[Show abstract][Hide abstract] ABSTRACT: Decreased mitochondrial oxidative metabolism is a hallmark bioenergetic characteristic of malignancy that may have an adaptive role in carcinogenesis. By stimulating proton leak, mitochondrial uncoupling proteins (UCP1-3) increase mitochondrial respiration and may thereby oppose cancer development. To test this idea, we generated a mouse model that expresses an epidermal-targeted keratin-5-UCP3 (K5-UCP3) transgene and exhibits significantly increased cutaneous mitochondrial respiration compared with wild type (FVB/N). Remarkably, we observed that mitochondrial uncoupling drove keratinocyte/epidermal differentiation both in vitro and in vivo. This increase in epidermal differentiation corresponded to the loss of markers of the quiescent bulge stem cell population, and an increase in epidermal turnover measured using a bromodeoxyuridine (BrdU)-based transit assay. Interestingly, these changes in K5-UCP3 skin were associated with a nearly complete resistance to chemically-mediated multistage skin carcinogenesis. These data suggest that targeting mitochondrial respiration is a promising novel avenue for cancer prevention and treatment.Oncogene advance online publication, 23 January 2012; doi:10.1038/onc.2011.630.
[Show abstract][Hide abstract] ABSTRACT: The novel uncoupling proteins (UCP2–5) are implicated in the mitochondrial control of oxidant production, insulin signaling,
and aging. Attempts to understand their functions have been complicated by overlapping expression patterns in most organisms.
Caenorhabditis elegans nematodes are unique because they express only one UCP ortholog, ceUCP4 (ucp4). Here, we performed detailed metabolic analyzes in genetically modified nematodes to define the function of the ceUCP4.
The knock-out mutant ucp4 (ok195) exhibited sharply decreased mitochondrial succinate-driven (complex II) respiration. However, respiratory coupling and electron
transport chain function were normal in ucp4 mitochondria. Surprisingly, isolated ucp4 mitochondria showed markedly decreased succinate uptake. Similarly, ceUCP4 inhibition blocked succinate respiration and import
in wild type mitochondria. Genetic and pharmacologic inhibition of complex I function was selectively lethal to ucp4 worms, arguing that ceUCP4-regulated succinate transport is required for optimal complex II function in vivo. Additionally, ceUCP4 deficiency prolonged lifespan in the short-lived mev1 mutant that exhibits complex II-generated oxidant production. These results identify a novel function for ceUCP4 in the regulation
of complex II-based metabolism through an unexpected mechanism involving succinate transport.
Preview · Article · Aug 2011 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: Studies were designed to examine the effects of dietary fats on metabolic effects of 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy). These effects included hyperthermia, expression of uncoupling protein (UCP1 and 3) in brown adipose tissue or skeletal muscle and plasma free fatty acid (FFA) levels.
Male Sprague-Dawley rats were fed either a high-fat diet (HFD, 60% kcal) or a lower fat isocaloric controlled diet (LFD, 10% kcal) for 28 days before MDMA challenge.
No significant differences were observed between LFD and HFD groups in terms of body weight, plasma thyroxine (T4) levels and expression of brown fat UCP1 or skeletal muscle UCP3 protein. HFD significantly raised levels of circulating FFA and potentiated the thermogenesis induced by MDMA (10 mg kg(-1), s.c.), compared to the effects of the LFD. Moreover, 30 and 60 min after MDMA administration, plasma FFA levels decreased in HFD animals, but were markedly elevated in the LFD group.
These results indicate that high-fat feeding regulates MDMA-induced thermogenesis by augmenting the activation of UCP rather than its expression.
Full-text · Article · Sep 2007 · British Journal of Pharmacology