维生素D改善2型糖尿病相关机制研究进展

2型糖尿病(T2DM)的病因和发病机制目前尚未完全阐明,但是从糖脂毒性到炎症学说,人们对其认识正逐步深化;维生素D的传统作用表现在调节钙磷代谢和促进骨质形成,随着多种细胞内1,25(OH)2D3受体的发现,维生素D在降低肿瘤、糖尿病、心血管疾病和肥胖等慢性疾病危险方面的作用正日益成为研究者们关注的焦点;本文将对维生素D在胰岛β细胞功能缺陷、胰岛素抵抗、免疫和炎症调节中的作用予以综述,重点介绍维生素D与T2DM相互关系的生理学机制,并从维生素D受体基因多态性方面解释人群实验中补充维生素D对2型糖尿病防治效果差异性产生的原因。     

中国人群维生素D营养状况

20世纪30年代人工合成维生素D后,维生素D一直被认定为是微量营养素,参与钙磷代谢,促进骨骼发育。但是近年来对维生素D代谢有了深入的研究,维生素D需要在体内转化成具有活性的维生素D,即25-OHD3和1,25-(OH)2D3后,才能发挥生理作用。几乎在身体各种器官组织内都有维生素D受体,维生素D通过这些受体发挥作用,因而维生素D被认定是激素类物质。维生素D具有广泛的作用:如提高免疫、预防自身免疫性疾病、骨关节炎、Ⅰ型糖尿病和Ⅱ型糖尿病、心血管病、抗肿瘤,甚至与改善肺功能、哮喘、脑发育及精神疾病有关[1],而调节钙磷代谢仅仅是它的一种营养功能。我国开展以血清25-OHD3水平评价维生素D营养的资     

维生素D新本领:预防儿童糖尿病

众所周知,维生素D的经典作用是促进钙质吸收预防儿童佝偻病,英国研究人员最近发现,给婴儿补充维生素D还可降低Ⅰ型糖尿病的危险.     

维生素D与糖尿病肾病的研究进展

糖尿病肾病是糖尿病常见的并发症之一,流行病学研究显示维生素D缺乏与糖尿病肾病的发生有关,维生素D可能是影响糖尿病肾病的重要因素。目前,维生素D缺乏与糖尿病肾病发病的关系及补充维生素D改善糖尿病肾病患者的状态成为研究的热点。此文总结近年国内外的相关研究,系统全面地从维生素D与糖尿病肾病关系、维生素D对糖尿病肾病保护作用机制以及维生素D在糖尿病肾病患者中的应用等方面介绍维生素D与糖尿病肾病之间关系的研究进展,重点介绍维生素D与糖尿病肾病相互关系的生理学机制,并从维生素D受体信号通路及基因多态性方面解释人群实验中补充维生素D对糖尿病肾病防治效果差异性产生的原因。未来,随着维生素D在糖尿病肾病发病机制中作用的进一步揭示,将为糖尿病肾病患者的治疗及并发症的预防提供更好的指导。     

宝宝补钙,别忘了晒太阳

维生素D和钙是一对好搭档 维生素D能促进钙的吸收,在没有维生素D的情况下,人体对钙的吸收就会大打折扣.因此,为了预防缺钙,单纯补钙效果差,还要及时补充维生素D;而阳光是最好的维生素D“活化剂”,经常给宝宝晒太阳,对有效补钙、预防佝偻病至关重要.     

幼儿不能盲目补钙

<正>调查显示,我国1~3岁婴幼儿饮食中的钙仍达不到需要量。为预防缺钙,正确的方法是:补充钙和维生素D。单纯补钙一般效果并不好,补钙的同时补充维生素D,有利于钙质吸收。维生素D的来源:一是多晒太阳,要尽量多露出皮肤。晒太阳不要隔着玻璃窗,玻璃会挡掉阳光中对皮肤合成维生素D有作用的紫外线。二是口服浓缩鱼肝油,如果缺钙明显     

