Fluctuations In Blood Glucose Concentrations Research Articles

Central cholinergic regulation of pancreatic polypeptide secretion in conscious dogs.

The secretion of pancreatic polypeptide (PP) is regulated by fluctuations in blood glucose concentrations and food intake, in which vagal-cholinergic mechanisms play an important role, especially for the cephalic phase of PP secretion. In this study, we examined whether central cholinergic mechanisms are also important for PP secretion by relaying information in the brain to the vagus nerve and the muscarinic cholinergic receptors in the pancreas. Atropine sulfate (20-200 micrograms) was administered into the lateral cerebral ventricle and its effects on the basal secretion of PP as well as the secretions stimulated by insulin-induced hypoglycemia (Actrapid MC, 0.25 U/kg) and a mixed meal (243 kcal) were studied in seven dogs. Intralateral cerebroventricular (ILV) atropine (100 and 200 micrograms) abolished the fluctuations in basal PP secretion without appearing in the plasma. Pretreatment with 20, 100, and 200 micrograms ILV atropine significantly decreased the PP response to insulin-induced hypoglycemia, with the integrated PP response to 58, 32, and 26% of that of controls respectively. Atropine (100 micrograms ILV) significantly reduced the postprandial PP secretion in both the cephalic and the gastrointestinal phases, whereas increased insulin and glucose levels were unaffected. Centrally administered atropine was able to suppress the basal secretion of PP as well as the secretions stimulated by hypoglycemia and food intake. These findings suggest that (1) the spontaneous release of PP is governed by an oscillating, central cholinergic tone, and (2) the stimulating PP secretion is, at least in part, regulated by the central cholinergic system.

Reducing Blood Glucose Variability by Use of Abdominal Insulin Injection Sites

Virtually all patients with type I diabetes are familiar with inexplicable fluctuations in blood glucose concentration that expose them to both hypoglycemia and hyperglycemia. It is commonly assumed that such fluctuations are due, in large part, to variations in food intake, physical activities, and emotional state. However, substantial day-to-day variation in blood glucose concentration is observed when diet, exercise, emotional state, insulin dosage, and timing of insulin administration are held constant. This suggests that variation in the rate of absorption of insulin from the subcutaneous injection sites may be an important factor causing those fluctuations. Variations in insulin absorption are increased if the anatomic regions used for injections are rotated. A recent study completed at the University of Minnesota Hospital and Clinic indicates that it is inadvisable for type I diabetic subjects to rotate insulin injection regions; rather, insulin injections should be confined to a single anatomic region (usually the abdomen) as this will decrease day-to-day variability in blood glucose concentration. Such a decrease should allow greater precision in adjusting insulin doses, thereby helping achieve good control.

Retinal oxygen consumption in vitro the effect of diabetes mellitus, oxygen and glucose

In diabetes mellitus, the retina is exposed to fluctuations in blood glucose concentrations, presumed decreases in oxygen availability and other metabolic disturbances induced by the disease. These metabolic phenomena may play a role in diabetic retinopathy. To understand these processes better, we measured oxygen consumption in vitro in retinas from normal and diabetic rabbits and examined the effect of oxygen and glucose concentration on retinal respiration. Retinal oxygen consumption is decreased in diabetic retinas compared to normal rabbit retinas (0.56 +/- 0.09 ml of oxygen per min per mg dry weight in normal and 0.40 +/- 0.07 ml of oxygen per min per mg dry weight in diabetic retinas). Retinal oxygen consumption is elevated if the oxygen tension is raised above normal in both groups. Glucose concentration did not significantly effect the oxygen consumption of the retina in either group.

Rotation of the Anatomic Regions Used for Insulin Injections and Day-to-Day Variability of Plasma Glucose in Type I Diabetic Subjects

Treatment of type I diabetes mellitus is hindered by the often large fluctuations in blood glucose concentration experienced by affected individuals. To determine to what extent day-to-day variation in blood glucose levels can be reduced if insulin is injected in the same anatomic region rather than in different regions using a rotational scheme, as is commonly recommended, 12 type I diabetic subjects were studied. Insulin injections were given in the abdomen for 3 days and rotated among arms, abdomen, and thighs for 3 days using a crossover design with random assignment of treatment order. Blood samples for measurement of plasma glucose levels were obtained at nine scheduled times on each day. Insulin dose, diet, and physical activity were held constant for each subject. During the abdominal injection period, the mean SD of plasma glucose levels and the mean variance of plasma glucose levels were both less at all nine time points than during the rotating injection period. Overall values for the SD of plasma glucose levels were 2.7 +/- 0.2 mmol/L for the abdominal injection period and 3.7 +/- 0.3 mmol/L for the rotating injection period. Overall values for the variance of plasma glucose levels were 9.2 +/- 1.4 mmol2/L2 for the abdominal injection period and 17.4 +/- 2.2 mmol2/L2 for the rotating injection period. We conclude that the common clinical practice of rotating the anatomic regions used for insulin injections increases day-to-day variation in blood glucose concentration. Use of a single anatomic region, eg, the abdomen, for all insulin injections may reduce this variation and allow greater precision in the adjustment of insulin doses.

Acute changes in blood glucose concentration do not promote thrombin generation or fibrin breakdown in type 1 diabetes.

To investigate the effect of blood glucose concentration on thrombin generation and fibrinolytic activity, six Type 1 patients had the blood glucose concentration maintained for 1 h at 5, 15, and 25 mmol l-1, and 8 patients underwent hypoglycaemia of 20 min duration after the blood glucose had been kept at 8 mmol l-1 for 1 h. During hyperglycaemia plasminogen activator activity rose from 214 (11-625) (median, range) to 478 (18-772) units (p less than 0.05) at a blood glucose of 5 mmol l-1 and to 511 (89-816) (p less than 0.05) and 535 (33-976) (p less than 0.05) units at a blood glucose of 15 and 25 mmol l-1, respectively. Cross-linked fibrin degradation products (FDP) were 45 and 53 micrograms l-1 at a blood glucose of 5 mmol l-1 and remained unchanged at higher glucose levels. Fibrinopeptide A was 1.3 (0.6-2.8) nmol l-1 at a blood glucose of 5 mmol l-1, and remained unchanged with hyperglycaemia, being 1.3 (0.9-1.3) nmol l-1 after 1h at 25 mmol l-1. During hypoglycaemia, plasminogen activator activity rose from 155 to 745 units (p less than 0.05) while both fibrinopeptide A and cross-linked FDP remained unchanged. The results indicate that acute fluctuations in blood glucose concentration do not lead to thrombin generation. Additionally, increased fibrinolytic activity measured in vitro is not associated with an increase in cross-linked FDP. This suggests that short-term hyper- and hypoglycaemia do not affect the end-products of the coagulation and fibrinolytic pathways.