Newsletter 02 2006.pdf - Sight and Life

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SIGHT AND LIFE 18 NEWSLETTER 2/2006 A supplementation in northern Ghana: effects on clinic attendance, hospital admissions, and child mortality. Lancet 342:7–12. 44. Vijayaraghavan K., Radhaiah G, Prakasam BS, Sarma KVR, Reddy V (1990). Effect of massive dose vitamin A on morbidity and mortality in Indian children. Lancet 336:1342–45. 45. Herrera MG, Nestel P, El Amin A, Fawzi WW, Mohamed KA, Weld L (1992). Vitamin A supplementation and child survival. Lancet 340:267–71. 46. Muhilal, Permeisih D, Idjradinata YR, Muherdiyantiningsih, Karyadi D (1988). Vitamin A-fortified monosodium glutamate and health, growth, and survival of children: a controlled field trial. Am J Clin Nutr 48:1271–6. 47. Rahmathullah L, Underwood BA, Thulasiraj RD, Milton RC, Ramaswamy K, Rahmathullah R, Babu G (1990). Reduced mortality among children in southern India receiving a small weekly dose of vitamin A. New Engl J Med 325:929–35. 48. Beaton GH, Martorell R, Aronson KJ, Edmonston B, McCabe G, Ross AC & Harvey B (1993). Effectiveness of vitamin A supplementation on childhood morbidity and mortality in developing countries. ACC/SCN State-of-the-art series, Nutrition Policy Discussion Paper No. 13. ACC/SCN, Geneva. 49. Fawzi WW, Chalmers TC, Herrera G & Mosheller F (1993). Vitamin A supplementation and child mortality. A meta-analysis. J Am Med Assoc 269: 896–903. 50. Glasziou PP & Mackerras DWM (1993). Vitamin A supplementation in infectious diseases: a meta-analysis. Brit Med J 306:366–70. 51. Pineda O (1998). Fortification of sugar with vitamin A. UNU Food Nutr Bull 19:131–6. 52. Bloem MW, Huq N, Gorstein J et al. (1996). Production of fruits and vegetables on the homestead is an important source of vitamin A among women in rural Bangladesh. Eur J Clin Nutr 50 (Suppl 3): S62–S67. 53. Underwood BA (2001). Vitamin A-related childhood blindness, mortality, and morbidity. Interventions for prevention. In: Primary and Secondary Preventive Nutrition. Eds: A. Bendich & RJ Deckelbaum, Totowa, NJ: Humana Press Inc. 54. Castenmiller JM, West CE (1998). Bioavailability and bioconversion of carotenoids. Ann Rev Nutr 18:19–38. 55. CGIAR Micronutrients Project. Update No. 1, October, 1996 and Update No. 2, October 1997, IFPRI, Washington D.C. 56. Bouis HS (Guest Editor) (2000). Special issue on improving human nutrition through agriculture. Food & Nutr Bull 21:252–567. 57. Paine JA, Shipton CA, Chaggar S, Howells RM, Kennedy MJ, Vernon G, Weight SY, Hinchliffe E, Adams JL, Silverstone AL, Drake R (2005). Improving the nutritional value of Golden Rice through increased pro-vitamin A content. Nature Biotechnology 23:482–487. 58. Van Jaarsveid PJ, Faber M, Tanumihardjo SA, et al. (2005). β-carotene-rich orange-fleshed sweet potato improves the vitamin A status of primary school children assessed with the modified-relative-dose response test. Am J Clin Nutr 81:1080–7. 59. Low J, Arimond M, Osman N, Osei AK et al. (2005). Towards sustainable nutrition improvement in rural Mozambique: Addressing macro- and micro-nutrient malnutrition through new cultivars and new behaviors. Project Report, December 2005. Carotene Research Interaction Group (CARIG) Annual Conference 2006, San Francisco Noel W Solomons, Center for Studies of Sensory Impairment, Aging and Metabolism, Guatemala City, Guatemala The 2006 Carotene Research Interaction Group (CARIG) Annual Conference was convened on Saturday, 1 April at the Argent Hotel in San Francisco. It accompanied the Experimental Biology 2006 meetings. This year’s conference was organized and chaired by Dr. Elizabeth Johnson of Tufts University in Boston, a member of the CARIG Steering Committee. The proceedings began with the fifth annual James Allen Olson Perspective in Carotenoids lecture at CARIG, delivered by Dr. Barbara Underwood. She was a close associate of the late Prof. Olson, including jointly working in Brazil and serving as colleagues on the International Vitamin A Consultative Group (IVACG). She spoke on the topic: Reflections: Four Decades with Vitamin A and Carotenoids. (the full text of the James Allen Olson memorial lecture appears on page 10 of this issue). The significance of the talk was, in many ways, to show just how recent in emergence are the facts and principles that we hold in common about assessing vitamin A status and on the necessity to develop public health intervention strategies against hypovitaminosis A. Dr. Underwood, as well as Prof. Olson, a founding member of CARIG and the force behind VARIG (the Vitamin A Research Interaction Group), were part of vitamin A discovery and consensus development. This was inspired by a crucial meeting held in Basel, Switzerland in 1960, assessing the existing knowledge on vitamin A and pointing the way to the important next steps in the programmatic conquest of hypovitaminosis A. Dr. Underwood recounted three decades of contributions from IVACG, founded in 1975, with about 35 experts in the vitamin A field in attendance. The lecture highlighted the steady and solid accumulation of accurate biological and epidemiological knowledge about vitamin A deficiency. This would lead to the mobilization of a worldwide public health effort based primarily on high-dose supplement capsules or fortification of staple foods such as sugar or cooking oil. Of special interest for a carotenoid biology audience was Barbara Underwood’s particular point of view regarding public health interventions. She accused the sometimes rancorous discussions in the 1990s concerning the true efficiency of bioconverting provitamin A to yield active vitamin A of retarding the progress toward developing
