The molecular basis for the beta-cell dysfunction that characterizes non-insulin-dependent diabetes mellitus (NIDDM) is unknown. The Zucker diabetic fatty (ZDF) male rat is a rodent model of NIDDM with a predictable progression from the prediabetic to the diabetic state. We are using this model to study beta-cell function during the development of diabetes with the goal of identifying genes that play a key role in regulating insulin secretion and, thus, may be potential targets for therapeutic intervention aimed at preserving or improving beta-cell function. As a first step, we have characterized morphology, insulin secretion, and pattern of gene expression in islets from prediabetic and diabetic ZDF rats. The development of diabetes was associated with changes in islet morphology, and the islets of diabetic animals were markedly hypertrophic with multiple irregular projections into the surrounding exocrine pancreas. In addition, there were multiple defects in the normal pattern of insulin secretion. The islets of prediabetic ZDF rats secreted significantly more insulin at each glucose concentration tested and showed a leftward shift in the dose-response curve relating glucose concentration and insulin secretion. Islets of prediabetic animals also demonstrated defects in the normal oscillatory pattern of insulin secretion, indicating the presence of impairment of the normal feedback control between glucose and insulin secretion. The islets from diabetic animals showed further impairment in the ability to respond to a glucose stimulus. Changes in gene expression were also evident in islets from prediabetic and diabetic ZDF rats compared with age-matched control animals. In prediabetic animals, there was no change in insulin mRNA levels. However, there was a significant 30-70% reduction in the levels of a large number of other islet mRNAs including glucokinase, mitochondrial glycerol-3-phosphate dehydrogenase, voltage-dependent Ca2+ and K+ channels, Ca(2+)-ATPase, and transcription factor Islet-1 mRNAs. In addition, there was a 40-50% increase in the levels of glucose-6-phosphatase and 12-lipoxygenase mRNAs. There were further changes in gene expression in the islets from diabetic ZDF rats, including a decrease in insulin mRNA levels that was associated with reduced islet insulin levels. Our results indicate that multiple defects in beta-cell function can be detected in islets of prediabetic animals well before the development of hyperglycemia and suggest that changes in the normal pattern of gene expression contribute to the development of beta-cell dysfunction.

Ultra-wideline 27Al NMR experiments are conducted on coordination compounds with 27Al nuclei possessing immense quadrupolar interactions that result from exceptionally nonspherical coordination environments. NMR spectra are acquired using a methodology involving frequency-stepped, piecewise acquisition of NMR spectra with Hahn-echo or quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) pulse sequences, which is applicable to any half-integer quadrupolar nucleus with extremely broad NMR powder patterns. Despite the large breadth of these central transition powder patterns, ranging from 250 to 700 kHz, the total experimental times are an order of magnitude less than previously reported experiments on analogous complexes with smaller quadrupolar interactions. The complexes examined feature three- or five-coordinate aluminum sites: trismesitylaluminum (AlMes3), tris(bis(trimethylsilyl)amino)aluminum (Al(NTMS2)3), bis[dimethyl tetrahydrofurfuryloxide aluminum] ([Me2-Al(mu-OTHF)]2), and bis[diethyl tetrahydrofurfuryloxide aluminum] ([Et2-Al(mu-OTHF)]2). We report some of the largest 27Al quadrupolar coupling constants measured to date, with values of C(Q)(27Al) of 48.2(1), 36.3(1), 19.9(1), and 19.6(2) MHz for AlMes3, Al(NTMS2)3, [Me2-Al(mu-OTHF)]2, and [Et2-Al(mu-OTHF)]2, respectively. X-ray crystallographic data and theoretical (Hartree-Fock and DFT) calculations of 27Al electric field gradient (EFG) tensors are utilized to examine the relationships between the quadrupolar interactions and molecular structure; in particular, the origin of the immense quadrupolar interaction in the three-coordinate species is studied via analyses of molecular orbitals.

Solid-state 63Cu and 65Cu NMR experiments have been conducted on a series of inorganic and organometallic copper(I) complexes possessing a variety of spherically asymmetric two-, three-, and four-coordinate Cu coordination environments. Variations in structure and symmetry, and corresponding changes in the electric field gradient (EFG) tensors, yield 63/65Cu quadrupolar coupling constants (CQ) ranging from 22.0 to 71.0 MHz for spherically asymmetric Cu sites. These large quadrupolar interactions result in spectra featuring quadrupolar-dominated central transition patterns with breadths ranging from 760 kHz to 6.7 MHz. Accordingly, Hahn-echo and/or QCPMG pulse sequences were applied in a frequency-stepped manner to rapidly acquire high S/N powder patterns. Significant copper chemical shielding anisotropies (CSAs) are also observed in some cases, ranging from 1000 to 1500 ppm. 31P CP/MAS NMR spectra for complexes featuring 63/65Cu-31P spin pairs exhibit residual dipolar coupling and are simulated to determine both the sign of CQ and the EFG tensor orientations relative to the Cu-P bond axes. X-ray crystallographic data and theoretical (Hartree-Fock and density functional theory) calculations of 63/65Cu EFG and CS tensors are utilized to examine the relationships between NMR interaction tensor parameters, the magnitudes and orientations of the principal components, and molecular structure and symmetry.

