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.

S6K1 has emerged as a critical signaling component in the development of insulin resistance through phosphorylation and inhibition of IRS-1 function. This effect can be triggered directly by nutrients such as amino acids or by insulin through a homeostatic negative-feedback loop. However, the role of S6K1 in mediating IRS-1 phosphorylation in a physiological setting of nutrient overload is unresolved. Here we show that S6K1 directly phosphorylates IRS-1 Ser-1101 in vitro in the C-terminal domain of the protein and that mutation of this site largely blocks the ability of amino acids to suppress IRS-1 tyrosine and Akt phosphorylation. Consistent with this finding, phosphorylation of IRS-1 Ser-1101 is increased in the liver of obese db/db and wild-type, but not S6K1 ^−/− , mice maintained on a high-fat diet and is blocked by siRNA knockdown of S6K1 protein. Finally, infusion of amino acids in humans leads to the concomitant activation of S6K1, phosphorylation of IRS-1 Ser-1101, a reduction in IRS-1 function, and insulin resistance in skeletal muscle. These findings indicate that nutrient- and hormonal-dependent activation of S6K1 causes insulin resistance in mice and humans, in part, by mediating IRS-1 Ser-1101 phosphorylation.

Plasma concentrations of amino acids are frequently elevated in insulin-resistant states, and a protein-enriched 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 μg/l) somatostatin clamp tests in the presence of low (∼1.6 mmol/l) and increased (∼4.6 mmol/l) plasma AA concentrations. Glucose turnover was measured with d-[6,6-²H₂]glucose. Intramuscular concentrations of glycogen and glucose-6-phosphate (G6P) were monitored using ¹³C and ³¹P nuclear magnetic resonance spectroscopy, respectively. A ∼2.1-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 μmol · l⁻¹ · min⁻¹; P < 0.01), which was accompanied by a reduction in G6P starting at 130 min (ΔG6P_{260–300 min}, 18 ± 19; control, 103 ± 33 μmol/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.

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 ∼6 vs. ∼2 mmol/l). Somatostatin-insulin-glucose clamps created conditions of low peripheral hyperinsulinemia (∼100 pmol/l, 0–180 min) and prandial-like peripheral hyperinsulinemia (∼430 pmol/l, 180–360 min). At low peripheral hyperinsulinemia, endogenous glucose production (EGP) did not change during amino acid infusion but decreased by ∼70% during saline infusion (EGP_{150–180 min} 11 ± 1 vs. 3 ± 1 μmol · kg⁻¹ · 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 ∼33% lower during amino acid infusion (R_{d330–360 min} 50 ± 4 vs. 75 ± 6 μmol · kg⁻¹ · min⁻¹, P = 0.002) indicating insulin resistance. In skeletal muscle biopsies taken before and after prandial-like peripheral hyperinsulinemia, plasma amino acid elevation markedly increased the ability of insulin to activate S6 kinase 1 compared with saline infusion (∼3.7- vs. ∼1.9-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 3α 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 acid–infused humans.

Background: Chronic adipose tissue inflammation is a hallmark of obesity, triggering the development of associated pathologies, particularly type 2 diabetes. Long-chain n−3 PUFAs reduce cardiovascular events and exert well-established antiinflammatory effects, but their effects on human adipose tissue inflammation are unknown.