Normalization of Insulin Sensitivity in the Obese Patient after Stable Weight Reduction with Biliopancreatic Diversion

Insulin resistance is a common feature in obese patients. To evaluate the modifications in insulin sensitivity after a bariatric operation such as Bilio-pancreatic diversion (BPD), three groups of subjects (14 normal controls (N); seven ex-obese patients (X) with at least 2 years at weight-stable conditions after BPD surgery; and eight morbidly obese patients (0)) were studied with intravenous (IVGTT) and oral (OGTT) glucose tolerance tests. The ratio of the area under the curve (AUC) for glucose over that of insulin was used as a measure of insulin sensitivity. All the following tests were conducted as Bonferroni-corrected pairwise t-tests, in case overall ANOVA was significant. No significant difference was found between N and X subjects, while obese patients showed a reduced AUCg/AUCI ratio with respect to the normal controls (O vs N: 0.01164 +/- 0.00039 vs 0.02392 +/- 0.0039, p < 0.05). IVGTT, AUCS: significant differences were found in each case: N vs X: 0.0591 +/- 0.0075 vs 0.1402 +/- 0.0399, p < 0.05; N vs 0:0.0591 +/- 0.0075 vs 0.0223 +/- 0.0031, p < 0.01; X vs 0:0.1402 +/- 0.0399 vs 0.0223 +/- 0.0031, p < 0.05. IVGTT-derived data were also analyzed using the minimal model of glucose kinetics; with this method, glucose effectiveness was significantly different between normal subject and obese subjects (0.0248 +/- 0.00288 Vs 0.00906 +/- 0.00135 per min, p < 0.001). The insulin sensitivity index was not significantly different between normal and ex-obese subjects, while both of these groups were significantly different from obese patients (N vs 0: 12.04 x 10&sup5; +/- 2.61 x 10&sup5; vs 3.29 x 10&sup5; +/- 0.61 x 10&sup5;, p < 0.066; X vs 0: 16.42 x 10&sup5; +/- 4.23 x 10&sup5; vs 3.29 x 10(1)+/- 0.61 x 10&sup5; per min per pM, p < 0.02). In conclusion, the present study indicates that, after a body weight reduction operation capable of almost re-establishing ideal body weight like BPD, obese individuals with a family history of obesity show a normalization of insulin response to glucose load.

Pharmacokinetic profile of dodecanedioic acid, a proposed alternative fuel substrate

Dodecanedioic acid (C12), a saturated, aliphatic dicarboxylic acid with 12 carbon atoms, was given as an intravenous bolus (800 mumol/kg of body weight [kgBW]) in male Wistar rats to study its pharmacokinetic profile. Because total plasma C12, which results from the sum of both free and albumin binding fractions, was measured by high-performance liquid chromatography, an in vitro experimental session was carried out to determine the binding curve of C12 in rat plasma. These data were then used to calculate the plasma C12 free fraction in in vivo experiments. The best fit obtained for the experimental data of albumin binding was obtained with the equation of reversible, saturable binding to one, two, or three classes of noninteracting equivalent sites. Only a single binding site was clearly identified with a dissociation constant of 147 mumol/L and a maximal predicted binding of 1.57 mol/mol albumin. The urinary excretion of C12 was 3.90 +/- 1.62% of the administered dose. The pharmacokinetic analysis was performed by one-compartment model with linear transfer to the tissues, taking into account simultaneously both plasma concentration and urine excretion data. The apparent volume of distribution of C12 was 0.248 +/- 0.035 L/kgBW, the apparent first order rate constant to the tissues was 0.0535 +/- 0.0123 min-1 and that from plasma to urine was 0.00206 +/- 0.00051 min-1. The C12 plasma half-life was 12.47 minutes. Renal clearance was 0.00051 L/kgBW per minute, whereas the systemic clearance was 0.0138 L/kgBW per minute. Because the renal clearance was much less than the rat inulin clearance reported in literature, the presence of C12 passive back-diffusion was hypothesized.

