Diurnal and Infradian Rhythms in Lipid Parameters of Indian Catfish,Heteropneustes fossilis

Twentyfour-hour variation in (14 C) acetate incorporation in the liver lipid, and lipid concentrations in the liver and muscle tissues were studied during different phases of the annual reproductive cycle in the female freshwater catfish, H. fossilis. A 24-h rhythm in hepatic lipogenic activity was validated. Lipid concentration in liver and muscle also varied in a rhythmic fashion (t = 24 h). The mesor and amplitude of these rhythms appeared to be modulated by the phase of the annual gonadal cycle of H. fossilis. All three lipid parameters, in addition, exhibited low frequency rhythms with a t = 6 months or 3 months. The results indicate that the time of the day and month of the year for sampling in any experiment involving examination of lipid metabolism are of critical importance.     

Seasonal fluctuation in lipid and cholesterol content of ovary, liver and blood serum in relation to annual sexual cycle in Heteropneustes fossilis (Bloch).

Seasonal fluctuation in lipid content of ovary and liver and cholesterol content of ovary, liver and serum in relation to annual reproductive cycle in H. fossilis has been worked out. Reduction in lipid content of liver was associated with decrease in hepatosomatic index (HSI) in prespawning and spawning phases. But there was an obvious increase in the lipid level of ovary in the above phases which coincided with enhanced gonadosomatic index (GSI) records. Serum and ovary showed a subsidence in their cholesterol contents in prespawning followed by increased level during spawning period. Substraction in liver cholesterol started in prespawning and continued till spawning phase and thereafter regained upward trend. Lipid and cholesterol levels in all organs studied along with GSI and HSI returned to initial values by the end of postspawning stage. Administration of clomid, sexovid, PGE1 and PGF2 alpha for a week did not induce any change in HSI, GSI, lipid and cholesterol values of liver and serum. However, these drugs were effective in suppressing the ovarian cholesterol within a week. The above drugs seem to affect cholesterol level indirectly since they trigger gonadotrophin secretion which in turn probably accelerated cholesterol utilization in ovary for increased steroid hormone output.     

Lipid changes in tissues from the cold-exposed,torpid and aroused pigmy mouse, Baiomys taylori

Brown fat, liver, heart and skeletal muscle tissue lipid, triglyeride, and protein have been quantitated during the pigmy mouse torpid cycle. Triglycerides appear to be the main tissue energy store for use of this organism throughout the cycle. Brown fat is depleted of its triglyceride from a control value of 3.48 mg per mg protein to 0.39 mg during torpor. There is a significant increase during arousal, 24 hr post-torpor. Data from liver extracts suggest a reverse trend. Skeletal muscle represents 24% of the mass of the mouse. The muscle triglycerides decrease to half that of the control and remain at that level until 24 hr post-torpor. No similarly significant trends are found in heart tissue. The total lipid levels of the tissues mirror the types of data already expressed for triglycerides. The decrease in muscle triglycerides may represent either endogenous utilization and/or the mobilization of these reserves to other organs such as the liver and brown fat.     

Ureogenesis in a freshwater teleost: an unusual sub-cellular localization of ornithine-urea cycle enzymes in the freshwater air-breathing teleost Heteropneustes fossilis.

Sub-cellular localization of different ornithine-urea cycle enzymes was studied in the liver and kidney of a freshwater air-breathing teleost. Carbamyl phosphate synthetase, ornithine transcarbamylase, and arginase were found to be localized inside the mitochondria, and argininosuccinate synthetase and argininosuccinate lyase were found in the soluble fraction. Mitochondrial localization of arginase, a feature known in marine elasmobranchs and toadfishes, indicates the evolutionary position of H. fossilis to be different from that of present day freshwater teleosts.     

Ultrastructure of spermatozoa correlated with phylogenetic relationship between Heteropneustes fossilis and Rana tigrina

A study using transmission electron microscopy (TEM) of the spermatozoa of Rana tigrina and Heteropneustes fossilis in all phases of the annual reproductive cycle revealed that there was a phylogenetic relationship between them. The spermatozoa of H. fossilis appeared horseshoe-shaped, somewhat oval or wedge-shaped at the anterior end and broader at the posterior end. The horseshoe-shaped spermatozoan nucleus was observed during spermiogenesis of R. tigrina but later changed into a finger shape at maturity. The posterior end of the nuclei of mature spermatozoa of R. tigrina was blunt. The extremely dense homogenized nucleus was capped with an acrosomal vesicle in both species suggesting a definite phylogenetic inter-relationship between them.     

