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Levanovich PE, Daugherty AM, Komnenov D, Rossi NF. Dietary fructose and high salt in young male Sprague Dawley rats induces salt-sensitive changes in renal function in later life. Physiol Rep 2022; 10:e15456. [PMID: 36117446 PMCID: PMC9483717 DOI: 10.14814/phy2.15456] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 08/20/2022] [Indexed: 06/15/2023] Open
Abstract
Dietary fructose and salt are associated with hypertension and renal disease. Dietary input during critical postnatal periods may impact pathophysiology in maturity. The highest consumption of fructose occurs during adolescence. We hypothesized that a diet high in fructose with or without high salt in young male Sprague Dawley rats will lead to salt-sensitive hypertension, albuminuria, and decreased renal function in maturity. Four groups were studied from age 5 weeks: 20% glucose + 0.4% salt (GCS-GCS) or 20% fructose + 4% salt throughout (FHS-FHS). Two groups received 20% fructose + 0.4% salt or 20% fructose + 4% salt for 3 weeks (Phase I) followed by 20% glucose + 0.4% salt (Phase II). In Phase III (age 13-15 weeks), these two groups were challenged with 20% glucose + 4% salt, (FCS-GHS) and (FHS-GHS), respectively. Each group fed fructose in Phase I exhibited significantly higher MAP than GCS-GCS in Phase III. Net sodium balance, unadjusted, or adjusted for caloric intake and urine flow rate, and cumulative sodium balance were positive in FHS during Phase I and were significantly higher in FCS-GHS, FHS-GHS, and FHS-FHS vs GCS-GCS during Phase III. All three groups fed fructose during Phase I displayed significantly elevated albuminuria. GFR was significantly lower in FHS-FHS vs GCS-GCS at maturity. Qualitative histology showed mesangial expansion and hypercellularity in FHS-FHS rats. Thus, fructose ingestion during a critical period in rats, analogous to human preadolescence and adolescence, results in salt-sensitive hypertension and albuminuria in maturity. Prolonged dietary fructose and salt ingestion lead to a decline in renal function with evidence suggestive of mesangial hypercellularity.
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Affiliation(s)
| | - Ana M. Daugherty
- Department of Psychology and Institute of GerontologyWayne State UniversityDetroitMichiganUSA
| | - Dragana Komnenov
- Department of Internal MedicineWayne State UniversityDetroitMichiganUSA
| | - Noreen F. Rossi
- Department of PhysiologyWayne State UniversityDetroitMichiganUSA
- Department of Internal MedicineWayne State UniversityDetroitMichiganUSA
- John D. Dingell VA Medical CenterDetroitMichiganUSA
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2
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Khor BH, Komnenov D, Rossi NF. Impact of Dietary Fructose and High Salt Diet: Are Preclinical Studies Relevant to Asian Societies? Nutrients 2022; 14:2515. [PMID: 35745245 PMCID: PMC9227020 DOI: 10.3390/nu14122515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 06/08/2022] [Accepted: 06/11/2022] [Indexed: 02/01/2023] Open
Abstract
Fructose consumption, especially in food additives and sugar-sweetened beverages, has gained increasing attention due to its potential association with obesity and metabolic syndrome. The relationship between fructose and a high-salt diet, leading to hypertension and other deleterious cardiovascular parameters, has also become more evident, especially in preclinical studies. However, these studies have been modeled primarily on Western diets. The purpose of this review is to evaluate the dietary habits of individuals from China, Japan, and Korea, in light of the existing preclinical studies, to assess the potential relevance of existing data to East Asian societies. This review is not intended to be exhaustive, but rather to highlight the similarities and differences that should be considered in future preclinical, clinical, and epidemiologic studies regarding the impact of dietary fructose and salt on blood pressure and cardiovascular health worldwide.
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Affiliation(s)
- Ban Hock Khor
- Faculty of Food Science and Nutrition, Universiti Malaysia Sabah, Kota Kinabalu 88400, Malaysia;
| | - Dragana Komnenov
- Department of Internal Medicine, Wayne State University, Detroit, MI 48201, USA;
| | - Noreen F. Rossi
- Department of Internal Medicine, Wayne State University, Detroit, MI 48201, USA;
- Department of Physiology, Wayne State University, Detroit, MI 48201, USA
- Division of Research, John D. Dingell VA Medical Center, Detroit, MI 38201, USA
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3
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Jensen LJ, Lund MA, Salomonsson M, Goetze JP, Jonassen TE, Holstein-Rathlou NH, Axelsen LN, Sørensen CM. Diet-induced hypertension in rats is associated with increased renal vasoconstrictor response to angiotensin II after imitated endothelial dysfunction. Microvasc Res 2022; 141:104333. [DOI: 10.1016/j.mvr.2022.104333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 12/21/2021] [Accepted: 01/24/2022] [Indexed: 11/16/2022]
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xu C, Yu J. Pathophysiological Mechanisms of Hypertension Development Induced by Fructose Consumption. Food Funct 2022; 13:1702-1717. [DOI: 10.1039/d1fo03381f] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
During the past several decades, there has been a dramatic increase in fructose consumption worldwide in parallel with epidemics of metabolic diseases. Accumulating evidence has suggested that excessive fructose consumption...
