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Chang DC, Xu X, Ferrante AW, Krakoff J. Reduced plasma albumin predicts type 2 diabetes and is associated with greater adipose tissue macrophage content and activation. Diabetol Metab Syndr 2019; 11:14. [PMID: 30774722 PMCID: PMC6367730 DOI: 10.1186/s13098-019-0409-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 01/31/2019] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Plasma albumin is reduced during inflammation. Obesity, a strong risk factor for type 2 diabetes (T2D), is associated with adipose tissue inflammation. However, whether albumin is associated with adipose tissue inflammation and whether it predicts T2D are unclear. METHODS Adults (predominantly American Indian) from a longitudinal study were included. Macrophage content and gene expression related to recruitment/activation were measured from subcutaneous adipose tissue (n = 51). The relationship between plasma albumin and adiposity (dual-energy X-ray absorptiometry or hydrodensitometry), glucose (oral glucose tolerance test), insulin action (hyperinsulinemic-euglycemic clamp), and insulin secretion (intravenous glucose tolerance test) were evaluated (n = 422). Progression to T2D was evaluated by Cox regression (median follow-up 8.8 years; 102 progressors). RESULTS Albumin was associated with macrophage markers including C1QB (r = - 0.30, p = 0.04), CSF1R (r = - 0.30, p = 0.03), and CD11b (r = - 0.36, p = 0.01). Albumin was inversely associated with body fat percentage (r = - 0.14, p = 0.003), fasting plasma glucose (r = - 0.17, p = 0.0003), and 2 h plasma glucose (r = - 0.11, p = 0.03), and was reduced in impaired glucose regulation compared with normal glucose regulation (mean ± SD: 39.4 ± 3.6 g/l and 40.1 ± 3.9 g/l, respectively; p = 0.049). Albumin predicted T2D, even after adjustment for confounders (HR, 0.75; 95% CI 0.58-0.96; p = 0.02; per one SD difference in albumin). CONCLUSIONS Reduced albumin is associated with an unfavorable metabolic profile, characterized by increased adipose tissue inflammation, adiposity, and glucose, and with an increased risk for T2D.
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Affiliation(s)
- Douglas C. Chang
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 4212N. 16th Street, Phoenix, AZ 85016 USA
| | - Xiaoyuan Xu
- Department of Medicine, The Naomi Berrie Diabetes Center, Columbia University, New York, NY USA
| | - Anthony W. Ferrante
- Department of Medicine, The Naomi Berrie Diabetes Center, Columbia University, New York, NY USA
| | - Jonathan Krakoff
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 4212N. 16th Street, Phoenix, AZ 85016 USA
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Bhat S, Jagadeeshaprasad MG, Venkatasubramani V, Kulkarni MJ. Abundance matters: role of albumin in diabetes, a proteomics perspective. Expert Rev Proteomics 2017; 14:677-689. [PMID: 28689445 DOI: 10.1080/14789450.2017.1352473] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
INTRODUCTION Human serum albumin (HSA) is a multifaceted protein with vital physiological functions. It is the most abundant plasma protein with inherent capability to bind to diverse ligands, and thus susceptible to various post-translational modifications (PTMs) which alter its structure and functions. One such PTM is glycation, a non-enzymatic reaction between reducing sugar and protein leading to formation of heterogeneous advanced glycation end products (AGEs). Glycated albumin (GA) concentration increases significantly in diabetes and is implicated in development of secondary complications. Areas covered: In this review, we discuss in depth, formation of GA and its consequences, approaches used for characterization and quantification of GA, milestones in GA proteomics, clinical relevance of GA as a biomarker, significance of maintaining abundant levels of albumin and future perspectives. Expert commentary: Elevated GA levels are associated with development of insulin resistance as well as secondary complications, in healthy and diabetic individuals respectively. Mass spectrometry (MS) based approaches aid in precise characterization and quantification of GA including early and advanced glycated peptides, which can be useful in prediction of the disease status. Thus GA has evolved to be one of the best candidates in the pursuit of diagnostic markers for prediction of prediabetes and diabetic complications.
