Murthy R. Akula

Synergistic effects of leucine and resveratrol on insulin sensitivity and fat metabolism in adipocytes and mice

BackgroundSirtuins are important regulators of glucose and fat metabolism, and sirtuin activation has been proposed as a therapeutic target for insulin resistance and diabetes. We have shown leucine to increase mitochondrial biogenesis and fat oxidation via Sirt1 dependent pathways. Resveratrol is a widely recognized activator of Sirt; however, the biologically-effective high concentrations used in cell and animal studies are generally impractical or difficult to achieve in humans. Accordingly, we sought to determine whether leucine would exhibit synergy with low levels of resveratrol on sirtuin-dependent outcomes in adipocytes and in diet-induced obese (DIO) mice.Methods3T3-L1 mouse adipocytes were treated with Leucine (0.5 mM), β-hydroxy-β-methyl butyrate (HMB) (5 μM) or Resveratrol (200 nM) alone or in combination. In addition, diet-induced obese mice were treated for 6-weeks with low (2 g/kg diet) or high (10 g/kg diet) dose HMB, Leucine (24 g/kg diet; 200% of normal level) or low (12.5 mg/kg diet) or high (225 mg/kg diet) dose resveratrol, alone or as combination with leucine-resveratrol or HMB-resveratrol.ResultsFatty acid oxidation, AMPK, Sirt1 and Sirt3 activity in 3T3-L1 adipocytes and in muscle cells, were significantly increased by the combinations compared to the individual treatments. Similarly, 6-week feeding of low-dose resveratrol combined with either leucine or its metabolite HMB to DIO mice increased adipose Sirt1 activity, muscle glucose and palmitate uptake (measured via PET/CT), insulin sensitivity (HOMAIR), improved inflammatory stress biomarkers (CRP, IL-6, MCP-1, adiponectin) and reduced adiposity comparable to the effects of high dose resveratrol, while low-dose resveratrol exerted no independent effect.ConclusionThese data demonstrate that either leucine or its metabolite HMB may be combined with a low concentration of resveratrol to exert synergistic effects on Sirt1-dependent outcomes; this may result in more practical dosing of resveratrol in the management of obesity, insulin-resistance and diabetes.

Synthesis of radioiodinated aryl iodides via boronate precursors.

Arylboronate esters are converted to iodine-123 labeled aryl iodides using no-carrier-added iodine-123 labeled sodium iodide in the presence of chloramine-T. High yields of radiochemically pure products are obtained.

Detection of overexpressed COX-2 in precancerous lesions of hamster pancreas and lungs by molecular imaging: implications for early diagnosis and prevention

The enzyme cyclooxygenase‐2 (COX‐2) is overexpressed in many cancers, cardiovascular disease, neurodegenerative disorders, and arthritis. Selective inhibitors of COX‐2 have been developed as therapeutics or preventive agents for these diseases. However, recent reports have revealed a significant increase in cardiovascular mortality in long‐term users of the COX‐2 inhibitors Vioxx and Celebrex, emphasizing the need for noninvasive tests that allow the identification of individuals whose COX‐2 levels are overexpressed prior to assignment to treatment with these drugs. In this study, we have prepared a radioiodinated analogue of the selective COX‐2 inhibitor celecoxib, and verified its binding to the COX‐2 enzyme in vitro. Biodistribution studies in hamsters demonstrated significantly higher levels of radiotracer in animals treated with the tobacco carcinogen NNK in lung, pancreas, and liver. Assessment of COX‐2 levels by whole‐body planar nuclear imaging two hours after injection of the radiotracer was suggestive of a distinct increase in COX‐2 in the pancreas and liver of a hamster treated for 10 weeks with NNK, in the lungs and liver of a second animal, and in the liver only, in two additional animals from the same treatment group. Immunostains showed selective overexpression of COX‐2 in pre‐neoplastic lesions of the pancreas and lungs in only those animals that showed tracer accumulation in these organs and in the livers of all NNK‐treated hamsters. Immunostains for COX‐1 yielded detectable reactions in the intestinal epithelium but not in pancreas, lungs, or liver, supporting the specificity of the tracer for COX‐2. Our data provide proof of principle for the hypothesis that molecular imaging with radiolabeled COX‐2 inhibitors can be used for the noninvasive monitoring of overexpressed COX‐2 levels.

A facile synthesis of radioiodinated (Z)-vinyl iodides via vinylboronates.

A direct radioiodination of (Z)-vinylboronic acid esters to the corresponding vinyl iodides using Na(123)I and chloramine-T is described. The boronates were prepared from vinyl iodides via palladium coupling reactions.