维生素D与糖尿病

<正>维生素D(vitamin D)属于脂溶性甾醇类化合物,其不仅能够调节机体内钙、磷代谢平衡,且能够影响机体的免疫功能及参与细胞增殖分化等生物学过程。由于维生素D具有多种生理功能,因此,它的缺乏与人类多种疾病的发生和发展有关。流行病学研究数据显示,缺乏维生素D与糖尿病的发生直接相关。在疾病动物模型中的研究结果也表明,缺乏维生素D会引发糖尿病;反之,补充维生素D有助于预防糖尿病的发     

孕妇血清25羟维生素D与血清离子钙检测结果分析

目的通过测定3 645例丽水市区孕妇血清25羟维生素D(25-OH-D)和血清离子钙(i Ca2+)水平,分析目前本市孕妇维生素D和血清离子钙的状况,预防妊娠期妇女维生素D及离子钙的缺乏对胎儿骨骼生长发育的影响。方法于2014年2月-2015年9月采集受试者血清后,采用化学发光法测定25羟维生素D,离子选择电极法测定离子钙。结果 2组维生素D缺乏的比率妊娠组为54.2%,对照组为42.3%,但妊娠组25羟维生素D严重缺乏率为35.7%,而对照组25羟维生素D严重缺乏率为1.65%。结论在妊娠妇女中普遍存在的25羟维生素D不足,但离子钙下降较为缓和,应加强25羟维生素D和钙的补充。     

维生素D在老年2型糖尿病患者中的作用

目的探讨维生素D在老年2型糖尿病患者中的作用。方法筛选没有接受胰岛素治疗以及服用过维生素D的老年2型糖尿病患者105例,其中维生素D缺乏的患者84例为研究组,给予每周一次维生素D3,至少服用8周;维生素D水平正常的21例为对照组;分析相关数据。结果 80.00%的老年2型糖尿病患者存在维生素D缺乏现象,患者BMI、FPG明显高于对照组(P<0.05)。研究组平均接受治疗84.13 d后,所有患者的血清25(OH)D水平均高于20ng/m L;与治疗前对比,FBG和QUICKI差异有统计学意义(P<0.01);但是在减少Hb A1c,FIN以及HOMA-B方面,差异并没有统计学意义(P>0.05)。结论老年2型糖尿病患者更容易出现维生素D缺乏现象,对于老年2型糖尿病患者补充维生素D能够降低患者空腹血糖。     

钙和维生素D补充减缓了老年人的牙齿丢失

口腔骨和牙齿丢失与非口腔骨丢失有关。补充钙和维生素D减缓了不同骨骼部位骨丢失的比率，但尚不了解钙和维生素D的摄入是否对口腔骨、从而对牙齿保留有影响。对此，进行了随机取样试验和随访研究。调研结果显示针对预防骨质疏松的钙和维生素D摄入水平对牙齿保留有益。     

维生素D和钙补充对糖尿病人或高危人群血糖和炎症标志物的Meta分析

目的 系统评价维生素D（VD）和钙联合补充对糖尿病患者及其高危人群的空腹血糖、胰岛素抵抗、炎症标志物等指标的影响。方法 检索4个主要数据库,搜索联合补充VD和钙相关的随机对照试验,检索时间限定均建库开始至2017年1月1日。结果 Meta分析结果显示,VD+钙补充组与对照组相比空腹血糖的浓度降低,此外,维生素D+钙补充组的HOMA - IR也显著下降。但对于高敏C反应蛋白和白介素 - 6,2组不存在统计学差异。结论 糖尿病人及其高危人群补充VD和钙可改善空腹血糖和胰岛素抵抗,但对炎症标志物的影响并不显著。     

硒和维生素E对大鼠糖尿病易感性的影响

目的 :　观察硒 ( Se)和维生素 E( VE)对糖尿病 ( DM)易感性的影响。方法 :　应用膳食低 Se复加注射链脲佐菌素 ( STZ)法制成大鼠 DM模型 ,补充一定剂量的 Se和 (或 ) VE,观察对大鼠 DM易感性的影响。结果 :　膳食低 Se、低 VE可明显增加大鼠 DM易感性 ,表现为血清 C肽水平和胰岛 C肽分泌贮备显著降低 ,血糖明显升高 ,并可显著增加 DM大鼠死亡率。在膳食中联合补充 0 .2 mg Se、50 0 mg VE/ kg,明显增加了 DM大鼠血清和胰岛 C肽含量、降低 DM大鼠血糖水平 ,亦使 DM大鼠死亡率显著降低。结论 :　在 DM亚临床状态下 ,联合补充适量 Se和 VE可改善胰岛内分泌细胞代谢偏移及功能紊乱 ,拮抗致病因素的胰岛损伤效应 ,降低 DM易感性。     

