α- or ß-Adrenergic blockade does not affect transplanted islet cell responses to hypoglycemia in type 1 diabetes.

Type 1 diabetes recipients of intrahepatic islet transplantation exhibit glucose-dependent suppression of insulin and activation of glucagon secretion in response to insulin-induced hypoglycemia associated with clinical protection from hypoglycemia. Whether sympathetic activation of adrenergic receptors on transplanted islets is required for these responses in defense against hypoglycemia is not known. To evaluate the adrenergic contribution to post-transplant glucose counterregulation, we performed a randomized, double-blind crossover study of responses during a hyperinsulinemic euglycemic-hypoglycemic clamp under phentolamine (α-adrenergic blockage), propranolol (ß-adrenergic blockage), or placebo infusion. Participants (5 female/4 male) were median (range) age 53 (34-63) years, diabetes duration 29 (18-56) years, post-transplant 7.0 (1.9-8.4) years, HbA1c 5.8 (4.5-6.8)%, insulin in-/dependent 5/4, all on tacrolimus-based immunosuppression. During the clamp, blood pressure was lower with phentolamine and heart rate lower with propranolol vs. placebo (P <0.05). There was no difference in suppression of endogenous insulin secretion (derived from C-peptide measurements) during the euglycemic or hypoglycemic phases, and while levels of glucagon were similar with phentolamine or propranolol vs. placebo, the increase in glucagon from eu- to hypoglycemia was greater with propranolol vs. placebo (P < 0.05). Pancreatic polypeptide was greater with phentolamine vs. placebo during the euglycemic phase (P < 0.05), and free fatty acids were lower and the glucose infusion rate higher with propranolol vs. placebo during the hypoglycemic phase (P < 0.05). These results indicate that neither physiologic α- nor ß-adrenergic blockade attenuates transplanted islet responses to hypoglycemia, suggesting sympathetic re-innervation of the islet graft is not necessary for post-transplant glucose counterregulation.

Validating and Establishing a Diagnostic Threshold for the Hypoglycemia Awareness Questionnaire Impaired Awareness Subscale.

OBJECTIVE: To evaluate the discriminant and convergent validities of the Hypoglycemia Awareness Questionnaire Impaired Awareness (HypoA-Q IA) subscale and establish a diagnostic threshold for the classification of impaired awareness of hypoglycemia (IAH) in adults with type 1 diabetes (T1D). METHODS: Twenty-one adults with T1D (male, 48%; median age, 36 years; and T1D duration, 21 years) completed the HypoA-Q IA subscale, Clarke, and hypoglycemia severity (HYPO) scores, continuous glucose monitoring, and hyperinsulinemic hypoglycemic clamp testing. Those with IAH defined by a Clarke score of ≥4 (n = 10) and who experienced severely problematic hypoglycemia and/or marked glycemic lability started automated insulin delivery as part of an 18-month intervention study with the 6-monthly paired assessment of the HypoA-Q IA subscale, Clarke score, HYPO score and continuous glucose monitoring, and hypoglycemic clamp testing at baseline and 6 and 18 months. RESULTS: The HypoA-Q IA subscale discriminated between those with and without IAH defined by the Clarke score (W = 110.5; P <.001). During intervention, the HypoA-Q IA subscale demonstrated convergent validity via significant relationships with the Clarke (r = 0.72; P <.001) and HYPO (r = 0.60; P <.001) scores; hypoglycemia exposure below 70 (r = 0.53; P <.01), 60 (r = 0.50; P <.01), and 54 (r = 0.48; P <.01) mg/dL; and autonomic symptom (r = -0.53; P <.05), epinephrine (r = -0.68; P <.001), and pancreatic polypeptide (r = -0.52; P <.05) responses to insulin-induced hypoglycemia. The receiver operating characteristic curve analysis revealed that the HypoA-Q IA subscale was an excellent predictor of an abnormal symptom response to insulin-induced hypoglycemia (area under the curve, 0.86) with a score of 12, which was the optimal threshold for IAH classification (sensitivity, 83%; specificity, 80%). CONCLUSION: These findings support the validity of the HypoA-Q IA subscale and propose a HypoA-Q IA diagnostic threshold to identify IAH in both clinical and research settings.

