Effect of Rosiglitazone on Insulin Sensitivity and Body Composition in Type 2 Diabetic Patients

Objective: To investigate the effects of rosiglitazone (RSG) on insulin sensitivity and regional adiposity (including intrahepatic fat) in patients with type 2 diabetes. Research Methods and Procedures: We examined the effect of RSG (8 mg/day, 2 divided doses) compared with placebo on insulin sensitivity and body composition in 33 type 2 diabetic patients. Measurements of insulin sensitivity (euglycemic hyperinsulinemic clamp), body fat (abdominal magnetic resonance imaging and DXA), and liver fat (magnetic resonance spectroscopy) were taken at baseline and repeated after 16 weeks of treatment. Results: There was a significant improvement in glycemic control (glycosylated hemoglobin −0.7 ± 0.7%, p ≤ 0.05) and an 86% increase in insulin sensitivity in the RSG group (glucose-disposal rate change from baseline: 17.5 ± 14.5 μmol glucose/min/kg free fat mass, p < 0.05), but no significant change in the placebo group compared with baseline. Total body weight and fat mass increased (p ≤ 0.05) with RSG (2.1 ± 2.0 kg and 1.4 ± 1.6 kg, respectively) with 95% of the increase in adiposity occurring in nonabdominal regions. In the abdominal region, RSG increased subcutaneous fat area by 8% (25.0 ± 28.7 cm², p = 0.02), did not alter intra-abdominal fat area, and reduced intrahepatic fat levels by 45% (−6.7 ± 9.7%, concentration relative to water). Discussion: Our data indicate that RSG greatly improves insulin sensitivity in patients with type 2 diabetes and is associated with an increase in adiposity in subcutaneous but not visceral body regions.     

Cytomorphology of lipomatous tumors of soft tissue

OBJECTIVE: To evaluate the cytomorphologic features of benign and malignant lipomatous tumors of soft tissue on fine needle aspirates (FNA) and determine if the variants of liposarcoma could be identified. STUDY DESIGN: FNA of histologically documented benign (51 cases) and malignant (39 cases) lipomatous tumors were reviewed. Twenty-six of the 51 FNA from lipomas and 34 of the 39 FNA from malignant lipomatous tumors were satisfactory for evaluation. RESULTS: FNA from 26 cases of lipomas were cellular, with lobulated, fibroadipose tissue. Thin and thick capillaries were seen in 92% and 65% of cases, though a chicken wire vascular pattern was seen in only 4 cases (15%). A cytodiagnosis of liposarcoma could be made in 23 cases (88%), and these could be further subtyped into well-differentiated (4 cases), myxoid (8), pleomorphic (4), round cell (3) and liposarcoma, ?type (4). Only 50% of the well-differentiated liposarcomas, 3 of the 10 pleomorphic liposarcomas and 8 of the 17 myxoid liposarcomas were diagnosed as such on FNA. Cytologic diagnosis of the remaining 9 cases of myxoid liposarcoma were pleomorphic liposarcoma (1); liposarcoma, ?type (3); malignant mesenchymal tumor (1); suspicious for malignancy (2); and benign (2). There were no false positives, but there were 3 false negative cases (1 well-differentiated and 2 myxoid liposarcoma). CONCLUSION: Lipomas can be diagnosed readily. Arborizing vessels can be seen in lipomas and should be interpreted with caution. Subclassification of liposarcomas on FNA is possible but not very reliable. Myxoid liposarcomas pose a problem, and aspirates from them can mimic a wide range of morphologic subtypes. The role of FNA in identification of variants of liposarcoma is limited.     

HLA-B27 misfolding is associated with aberrant intermolecular disulfide bond formation (dimerization) in the endoplasmic reticulum

The class I protein HLA-B27 confers susceptibility to inflammatory arthritis in humans and when overexpressed in rodents for reasons that remain unclear. We demonstrated previously that HLA-B27 heavy chains (HC) undergo endoplasmic reticulum (ER)-associated degradation. We report here that HLA-B27 HC also forms two types of aberrant disulfide-linked complexes (dimers) during the folding and assembly process that can be distinguished by conformation-sensitive antibodies W6/32 and HC10. HC10-reactive dimers form immediately after HC synthesis in the ER and constitute at least 25% of the HC pool, whereas W6/32-reactive dimers appear several hours later and represent less than 10% of the folded HC. HC10-reactive dimers accumulate in the absence of tapasin or beta(2)-microglobulin, whereas W6/32-reactive dimers are not detected. Efficient formation of W6/32-reactive dimers appears to depend on the transporter associated with antigen processing, tapasin, and beta(2)-microglobulin. The unpaired Cys(67) and residues at the base of the B pocket that dramatically impair HLA-B27 HC folding are critical for the formation of HC10-reactive ER dimers. Although certain other alleles also form dimers late in the assembly pathway, ER dimerization of HLA-B27 may be unique. These results demonstrate that residues comprising the HLA-B27 B pocket result in aberrant HC folding and disulfide bond formation, and thus confer unusual properties on this molecule that are unrelated to peptide selection per se, yet may be important in disease pathogenesis.     

