A consensus meeting was held in Vienna on September 8–9, 2013, to discuss diagnostic and therapeutic challenges surrounding development of diabetes mellitus after transplantation. The International Expert Panel comprised 24 transplant nephrologists, surgeons, diabetologists and clinical scientists, which met with the aim to review previous guidelines in light of emerging clinical data and research. Recommendations from the consensus discussions are provided in this article. Although the meeting was kidney-centric, reflecting the expertise present, these recommendations are likely to be relevant to other solid organ transplant recipients. Our recommendations include: terminology revision from new-onset diabetes after transplantation to posttransplantation diabetes mellitus (PTDM), exclusion of transient posttransplant hyperglycemia from PTDM diagnosis, expansion of screening strategies (incorporating postprandial glucose and HbA1c) and opinion-based guidance regarding pharmacological therapy in light of recent clinical evidence. Future research in the field was discussed with the aim of establishing collaborative working groups to address unresolved questions. These recommendations are opinion-based and intended to serve as a template for planned guidelines update, based on systematic and graded literature review, on the diagnosis and management of PTDM.

mTOR ͉ nutrient sensing ͉ amino acids ͉ insulin signaling

To examine the molecular mechanisms by which plasma amino acid elevation impairs insulin action, we studied seven healthy men twice in random order during infusion of an amino acid mixture or saline (total plasma amino acid ϳ6 vs. ϳ2 mmol/l). Somatostatin-insulinglucose clamps created conditions of low peripheral hyperinsulinemia (ϳ100 pmol/l, 0 -180 min) and prandial-like peripheral hyperinsulinemia (ϳ430 pmol/l, 180 -360 min). At low peripheral hyperinsulinemia, endogenous glucose production (EGP) did not change during amino acid infusion but decreased by ϳ70% during saline infusion (EGP 150 -180 min 11 ؎ 1 vs. 3 ؎ 1 mol ⅐ kg ؊1 ⅐ min ؊1 , P ‫؍‬ 0.001). Prandial-like peripheral hyperinsulinemia completely suppressed EGP during both protocols, whereas whole-body rate of glucose disappearance (R d ) was ϳ33% lower during amino acid infusion (R d 330 -360 min 50 ؎ 4 vs. 75 ؎ 6 mol ⅐ kg ؊1 ⅐ min ؊1 , P ‫؍‬ 0.002) indicating insulin resistance. In skeletal muscle biopsies taken before and after prandiallike peripheral hyperinsulinemia, plasma amino acid elevation markedly increased the ability of insulin to activate S6 kinase 1 compared with saline infusion (ϳ3.7-vs. ϳ1.9-fold over baseline). Furthermore, amino acid infusion increased the inhibitory insulin receptor substrate-1 phosphorylation at Ser312 and Ser636/639 and decreased insulin-induced phosphoinositide 3-kinase activity. However, plasma amino acid elevation failed to reduce insulin-induced Akt/protein kinase B and glycogen synthase kinase 3␣ phosphorylation. In conclusion, amino acids impair 1) insulin-mediated suppression of glucose production and 2) insulin-stimulated glucose disposal in skeletal muscle. Our results suggest that overactivation of the mammalian target of rapamycin/S6 kinase 1 pathway and inhibitory serine phosphorylation of insulin receptor substrate-1 underlie the impairment of insulin action in amino acidinfused humans. Diabetes 54:2674 -2684, 2005

Plasma concentrations of amino acids are frequently elevated in insulin-resistant states, and a proteinenriched diet can impair glucose metabolism. This study examined effects of short-term plasma amino acid (AA) elevation on whole-body glucose disposal and cellular insulin action in skeletal muscle. Seven healthy men were studied for 5.5 h during euglycemic (5.5 mmol/l), hyperinsulinemic (430 pmol/l), fasting glucagon (65 ng/ l), and growth hormone (0.4 g/l) somatostatin clamp tests in the presence of low (ϳ1.6 mmol/l) and increased (ϳ4.6 mmol/l) plasma AA concentrations. Glucose turnover was measured with D-[6,6-2 H 2 ]glucose. Intramuscular concentrations of glycogen and glucose-6-phosphate (G6P) were monitored using 13 C and 31 P nuclear magnetic resonance spectroscopy, respectively. A ϳ2.1-fold elevation of plasma AAs reduced whole-body glucose disposal by 25% (P < 0.01). Rates of muscle glycogen synthesis decreased by 64% (180 -315 min, 24 ؎ 3; control, 67 ؎ 10 mol ⅐ l ؊1 ⅐ min ؊1 ; P < 0.01), which was accompanied by a reduction in G6P starting at 130 min (⌬G6P 260 -300 min , 18 ؎ 19; control, 103 ؎ 33 mol/l; P < 0.05). In conclusion, plasma amino acid elevation induces skeletal muscle insulin resistance in humans by inhibition of glucose transport/phosphorylation, resulting in marked reduction of glycogen synthesis. Diabetes 51:599 -605, 2002 P lasma concentrations of alanine and particularly branched-chain amino acids (AAs) are elevated in insulin-resistant states such as obesity (1,2), and high dietary protein intake impairs glucose metabolism mainly by changing the utilization of gluconeogenic precursors (3-6).The mechanisms by which AAs could reduce skeletal muscle glucose uptake are as yet unclear. At the cellular level, availability of substrates for energy production, such as AAs and free fatty acids (FFAs), may play an important role in modulating the response to insulin (7). In vitro studies demonstrated that AAs may inhibit glucose utilization in skeletal muscle at various levels. AAs could decrease glucose oxidation by substrate competition with glucose (8,9) and/or reduce glucose uptake (10) by interaction with early steps of insulin signaling (11). Studies in humans, however, revealed controversial results. Infusion of AAs decreased forearm and whole-body glucose disposal in some (12-15), but not all (16,17), studies. Moreover, endogenous release of insulin (18) and glucagon (19) induced by plasma AA elevation might have obscured possible direct effects of AAs in those studies. Taking together all these factors, it is uncertain whether AAs directly induce skeletal muscle insulin resistance in vivo and if so, which mechanism (glucose uptake versus substrate competition) is responsible for such an effect.This study was therefore designed to examine effects of plasma AA elevation on skeletal muscle glucose metabolism by combining isotope dilution technique with in vivo nuclear magnetic resonance (NMR) spectroscopy of gastrocnemius muscle from healthy young humans. In vivo [ 13 C]NMR spectroscop...

