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Africa’s rapid population growth and high urban growth rates have been linked to increasing urbanisation of poverty and adverse urban health outcomes, raising intricate local and global policy ques...

Since 2015 there has been a surge of international agendas to address a range of global challenges: climate change (Paris Agreement), sustainable development (Agenda 2030), disaster risk reduction (Sendai Framework) and sustainable urban transformation (New Urban Agenda). Health is relevant to all of these agendas. Policymakers must now translate these global agendas into national level policies to implement the agreed goals in a coherent manner. However, approaches to synergise health activities within and across these agendas are needed, in order to achieve better coherence and maximise national level implementation. This research evaluated the framing of human health within these agendas. A content analysis of the agendas was conducted. Findings indicate (i) the importance of increased awareness of health systems strengthening as a helpful framework to guide the integration of health issues across the agendas, (ii) only two health themes had synergies across the agendas, (iii) the lack of a governance mechanism to support the integration of these four agendas to enable national (and sub-national) governments to more feasibly implement their ambitions, and (iv) the vital component of health leadership. Finally, planetary health is a relevant and timely concept that can support the urgent shift to a healthy planet and people.

The future of health in Africa is at an exciting juncture. African urban history provides a context for current urbanisation trends on the continent. Connecting fragmented disciplines and professio...

The question of how to achieve healthy, sustainable urban futures demands a singular emphasis. The scale and rate of change of modern urbanisation is unprecedented—so much so that it threatens the health gains of the past century. Urbanisation is the greatest ecological shift in human history, and in modern times has attained dimensions never seen before. We have mere decades to enact the greatest transformational change the planet has ever seen, if we are to safeguard a sustainable future. Indeed, the scope, scale, and ambition of transformative efforts need to accelerate dramatically, if humanity is to achieve sustainability before being overwhelmed by global change.

International audience; Trypanosoma brucei is a parasitic protist that undergoes a complex life cycle during transmission from its mammalian host (bloodstream forms) to the midgut of its insect vector (procyclic form). In both parasitic forms, most glycolytic steps take place within specialized peroxisomes, called glycosomes. Here, we studied metabolic adaptations in procyclic trypanosome mutants affected in their maintenance of the glycosomal redox balance. T. brucei can theoretically use three strategies to maintain the glycosomal NAD(+)/NADH balance as follows: (i) the glycosomal succinic fermentation branch; (ii) the glycerol 3-phosphate (Gly-3-P)/dihydroxyacetone phosphate (DHAP) shuttle that transfers reducing equivalents to the mitochondrion; and (iii) the glycosomal glycerol production pathway. We showed a hierarchy in the use of these glycosomal NADH-consuming pathways by determining metabolic perturbations and adaptations in single and double mutant cell lines using a combination of NMR, ion chromatography-MS/MS, and HPLC approaches. Although functional, the Gly-3-P/DHAP shuttle is primarily used when the preferred succinate fermentation pathway is abolished in the Delta pepck knock-out mutant cell line. In the absence of these two pathways (Delta pepck/(RNAi)FAD-GPDH.i mutant), glycerol production is used but with a 16-fold reduced glycolytic flux. In addition, the Delta pepck mutant cell line shows a 3.3-fold reduced glycolytic flux compensated by an increase of proline metabolism. The inability of the Delta pepck mutant to maintain a high glycolytic flux demonstrates that the Gly-3-P/DHAP shuttle is not adapted to the procyclic trypanosome context. In contrast, this shuttle was shown earlier to be the only way used by the bloodstream forms of T. brucei to sustain their high glycolytic flux.