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Affiliation(s)
- Shweta Bhat
- a Division of Biochemical Sciences , CSIR-National Chemical Laboratory , Pune , India
| | | | | | - Mahesh J Kulkarni
- a Division of Biochemical Sciences , CSIR-National Chemical Laboratory , Pune , India
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Chen Q, Lu M, Monks BR, Birnbaum MJ. Insulin Is Required to Maintain Albumin Expression by Inhibiting Forkhead Box O1 Protein. J Biol Chem 2015; 291:2371-8. [PMID: 26668316 DOI: 10.1074/jbc.m115.677351] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Indexed: 01/07/2023] Open
Abstract
Diabetes is accompanied by dysregulation of glucose, lipid, and protein metabolism. In recent years, much effort has been spent on understanding how insulin regulates glucose and lipid metabolism, whereas the effect of insulin on protein metabolism has received less attention. In diabetes, hepatic production of serum albumin decreases, and it has been long established that insulin positively controls albumin gene expression. In this study, we used a genetic approach in mice to identify the mechanism by which insulin regulates albumin gene transcription. Albumin expression was decreased significantly in livers with insulin signaling disrupted by ablation of the insulin receptor or Akt. Concomitant deletion of Forkhead Box O1 (Foxo1) in these livers rescued the decreased albumin secretion. Furthermore, activation of Foxo1 in the liver is sufficient to suppress albumin expression. These results suggest that Foxo1 acts as a repressor of albumin expression.
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Affiliation(s)
- Qing Chen
- From the Institute for Diabetes, Obesity, and Metabolism, Department of Biochemistry and Biophysics, and Graduate Group of Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
| | - Mingjian Lu
- From the Institute for Diabetes, Obesity, and Metabolism
| | - Bobby R Monks
- From the Institute for Diabetes, Obesity, and Metabolism
| | - Morris J Birnbaum
- From the Institute for Diabetes, Obesity, and Metabolism, Department of Biochemistry and Biophysics, and Graduate Group of Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and the Cardiovascular and Metabolic Disease Research Unit, Pfizer Inc., Cambridge, Massachusetts 02140
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Sekine S, Terada S, Aoyama T. Medium-chain triacylglycerol suppresses the decrease of plasma albumin level through the insulin-Akt-mTOR pathway in the livers of malnourished rats. J Nutr Sci Vitaminol (Tokyo) 2014; 59:123-8. [PMID: 23727642 DOI: 10.3177/jnsv.59.123] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Recent studies have shown that medium-chain triacylglycerol (MCT) improved serum albumin concentration in elderly people with protein-energy malnutrition (PEM) and in malnourished rats. However, the mechanism for this effect has not been clarified. Dietary MCT promotes insulin secretion from the pancreas, and insulin activates mammalian target of rapamycin (mTOR) complex 1 (mTORC1) via the activation of phosphoinositide 3-kinase (PI3K) and its downstream effecter, Akt. mTORC1 promotes mRNA translation through S6K and 4E-BP1. Therefore, we hypothesized that dietary MCT elevates albumin synthesis through promotion of insulin-Akt-mTOR transduction in the liver. To test this hypothesis, we measured phosphorylated Akt, mTOR and albumin in the livers of malnourished rats. In the present study we examined rats fed low-protein diets containing either MCT or long-chain triacylglycerol (LCT) with energy restriction. The plasma and liver albumin levels were significantly higher in the MCT-fed group than in the LCT-fed group. In addition, plasma insulin concentration, liver phosphorylated Akt/Akt and phosphorylated mTOR/mTOR levels were significantly higher in the MCT-fed group than in the LCT-fed group. These results suggest that one of the mechanisms for the albumin improvement effect of dietary MCT is the promotion of albumin synthesis through the insulin-Akt-mTOR signaling pathway of the liver.
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Affiliation(s)
- Seiji Sekine
- Central Research Laboratory, The Nisshin OilliO Group, Ltd., 1 Shinmei-cho, Yokosuka, Kanagawa, Japan.
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5
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Swift B, Pfeifer ND, Brouwer KLR. Sandwich-cultured hepatocytes: an in vitro model to evaluate hepatobiliary transporter-based drug interactions and hepatotoxicity. Drug Metab Rev 2010; 42:446-71. [PMID: 20109035 PMCID: PMC3097390 DOI: 10.3109/03602530903491881] [Citation(s) in RCA: 290] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Sandwich-cultured hepatocytes (SCH) are a powerful in vitro tool that can be utilized to study hepatobiliary drug transport, species differences in drug transport, transport protein regulation, drug-drug interactions, and hepatotoxicity. This review provides an up-to-date summary of the SCH model, including a brief history of, and introduction to, the use of SCH, as well as methodology to evaluate hepatobiliary drug disposition. A summary of the literature that has utilized this model to examine the interplay between drug-metabolizing enzymes and transport proteins, drug-drug interactions at the transport level, and hepatotoxicity as a result of altered hepatic transport also is provided.
