Purpose:To assess the muscular lipid content (LC) in different muscle groups of the lower leg by a magnetic resonance imaging technique working with chemical shift selective excitation, and comparison with anthropometric and metabolic data. Materials and Methods:Examinations were performed in 67 volunteers (54 male/13 female, age 29 Ϯ seven years) on a 1.5 T whole body imager, applying a highly selective spectral-spatial technique for fat selective MRI. LC was measured in six calf muscles and correlated with body mass index (BMI), percent body fat (PFAT), and insulin sensitivity (IS) of the subjects. . Insulin-resistant subjects showed slightly but not significantly increased LC compared to insulin-sensitive subjects in BMI-matched subgroups. Conclusion:The fat-selective MRI technique allows a reliable non-invasive measure of muscular lipids -even in muscle groups with inherent low LC -within a relatively short measurement time of about three minutes. The presented data reveal interesting interrelationships between LC and anthropometric and metabolic data, and therefore provide new insight into muscular fat metabolism.

Hyperglycemia causes insulin-receptor kinase (IRK) resistance in fat cells. We characterized the mechanism of IRK inhibition and studied whether it is the consequence of a glucose-induced stimulation of protein kinase C (PKC). Fat cells were incubated for 1 or 12 h in culture medium containing either a low-(5-mM) or high- (25-mM) glucose concentration. IRK was isolated, insulin binding was determined, and autophosphorylation was studied in vitro with [gamma-32P]ATP or was determined by Western blotting with anti-phosphotyrosine antibodies. Substrate phosphorylation was investigated with the artificial substrate poly(Glu80-Tyr20). Partially purified insulin receptor from rat fat cells, which were cultured under high-glucose conditions for 1 or 12 h, showed no alteration of insulin binding but a reduced insulin effect on autophosphorylation (30 +/- 7% of control) and poly(Glu80-Tyr20) phosphorylation (55.5 +/- 9% of control). Lineweaver-Burk plots of the enzyme kinetics revealed, beside a reduced Vmax, and increased KM (from 30 microM to 80 microM) for ATP of IRK from high-glucose-treated cells. Because a similar inhibition pattern was earlier found for IRK from fat cells after acute phorbol ester stimulation, we investigated whether activation of PKC might be the cause of the reduced IRK activity. We isolated PKC from the cytosol and the membrane fraction of high- and low-glucose fat cells and determined the diacylglycerol- and phospholipid-stimulated PKC activity toward the substrate histone. There was no significant change of cytosolic PKC; however, membrane-associated PKC activity was increased in high-glucose-treated cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Proteins of the kinesin superfamily are regulated in their motor activity as well as in their ability to bind to their cargo by carboxyl-terminal associating proteins and phosphorylation. KIF1C, a recently identified member of the KIF1/Unc104 family, was shown to be involved in the retrograde vesicle transport from the Golgi-apparatus to the endoplasmic reticulum. In a yeast two-hybrid screen using the carboxyl-terminal 350 amino acids of KIF1C as a bait, we identified as binding proteins 14-3-3 ␤, ␥, ⑀, and . In addition, a clone encoding the carboxyl-terminal 290 amino acids of KIF1C was found, indicating a potential for KIF1C to dimerize. Subsequent transient overexpression experiments showed that KIF1C can dimerize efficiently. However, in untransfected cells, only a small portion of KIF1C was detected as a dimer. The association of 14-3-3 proteins with KIF1C could be confirmed in transient expression systems and in untransfected cells and was dependent on the phosphorylation of serine 1092 located in a consensus binding sequence for 14-3-3 ligands. Serine 1092 was a substrate for the protein kinase casein kinase II in vitro, and inhibition of casein kinase II in cells diminished the association of KIF1C with 14-3-3␥. Our data thus suggest that KIF1C can form dimers and is associated with proteins of the 14-3-3 family.

We found a higher prevalence of the T45 G polymorphism in the adiponectin gene in women with PCOS compared to controls. This was not associated with a more insulin resistant phenotype in PCOS, however. Other frequent polymorphisms in genes related to insulin resistance and type 2 diabetes showed no association with PCOS.

The effect of bradykinin on glucose transporter translocation in isolated rat heart was compared with the effect of insulin. Hearts from male obese (fa/fa) Zucker rats were perfused under normoxic conditions and constant pressure in a classic Langendorff preparation with 12 mmol/l glucose as substrate, and a set of functional parameters was measured simultaneously. Bradykinin was administered at a concentration (10(-11) mmol/l) that did not increase coronary flow. Insulin was used at a concentration (8 x 10(-8) mmol/l) known to maximally stimulate glucose transport in this model. After 15 min of perfusion with insulin or bradykinin, subcellular membrane fractions of the heart were prepared, and distribution of glucose transporter protein (GLUT1 and GLUT4) in fractions enriched with surface membranes (transverse tubules [TTs] and sarcolemmal membranes [PMs]) and with low-density microsomal membranes (LDMs) were determined by immunoblotting with the respective antibodies. Both glucose transporter isoforms were translocated after stimulation with insulin (increased transporter protein content in the PM+TT-enriched fraction with a concomitant decrease in the LDM-enriched fraction) and, to a smaller extent, also with bradykinin. These data suggest that in hearts of insulin-resistant obese (fa/fa) Zucker rats, bradykinin interacts with or facilitates the translocation process of both GLUT1 and GLUT4.