Continuous Glucose Monitoring by Insulin-Treated Pilots Flying Commercial Aircraft Within the ARA.MED.330 Diabetes Protocol: A Preliminary Feasibility Study.

Background and Aims: A preliminary study compared the use of continuous glucose monitoring (CGM) with the use of self-monitored blood glucose (SMBG) by aircraft pilots with insulin-treated diabetes in the United Kingdom, Ireland, and Austria, certified to fly commercial aircraft within the European Aviation Safety Agency ARA.MED.330 protocol. Methods: SMBG and simultaneous interstitial glucose measurements using CGM (Dexcom G6®) were recorded during pre- and in-flight periods. Results: Eight male pilots (seven with type 1 diabetes and one with type 3c diabetes), median age of 48.5 years and median diabetes duration of 11.5 years, participated. The correlation coefficient (R) between 874 contemporaneously recorded SMBG and CGM values was 0.843, P < 0.001. The mean glucose concentration was 8.78 mmol/L (standard deviation [SD] 0.67) using SMBG compared with 8.71 mmol/L (SD 0.85) recorded using CGM. The mean absolute relative difference was 9.39% (SD 3.12). Conclusions: CGM using Dexcom G6 systems is a credible alternative to SMBG for monitoring glucose levels when insulin-treated pilots fly commercial aircraft. The study was registered with Clinical Trials.gov NCT04395378.

Effect of Dapagliflozin on Cardiac Function and Metabolic and Hormonal Responses to Exercise.

OBJECTIVE: This work aimed to investigate the effect of the SGLT2 inhibitor, dapagliflozin (DAPA), on cardiac function and the metabolic and hormonal response to moderate exercise in people with type 2 diabetes. METHODS: This was a double-blind, placebo-controlled crossover study with a 4-week washout period. Nine participants were randomly assigned to receive either 4 weeks of DAPA or 4 weeks of placebo. After each treatment, they underwent an exercise protocol with 2 consecutive 10-minute stages at a constant load corresponding to 40% and 70% maximal oxygen consumption (VO2max), coupled with hormonal and metabolic analysis. A blinded transthoracic echocardiogram was performed 3 days later. RESULTS: During the exercise protocol, glucose and lactate were lower (P < .0001 and P < .05, respectively) and ß-hydroxybutyrate (BOBH) and growth hormone (GH) were higher (P < .0005 and P = .01) following DAPA treatment compared to placebo. There was a trend for lower insulin with DAPA. Adrenalin, noradrenalin, and glucagon were not different. Following DAPA participants demonstrated an increased mean peak diastolic mitral annular velocity (e') in comparison to placebo (P = .03). The indexed left atrial volume and right ventricular e" were reduced following DAPA compared with placebo (P = .045 and P = .042, respectively). Arterial stiffness was not different between treatments (DAPA 9.35 ± 0.60 m/s; placebo 9.07 ± 0.72 m/s). CONCLUSION: During exercise, GH may be more important than catecholamines in driving the shift from glucose to fatty acid metabolism by SGLT2 inhibitors. The 4-week crossover design showed changes in cardiac function were rapid in onset and reversible.

The SGLT2 Inhibitor Dapagliflozin Increases the Oxidation of Ingested Fatty Acids to Ketones in Type 2 Diabetes.

