Oleanolic acid reduces hyperglycemia beyond treatment period with Akt/FoxO1-induced suppression of hepatic gluconeogenesis in type-2 diabetic mice.

The present study investigated the chronic efficacy of oleanolic acid (OA), a triterpenoid selected from our recent screening, on hyperglycemia in type-2 diabetic mice. C57BL/6J mice were fed a high-fat diet followed by low doses of streptozotocin to generate a type-2 diabetic model. OA (100 mg/kg/day) was administered orally for 2 weeks with its effects monitored for 6 weeks. High-fat feeding and streptozotocin generated a steady hyperglycemia (21.2 ± 1.1 mM) but OA administration reversed the hyperglycemia by ~60%. Interestingly, after the cessation of OA administration, the reversed hyperglycemia was sustained for the entire post-treatment period of the study (4 weeks) despite the reoccurrence of dyslipidemia. Examination of insulin secretion and pancreas morphology did not indicate improved ß-cell function as a likely mechanism. Urine glucose loss was decreased with substantial improvement of diabetic nephropathy after the OA treatment. Pair-feeding the OA-treated mice to an untreated group ruled out food intake as a main factor attributable for this sustained reduction in hyperglycemia. Studies with the use of glucose tracers revealed no increase in glucose influx into muscle, adipose tissue or liver in the OA-treated mice. Finally, we analyzed key regulators of gluconeogenesis in the liver and found significant increases in the phosphorylation of both Akt and FoxO1 after treatment with OA. Importantly, these increases were significantly correlated with a down-regulation of glucose-6-phosphatase expression. Our findings suggest triterpenoids are a potential source of new efficacious drugs for sustained control of hyperglycemia. The liver appears to be a major site of action, possibly by the suppression of hepatic glucose production via the Akt/FoxO1 axis.

Mice deficient in GEM GTPase show abnormal glucose homeostasis due to defects in beta-cell calcium handling.

AIMS AND HYPOTHESIS: Glucose-stimulated insulin secretion from beta-cells is a tightly regulated process that requires calcium flux to trigger exocytosis of insulin-containing vesicles. Regulation of calcium handling in beta-cells remains incompletely understood. Gem, a member of the RGK (Rad/Gem/Kir) family regulates calcium channel handling in other cell types, and Gem over-expression inhibits insulin release in insulin-secreting Min6 cells. The aim of this study was to explore the role of Gem in insulin secretion. We hypothesised that Gem may regulate insulin secretion and thus affect glucose tolerance in vivo. METHODS: Gem-deficient mice were generated and their metabolic phenotype characterised by in vivo testing of glucose tolerance, insulin tolerance and insulin secretion. Calcium flux was measured in isolated islets. RESULTS: Gem-deficient mice were glucose intolerant and had impaired glucose stimulated insulin secretion. Furthermore, the islets of Gem-deficient mice exhibited decreased free calcium responses to glucose and the calcium oscillations seen upon glucose stimulation were smaller in amplitude and had a reduced frequency. CONCLUSIONS: These results suggest that Gem plays an important role in normal beta-cell function by regulation of calcium signalling.

A gene expression signature for insulin resistance.

Insulin resistance is a heterogeneous disorder caused by a range of genetic and environmental factors, and we hypothesize that its etiology varies considerably between individuals. This heterogeneity provides significant challenges to the development of effective therapeutic regimes for long-term management of type 2 diabetes. We describe a novel strategy, using large-scale gene expression profiling, to develop a gene expression signature (GES) that reflects the overall state of insulin resistance in cells and patients. The GES was developed from 3T3-L1 adipocytes that were made "insulin resistant" by treatment with tumor necrosis factor-α (TNF-α) and then reversed with aspirin and troglitazone ("resensitized"). The GES consisted of five genes whose expression levels best discriminated between the insulin-resistant and insulin-resensitized states. We then used this GES to screen a compound library for agents that affected the GES genes in 3T3-L1 adipocytes in a way that most closely resembled the changes seen when insulin resistance was successfully reversed with aspirin and troglitazone. This screen identified both known and new insulin-sensitizing compounds including nonsteroidal anti-inflammatory agents, ß-adrenergic antagonists, ß-lactams, and sodium channel blockers. We tested the biological relevance of this GES in participants in the San Antonio Family Heart Study (n = 1,240) and showed that patients with the lowest GES scores were more insulin resistant (according to HOMA_IR and fasting plasma insulin levels; P < 0.001). These findings show that GES technology can be used for both the discovery of insulin-sensitizing compounds and the characterization of patients into subtypes of insulin resistance according to GES scores, opening the possibility of developing a personalized medicine approach to type 2 diabetes.

Effects of rosiglitazone on intramyocellular lipid accumulation in Psammomys obesus.