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Kovesdy CP, Adebiyi A, Rosenbaum D, Jacobs JW, Quarles LD. Novel Treatments from Inhibition of the Intestinal Sodium-Hydrogen Exchanger 3. Int J Nephrol Renovasc Dis 2021; 14:411-420. [PMID: 34880650 PMCID: PMC8646223 DOI: 10.2147/ijnrd.s334024] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 11/11/2021] [Indexed: 12/31/2022] Open
Abstract
Plasma membrane sodium–hydrogen exchangers (NHE) transport Na+ into cells in exchange for H+. While there are nine isoforms of NHE in humans, this review focuses on the NHE3 isoform, which is abundantly expressed in the gastrointestinal tract, where it plays a key role in acid–base balance and water homeostasis. NHE3 inhibition in the small intestine results in luminal sodium and water retention, leading to a general decrease in paracellular water flux and diffusional driving force, reduced intestinal sodium absorption, and increased stool sodium excretion. The resulting softer and more frequent stools are the rationale for the development of tenapanor as a novel, first-in-class NHE3 inhibitor to treat irritable bowel syndrome with constipation. NHE3 also has additional therapeutic implications in nephrology. Inhibition of intestinal NHE3 also lowers blood pressure by reducing intestinal sodium absorption. Perhaps, the most novel effect is its ability to decrease intestinal phosphate absorption by inhibiting the paracellular phosphate absorption pathway. Therefore, selective pharmacological inhibition of NHE3 could be a potential therapeutic strategy to treat not only heart failure and hypertension but also hyperphosphatemia. This review presents an overview of the molecular and physiological functions of NHE3 and discusses how these functions translate to potential clinical applications in nephrology.
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Affiliation(s)
- Csaba P Kovesdy
- Division of Nephrology, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Adebowale Adebiyi
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN, USA
| | | | | | - L Darryl Quarles
- Division of Nephrology, University of Tennessee Health Science Center, Memphis, TN, USA
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6
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Herman MA, Birnbaum MJ. Molecular aspects of fructose metabolism and metabolic disease. Cell Metab 2021; 33:2329-2354. [PMID: 34619074 PMCID: PMC8665132 DOI: 10.1016/j.cmet.2021.09.010] [Citation(s) in RCA: 97] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Revised: 09/02/2021] [Accepted: 09/13/2021] [Indexed: 02/06/2023]
Abstract
Excessive sugar consumption is increasingly considered as a contributor to the emerging epidemics of obesity and the associated cardiometabolic disease. Sugar is added to the diet in the form of sucrose or high-fructose corn syrup, both of which comprise nearly equal amounts of glucose and fructose. The unique aspects of fructose metabolism and properties of fructose-derived metabolites allow for fructose to serve as a physiological signal of normal dietary sugar consumption. However, when fructose is consumed in excess, these unique properties may contribute to the pathogenesis of cardiometabolic disease. Here, we review the biochemistry, genetics, and physiology of fructose metabolism and consider mechanisms by which excessive fructose consumption may contribute to metabolic disease. Lastly, we consider new therapeutic options for the treatment of metabolic disease based upon this knowledge.
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Affiliation(s)
- Mark A Herman
- Division of Endocrinology, Metabolism, and Nutrition, Duke University, Durham, NC, USA; Duke Molecular Physiology Institute, Duke University, Durham, NC, USA; Department of Pharmacology and Cancer Biology, Duke University, Durham, NC, USA.
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7
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Helsley RN, Moreau F, Gupta MK, Radulescu A, DeBosch B, Softic S. Tissue-Specific Fructose Metabolism in Obesity and Diabetes. Curr Diab Rep 2020; 20:64. [PMID: 33057854 DOI: 10.1007/s11892-020-01342-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/10/2020] [Indexed: 02/08/2023]
Abstract
PURPOSE OF REVIEW The objective of this review is to provide up-to-date and comprehensive discussion of tissue-specific fructose metabolism in the context of diabetes, dyslipidemia, and nonalcoholic fatty liver disease (NAFLD). RECENT FINDINGS Increased intake of dietary fructose is a risk factor for a myriad of metabolic complications. Tissue-specific fructose metabolism has not been well delineated in terms of its contribution to detrimental health effects associated with fructose intake. Since inhibitors targeting fructose metabolism are being developed for the management of NAFLD and diabetes, it is essential to recognize how inability of one tissue to metabolize fructose may affect metabolism in the other tissues. The primary sites of fructose metabolism are the liver, intestine, and kidney. Skeletal muscle and adipose tissue can also metabolize a large portion of fructose load, especially in the setting of ketohexokinase deficiency, the rate-limiting enzyme of fructose metabolism. Fructose can also be sensed by the pancreas and the brain, where it can influence essential functions involved in energy homeostasis. Lastly, fructose is metabolized by the testes, red blood cells, and lens of the eye where it may contribute to infertility, advanced glycation end products, and cataracts, respectively. An increase in sugar intake, particularly fructose, has been associated with the development of obesity and its complications. Inhibition of fructose utilization in tissues primary responsible for its metabolism alters consumption in other tissues, which have not been traditionally regarded as important depots of fructose metabolism.
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Affiliation(s)
- Robert N Helsley
- Division of Pediatric Gastroenterology, Department of Pediatrics, University of Kentucky College of Medicine, Lexington, KY, 40506, USA
| | - Francois Moreau
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA
| | - Manoj K Gupta
- Islet Cell and Regenerative Medicine, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA, 02215, USA
| | - Aurelia Radulescu
- Department of Pediatrics, University of Kentucky College of Medicine and Kentucky Children's Hospital, Lexington, KY, 40536, USA
| | - Brian DeBosch
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, 63131, USA
| | - Samir Softic
- Division of Pediatric Gastroenterology, Department of Pediatrics, University of Kentucky College of Medicine, Lexington, KY, 40506, USA.
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA.
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, 138 Leader Ave, Lexington, KY, 40506, USA.
