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Biomedical subjects

F Porcellati

Publications and source records attributed to F Porcellati.

15 recordsLinked to original sources
PubMed2002

Rate of fall of blood glucose and physiological responses of counterregulatory hormones, clinical symptoms and cognitive function to hypoglycaemia in Type I diabetes mellitus in the postprandial state.

AIMS/HYPOTHESIS: The aim of this study was to establish the effect of a rate of decreasing plasma glucose concentrations on responses to hypoglycaemia, i.e. release of counterregulatory hormones, perception of symptoms, deterioration of cognitive function, and rates of forearm noradrenaline spillover, in the postprandial condition and in the sitting position. METHODS: We studied 11 subjects with Type I (insulin-dependent) diabetes mellitus, twice during clamped insulin-induced hypoglycaemia (2.4 mmol/l) after eating in the sitting position. On one occasion, plasma glucose was decreased at the rate of 0.1+/-0.003 mmol x min(-1) x l(-1) (fast fall), on the other at the rate of 0.03+/-0.001 mmol x min(-1) x l(-1) (slow fall). Subjects underwent a control euglycaemic clamp study as well. RESULTS: In response to fast-fall as compared to slow-fall hypoglycaemia, which was about 30 min longer, cognitive tasks were performed as follows: Trail-Making B, PASAT 2 s, Digit Vigilance Test and Verbal Memory deteriorated more, adrenaline increased less (2.8+/-0.5 vs 3.5+/-0.7 nmol/l, p=0.03), forearm noradrenaline spillover was greater (6.5+/-1.0 vs 5.2+/-0.4 pmol x min(-1) x 100 ml(-1), p=0.04), and symptoms were no different. After recovery from hypoglycaemia, cognitive function was still deteriorated compared to the baseline with no difference between fast and slow-fall hypoglycaemia. The evident response of glucagon to postprandial hypoglycaemia contrasted with the blunted or absent response in the fasting state. CONCLUSION/INTERPRETATION: In the postprandial condition and sitting position, fast-fall hypoglycaemia is more dangerous than slow-fall, because it deteriorates cognitive function more, and activates responses of counterregulatory hormones less than slow-fall hypoglycaemia.

Adult↗
PubMed2000

Pharmacokinetics and pharmacodynamics of subcutaneous injection of long-acting human insulin analog glargine, NPH insulin, and ultralente human insulin and continuous subcutaneous infusion of insulin lispro.

To compare the pharmacokinetics/dynamics of the long-acting insulin analog glargine with NPH, ultralente, and continuous subcutaneous (SC) infusion of insulin lispro (continuous subcutaneous insulin infusion [CSII]), 20 C-peptide-negative type 1 diabetic patients were studied on four occasions during an isoglycemic 24-h clamp. Patients received SC injection of either 0.3 U/kg glargine or NPH insulin (random sequence, crossover design). On two subsequent occasions, they received either an SC injection of ultralente (0.3 U/kg) or CSII (0.3 U x kg(-1) x 24 h(-1)) (random sequence, crossover design). After SC insulin injection or CSII, intravenous (IV) insulin was tapered, and glucose was infused to clamp plasma glucose at 130 mg/dl for 24 h. Onset of action (defined as reduction of IV insulin >50%) was earlier with NPH (0.8 +/- 0.2 h), CSII (0.5 +/- 0.1 h), and ultralente (1 +/- 0.2 h) versus glargine (1.5 +/- 0.3 h) (P < 0.05) (mean +/- SE). End of action (defined as an increase in plasma glucose >150 mg/dl) occurred later with glargine (22 +/- 4 h) than with NPH (14 +/- 3 h) (P < 0.05) but was similar with ultralente (20 +/- 6 h). NPH and ultralente exhibited a peak concentration and action (at 4.5 +/- 0.5 and 10.1 +/- 1 h, respectively) followed by waning, whereas glargine had no peak but had a flat concentration/action profile mimicking CSII. Interindividual variability (calculated as differences in SD of plasma insulin concentrations and glucose infusion rates in different treatments) was lower with glargine than with NPH and ultralente (P < 0.05) but was similar with glargine and CSII (NS). In conclusion, NPH and ultralente are both peak insulins. Duration of action of ultralente is greater, but intersubject variability is also greater than that of NPH. Glargine is a peakless insulin, it lasts nearly 24 h, it has lower intersubject variability than NPH and ultralente, and it closely mimics CSII, the gold standard of basal insulin replacement.

