Reduction of insulin resistance by combined kidney-pancreas transplantation in type 1 (insulin-dependent) diabetic patients

Preserved insulin secretion and kidney function in recipients with functional pancreas grafts 1 year after transplantation: a single-center prospective observational study

OBJECTIVE

Successful simultaneous pancreas and kidney transplantation (SPK) or pancreas transplantation alone (PTA) restores glycemic control. Diabetes and impaired kidney function are common side effects of immunosuppressive therapy. This study addresses glucometabolic parameters and kidney function during the first year.

METHODS

We examined 67 patients with functioning grafts (SPK n = 30, PTA n = 37) transplanted between September 2011 and November 2016 who underwent repeated oral glucose tolerance tests (OGTTs) 8 and 52 weeks after transplantation. Another 19 patients lost their graft the first year post-transplant and 28 patients did not undergo repeated OGTTs and could not be studied. All patients received ATG induction therapy plus tacrolimus, mycophenolate and prednisolone. Glomerular filtration rate was measured before and 8 and 52 weeks after transplantation by serum clearance methods.

RESULTS

From week 8 to 52 after transplantation, mean fasting glucose decreased (SPK: 5.4 ± 0.7 to 5.1 ± 0.8 mmol/L, PTA: 5.4 ± 0.6 to 5.2 ± 0.7 mmol/L; both P < 0.05), and also 120-min post-OGTT glucose (SPK: 6.9 ± 2.9 to 5.7 ± 2.2 mmol/L; P = 0.07, PTA: 6.5 ± 1.7 to 5.7 ± 1.2 mmol/L; P < 0.05). Fasting C-peptide levels also decreased (SPK: 1500 ± 573 to 1078 ± 357 pmol/L, PTA: 1210 ± 487 to 1021 ± 434 pmol/L, both P < 0.005). Measured GFR decreased from enlistment to 8 weeks post transplant in PTA patients (94 ± 22 to 78 ± 19 mL/min/1.73 m2; P < 0.005), but did not deteriorate from week 8 to week 52 (SPK: 55.0 ± 15.1 vs 59.7 ± 11.3 ml/min/1.73 m²; P = 0.19, PTA: 76 ± 19 vs 77 ± 19 mL/min/1.73 m²; P = 0.74).

CONCLUSION

Glycemic control and kidney function remain preserved in recipients with functioning SPK and PTA grafts 1 year after transplantation.

Insulin resistance in type 1 diabetes mellitus

For long the presence of insulin resistance in type 1 diabetes has been questioned. Detailed metabolic analyses revealed 12%-61% and up to 20% lower whole-body (skeletal muscle) and hepatic insulin sensitivity in type 1 diabetes, depending on the population studied. Type 1 diabetes patients feature impaired muscle adenosine triphosphate (ATP) synthesis and enhanced oxidative stress, predominantly relating to hyperglycemia. They may also exhibit abnormal fasting and postprandial glycogen metabolism in liver, while the role of hepatic energy metabolism for insulin resistance remains uncertain. Recent rodent studies point to tissue-specific differences in the mechanisms underlying insulin resistance. In non-obese diabetic mice, increased lipid availability contributes to muscle insulin resistance via diacylglycerol/protein kinase C isoforms. Furthermore, humans with type 1 diabetes respond to lifestyle modifications or metformin by 20%-60% increased whole-body insulin sensitivity, likely through improvement in both glycemic control and oxidative phosphorylation. Intensive insulin treatment and islet transplantation also increase but fail to completely restore whole-body and hepatic insulin sensitivity. In conclusion, insulin resistance is a feature of type 1 diabetes, but more controlled trials are needed to address its contribution to disease progression, which might help to optimize treatment and reduce comorbidities.

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.

Hypoglycemia following pancreas transplantation

Mild symptoms of hypoglycemia in individuals with type 1 diabetes who have undergone pancreas transplantation are common, but biochemical evidence of hypoglycemia in these individuals often remains scant. Rarely, more overt cases with profound neuroglycopenic symptoms and documented hypoglycemia after transplantation have been described. Although the diagnosis of hypoglycemia in most cases of adrenergic symptoms alone, without documented hypoglycemia, remains questionable and likely not clinically significant, several potential etiologies have been identified in the more severe cases. This article reports a case with severe hypoglycemia after pancreas transplantation for type 1 diabetes, reviews several potential mechanisms underlying pancreas allograft-associated hypoglycemia, and discusses current treatment strategies for minimizing symptomatic hypoglycemia after transplant.

Glucose metabolism after pancreas-kidney transplantation

Simultaneous pancreas-kidney (SPK) transplantation is a promising treatment option for patients with type 1 diabetes and end-stage renal disease. Most of these patients can achieve normalization of glucose and hemoglobin A(1c) levels. Patient and graft survival continues to improve; however, defects in beta-cell function and insulin resistance can be seen over time after transplant. Various methods can be used to assess the SPK recipient for the development of hyperglycemia and graft dysfunction, with treatment aimed at minimizing diabetogenic immunosuppression, using agents that may preserve beta-cell function, and improving insulin resistance.

Atrial Natriuretic Peptide in Diabetic and Nondiabetic Patients With and Without Heart Transplantation

BACKGROUND

Natriuretic peptides are useful markers for risk stratification of patients with heart disease. However, conflicting results have been reported about circulating atrial natriuretic peptide (ANP) concentration in heart transplant recipients.

METHODS

To ascertain the effects of diabetes and acute insulin administration on plasma ANP concentrations in a model of heart denervation, we studied 12 diabetic (D-OHT) and 6 nondiabetic heart-transplanted (OHT) patients using the euglycemic-hyperinsulinemic clamp and oral glucose tolerance tests. Five patients with type 2 diabetes without heart transplantation (D) and 9 healthy subjects (NOR) matched for anthropometric features served as the controls.

RESULTS

Means baseline plasma ANP concentration was higher in D-OHT (82 +/- 15 pg/mL) than in OHT or NOR (27 +/- 4 or 30 +/- 5; P < .01), but was not different than D (69 +/- 12; P = .82). During the clamp plasma ANP showed similar increases in all groups (49 +/- 4, 39 +/- 3, 59 +/- 4, and 49 +/- 3% in D-OHT, OHT, D, and NOR; P < .02 vs basal, P = NS among groups). Plasma osmolarity and catecholamines were also not different among groups and did not increase during the clamp. Fasting plasma ANP concentrations correlated with plasma glucose concentrations measured 120 minutes after oral glucose tolerance testing.

CONCLUSIONS

Among heart transplantation recipients fasting plasma ANP concentrations were not different at 5 to 6 years after the surgical procedure than in nondiabetic controls. Increased ANP concentrations were observed among recipients with diabetes and among nontransplanted diabetic patients. Although the insulin-induced increment in ANP concentrations was not different among groups, circulating ANP was strongly associated with glucose tolerance status.

IRS-1 serine phosphorylation and insulin resistance in skeletal muscle from pancreas transplant recipients

Insulin-dependent diabetic recipients of successful pancreas allografts achieve self-regulatory insulin secretion and discontinue exogenous insulin therapy; however, chronic hyperinsulinemia and impaired insulin sensitivity generally develop. To determine whether insulin resistance is accompanied by altered signal transduction, skeletal muscle biopsies were obtained from pancreas-kidney transplant recipients (n = 4), nondiabetic kidney transplant recipients (receiving the same immunosuppressive drugs; n = 5), and healthy subjects (n = 6) before and during a euglycemic-hyperinsulinemic clamp. Basal insulin receptor substrate (IRS)-1 Ser (312) and Ser (616) phosphorylation, IRS-1-associated phosphatidylinositol 3-kinase activity, and extracellular signal-regulated kinase (ERK)-1/2 phosphorylation were elevated in pancreas-kidney transplant recipients, coincident with fasting hyperinsulinemia. Basal IRS-1 Ser (312) and Ser (616) phosphorylation was also increased in nondiabetic kidney transplant recipients. Insulin increased phosphorylation of IRS-1 at Ser (312) but not Ser (616) in healthy subjects, with impairments noted in nondiabetic kidney and pancreas-kidney transplant recipients. Insulin action on ERK-1/2 and Akt phosphorylation was impaired in pancreas-kidney transplant recipients and was preserved in nondiabetic kidney transplant recipients. Importantly, insulin stimulation of the Akt substrate AS160 was impaired in nondiabetic kidney and pancreas-kidney transplant recipients. In conclusion, peripheral insulin resistance in pancreas-kidney transplant recipients may arise from a negative feedback regulation of the canonical insulin-signaling cascade from excessive serine phosphorylation of IRS-1, possibly as a consequence of immunosuppressive therapy and hyperinsulinemia.

