Biochemical Study of DNA and RNA in Liver of Teleost: A Review

S. Saiyyad, S. A. Zoting, P. L. Ghodeswar,  U. S. Rahate,  Dr. Varsha Dhurvey,

doi:10.5281/zenodo.20126134

Review Paper | Open Access
Volume 04 | Issue 05 | Article Id IJPS/260404521

Biochemical Study of DNA and RNA in Liver of Teleost: A Review
S. Saiyyad* S. A. Zoting P. L. Ghodeswar U. S. Rahate Dr. Varsha Dhurvey
P.G.T. Department of Zoology RTM Nagpur University, Nagpur, Maharashtra (India).440033

Abstract

The liver is metabolic organ in teleost fishes and plays an important role in biochemical and physiological process. DNA and RNA, plays a crucial role in regulating growth, metabolic activity and protein synthesis in teleost fishes. Hepatic RNA content is highly responsive to dietary, developmental and environmental factors, while DNA levels remain relatively stable, serving as a genetic baseline. RNA/DNA ratios provide valuable insights into the liver’s metabolic status, growth potential and physiological condition. Present study focuses on biochemical studies on DNA and RNA in liver tissue of teleost. Studies indicate that variations in nucleic acid content reflect nutritional, environmental, and seasonal influences, making liver DNA and RNA reliable indicators of fish health and adaptive metabolic responses. Biochemical studies important for understanding enhances knowledge of liver physiology and supports effective monitoring of metabolic and growth-related processes in teleost’s.

Keywords

Teleost fish, liver, DNA, RNA and RNA/DNA ratio.

Introduction

Teleost fishes, comprising over 30,000 species, represent the largest and most ecologically diverse vertebrate group, inhabiting marine, freshwater and estuarine environments ^[1-2]. Their evolutionary success stems from remarkable physiological and behavioural adaptability. Among their organs, the liver is central to metabolic homeostasis, managing nutrient storage, detoxification and the regulation of carbohydrate, lipid and protein metabolism^[1-2]. Accordingly, its biochemical composition especially nucleic acid content provides a reliable indicator of cellular activity and overall metabolic status DNA and RNA are the principal nucleic acids that govern genetic regulation and protein synthesis. In teleost fishes, hepatic RNA levels vary in response to feeding regimes, environmental changes and metabolic demands, while DNA content generally remains stable within cells^[3-4]. As a result, the RNA/DNA ratio has been widely used as a reliable indicator of growth rate, metabolic efficiency and the capacity for protein synthesis ^[5-6]. RNA and DNA are essential nucleic acids present in all cells, including the liver of teleost fishes. DNA provides a stable measure of cell number and biomass, while RNA is directly involved in protein synthesis and cellular activity. Measuring RNA and DNA levels in liver tissue allows researchers to assess the molecular composition and basic biochemical status of fish cells ^[7-8-9]. Biochemical analyses often require cell quantity or cellularity as a reference parameter. Cellularity can be expressed in terms of cell number, cell volume, or cellular nucleic acid content and the RNA:DNA ratio is a measure of the balance between these two essential cellular components ^[10-11]. The accuracy of cellular nucleic acid content estimation directly affects the precision of the estimation of cellular parameters. Reliable estimation of RNA and DNA depends on the efficiency and accuracy of isolation and quantification methods.

The liver, being a central metabolism, detoxification and nutrient processing organ, is a most important target for organ-specific nucleic acid analysis. Although several studies have quantified both RNA and DNA in fish liver, these are quite limited. For example, ^[12] measured nuclear DNA content in a number of teleost species, but did not quantify RNA.Measuring nucleic acid content was previously used to evaluate tissue growth characteristics and protein synthesis in cultured and wild fish, including herring, Clupea harengus and mackerel, Scomber scombrus has been identified as suitable for studying the relationship between nucleic acid contents and protein and nucleotide accumulation ^[1³^]. The same has been shown for evaluating the relationship between DNA/RNA content and nucleotide composition with lipid content in the studies on herring ^[1³^].