Adult↗
PubMed1999

Alternate splicing in human Na+-MI cotransporter gene yields differentially regulated transport isoforms.

myo-Inositol is a ubiquitous intracellular organic osmolyte and phosphoinositide precursor maintained at millimolar intracellular concentrations through the action of membrane-associated Na+-myo-inositol cotransporters (SMIT). Functional cloning and expression of a canine SMIT cDNA, which conferred SMIT activity in Xenopus oocytes, predicted a 718-amino acid peptide homologous to the Na+-glucose cotransporter with a potential protein kinase A phosphorylation site and multiple protein kinase C phosphorylation sites. A consistent approximately 1.0- to 13.5-kb array of transcripts hybridizing with this cDNA are osmotically induced in a variety of mammalian cells and species, yet SMIT activity appears to vary among different tissues and species. An open reading frame on human chromosome 21 (SLC5A3) homologous to that of the canine cDNA (96.5%) is thought to comprise an intronless human SMIT gene. Recently, this laboratory ascribed multiply sized, osmotically induced SMIT transcripts in human retinal pigment epithelial cells to the alternate utilization of several 3'-untranslated SMIT exons. This article describes an alternate splice donor site within the coding region that extends the open reading frame into the otherwise untranslated 3' exons, potentially generating novel SMIT isoforms. In these isoforms, the last putative transmembrane domain is replaced with intracellular carboxy termini containing a novel potential protein kinase A phosphorylation site and multiple protein kinase C phosphorylation sites, and this could explain the heterogeneity in the regulation and structure of the SMIT.

Alternative Splicing↗
PubMed1998

Human Na(+)-myo-inositol cotransporter gene: alternate splicing generates diverse transcripts.

Na(+)-myo-inositol cotransport activity generally maintains millimolar intracellular concentrations of myo-inositol and specifically promotes transepithelial myo-inositol transport in kidney, intestine, retina, and choroid plexus. Glucose-induced, tissue-specific myo-inositol depletion and impaired Na(+)-myo-inositol cotransport activity are implicated in the pathogenesis of diabetic complications, a process modeled in vitro in cultured human retinal pigment epithelium (RPE) cells. To explore this process at the molecular level, a human RPE cDNA library was screened with a canine Na(+)-dependent myo-inositol cotransporter (SMIT) cDNA. Overlapping cDNAs spanning 3569 nt were cloned. The resulting cDNA sequence contained a 2154-nt open reading frame, 97% identical to the canine SMIT amino acid sequence. Genomic clones containing SMIT exons suggested that the cDNA is derived from at least five exons. Hypertonic stress induced a time-dependent increase, initially in a 16-kb transcript and subsequently in 11.5-, 9.8-, 8.5-, 3.8-, and approximately 1.2-kb SMIT transcripts, that was ascribed to alternate exon splicing using exon-specific probes and direct cDNA sequencing. The human SMIT gene is a complex multiexon transcriptional unit that by alternate exon splicing generates multiple SMIT transcripts that accumulate differentially in response to hypertonic stress.

Alternative Splicing↗
PubMed1997

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 approximately 20 to approximately 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/l, 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.

Adult↗
PubMed1994

Effects of glucose on sorbitol pathway activation, cellular redox, and metabolism of myo-inositol, phosphoinositide, and diacylglycerol in cultured human retinal pigment epithelial cells.