NEWSLETTER 2/2006 19 SIGHT AND LIFE sustainable food-based alternatives to alleviate hypovitaminosis A. With that issue now resolved by a new consensus within the Dietary Reference Intakes of 2001, she pointed to gathering momentum in the area of biofortification, citing the founding of the Harvest Plus Project. The emphasis of biofortification is on staple crops of abundant and regular consumption by developing-country populations. Crossbreeding for hybrid varieties of sweet potato (orange-fleshed varieties) and genetic modification in the second (high-carotene) generation of Golden Rice were examples in which daily individual vitamin A needs could be met from the abundant supplies of β-carotene in these biofortified tubers and grains. A slide from Barbara Underwood advocating a holistic approach. An important and newsworthy note at the end of Dr. Underwood’s presentation was her announcement of the transformation of the IVACG. What began with its first meeting in 1975 ended with its 22nd meeting in Lima, Peru in 2004. A successor, the Micronutrient Forum, will be launched in Istanbul, Turkey, 16–18 April 2007, with a broader and integrated mandate involving vitamin A, iron, zinc, iodine and folic acid in a public health context. Those of us who care about human vitamin A nutriture can derive lessons and standards in the message of Dr. Underwood’s Reflections. Lessons relate to how to set an agenda for inquiry to rapidly advance basic and applied knowledge, and standards to gauge the expectations for progress in redressing vitamin A deficiency problems. Should the interests of vitamin A get “lost in the shuffle” of multiple micronutrients and diluted scientific expertise and attention in the Forum, these Reflections may become the cudgel to demand the attention for vitamin A issues that were clearly championed by Underwood and Olson during the past four decades. The second plenary lecture on the program was delivered by Dr. Earl Harrison, senior scientist at the USDA Human Nutrition Center at Beltsville, Maryland. He spoke on the topic of Mechanisms Involved in the Intestinal Absorption of Dietary Carotenoids. This was a fitting and complementary companion theme to Dr. Underwood’s presentation with her emphasis on provitamin A carotenes from foods to supply vitamin A to deprived populations. To orient the audience, Dr. Harrison reviewed the conventional schematic aspects of dietary carotene uptake from the intestinal lumen into intestinal cells (enterocytes) and the options for its further passage either as the intact carotenoid or as a derivative retinoid. Dr. Harrison and his co-worker have advanced evidence that both simple diffusion and a receptormediated transport (carotene transporters) are involved in the usual absorptive physiology of carotenoids. The laboratory at Beltsville has used a novel, in-vitro cell culture model, that of the Caco cell monolayer in a directional absorption chamber, to explore the mechanisms of absorption of dietary carotenoids. The absorption chamber experiments revealed an 11% fractional absorption for β-carotene, which is not so far Earl Harrison from the rate documented for the intact human intestine. Kinetic experiments showing saturation kinetics under certain conditions, however, are a strong argument that a “facilitated transport” is operating, and this is in line with a receptor involvement. A clever set of experiments in Caco cell cultures, stellate (Ito) cell (hepatic fat storage cells) cultures, and cell-free microsomes (membrane envelopes) add credence to a transporter basis by showing stereo-specificity in uptake. In all three systems, different isomers of β-carotene were taken up to different extents. In descending order of uptake, affinity in the systems was revealed to be: all-trans β-carotene; 9-cis-β-carotene; and 13-cis-β-carotene. Bolstered by the coming together of cell-system evidence supporting a transported mechanism, Dr. Harrison’s research group has turned to identifying enzymes known to be located in the apical membrane of intact enterocytes, as candidates for involvement in the transporter mechanism. Their search has centered on so-called class-B scavenger receptors, extensively studied for their involvement in cholesterol uptake. This has led pharmacologists to develop inhibitory agents for receptor uptake. This laboratory has also used mouse models with deletion of genes of specific
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