Plasma levels of apoprotein B in patients with diabetes mellitus: the effect of glycemic control

Patients with diabetes mellitus often exhibit abnormalities in plasma lipoprotein concentrations. We have examined the effect of glycemic control (as assessed by hemoglobin A1 levels) on the concentrations of plasma lipoproteins and apoproteins in 109 patients with type I diabetes mellitus. HbA1 levels showed positive correlations with plasma LDL-cholesterol levels (r = 0.31; P less than 0.002) and triglyceride levels (r = 0.41; P less than 0.002), but not with HDL-cholesterol levels. The strongest correlation was between HbA1 and plasma levels of apoprotein B (r = 0.57; P less than 0.001). We have also examined the effect of long-term improvement in glycemic control (achieved with insulin infusion pump therapy) on plasma lipoproteins in six patients with type I diabetes. Patients were followed for 5 to 12 months, with mean (+/- SD) HbA1c levels decreasing from 11.4 +/- 2.5 to 9.1 +/- 1.8. Most, but not all, patients showed reduction in plasma LDL-cholesterol levels and increase in plasma HDL-cholesterol levels, but these did not reach statistical significance. Only the decrease in plasma apo B levels was statistically significant (from 112 +/- 38 mg/dL before pump therapy to 91 +/- 33 mg/dL at the end of the follow-up, P less than 0.05). We conclude that glycemic control plays an important role in regulating the levels of plasma LDL-cholesterol and triglycerides in patients with type I diabetes. Apoprotein B is a particularly sensitive indicator to alterations in glycemic control. It is possible that tight glycemic control may have "antiatherogenic" effects through reduction of apo B levels.

In vivo chloroquine-induced inhibition of insulin degradation in a diabetic patient with severe insulin resistance

We report on a 26-yr-old patient with an 11-yr history of insulin-dependent diabetes mellitus who exhibited insulin resistance with a requirement of up to 15,000 U of intravenous (i.v.) insulin/day. Attempts to diminish her insulin requirement by administration of sulfated insulin or Trasylol were unsuccessful, with the patient remaining resistant to subcutaneous (s.c.) and i.v. administration of pure pork insulin. Chloroquine phosphate therapy (500 mg twice a day) resulted in a decreased requirement for i.v. insulin (700 U/day as compared with the pretreatment requirement of 8400 U/day). Accelerated insulin degradation in s.c. fat tissue of the patient before treatment with chloroquine was demonstrated. This activity was decreased by 64% during chloroquine therapy. Inhibition of insulin degrading activity (IDA) during chloroquine therapy was associated with reductions in the leukocyte lysosomal enzymes alpha-galactosidase and hexosaminidase-A but not hexosaminidase-B and beta-glucuronidase. This study constitutes the first reported use of chloroquine for treatment of insulin resistance as a result of accelerated insulin degradation, and it provides evidence of the effectiveness of this agent in this rare condition.

The effects of blood glucose testing versus urine sugar testing on the metabolic control of insulin-dependent diabetic children

Glycosylated hemoglobin A1c was measured in 43 insulin-dependent diabetic children before and after training in blood glucose testing. These measurements were compared with those obtained from a group of matched controls who tested urine sugars for the same period. Mean HbA1c measurements for the blood glucose testing group were significantly improved at 6 mo after training in blood glucose testing, and were significantly lower than those measured in the urine sugar testing group. However, HbA1c levels in the blood glucose testing group were well above levels for nondiabetic persons, and were generally higher than those reported for adult insulin-dependent diabetic persons following training in blood glucose testing. Explanations for this difference were considered. It was noted that 81% of the trained children accepted and continued to use blood glucose testing for at least 9 mo after training.

Persistent leucine sensitivity following partial pancreatectomy and diazoxide treatment. Therapeutic response

Hyperinsulinemic hypoglycemia secondary to nesidioblastosis persisted in a 4-year-old girl despite a 95% pancreatectomy and high-dose diazoxide treatment. Current literature suggests that dietary treatment, specifically protein restriction, of patients who are receiving diazoxide is ineffective and that further surgical pancreatectomy is required. However, in this patient, marked leucine sensitivity was demonstrated and a subsequent reduction in leucine intake eliminated hypoglycemia and the need for total or nearly total pancreatectomy. Therefore, dietary alteration should be considered in some patients with hyperinsulinism as an adjunct to other medical treatment.