Kinetics of medium-chain triglycerides and free fatty acids in healthy volunteers and surgically stressed patients

To determine the hydrolysis rate of medium-chain triglycerides (MCTs) to medium-chain free fatty acids (MCFAs) and the disposition rate of MCFAs, five healthy volunteers (H) and eight surgically stressed patients (S) received 0.5 mL of Lipofundin 20% per kilogram body weight as an intravenous bolus. Serum MCTs (C8 and C10) and MCFAs were measured by high-performance liquid chromatography during the 120 minutes postinjection. A linear two-compartment model was found to be descriptive and robust: the apparent volumes of distribution were found to be similar in healthy and surgical subjects for both MCTs and MCFAs. The first-order transformation rate constant (hydrolysis) from MCTs to MCFAs was not significantly different between the H and S groups (overall 0.112 +/- 0.022/min, C8; 0.078 +/- 0.020/min, C10). The rate constant for tissue MCFA uptake from plasma was significantly different between S and H subjects both for C10 alone (H: 0.0337 +/- 0.0078; S: 0.1194 +/- 0.0240; p = .020) and for C8 and C10 together (H: 0.0382 +/- 0.0054; S: 0.1012 +/- 0.0168; p = .008), whereas it failed to attain significance when C8 alone was considered (H: 0.047 +/- 0.0077; S: 0.0829 +/- 0.0230; p = .210). These results show that use of MCTs is increased in surgical patients because of enhanced tissue uptake of the corresponding free fatty acids, whereas there does not seem to be an increase of MCT hydrolysis in response to acute disease. This would indicate that the stressed patient is in fact able to effectively use this alternative lipid substrate in the face of increased metabolic demand.

PC-based differential model fitting as a support for clinical research

A PC-based minimisation software written in C-language is described, which solves numerically both simple non-linear regression problems and problems expressed as systems of (unsolved) initial-value ordinary or partial differential equations. The software uses second-order iterated Runge-Kutta algorithm to approximate numerically the solution curves. It uses a quasi-Newton algorithm to minimize either sums of squares (weighted or unweighted) or NONMEM loss functions. Inverse Hessian approximation to the parameter dispersion and Monte Carlo generation of artificial samples are offered to test the robustness of the parameter values obtained. A real test problem is described, involving the hydrolysation of plasma Medium Chain Triglycerides to Free Fatty Acids and the uptake of these from plasma. Two competing models were evaluated, one involving linear terms for each transfer and one involving carrier-mediated, rate-limited hydrolysis and tissue absorption steps. The simpler linear model was found to be more robust and eventually used to describe the experimental data.

Dicarboxylic acids and glucose utilization in humans: effect of sebacate

Dicarboxylic acids have been proposed as an alternate lipid energetic substrate for total parenteral nutrition. No data are yet available on the possible effect of dicarboxylic acids on glucose metabolism in humans. Thus, we examined the effect of a continuous intravenous infusion of the sodium salt of the 10-carbon atom alyphatic dicarboxylic acid, sebacate (Sb), on insulin-dependent glucose metabolism in four control subjects, four patients with insulin-dependent diabetes mellitus, and four obese subjects. All subjects received a constant 5-hour infusion of saline or sebacate (6.6 g/h), in a randomized order on two different days. After 3 hours of infusion, a 120-minute euglycemic, hyperinsulinemic clamp procedure was performed (insulin infusion rate = 40 mU/m2 per minute). Glucose uptake, plasma sebacate, insulin, glucagon, C-peptide, and ketone bodies were measured. No significant differences in insulinemia were found among groups either during the saline infusion or the sebacate infusion. On the contrary, glucose uptake (molar) was significantly reduced during the sebacate vs the saline day in all three groups: 6.7 +/- 0.04 vs 3.7 +/- 1.3 in control subjects (p < .001), 4.6 +/- 0.4 vs 2.5 +/- 1.2 in patients with insulin-dependent diabetes mellitus (p < .001), and 4.8 +/- 0.5 vs 2.7 +/- 0.2 mg/kg per minute in obese subjects (p < .001). In conclusion, Sb administration was associated with a glucose-sparing effect as shown by the reduced glucose uptake in all patients studied. Sebacate did not stimulate insulin secretion, inasmuch as no modification of C-peptide plasma levels was observed after 3 hours of Sb infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum bile acid concentrations in mild liver cirrhosis

