Regional CZT myocardial perfusion reserve for the detection of territories with simultaneously impaired CFR and IMR in patients without obstructive coronary artery disease: a pilot study.

OBJECTIVES: To assess the diagnostic performances of CZT myocardial perfusion reserve (MPR) for the detection of territories with simultaneous impaired coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) in patients without obstructive coronary artery disease. METHODS: Patients were prospectively included before being referred for coronary angiography. All patients underwent CZT MPR before invasive coronary angiography (ICA) and coronary physiology assessment. Rest and dipyridamole-induced stress myocardial blood flow (MBF) and MPR were quantified using 99mTc-SestaMIBI and a CZT camera. Fractional flow reserve (FFR), Thermodilution CFR, and IMR were assessed during ICA. RESULTS: Between December 2016 and July 2019, 36 patients were included. 25/36 patients presented no obstructive coronary artery disease. A complete functional assessment was performed in 32 arteries. No territory presented a significant ischemia on CZT myocardial perfusion imaging. A moderate yet significant correlation was observed between regional CZT MPR and CFR (r = 0.4, P = .03). Sensitivity, specificity, positive and negative predictive value, and accuracy of regional CZT MPR versus the composite invasive criterion (impaired CFR and IMR) were 87 [47% to 99%], 92% [73% to 99%], 78% [47% to 93%], 96% [78% to 99%], and 91% [75% to 98%], respectively. All territories with a regional CZT MPR ≤ 1.8 showed a CFR < 2. Regional CZT MPR values were significantly higher in arteries with CFR ≥ 2 and IMR < 25 (negative composite criterion, n = 14) than in those with CFR < 2 and IMR ≥ 25 (2.6 [2.1 to 3.6] versus 1.6 [1.2 to 1.8]), P < .01). CONCLUSION: Regional CZT MPR presented excellent diagnostic performances for the detection of territories with simultaneously impaired CFR and IMR reflecting a very high cardiovascular risk in patients without obstructive coronary artery disease.

Islets-on-Chip: A Tool for Real-Time Assessment of Islet Function Prior to Transplantation.

Islet transplantation improves metabolic control in patients with unstable type 1 diabetes. Clinical outcomes have been improving over the last decade, and the widely used beta-score allows the evaluation of transplantation results. However, predictive pre-transplantation criteria of islet quality for clinical outcomes are lacking. In this proof-of-concept study, we examined whether characterization of the electrical activity of donor islets could provide a criterion. Aliquots of 8 human donor islets from the STABILOT study, sampled from islet preparations before transplantation, were characterized for purity and split for glucose-induced insulin secretion and electrical activity using multi-electrode-arrays. The latter tests glucose concentration dependencies, biphasic activity, hormones, and drug effects (adrenalin, GLP-1, glibenclamide) and provides a ranking of CHIP-scores from 1 to 6 (best) based on electrical islet activity. The analysis was performed online in real time using a dedicated board or offline. Grouping of beta-scores and CHIP-scores with high, intermediate, and low values was observed. Further analysis indicated correlation between CHIP-score and beta-score, although significance was not attained (R = 0.51, p = 0.1). This novel approach is easily implantable in islet isolation units and might provide means for the prediction of clinical outcomes. We acknowledge the small cohort size as the limitation of this pilot study.

Insight into continuous glucose monitoring: from medical basics to commercialized devices.

According to the latest statistics, more than 537 million people around the world struggle with diabetes and its adverse consequences. As well as acute risks of hypo- or hyper- glycemia, long-term vascular complications may occur, including coronary heart disease or stroke, as well as diabetic nephropathy leading to end-stage disease, neuropathy or retinopathy. Therefore, there is an urgent need to improve diabetes management to reduce the risk of complications but also to improve patient's quality life. The impact of continuous glucose monitoring (CGM) is well recognized, in this regard. The current review aims at introducing the basic principles of glucose sensing, including electrochemical and optical detection, summarizing CGM technology, its requirements, advantages, and disadvantages. The role of CGM systems in the clinical diagnostics/personal testing, difficulties in their utilization, and recommendations are also discussed. In the end, challenges and prospects in future CGM systems are discussed and non-invasive, wearable glucose biosensors are introduced. Though the scope of this review is CGMs and provides information about medical issues and analytical principles, consideration of broader use will be critical in future if the right systems are to be selected for effective diabetes management.