Altered glucose tolerance, insulin response, and insulin sensitivity after massive weight reduction subsequent to gastric bypass

We have studied an otherwise normal group of morbidly obese subjects and compared them with patients who had experienced massive weight loss after loop gastric bypass. Compared to normal controls (NLCs), morbidly obese control patients (OBCs) had abnormal glucose tolerance curves (after glucose ingestion), elevated basal insulin levels, and increased plasma insulin concentrations, suggesting insulin insensitivity. The latter has been corroborated by the measurement of decreased insulin binding in these patients. Postoperative (PO) patients were hyperglycemic after taking oral glucose, but all PO patients had a rapid decrease in plasma glucose concentration, half reaching hypoglycemic levels. PO basal insulin levels and insulin receptor number were not statistically different from those in NLCs, indicating up-regulation of insulin receptors (and therefore, increased insulin sensitivity) postoperatively. Hyperinsulinemia seen in the PO group (greater than that in OBCs, P less than 0.001) after administration of oral glucose occurred simultaneously with a doubling of plasma concentration of gastric inhibitory polypeptide. Massive weight loss in patients after gastric bypass was accompanied by an improvement in insulin receptor number, basal hyperinsulinemia, and glucose tolerance. In addition, postoperative patients demonstrated symptomatic reactive hypoglycemia which may have resulted from the hyperinsulinemia seen subsequent to ingestion of glucose.

The natural history of retinopathy in insulin-dependent juvenile-onset diabetes

We determined the cross-sectional natural history of retinopathy by prospective study of 461 insulin-dependent juvenile-onset diabetics. In so doing, we compared the sensitivity of ophthalmoscopy, photography, and fluorescein angiography in detecting retinopathy. Photography was far more reliable than ophthalmoscopy in detecting early retinopathy and equivalent to angiography. Retinopathy was not present at diagnosis of diabetes. After a lag period, the prevalence of retinopathy rose in sigmoidal fashion, reaching 50% at just over seven years duration, and asymptotically approaching 90% at 17--50 years. Proliferative retinopathy was first seen at 13 years duration, and its prevalence rose to 26% at 26--50 years. From the natural history we computed the dimensions of a proposed clinical trial to test the effect of tight metabolic control in prevention of retinopathy.

Effect of blood glucose control on retinal vascular permeability in insulin-dependent diabetes mellitus

Thirteen patients were instructed in a technique of self-management of insulin-dependent diabetes mellitus, using multiple home-monitored blood glucose determinations and multiple injections of regular insulin in conjunction with once-daily Ultra Lente insulin. Hemoglobin A1c and quantitative fluorescein fluorophotometry were used to assess blood glucose control and retinal permeability, respectively. In those patients achieving normal blood glucose control, retinal vascular leakage was statistically identical to that of a nondiabetic control population. In those patients less well controlled, retinal permeability did not differ statistically from values observed in a population of insulin-dependent diabetic patients under "standard" control. It is concluded that with "tight" control of blood sugar and normalized A1c hemoglobin, retinal permeability similarly is normalized.

Effect of intact parathyroid hormone on hepatic glucose release in the dog

The liver has been shown to remove parathyroid hormone (PTH) from its arterial circulation by a mechanism that is selective for the intact form of the peptide (PTH 1-84). The present studies demonstrate that PTH has biologic effects on the liver in vivo. Bovine PTH 1-84 stimulated hepatic glucose release in dogs with indwelling hepatic vein catheters from basal values of 31+/-8 to 68+/-9 mg/min per kg after bolus injections of PTH. The effect on hepatic glucose release was apparent by 5 min and persisted for the 80 min of observation. The NH(2)-terminal PTH fragment (syn b-PTH 1-34) had no effect. Bovine PTH 1-84 administered in doses designed to produce circulating levels of immunoreactive PTH similar to the endogenous levels observed in uremic dogs also increased the incorporation of (14)C from infused [(14)C]alanine into glucose, and increased estimated hepatic uptake of both chemical and [(14)C]alanine, while increasing hepatic glucose release. Thus, administration of "physiologic levels" of b-PTH 1-84 stimulated hepatic glucose release in part through increased gluconeogenesis in vivo, whereas syn b-PTH 1-34 had no demonstrable effect. Circulating levels of insulin rose after PTH administration, an increase which presumably represents a secondary response to the rise in glucose release. These results suggest that the liver is a target organ of PTH, and that PTH might potentially alter carbohydrate metabolism during hypersecretion. They also suggest that hepatic uptake of PTH may be related in part to production of a specific biologic effect rather than just simple peptide degradation.