Fasting serum conjugated bile salt concentrations were measured in a group of 20 patients with moderate post-hepatitis cirrhosis. Twenty healthy volunteers were used as controls. The individual conjugated bile acids were analyzed by a specific and sensitive method which couples reversed-phase high-performance liquid chromatography with mass spectrometry. Significantly elevated levels of the total and individual conjugated bile acids were found in cirrhotic patients. The predominant serum bile acids were conjugates of chenodeoxycholic acid. The conjugates of lithocholic acid were also increased; in subjects with normal liver function, on the contrary, they were found only in traces.

Hydra: a C-language environment for real-time DOS multitasking at the bedside

Patient monitoring at the bedside is an inherently parallel job, best handled by multiple individual tasks running concurrently. Cost and diffusion considerations strongly favor the use of PC's at the bedside, but their most widespread operating system, DOS, is not built for multitasking. Hence, a software platform in C language has been prepared, allowing the intermediate programmer to easily write independent modules which will then run simultaneously without conflicts. Such a platform aims at allowing effortless sharing of data among concurrently running processes, while providing strong insulation between tasks, enough to allow multiple copies of any one task to run simultaneously unknown to each other. A cooperative, memory sharing multitasking paradigm has been chosen, which offers fine granularity of timeslicing and low execution overhead at the price of some loss in generality of design. Speed, data exchange capability and number of stackable windows are greater than with commercial packages like Windows or LabWindows. Dynamical reprioritization of tasks is built in, allowing the computerized monitor to focus its attention and resources on urgent tasks.

Cholesterol crystallization-promoting activity of aminopeptidase-N isolated from the vesicular carrier of biliary lipids

Different hydrophobic glycoproteins are associated to native biliary vesicles, which are the major carrier of biliary cholesterol. Some of these proteins promote cholesterol crystallization, a key step in cholesterol gallstone formation. This study was specifically conducted to identify the 130 kDa biliary vesicle-associated glycoprotein and to determine its in vitro effect on the cholesterol crystal formation time. The 130 kDa vesicular glycoprotein was identified as aminopeptidase-N by amino acid sequencing and specific enzymatic assay. Polyclonal antibodies raised against aminopeptidase-N allowed us to determine its concentration in human hepatic bile, which varied from 17.3 to 57.6 micrograms/ml. Aminopeptidase-N showed a concentration-dependent cholesterol crystallization activity when it was added to supersaturated model bile at a concentration range usually found in native bile. Because of this promoting effect on in vitro cholesterol crystal formation, we suggest that biliary aminopeptidase-N may play a critical role in the pathogenesis of cholesterol gallstone disease.

Kinetics and thermogenesis of medium-chain monocarboxylic and dicarboxylic acids in man: sebacate and medium-chain triglycerides