Daily and annual variations of the hepatic glucose 6-phosphate dehydrogenase activity and seasonal changes in the body fats of the gilthead seabream Sparus aurata

In mammalians, Glucose 6-phosphate dehydrogenase (G6PDH) is clearly related with the daily cycle lipogenesis/lipolysis and therefore with the photoperiod and activity. In fish the temporally changes on the activity of this enzyme have not been described. In this work, annual and diurnal activity of G6PDH was investigated in the liver of Sparus aurata in different seasonal conditions of temperature and photoperiod. During experiment the fish were kept in cages under natural temperature and photoperiod while consuming a commercial diet. The months studied were chosen to establish if there is any influence on the G6PDH activity, because of the change in temperature and photoperiod (equal photoperiod and different temperature, March and October; different photoperiod and equal temperature, May and November; and different photoperiod and temperature, June and January). To study the enzyme activity along the day, the livers of six fish were removed every 3 hr during 24 hr. Annual activity was determined as the average activity during 1 day. Also the annual changes on fat content in muscle and digestive system were studied. The Vmax (maximum velocity) showed seasonal changes in period and phase of the rhythms and for the Km (Michaelis-Menten constant) a period of 24 hr was found in all sampled months, except March, the phase time moves depending on the month. In addition, the annual variations in muscular fat and G6PDH-specific activity seem to be more related to the reproductive stage than any other variable considered.     

Diurnal Regulation of Lipid Metabolism and Applications of Circadian Lipidomics

The circadian timing system plays a key role in orchestrating lipid metabolism. In concert with the solar cycle, the circadian system ensures that daily rhythms in lipid absorption, storage, and transport are temporally coordinated with rest-activity and feeding cycles. At the cellular level, genes involved in lipid synthesis and fatty acid oxidation are rhythmically activated and repressed by core clock proteins in a tissue-specific manner. Consequently, loss of clock gene function or misalignment of circadian rhythms with feeding cycles （e.g., in shift work） results in impaired lipid homeostasis. Herein, we review recent progress in circadian rhythms research using lipidomics, i.e., large-scale profiling of lipid metabolites, to characterize circadian-regulated lipid pathways in mammals. In mice, novel regulatory circuits involved in fatty acid metabolism have been identified in adipose tissue, liver, and muscle. Extensive diversity in circadian regulation of plasma lipids has also been revealed in humans using lipidomics and other metabolomics approaches. In future studies, lipidomics platforms will be increasingly used to better understand the effects of genetic variation, shift work, food intake, and drugs on circadian-regulated lipid pathways and metabolic health.     

Effects of stress and food deprivation on catfish, Heteropneustes fossilis (Bloch)

No significant changes in plasma cortisol and plasma osmolarity (the indicators of primary and secondary response respectively) were observed when the blood samples were obtained from unanaesthetized, anaesthetized and stressed catfish, H. fossilis. The results suggest that the catfish is fairly hardy and not easily susceptible to stress by routine laboratory handling. The sustained plasma glucose levels and decreased liver and muscle glycogen concentrations during cessation of feeding of the catfish suggest that during period of food deprivation, it draws its energy through glycogenolysis. Hence, in any study dealing with carbohydrate metabolism, the catfish needs to be fed during acclimation and experimental periods.     

Role of photoperiodicity and circadian rhythm of glucocorticoids in synchronizing the fluctuations in free-radical oxidation of lipids in rats

A biphasic circadian rhythm in the content of liver lipid peroxidation products has been demonstrated in male Wistar rats housed under the conditions of 12L: 12D, with 3 hours of morning and evening twilight. Maxima of the concentration of the products were observed in the morning and early at night. The rhythm of lipid anti-oxidative activity was found in an anti-phase. Inversion of both the L: D cycle and glucocorticoid circadian rhythms (cortisol injections) led after 14-16 days to the same shifts in the rhythm of anti-oxidative activity. The data indicate that glucocorticoids modulate the diurnal rhythms of lipid anti-oxidative activity and may be responsible for the shifts in the rhythms of free radical oxidation, induced by inversion of the L: D cycle.     

