Simone Pampanelli

Meticulous Prevention of Hypoglycemia Normalizes the Glycemic Thresholds and Magnitude of Most of Neuroendocrine Responses to, Symptoms of, and Cognitive Function During Hypoglycemia in Intensively Treated Patients With Short-Term IDDM

To test the hypothesis that hypoglycemia unawareness is largely secondary to recurrent therapeutic hypoglycemia in IDDM, we assessed neuroendocrine and symptom responses and cognitive function in 8 patients with short-term IDDM (7 yr) and hypoglycemia unawareness. Patients were assessed during a stepped hypoglycemic clamp, before and after 2 wk and 3 mo of meticulous prevention of hypoglycemia, which resulted in a decreased frequency of hypoglycemia (0.49 ± 0.05 to 0.045 ± 0.03 episodes/patient-day) and an increase in HbA1c (5.8 ± 0.3 to 6.9 ± 0.2%) (P < 0.05). We also studied 12 nondiabetic volunteer subjects. At baseline, lower than normal symptom and neuroendocrine responses occurred at lower than normal plasma glucose, and cognitive function deteriorated only marginally during hypoglycemia. After 2 wk of hypoglycemia prevention, the magnitude of symptom and neuroendocrine responses (with the exception of glucagon and norepinephrine) nearly normalized, and cognitive function deteriorated at the same glycemic threshold and to the same extent as in nondiabetic volunteer subjects. At 3 mo, the glycemic thresholds of symptom and neuroendocrine responses normalized, and surprisingly, some of the responses of glucagon recovered. We concluded that hypoglycemia unawareness in IDDM is largely reversible and that intensive insulin therapy and a program of intensive education may substantially prevent hypoglycemia and at the same time maintain the glycemic targets of intensive insulin therapy, at least in patients with IDDM of short duration.

Long-term recovery from unawareness, deficient counterregulation and lack of cognitive dysfunction during hypoglycaemia, following institution of rational, intensive insulin therapy in IDDM.

SummaryHypoglycaemia unawareness, is a major risk factor for severe hypoglycaemia and a contraindication to the therapeutic goal of near-normoglycaemia in IDDM. We tested two hypotheses, first, that hypoglycaemia unawareness is reversible as long as hypoglycaemia is meticulously prevented by careful intensive insulin therapy in patients with short and long IDDM duration, and that such a result can be maintained long-term. Second, that intensive insulin therapy which strictly prevents hypoglycaemia, can maintain long-term near-normoglycaemia. We studied 21 IDDM patients with hypoglycaemia unawareness and frequent mild/severe hypoglycaemia episodes while on “conventional” insulin therapy, and 20 nondiabetic control subjects. Neuroendocrine and symptom responses, and deterioration in cognitive function were assessed in a stepped hypoglycaemia clamp before, and again after 2 weeks, 3 months and 1 year of either intensive insulin therapy which meticulously prevented hypoglycaemia (based on physiologic insulin replacement and continuous education, experimental group, EXP, n=16), or maintenance of the original “conventional” therapy (control group, CON, n=5). At entry to the study, all 21 IDDM-patients had subnormal neuroendocrine and symptom responses, and less deterioration of cognitive function during hypoglycaemia. After intensive insulin therapy in EXP, the frequency of hypoglycaemia decreased from 0.5±0.05 to 0.045±0.02 episodes/patient-day; HbA1C increased from 5.83±0.18 to 6.94±0.13% (range in non-diabetic subjects 3.8–5.5%) over a 1-year period; all counterregulatory hormone and symptom responses to hypoglycaemia improved between 2 weeks and 3 months, with the exception of glucagon which improved at 1 year; and cognitive function deteriorated further as early as 2 weeks (p<0.05). The improvement in responses was maintained at 1 year. The improvement in plasma adrenaline and symptom responses inversely correlated with IDDM duration. In contrast, in CON, neither frequency of hypoglycaemia, nor neuroendocrine responses to hypoglycaemia improved. Thus, meticulous prevention of hypoglycaemia by intensive insulin therapy reverses hypoglycaemia unawareness even in patients with long-term IDDM, and is compatible with long-term near-normoglycaemia. Because carefully conducted intensive insulin therapy reduces, not increases the frequency of moderate/severe hypoglycaemia, intensive insulin therapy should be extended to the majority of IDDM patients in whom it is desirable to prevent/delay the onset/progression of microvascular complications.

