The Potential Impact of a 20% Tax on Sugar-Sweetened Beverages on Obesity in South African Adults: A Mathematical Model

Background/Objectives

The prevalence of obesity in South Africa has risen sharply, as has the consumption of sugar-sweetened beverages (SSBs). Research shows that consumption of SSBs leads to weight gain in both adults and children, and reducing SSBs will significantly impact the prevalence of obesity and its related diseases. We estimated the effect of a 20% tax on SSBs on the prevalence of and obesity among adults in South Africa.

Methods

A mathematical simulation model was constructed to estimate the effect of a 20% SSB tax on the prevalence of obesity. We used consumption data from the 2012 SA National Health and Nutrition Examination Survey and a previous meta-analysis of studies on own- and cross-price elasticities of SSBs to estimate the shift in daily energy consumption expected of increased prices of SSBs, and energy balance equations to estimate shifts in body mass index. The population distribution of BMI by age and sex was modelled by fitting measured data from the SA National Income Dynamics Survey 2012 to the lognormal distribution and shifting the mean values. Uncertainty was assessed with Monte Carlo simulations.

Results

A 20% tax is predicted to reduce energy intake by about 36kJ per day (95% CI: 9-68kJ). Obesity is projected to reduce by 3.8% (95% CI: 0.6%–7.1%) in men and 2.4% (95% CI: 0.4%–4.4%) in women. The number of obese adults would decrease by over 220 000 (95% CI: 24 197–411 759).

Conclusions

Taxing SSBs could impact the burden of obesity in South Africa particularly in young adults, as one component of a multi-faceted effort to prevent obesity.     

Complexes of human papillomavirus type 16 E6 proteins form pseudo-death-inducing signaling complex structures during tumor necrosis factor-mediated apoptosis

High-risk strains of human papillomavirus (HPV) such as HPV type 16 (HPV16) and HPV18 are causative agents of most human cervical carcinomas. E6, one of the oncogenes encoded by HPV16, possesses a number of biological and transforming functions. We have previously shown that the binding of E6 to host apoptotic proteins such as tumor necrosis factor (TNF) R1, the adaptor protein FADD, and procaspase 8 results in a significant modification of the normal flow of apoptotic events. For example, E6 can bind to and accelerate the degradation of FADD. In addition, full-length E6 binds to the TNF R1 death domain and can also bind to and accelerate the degradation of procaspase 8. In contrast, the binding of small splice isoforms known as E6* results in the stabilization of procaspase 8. In this report, we propose a model for the ability of HPV16 E6 to both sensitize and protect cells from TNF as well as to protect cells from Fas. We demonstrate that both the level of E6 expression and the ratio between full-length E6 and E6* are important factors in the modification of the host extrinsic apoptotic pathways and show that at high levels of E6 expression, the further sensitization of U2OS, NOK, and Ca Ski cells to TNF-mediated apoptosis is most likely due to the formation of a pseudo-death-inducing signaling complex structure that includes complexes of E6 proteins.     

Position of anthers at plating and its influence on anther callusing in rice

Effect of position of anthers at plating in relation to their ability to form callus was studied in rice (Oryza sativa var. Taipei 309). Among the callusing anthers, about 60% were those positioned on edge with one lobe in contact with the medium while the rest were flat with both lobes touching the medium. Anthers in both positions produced calli and regenerated green plants.Abbreviations 2,4-D 2,4-dichlorophenoxy acetic acid - NAA Naphthalene acetic acid - IAA Indole acetic acid - BAP Benzyl aminopurine - K Kinetin     

A new series of trpE vectors that enable high expression of nonfusion proteins in bacteria.

Expression of recombinant proteins in bacteria has facilitated the characterization of many gene products. However, the biochemical characterization of recombinant proteins is limited since the bacterially expressed proteins are often synthesized as fusion polypeptides. The presence of bacterial sequences in fusion proteins further limits the use of these proteins for generating antibodies since the bacterial sequences are also antigenic. We describe two new bacterial expression vectors based on the pATH series of plasmids. These vectors were made by precisely deleting all of the trpE coding sequences found in pATH. The new vectors have enabled us to express eukaryotic genes as nonfusion polypeptides. These altered plasmids can be used to insert any DNA sequence of interest through a multiple cloning site located just 3' of an ATG start codon. Protein expression is still under the control of the trp operon and is carried out at great efficiency when the bacteria are tryptophan deprived. Studies presented here test the expression system with neurofilament subunits, NF-L and NF-H. Large amounts of recombinant nonfusion proteins were produced. Also, a time course of induction shows that the production of the nonfusion proteins was under the control of the trp operon which is readily inducible after tryptophan starvation and addition of indoleacrylic acid. These vectors may be useful for the overexpression of many proteins in a form closely approximating their native state.     

Glucosylceramide synthase is essential for alfalfa defensin-mediated growth inhibition but not for pathogenicity of Fusarium graminearum

Antifungal defensins, MsDef1 and MtDef4, from Medicago spp., inhibit the growth of a fungal pathogen, Fusarium graminearum, at micromolar concentrations. However, molecular mechanisms by which they inhibit the growth of this fungus are not known. We have characterized a functional role of the fungal sphingolipid glucosylceramide in regulating sensitivity of the fungus to MsDef1 and MtDef4. A null mutation of the FgGCS1 gene encoding glucosylceramide synthase results in a mutant lacking glucosylceramide. The DeltaFggcs1-null mutant becomes resistant to MsDef1, but not to MtDef4. It shows a significant change in the conidial morphology and displays dramatic polar growth defect, and its mycelia are resistant to cell wall degrading enzymes. Contrary to its essential role in the pathogenicity of a human fungal pathogen, Cryptococcus neoformans, GCS1 is not required for the pathogenicity of F. graminearum. The DeltaFggcs1 mutant successfully colonizes wheat heads and corn silk, but its ability to spread in these tissues is significantly reduced as compared with the wild-type PH-1 strain. In contrast, it retains full virulence on tomato fruits and Arabidopsis thaliana floral and foliar tissues. Based on our findings, we conclude that glucosylceramide is essential for MsDef1-mediated growth inhibition of F. graminearum, but its role in fungal pathogenesis is host-dependent.     

Mitochondrial nucleoids maintain genetic autonomy but allow for functional complementation

Mitochondrial DNA (mtDNA) is packaged into DNA-protein assemblies called nucleoids, but the mode of mtDNA propagation via the nucleoid remains controversial. Two mechanisms have been proposed: nucleoids may consistently maintain their mtDNA content faithfully, or nucleoids may exchange mtDNAs dynamically. To test these models directly, two cell lines were fused, each homoplasmic for a partially deleted mtDNA in which the deletions were nonoverlapping and each deficient in mitochondrial protein synthesis, thus allowing the first unequivocal visualization of two mtDNAs at the nucleoid level. The two mtDNAs transcomplemented to restore mitochondrial protein synthesis but were consistently maintained in discrete nucleoids that did not intermix stably. These results indicate that mitochondrial nucleoids tightly regulate their genetic content rather than freely exchanging mtDNAs. This genetic autonomy provides a molecular mechanism to explain patterns of mitochondrial genetic inheritance, in addition to facilitating therapeutic methods to eliminate deleterious mtDNA mutations.