Effect of aldose reductase inhibition and insulin treatment on retinal capillary basement membrane thickening in BB rats

This study compared the effect of glycemic control with insulin to that of the aldose reductase inhibitor ponalrestat on capillary basement membrane thickening in the retinas of diabetic BB rats. Diabetic animals with or without ponalrestat treatment were compared with diabetic rats subjected to vigorous insulin therapy or nondiabetic control rats with or without ponalrestat treatment after 6 mo of follow-up. Untreated diabetic animals showed the characteristic capillary basement membrane thickening in both the superficial and deep capillary beds of the retina. Vigorous blood glucose control with insulin therapy was accompanied by a complete prevention of capillary basement membrane thickening in both capillary beds, whereas aldose reductase inhibitor treatment achieved a complete prevention of basement membrane thickening in the deep capillary bed but not in the superficial capillary bed of the diabetic retina. These findings suggest that the mechanisms responsible for capillary basement membrane thickening in diabetes may be varied and modulated by topographical peculiarities in various capillary beds.     

Hyperglycemia and development of glomerular pathology: diabetes compared with galactosemia

Dogs were randomly assigned to experimental galactosemia or diabetes, or to a normal untreated group, and diabetic animals were then randomly assigned to either poor or good glycemic control. At five years duration, kidneys from the animals were compared by quantitative stereology. Glomerulopathy appeared in the poor control diabetes group, and the thickness of glomerular capillary basement membrane, the glomerular tuft volume, and the fraction of glomerulus occupied by mesangium were each significantly greater than normal. The capillary filtering surface area per glomerulus was supranormal also, but nonetheless was subnormal relative to glomerular volume. The development of glomerulopathy was significantly inhibited in dogs assigned to good glycemic control. In galactosemic animals, the basement membrane thickness was greater than normal, but the glomerular volume, fractional and absolute volumes of mesangium, and capillary filtering surface area remained normal. The polyol concentration in renal cortex seemed elevated by galactosemia no less than by diabetes, and was highest in galactosemia. The galactosemic animals are known to have developed a retinopathy morphologically comparable to that of diabetic patients and diabetic dogs. Thus, sequelae of hyperglycemia sufficient to produce glomerular basement membrane thickening and retinopathy proved not necessarily sufficient to produce the mesangial expansion and glomerular hypertrophy typical of diabetes.     

Nonproteinuric diabetes-associated nephropathy in the Cohen rat model of type 2 diabetes

The Cohen diabetic rat is an experimental model reminiscent of human type 2 diabetes. The aim of this study was to characterize the development of end-organ damage in this model. Cohen diabetic sensitive (CDs) and Cohen diabetic resistant (CDr) rats were fed regular diet or a diabetogenic diet. Glucose tolerance, renal function, and renal and retinal histology were studied at set intervals. CDs fed diabetogenic diet were the only strain that expressed the diabetic metabolic phenotype. In this strain, urinary protein excretion did not increase with the development of diabetes, but plasma urea and creatinine levels increased and creatinine clearance decreased. Light microscopy revealed in CDs enlarged glomeruli with increased mesangial matrix and thickening of the glomerular capillary wall; electron microscopy demonstrated thickened basement membrane and mesangial abundance. There was increased staining for type IV collagen in glomeruli and interstitium of CDs. The retinas of diabetic CDs demonstrated pathology consistent with nonproliferative diabetic retinopathy. The histological findings in the kidneys, the absence of proteinuria, the impairment in glomerular filtration, and the development of retinopathy in CDs are consistent with diabetes-associated nephropathy that is similar to a nonalbuminuric type of nephropathy associated with type 2 diabetes in humans.     

Glomerular basement membrane metabolism in the diabetic rat. In vivo studies.

The effect of diabetes on the metabolism of the renal glomerular basement membrane has been studied in the rat with the aid of injected tracer doses of tritiated proline. At various times after administration of the labeled amino acid, the specific radioactivities of the proline and hydroxyproline of the basement membranes from alloxan diabetic rats were determined and compared with those of age-matched normal rats. In both normal and diabetic animals the incorporation of radioactivity into the basement membrane was slow and, after a maximum was reached, an extended period of almost constant specific activity of proline and hydroxyproline was observed. The diabetic basement membrane, however, differed from the normal by attaining specific activities of the amino acids which were about twice as high as normal (P less than 0.001 at 42 h after injection of radioisotope). Although the proline concentration of serum and renal cortical fluid was the same in normal and diabetic rats, there were substantial differences in the specific activity of this precursor amino acid in these pools that had to be taken into account to compare the two types of animals. The results of the present study are consistent with an accelerated rate of glomerular basement membrane polypeptide synthesis and proline hydroxylation in diabetes.     

