Created page with "===原因=== リボフラビンの欠乏は、通常、他の栄養素、特に他の水溶性ビタミンの欠乏とともにみられる。リボフラビンの欠乏は、一次的なもの（すなわち、通常の食事に含まれるビタミン源が乏しいために起こる）と、二次的なものがあり、腸での吸収に影響を及ぼすような病態の結果として起こることがある。二次的欠乏症は通常、体内で..."
Created page with "1935年、Paul Gyorgyは化学者Richard Kuhnと医師T. Wagner-Jaureggと共同で、B<sub>2</sub>を含まない餌で飼育したラットは体重が増加しないことを報告した。酵母からB<sub>2</sub>を単離したところ、明るい黄緑色の蛍光産物の存在が明らかになり、ラットに与えると正常な成長が回復した。回復した成長は蛍光の強さに正比例した。この観..."
There are rare genetic defects that compromise riboflavin absorption, transport, metabolism or use by flavoproteins. One of these is riboflavin transporter deficiency, previously known as [[Brown–Vialetto–Van Laere syndrome]]. Variants of the genes SLC52A2 and [[SLC52A3]] which code for [[Transport protein|transporter proteins]] RDVT2 and RDVT3, respectively, are defective. Infants and young children present with muscle weakness, [[cranial nerve]] deficits including hearing loss, sensory symptoms including sensory [[ataxia]], feeding difficulties, and respiratory distress caused by a [[Sensorimotor network|sensorimotor]] [[axon]]al [[neuropathy]] and cranial nerve pathology. When untreated, infants with riboflavin transporter deficiency have labored breathing and are at risk of dying in the first decade of life. Treatment with oral supplementation of high amounts of riboflavin is lifesaving.
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その他の先天性代謝異常には、[[glutaric acidemia type 2/ja|グルタル酸血症2型]]のサブセットとしても知られるリボフラビン応答性多発性[[acyl-CoA dehydrogenase/ja|アシル-CoAデヒドロゲナーゼ]]欠損症や、成人では高血圧のリスクと関連している[[methylenetetrahydrofolate reductase/ja|メチレンテトラヒドロ葉酸還元酵素]]のC677T変異体などがある。
Other inborn errors of metabolism include riboflavin-responsive multiple [[acyl-CoA dehydrogenase]] deficiency, also known as a subset of [[glutaric acidemia type 2]], and the C677T variant of the [[methylenetetrahydrofolate reductase]] enzyme, which in adults has been associated with risk of high blood pressure.
The assessment of riboflavin status is essential for confirming cases with non-specific symptoms whenever deficiency is suspected. Total riboflavin excretion in healthy adults with normal riboflavin intake is about 120 [[microgram]]s per day, while excretion of less than 40 micrograms per day indicates deficiency. Riboflavin excretion rates decrease as a person ages, but increase during periods of [[chronic stress]] and the use of some [[prescription drugs]].
Indicators used in humans are [[erythrocyte]] [[glutathione reductase]] (EGR), erythrocyte flavin concentration and urinary excretion. The ''erythrocyte glutathione reductase activity coefficient'' (EGRAC) provides a measure of tissue saturation and long-term riboflavin status. Results are expressed as an activity coefficient ratio, determined by enzyme activity with and without the addition of FAD to the culture medium. An EGRAC of 1.0 to 1.2 indicates that adequate amounts of riboflavin are present; 1.2 to 1.4 is considered low, greater than 1.4 indicates deficient. For the less sensitive "erythrocyte flavin method", values greater than 400 nmol/L are considered adequate and values below 270 nmol/L are considered deficient. Urinary excretion is expressed as nmol of riboflavin per gram of [[creatinine]]. Low is defined as in the range of 50 to 72 nmol/g. Deficient is below 50 nmol/g. Urinary excretion load tests have been used to determine dietary requirements. For adult men, as oral doses were increased from 0.5 mg to 1.1 mg, there was a modest linear increase in urinary riboflavin, reaching 100 micrograms for a subsequent 24-hour urine collection.Beyond a load dose of 1.1 mg, urinary excretion increased rapidly, so that with a dose of 2.5 mg, urinary output was 800 micrograms for a 24-hour urine collection.
