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Rochlin DH, Rizk NM, Mehrara B, Matros E, Sheckter CC. Free Flap Reconstruction in the Era of Commercial Price Transparency: What Are We Paying For? Plast Reconstr Surg 2024; 153:1187-1195. [PMID: 37621006 PMCID: PMC10894306 DOI: 10.1097/prs.0000000000011021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/26/2023]
Abstract
BACKGROUND Commercial rates for free flap reconstruction were not known publicly before the 2021 Hospital Price Transparency Final Rule. The purpose of this study was to examine commercial facility payments to characterize nationwide variation for microsurgical operations and identify opportunities to improve market effectiveness. METHODS A cross-sectional study was performed using 2022 commercial insurance pricing merged with hospital performance data. Facility payment rates were extracted for nine CPT codes for free flap operations. Price variation was quantified by means of across-hospital ratios and within-hospital ratios. Mixed effects linear models evaluated commercial rates relative to value, outcomes, and equity performance metrics, in addition to facility-level factors that included health care market concentration. RESULTS A total of 20,528 commercial rates across 675 hospitals were compiled. Across-hospital ratios ranged from 5.85 to 7.95, whereas within-hospital ratios ranged from 1.00 to 1.71. Compared with the lowest scoring hospitals (grade D), hospitals with an outcome grade of A and equity grades of B or C were associated with higher commercial rates ( P < 0.04); there were no significant differences in rate based on value. Higher commercial rates were also associated with nonprofit status and more concentrated markets ( P < 0.006). Lower commercial rates were correlated with safety-net and teaching hospitals ( P < 0.001). CONCLUSIONS Commercial rates for free flaps varied substantially both across and within hospitals. Associations of higher commercial rates with less competitive markets, and the lack of consistent association with value and equity, identify market failures. Additional work is needed to improve market efficiency for free flap operations.
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Affiliation(s)
- Danielle H. Rochlin
- Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center
| | - Nada M. Rizk
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University
| | - Babak Mehrara
- Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center
| | - Evan Matros
- Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center
| | - Clifford C. Sheckter
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University
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Rochlin DH, Rizk NM, Matros E, Wagner TH, Sheckter CC. Negotiated Rates for Surgical Cancer Care in the Era of Price Transparency-Prices Reflect Market Competition. Ann Surg 2024; 279:385-391. [PMID: 37678179 PMCID: PMC10840891 DOI: 10.1097/sla.0000000000006091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/09/2023]
Abstract
OBJECTIVE To measure commercial price variation for cancer surgery within and across hospitals. BACKGROUND Surgical care for solid-organ tumors is costly, and negotiated commercial rates have been hidden from public view. The Hospital Price Transparency Rule, enacted in 2021, requires all hospitals to list their negotiated rates on their website, thus opening the door for an examination of pricing for cancer surgery. METHODS This was a cross-sectional study using 2021 negotiated price data disclosed by US hospitals for the 10 most common cancers treated with surgery. Price variation was measured using within-hospital and across-hospital ratios. Commercial rates relative to cancer center designation and the Herfindahl-Hirschman Index at the facility level were evaluated with mixed effects linear regression with random intercepts per procedural code. RESULTS In all, 495,200 unique commercial rates from 2232 hospitals resulted for the 10 most common solid-organ tumor cancers. Gynecologic cancer operations had the highest median rates at $6035.8/operation compared with bladder cancer surgery at $3431.0/operation. Compared with competitive markets, moderately and highly concentrated markets were associated with significantly higher rates (HHI 1501, 2500, coefficient $513.6, 95% CI, $295.5, $731.7; HHI >2500, coefficient $1115.5, 95% CI, $913.7, $1317.2). National Cancer Institute designation was associated with higher rates, coefficient $3,451.9 (95% CI, $2853.2, $4050.7). CONCLUSIONS Commercial payer-negotiated prices for the surgical management of 10 common, solid tumor malignancies varied widely both within and across hospitals. Higher rates were observed in less competitive markets. Future efforts should facilitate price competition and limit health market concentration.