The effects on oxygen consumption and carbon dioxide production of a constant intravenous infusion of 0.15 g of disodium sebacate (Sb), the sodic salt of a medium-chain dicarboxylic acid with 10 carbon atoms, per kilogram of body weight per hour over 5 hours and a 50% mixture of medium- and long-chain triglycerides (MCT/LCT) were compared in 10 healthy men. Oxygen consumption and carbon dioxide production were measured by indirect calorimetry. Mean oxygen consumption was about 19% higher than the basal oxygen consumption at the end of MCT/LCT infusion but was only 5% higher than the basal oxygen consumption when Sb was infused. There was an eightfold increase in plasma beta-hydroxybutyrate and acetoacetate concentrations and a threefold increase in serum insulin levels during MCT/LCT infusion, but no significant change in ketone bodies and insulin from basal values was observed during and after Sb infusion. Pharmacokinetic parameters were also computed, showing an average apparent volume of distribution of 167 mL/kg of body weight for MCTs and 112 mL/kg of body weight for Sb. The t1/2 of MCTs was 50 minutes and that of Sb was 78 minutes. Urinary excretion of Sb and its beta-oxidative by-product, suberic acid, globally accounted for 48% of the given amount of Sb. In spite of its urinary loss and slower tissue uptake compared with MCTs, Sb avoided ketone body formation or elevation in insulin levels and did not induce a significant increase in oxygen consumption.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary kallikrein excretion in type 1 (insulin-dependent) diabetes mellitus

Kidney haemodynamics appear to change after the early phases of diabetic nephropathy: increases in glomerular filtration rate and in renal plasma flow have been widely reported, while kidney size is increased. As the renal kallikrein-kinin system has been demonstrated to regulate kidney blood circulation, we have evaluated the excretion of urinary kallikrein in 87 Type 1 (insulin-dependent) diabetic patients with and without hyperfiltration. Urinary kallikrein excretion was measured in 24-h urine collections. The esterolytic activity was determined by fluorimetric assay. The excretion of urinary kallikreins was significantly higher in hyperfiltering patients (472 +/- 125 esterase units/24 h) than in normofiltering (168 +/- 77 esterase units/24 h) and control subjects (151 +/- 39 esterase units/24 h), p < 0.001. Furthermore, we observed a positive correlation between urinary kallikrein excretion and glomerular filtration rate (r = 0.785). These data suggest that variations of kallikrein and kinin concentrations may play a role in the alteration of renal haemodynamics in Type 1 diabetes. It is possible that the kinin-kallikrein system, the renin-angiotensin system and the prostaglandins may interact to determine the haemodynamic alterations which are present in the diabetic disease.

Evidence of plasma CoQ10-lowering effect by HMG-CoA reductase inhibitors: a double-blind, placebo-controlled study

Inhibitors of HMG-CoA reductase are new safe and effective cholesterol-lowering agents. Elevation of alanine-amino transferase (ALT) and aspartate-amino transferase (AST) has been described in a few cases and a myopathy with elevation of creatinine kinase (CK) has been reported rarely. The inhibition of HMG-CoA reductase affects also the biosynthesis of ubiquinone (CoQ10). We studied two groups of five healthy volunteers treated with 20 mg/day of pravastatin (Squibb, Italy) or simvastatin (MSD) for a month. Then we treated 30 hypercholesterolemic patients in a double-blind controlled study with pravastatin, simvastatin (20 mg/day), or placebo for 3 months. At the beginning, and 3 months thereafter we measured plasma total cholesterol, CoQ10, ALT, AST, CK, and other parameters (urea, creatinine, uric acid, total bilirubin, gamma GT, total protein). Significant changes in the healthy volunteer group were detected for total cholesterol and CoQ10 levels, which underwent about a 40% reduction after the treatment. The same extent of reduction, compared with placebo was measured in hypercholesterolemic patients treated with pravastatin or simvastatin. Our data show that the treatment with HMG-CoA reductase inhibitors lowers both total cholesterol and CoQ10 plasma levels in normal volunteers and in hypercholesterolemic patients. CoQ10 is essential for the production of energy and also has antioxidative properties. A diminution of CoQ10 availability may be the cause of membrane alteration with consequent cellular damage.

