Adaptation of fatty acid composition to temperature--a study on carp (Cyprinus carpio L.) liver slices

The energy metabolism and transcriptomic responses of the Manila clam (Ruditapes philippinarum) under the low-temperature stress

Low temperature in winter poses a threat to the Manila clam Ruditapes philippinarum in North China. However, a number of low-temperature-tolerant clams could survive such condition. It is therefore of interest to explore the survival mechanisms underlying the cold tolerance of R. philippinarum. The Zebra II population of R. philippinarum (Zebra II) from North China and the native Putian population from South China were used as experimental materials. Both populations were stressed with low-temperature and the differences in their survival rates, energy metabolism and transcriptional responses were compared. The results shown that after cold treatment at -1.9 °C, survival rate of Zebra II was higher than that of the Putian group. For both groups, the respiration, ammonia excretion, and ingestion rates continuously decreased till 0 with reductions temperature. In addition, RNA-seq revealed that as compared with the Putian group, there were 3682 up-regulated differentially expressed genes (DEGs) and 3361 down-regulated DEGs in Zebra II group. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that these DEGs were mostly enriched in the purine, pyrimidine, and pyruvate metabolism pathways in Zebra II under low-temperature stress. Furthermore, qRT-PCR analysis further confirmed that Zebra II responded to low-temperature stress through upregulating genes involved in purine, pyrimidine, and pyruvate metabolism pathways. Taken together, all these results indicated that Zebra II has higher cold tolerance than the Putian group. Therefore, Zebra II is capable for overwintering in the intertidal zone of North China.

Under ice plankton and lipid dynamics in a subarctic lake

Climate warming causes shorter winters and changes in ice and snow cover in subarctic lakes, highlighting the need to better understand under-ice ecosystem functioning. The plankton community in a subarctic, oligotrophic lake was studied throughout the ice-covered season, focusing on lipid dynamics and life history traits in two actively overwintering copepods, Cyclops scutifer and Eudiaptomus graciloides. Whereas C. scutifer was overwintering in C-IV to C-V stage, E. graciloides reproduced under ice cover. Both species had accumulated lipids prior to ice-on and showed a substantial decrease in total lipid content throughout the ice-covered period: E. graciloides (60%-38% dw) and C. scutifer (73%-33% dw). Polyunsaturated fatty acids of algal origin were highest in E. graciloides and declined strongly in both species. Stearidonic acid (18:4n-3) content in E. graciloides was particularly high and decreased rapidly during the study period by 50%, probably due to reproduction. The copepods differed in feeding behavior, with the omnivore C. scutifer continuing to accumulate lipids until January, whereas the herbivorous E. graciloides accumulated lipids from under-ice primary production during the last months of ice-cover. Our findings emphasize the importance of lipid accumulation and utilization for actively overwintering copepods irrespective of the timing of their reproduction.

Muscle proximate composition of various food fish species and their nutritional significance: A review

Today, there is a growing awareness about the importance of eating nutritious foods and fish is gaining momentum as a result of its unique nutritional benefits. Fish are considered as nutritionally valuable part of the human diet because of the presence of both macronutrients (proteins, lipids and ash) and micronutrients (vitamins and minerals). These nutrients are indispensable in human nutrition and have proven to be involved in several metabolic functions. The nutritional content can be used to rank different fish species based on their nutritional and functional benefits, allowing consumers to make better decisions according to their requirements. Proximate composition of fish includes determination of moisture, protein, fat and ash contents, which constitutes about 96%-98% of the total constituents of the fish body. The study of these components gives us a clear understanding in assessing the energy value of the fishes. In the present study, an attempt has been made to provide a concise review about the proximate composition of various fish species from different parts of the world in order to evaluate the high-protein, low-fat food with excellent nutritional values and to enlighten the different exogenous and endogenous factors that are actually responsible for their variation. The review also provides an insight into the characteristics of the chemical composition of various fish species, which are gaining importance for the sector involving fish and fishery products for domestic and foreign trade and for appreciating as animal feed all over the world.

The molecular and metabolic program by which white adipocytes adapt to cool physiologic temperatures

Although visceral adipocytes located within the body's central core are maintained at approximately 37°C, adipocytes within bone marrow, subcutaneous, and dermal depots are found primarily within the peripheral shell and generally exist at cooler temperatures. Responses of brown and beige/brite adipocytes to cold stress are well studied; however, comparatively little is known about mechanisms by which white adipocytes adapt to temperatures below 37°C. Here, we report that adaptation of cultured adipocytes to 31°C, the temperature at which distal marrow adipose tissues and subcutaneous adipose tissues often reside, increases anabolic and catabolic lipid metabolism, and elevates oxygen consumption. Cool adipocytes rely less on glucose and more on pyruvate, glutamine, and, especially, fatty acids as energy sources. Exposure of cultured adipocytes and gluteal white adipose tissue (WAT) to cool temperatures activates a shared program of gene expression. Cool temperatures induce stearoyl-CoA desaturase-1 (SCD1) expression and monounsaturated lipid levels in cultured adipocytes and distal bone marrow adipose tissues (BMATs), and SCD1 activity is required for acquisition of maximal oxygen consumption at 31°C.

