Conservative management versus tonsillectomy in adults with recurrent acute tonsillitis in the UK (NATTINA): a multicentre, open-label, randomised controlled trial.

BACKGROUND: Tonsillectomy is regularly performed in adults with acute tonsillitis, but with scarce evidence. A reduction in tonsillectomies has coincided with an increase in acute adult hospitalisation for tonsillitis complications. We aimed to assess the clinical effectiveness and cost-effectiveness of conservative management versus tonsillectomy in patients with recurrent acute tonsillitis. METHODS: This pragmatic multicentre, open-label, randomised controlled trial was conducted in 27 hospitals in the UK. Participants were adults aged 16 years or older who were newly referred to secondary care otolaryngology clinics with recurrent acute tonsillitis. Patients were randomly assigned (1:1) to receive tonsillectomy or conservative management using random permuted blocks of variable length. Stratification by recruiting centre and baseline symptom severity was assessed using the Tonsil Outcome Inventory-14 score (categories defined as mild 0-35, moderate 36-48, or severe 49-70). Participants in the tonsillectomy group received elective surgery to dissect the palatine tonsils within 8 weeks after random assignment and those in the conservative management group received standard non-surgical care during 24 months. The primary outcome was the number of sore throat days collected during 24 months after random assignment, reported once per week with a text message. The primary analysis was done in the intention-to-treat (ITT) population. This study is registered with the ISRCTN registry, 55284102. FINDINGS: Between May 11, 2015, and April 30, 2018, 4165 participants with recurrent acute tonsillitis were assessed for eligibility and 3712 were excluded. 453 eligible participants were randomly assigned (233 in the immediate tonsillectomy group vs 220 in the conservative management group). 429 (95%) patients were included in the primary ITT analysis (224 vs 205). The median age of participants was 23 years (IQR 19-30), with 355 (78%) females and 97 (21%) males. Most participants were White (407 [90%]). Participants in the immediate tonsillectomy group had fewer days of sore throat during 24 months than those in the conservative management group (median 23 days [IQR 11-46] vs 30 days [14-65]). After adjustment for site and baseline severity, the incident rate ratio of total sore throat days in the immediate tonsillectomy group (n=224) compared with the conservative management group (n=205) was 0·53 (95% CI 0·43 to 0·65; <0·0001). 191 adverse events in 90 (39%) of 231 participants were deemed related to tonsillectomy. The most common adverse event was bleeding (54 events in 44 [19%] participants). No deaths occurred during the study. INTERPRETATION: Compared with conservative management, immediate tonsillectomy is clinically effective and cost-effective in adults with recurrent acute tonsillitis. FUNDING: National Institute for Health Research.

Tonsillectomy compared with conservative management in patients over 16 years with recurrent sore throat: the NATTINA RCT and economic evaluation.