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8
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Heyman SN, Bursztyn M, Szalat A, Muszkat M, Abassi Z. Fasting-Induced Natriuresis and SGLT: A New Hypothesis for an Old Enigma. Front Endocrinol (Lausanne) 2020; 11:217. [PMID: 32457696 PMCID: PMC7221140 DOI: 10.3389/fendo.2020.00217] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 03/26/2020] [Indexed: 11/17/2022] Open
Abstract
For years, physicians and scientists were enthralled by the enigmatic phenomenon of fasting-associated diuresis and natriuresis and their reversal by feeding. This abrupt response is most prominent in obese and hypertensive individuals, and if repeated once and again may lead to the attenuation of blood pressure and improve insulin sensitivity. The mechanisms involved in early natriuresis and diuresis remain speculative as the renin-angiotensin-aldosterone axis and natriuretic peptides are initially suppressed. Based on gained insight using sodium-glucose transporter 2 (SGLT-2) inhibitors, herein, we propose a role for enhanced post-prandial proximal tubular sodium uptake, mediated by increased glucose-sodium co-transport, as daily filtered glucose increases, and reduced sodium uptake when glucose reabsorption diminishes. This phenomenon might be more pronounced in diabetics due to prolonged post-prandial hyperglycemia and intense SGLT-driven transport. Our hypothesis may also provide a physiologic basis for fasting-related reduced blood pressure in hypertension. This theory deserves challenging by experimental and clinical studies.
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Affiliation(s)
- Samuel N. Heyman
- Department of Medicine, Hadassah Hebrew University Hospital, Mt. Scopus, Jerusalem, Israel
- *Correspondence: Samuel N. Heyman
| | - Michael Bursztyn
- Department of Medicine, Hadassah Hebrew University Hospital, Mt. Scopus, Jerusalem, Israel
| | - Auryan Szalat
- Department of Medicine, Hadassah Hebrew University Hospital, Mt. Scopus, Jerusalem, Israel
| | - Mordechai Muszkat
- Department of Medicine, Hadassah Hebrew University Hospital, Mt. Scopus, Jerusalem, Israel
| | - Zaid Abassi
- Department of Physiology and Biophysics, Ruth and Bruce Rappaport Faculty of Medicine, Technion-IIT, Haifa, Israel
- Department of Laboratory Medicine, Rambam Health Care Campus, Haifa, Israel
- Zaid Abassi
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9
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Fructose increases the activity of sodium hydrogen exchanger in renal proximal tubules that is dependent on ketohexokinase. J Nutr Biochem 2019; 71:54-62. [DOI: 10.1016/j.jnutbio.2019.05.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 05/20/2019] [Accepted: 05/21/2019] [Indexed: 11/22/2022]
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10
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Komnenov D, Levanovich PE, Rossi NF. Hypertension Associated with Fructose and High Salt: Renal and Sympathetic Mechanisms. Nutrients 2019; 11:nu11030569. [PMID: 30866441 PMCID: PMC6472002 DOI: 10.3390/nu11030569] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 02/26/2019] [Accepted: 03/04/2019] [Indexed: 02/06/2023] Open
Abstract
Hypertension is a leading cause of cardiovascular and chronic renal disease. Despite multiple important strides that have been made in our understanding of the etiology of hypertension, the mechanisms remain complex due to multiple factors, including the environment, heredity and diet. This review focuses on dietary contributions, providing evidence for the involvement of elevated fructose and salt consumption that parallels the increased incidence of hypertension worldwide. High fructose loads potentiate salt reabsorption by the kidney, leading to elevation in blood pressure. Several transporters, such as NHE3 and PAT1 are modulated in this milieu and play a crucial role in salt-sensitivity. High fructose ingestion also modulates the renin-angiotensin-aldosterone system. Recent attention has been shifted towards the contribution of the sympathetic nervous system, as clinical trials demonstrated significant reductions in blood pressure following renal sympathetic nerve ablation. New preclinical data demonstrates the activation of the renal sympathetic nerves in fructose-induced salt-sensitive hypertension, and reductions of blood pressure after renal nerve ablation. This review further demonstrates the interplay between sodium handling by the kidney, the renin-angiotensin-aldosterone system, and activation of the renal sympathetic nerves as important mechanisms in fructose and salt-induced hypertension.
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Affiliation(s)
- Dragana Komnenov
- Department of Physiology, Wayne State University, 4160 John R Street #908, Detroit, MI 48201, USA.
- Department of Internal Medicine, Wayne State University, 4160 John R Street #908, Detroit, MI 48201, USA.
| | - Peter E Levanovich
- Department of Physiology, Wayne State University, 4160 John R Street #908, Detroit, MI 48201, USA.
| | - Noreen F Rossi
- Department of Physiology, Wayne State University, 4160 John R Street #908, Detroit, MI 48201, USA.
- Department of Internal Medicine, Wayne State University, 4160 John R Street #908, Detroit, MI 48201, USA.
- John D. Dingell VA Medical Center, 4646 John R Street, Detroit, MI 48201, USA.
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11
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Ares GR, Kassem KM, Ortiz PA. Fructose acutely stimulates NKCC2 activity in rat thick ascending limbs by increasing surface NKCC2 expression. Am J Physiol Renal Physiol 2018; 316:F550-F557. [PMID: 30516424 DOI: 10.1152/ajprenal.00136.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The thick ascending limb (TAL) reabsorbs 25% of the filtered NaCl through the Na+-K+-2Cl- cotransporter (NKCC2). NKCC2 activity is directly related to surface NKCC2 expression and phosphorylation. Higher NaCl reabsorption by TALs is linked to salt-sensitive hypertension, which is linked to consumption of fructose in the diet. However, little is known about the effects of fructose on renal NaCl reabsorption. We hypothesized that fructose, but not glucose, acutely enhances TAL-dependent NaCl reabsorption by increasing NKCC2 activity via stimulation of surface NKCC2 levels and phosphorylation at Thr96/101. We found that fructose (5 mM) increased transport-related O2 consumption in TALs by 11.1 ± 3.2% ( P < 0.05). The effect of fructose on O2 consumption was blocked by furosemide. To study the effect of fructose on NKCC2 activity, we measured the initial rate of NKCC2-dependent thallium influx. We found that 20 min of treatment with fructose (5 mM) increased NKCC2 activity by 58.5 ± 16.9% ( P < 0.05). We then used surface biotinylation to measure surface NKCC2 levels in rat TALs. Fructose increased surface NKCC2 expression in a concentration-dependent manner (22 ± 5, 49 ± 10, and 101 ± 59% of baseline with 1, 5, and 10 mM fructose, respectively, P < 0.05), whereas glucose or a glucose metabolite did not. Fructose did not change NKCC2 phosphorylation at Thre96/101 or total NKCC2 expression. We concluded that acute fructose treatment increases NKCC2 activity by enhancing surface NKCC2 expression, rather than NKCC2 phosphorylation. Our data suggest that fructose consumption could contribute to salt-sensitive hypertension by stimulating NKCC2-dependent NaCl reabsorption in TALs.