Relative roles of insulin and hypoglycaemia on induction of neuroendocrine responses to, symptoms of, and deterioration of cognitive function in hypoglycaemia in male and female humans.

SummaryTo assess the relative roles of insulin and hypoglycaemia on induction of neuroendocrine responses, symptoms and deterioration of cognitive function (12 cognitive tests) during progressive decreases in plasma glucose, and to quantitate glycaemic thresholds, 22 normal, non-diabetic subjects (11 males, 11 females) were studied on four occasions: prolonged fast (n=8, saline euglycaemia study, SA-EU), stepped hypoglycaemia (plasma glucose plateaus of 4.3, 3.7, 3 and 2.3 mmol/l) or euglycaemia during insulin infusion at 1 and 2 mU·kg−1·min−1 (n=22, high-insulin hypoglycaemia and euglycaemia studies, HI-INS-HYPO and HI-INS-EU, respectively), and stepped hypoglycaemia during infusion of insulin at 0.35 mU· kg−1·min−1 (n=9, low-insulin hypoglycaemia study, LO-INS-HYPO). Insulin per se (SA-EU vs HI-INS-EU), suppressed plasma glucagon (∼20%) and pancreatic polypeptide (∼30%), whereas it increased plasma noradrenaline (∼R10%, p<0.05). Hypoglycaemia per se (HI-INS-HYPO vs HI-INS-EU) induced responses of counterregulatory hormones (CR-HORM), symptoms and deteriorated cognitive function. With the exception of suppression of endogenous insulin secretion, which had the lowest glycaemic threshold of 4.44±0.06 mmol/l, pancreatic polypeptide, glucagon, growth hormone, adrenaline and cortisol had similar glycaemic thresholds (∼3.8-3.6 mmol/l); noradrenaline (3.1±0.0 mmol/l), autonomic (3.05±0.06 mmol/l) and neuroglycopenic (3.05±0.05 mmol/l) symptoms had higher thresholds. All 12 tests of cognitive function deteriorated at a glycaemic threshold of 2.45±0.06 mmol/l, but 7 out of 12 tests were already abnormal at a glycaemic threshold of 2.89±0.06 mmol/l. Although all CR-HORM had a similar glycaemic threshold, the lag time of response (the time required for a given parameter to increase) of glucagon (15±1 min) and growth hormone (14±3 min) was shorter than adrenaline (19±3 min) and cortisol (39±4 min) (p<0.05). With the exception of glucagon (which was suppressed) and noradrenaline (which was stimulated), insulin per se (HI-INS-HYPO vs LO-INS-HYPO) did not affect the responses of CR-HORM, and did not influence the symptoms or the cognitve function during hypoglycaemia. Despite lower responses of glucagon, adrenaline and growth hormone (but not thresholds) in females than males, females were less insulin sensitive than males during stepped hypoglycaemia.

Demonstration of a critical role for free fatty acids in mediating counterregulatory stimulation of gluconeogenesis and suppression of glucose utilization in humans.