OBJECTIVE: To investigate the mechanism for increased ketogenesis following treatment with the SGLT2 inhibitor dapagliflozin in people with type 2 diabetes. RESEARCH DESIGN AND METHODS: The design was a double-blind, placebo-controlled, crossover study with a 4-week washout period. Participants received dapagliflozin or placebo in random order for 4 weeks. After each treatment, they ingested 30 mL of olive oil containing [U-13C]palmitate to measure ketogenesis, with blood sampling for 480 min. Stable isotopes of glucose and glycerol were infused to measure glucose flux and lipolysis, respectively, at 450-480 min. RESULTS: Glucose excretion rate was higher and peripheral glucose uptake lower with dapagliflozin than placebo. Plasma ß-hydroxybutyrate (BOHB) concentrations and [13C2]BOHB concentrations were higher and glucose concentrations lower with dapagliflozin than placebo. Nonesterified fatty acids (NEFAs) were higher with dapagliflozin at 300 and 420 min, but lipolysis at 450-480 min was not different. Triacylglycerol at all time points and endogenous glucose production rate at 450-480 min were not different between treatments. CONCLUSIONS: The increase in ketone enrichment from the ingested palmitic acid tracer suggests that meal-derived fatty acids contribute to the increase in ketones during treatment with dapagliflozin. The increase in BOHB concentration with dapagliflozin occurred with only minimal changes in plasma NEFA concentration and no change in lipolysis. This finding suggests a metabolic switch to increase ketogenesis within the liver.

Blood glucose monitoring by insulin-treated pilots of commercial and private aircraft: An analysis of out-of-range values.

AIM: To examine blood glucose measurements recorded as part of the diabetes protocol operated by the UK, Ireland and Austria, which allows commercial airline pilots with insulin-treated diabetes to fly. METHODS: An observational study was conducted in pilots with insulin-treated diabetes, granted medical certification to fly commercial or noncommercial aircraft, who recorded pre-flight and hourly in-flight blood glucose measurements. These values were correlated to a traffic light system (green 5.0 to 15.0 mmol/L; amber 4.0 to 4.9 mmol/L and 15.1 to 20.0 mmol/L; and red <4.0 mmol/L or >20.0 mmol/L) and studied for trends in glucose concentrations, time course within flight and any consequences. Pilot demographics were also analysed. RESULTS: Forty-four pilots (90%) recorded one or more blood glucose value outside the green range during the 7 years of the study. Pilot age, diabetes type and duration, and follow-up period were comparable among subgroups, and mean glycated haemoglobin did not differ before and after certification in a way which would indicate poorer glycaemic control in any subgroup. A total of 892 blood glucose values (2.31%) were outside the green range, with half reported in-flight at various time intervals. There were 48 (0.12%) low red range values recorded, 14 (0.04%) of which occurred in-flight; all but four were restored to within the green range by the time of the next measurement. Appropriate corrective action was taken for all out-of-range values, with no reports of pilot incapacitation from any cause. CONCLUSIONS: The traffic light system appears effective in identifying and reducing the frequency and severity of out-of-range values.

Pilots flying with insulin-treated diabetes.

People with diabetes treated with insulin have often faced blanket bans from safety-critical occupations, largely because of fear of incapacitation due to hypoglycaemia. Recent advances in insulin therapies, modes of administration, monitoring, and noninvasive monitoring techniques have allowed stereotypical views to be challenged. The aviation sector has led the way, in allowing pilots to fly while on insulin. Recently, countries that have traditionally been opposed to this have changed their minds, largely due to the increasing evidence of safety. The purpose of this review was to gather all available information to update clinicans. The physiology and pathophysiology underpinning glucose regulation and the management of diabetes in the air allowing certain insulin-treated pilots to fly are discussed.

Metabolic Effects of an SGLT2 Inhibitor (Dapagliflozin) During a Period of Acute Insulin Withdrawal and Development of Ketoacidosis in People With Type 1 Diabetes.