Sebacic acid binding to human plasma albumin

Sebacic (decanedioic) acid is a dicarboxylic acid proposed recently as an alternative energy substrate in total parenteral nutrition. In this paper, binding of sebacic acid to defatted human plasma albumin, also in the presence of decanoic acid, was studied by means of equilibrium dialysis. In addition, the binding of sebacic acid in human serum was investigated. Binding to defatted albumin was analysed by a model with two independent classes of sites with different affinity constants. The fitting procedure took into account some of the measurement errors that are likely to affect the equilibrium dialysis technique. We found for sebacic acid one binding site with affinity constant 3.69 x 10(4) M-1 and four to five sites with affinity constant 7.14 x 10(2) M-1. Association constants for decanoic acid are 3-4-fold larger than those of sebacic acid. Data of binding of sebacic acid in human serum suggested that only three to five of the low affinity sites are available for binding. When disodium sebacate is administered i.v. for total parenteral nutrition, a substantial fraction of sebacic anions is likely to be bound in serum.

A rapid GLC method for the direct analysis of plasma medium chain fatty acids

A new, rapid, gas-liquid-chromatographic (GLC) method for the direct determination of plasma medium-chain fatty acids (MCFA) (from C8 to C12) which does not require derivatization procedures is described. Analysis of underivatized MCFA by GLC showed a detection limit ranging from 0.50 to 0.217 microgram depending on chain length: the longer the chain, the higher the detection limit. Compared with the HPLC and GLC methods currently described in the literature, this GLC procedure appears to be easy, adequately sensitive, accurate and well reproducible for those MCFA, like n-octanoic and n-decanoic acids, present in plasma after p.o. or i.v. MCT administration and it requires a short time (about 30 min) for complete processing.

Turnover and oxidation rates of plasma-free fatty acids in obese patients treated with dexfenfluramine

In order to assess a possible direct metabolic effect of dexfenfluramine (dF) apart from its action on food intake reduction, 10 obese postmenopausal women and 10 obese men (BMI = 32.19 +/- 1.99 kg/m2) were studied in a single-blind fashion: 4 weeks on placebo (D-28 to D0) and 4 weeks on dF (D0 to D28). A balanced diet, computed on the basis of basal metabolic rate x 1.4, was followed throughout the study. The patients' alimentary diary was checked for compliance. FFA turnover and oxidation rate, using 1-14C palmitate intravenous infusion, was determined basally (D0), after single high-dose (30 mg, D1) and after long-term (15 mg b.i.d., D28) administration. Indirect calorimetric measurements were performed using a mass spectrometer, and the usual metabolic parameters were computed. The isotope method was used in order to assess plasma FFA oxidation rate. Plasma FFA were analyzed by high-performance liquid chromatography (HPLC) and specific activity was determined at 55, 60, 65 and 70 min by counting dpm in HPLC eluates corresponding to the retention time of palmitate. The turnover rate was not significantly modified after single high-dose dF administration when compared to basal values (6.24 +/- 1.62 at D1 vs. 5.63 +/- 2.07 mmol/kg/min at D0), but was significantly increased at D28 compared with D0 (6.35 +/- 1.96 mmol/kg/min; p < 0.05). A significant increase in FFA oxidation rate was observed with respect to basal values after dF administration both at D1 (0.81 +/- 0.33 at D1 vs. 0.61 +/- 0.21 mmol/kg/min at D0; p < 0.01) and at D28 (0.77 +/- 0.34 mmol/kg/min; p < 0.015).(ABSTRACT TRUNCATED AT 250 WORDS)

The nightly spontaneous alkalinization of the stomach

Authors evaluated eighty-four 24-hour intragastric pH recordings of 73 subjects in different pathophysiologic conditions. Among them there were 12 healthy subjects, 27 duodenal ulcer patients, 10 of whom were examined both before and after treatment with H2 receptor antagonists, 18 gastro-esophageal refluxers and 16 other patients who complained of dyspepsia of various origins. Authors observed a spontaneous nocturnal alkalinization phenomenon of the stomach (SNA) which began in the latter part of the night; its onset was strongly related with sleeping and interrupted by waking up. This phenomenon was absent in duodenal ulcer patients but could be restored by treatment with anti-H2 drugs. The authors, moreover, gave evidences of a relation between SNA and the vagal integrity and modulation of the gastric secretions.