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Affiliation(s)
- Brandon Swift
- University of North Carolina at Chapel Hill, 27599-7569, USA
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6
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Brown AC, Olver WI, Donnelly CJ, May ME, Naggert JK, Shaffer DJ, Roopenian DC. Searching QTL by gene expression: analysis of diabesity. BMC Genet 2005; 6:12. [PMID: 15760467 PMCID: PMC555939 DOI: 10.1186/1471-2156-6-12] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2004] [Accepted: 03/10/2005] [Indexed: 11/10/2022] Open
Abstract
Background Recent developments in sequence databases provide the opportunity to relate the expression pattern of genes to their genomic position, thus creating a transcriptome map. Quantitative trait loci (QTL) are phenotypically-defined chromosomal regions that contribute to allelically variant biological traits, and by overlaying QTL on the transcriptome, the search for candidate genes becomes extremely focused. Results We used our novel data mining tool, ExQuest, to select genes within known diabesity QTL showing enriched expression in primary diabesity affected tissues. We then quantified transcripts in adipose, pancreas, and liver tissue from Tally Ho mice, a multigenic model for Type II diabetes (T2D), and from diabesity-resistant C57BL/6J controls. Analysis of the resulting quantitative PCR data using the Global Pattern Recognition analytical algorithm identified a number of genes whose expression is altered, and thus are novel candidates for diabesity QTL and/or pathways associated with diabesity. Conclusion Transcription-based data mining of genes in QTL-limited intervals followed by efficient quantitative PCR methods is an effective strategy for identifying genes that may contribute to complex pathophysiological processes.
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Affiliation(s)
- Aaron C Brown
- The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA
| | - William I Olver
- The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA
| | | | - Marjorie E May
- The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA
| | - Jürgen K Naggert
- The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA
| | - Daniel J Shaffer
- The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA
| | - Derry C Roopenian
- The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA
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Miyake K, Ogawa W, Matsumoto M, Nakamura T, Sakaue H, Kasuga M. Hyperinsulinemia, glucose intolerance, and dyslipidemia induced by acute inhibition of phosphoinositide 3-kinase signaling in the liver. J Clin Invest 2002; 110:1483-91. [PMID: 12438446 PMCID: PMC151813 DOI: 10.1172/jci15880] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The physiological relevance of phosphoinositide 3-kinase (PI 3-K) signaling in the liver to fuel homeostasis was investigated. Systemic infusion of an adenovirus encoding a dominant negative mutant of PI 3-K ((Delta)p85) resulted in liver-specific expression of this protein and in inhibition of the insulin-induced activation of PI 3-K in the liver within 3 days, without affecting insulin signaling in skeletal muscle. Hepatic expression of (Delta)p85 led to hyperinsulinemia and to a marked increase in blood glucose concentration in response to oral glucose intake. The increases in both glycogen and glucose 6-phosphate content, as well as in Akt and glycogen synthase activities in the liver, that were induced by glucose intake were markedly impaired in mice expressing (Delta)p85. Despite an upregulation of mRNAs for gluconeogenic enzymes apparent in the liver of these animals, the fasting blood glucose concentration was increased only slightly, and the serum concentrations of gluconeogenic precursors were reduced. However, administration of pyruvate, a substrate for gluconeogenesis, resulted in an exaggerated increase in blood glucose concentration. In the fasted state, the mass of adipose tissue of the mice was about 1.5 times that in control mice. The mice also exhibited marked decreases in the serum concentrations of FFAs and triglyceride and suppression of insulin-induced PI 3-K activation in adipose tissue, probably due to the associated hyperinsulinemia. PI 3-K activity in the liver is thus essential for normal carbohydrate and lipid metabolism in living animals.
