Carlo Lalli

Acute, short-term hyperglycemia enhances shear stress-induced platelet activation in patients with type II diabetes mellitus

OBJECTIVES The aim of our study was to assess whether acute, short-term hyperglycemia affects platelet reactivity in patients with Type II diabetes mellitus (T2DM). BACKGROUND Hyperglycemic spikes are thought to precipitate ischemic events in T2DM. Previous studies have shown in vivo platelet activation in diabetes; however, no studies have assessed whether acute in vivo hyperglycemia induces further activation of platelets. METHODS In a cross-over, randomized, double-blind study, 12 patients with T2DM underwent 4 h of either acute hyperglycemia (13.9 mmol/l, 250 mg/dl) or euglycemia (5.5 mmol/l, 100 mg/dl). Shear stress-induced platelet activation, P-selectin and lysosomal integral membrane protein (LIMP) expression on platelets in the bleeding-time blood, urinary 11-dehydro-thromboxane B(2) (TxB(2)) excretion, von Willebrand factor:antigen (vWF:Ag), and von Willebrand factor:activity (vWF:activity) were measured before and after hyperglycemia or euglycemia. RESULTS Shear stress-induced platelet activation, P-selectin and LIMP expression on platelets in the bleeding-time blood, and urinary 11-dehydro-TxB(2) excretion increased significantly after hyperglycemic clamping, whereas no changes were observed after euglycemic clamping. Plasma vWF:Ag and vWF:activity increased strikingly in parallel fashion after hyperglycemic clamping, whereas no changes were observed after euglycemic clamping. CONCLUSIONS Our data demonstrate that acute, short-term hyperglycemia induces an increased activation of platelets exposed to high shear stress conditions in vitro (filtration method) or in vivo (bleeding time). In vivo platelet activation is reflected by an increased urinary excretion of 11-dehydro-TxB(2). The increased levels of vWF in the circulation correlate with the increase in platelet activation markers and may indicate some degree of causation. Acute, short-term hyperglycemia in T2DM may precipitate vascular occlusions by facilitating platelet activation.

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.

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.

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.

Strategies toward improved control during insulin lispro therapy in IDDM. Importance of basal insulin.

OBJECTIVE To examine whether overall glycemic control can be improved with insulin lispro by adjustment of the basal insulin regimen without an increased risk of hypoglycemia. RESEARCH DESIGN AND METHODS A 5-month open study was performed in 66 IDDM patients after they had been transferred from human regular insulin to insulin lispro as a premeal therapy. The premeal and basal insulin regimens were adjusted according to self-monitoring of blood glucose during the visits at 2-week to 1-month intervals. Diurnal glucose profile, hypoglycemic events, HbA1c, and patient satisfaction were evaluated. RESULTS The mean daily glucose level decreased from 9.2 ± 0.2 to 8.4 ± 0.2 mmol/l (P = 0.001) and HbA1c decreased from 8.8 ± 0.1 to 8.0 ± 0.1% (P < 0.001) (mean ± SD). The number of daily NPH injections increased from 1.4 ± 0.1 at baseline to 3.1 ± 0.1 at the end of the study. Total daily insulin dose increased by 3 U (7%) because of an 8-U (43%) rise in basal insulin, whereas premeal insulin dose decreased by 5 U (20%). The number of hypoglycemic episodes did not change during the study. Of the patients, 86% considered insulin lispro equal or better than human regular insulin. CONCLUSIONS Although the study was open, the date suggest that the appropriate combination of insulin lispro and basal insulin can improve postmeal hyperglycemia, HbA1c, and treatment satisfaction without increasing the risk of hypoglycemia.

Long-term intensive insulin therapy in IDDM: effects on HbA1c, risk for severe and mild hypoglycaemia, status of counterregulation and awareness of hypoglycaemia

SummaryThe present studies were designed to assess the percentage of HbA1c, frequency, and awareness of hypoglycaemia (H) during long-term intensive therapy (IT) of insulin-dependent diabetes mellitus (IDDM). From 1981 to 1994, 112 IDDM patients were on IT. HbA1c was 7.17±0.16% (non-diabetic subjects 3.8–5.5%), the frequency of severe H 0.01±0.009 episodes/patient-year, frequency of mild symptomatic H 35.6±2.9 episodes/patient-year. IDDM patients with HbA1c ≤ 5.5% (Group I, n=10), between 6.1–7.0% (Group II, n=12), and ≥ 7.6% (Group III, n=11) were studied to assess responses of counterregulatory hormones, symptoms and cognitive function during experimental, stepped H. Compared to 18 non-diabetic subjects, Group I exhibited high thresholds (plasma glucose had to decrease more than normal to evoke responses), and impaired responses of adrenaline, unawareness of H and delayed onset of cognitive dysfunction at the lowest glycaemic plateau (2.3 mmol/l). Group II had normal thresholds and responses, whereas Group III had low thresholds. Frequency of mild H was higher in Group I (54.5±1.9 episodes/patient-year) than in Group II and III (33.7±3.5 and 20.4±2.5 episodes/ patient-year, respectively, p<0.001) and correlated with percentage of HbA1c (r=−0.82). In conclusion: IT can maintain near-normal HbA1c and is compatible with low frequency of severe H. However, if HbA1c is less than 6.0%, mild, symptomatic H is excessively frequent and causes impaired counterregulation and H unawareness. Efforts should be made not only to maintain HbA1c ≤ 7.0%, but also to prevent, recognize and reverse iatrogenic H unawarenes during long-term IT of IDDM by maintaining HbA1c>6.0%.