OBJECTIVE: To determine the effect of the sodium-glucose cotransporter 2 inhibitor dapagliflozin on glucose flux, lipolysis, and ketone body concentrations during insulin withdrawal in people with type 1 diabetes. RESEARCH DESIGN AND METHODS: A double-blind, placebo-controlled crossover study with a 4-week washout period was performed in 12 people with type 1 diabetes using insulin pump therapy. Participants received dapagliflozin or placebo in random order for 7 days. Stable isotopes were infused to measure the glucose Ra, Rd, and lipolysis. At isotopic steady state, insulin was withdrawn, and the study was terminated after 600 min or earlier if blood glucose reached 18 mmol/L, bicarbonate <15 mmol/L, venous pH <7.35, or capillary ketones >5.0 mmol/L. RESULTS: At baseline, glucose Ra was significantly higher for the dapagliflozin group than the placebo group. Following insulin withdrawal, plasma glucose concentrations at the end point were significantly lower with dapagliflozin than placebo and glucose Rd area under the curve (AUC)0-180 min and ß-hydroxybutyrate (BOHB) AUC0-180 min were significantly higher. There was a small but significantly higher glycerol Ra (measure of lipolysis) AUC0-180 min with dapagliflozin. Nonesterified fatty acid concentrations were not different between treatments. When divided by BMI >27 and <27 kg/m2, basal glucose Ra, BOHB, and glycerol Ra AUC0-180 min were significantly higher in the low-BMI group with dapagliflozin treatment versus the low-BMI group with placebo. CONCLUSIONS: During insulin withdrawal, the increase in BOHB with dapagliflozin may be partially due to increased lipolysis. However, reduced renal excretion, reduced BOHB uptake by peripheral tissues, or a metabolic switch to increased ketogenesis within the liver may also play a role.

An Evaluation of the Safety of Pilots With Insulin-Treated Diabetes in Europe Flying Commercial and Noncommercial Aircraft.

OBJECTIVE: The risk of hypoglycemia in people with insulin-treated diabetes has debarred them from certain "safety-critical" occupations, including flying commercial aircraft. This report evaluates the effectiveness of a protocol enabling a large cohort of insulin-treated pilots to fly commercially. RESEARCH DESIGN AND METHODS: This was an observational study of pilots with insulin-treated diabetes who were granted medical certification to fly commercial and noncommercial aircraft. Clinical details, pre- and in-flight (hourly and 30 min before landing) blood glucose values were correlated against the protocol-specified ranges: green (5-15 mmol/L), amber (low, 4-4.9 mmol/L; high, 15.1-20 mmol/L), and red (low, <4 mmol/L; high, >20 mmol/L). RESULTS: A total of 49 pilots with type 1 (84%) or type 2 (16%) diabetes who had been issued class 1 or class 2 certificates were studied. Median diabetes duration was 10.9 years. Mean HbA1c was 7.2% (55.0 mmol/mol) before certification and 7.2% (55.1 mmol/mol) after certification (P = 0.97). Blood glucose values (n = 38,621) were recorded during 22,078 flying hours. Overall, 97.69% of measurements were within the green range, 1.42% within the low amber range, and 0.75% within the high amber range. Only 0.12% of readings were within the low red range and 0.02% within the high red range. Out-of-range readings declined from 5.7% in 2013 to 1.2% in 2019. No episodes of pilot incapacitation occurred, and glycemic control did not deteriorate. CONCLUSIONS: The protocol is practical to implement, and no events compromising safety were reported. This study represents what is, to our knowledge, the most extensive data set from people with insulin-treated diabetes working in a "safety-critical" occupation, which may be relevant when estimating risk in other safety-critical occupations.

Insulin detemir reduces weight gain as a result of reduced food intake in patients with type 1 diabetes.

OBJECTIVE: Insulin detemir lacks the usual propensity for insulin to cause weight gain. We investigated whether this effect was a result of reduced energy intake and/or increased energy expenditure. RESEARCH DESIGN AND METHODS: A 32-week, randomized crossover design trial was undertaken in 23 patients with type 1 diabetes. Patients on a basal-bolus regimen (with insulin aspart as the bolus insulin) were randomly assigned to insulin detemir or NPH insulin as a basal insulin for 16 weeks, followed by the other basal insulin for 16 weeks. At the end of each 16-week period, total energy expenditure, resting energy expenditure, diet-induced thermogenesis, activity energy expenditure, energy intake, weight change, glycemic control, hypoglycemic episodes, and hormones that affect satiety and fuel partitioning were measured. RESULTS: After 16 weeks, weight change was -0.69±1.85 kg with insulin detemir and +1.7±2.46 kg with NPH insulin (P<0.001). Total energy intake was significantly less with insulin detemir (2,016±501 kcal/day) than with NPH insulin (2,181±559 kcal/day) (P=0.026). There was no significant difference in any measure of energy expenditure, HbA1c percentage, or number of hypoglycemic episodes. Leptin was lower and resistin was higher with insulin detemir compared with NPH insulin (P=0.039, P=0.047). After the meal, ghrelin and pancreatic polypeptide levels (P=0.002, P=0.001) were higher with insulin detemir. CONCLUSIONS: The reduced weight gain with insulin detemir compared with NPH insulin is attributed to reduced energy intake rather than increased energy expenditure. This may be mediated by a direct or indirect effect of insulin detemir on the hormones that control satiety.

