Influence of glycemic control on interaction of very-low- and low-density lipoproteins isolated from type I diabetic patients with human monocyte-derived macrophages.

The VLDL and LDL fractions were isolated from 29 patients with type 1 diabetes at the time of admission to the hospital to restore glycemic control and again at discharge. These lipoprotein fractions were incubated with human monocyte-derived macrophages, and the rates of macrophage CE synthesis were determined. The rates of CE synthesis in human macrophages were significantly greater (P less than 0.005) when incubated with VLDL isolated from type I diabetic patients before compared with after glycemic control was attained and averaged 1.84 +/- 0.52 and 1.09 +/- 0.27 nmol (1.20 +/- 0.34 and 0.71 +/- 0.18 micrograms) [14C]cholesteryl oleate synthesized.mg cell protein-1 x 20 h-1, respectively. In contrast, when LDL isolated from the same patient during the same period was incubated with human macrophages, the rates of cellular cholesteryl ester synthesis did not differ significantly and averaged 4.23 +/- 1.26 and 3.91 +/- 0.96 nmol (2.75 +/- 0.82 and 2.55 +/- 0.63 micrograms) [14C]cholesteryl oleate synthesized.mg-1 cell protein.20 h-1, respectively. There was a significant increase in the total cholesterol content of VLDL isolated before glycemic control compared with that isolated after glycemic control was attained (P less than 0.05) resulting from a significant increase in the FC and CE (P less than 0.05) contents of these VLDL particles. There was a significant decrease in the ratio of FC to PL in VLDL, but not LDL, isolated after glycemic control (P less than 0.05). The percentage of apoE in VLDL was significantly decreased (P less than 0.05) after glycemic control was attained.(ABSTRACT TRUNCATED AT 250 WORDS)

Predicting insulin requirements for a portable insulin pump using the Biostator. Evidence for reversible insulin resistance in poorly controlled type I diabetics.

Glycemic control was achieved in 14 patients with insulin-dependent diabetes mellitus (IDDM) by 36-48-h treatment with a recently marketed clinical model, Biostator glucose controller (Life Science Instruments, Miles Laboratories, Elkhart, Indiana). Control was maintained by continuous subcutaneous insulin infusion with a portable pump, programmed using infusion profiles from the Biostator. Control of glycemic excursion with the Biostator was variable among patients. This control, reflected by the M-value or a blood glucose index (mean of pre-, peak, and 2-h postmeal levels for four meals) of each patient, correlated directly with their prior glycemic control, as assessed by hemoglobin A1c (HbA1c) level (r = 0.66, P less than 0.01 and r = 0.82, P less than 0.005, for M-value and blood glucose index, respectively). Total insulin infused by the Biostator/24 h overpredicted the subcutaneous infusion dose required on day 2 of pump treatment (183 +/- 11%, P less 0.001). Therefore, these data were not used to program the portable pump. Instead, total insulin dose was estimated using a dietary glucose/insulin (G/I) ratio. This ratio, derived from dietary total available glucose, urine glucose, and insulin dose/24 h during depot insulin treatment, accurately estimated total insulin for pump infusion (97 +/- 4%). The basal infusion rate of the Biostator between 2400 and 0600 h also exceeded the subcutaneous infusion requirement and was reduced to 40% for the initial pump basal rate. The remainder of the insulin (total minus basal) was distributed as premeal boluses according to the Biostator infusion profile for meals.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhancement of platelet aggregation by low-density lipoproteins from IDDM patients.

Low-density lipoprotein (LDL) is known to enhance platelet sensitivity to some aggregating agents. In this study, we observed that LDL isolated from patients with insulin-dependent diabetes mellitus (IDDM) enhanced thrombin-induced platelet aggregation to a greater extent than LDL isolated from matched controls (P less than .01). Thromboxane B2 production during aggregation was also significantly more enhanced by LDL isolated from IDDM than by control LDL (P less than .01). There was no difference in the lipid composition (free and esterified cholesterol, total phospholipids, and triglycerides) of LDL isolated from diabetic and control subjects. In contrast, the extent of glycosylation of LDL isolated from diabetic patients was significantly greater than that observed in LDL from normal subjects (P less than .01), and a positive correlation (r = .605, P less than .01) between the degree of LDL glycosylation and the rate of platelet aggregation was observed. LDL glycosylated in vitro enhanced thrombin-, collagen-, and adenosine 5'-diphosphate-induced platelet aggregation to a greater extent than control LDL (P less than .01). Although LDL glycosylated in vitro was taken up by platelets to a greater extent than control LDL (P less than .05), the lipid composition (free cholesterol and phospholipid) of platelets was not significantly changed. We postulate that an increased degree of glycosylation of LDL may enhance its uptake by platelets and lead to increased platelet reactivity to aggregating agents, probably by altering the structure of the platelet membrane. The enhancement of platelet aggregation by LDL may contribute to the accelerated development of atherosclerosis in diabetes mellitus.

