Showing papers in "Diabetes in 1979"

Glucose Intolerance and Aging: Evidence for Tissue Insensitivity to Insulin

Abstract: The relative contributions of impaired insulin secretion and of impaired tissue sensitivity to insulin to the glucose intolerance of aging were examined in 84 healthy volunteers, ranging in age from 21 to 84 yr, employing the hyperglycemie and euglycemic insulin clamp techniques, respectively. HYPERGLYCEMIC CLAMP. The blood glucose concentration was acutely raised and was maintained at 125 mg/dl above basal levels for 2 h. Since the glucose concentration was held constant, the glucose infusion rate was an index of glucose metabolism (M). In young subjects, M averaged 9.48 ± 0.40 mg/kg · min compared with 6.48 ± 0.28 in old subjects ( P < 0.001). When all subjects were considered together, a progressive age-related decline in M was observed ( r = –0.665, P < 0.001). The plasma insulin response (I) was biphasic, with an early burst within the first 6 min, followed by a phase of gradually increasing insulin concentration. No difference in either the early or late phases of insulin secretion was observed between young and old subjects. Consequently, the M/l (×100) ratio, an index of tissue sensitivity to endogenous insulin, decreased from 14.90 ± 1.01 to 10.98 ± 0.81 mg/kg min per μU/ml ( P < 0.005). EUGLYCEMIC INSULIN CLAMP. The plasma insulin concentration was acutely raised and was maintained at about 100 μU/ml above basal levels by a primed continuous infusion of insulin. The blood glucose concentration was held constant at the basal level by a variable glucose infusion. M/I (×100), again, was a measure of tissue sensitivity to insulin (exogenous) and was decreased in old (4.95 ± 0.31 mg/kg · min per μU/ml) versus young (6.95 ± 0.45) subjects ( P < 0.001). Hepatic glucose production was measured with tritiated glucose during the euglycemic clamp study; it declined similarly in young (to 0.13 ± 0.05 mg/kg · min) and old (to 0.09 ± 0.03 mg · min) subjects. In conclusion, under the present experimental conditions, employing intravenous glucose and/or insulin, impaired tissue sensitivity to insulin is the primary factor responsible for the decrease in glucose tolerance observed with advancing age. Since hepatic glucose production is normally suppressed by insulin in old subjects, the site of insulin resistance must reside in peripheral tissues. Beta cell response to glucose, as determined by the hyperglycemie clamp technique, cannot account for the age-related decline in M.

Malformations in Infants of Diabetic Mothers Occur Before the Seventh Gestational Week: Implications for Treatment

Abstract: In the present study we used a developmental morphologic approach to fix the latest time in development at which the malformations commonly reported in infants of diabetic mothers could occur. Developmental morphologic dating shows that the significantly more common congenital malformations in infants of diabetic mothers occur before the seventh week of gestation. This suggests that any therapeutic intervention aimed at decreasing the incidence of congenital malformations must be instituted during the critical early period.

Diabetic Neuropathy—New Concepts of Its Etiology

Abstract: INTRODUCTION Recent studies reveal that, whereas symptomatic distal symmetric polyneuropathy is present in roughly 25% of patients with diabetes mellitus, electrophysiologic evidence of abnormal peripheral nerve function can be obtained in nearly all diabetic subjects.\" Thus, if it is assumed that neuropathy exists whenever functional abnormalities of the peripheral nerves can be demonstrated, neuropathy is the most common of the so-called \"late complications of diabetes.\" Despite its ubiquity, however, our knowledge concerning the local factors responsible for the development of nerve dysfunction in the patient with diabetes is scanty. This review is concerned with the clinical, electrophysiologic, histologic, and biochemical concomitants of diabetic distal symmetric polyneuropathy that appear to shed some light on the underlying pathogenetic mechanisms. Since the isolated single and multiple mononeuropathies associated with diabetes mellitus are thought to be a result, at least in part, of vascular lesions that result in ischemic neuropathy, such lesions will not be discussed.\

Method for Large-Scale Isolation of Pancreatic Islets by Tissue Culture of Fetal Rat Pancreas

Abstract: Detailed studies of the maturation of stimulus-secretion coupling of the pancreatic B-cell requires a supply of isolated fetal islets, which has so far been difficult to obtain. To overcome this problem we have maintained minced and mildly collagenase-digested fetal rat pancreatic glands (21.5 days gestational age) in tissue culture to enable degeneration of the acinar part, leaving the endocrine cells in an isolated and surviving state. Indeed, after 1 wk in culture there was a complete separation between acinar and endocrine cells with the appearance of numerous discrete islets and the disappearance or dedifferentiation of the exocrine cells. Isolated islets were either free floating or attached on top of a monolayer of fibroblast-like cells. Their number after 1 wk in culture was estimated as about 90 per explanted fetal pancreas and a total yield of about 5000 isolated islets was easily achieved. Both light arid electron microscopic examinations showed an excellent structural preservation with a marked predominance of well-granulated B-cells. Numerous islets of the same weight as that measured in cultured islets of adult rats were regularly found after 1 wk in culture. The insulin concentration of the cultured fetal islets was related to the glucose concentration of the growth medium. A similar relationship was found with respect to the insulin release in response to glucose. Thus, fetal islets cultured for 8 days in growth media containing 11.1 or 22.2 mM glucose showed a marked and significant insulin response to glucose in batch-type incubations at the end of the culture period. By contrast, the glucose stimulation of insulin release was insignificant in islets cultured at 5.5 or 2.8 mM glucose. When the culture period was confined to 1 day, there were no effects of glucose on the insulin release irrespective of the glucose concentration of the growth medium. It is concluded that the present technique for tissue culture of fetal rat pancreas makes it possible to isolate substantial amounts of fetal islets predominantly composed of B-cells. The transition in vitro from a poor glucose sensitivity to an adult-type insulin response indicates that the technique can be used in further detailed studies of the molecular mechanisms involved in the growth and development of the pancreatic B-cell.