Insulin detemir and basal insulin therapy.

With the introduction of insulin detemir (Levemir [Novo Nordisk A/S, Bagsvaerd, Denmark]), a long-acting basal insulin analog, it is an opportune moment to reevaluate the use of basal insulin therapy and consider current treatment strategies, including the use of insulin detemir. This review examines the need for effective treatment options for diabetes and the economic burden of this disease. The importance of achieving glycemic control targets and the role of basal insulin therapy are discussed. Finally, the use of insulin detemir is briefly reviewed with a look at its clinical pharmacology, its use in basal insulin therapy, and its cost-effectiveness.

Preliminary development of the new individualized HDQoL questionnaire measuring quality of life in adult hypopituitarism.

OBJECTIVES: The objectives were (1) to report the preliminary development of the Hormone Deficiency-dependent Quality of Life (HDQoL) questionnaire, a new individualized questionnaire in which respondents rate personally applicable domains for importance and impact of hormonal deficiency and its treatment; (2) to evaluate the HDQoL's psychometric properties for adults with hypopituitarism including growth hormone deficiency (GHD). METHODS: Internal consistency reliability, aspects of validity, and sensitivity to change of the HDQoL were investigated in: (1) a cross-sectional survey of 157 adults with treated or untreated GHD; (2) a randomized, placebo-controlled study of 3 months' growth hormone (GH) withdrawal from 12 of 21 GH-treated adults. RESULTS: Thirteen of the original 18 HDQoL domains were relevant and important for GH-deficient adults. The shorter 13-item HDQoL had excellent internal reliability (Cronbach's alpha coefficient = 0.914, n = 109), and was sensitive to sex differences (cross-sectional study): women perceived worse present QoL than men [t(149.8) = 2.33, P = 0.021]. The HDQoL was sensitive to change (GH-withdrawal study) with a significant between-group difference in change in domain scores for things I can do physically[t(16) = 2.47, P = 0.025, 2-tailed], patients withdrawn from GH reporting greater negative impact of hormone deficiency on this domain at end-point. Qualitative work resulted in the addition of seven new HDQoL domains, including energy and bodily pain. CONCLUSION: The HDQoL, although at an early stage of development, proved useful in identifying expected changes following GH withdrawal. The extended 20-item version is recommended for further evaluation in assessing the impact of hypopituitarism on QoL.

Psychometric properties of two measures of psychological well-being in adult growth hormone deficiency.