Synthesis and Calcium Channel Antagonist Activity of 3-Arylmethyl 5-Isopropyl l,4-Dihydro-2,6-dimethyl-4-(pyridyl)-3,5-pyridinedicarboxylates

Unsymmetrical aryl(heteroaryl)methyl isopropyl ester analogues of nifedipine, in which the 2-nitrophenyl group at C-4 is replaced by a 2- or 3-pyridyl substituent, were synthesized and evaluated as calcium-channel antagonists using guinea pig ileal longitudinal smooth muscle. The point of attachment of the C-4 pyridyl substituent was a determinant of activity where the relative potency order was 2-pyridyl > 3-pyridyl. Within the C-4 2-pyridyl series of compounds, an electronegative substituent such as a trifluoromethyl or bromo at the 4 position of the benzyl ester substituent or a nitrogen atom at the 1 position of a 4-pyridylmethyl ester substituent, enhanced activity relative to the unsubstituted benzyl ester analogue. In contrast, in the C-4 3-pyridyl class of compounds, a variety of aryl(heteroaryl)methyl ester substituents did not alter potency to any significant extent. A number of compounds in the C-4 2-pyridyl series possessing 4-pyridylmethyl, 4-trifluoromethylbenzyl, 4-bromobenzyl, and 3-pyridylmethyl ester substituents were approximately equipotent to nifedipine. The aryl(heteroaryl)methyl ester and C-4 2-pyridyl substituents therefore appear to provide important interdependent contributions to calcium-channel antagonist activity.

Synthesis of [18F]FMISO in a flow-through microfluidic reactor: Development and clinical application

INTRODUCTION The PET radiotracer [(18)F]FMISO has been used in the clinic to image hypoxia in tumors. The aim of the present study was to optimize the radiochemical parameters for the preparation of [(18)F]FMISO using a microfluidic reaction system. The main parameters evaluated were (1) precursor concentration, (2) reaction temperature, and (3) flow rate through the microfluidic reactor. Optimized conditions were then applied to the batch production of [(18)F]FMISO for clinical research use. METHODS For the determination of optimal reaction conditions within a flow-through microreactor synthesizer, 5-400 μL the precursor and dried [(18)F]fluoride solutions in acetonitrile were simultaneously pushed through the temperature-controlled reactor (60-180 °C) with defined flow rates (20-120 μL/min). Radiochemical incorporation yields to form the intermediate species were determined using radio-TLC. Hydrolysis to remove the protecting group was performed following standard vial chemistry to afford [(18)F]FMISO. RESULTS Optimum reaction parameters for the microfluidic set-up were determined as follows: 4 mg/mL of precursor, 170 °C, and 100 μL/min pump rate per reactant (200 μL/min reaction overall flow rate) to prepare the radiolabeled intermediate. The optimum hydrolysis condition was determined to be 2N HCl for 5 min at 100 °C. Large-scale batch production using the optimized conditions gave the final, ready for human injection [(18)F]FMISO product in 28.4 ± 3.0% radiochemical yield, specific activity of 119 ± 26 GBq/μmol, and >99% radiochemical and chemical purity at the end of synthesis (n = 4). CONCLUSION By using the NanoTek microfluidic synthesis system, [(18)F]FMISO was successfully prepared with good specific activity and high radiochemical purity for human use. The product generated from large-scale batch production using flow chemistry is currently being used in clinical research.

A Convenient Synthesis of Hindered N-Aryl Substituted Cyclic Amines

Abstract An efficient and high yielding synthesis of N-substituted pyrrolidines and piperidines is described.

Isotope incorporation using organoboranes

Isotopes have played an important role in chemistry, biology, and medicine. For the last three decades, we have focused on the use of organoboron compounds as precursors to isotopically labeled physiologically active reagents. During that period, we have successfully developed methods for incorporating short- and long-lived isotopes of carbon, nitrogen, oxygen, and the halogens using a variety of reactive organoboron precursors. In addition, labeling strategies employing polymer-supported organoboron derivatives were developed. In this report, we present a short overview focused on the evolution of radiolabeling techniques based on boron chemistry.

Synthesis of 7-[123I]iodotacrine : A potential spect agent to map acetylcholinesterase

9-Amino-1,2,3,4-tetrahydroacridine (Tacrine), a cognitive enhancer, is an inhibitor of the enzyme acetylcholinesterase. The synthesis of no-carrier-added 7-[123I]iodotacrine, was accomplished in four steps for potential use in mapping acetylcholinesterase. Copyright

A facile synthesis of 6-alkyl-6,7-dihydro-5H-dibenz[c, e]azepines: Potent hypolipidemics

Abstract 6-Alkyl-6, 7-dihydro-5H-dibenz[c,e]azepines were synthesized in two steps in 63–88% overall yield by utilizing an efficient borane-tetrahydrofuran reduction of imides.