USTHB, Faculty of Biological Sciences, Laboratory of Biology and Physiology of Organisms, Neurobiology Team, USTHB, BP 32, El Alia, Bab Ezzouar, 16111 Algiers, Algeria.
Dr Yahia Fares University of Medea, Faculty of Sciences, 26000 medea, Algeria.
Folia Histochem Cytobiol. 2020;58(3):182-197. doi: 10.5603/FHC.a2020.0021. Epub 2020 Sep 22.
Biological rhythms, such as Light/Dark (LD) cycles, are an integral component of virtually all aspects of life. These rhythms are controlled in large part by circadian clocks, allowing the organism to adapt its internal rhythmic metabolism to changes in the external environment created by daily fluctuations in the LD cycle. Therefore, changes in the daily duration of the lighting could lead to adverse health consequences. The aim of the study was to investigate, in a nocturnal desert rodent, Gerbillus tarabuli, the effects of the LD cycle disruption on the structure of the hepatic tissue and the content of carbohydrate and lipid parameters as indicators of metabolic state.
The present study was conducted on two gerbil groups: control group was exposed to a standard lighting cycle (LD: 12:12), and the shifted group was subjected to a chronic disrupted LD cycle, alternating a standard cycle (LD: 12:12) with a modified cycle (LD: 20:4), i.e., the light phase of 24-h cycle was prolonged by 8 h on every second day during a period of 12 weeks. We used: (i) routine histology and histochemical staining for tissue analysis; (ii) immunohistochemistry (IHC) for MPO detection; (iii) biochemical methods for hepatic glycogen and lipids extraction and quantification. Blood metabolic parameters were assessed by enzymatic methods.
Our structural results indicate in the shifted group an alteration of tissue architecture, showing widely scattered inflammatory foci with many dilated sinusoids and prominent leukocyte infiltration with connective fibrotic extension. IHC revealed also increased hepatic myeloperoxidase (MPO) expression confirming neutrophils' presence. In parallel, the histochemical study revealed a strong depletion of hepatocytic glycogen and lipid inclusions; these observations were also supported by the measurements of glycogen and total lipids in extracted tissue indicating a reduction in liver content. These results were accompanied by a decrease in body weight relative to the reduction of food intake, as well as hyperglycemia and some alterations in serum lipid parameters (triglycerides and cholesterol) suggesting a metabolic disturbance.
We conclude that a phase difference between the endogenous activity rhythm of the species and the daily cycle of illumination has a strong impact on the liver morphology as well as on the metabolic activity of liver cells.
生物节律，如明暗（LD）周期，是生命几乎所有方面的一个组成部分。这些节律主要由昼夜节律钟控制，使生物体能够适应外部环境的变化，内部节律代谢适应 LD 周期的日常波动。因此，照明每日持续时间的变化可能导致健康不良后果。本研究的目的是研究夜间沙漠啮齿动物（Gerbillus tarabuli）中 LD 周期破坏对肝组织结构以及碳水化合物和脂质参数含量的影响，这些参数是代谢状态的指标。
本研究在两组沙鼠中进行：对照组暴露于标准光照周期（LD：12:12），移位组则受到慢性破坏的 LD 周期的影响，交替标准周期（LD：12:12）和修改周期（LD：20:4），即在每两天延长 24 小时周期的光相 8 小时，持续 12 周。我们使用了：（i）组织分析的常规组织学和组织化学染色；（ii）髓过氧化物酶（MPO）检测的免疫组织化学（IHC）；（iii）用于肝糖原和脂质提取和定量的生化方法。血液代谢参数通过酶法评估。
我们的结构结果表明，在移位组中，组织结构发生改变，显示出广泛分散的炎症灶，伴有许多扩张的窦和明显的白细胞浸润，伴有结缔组织纤维化延伸。IHC 还显示出肝髓过氧化物酶（MPO）表达增加，证实了中性粒细胞的存在。同时，组织化学研究还显示出肝细胞糖原和脂质内含物的强烈消耗；这些观察结果也得到了从组织中提取的糖原和总脂质测量的支持，表明肝脏含量减少。这些结果伴随着体重相对于食物摄入的减少而减少，以及高血糖和一些血清脂质参数（甘油三酯和胆固醇）的改变，表明代谢紊乱。
我们得出结论，物种内源性活动节律与每日光照周期之间的相位差对肝脏形态以及肝细胞的代谢活性有很大影响。
