Improved control of mealtime glucose excursions with coadministration of nateglinide and metformin.

OBJECTIVE: Nateglinide, a new short-acting D-phenylalanine derivative for treating type 2 diabetes, reduces mealtime blood glucose excursions by physiologic regulation of insulin secretion. This study evaluated the pharmacokinetic and pharmacodynamic interactions of nateglinide and metformin in subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS: A total of 12 type 2 diabetic subjects with the following baseline characteristics were enrolled: age, 56 +/- 13 years; BMI, 28.7 +/- 4.5 kg/m2; HbA1c, 8.4 +/- 1.3%; and fasting plasma glucose 13 +/- 2.8 mmol/l. All subjects had been previously treated with glyburide and were switched to metformin monotherapy for 3 weeks before study start. Subjects then randomly received, in combination with 500 mg metformin, either 120 mg nateglinide or placebo before meals for 1 day, followed by the alternate treatment 7 days later. After 1 week of washout from both drugs, subjects received 1 day of open-label nateglinide treatment. Plasma concentrations of glucose, insulin, nateglinide, and metformin were assessed frequently during inpatient periods. RESULTS: Postmeal plasma glucose levels were significantly lower in subjects treated with nateglinide plus metformin than in those treated with either drug alone (P < 0.001), especially after lunch and dinner. Coadministration of nateglinide and metformin did not affect the pharmacokinetics of either drug. All treatments were safe and well tolerated. CONCLUSIONS: Combination therapy with nateglinide and metformin was more effective than either treatment alone and did not result in any pharmacokinetic interactions. Coadministration of nateglinide and metformin appears to be an excellent option for treating patients with type 2 diabetes not controlled with monotherapy.

Short-term TPN containing n-3 fatty acids ameliorate lactic acidosis induced by endotoxin in guinea pigs.

We evaluated the effect of total parenteral nutrition (TPN) enriched with n-3 fatty acids on the physiologic response to endotoxin in guinea pigs. Animals were randomly assigned to receive TPN differing only in lipid source for 3.5 d. Group 1 received soybean fat emulsion (Intralipid) whereas group 2 received fish (menhaden) oil. During the last 7 h of TPN, animals were further randomized to have either saline or E coli endotoxin added to the infusate. Acid-base status and serum lactate concentrations were determined. Animals infused with soybean fat emulsions and endotoxin developed a significant metabolic acidosis, lactic acidemia, and decrease in mixed venous O2 compared with controls and fish-oil-treated animals (p less than 0.05). The significantly reduced serum lactate and higher mixed venous O2 in fish-oil-infused animals suggests that the underlying mechanism involves improvement in endotoxin-induced tissue hypoperfusion, presumably through alterations in prostaglandin metabolism.

Glycolytic support of adenine nucleotides in rat liver flush-preserved with UW or Collins' II. Importance of donor nutritional status.

Correlation of hepatocellular adenine nucleotides in donor liver with clinical posttransplant outcome has recently been reported. Our earlier work with rats has shown that pretreatment of donors with glucose effectively retards hepatocellular ATP losses in livers preserved in Collins' II solution through potentiation of their glycolytic capacity. The primary substrate--i.e., endogenous or exogenous glucose--was not identified. The current study was undertaken to compare the relative efficacy of the University of Wisconsin (UW) solution, which is devoid of glucose, with Collins' II in the support of adenine nucleotides through anaerobic glycolysis in flush-preserved rat liver. Adult rats were either pretreated with 25% dextrose or fasted prior to liver harvesting and preservation in either UW or Collins' II. Adenine nucleotide degradation and lactate production during preservation were assessed. For a given dietary pretreatment, losses of ATP and adenylate energy charge and lactate production were similar for UW- and Collins' II-preserved livers. Donor pretreatment with dextrose resulted in significantly higher ex vivo liver ATP, energy charge, and lactate regardless of the preservation solution. Salvageable nucleotide degradates were increased significantly in UW livers, presumably through the effects of allopurinol. These results demonstrate that effective support of adenine nucleotides by glycolysis in flush-preserved liver is independent of the presence of exogenous glucose but dependent upon the nutritional status of the donor prior to liver procurement.