In vitro studies indicate that FFA compete with glucose as an oxidative fuel in muscle and, in addition, stimulate gluconeogenesis in liver. During counterregulation of hypoglycemia, plasma FFA increase and this is associated with an increase in glucose production and a suppression of glucose utilization. To test the hypothesis that FFA mediate changes in glucose metabolism that occur during counterregulation, we examined the effects of acipimox, an inhibitor of lipolysis, on glucose production and utilization ([3-3H]glucose), and incorporation of [U-14C]-alanine into glucose during insulin-induced hypoglycemia. Eight normal volunteers were infused with insulin for 8 h to produce modest hypoglycemia (approximately 3 mM) on two occasions, first without acipimox (control) and then with acipimox administration (250 mg per os at 60 and 240 min). Despite identical plasma insulin concentrations, glucose had to be infused in the acipimox experiments (glucose-clamp technique) to maintain plasma glucose concentrations identical to those in control experiments. Acipimox completely prevented counterregulatory increases in lipolysis so that during the last 4 h plasma FFA were below baseline values and averaged 67 +/- 13 vs. 725 +/- 65 microM in control experiments, P < 0.001. Concomitantly, overall glucose production was reduced by 40% (5.5 +/- 11 vs. 9.3 +/- 0.7 mumol/kg per min, P < 0.001), and gluconeogenesis from alanine was reduced by nearly 70% (0.32 +/- 0.09 vs. 1.00 +/- 0.18 mumol/kg per min, P < 0.001), while glucose utilization increased by 15% (10.8 +/- 1.4 vs. 9.3 +/- 0.7 mumol/kg per min). We conclude that FFA play a critical role in mediating changes in glucose metabolism during counterregulation, and that under these conditions, FFA exert a much more profound effect on hepatic glucose production than on glucose utilization.

Better long-term glycaemic control with the basal insulin glargine as compared with NPH in patients with Type 1 diabetes mellitus given meal-time lispro insulin

Background  Glargine is a long‐acting insulin analogue potentially more suitable than NPH insulin in intensive treatment of Type 1 diabetes mellitus (T1 DM), but no study has proven superiority. The aim of this study was to test superiority of glargine on long‐term blood glucose (BG) as well as on responses to hypoglycaemia vs. NPH.

Pharmacokinetics, pharmacodynamics and glucose counterregulation following subcutaneous injection of the monomeric insulin analogue [Lys(B28),Pro(B29)] in IDDM

SummaryThe aim of these studies was to compare the pharmacokinetics, pharmacodynamics, counterregulatory hormone and symptom responses, as well as cognitive function during hypoglycaemia induced by s. c. injection of 0.15 IU/kg of regular human insulin (HI) and the monomeric insulin analogue [Lys(B28),Pro (B29)] (MI) in insulin-dependent-diabetic (IDDM) subjects. In these studies glucose was infused whenever needed to prevent decreases in plasma glucose below 3 mmol/l. After MI, plasma insulin increased earlier to a peak (60 vs 90 min) which was greater than after HI (294±24 vs 255±24 pmol/l), and plasma glucose decreased earlier to a 3 mmol/l plateau (60 vs 120 min) (p<0.05). The amount of glucose infused to prevent plasma glucose falling below 3 mmol/l was ∼three times greater after MI than HI (293±26 vs 90±25 μmol · kg−1 · 60–375 min−1, p<0.05). After MI, hepatic glucose production was more suppressed (0.7±1 vs 5.9±0.54 μmol · kg−1 · min−1) and glucose utilization was less suppressed than after HI (11.6±0.65 vs 9.1±0.11μmol · kg−1 · min−1) (p<0.05). Similarly, plasma NEFA, glycerol, and β-OH-butyrate were more suppressed after MI than HI (p<0.05), whereas plasma lactate increased only after MI, but not after HI. Responses of counterregulatory hormones, symptoms and deterioration in cognitive function during plasma glucose plateau of 3 mmol/l were superimposable after MI and HI (p=NS). Post-hypoglycaemia hyperglycaemia was greater after MI than HI (at 480 min 12.1±1 vs 11±1 mmol/l) because of greater hepatic glucose production during insulin waning which occurred at least 135 min earlier with MI as compared to HI (p<0.05). It is concluded that counterregulatory hormones, symptoms and deterioration in cognitive function during hypoglycaemia respond similarly after MI and HI. The biological effect of MI appears greater than that of HI for at least 4 h after the s.c. injection and appears as a good candidate for achieving optimal post-prandial glucose control in IDDM.