Outcomes of pancreas transplants for patients with type 2 diabetes mellitus

BACKGROUND

The objective of this study was to examine how effectively pancreas transplants provide long-term glucose control in patients with type 2 diabetes mellitus (DM). We used guidelines from the American Diabetes Association (ADA) and the World Health Organization (WHO) to appropriately classify recipients with type 2 DM (vs. type 1 DM).

RESULTS

From 1994 through 2002, a total of 17 patients with type 2 DM underwent a pancreas transplant at our center. Mean recipient age was 52.5 yr. The mean age at diabetes onset was 35.7 yr; mean duration, 16.8 yr. Most recipients had one or more secondary complications related to their diabetes: retinopathy (94%), neuropathy (76%), or nephropathy (65%). At the time of their transplant, three (18%) were on oral hypoglycemic agents alone and 14 (82%) were on insulin therapy. Of the 17 transplants, seven (41%) were a simultaneous pancreas-kidney transplant (SPK); four (24%), pancreas after kidney transplant (PAK); and six (35%), pancreas transplant alone (PTA). One recipient died during the perioperative period because of aspiration. The other 16 recipients became euglycemic post-transplant and had a functional graft at 1 yr post-transplant (patient and graft survival rates, 94%). Now, with a mean follow-up of 4.3 yr post-transplant, the patient survival rate is 71%. The four additional deaths were because of sepsis (n = 2), suicide (n = 1), and unknown cause (n = 1). All four of these recipients were insulin-independent at the time of death, although one was on an oral hypoglycemic agent. Of the 12 recipients currently alive, 11 remain euglycemic without requiring insulin therapy or oral hypoglycemic agents; one began insulin therapy 1.2 yr post-transplant (current daily dose, 60 units).

CONCLUSION

These findings suggest that pancreas transplants can provide excellent glucose control in recipients with type 2 DM. All 16 (94%) of our recipients whose transplant was technically successful were rendered euglycemic. Long-term results were comparable with those seen in transplant recipients with type 1 DM.

Development of islet-like cell clusters after pancreas transplantation in the spontaneously diabetic Torri rat

Pancreas transplantation (PTx) has evolved as a clinical therapy to achieve sustained euglycemia. However, it remains unclear if naive diseased islets of the pancreas benefit from the avoidance of glucose toxicity by PTx. In the present study, using an animal model of type 2 diabetes, the Spontaneously Diabetic Torii (SDT; RT1a) rat, we syngeneically transplanted nondiabetic 10-week-old pancreaticduodenal grafts into diabetic 25-week-old recipients. In the control SDT rats that received no treatment, hyperglycemia developed with a mean onset time of 25 +/- 3.9 weeks of age. Few normal islet cells were found from 25 weeks and none at 40 weeks. However, in the PTx rats, the onset age (graft age) of diabetes was significantly prolonged (47 +/- 18.2 weeks). Moreover, we found that the beta-cell mass was significantly increased in the naive pancreases of 40-week-old PTx recipients (PTx40-naive). Interestingly, islet-like cell clusters of varying size were found close to ductal structures of PTx40-naive pancreases, suggesting that these cells are derived from ductal cells. Furthermore, pancreatic and duodenal homeobox factor-1 (PDX-1) was more clearly expressed in the nuclei of PTx40-naive pancreatic islet-like cell clusters. Our results demonstrate the development of duct-derived beta cells in the pancreas of type 2 diabetic recipients after PTx.

Management of hyperglycaemia after pancreas transplantation: are new immunosuppressants the answer?

Pancreas transplantation is considered the optimal therapy for patients with diabetes mellitus who reach end-stage renal disease. Despite achievement of euglycaemia after this procedure, the progression to impaired pancreatic function and metabolic exhaustion still represents one of the major concerns that increase the risk of graft loss. This paper reviews the possible mechanisms that can induce post-transplant hyperglycaemia, including those related to immunosuppression and those non-related, and the new strategies available for minimising or preventing this complication. Different aetiologies can induce pancreatic dysfunction. Technical complications, acute pancreatitis and delayed graft function, mostly related to impaired insulin secretion, are considered the early causes for abnormal glucose control. In general, acute rejection does not affect the endocrine portion of the pancreas graft because islet destruction occurs later than the inflammation of the exocrine components. Hyperinsulinaemia and insulin resistance represent the main concern for the progression of blood glucose intolerance. The anastomotic techniques of the exocrine portion of the pancreas and the immunosuppressive regimens are of critical importance for the development of impaired glucose metabolism. Hyperinsulinaemia, as a result of the fact that systemic-enteric or systemic-bladder drainages reducing the hepatic clearance of insulin, has led to the introduction of more physiological techniques using portal drainage of the endocrine secretions. Experimental and clinical data have shown that many of the current immunosuppressants account, to a large degree, for the increased risk of the development of post-transplant hyperglycaemia. The most common maintenance regimen in pancreatic transplantation still consists of triple therapy with a combination of corticosteroids, calcineurin inhibitors (either ciclosporin [cyclosporine] or tacrolimus), and mycophenolate mofetil (MMF).The diabetogenic effects of corticosteroids and calcineurin inhibitors have resulted in the need for protocols able to minimise their use. Recent studies have shown the safety and efficacy of steroid-sparing or -free regimens. Sirolimus has shown powerful immunosuppressive potency in absence of nephrotoxicity and diabetogenicity. Multicentre and single-centre reports have demonstrated that both calcineurin inhibitor withdrawal and avoidance were possible when sirolimus was used in a concentration-controlled fashion, with low-dose corticosteroids and MMF. Although the experience with sirolimus in pancreatic transplantation is still limited, the results are promising. Patients affected by diabetic gastroparesis seem to better tolerate a regimen with sirolimus and low-dose tacrolimus than one with tacrolimus in combination with MMF.For successful, long-term results of pancreatic transplantation, it is crucial to combine donor selection, technical aspects, modified anastomotic techniques and new therapeutic approaches designed to minimise the metabolic and non-metabolic adverse effects of the immunosuppressive regimens.

EFFECT OF VENOUS DRAINAGE SITE ON INSULIN ACTION AFTER SIMULTANEOUS PANCREAS-KIDNEY TRANSPLANTATION

BACKGROUND

The aim of the present study was to determine the influence of the venous drainage site on insulin homeostasis in simultaneous pancreas-kidney (SPK) transplant recipients.

METHODS

The study included 12 SPK patients with portal venous drainage (P) and 11 SPK patients with systemic venous drainage (S) of pancreas allograft. All of the participants presented similar characteristics. The euglycemic hyperinsulinemic clamp was performed using a 0.4-mU/kg/min insulin infusion. An infusion of [6,6-(2)H2] glucose was used to determine glucose turnover at the basal state and during the clamp to determine liver and peripheral tissue sensitivity to insulin.

RESULTS

Minor changes in glycemia and insulinemia were shown: fasting plasma glucose was significantly higher in the SPK-P group and insulinemia was higher in the SPK-S group. Hepatic glucose production was similar in both groups. During the clamp, insulin levels were higher in SPK-S recipients, but hepatic glucose production was suppressed in both groups. Glucose use was lower in SPK-S recipients than in SPK-P recipients, 3.32 +/-1.41 mg/kg/min and 4.70 +/-1.64 mg/kg/min, respectively (P<0.02). Basal and under-clamp free fatty acid levels were similar. In addition, no significant difference in cholesterol and low-density lipoprotein levels was shown, whereas high-density lipoprotein levels were higher in the SPK-S group; triglycerides during fasting and under clamp were significantly higher in the SPK-P group.

CONCLUSIONS

In both groups, neither hepatic nor peripheral insulin resistance was detected. In SPK-S recipients, the authors have showed only a lower insulin clearance and a slight decreased peripheral responsiveness to insulin without modifications of lipid status.

Metabolic effects of a corticosteroid-free immunosuppressive regimen in recipients of pancreatic transplant

BACKGROUND

A corticosteroid (CS)-free immunosuppressive regimen may be considered less diabetogenic than treatments including CSs principally after pancreas transplantation.

METHODS

To test whether a CS-free immunosuppressive treatment is metabolically superior to a regimen including CSs, we prospectively studied 19 CS-free simultaneous pancreas and kidney (SPK) transplant recipients (body mass index=22+/-1 kg/m2; cyclosporine dose=400+/-19 mg/kg/day; azathioprine dose=77+/-8 mg/day; basal plasma C-peptide=1.3+/-0.12 ng/mL) and 12 matched CS-treated SPK transplant recipients (prednisone dose=9+/-1 mg/day; basal C-peptide=2.2+/-0.2 ng/mL) by means of the 6,6-2H(2)-glucose infusion and the euglycemic insulin clamp (1 mU/kg/min, insulin infusion rate). In addition, six renal transplant recipients receiving a CS-free regimen were also studied as a control group.

