EL-SEWER NutritionResearch Vol. 17. No. 3. 523-531.1997 pp. Copyright 8 1997 ELsevier Science Inc. RintedintheUSA. Allrightsresemd 0271-5317/97 $17.00 + .@I PII SO27L5317(97)00017-1 THE EFFECT OF BORON ON PLASMA TESTOSTERONE AND PLASMA LIPIDS IN RATS M.R. Naghii, MSPH and S. Samman, PhD Human Nutrition Unit, Department of Biochemistry University of Sydney, NSW, 2006, Australia ABSTRACT Recent studies have indicated that dietary boron can affect the concentration of steroid hormones in vivo. It has been suggested that the interaction between boron and steroid hormone metabolism is mediated by the hydroxylation process that steroids need to become biologically active. The increase in the concentration of some steroid hormones may impact favourably on cardiovascular and bone diseases. The following experiment was performed to determine the specificity of the effect of boron on steroid hormones and to determine the subsequent impact on plasma lipids in rats over a 4 week study period. Upon addition of boron (as boric acid) to the drinking water to provide 2 mg boron/rat/day, there was no change in body or testicular weight between the control and treatment groups. The addition of boric acid to the drinking water resulted in significant elevations in the plasma 1,25_dihydroxyvitamin D concentration at week 2 (PcO.01) and the plasma testosterone concentration at week 4 (PcO.05) relative to the control group. After 2 weeks, there was a significant decrease in the plasma triacylglycerol (PcO.05) and total HDL-cholesterol concentrations (PcO.05) in rats fed boric acid relative to their counterparts in the control group. However, at week 4 only HDLs-cholesterol was significantly lower (P<O.O02). The potentially favourable effects of increasing the concentrations of vitamin D, testosterone and oestrogen (as shown in other studies) on chronic diseases need to be balanced against the reduction in HDL3-cholesterol. copyright 0 1997 Elswier science Inc. Key words: Boron, Testosterone, Vitamin D, Lipids, Rats, INTRODUCTION Steroid hormones are implicated in the aetiology of a number of chronic diseases including coronary heart disease (CHD), arthritis and osteoporosis, particularly at the end of sexual maturation (1, 2). It is hypothesised that hypotestosteronaemia in men may be a risk factor for CHD (3) and recently testosterone was shown to be a potent relaxing agent for coronary arteries in the rabbit (4). Since oral (exogenous) steroids, such as oestrogen, have a primary passage through the hepatic circulation and may produce marked hepatocellular effects (5), elevating the concentration of endogenously produced steroid hormones represents a non-pharmacological strategy under some circumstances. It has been shown that the metabolism of steroid hormones can be influenced by boron (6-9). Of particular interest is the demonstration by Nielsen and colleagues (7) that low doses of boron resulted in an increase in the plasma concentration of both oestrogen and testosterone as well as an increase in calcium retention in postmenopausal women. Similarly, in a short-term supplementation trial in men (8), we have shown that 10 mg of boron induces an increase in the plasma concentration of oestrogen and testosterone. Correspondence to: Dr S Samman, Human Nutrition Unit, Department of Biochemistry, University of Sydney, NSW 2006 Australia. Fax 61-2-93516022 523