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Affiliation(s)
- Danielle H. Rochlin
- Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center
| | - Nada M. Rizk
- Division of Plastic and Reconstructive Surgery, Stanford University Medical Center
| | - Evan Matros
- Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center
| | | | - Clifford C. Sheckter
- Division of Plastic and Reconstructive Surgery, Stanford University Medical Center
- S-SPIRE. Department of Surgery, Stanford University
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Crowley JS, Liu FC, Rizk NM, Nguyen D. Concurrent management of lymphedema and breast reconstruction with single-stage omental vascularized lymph node transfer and autologous breast reconstruction: A case series. Microsurgery 2024; 44:e31017. [PMID: 36756715 DOI: 10.1002/micr.31017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 12/13/2022] [Accepted: 01/19/2023] [Indexed: 02/10/2023]
Abstract
INTRODUCTION The omentum has gained recent popularity in vascularized lymph node transfers (VLNT) as well as its novel use as a free flap for autologous breast reconstruction. The omentum has multiple unique advantages. It can be harvested laparoscopically or in an open fashion when utilized with abdominally-based free flaps. Additionally, it can be split into multiple flaps for simultaneous autologous breast reconstruction with VLNT or for multiple sites of VLNT. We present the safe and advantageous use of the omentum for VLNT with simultaneous autologous breast reconstruction in a series of patients. METHODS From the years 2019-2022, patients who underwent breast reconstruction with deep inferior epigastric artery perforator (DIEP) or muscle sparing tram (MS-TRAM) flaps with concurrent omental VLNT through a mini-laparotomy or breast reconstruction with Omental Fat-Augmented Free Flap (O-FAFF) with concurrent laparoscopic harvesting of omental VLNT were studied. Patient demographics included age, gender, comorbidities, prior radiation or chemotherapy, body mass index, complications, hospital length of stay, and surgical outcomes. RESULTS A total of seven patients underwent omental VLNT with breast reconstruction for a total of 12 breasts and eight limbs treated. Three of the patients underwent autologous breast reconstruction using omental free flap. The mean age was 52.3 (range 40-75) years and mean body mass index (BMI) was 29.3 (range 23-38) kg/m2 . The flap survival rate was 100%. All the patients had successful reduction of extremity circumference and improvement of symptoms. The range of follow-up was 5 to 19 months, with an average follow-up of 14.6 months. There was only one complication among our 7 patients: a patient with a BMI of 38 developed a post-surgical abdominal wound treated with local wound care. Otherwise, post-operative courses were uneventful, and no further complications were reported. CONCLUSION We demonstrate here additional evidence to the growing body of literature of the versatility and safety of the omentum to be utilized as an independent tool for surgical treatment of lymphedema as well as its simultaneous use with autologous breast reconstruction.
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Affiliation(s)
- Jiwon S Crowley
- Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Palo Alto, California, United States
| | - Farrah C Liu
- Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Palo Alto, California, United States
| | - Nada M Rizk
- Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Palo Alto, California, United States
| | - Dung Nguyen
- Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Palo Alto, California, United States
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Abstract
BACKGROUND Commercial payer-negotiated rates for cleft lip and palate surgery have not been evaluated on a national scale. The aim of this study was to characterize commercial rates for cleft care, both in terms of nationwide variation and in relation to Medicaid rates. METHODS A cross-sectional analysis was performed of 2021 hospital pricing data from Turquoise Health, a data service platform that aggregates hospital price disclosures. The data were queried by CPT code to identify 20 cleft surgical services. Within- and across-hospital ratios were calculated per CPT code to quantify commercial rate variation. Generalized linear models were used to assess the relationship between median commercial rate and facility-level variables and between commercial and Medicaid rates. RESULTS There were 80,710 unique commercial rates from 792 hospitals. Within-hospital ratios for commercial rates ranged from 2.0 to 2.9 and across-hospital ratios ranged from 5.4 to 13.7. Median commercial rates per facility were higher than Medicaid rates for primary cleft lip and palate repair ($5492.20 versus $1739.00), secondary cleft lip and palate repair ($5429.10 versus $1917.00), and cleft rhinoplasty ($6001.00 versus $1917.00; P < 0.001). Lower commercial rates were associated with hospitals that were smaller ( P < 0.001), safety-net ( P < 0.001), and nonprofit ( P < 0.001). Medicaid rate was positively associated with commercial rate ( P < 0.001). CONCLUSIONS Commercial rates for cleft surgical care demonstrated marked variation within and across hospitals, and were lower for small, safety-net, or nonprofit hospitals. Lower Medicaid rates were not associated with higher commercial rates, suggesting that hospitals did not use cost-shifting to compensate for budget shortfalls resulting from poor Medicaid reimbursement.