Exercise and Diabetes Mellitus

Abstract: (All are verbatim summaries) Wood, P. D.; Haskell, W. L; Stern, M. P.; Lewis, S.; and Perry, C. (Stanford Univ. Sch. of Med., CA): Plasma lipoprotein distributions in male and female runners. Ann. N.Y. Acad. Sci. 307:748-63, 1977. Recent studies have shown a consistent association between relatively low plasma concentrations of high-density lipoprotein (HDL) cholesterol and increased risk of coronary heart disease. A cross-sectional comparison was made of the distribution of plasma lipids and lipoproteins in groups of 41 male and 43 female long distance runners versus larger control groups matched for age and sex, randomly selected from northern California towns. The runners showed modestly lower total cholesterol concentrations, while their triglyceride levels were only 50% of control. HDL-cholesterol was higher in runners than controls (75 ± 14 vs 56 ± 14 mg/100 ml for women; 64 ± 13 vs 43 ± 10 for men), while low-density lipoprotein cholesterol was lower (113 ±133 vs 124 ±34 for women; 125 ±21 vs 139 ±32 for men). All differences were statistically significant (p < 0.05), and only partially attributable to known factors other than high physical activity level. Since the runners were predominantly normotensive, relatively lean, and exclusively nonsmokers, they appear to constitute a remarkably favored group with respect to risk of cardiovascular disease. Issekutz, B. (Dept. of Physiol., Sch. of Med., Dalhousie Univ., Halifax, N.S.): Energy mobilization in exercising dogs. Diabetes 28 (Suppl. 1):39-44, 1979. The relative importance of the three major energy stores— adipose tissue, liver and muscle glycogen—was studied in dogs during prolonged exercise (slope 15%, speed 100 m/min). Using palmitate-C and 3-H-glucose, the rates of release of FFA (Ra-FFA) and that of hepatic glucose (Ra-G) were measured simultaneously. Glucose-C (U) was used to estimate the rate of glycogenolysis in the working muscle (M-GLY) by measuring both glucose and lactate specific DIABETES, VOL. 28, FEBRUARY 1979 163 EXERCISE AND DIABETES MELLITUS activity in the plasma. The ratio Ra-FFA/Ra-G decreases from about 1 to 0.6 during exercise and, at the end of a 3-h run, some 90% of the energy expenditure could have been covered by Ra-FFA and an additional 40% from CHO sources. Blocking the /3-receptors (propranolol) during exercise caused a sharp decrease of both Ra-FFA and M-GLY with a significant increase of the metabolic clearance rate (MCR) of glucose. Since Ra-G could not match the rise of MCR, blood glucose declined prematurely. When the infusion of the ^-antagonist preceded the run, it suppressed the exercise-induced rise of plasma cAMP and increased the rate of decline of plasma glucose. Blockade of the a adrenergic system did not yield consistent and interpretable results. It is concluded that the continuous stimulation of the /3 adrenergic system and not the elevated energy demand is directly responsible for the mobilization of both FFA and muscle glycogen. The former is stimulated by norepinephrine and the latter by epinephrine. The excessive flow of energy sources is an attempt to reduce the glucose uptake of the muscle and to prevent hypoglycemia for as long as possible. Pirnay, F.; Lacroix, M.; Mosora, F.; Luyckx, A.; and Lefebvre, P. (Inst. Provincial E. Malvoz, Dept. of Atomic and Molecular Physics and Div. of Diabetes, Inst. of Med., Univ. of Liege, Belgium): Glucose oxidation during prolonged exercise evaluated with naturally labeled C-glucose. J. Appl. Physiol. 43:258-61, 1977. Using naturally enriched C-glucose as metabolic tracer, the utilization of exogenous glucose ingested during muscular exercise was investigated. Four subjects walked on an uphill treadmill for two hours, and three others for four hours. The energy expenditure, close to fifty percent of the individual maximum VO2, varied from 1.9 to 2.1 I of 02/min, while the heart rate ranged between 142 and 165 beats/min. The subjects, who were on a mixed diet and who had fasted overnight, were given 100g of naturally labeled C-glucose. Following this intake, the expired CO2 became rapidly enriched in carbon 13. The increase was observed as early as 15 minutes after the oral intake, and reached a maximum within 1 to 2 hours, when utilization of exogenous glucose varied between 500 and 650 mg/min, and represented as much as 55% of the carbohydrate metabolism and 24% of the total energy expenditure. Wahren, J.; Felig, P.; Ahlborg, G.; and Jorfeldt, L. (Dept. of Clin. Physiol., Karolinska Inst. of the Serafimer Hosp., Stockholm, Sweden, and Dept. of Intern. Med., Yale Univ. Sch. of Med., New Haven, CN): Glucose metabolism during leg exercise in man. J. Clin. Invest. 50:271525, 1971. Arterial concentrations and net substrate exchange across the leg and splanchnic vascular bed were determined for glucose, lactate, pyruvate, and glycerol in healthy postabsorptive subjects at rest and during 40 min of exercise on a bicycle ergometer at work intensities of 400, 800 and 1200 kg m/min. Rising arterial glucose levels and small decreases in plasma insulin concentrations were found during heavy exercise. Significant arterial-femoral venous differences for glucose were demonstrated both at rest and during exercise, their magnitude increasing with work intensity as well as duration of the exercise performed. Estimated glucose uptake by the leg increased 7-fold after 40 min of light exercise and 10to 20-fold at moderate to heavy exercise. Blood glucose uptake could at this time account for 28-37% of total substrate oxidation by leg muscle and 75-89% of the estimated carbohydrate oxidation. Splanchnic glucose production increased progressively during exercise reaching levels 3 to 5-fold above resting values at the heavy work loads. Close agreement was observed between estimates of total glucose turnover during exercise based on leg glucose uptake and splanchnic glucose production. Hepatic gluconeogenesis—estimated from splanchnic removal of lactate, pyruvate, glycerol and glycogenic amino acids—could supply a maximum of 25% of the resting hepatic glucose production but could account for only 6-11% of splanchnic glucose production after 40 min of moderate to heavy exercise. It is concluded that: (a) blood glucose becomes an increasingly important substrate for muscle oxidation during prolonged exercise of this type; (b) peripheral glucose utilization increases in exercise despite a reduction in circulating insulin levels; (c) increased hepatic output of glucose, primarily by means of augmented glycogenolysis, contributes to blood glucose homeostasis in exercise and provides an important source of substrate for exercising