Sorbitol (aldose reductase) pathway flux in diabetes perturbs intracellular metabolism by two putative mechanisms: reciprocal osmoregulatory depletion of other organic osmolytes e.g., myo-inositol, and alterations in NADPH/NADP+ and/or NADH/NAD+. The "osmolyte" and "redox" hypotheses predict secondary elevations in CDP-diglyceride, the rate-limiting precursor for phosphatidylinositol synthesis, but through different mechanisms: the "osmolyte" hypothesis via depletion of intracellular myo-inositol (the cosubstrate for phosphatidylinositol-synthase) and the "redox" hypothesis through enhanced de novo synthesis from triose phosphates. The osmolyte hypothesis predicts diminished phosphoinositide-derived arachidonyl-diacylglycerol, while the redox hypothesis predicts increased total diacylglycerol and phosphatidic acid. In high aldose reductase expressing retinal pigment epithelial cells, glucose-induced, aldose reductase inhibitor-sensitive CDP-diglyceride accumulation and inhibition of 32P-incorporation into phosphatidylinositol paralleled myo-inositol depletion (but not cytoplasmic redox, that was unaffected by glucose) and depletion of arachidonyl-diacylglycerol. 3 mM pyruvate added to the culture medium left cellular redox unaltered, but stimulated Na(+)-dependent myo-inositol uptake, accumulation, and incorporation into phosphatidylinositol. These results favor myo-inositol depletion rather than altered redox as the primary cause of glucose-induced aldose reductase-related defects in phospholipid metabolism in cultured retinal pigment epithelial cells.

Aldehyde Reductase↗
PubMed1993

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 approximately 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 (approximately 30% increase in norepinephrine concentration). In subjects with IDDM but without autonomic neuropathy, standing forearm vascular resistance increased approximately 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.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Effect of cigarette smoking and of a transdermal nicotine delivery system on glucoregulation in type 2 diabetes mellitus.

The effect of nicotine absorbed transdermally from a patch (TNS) and from cigarette smoking on insulin secretion and action in Type 2 diabetes has been compared. Twelve Type 2 diabetic smoking patients, aged 51 y, with diabetes for 9 y, treated either with diet and/or oral hypoglycaemic agents, were studied on three occasions, according to a double-blind, placebo-controlled, cross-over design. The subjects were investigated 12 h after their last cigarette or application of one patch of TNS 30 cm2 or TNS placebo, or whilst smoking their usual cigarette. Insulin secretion was assessed by a glucagon (1 mg IV) stimulation test. On a second occasion, insulin action was assessed by a hyperglycaemic-hyperinsulinaemic clamp, the spontaneous hyperglycaemia of the fasting state (8.61 mmol.l-1) being maintained during a 4 h insulin infusion (at 0.1 mU.kg-1.min-1 for the initial 2 h, and 1 mU.kg-1.min-1 during the last 2 h). TNS and the cigarette did not affect endogenous insulin secretion as compared to placebo. During the initial 2 h of the clamp study, plasma insulin increased from 88 to 155 pmol.l-1, hepatic glucose production (3-3H-glucose) was less suppressed after TNS (4.31 mumol.kg-1.min-1) than after placebo (2.5 mumol.kg-1.min-1), but was more suppressed than after cigarette smoking (5.61 mumol.kg-1.min-1). In the last 2 h of the clamp (plasma insulin 646 pmol.l-1), glucose utilization was less stimulated after TNS (36.1 mumol.kg-1.min-1) vs placebo (39.8 mumol.kg-1.min-1), but more than after cigarette smoking (33.6 mumol.kg-1.min-1), primarily because of a decrease in glucose storage.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Cutaneous↗
PubMed1992

Adrenergic mechanisms contribute to the late phase of hypoglycemic glucose counterregulation in humans by stimulating lipolysis.

