Reduced growth hormone secretion improves insulin sensitivity in adolescent girls with type 1 diabetes

Improved Generalized Predictive Control Algorithm for Blood Glucose Control of Type 1 Diabetes

Artificial pancreas (AP) is an important treatment for patients with Type 1 diabetes (T1D). The control algorithm adopted in an AP system determines its reliability and accuracy. The generalized predictive control (GPC) is a representative adaptive control algorithm and has been widely applied to AP systems. However, we found that the traditional GPC controller does not work well for adolescents with T1D because of their high-fluctuating blood glucose and high insulin resistance. Here, we propose an improved GPC algorithm with an adaptive reference glucose trajectory and an adaptive softening factor. The slopes of the reference trajectory and the value of softening factor are calculated real-time on the basis of the blood glucose concentration (BGC) variations. In silico testing was done using the US Food and Drug Administration (FDA) approved virtual patient software T1D mellitus. The BGC trace and density of 20 patient-subjects (10 adults and 10 adolescents) were recorded. Results showed that the average BGC percentage within the target regions (70-180 mg/dL) of the tests with adaptive reference glucose trajectory and softening factor for adolescents (0.93 ± 0.07) was significantly higher than that of the traditional GPC algorithm tests (0.88 ± 0.11), suggesting that the control quality of the blood glucose of adolescents is significantly improved with our GPC algorithm. Therefore, our improved GPC controller is effective and should have a good applicability in AP systems.

[Adjunctive therapies to glycaemic control of type 1 diabetes mellitus]

Since Diabetes Control and Complications Trial (DCCT), intensive therapy has been directed at achieving glucose and glycosylated hemoglobin (HbA1c) values as close to normal as possible regarding safety issues. However, hyperglycemia (especially postprandial hyperglycemia) and hypoglicemia continue to be problematic in the management of type 1 diabetes. The objective of associating other drugs to insulin therapy is to achieve better metabolic control lowering postprandial blood glucose levels. Adjunctive therapies can be divided in four categories based on their mechanism of action: enhancement of insulin action (e.g. the biguanides and thiazolidinediones), alteration of gastrointestinal nutrient delivery (e.g. acarbose and amylin) and other targets of action (e.g. pirenzepine, insulin-like growth factor I and glucagon-like peptide-1). Many of these agents have been found to be effective in short-term studies with decreases in HbA1c of 0.5-1%, lowering postprandial blood glucose levels and decreasing daily insulin doses.

Insulin sensitivity and lipolysis in adolescent girls with poorly controlled type 1 diabetes: effect of anticholinergic treatment

OBJECTIVES

Increased GH secretion could be one factor behind the impaired glycaemic control often seen in adolescent girls with type 1 diabetes. Because GH induces insulin resistance, treatment with anticholinergic agents, such as pirenzepine (PZP), has been used to reduce GH secretion. However, in a previous study of adolescent girls with type 1 diabetes, we observed an improvement in glycaemic control during 12 weeks of PZP therapy despite unchanged excretion of GH in urine. Considering the complex mechanisms behind urinary GH excretion, the effects of PZP on pituitary GH secretion or secretory pattern cannot be excluded. Thus, to assess the effect of anticholinergic treatment on metabolic control in adolescent girls with diabetes, we have investigated GH secretion, insulin sensitivity and lipolysis before and during treatment with PZP.

PATIENTS

Eleven adolescent girls with type 1 diabetes and poor metabolic control were investigated before and after treatment with PZP, 100 mg orally, twice a day for 3 weeks.

DESIGN

Serum samples for analysis of haemoglobin A1c and IGF-I were obtained in addition to serum profiles of GH, insulin and IGFBP-1 before and after 3 weeks of PZP treatment. Effects on insulin sensitivity and lipolysis were also assessed.

MEASUREMENTS

IGFBP-1 was measured every hour, whereas serum GH and insulin were measured every 20 min for 24 h. Insulin sensitivity was analysed with the hyperinsulinaemic euglycaemic clamp technique. The rate of lipolysis was assessed under basal conditions following a constant rate infusion of [1,1,2,3,3-2H5]-glycerol. In five girls, lipolysis was also estimated during the hyperinsulinaemic euglycaemic clamp.

RESULTS

There was a significant reduction in haemoglobin A1c levels (9.9 +/- 0.2%vs. 9.1 +/- 0.2; P < 0.0001) during 3 weeks of PZP treatment. In additional, the glucose requirement during the euglycaemic hyperinsulinaemic clamp increased by more than 30% (72.5 +/- 4.9 vs. 96.8 +/- 8.5 mg/m2/min; P = 0.003). However, we could not demonstrate any significant changes in GH secretion (area under the curve, basal levels or peak amplitude) or in the GH secretory pattern (peak height, peak length or interpeak interval). Concordantly, the IGF-I levels were statistically unchanged, as were IGFBP-1 concentrations. The rate of lipolysis did not change under basal conditions (3.40 +/- 0.53 vs. 3.04 +/- 0.54 micro mol/kg/min, n = 11, P = 0.54) or during the hyperinsulinaemic euglycaemic clamp (1.58 +/- 0.21 vs. 2.08 +/- 0.26 micro mol/kg/min; n = 5, P = 0.32).

CONCLUSIONS

Our observations of an increased glucose requirement during the clamp as well as a decrease in haemoglobin A1c demonstrate improved insulin sensitivity in the adolescent girls with diabetes following pirenzepine therapy. The mechanism behind the improvement is not clear, as neither secretion nor the secretory pattern of GH changed significantly. The persistently high levels of GH might explain the unaltered rate of lipolysis despite the improved insulin sensitivity. The observed improvement in glycaemic control in adolescent girls with type 1 diabetes following pirenzepine therapy is promising, although more studies on this topic are needed.

Growth hormone improves clinical status in prepubertal children with cystic fibrosis: results of a randomized controlled trial

OBJECTIVES

We conducted a 1-year randomized controlled trial to test the hypothesis that growth hormone (GH) improves the clinical status of children with cystic fibrosis.

STUDY DESIGN

Nineteen prepubertal children were randomized to control (NonTX, n = 9) or to daily injections of GH (0.3 mg/kg/wk) (GHTX, n = 10) for 1 year. Every 3 months height, weight, and lean tissue mass were measured. Caloric intake, resting energy expenditure, pulmonary function, and respiratory muscle strength were measured every 6 months, as were total number of hospitalizations and courses of outpatient intravenous antibiotics.

RESULTS

The GHTX group had significantly greater height, height velocity (NonTX = 3.8 +/- 1.4 cm/y, GHTX = 8.1 +/- 2.4 cm/y; P =.002), weight, weight velocity (NonTX = 2.1 +/- 0.9 kg/y, GHTX = 4.5 +/- 1.1 kg/y; P =.004), and change in lean tissue mass (NonTX = 2.1 +/- 1.6 kg, GHTX = 4.7 +/- 1.7 kg; P =.01) analyzed by the Student t test. The GHTX group had significant improvement in delta forced vital capacity compared with the year before study, and respiratory muscle strength improved. The number of hospitalizations and outpatient intravenous antibiotic courses significantly decreased in the GHTX group but did not change in the NonTX group. No subject had development of cystic fibrosis-related diabetes.

CONCLUSIONS

Results of the first randomized controlled trial of GH treatment in cystic fibrosis indicate that GH improves growth and clinical status.