Impact of ischemia time on islet isolation success and posttransplantation outcomes: A retrospective study of 452 pancreas isolations.

Many variables impact islet isolation, including pancreas ischemia time. The ischemia time upper limit that should be respected to avoid a negative impact on the isolation outcome is not well defined. We have performed a retrospective analysis of all islet isolations in our center between 2008 and 2018. Total ischemia time, cold ischemia time, and organ removal time were analyzed. Isolation success was defined as an islet yield ≥200 000 IEQ. Of the 452 pancreases included, 288 (64%) were successfully isolated. Probability of isolation success showed a significant decrease after 8 hours of total ischemia time, 7 hours of cold ischemia time, and 80 minutes of organ removal time. Although we observed an impact of ischemia time on islet yield, a probability of isolation success of 50% was still present even when total ischemia time exceeds 12 hours. Posttransplantation clinical outcomes were assessed in 32 recipients and no significant difference was found regardless of ischemia time. These data indicate that although shorter ischemia times are associated with better islet isolation outcomes, total ischemia time >12 hours can provide excellent results in appropriately selected donors.

Ten-year outcomes of islet transplantation in patients with type 1 diabetes: Data from the Swiss-French GRAGIL network.

To describe the 10-year outcomes of islet transplantation within the Swiss-French GRAGIL Network, in patients with type 1 diabetes experiencing high glucose variability associated with severe hypoglycemia and/or with functional kidney graft. We conducted a retrospective analysis of all subjects transplanted in the GRAGIL-1c and GARGIL-2 islet transplantation trials and analyzed components of metabolic control, graft function and safety outcomes over the 10-year period of follow-up. Forty-four patients were included between September 2003 and April 2010. Thirty-one patients completed a 10-year follow-up. Ten years after islet transplantation, median HbA1c was 7.2% (6.2-8.0) (55 mmol/mol [44-64]) versus 8.0% (7.1-9.1) (64 mmol/mol [54-76]) before transplantation (p < .001). Seventeen of 23 (73.9%) recipients were free of severe hypoglycemia, 1/21 patients (4.8%) was insulin-independent and median C-peptide was 0.6 ng/ml (0.2-1.2). Insulin requirements (UI/kg/day) were 0.3 (0.1-0.5) versus 0.5 (0.4-0.6) before transplantation (p < .001). Median (IQR) ß-score was 1 (0-4) (p < .05 when comparing with pre-transplantation values) and 51.9% recipients had a functional islet graft at 10 years. With a 10-year follow-up in a multicentric network, islet transplantation provided sustained improvement of glycemic control and was efficient to prevent severe hypoglycemia in almost 75% of the recipients.

Patients with highly unstable type 1 diabetes eligible for islet transplantation can be managed with a closed-loop insulin delivery system: A series of N-of-1 randomized controlled trials.

AIM: To compare the efficacy of the closed-loop Diabeloop for highly unstable diabetes (DBLHU) system with the open-loop predictive low glucose suspend (PLGS) system in patients with highly unstable type 1 diabetes (T1D) who experience acute metabolic events. METHODS: DBLHU-WP10 was an interventional, controlled, randomized, open-label study that comprised two cycles of N-of-1 trials (2-of-1 trials). Each trial consisted of two crossover 4-week periods of treatment with either DBLHU or PLGS in randomized order. The primary outcome was the percentage of time spent in the 70-180 mg/dL glucose range (time in range [TIR]). RESULTS: Five out of seven randomized patients completed the aggregated 2-of-1 trials. TIR was significantly higher with DBLHU (73.3% ± 1.7%) compared with PLGS (43.5% ± 1.7%; P < .0001). The percentage of time below 70 mg/dL was significantly lower with DBLHU (0.9% ± 0.4%) versus PLGS (3.7% ± 0.4%; P < .0001). DBLHU was also significantly superior to PLGS in reducing hyperglycaemic excursions and improving almost all other secondary outcomes, including glucose variability and satisfaction score. No adverse event could be related to the experimental treatment. CONCLUSIONS: DBLHU was superior to PLGS in improving the metabolic control of patients with highly unstable T1D who require an islet or pancreas transplant but who either have a contraindication or refuse to consent.

Improved human islets' viability and functionality with mesenchymal stem cells and arg-gly-asp tripeptides supplementation of alginate micro-encapsulated islets in vitro.