Automated Insulin Delivery for Hypoglycemia Avoidance and Glucose Counterregulation in Long-Standing Type 1 Diabetes with Hypoglycemia Unawareness.

Objective: Automated insulin delivery (AID) may benefit individuals with long-standing type 1 diabetes where frequent exposure to hypoglycemia impairs counterregulatory responses. This study assessed the effect of 18 months AID on hypoglycemia avoidance and glucose counterregulatory responses to insulin-induced hypoglycemia in long-standing type 1 diabetes complicated by impaired awareness of hypoglycemia. Methods: Ten participants mean ± standard deviation age 49 ± 16 and diabetes duration 34 ± 16 years were initiated on AID. Continuous glucose monitoring was paired with actigraphy to assess awake- and sleep-associated hypoglycemia exposure every 3 months. Hyperinsulinemic hypoglycemic clamp experiments were performed at baseline, 6, and 18 months postintervention. Hypoglycemia exposure was reduced by 3 months, especially during sleep, with effects sustained through 18 months (P ≤ 0.001) together with reduced glucose variability (P < 0.01). Results: Hypoglycemia awareness and severity scores improved (P < 0.01) with severe hypoglycemia events reduced from median (interquartile range) 3 (3-10) at baseline to 0 (0-1) events/person·year postintervention (P = 0.005). During the hypoglycemic clamp experiments, no change was seen in the endogenous glucose production (EGP) response, however, peripheral glucose utilization during hypoglycemia was reduced following intervention [pre: 4.6 ± 0.4, 6 months: 3.8 ± 0.5, 18 months: 3.4 ± 0.3 mg/(kg·min), P < 0.05]. There were increases over time in pancreatic polypeptide (Pre:62 ± 29, 6 months:127 ± 44, 18 months:176 ± 58 pmol/L, P < 0.01), epinephrine (Pre: 199 ± 53, 6 months: 332 ± 91, 18 months: 386 ± 95 pg/mL, P = 0.001), and autonomic symptom (Pre: 6 ± 2, 6 months: 6 ± 2, 18 months: 10 ± 2, P < 0.05) responses. Conclusions: AID led to a sustained reduction of hypoglycemia exposure. EGP in response to insulin-induced hypoglycemia remained defective, however, partial recovery of glucose counterregulation was evidenced by a reduction in peripheral glucose utilization likely mediated by increased epinephrine secretion and, together with improved autonomic symptoms, may contribute to the observed clinical reduction in hypoglycemia.

Effect of a low-carbohydrate diet versus a low-fat, calorie-restricted diet on adipokine levels in obese, diabetic participants.

The effect of dietary macronutrient composition on adipokine concentrations remains unclear. Greater reductions in leptin have been reported in participants who followed low-carbohydrate versus low-fat diets, although these studies did not adjust for the important effects of weight loss on adipokines. We investigated the effect of macronutrient composition on adipokine levels in 144 obese, diabetic participants who were randomly assigned to a low- carbohydrate (< 30 g/day) or low-fat diet (≤ 30% of calories from fat with a deficit of 500 kcal/day). Weight, adipokines, and dietary intake were assessed at baseline and 6 months. Complete data were available for 79 participants. At month 6, weight, leptin, adiponectin, and tumor necrosis factor-α concentrations did not differ significantly between groups (P > 0.05 for all variables). However, significant changes in leptin and adiponectin occurred over time (P < 0.001 and P < 0.012, respectively). Modest weight loss, rather than macronutrient composition, likely accounted for the favorable changes observed in leptin and adiponectin over time.