Oxidation-reduction potentials of cytochromes P-450 and ferredoxin in the bovine adrenal. Their modification by substrates and inhibitors

Regular Coffee Consumption Is Associated with Lower Regional Adiposity Measured by DXA among US Women

BACKGROUND

Coffee is among the most popular daily beverages in the United States. Importantly, coffee consumption has been associated with a lower risk of multiple health outcomes including a reduction in adiposity. DXA is a means to assess body fat and distribution.

OBJECTIVES

The aim of this study was to examine the relation between coffee consumption and DXA-assessed adiposity and adiposity distribution.

METHODS

Cross-sectional data from the NHANES were used. Participants were adults aged 20-69 y from the 2003-2004 and 2005-2006 waves. Information on coffee consumption was assessed through the FFQ (categorized as no coffee, 0 to <0.25 cup/d, 0.25 to <1 cup/d, 1 cup/d, 2-3 cups/d, or ≥4 cups/d). Both caffeinated and decaffeinated coffee consumption were included. Trunk fat and total fat percentage were measured via whole-body DXA scans. The association between coffee consumption and body fat was investigated using age-adjusted and multivariable-adjusted linear regression models which accounted for sample weights.

RESULTS

Higher coffee consumption was associated with significantly lower total body fat percentage and trunk body fat percentage in a dose-response manner (all P values < 0.05) among women. Although this dose-response relation was nonsignificant among men, men aged 20-44 y who drank 2-3 cups/d had 1.3% (95% CI: -2.7%, 0.1%) less total fat and 1.8% (95% CI: -3.3%, -0.4%) less trunk fat than those who did not consume coffee. Furthermore, the association between coffee consumption and body fat percentage exhibited for both caffeinated and decaffeinated coffee among women (all P for trend < 0.001) but not among men (all P for trend > 0.05).

CONCLUSIONS

The present study found a significant association between higher coffee consumption and lower DXA-measured adiposity. Moreover, a gender difference in this association in the general US adult population was also observed.

Plant type ferredoxins and ferredoxin-dependent metabolism

Ferredoxin (Fd) is a small [2Fe-2S] cluster-containing protein found in all organisms performing oxygenic photosynthesis. Fd is the first soluble acceptor of electrons on the stromal side of the chloroplast electron transport chain, and as such is pivotal to determining the distribution of these electrons to different metabolic reactions. In chloroplasts, the principle sink for electrons is in the production of NADPH, which is mostly consumed during the assimilation of CO2 . In addition to this primary function in photosynthesis, Fds are also involved in a number of other essential metabolic reactions, including biosynthesis of chlorophyll, phytochrome and fatty acids, several steps in the assimilation of sulphur and nitrogen, as well as redox signalling and maintenance of redox balance via the thioredoxin system and Halliwell-Asada cycle. This makes Fds crucial determinants of the electron transfer between the thylakoid membrane and a variety of soluble enzymes dependent on these electrons. In this article, we will first describe the current knowledge on the structure and function of the various Fd isoforms present in chloroplasts of higher plants and then discuss the processes involved in oxidation of Fd, introducing the corresponding enzymes and discussing what is known about their relative interaction with Fd.

Recollection of the early years of the research on cytochrome P450

Since the publication of the first paper on "cytochrome P450" in 1962, the biochemical research on this novel hemoprotein expanded rapidly in the 1960s and the 1970s as its principal roles in various important metabolic processes including steroid hormone biosynthesis in the steroidogenic organs and drug metabolism in the liver were elucidated. Establishment of the purification procedures of microsomal and mitochondrial P450s in the middle of the 1970s together with the introduction of molecular biological techniques accelerated the remarkable expansion of the research on P450 in the following years. This review paper summarizes the important developments in the research on P450 in the early years, for about two decades from the beginning, together with my personal recollections.