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Affiliation(s)
- Danielle H Rochlin
- From the Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center
| | - Nada M Rizk
- Division of Plastic and Reconstructive Surgery, Stanford University Medical Center
| | - Roberto L Flores
- Hansjörg Wyss Department of Plastic Surgery, New York University Grossman School of Medicine
| | - Evan Matros
- From the Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center
| | - Clifford C Sheckter
- Division of Plastic and Reconstructive Surgery, Stanford University Medical Center
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Abstract
Importance Breast reconstruction is costly, and negotiated commercial rates have been hidden from public view. The Hospital Price Transparency Rule was enacted in 2021 to facilitate market competition and lower health care costs. Breast reconstruction pricing should be analyzed to evaluate for market effectiveness and opportunities to lower the cost of health care. Objective To evaluate the extent of commercial price variation for breast reconstruction. The secondary objective was to characterize the price of breast reconstruction in relation to market concentration and payer mix. Design, Setting, and Participants This was a cross-sectional study conducted from January to April 2022 using 2021 pricing data made available after the Hospital Price Transparency Rule. National data were obtained from Turquoise Health, a data service platform that aggregates price disclosures from hospital websites. Participants were included from all hospitals with disclosed pricing data for breast reconstructive procedures, identified by Current Procedural Terminology (CPT) code. Main Outcomes and Measures Price variation was measured via within- and across-hospital ratios. A mixed-effects linear model evaluated commercial rates relative to governmental rates and the Herfindahl-Hirschman Index (health care market concentration) at the facility level. Linear regression was used to evaluate commercial rates as a function of facility characteristics. Results A total of 69 834 unique commercial rates were extracted from 978 facilities across 335 metropolitan areas. Commercial rates increased as health care markets became less competitive (coefficient, $4037.52; 95% CI, $700.12 to $7374.92; P = .02; for Herfindahl-Hirschman Index [HHI] 1501-2500, coefficient $3290.21; 95% CI, $878.08 to $5702.34; P = .01; both compared with HHI ≤1500). Commercial rates demonstrated economically insignificant associations with Medicare and Medicaid rates (Medicare coefficient, -$0.05; 95% CI, -$0.14 to $0.03; P = .23; Medicaid coefficient, $0.14; 95% CI, $0.07 to $0.22; P < .001). Safety-net and nonprofit hospitals reported lower commercial rates (coefficient, -$3269.58; 95% CI, -$3815.42 to -$2723.74; P < .001 and coefficient, -$1892.79; -$2519.61 to -$1265.97; P < .001, respectively). Extra-large hospitals (400+ beds) reported higher commercial rates compared with their smaller counterparts (coefficient, $1036.07; 95% CI, $198.29 to $1873.85, P = .02). Conclusions and Relevance Study results suggest that commercial rates for breast reconstruction demonstrated large nationwide variation. Higher commercial rates were associated with less competitive markets and facilities that were large, for-profit, and nonsafety net. Privately insured patients with breast cancer may experience higher premiums and deductibles as US hospital market consolidation and for-profit hospitals continue to grow. Transparency policies should be continued along with actions that facilitate greater health care market competition. There was no evidence that facilities increase commercial rates in response to lower governmental rates.