Use of the short-acting insulin analogue lispro in intensive treatment of type 1 diabetes mellitus : Importance of appropriate replacement of basal insulin and time-interval injection-meal

To establish whether lispro may be a suitable short‐acting insulin preparation for meals in intensive treatment of Type 1 diabetes mellitus (DM) in patients already in chronic good glycaemic control with conventional insulins, 69 patients on intensive therapy (4 daily s.c. insulin injections, soluble at each meal, NPH at bedtime, HbA1c <7.5 %) were studied with an open, cross‐over design for two periods of 3 months each (lispro or soluble). The % HbA1c and frequency of hypoglycaemia were assessed under four different conditions (Groups I–IV). Lispro was always injected at mealtime, soluble 10–40 min prior to meals (with the exception of Group IV). Bedtime NPH was continued with both treatments. When lispro replaced soluble with no increase in number of daily NPH injections (Group I, n = 15), HbA1c was no different (p = NS), but frequency of hypoglycaemia was greater (p < 0.05). When NPH was given 3–4 times daily, lispro (Group II, n = 18), but not soluble (Group III, n = 12) decreased HbA1c by 0.35 ± 0.25 % with no increase in hypoglycaemia. When soluble was injected at mealtimes, HbA1c increased by 0.18 ± 0.15% and hypoglycaemia was more frequent than when soluble was injected 10–40 min prior to meals (Group IV, n = 24) (p < 0.05). It is concluded that in intensive management of Type 1 DM, lispro is superior to soluble in terms of reduction of % HbA1c and frequency of hypoglycaemia, especially for those patients who do not use a time interval between insulin injection and meal. However, these goals cannot be achieved without optimization of basal insulin.

Contribution of Autonomic Neuropathy to Reduced Plasma Adrenaline Responses to Hypoglycemia in IDDM: Evidence for a Nonselective Defect

To determine the contribution of clinically overt diabetic autonomic neuropathy (DAN) to reduced plasma adrenaline responses to hypoglycemia in IDDM and to establish its selectivity for hypoglycemia, we studied 17 IDDM patients (7 without DAN [DAN−] and 10 with DAN [DAN+]), of whom 5 had and 5 did not have postural hypotension (DAN+PH+ and DAN+PH−, respectively), and 8 nondiabetic subjects on 2 different occasions, i.e., clamped hypoglycemia (steps from 5.0 to 2.2 mmol/l plasma glucose) and 30-min steady-state exercise at 55% VO2max. Recent antecedent hypoglycemia was meticulously prevented before the studies to exclude hypoglycemia as a cause of reduced responses of adrenaline to hypoglycemia. In DAN− patients, maximal responses of adrenaline to hypoglycemia were reduced (2.44 ± 0.58 nmol/l vs. 4.9 ± 0.54 nmol/l in nondiabetic patients) (P < 0.05). In DAN+, adrenaline responses initiated at a lower plasma glucose and were lower than in DAN− (DAN+PH−, 1.06 ± 0.38 nmol/l; DAN+PH+, 0.84 ± 0.27 nmol/l; P < 0.001, but NS between PH− and PH+). In response to exercise, adrenaline increased less in DAN− (0.89 ±0.11 nmol/l) patients than in nondiabetic subjects (1.19 ± 0.14 nmol/l; NS) and only to 0.36 ± 0.07 nmol/l in DAN+PH− and 0.23 ± 0.09 nmol/l in DAN+PH+ (P < 0.001 vs. DAN− and nondiabetic subjects). These results were confirmed when nondiabetic and DAN− subjects repeated the exercise at 60 watts (35 and 41% of Vo2max, respectively), i.e., at the same absolute workload of DAN+ patients. Thus, DAN (both PH+ and PH−) contributes to reduced responses of adrenaline to hypoglycemia independently of recent antecedent hypoglycemia. The adrenaline defect in DAN is not selective for hypoglycemia.

