By Billy Hammond (Copyright AELS)

People often worry about cholesterol, but cholesterol is needed to stabilize cell membranes and as a precursor to the bile salts and steroid hormones.

Cholesterol is either obtained in the diet or synthesized by a pathway that occurs in most cells of the body, but especially in the liver and intestinal cells. The adrenal cortex and gonads also synthesize cholesterol and use it for steroid hormone synthesis. Cholesterol synthesis requires acetyl CoA, which can be produced from glucose, fatty acids or amino acids.

Cholesterol gets packaged into chylomicrons in the intestine and Very Low-density Lipoprotein (VLDL) in the liver. It gets transported in the blood in the lipoprotein particles together with triacylglycerols. The chylomicrons are converted into chylomicron remnants. The VLDL gets converted into Intermediate-density Lipoprotein (IDL) and then into Low Density Lipoprotein (LDL) which returns to the liver. The liver uses the recycled cholesterol and the cholesterol synthesized from Acetyl CoA to produce VLDL and to synthesize bile salts.

Intracellular cholesterol taken from the blood lipoproteins decreases cholesterol synthesis within cells and increases its storage as cholesterol esters. It also decreases the synthesis of LDL receptors on cells.

High-density Lipoprotein (HDL) includes triacylglycerols and cholesterol, but it transfers apolipoprotein E (apo E) and apolipoprotein CII to chylomicrons and VLDL. After VLDL triacylglycerols are digested the apo E and apo CII are transferred back to HDL.

The HDL also gets cholesterol from other cell membranes and lipoproteins and changes it to cholesterol esters. After the transformation HDL either directly transports the cholesterol and cholesterol esters to the liver or moves the cholesterol esters to other proteins. In the end, the HDL returns the cholesterol and cholesterol esters to the liver in what is known as “reverse cholesterol transport.” This helps protect the body against atherosclerotic plaque formation by removing the cholesterol.

The liver synthesizes the acetyl CoA or uses the blood lipoproteins to produce bile salts. The bile salts are stored in the gall bladder and released into the intestine after eating. After helping with digestion, the bile salts go to the ileum, where they’re reabsorbed while a little less than 5% are excreted in the feces. The feces are the main disposal route for the cholesterol steroid nucleus.

The steroid hormones derived from cholesterol are the adrenal cortical hormones like cortisol and aldosterone, together with the adrenal sex steroids DHEA and androstenedione plus the gonadal hormones testosterone and estrogen.



コレステロールは食べ物から取り入れ、または肝臓細胞と腸細胞経路で合成される(他の細胞にも同じ回路はあるが、主に肝臓と腸細胞に集中されている)。副腎皮質と生殖腺もコレステロールを合成し、ステロイドホルモンに使われる。コレステロール合成にはグルコース、脂肪酸またはアミノ酸から製造するアセチル補酵素Aacetyl CoA)が必要。

腸にはコレステロールはカイロミクロンに、肝臓でVLDL (超低密度リポタンパク質 )にパッケージされる。それらのリポタンパクとトリアシルグリセロールの形で血液内に移動する。カイロミクロンはカイロミクロン・レムナント(残部)に変換される。VLDL(超低密度リポタンパク)は中間比重リポタンパクに変換されてからLDL(低比重リポ蛋白)に変換し、肝臓に戻される。肝臓はリサイクルされたコレステロールやアセチル補酵素Aacetyl CoA)から合成されたコレステロールをVLDL製造や胆汁塩合成に使う。



HDLは他の細胞膜やリポタンパク質からもコレステロールを得て、コレステロール・エステルに変換する。返還後HDLは直接コレステロールとコレステロール・エステルを肝臓に移行し、またはコレステロール・エステルを他のタンパク質に移行する。最終的にHDLはコレステロールとコレステロール・エステルを「reverse cholesterol transport[コレステロールの逆輸送]」と呼ばれるパスウェイで肝臓に戻す。このようにコレステロールを除き、動脈硬化斑形成から身体を守る。

肝臓はアセチル補酵素Aacetyl CoA)を合成し、または血液リポタンパク質を使って、胆汁塩を製造する。胆汁塩は胆嚢に保管し、食事の際、腸に分泌される。消化の役割を果たしてから、胆汁塩の殆どが回腸で再吸収され、僅かな5%未満が便で排出される。但し、便はコレステロール・ステロイド核の主な排出経路である。


By Billy Hammond (Copyright AELS)


English books by Billy Hammond published by AELS



I. Majoh Gakuin and Hikari Juku – Japanese Witch Schools Trilogy

1. Majoh Gakuin & Hikari Juku – Japanese Witch Schools

2. Lost Witch (The second book)

3. Fate & Magic (The final book in the trilogy)

II. Brindle – Scryer Extraordinaire Trilogy

1. Brindle – Scryer Extraordinaire

2. Brindle – Scryer Extraordinaire – Returns

3. Brindle – Scryer Extraordinaire – Challenges (The final book in the trilogy)

III. Fantasy fiction set in Japan

1. 21st Century Ninja

2. Regressed

3. Japanese Woman

IV. Fantasy fiction set outside of Japan

1. Dimension Jumpers