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Affiliation(s)
- Kazuaki Miyake
- Department of Clinical Molecular Medicine, Division of Diabetes, Digestive and Kidney Disease, Kobe University Graduate School of Medicine, Kobe, Japan
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Hamilton GA, Westmorel C, George AE. Effects of medium composition on the morphology and function of rat hepatocytes cultured as spheroids and monolayers. In Vitro Cell Dev Biol Anim 2002. [PMID: 11776971 DOI: 10.1290/1071-2690(2001)037<0656:eomcot>2.0.co;2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Primary hepatocytes cultured as monolayers or as spheroids were studied to compare the effects of four different culture media (Williams' E, Chee's, Sigma Hepatocyte, and HepatoZYME medium). Rat hepatocytes were cultured as conventional monolayers for 3 d or as spheroids for 2 wk. For spheroid formation a method was emplOyed that combined the use of a nonadherent substratum with rotation of cultures. Hepatocyte integrity and morphology were assessed by light and electron microscopy and by reduced glutathione content. Hepatocyte function was measured by albumin secretion and 7-ethoxycoumarin metabolism. Chee's medium was found to be optimal for maintenance of hepatocyte viability and function in monolayers, but it failed to support spheroid formation. For spheroid formation and for the maintenance of spheroid morphology and function, Sigma HM was found to be optimal. These results demonstrate that the medium requirements of hepatocytes differ markedly depending on the culture model employed. Spheroid culture allowed better preservation of morphology and function of hepatocytes compared with conventional monolayer culture. Hepatocytes in spheroids formed bile canaliculi. and expressed an actin distribution resembling that found in hepatocytes in vivo. Albumin secretion was maintained at the same level as that found during the first d in primary culture, and 7-ethoxycoumarin metabolism was maintained over 2 wk in culture at approximately 30% of the levels found in freshly isolated hepatocytes. The improved morphology and function of hepatocyte cultures as spheroids may provide a more appropriate in vitro model for certain applications where the maintenance of liver-specific functions in long-term culture is crucial.
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Affiliation(s)
- G A Hamilton
- Division of Biosciences, University of Hertfordshire, Hatfield, United Kingdom
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9
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Hamilton GA, Westmorel C, George AE. Effects of medium composition on the morphology and function of rat hepatocytes cultured as spheroids and monolayers. In Vitro Cell Dev Biol Anim 2001; 37:656-67. [PMID: 11776971 DOI: 10.1290/1071-2690(2001)037<0656:eomcot>2.0.co;2] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Primary hepatocytes cultured as monolayers or as spheroids were studied to compare the effects of four different culture media (Williams' E, Chee's, Sigma Hepatocyte, and HepatoZYME medium). Rat hepatocytes were cultured as conventional monolayers for 3 d or as spheroids for 2 wk. For spheroid formation a method was emplOyed that combined the use of a nonadherent substratum with rotation of cultures. Hepatocyte integrity and morphology were assessed by light and electron microscopy and by reduced glutathione content. Hepatocyte function was measured by albumin secretion and 7-ethoxycoumarin metabolism. Chee's medium was found to be optimal for maintenance of hepatocyte viability and function in monolayers, but it failed to support spheroid formation. For spheroid formation and for the maintenance of spheroid morphology and function, Sigma HM was found to be optimal. These results demonstrate that the medium requirements of hepatocytes differ markedly depending on the culture model employed. Spheroid culture allowed better preservation of morphology and function of hepatocytes compared with conventional monolayer culture. Hepatocytes in spheroids formed bile canaliculi. and expressed an actin distribution resembling that found in hepatocytes in vivo. Albumin secretion was maintained at the same level as that found during the first d in primary culture, and 7-ethoxycoumarin metabolism was maintained over 2 wk in culture at approximately 30% of the levels found in freshly isolated hepatocytes. The improved morphology and function of hepatocyte cultures as spheroids may provide a more appropriate in vitro model for certain applications where the maintenance of liver-specific functions in long-term culture is crucial.
