The preventive role of type 2 NKT cells in the development of type 1 diabetes

In the last two decades, natural killer T (NKT) cells have emerged as an important factor in preventing type 1 diabetes (T1D) when investigated in the experimental non‐obese diabetic (NOD) mouse model. So far, investigations have largely focused on type 1 NKT cells with invariant T‐cell receptors, whereas the role of type 2 NKT cells with diverse T‐cell receptors is less well understood. However, there have been several findings which indicate that in fact type 2 NKT cells may regulate the progression of type 1 diabetes in NOD mice, including a fraction of these cells which recognize β‐cell‐enriched sulfatide. Therefore, the focus for this review is to present the current evidence of the effect of type 2 NKT cells on the development of T1D. In general, there is still uncertainty surrounding the mechanism of activation and function of NKT cells. Here, we present two models of the effector mechanisms, respectively, Th1/Th2 polarization and the induction of tolerogenic dendritic cells (DC). In conclusion, this review points to the importance of immunoregulation by type 2 NKT cells in preventing the development of T1D and highlights the induction of tolerogenic DC as a likely mechanism. The possible therapeutic role of type 1 and type 2 NKT cells are evaluated and future experiments concerning type 2 NKT cells and T1D are proposed.     

Density functional theory in surface chemistry and catalysis

Recent advances in the understanding of reactivity trends for chemistry at transition-metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. The current status of the field is discussed with an emphasis on the role of coupling theory and experiment and future challenges.     

Sustained low‐dose growth hormone therapy optimizes bioactive insulin‐like growth factor‐I level and may enhance CD4 T‐cell number in HIV infection

High‐dose recombinant human growth hormone (rhGH) (2–6 mg/day) regimes may facilitate T‐cell restoration in patients infected with human immunodeficiency virus (HIV) on highly active antiretroviral therapy (HAART). However, high‐dose rhGH regimens increase insulin‐like growth factor‐I (IGF‐I) to supra‐physiological levels associated with severe side effects. The present study investigated whether lower doses of rhGH may improve T‐cell restoration in patients infected with HIV following an expedient response of total and bioactive (i.e., free) IGF‐I. A previous 16‐week pilot‐study included six HIV‐infected patients on stable HAART to receive rhGH 0.7 mg/day, which increased total (+117%, P < 0.01) and free (+155%, P < 0.01) IGF‐I levels. The study was extended to examine whether continuous use of low‐dose rhGH (0.7 mg/day until week 60; 0.4 mg/day from week 60 to week 140) would maintain expedient IGF‐I levels and improve CD4 T‐cell response. Total and free IGF‐I increased at week 36 (+97%, P < 0.01 and +125%, P < 0.01, respectively) and week 60 (+77%, P = 0.01 and +125%, P < 0.01) compared to baseline levels (161 ± 15 and 0.75 ± 0.11 µg/L). CD4 T‐cell number increased at week 36 (+15%, P < 0.05) and week 60 (+31%, P = 0.01) compared to baseline levels (456 ± 55 cells/µL). Following rhGH dose reduction, total IGF‐I and CD4 T‐cell number remained increased at week 88 (+44%, P = 0.01 and +33%, P < 0.01) and week 140 (+46%, P = 0.07 and +36%, P = 0.02) compared to baseline levels. These data support the notion that low‐dose rhGH regimens may increase expediently total and bioactive IGF‐I and improve T‐cell restoration in patients infected with HIV on HAART. J. Med. Virol. 82:197–205, 2010. © 2009 Wiley‐Liss, Inc.     