African trypanosomes possess high levels of alanine aminotransferase (EC 2.6.1.2), although the function of their activity remains enigmatic, especially in slender bloodstream forms where the metabolism of ketoacids does not occur. Therefore, the gene for alanine aminotransferase enzyme in Trypanosoma brucei (TbAAT) was characterized and its function assessed using a combination of RNA interference and gene knockout approaches. Surprisingly, as much as 95% or more of the activity appears to be unnecessary for growth of either bloodstream or procyclic forms respiring on glucose. A combination of RNA interference and NMR spectroscopy revealed an important role for the activity in procyclic forms respiring on proline. Under these conditions, the major end product of proline metabolism is alanine, and a reduction in TbAAT activity led to a proportionate decrease in the amount of alanine excreted along with an increase in the doubling time of the cells. These results provide evidence of a role for alanine aminotransferase in the metabolism of proline in African trypanosomes by linking glutamate produced by the initial oxidative steps of the pathway with pyruvate produced by the final oxidative step of the pathway. This step appears to be essential when proline is the primary carbon source, which is likely to be the physiological situation in the tsetse fly vector.

Malaria and trypanosomiasis are diseases which afflict millions and for which novel therapies are urgently required. We have tested two well-characterized cell-penetrating peptides (CPPs) for antiparasitic activity. One CPP, designated TP10, has broad-spectrum antiparasitic activity against Plasmodium falciparum , both blood and mosquito stages, and against blood-stage Trypanosoma brucei brucei .

International audience; The Trypanosoma brucei procyclic form resides within the digestive tract of its insect vector, where it exploits amino acids as carbon sources. Threonine is the amino acid most rapidly consumed by this parasite, however its role is poorly understood. Here, we show that the procyclic trypanosomes grown in rich medium only use glucose and threonine for lipid biosynthesis, with threonine's contribution being approximate to 2.5 times higher than that of glucose. A combination of reverse genetics and NMR analysis of excreted end-products from threonine and glucose metabolism, shows that acetate, which feeds lipid biosynthesis, is also produced primarily from threonine. Interestingly, the first enzymatic step of the threonine degradation pathway, threonine dehydrogenase (TDH, EC 1.1.1.103), is under metabolic control and plays a key role in the rate of catabolism. Indeed, a trypanosome mutant deleted for the phosphoenolpyruvate decarboxylase gene (PEPCK, EC 4.1.1.49) shows a 1.7-fold and twofold decrease of TDH protein level and activity, respectively, associated with a 1.8-fold reduction in threonine-derived acetate production. We conclude that TDH expression is under control and can be downregulated in response to metabolic perturbations, such as in the PEPCK mutant in which the glycolytic metabolic flux was redirected towards acetate production.

The Trypanosoma brucei procyclic form resides within the digestive tract of its insect vector, where it exploits amino acids as carbon sources. Threonine is the amino acid most rapidly consumed by this parasite, however its role is poorly understood. Here, we show that the procyclic trypanosomes grown in rich medium only use glucose and threonine for lipid biosynthesis, with threonine's contribution being ∼ 2.5 times higher than that of glucose. A combination of reverse genetics and NMR analysis of excreted end-products from threonine and glucose metabolism, shows that acetate, which feeds lipid biosynthesis, is also produced primarily from threonine. Interestingly, the first enzymatic step of the threonine degradation pathway, threonine dehydrogenase (TDH, EC 1.1.1.103), is under metabolic control and plays a key role in the rate of catabolism. Indeed, a trypanosome mutant deleted for the phosphoenolpyruvate decarboxylase gene (PEPCK, EC 4.1.1.49) shows a 1.7-fold and twofold decrease of TDH protein level and activity, respectively, associated with a 1.8-fold reduction in threonine-derived acetate production. We conclude that TDH expression is under control and can be downregulated in response to metabolic perturbations, such as in the PEPCK mutant in which the glycolytic metabolic flux was redirected towards acetate production.