Background: The place of tonsillectomy in the management of sore throat in adults remains uncertain. Objectives: To establish the clinical effectiveness and cost-effectiveness of tonsillectomy, compared with conservative management, for tonsillitis in adults, and to evaluate the impact of alternative sore throat patient pathways. Design: This was a multicentre, randomised controlled trial comparing tonsillectomy with conservative management. The trial included a qualitative process evaluation and an economic evaluation. Setting: The study took place at 27 NHS secondary care hospitals in Great Britain. Participants: A total of 453 eligible participants with recurrent sore throats were recruited to the main trial. Interventions: Patients were randomised on a 1 : 1 basis between tonsil dissection and conservative management (i.e. deferred surgery) using a variable block-stratified design, stratified by (1) centre and (2) severity. Main outcome measures: The primary outcome measure was the total number of sore throat days over 24 months following randomisation. The secondary outcome measures were the number of sore throat episodes and five characteristics from Sore Throat Alert Return, describing severity of the sore throat, use of medications, time away from usual activities and the Short Form questionnaire-12 items. Additional secondary outcomes were the Tonsil Outcome Inventory-14 total and subscales and Short Form questionnaire-12 items 6 monthly. Evaluation of the impact of alternative sore throat patient pathways by observation and statistical modelling of outcomes against baseline severity, as assessed by Tonsil Outcome Inventory-14 score at recruitment. The incremental cost per sore throat day avoided, the incremental cost per quality-adjusted life-year gained based on responses to the Short Form questionnaire-12 items and the incremental net benefit based on costs and responses to a contingent valuation exercise. A qualitative process evaluation examined acceptability of trial processes and ramdomised arms. Results: There was a median of 27 (interquartile range 12-52) sore throats over the 24-month follow-up. A smaller number of sore throats was reported in the tonsillectomy arm [median 23 (interquartile range 11-46)] than in the conservative management arm [median 30 (interquartile range 14-65)]. On an intention-to-treat basis, there were fewer sore throats in the tonsillectomy arm (incident rate ratio 0.53, 95% confidence interval 0.43 to 0.65). Sensitivity analyses confirmed this, as did the secondary outcomes. There were 52 episodes of post-operative haemorrhage reported in 231 participants undergoing tonsillectomy (22.5%). There were 47 re-admissions following tonsillectomy (20.3%), 35 relating to haemorrhage. On average, tonsillectomy was more costly and more effective in terms of both sore throat days avoided and quality-adjusted life-years gained. Tonsillectomy had a 100% probability of being considered cost-effective if the threshold for an additional quality-adjusted life year was £20,000. Tonsillectomy had a 69% probability of having a higher net benefit than conservative management. Trial processes were deemed to be acceptable. Patients who received surgery were unanimous in reporting to be happy to have received it. Limitations: The decliners who provided data tended to have higher Tonsillectomy Outcome Inventory-14 scores than those willing to be randomised implying that patients with a higher burden of tonsillitis symptoms may have declined entry into the trial. Conclusions: The tonsillectomy arm had fewer sore throat days over 24 months than the conservative management arm, and had a high probability of being considered cost-effective over the ranges considered. Further work should focus on when tonsillectomy should be offered. National Trial of Tonsillectomy IN Adults has assessed the effectiveness of tonsillectomy when offered for the current UK threshold of disease burden. Further research is required to define the minimum disease burden at which tonsillectomy becomes clinically effective and cost-effective. Trial registration: This trial is registered as ISRCTN55284102. Funding: This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 12/146/06) and is published in full in Health Technology Assessment; Vol. 27, No. 31. See the NIHR Funding and Awards website for further award information.

Tonsillectomy is an operation to take out the pair of tonsil glands at the back of the throat. It is an option for adults who suffer from repeated, severe sore throats. Adults who have a tonsillectomy say that they get fewer sore throats afterwards, but it is not clear whether or not they would have got better over time without the operation. There is pressure on doctors to limit the number of tonsillectomies carried out. At the same time, emergency hospital admissions for adults with severe throat infections have been increasing. NAtional Trial of Tonsillectomy IN Adults aimed to find out whether tonsillectomy is an effective and worthwhile treatment for repeated severe sore throats or whether patients would be better off treated without an operation. A total of 453 patients from 27 hospitals in Great Britain took part in the study. Patients were assigned at random to receive either tonsillectomy or conservative management (treatment as needed from their general practitioner). We measured how many sore throats patients had in the next 2 years by sending them text messages every week. We asked about the impact of their sore throats on their quality of life and time off work, and looked at the costs of treatment. We also interviewed 47 patients, general practitioners and hospital staff about their experiences of tonsillectomy and NAtional Trial of Tonsillectomy IN Adults. The typical patient in the tonsillectomy arm had 23 days of sore throat compared with 30 days of sore throat in the conservative management arm. Tonsillectomy resulted in higher quality of life. We looked to see whether or not it was only those with the most severe sore throats who benefited from tonsillectomy, but we found that patients with more or less severe sore throats at the start all did better with tonsillectomy. Patients who had a tonsillectomy were happy to have undertaken this. Our findings suggest a clear benefit of tonsillectomy using modest additional NHS resources for adults with repeated severe sore throats.