RESULTS

In the postabsorptive state, CS-treated SPK transplant recipients demonstrated comparable plasma glucose levels but higher plasma insulin levels than CS-free SPK transplant recipients. Plasma triglyceride levels were significantly higher in CS-treated SPK patients than in CS-free SPK patients (1.16+/-0.16 mg/dL vs. 0.88+/-0.08; P<0.05). High-density lipoprotein and apoprotein A(1) levels were similar in both groups. No difference was observed in pyruvate, lactate, beta-OH-butyrate, and basal endogenous glucose production in all three groups of patients studied. During euglycemic hyperinsulinemia, the inhibition of endogenous glucose production and the stimulation of tissue glucose disposal were not statistically different among the three groups.

CONCLUSIONS

SPK recipients receiving chronic low-dose CS maintenance therapy do not present a lower glucose disposal than CS-free recipients. Nonetheless, this is obtained at the expense of a higher endogenous insulin secretion, which can cause an alteration of the triglyceride profile.

Islet transplantation improves vascular diabetic complications in patients with diabetes who underwent kidney transplantation: a comparison between kidney-pancreas and kidney-alone transplantation

BACKGROUND

The aim of this study was to evaluate the effects of islet transplantation on patient survival and diabetic vascular complications.

METHODS

Thirty-seven type 1 uremic diabetic kidney transplant patients underwent islet transplantation (KI group). Uremic type 1 diabetic kidney-pancreas (KP group, n=162), kidney-alone (KD group, n=42) transplant patients, and uremic type 1 diabetic patients still on hemodialysis (HD+DM group, n=196) constituted the control groups for survival and endothelial morphology.

RESULTS

Patient survival was similar in the KI and KP groups and higher than in the HD+DM group (P<0.05). Patients experiencing long-term islet function (KI-successful [KI-s], n=24) showed a better survival (100%, 100%, and 90%) than those in the KI group who lost islet function (KI-unsuccessful [KI-u], n=13) (84%, 75%, and 45%) at 1, 4 and 7 years, respectively (P=0.02). The cardiovascular death rate for the KI group (18%) was similar to the KD group (19%) but lower when the KI-s group is considered alone (5%), and showed a cardiovascular death rate similar to the KP group (8%). The KI-s group showed a good metabolic profile, with reduction of exogenous insulin requirement and persistent C-peptide secretion, as compared with the KI-u group. The endothelial morphology was evaluated with a skin biopsy obtained in all groups. The KI-s and the KP groups demonstrated decreased signs of endothelial injury compared with the KI-u and HD+DM groups. The KI group showed a better atherothrombotic profile than the HD+DM group, with higher levels of natural anticoagulant protein.

CONCLUSIONS

Successful islet transplantation improves survival, atherothrombotic profile, and endothelial morphology in uremic type 1 diabetic kidney transplant patients.

Long-term beneficial effect of islet transplantation on diabetic macro-/microangiopathy in type 1 diabetic kidney-transplanted patients

OBJECTIVE

Our aim was to evaluate the long-term effects of transplanted islets on diabetic macro-/microangiopathy in type 1 diabetic kidney-transplanted patients.

RESEARCH DESIGN AND METHODS

A total of 34 type 1 diabetic kidney-transplanted patients underwent islet transplantation and were divided into two groups: successful islet-kidney transplantation (SI-K; 21 patients, fasting C-peptide serum concentration >0.5 ng/ml for >1 year) and unsuccessful islet-kidney transplantation (UI-K; 13 patients, fasting C-peptide serum concentration <0.5 ng/ml). Patients cumulative survival, cardiovascular death rate, and atherosclerosis progression were compared in the two groups. Skin biopsies, endothelial dependent dilation (EDD), nitric oxide (NO) levels, and atherothrombotic risk factors [von Willebrand factor (vWF) and D-dimer fragment (DDF)] were studied cross-sectionally.

RESULTS

The SI-K group showed a significant better patient survival rate (SI-K 100, 100, and 90% vs. UI-K 84, 74, and 51% at 1, 4, and 7 years, respectively, P = 0.04), lower cardiovascular death rate (SI-K 1/21 vs. UI-K 4/13, chi(2) = 3.9, P = 0.04), and lower intima-media thickness progression than the UI-K group (SI-K group: delta1-3 years -13 +/- 30 micro m vs. UI-K group: delta1-3 years 245 +/- 20 micro m, P = 0.03) with decreased signs of endothelial injuring at skin biopsy. Furthermore, the SI-K group showed a higher EDD than the UI-K group (EDD: SI-K 7.8 +/- 4.5% vs. UI-K 0.5 +/- 2.7%, P = 0.02), higher basal NO (SI-K 42.9 +/- 6.5 vs. UI-K 20.2 +/- 6.8 micro mol/l, P = 0.02), and lower levels of vWF (SI-K 138.6 +/- 15.3 vs. UI-K 180.6 +/- 7.0%, P = 0.02) and DDF (SI-K 0.61 +/- 0.22 vs. UI-K 3.07 +/- 0.68 micro g/ml, P < 0.01). C-peptide-to-creatinine ratio correlated positively with EDD and NO and negatively with vWF and DDF.

CONCLUSIONS

Successful islet transplantation improves survival, cardiovascular, and endothelial function in type 1 diabetic kidney-transplanted patients.

Fasting blood sample-based assessment of insulin sensitivity in kidney-pancreas-transplanted patients

OBJECTIVE

To ascertain whether simple indexes of insulin sensitivity based on a fasting blood sample may be reliable measures of insulin sensitivity in combined kidney-pancreas- transplanted patients.

RESEARCH DESIGN AND METHODS

Estimates of insulin sensitivity based on fasting plasma glucose, insulin (homeostasis model assessment of insulin sensitivity [HOMA-IS], Quantitative Insulin Sensitivity Check Index [QUICKI]), and free fatty acid (revised QUICKI) concentrations were compared with insulin sensitivity as assessed with the gold standard technique (euglycemic-hyperinsulinemic clamp) in 22 patients who had undergone kidney-pancreas transplantation (KP-Tx) and 18 matched healthy subjects (NOR).

RESULTS

In KP-Tx patients, indexes based on the glucose-insulin product, HOMA-IS (r = 0.47, P = 0.03) and QUICKI (r = 0.47, P = 0.03), were shown to be reliable measures of insulin sensitivity. The introduction of fasting plasma free fatty acid concentration in the revised QUICKI (r = 0.76, P < 0.0001) considerably improved the power of prediction of the clamp-based measure of insulin sensitivity as observed in the healthy control subjects (r = 0.83, P < 0.0001).

CONCLUSIONS

This study shows that in KP-Tx patients, HOMA-IS and QUICKI are reliable measures of insulin sensitivity; the additional incorporation of fasting plasma free fatty acid concentration into the glucose-insulin product (revised QUICKI) resulted in a considerably more powerful index.

Energy metabolism in diabetic and nondiabetic heart transplant recipients

OBJECTIVE

This study examined the metabolic effects of heart transplantation in patients in end-stage cardiac failure.

RESEARCH DESIGN AND METHODS

A total of 18 patients after heart transplantation for end-stage heart disease (age 47 +/- 3 years; transplant age 5.5 +/- 1.5 years; BMI 25.8 +/- 0.8 kg/m(2); cyclosporin A 4.2 +/- 0.6 mg/[kg.day]; azathioprine 0.87 +/- 0.31 mg/[kg.day]), 12 patients with type 2 diabetes (D-Tx), and 6 patients without type 2 diabetes (Tx) were studied by means of 1) an oral glucose tolerance test (OGTT) to assess the beta-cell secretory response, 2) a euglycemic-hyperinsulinemic (1 mU/[kg.min]) clamp combined with indirect calorimetry and a primed continuous infusion of [6,6-2H2]glucose and [1-13C]leucine to measure postabsorptive and insulin-stimulated carbohydrate and protein metabolism, and 3) 1H-NMR spectroscopy of the calf muscles to measure intramyocellular triglyceride (IMCL) content. The patients were selected from 480 transplant patients in whom there was a 6% prevalence of type 2 diabetes. Five healthy subjects matched for anthropometric parameters served as control subjects (CON).

RESULTS

Tx had postabsorptive and insulin-stimulated glucose, leucine, and free fatty acid metabolism, as well as IMCL content, similar to that of CON. D-Tx were characterized by a reduced secretory response during the OGTT and peripheral insulin resistance with respect to glucose metabolism, which was paralleled by increased plasma free fatty acid concentrations and IMCL content. A defective insulin-dependent suppression of the endogenous leucine flux (index of proteolysis) was also evident during the clamp in D-Tx.

CONCLUSIONS

Heart transplantation, notwithstanding the immunosuppressive therapy, was characterized by a normal postabsorptive and insulin-stimulated glucose, leucine, and free fatty acid metabolism in Tx. In contrast, insulin resistance with respect to glucose, free fatty acids, and protein metabolism was present in D-Tx regardless of whether diabetes was preexisting or consequent to heart transplantation.