BACKGROUND: Psychometric properties of two measures of psychological well-being were evaluated for adults with growth hormone deficiency (GHD): the General Well-being Index, (GWBI)--British version of the Psychological General Well-being Index, and the 12-item Well-being Questionnaire (W-BQ12). METHODS: Reliability, structure and other aspects of validity were investigated in a cross-sectional study of 157 adults with treated or untreated GHD, and sensitivity to change in a randomised placebo-controlled study of three months' growth hormone (GH) withdrawal from 12 of 21 GH-treated adults. RESULTS: Very high completion rates were evidence that both questionnaires were acceptable to respondents. Factor analyses did not indicate the existence of useful GWBI subscales, but confirmed the validity of calculating a GWBI Total score. However, very high internal consistency reliability (Cronbach's alpha = 0.96, N = 152), probably indicated some item redundancy in the 22-item GWBI. On the other hand, factor analyses confirmed the validity of the three W-BQ12 subscales of Negative Well-being, Energy, and Positive Well-being, each having excellent internal reliability (alphas of 0.86, 0.86 and 0.88, respectively, N from 152 to 154). There was no sign of item redundancy in the highly acceptable Cronbach's alpha of 0.93 (N = 148) for the whole W-BQ12 scale. Whilst neither questionnaire found significant differences between GH-treated and non-GH-treated patients, there were correlations (for GH-treated patients) with duration of GH treatment for GWBI Total (r = -0.36, p = 0.001, N = 85), W-BQ12 Total (r = 0.35, p = 0.001, N = 88) and for all W-BQ12 subscales: thus the longer the duration of GH treatment (ranging from 0.5 to 10 years), the better the well-being. Both questionnaires found that men had significantly better overall well-being than women. The W-BQ12 was more sensitive to change than the GWBI in the GH-Withdrawal study. A significant between-group difference in change in W-BQ12 Energy scores was found [t(18) = 3.25, p = 0.004, 2-tailed]: patients withdrawn from GH had reduced energy at end-point. The GWBI found no significant change. CONCLUSION: The W-BQ12 is recommended in preference to the GWBI to measure well-being in adult GHD: it is considerably shorter, has three useful subscales, and has greater sensitivity to change.

Low-density lipoprotein apolipoprotein B100 turnover in hypopituitary patients with GH deficiency: a stable isotope study.

BACKGROUND: Epidemiological studies suggest that hypopituitary patients have an increased risk for cardiovascular mortality. The dyslipidaemia associated with this condition is often characterised by an increase in total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol (LDL-C) and may contribute to these findings. The underlying mechanisms are not fully elucidated. MATERIALS AND METHODS: LDL apolipoprotein B (apoB) production rate and metabolic clearance rate were measured in seven patients with hypopituitarism (including GH deficiency) under stable conventional replacement therapy (three males and four females; age 40-16.1 years; body mass index 29.0-6.1 kg/m(2) (means +/- s.d.)) and seven age-, gender- and body mass index-matched control subjects with an infusion of 1-(13)C-leucine. Fasting lipid profile and lipid composition of LDL were also measured. RESULTS: Fasting TC, triglycerides (TG), high-density lipoprotein-C, LDL-C and free fatty acid concentrations were not different between hypopituitary patients and control subjects. LDL-TG (P < 0.006) and LDL-TG/LDL apoB ratio (P < 0.02) were significantly increased in hypopituitary patients. LDL apoB pool size was not statistically different between patients and control subjects. In the hypopituitary patients, LDL apoB metabolic clearance rate (P < 0.05) and LDL apoB production rate (P < 0.02) were lower than in the control subjects. CONCLUSIONS: The present results suggest that LDL apoB turnover and LDL composition is altered in hypopituitary patients. Whether these findings explain the increased risk for cardiovascular disease in hypopituitary patients remains to be established.

Insulin-like growth factor I has a direct effect on glucose and protein metabolism, but no effect on lipid metabolism in type 1 diabetes.

There is evidence of a metabolic role for IGF-I in type 1 diabetes, but it is unclear whether IGF-I acts indirectly by reducing GH secretion or has direct effects. Using stable isotopes we have investigated, on three separate occasions, the effect of a pulse of recombinant human GH, a sc injection of recombinant human IGF-I, and a placebo on glucose, lipid, and protein metabolism in subjects with type 1 diabetes during a basal insulin infusion and a hyperinsulinemic euglycemic clamp. Endogenous GH secretion was suppressed with octreotide. IGF-I reduced the hepatic glucose production rate (Ra), increased peripheral glucose uptake, and reduced protein breakdown during the basal insulin infusion (P < 0.05, P < 0.005, and P < 0.05, respectively, vs. placebo) and the hyperinsulinemic euglycemic clamp (P < 0.05, P < 0.005, and P < 0.05, respectively, vs. placebo). IGF-I had no effect on glycerol Ra, an index of lipolysis. GH increased glucose and glycerol Ra during the basal insulin infusion (P < 0.005 vs. placebo study), but the effects were no different from placebo during the clamp. In conclusion, IGF-I had a direct effect on glucose and protein metabolism, which was maintained during the hyperinsulinemic euglycemic clamp. This suggests that IGF-I acts in concert with insulin and may have an important role in maintaining glucose homeostasis and protein metabolism in type 1 diabetes.