Three studies were performed on nine normal volunteers to assess whether catecholamine-mediated lipolysis contributes to counterregulation to hypoglycemia. In these three studies, insulin was intravenously infused for 8 h (0.30 mU.kg-1.min-1 from 0 to 180 min, and 0.40 mU.kg-1.min-1 until 480 min). In study I (control study), only insulin was infused; in study II (direct + indirect effects of catecholamines), propranolol and phentolamine were superimposed to insulin and exogenous glucose was infused to reproduce the same plasma glucose (PG) concentration of study I. Study III (indirect effect of catecholamines) was the same as study II, except heparin (0.2 U.kg-1.min-1 after 80 min), 10% Intralipid (1 ml.min-1 after 160 min) and variable glucose to match PG of study II, were also infused. Glucose production (HGO), glucose utilization (Rd) [3-3H]glucose, and glucose oxidation and lipid oxidation (LO) (indirect calorimetry) were determined. In all three studies, PG decreased from approximately 4.8 to approximately 2.9 mmol/liter (P = NS between studies), and plasma glycerol and FFA decreased to a nadir at 120 min. Afterwards, in study I plasma glycerol and FFA increased by approximately 75% at 480 min, but in study II they remained approximately 40% lower than in study I, whereas in study III they rebounded as in study I (P = NS). In study II, LO was lower than in study I (1.69 +/- 0.13 vs. 3.53 +/- 0.19 mumol.kg-1.min-1, P less than 0.05); HGO was also lower between 60 and 480 min (7.48 +/- 0.57 vs. 11.6 +/- 0.35 mumol.kg-1.min-1, P less than 0.05), whereas Rd was greater between 210 and 480 min (19 +/- 0.38 vs. 11.4 +/- 0.34 mumol.kg-1.min-1, respectively, P less than 0.05). In study III, LO increased to the values of study I; between 4 and 8 h, HGO increased by approximately 2.5 mumol.kg-1.min-1, and Rd decreased by approximately 7 mumol.kg-1.min-1 vs. study II. We conclude that, in a late phase of hypoglycemia, the indirect effects of catecholamines (lipolysis mediated) account for at least approximately 50% of the adrenergic contribution to increased HGO, and approximately 85% of suppressed Rd.

Adult↗
PubMed1990

[Usefulness of plantar pressure measurement for the prevention and treatment of neuropathic diabetic foot].

A disease of the legs, and more specifically of the feet, is a frequent occurrence in diabetic patients and can lead to the major risk of amputation. The pathogenesis of this disease is complex and due to vascular damage and neuropathy. The neuropathic ulcer is a typical clinical manifestation of the "diabetic foot". The pathogenesis of this manifestation is discussed. The most important thing is to prevent this disease. The diabetologist must regularly examine the feet of the patients and measure the foot pressure. We discuss a new instrument, the Dynamic System, which we believe of great help to diabetologist in measuring the foot pressure of diabetic patients.

Diabetic Neuropathies↗
PubMed1989

Effect of pyridoxal 5'-phosphate and valproic acid on phospholipid synthesis in neuroblastoma NA.

Phospholipid metabolism in neuroblastoma cells in monolayer culture after acute exposure to pyridoxal phosphate (PLP) has been studied. (a) A strong depression of the rate of biosynthesis of cellular phospholipids from labeled choline and ethanolamine, is demonstrated in neuroblastoma cells grown in culture media containing PLP. (b) Valproic acid reverses the effect of PLP on ethanolamine and choline incorporation into cell lipid. Other anticonvulsants (clonazepam, diazepam, carbamazepine, diphenylhydantoin and ethosuximide) have little or no effect on reversing the inhibition of lipid synthesis produced by PLP. (c) PLP decreases the cellular uptake of choline. This effect might be responsible for the decreased lipid synthesis and is partially reversed by valproic acid. (d) The energy charge of the cell is not affected by either PLP or valproic acid, but it is diminished by the two compounds together. (e) The degradation of choline lipids is decreased by PLP and valproic acid. The hydrolysis of phosphocholine and the outflow of choline from cultured cells is also affected by the drugs. Variations of ethanolamine and choline transport should not be due to any effects of PLP or valproic acid on the lipid phase of the membranes since these molecules have no effect on the permeability of liposomes. (f) It is concluded that ethanolamine and choline lipid metabolism in cultured neuroblastoma cells is influenced by PLP and/or valproic acid, probably through a mechanism involving the transport of precursors across the membrane, although other mechanisms cannot be ruled out.

Energy Metabolism↗