Pupillary signs in diabetic autonomic neuropathy.

Pupillary function was investigated in 36 insulin-dependent diabetics and 36 controls matched for age and sex. About half of the diabetics had evidence of peripheral somatic or autonomic neuropathy, or both. The diabetic patients had abnormally small pupil diameters in the dark and less fluctuation in pupil size (hippus) during continuous illumination than the controls. They also had reduced reflex responses to light flashes of an intensity adjusted for individual retinal sensitivities. The pupillary findings were compared with results of five tests of cardiovascular function and five tests of peripheral sensory and motor nerve function. Almost all the patients with autonomic neuropathy had pupillary signs, which we therefore conclude are a common manifestation of diabetic autonomic neuropathy.     

Age-related arterial calcification in rats

In man, i) arteries calcify with age and ii) age-linked arterial calcification is amplified by vascular pathology such as hypertension or arteriosclerosis. Age-linked arterial calcification has a bad prognosis but drugs to prevent it are lacking. This is partially due to the lack of appropriate animal models. This paper looks at the extent to which arteries calcify with age in the rat and whether hypertension or arteriosclerosis amplifies such calcification. Total calcium levels were determined by acid digestion and flame spectrophotometry and intracellular calcium levels ([Ca2+]i) by the intracellular calcium-sensitive dye, fura-2. Arteries contained up to 5 times more calcium than other soft tissues. Arteries progressively calcified with age whereas other soft tissues did not. Accumulation of calcium with age was essentially extracellular. Hypertension had no effect on age-related arterial calcification. Calcification of the same order as in man was produced in a rat model of arteriosclerosis (vitamin D plus nicotine treatment). In conclusion, as in man, age-linked, organ-specific arterial calcification does occur in rats but its intensity is far less. Arterial calcification of a similar degree to that observed in man can be obtained in rats by hypervitaminosis D plus nicotine.     

胰岛素样生长因子与糖尿病神经病变

糖尿病神经病变给糖尿病患者造成严重危害,但其发生机制至今未明。最近研究表明：胰岛素样生长因子（ＩＧＦｓ）对感觉、运动及交感神经元具有支持营养作用;临床糖尿病患者及实验性糖尿病大鼠体内ＩＧＦｓ活性及ＩＧＦｓ ｍＲＮＡ表达水平下降;补充ＩＧＦｓ可减轻糖尿病神经损害程度。上述研究提示ＩＧＦｓ活性下降在糖尿病神经病变的发生中起重要作用。     

Calcium signaling in diabetic neuropathy

Diabetic neuropathy is a frequent complication of diabetes mellitus, for which no adequate clinical treatment is currently available. One of the main reasons for the absence of effective treatment of this disease is that information on how metabolic, vascular, and other abnormalities involved in the pathogenesis of diabetic neuropathy lead to dysfunction of nerve cells and pathways remains insufficient. Recent studies demonstrated that substantial abnormalities of calcium homeostasis in input neurons of the somatosensory nociceptive system are associated with many symptoms of diabetic neuropathy. Although proof of the causal linkage between calcium abnormalities and neuropathic complications is not conclusive, current research in neuroscience mostly indicates that such a linkage exists. Practically all known modifications of synaptic transmission in both central and peripheral nervous systems result from calcium-dependent modifications of the molecular players involved in this transmission. This is why the main goal of our review is to analyze in detail the fundamental cellular and molecular calcium-regulating mechanisms that are deteriorated in diabetes. As an important end-point of the proposed review, the capability of a widely used calcium channel blocker, nimodipine, to correct cytosolic and endoplasmic reticulum calcium abnormalities in neurons of the dorsal root ganglia and spinal dorsal horn and possible curative value of this agent in diabetic neuropathy are discussed.Neirofiziologiya/Neurophysiology, Vol. 36, No. 4, pp. 348–353, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Cerebrovascular reactivity and hypercapnic respiratory drive in diabetic autonomic neuropathy.

