The geographic hypothesis and lactose malabsorption

Simoons, Frederick J.

doi:10.1007/bf01263095

Cited by 300 publications

(120 citation statements)

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“…In most humans, programmed loss of enzyme activity occurs during childhood, but persistence of lactase throughout life is not uncommon and is the norm in certain racial groups (1,2). Whereas recent studies of the molecular biology of human lactase have provided important information concerning the evolution and structure of the protein (3,4), the regulatory mechanisms controlling enzyme expression remain to be determined.…”

mentioning

confidence: 99%

The biosynthetic basis of adult lactase deficiency.

Witte

Lloyd²,

Lorenzsonn³

et al. 1990

J. Clin. Invest.

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The intestinal brush-border enzyme lactase splits lactose into its component monosaccharides, glucose and galactose. Relative deficiency of the enzyme during adulthood is a common condition worldwide and is frequently associated with symptoms of lactose intolerance. We studied the synthesis and processing of lactase in normal and adult hypolactasic subjects using human intestinal explants in organ culture. Metabolic labeling experiments in our control subjects with I35Slmethio-nine followed by immunoprecipitation, sodium dodecyl sulfate-polyacrylamide-gel electrophoresis, and fluorography demonstrated that newly synthesized lactase is initially recognized as a precursor molecule with a relative molecular weight (Mr) of 205,000. Over the course of several hours most of the labeled lactase was converted to a mature form of 150,000 Mr. Transiently appearing forms of 215,000 and 190,000 M, were identified and were felt to represent intermediary species generated during intracellular processing.We identified two distinct alterations in lactase biosynthesis accounting for adult hypolactasia. Studies in three deficient subjects demonstrated markedly reduced synthesis of the precursor protein though posttranslational processing appeared identical to normal. Multiple studies in a fourth deficient subject demonstrated synthesis of ample amounts of precursor lactase but reduced conversion to the mature active form of the enzyme. (J. Clin. Invest. 1990Invest. . 86:1338Invest. -1342

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mentioning

confidence: 99%

The biosynthetic basis of adult lactase deficiency.

Witte

Lloyd²,

Lorenzsonn³

et al. 1990

J. Clin. Invest.

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“…A prevalência de intolerância à lactose difere consideravelmente por raça (90% em chineses, 60% em asiáticos e 40% na população do mediterrâneo oriental). No noroeste da Europa apenas 10% das pessoas são intolerantes à lactose (39) . Muitos dos que sofrem reconhecem a ligação com produtos lácteos e os evita.…”

Section: Anamneseunclassified

[No Title Available]

Spiller

Thompson²

2012

Arq. Gastroenterol.

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Os principais sintomas de origem intestinal são: dor abdominal ou desconforto, hábito intestinal alterado, distensão abdominal e borborigmos. Dor abdominal/desconfortoAs características da dor abdominal incluem a localização, a irradiação (se houver), o caráter (ardor, em pontadas, cólicas), padrão e duração (desde o início e a duração da crise) e fatores precipitantes e de alívio. Dor abdominal ou desconforto de origem gastrointestinal funcional surge da estimulação dos nervos viscerais: normalmente é difusa e mal localizada, muitas vezes no abdome inferior ou central. Quando perguntado para demonstrá-la, o paciente pode usar uma mão estendida, colocada sobre a área. Dados que sugerem a origem gastrointestinal da dor abdominal incluem exacerbação ao comer e alívio por defecação, sendo esta última parte dos critérios diagnósticos para síndrome do intestino irritável (SII). No entanto, apesar da alimentação aumentar a motilidade do cólon, pode produzir desconforto por meia hora depois , sendo característica de muitas doenças gastrointestinais. Portanto, a dor após refeições não faz parte dos critérios diagnósticos para a SII.Em contraste, quando doença visceral está associada com a estimulação dos neurônios somáticos, a dor é localizada mais precisamente. Diverticulite e apendicite são exemplos de doença intra-abdominal que, inicialmente são mal localizados, porque uma leve inflamação afeta apenas os neurônios viscerais. No entanto, quando a inflamação progride e atinge o peritônio parietal, a dor abdominal somática mais precisamente localizada é experimentada. Outros exemplos incluem a irradiação para as costas, que é típica de doença pancreática ou de úlcera duodenal penetrante.Dor em parede abdominal devida à hérnia de Spigelian (hérnia através da fáscia aponeurótica lateral ao músculo retoabdominal), lesão no músculo reto ou síndrome de dor em costelas é também localizada com mais precisão. Dor de tais causas pode ser identificada pelo teste do Carnett, no qual o paciente dobra seus braços sobre o peito e levanta sua cabeça contra a resistência suave. Exacerbação da dor por enrijecer os músculos retos desta forma, indica um distúrbio de parede abdominal (1) . Dor na caixa torácica é também precisamente localizada e agravada pela pressão local ou compressão. Reconhecimento precoce destas fontes somáticas menos comuns de dor abdominal pode evitar muita investigação fútil (2) . A dor abdominal da SII é visceral por natureza e geralmente episódica e imprevisível. Períodos de dor reaparecem durante uma mediana (intervalo) de 3 dias (2)(3)(4)(5)(6)(7)(8) , intercalados com alguns dias sem dor (3) . No entanto, em alguns casos, períodos dolorosos podem ser mais prolongados. Uma característica crucial da dor abdominal de SII é a associação temporal com hábito intestinal alterado. Uma alteração na frequên-cia e consistência das evacuações simultânea com a dor é um fenômeno usado nos critérios de Manning. Para a SII, esses recursos têm sensibilidade de SII desde 0,39 -0.6 e uma especificidade de 0,66 -0,77 com relação ...