The pathophysiology of experimental insulin-deficient diabetes in the monkey. Implications for pancreatic transplantation.

In an 11-year study of experimental insulin-deficient diabetes (IDDM) induced in rhesus monkeys by streptozotocin or total pancreatectomy, the authors have found that pathophysiologic changes occur in eye and kidney, which closely resemble the early stages of human insulin deficient diabetes mellitus (IDDM). In addition, morphologic changes of thickening of glomerular capillary basement membrane and expansion of mesangial matrix (by light microscopy) appear within 3 years of onset of hyperglycemia. However, progression to irreversible complications of advanced diabetic nephropathy or proliferative retinopathy, have not occurred. This animal model resembles human disease in that the animals tend to become ketotic unless maintained with exogenous insulin; C-peptide production is low to absent, and large amounts of glycosylated hemoglobin develop within a month of onset. The monkeys differ from humans in the absence of hypertension and hyperlipidemia. The authors suggest that the abnormalities in basement membrane form and function caused by hyperglycemia form the necessary background upon which other factors, such as hypertension and hyperlipidemia, then act to cause irreversible complications. The role of pancreatic transplantation is in prevention of these background changes.     

Difference in effect of cultured fetal pancreas transplants on retinal and renal capillary basement membrane thickness in diabetic mice

The goal of endocrine pancreas transplants should be the prevention of diabetic complications. The differential effect of grafts of organ-cultured fetal mouse pancreas on diabetic complications in the retina and kidney was tested by comparing capillary basement membrane thickness (BMT) in mice made diabetic with streptozotocin and transplanted either early or late, or treated with insulin. BALB/c female mice were grafted with a single organ-cultured syngeneic fetal pancreas at either 3 weeks or 7 months after induction of diabetes. Controls were sex- and age-matched nondiabetic; diabetic untreated; and diabetic insulin-treated mice. All mice were killed at 20 months of age and their eyes and kidneys fixed for electron microscopy. BMT was measured on coded micrographs. In all mice glomerular capillary BM were thicker than retinal capillary BM. Mice grafted early after the induction of diabetes had normal BMT in both sites, while those transplanted after 6 months of disease had normal retinal, but thickened glomerular, capillary BM. In each case the late-transplanted animals had BM thickness significantly less than the insulin-treated or untreated diabetics.     

Free flaps: an overview.

The free flap represents a dramatic one-stage procedure for distant transfer of skin flaps. The operative technique consists of: identification of healthy recipient vessels; isolation of viable island skin flap; distant transfer followed by revascularization via microvascular anastomoses. New techniques warrant classification of free tissue transfers into single tissue transfers (skin, muscle, bone, nerve) and compound tissue transfers (osteocutaneous, musculocutaneous). When compared to conventional techniques, free flap transfers offer shorter hospitalization and immobilization as well as a greater reconstructive potential. However, their utilization mandates extensive experience in multiple microvascular techniques and clinical microsurgery.     

Kidney morphology in experimental hyperglycemia

To evaluate the role of hyperglycemia in the pathogenesis of diabetic nephropathy, the kidneys from dogs experimentally galactosemic for 5 yr have been compared with the kidneys from age-matched normal dogs and dogs with alloxan-induced diabetes for 5 yr. The width of glomerular capillary basement membrane and the quantity of plasma protein immunohistochemically demonstrable in the basement membrane were supranormal in the galactosemics, as they were in the diabetics. In contrast, kidney weight, mesangial volume, and the prevalence of obliterated glomeruli, glomerular exudates, and mesangial nodules in the galactosemic animals were comparable to those of normal animals and clearly were less than observed in the insulin-deficient diabetic animals. These galactosemic dogs are known to have developed a retinopathy morphologically indistinguishable from that of diabetic patients and dogs. Thus, galactosemia sufficient to produce diabetic-like lesions in the glomerular basement membrane and retina was found to be nevertheless insufficient to elicit several renal abnormalities that are typical of diabetes. The polyol concentration in erythrocytes was greater than normal in the galactosemics and the diabetics and was greatest in the galactosemics. The absence of mesangial expansion, glomerular obliteration, and nephromegaly in galactose-fed dogs raises the possibility that these abnormalities in diabetes are not a result of excessive polyol pathway activity.     

The influence of diabetes on free flap transfer: II. The effect of ischemia on flap survival.

