GLP-1-mediated delivery of tesaglitazar improves obesity and glucose metabolism in male mice

Dual agonists activating the peroxisome proliferator-activated receptors alpha and gamma (PPARɑ/ɣ) have beneficial effects on glucose and lipid metabolism in patients with type 2 diabetes, but their development was discontinued due to potential adverse effects. Here we report the design and preclinical evaluation of a molecule that covalently links the PPARɑ/ɣ dual-agonist tesaglitazar to a GLP-1 receptor agonist (GLP-1RA) to allow for GLP-1R-dependent cellular delivery of tesaglitazar. GLP-1RA/tesaglitazar does not differ from the pharmacokinetically matched GLP-1RA in GLP-1R signalling, but shows GLP-1R-dependent PPARɣ-retinoic acid receptor heterodimerization and enhanced improvements of body weight, food intake and glucose metabolism relative to the GLP-1RA or tesaglitazar alone in obese male mice. The conjugate fails to affect body weight and glucose metabolism in GLP-1R knockout mice and shows preserved effects in obese mice at subthreshold doses for the GLP-1RA and tesaglitazar. Liquid chromatography-mass spectrometry-based proteomics identified PPAR regulated proteins in the hypothalamus that are acutely upregulated by GLP-1RA/tesaglitazar. Our data show that GLP-1RA/tesaglitazar improves glucose control with superior efficacy to the GLP-1RA or tesaglitazar alone and suggest that this conjugate might hold therapeutic value to acutely treat hyperglycaemia and insulin resistance.

UPLC-MS/MS analysis of the Michaelis-Menten kinetics of CYP3A-mediated midazolam 1'- and 4-hydroxylation in rat brain microsomes

Midazolam (MDZ) is a short-acting benzodiazepine with rapid onset of action, which is metabolized by CYP3A isoenzymes to two hydroxylated metabolites, 1'-hydroxymidazolam and 4-hydroxymidazolam. The drug is also commonly used as a marker of CYP3A activity in the liver microsomes. However, the kinetics of CYP3A-mediated hydroxylation of MDZ in the brain, which contains much lower CYP content than the liver, have not been reported. In this study, UPLC-MS/MS and metabolic incubation methods were developed and validated for simultaneous measurement of low concentrations of both hydroxylated metabolites of MDZ in brain microsomes. Different concentrations of MDZ (1-500 µM) were incubated with rat brain microsomes (6.25 µg) and NADPH over a period of 10 min. After precipitation of the microsomal proteins with acetonitrile, which contained individual isotope-labeled internal standards for each metabolite, the analytes were separated on a C₁₈ UPLC column and detected by a tandem mass spectrometer. Accurate quantitation of MDZ metabolism in the brain microsomes presented several challenges unique to this tissue, which were resolved. The optimized method showed validation results in accordance with the FDA acceptance criteria, with a linearity ranging from 1 to 100 nM and a lower limit of quantitation of 0.4 pg on the column for each of the two metabolites. The method was successfully used to determine the Michaelis-Menten (MM) kinetics of MDZ 1'- and 4-hydroxylase activities in rat brain microsomes (n = 5) for the first time. The 4-hydroxylated metabolite had 2.4 fold higher maximum velocity (p < 0.01) and 1.9 fold higher (p < 0.05) MM constant values than the 1'-hydroxylated metabolite. However, intrinsic clearance values of the two metabolites were similar. The optimized analytical and metabolic incubation methods reported here may be used to study the effects of various pathophysiological and pharmacological factors on the CYP3A-mediated metabolism of MDZ in the brain.

Optimization of Truncated Glucagon Peptides to Achieve Selective, High Potency, Full Antagonists

Antagonism of glucagon's biological action is a proven strategy for decreasing glucose in diabetic animals and patients. To achieve full, potent, and selective suppression, we chemically optimized N-terminally truncated glucagon fragments for the identification and establishment of the minimum sequence peptide, [Glu9]glucagon(6-29) amide (11) as a full antagonist in cellular signaling and receptor binding (IC₅₀ = 36 nM). Substitution of Phe6 with l-3-phenyllactic acid (Pla) produced [Pla6, Glu9]glucagon(6-29) amide (21), resulting in a 3-fold improvement in receptor binding (IC₅₀ = 12 nM) and enhanced antagonist potency. Further substitution of Glu9 and Asn28 with aspartic acid yielded [Pla6, Asp28]glucagon amide (26), which demonstrated a further increase in inhibitory potency (IC₅₀ = 9 nM), and improved aqueous solubility. Peptide 26 and a palmitoylated analogue, [Pla6, Lys10(γGluγGlu-C16), Asp28]glucagon(6-29) amide (31), displayed sustained duration in vivo action that successfully reversed glucagon-induced glucose elevation in mice.

