The molecular basis of lactose intolerance.

A staggering 4000 million people cannot digest lactose, the sugar in milk, properly. All mammals, apart from white Northern Europeans and few tribes in Africa and Asia, lose most of their lactase, the enzyme that cleaves lactose into galactose and glucose, after weaning. Lactose intolerance causes gut and a range of systemic symptoms, though the threshold to lactose varies considerably between ethnic groups and individuals within a group.

Measurement of breath hydrogen and methane, together with lactase genotype, defines the current best practice for investigation of lactose sensitivity.

Background: Currently, there is no 'gold standard' for detecting patients with sensitivity to lactose. Biochemical investigation by a breath hydrogen test alone detects <50% cases. Breath methane and symptoms are not recorded as standard practice.

Methylglyoxal and other carbohydrate metabolites induce lanthanum-sensitive Ca2+ transients and inhibit growth in E. coli.

The results here are the first demonstration of a family of carbohydrate fermentation products opening Ca2+ channels in bacteria. Methylglyoxal, acetoin (acetyl methyl carbinol), diacetyl (2,3 butane dione), and butane 2,3 diol induced Ca2+ transients in Escherichia coli, monitored by aequorin, apparently by opening Ca2+ channels. Methylglyoxal was most potent (K(1/2) = 1 mM, 50 mM for butane 2,3 diol).

Fermentation product butane 2,3-diol induces Ca2+ transients in E. coli through activation of lanthanum-sensitive Ca2+ channels.

The results here are the first demonstration of a physiological agonist opening Ca2+ channels in bacteria. Bacteria in the gut ferment glucose and other substrates, producing alcohols, diols, ketones and acids, that play a key role in lactose intolerance, through the activation of Ca2+ and other ion channels in host cells and neighbouring bacteria. Here we show butane 2,3-diol (5-200mM; half maximum 25mM) activates Ca2+ transients in E.

The molecular basis of lactose intolerance.

A staggering 4000 million people cannot digest lactose, the sugar in milk, properly. All mammals, apart from white Northern Europeans and few tribes in Africa and Asia, lose most of their lactase, the enzyme that cleaves lactose into galactose and glucose, after weaning. Lactose intolerance causes gut and a range of systemic symptoms, though the threshold to lactose varies considerably between ethnic groups and individuals within a group.

Darwin's illness revealed.

After returning from the Beagle in 1836, Charles Darwin suffered for over 40 years from long bouts of vomiting, gut pain, headaches, severe tiredness, skin problems, and depression. Twenty doctors failed to treat him. Many books and papers have explained Darwin's mystery illness as organic or psychosomatic, including arsenic poisoning, Chagas' disease, multiple allergy, hypochondria, or bereavement syndrome.

Lactose causes heart arrhythmia in the water flea Daphnia pulex.

The cladoceran Daphnia pulex is well established as a model for ecotoxicology. Here, we show that D. pulex is also useful for investigating the effects of toxins on the heart in situ and the toxic effects in lactose intolerance.