Precocious ovarian recrudescence and induced off–season spawning of Heteropneustes fossilis by D-Lys6 salmon gonadotropin releasing hormone analog (sGnRH-A)

The feasibility of photothermal treatment and use of salmon gonadotropin releasing hormone analogue (sGnRH-A) for induced spawning of Heteropneustes fossilis outside the spawning season was investigated. Fish were maintained at 30° C and 14 h light (L)/10 h dark (D) for 60 days between the post-spawning season and preparatory season. Fish attained gonadal maturity 4 months earlier compared to the natural spawning season. Mature fish were induced to spawn by D-Lys⁶ sGnRH-A at a dose of 25 μg kg⁻¹ body weight. The eggs obtained were fertilizable. Injection of D-Lys⁶ sGnRH-A at different time points during the photodiurnal cycle did not influence the latency period and spawning of H. fossilis .     

Malondialdehyde content and circadian variations in brain, kidney, liver, and plasma of mice

In aerobic organisms, the use of oxygen (O(2)) to produce energy is associated with the production of Reactive Oxygen Species (ROS), which reacts with biological molecules to produce oxidized metabolites such as malondialdehyde (MDA). This experiment focused on male Swiss mice 12 weeks of age synchronized for 3 weeks by the 12 h light (rest)/12 h dark (activity) span. Different and comparable groups of animals (n=10) were sacrificed at six different circadian stages: 1, 5, 9, 13, 17, and 21 h after light onset (HALO). The 24 h mean MDA level varied among organs of mice in non-stress conditions and was comparable in brain and liver but lower than in kidney. As the MDA 24 h status constitutes only a part of ROS damages in sites differing by their oxygen use, lipid composition, and detoxification capacity, the temporal patterns of their MDA content were comparatively studied in relationship to the animal rest-activity cycle. The results revealed significant circadian rhythms with the peak time located during the rest span (approximately =5 HALO) for both brain and liver, but during the activity span for the kidney ( approximately =21 HALO) and plasma (approximately =13 HALO). This chronobiological study showed that under physiological conditions, lipid peroxidation depends on several factors. The MDA peak/trough might be used as a tool to detect moments of high/low sensitivity of tissues to ROS attack in rodents.     

Effect of starvation on tissue and serum gluconeogenic enzymes, alkaline phosphatase and tissue glycogen in the freshwater catfish, Heteropneustes fossilis (Bloch).

The influence of starvation has been studied on tissue and serum G-6Pase F-D-Pase and alkaline phosphatase activities and on the muscle and liver glycogen content of the freshwater catfish H. fossilis (Bloch). A marked increase in G-6Pase and F-D-Pase activities and a fall in the muscle and liver glycogen content recorded during 40 day starvation. The rise in gluconeogenic enzymes during starvation may be due to glucocorticoid stimulation. Alkaline phosphatase activity was found to decline markedly during starvation. The decline in enzyme activity is attributed to some factors like a fall in the rate of synthesis caused by lowered metabolic demands and to electrolyte imbalance caused by tissue overhydration. The fall in glycogen content may be related to the starved condition of the fish. Elevation in glycogen content and alkaline phosphatase activity and a fall in gluconeogenic enzymes were noted when feeding had been resumed.     

Effect of dietary lipid level on fatty acid beta-oxidation and lipid composition in various tissues of haddock,Melanogrammus aeglefinus L

Haddock (Melanogrammus aeglefinus) is a gadoid fish species that deposits dietary lipid mainly in the liver. The fatty acid (FA) beta-oxidation activity of various tissues was evaluated in juvenile haddock fed graded levels of lipid. The catabolism of a radiolabelled FA, [1-(14)C]palmitoyl-CoA, through peroxisomal and mitochondrial beta-oxidation was determined in the liver, red and white muscle of juvenile haddock fed 12, 18 and 24% lipid in the diet. There was no significant increase in the mitochondrial or peroxisomal beta-oxidation activity in the tissues tested as the dietary lipid level increased from 12 to 24%. Peroxisomes accounted for 100% of the beta-oxidation observed in the liver, whereas mitochondrial beta-oxidation dominated in the red (91%) and white muscle (97%) of juvenile haddock. Of the tissues tested, red muscle possessed the highest specific activity for beta-oxidation expressed on a per mg protein or per g wet weight basis. However, white muscle, which forms over 50% of the body mass in gadoid fish was the most important tissue in juvenile haddock for overall FA catabolism. The total lipid and FA composition of these tissues were also determined. This study confirmed that the liver was the major lipid storage organ in haddock. The hepatosomatic index (HSI; 10.0-15.2%) and lipid (73.8-79.3% wet wt.) in the liver increased significantly as dietary lipid was increased from 12 to 24% lipid. There was no significant increase in the lipid composition of the white muscle (0.8% wet wt.), red muscle (1.9% wet wt.) or heart (2.5% wet wt.).     

