Biotin is the cofactor of carboxylases [pyruvate (PC), propionyl-CoA (PCC), 3-methyl crotonyl-CoA and acetyl-CoA], to which it is covalently bound by the action of holocarboxylase synthetase (HCS). We have studied whether biotin also regulates their expression, as it does other, nonrelated enzymes (e.g., glucokinase, phosphoenol pyruvate carboxykinase, guanylate cyclase). For this purpose, HCS, PC and PCC mRNAs were studied in biotin-deficient rat liver, kidney, muscle and brain of biotin-deficient rats. PC- and PCC-specific activities and protein masses were also measured. The 24-h time course of HCS mRNA in deficient rats was examined after biotin supplementation. HCS mRNA was significantly reduced during vitamin deficiency. It increased in deficient rats after biotin was injected, reaching control levels 24 h after administration. These changes seem to be the first known instance in mammals of an effect of a water-soluble vitamin on a mRNA functionally related to it. In contrast, the decreased activities of the carboxylases were associated with reductions in the amounts of their enzyme proteins except in brain. However, their mRNA levels were not affected. There are no reports on these types of vitamin affecting the mRNA or protein levels of their apoenzymes or their products. This work provides evidence for biotin being a modulator of the genetic expression of the enzymes involved in its function as a cofactor. As such, it may be a useful model for probing a similar role for other water-soluble vitamins.

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Several thousand young Americans visit the bars in Tijuana, Mexico, each weekend night, raising concerns on both sides of the border. Measures implemented in San Diego, California, and Tijuana have successfully reduced the number of American visitors to Mexican bars. Although San Diego policies have been well-documented, this is the first article on investigation of measures enacted south of the border. Information on Tijuana alcohol policies was obtained from a survey of 29-36 bars from 1997 to 1999. The Tijuana police provided data on Americans arrested in Tijuana from 1998 to 1999. Our study found alcohol regulations are poorly enforced in Tijuana, suggesting that regulatory agencies are captured by bar owners. However, such a capture may be weakening. The importance of identifying and supporting Mexican interest groups, as opposed to the bar owners, as a mechanism to impede the capture of Tijuana's regulatory agencies is discussed. The number of Americans involved in alcohol-related crimes in Tijuana sharply decreased over time. However, such a success is largely related to the success of the San Diego efforts in reducing the number of American visitors to Tijuana. Also, by demonstrating the racial/ethnic heterogeneity of American visitors to Tijuana bars, our study points out the need for prevention policies designed north of the border to take such heterogeneity into account.

No abstract