Abnormal agonist-stimulated cardiac parasympathetic acetylcholine release in streptozocin-induced diabetes

We examined the effect of three distinct depolarizing conditions on [3H]ACh release from cardiac postganglionic parasympathetic neurons in age-matched controls and insulin-treated STZ-induced diabetic rats to determine whether alterations in neurotransmitter release were present in the diabetic group. The effect of TTX, which exerts a use- and voltage-dependent block of sodium channels, was examined on the release of ACh stimulated by SRIF14 (preferentially acts at the cell body). We also studied the effect of STZ-induced diabetes on [3H]ACh release by the relatively site-specific depolarizing agent VT (preferentially acts at the axon) and high potassium (non-site-specific). Basal, SRIF14-(10(-7) M), VT-(10(-4) M), and K+ (100 mM)-stimulated [3H]ACh release was similar in control and STZ-induced diabetic animals. However, in STZ-induced diabetic but not control rats, SRIF14-induced [3H]ACh release was resistant to TTX (2 x 10(-7) M). In addition, the response to submaximal K+ (25 mM) stimulation was greater in STZ-induced diabetic compared with control animals. Treatment with insulin corrected these abnormalities. These data indicate that in the acute STZ-induced diabetic rat, SRIF14-, VT-, and high K(+)-evoked release of ACH is not impaired, which suggests that the mechanisms associated with ACh storage and release in postganglionic cardiac parasympathetic neurons are not affected in this model.(ABSTRACT TRUNCATED AT 250 WORDS)

[Lactic acidosis, hyperamylasemia, and phenformin]

Phenformin is still used in the therapy of non-insulin dependent diabetes in association with sulphonylureas. The controindications to the use of this drug often are not kept in due consideration. It is therefore often possible to observe cases of irreversible lactic acidosis with lethal outcome. In this paper, three cases of lactic acidosis from phenformin administration are reported. Some characteristics of this clinical picture are underscored: accompanying ketoacidosis, hyperamylasemia. On the basis of their observation, the Authors conclude that those diabetic patients who can be treated with diet alone or with diet and sulphonylureas must not be treated with phenformin. Metformin is then proposed as a more flexible and safer drug.

Acute myopathy associated with chronic licorice ingestion: reversible loss of myoadenylate deaminase activity

A patient with acute rhabdomyolysis and absence of myoadenylate deaminase (MADA) associated with chronic licorice intoxication is presented. Clinical and laboratory examination of the patient and morphologic study over skeletal muscle were performed. The major effect of licorice intoxication is hypokalemia, which may explain most of the observed clinical symptoms and morphological changes. The absence of MADA may be a consequence of the direct toxic effect of licorice glycosides. To our knowledge, this is the first report in which a lack of MADA and chronic licorice intoxication has been shown to be associated with clinical, histochemical, biochemical, and morphological changes, which were completely reversed with potassium supplementation and licorice withdrawal.

Twenty-four-hour intragastric pH-metry: H2-receptor antagonist restoration of nightly gastric spontaneous alkalinization in duodenal ulcer healing

Continuous 24-hour intragastric pH monitoring allows the evaluation of spontaneous late night gastric alkalinization phenomenon (SNA). This nocturnal increase of intragastric pH is strongly evident in healthy volunteers but is insignificant in patients with active duodenal ulcer. Gastric acidity was monitored by 24-hour continuous pH-metry in nine patients with active duodenal ulcer disease before and after two weeks of therapy with ranitidine. A twice daily dose of the drug (150 mg at 08.00 h and 150 mg at 20.00 h) was orally administered to each subject. Before treatment the ulcer patients did not show the SNA phenomenon, but the therapy led it to reappear. Ranitidine significantly reduced the time during which the gastric acidity was lower than 4 pH units; moreover the drug was effective on the ulcer healing during a period as brief as two weeks of therapy. At least a complete healing of the duodenal ulcer could be seen in patients whose overall gastric acidity time was reduced almost to the 40% of the pre-treatment value, meal times excluded from the pH-metric calculation.

