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The halophilic archaeon Haloferax volcanii contains three operons encoding 2-oxoacid dehydrogenase complexes (OADHCs) OADHC1-OADHC3. However, the biological role of these OADHCs is not known as previous studies have demonstrated that they cannot use any of the known OADHC substrates. Even the construction of single mutants in all three oadhc operons, reported recently, could not identify a substrate. Therefore, all three possible double mutants and a triple mutant were generated, and single, double and triple mutants were compared to the wild-type. The four mutants devoid of a functional OADHC1 had a reduced growth yield during nitrate-respirative growth on tryptone. A metabolome analysis of the medium after growth of the triple mutant in comparison to the wild-type revealed that the mutant was unable to degrade isoleucine and leucine, in contrast to the wild-type. It was shown that oadhc1 mutants were unable to grow in synthetic medium on isoleucine, in contrast to the other mutants and the isogenic parent strain. However, all strains grew indistinguishably on valine and leucine. The transcript of the oadhc1 operon was highly induced during growth on isoleucine. However, attempts to detect enzymic activity were unsuccessful, while the branched-chain OADHC (BCDHC) of Pseudomonas putida could be measured easily. Therefore, the growth capability of the triple mutant and the wild-type on the two first degradation intermediates of isoleucine was tested and provided further evidence that OADHC is involved in isoleucine degradation. Taken together, the results indicate that OADHC1 is a specialized BCDHC that uses only one (or maximally two) of the three branched-chain 2-oxoacids, in contrast to BCDHCs from other species.

Background and Purpose-Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors modulating metabolic and inflammatory responses of phagocytes to stimuli such as fatty acids and their metabolites. We studied the role of PPARs in macrophages exposed to low-density lipoprotein (LDL) modified by secretory phospholipase A 2 (PLA). Methods and Results-By analyzing PPAR ligand-binding domain luciferase reporter activation, we observed that PLA-LDL transactivates PPAR␣ and PPAR␦, but not PPAR␥. We confirmed that PLA-LDL induced PPAR response element reporter activation by endogenous PPAR␣ and PPAR␦ in human THP-1 macrophages. 1 Foam cell formation is usually associated with signs of inflammation, and inflammation accompanies atherosclerosis through all stages of lesion progression. 2 However, on uptake of lipoproteins, macrophages also exhibit homeostatic responses to lower lipid accumulation and to attenuate inflammation. The nuclear receptor family of peroxisome proliferator-activated receptors (PPARs), consisting of PPAR␣, PPAR␥, and PPAR␦, plays an important role in regulating lipid metabolism and inflammation in macrophages and other vascular cells. 3 The activation of PPARs was described for oxidized low-density lipoprotein (oxLDL), 4,5 oxidized phospholipids, 6 or very LDL (VLDL). 7 The lipolysis of lipoproteins (eg, by lipoprotein lipase [LPL] or endothelial lipase) may also generate potent PPAR ligands. 7-10 A consequence of PPAR activation is enhanced cholesterol efflux from macrophages 5,11 and reduced inflammation. 12 Initially, only PPAR␣ and PPAR␥ were ascribed a clear antiatherosclerotic effect, 13 whereas some ambiguity existed about the contribution of PPAR␦ to atherosclerosis development, given its positive involvement in macrophage lipid accumulation 14 and the antiatherosclerotic effects of PPAR␦ gene deletion. 15 However, recent studies 16,17 clearly showed antiatherogenic effects of PPAR␦, especially under proinflammatory conditions. In addition, PPAR␥ and PPAR␦ activation favors a macrophage phenotype switch towards an alternatively activated M2 phenotype. 18 This macrophage phenotype switch is supposed to reduce inflammation and contribute to the beneficial effects of PPAR agonists to ameliorate insulin resistance and possibly atherosclerosis. 19 -22 LDL modified by secretory phospholipase A 2 (PLA-LDL) is readily taken up by macrophages, resulting in foam cell formation. 23,24 These events underlie a well-described proatherogenic action of secretory phospholipases A 2 . 25,26 The intracellular mechanisms accompanying PLA-LDL-induced foam cell formation are less understood. In monocytic cells, we noticed that PLA-LDL activated the cytoprotective phosphatidylinositol 3-kinase-Akt pathway, which was attributed to PLA-LDLassociated nonesterified fatty acids (NEFAs). 27 Here we report that PLA-LDL, via its associated NEFA, activates PPAR␣ and PPAR␦ in human macrophages. MethodsFor a description of oil red staining, intracellular cholesterol and triglyceride a...

Hypoxia was shown to reduce insulin concentrations at rest and during exercise. However, some studies have also demonstrated increases in the hormone associated with arterial desaturation. This study was conducted in order to decide [1] whether acute alveolar hypoxia increased or decreased the circulating insulin levels, and [2] to elucidate whether interactions of insulin with other hormones were of relevance in this respect. Glucose (GLU), insulin (INS), c-peptide (CP), adrenaline and noradrenaline (CATs), atrial natriuretic peptide (ANP) and cortisol (CORT) as well as the capillary blood gases were determined in 15 healthy fasting male volunteers (age: 26.2 +/- 2.8 years, body mass index: 22.4 +/- 2.7 kg.m-2). On two separate test days the subjects breathed, in random order, either normal air (N) or a gas mixture with reduced oxygen content (H; FIO2: 0.14). Measurements were made at rest as well as during an incremental cycle exercise in a supine position (increments of 6 min and 50 W) at 100 W and 150 W, at volitional exhaustion (N: 227 +/- 36 W; H: 200 +/- 32 W) as well as in the 5th min of recovery. Arterial desaturation was seen throughout on H-day. At rest all hormones and GLU were normal and showed no influence of H. During exercise INS remained constant on N-day, increased on H-day and was significantly higher with H than with N, most pronounced at 150 W and at volitional exhaustion with 20%, respectively. For CP and GLU no significant exercise-induced changes were seen on either test day and no influence of H was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

To clarify which endocrine modifications can be observed in acute hypoxaemic respiratory failure, 15 severely ill male patients [PAT; median age: 61 (range: 48 years); median height: 173 (range: 12) cm; median mass: 73 (range 31) kg] were investigated immediately upon admission to an intensive care unit (ICU) for this clinical disorder. Before starting treatment, the blood gases were measured and a number of selected hormones with special relevance for an ICU setting were determined. These are known to be modified by acute hypoxaemia in healthy subjects and to possess glucoregulatory properties, or an influence upon cardiocirculation or the vascular volume regulation: insulin, cortisol, adrenaline, noradrenaline, atrial natriuretic peptide, renin, aldosterone, angiotensin converting enzyme, and endothelin-I (ET). To elucidate whether potential endocrine changes resulted from acute hypoxaemia alone, the underlying disease, or unspecific influences connected with the ICU setting, all measurements were compared to those of a completely healthy reference group (REF) with comparable acute experimental hypoxaemia. The latter state was achieved by having the REF breathe a gas mixture with the oxygen content reduced to 14% (H). In the REF, neither the medians nor the distribution of endocrinologic measurements were modified significantly by acute hypoxaemia. In the PAT, the medians were increased considerably, yet with a slight diminution of ET. The distribution of individual values was considerably broader than in the REF with H. In conclusion, considerable increases in the means of the above hormones, with the exception of ET, can be registered in severely ill patients admitted to ICUs with acute hypoxaemic failure. However, such modifications cannot be considered attributable exclusively to acute arterial hypoxaemia. The underlying clinical disorders, such as septicaemia or an unspecific endocrine epiphenomenon, including severe and not only hypoxaemic stress, seem to be predominant.