Regulation of cholesterol movement to mitochondrial cytochrome P450scc in steroid hormone synthesis

Transfer of cholesterol to cytochrome P450scc is generally the rate-limiting step in steroid synthesis. Depending on the steroidogenic cell, cholesterol is supplied from low or high density lipoproteins (LDL or HDL) or de novo synthesis. ACTH and gonadotropins stimulate this cholesterol transfer prior to activation of gene transcription, both through increasing the availability of cytosolic free cholesterol and through enhanced cholesterol transfer between the outer and inner mitochondrial membranes. Cytosolic free cholesterol from LDL or HDL is primarily increased through enhanced cholesterol ester hydrolysis and suppressed esterification, but increased de novo synthesis can be significant. Elements of the cytoskeleton, probably in conjunction with sterol carrier protein(2) (SCP(2)), mediate cholesterol transfer to the mitochondrial outer membranes. Several factors contribute to the transfer of cholesterol between mitochondrial membranes; steroidogenesis activator peptide acts synergistically with GTP and is supplemented by SCP(2). 5-Hydroperoxyeicosatrienoic acid, endozepine (at peripheral benzodiazepine receptors), and rapid changes in outer membrane phospholipid content may also contribute stimulatory effects at this step. It is suggested that hormonal activation, through these factors, alters membrane structure around mitochondrial intermembrane contact sites, which also function to transfer ADP, phospholipids, and proteins to the inner mitochondria. Cholesterol transfer may occur following a labile fusion of inner and outer membranes, stimulated through involvement of cardiolipin and phosphatidylethanolamine in hexagonal phase membrane domains. Ligand binding to benzodiazepine receptors and the mitochondrial uptake of 37 kDa phosphoproteins that uniquely characterize steroidogenic mitochondria could possibly facilitate these changes. ACTH activation of rat adrenals increases the susceptibility of mitochondrial outer membranes to digitonin solubilization, suggesting increased cholesterol availability. Proteins associated with contact sites were not solubilized, indicating that this part of the outer membrane is resistant to this treatment. Two pools of reactive cholesterol within adrenal mitochondria have been distinguished by different isocitrate- and succinate-supported metabolism. These pools appear to be differentially affected in vitro by the above stimulatory factors.

Ferritin in normal human peripheral blood T-lymphocyte subpopulations

Six peripheral blood lymphoid fractions (total lymphocytes, non-T, T, Tar (autologous rosette-forming T cells/precursor), T mu (helper), and T gamma (suppressor) lymphocytes) isolated through rosetting procedures were examined for the presence of ferritin by a direct immunofluorescence technique. Although ferritin was present in all lymphoid fractions studied, a significantly higher proportion of ferritin-containing cells were detected in the T-cell fraction than in the non-T-cell fraction, (mean +/- SD = 7.9 +/- 1.6% and 5.0 +/- 1.2%, respectively). T mu- and T gamma-cell fractions showed a twofold increase in the number of ferritin-positive cells (14.1 +/- 1.4% and 15.4 +/- 2.6%, respectively), as compared with Tar (7.0 +/- 0.9%)-and total lymphocyte (6.9 +/- 1.3%)-cell fractions. These results indicate that ferritin is preferentially distributed in T mu and T gamma lymphocytes and may constitute the basis for explaining some of the roles exercised by these cells in the control of other biological systems.

Iron binding proteins in selected human peripheral blood cell sets: immunofluorescence

Selected populations of human peripheral blood T lymphocytes, B lymphocytes, monocytes and polymorphonuclear cells were examined for their intracellular content of lactoferrin transferrin and ferritin by an indirect immunofluorescence technique. Lactoferrin was found in polymorphs but not in lymphoid cells. Two different lactoferrin staining patterns were observed which we designated 'perinuclear', characterized by a ring of positive material round the nucleus, and cytoplasmic, in which most positive material was distributed in the cytoplasm. The former staining pattern was found in high density polymorphs the latter was associated with low density polymorphs occasionally found contaminating the peripheral blood mononuclear cell suspension. After incubation in vitro, the perinuclear pattern changed to cytoplasmic staining. Transferrin was found in T cells and polymorphs. In contrast, only a few transferrin containing cells were detected in the B cell and monocyte fractions. Following overnight incubation, a halo of positive material was found surrounding T cells stained for transferrin, suggesting that T cells released transferrin during incubation. Ferritin was also found in T cells and adherent cells. Following latex particle ingestion, the intensity of ferritin staining was markedly increased. Only a small proportion of lymphoid cells and monocytes stained for transferrin or ferritin in the total peripheral blood mononuclear cell suspension. The results indicate, therefore, that in response to manipulation procedures used routinely for the selection of human peripheral blood lymphoid cells, detectable amounts of transferrin and ferritin are present in T but not B cells. The fact that T cells are equipped with proteins known to participate in binding and storage of iron may constitute, at least in part, the basis for the contribution of these cells to the regulation of other major biological systems.