The beta cell function in NIDDM patients with secondary failure: a three year follow-up of combined oral hypoglycemic and insulin therapy

Eleven Type 2 (non-insulin-dependent) diabetic patients, islet cell autoantibodies negative, nonobese with secondary failure to oral hypoglycemic agents (OHA) [glyburide (7.5 mg/day) and phenformin (75 mg/day)] and HbA1c 10.2 +/- 0.6% were studied. Insulin receptors on circulating monocytes, glucose utilization at supraphysiological insulin concentrations, and plasma C-peptide after i.v. glucagon were evaluated before and after 2 months of combined therapy with OHA and insulin (Ultratard HM Novo). A significant improvement was demonstrated in HbA1c and glycemia after two months of treatment. Glucose MCR was increased after two months of treatment whilst basal C-peptide was decreased as well as receptor binding to monocytes. After three years of combined therapy, body weight, glycemia and HbA1c did not increase. After three years the C-peptide basal values were significantly increased with respect to values found after 2 months of therapy. These results demonstrate that insulin treatment may restore insulin sensitivity in NIDDM patients resistant to OHA treatment and that after three years there is no exhaustion of B-cell function.

Nonselective loss of contrast sensitivity in visual system testing in early type I diabetes

OBJECTIVE

Psychophysical methods in patients with diabetes mellitus reveal deficits of central or foveal vision. Our aim was to evaluate the contrast-sensitivity thresholds in 24 insulin-dependent (type I) diabetic patients with a short disease duration and without retinopathy, taking into account metabolic control.

RESEARCH DESIGN AND METHODS

The control group consisted of age-matched nondiabetic subjects. None had visual or systemic symptoms. Contrast sensitivity measured at eight different spatial frequencies to sinusoidal bar patterns of 0.6-12.2 cycles/deg can detect functional defects in the spatially sensitive retinal ganglion cells or in higher visual pathways. We performed two different temporal types of contrast-sensitivity testing, dynamic (8 Hz) and static (0 Hz).

RESULTS

Significant losses with dynamic contrast-sensitivity test at all but the highest spatial frequencies (i.e., 12.2 cycles/deg) were shown, whereas there was significant attenuation of contrast sensitivity at five spatial frequencies (1.0, 1.4, 2.2, 7.1, and 9.6 cycles/deg) in the static mode. Grating losses (less than 2SD of control means) of contrast sensitivity were found in 33.3% (dynamic) and in 72.9% (static) of eyes of diabetic patients. HbA1c values were positively correlated at variable spatial frequencies (1.0, 1.4, and 2.2 cycles/deg for dynamic test and 0.6, 1.0, 1.4, 2.2, 4.8, and 7.1 cycles/deg for static test).

CONCLUSIONS

Our results suggest an early, generally nonselective neuronal damage of visual pathways that occurs before the onset of clinically detectable retinopathy. The visual deficit may be related directly to the effects of diabetes; repetitive minor hypoglycemic insults may contribute more than a marked hyperglycemic condition to the mechanisms underlying physiological changes along the optic nerve.