Vitamin D and bone health in postmenopausal women

Osteoporosis, a disease of increased skeletal fragility, is becoming increasingly common as the U.S. population ages. Adequate vitamin D and calcium intake is the cornerstone of osteoporosis prevention and treatment. Age-related changes in vitamin D and calcium metabolism increase the risk of vitamin D insufficiency and secondary hyperparathyroidism. Although longitudinal data have suggested a role of vitamin D intake in modulating bone loss in perimenopausal women, studies of vitamin D and calcium supplementation have failed to support a significant effect of vitamin D and calcium during early menopause. There is a clearer benefit in vitamin D and calcium supplementation in older postmenopausal women. Vitamin D intake between 500 and 800 IU daily, with or without calcium supplementation, has been shown to increase bone mineral density (BMD) in women with a mean age of approximately 63 years. In women older than 65, there is even more benefit with vitamin D intakes of between 800 and 900 IU daily and 1200-1300 mg of calcium daily, with increased bone density, decreased bone turnover, and decreased nonvertebral fractures. The decreases in nonvertebral fractures may also be influenced by vitamin D-mediated decreases in body sway and fall risk. There are insufficient available data supporting a benefit from vitamin D supplementation alone, without calcium, to prevent osteoporotic fracture in postmenopausal women.     

Focus on vitamin D, inflammation and type 2 diabetes

The initial observations linking vitamin D to type 2 diabetes in humans came from studies showing that both healthy and diabetic subjects had a seasonal variation of glycemic control. Currently, there is evidence supporting that vitamin D status is important to regulate some pathways related to type 2 diabetes development. Since the activation of inflammatory pathways interferes with normal metabolism and disrupts proper insulin signaling, it is hypothesized that vitamin D could influence glucose homeostasis by modulating inflammatory response. Human studies investigating the impact of vitamin D supplementation on inflammatory biomarkers of subjects with or at high risk of developing type 2 diabetes are scarce and have generated conflicting results. Based on available clinical and epidemiological data, the positive effects of vitamin D seem to be primarily related to its action on insulin secretion and sensitivity and secondary to its action on inflammation. Future studies specifically designed to investigate the role of vitamin D on type 2 diabetes using inflammation as the main outcome are urgently needed in order to provide a more robust link between vitamin D, inflammation and type 2 diabetes.     

Update on vitamin D and type 2 diabetes

The prevalence of type 2 diabetes mellitus continues to climb in many parts of the globe in association with the rise in obesity. Although the latter is clearly a predominant factor in the pathogenesis of type 2 diabetes, other modifiable lifestyle factors such as exercise, alcohol consumption, smoking, and certain nutritional factors, such as vitamin D deficiency, are also believed to play a role. In contrast to the findings of observational studies, information pooled from vitamin D intervention trials lack conclusive evidence in support of vitamin D supplementation and changes in diabetes risk or measures of glucose intolerance, although an effect on insulin resistance may exist. Well-designed trials that focus on intermediate biomarkers of diabetes risk in response to increased vitamin D intake are still needed. It will be important to include in the design of these studies selection of insulin-resistant study subjects who have a low (< 50 nmol/L) initial serum vitamin D (25-hydroxyvitamin D) status and administration of sufficient vitamin D to adequately increase their vitamin D status to > 75 nmol/L serum 25-hydroxyvitamin D.     