Chronic Hyperinsulinemia in the Fetal Rhesus Monkey: Effects on Fetal Growth and Composition

Abstract: The delivery of 19 U of insulin a day for 21 days to the rhesus monkey fetus, coupled with the permeability properties of the placenta, has made it possible to produce fetal hyperinsulinemia in the presence of euglycemia. Fetal plasma insulin concentrations of 3525 μU/ml were attained with no apparent effects on the mother. In fetal macrosomia, a 34% increase in body weight was observed above the expected weight for gestational age (466 vs. 348 g). Relative organomegaly, matched for gestational age of fetal weight, was seen in the hyperinsulinemic fetuses with enlarged livers, placentas, hearts, and spleens. Liver composition in the fetuses was only slightly affected by hyperinsulinemia. Glycogen concentration was elevated, but not sufficiently, to explain the relative hepatomegaly produced. The lipid, protein, DNA, and RNA concentrations were not affected by hyperinsulinemia. Based on the similar DNA concentrations and protein/DNA ratios observed in hyperinsulinemic and control groups, the hepatomegaly appears to be the result of insulin-stimulated hyperplasia and not of hypertrophy. In the presence of normal plasma concentrations of growth substrates, insulin in the subhuman fetus has been shown to be a growth-promoting hormone that has specific growth-stimulating effects.

Nonenzymatic glucosylation of serum proteins in diabetes mellitus.

Abstract: The extent of nonenzymatic glucosylation of serum protein in control and diabetic subjects was measured by a chemical procedure using thiobarbituric acid. A mean value of 0.81 (+/- 0.21 SD) nmol glucose per milligram serum protein was observed in the control group. Diabetics displayed elevated levels of glucosylated serum proteins, up to 4 nmol glucose per milligram protein. Glucosylation of serum protein correlated strongly with fasting blood sugar (r = 0.71), percent hemoglobin A1 (r = 0.79), and percent glucosylated albumin (r = 0.99). There was no overlap between control and diabetic groups, i.e., within 3 SD of the mean of controls. These studies indicate that the assay for glucosylated serum protein appears to be an especially sensitive indicator of the degree of hyperglycemia in diabetes.

Gastric Inhibitory Polypeptide Enhanced Lipoprotein Lipase Activity in Cultured Preadipocytes

Abstract: Fat feeding stimulated the release of gastric inhibitory polypeptide (GIP) without concomitant insulin secretion. Since antilipolytic effects of GIP have been demonstrated and the uptake of triglyceride fatty acid by adipose tissue postprandially is a process reciprocally regulated with lipolysis, a stimulatory role of GIP on adipose tissue lipoprotein lipase activity may be present. After cultured preadipocytes were incubated for 2 h with GIP, the release of lipoprotein lipase activity into the culture medium and the total cellular activity present in acetone-ether powders of cells were measured. GIP stimulated significant increases in the lipoprotein lipase activity released into the culture medium and in cells. A dose response relationship was strongest for the effect of GIP on the enzyme activity in extracts of acetone-ether powders of the cells. The increased lipoprotein lipase activity produced by GIP could provide a mechanisms for clearance of chylomicron triglyceride after feeding in man.