INTRODUCTION: The extension of islet transplantation to a wider number of type 1 diabetes patients is compromised by severe adverse events related to the immunosuppressant therapy required for allogenic islet transplantation. In this context, microencapsulation offers the prospects of immunosuppressive-free therapy by physically isolating islets from the immune system. However, current biomaterials need to be optimized to: improve biocompatibility, guaranty the maintenance of graft viability and functionality, and prevent fibrosis overgrowth around the capsule in vivo. Accumulating evidence suggest that mesenchymal stem cells (MSCs) and anchor points consisting of tripeptides arg-gly-asp (RGD) have cytoprotective effects on pancreatic islets. Here, we investigated the effect of supplementing reference M-rich alginate microcapsules with MSCs and RGD-G rich alginate on bioprocessing as well as on human pancreatic islets viability and functionality. METHODS: We characterized the microcapsules components, and then for the new microcapsule composite product: we analyzed the empty capsules biocompatibility and then investigated the benefits of MSCs and RGD-G rich alginate on viability and functionality on the encapsulated human pancreatic islets in vitro. We performed viability tests by confocal microscopy and glucose stimulated insulin secretion (GSIS) test in vitro to assess the functionality of naked and encapsulated islets. RESULTS: Encapsulation in reference M-rich alginate capsules induced a reduction in viability and functionality compared to naked islets. This side-effect of encapsulation was in part counteracted by the presence of MSCs but the restoration was complete with the combination of both MSCs and the RGD-G rich alginate. CONCLUSIONS: The present findings show that bioprocessing a favorable composite environment inside the M-rich alginate capsule with both MSCs and RGD-G rich alginate improves human islets survival and functionality in vitro.

Pancreas collagen digestion during islet of Langerhans isolation-a prospective study.

The success of pancreas islet isolation largely depends on donor characteristics, including extracellular matrix composition of which collagen is the main element. We hypothesized that isolation yields are proportional to collagen digestion percentage, and aimed to determine a threshold that predicts isolation success. The amount of pancreas collagen (I-V) was determined using colorimetry prior to and after the digestion process in 52 human islet isolations. Collagen I-V and VI were also assessed histologically. We identified a collagen digestion threshold of ≥ 60% as an independent factor beyond which an islet preparation has a ninefold increased odds of yielding ≥ 250 000 islet equivalents (IEQ) (P = 0.009) and a sixfold increased odds of being transplanted (P = 0.015). Preparations with ≥ 60% collagen digestion (n = 35) yielded 283 017 ± 164 214 IEQ versus 180 142 ± 85 397 in the < 60% collagen digestion group (n = 17) (P = 0.016); respectively 62.9% versus 29.4% of those were transplanted (P = 0.024). Common donor characteristics, initial collagen content, enzyme blend, and digestion times were not associated with collagen digestion percentage variations. Donor age positively correlated with the amount of collagen VI (P = 0.013). There was no difference in islet graft survival between high and low digestion groups. We determined that a 60% pancreas collagen digestion is the threshold beyond which an islet isolation is likely to be successful and transplanted.

Respective effects of oxygen and energy substrate deprivation on beta cell viability.

Deficit in oxygen and energetic substrates delivery is a key factor in islet loss during islet transplantation. Permeability transition pore (PTP) is a mitochondrial channel involved in cell death. We have studied the respective effects of oxygen and energy substrate deprivation on beta cell viability as well as the involvement of oxidative stress and PTP opening. Energy substrate deprivation for 1h followed by incubation in normal conditions led to a cyclosporin A (CsA)-sensitive-PTP-opening in INS-1 cells and human islets. Such a procedure dramatically decreased INS-1 cells viability except when transient removal of energy substrates was performed in anoxia, in the presence of antioxidant N-acetylcysteine (NAC) or when CsA or metformin inhibited PTP opening. Superoxide production increased during removal of energy substrates and increased again when normal energy substrates were restored. NAC, anoxia or metformin prevented the two phases of oxidative stress while CsA prevented the second one only. Hypoxia or anoxia alone did not induce oxidative stress, PTP opening or cell death. In conclusion, energy substrate deprivation leads to an oxidative stress followed by PTP opening, triggering beta cell death. Pharmacological prevention of PTP opening during islet transplantation may be a suitable option to improve islet survival and graft success.

Diabetes in spotlight: current knowledge and perspectives of photobiomodulation utilization.