Because abnormalities in cerebrovascular reactivity (CVR) in subjects with long-term diabetes could partly be ascribed to autonomic neuropathy and related to central chemosensitivity, CVR and the respiratory drive output during progressive hypercapnia were studied in 15 diabetic patients without (DAN-) and 30 with autonomic neuropathy (DAN+), of whom 15 had postural hypotension (PH) (DAN+PH+) and 15 did not (DAN+PH-), and in 15 control (C) subjects. During CO(2) rebreathing, changes in occlusion pressure and minute ventilation were assessed, and seven subjects in each group had simultaneous measurements of the middle cerebral artery mean blood velocity (MCAV) by transcranial Doppler. The respiratory output to CO(2) was greater in DAN+PH+ than in DAN+PH- and DAN- (P < 0.01), whereas a reduced chemosensitivity was found in DAN+PH- (P < 0.05 vs. C). MCAV increased linearly with the end-tidal PCO(2) (PET(CO(2))) in DAN+PH- but less than in C and DAN- (P < 0.01). In contrast, DAN+PH+ showed an exponential increment in MCAV with PET(CO(2)) mainly >55 Torr. Thus CVR was lower in DAN+ than in C at PET(CO(2)) <55 Torr (P < 0.01), whereas it was greater in DAN+PH+ than in DAN+PH- (P < 0.01) and DAN- (P < 0.05) at PET(CO(2)) >55 Torr. CVR and occlusion pressure during hypercapnia were correlated only in DAN+ (r = 0.91, P < 0.001). We conclude that, in diabetic patients with autonomic neuropathy, CVR to CO(2) is reduced or increased according to the severity of dysautonomy and intensity of stimulus and appears to modulate the hypercapnic respiratory drive.     

Vagal impairment of gastric secretion in diabetic autonomic neuropathy.

Gastric acid output in response to insulin-induced hypoglycaemia and pentagastrin was measured in 18 diabetic patients with symptoms of autonomic neuropathy. Two patients had achlorhydria but the rest responded normally to pentagastrin. The acid output evoked by insulin-induced hypoglycaemia was low in 10 of the 16 patients who secreted acid in response to pentagastrin. These changes suggest that vagal impairment is common in diabetics with autonomic symptoms, which might explain the infrequency of duodenal ulcer in diabetics.     

Medial artery calcification of uremic patients: a histological, histochemical and ultrastructural study

Recent findings suggest that vascular calcification (VC) is an active process similar to bone mineralization, the vascular smooth muscle cells (VSMCs) undergoing phenotypic differentiation into osteoblastic cells and synthesizing calcification-regulating proteins found in bone. This study has investigated the VC process of uremic patients, with a morphologic approach. Epigastric artery samples from 49 uremic, non-diabetic patients were taken during kidney transplantation. Sections from paraffin-embedded samples were stained with hematoxylin/eosin and von Kossa. CD68 was immunohistochemically detected, and sections from frozen samples were stained with Oil Red O. Deeply calcified samples were stained with Picrosirius Red, PAS, and Alcian blue. Specimens from one patient with moderate and one with severe VC were examined under the electron microscope. None of the samples had atherosclerosis. Calcifications were found in the media of 38 patients. In 23, dot-like calcifications were irregularly scattered near the adventitia (light VC); in 11, granular calcifications formed concentric rings near the adventitia (moderate-advanced VC); in 4, zones of consolidated calcifications were found (severe VC). These zones were poor in collagen, glycoproteins and proteoglycans. In cases with moderate or severe VC, VSCMs showed necrotic changes. Matrix vesicles could be recognized in the extracellular spaces. In cases with severe VC, uncalcified or partially calcified membranous bodies were found, together with Liesegang rings. Patches of fibrin were also found. These findings point to a mainly degenerative mechanism of VC, which proceeds from the outer portion of the media. An active mechanism, however, cannot be excluded. A unifying hypothesis is suggested.     