Evidence of Increased Systemic Glucose Production and Gluconeogenesis in an Early Stage of NIDDM

To assess the mechanisms of fasting hyperglycemia in NIDDM patients with mild elevation of fasting plasma glucose (FPG) compared with NIDDM patients with overt hyperglycemia, we studied 29 patients with NIDDM, who were divided in two groups according to their fasting plasma glucose (<7.8 and ≥7.8 mmol/l for groups A and B, respectively), and 16 control subjects who were matched with NIDDM patients for age, sex, and body mass index. All subjects were infused with ]3-3H]glucose between 10:00 P.M. and 10:00 A.M. during overnight fasting to determine glucose fluxes. In 27 subjects (17 diabetic and 10 control), ]U-14C]alanine was simultaneously infused between 4:00 A.M. and 10:00 A.M. to measure gluconeogenesis (GNG) from alanine. Arterialized- venous plasma samples were collected every 30 min for measurement of glucose fluxes, GNG, and glucoregulatory hormones. In group A, plasma glucose, rate of systemic glucose production (SGP), and GNG were greater than in control subjects (7.2 ± 0.2 vs. 4.9 ± 0.1 mmol/l, 10.9 ± 0.2 vs. 9.5 ± 0.3 μmol · kg−1 · min−1, and 0.58 ± 0.04 vs. 0.37 ± 0.02 μmol · kg−1 · min−1, respectively, for group A and control subjects; mean value 8:00 A.M.-10:00 A.M., all P < 0.05). Both increased SGP and GNG correlated with plasma glucose in all subjects (r = 0.77 and r = 0.75, respectively, P < 0.005). Plasma counterregulatory hormones did not differ in NIDDM patients compared to control subjects. The present studies demonstrate that SGP and GNG are increased in NIDDM patients without overt fasting hyperglycemia.Thus these metabolic abnormalities primarily contribute to early development of overnight and fasting hyperglycemia in NIDDM.

Effects of the Short-Acting Insulin Analog [Lys(B28),Pro(B29)] on Postprandial Blood Glucose Control in IDDM

OBJECTIVE To establish the effects of the short-acting insulin analog Lispro versus human regular insulin (Hum-R) on postprandial metabolic control in IDDM. RESEARCH DESIGN AND METHODS Four studies were performed in 10 C-peptide-negative IDDM patients. Lispro or Hum-R (0.15 U/kg) or Lispro + NPH (0.07 U/kg) or Hum-R + NPH were injected subcutaneously 30 min (Hum-R) or 5 min (Lispro) before lunch. Preprandial plasma glucose (PG) was maintained on all four occasions at ∼ 7.3 mmol/l by intravenous insulin. RESULTS After subcutaneous Lispro injection, plasma free insulin (FIRI) was greater between 0 and 2 h (233 ± 22 pmol/l) than after Hum-R (197 ± 25 pmol/l) but lower between 2.25 and 7 h (81 ± 10 vs. 104 ± 13 pmol/l, P < 0.05). After Lispro, PG was lower versus Hum-R for 3 h (7.4 ± 0.6 vs. 8.3 ± 0.9 mmol/l) but subsequently increased more than after Hum-R (3.25-7h, 11.3 ± 1 vs. 9.6 ± 1.2 mmol/l), resulting in a 7-h postprandial PG greater than Hum-R (9.4 ± 0.5 vs. 8.8 ± 0.6 mmol/l) (all P < 0.05). Addition of NPH to Lispro increased the 2.5-to 7-h FIRI to 110 ± 11 pmol/l and decreased the 3.25- to 7-h PG to 7.7 ± 0.8 pmol/l, resulting in 0- to 7-h PG (7.3 ± 0.3 mmol/l) lower than after Hum-R + NPH (7.9 ± 0.5 pmol/l) (P < 0.05). CONCLUSIONS At meals, in order for Lispro to improve postprandial blood glucose not only at 2-h, but also over a 7-h period in C-peptide–negative IDDM, basal insulin must be optimally replaced.