Insulin-dependent diabetes mellitus causes microangiopathic changes in many tissues, including skin and muscle. It is not known if such changes are detrimental to free flap transfer, particularly after extended ischemia. To address this issue, we used an experimental design by using a syngeneic rat strain (Lewis) for free groin flap and muscle flap transplantations from streptozotocin-induced diabetic rats (2 month's duration of symptoms) to normal rats. Flaps from age-matched normal donors were transplanted to normal recipients for control comparisons. Groin flaps were stored ischemically for 12 or 18 hours at room temperature, or for 48 hours in the cold (4 degrees C) before transplantation. Flap survival and vascular patency were assessed at 7 days. Cutaneous maximus muscle flaps were transplanted to the groins of recipients after 6 hours of room temperature ischemia. Vascular patency, muscle viability, flap weight change (edema), and dehydrogenase activity were assessed after 2 days of reperfusion. Seventy percent, 67%, and 73% of diabetic groin flaps survived after 12, 18, or 48 (cold) hours of ischemia, respectively, in comparison with 90%, 73%, and 87% of normal flaps undergoing the same respective ischemia periods. The differences were not significant, even when the data were pooled (p greater than 0.1). Muscle flaps also showed no significant differences for the parameters studied. These results support the use of microvascular reconstructive surgery in diabetic patients, suggesting that moderate ischemic challenges do not compromise free flap transfer or extremity replantation.     

Relationship of muscle capillary basement membrane to renal structure and function in diabetes mellitus

Muscle capillary basement membrane (MCBM) thickening has been considered to reflect microvascular changes in other tissues in diabetes mellitus. To explore the relationships between MCBM width and nephropathy, 27 patients aged 22-55 yr with type I diabetes for 14-33 yr were studied with creatinine clearances, urinary albumin excretion rates, multiple blood pressure measurements, glycosylated hemoglobin measurements, and renal and quadriceps muscle biopsies that were evaluated using standard stereologic techniques. MCBM width did not correlate with age, duration of diabetes, creatinine clearance, urinary albumin excretion, or fractional volume of the glomerular mesangium. MCBM width did correlate, although weakly, with glomerular basement membrane width (r = 0.47) and glycosylated hemoglobin (r = 0.44). There was no difference in MCBM width between patients with and without clinical nephropathy. Patients with normal fractional volume of mesangium exhibited a full range of MCBM width. Thus, while MCBM width may reflect glycemic control and glomerular basement membrane thickening, it does not relate to the functional or structural renal changes associated with progressive diabetic nephropathy.     

Continuous local intraarterial infusion of antithrombotic agents for epigastric flap transfer in rabbit

In free tissue transfer, the recipient arteries and veins are often damaged by injury, and their lumens are often narrowed due to thickening of the intima. These factors are considered paramount in the poor success rate of free tissue transfers. In the reported study, the authors examined the effects of continuous intraarterial infusion with heparin and urokinase in experimental epigastric flap transfer. By intraarterial infusion, the drug concentration at the target site could be significantly increased. The viability of an epigastric flap transferred to a recipient site with thickened arterial intima was significantly improved in a rabbit model by a seven-day continuous local intraarterial infusion of heparin at 10 U/kg/hr and urokinase at 100 IU/kg/hr, compared with control or intravenous infusion. Use of an anticoagulant with a fibrinolytic enzyme is considered to be the best choice for a successful outcome in flap transfer.     

Significant muscle capillary basement membrane thickening in spontaneously diabetic Mystromys albicaudatus.

Skeletal muscle capillary basement membrane thickness was determined in age- and sex-matched normal and spontaneously diabetic Mystromys albicaudatus. In nondiabetic animals the average basement membrane thickness was 482.6+/-48.7 A as against 779.0+/-319.9 A in the diabetic ones. This difference was statistically significant at P less than 0.005.     

Development of early lesions of microangiopathy in chronically diabetic monkeys

A chronic diabetic state was produced in Macaca fuscatus , and these diabetic monkeys were kept without insulin treatment for up to 25 mo. The metabolic derangements were characterized by hyperglycemia, insulinopenia, hyperglucagonemia, ketonemia, and hyperlipidemia. Significant thickening of the capillary basement membrane of the gastrocnemius muscle was observed in the chronically diabetic monkeys, and became obvious in the course of diabetic state; 732 +/- 35 A in controls, 750 +/- 58 A in diabetic monkeys with duration of 4 mo, and 1165 +/- 112 A in those with duration of more than 11 mo. In addition to duration of the diabetic state, severity of hyperglycemia is also thought to play an important role in the capillary basement membrane thickening judging from the fact that diabetic monkeys with constant hyperglycemia showed a greater membrane thickening. Ultrastructural alterations, such as significant thickening of glomerular basement membrane and increase of mesangial matrix, were observed in kidney as well. These results indicate that diabetic microangiopathy has been produced by metabolic derangements characterized by chronic hyperglycemia, insulinopenia, and hyperlipidemia.     