Introduction: Diabetes is a global health concern characterized by chronic hyperglycemia resulting from insulinopenia and/or insulin resistance. The rising prevalence of diabetes and its associated complications (ulcers, periodontitis, healing of bone defect, neuropathy, retinopathy, cardiopathy and nephropathy) necessitate innovative therapeutic approaches. Photobiomodulation (PBM), involves exposing tissues and cells to low-energy light radiation, leading to biological effects, largely via mitochondrial activation. Methods: This review evaluates preclinical and clinical studies exploring the potential of PBM in diabetes and its complications, as well all clinical trials, both planned and completed, available on ClinicalTrials database. Results: This review highlights the variability in PBM parameters across studies, hindering consensus on optimal protocols. Standardization of treatment parameters and rigorous clinical trials are needed to unlock PBM's full therapeutic potential. 87 clinical trials were identified that investigated PBM in diabetes mellitus (with 5,837 patients planned to be treated with PBM). Clinical trials assessing PBM effects on diabetic neuropathy revealed pain reduction and potential quality of life improvement. Studies focusing on wound healing indicated encouraging results, with PBM enhancing angiogenesis, fibroblast proliferation, and collagen density. PBM's impact on diabetic retinopathy remains inconclusive however, requiring further investigation. In glycemic control, PBM exhibits positive effects on metabolic parameters, including glucose tolerance and insulin resistance. Conclusion: Clinical studies have reported PBM-induced reductions in fasting and postprandial glycemia without an increased hypoglycemic risk. This impact of PBM may be related to its effects on the beta cells and islets in the pancreas. Notwithstanding challenges, PBM emerges as a promising adjunctive therapy for managing diabetic neuropathy, wound healing, and glycemic control. Further investigation into its impact on diabetic retinopathy and muscle recovery is warranted.

Managing blood glucose levels with a hybrid closed-loop system in a patient with type 1 diabetes mellitus on enteral nutrition: A case report.

The achievement of glycemic management is challenging in patients with diabetes on enteral nutrition, limited literature exists on hybrid closed-loop systems' efficacy in such a situation. We described the case of a patient with type 1 diabetes treated by advanced hybrid closed loop on enteral nutrition with satisfactory glycemic management.

From the Clinical to the Bench: Exploring the Insulin Modulation Effects of Tacrolimus and Belatacept.

Calcineurin inhibitors (CNIs) are critical in preventing rejection posttransplantation but pose an increased risk of post-transplant diabetes (PTD). Recent studies show that late conversion from CNIs to belatacept, a costimulation blocker, improves HbA1c in kidney transplant recipients with PTD or de novo diabetes. This study investigates whether the observed effects on PTD stem solely from CNI withdrawal or if belatacept influences PTD independently. The study assessed the impact of tacrolimus and belatacept on insulin secretion in MIN6 cells (a beta cell line) and rat islets. Tacrolimus and belatacept were administered to the cells and islets, followed by assessments of cell viability and insulin secretion. Tacrolimus impaired insulin secretion without affecting cell viability, while belatacept showed no detrimental effects on either parameter. These findings support clinical observations of improved HbA1c upon switching from tacrolimus to belatacept. Belatacept holds promise in islet or pancreas transplantation, particularly in patients with unstable diabetes. Successful cases of islet transplantation treated with belatacept without severe hypoglycemia highlight its potential in managing PTD. Further research is needed to fully understand the metabolic changes accompanying the transition from CNIs to belatacept. Preserving insulin secretion emerges as a promising avenue for investigation in this context.

Closed-Loop Insulin Therapy for People With Type 2 Diabetes Treated With an Insulin Pump: A 12-Week Multicenter, Open-Label Randomized, Controlled, Crossover Trial.