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Affiliation(s)
- Gustavo R Ares
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - Kamal M Kassem
- Department of Internal Medicine, University of Cincinnati Medical Center , Cincinnati, Ohio
| | - Pablo A Ortiz
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan.,Department of Physiology, Wayne State University , Detroit, Michigan
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12
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Li L, Byrd M, Doh K, Dixon PD, Lee H, Tiwari S, Ecelbarger CM. Absence of renal enlargement in fructose-fed proximal-tubule-select insulin receptor (IR), insulin-like-growth factor receptor (IGF1R) double knockout mice. Physiol Rep 2018; 4:4/23/e13052. [PMID: 27923977 PMCID: PMC5357825 DOI: 10.14814/phy2.13052] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 10/25/2016] [Accepted: 11/02/2016] [Indexed: 02/02/2023] Open
Abstract
The major site of fructose metabolism in the kidney is the proximal tubule (PT). To test whether insulin and/or IGF1 signaling in the PT is involved in renal structural/functional responses to dietary fructose, we bred mice with dual knockout (KO) of the insulin receptor (IR) and the IGF1 receptor (IGF1R) in PT by Cre-lox recombination, using a γ-glutamyl transferase promoter. KO mice had slightly (~10%) reduced body and kidney weights, as well as, a reduction in mean protein-to-DNA ratio in kidney cortex suggesting smaller cell size. Under control diet, IR and IGF1R protein band densities were 30-50% (P < 0.05) lower than WT, and the relative difference was greater in male animals. Male, but not female KO, also had significantly reduced band densities for Akt (protein kinase B), phosphorylated AktT308 and IRY1162/1163 A high-fructose diet (1-month) led to a significant increase in kidney weight in WT males (12%), but not in KO males or in either genotype of female mice. Kidney enlargement in the WT males was accompanied by a small, insignificant fall in protein-to-DNA ratio, supporting hyperplasia rather than hypertrophy. Fructose feeding of male WT mice led to significantly higher sodium bicarbonate exchanger (NBCe1), sodium hydrogen exchanger (NHE3), sodium phosphate co-transporter (NaPi-2), and transforming growth factor-β (TGF-β) abundances, as compared to male KO, suggesting elevated transport capacity and an early feature of fibrosis may have accompanied the renal enlargement. Overall, IR and/or IGF1R appear to have a role in PT cell size and enlargement in response to high-fructose diet.
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Affiliation(s)
- Lijun Li
- Department of Medicine, Georgetown University, Washington, District of Columbia
| | - Marcus Byrd
- Department of Medicine, Georgetown University, Washington, District of Columbia
| | - Kwame Doh
- Department of Medicine, Georgetown University, Washington, District of Columbia
| | - Patrice D Dixon
- Department of Medicine, Georgetown University, Washington, District of Columbia
| | - Hwal Lee
- Department of Medicine, Georgetown University, Washington, District of Columbia
| | - Swasti Tiwari
- Department of Medicine, Georgetown University, Washington, District of Columbia.,Department of Molecular Medicine & Biotechnology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
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Zenner ZP, Gordish KL, Beierwaltes WH. Free radical scavenging reverses fructose-induced salt-sensitive hypertension. Integr Blood Press Control 2017; 11:1-9. [PMID: 29296095 PMCID: PMC5741067 DOI: 10.2147/ibpc.s147674] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
We have previously reported that a moderate dietary supplementation of 20% fructose but not glucose leads to a salt-sensitive hypertension related to increased proximal sodium–hydrogen exchanger activity and increased renal sodium retention. We also found that while high salt increased renal nitric oxide formation, this was retarded in the presence of fructose intake. We hypothesized that at least part of the pathway leading to fructose-induced salt-sensitive hypertension could be due to fructose-induced formation of reactive oxygen species and inappropriate stimulation of renin secretion, all of which would contribute to an increase in blood pressure. We found that both 20% fructose intake and a high-salt diet stimulated 8-isoprostane excretion. The superoxide dismutase (SOD) mimetic tempol significantly reduced this elevated excretion. Next, we placed rats on a high-salt diet (4%) for 1 week in combination with normal rat chow or 20% fructose with or without chronic tempol administration. A fructose plus high-salt diet induced a rapid increase (15 mmHg) in systolic blood pressure and reversed high salt suppression of plasma renin activity. Tempol treatment reversed the pressor response and restored high salt suppression of renin. We conclude that fructose-induced salt-sensitive hypertension is driven by increased renal reactive oxygen species formation associated with salt retention and an enhanced renin–angiotensin system.
