**3. Taurine and cholesterol metabolism**

274 Lipoproteins – Role in Health and Diseases

**Shellfish** 

**Table 1.** Taurine content in various food sources

**2.4. Taurine and associated health benefits** 

**Coho salmon, white muscle** 23 [40] **Coho salmon, dark muscle** 275 [40] **Eel, white muscle** 7 [40] **Eel, dark muscle** 65 [40] **Catfish, white muscle** 193 [40] **Catfish, dark muscle** 465 [40] **Tilapia, white muscle** 75 [40] **Tilapia, dark muscle** 649 [40] **Carp, white muscle** 129 [40] **Carp, dark muscle** 579 [40] **Char, white muscle** 15 [40] **Char, dark muscle** 190 [40] **Sweet smelt, white muscle** 137 [40] **Sweet smelt, dark muscle** 294 [40]

**Peeled shrimps (Northern)** 220 ± 2 [34] **Blue mussels** 510 ± 12 [34] **Mussel** 655 ± 72 [21] **Mussel** 349 [43] **Clams** 520 ± 97 [21, 43] **Scallops** 827 ± 15 [21] **Scallop** 332 [43] **Oysters** 396 ± 29 [21]

Another food item where taurine is supplemented is in infant formulas. This practice started in the early 1980s after recognizing that preterm infants fed infant formulas had lower urine and plasma concentrations than infants fed pooled human milk [55]. The necessity of this supplementation remains disputed as clinical studies have not provided evidence of any clinical effects of growth and development in preterm or low birth weight infants [56]. High concentrations of taurine in the developing brain [57], as well as results from various animal

An increased dietary intake of taurine has been associated with multiple beneficial health outcomes. Epidemiological data and animal studies suggests that dietary intake of taurine has beneficial effects on cardiovascular disease (CVD) [33, 60-62]. Perhaps the best characterized attribution of taurine is the antihypertensive effect although there are still questions about the exact mechanisms of action [63-66]. A long term effect of hypertension is the development of hypertrophy of the left ventricle, in which Angiotensin II (Ang II) plays an important role. Several studies have shown that taurine

studies clearly indicate the importance of taurine in neurodevelopment [58, 59].

Perhaps the best studied function of taurine is its role in cholesterol metabolism. Cholesterol is metabolized and broken down to cholic acids, conjugated to taurine or glycine, and excreted in the bile [77].

#### **3.1. Effects of taurine on circulating cholesterol levels**

High blood cholesterol levels is the most pronounced risk factor for developing atherosclerosis, vascular inflammation and hardening of the arteries associated with excess cholesterol deposition in the vasculature. Taurine has generally been associated with a beneficial effect on blood cholesterol levels. Cholesterol is metabolized and broken down to cholic acids, conjugated to taurine or glycine, and excreted in the bile [77]. The conjugation pattern varies considerably across species. In dog and rat bile acids are entirely conjugated to taurine, whereas rabbits have all their bile acids conjugated to glycine. Species where glycine-conjugated bile acids dominate have higher blood cholesterol levels and are more susceptible to dietary induced hypercholesterolemia, and based on these observations it was hypothesized that dietary taurine might counteract dietary induced increase in blood cholesterol [2].

#### *3.1.1. Effects of taurine on cholesterol levels in mice*

Several studies have investigated the effect of dietary intake of taurine on lipids in different mice strains. Six months administration of 1% taurine (w/v) to the drinking water given to C57BL7/6J mice fed a high-fat diet resulted in reduced serum LDL and VLDL cholesterol and increased serum HDL cholesterol [78]. Similar results were obtained in a small study using the same mouse strain, where 1% taurine (w/w) added to a high cholesterol diet reduced serum triglycerides, total cholesterol and VLDL+LDL cholesterol levels already after 4 weeks treatment [79]. Cholesterol-fed and streptozotocin (STZ)-induced diabetic male ICR mice were given a diet enriched with 2% cholesterol (w/w) and 0.5% cholate (w/w) for 10 weeks [80]. In addition, mice received a daily dose of saline or taurine (50 or 100 mg/kg p.o.). Both taurine-treated groups had lower serum total and LDL cholesterol compared to the STZ/saline group.

In more extreme models such as apolipoprotein E-deficient (apoE-/-) mice fed a normal rodent chow supplemented with 2% taurine (w/w) for 12 weeks, serum VLDL, LDL and total cholesterol levels increased compared to mice without taurine supplementation [81]. Similar results has been reported for extreme spontaneously hyperlipidemic mice (SHL; KOR-*Apoeshl*), where 12 weeks treatment with 1% taurine (w/v) added to the drinking water increased serum HDL-cholesterol but did not affect serum total cholesterol or VLDL+LDL cholesterol levels [82].