Thermal response of two sexually dimorphic Calopteryx (Odonata) over an ambient temperature range

Organisms may internally or behaviorally regulate their body temperatures or conform to the ambient air temperatures. Previous evidence is mixed on whether wing pigmentation influences thermoregulation in various odonates.We investigated the thermal response of sympatric North American Calopteryx aequabilis and Calopteryx maculata with a thermal imaging study across a 25°C ambient temperature range.We found that regressions of thorax temperature on ambient temperature standardized by species had similar slopes for male and female C. maculata, but females were consistently 1.5°C warmer than males. In contrast, the sexes of C. aequabilis differed in slope, with C. aequabilis females having a slope less than 1.0 and males having a slope greater than 1.0.We found that regressions of thorax temperature on ambient temperature standardized by sex had similar slopes for males and females of both species, but C. maculata females were consistently 2.1°C warmer than C. aequabilis females.Given that C. aequabilis is strongly sexually dimorphic in pigment, but C. maculata is not, our findings suggest that wing pigmentation may influence thermal response rate in sympatric populations of both species.

Ins and Outs of Interpreting Lipidomic Results

Membrane lipids are essential for life; however, research on how cells regulate cell lipid composition has been falling behind for quite some time. One reason was the difficulty in establishing analytical methods able to cope with the cell lipid repertoire. Development of a diversity of mass spectrometry-based technologies, including imaging mass spectrometry, has helped to demonstrate beyond doubt that the cell lipidome is not only greatly cell type dependent but also highly sensitive to any pathophysiological alteration such as differentiation or tumorigenesis. Interestingly, the current popularization of metabolomic studies among numerous disciplines has led many researchers to rediscover lipids. Hence, it is important to underscore the peculiarities of these metabolites and their metabolism, which are both radically different from protein and nucleic acid metabolism. Once differences in lipid composition have been established, researchers face a rather complex scenario, to investigate the signaling pathways and molecular mechanisms accounting for their results. Thus, a detail often overlooked, but of crucial relevance, is the complex networks of enzymes involved in controlling the level of each one of the lipid species present in the cell. In most cases, these enzymes are redundant and promiscuous, complicating any study on lipid metabolism, since the modification of one particular lipid enzyme impacts simultaneously on many species. Altogether, this review aims to describe the difficulties in delving into the regulatory mechanisms tailoring the lipidome at the activity, genetic, and epigenetic level, while conveying the numerous, stimulating, and sometimes unexpected research opportunities afforded by this type of studies.

Non-Mammalian Vertebrates: Distinct Models to Assess the Role of Ion Gradients in Energy Expenditure

Animals store metabolic energy as electrochemical gradients. At least 50% of mammalian energy is expended to maintain electrochemical gradients across the inner mitochondrial membrane (H⁺), the sarcoplasmic reticulum (Ca⁺⁺), and the plasma membrane (Na⁺/K⁺). The potential energy of these gradients can be used to perform work (e.g., transport molecules, stimulate contraction, and release hormones) or can be released as heat. Because ectothermic species adapt their body temperature to the environment, they are not constrained by energetic demands that are required to maintain a constant body temperature. In fact, ectothermic species expend seven to eight times less energy than similarly sized homeotherms. Accordingly, ectotherms adopt low metabolic rates to survive cold, hypoxia, and extreme bouts of fasting that would result in energy wasting, lactic acidosis and apoptosis, or starvation in homeotherms, respectively. Ectotherms have also evolved unique applications of ion gradients to allow for localized endothermy. Endothermic avian species, which lack brown adipose tissue, have been integral in assessing the role of H⁺ and Ca⁺⁺ cycling in skeletal muscle thermogenesis. Accordingly, the diversity of non-mammalian vertebrate species allows them to serve as unique models to better understand the role of ion gradients in heat production, metabolic flux, and adaptation to stressors, including obesity, starvation, cold, and hypoxia.

Dietary Fatty Acids and Temperature Modulate Mitochondrial Function and Longevity in Drosophila

Fluctuations in temperature and resource availability are conditions many organisms contend with in nature. Specific dietary nutrients such as fatty acids play an essential role in reproduction, cold adaptation, and metabolism in a variety of organisms. The present study characterizes how temperature and diet interact to modulate Drosophila physiology and life span. Flies were raised on media containing specific saturated, monounsaturated, or polyunsaturated fatty acids supplements at low concentrations and were placed in varied thermal environments. We found that dietary long-chain polyunsaturated fatty acids improve chill coma recovery and modulate mitochondrial function. Additionally, monounsaturated and polyunsaturated fatty acid food supplements were detrimental to life span regardless of temperature, and antioxidants were able to partially rescue this effect. This study provides insight into environmental modulation of Drosophila physiology and life span.

