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A statistically significant inverse association was generally found between plasma total lipid, cholesterol, or phospholipid and biotin status of 300-day-old male inbred BHE (IN-BHE) rats. Plasma, liver, and carcass lipid of both sexes generally had a significant direct association with liver lactate dehydrogenase activity; an inverse association in males resulted with improved biotin status. Elevated plasma lactate indicative of anaerobic glycolysis was found. It is proposed that an increased reductive environment - a consequence of accumulated NADH - could account for enhanced triglyceride synthesis and that this effect could explain the obesity in the IN-BHE rats. After the injection of 300 mug of biotin, plasma levels of lactate and pyruvate fell in male rats, indicating a stimulatory effect of biotin upon the oxidative pathways in these animals.

The effects of biotin deprivation on various plasma constituents were studied in male Sprague-Dawley rats, some of which were also treated with sodium nitrate (NaNO2), extra niacin or linoleate. A basal diet containing 15% pork fat (lard), 30% egg white and sucrose, was fed for 7 weeks, with or without a weekly supplement of 150 microgram biotin and the other substances mentioned. Biotin-deprived rats ate significantly less food, gained less weight and had lower food efficiency ratios than biotin-supplemented rats. Rats given NaNO2 in the drinking water had significantly higher levels of methemoglobin than those without it; values were highest when extra niacin or linoleate was added to the diet. Lactate was highest in deprived rats and was lowest in rats supplemented with biotin alone. Blood lipids were higher with than without biotin, regardless of NaNO2. Levels of phospholipids and triglycerides were highest when extra niacin was added to the diet. Further studies are needed to define the role of biotin in oxidation-reduction reactions and in regulation of lipid metabolism.

A double-blind study of the effect of biotin supplementation (0.9 mg/day) of self-selected diets on plasma lipids and other plasma constituents was carried out in 40 men and women, age 30 to 60 years, for 71 days. Comparison of percent change from control levels showed significant treatment effects on more plasma constitutents than did comparison of the means of the actual levels. In an analysis of period of period changes, the largest differences were observed generally during the first two weeks after supplementation when small but statistically significant positive changes for biotin-treated men and women differed significantly from changes for the placebo-treated in total lipid, total phospholipid, and alpha + beta lipoprotein cholesterol. At the end of the study, these levels were at or below initial levels. Plasma biotin levels were elevated by biotin supplementation. There was a negative correlation between biotin levels and total plasma lipids. Responses os some lipid constituents of plasma were greater in volunteers who initially had elevated levels of lipids than in those who initially had normal levels of lipids. It is concluded that human requirements for biotin should be studied by new approaches and with modern techniques. Questions raised regarding the role bo biotin in the lipid metabolism of normal men and women should be investigated further.