Lower limb arterio-venous shunts, autonomic neuropathy and diabetic foot

We have quantitatively assessed the percentage of lower limb arterio-venous (a-v) shunting using a radioisotopic technique and correlated it with autonomic neuropathy evaluated by cardiovascular tests. We have studied three groups of diabetic patients: Group A, 12 non-neuropathic subjects without foot lesions; Group B, 12 neuropathic subjects without foot lesions; Group C, 12 neuropathic subjects with recurrent foot ulcers. Shunting was higher in Group C (10.4 +/- 2.7%) than in Group B (6.8 +/- 2.3%, P less than 0.01) and Group A (3.8 +/- 1.2%, P less than 0.001). Shunts in Group B were higher than in Group A (P less than 0.05). All the tests exploring autonomic function were more impaired in Groups B and C than in Group A, with no difference between Groups B and C. A direct correlation was found between a-v shunting and the following cardiovascular tests: postural hypotension (PH) (r = 0.41, P less than 0.02), sustained handgrip (SH) (r = 0.56, P less than 0.001), deep breathing (DB) (r = 0.40, P less than 0.005) and lying to standing (LS) (r = 0.44, P less than 0.01). A positive correlation was also found between a-v shunts and duration of the disease (r = 0.62, P less than 0.001). Arterio-venous shunting was found to be directly related to autonomic neuropathy even if the higher shunting found in the patients with foot ulcers was not related to a higher degree of autonomic involvement; in addition, this group of patients was characterized by having a more advanced sensory and motor neuropathy. In conclusion, autonomic neuropathy, through its influence on a-v shunts, may play a role in the pathogenesis of diabetic foot, but peripheral neuropathy probably plays a key role in conditioning the development of the overt clinical manifestations of diabetic foot.

Analysis of serum conjugated bile acids by high performance liquid chromatography and mass spectrometry

A high performance liquid chromatography (HPLC) mass spectrometry (MS) system for the analysis of glycine and taurine conjugated bile acids in human fasting and postprandial sera is described. Following purification on thin layer chromatograms conjugated bile acids were separated in a RP-18 5 microns column with methanol 0.02 M KH2PO4 buffer pH 5.10 as the mobile phase at a flow rate of 1 ml/min and assayed by direct injection MS. The bile acid fractions were assayed by MS. The amounts of conjugated bile acids in the postprandial sera of 15 subjects with normal liver function were significantly higher (p less than 0.05) than in fasting ones and the glycine/taurine ratio was about 1 for both. The method is better suited for a specific research area in experiments requiring a high level of accuracy.

Metabolic effects and disposition of sebacate, an alternate dicarboxylic fuel substrate

Disodium sebacate is a 10-carbon-atom dicarboxylic acid, proposed as substrate for parenteral nutrition. We investigated its pharmacokinetic profile and thermogenic effect during a short-time infusion (5 h at 10 g/h) in 7 male volunteers. Sebacate in serum and urine was measured by high-performance liquid chromatography. A single-compartment model with two linear elimination routes was fitted. Metabolic measurements (VO2, VCO2, respiratory quotient, metabolic rate) were continuously performed for 8 h (5 h during and 3 h after the infusion) by a canopy indirect calorimeter. The apparent volume of distribution of sebacate was 8.39 +/- 0.69 liters, and the plasma fractional removal rate constant was 0.0086 +/- 0.00077 min-1. The average half-life and plasma clearance were 80.6 min and 72 ml/min, respectively. The increase in metabolic rate, the decrease in respiratory quotient and the changes in ketone body, glucagon and insulin levels during the infusion were not significant. 24-hour catecholamine excretion was within normal limits. Calories administered by sebacate seem to be available for utilization without relevant metabolic side effects.

Tracer study of metabolism and tissue distribution of sebacic acid in rats

The present study investigates the metabolic disposition of sebacic acid in rats. Three groups of experimental animals received different doses of disodium sebacate with 25 microCi of 14C-labeled molecule by intravenous injection. In the first group radioactivity plasma elimination curves were examined for two administered doses (80 and 160 mg). In the second group, expired 14CO2, urine tracer and feces tracer were counted after intravenous administration of 160 mg of sebacate. The animals of the third group were sacrificed at different times after intravenous administration of 160 mg of sebacate, and tracer elimination curves were obtained for several organs. The plasma half-life of sebacate is 38.71 min; about 35% of the administered tracer was excreted in the urine as unchanged sebacate; about 25% was eliminated as 14CO2 in expired air. Disposition of sebacate was complete within 4 h of administration. The sebacate half-life is longest in adipose tissue (135 min) and in liver (74 min), sites of likely transformation. In all other organs examined, the sebacate half-life is similar to that in plasma.