Severe hyperglycemia: effects of rehydration on endocrine derangements and blood glucose concentration.

Abstract: Diabetic ketoacidosis is associated with an excess secretion of counterregulatory hormones The effect of rehydration on these endocrine derangements before insulin administration is unknown Therefore, we measured the effect of rehydration with hypoosmolal fluid (220 mosmol/kg) on blood glucose (BG), immunoreactive insulin (IRI), immunoreactive C-peptide (IRCP), immunoreactive glucagon (IRG), human pancreatic polypeptide (hPP), growth hormone (GH), prolactin (PRL), cortisol, aldosterone, renin (PRC), epinephrine, norepinepnrine, and parathyroid hormone (PTH) in ketoacidotic diabetic patients [pH 703 ± 005 (SEM); n = 8] and in patients (n = 2) with nonketotic hyperglycemia (BG, 298 mmol/L and 468 mmol/L) The cumulative net fluid balance after rehydration was 4364 ± 690 ml Basal insulin was inappropriately low, and IRCP was below the normal range (15 ± 05 ng/ml) Serum osmolality fell during hypoosmolal rehydration (n = 9) from 335 ± 11 to 315 ± 9 mosmol/kg Rehydration with hypoosmolal fluid with bicarbonate added at a pH of less than 72 induced a fall in BG ranging from 61 mmol/L to 226 mmol/L, or of 167% to 798% of the initial BG level, as well as a decrease in plasma lactate and urinary glucose These effects were paralleled by a decrease in IRG, cortisol, epinephrine, norepinephrine, aldosterone, and PRC No fall in BG was seen in one patient whose dehydrated state was maintained by infusion of isotonic saline Low dose insulin treatment was initiated in all patients immediately when no further fall in blood glucose levels was achieved We conclude that rehydration improves the metabolic situation in severe diabetic hyperglycemia and ketoacidosis by reducing (a) the availability of counterregulatory hormones and (b) peripheral insulin resistance on a cellular level Thus, proper rehydration will support the beneficial action of simultaneous low dose insulin treatment in patients with severe hyperglycemia

Normalization of the Paradoxic Secretion of Glucagon in Diabetics Who Were Controlled by the Artificial Beta Cell

Abstract: Since it is important to elucidate the precise significance of pancreatic A-cell hypersecretion in the pathogenesis of diabetes mellitus, the change in the immunoreactive glucagon (IRG) response to 100 g oral glucose challenges was studied in diabetics whose blood glucose responses and plasma immunoreactive insulin concentrations (IRI) simulated those in normal subjects with the aid of the artificial beta cell system that we developed originally. In six nonobese adult-onset and four insulin-dependent diabetics whose blood glucose responses and plasma insulin concentrations after 100 g oral glucose load were made equivalent to those seen in normal subjects by the artificial beta cell, the glucagon release was similar to the response in normal subjects. In one insulin-dependent diabetic with high anti-insulin-binding capacity, the blood glucose response after an oral glucose challenge was not normalized by the artificial beta cell and the glucagon secretion was paradoxically increased. This fact suggested that the paradoxic rise in glucagon, seen in response to an oral glucose load in some diabetics, is secondary to insulin deficiency.

Physical training and glucose tolerance in middle-aged men with chemical diabetes.

Abstract: Mature onset of diabetes is an increasing problem in Western populations. A change in dietary habits and a lowered physical activity level may be contributing to this development. Both obesity and physical working capacity are related to glucose tolerance,and a high frequency of pathological oral glucose intolerance is also found among men who are unfit and obese.Middle-aged men who are normoglycemic but have a pathological oral glucose tolerance test (OGTT) have an increased risk for developing diabetes. Moreover, cardiovascular diseases are also more common among these men.In obese men the insulin level during OGTT was reduced by physical training.The question then arises whether middle-aged men with pathological OGTT and similar body weights as age-matched controls also can benefit from physical training. We present a summary of several studies still in progress that deal with this question.

Effects of Streptozotocin-induced Diabetes on Insulin Binding, Glucose Transport, and Intracellular Glucose Metabolism in Isolated Rat Adipocytes