Factors influencing Islet of Langerhans graft function and monitoring

Transplantation of islet of Langerhans represents a viable therapeutic option for insulin-dependent diabetes mellitus. Dramatic progress has been recently reported with the introduction of a glucocorticoid-free immunosuppressive regimen that improved success rate, namely, insulin independence for 1 year or more, from 8% to 100%. The fate of islet grafts is determined by many concurrent phenomena, some of which are common to organ grafts (i.e. rejection), while others are unique to nonvascularized cell transplants, including transplant cell mass and viability, as well as nonspecific inflammation at the site of implant. Moreover, islet grafts lack clinical markers of early rejection, making it difficult to recognize imminent rejection and to implement intervention with graft-saving immunosuppressive regimens. In the present review, we will address the problems influencing islet graft success and the monitoring of islet cell graft function.

Prediction of the long-term metabolic success of the pancreatic graft function

BACKGROUND

Strategies to prevent the return to the diabetic state for graft loss or failure or any other cause after pancreas transplantation require the identification of the subjects at risk. This study evaluated whether daily glucose, insulin, and c-peptide profiles and studies of insulin sensitivity and secretion after transplantation predict pancreatic graft failure.

METHODS

Fifty-three subjects with type 1 diabetes with end-stage renal failure who received a combined pancreas and kidney transplant underwent the following procedures 1 year after transplantation: 1-day metabolic profiles, sampling every 2 hours for plasma glucose, serum insulin, and c-peptide (n=51); an intravenous glucose tolerance test (IVGTT) to evaluate insulin secretion (n=48); and an euglycemic insulin clamp to evaluate insulin sensitivity (M value, n=14). The recipients were then followed up to 8 years (mean follow-up 4.8+/-0.3 years) to evaluate the return to the diabetic state.

RESULTS

Survival analysis showed that plasma glucose in the profiles and insulin secretion in IVGTT were strongly related to the risk of returning to the diabetic state. A cutoff value of mean daily plasma glucose >127 mg/dL, corresponding to the top quartile of the mean plasma glucose distribution in the profiles, predicted the return to the diabetic state within 4 years from transplantation with a 93% specificity and a 100% sensitivity. A cutoff value of insulin delta peak <32 microU/ml in the IVGTT predicted the return to the diabetic state within 4 years from transplantation with a 75% specificity and a 75% sensitivity. In contrast, the M value in the clamp was devoid of predictive value.

CONCLUSIONS

This study indicates that the mean 24-h plasma glucose 1 year after transplantation is the strongest predictor of the return to the diabetic state. The risk is related to defects in insulin secretion and not to insulin resistance. Metabolic profiles can be used to screen the subjects at risk to strictly monitor the graft function and to investigate early determinants of graft failure.

Pancreatic islet transplantation in the treatment of diabetes mellitus

This chapter reviews current developments and future directions in clinical islet transplantation. With the recent introduction of glucocorticoid-free immunosuppressive therapies and improved methods for islet isolation, the success of the procedure has increased substantially. Challenges ahead include progress with international multicentre trials, development of single donor protocols, progress in clinical tolerance based therapies to lower overall risk of immunosuppression, and ultimately finding an alternative source to provide effective therapy for more patients with diabetes. Recent advances in stem cell biology and xenotransplantation may soon provide this opportunity.

The effect of systemic versus portal insulin delivery in pancreas transplantation on insulin action and VLDL metabolism

Combined kidney-pancreas transplantation (KPT) with anastomosis of the pancreatic vein to the systemic circulation (KPT-S) or to the portal circulation (KPT-P) provides a human model in which the chronic effects of portal versus systemic insulin delivery on glucose and VLDL metabolism can be examined. Despite similar plasma glucose and C-peptide levels, KPT-S (n = 9) had an approximate twofold elevation of fasting and intravenous glucose-stimulated plasma insulin levels compared with both KPT-P (n = 7) and healthy control subjects (n = 15). The plasma free fatty acid (FFA) levels were elevated in both transplant groups versus control subjects, but the plasma insulin elevation necessary to lower plasma FFA by 50% was approximately two times higher in KPT-S versus KPT-P and control subjects. Endogenous glucose production was similar in KPT-S and KPT-P, despite approximately 35% higher hepatic insulin levels in the latter, and was suppressed to a greater extent during a euglycemic-hyperinsulinemic clamp in KPT-S versus KPT-P. Total-body glucose utilization during the euglycemic-hyperinsulinemic clamp was approximately 40% lower in KPT-S versus KPT-P, indicating peripheral tissue but not hepatic insulin resistance in KPT-S versus KPT-P. Both transplant groups had an approximate twofold elevation of triglyceride (TG)-rich lipoprotein apolipoprotein B (apoB) and lipids versus control subjects. Elevation of VLDL-apoB and VLDL-TG in both transplant groups was entirely explained by an approximately 50% reduction in clearance of VLDL compared with healthy control subjects. In the presence of increased FFA load but in the absence of hepatic overinsulinization and marked hepatic insulin resistance, there was no elevation of VLDL secretion in KPT-S versus KPT-P and control subjects. These findings suggest that chronic systemic hyperinsulinemia and peripheral tissue insulin resistance with the consequent elevation of plasma FFA flux are insufficient per se to cause VLDL overproduction and that additional factors, such as hepatic hyperinsulinemia and/or gross insulin resistance, may be an essential prerequisite in the pathogenesis of VLDL overproduction in the common form of the insulin resistance syndrome.

Effects of kidney-pancreas transplantation on atherosclerotic risk factors and endothelial function in patients with uremia and type 1 diabetes

Cardiovascular disease and the development of coronary artery disease play a pivotal role in increasing mortality in patients with type 1 diabetes. The aim of our study was to evaluate the effects of pancreas transplantation on atherosclerotic risk factors, endothelial-dependent dilation (EDD), and progression of intima media thickness (IMT) in patients with uremia and type 1 diabetes after kidney-alone (KA) or kidney-pancreas (KP) transplantation. A cross-sectional study comparing two groups of patients with type 1 diabetes was performed. Sixty patients underwent KP transplantation and 30 patients underwent KA transplantation. Age and cardiovascular risk profile were comparable in patients before transplantation. In all patients, atherosclerotic risks factors (lipid profile, fasting and post-methionine load plasma homocysteine, von Willebrand factor levels, D-dimer fragments, and fibrinogen) were assessed and Doppler echographic evaluation of IMT and endothelial function with flow-mediated and nitrate dilation of the brachial artery was performed. Twenty healthy subjects were chosen as controls (C) for EDD. Compared with patients undergoing KA transplantation, patients undergoing KP transplantation showed lower values for HbA1c (KP = 6.2 +/- 0.1% vs. KA = 8.4 +/- 0.5%; P < 0.01), fasting homocysteine (KP = 14.0 +/- 0.7 mcromol/l vs. KA = 19.0 +/- 2.0 micromol/l; P = 0.02), von Willebrand factor levels (KP = 157.9 +/- 8.6% vs. KA = 212.5 +/- 16.2%; P < 0.01), D-dimer fragments (KP = 0.29 +/- 0.02 microg/ml vs. KA = 0.73 +/- 0.11 microg/ml;P < 0.01), fibrinogen (KP = 363.0 +/- 11.1 mg/dl vs. KA = 397.6 +/- 19.4 mg/dl; NS), triglycerides (KP = 122.7 +/- 8.6 mg/dl vs. KA = 187.0 +/- 30.1 mg/dl; P = 0.01), and urinary albumin excretion rate (KP = 13.5 +/- 1.9 mg/24 h vs. KA = 57.3 +/- 26.3 mg/24 h; P < 0.01). Patients undergoing KP transplantation showed a normal EDD (KP = 6.21 +/- 2.42%, KA = 0.65 +/- 2.74%, C = 8.1 +/- 2.1%; P < 0.01), whereas no differences were observed in nitrate-dependent dilation. Moreover, IMT was lower in patients undergoing KP transplantation than in patients undergoing KA transplantation (KP = 0.74 +/- 0.03 mm vs. KA = 0.86 +/- 0.09 mm; P = 0.04). Our study showed that patients with type 1 diabetes have a lower atherosclerotic risk profile after KP transplantation than after KA transplantation. These differences are tightly correlated with metabolic control, fasting homocysteine levels, lower D-dimer fragments, and lower von Willebrand factor levels. Normal endothelial function and reduction of IMT was observed only in patients undergoing KP transplantation.

