P. Brunetti

Relation Between Serum Uric Acid and Risk of Cardiovascular Disease in Essential Hypertension: The PIUMA Study

The question of serum uric acid as an independent risk factor in subjects with essential hypertension remains controversial. For up to 12 years (mean, 4.0) we followed 1720 subjects with essential hypertension. At entry, all subjects were untreated and all were carefully screened for absence of cardiovascular disease, renal disease, cancer, and other important disease. Outcome measures included total cardiovascular events, fatal cardiovascular events, and all-cause mortality. During 6841 person-years of follow-up there were 184 cardiovascular events (42 fatal) and 80 deaths from all causes. In the 4 quartiles of serum uric acid (division points: 0.268, 0.309, and 0.369 mmol/L [4.5, 5.2, and 6.2 mg/dL] in men; 0.190, 0.232, and 0.274 mmol/L [3.2, 3.9, and 4.6 mg/dL] in women), the rate (per 100 person-years) of cardiovascular events was 2.51, 1.48, 2.66, and 4.27, that of fatal cardiovascular events was 0.41, 0.33, 0.38, and 1.23, and that of all-cause deaths was 1.01, 0.55, 0.93, and 2.01, respectively. The relation between uric acid and event rate was J-shaped in both genders. After adjustment for age, gender, diabetes, total cholesterol/HDL cholesterol ratio, serum creatinine, left ventricular hypertrophy, ambulatory blood pressure, and use of diuretics during follow-up, uric acid levels in the highest quartile were associated with increased risk for cardiovascular events (relative risk, 1.73; 95% CI, 1.01 to 3.00), fatal cardiovascular events (relative risk, 1.96; 95% CI, 1.02 to 3.79), and all-cause mortality (relative risk, 1.63; 95% CI, 1.02 to 2.57) in relation to the second quartile. In untreated subjects with essential hypertension, raised uric acid is a powerful risk marker for subsequent cardiovascular disease and all-cause mortality.

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.

Acute Antihyperglycemic Mechanisms of Metformin in NIDDM: Evidence for Suppression of Lipid Oxidation and Hepatic Glucose Production

To establish the antihyperglycemic mechanisms of metformin in non-insulin-dependent diabetes mellitus (NIDDM) independently of the long-term, aspecific effects of removal of glucotoxicity, 21 NIDDM subjects (14 obese, 7 nonobese) were studied on two separate occasions, with an isoglycemic (plasma glucose ∼9 mM) hyperinsulinemic (two-step insulin infusion, 2 h each, at the rate of 4 and 40 mU · m−2 · min−1) clamp combined with [3−3H]glucose infusion and indirect calorimetry, after administration of either metformin (500 mg per os, at –5 and –1 h before the clamp) or placebo. Compared with placebo, hepatic glucose production (HGP) decreased ∼30% more after metformin (from 469 ± 50 to 330 ± 54 μmol/min), but glucose uptake did not increase. Metformin suppressed free fatty acids (FFAs) by ∼17% (from 0.42 ± 0.04 to 0.35 ± 0.04 mM) and lipid oxidation by ∼25% (from 4.5 ± 0.4 to 3.4 ± 0.4 μmol · kg−1 · min−1) and increased glucose oxidation by ∼ 16% (from 16.2 ± 1.4 to 19.3 ± 1.3 μmol.kg−1 · min−1) compared with placebo (P < 0.05), but did not affect nonoxidative glucose metabolism, protein oxidation, or total energy expenditure. Suppression of FFA and lipid oxidation after metformin correlated with suppression of HGP (r = 0.70 and r = 0.51, P < 0.001). The effects of metformin in obese and nonobese subjects were no different. We conclude that the specific, antihyperglycemic effects of metformin in the clinical condition of hyperglycemia in NIDDM are primarily due to suppression of HGP, not stimulation of glucose uptake, and are mediated, at least in part, by suppression of FFA and lipid oxidation.

Circulating Insulin and Insulin Growth Factor-1 Are Independent Determinants of Left Ventricular Mass and Geometry in Essential Hypertension

BACKGROUND It is unclear whether insulin and insulin-like growth factor-1 (IGF-1) are independent determinants of left ventricular (LV) mass in essential hypertension. METHODS AND RESULTS We studied 101 never-treated nondiabetic subjects with essential hypertension. All had 24-hour noninvasive ambulatory blood pressure (ABP) monitoring and a 75-g oral glucose tolerance test. We determined fasting glucose, insulin, and IGF-1 and postload glucose and insulin 2 hours after glucose. Insulin resistance was estimated by the homeostasis model assessment (HOMA(IR)) formula. LV mass showed an association with body mass index (BMI) (r=0.47; P<0.01), postload insulin (r=0.54; P<0.01), HOMA(IR) (r=0.39; P<0.01), and IGF-1 (r=0. 43; P<0.01) and a weaker association with average 24-hour systolic and diastolic ABPs (r=0.29 and r=0.26; P<0.05) and basal insulin (r=0.31; P<0.05). Relative wall thickness was positively related to IGF-1 (r=0.39; P<0.01) but not to fasting or 2-hour postload insulin, HOMA(IR), and glucose. In a multiple regression analysis, the final LV mass model (R(2)=0.64) included IGF-1, postload insulin, average 24-hour systolic ABP, sex, and BMI. IGF-1 and postload insulin accounted for >40% of variability of LV mass. The final model (R(2)=0.36) for relative wall thickness included IGF-1 (16% total explained variability), average 24-hour systolic ABP, sex, BMI, and age but not insulin and HOMA(IR). CONCLUSIONS These data indicate that insulin and IGF-1 are powerful independent determinants of LV mass and geometry in untreated subjects with essential hypertension and normal glucose tolerance.

