Vertical sleeve gastrectomy improves indices of metabolic disease in rodent model of surgical menopause.

OBJECTIVE: Although women are the most common recipients of weight loss surgeries for the amelioration of the comorbidities of obesity, few studies have addressed the efficacy of these procedures with specific attention to reproductive stage. Here we ask in a rodent model of vertical sleeve gastrectomy (VSG) whether improvements to metabolic health are realized in women having received surgical menopause. Specifically we were interested in knowing whether rats made menopausal through surgical means would exhibit persistent hepatic steatosis as reported in previously pregnant, freely cycling female VSG rats or if it is resolved as reported in male VSG rats. METHODS: All the rats first received ovariectomy (OVX) and then were placed on high-fat diet before either sham or VSG surgery (N = 12, 9) and then were monitored for resolution of obesity-related comorbidities. RESULTS: VSG was sufficient to reduce weight and adiposity in OVX females in comparison to obese rats (P < 0.001). Glucose tolerance (P < 0.05) was improved in OVX-VSG females with no change in insulin sensitivity. Both circulating (P < 0.01) and hepatic triglyceride (P < 0.01) levels were also reduced after VSG. Liver integrity was improved in OVX-VSG in comparison to OVX-obese as reflected by reduced aspartate aminotransferase levels (P < 0.05). The ability of mitochondria to generate adenosine triphosphate was maintained, and an increase in complex IV may decrease the production of mitochondrial reactive oxygen species. CONCLUSIONS: Taken together, VSG in OVX rats experience many positive benefits including the resolution of hepatic steatosis that persists in reproductively intact female rats after VSG.

Membrane-Anchored Cyclic Peptides as Effectors of Mitochondrial Oxidative Phosphorylation.

The echinocandins are membrane-anchored, cyclic lipopeptides (CLPs) with antifungal activity due to their ability to inhibit a glucan synthase located in the plasma membrane of fungi such as Candida albicans. A hydrophobic tail of an echinocandin CLP inserts into a membrane, placing a six-amino acid cyclic peptide near the membrane surface. Because processes critical for the function of the electron transfer complexes of mitochondria, such as proton uptake and release, take place near the surface of the membrane, we have tested the ability of two echinocandin CLPs, caspofungin and micafungin, to affect the activity of electron transfer complexes in isolated mammalian mitochondria. Indeed, caspofungin and micafungin both inhibit whole chain electron transfer in isolated mitochondria at low micromolar concentrations. The effects of the CLPs are fully reversible, in some cases simply via the addition of bovine serum albumin to bind the CLPs via their hydrophobic tails. Each CLP affects more than one complex, but they still exhibit specificity of action. Only caspofungin inhibits complex I, and the CLP inhibits liver but not heart complex I. Both CLPs inhibit heart and liver complex III. Caspofungin inhibits complex IV activity, while, remarkably, micafungin stimulates complex IV activity nearly 3-fold. Using a variety of assays, we have developed initial hypotheses for the mechanisms by which caspofungin and micafungin alter the activities of complexes IV and III. The dication caspofungin partially inhibits cytochrome c binding at the low-affinity binding site of complex IV, while it also appears to inhibit the release of protons from the outer surface of the complex, similar to Zn(2+). Anionic micafungin appears to stimulate complex IV activity by enhancing the transfer of protons to the O2 reduction site. For complex III, we hypothesize that each CLP binds to the cytochrome b subunit and the Fe-S subunit to inhibit the required rotational movement of the latter.

Early alterations in platelet mitochondrial function are associated with survival and organ failure in patients with septic shock.

INTRODUCTION: The objective of the study is to determine if changes in platelet mitochondrial function in patients with sepsis are present early after presentation and the association of these changes with clinical outcomes and systemic metabolic function. MATERIALS AND METHODS: This is a prospective observational cohort study of a convenience sample of patients with severe sepsis. Mitochondrial function of intact, nonpermeabilized platelets suspended in their own plasma was estimated using high-resolution respirometry. Unstimulated basal respiration, oligomycin-induced state 4, and maximal respiratory rate after serial titrations of carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone were measured. Organ failure was estimated using Sequential Organ Failure Assessment score, and patients were followed up until 28 days to determine survival. Lactate levels were measured in all patients, and a subset of patients had lactate/pyruvate (L/P) ratios measured. RESULTS: Twenty-eight patients were enrolled, 21 of whom survived. Initial Sequential Organ Failure Assessment score and lactate levels were 8.5 (interquartile range [IQR], 6-10) and 2.3 (IQR, 1.2-3.5) respectively, whereas the median L/P ratio was 23.4 (IQR, 15.2-38). Basal and maximal respiratory rates were significantly higher among nonsurvivors compared to survivors (P = .02 and P = .04), whereas oligomycin-induced state 4 respiration was not statistically different between groups (P = .15). We found a significant association between maximal respiration and organ failure (P = .03) and both basal and maximal rates with initial lactate level (P = .04, P = .02), but not with L/P ratio. CONCLUSIONS: Differences in platelet mitochondrial function between survivors and nonsurvivors are present very early in the hospital course and are associated with organ failure and lactate.

Loss of STAT3 in mouse embryonic fibroblasts reveals its Janus-like actions on mitochondrial function and cell viability.

STAT3 has been implicated in mitochondrial function; however, the physiological relevance of this action is not established. Here we studied the importance of STAT3 to the cellular response to stimuli, TNFα and serum deprivation, which increase mitochondrial reactive oxygen species (ROS) formation. Experiments were performed using wild type (WT) and STAT3 knockout (KO) mouse embryonic fibroblasts (MEF). Both WT and STAT3 KO MEF expressed similar levels of tumor necrosis factor receptor 1 (TNFR1) and exhibited comparable IκBα degradation with TNFα. However, in the absence of STAT3 nuclear accumulation of NFκB p65 with TNFα was attenuated and induction of the survival protein c-FLIPL was eliminated. Nonetheless, WT MEF were more sensitive to TNFα-induced death which was attributed to necrosis. Deletion of STAT3 decreased ROS formation induced by TNFα and serum deprivation. STAT3 deletion was associated with lower levels of complex I and rates of respiration. Relative to WT cells, mitochondria of STAT3 KO cells released significantly more cytochrome c in response to oxidative stress and had greater caspase 3 cleavage due to serum deprivation. Our findings are consistent with STAT3 being important for mitochondrial function and cell viability by ensuring mitochondrial integrity and the expression of pro-survival genes.