Randomized controlled trial of vitamin D supplementation in older people to optimize bone health.

Background: Vitamin D insufficiency is common in older people and may lead to increased bone resorption, bone loss, and increased falls and fractures. However, clinical trials assessing the effect of vitamin D supplementation on bone mineral density (BMD) have yielded conflicting results. Objectives: This study examined the effect of vitamin D supplementation on BMD at the hip, using dual-energy X-ray absorptiometry. Methods: A total of 379 adults aged ≥70 y (48% women; mean age: 75 y) from the northeast of England were randomly allocated to 1 of 3 doses of vitamin D3 [12,000 international units (IU), 24,000 IU, or 48,000 IU] given once a month. The primary outcome was change in BMD (ΔBMD) at the hip. Secondary endpoints comprised the dose effects on femoral neck BMD, falls, circulating calciotropic hormones, bone turnover markers, and adverse events. Results: The mean ± SD baseline plasma 25-hydroxyvitamin D [25(OH)D] concentration was 40.0 ± 20.1 nmol/L, which increased after 12 mo to a mean 25(OH)D of 55.9, 64.6, or 79.0 nmol/L for participants receiving a monthly dose of 12,000, 24,000, or 48,000 IU, respectively (P < 0.01 for difference). There was no between-group difference in ΔBMD. However, parathyroid hormone concentrations decreased in all 3 groups, with a significantly greater decrease in the 48,000-IU group compared with the 12,000-IU group (P < 0.01). There were no differences in any adverse events between groups, with 3 cases of hypercalcemia, none of nephrolithiasis, and 249 falls observed. Conclusions: There was no difference in change in BMD over 12 mo between the 3 doses of vitamin D, suggesting no effect of the intervention or a similar attenuation of the anticipated decrease in BMD over 12 mo. The treatment was safe and effective in increasing plasma 25(OH)D concentrations, with no dose-related adverse events. This trial was registered at the EU Clinical Trials Register (EudraCT 2011-004890-10) and the ISRCTN Registry (ISRCTN35648481).

Continuous low-dose antibiotic prophylaxis for adults with repeated urinary tract infections (AnTIC): a randomised, open-label trial.

BACKGROUND: Repeated symptomatic urinary tract infections (UTIs) affect 25% of people who use clean intermittent self-catheterisation (CISC) to empty their bladder. We aimed to determine the benefits, harms, and cost-effectiveness of continuous low-dose antibiotic prophylaxis for prevention of recurrent UTIs in adult users of CISC. METHODS: In this randomised, open-label, superiority trial, we enrolled participants from 51 UK National Health Service organisations. These participants were community-dwelling (as opposed to hospital inpatient) users of CISC with recurrent UTIs. We randomly allocated participants (1:1) to receive either antibiotic prophylaxis once daily (prophylaxis group) or no prophylaxis (control group) for 12 months by use of an internet-based system with permuted blocks of variable length. Trial and laboratory staff who assessed outcomes were masked to allocation but participants were aware of their treatment group. The primary outcome was the incidence of symptomatic, antibiotic-treated UTIs over 12 months. Participants who completed at least 6 months of follow-up were assumed to provide a reliable estimate of UTI incidence and were included in the analysis of the primary outcome. Change in antimicrobial resistance of urinary and faecal bacteria was monitored as a secondary outcome. The AnTIC trial is registered at ISRCTN, number 67145101; and EudraCT, number 2013-002556-32. FINDINGS: Between Nov 25, 2013, and Jan 29, 2016, we screened 1743 adult users of CISC for eligibility, of whom 404 (23%) participants were enrolled between Nov 26, 2013, and Jan 31, 2016. Of these 404 participants, 203 (50%) were allocated to receive prophylaxis and 201 (50%) to receive no prophylaxis. 1339 participants were excluded before randomisation. The primary analysis included 181 (89%) adults allocated to the prophylaxis group and 180 (90%) adults in the no prophylaxis (control) group. 22 participants in the prophylaxis group and 21 participants in the control group were not included in the primary analysis because they were missing follow-up data before 6 months. The incidence of symptomatic antibiotic-treated UTIs over 12 months was 1·3 cases per person-year (95% CI 1·1-1·6) in the prophylaxis group and 2·6 (2·3-2·9) in the control group, giving an incidence rate ratio of 0·52 (0·44-0·61; p<0·0001), indicating a 48% reduction in UTI frequency after treatment with prophylaxis. Use of prophylaxis was well tolerated: we recorded 22 minor adverse events in the prophylaxis group related to antibiotic prophylaxis during the study, predominantly gastrointestinal disturbance (six participants), skin rash (six participants), and candidal infection (four participants). However, resistance against the antibiotics used for UTI treatment was more frequent in urinary isolates from the prophylaxis group than in those from the control group at 9-12 months of trial participation (nitrofurantoin 12 [24%] of 51 participants from the prophylaxis group vs six [9%] of 64 participants from the control group with at least one isolate; p=0·038), trimethoprim (34 [67%] of 51 vs 21 [33%] of 64; p=0·0003), and co-trimoxazole (26 [53%] of 49 vs 15 [24%] of 62; p=0·002). INTERPRETATION: Continuous antibiotic prophylaxis is effective in reducing UTI frequency in CISC users with recurrent UTIs, and it is well tolerated in these individuals. However, increased resistance of urinary bacteria is a concern that requires surveillance if prophylaxis is started. FUNDING: UK National Institute for Health Research.