Long-Term Intensive Therapy of IDDM Patients With Clinically Overt Autonomic Neuropathy: Effects on Hypoglycemia Awareness and Counterregulation

To test the hypothesis that hypoglycemia unawareness and impaired counterregulation are reversible after meticulous prevention of hypoglycemia in IDDM patients with diabetic autonomic neuropathy (DAN), 21 patients (8 without DAN [DAN−]; 13 with DAN [DAN+]; of the latter, 7 had orthostatic hypotension [DAN+PH+] and 6 did not [DAN+PH−]) and 15 nondiabetic subjects were studied during stepped hypoglycemia (plateau plasma glucose decrements from 5.0 to 2.2 mmol/l) before and 6 months after prevention of hypoglycemia (intensive therapy). After 6 months, frequency of mild hypoglycemia decreased from ∼20 to ∼2 episodes/patient-month while HbA1c increased from 6.2 ± 0.3 to 6.9 ± 0.2% (P < 0.05). Responses of adrenaline improved more in DAN− patients (from 1.17 ± 0.12 to 2.4 ± 0.22 nmol/l) than in DAN+PH− (from 0.75 ± 0.25 to 1.56 ± 0.23 nmol/l) and DAN+PH+ patients (from 0.80 ± 0.24 to 1.15 ± 0.27 nmol/l, P < 0.05) but remained lower than in nondiabetic subjects (4.9 ± 0.37 nmol/1, P < 0.05), whereas glycemic thresholds normalized only in DAN−, not DAN+. Autonomic symptoms of hypoglycemia improved but remained lower in DAN− (6.2 ± 0.6) than in nondiabetic subjects (8.1 ± 1.1) and lower in DAN+PH+ (4 ± 0.8) than in DAN+PH− subjects (5.1 ± 0.8, P < 0.05), whereas neuroglycopenic symptoms normalized (NS). Cognitive function deteriorated less before than after prevention of hypoglycemia (P < 0.05). Thus, intensive therapy with emphasis on preventing hypoglycemia reverses hypoglycemia unawareness in DAN+ patients despite marginal improvement of adrenaline responses, results in low frequency of hypoglycemia despite impaired counterregulation, and maintains HbA1c in the range of intensive therapy. We conclude that DAN, long IDDM duration per se, and antecedent recent hypoglycemia contribute to different extents to impaired adrenaline responses and hypoglycemia unawareness.

Mechanisms of Arterial Hypotension After Therapeutic Dose of Subcutaneous Insulin in Diabetic Autonomic Neuropathy

To assess whether a therapeutic, subcutaneous injection of insulin exerts hemodynamic effects in subjects with IDDM, 0.2 U/kg regular insulin was injected subcutaneously in 17 IDDM subjects: 6 without autonomic neuropathy, 7 with autonomic neuropathy and othostatic hypotension, and 4 with autonomic neuropathy but without orthostatic hypotension. Plasma glucose was maintained at ∼8.5 mM throughout the studies. Mean blood pressure, plasma norepinephrine concentration, forearm vascular resistances, and calf venous volume were measured before and 120 min after subcutaneous insulin, in the supine position and 5 min after standing. Supine plasma volume ([125I]albumin and [131I]albumin) was measured before and after subcutaneous injection of insulin. In all three groups, subcutaneous insulin activated the sympathetic nervous system (∼30% increase in norepinephrine concentration). In subjects with IDDM but without autonomic neuropathy, standing forearm vascular resistance increased ∼70% less after subcutaneous insulin, but supine or standing mean blood pressure did not decrease. In contrast, in subjects with IDDM with autonomic neuropathy and orthostatic hypotension, subcutaneous insulin decreased supine mean blood pressure (from 99 ± 3 to 94 ± 5 mmHg) and exaggerated the standing decrement in mean blood pressure (24 ± 3 vs. 19 ± 2 mmHg) (P < 0.05). This was associated with a decrease in forearm vascular resistance. Similarly, in subjects with IDDM with autonomic neuropathy without orthostatic hypotension, subcutaneously injected insulin decreased supine mean blood pressure (from 95 ± 2 to 89 ± 2 mmHg) and standing mean blood pressure by 8 ± 1 mmHg (P < 0.05). Calf venous volume was not affected by subcutaneous insulin in any of the three groups. Plasma volume did not change after subcutaneous insulin in subjects with IDDM without autonomic neuropathy, whereas it decreased in those with autonomic neuropathy and orthostatic hypotension from 1.692 ± 0.069 to 1.610 ± 0.064 L/m2, without orthostatic hypotension from 1.631 ± 0.027 to 1.593 ± 0.024 L/m2 P < 0.05). No hemodynamic effects were observed when subjects with IDDM were restudied in a control experiment where placebo (distilled water), not insulin, was injected subcutaneously. In conclusion, therapeutic doses of subcutaneous insulin activate the sympathetic nervous system; decrease blood pressure in subjects with IDDM with autonomic neuropathy, but not in those without, primarily by decreasing arterial vascular resistances and plasma volume; and have no effects of capacitance vessels. Thus, in subjects with IDDM without autonomic neuropathy, greater activation of sympathetic nervous system after subcutaneous injection of insulin prevents orthostatic hypotension. In contrast, in subjects with IDDM with autonomic neuropathy, the sympathetic nervous system failure unmasks the inhibition of sympathetic vasoconstriction by insulin, and blood pressure decreases, in part possibly because of insulin-induced decrease in plasma volume.