Pompeo Pessotto

Selective Reversible Inhibition of Liver Carnitine Palmitoyl-Transferase 1 by Teglicar Reduces Gluconeogenesis and Improves Glucose Homeostasis

OBJECTIVE We 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 METHODS Glucose 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. RESULTS In 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. CONCLUSIONS Teglicar, 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.

Isolation and pharmacological activities of the Tecoma stans alkaloids

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 5beta-Hydroxyskitanthine, early called Base C, and Boschniakine were inactive both in vivo and in vitro assays.

Reversible Carnitine Palmitoyltransferase Inhibitors with Broad Chemical Diversity as Potential Antidiabetic Agents

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.

The effect of exogenous L-carnitine on fat diet-induced hyperlipidemia in the rat

In rats receiving a fat diet (75% Altromin R and 25% olive oil) ad libitum for 15 hours, an orally administered dose of 500 mg/kg L-carnitine produces: an increase in serum carnitine and acetyl-carnitine levels; a decrease in serum triglyceride (TG) and free fatty acid (FFA) levels; a normalization of the heart and liver carnitine pattern; a reduction of myocardial neutral lipase (NL) activity, without affecting lipoprotein lipase (LPL) of the heart. Under these experimentally-induced conditions, L-carnitine stimulates the excretion of acyl groups as acyl-carnitines with the urine. Acylcarnitines are practically absent from the urine of control animals.

2-{3-[2-(4-chlorophenyl)ethoxy]-phenylthio}-2-methylpropanoic acid : a fibrate-like compound with hypolipidemic and antidiabetic activity

Diabetes is a complex metabolic disease which has reached epidemic proportions; its continuously increasing incidence is a consequence of the excessive caloric intake and lack of physical activity that characterize the western lifestyle. The progressive impairment of insulin sensitivity and eventual deterioration of b-cell function are the underlying causes of the overt disease. The classical and commonly used treatments for lowering glycemia are the insulin secretagogues, such as the sulfonylureas, and metformin, an insulin sensitizer with a mechanism of action that is still under investigation. In recent years rosiglitazone and pioglitazone have entered the market as insulin sensitizers and anti-hyperglycemic drugs. They are representatives of the new thiazolidinedione (TDZ) class of agents, which elicit their effects through activation of the g isoform of the nuclear peroxisome proliferator-activated receptor (PPARg). 6] The activity of TDZs in humans is accompanied by weight gain and risk of edema, whereas the liver toxicity observed with troglitazone, the first marketed (and soon thereafter withdrawn) representative of this family, seems to be more the result of its particular chemical structure than of its TDZ class-related mechanism of action. Despite an improvement in the ability to control glycemia, the prevention and management of the negative cardiovascular aspects of the disease remain the focus of open primary research, as such aspects rank diabetes the fourth leading cause of mortality in developed countries. In this context, a drug that is able to effectively correct dyslipidemia as well as hyperglycemia and insulin sensitivity is certainly of great interest. Fibrates such as fenofibrate and bezafibrate have been widely used for decades as hypolipidemic, antiatherosclerotic, and cardioprotective agents, and are known to act through the activation of the a isoform of PPAR (PPARa). For these reasons, compounds that activate both PPARa and PPARg receptors (PPARa/g mixed agonists) are considered to be very promising targets (ref. [15] and references therein), but only a few of them bear fibrate-related structures. In the last few years, new hypolipidemic PPARa agonists with improved potency and selectivity have also appeared, such as GW9578 and its closely related analogue GW7647, both of which are characterized by a thioisobutyrate moiety. During our search for new hypolipidemic and anti-hyperglycemic agents, we found quite unexpectedly that compound 3 (Scheme 1), which is structurally related to the fibrates, considerably improves diabetic conditions in C57BL/KsJ db/db diabetic mice (Table 1). In particular, the decrease in glucose level was similar to that effected by rosiglitazone, even if 3 was administered at a higher dose (25 instead of 5 mgkg , twice a day by oral gavage for 25 days), with greatly improved homogeneity of values. This last point should not be underestimated, as in our experience, not all animals in experimental groups respond to rosiglitazone and similar compounds. The same has also been reported in studies with humans. In an oral glucose tolerance test (OGTT) after 19 days of treatment, the glycemic area under curve (AUC) was considerably lower in the case of 3 with respect to control and fibrate results, and [a] Dr. F. Giannessi Department of Endocrinology and Metabolism Sigma-Tau S.p.A Via Pontina km 30400, 00040 Pomezia, Rome (Italy) Fax: (+39)06-9139-3988 E-mail : fabio.giannessi@sigma-tau.it [b] Prof. F. De Angelis Department of Chemistry, Chemical Engineering, and Materials University of L’Aquila, Coppito, 67010 L’Aquila (Italy) Fax: (+39)0862-433753 E-mail : deangeli@univaq.it [c] Dr. N. Dell’Uomo, Dr. E. Tassoni, Dr. T. Brunetti, Dr. M. O. Tinti Department of Chemical Research Sigma-Tau S.p.A (Italy) [d] Dr. P. Pessotto, Dr. A. F. Sciarroni, Dr. F. M. Milazzo, A. Peschechera Department of Endocrinology and Metabolism Sigma-Tau S.p.A (Italy) [e] Dr. P. Carminati Director of Research & Development Department Sigma-Tau S.p.A (Italy) Supporting information for this article is available on the WWW under http://www.chemmedchem.org or from the author.

Quaternary nitrogen compounds affect carnitine distribution in rats. Particular emphasis on edrophonium.

Edrophonium (ethyl(m-hydroxyphenyl)dimethylamine) acutely modifies carnitine levels in different rat tissues, increasing hepatic and reducing blood and renal levels. After 2 h edrophonium treatment, the total serum carnitine levels were decreased by 16 (P < 0.001) and 33 (P < 0.001) percent in fed and fasted rats respectively compared to control, and in kidney the levels decreased by 11 (P < 0.05) and 34 (P < 0.001) percent whereas in liver the edrophonium treatment increased the levels by 43 (P < 0.001) and 59 (P < 0.001) percent. The edrophonium action does not depend on the route of administration or on the nutritional state of the animal. Its activity on carnitine levels is neither accompanied by significant variation of serum parameters of carbohydrate, fat and protein metabolism nor of insulin levels. The edrophonium activity is not related to cholinergic action, as physostigmine and ambenonium at concentrations known to increase cholinergic activity do not modify carnitine distribution in tissues. Trimethylphenylammonium (TPA) and trimethyl(p-aminophenyl)ammonium (TPA.NH2), compounds structurally similar to edrophonium, are on the contrary active on levels of carnitine and this effect is not related to their cholinergic potency. In 24 h fasted rats after the TPA and TPA. NH2 treatment, the total serum carnitine levels were decreased by 32 (P < 0.001) and 13 (n.s.) percent respectively compared to control, and in kidney the levels decreased by 15 (P < 0.02) and 5 (n.s.) percent, whereas in liver the treatment increased the levels by 72 (P < 0.001) and 45 (P < 0.01) percent. Moreover atropine, an acetylcholine antagonist, affects carnitine distribution in a way similar to edrophonium. Edrophonium activity on carnitine distribution, probably affects (inter)cellular carnitine transport by direct action on plasma membrane. Effect on capillary endothelium may be responsible for its observed action on muscle contraction force in imminent ischemia.