Early metabolic markers that anticipate loss of insulin independence in type 1 diabetic islet allograft recipients.

The objective of this study was to identify predictors of insulin independence and to establish the best clinical tools to follow patients after pancreatic islet transplantation (PIT). Sequential metabolic responses to intravenous (I.V.) glucose (I.V. glucose tolerance test [IVGTT]), arginine and glucose-potentiated arginine (glucose-potentiated arginine-induced insulin secretion [GPAIS]) were obtained from 30 patients. We determined the correlation between transplanted islet mass and islet engraftment and tested the ability of each assay to predict return to exogenous insulin therapy. We found transplanted islet mass within an average of 16 709 islet equivalents per kg body weight (IEQ/kg BW; range between 6602 and 29 614 IEQ/kg BW) to be a poor predictor of insulin independence at 1 year, having a poor correlation between transplanted islet mass and islet engraftment. Acute insulin response to IVGTT (AIR(GLU) ) and GPAIS (AIR(max) ) were the most accurate methods to determine suboptimal islet mass engraftment. AIR(GLU) performed 3 months after transplant also proved to be a robust early metabolic marker to predict return to insulin therapy and its value was positively correlated with duration of insulin independence. In conclusion, AIR(GLU) is an early metabolic assay capable of anticipating loss of insulin independence at 1 year in T1D patients undergoing PIT and constitutes a valuable, simple and reliable method to follow patients after transplant.

Correction of insulin sensitivity and glucose disposal after pancreatic islet transplantation: preliminary results.

AIMS: Pancreatic islet transplantation (PIT) represents a potential curative treatment for patients with type 1 diabetes, but only 10-15% of patients remain insulin independent 5 years post-transplant. It is not known whether intrinsic insulin resistance exacerbated by immunosuppression plays a pivotal role in low graft survival. The study objective was to understand the changes in insulin resistance, glucose effectiveness (S(g)) and free fatty acid dynamics (FFAd) before and after PIT. METHODS: Insulin sensitivity index (S(i)), S(g) and FFAd were measured before and after PIT in 10 lean patients, 8 of whom reached insulin independence. Modified Bergman minimal model of frequently sampled intravenous glucose tolerance tests were performed pretransplant and at 12 months post-transplant. Nine non-diabetic control (NDC) subjects matched by age, gender and BMI were used. RESULTS: Pretransplant S(i) and S(g) were 3.5 ± 0.8 × 10(-5)/min/(pmol/l) and 0.74 ± 0.24 × 10(-2)/min, respectively. S(i) was significantly lower than matched NDCs [10.8 ± 0.6 × 10(-5)/min/(pmol/l), p < 0.004]; S(g) did not reach statistical significance (1.27 ± 0.22 × 10(-2)/min, p = 0.25). Compared to pretransplant values, mean post-transplant S(i) and S(g) were 9.6 ± 1.3 × 10(-5)/min/(pmol/l)and 1.28 ± 0.22 ×10(-2)/min, respectively, indicating significant improvement for S(i) but not S(g) (p = 0.008 and p = 0.06). Twelve-month post-PIT compared to NDC values were not significantly different (p = 0.58 and 0.97, respectively). In addition, fractional disposal rate for FFA which directly depends on the endogenous insulin release (10-20 min) nearly normalized after PIT (p = 0.06). CONCLUSION: These preliminary findings demonstrate that PIT can restore glucose disposal and insulin sensitivity and partially correct glucose effectiveness and FFAd.

Clinically stable human renal allografts contain histological and RNA-based findings that correlate with deteriorating graft function.

