Hans-U. Häring

Fast elevation of the intramyocellular lipid content in the presence of circulating free fatty acids and hyperinsulinemia: a dynamic 1H-MRS study.

The influence of a short‐term elevation of free fatty acids (FFAs) on intramyocellular lipids (IMCL) under hyperinsulinemic conditions was monitored in five healthy male subjects in the course of a 5‐hr hyperinsulinemic glucose clamp. During the glucose clamp a lipid emulsion (Intralipid 20®) and heparin were administered intravenously. IMCL was quantified in the tibialis anterior (TA) and the soleus (SOL) muscle by 1H‐MRS. A rapid elevation of the IMCL pool was found in both muscles (61% in TA and 22% in SOL) in the 5‐hr time period. A control hyperinsulinemic glucose clamp in the same study group, repeated without elevation of circulating FFAs, did not lead to significant changes in IMCL for both muscles. The present study shows for the first time that only the combination of high concentrations of FFAs and insulin lead to marked storage of lipids in skeletal muscle cells in humans. Magn Reson Med 45:179–183, 2001.

The Kinesin-like Motor Protein KIF1C Occurs in Intact Cells as a Dimer and Associates with Proteins of the 14-3-3 Family

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 β, γ, ε, and ζ. 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 IIin vitro, and inhibition of casein kinase II in cells diminished the association of KIF1C with 14-3-3γ. Our data thus suggest that KIF1C can form dimers and is associated with proteins of the 14-3-3 family.

Lipid content in the musculature of the lower leg assessed by fat selective MRI: Intra‐ and interindividual differences and correlation with anthropometric and metabolic data

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.

Long term effect of a structured inpatient diabetes teaching and treatment programme in type 2 diabetic patients: influence of mode of follow-up

Structured diabetes teaching and treatment programmes (STTP) are increasingly offered for patients with diabetes to improve metabolic control. We prospectively studied the long term-effect of STTP on metabolic control and knowledge of diabetes in patients with type 2 diabetes. In addition, differences in the mode of follow-up by a university diabetes centre (UDC) versus general practitioner (GP) were assessed. Of the 64 patients with type 2 diabetes (61 +/- 10 years old, diabetes duration 11 +/- 7 years) included in the study 52 could be reevaluated after 2 years. Of those, 31 were followed up by the UDC and 21 by their GPs who received detailed follow-up instructions from the UDC. In all patients, HbA1c decreased from 9.1 +/- 0.3% before the programme to 8.3 +/- 0.3% 2 years after the programme (P = 0.004), whereas body mass index increased from 28.8 +/- 0.8 to 30.3 +/- 0.9 kg/m2 (P < 0.001). Patients had a significantly better knowledge of diabetes and diet 2 years after the programme. For all parameters tested, none of the changes differed between patients managed by the UDC versus those managed by their GP. However, patients who chose follow-up by the UDC were more obese and had a better knowledge of diabetes. In conclusion, the STTP for patients with type 2 diabetes was effective in improving the long-term glycaemic control and knowledge of diabetes. Moreover, with precise therapeutic goals and follow-up instructions given to patient and GP this improvement was independent of the mode of outpatient follow-up.

TPA inhibits insulin stimulated PIP hydrolysis in fat cell membranes: Evidence for modulation of insulin dependent phospholipase C by proteinkinase C

Proteinkinase-C (PKC) stimulating phorbolesters induce in vitro insulin resistance of isolated adipocytes. This effect might be explained by an inhibition of insulin signal transduction at the level of the insulin receptor kinase. There is now some evidence that a phospholipase C is a potential candidate as a signal transducer at the postreceptor level. In order to determine whether phorbol esters might inhibit insulin signalling also at the level of a phospholipase C, we studied the insulin dependent [3H] phosphatidylinositol 4-monophosphate (PIP) hydrolysis of fat cell membranes. PIP hydrolysis was measured after in vitro stimulation with and without insulin. Insulin stimulated PIP hydrolysis in a dose dependent way. When plasma membranes from phorbolester (TPA) treated fat cells were used, this insulin stimulated phospholipase C activity was suppressed, provided, membranes have been prepared in a buffer containing serine phosphatase inhibitors. These data suggest that fat cell membranes contain an insulin dependent phospholipase C which is inhibited by TPA most likely via serine phosphorylation through proteinkinase C.

Disseminated epitheloid hemangioendothelioma mimicking symptoms of systemic vasculitis.

Background: Epitheloid hemangioendothelioma is a rare malignant tumor which can involve bones, liver, lungs, kidneys, deep soft tissue, muscles, dermis, and central nervous system. Multifocal disease occurs in 10% of the cases. The clinical presentation results from occlusion of small blood vessels due to the disease itself or as a paraneoplastic syndrome. Case Report: We present a patient with symptoms suggesting systemic vasculitis (ESR and CRP elevated, weight loss, arthralgia, livedoid rash, and skin ulcerations) who finally was diagnosed having a disseminated epitheloid hemangioendothelioma when PET scan revealed hypermetabolic multifocal skeletal and soft tissue lesions. Discussion: Diseases mimicking systemic vasculitis and the value of PET in this setting are discussed.

The inhibitory effect of 2‐deoxyglucose on insulin receptor autophosphorylation does not depend on known serine phosphorylation sites or other conserved serine residues of the receptor β‐subunit

Hyperglycemia induces insulin resistance in diabetic patients. It is known that supraphysiological levels of D‐glucose or 2‐deoxyglucose inhibit the insulin receptor and it is speculated that this effect is mediated by serine phosphorylation of the insulin receptor β‐subunit and other proteins of the insulin signaling chain. To test this hypothesis we prepared point mutations of the human insulin receptor where serine was exchanged to alanine at 16 different positions, either at known phosphorylation sites or at positions which are conserved in different tyrosine kinase receptors. These receptor constructs were expressed in HEK 293 cells and the effect of 2‐deoxyglucose (25 mM) on insulin (100 nM) induced receptor autophosphorylation was studied. 2‐Deoxyglucose consistently inhibits insulin stimulated autophosphorylation of all constructs to the same degree as observed in wild‐type human insulin receptor. The data suggest that none of the chosen serine positions are involved in 2‐deoxyglucose induced receptor inhibition.