Myocardial metabolism studied during warm blood antero-retrograde reperfusion in ischaemic human hearts

We propose modified warm blood antegrade-retrograde reperfusion (WBARR) of arrested hearts as a metabolic model with which to study substrate exchange and energy metabolism during the recovery phase after 90 min of ischaemia in man. Eleven anaesthetized patients undergoing aorto-coronary bypass were studied during WBARR. The protocol was designed as follows: period 1, a warm blood reperfusion with potassium (3 min); period 2, a warm blood reperfusion without potassium (2 min). The perfusion flow rate averaged 250+/-2 ml/min at the beginning of period 1 and 218+/-19 ml/min at the beginning and at the end of period 2; the perfusion was performed antegradely and retrogradely in the arrested hearts. Samples were simultaneously taken from the coronary venous sinus (CVS) and from the aortic root needle (AR). At the beginning of WBARR lactate release was 85+/-44 micromol/min and at the end it had significantly decreased to 21+/-99 micromol/min (P<0.03). Simultaneously, non-esterified fatty acids (NEFA) and beta-hydroxy-butyrate were initially released (71+/-61 and 22+/-66 micromol/min, respectively), while at the end of the WBARR there was an uptake of both NEFA (20+/-22 micromol/min; P<0.01) and beta-hydroxy-butyrate (12+/-35 micromol/min; P=0.290). Alanine, glycerol and branched chain amino acid balance across the heart did not significantly change. In summary after 90 min of ischaemia the heart energy metabolism is mainly anaerobic and based on glucose consumption, with lactate, NEFA and amino acids, which are mainly released. After 5 min of WBARR (recovery from ischaemia), lactate release is significantly reduced and NEFA becomes the energy supply of the heart. In conclusion, (1) WBARR is a valuable method with which to study myocardial metabolism in anaesthetized humans and may be combined with the use of tracers; (2) the study of myocardial metabolism in arrested hearts eliminates the imprecisions arising from the noncontinuous coronary blood flow; (3) NEFA become an important source of energy utilized by human hearts in the recovery phase from ischaemia.

Independence of dimethylamiloride-sensitive Li+ efflux pathways and Na+-Li+ countertransport in human erythrocytes

The in vivo function of the erythrocyte Na+-Li+ countertransport (SLC) is unknown. Whether SLC may reflect an operational mode of the widespread Na+-H+ exchanger (NHE) or may otherwise be expression of an independent membrane transport, remains presently unclear. We explored the presence of 5-(N,N-dimethyl)-amiloride (DMA)-sensitive Li+ pathways in human erythrocytes where the activity of the Na+ pump, Na+-K+ cotransport and anion exchange were suitably inhibited. A total of 0.02 mM DMA had no effect on SLC as expected, but gave a significant inhibition of Li+ efflux into both Na+ and Na+-free media. This DMA-sensitive Li+ pathway, but not SLC, was significantly enhanced by hyperosmolar cell shrinkage, which is a characteristic feature of NHE. In conclusion, DMA-sensitive Li+ pathways, possibly mediated by NHE, are present in erythrocytes and coexist with the DMA-insensitive, SLC. This finding supports the notion that SLC is independent of amiloride-sensitive NHE.

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.

Imaging of the buffering effect of insulin antibodies in the autoimmune hypoglycemic syndrome