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Affiliation(s)
- Danielle H. Rochlin
- Division of Plastic and Reconstructive Surgery, Stanford University Medical Center, Palo Alto, California,Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Nada M. Rizk
- Division of Plastic and Reconstructive Surgery, Stanford University Medical Center, Palo Alto, California
| | - Evan Matros
- Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Todd H. Wagner
- S-SPIRE, Department of Surgery, Stanford University, Palo Alto, California
| | - Clifford C. Sheckter
- Division of Plastic and Reconstructive Surgery, Stanford University Medical Center, Palo Alto, California,S-SPIRE, Department of Surgery, Stanford University, Palo Alto, California
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Do SC, Rizk NM, Druzin ML, Simard JF. Does Hydroxychloroquine Protect against Preeclampsia and Preterm Delivery in Systemic Lupus Erythematosus Pregnancies? Am J Perinatol 2020; 37:873-880. [PMID: 31899930 DOI: 10.1055/s-0039-3402752] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
OBJECTIVE Systemic lupus erythematosus (SLE) increases the risk of complications in pregnancy. Hydroxychloroquine (HCQ) decreases flares and neonatal lupus syndrome. Limited evidence suggests that HCQ also reduces preeclampsia and preterm birth in SLE pregnancies. We studied whether HCQ was associated with lower odds of preeclampsia and preterm delivery in SLE pregnancies. STUDY DESIGN We conducted a retrospective cohort study of 129 deliveries of 110 patients with SLE delivered at a single institution (2000-2017). HCQ exposure and preeclampsia, along with other clinical data, were extracted from chart review. Crude and multivariable-adjusted logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS A total of 41% were exposed to HCQ, of whom 13.5% were complicated by preeclampsia versus 26.3% unexposed to HCQ (adjusted OR = 0.5; 95% CI: 0.2-1.4). The difference was pronounced for first pregnancies (7 vs. 44%), but power was limited. The difference in preterm deliveries was less pronounced comparing HCQ-exposed pregnancies with HCQ-unexposed pregnancies (34 vs. 40.8%; OR = 0.3; 95% CI: 0.3-1.5). CONCLUSION Pregnant SLE patients trended toward less preeclampsia and preterm delivery when treated with HCQ. Future larger studies are needed to increase the statistical power, account for additional potential confounders, and more fully account for parity.
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Affiliation(s)
- Samantha C Do
- Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, California
| | - Nada M Rizk
- Division of Epidemiology, Department of Health Research and Policy, Stanford University School of Medicine, Stanford, California
| | - Maurice L Druzin
- Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, California
| | - Julia F Simard
- Division of Epidemiology, Department of Health Research and Policy, Stanford University School of Medicine, Stanford, California.,Division of Immunology and Rheumatology, Department of Medicine, Stanford University School of Medicine, Stanford, California
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Abstract
Previous studies have demonstrated that tumor necrosis factor-alpha (TNF-alpha) production from adipose tissue is elevated in obese animal models and in obese humans. It plays an important role in the induction of insulin resistance in experimental animals. In this study, we examined hypothalamic tissue expression of TNF-alpha and its receptors and TNF-alpha expression of adipose tissue in lean C57BLKSJ+/+ and obese polygenic New Zealand obese (NZO) mice. Obese animals exhibited hyperglycemia, hyperinsulinemia, hypertriglyceridemia, and hypercholesterinemia. Using RT-PCR, we observed increased expression (2.4-fold) of TNF receptor 2 (p75) in the hypothalamus of obese mice. TNF-alpha expression in adipose tissue of obese mice was eight times higher than in controls. TNF-alpha and TNF receptor 1 (p55) expression in hypothalamic tissue was similar in obese and lean animals. These results suggest that the hypothalamic TNF receptor 2 (p75) might play a role in obesity by modulating the actions of TNF-alpha in conditions of leptin resistance.
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Affiliation(s)
- N M Rizk
- Physiology Department, Mansoura Faculty of Medicine, Mansoura University, Egypt
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Rizk NM, Stammsen D, Preibisch G, Eckel J. Leptin and tumor necrosis factor-alpha induce the tyrosine phosphorylation of signal transducer and activator of transcription proteins in the hypothalamus of normal rats in vivo. Endocrinology 2001; 142:3027-32. [PMID: 11416024 DOI: 10.1210/endo.142.7.8225] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Tumor necrosis factor-alpha (TNFalpha) reduces food intake and participates in the regulation of energy homeostasis. However, TNFalpha signaling in the brain and the potential interaction with leptin have not been investigated to date. Here we studied the tyrosine phosphorylation of STAT (signal transducer and activator of transcription) proteins in the hypothalamus of normal rats after iv injection of recombinant murine leptin or TNFalpha or coinjection of both cytokines. Immunoblot analysis of hypothalamic lysates with a phospho-specific STAT3 antibody showed a 6- to 7-fold stimulation of STAT3 tyrosine phosphorylation in response to both leptin and TNFalpha. Importantly, when coinjecting both cytokines, a remarkable synergistic activation (24-fold increase in STAT3 phosphorylation) could be detected. No other STAT proteins (STAT1, STAT5) were activated by leptin, whereas TNFalpha injection resulted in a dose-dependent phosphorylation of hypothalamic STAT5. In contrast to its action in the brain, leptin was unable to produce STAT3 phosphorylation in the liver, either alone or in combination with TNFalpha. These data show that TNFalpha, independently of leptin, activates hypothalamic STAT signaling pathways and enhances leptin action at the level of STAT3. We therefore suggest that TNFalpha may represent a modulator of leptin action in the hypothalamus.
