Improvement of glucose tolerance in Zucker diabetic fatty rats by long-term treatment with the dipeptidyl peptidase inhibitor P32/98: comparison with and combination with rosiglitazone

AIM: The aim of this study was to investigate the effect of long-term treatment with the dipeptidyl peptidase inhibitor P32/98 and its combination with rosiglitazone on blood glucose control and islet of Langerhans histology in male Zucker diabetic fatty (ZDF) rats, when treatment begins before or after the development of overt diabetes. METHODS: ZDF rats were treated with P32/98 from the age of 9, 12 or 15 weeks. Rosiglitazone maleate was given to a separate group from the age of 13 weeks. P32/98 was given to all of these rosiglitazone-treated rats from 16 weeks of age. Rosiglitazone maleate was also given from 16 weeks of age to half the rats that were given P32/98 from 9 weeks of age. The compounds were given by oral gavage until the rats were 14 weeks old and then in the diet. The experiment was terminated at the age of 20-21 weeks. Blood glucose, plasma insulin and oral glucose tolerance were measured at intervals; islet histology was assessed terminally. RESULTS: P32/98 improved glucose tolerance after both single and multiple doses when treatment started at 9 weeks of age, also after the third week of treatment when treatment began at 12 or 15 weeks of age. P32/98 reduced daytime blood glucose when treatment began at 12 weeks. Treatment with rosiglitazone increased food intake and body weight, and after 2 weeks, reduced daytime blood glucose, water intake and the area under the glucose tolerance curve. A single dose of P32/98 markedly improved glucose tolerance in rosiglitazone-treated rats. When treatment had begun at 9 weeks of age, P32/98 stimulated insulin secretion in some glucose tolerance tests. Neither P32/98 nor rosiglitazone affected pancreatic insulin content, nor did they have clear effects on islet histology. CONCLUSION: P32/98 elicited a sustained improvement in glucose tolerance in both prediabetic and diabetic ZDF rats. The effects of P32/98 on glucose and insulin were similar to those of rosiglitazone, and in contrast to rosiglitazone, P32/98 did not increase food intake or body weight. However, neither compound was especially effective at improving diabetes in ZDF rats when treatment began at 9, 12 or 15 (P32/98) or 13 (rosiglitazone) weeks of age.     

Transitions from first substance use to substance use disorders in adolescence: Is early onset associated with a rapid escalation?

BackgroundEarly substance use (SU) in adolescence is known to be associated with an elevated risk of developing substance use disorders (SUD); it remains unclear though whether early SU is associated with more rapid transitions to SUD.ObjectiveTo examine the risk and speed of transition from first SU (alcohol, nicotine, cannabis) to SUD as a function of age of first use.MethodsN = 3021 community subjects aged 14–24 years at baseline were followed-up prospectively over 10-years. SU and SUD were assessed using the DSM-IV/M-CIDI.Results(1) The conditional probability of substance-specific SU-SUD transition was the greatest for nicotine (36.0%) and the least for cannabis (18.3% for abuse, 6.2% for dependence) with alcohol in between (25.3% for abuse; 11.2% for dependence). (2) In addition to confirming early SU as a risk factor for SUD we find: (3) higher age of onset of any SU to be associated with faster transitions to SUD, except for cannabis dependence. (4) Transitions from first cannabis use (CU) to cannabis use disorders (CUD) occurred faster than for alcohol and nicotine. (5) Use of other substances co-occurred with risk and speed of transitions to specific SUDs.ConclusionType of substance and concurrent use of other drugs are of importance for the association between age of first use and the speed of transitions to substance use disorders. Given that further research will identify moderators and mediators affecting these differential associations, these findings may have important implications for designing early and targeted interventions to prevent disorder progression.     

Caerulein or taurocholate induced enzymatic and histologic alterations in the isolated perfused rat pancreas