All living organisms depend on NADPH production to feed essential biosyntheses and for oxidative stress defense. Protozoan parasites such as the sleeping sickness pathogen Trypanosoma brucei adapt to different host environments, carbon sources, and oxidative stresses during their infectious life cycle. The procyclic stage develops in the midgut of the tsetse insect vector, where they rely on proline as carbon source, although they prefer glucose when grown in rich media. Here, we investigate the flexible and carbon source-dependent use of NADPH synthesis pathways in the cytosol of the procyclic stage. The T. brucei genome encodes two cytosolic NADPH-producing pathways, the pentose phosphate pathway (PPP) and the NADP-dependent malic enzyme (MEc). Reverse genetic blocking of those pathways and a specific inhibitor (dehydroepiandrosterone) of glucose-6-phosphate dehydrogenase together established redundancy with respect to H2O2 stress management and parasite growth. Blocking both pathways resulted in similar to 10-fold increase of susceptibility to H2O2 stress and cell death. Unexpectedly, the same pathway redundancy was observed in glucose-rich and glucose-depleted conditions, suggesting that gluconeogenesis can feed the PPP to provide NADPH. This was confirmed by (i) a lethal phenotype of RNAi-mediated depletion of glucose-6-phosphate isomerase (PGI) in the glucose-depleted Delta mec/Delta mec null background, (ii) an similar to 10-fold increase of susceptibility to H2O2 stress observed for the Delta mec/Delta mec/(RNAi)PGI double mutant when compared with the single mutants, and (iii) the C-13 enrichment of glycolytic and PPP intermediates from cells incubated with [U-C-13] proline, in the absence of glucose. Gluconeogenesis-supported NADPH supply may also be important for nucleotide and glycoconjugate syntheses in the insect host.

Trypanosoma brucei is a kinetoplastid parasite of medical and veterinary importance. Its digenetic life cycle alternates between the bloodstream form in the mammalian host and the procyclic form (PCF) in the bloodsucking insect vector, the tsetse fly. PCF trypanosomes rely in the glucose-depleted environment of the insect vector primarily on the mitochondrial oxidative phosphorylation of proline for their cellular ATP provision. We previously identified two T. brucei mitochondrial carrier family proteins, TbMCP5 and TbMCP15, with significant sequence similarity to functionally characterized ADP/ATP carriers from other eukaryotes. Comprehensive sequence analysis confirmed that TbMCP5 contains canonical ADP/ATP carrier sequence features, whereas they are not conserved in TbMCP15. Heterologous expression in the ANC-deficient yeast strain JL1Δ2Δ3u(-) revealed that only TbMCP5 was able to restore its growth on the non-fermentable carbon source lactate. Transport studies in yeast mitochondria showed that TbMCP5 has biochemical properties and ADP/ATP exchange kinetics similar to those of Anc2p, the prototypical ADP/ATP carrier of S. cerevisiae. Immunofluorescence microscopy and Western blot analysis confirmed that TbMCP5 is exclusively mitochondrial and is differentially expressed with 4.5-fold more TbMCP5 in the procyclic form of the parasite. Silencing of TbMCP5 expression in PCF T. brucei revealed that this ADP/ATP carrier is essential for parasite growth, particularly when depending on proline for energy generation. Moreover, ADP/ATP exchange in isolated T. brucei mitochondria was eliminated upon TbMCP5 depletion. These results confirmed that TbMCP5 functions as the main ADP/ATP carrier in the trypanosome mitochondrion. The important role of TbMCP5 in the T. brucei energy metabolism is further discussed.

Insect stage trypanosomes use an "acetate shuttle" to transfer mitochondrial acetyl-CoA to the cytosol for the essential fatty acid biosynthesis. The mitochondrial acetate sources are acetate: succinate CoA-transferase (ASCT) and an unknown enzymatic activity. We have identified a gene encoding acetyl-CoA thioesterase (ACH) activity, which is shown to be the second acetate source. First, RNAi-mediated repression of ASCT in the ACH null background abolishes acetate production from glucose, as opposed to both single ASCT and ACH mutants. Second, incorporation of radiolabeled glucose into fatty acids is also abolished in this ACH/ASCT double mutant. ASCT is involved in ATP production, whereas ACH is not, because the ASCT null mutant is similar to 1000 times more sensitive to oligomycin, a specific inhibitor of the mitochondrial F-0/F-1-ATP synthase, than wild-type cells or the ACH null mutant. This was confirmed by RNAi repression of the F-0/F-1-ATP synthase F-1 beta subunit, which is lethal when performed in the ASCT null background but not in the wild-type cells or the ACH null background. We concluded that acetate is produced from both ASCT and ACH; however, only ASCT is responsible, together with the F-0/F-1-ATP synthase, for ATP production in the mitochondrion.