Circadiane Uhren und Energiemetabolismus

Chrononutrition – circadian clocks and energy metabolism Genetically encoded endogenous clocks regulate 24‐hour rhythms of physiology and behavior. A central pacemaker residing in the suprachiasmatic nucleus synchronizes peripheral clocks found in all tissues with each other and with the external day‐night cycle. One function of circadian clocks is the regulation of energy metabolism via rhythmic activation of tissue‐specific clock‐controlled genes. In the liver, genes involved in glucose and lipid metabolism are regulated in this fashion, while in adipocytes, fatty acid release and adipokine secretion are controlled by the circadian clock. Disruption of circadian rhythms as seen, for example, in shift workers promotes the development of metabolic disorders such as obesity and type‐2 diabetes.     

Further demonstration of the ambient temperature dependence of the annual biological cycles in the edible dormouse,Glis glis

Summary In the male edible dormouse, it has been proposed that the annual temperature cycle is the major external factor triggering annual biological rhythms in this hibernating species. The present study was designed to explore (i) the effects of suppression of the annual thermoperiodic cycle under natural photoperiodic conditions, and (ii) the effects of acute exposure to a warm environment on basal plasma T4 levels observed during hibernation. The results of the first experiment demonstrate an absence of circannual cycles of hibernation, body weight, and endocrine thyroid and gonadal functions in the absence of annual fluctuations of temperature (constant warm environment at 24°C) despite the maintenance of a normal photoperiodic cycle. On the other hand, acute exposure to 24°C during the late stage of hibernation stimulated thyroid function as expressed by a consistent transitory rise in plasma T4 concentrations, which was maximal within 7 days and restored to basal levels after 14 days. These findings are in close agreement with the concept that in the edible dormouse, the annual thyroid cycle is synchronized with the annual temperature cycle. Moreover, the present study, combined with prior data indicating that the thyroid cycle induces the testis cycle, suggests that the ambient temperature cycle may be intricately involved in the control of neuroendocrine cycles in dormice, although the mechanism is still unknown.     

The 11-year cycle in human births

The annual numbers of human births were analyzed with regard to an 11-year cycle. The annual values were obtained from seven different regions: Australia, Germany, England and Wales, New Zealand, Japan, Switzerland, and the USA. Fifty-five annual values were obtained from each region for the years 1930 to 1984, comprising approximately five sunspot cycles. For each region the annual values were formed into 5 by 11 matrices; the eleven column means obtained were standardized, and plotted. A periodic regression technique, utilizing the fitting functions of the Fourier series, was used to evaluate the temporal order in the column means. Eleven-year rhythms were found and compared with solar and geophysical variables. Correlations were found with sunspots and solar flares, with terrestrial measures of magnetic disturbances (the magnetic indices derived from the K-index), and with temperature. The correlation of conceptions with the 11-year solar cycle may be a potential guide in the selection of further variables for the control and regulation of the rhythms in human conceptions.     

Aging-related oxidative stress depends on dietary lipid source in rat postmitotic tissues

We investigate mitochondrial-lipid peroxidation of mitotic (liver) and postmitotic (heart and skeletal muscle) tissues of rats fed lifelong on two different lipid sources: virgin olive oil (monounsaturated fatty acids) and sunflower oil (n–6 polyunsaturated fatty acids). Two groups of 80 rats each were fed over 24 months on a diet differing in the lipid source (virgin olive oil or sunflower oil). Twenty rats per group were killed at 6, 12, 18, and 24 months; liver, heart, and skeletal muscle mitochondria were isolated and the lipid profile, hydroperoxides, vitamin E, and ubiquinone as well as catalase activity measured. Lipid peroxidation was higher in postmitotic tissues, and sunflower oil led to a higher degree of polyunsaturation and peroxidation. The levels of -tocopherol adapted to oxidative stress and preferentially accumulated during aging in heart and skeletal muscle. In conclusion, the type of dietary fat should be considered in studies on aging, since oxidative stress is directly modulated by this factor. This study confirms that postmitotic tissues are more prone to oxidative stress during aging and proposes a hypothesis to explain this phenomenon.