Structure and expression of fatty acid desaturases

Fatty acid desaturases are enzymes that introduce double bonds into fatty acyl chains. They are present in all groups of organisms, i.e., bacteria, fungi, plants and animals, and play a key role in the maintenance of the proper structure and functioning of biological membranes. The desaturases are characterized by the presence of three conserved histidine tracks which are presumed to compose the Fe-binding active centers of the enzymes. Recent findings on the structure and expression of different types of fatty acid desaturase in cyanobacteria, plants and animals are reviewed in this article. Roles of individual desaturases in temperature acclimation and principles of regulation of the desaturase genes are discussed.

The fatty acid constitution and ordering state of membranes in dominant temperature-sensitive lethal mutation and wild-type Drosophila melanogaster larvae

The ordering state and changes in fatty acid composition of microsomal (MS) and mitochondrial (MC) membranes of two dominant temperature-sensitive (DTS) lethal mutations and the wild-type Oregon-R strain larvae of Drosophila melanogaster have been studied at 18 and 29 degrees C and after temperature-shift experiments. The membranes of wild-type larvae have a stable ordering state, with "S" values between 0.6 (18 degrees C) and 0.5 (29 degrees C) in both membranes which remained unchanged in shift experiments, although the ratios of saturated/unsaturated fatty acids were changed as expected. The strongly DTS mutation 1(2) 10DTS forms very rigid membranes at the restrictive temperature (29 degrees C) which cannot be normalized after shift down, while shift up or development at the permissive temperature results in normal ordering state. This mutant is less able to adjust MS and MC fatty acid composition in response to the growth temperature than the wild type. The less temperature-sensitive 1(2)2DTS allele occupies an intermediate state between Oregon-R and 1(2)10DTS in both respects. We assume and the genetical data suggest that the DTS mutant gene product is in competition with the wild-type product, resulting in a membrane structure which is not able to accommodate to the restrictive temperature.

The fatty acid constitution and ordering state of membranes in dominant temperature-sensitive lethal mutation and wild-type Drosophila melanogaster larvae

The ordering state and changes in fatty acid composition of microsomal (MS) and mitochondrial (MC) membranes of two dominant temperature-sensitive (DTS) lethal mutations and the wild-type Oregon-R strain larvae of Drosophila melanogaster have been studied at 18 and 29 degrees C and after temperature-shift experiments. The membranes of wild-type larvae have a stable ordering state, with "S" values between 0.6 (18 degrees C) and 0.5 (29 degrees C) in both membranes which remained unchanged in shift experiments, although the ratios of saturated/unsaturated fatty acids were changed as expected. The strongly DTS mutation 1(2) 10DTS forms very rigid membranes at the restrictive temperature (29 degrees C) which cannot be normalized after shift down, while shift up or development at the permissive temperature results in normal ordering state. This mutant is less able to adjust MS and MC fatty acid composition in response to the growth temperature than the wild type. The less temperature-sensitive 1(2)2DTS allele occupies an intermediate state between Oregon-R and 1(2)10DTS in both respects. We assume and the genetical data suggest that the DTS mutant gene product is in competition with the wild-type product, resulting in a membrane structure which is not able to accommodate to the restrictive temperature.

Manipulation of plasma membrane physical state affects desaturase activity in rat lymphocytes

Thymocytes, obtained from young rats, were incubated in the presence of either diheptadecanoylphosphatidylcholine or dioleylphosphatidylcholine vesicles and desaturation of either [1-14C]stearic acid or [1-14C]linoleic acid was followed in the endoplasmic reticulum. Incubation with diheptadecanoylphosphatidylcholine resulted in an accumulation of heptadecanoic acid in the plasma membrane, but not in the endoplasmic reticulum and mitochondria, and an increase in membrane ordering as assessed by diphenylhexatriene fluorescence polarization. A shift to higher temperature of the phase separation in the plasma membrane was also observed. Both delta 9 and delta 6 desaturase activities were enhanced in these cells, with delta 6 responding more intensly. Accumulation of oleic acid in the plasma membrane could not be observed when the cells were incubated in the presence of dioleylphosphatidylcholine vesicles, but all the membranes separated, including the microsomes, became more fluid. This can be attributed to removal of cholesterol by the vesicles. Fluidization of plasma membrane and endoplasmic reticulum depressed the conversion of stearate to oleate and linoleate to gamma-linolenate. It is concluded that there is an exchange of information between the plasma membrane and the endoplasmic reticulum in order to maintain the proper fluidity relationships and that this occurs without transfer of lipids from the former to the latter.