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“…We tested the hypothesis that high levels of lactase persistence in a population was related to a history of milk-based pastoralism (Simoons, 1969(Simoons, , 1970(Simoons, , 1978. We also tested for correlations with levels of sunshine and aridity, which relate to other hypotheses for the evolution of lactase persistence (Flatz and Rotthauwe, 1973;Cook and Al-Torki, 1975;Cook, 1978).…”

Section: The Evolution Of Lactose Tolerance As An Adaptation To Pastomentioning

confidence: 99%

Testing evolutionary hypotheses about human biological adaptation using cross-cultural comparison

Mace

Jordan

Holden

2003

Comparative Biochemistry and Physiology Part A: Molecular &

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Physiological data from a range of human populations living in different environments can provide valuable information for testing evolutionary hypotheses about human adaptation. By taking into account the effects of population history, phylogenetic comparative methods can help us determine whether variation results from selection due to particular environmental variables. These selective forces could even be due to cultural traits-which means that geneculture co-evolution may be occurring. In this paper, we outline two examples of the use of these approaches to test adaptive hypotheses that explain global variation in two physiological traits: the first is lactose digestion capacity in adults, and the second is population sex-ratio at birth. We show that lower than average sex ratio at birth is associated with high fertility, and argue that global variation in sex ratio at birth has evolved as a response to the high physiological costs of producing boys in high fertility populations. ᮊ 2003 Elsevier Science Inc. All rights reserved.Keywords: Comparative method; Human sex ratio; Lactose tolerance; Phylogeny; Gene-culture co-evolution; Adaptation; Maternal mortality; Natural selection 1. A phylogenetic approach to testing evolutionary hypotheses using cross-cultural data Physiological data from a range of human populations living in different environments can provide valuable information for testing evolutionary hypotheses about human adaptation. The comparative method can help us determine whether variation results from selection due to environmental factors, or is possibly selected for by cultural forces (which means that gene-culture co-evolution is occurring). However, a simple, statistical correlation between traits across cultures is complicated by the non-independence of cultures, as was first recognized in the 19th century by Francis Galton. The same problem applies in cross-species comparisons. Evolutionary biologists have developed phylogenetic comparative methods that can take account of the hierarchical inter-relatedness of species and test for the co-evolution of traits on phylogenetic trees. Mace and Pagel (1994) argued that similar approaches can be used to test crosscultural hypotheses. In this paper, we will outline two examples of the use of these approaches to test adaptive hypotheses explaining global variation in two physiological traits: the first is lactose digestion capacity in adults, and the second is population sex-ratio at birth. In the case of lactose

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The geographic hypothesis and lactose malabsorption

Cited by 300 publications

References 117 publications

The biosynthetic basis of adult lactase deficiency.

The biosynthetic basis of adult lactase deficiency.

[No Title Available]

Testing evolutionary hypotheses about human biological adaptation using cross-cultural comparison

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