Insulin autoimmune hypoglycemia is characterized by recurrent hypoglycemia and high levels of immunoreactive insulin in the presence of insulin autoantibodies. The mechanisms inducing hypoglycemia are largely unknown. An [123I]insulin scintigraphic scanning was performed to directly demonstrate the effect of antibodies on insulin biodistribution in one patient with this syndrome both before and after treatment. The patient had insulin autoantibodies IgG3 lambda, which had a single site dissociation constant (Kd = 10(-7) mol/L, by Scatchard analysis), a very fast dissociation rate of immune complexes, and a very rapid association of [125I]insulin. Insulin receptors on red blood cells were down-regulated. The [123I]insulin scintigraphic study imaged the buffering effect of antibodies on insulin bioavailability. [123I]Insulin was not removed from the blood, and no liver or kidney uptake of the hormone occurred. The frequency and severity of hypoglycemic episodes required treatment. Insulin antibody levels decreased and [123I]insulin biodistribution improved after treatment with plasmapheresis and prednisone. Improved hormone bioavailability was further evidenced by the reduction in the hypoglycemic delay after i.v. insulin from 90 min before any treatment to 60 min after plasmapheresis and 30 min after steroid administration. Glucose tolerance was normal after treatment. Plasmapheresis followed by steroid treatment can lower the insulin antibody concentration, abolish severe hypoglycemia, and improve insulin biodistribution and glucose tolerance in insulin autoimmune hypoglycemia.

Personality traits and metabolic control: a study in insulin-dependent diabetes mellitus patients

BACKGROUND

In the present study the authors evaluated the relationship between personality traits (according to DSM-III-R) and poor metabolic control in an adult onset insulin-dependent diabetes mellitus sample (n = 77).

METHODS

Personality traits were assessed with the Personality Diagnostic Questionnaire--Revised. Metabolic control was evaluated through glycosilated hemoglobin (HbA1c): poor metabolic control was defined as HbA1c > or = 9% (normal values < 6.0%).

RESULTS

Principal Component Analysis revealed three personality profiles: 'Cluster A/C Mixed', 'Cluster B Dependent' and 'Cluster B Aggressive'. Oneway ANCOVA, using sex as covariate, revealed a significant association (p = 0.01) only between poor metabolic control and Cluster B Dependent profile. No correlation was found between HbA1c and the other profiles.

CONCLUSION

These data suggest that a specific personality profile is associated with poor metabolic control.

Glucose turnover and insulin clearance after growth hormone treatment in girls with Turner's syndrome

The study was performed to elucidate, by means of a euglycemic-hyperinsulinemic clamp, whether insulin sensitivity, lipid levels, posthepatic insulin delivery, and insulin clearance are impaired in girls with Turner's syndrome in the absence of previous treatment (T0) and after 6 (T6) and 12 (T12) months of growth hormone (GH) therapy (GHT). The study was performed in six girls with Turner's syndrome and eight healthy girls. We found that previously untreated girls with Turner's syndrome had a normal insulin activity on glucose metabolism. GHT progressively and significantly decreased hepatic insulin sensitivity. In fact, residual hepatic glucose release (HGR), which was 19.6 +/- 4.7 mg/m2. min at T0, doubled at T6 (39.3 +/- 5.1 mg/m2.min) and showed a threefold increase at T12 (68.7 +/- 10.8 mg/m2.min, P < .05 v T0). On the contrary, GHT did not show an appreciable influence on peripheral insulin sensitivity. Insulin clearance was higher in girls with Turner's syndrome than in control girls at T0 (30.0 +/- 2.8 v 20.2 +/- 1.1 mL.kg-1.min-1). It decreased to normal values at T6 (18.2 +/- 2.0 mL.kg-1.min-1, P < .05 v T0) and remained at normal levels at T12 (23.8 +/- 2.9 mL.kg-1. min-1). The posthepatic insulin delivery rate significantly increased at T6 and T12, suggesting increased insulin secretion. In conclusion, we found that insulin-stimulated glucose turnover was normal in girls with Turner's syndrome before therapy. One year of GHT was successful in stimulating the growth rate, but significantly decreased the insulin suppressibility on HGR with only slight changes in peripheral insulin sensitivity. In addition, an increase in the insulin posthepatic delivery rate and a normalization of insulin clearance were present, probably to counteract hepatic insulin resistance.

Glibenclamide: an old drug with a novel mechanism of action?

