Diurnal expression of the rat intestinal sodium–glucose cotransporter 1 (SGLT1) is independent of local luminal factors

Stearns, Adam T.; Balakrishnan, Anita; Rhoads, David B.; Ashley, Stanley W.; Tavakkolizadeh, Ali

doi:10.1016/j.surg.2008.11.004

Cited by 25 publications

(33 citation statements)

References 37 publications

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“…Western blotting of sham mucosa resulted in a single Sglt1 band, with an apparent mass of 73 kDa. This is consistent with our previous experience (36), with the native Sglt1 band running with an apparent molecular mass of 68 -73 kDa (Fig. 6B).…”

supporting

confidence: 93%

“…Alongside the native Sglt1 band (73 kDa), was a second band forming a tight doublet, at ϳ6 kDa lighter than the native species (67 kDa). This apparent difference in molecular weight is consistent with our previously described deglycosylated form (36). There was a third species also, apparently less mobile and with an estimated molecular mass at 88 kDa, 15 kDa heavier than the native band.…”

supporting

confidence: 91%

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Impact of Roux-en-Y gastric bypass surgery on rat intestinal glucose transport

Stearns

Balakrishnan

Tavakkolizadeh

2009

American Journal of Physiology-Gastrointestinal and Liver Physi

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Stearns AT, Balakrishnan A, Tavakkolizadeh A. Impact of Roux-en-Y gastric bypass surgery on rat intestinal glucose transport. Am J Physiol Gastrointest Liver Physiol 297: G950-G957, 2009. First published September 3, 2009 doi:10.1152/ajpgi.00253.2009.-Roux-en-Y gastric bypass (RYGB) has become the gold-standard bariatric procedure, partly because of the rapid resolution of accompanying diabetes. There is increasing evidence this is mediated by duodenal exclusion. We hypothesize that duodenal exclusion suppresses intestinal Na ϩ /glucose cotransporter SGLT1-mediated glucose transport, improving glucose handling, and aimed to test this in a rodent RYGB model. Sprague-Dawley rats underwent sham procedure or duodenal exclusion by RYGB (10 cm Roux, 16 cm biliopancreatic limbs). Animals were maintained for 3 wk on a Western diet, before harvest at 10 AM, 4 PM, and 10 PM. Sections were taken from each limb for hematoxylin and eosin staining, and morphological assessment was performed. Functional glucose uptake studies, along with Western blotting and quantitative PCR, were performed on Roux limb. Histology showed morphometric changes in Roux and common limbs, with increase in villus height and crypt depth compared with BP and sham jejunum. Despite this, glucose transport was reduced by up to 68% (P Ͻ 0.001) in the Roux limb compared with sham jejunum. Normal diurnal rhythms in glucose uptake were ablated. This occurred at a posttranscriptional level, with little change in message but appearance of different weight species of Sglt1 on Western blotting. We have shown duodenal exclusion significantly influences both intestinal structure and glucose transport function, with glucose absorptive capacity reduced after RYGB. This provides a novel mechanistic explanation for some of the antidiabetic effects of RYGB. bariatric surgery; diabetes; sglt1 OBESITY, TOGETHER WITH ASSOCIATED Type 2 diabetes mellitus (T2DM), has become a surgical disease (29). Bariatric surgery now represents the first-line treatment for morbid obesity, leading to resolution of obesity-related comorbidities such hypertension, sleep apnea, and T2DM and consequently improved life expectancy (1, 9, 35).Roux-en-Y gastric bypass (RYGB) is regarded as the goldstandard therapy for weight loss, with 60 -70% excess weight loss at two years (7). An important observation is the rapid associated resolution of T2DM, achieved prior to any significant weight loss; 84% of all patients had complete remission of T2DM, often within days after surgery (7). These impressive results have led many to regard RYGB as a metabolic operation. Unfortunately, 70% of T2DM patients do not fulfill the weight criteria to be eligible for bariatric surgery. Although there has been debate about the role of this procedure in T2DM in less obese patients, the invasive nature of the procedure has prevented widespread acceptance (10,23,34).Unfortunately, the mechanisms underlying diabetes resolution in RYGB remain unclear, limiting development of less invasive alternatives. A major feature of T...

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confidence: 93%

supporting

confidence: 91%

Impact of Roux-en-Y gastric bypass surgery on rat intestinal glucose transport

Stearns

Balakrishnan

Tavakkolizadeh

2009

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…It has previously been shown that N-glycosylation in the extracellular loop domain of the proton pump H-K-ATPase contributes to protection from trypsinolysis (11,63). Interestingly, Stearns et al (60) observed in the rat in situ that isolated jejunum loops, which are not exposed to luminal contents, express both unglycosylated and glycosylated SGLT1, while only glycosylated SGLT1 was expressed in the normal jejunum, which is exposed to luminal contents. Another possible protection mechanism from proteolytic degradation is viscoelastic mucus gel that provides a physical barrier (34).…”

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confidence: 99%

Role ofN-glycosylation in cell surface expression and protection against proteolysis of the intestinal anion exchanger SLC26A3

