Neurophysiological study of the effect of combined kidney and pancreas transplantation on diabetic neuropathy: a 2-year follow-up evaluation

Neurologic complications of pancreas and small bowel transplantation

In the past decade, substantial improvements in patient and graft survival for pancreas and small bowel transplants have been achieved. Despite this progress, many patients still develop neurologic complications in the course of their illness. Small bowel transplants produce more neurologic complications because of the complex metabolic environment in which the procedure is performed and because of the intense immune suppression necessitated by the greater immunogenicity of the intestinal mucosa. Pancreas transplants stabilize and/or improve the signs and symptoms of diabetic neuropathy over time. Because transplantation of the pancreas is often coupled with a kidney transplant and small intestine with liver, neurologic complications in these patients sometimes reflect problems involving the organ partner or both organs. The spectrum of neurologic complications for pancreas and small bowel transplant recipients is similar to other organ transplants but their frequency varies depending on the type of transplant performed.

Transplantation of the pancreas

Pancreas transplantation consistently induces insulin-independence in beta-cell-penic diabetic patients, but at the cost of major surgery and life-long immunosuppression. One year after grafting, patient survival rate now exceeds 95 % across recipient categories, while insulin independence is maintained in some 85 % of simultaneous pancreas and kidney recipients and in nearly 80 % of solitary pancreas transplant recipients. The half-life of the pancreas graft currently averages 16.7 years, being the longest among extrarenal grafts, and substantially matching the one of renal grafts from deceased donors. The difference between expected (100 %) and actual insulin-independence rate is mostly explained by technical failure in the postoperative phase, and rejection in the long-term period. Death with a functioning graft remains a further major issue, especially in uremic patients who have undergone prolonged periods of dialysis. Refinements in graft preservation, surgical techniques, immunosuppression, and prophylactic treatments are expected to further improve the results of pancreas transplantation.

Increased weakness after pancreas and kidney transplantation

BACKGROUND

Already there is evidence that simultaneous pancreas and kidney (SPK), or pancreas after kidney (PAK) transplantation, in patients with type 1 diabetes mellitus and end-stage kidney disease prevents worsening of diabetic polyneuropathy, but neuropathic improvement is delayed and incomplete.

METHODS

In 85 patients with type 1 diabetes mellitus who underwent SPK or PAK transplantations, we performed sequential neuromuscular evaluations before, every 3 months after, and yearly after transplantation, quantitating muscle weakness separately from overall severity of polyneuropathy.

RESULTS

We found that, on average, the weakness subscore of the Neuropathy Impairment Score of the lower limbs [NIS(LL)-W] was significantly worse at 3, 6, 9, and 12 months (by about 5 points) than at baseline. By contrast, for these times after transplantation, a composite score of nerve conduction abnormalities, an independent measure of severity of polyneuropathy, was not significantly worse and, in fact, was significantly improved. In multivariate analysis, length of hospital stay correlated with the increased weakness.

CONCLUSIONS

We conclude that: (1) increased neuromuscular impairment after transplantation is mainly due to muscle weakness and not to worsening polyneuropathy; (2) in multivariate analysis, duration of hospitalization after transplantation was significantly associated with this increased weakness; (3) increased weakness is probably due to development of myopathy, which may be related to graft rejection, immunosuppression, sepsis, and intercurrent infections; (4) in future transplantation trials, weakness should be evaluated separately from neuropathic status, and the lowest efficacious dosages of immunotherapy should be used; and (5) essentially all diabetic patients reported that SPK or PAK transplantation was worthwhile because it freed them from diabetic lifestyle concerns.

Pancreatic and islet transplantation

Diabetes mellitus is the most devastating chronic disease of all time. This review discusses the current therapies for type 1 diabetes that are predicated on the restoration of insulin secretion by transplantation. Recent developments in vascularized pancreas transplantation have led to a dramatic increase in the number of these procedures performed worldwide, with over 10,000 cases reported currently to the International Pancreas Transplant Registry. Although the procedure contributes to a significant improvement in quality of life, compared with traditional insulin therapy, it still suffers from a number of shortcomings, including a persistently high postoperative morbidity rate and the requirement of long-term immunosuppression. Islet transplantation is therefore being pursued actively as an equally efficient means of restoring normoglycemia, but without the attendant morbidity of the whole-organ procedure, and hopefully with a significantly reduced need for immunosuppression.

Clinical islet cell transplantation. Are we there yet?

Diabetes mellitus is perhaps the most devastating chronic disease of all time. A brief history of the evolution of treatment modalities is provided, culminating in the rationale for the physiologic replacement of a functioning beta-cell mass by transplantation. Vascularized pancreas transplantation is discussed briefly as an introduction to the transplantation of the isolated islet. A detailed review of the current state of human islet transplantation for the cure of diabetes is then described. Finally, areas for future development are highlighted.

Does peripheral neuropathy invariably accompany nephropathy in type 1 diabetes mellitus?

