of cAMP on δ-aminolevulinate synthase mRNA biosynthesis in isolated hepatocytes from normal and experimental diabetic rats. We have demonstrated that the potentiation by dibutyryl cAMP of the phenobarbital-mediated induction of δ-aminolevulinate synthase enzyme activity, observed in our previously reported studies, reflects an increased amount of its mRNA. The inducing effect exerted by phenobarbital on the biosynthesis of δ-aminolevulinate synthase mRNA in diabetic hepatocytes is greater than that observed in normal cells. This enhanced response to the increased level of endogenous cAMP in diabetic hepatocytes is apparently sufficient for a maximum activation of the cAMP-dependent protein kinase. The present results suggest that in rat liver dibutyryl cAMP modulates δ-aminolevulinate synthase mRNA biosynthesis by acting predominantly, if not exclusively, at the level of gene transcription.Key words: δ-aminolevulinate synthase mRNA, phenobarbital, cAMP, diabetic rat hepatocytes.

Loss of suppression of GSH synthesis at low cell density in primary cultures of rat hepatocytes

1992 ◽  
Vol 263 (6) ◽  
pp. C1181-C1189 ◽  
Author(s):  
S. C. Lu ◽  
J. L. Ge
Keyword(s):  
Actinomycin D ◽  
Primary Cultures ◽  
Rat Hepatocytes ◽  
Cell Number ◽  
Density Effect ◽  
Synthetase Activity ◽  
Active Growth ◽  
Adult Rat ◽  
Adult Rat Hepatocytes ◽  
The Media

Primary cultures of adult rat hepatocytes shift into the growth phase when plated at low density (LD). We used this model to examine changes in glutathione (GSH) metabolism, since cells undergoing active growth may be more susceptible to environmental toxins. When primary cultures of adult rat hepatocytes were plated on collagen or Matrigel-precoated dishes, cell number and GSH varied inversely. This density effect on cell GSH occurred as early as 2 h after plating, when the media contained 1 mM methionine, but was delayed until 20 h if the media contained only 0.5 mM cystine. The density effect on GSH synthesis occurred in the absence of serum, hormones, changes in cell volume, GSH efflux, ATP levels, and uptake of methionine or cystine and was blocked by cycloheximide or actinomycin D. When methionine was available, the cellular cysteine level was 65% higher at LD than at high density (HD). gamma-Glutamylcysteine synthetase (GCS) activity was 64% higher at LD than at HD. GSH synthetase activity was unaffected by density. Both the increase in cellular cysteine levels and GCS activity were blocked by cycloheximide and actinomycin D. When cells were cocultured using cluster plates and Transwell inserts for 4 h, cell GSH of HD cells was unaffected by the density of cocultured cells; however, LD cells exhibited significantly lower GSH and GCS activity when cocultured with HD cells than when cocultured with LD cells. Cysteine levels were elevated in the LD cells regardless of the density of cocultured cells.(ABSTRACT TRUNCATED AT 250 WORDS)

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