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Stabilized rice bran (SRB), a source of complex carbohydrates, tocols, gamma-oryzanols, and polyphenols, was treated with carbohydrases and heat to yield two fractions, rice bran water solubles (RBWS), and rice bran fiber concentrates (RBFC). Stabilized rice bran and its fractions were fed for 60 days to insulin-dependent and noninsulin-dependent diabetes mellitus (IDDM = Type I and NIDDM = Type II) subjects to determine possible effects on serum hemoglobin, carbohydrate and lipid parameters. The Type I subjects (n = 22, 26, and 20) fed Stabilized rice bran, rice bran water solubles, and rice bran fiber concentrates plus AHA Step-1 diet reduced glycosylated hemoglobin 1%, 11%, and 10%, respectively. The fasting serum glucose levels were also reduced significantly (P < 0.01) with stabilized rice bran (9%), rice bran water solubles (29%), and rice bran fiber concentrates (19%).The Type II subjects (n = 31, and 26) fed rice bran water solubles and rice bran fiber concentrates plus AHA Step-1 diet had decreased levels of glycosylated hemoglobin (15% and 11%) and fasting glucose (33% and 22%; P < 0.001), respectively. Serum insulin levels were increased (4%) with rice bran water solubles in both types of diabetes. The reduction of glycosylated hemoglobin and a slight increase in insulin levels indicate that consumption of rice bran water solubles can control blood glucose levels in human diabetes. Serum total cholesterol, LDL-cholesterol, apolipoprotein B, and triglycerides levels were reduced with rice bran fiber concentrates in the Type I (10, 16, 10, 7%) and Type II groups (12, 15, 10, 8%), respectively. These results indicate that rice bran water solubles significantly reduces hyperglycemia (P < 0.01), whereas rice bran fiber concentrates reduces hyperlipidemia (P < 0.05) in both types of diabetes. Therefore, these natural products can be used as nutritional supplements for the control of both types of diabetes mellitus in humans.

Tocotrienols exert hypocholesterolemic action in humans and animals. Lovastatin is widely used for that purpose. Both agents work by suppressing the activity of beta-hydroxy-beta-methylglutaryl coenzyme A reductase through different mechanisms, post-transcriptional vs competitive inhibition. A human study with 28 hypercholesterolemic subjects was carried out in 5 phases of 35 days each, to check the efficacy of tocotrienol-rich fraction (TRF(25)) of rice bran alone and in combination with lovastatin. After placing subjects on the American Heart Association (AHA) Step-1 diet (phase II), the subjects were divided into two groups, A and B. The AHA Step-1 diet was continued in combination with other treatments during phases III to V. Group A subjects were given 10 mg lovastatin, 10 mg lovastatin plus 50 mg TRF(25), 10 mg lovastatin plus 50 mg alpha-tocopherol per day, in the third, fourth, and fifth phases, respectively. Group B subjects were treated exactly to the same protocol except that in the third phase, they were given 50 mg TRF(25) instead of lovastatin.The TRF(25) or lovastatin plus AHA Step-1 diet effectively lower serum total cholesterol (14%, 13%) and LDL-cholesterol (18%, 15% P < 0.001), respectively, in hypercholesterolemic subjects. The combination of TRF(25) and lovastatin plus AHA Step-1 diet significantly reduces of these lipid parameters of 20% and 25% (P < 0.001) in these subjects. Substitution of TRF(25) with alpha-tocopherol produces insignificant changes when given with lovastatin. Especially significant is the increase in the HDL/LDL ratio to 46% in group (A) and 53% (P < 0.002) in group (B). These results are consistent with the synergistic effect of these two agents. None of the subjects reported any side-effects throughout the study of 25-weeks. In the present study, the increased effectiveness of low doses of tocotrienols (TRF(25)) as hypocholesterolemic agents might be due to a minimum conversion to alpha-tocopherol. The report also describes in vivo the conversion of gamma-[4-3H]-, and [14C]-desmethyl (d-P(21)-T3) tocotrienols to alpha-tocopherol.

Tocotrienols are effective in lowering serum total and LDL-cholesterol levels by inhibiting the hepatic enzymic activity of beta-hydroxy-beta-methylglutaryl coenzymeA (HMG-CoA) reductase through the post-transcriptional mechanism. alpha-Tocopherol, however, has an opposite effect (induces) on this enzyme activity. Since tocotrienols are also converted to tocopherols in vivo, it is necessary not to exceed a certain dose, as this would be counter-productive. The present study demonstrates the effects of various doses of a tocotrienol-rich fraction (TRF25) of stabilized and heated rice bran in hypercholesterolemic human subjects on serum lipid parameters. Ninety (18/group) hypercholesterolemic human subjects participated in this study, which comprised three phases of 35 days each. The subjects were initially placed on the American Heart Association (AHA) Step-1 diet and the effects noted. They were then administered 25, 50, 100, and 200 mg/day of TRF25 while on the restricted (AHA) diet. The results show that a dose of 100 mg/day of TRF25 produce maximum decreases of 20, 25, 14 (P