Increased platelet arachidonic acid metabolism in diabetes mellitus.

Platelets obtained from some diabetic patients show enhanced in vitro platelet aggregation. This study sought to determine if platelet obtained from insulin-dependent diabetic subjects synthesize increased quantities of the labile aggregating substance, thromboxane A2 (TXA2), and if it may play a role in the enhanced platelet aggregation. Arachidonic acid (1 mM)-stimulated TXA2 synthesis, as determined via radioimmunoassay of its stable metabolite TXB2, was significantly greater (P less than 0.01, N = 12) in platelet-rich plasma obtained from diabetics compared with matched controls. Arachidonic acid-stimulated TXB2 synthesis in the diabetic platelet-rich plasma was positively correlated with the ambient fasting plasma glucose (r = 0.61, P less than 0.02, N = 15). Platelet aggregation induced by arachidonic acid (0.4-0.8 mM) was inhibited significantly less by 13-azaprostanoic acid (P less than 0.04, N = 14), a competitive antagonist of the actions of prostaglandin H2 or TXA2 on platelets, compared with matched controls. The results support the notion that platelets obtained from some insulin-dependent diabetic subjects manifest increased synthesis of TXA2, which may contribute to the enhanced platelet aggregation.

Platelet function during continuous insulin infusion treatment in insulin-dependent diabetic patients.

Patients with diabetes mellitus manifest increased in vitro platelet aggregation and increased synthesis of the proaggregant and vasoconstrictor, thromboxane A2 (TXA2). We studied the effects of continuous insulin infusion treatment on platelet aggregation and arachidonic acid (AA)-stimulated platelet TXA2 synthesis (15 and 30 s post-AA, 1 mM) in 16 type I diabetic patients. Strict glycemic control was induced with the Biostator for 2 days and maintained for 12-14 days with continuous subcutaneous insulin infusion (CSII). The average premeal plasma glucose level (4/day) fell from 184 +/- 15, before treatment, to 107 +/- 6 mg/dl on the final day (P less than 0.001). After control, platelet synthesis of TXA2, measured by radioimmunoassay of its stable metabolite, immunoreactive TXB2 (iTXB2), decreased in all patients (30 s: 276 +/- 31 versus 199 +/- 28 ng iTXB2/ml/5 X 10(5) platelets; P less than 0.05). The reduction in platelet iTXB2 synthesis (15 and 30 s) was greater in poorly controlled patients (HbA1c greater than 12%; N = 8), and for all patients the decrease in iTXB2 (15 and 30 s) was correlated with the prestudy HbA1c level (15 s: r = 0.6; P less than 0.01). In contrast, platelet aggregation responses did not improve during intensive insulin treatment. The ED50 for AA (dose producing 50% maximum aggregation at 1 min) was unchanged after 2 wk of treatment and the ED50 for aggregation induced by ADP fell significantly in patients with HbA1c greater than 12% (2.8 +/- 1.3 versus 1.2 +/- 0.6 microM; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of insulin-like growth factor I (IGF-I) responsiveness of fibroblasts of children with short stature: identification of a patient with IGF-I resistance.