OBJECTIVE: To examine the effects of rosiglitazone in intramyocellular lipid (IMCL) content in diabetic Psammomys obesus using novel electron microscopy technologies. BACKGROUND: P. obesus is an unique polygenic model of obesity and type 2 diabetes. Male diabetic P. obesus were treated daily with 5 mg/Kg Rosiglitazone by oral gavage for 14 days. Data were compared with a group of age-matched diabetic P. obesus treated with saline vehicle. METHODS: Assessment of insulin resistance and adiposity were determine before and after the treatment period by oral glucose tolerance test (oGTT) and dual energy X-ray absorptiometry (DEXA) analysis. We used a new scanning electron microscopy technology, (WETSEM) to investigate the effects of rosiglitazone administration on IMCL content, size and distribution in red gastrocnemius muscle. RESULTS: Rosiglitazone treatment improved glucose tolerance in P. obesus with no difference in the overall body fat content although a significant reduction in subscapular fat mass was observed. Rosiglitazone changed the distribution of lipid droplet size in skeletal muscle. Treated animals tended to have smaller lipid droplets compared with saline-treated controls. CONCLUSIONS: Since smaller IMCL droplets are associated with improvements in insulin sensitivity, we propose that this may be an important mechanism by which rosiglitazone affects glucose tolerance.

Inhibition of inosine monophosphate dehydrogenase reduces adipogenesis and diet-induced obesity.

We previously described a putative role for inosine monophosphate dehydrogenase (IMPDH), a rate-limiting enzyme in de novo guanine nucleotide biosynthesis, in lipid accumulation. Here we present data which demonstrate that IMPDH activity is required for differentiation of preadipocytes into mature, lipid-laden adipocytes and maintenance of adipose tissue mass. In 3T3-L1 preadipocytes inhibition of IMPDH with mycophenolic acid (MPA) reduced intracellular GTP levels by 60% (p<0.05) and blocked adipogenesis (p<0.05). Co-treatment with guanosine, a substrate in the salvage pathway of nucleotide biosynthesis, restored GTP levels and adipogenesis demonstrating the specificity of these effects. Treatment of diet-induced obese mice with mycophenolate mofetil (MMF), the prodrug of MPA, for 28 days did not affect food intake or lean body mass but reduced body fat content (by 36%, p=0.002) and adipocyte size (p=0.03) and number. These data suggest that inhibition of IMPDH may represent a novel strategy to reduce adipose tissue mass.

The subcellular fractionation properties and function of insulin receptor substrate-1 (IRS-1) are independent of cytoskeletal integrity.

Efficient insulin action requires spatial and temporal coordination of signaling cascades. The prototypical insulin receptor substrate, IRS-1 plays a central role in insulin signaling. By subcellular fractionation IRS-1 is enriched in a particulate fraction, termed the high speed pellet (HSP), and its redistribution from this fraction is associated with signal attenuation and insulin resistance. Anecdotal evidence suggests the cytoskeleton may underpin the localization of IRS-1 to the HSP. In the present study we have taken a systematic approach to examine whether the cytoskeleton contributes to the subcellular fractionation properties and function of IRS-1. By standard microscopy or immunoprecipitation we were unable to detect evidence to support a specific interaction between IRS-1 and the major cytoskeletal components actin (microfilaments), vimentin (intermediate filaments), and tubulin (microtubules) in 3T3-L1 adipocytes or in CHO.IR.IRS-1 cells. Pharmacological disruption of microfilaments and microtubules, individually or in combination, was without effect on the subcellular distribution of IRS-1 or insulin-stimulated tyrosine phosphorylation in either cell type. Phosphorylation of Akt was modestly reduced (20-35%) in 3T3-L1 adipocytes but not in CHO.IR.IRS-1 cells. In cells lacking intermediate filaments (Vim(-/-)) IRS-1 expression, distribution and insulin-stimulated phosphorylation appeared normal. Even after depolymerisation of microfilaments and microtubules, insulin-stimulated phosphorylation of IRS-1 and Akt were maintained in Vim(-/-) cells. Taken together these data indicate that the characteristic subcellular fractionation properties and function of IRS-1 are unlikely to be mediated by cytoskeletal networks and that proximal insulin signaling does not require an intact cytoskeleton.

Improved glucose homeostasis and enhanced insulin signalling in Grb14-deficient mice.

