Ryuzo Kawamori

WEARABLE ARTIFICIAL ENDOCRINE PANCREAS WITH NEEDLE-TYPE GLUCOSE SENSOR

Miniaturisation of the bedside artificial endocrine pancreas in necessary to provide a means of restoring physiological glycaemic excursions in diabetic patients in the long term. One of the remaining problems in producing such a sophisticated device is the difficulty in developing a sufficiently small glucose-monitoring system. A needle-type glucose sensor has been developed which is suitable for use in a closed-loop glycaemic control system. The wearable artificial endocrine pancreas, incorporating the needle-type glucose sensor, a computer calculating infusion rates of insulin, glucagon, or both, and infusion pumps, was tested in pancreatectomised dogs: the device produced perfect control of blood glucose for up to 7 days.

Glycaemic Control in Pancreatectomized Dogs with a Wearable Artificial Endocrine Pancreas

SummaryA needle-type glucose sensor has been developed using a platinum electrode covered with immobilized glucose oxidase. Experiments with albumin-saline solution in vitro showed that at 5.5 mmol/l glucose concentration the output current generated was 1.2±0.4 nA (mean ± SD). The current increased as a linear function of glucose concentration over the range (0–27.7 mmol/l). The response time to reach 90% of the final plateau value was 16.2±6.2 s. The signal-to-noise ratio of the sensor was 15.8±2.6 decibels. The temperature coefficient in output was 2.3±1.0%/°C. The current output was not affected significantly by changes in oxygen tension of the solution in the range 25–150 mmHg.In vivo, the output current of sensors inserted into the subcutaneous tissues of dogs was directly related to blood glucose concentrations after oral glucose or meals. Daily checking of the sensors maintained in subcutaneous tissues in five dogs showed that the sensitivity decreased gradually to 87.2±7.6% at 72 h, and dropped significantly to 57.4±7.0% of the initial output by 96 h.A wearable artificial endocrine pancreas (18.0 × 17.7 × 7.9 cm, 700 g) was developed, consisting of a needle-type glucose sensor, a microcomputer system and a pump driving mechanism. Three pancreatectomized dogs were fitted with the system by inserting the sensor into subcutaneous tissue. By renewing the sensor every fourth day, the device could maintain the daily glucose variations in diabetic dogs within the range 5–9.5 mmol/l for 7 days.

Atherosclerosis in carotid artery of young IDDM patients monitored by ultrasound high-resolution B-mode imaging

Ultrasound high-resolution B-mode imaging was used to assess the carotid arteries in 105 patients with insulin-dependent diabetes mellitus (IDDM), 4–25 years of age, with duration of diabetes ranging from 0.5–17 years, 529 patients with non-insulin-dependent diabetes (NIDDM), 31–86 years of age, with duration of diabetes ranging from 0.5–49 years, and 104 nondiabetic healthy subjects, 7–76 years of age, to determine the intimal plus medial thickness (IMT) of the arterial wall. The IMT values for IDDM patients 10–19 years of age (0.525 ± 0.123 mm, n = 68) or 20–25 years of age (0.696 ± 0.124 mm, n = 14) were significantly > those in age-matched nondiabetic subjects (0.444 ± 0.057 mm, n = 12, P = 0.01169; 0.538 ± 0.098 mm, n = 34, P < 0.00006). NIDDM patients showed IMT values equivalent to those in normal adults ≥ 20 years of age. Multiple regression analysis showed that IMT in IDDM patients was positively related to the duration of diabetes (P = 0.00061) as well as to age (P = 0.00046). No other possible risk factors, such as serum total cholesterol level, serum high-density lipoprotein (HDL)-cholesterol level, serum low-density lipoprotein-cholesterol level, serum triglycerides, serum lipoprotein(a) level, or systolic or diastolic blood pressure, have shown significant correlations with IMT in IDDM patients. However, non-HDL-cholesterol, smoking, and systolic hypertension were independently responsible for increases in IMT values of NIDDM patients as well as age and duration of diabetes. The partial regression coefficient of IMT for duration of diabetes (0.00978 mm/year) consistent with that of IMT for age (0.00848–0.00909 mm/year) in nondiabetic and diabetic subjects indicated that diabetes led to carotid atherosclerosis that was twice as advanced in children and adolescents with IDDM. Ultrasound high-resolution B-mode imaging revealed atherosclerosis in the carotid arteries of young IDDM patients on in vivo examination. Diabetes as well as aging can advance atherosclerosis in the carotid arteries of young diabetic patients. The IMT of carotid arteries, which can be measured noninvasively and frequently, may be an important indicator of atherosclerosis, even in young IDDM patients.

