4-hydroxyisoleucine and Diabetes-Mellitus--Type-2

4-Hydroxyisoleucine (4-HIL) is a compound found in Trigonella foenum-graecum (fenugreek) seeds, which have been used as part of traditional medicine to treat diabetes mellitus. The synthesis of 4-HIL on a large scale is possible using fermentation methods (artificial synthesis) involving the isolation of the L-isoleucine dioxygenase gene from Bacillus thuringiensis, which can yield a greater quantity of 4-HIL than that produced with conventional methods (82 % attained with fermentation methods vs. 0.6-39 % attained with conventional methods). In studies of rats and humans, T. foenum-graecum improved laboratory parameters associated with renal dysfunction and dyslipidemia, increased levels of antioxidants and hormones that are altered in patients with type 2 diabetes mellitus (T2DM), and decreased fasting blood glucose, 2-h postprandial plasma glucose, and glycated hemoglobin. Similarly, in in vitro and preclinical studies, 4-HIL decreased glucose levels, hepatic glucose production, glucose/insulin ratios, indicators of hepatic damage, triglycerides, and total cholesterol, and increased utilization of glucose and levels of high-density lipoprotein cholesterol. Studies in humans are needed to determine whether 4-HIL is safer and more effective than current medications for the treatment of T2DM.

Topics: Animals; Antioxidants; Blood Glucose; Diabetes Mellitus, Type 2; Drug Evaluation, Preclinical; Humans; Isoleucine; Plants, Medicinal; Rats; Trigonella

Trigonelline (TR), 4-hydroxyisoleucine (4-HI), and diosgenin (DG) are the main bioactives of the purified standardized extract of the popular plant Trigonella foenum-graecum L. (TFG), and it has been proven effective for the treatment of various diseases. However, to the best of our knowledge, no study has investigated the pharmacokinetic parameters of purified standardized T. foenum-graecum extract in normal and diabetic Wistar rats. The present study has developed and validated a rapid, reliable, and sensitive simultaneous ultra-performance liquid chromatography MS method to estimate these bioactives. The chromatographic separation was achieved using methanol, acetonitrile, and 0.1% formic acid with the ideal gradient flow system on a BEH Shield RP 18 column. A positive electrospray ionization mode was selected to estimate m/z values of TR (138.14 > 94.63), 4-HI (148.19 > 74.08), and DG (415.54 > 271.33). The method was robust and reproducible over the linearity range of 60-5000, 6-5000, and 15-5000 ng/mL for TR, 4-HI, and DG, respectively. Using this novel validated method, we investigated the pharmacokinetic parameters of bioactives using Phoenix WinNonlin version 8.0 (Certera) in normal and diabetic rats. The assay was successfully applied for the estimation of pharmacokinetic parameters using noncompartmental analysis. This investigation shows that the absorption rate increased, whereas distribution and elimination processes slowed down in diabetic rats compared with normal rats.

Topics: Alkaloids; Animals; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Diosgenin; Female; Isoleucine; Limit of Detection; Linear Models; Plant Extracts; Rats; Rats, Wistar; Reproducibility of Results; Trigonella

Trigonella foenum-graecum, commonly known as fenugreek, is an annual herbaceous plant. From the seeds of T. foenum-graecum an unusual amino acid, 4-hydroxyisoleucine 5, has been isolated, which significantly decreased the plasma triglyceride levels by 33% (P<0.002), total cholesterol (TC) by 22% (P<0.02), and free fatty acids by 14%, accompanied by an increase in HDL-C/TC ratio by 39% in the dyslipidemic hamster model.

Topics: Administration, Oral; Animals; Cholesterol; Cholesterol, HDL; Cricetinae; Diabetes Mellitus, Type 2; Dietary Fats; Disease Models, Animal; Drug Evaluation, Preclinical; Fatty Acids; Hypoglycemic Agents; Hypolipidemic Agents; Isoleucine; Male; Molecular Structure; Seeds; Structure-Activity Relationship; Triglycerides; Trigonella

We have recently shown in vitro that 4-hydroxyisoleucine (4-OH-Ile), an amino acid extracted from fenugreek seeds, potentiates insulin secretion in a glucose-dependent manner. The present study was designed to investigate whether 4-OH-Ile could exert in vivo insulinotropic and antidiabetic properties. For this purpose, intravenous or oral glucose tolerance tests (IVGTTs and OGTTs, respectively) were performed not only in normal animals but also in a type II diabetes rat model. During IVGTT in normal rats or OGTT in normal dogs, 4-OH-Ile (18 mg/kg) improved glucose tolerance. The lactonic form of 4-OH-Ile was ineffective in normal rats. In non-insulin-dependent diabetic (NIDD) rats, a single intravenous administration of 4-OH-Ile (50 mg/kg) partially restored glucose-induced insulin response without affecting glucose tolerance; a 6-day subchronic administration of 4-OH-Ile (50 mg/kg, daily) reduced basal hyperglycemia, decreased basal insulinemia, and slightly, but significantly, improved glucose tolerance. In vitro, 4-OH-Ile (200 microM) potentiated glucose (16.7 mM)-induced insulin release from NIDD rat-isolated islets. So, the antidiabetic effects of 4-OH-Ile on NIDD rats result, at least in part, from a direct pancreatic B cell stimulation.

Topics: Acids; Animals; Diabetes Mellitus, Type 2; Glucose Tolerance Test; Hypoglycemic Agents; Insulin; Insulin Secretion; Islets of Langerhans; Isoleucine; Male; Niacinamide; Rats; Rats, Wistar; Reference Values