老年人容易因衰老而出现厌食症。最近发现了延髓腹外侧区(RVLM)中的延髓头端C1(rC1)儿茶酚胺能神经元在食物摄入控制中的作用。已经确定这些神经元调节心血管功能。
本研究旨在确定年龄对延髓C1(rC1)神经元在介导摄食反应中的功能的影响。
使用3月龄(n=22)和24月龄(n=22)的雄性SpragueDawley大鼠,并进一步分为两个亚组;1)具有2-脱氧-d-葡萄糖(2DG)的治疗组和2)媒介物组。喂养激素如胆囊收缩素(CCK),使用酶联免疫吸附测定(ELISA)分析生长素释放肽和瘦素。小心解剖大鼠脑,以获得脑干RVLM区域。进行进一步分析以确定RVLM中与摄食途径相关的蛋白质和基因的水平。酪氨酸羟化酶(TH)的蛋白表达,在Serine40磷酸化TH(pSer40TH),AMP激活蛋白激酶(AMPK),通过蛋白质印迹测定磷酸化AMPK(磷酸AMPK)和神经肽YY5受体(NPY5R)。TH的表达,通过实时PCR测定AMPK和NPY基因。
这项研究表明,在2DG给药后,年轻和老年大鼠的血糖水平升高。老年大鼠基础时血浆CCK-8浓度较高,幼鼠2DG给药时血浆CCK-8浓度升高,但是瘦素和饥饿素没有变化。老年大鼠显示较高的TH和较低的AMPKmRNA水平。葡萄糖化降低了年轻大鼠的AMPKmRNA水平,而老年大鼠的THmRNA水平降低。老年rC1神经元显示较高的NPY5R蛋白水平。在葡萄糖化之后,rC1神经元在不同年龄产生不同的分子变化,在年轻的老鼠中,AMPK磷酸化水平升高,在老年大鼠中,TH磷酸化水平升高。
这些发现表明,至少rC1神经元的葡萄糖反调节反应,有助于年轻和老年大鼠应对葡萄糖代谢的能力。rC1神经元内年龄诱导的分子变化可能会减弱葡萄糖的反应。这种情况可以解释老年人喂养反应的损害。
Older people are likely to develop anorexia of aging. Rostral C1 (rC1) catecholaminergic neurons in rostral ventrolateral medulla (RVLM) are recently discovered its role in food intake control. It is well established that these neurons regulate cardiovascular function.
This study aims to determine the effect of age on the function of rostral C1 (rC1) neurons in mediating feeding response.
Male Sprague Dawley rats at 3-months (n = 22) and 24-months (n = 22) old were used and further divided into two subgroups; 1) treatment group with 2-deoxy-d-glucose (2DG) and 2) vehicle group. Feeding hormones such as cholecystokinin (CCK), ghrelin and leptin were analysed using enzyme-linked immunosorbent assay (ELISA). Rat brain was carefully dissected to obtain the brainstem RVLM region. Further analysis was carried out to determine the level of proteins and genes in RVLM that were associated with feeding pathway. Protein expression of tyrosine hydroxylase (TH), phosphorylated TH at Serine40 (pSer40TH), AMP-activated protein kinase (AMPK), phosphorylated AMPK (phospho AMPK) and neuropeptide Y Y5 receptor (NPY5R) were determined by western blot. Expression of TH, AMPK and NPY genes were determined by real-time PCR.
This study showed that blood glucose level was elevated in young and old rats following 2DG administration. Plasma CCK-8 concentration was higher in the aged rats at basal and increased with 2DG administration in young rats, but the leptin and ghrelin showed no changes. Old rats showed higher TH and lower AMPK mRNA levels. Glucoprivation decreased AMPK mRNA level in young rats and decreased TH mRNA in old rats. Aged rC1 neurons showed higher NPY5R protein level. Following glucoprivation, rC1 neurons produced distinct molecular changes across age in which, in young rats, AMPK phosphorylation level was increased and in old rats, TH phosphorylation level was increased.
These findings suggest that glucose-counterregulatory responses by rC1 neurons at least, contribute to the ability of young and old rats in coping glucoprivation. Age-induced molecular changes within rC1 neurons may attenuate the glucoprivic responses. This situation may explain the impairment of feeding response in the elderly.