Simultaneous pancreas-kidney transplantation reduces excess mortality in type 1 diabetic patients with end-stage renal disease.

BACKGROUND: Diabetic renal disease continues to be the most significant cause of end-stage renal disease (ESRD) in the United States. Renal transplantation improves diabetic ESRD patient survival; however, the diabetic state remains associated with poor patient survival. Simultaneous pancreas-kidney (SPK) transplantation can restore normoglycemia and thus may improve outcomes. METHODS: We assessed the impact of SPK on age-range-matched type 1 diabetic patients who underwent renal transplantation at a single center. The observed/expected life span and annual mortality rates (AMRs) were used as measures of survival. A Cox proportional hazards analysis was used to analyze the impact of potential variables on mortality in SPK recipients. RESULTS: SPK transplantation (N = 335) increased the observed/expected life span compared with diabetic cadaveric (DM-Cad, N = 147) and live-donor (DM-Live, N = 160) transplant recipients (P = 0.004) and significantly reduced the AMRs (SPK, 1. 5%; DM-Cad, 6.27%; DM-Live, 3.65%, P = 0.008, SPK vs. other DM). Moreover, the SPK observed/expected life span and AMR were not significantly different from that of age-range-matched nondiabetic transplant recipients (N = 492). The only variable that was significantly associated with patient survival was discharge serum creatinine (relative risk 1.16, P < or = 0.0154). CONCLUSION: These data demonstrate that SPK improves the ability for type 1 diabetic patients to live more of their expected life span. This suggests that glycemic control, even as a late intervention in a diabetic patient's lifetime, may beneficially affect survival.

Using renal transplantation to evaluate a simple approach for predicting the impact of end-stage renal disease therapies on patient survival: observed/expected life span.

The effectiveness of therapy for a chronic disease can be assessed by evaluating the length of time that a patient survives after receiving treatment. We used a novel means for measuring the effectiveness of renal replacement therapy for patients with end-stage renal disease (ESRD): the ratio of observed life span divided by expected life span. This ratio incorporated observed life span for patients from the time of ESRD and expected life span based on state-specific life-table analyses. A total of 3,782 individuals with ESRD were analyzed (average follow-up, 14.2 +/- 4.9 years); 3, 192 patients in that group received a kidney transplant at some point during their course of ESRD. For each patient, we determined a curve of observed/expected life span. Separate patient groups were analyzed to determine the median population observed/expected life span or the percentage of patients who reached 0.5 observed/expected life span. Younger transplant recipients (<21 years) had a median observed/expected life span of 67%, significantly greater than the median observed/expected life span for those aged 21 to 40 years (49%; P = 0.01) and 41 to 60 years (47%; P = 0.01). Surprisingly, 57% of the patients aged older than 60 years reached their median observed/expected life span (P = 0.02 versus <21 years; P = not significant against all others). A Cox proportional hazards model identified era of immunosuppression (hazards ratio, 0.32) and atherosclerotic vascular disease-related ESRD (hazards ratio, 2.07) as significant variables influencing patient survival and observed/expected life span. This simple ratio is easy to use and may be a helpful tool for assessing the survival benefits of risk-factor modifications and therapeutic advances in transplantation and ESRD care.

Hyperreninemic hypertension secondary to a subcapsular perinephric hematoma in a patient with polyarteritis nodosa.

Page kidney is the name ascribed to a rare syndrome of hyperreninemic hypertension caused by unilateral compressive perinephritis. Blood or fluid that accumulates in the perinephric subcapsular space compresses the renal parenchyma leading to ischemia. This syndrome is analogous to the description of cellophane-induced perinephritis by Page in 1939. Page kidney typically presents in healthy young men after blunt trauma to the flank or abdomen, although cases have been noted after medical or surgical interventions. We report a case of a Page kidney in a young man with hepatitis B virus-associated polyarteritis nodosa. The patient presented with severe hypertension, hypokalemia, hyperreninemia, and radiographic evidence of a unilateral subcapsular hematoma. Perinephric hemorrhage developed because of necrotizing vascular inflammation and spontaneous or traumatic vascular rupture. In patients who present with new-onset hypertension and hypokalemia with a history of trauma or coexisting vasculitis, the presence of a Page kidney should be considered.

Bleaching of membrane-bound merocyanine 540 in conjunction with free radical-mediated lipid peroxidation.

The lipophilic dye merocyanine 540 (MC540) can photosensitize potentially lethal cell membrane damage as well as its own degradation (bleaching). Photobleaching in a test membrane, the human erythrocyte ghost has been examined. White light irradiation of MC540-sensitized ghosts resulted in lipid hydroperoxide (LOOH) formation, low-level thiobarbituric acid (TBA) reactivity, and dye bleaching (A568 decay). When the reaction was carried out in the presence of ascorbate (AH-), and added Fe3+, there was a large enhancement of TBA reactivity (indicative of free radical-mediated lipid peroxidation) and concomitant increase in the rate of photobleaching. Rapid bleaching also occurred when MC540 was incubated in the dark with ghosts that had been photoperoxidized with another dye (a phthalocyanine) and then exposed to AH-. The extent of bleaching in this system was found to be proportional to the starting level of LOOH. Like the wave of free radical lipid peroxidation that accompanied it, dye bleaching in AH(-)-treated, preperoxidized ghosts was stimulated by supplemental Fe3+, inhibited by desferrioxamine or butylated hydroxytoluene (BHT), but unaffected by catalase or superoxide dismutase. From this and related evidence, we deduce that: (1) in the absence of Fe3+/AH-, photoperoxidation and photobleaching occur independently and are nonradical, singlet oxygen-mediated processes; and (2) in the presence of Fe3+/AH-, 1-electron reduction of photogenerated LOOHs results in a surge of lipid peroxidation that amplifies dye loss via free radical processes. MC540 bleaching might be exploited as a relatively simple and sensitive indicator of lipid autoxidation in isolated membranes and cells.