Abstract: Insulin receptors and various aspects of glucose metabolism were studied in isolated adipocytes from insulin-deficient streptozotocin (STZ)-treated diabetic rats. Severe diabetes was induced by high dose (55 mg/kg) STZ administration and mild diabetes was induced by low dose (40 mg/kg) STZ treatment. The high dose STZ group (morning plasma glucose level of 511 ± 32 mg/dl) became markedly catabolic and gained weight at a rate of only 0.6 ± 0.9 g/day as compared with 6.7 ± 0.8 g/day for controls. The low dose STZ group gained weight at a near normal rate (5.8 ± 0.7 g/day) despite modest hyperglycemia (morning plasma glucose 214 ± 36 ng/100 ml) and hypoinsulinemia. Insulin binding to receptors was increased 25% in the low dose group due to greater receptor capacity with no change in affinity and was increased 105% in the high dose group due to enhanced receptor affinity and capacity. Glucose transport activity was decreased in adipocytes from the diabetic animals, and, in addition, all aspects of intracellular glucose metabolism studied were depressed. These effects were greatest in the high dose group. In summary, (a) in severely diabetic, catabolic animals, insulin binding to receptors is increased due to enhanced receptor capacity and affinity; in mildly diabetic rats only receptor capacity is increased; (b) glucose transport activity and intracellular pathways of glucose metabolism are impaired in insulin-deficient diabetic animals, most likely due to hypoinsulinemia; and (c) the cellular insulin resistance of insulin-deficient diabetes is due to multiple defects in effector systems distal to the insulin receptor.

The effect of physical training on glucose tolerance and plasma lipids in maturity-onset diabetes.

Abstract: In a general population, physical fitness is inversely associated with a variety of risk factors for coronary artery disease. These factors include heart rate, body weight, adiposity, systolic blood pressure, glucose tolerance and serum cholesterol, and triglycerides." In much the same way, high-density lipoprotein cholesterol is elevated in physically fit individuals, and when low, is associated with an increased incidence of atherosclerotic vascular disease.In previously untrained subjects, physical training regimens have usually been shown to decrease plasma triglycerides" and cause a shift in cholesterol from lowto high-density lipoproteins.Training programs produced only a modest improvement in glucose tolerance, if any; however, less insulin is required for improvement, thus suggesting enhanced insulin sensitivity.'' It is not known whethertraining enhances insulin sensitivity in patients with diabetes and whether this results in a greater improvement in glucose tolerance than is reported in control subjects. In an attempt to answer these questions, we assessed the effects of physical training on glucose tolerance and serum insulin in several patients with maturity-onset diabetes. This report describes the effects of 3-6 months of physical training on a bicycle ergometer in six middle-aged men in whom diabetes was associated with fasting hyperglycemia and deficient insulin secretion. The effect of the training regimen on plasma triglycerides and cholesterol is also described.

Normalization of the growth hormone and catecholamine response to exercise in juvenile-onset diabetic subjects treated with a portable insulin infusion pump.

Abstract: The plasma growth hormone, epinephrine, and norephinephrine responses to cycle ergometer exercise (15 min at 1 W/kg) were examined in 10 juvenile-onset, insulin-dependent diabetics (ages 10–32 yr) during conventional insulin treatment and after 7 and 14 days of treatment with a portable subcutaneous insulin infusion system that normalizes plasma glucose. During conventional insulin treatment (mean plasma glucose, 205 ± 22 mg/dl), the growth hormone response to exercise was sevenfold greater than in normal controls (P

Plasma vasopressin in uncontrolled diabetes mellitus.

Abstract: Concentrations of the antidiuretic hormone, arginine vasopressin, were measured in 28 patients with severe hyperglycemia to determine if abnormalities in hormonal regulation of water excretion could contribute to the extreme dehydration of uncontrolled diabetes mellitus. Vasopressin levels were markedly elevated in both nonketotic and ketotic patients, indicating that vasopressin deficiency plays no role in the polyuria that accompanies hyperglycemia. Instead, the observed increases in vasopressin represent an ineffective effort to conserve water in the face of an overwhelming solute diuresis caused by the glucosuria. The reasons for such marked elevations in plasma vasopressin in these diabetic patients are multifactorial. Both groups of diabetic patients had evidence of hypovolemia, which was sufficient in magnitude to stimulate vasopressin release. Furthermore, nausea provided an independent stimulus to vasopressin secretion in many patients. Osmotic stimulation might have resulted from the large fraction of unidentified plasma solutes, but this factor alone was not sufficient to explain the markedly increased concentrations of vasopressin. Whether such elevations in vasopressin could have metabolic and/or hemodynamic effects in uncrontrolled diabetes remains to be established.

High Prevalence of Diabetes in Young Pima Indians: Evidence of Phenotypic Variation in a Genetically Isolated Population

Abstract: Medical records of the Pima Indian population aged 0–24 yr were reviewed for a diagnosis of diabetes before initiation of glucose tolerance testing. None of 1556 subjects below age 15, but 6 of 657 aged 15–24, had a previous diagnosis. Of the six known diabetics, five had been treated with insulin and four had had ketoacidosis. Subsequently, plasma glucose levels were determined after a 75-g oral carbohydrate load in 1712 subjects aged 5–24 yr, which is about 78% of the eligible population. Previously diagnosed diabetes and asymptomatic hyperglycemia were more frequent in subjects 15–24 yr old than were reported in other populations. Glucose intolerance in young Pimas was associated with obesity. In Pima offspring, the presence of diabetes in both parents was related to glucose tolerance in those above but not below the age of 15 yr. Both asymptomatic hyperglycemia and insulin-requiring diabetes occurred frequently in young Pimas, suggesting that these syndromes represent the clinical spectrum of a single disease in the Pima Indian.

Glomerular Basement Membrane Metabolism in the Diabetic Rat: In Vivo Studies

Abstract: 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 < 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.