This review is meant to give to the readers an overview of the pharmacokinetics, pharmacodynamics, mechanism(s) of action and therapeutical indications of the sulfonylurea compound glibenclamide, which is a cardinal drug in the treatment of type 2 diabetes mellitus. Data produced in our own laboratory over the past 15 years will be presented, along with reference to the main literature in the field. As pharmacokinetics is concerned, special emphasis will be placed on the detrimental effect of hyperglycemia in the intestinal absorption of this class of drugs. Both beta-cell and extrapancreatic effects of glibenclamide will be highlighted. The mechanism of action of the drug consists in the inhibition of the ATP-sensitive K+ channels, which leads to depolarization of the cells and insulin secretion. Based on the same mechanism are also the extrapancreatic action of the drug at the liver, skeletal muscle, heart muscle and smooth muscle sites. The newly discovered possible physiological actions of the C-peptide molecule [suggesting a stimulatory effect of C-peptide on the Na+, K+ (ATPase) pump and on diabetic complications], cast a new light on all therapeutic approaches (like sulfonylurea class of compounds and whole pancreas or islet of Langerhans transplantation), which induce/replace both insulin and C-peptide secretion.

[Is echography an adequate method for assessing the thickness of intra-abdominal fat? A comparison with computed tomography]

PURPOSE

The methods to measure intraabdominal fat amount and to distinguish visceral from subcutaneous fat are useful and needed because visceral obese people are at risk of developing cardiovascular disorders. We investigated US capabilities in measuring intraabdominal fat thickness and distribution distinguishing visceral from subcutaneous fat. The results were compared with those obtained with CT, the gold standard, and with the waist-hip ratio (W/H).

MATERIAL AND METHODS

Thirty obese women admitted to the Internal Medicine I Department, Ospedale S. Raffaele (Milan, Italy) were examined. The patients, aged 18-60 years and with BMI ranging 29.0-47.3, were submitted to consecutive double blind measurements with US and CT. The following anthropometric values were compared for every patient: W/H, US visceral/subcutaneous thickness, CT visceral/subcutaneous thickness, CT visceral area, CT subcutaneous adipose area and CT visceral/subcutaneous adipose area.

RESULTS

The classification of visceral obesity by W/H (> .85) was confirmed by CT visceral/subcutaneous adipose area (> .491). The W/H correlated significantly with CT visceral/subcutaneous adipose thickness and CT visceral/subcutaneous adipose area (r = .52, p < .004; r = .51, p < .004), but not with US visceral/subcutaneous adipose thickness (r = .42, p < .06). Significant correlations were found between Ct visceral/subcutaneous adipose area and with both US and CT visceral/subcutaneous adipose thickness (r = .59, p < .006; = .71, p < .0001). A high correlation was found between US visceral/subcutaneous adipose thickness and CT visceral/subcutaneous adipose thickness (r = .96, p < .0001).

CONCLUSION

Analyzing the results of the different methods, we conclude that US can always be used to study abdominal fat amount and distribution in obese women because this method exhibits significant correlations with CT, the gold standard. The W/H is not sufficient to distinguish visceral from subcutaneous intraabdominal fat.

Amelioration of nerve conduction velocity following simultaneous kidney/pancreas transplantation is due to the glycaemic control provided by the pancreas

Diabetic polyneuropathy is a common, disabling chronic complication of diabetes mellitus. Previous studies have suggested that combined pancreas-kidney transplantation can ameliorate nerve conduction. The relative contribution of the correction of hyperglycaemia and uraemia on nerve function is still a matter of debate. Nerve conduction velocity (NCV) was assessed before and after simultaneous pancreas and kidney transplantation, and before and after pancreas graft failure in five insulin-dependent diabetic (IDDM) patients affected by severe diabetic polyneuropathy. Sensory and motor NCV were recorded in five nerves and expressed as a cumulative index for each patient. Metabolic control was evaluated by fasting blood glucose and glycosylated haemoglobin levels. NCV index was below normal values before transplant: -3.8 +/- 0.7 (normal value: 0.89), improved 1 and 2 years after transplant: -3.1 +/- 1.3 and -2.6 +/- 0.9 (p = 0.0019), stabilised until pancreas failure and deteriorated to pre-transplant values 2 years after pancreas graft failure: -3.6 +/- 1.0 (p = 0.034). Fasting blood glucose levels worsened after pancreas graft failure. HbA1c levels, in the normal range during functioning pancreas graft (6.6 +/- 0.6%), deteriorated after its failure (8.0 +/- 0.6%, p = 0.04). Kidney function was preserved. These data support a positive effect of pancreas transplantation per se on NCV in IDDM subjects with diabetic polyneuropathy, thus demonstrating that metabolic control provided by a self-regulated source of insulin not only halts but also ameliorates nerve function, even if polyneuropathy is advanced.