Trends and perspectives in pancreas and simultaneous pancreas and kidney transplantation

Pancreas transplantation is still the best option to achieve normoglycaemia and insulin independence in patients with type I diabetes. As a result of improvements in surgical techniques, immunosuppression and patient selection, one year survival rates of 95, 83, and 88% for patient, pancreas, and kidney survival, respectively, are reported for patients with simultaneous pancreas and kidney transplantation. The main goals for the future are to reduce postoperative morbidity, to identify the relevant indications for single pancreas transplantation, to adopt the best surgical technique for individual patients' needs (bladder versus enteric drainage with or without portal venous delivery of insulin), and to develop immunosuppressive strategies with low nephrotoxic and diabetogenic potential.

Metabolic effects of restoring partial beta-cell function after islet allotransplantation in type 1 diabetic patients

Successful intraportal islet transplantation normalizes glucose metabolism in diabetic humans. To date, full function is not routinely achieved after islet transplantation in humans, with most grafts being characterized by only partial function. Moreover, the duration of full function is variable and cannot be sufficiently predicted with available methods. In contrast, most grafts retain partial function for a long time. We hypothesized that partial function can restore normal protein and lipid metabolism in diabetic individuals. We studied 45 diabetic patients after islet transplantation. Labeled glucose and leucine were infused to assess whole-body glucose and protein turnover in 1) 6 type 1 diabetic patients with full function after intraportal islet transplantation (FF group; C-peptide > 0.6 nmol/l; daily insulin dosage 0.03 +/- 0.02 U x kg(-1) body wt x day(-1); fasting plasma glucose < 7.7 mmol/l; HbA1c < or = 6.5%), 2) 17 patients with partial function (PF group; C-peptide > 0.16 nmol/l; insulin dosage < 0.4 U x kg(-1) body wt x day(-1)), 3) 9 patients with no function (NF group; C-peptide < 0.16 nmol/l; insulin dosage > 0.4 U x kg(-1) body wt x day(-1)), and 4) 6 patients with chronic uveitis as control subjects (CU group). Hepatic albumin synthesis was assessed in an additional five PF and five healthy volunteers by means of a primed-continuous infusion of [3,3,3-2H3]leucine. The insulin requirement was 97% lower than pretransplant levels for the FF group and 57% lower than pretransplant levels for the PF group. In the basal state, the PF group had a plasma glucose concentration slightly higher than that of the FF (P = 0.249) and CU groups (P = 0.08), but was improved with respect to the NF group (P < 0.01). Plasma leucine (101.1 +/- 5.9 micromol/l) and branched-chain amino acids (337.6 +/- 16.6 micromol/l) were similar in the PF, FF, and CU groups, and significantly lower than in the NF group (P < 0.01). During insulin infusion, the metabolic clearance rate of glucose was defective in the NF group versus in the other groups (P < 0.01). Both the basal and insulin-stimulated proteolytic and proteosynthetic rates were comparable in the PF, FF, and CU groups, but significantly higher in the NF group (P = 0.05). In addition, the PF group had a normal hepatic albumin synthesis. Plasma free fatty acid concentrations in the PF and FF groups were similar to those of the CU group, but the NF group showed a reduced insulin-dependent suppression during the clamp. We concluded that the restoration of approximately 60% of endogenous insulin secretion is capable of normalizing the alterations of protein and lipid metabolism in type 1 diabetic kidney recipients, notwithstanding chronic immunosuppressive therapy. The results of the present study indicate that "success" of islet transplantation may be best defined by a number of metabolic criteria, not just glucose concentration/metabolism alone.

Does glucagon stimulation predict oral glucose tolerance in patients after simultaneous pancreas-kidney transplantation?

BACKGROUND

Exogenous glucagon rapidly stimulates insulin secretion. This test has been used to estimate insulin secretory capacity, which may predict oral glucose tolerance in patients after pancreas transplantation.

METHODS

In 32 pancreas-kidney transplant recipients, in 10 nondiabetic kidney transplant recipients, and in 9 healthy control subjects, a glucagon stimulation test (1 mg i.v.) and a 75-g oral glucose tolerance test were performed with determination of glucose, insulin, and C-peptide profiles.

RESULTS

Of 16 pancreas transplant recipients with the lowest insulin responses after glucagon, 7 had an impaired oral glucose tolerance, in contrast to 1 of 16 with high insulin responses (P=0.037). A low insulin response after glucagon was associated with significantly lower 120-min glucose concentrations (P=0.043) and a lower integrated incremental insulin response after oral glucose (P=0.006).

CONCLUSIONS

In pancreas-kidney transplant recipients, a low insulin response after intravenous glucagon predicts a reduced insulin response after oral glucose and an impaired oral glucose tolerance. This simple test may be helpful in the follow-up of pancreas transplant recipients.

Effect of hemipancreatectomy and of pancreatic diversion on the tolerance to a glucose load in humans

BACKGROUND

The role of the pattern, quantity and site of insulin secretion in the tolerance to a glucose challenge is not fully evaluated in humans because it is difficult to obtain appropriate clinical models.

DESIGN

To address this issue, we studied subjects with reduced pancreatic mass (hemipancreatectomized, HEMI), systemic insulin delivery (pancreas transplant recipients, PTX), and two control groups (healthy, CON; and with uveitis on the same immunosuppression as PTX, UVE), with an hyperglycaemic clamp (study 1, + 4.2 mmol L-1), using a repeat experiment (study 2) with a fixed glucose infusion, calculated to increase by 35% that in study 1.

RESULTS

In study 1, CON increased glucose uptake to 20 +/- 3 micromol kg-1 min-1 after a biphasic insulin response. In study 2, CON further increased the glucose uptake via an increment in prehepatic insulin secretion that stimulated insulin sensitivity without changes in peripheral insulin and glucose concentrations. HEMI and PTX had 35% less glucose uptake in study 1, compared to CON, and increased glucose concentrations (+ 1.6 mmol L-1) in study 2. UVE had an intermediate defect. The causes of intolerance were different: HEMI had a defective first-phase insulin secretion (50% peripheral insulin concentrations) but maintained insulin sensitivity; PTX had normal peripheral insulin but only one-third of the insulin sensitivity of CON.

CONCLUSIONS

Hemipancreatectomy and systemic insulin delivery impair first-phase insulin secretion; second-phase peripheral insulinization (HEMI); insulin sensitivity (PTX); and a mechanism evidentiated in study 2 of CON that increases insulin sensitivity in response to prehepatic insulin secretion (both groups). Failure of these mechanisms is largely compensated by hyperglycaemia.

Insulin secretion and sensitivity after simultaneous pancreas-kidney transplantation estimated by continuous infusion of glucose with model assessment

BACKGROUND

Monitoring of insulin secretion and sensitivity after pancreas transplantation remains a practical problem.

METHODS

We introduced the simple structural model, continuous infusion of glucose with model assessment (CIGMA), to obtain insulin secretion and insulin sensitivity estimations after 35 successful simultaneous pancreas-kidney transplantations. Eighteen non-diabetic kidney transplant recipients were used as control group.

RESULTS

The baseline characteristics were equal between the two groups except for higher fasting insulin levels in the pancreas transplant group. After the 1-hr CIGMA glucose load, the pancreas transplant group reached a mean +/- SD blood glucose of 8.2+/-1.7 mmol/L compared with 7.3+/-1.0 mmol/L in the control group (P = 0.05). Concurrent stimulated insulin and C-peptide levels were 48+/-28 mU/L and 2.3+/-0.9 nmol/L in the pancreas transplant group compared with 36+/-21 mU/L and 2.9+/-1.1 nmol/L in the control group (P = 0.1 and P = 0.03, respectively). Both the CIGMA estimation for secretion as well as the CIGMA estimation for sensitivity were lower in pancreas transplant group (P = 0.003 and P = 0.01, respectively). Mean +/- SE coefficients of variation for the model estimations were 15+/-4% for secretion and 17+/-6% for sensitivity.

CONCLUSIONS

We conclude that CIGMA can be used clinically to evaluate carbohydrate metabolism in pancreas-kidney transplant recipients. These patients have a reduction in insulin secretory capacity and evidence of more insulin resistance than non-diabetic kidney transplant recipients.

Effect of venous drainage site on insulin action after pancreas transplantation in the rat--is there insulin resistance and a risk for atherosclerosis?