Insulin Resistance Caused by Massive Degradation of Subcutaneous Insulin

Abstract: Severe resistance to subcutaneous insulin but sensitivity to intravenous insulin persisted for 15 months in a 17-year-old diabetic girl. Heat-labile insulin-degrading activity was present in the patient's ketotic sera and in the 100,000 g fraction (soluble fraction) of adipose tissue. Serum-degrading activity was not inhibited by N-ethylmaleimide. The soluble fraction also degraded glucagon and B chain but not growth hormone or myoglobin. It was inhibited by incubation with the patient's nonketotic sera, normal sera, or Trasylol. Glutathione-insulin-transhydrogenase (GIT) activity was 66% of normal. The biopsy of adipose tissue at remission showed a normal level of insulin- and glucagon-degrading activity. The activity was eluted from Sephadex G200 as a single peak and had properties consistent with those of the insulin-specific protease (ISP). The increased degrading activity present during insulin resistance had properties not shared with ISP, suggesting the presence of an uncharacterized protease.

Principles of nutrition and dietary recommendations for individuals with diabetes mellitus: 1979. American Diabetes Association.

Abstract: In 1971 the Committee on Food and Nutrition of the American Diabetes Association published a special report entitled \"Principles of Nutrition and Dietary Recommendations for Patients with Diabetes Mellitus.\" Publication of the report was prompted by new and emerging information regarding effects of diet on blood glucose concentration in diabetic persons and by information relating aberrations of blood lipid levels, particularly cholesterol, with atherosclerosis in the general population. The present report updates these original principles and recommendations and is based on information accumulated since 1971.

Catecholamines and exercise.

Abstract: NOREPINEPHRINE Rise in plasma norepinephrine is correlated with an increase in heart rate, provided that the latter is mediated by the sympathetic nervous system. This is the case during exercise, with the exception of the initial rise in heart rate, which is due to withdrawal of vagal tone. Correspondingly, there is no rise in plasma norepinephrine during light work. The increase in heart rate that occurs when one stands up is mediated by sympathetic nerves, and plasma norepinephrine increases. Figure 1 shows the relationship between rise in heart rate and rise in plasma norepinephrine upon standing and during exercise. When one stands up, a part of the increase in plasma norepinephrine is independent of any change in heart rate, but there is a further rise in norepinephrine that is correlated to the rise in heart rate. During exercise there is no rise in plasma norepinephrine provided the increase in heart rate at steady state is less than approximately 25 beats/min. During an exercise requiring higher increases in heart rate, these increases are paralleled by increases in plasma norepinephrine. The greater rise in plasma norepinephrine when standing as compared with the rise in norepinephrine during exercise (with a comparable increase in heart rate) is explained, in part, by the different autonomic nervous mechanisms in-

Comparison of a Colorimetric Assay for Glycosylated Hemoglobin with Ion-exchange Chromatography

Abstract: Because levels of glycosylated hemoglobin (GHb) are increased in diabetes and reflect the previous metabolic control, clinicians and clinical investigators are finding increasing applications for measurements of GHb in diabetic patients. We report the characterization of a colorimetric assay procedure for GHb and compare its performance with that of a commonly used assay by ion-exchange chromatography. Although results of GHb determination by both methods correlate highly (r = 0.946, P less than 0.001), the two procedures estimate different glycosylated fractions. The colorimetric procedure is nonstoichiometric, requiring careful standardization of assay conditions, including the concentration of total hemoglobin in the assayed aliquot, to achieve precision and permit comparison of results. We characterized the effect of storage of hemolysates or packed erythrocytes on the subsequent determination of GHb by both methods. Determinations of GHb by the colorimetric method, but not by column chromatography, are reproducible on hemolysates or packed erythrocytes on the subsequent determination of GHb by both methods. Determinations of GHb by the colorimetric method, but not by column chromatography, are reproducible on hemolysates or packed erythrocytes stored frozen for at least 5 mo. A unique advantage of the colorimetric procedure is the capability to estimate GHb levels when variant hemoglobins, including fetal and sickle hemoglobins, are present.

Capillary basal laminar thichness in diabetic human myocardium.

Abstract: Biopsied myocardial tissue was obtained from 24 patients electing coronary arterial bypass surgery who were divided into three groups: chemical diabetics (CD) with normal fasting blood sugar levels and incidentally encountered elevated glucose levels after sugar loading; overt diabetics (OD) requiring insulin treatment; and euglycemic, nondiabetic patients (ND) serving as a control group. Specimens from the left anterior apical segment of the heart were processed for ultrastructural examination, with special emphasis on determining capillary basal laminar thickness with the aid of morphometric techniques. Results of this study indicate that (1) a statistically significant increase in basal laminar thickness is evident in myocardial tissue of OD patients; (2) incipient alterations in laminar width are demonstrable in the CD group; (3) the predominant morphologic abnormalities, which we have examined in the parenchymal tissue of the biopsied hearts, namely myocardial hypertrophy and interstitial fibrosis, are present to a comparable degree in all three groups of patients; and (4) the average thickness of basal laminae around myocardial capillaries tends to be narrower compared with measurements reported in other tissue compartments.