Vitreous fluorophotometry in juvenile-onset diabetes mellitus

Vitreous fluorophotometry was carried out in 99 juvenile-onset, insulin-dependent diabetics and 31 control subjects. The mean vitreous fluorescein concentration one hour after intravenous administration of fluorescein, 7 mg/kg, was 5.4 +/- 0.3 ng/ml (mean +/- SEM) for controls and 9.5 +/- 0.4 ng/ml for diabetics (P less than .005). Diabetic patients with or without background retinopathy, when randomly matched for age or duration of their disease, had similar vitreous fluorophotometry measurements. The break-down of the blood-retinal barrier to fluorescein appears to be the earliest detectable ocular abnormality of diabetes.

Quantitative vitreous fluorophotometry. A sensitive technique for measuring early breakdown of the blood-retinal barrier in young diabetic patients

Vitreous and aqueous humor fluorescein concentrations were measured one hour after graded intravenous fluorescein was given to 20 juvenile diabetics, ages 20 to 40, with and without retinopathy, and to 12 controls of similar age. Vitreous fluorescein concentrations were significantly higher in diabetics, indicating breakdown of the blood-retinal barrier. Mean vitreous fluorescein values were 10.66 +/- 0.65 for the diabetics and 4.28 +/- 0.37 ng./ml. for the controls. Breakdown of the blood-retinal barrier was also confirmed in diabetics under the age of 20 without retinopathy. The blood-aqueous barrier was similarly altered in diabetics. Vitreous fluorophotometry quantitatively measures breakdown of the blood-retinal barrier, possibly the earliest detectable ocular vascular abnormality in juvenile diabetic patients.

Cholinergic blockade in reactive hypoglycemia

The effects of cholinergic blockade on the plasma glucose and insulin responses during oral and intravenous glucose administration were studied. Propantheline (30 mg.) was given by mouth 45 minutes before standard glucose tolerance testing to produce symptomatic chollinergic blockade. In 10 normal subjects a flattening of the over-all plasma glucose response to oral glucose was observed compared with the control test, whereas insulin secretion was not different. In seven patients with repeated episodes of symptomatic reactive hypoglycemia, cholinergic blockade eliminated both symptomatic and chemical hypoglycemia in each, raising the mean nadir glucose from 44 +/- 4 mg./dl. to 84 +/- 8 mg./dl. (p less than 0.01) and significantly reducing insulin secretion. In contrast, following intravenous glucose challenge, cholinergic blockade produced no significant difference in the rate of glucose utilization or insulin secretion in either group. These results are compatible with the hypothesis that excessive vagal stimulation may contribute to the hypoglycemia seen in patients with reactive hypoglycemia but suggest that the predominant effect is on the gastrointestinal tract rather than on pancreatic islets directly. These studies confirm that anticholinergic drugs may be useful adjuvants in treating these patients.

Apolipoprotein B levels and altered lipoprotein composition in diabetes

Hyperlipoproteinemia is found in only 25 to 50 per cent of persons with diabetes. However, carbohydrate, lipid and lipoprotein metabolism are so closely related that one would expect some alterations in lipoprotein metabolism in nearly all diabetic subjects. We wondered whether the metabolism of lipoproteins in normoUpemic diabetic patients was normal and whether the metabolism of lipoproteins in subjects with hyperlipoproteinemia and diabetes differed from those without diabetes. As a first approach to these questions, the levels of lipoprotein lipids and apoUpoproteins were determined in ninety-seven diabetics and seventy-two nondiabetics, and lipoprotein compositions were computed. Among those with diabetes, seventy-one were normoUpemic—twelve were type Ila and fourteen were type IV. In each of the diabetic groups, low density and high density lipoproteins were enriched in triglyceride (p < 0.01). These alterations in lipoprotein composition were not accounted for by differences in treatment modality, sex, race, age, or ponderal index. Thus the presence of diabetes itself appears to result in altered low and high density lipoprotein compositions. The mechanism(s) for the changes in the high density lipoproteins is (are) unknown, but in light of present knowledge the presence of triglyceride-enriched LDL could mean that a less dense moiety of low density lipoproteins may be accumulating in diabetic plasma, and this could result from altered rates of turnover of ApoB containing lipoproteins. Of course appropriate studies are needed to confirm this formulation.