To examine the effect of increased hexosamine flux in liver, the rate-limiting enzyme in hexosamine biosynthesis (glutamine:fructose-6-phosphate amidotransferase [GFA]) was overexpressed in transgenic mice using the PEPCK promoter. Liver from random-fed transgenic mice had 1.6-fold higher GFA activity compared with nontransgenic control littermates (276 ± 24 pmol · mg -1 · min -1 in transgenic mice vs. 176 ± 18 pmol · mg -1 · min -1 in controls, P < 0.05) and higher levels of the hexosamine end product UDP-N-acetyl glucosamine (288 ± 11 pmol/g in transgenic mice vs. 233 ± 10 pmol/g in controls, P < 0.001). Younger transgenic mice compared with control mice had lower fasting serum glucose (4.8 ± 0.5 mmol/l in transgenic mice vs. 6.5 ± 0.8 mmol/l in controls, P < 0.05) without higher insulin levels (48.0 ± 7.8 pmol/l in transgenic mice vs. 56.4 ± 5.4 pmol/l in controls, P = NS); insulin levels were significantly lower in transgenic males (P < 0.05). At 6 months of age, transgenic animals had normal insulin sensitivity by the hyperinsulinemic clamp technique. Hepatic glycogen content was higher in the transgenic mice (108.6 ± 5.2 µmol/g in transgenic mice vs. 32.8 ± 1.3 µmol/g in controls, P < 0.01), associated with an inappropriate activation of glycogen synthase. Serum levels of free fatty acids (FFAs) and triglycerides were also elevated (FFAs, 0.67 ± 0.03 mmol/l in transgenic mice vs. 0.14 ± 0.01 in controls; triglycerides, 1.34 ± 0.15 mmol/l in transgenic mice vs. 0.38 ± 0.01 in controls, P < 0.01). Older transgenic mice became heavier than control mice and exhibited relative glucose intolerance and insulin resistance. The glucose disposal rate at 8 months of age was 154 ± 5 mg · kg -1 · min -1 in transgenic mice vs. 191 ± 6 mg · kg -1 · min -1 in controls (P < 0.05). We conclude that hexosamines are mediators of glucose sensing for the regulation of hepatic glycogen and lipid metabolism. Increased hexosamine flux in the liver signals a shift toward fuel storage, resulting ultimately in obesity and insulin resistance.

We report a strategic synthesis of poly(cyclosilane), a well-defined polymer inspired by crystalline silicon. The synthetic strategy relies on the design of a functionalized cyclohexasilane monomer for transition-metal-promoted dehydrocoupling polymerization. Our approach takes advantage of the dual function of the phenylsilyl group, which serves a crucial role both in the synthesis of a novel α,ω-oligosilanyl dianion and as a latent electrophile. We show that the cyclohexasilane monomer prefers a chair conformation. The monomer design ensures enhanced reactivity in transition-metal-promoted dehydrocoupling polymerization relative to secondary silanes, such as methylphenylsilane. Comprehensive NMR spectroscopy yields a detailed picture of the polymer end-group structure and microstructure. Poly(cyclosilane) has red-shifted optical absorbance relative to the monomer. We synthesize a σ-π hybrid donor-acceptor polymer by catalytic hydrosilylation.

Insulin secretion from the isolated perfused pancreas is characterized by pulses occurring every 5-15 min. The present experiments were performed to explore the role of glucose in regulating these pulses. The pancreata from 12 Wistar (W), 12 Zucker diabetic fatty (ZDF), and 6 nondiabetic lean Zucker control (ZC) male rats were isolated and perfused at 37 degrees C with an oxygenated Krebs Ringer solution containing bovine serum albumin and glucose. In W and ZDF, insulin secretion was pulsatile during constant glucose, as assessed by pulse analysis (ULTRA). The pulse period in W was significantly shorter than in ZDF (7.1 +/- 0.6 vs. 14.7 +/- 1.0 min; P < 0.001), whereas the median relative pulse amplitude was not different. When glucose was administered as a series of 10-min sine waves, spectral analysis showed that the normalized spectral power at 10 min was greater in W and ZC compared with ZDF (34.2 +/- 5.9 and 32.9 +/- 2.9 vs. 3.2 +/- 0.9; P < 0.0001), demonstrating entrainment of the insulin pulses to the exogenous glucose oscillations in W and ZC but not in ZDF. Furthermore, in ZDF, the insulin secretory rates were not higher when 28 mM rather than 7 mM glucose were used. In additional studies, islets of Langerhans from one W, three ZDF, and three ZC rats were isolated and perifused using an oscillatory glucose concentration. Single and groups of islets were studied. Islets from diabetic rats demonstrated the same lack of entrainment by glucose seen in the perfused pancreas, suggesting that the defect is at the cellular level.(ABSTRACT TRUNCATED AT 250 WORDS)

In the search for new cathode materials for rechargeable lithium batteries, conversion-type materials have great potential because of their ability to achieve high specific capacities via the full utilization of transition metal oxidation states. Here, we report for the first time that copper phosphate can be used as a novel high-capacity cathode for rechargeable Li batteries, capable of delivering a reversible capacity of 360 mAh/g with two discharge plateaus of 2.7 and 2.1 V at 400 mA/g. The underlying reaction involves the formation as well as the oxidation of metallic Cu. The solid-state NMR, in situ XAFS, HR-TEM and XRD results clearly indicate that Cu can react with Li 3 PO 4 to form copper phosphate and Li x Cu y PO 4 during the charging process, largely determining the reversibility of Cu 3 (PO 4 ) 2 . This new reaction scheme provides a new venue to explore polyanion-type compounds as high-capacity cathode materials with conversion reaction processes.

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