The effects of chronic fish oil feeding in rats on protein catabolism induced by recombinant mediators.

The influence of dietary lipid manipulation with menhaden or safflower oil on changes in protein metabolism in rats receiving recombinant interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha/cachectin (TNF), or both combined (COINF) was examined. Whole-body protein kinetics, energy expenditure, nitrogen excretion, and liver and muscle protein synthesis were studied using tracer quantities of L-[1-14C]-leucine. Rats fed menhaden oil, high in omega-3 fatty acids, had significantly lower rates of leucine oxidation compared to safflower-fed rats after monokine infusion (P less than .05). However, muscle protein synthetic rates and the specific activity of free leucine in plasma and muscle indicated greater net muscle-protein breakdown in animals fed fish oil or receiving monokines. Rats fed omega-3 fatty acids had significantly larger livers as percent of body weight and more total liver protein than safflower oil controls (P less than .0001). Liver weight was further increased by monokines, particularly TNF and COINF (P less than .001) in both diet groups, suggesting that net hepatic anabolism occurred at the expense of net skeletal protein catabolism. Monokines as a group and COINF significantly decreased whole-body leucine flux and incorporation into protein; no effect of menhaden oil was noted. In addition, monokines increased nitrogen excretion during the 24-hour experimental period (P less than .05), and total energy expenditure rose significantly in all groups receiving IL-1 beta and COINF. The recombinant monokines IL-1 beta and TNF, particularly when coinfused, are able to reproduce many of the protein anabolic and catabolic consequences seen following infection and injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Single-dose pharmacokinetics of nateglinide in subjects with hepatic cirrhosis.

This single-dose, open-label, parallel-group study compared the pharmacokinetics and tolerability of 120 mg doses of nateglinide, a physiologic mealtime glucose regulator for type 2 diabetes, in 8 subjects with cirrhosis and 8 matched healthy subjects. In both groups, plasma concentration peaked in a median of 0.5 hours, and mean terminal elimination half-lives were comparable. Mean +/- SD pharmacokinetic parameters in cirrhotic versus healthy subjects were slightly different (Cmax, 7.7 +/- 4.9 vs. 5.6 +/- 1.3 micrograms/ml; AUC(0-t), 18.5 +/- 7.5 vs. 14.2 +/- 2.1 micrograms.h/ml, respectively). Mean apparent total clearance and mean renal clearance in both groups were comparable. Mean protein-bound fractions were equivalent; binding appeared unaltered by metabolites. One cirrhotic and 2 healthy subjects each reported one adverse event. No statistically significant or clinically relevant alteration in pharmacokinetic parameters of nateglinide resulted from hepatic dysfunction, and it was well tolerated; therefore, adjustment of nateglinide dosage is not required in subjects with mild to moderate cirrhosis.

Effect of tracer and intravenous fat emulsion on the measurement of reticuloendothelial system function.

Since the addition of lipid to intravenous feeding formulas, animal and human studies have shown impairment of the reticuloendothelial system (RES) due to slow rates of clearance and gradual accumulation of long chain triglycerides (LCT) in the liver. Medium chain triglycerides (MCT) accumulate only minimally in the liver and do not impair the RES. However, results from animal studies using technetium sulfur colloid (TSC) to assess RES function have been inconclusive. The present study reevaluates RES function after lipid infusion in guinea pigs as measured by organ distribution of TSC. Guinea pigs were fed 300 kcal/kg/day of total parenteral nutrition (TPN) for 2.5 days, with 50% of nonprotein calories as fat in the form of LCT or MCT, then injected intravenously with 2.5 or 25 microCi of TSC, and uptake by liver, spleen, and lungs was determined. Liver, lungs, and spleen all increased in size after TPN with LCT or MCT. Liver TSC uptake was significantly affected by the dose of TSC (p less than 0.05), with the high dose probably inducing an increased capacity of the liver to clear TSC from the blood. Liver uptake was not influenced by diet, but feeding MCT did significantly stimulate lung uptake of TSC (p less than 0.0001). This suggests that the hepatic TSC uptake system is not saturable, and may not be an appropriate measure of Kupffer cell function since the colloid is not phagocytosed. However, TSC blood clearance remains an excellent prognostic indicator for bacteremia and mortality in humans, and is useful for measuring global RES function.