BACKGROUND: Chronic rejection (CR) remains idiopathic, difficult to prospectively identify, and once detected, unresponsive to increased immunosuppression. We hypothesized that clinically stable human renal allografts have ongoing evidence of injury and immune activity, and that this correlates with the worsening of allograft function characteristic of CR. METHODS: The allografts of 40 stable renal allograft recipients were biopsied 2-3 years after transplantation. Biopsies were processed for histology and RNA extraction. RNA was evaluated by semi-quantitative RT-polymerase chain reaction for CD3y mRNA (a marker of T cell receptor turnover), and mRNA from cytokine genes previously shown to be transcribed during acute rejection: tumor necrosis factor-alpha, interferon-gamma, interleukin- (IL) 1beta, IL-2, IL-4, IL-6, and IL-8. Clinical parameters including urine protein and glomerular filtration rate were measured the day of biopsy. Findings were then compared with clinical outcome to establish associations between subclinical inflammation and graft dysfunction. Allograft function was measured again 2 years after biopsy and correlated with findings at the time of biopsy. RESULTS: Cytokine transcripts and histological evidence of injury were detected in more than two-thirds of stable grafts. The degree of the lymphocytic infiltrate correlated with the degree of proteinuria (P=0.034) and histological fibrosis (P=0.005). Similarly, the degree of intragraft CD3y transcription correlated with increasing proteinuria (P=0.043). IL-6 and IL-8 transcripts were also correlated with evidence of graft injury. After 2 years, those biopsies originally found to have evidence of fibrosis, tubular atrophy, or CD3gamma transcription had worsening graft function as determined by creatinine and glomerular filtration rate. CONCLUSIONS: These data demonstrate that significant injury and immune activity can be detected in patients who are stable on clinical grounds. Undetected subclinical graft injury may be a cause of chronic allograft rejection.

Renin-angiotensin system gene expression in post-transplant hypertension predicts allograft function.

BACKGROUND: Registry analyses and single-center studies have demonstrated that hypertension significantly increases the risk for chronic graft loss. The graft itself may contribute to posttransplant hypertension, and intragraft vasoactive hormones therefore, may be dysregulated in posttransplant hypertension. METHODS: We used the reverse-transcription polymerase chain reaction to assess the intragraft regulation of renin-angiotensin system transcripts in biopsy samples from 42 stable renal transplant patients with posttransplant hypertension. We also examined mRNA expression of inducible nitric oxide synthase, transforming growth factor-beta (TGF-beta), select cytokines, and metalloproteinase transcripts in biopsy tissue. Polymerase chain reaction products were quantitated using high performance liquid chromatography and normalized to beta-actin mRNA expression. Serum creatinine, glomerular filtration rate or creatinine clearance and tubular atrophy on biopsy were concurrently assessed. RESULTS: Renin and select Thl cytokine mRNA expression correlated with blood pressure. Type 1 angiotensin II receptor mRNA expression significantly correlated with glomerular filtration rate or creatinine clearance (P = 0.034) and inversely correlated with Th1 cytokines, inducible nitric oxide synthase, and cyclooxygenase-1 mRNA expression (P< or =0.013 for each). Type 1 angiotensin II receptor mRNA also approached a significant inverse correlation with TGF-beta mRNA expression (P = 0.09). Conversely, angiotensin-converting enzyme mRNA expression directly correlated with Thl cytokine (P< or =0.008 for each) and TGF-beta mRNA expression (P = 0.006). Type 1 angiotensin II receptor mRNA expression also correlated with matrix metalloproteinase-1 promoter region, tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) and tissue inhibitor of matrix metalloproteinase-3 mRNA expression. Notably, matrix metalloproteinase-1 promoter region, tissue inhibitor of matrix metalloproteinase-2, and tissue inhibitor of matrix metalloproteinase-3 inversely correlated with TGF-beta mRNA expression (P< or =0.0027 for each). Type 1 angiotensin II receptor mRNA expression at biopsy directly correlated with glomerular filtration rate at 2 year's follow-up. However, angiotensin-converting enzyme mRNA expression at biopsy inversely correlated with glomerular filtration rate at 2 year's follow-up. CONCLUSIONS: These data suggest that allograft-level RAS gene expression may be predictive of future graft function in the setting of diastolic hypertension.

Maturation of pulmonary input impedance spectrum in infants and children with ventricular septal defect.