Gene targeting was used to characterize the physiological role of growth factor receptor-bound (Grb)14, an adapter-type signalling protein that associates with the insulin receptor (IR). Adult male Grb14(-/-) mice displayed improved glucose tolerance, lower circulating insulin levels, and increased incorporation of glucose into glycogen in the liver and skeletal muscle. In ex vivo studies, insulin-induced 2-deoxyglucose uptake was enhanced in soleus muscle, but not in epididymal adipose tissue. These metabolic effects correlated with tissue-specific alterations in insulin signalling. In the liver, despite lower IR autophosphorylation, enhanced insulin-induced tyrosine phosphorylation of insulin receptor substrate (IRS)-1 and activation of protein kinase B (PKB) was observed. In skeletal muscle, IR tyrosine phosphorylation was normal, but signalling via IRS-1 and PKB was increased. Finally, no effect of Grb14 ablation was observed on insulin signalling in white adipose tissue. These findings demonstrate that Grb14 functions in vivo as a tissue-specific modulator of insulin action, most likely via repression of IR-mediated IRS-1 tyrosine phosphorylation, and highlight this protein as a potential target for therapeutic intervention.

Characterization of a distinct plasma membrane macrodomain in differentiated adipocytes.

Caveolae are small invaginations of the cell surface that are abundant in mature adipocytes. A recent study (Kanzaki, M., and Pessin, J. E. (2002) J. Biol. Chem. 277, 25867-25869) described novel caveolin- and actin-containing structures associated with the adipocyte cell surface that contain specific signaling proteins. We have characterized these structures, here termed "caves," using light and electron microscopy and observe that they represent surface-connected wide invaginations of the basal plasma membrane that are sometimes many micrometers in diameter. Rather than simply a caveolar domain, these structures contain all elements of the plasma membrane including clathrin-coated pits, lipid raft markers, and non-raft markers. GLUT4 is recruited to caves in response to insulin stimulation. Caves can occupy a significant proportion of the plasma membrane area and are surrounded by cortical actin. Caveolae density in caves is similar to that on the bulk plasma membrane, but because these structures protrude much deeper into the plane of focus of the light microscope molecules such as caveolin and other plasma membrane proteins appear more concentrated in caves. We conclude that the adipocyte surface membrane contains numerous wide invaginations that do not represent novel caveolar structures but rather large surface caves.

Un nuevo abordaje quirúrgico para la tenosinovitis estenosante digital / A new surgical boarding for stenosing digital tenosynovitis

Entre mayo 1996 y mayo 2001, 74 pacientes fueron operados bajo técnica de un nuevo abordaje quirúrgico para la tenosinovitis estenosante digital en el Centro Médico Paraíso, Maracaibo, estado Zulia - Venezuela. La técnica consistió en la apertura longitudinal con hojillas especiales bajo visión magnificada de la polea A1 de los tendones flexores, a través de una incisión en el pliegue de flexión de la articulación metacarpofalángica de los digitos afectados. El método resultó ser efectivo en el 100 por ciento de los casos con un 86,48 por ciento de resultados excelentes y un 12,16 por ciento de buenos. No hubo complicaciones ni repetición de los síntomas. Por lo tanto, recomendamos la técnica como método quirúrgico alternativo, ya que ofrece visión directa mientras se realiza el corte de la polea de una manera sencilla y menos traumática

Laminotomía y disquectomía bilateral en el tratamiento de la compresión radicular lumbar / Bilateral laminotomy and diskectomy in the treatment of the compression lumbar radicular

Para el tratamiento de la compresión radicular lumbar se presentan los resultados obtenidos utilizando la laminotomía bilateral asociada a disquectomía bilateral, en 235 pacientes que sufrían de lumbago o lumbociática iricapacitante. El procedimiento quirúrgico incluye una amplia laminotomia bilateral, facetectomía parcial y bilateral, tanto superiores como inferiores, disquectomía bilateral, ostectomía en V parcial de las apófisis espinosas comprometidas y foraminotomía uni o bilateral cuando estuvieron indicadas. El tiempo de evolución promedio preoperatorio fue de 14 años y tres meses. Todos los pacientes fueron estudiados clínicamente incluyendo exámenes musculares, neurológicos y de laboratorio. Radiográficamente se analizaron radiografías estáticas y dinámicas de la columna vertebral lumbar y en todos se practicó tomografía axial computarizada desde el segmento 1.3 al sacro. El control postoperatorio promedio fue de 6 años y tres meses. 92,5 por ciento de los pacientes presentaron un resultado excelente. En dos pacientes no se obtuvieron cambios significativos y no hubo resultados negativos. El 88,87 por ciento de los pacientes que presentaron déficit motor, regresaron a la normalidad. La sensibilidad fue recuperada en el 95,63 por ciento de los pacientes, el 96,50 por ciento recuperó la movilidad de la columna vertebral, el 96,59 por ciento de ellos regresaron a sus actividades habituales en 4 a 6 semanas promedio. No se presentaron complicaciones intraoperatorias, postoperatorias ni de tipo infeccioso. Se concluye que el método es beneficioso y justificable su aplicación en nuestro medio