Theophylline Pharmacokinetics in Foetal Sheep: Maternal Metabolic Capacity is the Principal Driver

Understanding theophylline pharmacokinetics (PK) in the foetus is essential to prevent in utero toxicity and optimize prophylactic therapies. Previous studies in pregnancy have been obfuscated by maternal dosing and inadequate sampling in the foetus; both render modelling of foetal PK difficult. Six ewes carrying singleton foetuses received theophylline (60 mg) into the foetal jugular vein. Blood samples were drawn from the foetus and ewe over 36 hr. Serum concentrations were measured. Maternal and foetal pharmacokinetic parameters were estimated. Foetal non-compartmental pharmacokinetic parameters were as follows: half-life 7.37 ± 1.22 hr; volume of distribution 44.62 ± 11.45 L; area under the curve 14.82 ± 2.71 hr/(μg/mL); and clearance 4.15 ± 0.70 L/hr. Rapid theophylline distribution across the placenta was observed. Maternal non-compartmental pharmacokinetic parameters were as follows: half-life 6.54 ± 2.44 hr; volume of distribution 32.48 ± 9.99 L; area under the curve 16.28 ± 4.53 hr/(μg/mL); and clearance 3.69 ± 1.47 L/hr. Foetal and ewe serum concentration-time profiles were fit together into a 3-compartment population pharmacokinetic model, and parameters were as follows: central volume 1.38 ± 0.11 L; 2nd peripheral compartment volume 3.11 ± 0.29 L; 3rd peripheral compartment volume 60.14 ± 6.02 L; elimination clearance 9.89 ± 0.90 L/hr; distribution clearance between central and 2nd compartment 30.87 ± 2.31 L/hr; and distribution clearance between 2nd and 3rd compartments 13.89 ± 1.11 L/hr. Cytochrome P4501A expression was robust in maternal liver; negligible activities were observed in placenta, foetal liver and foetal kidney. In vitro protein binding of theophylline was 30% lower in foetal serum compared to maternal serum (29.7 ± 4.4 versus 42.0 ± 3.6%-bound). Free concentrations were lower in the foetus than in the ewe, suggesting active transport across placenta. In summary, foetal clearance of theophylline is attributable to rapid distribution into the maternal circulation across the placenta followed by greater maternal protein binding and metabolic activity.

Maternal low-protein diet alters the expression of real-time quantitative polymerase chain reaction reference genes in an age-, sex-, and organ-dependent manner in rat offspring

Altered perinatal environment, often manifested as low birth weight, is thought to contribute to greater susceptibility for hypertension, hyperlipidemia, and diabetes as a result of epigenetic modifications and alteration of transcriptional activity for key genes. Real-time polymerase chain reaction is a useful technique for the quantitative determination of differences in transcriptional activity. Real-time quantitative polymerase chain reaction data analyses require normalization of transcriptional activity of target genes to an endogenous control, usually a reference gene. In response to reports of altered expression of reference genes in various experimental models, we hypothesized that adverse perinatal environment alters reference gene expression. We examined the expression of the following reference genes in the offspring of a rodent maternal low-protein diet model: β-actin, hypoxanthine phosphoribosyltransferase 1, TATA-box-binding protein, glyceraldehyde-3-phosphate dehydrogenase, and glucuronidase-β in brain, heart, kidneys, and intestines. We found altered expression in brain, heart, and kidneys for each of the reference genes measured; these effects were age, organ, and sex dependent. Glyceraldehyde-3-phosphate dehydrogenase and glucuronidase-β were found to be the least affected by these variables, whereas hypoxanthine phosphoribosyltransferase 1 was the most inconsistent. Our findings underscore the importance of empirical determination of a reliable reference gene for real-time polymerase chain reaction studies in the low-protein diet model.

Ethical decision-making made easier. The use of decision trees in case management

Case managers have never before faced the multitude of difficult ethical dilemmas that now confront them daily. Legal, medical, social, and ethical considerations often fly in the face of previously reliable intuitions. The importance and urgency of facing these dilemmas head-on has resulted in clear calls for action. What are the appropriate legal, ethical, and professional parameters for effective decision making? Are normatively sensitive, but also practically sensible protocols possible? In an effort to address these concerns, Alternatives for the Older Adult, Inc., Rock Island, Illinois established an ethics committee to look into possible means of resolving or dissolving commonly occurring dilemmas. As a result of year-long deliberations, the committee formulated a decision-making strategy whose central apparatus is the decision tree--a flowchart of reasonable decisions and their consequent implications. In this article, we explore the development of this approach as well as the theory that underlies it.

A simplified valgus osteotomy of the proximal femur in children

Valgus osteotomy of the hip is required in a number of orthopedic conditions in children. We present a simplified valgus osteotomy in which a dynamic compression plate is used. This technique has the advantages of using easily available equipment, requiring only one osteotomy, and providing immediate rigid fixation while not violating the proximal femoral physis. We have used this simplified technique for valgus osteotomy in six hips in four children with excellent fixation, good maintenance of correction, and no complications.

M-mode and two-dimensional echocardiography of pulmonary emboli

The transit of peripheral emboli on two-dimensional echocardiography through the right side of the heart has not been reported before, to the best of our knowledge. Although this finding was fortuitous and unexpected in view of the transient and unpredictable nature of systemic venous emboli, it was a clinically important finding since it alerted the physician and ultimately changed the therapeutic approach. We suggest that echocardiography can detect impending pulmonary emboli by identifying random, bizarre signals reflected from the fibrin particles in the right atrium and right ventricle. Other conditions, as already mentioned, must first be excluded in order to arrive at the correct diagnosis.