The response to endotoxin in guinea pigs after intravenous black currant seed oil.

The influence on the metabolic response to endotoxin of three days of total parenteral nutrition with lipids high in gammalinolenic acid (18:3 omega 6, GLA) compared to soy oil (SO) was examined in acute operatively stressed guinea pigs. GLA is the precursor of dihomogammalinolenic acid (DHLA), the substrate for synthesis of "1" series prostaglandins such as PGE1, which have previously been shown to be protective in endotoxin lung injury and traumatic shock. Guinea pigs fed an intravenous diet containing black currant seed oil (BCO) emulsion (20% GLA) or soy oil emulsion (0% GLA) for 2.5 days had their arterial pH, pCO2, pO2, and bicarbonate measured at baseline and hourly during a 7-hr infusion of endotoxin (lipopolysaccharide (LPS), 2mg/kg) or saline. Plasma lactate and fatty acid profile analyses were performed at the end of the LPS infusion. Increased levels of GLA and DHLA were present in the plasma phospholipid fraction of animals fed the black currant seed oil diet, while soy-fed animals had only trace amounts of GLA. In addition, the ratio of DHLA to arachidonate was higher in animals receiving the black currant seed oil total parenteral nutrition (TPN). After 2 hr of LPS infusion, all animals exhibited the typical shock response resulting in metabolic acidosis characterized by a significant (p less than 0.05) drop in pH from 7.34 +/- .02 (SO) and 7.39 +/- .02 (BCO) at baseline to 7.14 +/- .05 and 7.22 +/- .04 by 7 hr for SO and BCO groups, respectively. Plasma lactate values at the end of the infusion were significantly elevated compared to saline in both groups (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Serum fatty acid profiles after intravenous medium chain triglyceride administration.

The serum fatty acid profiles of patients receiving either intravenous medium or long chain triglycerides were studied. Seventeen hospitalized patients, dependent on total parenteral nutrition, were randomly enrolled into a prospective study. The total parenteral nutrition (TPN) delivered amino acids and glucose and either a 75% medium chain triglyceride and 25% long chain triglyceride (MCT group) physical mixture or all long chain triglyceride (LCT group), as the respective fat sources. The amino acids and glucose were given continuously, and the lipid was given for 10 hours each day over five days. Fatty acid profiles on serum triglycerides and free fatty acids were done in the morning before any lipid was given and also later in the afternoon, near the end of the lipid administration, on days 1, 3 and 5. Medium chain fatty acids rose quickly in the triglyceride fraction in patients given MCT. Rapid MCT hydrolysis occurred as evidenced by the appearance of medium chain fatty acids in the free fatty acid fraction in the afternoon sampling. Clearance of the hydrolyzed medium chain free fatty acids (MCFFA) occurred so that little, if any, were present in the morning sampling one day later. Long chain fatty acids, as either triglycerides or free fatty acids, showed expected increases during the daily infusion, but not of such relative magnitude as the medium chain fatty acids. Medium chain fatty acid incorporation into the phospholipid or cholesterol ester fractions by the end of the five-day feeding period was present but minimal.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral absorption of CGS-20625, an insoluble drug, in dogs and man.