Continuous low-dose antibiotic prophylaxis to prevent urinary tract infection in adults who perform clean intermittent self-catheterisation: the AnTIC RCT.

BACKGROUND: People carrying out clean intermittent self-catheterisation (CISC) to empty their bladder often suffer repeated urinary tract infections (UTIs). Continuous once-daily, low-dose antibiotic treatment (antibiotic prophylaxis) is commonly advised but knowledge of its effectiveness is lacking. OBJECTIVE: To assess the benefit, harms and cost-effectiveness of antibiotic prophylaxis to prevent UTIs in people who perform CISC. DESIGN: Parallel-group, open-label, patient-randomised 12-month trial of allocated intervention with 3-monthly follow-up. Outcome assessors were blind to allocation. SETTING: UK NHS, with recruitment of patients from 51 sites. PARTICIPANTS: Four hundred and four adults performing CISC and predicted to continue for ≥ 12 months who had suffered at least two UTIs in the previous year or had been hospitalised for a UTI in the previous year. INTERVENTIONS: A central randomisation system using random block allocation set by an independent statistician allocated participants to the experimental group [once-daily oral antibiotic prophylaxis using either 50 mg of nitrofurantoin, 100 mg of trimethoprim (Kent Pharmaceuticals, Ashford, UK) or 250 mg of cefalexin (Sandoz Ltd, Holzkirchen, Germany); n = 203] or the control group of no prophylaxis (n = 201), both for 12 months. MAIN OUTCOME MEASURES: The primary clinical outcome was relative frequency of symptomatic, antibiotic-treated UTI. Cost-effectiveness was assessed by cost per UTI avoided. The secondary measures were microbiologically proven UTI, antimicrobial resistance, health status and participants' attitudes to antibiotic use. RESULTS: The frequency of symptomatic antibiotic-treated UTI was reduced by 48% using prophylaxis [incidence rate ratio (IRR) 0.52, 95% confidence interval (CI) 0.44 to 0.61; n = 361]. Reduction in microbiologically proven UTI was similar (IRR 0.49, 95% CI 0.39 to 0.60; n = 361). Absolute reduction in UTI episodes over 12 months was from a median (interquartile range) of 2 (1-4) in the no-prophylaxis group (n = 180) to 1 (0-2) in the prophylaxis group (n = 181). The results were unchanged by adjustment for days at risk of UTI and the presence of factors giving higher risk of UTI. Development of antimicrobial resistance was seen more frequently in pathogens isolated from urine and Escherichia coli from perianal swabs in participants allocated to antibiotic prophylaxis. The use of prophylaxis incurred an extra cost of £99 to prevent one UTI (not including costs related to increased antimicrobial resistance). The emotional and practical burden of CISC and UTI influenced well-being, but health status measured over 12 months was similar between groups and did not deteriorate significantly during UTI. Participants were generally unconcerned about using antibiotics, including the possible development of antimicrobial resistance. LIMITATIONS: Lack of blinding may have led participants in each group to use different thresholds to trigger reporting and treatment-seeking for UTI. CONCLUSIONS: The results of this large randomised trial, conducted in accordance with best practice, demonstrate clear benefit for antibiotic prophylaxis in terms of reducing the frequency of UTI for people carrying out CISC. Antibiotic prophylaxis use appears safe for individuals over 12 months, but the emergence of resistant urinary pathogens may prejudice longer-term management of recurrent UTI and is a public health concern. Future work includes longer-term studies of antimicrobial resistance and studies of non-antibiotic preventative strategies. TRIAL REGISTRATION: Current Controlled Trials ISRCTN67145101 and EudraCT 2013-002556-32. FUNDING: This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment Vol. 22, No. 24. See the NIHR Journals Library website for further project information.

