Serum Levels of Soluble CD26/Dipeptidyl Peptidase-IV in Type 2 Diabetes Mellitus and Its Association with Metabolic Syndrome and Therapy with Antidiabetic Agents in Malaysian Subjects

BackgroundA soluble form of CD26/dipeptidyl peptidase-IV (sCD26/DPP-IV) induces DPP-IV enzymatic activity that degrades incretin. We investigated fasting serum levels of sCD26/DPP-IV and active glucagon-like peptide-1 (GLP-1) in Malaysian patients with type 2 diabetes mellitus (T2DM) with and without metabolic syndrome (MetS), as well as the associations between sCD26/DPP-IV levels, MetS, and antidiabetic therapy.MethodsWe assessed sCD26/DPP-IV levels, active GLP-1 levels, body mass index (BMI), glucose, insulin, A1c, glucose homeostasis indices, and lipid profiles in 549 Malaysian subjects (including 257 T2DM patients with MetS, 57 T2DM patients without MetS, 71 non-diabetics with MetS, and 164 control subjects without diabetes or metabolic syndrome).ResultsFasting serum levels of sCD26/DPP-IV were significantly higher in T2DM patients with and without MetS than in normal subjects. Likewise, sCD26/DPP-IV levels were significantly higher in patients with T2DM and MetS than in non-diabetic patients with MetS. However, active GLP-1 levels were significantly lower in T2DM patients both with and without MetS than in normal subjects. In T2DM subjects, sCD26/DPP-IV levels were associated with significantly higher A1c levels, but were significantly lower in patients using monotherapy with metformin. In addition, no significant differences in sCD26/DPP-IV levels were found between diabetic subjects with and without MetS. Furthermore, sCD26/DPP-IV levels were negatively correlated with active GLP-1 levels in T2DM patients both with and without MetS. In normal subjects, sCD26/DPP-IV levels were associated with increased BMI, cholesterol, and LDL-cholesterol (LDL-c) levels.ConclusionSerum sCD26/DPP-IV levels increased in T2DM subjects with and without MetS. Active GLP-1 levels decreased in T2DM patients both with and without MetS. In addition, sCD26/DPP-IV levels were associated with Alc levels and negatively correlated with active GLP-1 levels. Moreover, metformin monotherapy was associated with reduced sCD26/DPP-IV levels. In normal subjects, sCD26/DPP-IV levels were associated with increased BMI, cholesterol, and LDL-c.     

Kinetics of Ca+ adsorption and cationic selectivity with a synaptic membrane protein

A study was conducted on the adsorption of ⁴⁵Ca²⁺ to a surface film of a hydrophobic protein derived from synaptic membranes isolated from bovine cerebellum. A kinetic analysis of Ca²⁺ displacement from the protein by various metal and organic cations could be described by a rate law based on diffusion and displacement. The relative rate constants for the displacement of bound Ca²⁺ were in the order Li⁺ <Na⁺, Rb⁺ <Cs⁺ <K⁺, NH₄⁺. Among the alkaline earth series the sequence was Mg²⁺, Sr²⁺ <Ba²⁺. Ca²⁺ adsorption could be described by a theoretical formulation which takes into account an interfacial energy and potential barrier as well as the diffusional process. An attempt was made to consider the effect of energy of hydration of the cations, surface charge, and the chemical environment at the interface on catonic selectivity. The behavior of the cations in this system significantly resemble their behavior in natural membranes, particularly excitatory ones. The structural and physicochemical environment of the protein at the interface is discussed in relation to Ca²⁺ binding and cationic selectivity.     