Selective inhibitors of GTP synthesis impede exocytotic insulin release from intact rat islets.

To investigate whether GTP concentrations can be a regulatory step in exocytotic hormone secretion, we treated isolated rat islets with mycophenolic acid (MPA) or mizoribine, two selective inhibitors of de novo GTP synthesis. When islets were cultured overnight in purine-free medium containing the drug, MPA reduced GTP levels by up to 81 +/- 1%; guanine circumvented this block via the nucleotide "salvage" pathway. MPA concomitantly inhibited glucose (16.7 mM)-induced insulin secretion in batch-type incubations (or perifusions), by up to 68% at 50 micrograms/ml. Although the inhibition of secretion occurred over a similar concentration range as the reduction in total GTP content, the two variables were not directly correlated. However, the secretory effects also were prevented by adding guanine, but not hypoxanthine or xanthine, to the culture medium. Similar results for GTP content and insulin release were seen using mizoribine. Insulin content was modestly (-18%) reduced by MPA but indices of fractional release (release/insulin content) were also markedly impaired. Although MPA also reduced ATP levels more modestly (-39%) and increased UTP (+87%), these were not the cause of the secretory defect since adenine restored ATP and UTP nearly to normal, but did not alter the reduction in GTP content or insulin secretion. MPA also inhibited secretion induced by amino acid or by a phorbol ester but had virtually no effect on release induced by a depolarizing concentration of K+, suggesting that GTP depletion does not merely impede Ca+ influx or directly block Ca(2+)-activated exocytosis. However, a severe reduction of GTP content did not prevent the pertussis toxin-sensitive inhibition of insulin release induced by epinephrine, suggesting that the function of heterotrimeric GTP-binding proteins is not limited by ambient GTP concentrations. Although these studies do not elucidate the exact site(s) in the exocytotic cascade which depend on intact GTP stores, they do provide the first direct evidence that GTP is required (and can be rate limiting) for insulin release.

Photosensitized lipid peroxidation and enzyme inactivation by membrane-bound merocyanine 540: reaction mechanisms in the absence and presence of ascorbate.

The lipophilic photosensitizing dye merocyanine 540 (MC540) is being studied intensively as an antitumor and antiviral agent. Since plasma membranes are believed to be the principal cellular targets of MC540-mediated photodamage, we have studied membrane damage in a well characterized test system, the human erythrocyte ghost. When irradiated with white light, MC540-sensitized ghosts accumulated lipid hydroperoxides (LOOHs derived from phospholipids and cholesterol) at a rate dependent on initial dye concentration. Neither desferrioxamine nor butylated hydroxytoluene inhibited LOOH formation, suggesting that Type I (iron-mediated free radical) chemistry is not important. By contrast, azide inhibited the reaction in a dose-dependent fashion, implicating a Type II (singlet oxygen, 1O2) mechanism. Stern-Volmer analysis of the data gave a 1O2 quenching constant approximately 50 times lower than that determined for an extramembranous target, lactate dehydrogenase (the latter value agreeing with literature values). This suggests that 1O2 reacts primarily at its membrane sites of origin and that azide has limited access to these sites. Using [14C]cholesterol-labeled membranes and HPLC with radiodetection, we identified 3 beta-hydroxy-5 alpha-cholest-6-ene-5-hydroperoxide as the major cholesterol photoproduct, thereby confirming 1O2 intermediacy. Irradiation of MC540-sensitized membranes in the presence of added iron and ascorbate resulted in a large burst of lipid peroxidation, as shown by thiobarbituric acid reactivity and appearance of 7-hydroperoxycholesterol and 7-hydroxycholesterol as major oxidation products. Amplification of MC540-initiated lipid peroxidation by iron/ascorbate (attributed to light-independent reduction of nascent photoperoxides, with ensuing free radical chain reactions) could prove useful in augmenting MC540's phototherapeutic effects.

Photodynamic action of merocyanine 540 in artificial bilayers and natural membranes: action spectra and quantum yields.

The action spectra and quantum yields for singlet oxygen (1O2) generation by merocyanine 540 (MC540) in liposomes and isolated erythrocyte membranes were obtained using electron spin resonance techniques. Oxygen consumption was measured by spin label oximetry in the presence of histidine for fully-saturated dimyristoylphosphatidylcholine vesicles, mono-unsaturated 1-palmitoyl-2-oleoylphosphatidylcholine vesicles and erythrocyte membranes. The quantum yield for the photogeneration of 1O2 by membrane-bound MC540 in aqueous buffer was determined to be 0.065 +/- 0.005, which is approx. 1/10 of the value determined for Rose Bengal under similar conditions. Using unilamellar liposomes and isolated erythrocyte membranes containing MC540 at different monomer/dimer ratios, we have observed that the action spectra of 1O2 generation closely overlap the absorption spectra of the monomeric dye in these systems. It is likely that factors which affect the monomer-dimer equilibrium of MC540 will influence the production of 1O2. These findings have important implications for the phototherapeutic efficacy of MC540.