Adjuvantes no tratamento da hiperglicemia do diabetes melito tipo 1: [revisão] / Adjunctive therapies to glycaemic control of type 1 diabetes mellitus: [review]

Desde o Diabetes Control and Complications Trial (DCCT), a terapia insulínica intensiva tem sido direcionada para alcançar valores de glicemia e hemoglobina glicada (HbA1c) tão próximos do normal quanto a segurança permita. Entretanto, a hiperglicemia (especialmente a hiperglicemia pós-prandial) e a hipoglicemia continuam a ser um problema no manejo do diabetes tipo 1. O objetivo de associar outras drogas à terapia insulínica é diminuir a glicemia pós-prandial. A terapia adjunta pode ser dividida em três grupos, conforme seu mecanismo de ação: 1. Aumento da ação da insulina (metformina e tiazolidinedionas); 2. Alteração da liberação de nutrientes no trato gastrintestinal (acarbose e amilina); 3. Outros modos de ação [pirenzepina, fator de crescimento insulina-símile (IGF-1) e peptídeo semelhante ao glucagon 1 (GLP-1). Muitos desses agentes mostraram, em estudos de curto prazo, diminuição de 0,5 por cento a 1 por cento na HbA1c, diminuir a hiperglicemia pós-prandial e as doses diárias de insulina.

Since Diabetes Control and Complications Trial (DCCT), intensive therapy has been directed at achieving glucose and glycosylated hemoglobin (HbA1c) values as close to normal as possible regarding safety issues. However, hyperglycemia (especially postprandial hyperglycemia) and hypoglicemia continue to be problematic in the management of type 1 diabetes. The objective of associating other drugs to insulin therapy is to achieve better metabolic control lowering postprandial blood glucose levels. Adjunctive therapies can be divided in four categories based on their mechanism of action: enhancement of insulin action (e.g. the biguanides and thiazolidinediones), alteration of gastrointestinal nutrient delivery (e.g. acarbose and amylin) and other targets of action (e.g. pirenzepine, insulin-like growth factor I and glucagon-like peptide-1). Many of these agents have been found to be effective in short-term studies with decreases in HbA1c of 0.5-1 percent, lowering postprandial blood glucose levels and decreasing daily insulin doses.

Spinal Gabapentin and Antinociception: Mechanisms of Action

Spinal gabapentin has been known to show the antinociceptive effect. Although several assumptions have been suggested, mechanisms of action of gabapentin have not been clearly established. The present study was undertaken to examine the action mechanisms of gabapentin at the spinal level. Male SD rats were prepared for intrathecal catheterization. The effect of gabapentin was assessed in the formalin test. After pretreatment with many classes of drugs, changes of effect of gabapentin were examined. General behaviors were also observed. Intrathecal gabapentin produced a suppression of the phase 2 flinching, but not phase 1 in the formalin test. The antinociceptive action of intrathecal gabapentin was reversed by intrathecal NMDA, AMPA, D-serine, CGS 15943, atropine, and naloxone. No antagonism was seen following administration of bicuculline, saclofen, prazosin, yohimbine, mecamylamine, L-leucine, dihydroergocristine, or thapsigargin. Taken together, intrathecal gabapentin attenuated only the facilitated state. At the spinal level, NMDA receptor, AMPA receptor, nonstrychnine site of NMDA receptor, adenosine receptor, muscarinic receptor, and opioid receptor may be involved in the antinociception of gabapentin, but GABA receptor, L-amino acid transporter, adrenergic receptor, nicotinic receptor, serotonin receptor, or calcium may not be involved.

Muscarinic M1 and M3 receptor in rat striatum: A binding study

In this study, the authors set out to determine the presence of M3 muscarinic receptors in rat striatum by examining the binding of [3H]N-methyl-scopolamine([3H]NMS) to striatal membranes and its displacement by antagonists with different affinity for M1 and M3 muscarinic receptors (pirenzepine; 4-diphenylacetoxy-N-methylpiperidine methiodide, 4-DAMP; and the p-fluoro analog of hexahydro-sila-difenidol, pFHHSiD). The specific binding of [3H]NMS to membranes from rat striatum (551 ñ 40 fmol.mg prot.-1, KD 0.11 ñ 0.01 nM) was displaced in a concentration-dependent manner by all three antagonists tested. Inhibition curves best fit to a single-site model for 4-DAMP(pKi 9.1 ñ 0.1), whereas for both pirenzepine and pFHHSiD, the best fit was to the two-site model. The pKi values for the high-affinity (8.0 ñ 0.2) and low-affinity (6.7 ñ 0.2) components for pirenzepine-mediated inhibition of [3H]NMS binding correspondend to those reported for M1 and M3 receptors, respectively. The pKi values for the high-affinity (7.7 ñ 0.1) and low-affinity (7.1 ñ 0.2) components for pFHHSiD inhibition were in good agreement with those reported for M3 and M1 receptors, respectively. Altogether, these results indicate the presence in rat striatum of both M1 and M3 muscarinic receptors. These findings might be relevant to the design and use of mucarinic antagonists in the treatment of neurological disorders such as Parkinson's disease

Subcellular distribution and pharmacological characterization of muscarinic receptors in tracheal smooth muscle

: Subcellular fractions isolated from tracheal smooth muscle have been identified using biochemical markers and measuring the [3H]QNB muscarinic receptor binding activity in these fractions. This muscarinic receptor (mAchR) activity was slightly enriched 1.6 times in the crude mitochondrial fraction (M), 2.6 times in the crude microsomal fraction (P), and greatly enriched in the highly purified plasma membranes fractions, being 5.3 times in a heavy plasma membrane fraction designed as P2 and 9.1 times in a light plasma membrane fraction named P1 fraction. The muscarinic receptor subtypes present in the subcellular fractions were identified using competition experiments. The binding of five selective antagonists, pirenzepine, AF-DX 116, hexahydrodifenidol, methoctramine and 4-DAMP were examined. In this sense, the M1 antagonist pirenzepine showed pKi's values between 6.44-7.45 and the M2 antagonist AF-DX 116 showed pKi's values ranging from 6.75 to 7.45 being the lowest pKi's values here described. The antagonist hexahydrodifenidol showed higher affinities than pirenzepine-derivated compounds with pKi's values from 7.25 to 7.65. The antagonist 4-DAMP exhibited pKi's values from 8.18-8.41. Finally, methoctramine showed similar affinities as 4-DAMP, with pKi's ranging from 8.09 to 8.22 suggesting the existence of M2 receptors in these fractions. These data suggest that M2 mAchR are present in all articulate fractions here studied. It is important to emphasize that the M2 muscarinic receptor presents in the light plasma membrane fraction (P1) shows poor selectivity towards the muscarinic antagonists being different from the M2 mAchRs associated with other subcellular fractions isolated from bovine tracheal smooth muscle