Prostaglandins in cerebrospinal fluid of healthy human volunteers, abstinent alcoholics and rhesus monkeys

A sensitive and selective assay for measuring prostaglandins in cerebrospinal fluid has been developed, based on the selected-ion-monitoring, electron-capture negative ionization GC/MS detection for the MO-PFB-TMS derivatives of prostaglandins E2, E1, F2 alpha, F1 alpha, and 6-keto-F1 alpha. Improvements over previously published assay procedures have been made, and the new assay has been applied to measurement of prostaglandin concentrations in lumbar CSF of healthy human volunteers, abstinent alcoholic patients, in cisternal CSF of Rhesus monkeys, and continuously sampled lumbar CSF of awake Rhesus monkeys. Results indicated that the concentrations of PGE2, PGE1, PGF1 alpha, and 6-keto-PGF1 alpha were below 15 pg/mL CSF in lumbar CSF of healthy humans and abstinent alcoholics, and in cisternal CSF of Rhesus monkeys. In contrast, continuously sampled lumbar CSF of awake Rhesus monkeys contained more than 200 pg/mL of PGE2, PGF2 alpha, and 6-keto-PGF1 alpha, probably present as a result of local production.     

Initial steps of phloroglucinol metabolism in Penicillium simplicissimum

The pathway for the aerobic catabolism of 1,3,5-trihydroxybenzene (phloroglucinol) by a new strain of Penicillium was investigated using both in vivo and in vitro cell-free systems. The fungal strain was isolated by enrichment on phloroglucinol and identified as P. simplicissimum (Oud) Thom. It grew optimally at pH 5.5 and 27°C with 119 mM (1.5%w/v) of phloroglucinol in a basal mineral salts medium. Vapours of the crystalline substrate placed in a Petri-plate lid supported the growth of the fungal colonies on the agar surface. Mycelia grown on phloroglucinol accumulated 1,2,4-trihydroxybenzene and resorcinol in the medium. Washed, resting mycelia grown on phloroglucinol, when resuspended in a buffer utilized oxygen in the presence of catechol, resorcinol, pyrogallol and phloroglucinol. A NADPH-dependent reductase in the cell-free extract reduced phloroglucinol to dihydrophloroglucinol. This electron donor could not be replaced by NADH. Resorcinol hydroxylase, phloroglucinol reductase, catechol-1,2-oxygenase, and catechol-2,3-oxygenase were detected in cell-free extracts of mycelia grown on phloroglucinol. The possible steps in the degradation of phloroglucinol are discussed.     

Effect of incubation conditions, inhibitors, 2-mercaptoethanol and testosterone on RNA synthesis in ram spermatozoa

In vitro studies on RNA synthesis using washed ram spermatozoa were carried out by measuring the incorporation of (3)H-uridine into RNA. Penicillin-G (100 mug/ml medium) was added to prevent contamination by microorganisms. Spermatozoa were quickly separated from seminal plasma by washing twice in Tris-HCl buffer (at pH 7.2) and centrifuged at 1,000 g for 5 min. Washed spermatozoa were then diluted to 1 10 , 1 20 or 1 40 (v/v) by the same buffer system (containing 400 mg% glucose) and were incubated in air at 37 degrees C for 1, 2 and 4 h. Results indicated that the rate of RNA synthesis was maximal at 1 40 semenbuffer dilution (5-8 x 10(7) spermatozoa/ml) and increased linearly up to 4 h of incubation. The rate of RNA synthesis at 1 40 dilution also increased linearly as the dose of exogenous glucose substrate was increased up to 400 mg%. Denaturation of the ram spermatozoa by 1% HgCl(2) caused almost complete inhibition of RNA synthesis that amounted to 97% of the control samples. Incubation of spermatozoa with 50, 100 or 200 mug/ml chloramphenicol also inhibited uridine incorporation by 86 to 94%, while equivalent doses of cycloheximide did not. On the other hand, the incorporation of (3)H-uridine into the RNA of ram spermatozoa was significantly enhanced by graded doses of 2-mercaptoethanol (0.2, 0.4 and 0.8 muM) and of testosterone (15 and 30 mug/ml). The results of this study indicate RNA synthesis, mainly of mitochondrial origin, by mature ram sperm. The data also suggest a role for intracellular cyclic adenosine monophosphate in the regulation of sperm RNA synthesis.     