Enteral absorption of water-in-oil-in-water insulin emulsions in rabbits

SummaryWater-in-oil-in-water (W/O/W) insulin emulsions with a concentration of 100 U/ml of insulin were prepared, and the possible absorption of insulin in emulsion form was examined. The following results were obtained: W/O/W insulin emulsions were quite resistant to proteolytic enzymes in vitro. In the presence of pancreatic lipase, however, W/O/W insulin emulsion gradually lost its activity by the action of proteolytic enzymes. When administered to the jejunum at doses over 10 U/kg, a significant and consistent increase in plasma insulin was observed, followed by a fall in blood glucose. The infusion of W/O/W insulin emulsions into the jejunum was three to four times more effective than the administration of aqueous insulin. Insulin, when administered to the stomach, did not cause hypoglycemia at doses up to 150 U/kg. When W/O/W insulin emulsions were administered orally, on the other hand, definite responses were observed in 3 out of 7 rabbits with 100 U/kg and in 4 out of 7 rabbits with 150 U/kg. For developing an effective method for oral administration of insulin, the present results indicate a possible means of protecting insulin molecule from proteolytic destruction, and of facilitating intestinal absorption of insulin.

Short-Term Treatment of Alloxan-Diabetic Rats with Intrajejunal Administration of Water-in-Oil-in-Water Insulin Emulsions

Alloxan-diabetic rats with fasting blood glucose levels above 300 mg./100 ml. were treated with intrajejunal administration of water-in-oil-in-water (W/O/W) insulin emulsions via an indwelling catheter at a dose of either 25 or 50 U./100 gm. body weight, three times daily for five to fourteen days. The course of diabetes was followed by determinations of glucose levels in blood and urine. During treatment a significant reduction in urinary glucose levels was observed in all rats studied. In two rats treated with 25 U./100 gm., fasting blood glucose levels did not change significantly. In four of five rats treated with 50 U./100 gm., W/O/W insulin emulsions significantly lessened hyperglycemia during treatment. Quantitative estimates suggested that the effectiveness of 50 U./100 gm. of intrajejunal W/O/W insulin emulsions was comparable to that after intramuscular regular insulin at doses between 1 and 2 U./100 gm. These results would indicate that diabetes can be controlled by enteral administration of insulin preparations.

Enhanced bioavailability of insulin after rectal administration with enamine as adjuvant in depancreatized dogs

Rectal absorption of insulin by depancreatized dogs was significantly enhanced by the coadministration of enamine as a suppository adjuvant and if this was followed by a further suppository containing enamine alone, the insulin absorption was even further enhanced. The additional enamine suppository resulted in high serum insulin concentrations for a longer time and effected a significant decrease in serum glucose concentrations. To decrease serum glucose concentrations effectively in depancreatized dogs, serum insulin levels had to remain high for a long period of time, rather than be transient.

Effect of strict metabolic control on glucose handling by the liver and peripheral tissues in non-insulin-dependent diabetes mellitus

To examine the effect of strict glycemic control on the insulin resistance of non-insulin-dependent diabetes mellitus (NIDDM), we applied euglycemic hyperinsulinemic clamp combined with an oral glucose load (OGL) to nine non-obese subjects with NIDDM and quantitated insulin-mediated glucose uptake by the liver (HGU) and peripheral tissues (PGU) simultaneously before and after 3 to 4 weeks of intimate glycemic control by preprandial regular insulin injections 3 times a day. The glucose infusion rate (GIR) required to maintain euglycemia during the clamp before OGL was considered as PGU. After OGL, the fraction of ingested glucose that is not extracted by the liver enters the systemic circulation and reduces the GIR required for the clamp. HGU was calculated from the difference between the amount of OGL and the cumulative decrements in GIR after OGL and was expressed as the ratio to the amount of OGL (%). Three to 4 weeks after initiation of strict metabolic control, FPG and HbA1c levels significantly improved (9.1 +/- 0.5 vs. 6.4 +/- 0.4 mmol/l, and 11.2 +/- 0.8 vs. 8.3 +/- 0.3%, P < 0.05). HGU significantly increased to 33.1 +/- 9.5 from 14.5 +/- 4.8%, while PGU did not change (38.2 +/- 5.2 vs. 37.4 +/- 3.9 mumol/kg.min). These data suggest that short-term strict metabolic control ameliorates insulin resistance in NIDDM mainly at the hepatic level.