The aim of the present study was to determine the influence of the venous drainage site on insulin homeostasis and the possible risk for atherosclerosis development after pancreas transplantation. We studied inbred rats that received pancreas transplants with either systemic (STX) or portal (PTX) venous drainage after prior induction of diabetes with streptozotocin and sham-operated controls. The observation period was 6 months. Fasting plasma glucose and insulin levels were similar in all 3 groups, but fasting plasma glucagon levels were elevated in STX (mean +/- SEM, 282+/-35 ng/L) in comparison to PTX rats (119+/-9 ng/L, P < .05), although the difference versus the control group (191+/-31 ng/L) was insignificant. Glucose utilization and hepatic glucose production (HGP), assessed by a dose-response euglycemic-hyperinsulinemic clamp in combination with tritiated glucose infusion, were similar in all 3 groups. The groups were also similar with respect to the molar ratio of plasma C-peptide and insulin during basal steady state and the metabolic clearance rate (MCR) of insulin during the clamp studies, suggesting an unchanged hepatic insulin extraction (HIE) after transplantation with either technique. Factors known to be related to atherosclerosis, ie, blood pressure, intracellular magnesium, and fasting levels of plasma cholesterol, triglycerides, and high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, were similar in all 3 groups. Light microscopy of the aorta showed a slightly thicker intima in STX rats (24.3+/-0.5 microm, P < .05) versus PTX rats (21.4+/-0.7 microm) and control (21.4+/-0.6 microm); however, atherosclerosis-like lesions were absent in all 3 groups. In conclusion, in a rat model with streptozotocin-diabetes and pancreas transplantation but no need for immunosuppression, both systemic and portal venous drainage avoid peripheral and hepatic insulin resistance; also, there is no increased risk for atherosclerosis.

Contribution of reduced insulin sensitivity and secretion to the pathogenesis of hepatogenous diabetes: effect of liver transplantation

Diabetes mellitus frequently complicates cirrhosis but the pathogenic mechanisms are unknown. To assess the contribution of reduced insulin action and secretion, 24 cirrhotic-diabetic patients waiting for liver transplant because of an unresectable hepatocarcinoma underwent an oral glucose tolerance test (OGTT) to assess the beta-cell function and an insulin clamp combined with [3-(3)H]glucose infusion to measure whole body glucose metabolism before and 2 years after the transplant. Seven cirrhotic nondiabetic patients, 11 patients with chronic uveitis on similar immunosuppressive therapy, and 7 healthy subjects served as control groups. Cirrhotic patients showed a profound insulin resistance, and diabetics in addition also showed increased endogenous glucose production (P <.05) and insulin deficiency during the OGTT (P <.05). Liver transplantation normalized endogenous glucose production and insulin sensitivity but failed to cure diabetes in 8 of the 24 patients because a markedly low insulin response during the OGTT. Age, body mass index, family history of diabetes, immunosuppressive drugs, and pathogenesis of cirrhosis did not predict in whom liver transplant was going to cure diabetes. On the contrary, a reduced secretory response characterized the patients in whom the transplant would not be curative. In summary, insulin resistance was a primary event complicating cirrhosis but additional beta-cell secretory defects were crucial for development of diabetes. Liver transplantation, lessening insulin resistance, cured hepatogenous diabetes in 67% of cirrhotic-diabetic patients; nevertheless 33% were still diabetics because the persistence of a reduced beta-cell function, which makes these patients eventually eligible for combined islet transplantation.

The effects of maintenance doses of FK506 versus cyclosporin A on glucose and lipid metabolism after orthotopic liver transplantation

BACKGROUND

Posttransplant diabetes mellitus (PTDM) has gained widespread attention due to the micro and macro-vascular complications that increase the morbidity and mortality of patients receiving solid organs. The higher incidence of PTDM has been mainly attributed to the immunosuppressive therapy. Therefore, this study compares the metabolic side effects of low dose maintenance therapy of FK-506 and Cyclosporin A (CsA) in 14 patients 1 year after orthotopic liver transplant and analyzes possible factors that contribute to the development of PTDM.

METHODS

Two groups (n=7) differing in their immunosuppressive regimen (FK506 or CsA) were matched to eight control subjects and compared to each other. The effects of in vivo insulin action were assessed by means of the euglycemic hyperinsulinemic clamp technique. Arginine stimulation tests at normo- (5.5 mM) and hyperglycemic (15 mM) levels were performed and the acute insulin, C-peptide, and glucagon response (2-5 min) to arginine were determined.

RESULTS

Insulin sensitivity (total glucose disposal) was statistically lower in patients treated with FK-506 and CsA (5.05+/-0.47 and 5.05+/-0.42 mg/kg/min) as compared to controls (6.62+/-0.38 mg/kg/min) (P<0.02), with a significantly higher nonoxidative glucose disposal for the control group (P<0.01), and lower free fatty acid levels (P<0.05). Absolute values for acute insulin response were higher but not significantly different for the transplanted groups. The lower percentage of increase of insulin release after arginine stimulation observed in the FK-506 and CsA groups as compared with controls (754%+/-100, 644%+/-102 vs. 1191%+/-174) (P<0.03 and 0.02, respectively), suggests a reduced beta cell secretory reserve in both treated groups. Also, the acute glucagon response to arginine during hyperglycemia declined less in the FK-506 (28%) and CsA groups (29%) compared with controls (48%) (P<0.05) indicating a defect in the pancreatic beta cell-alpha cell axis.

CONCLUSIONS

There are no major metabolic differences on low maintenance doses between FK-506 and CsA. Both immunosuppressant agents contribute to the development of PTDM at different levels.

Vascularized pancreas allotransplantation--clinical indications and outcome

AIMS

This review examines the status of vascularized pancreas transplantation as a treatment for Type 1 diabetes mellitus (DM).

METHODS

The world literature, with a particular emphasis on data from the International Pancreas Transplant Registry (IPTR), is reviewed and interpreted particularly for clinical indications and outcome.

RESULTS

Over 9000 cases of vascularized pancreas transplant (VPT) have been registered, with insulin dependence approaching 82% at 1 year with 94% patient survival. The majority of transplants are simultaneous pancreas and kidney (SPK) transplants, with far fewer pancreas after kidney (PAK) or pancreas transplants alone (PTA). The success rates differ between the procedures but are generally improving as technical advances, improvements in immunosupression and greater experience are gained. The most obvious advantage is an improved quality of life (QoL) but there are risks associated with the procedure and with the immunosuppression. There is some evidence coming to light of a very slow beneficial effect on microvascular complications.

CONCLUSIONS

VPT is an attractive option to offer Type 1 DM patients who need or already have a renal allograft. Patients have to decide between the increased surgical risk and the risks of long-term immunosuppression and the benefits of improved QoL. In the absense of end-stage renal failure (ESRF) there is no justification for PTA, except where the diabetes itself poses a greater risk to life than the transplantation procedure.

Circulating proinsulin levels in insulin-dependent diabetic patients after whole pancreas-kidney transplantation

Disproportional hyperproinsulinemia is a sensitive marker for beta-cell dysfunction. The objective of this study was to assess the proinsulin profile in persons with insulin-dependent diabetes mellitus (IDDM) after pancreas-kidney transplantation. We determined serum insulin, C-peptide, and proinsulin concentrations during an oral glucose challenge in five pancreas-kidney transplant recipients, nine nondiabetic kidney transplant recipients, and 17 normal subjects. Basal proinsulin concentrations were significantly increased in pancreas-kidney recipients (geometric mean [+/-1 SE range], 6.0 [5.5 to 6.4] pmol/L) and kidney recipients (6.4 [5.4 to 7.5] pmol/L) compared with the normal subjects (2.8 [2.5 to 3.2] pmol/L). Integrated proinsulin concentrations during the oral glucose load were also higher in pancreas-kidney recipients (1.4 [1.1 to 1.8] nmol/L x min) and kidney recipients (1.5 [1.2 to 2.0] nmol/L x min) versus normal subjects (0.8 [0.7 to 0.9] nmol/L x min). There was no difference in basal or integrated proinsulin concentrations between the two transplant groups. Even after adjustment for the glomerular filtration rate (GFR), basal and incremental proinsulin concentrations continued to be higher in the transplant groups than in the normal subjects. Proinsulin to C-peptide molar ratios both before and after the glucose load were similar in the three groups. From these findings, we conclude that pancreas-kidney transplantation provokes proportional hyperproinsulinemia, which is closely associated with its reduced clearance in the kidneys.

Hypoglycaemia following pancreatic allograft transplantation

Pancreatic transplantation is an established treatment for patients with insulin-dependent diabetes mellitus. Side-effects are mainly related to surgical complications, immunosuppressive therapy and graft rejection. We report on two patients having recurrent hypoglycaemic events following pancreatic transplantation. The cause of hypoglycaemia in our patients remained obscure. Hypoglycaemia following pancreatic transplantation has been described. Hypoglycaemic events may appear years after transplantation. In the article we review three possible mechanisms of hypoglycaemia: hyperinsulinaemia, secondary to systemic drainage (due to loss of first pass hepatic insulin clearance), presence of anti-insulin antibodies and persistence of counter-regulatory abnormalities. Physicians and patients should be aware of possible hypoglycaemia events following transplantation.