Automated determination of parameters describing power spectra of micrograph images in electron microscopy

The current theory of image formation in electron microscopy has been semi-quantitatively successful in describing data. The theory involves parameters due to the transfer function of the microscope (defocus, spherical aberration constant, and amplitude constant ratio) as well as parameters used to describe the background and attenuation of the signal. We present empirical evidence that at least one of the features of this model has not been well characterized. Namely the spectrum of the noise background is not accurately described by a Gaussian and associated "B-factor;" this becomes apparent when one studies high-quality far-from focus data. In order to have both our analysis and conclusions free from any innate bias, we have approached the questions by developing an automated fitting algorithm. The most important features of this routine, not currently found in the literature, are (i). a process for determining the cutoff for those frequencies below which observations and the currently adopted model are not in accord, (ii). a method for determining the resolution at which no more signal is expected to exist, and (iii). a parameter-with units of spatial frequency-that characterizes which frequencies mainly contribute to the signal. Whereas no general relation is seen to exist between either of these two quantities and the defocus, a simple empirical relationship approximately relates all three.     

Yeast Pak1 kinase associates with and activates Snf1

Members of the Snf1/AMP-activated protein kinase family are activated under conditions of nutrient stress by a distinct upstream kinase. Here we present evidence that the yeast Pak1 kinase functions as a Snf1-activating kinase. Pak1 associates with the Snf1 kinase in vivo, and the association is greatly enhanced under glucose-limiting conditions when Snf1 is active. Snf1 kinase complexes isolated from pak1Delta mutant strains show reduced specific activity in vitro, and affinity-purified Pak1 kinase is able to activate the Snf1-dependent phosphorylation of Mig1 in vitro. Purified Pak1 kinase promotes the phosphorylation of the Snf1 polypeptide on threonine 210 within the activation loop in vitro, and an increased dosage of the PAK1 gene causes increased Snf1 threonine 210 phosphorylation in vivo. Deletion of the PAK1 gene does not produce a Snf phenotype, suggesting that one or more additional protein kinases is able to activate Snf1 in vivo. However, deletion of the PAK1 gene suppresses many of the phenotypes associated with the deletion of the REG1 gene, providing genetic evidence that Pak1 activates Snf1 in vivo. The closest mammalian homologue of yeast Pak1 kinase, calcium-calmodulin-dependent protein kinase kinase beta, may play a similar role in mammalian nutrient stress signaling.     

Growth and nutritional status of Khasi boys in Northeast India relating to exogamous marriages and socioeconomic classes

The Khasis are one of the matrilineal tribes of Meghalaya in Northeast India. They belong to the Indo-Mongoloid racial stock, and speak the Monkhmer language of the Austro-Asiatic group. They have their own traditional religion (Niam Khasi), but about 65% of them have converted to Christianity. A few Khasi members have also embraced Islam through matrimonial relationship with immigrant Muslim males. The present study was based on a cross-sectional sample of 1,351 urban Khasi boys aged 3-18 years belonging to these three religious groups, with a view to understanding the effects of socioeconomic factors on growth and nutritional status, using anthropometric variables such as weight and height. The findings showed that about 60%, 29%, and 6% of these boys were below -2 Z-scores of the US National Center for Health Statistics (NCHS) references in respect of weight for age, height for age, and body mass index for age, respectively. The logistic regression coefficient (beta +/- standard error) indicated that the prevalence of low weight for age (below -2 Z-scores of the NCHS references) was positively associated with age (0.088 +/- 0.014, P<0.0001), while it was inversely associated with household income (-1.216 +/- 0.030, P<0.0001). Likewise, low height for age Z-score was negatively associated with household income (-1.056 +/- 0.130, P<0.0001), although such a relationship was not significant in the case of low body mass index for age (-0.169 +/- 0.229, P>0.05). There were also significant differences between religious groups in respect of anthropometric variables. Allowing for household income, the ANCOVA test indicated that Muslim Khasi boys, who were the offspring of intermarriages between Khasi females and immigrant Muslim males, were significantly heavier and taller than Christian and Niam Khasi boys almost across ages. From about 3-10 years of age, Muslim Khasi boys were, on average, comparable to the 5th and 25th percentiles of the NCHS references of height and weight, respectively. Although it looks as though genetic mechanisms like heterosis and/or gene flow might also be associated with the larger body size in Muslim boys, such a conjecture could only be substantiated or refuted by further studies concerning genetic and more socioeconomic data on both immigrant and nonimmigrant populations.     

Isolation of mutations in the catalytic domain of the snf1 kinase that render its activity independent of the snf4 subunit

Activation of the Snf1 kinase requires at least two events, phosphorylation of the activation loop on threonine 210 and an Snf4-dependent process that is not completely defined. Snf4 directly interacts with a region of the regulatory domain of Snf1 that may otherwise act as an autoinhibitory domain. In order to gain insight into the regulation of Snf1 kinase by Snf4, deletions in the regulatory domain of the catalytic subunit were engineered and tested for their effect on Snf1 function in the absence of Snf4. Deletion of residues 381 to 488 from the Snf1 protein resulted in a kinase that was activated by glucose limitation even in the absence of the Snf4 protein. A larger deletion (amino acids 381 to 608) encompassing virtually the entire regulatory domain resulted in complete inactivation of the Snf1 kinase even in the presence of Snf4. A genetic screen for amino acid substitutions that conferred an Snf4-independent phenotype identified four point mutations in the Snf1 catalytic domain. One very conservative mutation, leucine 183 to isoleucine, conferred nearly wild-type levels of Snf1 kinase function in the absence of the Snf4 protein. Purified Snf1 kinase was inactive when isolated from snf4Δ cells, whereas the Snf1-L183I kinase exhibited significant activity in the absence of Snf4. Our data support the idea that Snf1 kinase activity is constrained in cis by an autoinhibitory domain and that the Snf4-mediated activation of Snf1 can be bypassed by subtle conformational changes in the catalytic domain of the Snf1 kinase.