Lactose intolerance pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahda Alihashemi M.D. [2]
Overview
The exact pathogenesis of [disease name] is not fully understood.
OR
It is thought that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].
OR
[Pathogen name] is usually transmitted via the [transmission route] route to the human host.
OR
Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.
OR
[Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].
OR
The progression to [disease name] usually involves the [molecular pathway].
OR
The pathophysiology of [disease/malignancy] depends on the histological subtype.
Pathophysiology
Pathogenesis
- The exact pathogenesis of [disease name] is not fully understood.These symptoms have been attributed to lactose malabsorption, which results from low levels of small intestinal lactase, which may be due to mucosal injury or, much more commonly, reduced genetic expression of the enzyme lactase-phlorizin hydrolase
OR
- It is thought that lactose intolerance is the result of lactose malabsorption that it is caused by low level of small intestinal lactase.
- The most important causes of low level of small intestinal lactase are:
- Mucosal injury
- Reduced genetic expression of the enzyme lactase-phlorizin hydrolase
- Lactose is metabolized by intestinal lactase to galactose and glucose in villous enterocytes and then are uptaked by Na+/glucose cotransporter (SGLT1). [1][2]
- In colon, unabsorbed lactose is converted to hydrogen gas and short chain fatty acids such as acetate, butyrate and propionate by intestinal bacteria and creates symtoms of lactose intolerance.
- Milk drinkers has greater lactase activity compare with non-drinkers [3]
- The lactase activity was significantly greater in milk drinkers than non-drinkers. And, internationally, the active is higher in those nationalities whose milk consumption is greater. 3. Lactase is an adaptive enzyme and rather easily induced by lactose load feeding in animals. From the data of our own and of the literature, it was further confirmed that environmental factors play a more important role than genetic factors in the etio-pathogenesis of milk intolerance.
- / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].
- it is thought that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].
- [Pathogen name] is usually transmitted via the [transmission route] route to the human host.
- Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.
- [Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].
- The progression to [disease name] usually involves the [molecular pathway].
- The pathophysiology of [disease/malignancy] depends on the histological subtype.
Genetics
- Lactose intolerance is transmitted in an autosomal recessive pattern.[4]
- Persistence of intestinal lactase until adulthood is inherited as an autosomal-dominant characteristic[5]
- Genes involved in the pathogenesis of lactose intolerance include [gene1], [gene2], and [gene3]. identified two single nucleotide polymorphisms (SNPs), C/T(-13910) and G/A(-22018), associated with adult-type hypolactasia by studying LPH mRNA levels in intestinal biopsy samples with different genotypes.[4]
- The development of [disease name] is the result of multiple genetic mutations.
Associated Conditions
Gross Pathology
- On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].
Microscopic Pathology
- On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].
References
- ↑ Maiuri L, Raia V, Potter J, Swallow D, Ho MW, Fiocca R, Finzi G, Cornaggia M, Capella C, Quaroni A (1991). "Mosaic pattern of lactase expression by villous enterocytes in human adult-type hypolactasia". Gastroenterology. 100 (2): 359–69. PMID 1702075.
- ↑ Martín MG, Turk E, Lostao MP, Kerner C, Wright EM (1996). "Defects in Na+/glucose cotransporter (SGLT1) trafficking and function cause glucose-galactose malabsorption". Nat. Genet. 12 (2): 216–20. doi:10.1038/ng0296-216. PMID 8563765.
- ↑ Yoshida Y, Sasaki G, Goto S, Yanagiya S, Takashina K (1975). "Studies on the etiology of milk intolerance in Japanese adults". Gastroenterol. Jpn. 10 (1): 29–34. PMID 1234085.
- ↑ 4.0 4.1 Enattah NS, Sahi T, Savilahti E, Terwilliger JD, Peltonen L, Järvelä I (2002). "Identification of a variant associated with adult-type hypolactasia". Nat. Genet. 30 (2): 233–7. doi:10.1038/ng826. PMID 11788828.
- ↑ Scrimshaw NS, Murray EB (1988). "The acceptability of milk and milk products in populations with a high prevalence of lactose intolerance". Am. J. Clin. Nutr. 48 (4 Suppl): 1079–159. PMID 3140651.
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Lactose Intolerance Microchapters |
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Diagnosis |
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Treatment |
|
Case Studies |
|
Lactose intolerance pathophysiology On the Web |
|
American Roentgen Ray Society Images of Lactose intolerance pathophysiology |
|
Risk calculators and risk factors for Lactose intolerance pathophysiology |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [3]
Pathophysiology
Physiology
Without lactase, the lactose disaccharide in many dairy products remains uncleaved and can not be absorbed through the intestinal wall into the bloodstream, so remains in the intestines. Enteral bacteria adapt to the relative abundance of this undigested sugar and their operons quickly switch over to lactose metabolism, which produces copious amounts of gas by fermentation.
This also causes a range of unpleasant abdominal symptoms, including stomach cramps, bloating, flatulence and diarrhea. As with other unabsorbed sugars (mannitol), the lactose raises the osmotic pressure of the colon contents, preventing the colon from reabsorbing water and hence causing a laxative effect to add to the excessive gas production.
Genetics
The gene is expressed and the enzyme synthesized if at least one of the two genes are present. Only when both gene expressions are affected is lactase enzyme synthesis reduced, which in turn reduces lactose digestion.[1] Lactose tolerance (lactase persistence) is the dominant allele. Lactose intolerance is an autosomal recessive trait.
The normal mammalian condition is for the young of a species to experience reduced lactose (milk sugar) production at the end of the weaning period (a species-specific length of time). In non dairy consuming societies, lactase production usually drops about 90% during the first four years of life, although the exact drop over time varies widely. However, certain human populations have a mutation on chromosome 2 which results in a bypass of the common shutdown in lactase production, making it possible for members of these populations to continue consumption of fresh milk and other dairy products throughout their lives.
Pathological lactose intolerance can occur due to celiac disease, which damages the villi in the small intestine that produce lactase. This lactose intolerance is temporary. Lactose intolerance associated with coeliac disease ceases after the patient has been on a gluten-free diet long enough for the villi to recover.
Certain people who report problems with consuming lactose are not actually lactose intolerant. In a study of 323 Sicilian adults, Carroccio et al. (1998) found only 4% were both lactose intolerant and lactose maldigesters, while 32.2% were lactose maldigesters but did not test as lactose intolerant. However, Burgio et al. (1984) found that 72% of 100 Sicilians were lactose intolerant in their study and 106 of 208 northern Italians (i.e., 51%) were lactose intolerant.