Prevention of vascular complications of diabetes by pancreatic islet transplantation.

Isolated pancreatic islets from Wistar-Lewis rats were transplanted into the liver of diabetic allogeneic recipients to assess ability to prevent diabetic renal and ophthalmic complications. At nine months, the diabetic animals without transplants showed significant increase in PAS-positive material in the renal glomerular mesangium and thickening of glomerular arterioles as compared with normal nondiabetic animals. New vessel formation was also significant in the retina and retinal capillary dilation. Animals in which diabetes had been corrected by early pancreatic islet transplantation were completely protected from these changes, showing no significant pathologic change when compared with normal animals.     

Relationships between microvascular function and capillary structure in diabetic and nondiabetic human skin

Despite the commonly held view that abnormalities in capillary morphology, in particular thickening of the capillary basement membrane, are partly responsible for diabetic ischemia, few studies have correlated anatomic and hemodynamic variables in the same diabetic subjects. In a previous study of 24 type II (non-insulin-dependent) diabetic subjects and 24 age-matched control subjects, we showed that a standard finger exercise vasodilated cutaneous forearm vessels nearly equally (51%), but the postarteriolar flow responded differently between groups. Nondiabetic subjects increased flow by recruitment of capillaries, whereas diabetic subjects did so by capillary flow augmentation. Moreover, resting permeability-surface area product (PS) to pentetic acid was 85% higher in diabetic than nondiabetic subjects. In this study, these same subjects had their forearm skin biopsied and examined morphometrically by electron microscopy for capillary radius, basement membrane thickness, endothelial cell density, and a folding index of luminal membrane reduplication. All morphological variables were correlated stepwise in a saturated, analysis of covariance model with the physiological results. The correlations were sparse and specifically excluded basement membrane thickness. The highest r2 value was .432 between resting PS and a ratio of capillary density to endothelial cell number per capillary. These studies show little evidence that diabetic microvascular physiological variables are tightly connected to morphometric changes except for minor permeability changes, which rise with capillary density and decrease with endothelial cell number. Because PS to pentetic acid is increased in diabetic subjects at any level of capillary density, it seems reasonable that permeability may be increased above that of nondiabetic subjects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Non-enzymatic glycation and altered renal structure and function in the diabetic rat

Renal functional parameters including creatinine clearance, urinary albumin excretion, basement membrane thickening, and levels of non-enzymatic glycation of glomerular basement membrane were studied in rats rendered diabetic with streptozotocin. Diabetic animals had elevated, glycated hemoglobin levels (P less than 0.05), increased creatinine clearance, and urinary albumin excretion rates (P less than 0.05) as compared to insulin treated diabetic (euglycemic), age-matched, and streptozotocin non-diabetic animals. The level of non-enzymatic glycation of glomerular basement membrane was significantly elevated (P less than 0.05) in the diabetic animals as well, with the level of non-enzymatic glycation of all animals, correlating (P less than 0.05) to the average blood glucose level of each animal. Despite changes in functional parameters, and increased levels of non-enzymatic glycation between the diabetic and euglycemic animals, there was no difference in glomerular basement membrane thickness between the two groups. However, there was a difference between all diabetic euglycemics and the age-matched control animals. We hypothesize that increased glycation of glomerular basement membrane may alter renal function, possibly by affecting the net charge of the glomerular filtration barrier. However, glomerular basement membrane thickening per se does not affect the functional changes which have been observed, thus casting doubt upon its role in the development of diabetic nephropathy.     

A case of idiopathic nodular glomerulosclerosis with fibrin caps

We report a case of idiopathic nodular glomerulosclerosis (ING) mimicking diabetic Kimmelstiel–Wilson glomerulopathy. A 72-year-old man suffering from nephritic syndrome and renal dysfunction had no prior history of diabetes mellitus, but had impaired glucose tolerance and a history of hypertension and smoking. A kidney biopsy showed increased mesangial matrix with Kimmelstiel–Wilson-like nodules, glomerular basement membrane thickening and capillary microaneurysms. Additionally, a large amount of fibrin caps detectable as electron-dense subendothelial material by electron microscopy were observed. Although ING with fibrin caps has been rarely reported, the large number of fibrin caps seen in this case may be due to the advanced clinical stage.     