Insulin suppository: enhanced rectal absorption of insulin using an enamine derivative as a new promoter

basic solution. One of the major degradation products of triamcinolone in basic media is the D-homosteroid I11 (Timmins & Gray, unpublished observations) and this reaction is therefore not dependent on an enolization step. D-homosteroids were not observed as major degradation products of triamcinolone acetonide. In summary, it may be seen that in neutral and basic media the presence of the acetonide function stabilizes the steroid ketal in comparison with the parent 1601hydroxysteroid, preventing hydroxide ion-catalysed decomposition to the D-homosteroid. Below pH 7 the shape of the pH-rate profile for the steroid ketal is almost identical to that for the parent 1601-hydroxy steroid. The shape of the pH-rate profile for the steroid ketal can be explained in terms of enol formation ionization of the enol whereas this has little influence on the decomposition of the parent 16a-hydroxysteroid. The decomposition of the steroid ketal thus parallels that of steroids possessing no C16 hydroxyl such as hydrocortisone.

Ubiquitous, but variable, expression of two alternatively spliced mRNAs encoding mouse homologues of transcription factors E47 and E12

Two basic helix-loop-helix (bHLH) transcription factors, E47 and E12, are involved in cell-specific gene expression as part of dimeric complexes which interact with the cis-acting motif E-box. Although both generated from a single gene (E2A) by means of alternative splicing, the structural difference in these bHLH regions between the two suggests that the two bHLH proteins may differ in some of their functions. As a step toward elucidating the individual implications of E47 and E12, we investigated the mRNA expression ratios of their homologues (A1 and kA1, respectively) in mouse tissues and cell lines. Both the A1 and kA1 mRNAs were ubiquitously expressed in all tissues examined. However, their ratios varied: e.g., skeletal muscle, 2.2 +/- 0.3 (mean +/- SE); spleen, 2.0 +/- 0.2; pancreatic islet cells, 1.2 +/- 0.2. The A1/kA1 ratios in the cell lines investigated were similar to those of their original tissues. In conclusion, the ubiquity in mRNA expression observed for both the E47 and E12 homologues in mouse provides support for their involvement in a broad range of transcriptional regulation. The variation in the A1/kA1 expression ratios, on the other hand, supports the idea that A1 (E47) and kA1 (E12) each have some unique roles in the functions of these E2A gene-encoded bHLH proteins.

Increased hepatic glucose production and decreased hepatic glucose uptake at the prediabetic phase in the Otsuka Long-Evans Tokushima Fatty rar model

To investigate the time course of the hepatic glucose metabolism in non-insulin-dependent diabetes (NIDDM), we measured hepatic glucose production (HGP) and first-pass uptake of portal glucose infusion by the liver (HGU) using dual-tracer methods in a NIDDM model, Otsuka Long-Evans Tokushima Fatty (OLETF) rats, and in normal controls, Long-Evans Tokushima Otsuka (LETO) rats, at 8, 14, and 28 weeks of age (n = 5, respectively). The fasting plasma glucose level in OLETF rats was significantly higher than in LETO rats at 28 weeks of age (8.9 +/- 1.7 v 6.3 +/- 0.4 mmol/L, P < .01), while there was no significant difference at 8 and 14 weeks. Hyperinsulinemia in OLETF rats appeared at > or = 8 weeks of age. Basal HGP was significantly higher in OLETF than in LETO rats at 8 and 28 weeks (8 weeks, 12.7 +/- 1.7 v 9.4 +/- 1.8 mg x kg(-1) x min(-1), P < .05; 28 weeks, 10.9 +/- 1.6 v 7.1 +/- 1.3 mg x kg(-1) x min(-1), P < .01). At 14 weeks, basal HGP was not significantly different between OLETF and LETO rats. However, at all study points, HGU during a portal glucose infusion was significantly lower in OLETF than in LETO rats (8 weeks, 0.9 +/- 0.2 v 2.3 +/- 0.5, P < .01; 14 weeks, 0.8 +/- 0.3 v 1.4 +/- 0.3, P < .05; 28 weeks, 0.7 +/- 0.2 v 1.4 +/- 0.3 mg x kg(-1) x min(-1), P < .01). Fasting plasma free fatty acid (FFA) levels were not significantly different between OLETF and LETO, except at 8 weeks. Suppression of plasma FFA levels by endogenous insulin during a portal glucose infusion was impaired in OLETF rats compared with LETO rats. In summary, this study demonstrates that derangement of hepatic glucose handling, such as increased basal HGP and decreased HGU, is observed in obese NIDDM model OLETF rats at the prediabetic phase when hyperglycemia is still not apparent. Furthermore, these derangements may be accompanied by impaired lipid metabolism.