In patients with Type 1 diabetes mellitus complicated by diabetic nephropathy and retinopathy, it is usually believed that significant neuropathy is almost universal, but few studies have directly addressed this. This study assessed neuropathy in 91 such subjects, using vibration perception thresholds (VPT) and the neuropathy disability score (NDS). A total of 34% of subjects had no neuropathy on age adjusted VPT (z score) and 26% had no neuropathy on NDS. The severity of neuropathy as measured by VPT z score was related to increasing glycated haemoglobin (P = 0.02) and male sex (P = 0.03), and NDS was independently associated with age (P < 0.0001) and HbA1c (P = 0.003). These factors together accounted for only 12 and 31% of the total variance in VPT z score and NDS, respectively. In conclusion, the study has shown that a significant proportion of patients with diabetic nephropathy are free of neuropathy, but the full explanation for their protection from neuropathy is unclear.

Long-term effects of pancreatic transplantation on diabetic neuropathy

Restoration of a long-lasting euglycemic state by a functioning pancreatic transplantation (PTx) is the most logical treatment for insulin-dependent diabetes mellitus and for amelioration of secondary complications, including neuropathy. We evaluated neurological function by clinical examination, nerve conduction studies, and autonomic function tests in 115 patients with a functioning PTx and in 92 control patients treated with insulin, at baseline and 1, 2, 3.5, 5, 7, and 10 years later. In control patients, neuropathy progressively worsened during follow-up. The clinical examination score and composite indices of abnormality of motor and sensory nerve conduction decreased significantly at all intervals tested. Autonomic function indices also decreased, but significantly only after 1 year. In patients who received a successful PTx the neuropathy improved. The motor and sensory nerve conduction indices increased significantly at all intervals after transplantation, whereas the clinical examination and autonomic tests improved only slightly. Patients who received either a PTx alone, a PTx after a kidney graft, or simultaneous pancreatic and kidney transplantations improved similarly over the follow-up. These results indicate that a functioning PTx halts the progression and improves the signs of diabetic polyneuropathy by restoration of a normoglycemic state.

Subacute uremic and diabetic polyneuropathy

We present 4 patients who had a subacute, predominantly motor polyneuropathy associated with diabetes mellitus and end-stage renal disease. Electrophysiological studies and muscle biopsy indicated a primary axonal degeneration of nerve with secondary segmental demyelination, and mild to moderate, acute and chronic denervation of muscle. A relative absence of denervation potentials on needle electromyography was an unusual feature. Three of our patients improved with a switch from conventional to high-flux hemodialysis. We speculate on possible mechanisms.

The efficacy of aldose reductase inhibitors in the management of diabetic complications. Comparison with intensive insulin treatment and pancreatic transplantation

Recently, aldose reductase inhibitors (ARIs) have been registered in several countries for the improvement of glycaemic control. However, their efficacy is still controversial. ARIs inhibit the enhanced flux of glucose through the polyol pathway. As such, they can never be more effective than normoglycaemia, and so their potential benefits and limitations should be considered relative to the effects of prolonged euglycaemia. The clinical effects of ARIs can be put into perspective by assessing the effects of improved glycaemic control attained in randomised trials of intensive insulin treatment [such as the Diabetes Control and Complications Trial (DCCT)] and after pancreatic transplantation. Although direct comparison of these 3 interventions is hampered by differences in patient populations, duration and methods of follow-up and in the potency of ARIs, the effects of these 3 metabolic interventions and their course in time appear remarkably similar. For neuropathy, all 3 interventions induce an increase in average motor nerve conduction velocity of approximately 1 m/sec during the first months of treatment. At the same time, improvement of painful symptoms may occur. These changes probably largely represent a metabolic amelioration of the condition of the nerves. Around the second year of treatment with all 3 forms of metabolic improvement, an acceleration of nerve conduction of a similar magnitude occurs, with signs of structural nerve regeneration and some sensory recuperation. Experience with ARIs in nephropathy is still limited, but similar improvements in glomerular filtration rate and, less consistently, in urinary albumin excretion were found during short term normoglycaemia produced by all 3 forms of treatment. Comparison of a small number of studies, however, shows differences between intensive insulin regimens, pancreatic transplantation and ARIs in effects on retinopathy. Retinopathy often temporarily deteriorates in the early phases of improved glycaemic control, but this is not noted with ARIs. New microaneurysm formation was slightly reduced in a single long term study with the ARI sorbinil, but the preventive effects on the overall levels of retinopathy seemed less strong than in normoglycaemia trials of similar duration. However, the pharmacodynamic effects on inhibiting the polyol pathway differ among ARIs, and the half-life of the inhibiting effect of sorbinil may have been too short for a complete reduction of polyol pathway activity. The trials of prolonged intensive insulin therapy and pancreatic transplantation have demonstrated that very strict metabolic control must be maintained continuously for many years before a significant reduction of complications can be demonstrated.(ABSTRACT TRUNCATED AT 400 WORDS)