Antiplatelet therapy in the primary prevention of cardiovascular disease in patients with chronic obstructive pulmonary disease: protocol of a randomised controlled proof-of-concept trial (APPLE COPD-ICON 2).

INTRODUCTION: The antiplatelet therapy in the primary prevention of cardiovascular disease in patients with chronic obstructive pulmonary disease (APPLE COPD-ICON2) trial is a prospective 2×2 factorial, double-blinded proof-of-concept randomised controlled trial targeting patients with chronic obstructive pulmonary disease (COPD) at high risk of cardiovascular disease. The primary goal of this trial is to investigate if treatment with antiplatelet therapy will produce the required response in platelet function measured using the Multiplate test in patients with COPD. METHODS AND ANALYSIS: Patients with COPD are screened for eligibility using inclusion and exclusion criteria. Eligible patients are randomised and allocated into one of four groups to receive aspirin plus placebo, ticagrelor plus placebo, aspirin plus ticagrelor or placebo only. Markers of systemic inflammation, platelet reactivity, arterial stiffness, carotid intima-media thickness (CIMT), lung function and quality of life questionnaires are assessed. The primary outcome consists of inhibition (binary response) of aspirin and ADP-induced platelet function at 6 months. Secondary outcomes include changes in inflammatory markers, CIMT, non-invasive measures of vascular stiffness, quality of life using questionnaires (EuroQol-five dimensions-five levels of perceived problems (EQ5D-5L), St. George's COPD questionnaire) and to record occurrence of repeat hospitalisation, angina, myocardial infarction or death from baseline to 6 months. Safety outcomes will be rates of major and minor bleeding, forced expiratory volume in 1 s, forced vital capacity and Medical Research Council dyspnoea scale. ETHICS AND DISSEMINATION: The study was approved by the North East-Tyne and Wear South Research Ethics Committee (15/NE/0155). Findings of the study will be presented in scientific sessions and published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ISRCTN43245574; Pre-results.

Antibiotic treatment for intermittent bladder catheterisation with once daily prophylaxis (the AnTIC study): Study protocol for a randomised controlled trial.

BACKGROUND: Clean intermittent self-catheterisation is an important management option for people who cannot empty their bladder effectively. Recurrent urinary tract infections are common in these patients. Data from recent studies suggest that antibiotic prophylaxis may be beneficial in reducing infection risk, but the effectiveness of this intervention remains uncertain. METHODS/DESIGN: This is a 52-site, patient randomised superiority trial set in routine care comparing an experimental strategy of once daily antibiotic prophylaxis for 12 months against a control strategy of no prophylaxis in people who carry out self-catheterisation and suffer recurrent urinary tract infections. The primary outcome is number of urinary tract infections during a 12-month treatment period. Both groups will otherwise receive usual care including on demand treatment courses of antibiotics for urinary tract infection. Participants and their clinicians will not be blinded to the allocated intervention, but central trial staff managing and analysing trial data will, as far as possible, be unaware of participant allocation. The analysis will follow intention-to-treat principles. DISCUSSION: This trial was commissioned and funded by the United Kingdom National Health Service following prioritisation of the research question by the National Institute for Health and Care Excellence. TRIAL REGISTRATION: ISRCTN67145101 EUDRACT2013-002556-32. Registered on 25 October 2013.