Background  Early events in the pathogenesis of experimental acute pancreatitis are intensively studied using isolated cells or animal models. However, the results and their interpretations are dependent on the complexity of biological structures. Therefore, we proposed that studies on isolated perfused pancreas can give additional information about processes leading to acinar cell injury. This hypothesis was examined adapting the well-established caerulein hyperstimulation model and the taurocholate model of acute pancreatitis to the extracorporeal perfused isolated rat pancreas. Materials and methods  The pancreas was removed with the duodenum including the arterial supply. A continuous perfusion of the organ was performed with a modified Krebs–Ringer bicarbonate buffer. Intraarterial caerulein application or an intraductal taurocholate (3.5%) application were used to induce acinar cell injury which was determined as the release of amylase, lipase and lactate dehydrogenase into the portal outflow medium and into the transudation fluid and by examination of histological alterations. Trypsinogen release and activation was followed by analysis of trypsinogen activation peptide (TAP) in the transudation fluid and in pancreatic tissue. Results  Perfusion of isolated rat pancreas with supramaximal concentrations of caerulein or retrograde injection of taurocholate (3.5%) resulted in acinar cell injury indicated by elevated levels of amylase and lipase into the perfusate and into the transudation fluid. TAP levels in the transudation fluid significantly increased after perfusion with caerulein or retrograde injection of taurocholate (3.5%). The histological alterations after taurocholate application include oedema and necrosis and show significant differences to the control perfusion. Extensive pancreatic necroses were not observed after caerulein hyperstimulation. Conclusions  The isolated perfused rat pancreas is a useful model to investigate pathophysiological mechanisms which are relevant for the early phase of acute pancreatitis. The caerulein and the taurocholate models are transferable to the isolated rat pancreas. Studies on isolated perfused rat pancreas enable pathophysiological investigations of the exocrine pancreas without influence of systemic components, but with preserved morphology.     

The Par6alpha/aPKC complex regulates Akt1 activity by phosphorylating Thr34 in the PH-domain

A single nucleotide polymorphism in the partitioning defective protein-6alpha (Par6alpha) promoter is coupled with lower Par6alpha expression and better insulin sensitivity, whereas overexpression of Par6alpha in C2C12 myoblasts inhibits insulin-induced protein kinase B/Akt1 activation and glycogen synthesis. Here we show that a direct interaction of Par6alpha with atypical protein kinase C (aPKC) is crucial for this inhibition. A DeltaPB1-Par6alpha deletion mutant that does not interact with aPKC neither increased aPKC activity nor interfered with insulin-induced Akt1 activation in C2C12 cells. Further, T34 phosphorylation of Akt1 through aPKC is important for inhibition of Akt1. When Par6alpha was overexpressed, activation of wild-type Akt1 (-59.3%; p=0.049), but not T34A-Akt1 (+2.9%, p=0.41) was reduced after insulin stimulation. The resistance of T34A-Akt1 to Par6alpha/aPKC-mediated inhibition was also reflected by reconstitution of insulin-induced glycogen synthesis. In summary, Par6alpha-mediated inhibition of insulin-dependent glycogen synthesis in C2C12 cells depends on the direct interaction of Par6alpha with aPKC and on aPKC-mediated T34 phosphorylation of Akt1.     

Gallstone disease

Gallstone disease is one of the most prevalent gastrointestinal diseases with a substantial burden to health care systems that is supposed to increase in ageing populations at risk. Aetiology and pathogenesis of cholesterol gallstones still are not well defined, and strategies for prevention and efficient nonsurgical therapies are missing. This review summarizes current concepts on the pathogenesis of cholesterol gallstones with focus on the uptake and secretion of biliary lipids and special emphasis on recent studies into the genetic background.     

Pharmacokinetics of mycophenolic acid in renal insufficiency

Mycophenolate mofetil (MMF) is now widely used in solid organ transplantation. MMF is rapidly converted to its active form, mycophenolic acid (MPA), upon reaching the systemic circulation. MPA is metabolized to its glucuronide metabolite, mycophenolic acid glucuronide (MPAG), by glucoronyl transferases in the liver and possibly elsewhere. MPAG is then excreted by the kidney. MPA is extensively and avidly bound to serum albumin. Previous studies have demonstrated that it is only the free (non-protein-bound) fraction of MPA that is available to exert its action. In vivo and in vitro studies demonstrate that renal insufficiency decreases the protein binding of MPA and increases free MPA concentrations. This decrease in protein binding seems to be caused both by the uremic state itself and by competition with the retained metabolite MPAG. The disposition of MPA in patients with severe renal impairment may be significantly affected by this change in protein binding.     

Low bioavailability of cyclosporine microemulsion and tacrolimus in a small bowel transplant recipient: possible relationship to intestinal P-glycoprotein activity

With intestine transplants the allograft is dependent on itself for maintenance of adequate immunosuppression. We evaluated an intestinal transplant recipient who required very large doses of either tacrolimus or cyclosporine emulsion to achieve acceptable blood concentrations. Pharmacokinetic studies revealed bioavailabilities of 2% and 6% respectively, while D-xylose and B12 absorption were found to be within normal limits and fecal fat was only slightly increased, suggesting that there was a selective absorptive defect for these drugs. Biopsies of the allograft ileum revealed a high P-glycoprotein activity compared to the jejunum or to intestinal biopsies from other normal subjects. This may be a contributing factor to poor immunosuppressive drug absorption in this patient and others.