Oral bioavailability of highly water-insoluble drugs is often quite limited and variable, requiring the development of improved formulations. Animal models are an essential aspect of the design and testing of such formulations designed to improve absorption in man. The present report compares the absorption of CGS-20625, an insoluble drug, in dog and man after oral administration of the drug as a powder, a solid dispersion capsule, and after gastric and duodenal administration in PEG 400 solution. CGS-20625 powder (20 mg) given orally exhibited slow, delayed absorption in both dog and man, with a Cmax of 0.26 +/- 0.07 microgram/ml at Tmax of 3 hr in dog, and 0.01 +/- 0.004 microgram/ml at 2 hr in man. Administration of CGS-20625 in PEG 400 solution improved absorption in dog and man, with a Cmax of 1.2 +/- 0.10 microgram/ml at Tmax of 0.25 hr in dog, and a Cmax of 0.10 +/- 0.04 microgram/ml at 0.5 hr in man. Tmax after administration of the hard gelatin capsule formulation was 0.9 and 1.0 hr in dog and man, with Cmax of 0.89 +/- 0.16 and 0.052 +/- 0.014 microgram/ml, respectively. Absolute bioavailability of CGS-20625 powder in the dog was 0.67 +/- 0.21, whereas the bioavailabilities of the powder and the capsule relative to the PEG 400 solution were 0.84 and 1.1, respectively, in dog, and 0.41 and 0.85 respectively, in man. No significant benefits of duodenal administration were observed. Plasma levels were approximately 10-fold greater and oral clearance was approximately 5-fold less in the dog than in man. Furthermore, pharmacokinetic data were less variable and relative bioavailability was greater in dogs than in humans. Physiological factors in the gastrointestinal tract or greater first-pass metabolism in man may account for these species differences. The relative rate and extent of CGS-20625 absorption were similar between dog and man, in the order of powder < capsule < PEG 400 solution. In addition, in vivo absorption rates in both species reflect in vitro dissolution differences between the powder and the capsule. These data strongly support the use of the dog as a model for developing improved formulations of CGS-20625. Further investigation of the dog as a model to evaluate insoluble drug absorption is warranted.

Multiple-dose pharmacokinetics confirm no accumulation and dose proportionality of the novel promotile drug tegaserod (HTF 919).

OBJECTIVE: To evaluate the steady-state pharmacokinetics (PK) and dose proportionality of the selective 5-HT4 receptor partial agonist tegaserod (HTF 919) in healthy subjects. METHODS: Eighteen subjects were given 2, 6, or 12-mg doses of tegaserod twice daily (b.i.d.) for 5 days, with PK and safety assessments made during the 12 h or 24 h following first administration, and 12 h after the final dose. RESULTS: Tegaserod was rapidly absorbed [time to reach measured maximum plasma concentration after multiple administrations (tmax,ss) 1 h]. Steady-state PK were consistent with single-dose PK characteristics supporting that there was no accumulation of tegaserod in plasma based on systemic exposure. Mean measured maximum plasma concentration after multiple administrations (Cmax,ss) and area under the plasma concentration-time curve over one dosing interval (tau, 0-12 h after drug administration, AUC tau) were between 0.7 +/- 0.3 ng/ml and 5.6 +/- 2.9 ng/ml and 2.4 +/- 1.3 h.ng/ml and 20.4 +/- 14.0 h.ng/ml, respectively, indicating dose-proportional PK of tegaserod in the range 2-12 mg b.i.d. Tegaserod was safe and well tolerated. No serious adverse events were reported. CONCLUSION: Tegaserod exhibits no accumulation and dose-proportional PK after multiple doses.

Decreased loss of liver adenosine triphosphate during hypothermic preservation in rats pretreated with glucose: implications for organ donor management.

Recent studies of human donor livers indicate an association between ex vivo hepatocellular adenosine triphosphate and posttransplant graft function. To test the hypothesis that prior glucose loading of donor liver would optimize its adenosine triphosphate production and adenylate energy charge during ex vivo organ preservation, adult male rats were randomized to receive either intravenous dextrose or saline for 44 h. After this infusion, a liver lobe was exposed and freeze-clamped (time 0). The remaining liver was quickly flushed, excised, and stored in Collins' II solution at 2 degrees C for 8 h. Additional lobes were freeze-clamped at 1, 4, and 8 h. Liver adenosine triphosphate, total nucleoside triphosphates, and energy charge losses were significantly reduced in the dextrose-treated rats in comparison with saline-treated rats during the first 4 h of preservation. Although the livers from rats receiving intravenous dextrose were able to generate lactate, their glycogen stores were not utilized appreciably, suggesting that exogenous glucose served as a substrate for anaerobic glycolysis. Unesterified choline levels of the fasted rat livers were significantly higher than those from the rats receiving intravenous dextrose by the first hour, indicative of increased membrane breakdown. These results indicate that prior infusion of glucose enhances the capacity of the ex vivo liver, presumably through the induction and stabilization of key glycolytic enzymes, to anaerobically generate adenosine triphosphate. Administration of glucose to liver donors before organ procurement may improve post-transplant graft function by reducing the loss of hepatocellular energy, retarding membrane damage, and fostering glycogen storage for use in the early postoperative period.