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Affiliation(s)
- G A Hamilton
- Division of Biosciences, University of Hertfordshire, Hatfield, United Kingdom
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10
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Ahlman B, Charlton M, Fu A, Berg C, O'Brien P, Nair KS. Insulin's effect on synthesis rates of liver proteins. A swine model comparing various precursors of protein synthesis. Diabetes 2001; 50:947-54. [PMID: 11334437 DOI: 10.2337/diabetes.50.5.947] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Insulin's effect on the synthesis of liver proteins remains to be fully defined. Previous studies using various surrogate measures of amino acyl-tRNA have reported variable results of insulin's effect on liver protein synthesis. We determined the effect of insulin with or without amino acid supplementation on the synthesis rates of liver proteins (tissue, albumin, and fibrinogen) using L-[1-13C]Leu as a tracer in 24 male miniature swine. In addition, we compared the isotopic enrichment of different precursors of liver proteins with that of amino acyl-tRNA using L-[1-13C]Leu and L-[15N]Phe as tracers. Although liver tissue fluid enrichment of [13C]Leu and [15N]Phe and that of plasma [13C]ketoisocaproatic acid (KIC) were very similar to that of tRNA, plasma isotopic enrichment of both Leu and Phe were substantially higher (P < 0.01) and VLDL apolipoprotein-B100 enrichment was lower (P < 0.01) than the respective amino acyl-tRNA enrichment. Plasma KIC enrichment most accurately predicted leucyl-tRNA enrichment, whereas plasma Leu enrichment was best correlated with that of tRNA. Neither insulin alone nor insulin plus amino acid infusion had an effect on liver tissue protein synthesis. In contrast, insulin alone decreased the albumin synthesis rate, and insulin with amino acids maintained the albumin synthesis rate. Insulin with or without amino acids inhibited the fibrinogen synthesis rate. These results, based on synthetic rates using amino acyl-tRNA, were consistent with those obtained using KIC or tissue fluid Leu or Phe as precursor pools. These studies demonstrated that plasma KIC enrichment is a convenient and reliable surrogate measure of leucyl-tRNA in liver. We also concluded that insulin has differential effects on the synthesis rates of liver proteins. Whereas insulin with or without amino acid supplement has no acute effect on the synthesis of liver tissue protein, insulin has a substantial inhibitory effect on fibrinogen synthesis. In contrast, insulin administration along with amino supplement is necessary to maintain albumin synthesis rate.
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Affiliation(s)
- B Ahlman
- Endocrine Research Unit, Division of Endocrinology and Metabolism, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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12
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Lu SC, Ge JL, Kuhlenkamp J, Kaplowitz N. Insulin and glucocorticoid dependence of hepatic gamma-glutamylcysteine synthetase and glutathione synthesis in the rat. Studies in cultured hepatocytes and in vivo. J Clin Invest 1992; 90:524-32. [PMID: 1353765 PMCID: PMC443130 DOI: 10.1172/jci115890] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We reported that glucagon and phenylephrine decrease hepatocyte GSH by inhibiting gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in GSH synthesis (Lu, S.C., J. Kuhlenkamp, C. Garcia-Ruiz, and N. Kaplowitz. 1991. J. Clin. Invest. 88:260-269). In contrast, we have found that insulin (In, 1 microgram/ml) and hydrocortisone (HC, 50 nM) increased GSH of cultured hepatocytes up to 50-70% (earliest significant change at 6 h) with either methionine or cystine alone as the sole sulfur amino acid in the medium. The effect of In occurred independent of glucose concentration in the medium. Changes in steady-state cellular cysteine levels, cell volume, GSH efflux, or expression of gamma-glutamyl transpeptidase were excluded as possible mechanisms. Both hormones are known to induce cystine/glutamate transport, but this was excluded as the predominant mechanism since the induction in cystine uptake required a lag period of greater than 6 h, and the increase in cell GSH still occurred when cystine uptake was blocked. Assay of GSH synthesis in extracts of detergent-treated cells revealed that In and HC increased the activity of GCS by 45-65% (earliest significant change at 4 h) but not GSH synthetase. In and HC treatment increased the Vmax of GCS by 31-43% with no change in Km. Both the hormone-mediated increase in cell GSH and GCS activity were blocked with either cycloheximide or actinomycin D. Finally, when studied in vivo, streptozotocin-treated diabetic and adrenalectomized rats exhibited lower hepatic GSH levels and GCS activities than respective controls. Both of these abnormalities were prevented with hormone replacement. Thus, both in vitro and in vivo, In and glucocorticoids are required for normal expression of GCS.