Prevention of basement membrane thickening in retinal capillaries by a novel inhibitor of aldose reductase, tolrestat

A diabetic-like thickening of retinal capillary basement membranes induced in rats fed for 207 consecutive days a diet containing 50% galactose was prevented by the addition to the diet of tolrestat, a potent, structurally novel inhibitor of aldose reductase. Analysis of electron micrographs (X 25,000) of capillaries from the outer plexiform layer of the retina by computer planimetry showed that the basement membranes were approximately twofold thicker in rats fed galactose than in those fed either a standard diet or a diet containing galactose and tolrestat in doses of 43 or 57 mg/kg/day. The thickening of basement membranes in galactose-fed rats was accompanied by other ultrastructural alterations mimicking changes typical of diabetic microangiopathy, such as multilamination and the formation of vacuoles and dense inclusions. Therefore, the galactosemic rat represents a useful model for studying basement membrane-related complications of diabetes and their possible prevention by aldose reductase inhibitors.     

Distal revascularization and microvascular free tissue transfer: an alternative to amputation in ischemic lesions of the lower extremity

Most lower extremity amputations result from complications of diabetes and arterio-sclerotic occlusive diseases below the inguinal ligament. Improved limb salvage has been achieved by an aggressive approach to distal revascularization in the severely ischemic lower extremity. There remains, however, a high incidence of amputation resulting from progression of the ulceration or gangrene into deeper and less well-vascularized tissues, such as tendon and bone. Even in the nonischemic extremity, such wounds rarely heal without flap coverage. Microvascular free tissue transfers promote healing by providing coverage with healthy, nondiseased, well-vascularized tissue for these difficult defects. Successful free flap transfer requires a high-pressure recipient inflow vessel. In contrast to individuals with nonarteriosclerotic lesions, many individuals with nonhealing ischemic lesions have no acceptable artery demonstrated on high-resolution angiography to serve as a recipient vessel. Limb salvage has been achieved in four candidates for amputation utilizing distal revascularization followed by free tissue transfer coverage of the ischemic lower leg defects.     

Clinical outcomes and peritoneal histology in patients starting peritoneal dialysis are related to diabetic status and serum albumin levels

Peritoneal morphological changes seem to be related to dialysis solutions bioincompatibility and to infections, but the uremic milieu per se may also contribute to peritoneal changes. The influence of diabetes and diabetes-associated comorbidities on peritoneal histological changes in the pre-dialysis stage have been insufficiently studied. The aim of this study is to analyze the effect of diabetes and serum albumin levels on peritoneal histology and certain clinical variables such as peritoneal permeability, technique failure, and general mortality in patients starting peritoneal dialysis (PD) treatment. Eighteen PD patients without diabetes (uremic non-diabetic group, U-ND) and 65 with diabetes (uremic diabetic group, U-D) were studied prospectively. Clinical and biochemical variables were registered, and a parietal peritoneum biopsy was obtained at the time of the peritoneal catheter placement. Peritoneal histology was evaluated by light microscopy and immunohistochemistry. A control group of 15 non-uremic, non-diabetic (NU-ND) patients who underwent non-complicated elective abdominal surgery was also studied and used as control. The proportion of patients with peritoneal morphological changes as evaluated by light microscopy was higher in the two groups of uremic patients than in the control. The U-D group had higher mesothelial loss (40.9 vs 29.4%), higher mesothelial basement membrane thickening (45.5 vs 23.5%), higher proportion of vascular wall thickening/sclerosis (39.7 vs 11.1%), and higher proportion of inflammatory infiltrate (45.4 vs 23.6%) than the U-ND group. Uremic patients had lower density of mesothelial cells and higher density of inflammatory cells than the control, as evaluated by immunohistochemistry. These changes were even more striking in the U-D group than in the U-ND group. On the other hand, inflammatory infiltration to the peritoneum, mesothelial cell loss, and mesothelial basement membrane thickening were associated with higher technique failure and mortality. However, when the serum albumin level was introduced into the model, the aforementioned associations became nonsignificant. In conclusion, uremia and diabetes were associated with important peritoneal histological changes before starting PD treatment. Diabetes associated with uremia was more strongly related to the peritoneal changes than uremia per se. Hypoalbuminemia and peritoneal inflammatory infiltrate were markedly associated with technique failure and mortality in patients starting PD treatment.