Hayashi

Yamashita

2012

American Journal of Physiology-Cell Physiology

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Ϫ exchanger that plays a major role in Cl Ϫ absorption from the intestine. Its mutation causes congenital chloridelosing diarrhea. It has been shown that SLC26A3 are glycosylated, with the attached carbohydrate being extracellular and perhaps modulating function. However, the role of glycosylation has yet to be clearly determined. We used the approaches of biochemical modification and site-directed mutagenesis to prevent glycosylation. Deglycosylation experiments with glycosidases indicated that the mature glycosylated form of SLC26A3 exists at the plasma membrane, and a putative large second extracellular loop contains all of the N-linked carbohydrates. Deglycosylation of SLC26A3 causes depression of transport activity compared with wild-type, although robust intracellular pH changes were still observed, suggesting that N-glycosylation is not absolutely necessary for transport activity. To localize glycosylation sites, we mutated the five consensus sites by replacing asparagine (N) with glutamine. Immnoblotting suggests that SLC26A3 is glycosylated at N153, N161, and N165. Deglycosylation of SLC26A3 causes a defect in cell surface processing with decreased cell surface expression. We also assessed whether SLC26A3 is protected from tryptic digestion. While the mature glycosylated SLC26A3 showed little breakdown after treatment with trypsin, deglycosylated SLC26A3 exhibited increased susceptibility to trypsin, suggesting that the oligosaccharides protect SLC26A3 from tryptic digestion. In conclusion, our data indicate that N-glycosylation of SLC26A3 is important for cell surface expression and for protection from proteolytic degradation that may contribute to the understanding of pathogenesis of congenital disorders of glycosylation. chloride transport; glycosylation; intestine; proteolytic enzymes CHLORIDE IONS PLAY MANY PHYSIOLOGICAL roles, including regulation of cell volume, fluid secretion, and acid-base balance (1,5,49). Efficient absorption of Cl Ϫ from the intestine is important to maintain optimal levels of Cl Ϫ in the body. SLC26A3 is expressed in the apical membrane of intestinal epithelial cells and is thought to play a critical role in Cl Ϫ absorption and fluid homeostasis, in collaboration with Na ϩ

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“…Several transporters involved in absorption of carbohydrates and small peptides exhibit robust circadian fluctuations that seem to be regulated by two pathways. The first pathway involves food intake and is mediated by gut luminal signals, whereas the second one involves systemic entrainment pathways (21,22,35,40). In addition to nutrient absorption in the small intestine, the colonic absorption of some electrolytes and volatile fatty acids (5, 41, 42) and some intestinal secretory activity (4, 31, 32) exhibit diurnal rhythmicity.…”

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confidence: 99%

Circadian regulation of electrolyte absorption in the rat colon

Soták

Polidarová

Musı́lková

et al. 2011

American Journal of Physiology-Gastrointestinal and Liver Physi

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Soták M, Polidarová L, Musílková J, Hock M, Sumová A, Pácha J. Circadian regulation of electrolyte absorption in the rat colon. Am J Physiol Gastrointest Liver Physiol 301: G1066-G1074, 2011. First published September 8, 2011 doi:10.1152/ajpgi.00256.2011The intestinal transport of nutrients exhibits distinct diurnal rhythmicity, and the enterocytes harbor a circadian clock. However, temporal regulation of the genes involved in colonic ion transport, i.e., ion transporters and channels operating in absorption and secretion, remains poorly understood. To address this issue, we assessed the 24-h profiles of expression of genes encoding the sodium pump (subunits Atp1a1 and Atp1b1), channels (␣-, ␤-, and ␥-subunits of Enac and Cftr), transporters (Dra, Ae1, Nkcc1, Kcc1, and Nhe3), and the Na ϩ /H ϩ exchanger (NHE) regulatory factor (Nherf1) in rat colonic mucosa. Furthermore, we investigated temporal changes in the spatial localization of the clock genes Per1, Per2, and Bmal1 and the genes encoding ion transporters and channels along the crypt axis. In rats fed ad libitum, the expression of Atp1a1, ␥Enac, Dra, Ae1, Nhe3, and Nherf1 showed circadian variation with maximal expression at circadian time 12, i.e., at the beginning of the subjective night. The peak ␥Enac expression coincided with the rise in plasma aldosterone. Restricted feeding phase advanced the expression of Dra, Ae1, Nherf, and ␥Enac and decreased expression of Atp1a1. The genes Atp1b1, Cftr, ␣Enac, ␤Enac, Nkcc1, and Kcc1 did not show any diurnal variations in mRNA levels. A low-salt diet upregulated the expression of ␤Enac and ␥Enac during the subjective night but did not affect expression of ␣Enac. Similarly, colonic electrogenic Na ϩ transport was much higher during the subjective night than the subjective day. These findings indicate that the transporters and channels operating in NaCl absorption undergo diurnal regulation and suggest a role of an intestinal clock in the coordination of colonic NaCl absorption. rhythm; intestinal transport; transporters; channels VARIOUS FUNCTIONS OF THE INTESTINE such as motility, epithelial cell proliferation, digestion, and transport exhibit diurnal activities (9,13,30). Several transporters involved in absorption of carbohydrates and small peptides exhibit robust circadian fluctuations that seem to be regulated by two pathways. The first pathway involves food intake and is mediated by gut luminal signals, whereas the second one involves systemic entrainment pathways (21,22,35,40). In addition to nutrient absorption in the small intestine, the colonic absorption of some electrolytes and volatile fatty acids (5, 41, 42) and some intestinal secretory activity (4, 31, 32) exhibit diurnal rhythmicity.Functional circadian clocks operate in both the small (6, 23, 25) and large intestine (10,33,24). The molecular clock mechanism is based on interaction between transcription-based feedback loops. The transcription factors CLOCK and BMAL1 drive the transcription of Per, Cry, Rev-erb␣, and Ror␣ clock genes by binding CLO...

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Diurnal expression of the rat intestinal sodium–glucose cotransporter 1 (SGLT1) is independent of local luminal factors

Cited by 25 publications

References 37 publications

Impact of Roux-en-Y gastric bypass surgery on rat intestinal glucose transport

Impact of Roux-en-Y gastric bypass surgery on rat intestinal glucose transport

Role ofN-glycosylation in cell surface expression and protection against proteolysis of the intestinal anion exchanger SLC26A3

Circadian regulation of electrolyte absorption in the rat colon

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