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Affiliation(s)
- Zachary P Zenner
- Department of Internal Medicine, Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit, MI, USA
| | - Kevin L Gordish
- Department of Internal Medicine, Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit, MI, USA
| | - William H Beierwaltes
- Department of Internal Medicine, Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit, MI, USA
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14
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Dietary Fructose Enhances the Ability of Low Concentrations of Angiotensin II to Stimulate Proximal Tubule Na⁺ Reabsorption. Nutrients 2017; 9:nu9080885. [PMID: 28813008 PMCID: PMC5579678 DOI: 10.3390/nu9080885] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/10/2017] [Accepted: 08/11/2017] [Indexed: 11/18/2022] Open
Abstract
Fructose-enriched diets cause salt-sensitive hypertension. Proximal tubules (PTs) reabsorb 70% of the water and salt filtered through the glomerulus. Angiotensin II (Ang II) regulates this process. Normally, dietary salt reduces Ang II allowing the kidney to excrete more salt, thereby preventing hypertension. We hypothesized that fructose-enriched diets enhance the ability of low concentrations of Ang II to stimulate PT transport. We measured the effects of a low concentration of Ang II (10−12 mol/L) on transport-related oxygen consumption (QO2), and Na/K-ATPase and Na/H-exchange (NHE) activities and expression in PTs from rats consuming tap water (Control) or 20% fructose (FRUC). In FRUC-treated PTs, Ang II increased QO2 by 14.9 ± 1.3 nmol/mg/min (p < 0.01) but had no effect in Controls. FRUC elevated NHE3 expression by 19 ± 3% (p < 0.004) but not Na/K-ATPase expression. Ang II stimulated NHE activity in FRUC PT (Δ + 0.7 ± 0.1 Arbitrary Fluorescent units (AFU)/s, p < 0.01) but not in Controls. Na/K-ATPase activity was not affected. The PKC inhibitor Gö6976 blocked the ability of FRUC to augment the actions of Ang II. FRUC did not alter the inhibitory effect of dopamine on NHE activity. We conclude that dietary fructose increases the ability of low concentrations of Ang II to stimulate PT Na reabsorption via effects on NHE.
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15
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Frame AA, Wainford RD. Renal sodium handling and sodium sensitivity. Kidney Res Clin Pract 2017; 36:117-131. [PMID: 28680820 PMCID: PMC5491159 DOI: 10.23876/j.krcp.2017.36.2.117] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 12/27/2016] [Indexed: 01/11/2023] Open
Abstract
The pathophysiology of hypertension, which affects over 1 billion individuals worldwide, involves the integration of the actions of multiple organ systems, including the kidney. The kidney, which governs sodium excretion via several mechanisms including pressure natriuresis and the actions of renal sodium transporters, is central to long term blood pressure regulation and the salt sensitivity of blood pressure. The impact of renal sodium handling and the salt sensitivity of blood pressure in health and hypertension is a critical public health issue owing to the excess of dietary salt consumed globally and the significant percentage of the global population exhibiting salt sensitivity. This review highlights recent advances that have provided new insight into the renal handling of sodium and the salt sensitivity of blood pressure, with a focus on genetic, inflammatory, dietary, sympathetic nervous system and oxidative stress mechanisms that influence renal sodium excretion. Increased understanding of the multiple integrated mechanisms that regulate the renal handling of sodium and the salt sensitivity of blood pressure has the potential to identify novel therapeutic targets and refine dietary guidelines designed to treat and prevent hypertension.
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Affiliation(s)
- Alissa A Frame
- Department of Pharmacology & Experimental Therapeutics and The Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, USA
| | - Richard D Wainford
- Department of Pharmacology & Experimental Therapeutics and The Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, USA
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Castelo-Branco RC, Leite-Dellova DCA, Fernandes FB, Malnic G, de Mello-Aires M. The effects of angiotensin-(1-7) on the exchanger NHE3 and on [Ca 2+] i in the proximal tubules of spontaneously hypertensive rats. Am J Physiol Renal Physiol 2017; 313:F450-F460. [PMID: 28490531 DOI: 10.1152/ajprenal.00557.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 05/02/2017] [Accepted: 05/03/2017] [Indexed: 11/22/2022] Open
Abstract
The acute effects of angiotensin-1-7 [ANG-(1-7)] on the reabsorptive bicarbonate flow (J[Formula: see text]) were evaluated using stationary microperfusion in vivo in the proximal tubules of spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar-Kyoto (WKY) rats, using a microelectrode sensitive to H+ In WKY rats, the control J[Formula: see text] was 2.40 ± 0.10 nmol·cm-2·s-1 (n = 120); losartan (10-7 M) or A779 (10-6 M, a specific Mas antagonist), alone or in combination with losartan, decreased the J[Formula: see text] ANG-(1-7) had biphasic effects on J[Formula: see text]: at 10-9 M, it inhibited, and at 10-6, it stimulated the flow. S3226 [10-6 M, a specific Na+-H+ exchanger 3 (NHE3) antagonist] decreased J[Formula: see text] and changed the stimulatory effect of ANG-(1-7) to an inhibitory one but did not alter the inhibitory action of ANG-(1-7). In SHR, the control J[Formula: see text] was 2.04 ± 0.13 nmol·cm-2·s-1 (n = 56), and A779 and/or losartan reduced the flow. ANG-(1-7) at 10-9 M increased J[Formula: see text], and ANG-(1-7) at 10-6 M reduced it. The effects of A779, losartan, and S3226 on the J[Formula: see text] were similar to those found in WKY rats, which indicated that in SHR, the ANG-(1-7) action on the NHE3 was via Mas and ANG II type 1. The cytosolic calcium in the WKY or SHR rats was ~100 nM and was increased by ANG-(1-7) at 10-9 or 10-6 M. In hypertensive animals, a high plasma level of ANG-(1-7) inhibited NHE3 in the proximal tubule, which mitigated the hypertension caused by the high plasma level of ANG II.