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Affiliation(s)
- S C Lu
- Department of Medicine, University of Southern California School of Medicine, Los Angeles 90033
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De Feo P, Gaisano MG, Haymond MW. Differential effects of insulin deficiency on albumin and fibrinogen synthesis in humans. J Clin Invest 1991; 88:833-40. [PMID: 1909352 PMCID: PMC295469 DOI: 10.1172/jci115384] [Citation(s) in RCA: 117] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Insulin deficiency decreases tissue protein synthesis, albumin mRNA concentration, and albumin synthesis in rats. In contrast, insulin deficiency does not change, or, paradoxically, increases estimates of whole body protein synthesis in humans. To determine if such estimates of whole body protein synthesis could obscure potential differential effects of insulin on the synthetic rates of individual proteins, we determined whole body protein synthesis and albumin and fibrinogen fractional synthetic rates using 5-h simultaneous infusions of [14C]leucine and [13C]bicarbonate, in six type 1 diabetics during a continuous i.v. insulin infusion (to maintain euglycemia) and after short-term insulin withdrawal (12 +/- 2 h). Insulin withdrawal increased (P less than 0.03) whole body proteolysis by approximately 35% and leucine oxidation by approximately 100%, but did not change 13CO2 recovery from NaH13CO3 or estimates of whole body protein synthesis (P = 0.21). Insulin deficiency was associated with a 29% decrease (P less than 0.03) in the albumin fractional synthetic rate but a 50% increase (P less than 0.03) in that of fibrinogen. These data provide strong evidence that albumin synthesis in humans is an insulin-sensitive process, a conclusion consistent with observations in rats. The increase in fibrinogen synthesis during insulin deficiency most likely reflects an acute phase protein response due to metabolic stress. These data suggest that the absence of changes in whole body protein synthesis after insulin withdrawal is the result of the summation of differential effects of insulin deficiency on the synthesis of specific body proteins.
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Affiliation(s)
- P De Feo
- Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota 55905
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Maher JJ, McGuire RF. Extracellular matrix gene expression increases preferentially in rat lipocytes and sinusoidal endothelial cells during hepatic fibrosis in vivo. J Clin Invest 1990; 86:1641-8. [PMID: 2243137 PMCID: PMC296914 DOI: 10.1172/jci114886] [Citation(s) in RCA: 332] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Whether parenchymal or nonparenchymal liver cells play a predominant role in the pathophysiology of hepatic fibrosis has not been firmly established in vivo. We have addressed this question by quantitating the relative abundance of specific mRNAs for collagen types I, III, and IV, and laminin in purified populations of hepatocytes, sinusoidal endothelial cells, and lipocytes from normal and fibrotic rat liver. In normal liver, type I collagen gene expression was minimal in all cell types; mRNA for types III and IV collagen were apparent in endothelial cells and lipocytes, but not in hepatocytes. Laminin mRNA was present in all cell types. Induction of fibrogenesis by either bile duct ligation or carbon tetrachloride administration was associated with a substantial increase in mRNA for types I and III collagen in nonparenchymal cells. Lipocytes from fibrotic animals exhibited a greater than 30-fold increase in type I collagen mRNA relative to normal lipocytes, and greater than 40-fold relative to hepatocytes. Type III collagen mRNA reached 5 times that in normal lipocytes and greater than 120 times that in hepatocytes. Endothelial cells exhibited an isolated increase in type I collagen mRNA, reaching five times that in normal liver. Type IV collagen and laminin gene expression were not significantly increased in nonparenchymal cells during fibrogenesis; in fact, mRNA for type IV collagen and laminin decreased by up to 50% in endothelial cells. Despite the pronounced changes that occurred in matrix gene expression in nonparenchymal cells during fibrogenesis, no change was noted in hepatocytes. We conclude that nonparenchymal liver cells, particularly lipocytes, are important effectors of hepatic fibrosis in vivo.