To determine whether pulmonary vascular disease can be detected in infants with ventricular septal defect (VSD) by the presence of an increase in the frequency of the impedance modulus minimum of the pulmonary input impedance spectrum, as has been implied for older children, spectra of 25 infants (2 years or younger) (group 1) were compared with spectra of 20 children (ages 2 to 7 years) (group 2). Groups were subdivided according to mean pulmonary artery (PA) pressure: those with moderate pressure levels (35 mm Hg or less, groups 1A and 2A) and those with high pressure levels (at least 40 mm Hg, groups 1B and 2B). Pulmonary vascular resistance, characteristic impedance and frequency of the modulus minimum were significantly lower in group 2A than in group 1A. The decrease in pulmonary vascular resistance and characteristic impedance with increasing age was consistent with body surface area increases; however, the shift in frequency of the modulus minimum could be more easily related to a decrease in the pulse wave velocity than to a shift in the primary reflection site. Pulmonary vascular resistance, characteristic impedance and the frequency of the first modulus minimum were comparable in groups 1B and 2B; however, none of the patients in group 1B had evidence of pulmonary damage, whereas 3 of 4 group 2B patients had microscopically apparent pulmonary vascular disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Type 2 angiotensin II receptor expression in human renal allografts: an association with chronic allograft nephropathy.

AIMS: The renin-angiotensin system (RAS) has been implicated in renal fibrosis through activation of the type I angiotensin II (Ang II) receptor (AT1R). Whether the other predominant Ang II receptor, the type 2 Ang II receptor (AT2R), has a fibrotic or sparing role in adult human renal tissue is unknown. MATERIALS AND METHODS: We used the reverse-transcription polymerase chain reaction (RT-PCR) to assess intragraft AT2R mRNA expression in biopsy samples from 23 renal transplant recipients. Potential correlations between intragraft AT2R mRNA. matrix-modulating genes and histologic evidence of chronic rejection were assessed. RESULTS: AT2R mRNA was confirmed by sequence analysis of the RT-PCR product. AT2R mRNA expression directly correlated with angiotensinogen (Spearman correlation coefficient (r(s)) 0.72; p = 0.0011) mRNA expression, and interestingly, AT2R mRNA inversely correlated with inflammatory gene expression in the biopsy samples. However, AT2R mRNA directly correlated with transforming growth factor-beta (TGF-beta) (r(s) 0.59: p = 0.044), matrix metalloproteinase-1 (MMP-1) (r(s) 0.83; p = 0.001), tissue inhibitor of metalloproteinase-2 (TIMP-2) (r(s) 0.74; p = 0.001) and TIMP-3 (r(s) 0.80; p = 0.001) mRNA expression. Moreover, AT2R mRNA and protein expression was significantly greater in the patients with biopsy-proven chronic allograft nephropathy (n = 9; p = 0.045 vs. no chronic allograft nephropathy and donor biopsy samples for mRNA analyses). CONCLUSIONS: These data demonstrate that AT2R mRNA is expressed in adult human renal tissue in the setting of renal transplantation. Its apparent association with matrix-modulating genes raises the hypothesis that AT2R mRNA expression may be linked with extracellular matrix regulation in the setting of chronic allograft nephropathy.

Infant pulmonary vascular model based on the pulmonary input impedance spectrum.

A mathematical model of the infant pulmonary vascular system was developed by altering an adult model to fit the hemodynamic properties of an infant pulmonary vascular bed. The model was designed for infants between the ages of 1 and 2 years with both normal and high mean pulmonary artery pressures (PAPs). The resulting infant model was evaluated on the basis of the computed parameters of cumulative length, volume and resistance of the pulmonary vascular bed, as well as on the basis of comparisons of the model spectra with actual computed spectra for ventricular septal defect patients who were of comparable age, had comparable mean PAPs and were not diagnosed as having pulmonary vascular disease. It was observed that the first minimum and first maximum in the modulus of the input impedance spectrum of the infant model for both normal and high mean PAPs occurred at a higher frequency than in the adult model. These observations led to the conclusion that there is a natural, age-related shift in the input impedance spectrum of infants which is not necessarily indicative of pulmonary impairment.