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Affiliation(s)
| | - Deise C A Leite-Dellova
- Department of Basic Sciences, Faculdade de Zootecnia e Engenharia de Alimentos, University of São Paulo, Pirassununga, Brazil; and
| | - Fernanda Barrinha Fernandes
- Presbiteriana Mackenzie University of São Paulo and Department of Nephrology, Federal University of São Paulo-Universidade Estadual Paulista, São Paulo, Brazil
| | - Gerhard Malnic
- Department of Physiology and Biophysics, Biomedical Sciences Institute, University of São Paulo, São Paulo, Brazil
| | - Margarida de Mello-Aires
- Department of Physiology and Biophysics, Biomedical Sciences Institute, University of São Paulo, São Paulo, Brazil
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Xu C, Lu A, Lu X, Zhang L, Fang H, Zhou L, Yang T. Activation of Renal (Pro)Renin Receptor Contributes to High Fructose-Induced Salt Sensitivity. Hypertension 2016; 69:339-348. [PMID: 27993957 DOI: 10.1161/hypertensionaha.116.08240] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 08/09/2016] [Accepted: 11/28/2016] [Indexed: 12/16/2022]
Abstract
A high-fructose diet is shown to induce salt-sensitive hypertension, but the underlying mechanism largely remains unknown. The major goal of the present study was to test the role of renal (pro)renin receptor (PRR) in this model. In Sprague-Dawley rats, high-fructose intake increased renal expression of full-length PRR, which were attenuated by allopurinol. High-fructose intake also upregulated renal mRNA and protein expression of sodium/hydrogen exchanger 3 and Na/K/2Cl cotransporter, as well as in vivo Na/K/2Cl cotransporter activity, all of which were nearly completely blocked by a PRR decoy inhibitor PRO20 or allopurinol treatment. Parallel changes were observed for indices of intrarenal renin-angiotensin-system including renal and urinary renin and angiotensin II levels. Radiotelemetry demonstrated that high-fructose or a high-salt diet alone did not affect mean arterial pressure, but the combination of the 2 maneuvers induced a ≈10-mm Hg increase of mean arterial pressure, which was blunted by PRO20 or allopurinol treatment. In cultured human kidney 2 cells, both fructose and uric acid increased protein expression of soluble PRR in a time- and dose-dependent manner; fructose-induced PRR upregulation was inhibited by allopurinol. Taken together, our data suggest that fructose via uric acid stimulates renal expression of PRR/soluble PRR that stimulate sodium/hydrogen exchanger 3 and Na/K/2Cl cotransporter expression and intrarenal renin-angiotensin system to induce salt-sensitive hypertension.
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Affiliation(s)
- Chuanming Xu
- From the Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China (C.X., A.L., X.L., L.Z., H.F., L.Z., T.Y.); Internal Medicine, University of Utah, Salt Lake City (C.X., X.L., T.Y.); and Veterans Affairs Medical Center, Salt Lake City, Utah (X.L., T.Y.)
| | - Aihua Lu
- From the Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China (C.X., A.L., X.L., L.Z., H.F., L.Z., T.Y.); Internal Medicine, University of Utah, Salt Lake City (C.X., X.L., T.Y.); and Veterans Affairs Medical Center, Salt Lake City, Utah (X.L., T.Y.)
| | - Xiaohan Lu
- From the Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China (C.X., A.L., X.L., L.Z., H.F., L.Z., T.Y.); Internal Medicine, University of Utah, Salt Lake City (C.X., X.L., T.Y.); and Veterans Affairs Medical Center, Salt Lake City, Utah (X.L., T.Y.)
| | - Linlin Zhang
- From the Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China (C.X., A.L., X.L., L.Z., H.F., L.Z., T.Y.); Internal Medicine, University of Utah, Salt Lake City (C.X., X.L., T.Y.); and Veterans Affairs Medical Center, Salt Lake City, Utah (X.L., T.Y.)
| | - Hui Fang
- From the Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China (C.X., A.L., X.L., L.Z., H.F., L.Z., T.Y.); Internal Medicine, University of Utah, Salt Lake City (C.X., X.L., T.Y.); and Veterans Affairs Medical Center, Salt Lake City, Utah (X.L., T.Y.)
| | - Li Zhou
- From the Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China (C.X., A.L., X.L., L.Z., H.F., L.Z., T.Y.); Internal Medicine, University of Utah, Salt Lake City (C.X., X.L., T.Y.); and Veterans Affairs Medical Center, Salt Lake City, Utah (X.L., T.Y.)
| | - Tianxin Yang
- From the Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China (C.X., A.L., X.L., L.Z., H.F., L.Z., T.Y.); Internal Medicine, University of Utah, Salt Lake City (C.X., X.L., T.Y.); and Veterans Affairs Medical Center, Salt Lake City, Utah (X.L., T.Y.).