Effects of formoterol or salmeterol on impulse oscillometry in patients with persistent asthma.

BACKGROUND: Effects of small-particle long-acting ß-agonists on the small airways have been poorly documented. OBJECTIVE: We used impulse oscillometry (IOS) to compare single and repeated dosing effects of small- and large-particle long-acting ß-agonists. METHODS: After a 1- to 2-week run-in period, patients received either 12 µg of small-particle hydrofluoroalkane 134a-formoterol solution or 50 µg of large-particle salmeterol dry powder twice daily plus inhaled corticosteroid for 1 to 2 weeks with a 1- to 2-week washout period in between. Measurements were made over 60 minutes after the first and last doses. RESULTS: Sixteen patients completed the study as follows: mean age, 43 years; FEV1, 80%; forced midexpiratory flow between 25% and 75% of forced vital capacity (FEF(25-75)), 48%; total airway resistance at 5 Hz, 177%; peripheral airway resistance as the difference between 5 and 20 Hz, 0.18 kPa·L(-1)·s; Asthma Control Questionnaire score, 0.76; and inhaled corticosteroid dosage, 550 µg/d. There were significantly greater improvements with formoterol versus salmeterol in all IOS outcomes and FEF25-75, but not FEV1, at 5 minutes after the first dose, which were not sustained over 60 minutes. After the last dose, all IOS outcomes, but not FEV1 or FEF(25-75), were significantly better with formoterol over the entire 60 minutes: mean difference at 60 minutes between formoterol and salmeterol in total airway resistance at 5 Hz, 7.50% (95% CI, 1.56% to 13.43%, P = .02); central airway resistance at 20 Hz, 5.37% (95% CI, 0.13% to 10.62%, P = .045); peripheral airway resistance as the difference between 5 and 20 Hz, 12.76% (95% CI, 1.28% to 24.24%, P = .03); reactance area under the curve, 19.46% (95% CI, 7.56% to 31.36%, P = .003); reactance at 5 Hz, 11.19% (95% CI, 4.62% to 17.76%, P = .002); and resonant frequency, 9.34% (95% CI, 3.21% to 15.47%, P = .005). Peak expiratory flow significantly improved to a similar degree with both drugs. CONCLUSION: Significant improvements in IOS outcomes but not spirometry results occurred after chronic dosing with formoterol compared with salmeterol. This might reflect better deposition to the entire lung, including the small airways.

Structural basis for the recruitment of glycogen synthase by glycogenin.

Glycogen is a primary form of energy storage in eukaryotes that is essential for glucose homeostasis. The glycogen polymer is synthesized from glucose through the cooperative action of glycogen synthase (GS), glycogenin (GN), and glycogen branching enzyme and forms particles that range in size from 10 to 290 nm. GS is regulated by allosteric activation upon glucose-6-phosphate binding and inactivation by phosphorylation on its N- and C-terminal regulatory tails. GS alone is incapable of starting synthesis of a glycogen particle de novo, but instead it extends preexisting chains initiated by glycogenin. The molecular determinants by which GS recognizes self-glucosylated GN, the first step in glycogenesis, are unknown. We describe the crystal structure of Caenorhabditis elegans GS in complex with a minimal GS targeting sequence in GN and show that a 34-residue region of GN binds to a conserved surface on GS that is distinct from previously characterized allosteric and binding surfaces on the enzyme. The interaction identified in the GS-GN costructure is required for GS-GN interaction and for glycogen synthesis in a cell-free system and in intact cells. The interaction of full-length GS-GN proteins is enhanced by an avidity effect imparted by a dimeric state of GN and a tetrameric state of GS. Finally, the structure of the N- and C-terminal regulatory tails of GS provide a basis for understanding phosphoregulation of glycogen synthesis. These results uncover a central molecular mechanism that governs glycogen metabolism.