Combined growth hormone/insulin-like growth factor I in addition to glutamine-supplemented TPN results in net protein anabolism in critical illness.

Protein loss leading to reduced lean body mass is recognized to contribute to the high levels of morbidity and mortality seen in critical illness. This prospective, randomized, controlled study compared the effects of conventional parenteral nutrition (TPN), glutamine-supplemented (0.4 g.kg-1.day-1) TPN (TPNGLN), and TPNGLN with combined growth hormone (GH, 0.2 IU.kg-1.day-1) and IGF-I (160 microg.kg-1.day-1) on protein metabolism in critical illness. Nineteen mechanically ventilated subjects [64 +/- 3 yr, body mass index (BMI) 23.8 +/- 1.3, kg/m2] were initially studied in the fasting state (study 1) and subsequently after 3 days of nutritional with/without hormonal support (study 2). All had recently been admitted to the ICU and the majority were postemergency abdominal surgery (APACHE II 17.5 +/- 1.0). Protein metabolism was assessed using a primed constant infusion of [1-13C]leucine. Conventional TPN contained mixed amino acids, Intralipid, and 50% dextrose. TPNGLN, unlike TPN alone, resulted in an increase in plasma glutamine concentration ( approximately 50%, P < 0.05). Both TPN and TPNGLN decreased the rate of protein breakdown (TPN 15%, P < 0.002; TPNGLN 16%, P < 0.05), but during these treatments the patients remained in a net negative protein balance. Combined treatment with TPNGLN + GH/IGF-I increased plasma IGF-I levels (10.3 +/- 0.8 vs. 48.1 +/- 9.1 nmol/l, study 1 vs. study 2, P < 0.05), and in contrast to therapy with nutrition alone, resulted in net protein gain (-0.75 +/- 0.14 vs. 0.33 +/- 0.12 g protein.kg-1.day-1, study 1 vs. study 2, P < 0.05). Therapy with GH/IGF-I + TPNGLN, unlike nutrition alone, resulted in net positive protein balance in a group of critically ill patients.

Effect of IGF-I therapy on VLDL apolipoprotein B100 metabolism in type 1 diabetes mellitus.

Abnormal lipid metabolism may be related to the increased cardiovascular risk in type 1 diabetes. Secretion and clearance rates of very low density lipoprotein (VLDL) apolipoprotein B100 (apoB) determine plasma lipid concentrations. Type 1 diabetes is characterized by increased growth hormone (GH) secretion and decreased insulin-like growth factor (IGF) I concentrations. High-dose IGF-I therapy improves the lipid profile in type 1 diabetes. This study examined the effect of low-dose (40 microg.kg(-1).day(-1)) IGF-I therapy on VLDL apoB metabolism, VLDL composition, and the GH-IGF-I axis during euglycemia in type 1 diabetes. Using a stable isotope technique, VLDL apoB kinetics were estimated before and after 1 wk of IGF-I therapy in 12 patients with type 1 diabetes in a double-blind, placebo-controlled trial. Fasting plasma triglyceride (P < 0.03), VLDL-triglyceride concentrations (P < 0.05), and the VLDL-triglyceride-to-VLDL apoB ratio (P < 0.002) significantly decreased after IGF-I therapy, whereas VLDL apoB kinetics were not significantly affected by IGF-I therapy. IGF-I therapy resulted in a significant increase in IGF-I and a significant reduction in GH concentrations. The mean overnight insulin concentrations during euglycemia decreased by 25% after IGF-I therapy. These results indicate that low-dose IGF-I therapy restores the GH-IGF-I axis in type 1 diabetes. IGF-I therapy changes fasting triglyceride concentrations and VLDL composition probably because of an increase in insulin sensitivity.