In vitro and in situ permeability of a 'second generation' hydroxypyridinone oral iron chelator: correlation with physico-chemical properties and oral activity.

PURPOSE: The in vitro and in situ transport of CGP 65015 ((+)-3-hydroxy-1-(2-hydroxyethyl)-2-hydroxyphenyl-methyl-1H-pyridin-4-on e), a novel oral iron chelator, is described. The predictive power of these data in assessing intestinal absorption in man is described. METHODS: Caco-2 epithelial monolayer and in situ rat jejunum perfusion intestinal permeability models were utilized. In vivo iron excretion and preliminary animal pharmacokinetic experiments were described. Ionization constants and octanol/aqueous partition coefficients were measured potentiometrically. Solubilities and intrinsic dissolution rates were determined using standard procedures. RESULTS: Caco-2 cell (Papp approximately 0.25 x 10(-6) cm x s(-1)) and rat jejunum (Pw approximately 0.4) permeabilities of CGP 65015 were determined. The log D(pH 7.4) of CGP 65015 was 0.58 and its aqueous solubility was < 0.5 mg x ml(-1) (pH 3-9). The intrinsic dissolution rate of CGP 65015 in USP simulated intestinal fluid was 0.012 mg x min(-1) x cm(-2). CGP 65015 promotes iron excretion effectively and dose dependently in animals. CONCLUSIONS: Caco-2 and rat intestinal permeabilities predict incomplete oral absorption of CGP 65015 in man. Preliminary rat pharmacokinetics support this. Physico-chemical data are, also, in line and suggest that CGP 65015 may, in addition, be solubility/dissolution rate limited in vivo. Nevertheless, early animal pharmacological data demonstrate that CGP 65015 is a viable oral iron chelator candidate.

Molecular basis of cardiac troponin T isoform heterogeneity in rabbit heart.

In the rabbit heart, multiple isoforms of cardiac troponin T (cTnT1 through cTnT5, from largest in size to smallest), a protein essential for calcium-regulated myofibrillar ATPase activity, have been identified, and a correlation has been found between these isoforms and myofilament sensitivity to calcium. We have sought to establish the molecular basis of this diversity. Restriction-digest analysis of genomic DNA has indicated that the rabbit cTnT gene is a single-copy gene. cTnT cDNA clones were isolated from cDNA libraries, yielding a consensus sequence for the protein. Newborn rabbit heart cDNAs, obtained using the reverse-transcriptase polymerase chain reaction (RT-PCR), were amplified using primers derived from this cDNA. Three full-length cDNAs that differed by the inclusion or exclusion of three short nucleotide sequences within the cDNAs were obtained. Amplification in the 5' half of the cDNAs confirmed that multiple cTnT products arose because of the variable inclusion of an 18- and a 30-nt sequence. The 30-nt sequence has homology with previously described alternatively spliced exons in rat and chicken cTnT, whereas the 18-nt sequence has not been described previously. RT-PCR in the 3' half of the cDNAs confirmed an additional region of heterogeneity: the presence, in part or in full, or absence of a 9-nt region, which matches the alternatively spliced exon 12 described for rat cTnT. In vitro transcription and translation of four cDNA clones containing both the 18- and 30-nt sequences, the 30-nt sequence, the 18-nt sequence, or neither generated protein isoforms that comigrated with cTnT1, cTnT2, cTnT3, and cTnT4, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)