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Affiliation(s)
- J J Maher
- Liver Core Center, University of California, San Francisco 94110
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15
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Miller LL, Treat DE, Fridd B, Wemett D. Effects of streptozotocin diabetes in the rat on blood levels of ten specific plasma proteins and on their net biosynthesis by the isolated perfused liver. Hepatology 1990; 11:635-45. [PMID: 2139429 DOI: 10.1002/hep.1840110417] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Adult male Sprague-Dawley rats with streptozotocin-induced diabetes (6 to 8 wk duration), treated or untreated with insulin, were studied with two aims: (a) to ascertain whether protracted diabetes in the rat is associated with changes in circulating plasma protein levels analogous to those reported in human diabetic patients with clinical evidence of complications; (b) to evaluate the effects of experimental diabetes on the net cumulative biosynthesis of 10 specific plasma proteins by the isolated liver, perfused for 24 hr. Samples of liver donor plasma and samples of perfusate were analyzed by single radial immunodiffusion or by rocket immunoelectrophoresis for albumin, alpha 1-macroglobulin and the acute phase glycoproteins: fibrinogen, alpha 1-acid glycoprotein (Darcy), alpha 1-acid glycoprotein (Kawasaki), haptoglobin, alpha 2-(acute phase) globulin, hemopexin, C3-complement and ceruloplasmin. Diabetes (6 to 8 wk), untreated with insulin, resulted in significantly increased liver donor plasma levels of alpha 1-acid glycoprotein (Darcy) and alpha 1-acid glycoprotein (Kawasaki); plasma levels of hemopexin and of C3 decreased to 75% and 30% of normal, respectively. Insulin treatment of diabetic liver donors for 6 to 8 wk prevented the increase in alpha 1-acid glycoprotein (Darcy) and alpha 1-acid glycoprotein (Kawasaki) and minimized the decrease in C3 to 75% of normal. Perfused livers from untreated diabetic rats (6 to 8 wk) showed slightly decreased cumulative synthesis and secretion of alpha 1-acid glycoprotein (Darcy); however, synthesis of albumin was reduced to 35% of normal and that of eight glycoproteins ranged from 25% of normal (fibrinogen) to 12% of normal (C3). The striking in vitro induction of increased synthesis of acute-phase proteins by cortisol plus insulin in the isolated perfused normal liver was in contrast to the severely attenuated induction in perfused livers of untreated diabetic rats, which ranges from 50% of normal for alpha 1-acid glycoprotein (Darcy) to 5% of normal (C3). Severely negative perfusate nitrogen balance and impaired glucose utilization by perfused untreated diabetic livers contrasted with positive nitrogen balance and good glucose utilization of normal livers in response to insulin plus cortisol. The plasma protein synthetic capacity and the in vitro response to insulin plus cortisol of perfused livers from insulin-treated diabetic rats were normal for seven of the proteins but moderately decreased for albumin, haptoglobin and C3.
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Affiliation(s)
- L L Miller
- Department of Biophysics, School of Medicine and Dentistry, University of Rochester, New York 14642
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Stumpo DJ, Blackshear PJ. Insulin and growth factor effects on c-fos expression in normal and protein kinase C-deficient 3T3-L1 fibroblasts and adipocytes. Proc Natl Acad Sci U S A 1986; 83:9453-7. [PMID: 3540941 PMCID: PMC387156 DOI: 10.1073/pnas.83.24.9453] [Citation(s) in RCA: 103] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
We investigated the expression of the protooncogene c-fos in 3T3-L1 fibroblasts and adipocytes in response to a variety of growth-promoting agents in normal cells and in cells preincubated with phorbol esters to deplete them of protein kinase C. There was a rapid accumulation of c-fos mRNA in fibroblasts and adipocytes treated with phorbol 12-myristate 13-acetate, platelet-derived growth factor, fibroblast growth factor, fetal calf serum, bombesin, and insulin, especially in the adipocytes. Phorbol 12-myristate 13-acetate pretreatment abolished the increase in c-fos mRNA due to additional phorbol 12-myristate 13-acetate treatment and decreased but did not eliminate the ability of platelet-derived growth factor, fibroblast growth factor, fetal calf serum, bombesin, and insulin to stimulate c-fos mRNA. These data suggested that c-fos mRNA could be induced in serum-deprived 3T3-L1 fibroblasts and adipocytes by at least two separate pathways, one involving protein kinase C and the other independent of protein kinase C. In the very insulin-sensitive 3T3-L1 adipocytes, insulin rapidly and transiently increased c-fos expression (c-fos mRNA appeared by 15 min and disappeared after 60 min) via interaction with its own cellular receptor, rather than by interacting with receptors for one of the insulin-like growth factors. Cycloheximide treatment in combination with insulin or phorbol 12-myristate 13-acetate resulted in superinduction of c-fos mRNA. We conclude that insulin can rapidly stimulate c-fos mRNA accumulation in 3T3-L1 adipocytes and that part of the growth factor-stimulated increase in this mRNA that occurs in protein kinase C-deficient cells may be due to activation of a pathway similar or identical to that activated by insulin.
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