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Abstract
We are currently in the midst of an epidemic of metabolic disorders, which may, in part, be explained by excess fructose intake. This theory is supported by epidemiological observations as well as experimental studies in animals and humans. Rising consumption of fructose has been matched with growing rates of hypertension, leading to concern from public health experts. At this stage, the mechanisms underlying fructose-induced hypertension have not been fully characterized and the bulk of our knowledge is derived from animal models. Animal studies have shown that high-fructose diets up-regulate sodium and chloride transporters, resulting in a state of salt overload that increases blood pressure. Excess fructose has also been found to activate vasoconstrictors, inactivate vasodilators, and over-stimulate the sympathetic nervous system. Further work is required to determine the relevance of these findings to humans and to establish the level at which dietary fructose increases the risk of developing hypertension
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Lírio LM, Forechi L, Zanardo TC, Batista HM, Meira EF, Nogueira BV, Mill JG, Baldo MP. Chronic fructose intake accelerates non-alcoholic fatty liver disease in the presence of essential hypertension. J Diabetes Complications 2016; 30:85-92. [PMID: 26597602 DOI: 10.1016/j.jdiacomp.2015.10.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 10/03/2015] [Accepted: 10/14/2015] [Indexed: 12/22/2022]
Abstract
BACKGROUND The growing epidemic of metabolic syndrome has been related to the increased use of fructose by the food industry. In fact, the use of fructose as an ingredient has increased in sweetened beverages, such as sodas and juices. We thus hypothesized that fructose intake by hypertensive rats would have a worse prognosis in developing metabolic disorder and non-alcoholic fatty liver disease. METHODS Male Wistar and SHR rats aged 6weeks were given water or fructose (10%) for 6weeks. Blood glucose was measured every two weeks, and insulin and glucose sensitivity tests were assessed at the end of the follow-up. Systolic blood pressure was measure by plethysmography. Lean mass and abdominal fat mass were collected and weighed. Liver tissue was analyzed to determine interstitial fat deposition and fibrosis. RESULTS Fasting glucose increased in animals that underwent a high fructose intake, independent of blood pressure levels. Also, insulin resistance was observed in normotensive and mostly in hypertensive rats after fructose intake. Fructose intake caused a 2.5-fold increase in triglycerides levels in both groups. Fructose intake did not change lean mass. However, we found that fructose intake significantly increased abdominal fat mass deposition in normotensive but not in hypertensive rats. Nevertheless, chronic fructose intake only increased fat deposition and fibrosis in the liver in hypertensive rats. CONCLUSIONS We demonstrated that, in normotensive and hypertensive rats, fructose intake increased triglycerides and abdominal fat deposition, and caused insulin resistance. However, hypertensive rats that underwent fructose intake also developed interstitial fat deposition and fibrosis in liver.
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Affiliation(s)
- Layla Mendonça Lírio
- Department of Physiological Sciences, Federal University of Espírito Santo, Av Marechal Campos 1468, Maruipe, 29042-755, Vitória, ES, Brazil
| | - Ludimila Forechi
- Department of Physiological Sciences, Federal University of Espírito Santo, Av Marechal Campos 1468, Maruipe, 29042-755, Vitória, ES, Brazil
| | - Tadeu Caliman Zanardo
- Department of Morphology, Federal University of Espírito Santo, Av Marechal Campos 1468, Maruipe, 29042-755, Vitória, ES, Brazil
| | - Hiago Martins Batista
- Department of Pharmacy and Nutrition, Federal University of Espírito Santo, Rod Alto Universitário, Guararema, 29500-000, Alegre, ES, Brazil
| | - Eduardo Frizera Meira
- Department of Physiological Sciences, Federal University of Espírito Santo, Av Marechal Campos 1468, Maruipe, 29042-755, Vitória, ES, Brazil; Department of Pharmacy and Nutrition, Federal University of Espírito Santo, Rod Alto Universitário, Guararema, 29500-000, Alegre, ES, Brazil
| | - Breno Valentim Nogueira
- Department of Morphology, Federal University of Espírito Santo, Av Marechal Campos 1468, Maruipe, 29042-755, Vitória, ES, Brazil
| | - José Geraldo Mill
- Department of Physiological Sciences, Federal University of Espírito Santo, Av Marechal Campos 1468, Maruipe, 29042-755, Vitória, ES, Brazil
| | - Marcelo Perim Baldo
- Department of Physiological Sciences, Federal University of Espírito Santo, Av Marechal Campos 1468, Maruipe, 29042-755, Vitória, ES, Brazil.
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20
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Ares GR, Ortiz PA. Direct renal effects of a fructose-enriched diet: interaction with high salt intake. Am J Physiol Regul Integr Comp Physiol 2015; 309:R1078-81. [PMID: 26447210 DOI: 10.1152/ajpregu.00156.2015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 09/30/2015] [Indexed: 01/12/2023]
Abstract
Consumption of fructose has increased during the last 50 years. Excessive fructose consumption has a detrimental effect on mammalian health but the mechanisms remain unclear. In humans, a direct relationship exists between dietary intake of added sugars and increased risk for cardiovascular disease mortality (52). While the causes for this are unclear, we recently showed that fructose provided in the drinking water induces a salt-dependent increase in blood pressure in Sprague-Dawley rats in a matter of days (6). However, little is known about the effects of fructose in renal salt handling and whether combined intake of high fructose and salt can lead to salt-sensitive hypertension before the development of metabolic abnormalities. The long-term (more than 4 wk) adverse effects of fructose intake on renal function are not just due to fructose but are also secondary to alterations in metabolism which may have an impact on renal function. This minireview focuses on the acute effect of fructose intake and its effect on salt regulation, as they affect blood pressure.