Medial calcification in the arterial wall of smooth muscle cell‐specific Smpd1 transgenic mice: A ceramide‐mediated vasculopathy

Arterial medial calcification (AMC) is associated with crystallization of hydroxyapatite in the extracellular matrix and arterial smooth muscle cells (SMCs) leading to reduced arterial compliance. The study was performed to test whether lysosomal acid sphingomyelinase (murine gene code: Smpd1)‐derived ceramide contributes to the small extracellular vesicle (sEV) secretion from SMCs and consequently leads to AMC. In Smpd1^trg/SM^cre mice with SMC‐specific overexpression of Smpd1 gene, a high dose of Vit D (500 000 IU/kg/d) resulted in increased aortic and coronary AMC, associated with augmented expression of RUNX2 and osteopontin in the coronary and aortic media compared with their littermates (Smpd1^trg/SM^wt and WT/WT mice), indicating phenotypic switch. However, amitriptyline, an acid sphingomyelinase (ASM) inhibitor, reduced calcification and reversed phenotypic switch. Smpd1^trg/SM^cre mice showed increased CD63, AnX2 and ALP levels in the arterial wall, accompanied by reduced co‐localization of lysosome marker (Lamp‐1) with multivesicular body (MVB) marker (VPS16), a parameter for lysosome‐MVB interaction. All these changes related to lysosome fusion and sEV release were substantially attenuated by amitriptyline. Increased arterial stiffness and elastin disorganization were found in Smpd1^trg/SM^cre mice as compared to their littermates. In cultured coronary arterial SMCs (CASMCs) from Smpd1^trg/SM^cre mice, increased P_i concentrations led to markedly increased calcium deposition, phenotypic change and sEV secretion compared with WT CASMCs, accompanied by reduced lysosome‐MVB interaction. However, amitriptyline prevented these changes in P_i‐treated CASMCs. These data indicate that lysosomal ceramide plays a critical role in phenotype change and sEV release in SMCs, which may contribute to the arterial stiffness during the development of AMC.     

Glycochelates and the etiology of diabetic peripheral neuropathy

People with diabetes are prone to develop peripheral vascular and nerve abnormalities which, in extreme cases, can lead to limb amputations. Although numerous theories have been advanced for these complications, no firm explanation is yet available. Recently, evidence has appeared suggesting that these vascular and nerve abnormalities may involve transition metals; administration of chelators such as desferrioxamine has been shown to prevent or actually reverse slowed peripheral nerve conduction and neuronal blood flow, as well as impaired endothelium-dependent arterial relaxation. Here, we argue that (i) the heavily glycated proteins known to accumulate in people with diabetes gain an increased affinity for transition metals such as iron and copper, (ii) as a result, proteins such as elastin and collagen within the arterial wall-which are known to be particularly heavily glycosylated in diabetes-may accumulate bound metal, especially copper, (iii) the bound metal causes the catalytic destruction of endothelium derived relaxing factor (nitric oxide or a derivative thereof), thereby engendering a state of chronic vasoconstriction. The resulting impairment of blood flow to peripheral nerves restricts the delivery of oxygen and nutrients and, in extremis, nerve death eventuates. If this hypothesis is proved correct, there are important implications for the development of novel pharmaceuticals for the treatment of diabetic peripheral neuropathy.     

Ghrelin reverses experimental diabetic neuropathy in mice

Ghrelin, an acylated peptide produced in the stomach, increases food intake and growth hormone secretion, suppresses inflammation and oxidative stress, and promotes cell survival and proliferation. We investigated the pharmacological potential of ghrelin in the treatment of polyneuropathy in uncontrolled streptozotocin (STZ)-induced diabetes in mice. Ghrelin or desacyl-ghrelin was administered daily for 4 weeks after STZ-induced diabetic polyneuropathy had developed. Ghrelin administration did not alter food intake, body weight gain, blood glucose levels, or plasma insulin levels when compared with mice given saline or desacyl-ghrelin administration. Ghrelin administration ameliorated reductions in motor and sensory nerve conduction velocities in diabetic mice and normalized their temperature sensation and plasma concentrations of 8-isoprostaglandin α, an oxidative stress marker. Desacyl-ghrelin failed to have any effect. Ghrelin administration in a mouse model of diabetes ameliorated polyneuropathy. Thus, ghrelin’s effects represent a novel therapeutic paradigm for the treatment of this otherwise intractable disorder.     