Kidney tissue somatomedin C and initial renal growth in diabetic and uninephrectomised rats

Summary Kidney growth after induction of experimental diabetes in rats was compared to compensatory renal growth in response to unilateral nephrectomy. After 4 days of diabetes, kidney weight had increased from 816±21 mg (SEM) to 940±42 mg (15%). In insulin-treated diabetic rats kidney weight was unchanged at the end of the study, namely 828±15 mg.In unilaterally nephrectomised rats kidney weight increased from 840±20 mg (SEM) to 1050±60 mg during 4 days (24%). We observed increased kidney content of somatomedin C in both diabetic and uninephrectomised rats. In untreated diabetic rats it was maximal after 48 h, with an increase of 77% (3469±312 ng/g (SEM) versus 1961±173 ng/g). After 4 days the somatomedin C content had returned to initial levels. In insulin-treated rats somatomedin C content did not increase during the observation period. The somatomedin C content of the remaining kidney after unilateral nephrectomy was maximal after 24 h with an increase of 58% (from 1340±203 ng/g (SEM) to 2122±214 ng/g). The somatomedin C content returned to normal at day 4. Serum somatomedin C declined insignificantly in diabetic animals during the experimental period, but a significant decrease (p<0.02) was found in uninephrectomised rats. This study demonstrates that kidney somatomedin C peaks during the first or second day after uninephrectomy or induction of diabetes, respectively, and that insulin treatment sufficient to prevent kidney growth abolishes the increase. These similar rapid initial hypertrophies/hyperplasies may thus be dependent on local somatomedin C formation.     

Transient increase in renal insulin-like growth factor binding proteins during initial kidney hypertrophy in experimental diabetes in rats

Summary The insulin-like growth factors, insulin-like growth factor I and insulin-like growth factor II are bound to six distinct classes of insulin-like growth factor binding proteins (IGFBPs) in the circulation and in extracellular fluids. Diabetic renal hypertrophy is preceded by a transient increase in kidney insulin-like growth factor I suggestive of a renotropic function for insulin-like growth factor I. In order to examine a possible involvement of IGFBPs in initial diabetic kidney growth and in kidney insulin-like growth factor I accumulation, we studied rat kidney IGFBPs by ligand blotting during the first 4 days after induction of diabetes. Six distinct bands were identified in kidney and liver tissue with apparent molecular weight values of 38–47 (doublet), 34, 30, 24 and 20 kDa. The 38–47 kDa doublet band probably corresponds to the insulin-like growth factor binding subunit of IGFBP-3, the 24 kDa band to IGFBP4 and the 30 kDa band to IGFBP-1 and/or IGFBP-2, as these IGFBPs in rats have similar molecular weight. In untreated diabetic rats a transient increase in the kidney 30 kDa band was demonstrable 24 h after induction of diabetes with a maximal rise (two-fold) after 48 h, followed by a decrease to baseline values after 4 days. In untreated diabetic rats the 38–47 kDa doublet band also increased (two-fold) in kidney during the first 2 days after induction of diabetes, followed by a subsequent decrease. Insulin-treatment prevented both the increase in the 30 kDa and in the 38–47 kDa bands. Kidney weight in untreated diabetic rats increased by 26 % after 4 days. In conclusion, the present study shows a transient increase in the 30 kDa and the 38–47 kDa IGFBP species in hypertrophying diabetic kidneys, contemporarily with the previously described transient increase in extractable kidney insulin-like growth factor I content. These findings support the concept that IGFBPs may be involved in the action of insulin-like growth factor I and possibly in the diabetic kidney insulin-like growth factor I accumulation.     

Hypomethylation and up-regulation of PD-1 in T cells by azacytidine in MDS/AML patients: A rationale for combined targeting of PD-1 and DNA methylation

The hypomethylating agents (HMAs) are standard therapy for patients with higher-risk myelodysplastic syndrome (MDS); however, the majority of the patients will lose their response to HMAs over time due to unknown mechanisms. It has recently been shown that T cell expression of the immunoinhibitory receptor PD-1 is regulated by DNA methylation. In 12 of 27 patients (44%) PD-1 promoter demethylation was observed in sorted peripheral blood T cells isolated over consecutive cycles of treatment with 5-azacytidine (5-aza). The PD-1 promoter demethylation correlated with an increase in PD-1 expression. Moreover, demethylation of the PD-1 promoter correlated with a significantly worse overall response rate (8% vs. 60%, p = 0.014), and a trend towards a shorter overall survival (p = 0.11) was observed. A significantly higher baseline methylation level of the PD-1 promoter was observed in T cells of non-responding patients compared to healthy controls (p = 0.023).Accordingly, in addition to their beneficial function, HMAs induce PD-1 expression on T cells in the MDS microenvironment, thereby likely hampering the immune response against the MDS blasts. Thus, we suggest that activation of the PD-1 checkpoint during HMA treatment can be a possible resistance mechanism, which may be overcome by combination therapy with a PD-1 pathway inhibitor.     