OBJECTIVE: Continuous glucose monitoring (CGM) combined with continuous subcutaneous insulin infusion (CSII) achieves better glycemic control than multi-injection therapy in people with type 2 diabetes. The effectiveness of closed-loop therapy needs to be further evaluated in this population. RESEARCH DESIGN AND METHODS: The study objective was to measure the impact of a hybrid closed-loop device (DBLG1) compared with CSII + CGM on glycemic control in people with type 2 diabetes previously treated with CSII. The randomized, controlled, crossover, two-period, open-label, and multicenter study was conducted from August 2022 to July 2023 in 17 individuals (9 to receive 6 weeks of CSII + CGM first and 8 to receive 6 weeks of closed-loop therapy first). The primary end point was the percentage time in range (TIR: 70-180 mg/dL). Secondary outcomes were other CGM-glucose metrics, physical activity, and sleep objectively measured using 1-week actimetry. RESULTS: Data were analyzed using a modified intention-to-treat approach. Mean age was 63 (SD 9) years and 35% were women. Mean HbA1c at inclusion was 7.9% (SD 0.9). TIR increased to 76.0% (interquartile range 69.0-84.0) during the closed-loop condition vs. 61.0% (interquartile range 55.0-70.0) during the CSII + CGM condition; mean difference was 15.0 percentage points (interquartile range 8.0-22.0; P < 0.001). Analyses of secondary end points showed a decrease in time above range, in glucose management indicator, in glucose variability, and an increase in daily insulin dose. Actimetric sleep analysis showed an improvement in sleep fragmentation during closed-loop treatment. CONCLUSIONS: Closed-loop therapy improved glycemic control above than did CSII + CGM in people with type 2 diabetes.

Matrix design for optimal pancreatic ß cells transplantation.

New therapeutic approaches to treat type 1 diabetes mellitus relies on pancreatic islet transplantation. Here, developing immuno-isolation strategies is essential to eliminate the need for systemic immunosuppression after pancreatic islet grafts. A solution is the macro-encapsulation of grafts in semipermeable matrixes with a double function: separating islets from host immune cells and facilitating the diffusion of insulin, glucose, and other metabolites. This study aims to synthesize and characterize different types of gelatin-collagen matrixes to prepare a macro-encapsulation device for pancreatic islets that fulfill these functions. While natural polymers exhibit superior biocompatibility compared to synthetic ones, their mechanical properties are challenging to reproduce. To address this issue, we conducted a comparative analysis between photo-crosslinked gelatin matrixes and chemically crosslinked collagen matrixes. We show that the different crosslinkers and polymerization methods influence the survival and glucose-stimulated insulin production of pancreatic ß cells (INS1) in vitro, as well as the in vitro and in vivo stability of the matrix and the immuno-isolation in vivo. Among the matrixes, the stiff multilayer GelMA matrixes (8.5 kPa), fabricated by digital light processing, were the best suited for pancreatic ß cells macro-encapsulation regarding these parameters. Within the alveoli of this matrix, pancreatic ß cells spontaneously formed aggregates.

12-Month Real-Life Efficacy of the MiniMed 780G Advanced Closed-Loop System in Patients Living with Type 1 Diabetes: A French Observational, Retrospective, Multicentric Study.

Aim: To evaluate the evolution of glycemic outcomes in patients living with type 1 diabetes (T1D) after 1 year of use of the MiniMed 780G advanced hybrid closed-loop (AHCL) system. Methods: We conducted an observational, retrospective, multicentric study in 20 centers in France. The primary objective was to evaluate the improvement in glycemic control after 1-year use of AHCL. The primary endpoint was the variation of time in range (TIR) between pre-AHCL and after 1-year use of AHCL. Secondary objectives were to analyze the glycemic outcomes after 3, 6, and 12 months of AHCL use, the safety, and the long-term observance of AHCL. Results: Two hundred twenty patients were included, and 200 were analyzed for the primary endpoint. 92.7% of patients continued to use AHCL. After 1 year of use of AHCL, TIR was 72.5% ± 10.6% (+9.1%; 95% confidence interval [CI] [7.6-10.5] compared to pre-AHCL initiation, P < 0.001), HbA1c 7.1% ± 0.7% (-0.5%; 95% CI [-0.6 to -0.4]; P < 0.001), time below range 2.0% [1.0; 3.0] (0.0% [-2.0; 0.0], P < 0.001), and time above range 24.8% ± 10.9% (-7.3%; 95% CI [-8.8 to -5.7]; P < 0.001). More patients achieved the glycemic treatment goals of HbA1c <7.0% (45.1% vs. 18.1%, P < 0.001) and TIR >70% (59.0% vs. 29.5% P < 0.001) when compared with pre-AHCL. Five patients experienced severe hypoglycemia events and two patients experienced ketoacidosis. Conclusion: After 1 year of use of AHCL, people living with T1D safely improved their glucose control and a higher proportion of them achieved optimal glycemic control.

Islet-after-kidney transplantation versus kidney alone in kidney transplant recipients with type 1 diabetes (KAIAK): a population-based target trial emulation in France.