Somatomedins are important mediators of GH action on skeletal tissues. A possible cause of growth failure, therefore, is impaired somatomedin (Sm) responsiveness of the target tissues. To investigate Sm responsiveness, we studied fibroblasts from 11 normal-statured individuals and 9 patients with short stature. Five of the short patients had normal serum GH and normal or increased Sm levels and, therefore, are considered possibly to be Sm resistant. The other short patients include 2 with Laron-type dwarfism and 2 with GH resistance of undefined type. As a measure of Sm responsiveness, we determined the ability of insulin-like growth factor I (IGF-I; Sm-C) to stimulate uptake of [3H]alpha-aminoisobutyric acid by fibroblasts. The mean ED50 of the 11 normal fibroblast cell lines was 3.2 +/- 0.9 (+/- SD) ng/ml. Fibroblasts from 8 of the 9 short-statured patients had ED50 values within the normal range. This included 2 fibroblast lines isolated from children with Laron-type dwarfism. Fibroblasts from 1 patient, however, were significantly less sensitive to IGF-I in 9 separate assays, with an ED50 of 10.7 +/- 1.8 ng/ml. Fibroblasts from the mother of the patient had an ED50 of 5.0 +/- 1.4 ng/ml, and fibroblasts from the father had an ED50 of 4.3 +/- 0.7 ng/ml, both above the normal mean. Measurements of [125I]IGF-I binding by suspended fibroblasts from this patient and her parents failed to demonstrate significant abnormalities in either the number of binding sites or the affinity of binding. We conclude that the ability of IGF-I to stimulate [3H]alpha-aminoisobutyric acid uptake by human fibroblasts provides a useful method of identifying short children with Sm resistance. Of five patients with clinical evidence of possible Sm resistance, fibroblasts from one consistently were hyporesponsive to IGF-I. Cells from two patients with Laron-type dwarfism were normally responsive to IGF-I.

Urinary kallikrein excretion in insulin-dependent diabetes mellitus and its relationship to glycemic control.

The renal kallikrein-kinin system is thought to be involved in vasoregulatory and epithelial ion-transporting processes. Renal kallikrein has not been studied in patients with diabetes mellitus, a disease in which abnormalities of renal hemodynamics and electrolyte handling occur. The urinary excretion of this kallikrein was measured in 20 type I diabetic patients and 10 normal subjects. On a 120-meq Na diet, daily kallikrein excretion, determined by both esterase activity and direct RIA, in 12 poorly controlled diabetic patients [hemoglobin A1c (HbA1c) = 14.2 +/- 0.5% (mean +/- SEM)] was significantly greater (P less than 0.05) than excretion in 8 diabetic patients in good to moderately good control (HbA1c = 9.4 +/- 0.5%) or in 10 normal subjects. In these groups, urinary esterase activities were 9.4 +/- 1.0, 6.1 +/- 1.4, and 6.7 +/- 0.5 esterase units/24 h, respectively. Corresponding excretion values of immunoreactive kallikrein were 171 +/- 14, 118 +/- 26, and 123 +/- 11 micrograms/24 h. Creatinine clearances were similar in the three groups. Urinary kallikrein was also measured in 8 diabetic and 8 normal subjects during 7 subsequent days of 10 meq Na intake. It increased less in diabetic patients than in normal subjects during Na depletion (P less than 0.02). The increase in urinary kallikrein in the diabetic patients was inversely related to their HbA1c levels (r = 0.88; P less than 0.01). The effect of glycemic control on urinary kallikrein excretion was determined in nine diabetic patients. Initial glycemic control was achieved using an artificial endocrine pancreas (Biostator) and was maintained by continuous sc insulin infusion with a portable pump. Before glycemic control, urinary kallikrein was 190 +/- 30 micrograms/24 h (by RIA). After 8-12 days of glycemic control, excretion fell to 144 +/- 23 micrograms/24 h (P less than 0.02). The abnormalities in kallikrein excretion in diabetic patients were not correlated with differences in water, electrolyte, protein, glucose, or aldosterone excretion in any of the studies. These results show that kallikrein excretion was increased in patients with poorly controlled insulin-dependent diabetes, and excretion rose less in diabetic subjects with low Na intake than in normal subjects. Strict glycemic control decreased urinary kallikrein excretion. These findings suggest that the renal kallikrein-kinin system is functioning abnormally in diabetes mellitus.

Nervous system involvement in type IV glycogenosis.

A 30-month-old girl exhibited the 19th known case of type IV glycogenosis. Extensive involvement of the nervous system was found at autopsy. This represents only the second patient in whom the fine structure of the CNS and skeletal muscle has been described. We have also identified the abnormal polysaccharide in peripheral nerve, a finding that, to our knowledge, has not been reported previously. Our review of the literature indicates that approximately 50% of these patients exhibit signs or symptoms referable to the neuromuscular system. Most clinical and pathologic studies have focused on the severe liver involvement; insufficient attention has been directed toward the nervous system. This emphasizes the need for more detailed neurologic and neuropathologic examinations of children with type IV glycogenosis.