Diagnostic accuracy of anaesthesiologists’ prediction of difficult airway management in daily clinical practice: a cohort study of 188 064 patients registered in the Danish Anaesthesia Database

Both the American Society of Anesthesiologists and the UK NAP4 project recommend that an unspecified pre‐operative airway assessment be made. However, the choice of assessment is ultimately at the discretion of the individual anaesthesiologist. We retrieved a cohort of 188 064 cases from the Danish Anaesthesia Database, and investigated the diagnostic accuracy of the anaesthesiologists’ predictions of difficult tracheal intubation and difficult mask ventilation. Of 3391 difficult intubations, 3154 (93%) were unanticipated. When difficult intubation was anticipated, 229 of 929 (25%) had an actual difficult intubation. Likewise, difficult mask ventilation was unanticipated in 808 of 857 (94%) cases, and when anticipated (218 cases), difficult mask ventilation actually occurred in 49 (22%) cases. We present a previously unpublished estimate of the accuracy of anaesthesiologists’ prediction of airway management difficulties in daily routine practice. Prediction of airway difficulties remains a challenging task, and our results underline the importance of being constantly prepared for unexpected difficulties.     

HTLV-III Antibody Testing in Three Danish Blood Banks

Abstract. The Organon Teknika Vironostika anti-HTLV-III/LAV test was evaluated in three Danish blood banks. The evaluation comprised in total 3,940 consecutive donors. In all three blood banks the tests were carried out exactly according to the manufacturer's instructions, using a low cut-off value defined as (4 + )/5, where and are means of optical densities of known negative and positive samples. By this method the overall frequency of repeatably positive samples was 0.30%. When tested by Western blot, however, none of these samples were shown to contain specific antibodies against HTLV-III/LAV proteins. When testing different categories of patients, only sera containing HLA antibodies gave rise to false-positive reactions. Finally, important differences in the results were observed regarding sample preparation, single or dual wavelength optical density readings, and the experience of the technical staff.     

The effect of growth hormone on insulin-like growth factor I and bone metabolism in distraction osteogenesis.

Limb lengthening in the left tibia of 30 mature female Yucatan micropigs was performed using distraction osteogenesis. A treatment group of 15 animals received recombinant porcine growth hormone (r-pGH) (100 microg/kg/day) while the others served as controls. Serial serum measurements of total insulin-like growth factor I (IGF-I), free IGF-I, IGF binding proteins -1, -2, -3 and -4 (IGFBP-1 to -4) were performed. Bone-specific alkaline phosphatase (bone-ALP) and the serum carboxyl-terminal telopeptide of type I collagen (ICTP) were measured as bone turnover markers. The GH-treated animals showed a significant increase in total IGF-I, free IGF-I and IGFBP-3 after surgery (P<0.001). Similarly, the treated animals showed a significantly higher level of bone-ALP (P<0.001) throughout the experiment compared to the controls. There was a significant correlation between bone-ALP and total IGF-I (r=0.76) in the GH-treated group and an even higher correlation for free IGF-I (r=0.90). There was no difference in the ICTP serum levels between the two groups. These data indicate that the application of species-specific growth hormone results in a stimulation of bone formation in distraction osteogenesis which may be mediated by IGF-I. The stronger correlation between free IGF-I and bone-ALP indicates that the anabolic effect of IGF-I may be regulated through the IGFBPs by binding and inactivating IGF-I.