OBJECTIVEWe have developed a new antihyperglycemic agent (teglicar) through the selective and reversible inhibition of the liver isoform of carnitine palmitoyl-transferase 1 (L-CPT1).RESEARCH DESIGN AND METHODSGlucose production was investigated in isolated hepatocytes and during pancreatic clamps in healthy rats. Chronic treatments on C57BL/6J, db/db, high-fat fed mice, and rats were performed to understand glucose metabolism and insulin sensitivity.RESULTSIn isolated hepatocytes, teglicar concentration dependently reduced ketone bodies and glucose production up to 72 and 50%, respectively. In rats, teglicar reduced the endogenous glucose production (−62%) without affecting peripheral glucose utilization. Heart 2-[3H]deoxyglucose uptake in mice was also not affected, confirming in vivo the drug selectivity toward L-CPT1. Chronic treatment in db/db mice (50 mg/kg/bid; 45 days) reduced postabsorptive glycemia (−38%), water consumption (−31%), and fructosamine (−30%). Such antidiabetic activity was associated with an improved insulin sensitivity assessed by the insulin tolerance test. A significant 50% increase in hepatic triglyceride content (HTGC) was found, although plasma alanineaminotransferase was not altered. In addition, long-term teglicar administration to high-fat fed C57BL/6J mice normalized glycemia (−19%) and insulinemia (−53%). Long-term teglicar administration (30 days, 80 mg/kg) in healthy overnight-fasted rats slightly reduced basal glycemia (−20%, ns), reduced basal insulin levels by 60%, doubled triglycerides, and increased free-fatty acids (+53%). HTGC was markedly increased, but liver and peripheral insulin sensitivity assessed by hyperinsulinemiceuglycemic clamp were not affected.CONCLUSIONSTeglicar, in vitro and in animal models, reduces gluconeogenesis and improves glucose homeostasis, refreshing the interest in selective and reversible L-CPT1 inhibition as a potential antihyperglycemic approach.

The synthesis and pharmacological activity of reversible CPT I inhibitors as potential antiketotic and antidiabetic drugs are reported. Such inhibitors constitute a series of enantiomerically pure aminocarnitine derivatives having the general formula (CH3)3N+CH2CH(ZR)CH2COO- (with Z = ureido, carbamate, sulfonamide, and sulfamide moieties; R = C7-C14 linear alkyl chains). A primary pharmacological screening based on the evaluation of CPT I activity in intact rat liver (L-CPT I) mitochondria revealed the best activity for the (R) forms of ureidic derivative 17 (ZR = NHCONHR, R = C14), sulfonamidic derivative 7 (ZR = NHSO2R, R = C12), and sulfamidic derivative 9 (ZR = NHSO2NHR, R = C11). The IC50 values are 1.1, 0.7, and 0.8 microM, respectively. For the carbamic derivative 11 (ZR = NHCOOR, R = C8), an IC50 of 9.5 microM was observed. In addition, an extraordinarily high selectivity toward the liver isoform with respect to the heart isoform (muscle-CPT I identical with M-CPT I) was found for the ureidic compound 17 (IC50(M-CPT I) vs IC50(L-CPTI) = 39.4), as well as for other ureidic or carbamic compounds. Diabetic db/db mice treated orally with 17 and 7 for 45 days at a dose of 50 mg/kg twice a day showed a good reduction of serum glucose levels with respect to the untreated db/db mice (p < 0.01). In addition, 17 showed antiketotic activity in normal fasted rats. 17 has been selected for development as a potential antiketotic and antidiabetic drug.

Tecoma stans is a plant traditionally used in Mexico for the control of diabetes. Amongst the alkaloids isolated from the plant harvested in Egypt, Tecomine was shown to be one of the compounds responsible for the hypoglycemic action. Given the interest in substances able to treat type II diabetes, we isolated the main alkaloids present in the plant growing in Egypt and Brazil and tested them in vivo on db/db mice. Contrary to previous literature reports on different animal models, Tecomine was unable to modify glycemia; the only effect seen being a decrease in plasma cholesterol levels. On the contrary, when tested in vitro on glucose uptake in white adipocytes, the compound showed a marked effect. The two other alkaloids isolated, namely 5b-Hydroxyskitanthine, early called Base C, and Boschniakine were inactive both in vivo and in vitro assays.

A series of carnitine related compounds of general formula XCH(2)CHZRCH(2)Y were evaluated as CPT I inhibitors in intact rat liver (L-CPT I) and heart mitochondria (M-CPT I). Derivative 27 (ZR = -HNSO(2)R, R = C(12), X = trimethylammonium, Y = carboxylate, (R) form) showed the highest activity (IC(50) = 0.7 microM) along with a good selectivity (M-CPT I/L-CPTI IC(50) ratio = 4.86). Diabetic db/db mice treated orally with 27 showed a significant reduction of serum glucose levels.