A method for assessing catheter patency in implanted pumps for long-term intraperitoneal insulin delivery

Catheter complications are a common problem during long-term insulin therapy with implanted pumps. The purpose of this study was to test the feasibility of imaging intraperitoneal catheters with technetium (Tc) 99m in implantable devices for insulin delivery. Testing physical stability of an insulin/Tc 99 mixture did not show formation of insulin aggregates during a period up to 48 h on a rotating wheel. Five hundred microCurie (equal to 18 MBq) of Tc 99m were injected in the flush port of a pump for intraperitoneal insulin delivery implanted in patients with type I (insulin dependent) diabetes mellitus, and gamma camera images were obtained for 30 min. In patent catheters the tracer rapidly imaged the whole length of the catheter while in occluded catheters the tracer remained in the flush port, imaging only the portion of the catheter before the occlusion. In patent catheters in which insulin absorption was impaired, the tracer rapidly imaged the whole length of the catheter, but its removal from the peritoneum was delayed. Tc 99m imaging of intraperitoneal catheters for insulin delivery can be used to assess catheter patency and impaired delivery into the peritoneal cavity.

Value of abdominal sonography and MR imaging at 0.5 T in preoperative detection of pancreatic insulinoma: a comparison with dynamic CT and angiography

BACKGROUND

Abdominal sonography, computed tomography (CT), angiography, and magnetic resonance (MR) imaging are the most widely used modalities for preoperative localization of insulinomas. CT and angiography are generally considered the techniques of reference, and the role of sonography and MR imaging in these patients is controversial. The purpose of this study was to compare these four modalities in a group of patients with pancreatic insulinoma and determine an effective radiological approach to this disease.

METHODS

Twenty-eight patients with clinical and biochemical signs of pancreatic insulinoma underwent abdominal sonography, MR imaging at 0.5 T (spin echo technique), bolus dynamic CT, and digital subtraction angiography. Examinations were evaluated independently for the presence, size, and location of the lesions; preoperative diagnoses were compared with surgical findings based on palpation and intraoperative sonography. Tumoral vascularity was histologically graded. Sensitivities of the four imaging techniques were calculated and compared with the size, location, and vascularity of the tumors. Detection rates of combined techniques were finally determined.

RESULTS

At surgery, 29 lesions in the 28 patients were found (range = 0.8-4.3 cm, average = 1.65 cm). Sensitivities of abdominal sonography. MR imaging, CT, and angiography were 79.3%, 65.5%, 44.8%, and 69% respectively. Correct localization of tumor was achieved in 96.6% of cases by a combination of sonography and MR imaging and in 72.4% of cases by using CT with angiography.

CONCLUSION

In our experience, sonography and MR imaging performed well in the preoperative detection of pancreatic insulinoma. Therefore, we believe that the combination of abdominal sonography and MR imaging may represent the first radiological approach in clinically suspected insulinomas and that CT and angiography should be reserved for negative and/or doubtful cases.