Opposite Effects of Insulin and Glucagon in Acute Hormonal Control of Hepatic Lipogenesis

Abstract: Conditions for the isolation of rat hepatocytes that are responsive to insulin with regard to fatty acid synthesis were explored. Cells prepared according to the procedure of Ingebretsen and Wagle require the presence of fetal calf serum for insulin expression. Cells isolated by the Seglen method are the preparation of choice, since they respond to insulin in a simple, well-defined medium and, moreover, show much higher basal rates of fatty acid synthesis. In the latter cells isolated from fed male rats, the rate of fatty acid synthesis, as determined by tritium incorporation from [3H]H2O at 37 degrees C, is enhanced within 30 min after addition of insulin to the incubation medium; with glucagon, it is depressed. In the presence of insulin, the cellular content of malonyl coenzyme A is noticeably increased, whereas the concentrations of pyruvate, lactate, and citrate are not markedly affected. Glucagon, on the other hand, decreases the concentrations of all four intermediates. The activity of acetyl-CoA carboxylase is stimulated and depressed after addition of insulin and glucagon, respectively. In all conditions tested, the activity of acetyl-CoA carboxylase correlates with the rate of fatty acid synthesis, which in turn correlates with the cellular level of malonyl-CoA.

Effect of a High Carbohydrate Diet on Insulin Binding to Adipocytes and on Insulin Action in vivo in Man

Abstract: We studied the effects of short-term (5 days) and long-term (2 wk) high carbohydrate (75%) feedings on insulin binding to isolated adipocytes and insulin sensitivity in vivo in normal subjects. Ingestion of the high carbohydrate diet led to daylong hyperinsulinemia in both short- and long-term groups. Insulin binding to isolated adipocytes was decreased in both groups; in the short-term groups this decrease in insulin binding was caused by a decrease in the receptor affinity, whereas in the long-term group it was caused by a decrease in receptor number. On the other hand, despite this decrease in insulin binding, total in vivo insulin sensitivity was markedly improved in both groups. In conclusion, (1) the short-term adaptive response of the insulin receptor is a decrease in binding affinity whereas the long-term response is a decrease in receptor number, (2) sustained and chronic hyperinsulinemia can lead to a decrease in the number of cellular insulin receptors, (3) high carbohydrate diets lead to a general increase in insulin's ability to promote glucose removal from plasma, and (4) the paradox of enhanced insulin sensitivity in the face of decreased insulin binding can be explained if high carbohydrate diets also lead to an increase in the activity of steps in glucose metabolism distal to the insulin receptor.

Glycosylated Hemoglobins: Increased Glycosylation of Hemoglobin A in Diabetic Patients

Abstract: The components of the hemoglobin-A1 fraction--hemoglobins A1a--c--arise from nonenzymatic glycosylation of hemoglobin A at the beta-chain N-terminal amino groups and can be resolved from hemoglobin A by cation exchange chromatography. Glycosylation can also occur at the alpha-chain N-terminals as well as the epsilon-amino groups of lysine residues of both alpha- and beta-chains; this results in glycosylated species appearing in the hemoglobin-A fraction. In this study, we determined the extent of hemoglobin-A glycosylation using a colorimetric chemical method specific for the detection of ketoamine-linked hexoses in proteins. We demonstrate increased glycosylation of the main hemoglobin-A fraction in diabetic patients, which correlates significantly (r = 0.72, P less than 0.001) with the hemoglobin-A1 percentage determined by column chromatography in the corresponding hemolysates. This finding provides the basis for the application of this chemical procedure to the measurement of total glycosylation of hemoglobin.

The Correlation of Arteriosclerosis Obliterans with Lipoproteins in Insulin-Dependent and Non-Insulin-Dependent Diabetes

Abstract: Risk factors for arteriosclerosis, such as age, duration of diabetes, sex, and plasma lipoprotein levels, were correlated with the presence of arteriosclerosis obliterans (ASO) as determined by noninvasive methods in 485 of 506 subjects studied with diabetes mellitus. The diabetic subjects were separated into two major groups for analysis: insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM). The NIDDM group was subdivided into those treated by diet (NIDDM-D), sulfonylureas (NIDDM-S), and insulin (NIDDM-I). Overall, lipoprotein levels in the diabetics were higher than in an age- and sex-adjusted nondiabetic group. Cholesterol levels were elevated in all females and HDL cholesterol levels were depressed in diet- and sulfonylurea-treated females. VLDL levels were most elevated in diet-treated subjects followed by sulfonylurea-treated subjects; VLDL levels in insulin-treated subjects were not elevated. The prevalence of ASO is related to different factors in each group. In IDDM and NIDDM-I subjects, VLDL triglyceride, LDL cholesterol, and duration of diabetes or age are important risk indicators. By contrast, in NIDDM-S subjects, age alone is the significant risk indicator, and in NIDDM-D subjects, inverse HDL cholesterol correlated with ASO. While males have a higher prevalence of ASO than females, the difference is not statistically significant in any group. Other possible factors, such as hypertension, smoking, and obesity, were not considered in this initial analysis.