Insulin secretion rates estimated by two mathematical methods in pancreas-kidney transplant recipients

After pancreas-kidney transplantation, it is difficult to obtain an accurate estimate of the insulin secretion of the pancreas graft, since several pitfalls are involved using peripheral C-peptide and/or insulin measurements in this determination. In this study, the individual kinetic parameters of C-peptide and then the rates of insulin secretion were estimated by two mathematical methods, the deconvolution method and the "combined model" during slow (oral glucose) and fast (intravenous glucagon) changes in insulin secretion in six successful pancreas-kidney transplant recipients with systemic delivery of insulin (Px), six nondiabetic kidney-transplant recipients with portal insulin secretion (Kx), six nondiabetic controls (NS), and six C-peptide-negative insulin-dependent diabetes mellitus patients (IDDM). Decreased C-peptide clearance and basal and poststimulatory hyperinsulinemia were found in both Px and Kx compared with NS (P < 0.05). Similar glucose responses were observed after intravenous glucagon in all groups, whereas the responses after oral glucose were 30% higher in Px and Kx than in NS (P < 0.05). During oral glucose and after intravenous glucagon, both mathematical methods resulted in significantly lower maximal and incremental insulin secretion rates (ISR) in Px than in Kx (P < 0.05). In contrast, calculations of incremental ISR in NS and Px induced by the two beta-cell stimuli were about the same but significantly higher in Kx than in NS (P < 0.05). These results differed markedly from those obtained using peripheral measurements of insulin and C-peptide alone. In conclusion, when C-peptide clearance and insulin metabolism change, such as in pancreas-kidney transplant recipients, accurate evaluation of insulin secretion from the graft can be obtained only by using individual kinetics of the peptides before calculating the ISR. This study also clearly demonstrates that insulin secretion after pancreas transplantation is still defective.

Improvement of glucose/insulin metabolism reduces hypertension in insulin-dependent diabetes mellitus recipients of kidney-pancreas transplantation

There is increasing evidence that metabolic disorders are common in patients with hypertension. To evaluate the relationship between glucose/insulin metabolism and hypertension in diabetes, 61 hypertensive uremic insulin-dependent diabetes mellitus patients who were recipients of kidney or pancreas/kidney transplants were studied through a 1-year follow-up. Twenty of them received a kidney (K) transplant alone, 13 received a kidney and segmental pancreas (KSP), and 28 received a kidney and whole pancreas (KWP) with duodenocystostomy. All subjects received the same immunosuppressive treatment including steroids, azathioprine, and cyclosporine. The three groups of patients were comparable for biochemical parameters, clinical characteristic, cyclosporine levels, and renal function (creatinine < 2 mg/dl). The association between hypertension and type of transplant was evaluated according a global chi-square test, then the results were broken down into two components to test for differences in hypertension between KP versus K and KWP versus KSP groups. The improvement of hypertension rate was statistically associated with KP transplant the first week after surgery, at discharge, and 1 year after transplantation (hypertension% at 1 week: KWP = 75, KSP = 23 vs. K = 70, P = 0.004; at discharge: KWP = 39, KSP = 31 vs. K = 75, P = 0.017; at 1 yr: KWP = 44, KSP = 54 vs. K = 85, P = 0.02). One year after graft fasting, free immunoreactive insulin as well as glycosylated hemoglobin and glucose levels were statistically lower in the KP groups than in the K-alone recipients. The improvement of hypertension observed in KP recipients suggests a key role of glucose and insulin metabolism on pathogenesis of diabetic hypertension.

Regulation of glucose homeostasis in humans with denervated livers

The liver plays a major role in regulating glucose metabolism, and since its function is influenced by sympathetic/ parasympathetic innervation, we used liver graft as a model of denervation to study the role of CNS in modulating hepatic glucose metabolism in humans. 22 liver transplant subjects were randomly studied by means of the hyperglycemic/ hyperinsulinemic (study 1), hyperglycemic/isoinsulinemic (study 2), euglycemic/hyperinsulinemic (study 3) as well as insulin-induced hypoglycemic (study 4) clamp, combined with bolus-continuous infusion of [3-3H]glucose and indirect calorimetry to determine the effect of different glycemic/insulinemic levels on endogenous glucose production and on peripheral glucose uptake. In addition, postabsorptive glucose homeostasis was cross-sectionally related to the transplant age (range = 40 d-35 mo) in 4 subgroups of patients 2, 6, 15, and 28 mo after transplantation. 22 subjects with chronic uveitis (CU) undergoing a similar immunosuppressive therapy and 35 normal healthy subjects served as controls. The results showed that successful transplantation was associated with fasting glucose concentration and endogenous glucose production in the lower physiological range within a few weeks after transplantation, and this pattern was maintained throughout the 28-mo follow-up period. Fasting glucose (4. 55+/-0.06 vs. 4.75+/-0.06 mM; P = 0.038) and endogenous glucose production (11.3+/-0.4 vs. 12.9+/-0.5 micromol/[kg.min]; P = 0.029) were lower when compared to CU and normal patients. At different combinations of glycemic/insulinemic levels, liver transplant (LTx) patients showed a comparable inhibition of endogenous glucose production. In contrast, in hypoglycemia, after a temporary fall endogenous glucose production rose to values comparable to those of the basal condition in CU and normal subjects (83+/-5 and 92+/-5% of basal), but it did not in LTx subjects (66+/-7%; P < 0.05 vs. CU and normal subjects). Fasting insulin and C-peptide levels were increased up to 6 mo after transplantation, indicating insulin resistance partially induced by prednisone. In addition, greater C-peptide but similar insulin levels during the hyperglycemic clamp (study 1) suggested an increased hepatic insulin clearance in LTx as compared to normal subjects. Fasting glucagon concentration was higher 6 mo after transplantation and thereafter. During euglycemia/hyperinsulinemia (study 3), the insulin-induced glucagon suppression detectable in CU and normal subjects was lacking in LTx subjects; furthermore, the counterregulatory response during hypoglycemia was blunted. In summary, liver transplant subjects have normal postabsorptive glucose metabolism, and glucose and insulin challenge elicit normal response at both hepatic and peripheral sites. Nevertheless, (a) minimal alteration of endogenous glucose production, (b) increased concentration of insulin and glucagon, and (c) defective counterregulation during hypoglycemia may reflect an alteration of the liver-CNS-islet circuit which is due to denervation of the transplanted graft.

Metabolism of oral glucose in pancreas transplant recipients with normal and impaired glucose tolerance

To gain insight into the pathophysiology of impaired glucose tolerance in pancreas transplantation, glucose kinetics and insulin secretion were assessed after an oral glucose load in four combined pancreas-kidney recipients with impaired glucose tolerance (IPx), in five combined pancreas-kidney recipients with normal glucose tolerance, in six nondiabetic kidney transplant recipients, and in eight normal subjects employing a dual isotope technique, beta-Cell function was evaluated by calculating prehepatic insulin secretion rates, which subsequently were correlated to the ambient glucose concentrations to obtain an index of beta-cell responsiveness. Oxidative and nonoxidative glucose metabolism were assessed by indirect calorimetry. Basal insulin secretion rates, the glucose-stimulated early insulin secretion rates, as well as beta-cell responsiveness were markedly reduced in IPx than in the glucose-tolerant transplant subjects. Total systemic glucose appearance was similar in the groups with apparently comparable inhibition of systemic glucose release and increase in exogenous glucose appearance. The hyperglycemic response in IPx was due to a significant reduction in the glucose disappearance rates during the first 2 h after glucose ingestion. Nonoxidative glucose metabolism increased significantly less in IPx than in glucose-tolerant groups. Glucagon secretion was less suppressed in the early part of the study in IPx, which may have contributed to the excessive hyperglycemia. In conclusion, IPx after pancreas transplantation was characterized by 1) impaired early insulin secretion, 2) reduced beta-cell responsiveness, 3) reduced glucose uptake, 4) impaired nonoxidative glucose metabolism, and 5) impaired early inhibition of glucagon secretion.