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==歴史==
==History==
{{Anchor|History}}
The name "riboflavin" comes from "[[ribose]]" (the sugar whose [[reduction (chemistry)|reduced]] form, [[ribitol]], forms part of its structure) and "[[Flavin group|flavin]]", the ring-moiety that imparts the yellow color to the oxidized molecule (from Latin ''flavus'', "yellow"). The reduced form, which occurs in metabolism along with the oxidized form, appears as orange-yellow needles or crystals. The earliest reported identification, predating any concept of vitamins as essential nutrients, was by Alexander Wynter Blyth. In 1879, Blyth isolated a water-soluble component of cows' milk whey, which he named "lactochrome", that [[fluorescence|fluoresced]] yellow-green when exposed to light.
In the early 1900s, several research laboratories were investigating constituents of foods, essential to maintain growth in rats. These constituents were initially divided into fat-soluble "vitamine" A and water-soluble "vitamine" B. (The "e" was dropped in 1920.) Vitamin B was further thought to have two components, a heat-labile substance called B<sub>1</sub> and a heat-stable substance called B<sub>2</sub>. Vitamin B<sub>2</sub> was tentatively identified to be the factor necessary for preventing [[pellagra]], but that was later confirmed to be due to [[Niacin (nutrient)|niacin]] (vitamin B<sub>3</sub>) deficiency. The confusion was due to the fact that riboflavin (B<sub>2</sub>) deficiency causes [[stomatitis]] symptoms similar to those seen in pellagra, but without the widespread peripheral skin lesions. For this reason, early in the history of identifying riboflavin deficiency in humans the condition was sometimes called "pellagra sine pellagra" (pellagra without pellagra).
In 1935, [[Paul Gyorgy]], in collaboration with chemist [[Richard Kuhn]] and physician T. Wagner-Jauregg, reported that rats kept on a B<sub>2</sub>-free diet were unable to gain weight. Isolation of B<sub>2</sub> from yeast revealed the presence of a bright yellow-green fluorescent product that restored normal growth when fed to rats. The growth restored was directly proportional to the intensity of the fluorescence. This observation enabled the researchers to develop a rapid chemical bioassay in 1933, and then isolate the factor from egg white, calling it ovoflavin. The same group then isolated the a similar preparation from whey and called it lactoflavin. In 1934, Kuhn's group identified the chemical structure of these flavins as identical, settled on "riboflavin" as a name, and were also able to synthesize the vitamin.
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1937年頃、リボフラビンは「ビタミンG」とも呼ばれていた。1938年、Richard KuhnはB<sub>2</sub>とB<sub>6</sub>を含むビタミンの研究で[[:en:Nobel Prize in Chemistry|ノーベル化学賞]]を受賞した。1939年、William H. SebrellとRoy E. Butlerが行った臨床試験により、リボフラビンが人間の健康に不可欠であることが確認された。リボフラビンの少ない食事を与えられた女性は口内炎やその他の欠乏症状を呈したが、合成リボフラビンで治療すると症状は回復した。サプリメントを中止すると症状は再発した。
Circa 1937, riboflavin was also referred to as "Vitamin G". In 1938, Richard Kuhn was awarded the [[Nobel Prize in Chemistry]] for his work on vitamins, which had included B<sub>2</sub> and B<sub>6</sub>. In 1939, it was confirmed that riboflavin is essential for human health through a clinical trial conducted by William H. Sebrell and Roy E. Butler. Women fed a diet low in riboflavin developed stomatitis and other signs of deficiency, which were reversed when treated with synthetic riboflavin. The symptoms returned when the supplements were stopped.
1937年頃、リボフラビンは「ビタミンG」とも呼ばれていた。1938年、Richard KuhnはB2とB6を含むビタミンの研究でノーベル化学賞を受賞した。1939年、William H. SebrellとRoy E. Butlerが行った臨床試験により、リボフラビンが人間の健康に不可欠であることが確認された。リボフラビンの少ない食事を与えられた女性は口内炎やその他の欠乏症状を呈したが、合成リボフラビンで治療すると症状は回復した。サプリメントを中止すると症状は再発した。