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Affiliation(s)
- N M Rizk
- Molecular Cardiology, German Diabetes Research Institute, D-40225 Duesseldorf, Germany
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Abstract
OBJECTIVE Increased levels of hypothalamic neuropeptide-Y (NPY) are thought to contribute to the manifestation of the obese phenotype. The aim of this study was to characterize the interactions between leptin, insulin and NPY in the pathogenesis of polygenic obesity. DESIGN AND METHODS A polygenic obese animal model, the New Zealand obese mouse (NZO) and its age-matched control, was used to assess the hypothalamic mRNA expression of NPY, the insulin receptor (IR) and the leptin receptor (Ob-Rb), by semiquantitative polymerase chain reaction. Experiments were performed early (at eight weeks old) and late (at 40 weeks old) in the life of these animals. RESULTS Serum glucose was significantly elevated in obese mice. Serum insulin levels were not different between obese and lean mice, whereas serum leptin levels were significantly elevated in obese mice and increased continuously during life [reaching extremely high values at 40 weeks (41.5+/-4.1 vs 3.4+/-0.25 ng/ml for obese and lean, respectively). The hypothalamic expression of NPY mRNA was significantly higher in NZO mice compared to controls at both eight weeks (2.3-fold) and 40 weeks (1.9-fold), respectively, whereas expression of IR and Ob-Rb remained unaffected. CONCLUSION Increased hypothalamic expression of NPY due to leptin resistance, may be involved in the development of polygenic obesity. Unchanged Ob-Rb expression suggests that either a defective hypothalamic uptake or defects in Ob-Rb signalling underly this process.
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Affiliation(s)
- N M Rizk
- Mansoura University, Department of Physiology, Egypt
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Abstract
OBJECTIVE To assess the quality of life and functional status of patients who have undergone hemimandibulectomy based on the type of reconstructive procedure performed. STUDY DESIGN Survey, retrospective. METHODS Twenty-one patients who had undergone hemimandibulectomy and had similar defects were divided into two groups based on the reconstructive technique utilized. Eleven patients were placed in the soft tissue reconstruction group. Ten patients were placed in the mandible reconstruction group. All patients were assessed for: function, utilizing the Performance Status Scale, and quality of life, using a general cancer questionnaire (FACT-G) and a series of questions specific for head and neck cancer patients. RESULTS Mandible reconstruction produced a perceived better physical appearance (P = .02), better eating ability (P = .04), and a better overall quality of life (P = .002). The mandible reconstruction cohort consistently outscored the soft tissue cohort on all questionnaires. CONCLUSION Restoration of mandibular continuity after hemimandibulectomy leads to improved function and a superior quality of life in appropriately selected patients.
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Affiliation(s)
- K M Wilson
- University of Cincinnati, Department of Otolaryngology, Ohio 45267-0528, USA
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Rizk NM, Meier DA, Pastorek DJ, Krakower GR, Kissebah AH. Glucose utilization in muscle fiber types: use of the partial pancreatectomized rat model to distinguish effects of glucose and insulin on insulin resistance. Mol Genet Metab 1998; 65:44-50. [PMID: 9787094 DOI: 10.1006/mgme.1998.2736] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have used the partially pancreatectomized infusion model in order to examine individual and combined effects of glucose and insulin on insulin resistance in rat skeletal muscles. Infusing glucose or insulin can produce animals which are hyperglycemic, hyperinsulinemic, or both. Individual and combined effects of chronic hyperglycemia and hyperinsulinemia on basal and insulin-mediated glucose utilization indices in glycolytic and oxidative muscle fibers were examined by 2-deoxyglucose uptake. Hyperglycemia reduced the basal glucose utilization index by 49% and hyperinsulinemia by 55%, while combined hyperglycemia + hyperinsulinemia diminished 2-deoxyglucose uptake by 69%. Maximally insulin-stimulated utilization was diminished only 28% under hyperglycemia but by 81% in the hyperinsulinemic state. In order to assess utilization in individual muscle fibers, uptake was examined in three tissues of differing fiber composition. The slow-twitch oxidative soleus muscle demonstrated greater basal uptake than the fast-twitch gastrocnemius (glycolytic) and quadriceps (oxidative) muscles. In addition basal (though not maximally insulin-stimulated) glucose utilization in the fast-twitch fibers was affected by chronic glucose and insulin to a greater extent than the slow-twitch soleus muscle, indicating that chronic hyperglycemia is more likely to precipitate insulin resistance in fast-twitch muscles. Significant differences in glucose metabolism among muscle fiber types suggests that results from insulin resistance studies in mixed muscles may be skewed according to their fiber composition.