Modes of operation of an electroneutral Na+/Li+ countertransport in human skin fibroblasts

An elevated activity of erythrocyte Na+/Li+ countertransport (SLC) is an intermediate phenotype of human essential hypertension, but cells other than erythrocytes have not been studied. Therefore, we have examined several transport modes of Na+/Li+ exchange in human skin fibroblasts. External Na+-stimulated Li+ efflux was 152 +/- 31 (SE) nmol x mg protein(-1) x min(-1) (n = 8). At intracellular pH 7.3, intracellular Na+-stimulated Li+ influx, intracellular Li+-stimulated Na+ influx, and external Li+-stimulated Na+ efflux were very similar, indicating the presence of a tightly coupled 1:1 SLC. This pathway was not affected by 5-(N,N-dimethyl)-amiloride and changes in the membrane potential, but phloretin and intracellular acidification (intracellular pH 6.8) were markedly inhibitory. Kinetic analyses of the external Na+ site also compared with SLC, although the internal site appeared to show a low affinity for Li+. We conclude that an SLC pathway similar to that in human erythrocytes is expressed in human skin fibroblasts.

Cancer arising after pancreas and/or kidney transplantation in a series of 99 diabetic patients

OBJECTIVE

Recipients of solid organ transplants have an increased risk of developing certain types of malignancies as compared with the general population. The majority of the literature has reported on neoplasms in kidney and heart transplant recipients.

RESEARCH DESIGN AND METHODS

We describe 9 neoplasms occurring in 7 out of 73 IDDM patients after simultaneous pancreas and kidney transplantation. No cases were recorded among 26 IDDM recipients of kidney transplantation.

RESULTS

Among the neoplasms found were 2 cases of posttransplant lymphoproliferative disorder (PTLD), malignant melanoma, basal-cell and squamous-cell carcinoma of the skin in the same patient, squamous-cell carcinoma in situ of the vulva, hepatocarcinoma, small-cell lung cancer, and ductal carcinoma of the breast. Four patients died. Among immunological risk factors, over-immunosuppression for steroid-resistant kidney rejection was administered only in the 2 cases of PTLD.

CONCLUSIONS

Increased dosage of immunosuppressive agents may be necessary in some patients of prevent or treat rejection in view of their reduced survival on hemodialysis.

Insulin and glucagon release of human islets in vitro: effects of chronic exposure to glucagon

Hyperglucagonemia is commonly found in insulin-dependent as well as in non-insulin-dependent diabetes mellitus, and is likely to be caused by absolute or relative insulin deficiency. The aim of the present study was to evaluate whether a chronic glucagon exposure (1.0 microM for 4 h) modifies the insulin response to acute stimuli with glucagon (1.0 microM), arginine (10.0 mM) and glucose (16.7 mM), or the glucagon response to arginine and glucose, in human islets. Chronic exposure to glucagon did not affect the insulin response to glucose and arginine, but inhibited its response to glucagon (44.6 +/- 9.3 vs 168.6 +/- 52.3 pg/islet per 20 min, P < 0.05); the latter effect was not observed when exposure to glucagon was discontinuous (2.0 microM glucagon alternated with control medium for 30 min periods). The chronic exposure to glucagon also reduced the glucagon response to arginine (- 4.9 +/- 5.7 vs 19.9 +/- 7.9 pg/islet per 20 min, P < 0.05) without affecting the inhibition of glucagon release exerted by glucose. These data indicate that chronic exposure to glucagon desensitizes pancreatic alpha and beta cells in response to selected stimuli.

Islet transplantation in IDDM patients

This single-centre study investigated parameters that positively correlated with the success rate after islet allotransplantation in insulin-dependent diabetic (IDDM) patients. Twenty-one intrahepatic, fresh islet transplantations were performed in 20 IDDM patients (one patient had two transplants), after or simultaneous with kidney transplantation. The correlation between number and purity of transplanted islets and final outcome was investigated. One patient died of a cardiac arrest several hours after islet transplantation; this patient was not included in the follow-up analysis. Three patients (15%) experienced acute, irreversible, early failure of islet function, which was considered as a 'presumed rejection'. Nine patients (45%) achieved either complete insulin-independence (seven cases) or a reduction (> 50%) of exogenous insulin requirement (two cases), with sustained serum C-peptide secretion (0.89 +/- 0.04 nmol/l; duration: 21 +/- 7 months, range 2-58 months). Liver biopsy, performed 3 years after transplantation in one successful case, showed normal islets within the hepatic parenchyma. Eight cases (40%) did not show any metabolic effect of islet transplantation, with low serum C-peptide levels ('presumed function exhaustion'). Metabolic investigations performed in successful cases showed an early phase of insulin release after arginine, mild and reversible postprandial hyperglycaemia and normal HbA1c levels. Success of islet transplantation positively correlates with the number (p < 0.05) of the transplanted islets. Islet transplantation is a safe procedure, with 45% success rate, in terms of insulin-independence or relevant reductions of exogenous insulin requirement, although success can be transient.