BACKGROUND: Islet transplantation has been associated with better metabolic control and quality of life than insulin treatment alone, but direct evidence of its effect on hard clinical endpoints is scarce. We aimed to assess the effect of islet transplantation on patient-graft survival in kidney transplant recipients with type 1 diabetes. METHODS: In this retrospective cohort study, we enrolled all patients with type 1 diabetes who received a kidney graft in France during the study period, identified from the CRISTAL nationwide registry. Non-inclusion criteria included recipients from transplant centres that never proposed islet transplantation during the study period, recipients with a functional pancreas throughout the follow-up duration, recipients with more than two kidney transplants, HLA-sensitised recipients, recipients with less than 1 year of follow-up after kidney transplantation, misclassified recipients with type 2 diabetes, recipients aged over 65 years, recipients of kidney grafts from Donation after Circulatory Death donors, recipient with HIV or hepatitis, recipients with cancer, and recipients of combined liver-kidney transplants. Patients who also received islet-after-kidney (IAK) transplantation were compared with controls who received kidney transplantation alone according to a 1:2 matching method based on time-dependent propensity scores, ensuring patients comparability at the time of islet transplantation. The primary outcome was patient-graft survival, a composite outcome defined by death, re-transplantation, or return to dialysis. FINDINGS: Between Jan 1, 2000, and Dec 31, 2017, 2391 patients with type 1 diabetes were identified as having received a kidney transplant, 47 patients of whom also received an islet transplantation. 2002 patients were not eligible for islet transplantation and 62 were excluded due to missing data. 327 eligible recipients from 15 centres were included in the study dataset for the target trial emulation. 40 patients who received IAK transplantation were successfully matched to 80 patients who received kidney transplantation alone. 13 (33%) of 40 patients in the IAK transplantation group returned to dialysis or died, compared with 36 (45%) of 80 patients in the kidney transplantation alone group. We found a significant benefit of islet transplantation compared with kidney transplantation alone on patient-graft survival, with a hazard ratio (HR) of 0·44 (95% CI 0·23-0·88; p=0·022), mainly explained by a protective effect on the risk of death (HR 0·41, 0·13-0·91; p=0·042). There was no meaningful association between IAK and death-censored graft survival (0·73, 0·30-1·89; p=0·36). INTERPRETATION: In kidney transplant recipients with type 1 diabetes, IAK transplantation was associated with a significantly better patient-graft survival compared with kidney transplantation alone, mainly due to a protective effect on the risk of death. These results potentially serve as compelling grounds for advocating wider access to islet transplantation in patients with type 1 diabetes undergoing kidney transplant, as reimbursement of islet transplantation is provided in few countries worldwide. FUNDING: Programme Hospitalier de la Recherche Clinique, Fondation pour la Recherche Medicale, and Fonds de Dotation Line Renaud-Loulou Gasté.

Inhibition of complex I regulates the mitochondrial permeability transition through a phosphate-sensitive inhibitory site masked by cyclophilin D.

Inhibition of the mitochondrial permeability transition pore (PTP) has proved to be an effective strategy for preventing oxidative stress-induced cell death, and the pore represents a viable cellular target for drugs. Here, we report that inhibition of complex I by rotenone is more effective at PTP inhibition than cyclosporin A in tissues that express low levels of the cyclosporin A mitochondrial target, cyclophilin D; and, conversely, that tissues in which rotenone does not affect the PTP are characterized by high levels of expression of cyclophilin D and sensitivity to cyclosporin A. Consistent with a regulatory role of complex I in the PTP-inhibiting effects of rotenone, the concentrations of the latter required for PTP inhibition precisely match those required to inhibit respiration; and a similar effect is seen with the antidiabetic drug metformin, which partially inhibits complex I. Remarkably (i) genetic ablation of cyclophilin D or its displacement with cyclosporin A restored PTP inhibition by rotenone in tissues that are otherwise resistant to its effects; and (ii) rotenone did not inhibit the PTP unless phosphate was present, in striking analogy with the phosphate requirement for the inhibitory effects of cyclosporin A [Basso et al. (2008) J. Biol. Chem. 283, 26307-26311]. These results indicate that inhibition of complex I by rotenone or metformin and displacement of cyclophilin D by cyclosporin A affect the PTP through a common mechanism; and that cells can modulate their PTP response to complex I inhibition by modifying the expression of cyclophilin D, a finding that has major implications for pore modulation in vivo.