International audience; A single copy gene, encoding a protein highly similar to transketolase from other systems, was identified in the Trypanosoma brucei genome. The gene was expressed in E. coil and the purified protein demonstrated transketolase activity with Km values of 0.2 mM and 0.8 mM respectively for xylulose 5-phosphate and ribose 5-phosphate. A peroxisomal targeting signal (PTS-1) present at the C-terminus of the protein suggested a glycosomal localisation. However, subcellular localisation experiments revealed that while the protein was present in glycosomes it was found mainly within the cytosol and thus has a dual localisation. Transketolase activity was absent from the long slender bloodstream form of the parasite and the protein was not detectable in this life cycle stage, with the RNA present only at low abundance, indicating a strong differential regulation, being present predominantly in the procyclic form. The gene was knocked out from procyclic T. brucei and transketolase activity was lost but no growth phenotype was evident in the null mutants. Metabolite profiling to compare wild type and TKT null mutants revealed substantial increases in transketolase substrate metabolites coupled to loss of sedoheptulose 7-phosphate, a principal product of the transketolase reaction. (C) 2011 Elsevier B.V. All rights reserved.

SUMMARYParasites that often grow anaerobically in their hosts have adopted a fermentative strategy relying on the production of partially oxidized end products, including lactate, glycerol, ethanol, succinate and acetate. This review focuses on recent progress in understanding acetate production in protist parasites, such as amoebae, diplomonads, trichomonads, trypanosomatids and in the metazoan parasites helminths, as well as the succinate production pathway(s) present in some of them. We also describe the unconventional organisation of the tricarboxylic acid cycle associated with the fermentative strategy adopted by the procyclic trypanosomes, which may resemble the probable structure of the primordial TCA cycle in prokaryotes.

African trypanosomes possess high levels of alanine aminotransferase (EC 2.6.1.2), although the function of their activity remains enigmatic, especially in slender bloodstream forms where the metabolism of ketoacids does not occur. Therefore, the gene for alanine aminotransferase enzyme in Trypanosoma brucei (TbAAT) was characterized and its function assessed using a combination of RNA interference and gene knockout approaches. Surprisingly, as much as 95% or more of the activity appears to be unnecessary for growth of either bloodstream or procyclic forms respiring on glucose. A combination of RNA interference and NMR spectroscopy revealed an important role for the activity in procyclic forms respiring on proline. Under these conditions, the major end product of proline metabolism is alanine, and a reduction in TbAAT activity led to a proportionate decrease in the amount of alanine excreted along with an increase in the doubling time of the cells. These results provide evidence of a role for alanine aminotransferase in the metabolism of proline in African trypanosomes by linking glutamate produced by the initial oxidative steps of the pathway with pyruvate produced by the final oxidative step of the pathway. This step appears to be essential when proline is the primary carbon source, which is likely to be the physiological situation in the tsetse fly vector.

Efficient synthetic routes have been developed for the preparation of two new polyazamacrocycles tagged with structural motifs recognised by the Trypanosoma brucei P2 aminopurine transporter. Biological testing of these compounds showed highly selective anti-protozoal activity against trypanosomes.

A focused library of C2-substituted-1,4,7,10-tetraazacyclododecanes was synthesised and the compounds were tested for their ability to kill trypanosome and malaria parasites. Several compounds showed significant in vitro activity and were selectively active against the parasites over human embryonic kidney cells used as a counter screen.