Plasminogen activator inhibitor 1 (PAI-1) inhibits plasminogen activators (u-PA and t-PA) by forming stable complexes endocytosed via a low-density lipoprotein receptor superfamily member-dependent mechanism. PAI-1 circulates actively in plasma and latently in platelets but is also secreted and deposited into the matrix by several cells, where it participates in tissue repair processes.

No effective interventions to reduce risk for new-onset diabetes after transplantation (NODAT), a condition associated with postoperative hyperglycemia and reduced patient and graft survival, have been established. In this 1-year, proof-of-concept clinical trial, we randomly assigned 50 renal transplant recipients to immediate-postoperative isophane insulin for evening blood glucose $140 mg/dl (treatment group) or short-acting insulin and/or oral antidiabetic agents for blood glucose $180-250 mg/dl (standard-of-care control group). We included only patients without a history of diabetes who received tacrolimus. By the third postoperative evening, all patients in the treatment group had blood glucose $140 mg/dl and were subsequently treated with basal insulin; during the first 3 weeks after transplantation, the mean 6 SD daily insulin dosage was 17611 IU/d. Among controls, 23 (92%) of 25 had blood glucose $200 mg/dl and 18 (72%) of 25 received standard-of-care antihyperglycemic treatment. Asymptomatic hypoglycemia occurred five times in the treatment group and once in the control group. Throughout follow-up, the treatment group had 73% lower odds of NODAT (odds ratio, 0.27) than the control group, and hemoglobin A1c was on average 0.38% lower in the treatment group than the control group. Twelve months after transplantation, all patients in the treatment group were insulin-independent, whereas 7 (28%) of 25 controls required antidiabetic agents. The groups did not differ for insulin sensitivity, but the treatment group showed better b-cell function throughout the 1-year follow-up. In conclusion, this study suggests regimens that include basal insulin significantly reduce the odds for NODAT after renal transplantation, presumably via insulin-mediated protection of b cells.

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The nutrient-sensitive kinase mammalian target of rapamycin (mTOR) and its downstream target S6 kinase (S6K) are involved in amino acid-induced insulin resistance. Whether the mTOR/S6K pathway directly modulates glucose metabolism in humans is unknown. We studied 11 healthy men (29 years old, BMI 23 kg/m 2 ) twice in random order after oral administration of 6 mg rapamycin, a specific mTOR inhibitor, or placebo. An amino acid mixture was infused to activate mTOR, and somatostatin-insulin-glucose clamps created conditions of low peripheral hyperinsulinemia (ϳ100 pmol/l, 0 -180 min) and prandial-like peripheral hyperinsulinemia (ϳ450 pmol/l, 180 -360 min). Glucose turnover was assessed using D-[6,6-2 H 2 ]glucose infusion (n ‫؍‬ 8). Skeletal muscle biopsies were performed at baseline and during prandial-like peripheral hyperinsulinemia (n ‫؍‬ 3). At low peripheral hyperinsulinemia, whole-body glucose uptake was not affected by rapamycin. During prandial-like peripheral hyperinsulinemia, rapamycin increased glucose uptake compared with placebo by 17% (R dԽ300 -360 min , 75 ؎ 5 vs. 64 ؎ 5 mol ⅐ kg ؊1 ⅐ min ؊1 , P ‫؍‬ 0.0008). Rapamycin affected endogenous glucose production neither at baseline nor during low or prandial-like peripheral hyperinsulinemia. Combined hyperaminoacidemia and prandial-like hyperinsulinemia increased S6K phosphorylation and inhibitory insulin receptor substrate-1 (IRS-1) phosphorylation at Ser312 and Ser636 in the placebo group. Rapamycin partially inhibited this increase in mTOR-mediated S6K phosphorylation and IRS-1 Ser312 and Ser636 phosphorylation. In conclusion, rapamycin stimulates insulin-mediated glucose uptake in man under conditions known to activate the mTOR/S6K pathway. Diabetes 56:1600-1607, 2007 T ype 2 diabetes is closely linked to obesity and insulin resistance (1-3). In addition to polygenic predisposition, environmental factors including quality and quantity of food supply, dietary behavior, and physical activity are of major importance for the development of type 2 diabetes (4,5). The availability of nutrients plays a pivotal role in the modulation of insulin action (6,7). In industrialized countries, nutrient excess comprises high intake of not only fat but also proteins (8). A chronic excess in protein intake is associated with insulin resistance, glucose intolerance, and type 2 diabetes (9 -12). We have shown that a short-term rise in plasma free fatty acids (FFAs) (13-15) or amino acids (16 -18) leads to decreased insulin-stimulated whole-body glucose disposal, which is preceded by an impaired rise in intramuscular glucose-6-phosphate concentrations and followed by reduction in rates of glycogen synthesis. These findings indicate that both FFAs and amino acids directly inhibit skeletal muscle glucose transport/phosphorylation (17).The mammalian target of rapamycin (mTOR) pathway (19) could be involved in sensing of nutrient availability and modulation of insulin action in vivo. Recent reports indicate that the activity of the mTOR pathway is increased in rodent models ...