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Affiliation(s)
- Gustavo R Ares
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan; and
| | - Pablo A Ortiz
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan; and Department of Physiology, Wayne State University, Detroit, Michigan
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21
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Crajoinas RO, Pessoa TD, Rodrigues MV, Malnic G, Girardi ACC. Changes in the activity and expression of protein phosphatase-1 accompany the differential regulation of NHE3 before and after the onset of hypertension in spontaneously hypertensive rats. Acta Physiol (Oxf) 2014; 211:395-408. [PMID: 24666699 DOI: 10.1111/apha.12288] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2013] [Revised: 11/18/2013] [Accepted: 03/18/2014] [Indexed: 12/14/2022]
Abstract
AIM The Na(+) /H(+) exchanger NHE3 activity decreases in the proximal tubule of spontaneously hypertensive rats (SHRs) as blood pressure increases, and this reduction is correlated with higher NHE3 phosphorylation levels at the PKA consensus site serine 552. This study tested the hypothesis that this lowered NHE3 activity is associated with an increase in PKA activity and expression, and/or a decrease in protein phosphatase-1 (PP1) activity and expression. METHODS Proximal tubule NHE3 activity was measured as the rate of bicarbonate reabsorption by stationary microperfusion. NHE3 phosphorylation and protein expression were determined by immunoblotting. PKA and PP1 activities were determined using specific substrates under optimal enzymatic conditions. RESULTS The PKA activator, 6-MB-cAMP, increased the phosphorylation levels of NHE3 at serine 552 in the renal cortex; this increase happens to a much greater extent in young pre-hypertensive SHRs (Y-SHRs) compared to adult SHRs with established hypertension (A-SHRs). Likewise, the inhibitory effect of 6-MB-cAMP on NHE3 transport activity was much more pronounced in the proximal tubules of Y-SHRs than in those of A-SHRs. Renal cortical activity of PKA was not significantly different between Y-SHRs and A-SHRs. On the other hand, Y-SHRs exhibited higher protein phosphatase 1 (PP1) activity, and their expression of the PP1 catalytic subunit PP1α in the renal cortex was also higher than in A-SHRs. CONCLUSION Collectively, these results support the idea that the lower NHE3 transport activity and higher phosphorylation occurring after the development of hypertension in SHRs are due, at least in part, to reduced PP1-mediated dephosphorylation of NHE3 at serine 552.
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Affiliation(s)
- R. O. Crajoinas
- Laboratory of Genetics and Molecular Cardiology; Heart Institute (InCor); University of São Paulo Medical School; São Paulo Brazil
| | - T. D. Pessoa
- Department of Physiology and Biophysics; Institute of Biomedical Sciences; University of São Paulo; São Paulo Brazil
| | - M. V. Rodrigues
- Laboratory of Genetics and Molecular Cardiology; Heart Institute (InCor); University of São Paulo Medical School; São Paulo Brazil
| | - G. Malnic
- Department of Physiology and Biophysics; Institute of Biomedical Sciences; University of São Paulo; São Paulo Brazil
| | - A. C. C. Girardi
- Laboratory of Genetics and Molecular Cardiology; Heart Institute (InCor); University of São Paulo Medical School; São Paulo Brazil
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Cabral PD, Hong NJ, Hye Khan MA, Ortiz PA, Beierwaltes WH, Imig JD, Garvin JL. Fructose stimulates Na/H exchange activity and sensitizes the proximal tubule to angiotensin II. Hypertension 2013; 63:e68-73. [PMID: 24379189 DOI: 10.1161/hypertensionaha.113.02564] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The proximal nephron reabsorbs 60% to 70% of the fluid and sodium and most of the filtered bicarbonate via Na/H exchanger 3. Enhanced proximal nephron transport is implicated in hypertension. Our findings show that a fructose-enriched diet causes salt sensitivity. We hypothesized that fructose stimulates luminal Na/H exchange activity and sensitizes the proximal tubule to angiotensin II. Na/H exchange was measured in rat proximal tubules as the rate of intracellular pH (pHi) recovery in fluorescent units/s. Replacing 5 mmol/L glucose with 5 mmol/L fructose increased the rate of pHi recovery (1.8±0.6 fluorescent units/s; P<0.02; n=8). Staurosporine, a protein kinase C inhibitor, blocked this effect. We studied whether this effect was because of the addition of fructose or removal of glucose. The basal rate of pHi recovery was first tested in the presence of a 0.6-mmol/L glucose and 1, 3, or 5 mmol/L fructose added in a second period. The rate of pHi recovery did not change with 1 mmol/L but it increased with 3 and 5 mmol/L of fructose. Adding 5 mmol/L glucose caused no change. Removal of luminal sodium blocked pHi recovery. With 5.5 mmol/L glucose, angiotensin II (1 pmol/L) did not affect the rate of pHi recovery (change, -1.1±0.5 fluorescent units/s; n=9) but it increased the rate of pHi recovery with 0.6 mmol/L glucose/5 mmol/L fructose (change, 4.0±2.2 fluorescent units/s; P<0.02; n=6). We conclude that fructose stimulates Na/H exchange activity and sensitizes the proximal tubule to angiotensin II. This mechanism is likely dependent on protein kinase C. These results may partially explain the mechanism by which a fructose diet induces hypertension.
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Affiliation(s)
- Pablo D Cabral
- Department of Physiology and Biophysics, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106-4970.
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Pasham V, Rotte A, Gu S, Yang W, Bhandaru M, Rexhepaj R, Pathare G, Lang F. Upregulation of intestinal NHE3 following saline ingestion. Kidney Blood Press Res 2013; 37:48-57. [PMID: 23548792 DOI: 10.1159/000343401] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/19/2013] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Little is known about the effect of salt content of ingested fluid on intestinal transport processes. Osmosensitive genes include the serum- and glucocorticoid-inducible kinase SGK1, which is up-regulated by hyperosmolarity and cell shrinkage. SGK1 is in turn a powerful stimulator of the intestinal Na(+)/H(+) exchanger NHE3. The present study was thus performed to elucidate, whether the NaCl content of beverages influences NHE3 activity. METHODS Mice were offered access to either plain water or isotonic saline ad libitum. NHE3 transcript levels and protein abundance in intestinal tissue were determined by confocal immunofluorescent microscopy, RT-PCR and western blotting, cytosolic pH (pHi) in intestinal cells from 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) fluorescence and Na(+)/H(+) exchanger activity from the Na(+) dependent realkalinization following an ammonium pulse. RESULTS Saline drinking significantly enhanced fluid intake and increased NHE3 transcript levels, NHE3 protein and Na(+)/H(+) exchanger activity. CONCLUSIONS Salt content of ingested fluid has a profound effect on intestinal Na(+)/H(+) exchanger expression and activity.
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Affiliation(s)
- Venkanna Pasham
- Department of Physiology, University of Tübingen, Tübingen, Germany
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