Long-term continuous intravenous insulin therapy with a portable insulin dosage-regulating apparatus.

Abstract: A portable insulin dosage-regulating apparatus (PIDRA) was used with five volunteer diabetic subjects for periods ranging from 1 wk to more than 3 months to explore the possibilities of achieving near normoglycemic control over long time periods with such an apparatus. PIDRA consists of a matchbox size pump with insulin reservoir and a pocket size electronic control box. It can infuse a preprogrammed basal rate of insulin plus externally manipulated supplementary doses in rectangular profiles. The quality of blood glucose control was monitored with the Miles Biostator and through self-testing by the patient in the outpatient phases. Under inpatient conditions, the relatively simple PIDRA insulin administration profile was almost as effective in achieving normoglycemia as the Biostator, and good control could be maintained over long periods of time. The apparatus allows considerably greater ease in variation of insulin dosage with less risk of hypoglycemic epidoses as compared with conventional subcutaneous injections. Several technical problems remain to be solved, but it is concluded that PIDRA represents a viable alternative as a means of achieving tight control, at least as a step toward the goal of an implanted glucose-contingent insulin infusion system.

Fatty Acid Desaturation in Experimental Diabetes Mellitus

Abstract: Microsomal fatty acid desaturation is defective in streptozotocin-induced experimental diabetes. This defect is correctable by insulin treatment. The electron transport chain needed for microsomal fatty acid desaturation was studied in liver microsomes of streptozotocin diabetic rats, and the defect was localized to the terminal desaturase enzyme. Cytochrome b5 levels were elevated in the face of decreased fatty acid desaturation and returned to normal after 48 h of insulin treatment; 2 U of regular insulin every 6 h for 24 h repaired the fatty acid desaturation defect, while 0.5 U failed to correct the defect. Both the delta 6 and delta 9 desaturase defects (linoleic acid and stearoyl-CoA desaturation) required similar amounts of insulin and periods of time for correction, although these are different enzymes. This is consistent with the desaturation defect being due to a protein synthetic effect. Diabetic rats treated twice daily with injections of 4 U of NPH insulin showed a "super" repair of their desaturase defect by 48 h: delta 9 desaturase activity increased eight times over control activity, while delta 6 desaturase activity increased two and one-half times over control activity. This, together with the fact that delta 6 desaturase activity in diabetes (64% of control) is altered less than is delta 9 desaturase activity (22% of control), indicates that delta 6 desaturase enzyme activity is less responsive to insulin than is delta 9 desaturase enzyme activity. The physiologic significance of altered fatty acid desaturation in diabetes mellitus is unknown.

Impaired Cardiovascular Responses to Graded Exercise in Diabetic Autonomic Neuropathy

Abstract: Six juvenile diabetics [age, 31 ± 2 yr (mean and SEM); duration of diabetes, 15 ± 4 yr] with signs of autonomic neuropathy (decreased beat-to-beat variation in heart rate during deep breathing) and seven control patients of similar age (27 ± 1 yr) and duration of diabetes (14 ± 2 yr) performed graded exercise oh an ergometer cycle. Resting heart rate was higher and the increase in heart rate at the lowest work load (50 W) was diminished in patients with autonomic neuropathy compared with control patients ( P < 0.001), indicating a vagal defect. The relationships in autonomic neuropathy between heart rate and systolic blood pressure, respectively, and relative work load (expressed as oxygen uptake — in percent—of individual maximal oxygen uptake) were identical with previous findings in normal subjects during beta-adrenergic receptor blockade, indicating impaired sympathetic activity. Maximal heart rate was 157 ± 9 min−1 in autonomic neuropathy and 181 ± 4 in controls, P < 0.05; maximal systolic blood pressure was 179 ± 11 mm Hg and 197 ± 5, respectively. The greatest tolerable work load was significantly less in patients with autonomic neuropathy (125 ± 13 vs. 161 ± 9 w, P < 0.05). Similarly, maximal oxygen uptake was reduced (1.68 ± 0.21 vs. 2.78 ± 0.18 L/min, 25 ± 3 vs. 38 ± 2 ml/min/kg, P < 0.005). In conclusion, diabetics with decreased beat-to-beat variation in heart rate displayed signs of cardiovascular dysfunction of parasympathetic as well as sympathetic origin during graded exercise.

Higher Levels of Erythrocyte Membrane Microviscosity in Diabetes

Abstract: Significantly higher levels of erythrocyte membrane microviscosity (MV) [η: 5.22 ± 0.17 (4.70–5.92), mean ± SD (range), poise, N = 67, P N = 22]. No significant differences in MV existed between males and females, nor was MV significantly correlated with diabetic age, duration of diabetes, plasma cholesterol, cholesterol/phospholipid ratios, and plasma lecithin :cholesterol acyltransferase activities. No significant difference in MV was observed between groups with or without diabetic retinopathy. There was, however, significantly higher MV [5.29 ± 0.19 (5.00–5.92), N = 20, P 140 mg/dl than that [5.19 ± 0.15 (4.70–5.46), N = 47] in the group with FBG