Comparative effects of vitamin K and vitamin D supplementation on calcium balance in young rats fed normal or low calcium diets

We examined the effect of vitamin K and vitamin D supplementation on calcium balance in young rats fed a normal or low calcium diet. Eighty female Sprague-Dawley rats, 6 wk of age, were randomized by the stratified weight method into eight groups with 10 rats in each group: 0.5% (normal) or 0.1% (low) calcium diet, 0.5% or 0.1% calcium diet+vitamin K (vitamin K2, menatetrenone, 30 mg/100 g, food intake), 0.5% or 0.1% calcium diet+vitamin D (25 microg/100 g, food intake), and 0.5% or 0.1% calcium diet+vitamin K+vitamin D. The duration of the study was 10 wk. Vitamin K supplementation promoted the reduction in urinary calcium excretion and retarded the abnormal elevation of serum PTH level in rats fed a low calcium diet, and stimulated intestinal calcium absorption in rats fed a normal calcium diet. Vitamin D supplementation stimulated intestinal calcium absorption with prevention of the abnormal elevation of serum PTH levels and prevented hypocalcemia in rats fed a low calcium diet, and stimulated intestinal calcium absorption in rats fed a normal calcium diet. The stimulation of intestinal calcium absorption was associated with increased serum 1,25-dihydroxyvitamin D levels. An additive effect of vitamin K and vitamin D on intestinal calcium absorption was found only in rats fed a normal calcium diet. This study shows the differential effects of vitamin K and vitamin D supplementation on calcium balance in young rats fed a normal or low calcium diet.     

Combined Calcium and Vitamin D Supplementation Reduces Bone Loss and Fracture Incidence in Older Men and Women

A recent supplementation study of 389 men and women over the age of 65 years was conducted to address the impact of combined calcium and vitamin D supplementation on nonvertebral fracture incidence and maintenance of bone mass. Daily supplementation with 500 mg calcium and 700 IU vitamin D for 3 years moderately reduced bone loss at several sites and significantly decreased the rate of nonvertebral fractures, compared with a placebo group. Optimal intake of both calcium and vitamin D may be an easily implemented strategy to maintain existing bone mass and reduce the risk of fracture in older men and women.     

Vitamin D supplementation and depression in the women's health initiative calcium and vitamin D trial

While observational studies have suggested that vitamin D deficiency increases risk of depression, few clinical trials have tested whether vitamin D supplementation affects the occurrence of depression symptoms. The authors evaluated the impact of daily supplementation with 400 IU of vitamin D(3) combined with 1,000 mg of elemental calcium on measures of depression in a randomized, double-blinded US trial comprising 36,282 postmenopausal women. The Burnam scale and current use of antidepressant medication were used to assess depressive symptoms at randomization (1995-2000). Two years later, women again reported on their antidepressant use, and 2,263 completed a second Burnam scale. After 2 years, women randomized to receive vitamin D and calcium had an odds ratio for experiencing depressive symptoms (Burnam score ≥0.06) of 1.16 (95% confidence interval: 0.86, 1.56) compared with women in the placebo group. Supplementation was not associated with antidepressant use (odds ratio = 1.01, 95% confidence interval: 0.92, 1.12) or continuous depressive symptom score. Results stratified by baseline vitamin D and calcium intake, solar irradiance, and other factors were similar. The findings do not support a relation between supplementation with 400 IU/day of vitamin D(3) along with calcium and depression in older women. Additional trials testing higher doses of vitamin D are needed to determine whether this nutrient may help prevent or treat depression.     

The Potential Protective Action of Vitamin D in Hepatic Insulin Resistance and Pancreatic Islet Dysfunction in Type 2 Diabetes Mellitus

Vitamin D deficiency (i.e., hypovitaminosis D) is associated with increased insulin resistance, impaired insulin secretion, and poorly controlled glucose homeostasis, and thus is correlated with the risk of metabolic diseases, including type 2 diabetes mellitus (T2DM). The liver plays key roles in glucose and lipid metabolism, and its dysregulation leads to abnormalities in hepatic glucose output and triglyceride accumulation. Meanwhile, the pancreatic islets are constituted in large part by insulin-secreting β cells. Consequently, islet dysfunction, such as occurs in T2DM, produces hyperglycemia. In this review, we provide a critical appraisal of the modulatory actions of vitamin D in hepatic insulin sensitivity and islet insulin secretion, and we discuss the potential roles of a local vitamin D signaling in regulating hepatic and pancreatic islet functions. This information provides a scientific basis for establishing the benefits of the maintenance, or dietary manipulation, of adequate vitamin D status in the prevention and management of obesity-induced T2DM and non-alcoholic fatty liver disease.