Metabolic effects of liver transplantation in cirrhotic patients

To assess whether liver transplantation (LTx) can correct the metabolic alterations of chronic liver disease, 14 patients (LTx-5) were studied 5+/-1 mo after LTx, 9 patients (LTx-13) 13+/-1 mo after LTx, and 10 patients (LTx-26) 26+/-2 months after LTx. Subjects with chronic uveitis (CU) and healthy volunteers (CON) were also studied. Basal plasma leucine and branched-chain amino acids were reduced in LTx-5, LTx-13, and LTx-26 when compared with CU and CON (P < 0.01). The basal free fatty acids (FFA) were reduced in LTx-26 with respect to CON (P < 0.01). To assess protein metabolism, LTx-5, LTx-13, and LTx-26 were studied with the [1-14C]leucine turnover combined with a 40-mU/m2 per min insulin clamp. To relate changes in FFA metabolism to glucose metabolism, eight LTx-26 were studied with the [1-14C]palmitate and [3-3H]glucose turnovers combined with a two-step (8 and 40 mU/m2 per min) euglycemic insulin clamp. In the postabsorptive state, LTx-5 had lower endogenous leucine flux (ELF) (P < 0.005), lower leucine oxidation (LO) (P < 0.004), and lower non-oxidative leucine disposal (NOLD) (P < 0.03) with respect to CON (primary pool model). At 2 yr (LTx-26) both ELF (P < 0.001 vs. LTx-5) and NOLD (P < 0.01 vs. LTx-5) were normalized, but not LO (P < 0.001 vs. CON) (primary and reciprocal pool models). Suppression of ELF by insulin (delta-reduction) was impaired in LTx-5 and LTx-13 when compared with CU and CON (P < 0.01), but normalized in LTx-26 (P < 0.004 vs. LTx-5 and P = 0.3 vs. CON). The basal FFA turnover rate was decreased in LTx-26 (P < 0.01) and CU (P < 0.02) vs. CON. LTx-26 showed a lower FFA oxidation rate than CON (P < 0.02). Tissue glucose disposal was impaired in LTx-5 (P < 0.005) and LTx-13 (P < 0.03), but not in LTx-26 when compared to CON. LTx-26 had normal basal and insulin-modulated endogenous glucose production. In conclusion, LTx have impaired insulin-stimulated glucose, FFA, and protein metabolism 5 mo after surgery. Follow-up at 26 mo results in (a) normalization of insulin-dependent glucose metabolism, most likely related to the reduction of prednisone dose, and, (b) maintenance of some alterations in leucine and FFA metabolism, probably related to the functional denervation of the graft and to the immunosuppressive treatment.

Increased serum concentration of carbohydrate-deficient transferrin in patients with combined pancreas and kidney transplantation

Serum concentration of carbohydrate-deficient transferrin (cCDT) is used for laboratory diagnosis and follow-up of chronic alcohol abuse. In analyzing by CDTect-RIA (Pharmacia) sera from outpatients with combined pancreas and kidney transplantation and no excessive alcohol consumption, we found above-normal values for cCDT and CDT/transferrin ratios (CDT/Tf) in more than half of the samples. Isoelectric focusing of these samples showed distinct bands of carbohydrate-deficient isotransferrins, supporting the abnormal findings from the CDTect assay. In contrast, diabetics and outpatients who had received only kidney transplants showed normal values for cCDT, CDT/Tf, and isotransferrin patterns. Increased serum Tf, sialidase-producing microorganisms, and immunosuppressive medication were eliminated as causes of these abnormal cCDT and CDT/Tf results. Successful pancreas transplantation leads to hyperinsulinemia and normoglycemia, in contrast to hypoinsulinemia and hyperglycemia in the patients who receive kidney transplants alone. These factors may have pathogenic importance for CDT increase, yielding results falsely interpreted as positive with respect to alcohol abuse in patients with combined pancreas and kidney transplantation.

Clinical determinants of glucose homeostasis after pancreas transplantation

Although successful simultaneous pancreas and kidney transplantation (SPK) achieves normoglycemia in the majority of diabetic recipients with end-stage renal disease, little is known about the factors that influence long-term endocrine function. In this prospective study of 48 bladder-drained SPK patients, 209 oral glucose tolerance tests were performed between 3 months and 6 years after transplantation. Normal fasting glucose levels and systemic hyperinsulinemia were stable for up to 6 years after SPK. Multivariate analysis revealed that increased area-under-curve (AUC) levels of C-peptide 3 months after transplantation were predicted by short surgical pancreas anastomosis time, greater recipient body weight, and total HLA mismatch score. Episodes of acute pancreas rejection were not associated with reduced allograft insulin output in the long term. Insulin output, stimulated by oral glucose tolerance tests and assessed by the ratio of AUC insulin to AUC glucose, fell gradually after transplantation and was decreased by an elevated serum calcium level and high cyclosporine dose. The ratio of fasting insulin to glucose, which acts as a marker of peripheral insulin resistance, fell with time after transplantation and was increased by greater body weight, higher prednisolone dose, and lower cyclosporine dose. The inhibitory effect of cyclosporine on both fasting and postprandial insulin output was, however, minor when quantified by multivariate analysis. Endocrine function of the transplanted pancreas was not correlated with its exocrine function measured by urinary amylase excretion, nor was there a correlation with change in renal function measured by isotopic glomerular filtration rate. In summary, simultaneous pancreas and kidney transplantation leads to excellent long-term glucose homeostasis maintained at the expense of systemic hyperinsulinemia. The key factors adversely affecting peripheral resistance in SPK were corticosteroid therapy, body weight, and time after transplantation. The susceptibility of islets to ischemia-reperfusion injury, as quantitated by surgical anastomosis time, may have implications for islet transplantation programs, as may the relative resistance of islets to allograft rejection. Glucose homeostasis after SPK, while remaining abnormal, may be used as the standard against which islet transplantation must be measured.

Metabolic effects of successful intraportal islet transplantation in insulin-dependent diabetes mellitus

The intraportal injection of human pancreatic islets has been indicated as a possible alternative to the pancreas transplant in insulin-dependent diabetic patients. Aim of the present work was to study the effect of intraportal injection of purified human islets on: (a) the basal hepatic glucose production; (b) the whole body glucose homeostasis and insulin action; and (c) the regulation of insulin secretion in insulin-dependent diabetes mellitus patients bearing a kidney transplant. 15 recipients of purified islets from cadaver donors (intraportal injection) were studied by means of the infusion of labeled glucose to quantify the hepatic glucose production. Islet transplanted patients were subdivided in two groups based on graft function and underwent: (a) a 120-min euglycemic insulin infusion (1 mU/kg/min) to assess insulin action; (b) a 120-min glucose infusion (+75 mg/di) to study the pattern of insulin secretion. Seven patients with chronic uveitis on the same immunosuppressive therapy as grafted patients, twelve healthy volunteers, and seven insulin-dependent diabetic patients with combined pancreas and kidney transplantation were also studied as control groups. Islet transplanted patients have: (a) a higher basal hepatic glucose production (HGP: 5.1 +/- 1.4 mg/kg/ min; P < 0.05 with respect to all other groups) if without graft function, and a normal HGP (2.4 +/- 0.2 mg/kg/min) with a functioning graft; (b) a defective tissue glucose disposal (3.9 +/- 0.5 mg/kg/min in patients without islet function and 5.3 +/- 0.4 mg/kg/min in patients with islet function) with respect to normals (P < 0.01 for both comparisons); (c) a blunted first phase insulin peak and a similar second phase secretion with respect to controls. In conclusion, in spite of the persistence of an abnormal pattern of insulin secretion, successful intraportal islet graft normalizes the basal HGP and improves total tissue glucose disposal in insulin-dependent diabetes mellitus.

Determinants of a normal (versus impaired) oral glucose tolerance after combined pancreas-kidney transplantation in IDDM patients

After successful pancreas transplantation, insulin-dependent diabetic patients are characterized by a normal or at worst impaired oral glucose tolerance (World Health Organisation criteria). It is not known which pathophysiological mechanisms cause the difference between normal and impaired oral glucose tolerance. Therefore, we studied 41 patients after successful combined pancreas-kidney transplantation using stimulation in the fasting state with oral glucose (75 g), intravenous glucose (0.33 g/kg) and glucagon bolus injection (1 mg i.v.). Glucose (glucose oxidase), insulin and C-peptide (immunoassay) were measured. Repeated-measures analysis of variance and multiple regression analysis were used to analyse the results which showed: 28 patients had a normal, and 13 patients had an impaired oral glucose tolerance. Impaired oral glucose tolerance was associated with a greatly reduced early phase insulin secretory response (insulin p < 0.0001; C-peptide p = 0.037). Age (p = 0.65), body mass index (p = 0.94), immunosuppressive therapy (cyclosporin A p = 0.84; predniso(lo)ne p = 0.91; azathioprine p = 0.60) and additional clinical parameters were not different. Reduced insulin secretory responses in patients with impaired oral glucose tolerance were also found with intravenous glucose or glucagon stimulations. Exocrine secretion (alpha-amylase in 24-h urine collections) also demonstrated reduced pancreatic function in these patients (-46%; p = 0.04). Multiple regression analysis showed a significant correlation of 120-min glucose with ischaemia time (p = 0.003) and the number of HLA-DR mismatches (p = 0.026), but not with HLA-AB-mismatches (p = 0.084). In conclusion, the pathophysiological basis of impaired oral glucose tolerance after pancreas transplantation is a reduced insulin secretory capacity. Transplant damage is most likely caused by perioperative influences (ischaemia) and by the extent of rejection damage related, for example, to DR-mis-matches.