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.

Reversibility of Unawareness of Hypoglycemia in Patients with Insulinomas

BACKGROUND A lack of appropriate autonomic warning symptoms before the development of neuroglycopenia occurs frequently in patients with diabetes mellitus. The pathogenesis of this phenomenon is unclear, but it is associated with intensive insulin therapy, prolonged duration of diabetes, frequent episodes of hypoglycemia, and impaired glucose counterregulation. Recently, it has been proposed that repeated episodes of hypoglycemia may themselves induce the phenomenon. METHODS To test this hypothesis and to determine whether the phenomenon is reversible, we assessed autonomic and neuroglycopenic symptoms, counterregulatory hormonal responses, and cognitive function during stepped hypoglycemic-clamp studies in 6 patients with insulinomas before and approximately six months after curative surgery and in 14 normal subjects matched for age, weight, and sex. RESULTS Before surgery, the patients with insulinomas had lower scores than the normal subjects for autonomic symptoms (mean [+/- SD], 3.5 +/- 0.8 vs. 9.6 +/- 4.5) and neuroglycopenic symptoms (2.8 +/- 1.5 vs. 8.9 +/- 5.3). The patients also had impaired counterregulatory hormonal responses (their plasma epinephrine, norepinephrine, glucagon, growth hormone, and cortisol responses before surgery were 187 +/- 227 pg per milliliter [1.03 +/- 1.25 nmol per liter], 223 +/- 85 pg per milliliter [1.32 +/- 0.50 nmol per liter], 86 +/- 21 ng per liter, 7.4 +/- 5.2 micrograms per liter, and 12.1 +/- 1.5 micrograms per deciliter [334 +/- 41 nmol per liter], respectively, as compared with 842 +/- 439 pg per milliliter [4.63 +/- 2.41 nmol per liter], 519 +/- 150 pg per milliliter [3.07 +/- 0.89 nmol per liter], 201 +/- 58 ng per liter, 25.3 +/- 13.7 micrograms per liter, and 26.3 +/- 1.2 micrograms per deciliter [726 +/- 33 nmol per liter] in the normal subjects) and less deterioration in cognitive function than the normal subjects during hypoglycemia (sum of z scores for seven tests of cognitive function, 1.7 +/- 1.9 vs. 8.9 +/- 3.5) (P < 0.02 for all comparisons). Surgical cure reversed all these abnormalities (P not significant for all comparisons with the normal subjects). CONCLUSIONS Hypoglycemia itself can induce unawareness of the autonomic and neuroglycopenic symptoms of hypoglycemia and decrease the counterregulatory hormonal responses to hypoglycemia.

Long-term therapy with addition of pioglitazone to metformin compared with the addition of gliclazide to metformin in patients with type 2 diabetes: a randomized, comparative study.

This 52‐week, randomized, double‐blind study compared the efficacy and safety of metformin plus pioglitazone with the established combination of metformin plus gliclazide in type 2 diabetes mellitus.

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 Dawn Phenomenon in Normal Human Volunteers

To ascertain whether the dawn phenomenon occurs in nondiabetic individuals and, if so, whether it is due to an increase in glucose production or a decrease in glucose utilization, we determined plasma concentrations of glucose, insulin, C-peptide, and counter regulatory hormones, as well as rates of glucose production, glucose utilization, and insulin secretion at one-halfhourly intervals between 1:00 and 9:00 a.m. in eight normal volunteers. After 5:30 a.m., plasma glucose, insulin, and C-peptide concentrations all increased significantly; rates of glucose production, glucose utilization, and insulin secretion also increased (all P < 0.05). Plasma cortisol, epinephrine, and norepinephrine increased significantly from nocturnal nadirs between 4:00 and 6:30 a.m. Plasma growth hormone, which had increased episodically between 1:00 and 4:30 a.m., decreased thereafter nearly 50% (P < 0.05). Plasma glucagon did not change significantly throughout the period of observation. These results indicate that a dawn-like phenomenon, initiated by an increase in glucose production, occurs in nondiabetic individuals. Thus, early morning increases in plasma glucose concentrations and insulin requirements observed in IDDM and NIDDM may be an exaggeration of a physiologic circadian variation in hepatic insulin sensitivity induced by antecedent changes in catecholamine and/or growth hormone secretion.

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.