Opioid receptor antagonist affinity ligands: 6β-bromoacetamido-6-desoxynaltrexone and 6β-thioglycolamido-6-desoxynaltrexone

The present study, utilizing thioglycolamido as the reactive group, describes the synthesis and pharmacology of a new opioid antagonist affinity ligand, 6-thioglycolamido-6-desoxynaltrexone (TAN) and compares TAN with a related known compound, 6-bromoacetamido-6-desoxynaltrexone (BAN). Both compounds were tested for their reversible and irreversible inhibition of [³H]naloxone binding to calf brain membranes. Reversible binding of BAN and TAN had K_i values of 1×10^–9 and 1×10^–10 M, respectively as determined by log probit plots. Irreversible binding was determined after extensive washing to remove all non-covalently bound ligand. At a concentration of 5×10^–8 and 1×10^–8 M for BAN and TAN irreversible binding was inhibited 50% of the maximum value. A study of the time course of irreversible inhibition of [³H]naloxone binding revealed that maximal inhibition occurred within 5 min with a concentration of 1×10^–7 M of either agent. TAN but not BAN when administered systematically to mice produced an antinociceptive effect as measured by the writhing test. When administered intracerebraventricularly BAN did not block morphine-induced analgesia for more than 2 hr; whereas, with a single ED₅₀ dose of 20 nmoles of TAN i.c.v. morphine-induced analgesia was almost completely blocked for a period of over 24 hr, as determined by the tail flick test. Although the SH group of TAN were required for the covalent interaction with opioid receptors, the site of TAN's interaction appears to involve other than protein SH groups.     

The biochemical and behavioral effects of phospholipase A2 and morphine microinjections in the periaqueductal gray of the rat

In order to characterize the in vivo action of phospholipase A2 (PLA2) on opiate receptors and opiate-induced behaviors, the effects of injections of PLA2 into the periaqueductal gray region (PAG) of the rat were assessed on free fatty acid (FFA) release, opiate-binding levels, and morphine-induced behaviors. Rats received bilateral PAG injections of 2 micrograms of PLA2 while anesthetized. One hour later, regions around the cannulae tracts in PLA2-treated rats contained over 2.5 times more FFA than saline-injected controls, and 3H-dihydromorphine binding was reduced on average more than 70%. In another series of experiments, conscious rats were given 2 micrograms of PLA2 prior to 10 micrograms of morphine through cannulae chronically implanted into the PAG. PLA2 did not significantly attenuate morphine-induced analgesia as measured by the tail-flick test to radiant heat, but did prevent the explosive motor behavior observed following morphine injections alone. PLA2 by itself did not induce analgesia, but did cause explosive motor behavior 2 hr after the injections. Neither lysophosphatidylcholine nor trypsin resulted in motor seizures following PAG injections. It was concluded that the behavioral effects of PLA2 result from the unique properties of the enzyme, rather than generalized membrane damage, and that the opioid sites and mechanisms that mediate analgesia are different from those associated with explosive motor behavior.     

Synaptic effects of the synthetic pyrethroid resmethrin in rat brain in vitro

Resmethrin (30 microM) induced release of transmitters was not affected by manipulation of the Na+ current with either choline or tetrodotoxin agents which readily reversed the effects of veratridine, deltamethrin and cypermethrin. Resmethrin (I50: 2.2 microM) inhibited the ATP dependent uptake of Ca2+ but deltamethrin and cypermethrin were much less effective. Resmethrin also displaced Ca2+ from crude synaptosomal membranes. The release promoting effects of resmethrin in rat brain in vitro are better explained by its effects on Ca2+ rather than through a specific effect on the Na+ channel. In contrast, the effects of deltamethrin and cypermethrin promote transmitter release by a Na+ dependent process.