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Affiliation(s)
- N M Rizk
- Faculty of Medicine, Mansoura University, Mansoura, Egypt
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Abstract
Defects in glucose uptake are among the primary defects associated with peripheral insulin resistance, but fundamental mechanisms leading to this state are poorly understood. In order to elucidate mechanisms leading toward defects in glucose transport, we have used a partially pancreatectomized infusion (PxI) animal model with infusions of saline, glucose, or insulin to examine individual and combined effects of hyperglycemia and hyperinsulinemia on skeletal muscle glucose utilization. Moderate hyperglycemia induced by pancreatectomy reduced basal hindlimb muscle glucose utilization by 57% without affecting maximal insulin-stimulated glucose utilization; insulin administered in an amount sufficient to correct this hyperglycemia did not alter basal glucose utilization, but maximal insulin-stimulated glucose utilization was sharply diminished (75%); hyperglycemia with hyperinsulinemia similarly reduced basal and maximal insulin-stimulated glucose utilization. In order to establish the role of the glucose transporter protein in these insulin-resistant states, we quantified GLUT 4 content by immunoblotting and GLUT 4 mRNA by solution hybridization/RNAse protection assays. Hyperglycemia (2 weeks) reduced total muscle GLUT 4 protein content (53%) and mRNA (46%), while subsequent hyperinsulinemia (72 h) with either normo- or hyperglycemia partially restored both total GLUT 4 protein and mRNA levels. As insulin-stimulated GLUT 4 content in plasma membranes was not diminished by combined hyperglycemia/hyperinsulinemia, these results indicate functional GLUT 4 translocation in this model and suggest suppression of GLUT 4 transporter activity.
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Affiliation(s)
- N M Rizk
- Faculty of Medicine, Department of Physiology, Mansoura University, Egypt
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Hassan SS, Rizk NM. Miniaturized graphite sensors doped with metal-bathophenanthroline complexes for the selective potentiometric determination of uric acid in biological fluids. Analyst 1997; 122:815-9. [PMID: 9338988 DOI: 10.1039/a701038i] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Miniaturized poly(vinyl chloride) matrix membrane sensors in an all-solid-state graphite support, responsive to urate anion, were developed. The membranes incorporate lipophilic ion-pair complexes of urate anion with ruthenium(III), iron(II), nickel(II) and copper(I) bathophenanthroline (4,7-diphenyl-1,10-phenanthroline) counter cations. The sensors demonstrate a near-Nernstian response to urate over the concentration range 1 x 10(-2)-1 x 10(-5) mol l-1 and have micromolar detection limits and good selectivity properties. The response is virtually unaffected by pH changes in the range 7-10 and the response times are 5-10 s in aqueous solutions and in human serum and urine samples. A flow injection detector incorporating an iron(II) bathophenanthroline-urate graphite sensor was used for continuous monitoring of uric acid. The minimum detectable concentration was approximately 8 micrograms ml-1 and the sample throughput was approximately 120 h-1. Direct potentiometric determination of uric acid in the static and hydrodynamic modes of operation over the range 15 micrograms ml-1-1.5 mg ml-1 showed average recoveries of 98.7 and 97.8% with RSDs of 0.6 and 0.7%, respectively. Application of the method to the determination of uric acid in human serum and urine gave results that compared favourably with those obtained by the standard spectrophotometric method.
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Affiliation(s)
- S S Hassan
- Department of Chemistry, Faculty of Science, Ain Shams University, Cairo, Egypt
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