VEGF gene polymorphism association with diabetic neuropathy

Vascular factors beside metabolic problems are involved in both etiopathogenesis of diabetic neuropathy, and more remarkably, later in “repair” phase, that governs the net balance between neuro-regenerative/degenerative reactions. Regarding ischemic nature of diabetic neuropathy that highlights necessity of blood vessels re-establishment during tissue healing, VEGF (vascular endothelial growth factor) has been recently the subject of extensive investigations in diabetic neuropathy (DNU). This growth factor possesses angiogenic potentials in addition to the hemodynamic functions. The distribution of VEGF gene polymorphisms at positions −7*C/T, −1001*G/C, −1154*G/A and −2578*C/A were analysed by ARMS–PCR in 248 type 1 diabetic British-Caucasian subjects (81 DNU+, 167 DNU−). We have found that distribution of a VEGF gene polymorphism at promoter region (−7*C/T) was significantly different between diabetic subjects with vs. without neuropathy and the allele (C) conferred susceptibility to DNU (P = 0.02; OR = 1.78, 95% CI 1.0–3.1). The present study indicates that polymorphism of the VEGF gene at position −7*C/T might be implicated in the pathogenesis of diabetic neuropathy as it may harbour some functional/regulatory potential in VEGF gene expression. However, this requires further studies in order to better understand its phenotypic impact and to investigate the prognostic value of this polymorphism in diabetic neuropathy as a chronic complication of diabetes.     

Therapy with antioxidants in human diabetic neuropathy

Increased oxidative stress has been implicated in the pathogenesis of diabetic polyneuropathy (DPN). Antioxidant treatment with alpha-lipoic acid (ALA) has been shown to prevent or ameliorate experimental diabetic neuropathy, providing the rationale for treatment in humans. A recent meta-analysis including four controlled clinical trials provided evidence that treatment with ALA (600 mg/day i.v.) over 3 weeks is safe and significantly improves both neuropathic symptoms and deficits to a clinically meaningful degree in patients with symptomatic DPN. Moreover, oral treatment for 4–7 months tends to ameliorate neuropathic deficits and cardiac autonomic neuropathy. Clinical and postmarketing surveillance studies have revealed a highly favorable safety profile of this drug. Based on these findings, a pivotal long-term multicenter trial of oral treatment with ALA (NATHAN 1 Study) is under way aimed at slowing the progression of DPN.     

体外培养主动脉细胞钙化作用研究

目的：初步探讨主动脉钙化的机制。方法：外殖块法分离培养家兔主动脉平滑肌细胞,进行vonKossa染色以显示钙化,生化法检测细胞内外不溶性钙。放兔法测定培养上清骨钙素的含量。RT-PCR方法检测X型胶原mR-NA的表达。结果：25-羟基胆固醇（A组）和β-甘油磷酸盐（B组）分别培养的传代细胞均可见多个细胞结节,且细胞结节von kossa染色阳性;而对照组（C组）无细胞结节形成,von kossa染色阴性,前二者每孔不溶性钙沉积量,以及培养上清中骨钙素含量明显高于后者,且A、B两组X型胶原mRNA的表达为阳性。结论：25-羟基胆固醇、β-甘油磷酸盐均可促进主动脉中膜细胞发生钙化,主动脉中膜在钙化过程中与成骨细胞相似,骨钙素分泌增多且有X型胶原mRNA的表达。