Effects of low-dose heparin infusion on arterial endothelin-1 release in humans

BACKGROUND

The aim of this study was to evaluate the effect of low-dose heparin infusion on arterialized endothelin-1 (ET-1) release in the presence of fasting or high insulin levels in healthy humans.

METHODS AND RESULTS

Eleven normal subjects underwent two tests in random order lasting 240 minutes. A primed (250 IU), continuous heparin (600 IU/h) infusion was performed in test 1; saline was infused in test 2 as control. At 120 minutes, a euglycemic hyperinsulinemic clamp (25 mU.kg-1.h-1) was started that lasted 2 hours in both tests. Two hours after heparin infusion (test 1), ET-1 levels decreased by 32% (3.52 +/- 0.60 to 3.02 +/- 0.73 pg/mL), while nitric oxide (NO) and forearm blood flow increased by 29% and 14%, respectively. During saline infusion, ET-1, nitric oxide, and forearm blood flow remained unchanged. There was a significant interaction between the effect of decreasing ET-1 levels and the heparin treatment (F, 4.06; df, 3.30; P < .01). The decrease in ET-1 levels was significantly correlated with the increase in forearm blood flow in test 1 (r = .74; P < .01) but not in test 2. During the heparin/insulin period, ET-1 increased by 25%, returning to fasting values; nitric oxide levels increased by 12%; and forearm blood flow remained unchanged.

CONCLUSIONS

The present study showed that it is possible to decrease ET-1 levels by use of low-dose heparin infusion in humans. This effect seems mediated by a simultaneous increase in nitric oxide levels and is completely reversed by a mild increase in insulin concentrations.

Prevalence of diabetic peripheral neuropathy and its relation to glycaemic control and potential risk factors: the EURODIAB IDDM Complications Study

The EURODIAB IDDM Complications Study involved the examination of 3250 randomly selected insulin-dependent diabetic patients, from 31 centres in 16 European countries. Part of the examination included an assessment of neurological function including neuropathic symptoms and physical signs, vibration perception threshold, tests of autonomic function and the prevalence of impotence. The prevalence of diabetic neuropathy across Europe was 28% with no significant geographical differences. Significant correlations were observed between the presence of diabetic peripheral neuropathy with age (p < 0.05), duration of diabetes (p < 0.001), quality of metabolic control (p < 0.001), height (p < 0.01), the presence of background or proliferative diabetic retinopathy (p < 0.01), cigarette smoking (p < 0.001), high-density lipoprotein cholesterol (p < 0.001) and the presence of cardiovascular disease (p < 0.05), thus confirming previous associations. New associations have been identified from this study - namely with elevated diastolic blood pressure (p < 0.05), the presence of severe ketoacidosis (p < 0.001), an increase in the levels of fasting triglyceride (p < 0.001), and the presence of microalbuminuria (p < 0.01). All the data were adjusted for age, duration of diabetes and HbA1c. Although alcohol intake correlated with absence of leg reflexes and autonomic dysfunction, there was no overall association of alcohol consumption and neuropathy. The reported problems of impotence were extremely variable between centres, suggesting many cultural and attitudinal differences in the collection of such information in different European countries. In conclusion, this study has identified previously known and new potential risk factors for the development of diabetic peripheral neuropathy.