The lipid composition of cellular membranes is regulated to maintain membrane fluidity.A key enzyme involved in this process is the membrane-bound stearoyl-Co A desaturase (SCD) which is the rate-limiting enzyme in the cellular synthesis of monounsaturated fatty acids from saturated fatty acids.The sequence between –201 to –54 in the SCD2 gene is 77% identical to the sequence between –472 to –325 in the SCD1 gene (Fig. The regulatory elements responsible for polyunsaturated fatty acid and cholesterol regulation of the SCD genes are contained in the sequences within the conserved region.In the past several years we have studied the genetic regulation of the mouse stearoyl-Co A desaturase by dietary and hormonal factors and also during fat cell differentiation.Like SCD2, SCD1 m RNA is expressed to a lesser extent in kidney, spleen, heart, and lung in response to a high carbohydrate diet.The SCD2 expression in brain is induced during the development of neonatal mice (17) and down-regulated during the development of mouse lymphocytes (18).It has been recognized that irrespective of diet, the major storage fatty acids in human adipose tissue are oleate and palmitoleate (1).Why this is the case has not been satisfactorily addressed.
Other SCD c DNAs and genes have been isolated from different species including yeast (13), ovine (14), and hamster (15), and the regulation of their expression is currently being studied by several research groups.
SRE, sterol regulatory element; NF-Y, CCAAT-binding factor or nuclear factor Y binding site; C/EBP, CCAAT enhancer binding protein sequence.
Oleic acid and palmitoleic acid are the major monounsaturated fatty acids in fat depots and membrane phospholipids.
The current Proposition 65 list is available on-line below, as a pdf or Excel download or through West Law.
The Excel document also includes the listing mechanism for each chemical listing and the safe harbor level, if one has been adopted.