Glucose-6-phosphate-mediated activation of liver glycogen synthase plays a key role in hepatic glycogen synthesis.

The liver responds to an increase in blood glucose levels in the postprandial state by uptake of glucose and conversion to glycogen. Liver glycogen synthase (GYS2), a key enzyme in glycogen synthesis, is controlled by a complex interplay between the allosteric activator glucose-6-phosphate (G6P) and reversible phosphorylation through glycogen synthase kinase-3 and the glycogen-associated form of protein phosphatase 1. Here, we initially performed mutagenesis analysis and identified a key residue (Arg(582)) required for activation of GYS2 by G6P. We then used GYS2 Arg(582)Ala knockin (+/R582A) mice in which G6P-mediated GYS2 activation had been profoundly impaired (60-70%), while sparing regulation through reversible phosphorylation. R582A mutant-expressing hepatocytes showed significantly reduced glycogen synthesis with glucose and insulin or glucokinase activator, which resulted in channeling glucose/G6P toward glycolysis and lipid synthesis. GYS2(+/R582A) mice were modestly glucose intolerant and displayed significantly reduced glycogen accumulation with feeding or glucose load in vivo. These data show that G6P-mediated activation of GYS2 plays a key role in controlling glycogen synthesis and hepatic glucose-G6P flux control and thus whole-body glucose homeostasis.

A noncanonical, GSK3-independent pathway controls postprandial hepatic glycogen deposition.

Insulin rapidly suppresses hepatic glucose production and slowly decreases expression of genes encoding gluconeogenic proteins. In this study, we show that an immediate effect of insulin is to redirect newly synthesized glucose-6-phosphate to glycogen without changing the rate of gluconeogenesis. This process requires hepatic Akt2, as revealed by blunted insulin-mediated suppression of glycogenolysis in the perfused mouse liver, elevated hepatic glucose production during a euglycemic-hyperinsulinemic clamp, or diminished glycogen accumulation during clamp or refeeding in mice without hepatic Akt2. Surprisingly, the absence of Akt2 disrupted glycogen metabolism independent of GSK3α and GSK3ß phosphorylation, which is thought to be an essential step in the pathway by which insulin regulates glycogen synthesis through Akt. These data show that (1) the immediate action of insulin to suppress hepatic glucose production functions via an Akt2-dependent redirection of glucose-6-phosphate to glycogen, and (2) insulin increases glucose phosphorylation and conversion to glycogen independent of GSK3.

AMP-activated protein kinase phosphorylates and inactivates liver glycogen synthase.

Recombinant muscle GYS1 (glycogen synthase 1) and recombinant liver GYS2 were phosphorylated by recombinant AMPK (AMP-activated protein kinase) in a time-dependent manner and to a similar stoichiometry. The phosphorylation site in GYS2 was identified as Ser7, which lies in a favourable consensus for phosphorylation by AMPK. Phosphorylation of GYS1 or GYS2 by AMPK led to enzyme inactivation by decreasing the affinity for both UDP-Glc (UDP-glucose) [assayed in the absence of Glc-6-P (glucose-6-phosphate)] and Glc-6-P (assayed at low UDP-Glc concentrations). Incubation of freshly isolated rat hepatocytes with the pharmacological AMPK activators AICA riboside (5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside) or A769662 led to persistent GYS inactivation and Ser7 phosphorylation, whereas inactivation by glucagon treatment was transient. In hepatocytes from mice harbouring a liver-specific deletion of the AMPK catalytic α1/α2 subunits, GYS2 inactivation by AICA riboside and A769662 was blunted, whereas inactivation by glucagon was unaffected. The results suggest that GYS inactivation by AMPK activators in hepatocytes is due to GYS2 Ser7 phosphorylation.