Inhibition of pancreatic glucagon responses to arginine by human insulin (recombinant DNA) and purified porcine insulin in normal and diabetic subjects

Blood into beta-cells: can adult stem cells be used as a therapy for Type 1 diabetes?

In the past 10 years there have been substantial developments in adult stem cell research, and the transplantation of these cells now holds great promise for regenerative medicine, such as in the treatment of Type 1 diabetes. A large proportion of studies have focused on stem cells sourced from hematopoietic tissues: bone marrow, umbilical cord blood and peripheral blood. Attempts to transdifferentiate these cells into insulin-producing cells, both in vivo and in vitro, have produced conflicting results. Although insulin production and normalization of blood glucose levels have been described in some studies, the true mechanism of stem cell plasticity remains in question - are the functional changes seen due to true transdifferentiation or do they result from cell fusion or other factors? There is evidence that stem cell plasticity is a true phenomenon, but whether it will ever be of therapeutic benefit for Type 1 diabetes remains uncertain.

Hypoglycaemia induced by exogenous insulin--'human' and animal insulin compared

AIMS

A systematic review of the literature was carried out to examine whether published evidence suggests a difference in the frequency and awareness of hypoglycaemia induced by 'human' and animal insulin.

METHODS

The review identified randomized controlled trials and studies of other designs including observational comparisons, case series and case reports in which the use of 'human' insulin was compared to animal insulin in people with diabetes. These were identified from bibliographic databases and hand-searches of key journals. The main outcome measures were frequency, severity, awareness and symptoms of insulin induced hypoglycaemia.

RESULTS

Fifty-two randomized controlled trials, 37 of double-blind design, were identified which included one or more of the relevant outcome measures. Of these, 21 specifically investigated hypoglycaemic frequency and awareness as primary outcomes (six in people with previously reported reduced hypoglycaemic awareness). The remainder of the identified trials reported hypoglycaemic outcomes as a secondary or incidental outcome during comparative investigations of efficacy or immunogenicity. Seven of the double-blind studies reported differences in frequency of hypoglycaemia or awareness of symptoms, although none of the studies which selected subjects on the basis of previously reported impaired awareness demonstrated significant differences between insulin species. Four of the unblinded trials reported differences in hypoglycaemia. This reached statistical significance in two of the studies. A further 56 studies of other designs and case reports were considered. In addition to the 10 case reports describing individuals with impaired hypoglycaemic awareness, nine studies reported differences in the incidence and manifestation of hypoglycaemia during 'human' insulin treatment. Notably, none of the four population time trend studies found any relationship between the increasing use of 'human' insulin and hospital admission for hypoglycaemia or unexplained death among those with diabetes. The largest case series could find no support for the hypothesis that an influence of treatment with 'human' insulin on hypoglycaemia had contributed to any of the 50 deaths investigated. When all types of studies considered are ranked in order of rigour (according to the accepted 'hierarchy of evidence'), it is the least rigorous which lend most support to the notion that treatment with 'human' insulin has an effect on the frequency, severity or symptoms of hypoglycaemia.

CONCLUSIONS

Evidence does not support the contention that treatment with 'human' insulin per se affects the frequency, severity or symptoms of hypoglycaemia. However, a number of studies, mainly those of less rigorous design, describe an effect when people are transferred from animal insulin to 'human' insulin. It is not possible to state how common this is or whether the phenomenon is specific to 'human' insulin or an effect resulting from stricter glycaemic control (perhaps compounded, in some cases, by neurological complications in long-standing diabetes). This remaining uncertainty makes it essential that insulin from animal sources continues to be available so that clinicians and patients may retain this choice of treatment.

Does pancreas transplantation influence the course of diabetic retinopathy?

Between March 1983 and December 1989 a total of 57 pancreas transplants were performed in 54 patients, of whom 49 also received a kidney for end-stage diabetic nephropathy. Of the surviving 44 patients, 39 had regular pre-operative and post-operative ophthalmological examinations. Diabetic retinopathy was classified according to the original "Early treatment diabetic retinopathy study" (ETDRS) protocol. At the time of this analysis a total of 25 patients had a functioning pancreas transplant and 23 of them also a functioning renal allograft after a mean observation time of 43.2 months (Group 1). They were all free of exogenous insulin, HbA1c being 6.2% (5.1-6.9%; normal value 4.2-5.9%). Fourteen patients in Group 2 lost their pancreas transplant during the first four years. Six of them still have a functioning renal allograft, four patients regularly undergo hemodialysis. Mean HbA1c is 7.5% (5.7-9.2%). Before transplantation, grade of retinopathy according the ETDRS protocol was 6.7 (2-10) in group 1 patients and 7.9 (3-10) in group 2. In group 1 patients stabilisation of retinopathy was observed in 33 eyes (73.3%) and clear improvement achieved in 4 eyes (8.8%). Detoriation occurred in 8 eyes (17.7%) only. In group 2, 14 eyes (54%) remained stable, whereas progression of the disease continued in 12 eyes (46%). From these results it is concluded that the course of diabetic retinopathy is positively influenced by successful pancreas transplantation.