In rainbow trout (Parasalmo mykiss), liver RNA/DNA ratios and activities of citrate synthase, cytochrome C oxidase, and lactate dehydrogenase were measured over a period of several months. It was found that RNA/DNA ratios could serve as an index of tissue growth and biomass production. The activities of these three enzymes were highly correlated with RNA/DNA ratio and this could be a result of the same stimulatory pool mechanism for the synthesis of the enzymes and structural proteins.^[14]The level of nucleic acid in an organism is one of the central parameters in the assessment of various physiological conditions such as cell proliferation, biomass buildup and energy requirement. DNA and RNA content in different tissues of Notopterus notopterus was analyzed during the reproductive cycle to extrapolate the variation in nucleic acid levels in the liver during different reproductive phases of the fish. The results of the analysis indicate that nucleic acid levels vary with tissue and phase of reproduction. The findings reveal the dynamic character of nucleic acids and provide insight into nucleic acid turnover relative to the phases of the reproductive cycle and the metabolism of the specific organ.

Tissue specific variations in the RNA:DNA ratio in Channa punctatus under different feeding conditions. They found that liver exhibited distinct RNA:DNA ratios depending on nutritional status, demonstrating that the RNA:DNA ratio is a useful biochemical indicator for assessing tissue-specific metabolic activity and energy allocation in fish^[6]. DNA and RNA are crucial biomolecules involved in the structure and functionality of all living cells, including those found in teleost fishes^[16]. The liver is particularly metabolically active, carrying out vital functions such as nutrient processing, enzyme production and detoxification. Because of its significant metabolic activity, the liver contains considerable amounts of nucleic acids, which makes it an excellent organ for examining DNA and RNA as indicators of cellular function, metabolic activity and growth potential of tissues .^[17]

DNA

From the reviewed studies, liver DNA content in fish remains relatively constant under different dietary, environmental, seasonal and physiological conditions. In Oreochromis niloticus, dietary protein variation and starvation did not significantly alter in liver DNA levels ^[18]. Similarly, pesticide exposure in Catla catla ^[19] and temperature stress in Cirrhinus mrigala ^[20] showed stable DNA content despite metabolic disturbances. Growth and feeding studies in Labeo rohita ^[21], Clarias gariepinus ^[22], Channa striata ^[23], Mystus vittatus ^[24] and Heteropneustes fossilis ^[25] consistently reported minimal variation in liver DNA levels. Even with seasonal variations in Oncorhynchus mykiss ^[26] and pollution stress in Mugil cephalus ^[27], DNA was relatively stable. These results suggested that liver DNA is a mirror of tissue cellularity and a constant reference parameter in biochemical studies.

RNA

Liver RNA content fluctuates notably as a response to the nutritional state, environmental stress, growth, and physiological conditions, unlike DNA. Oreochromis niloticus liver RNA levels increased due to higher dietary protein , while starvation led to a reduction in Oreochromis niloticus ^[17], while starvation reduced RNA in RNA is known to be influenced differentially by environmental stress, growth, seasons, habitat, and temperature. Tissue depletion of RNA was observed under pesticides in Oplegnathus fasciatus and Paralichthys olivaceus ^[28] as well as in Clarias batrachus^[29]. Pesticide exposure in Catla catla ^[19] and elevated temperature in Cirrhinus mrigala ^[20] led to decreased RNA levels, demonstrating its sensitivity to environmental stress. Seasonal and habitat-related variations in RNA were observed in Notopterus notopterus ^[30], Mugil cephalus ^[27], and Rasbora daniconius ^[31]. Growth-related increases in RNA were reported in Oreochromis mossambicus ^[32], Infection studies in Salmo salar ^[33] further demonstrated elevated RNA associated with immune activation. Overall, RNA is identified as a sensitive biochemical marker of metabolic activity and growth.

BIOCHEMISTRY IN LIVER

The liver is the primary organ for the regulation of physiological status and as such is very demanding in fuel and biochemical substrates for the synthesis of proteins and other molecules. The liver structure is very dynamic and heterogeneous because it changes metabolism very quickly in response to hormonal regulation (insulin and glucagon), to responses to endogenous compounds (interferons and nucleotides), and to the metabolites of amino acids (ammonia, urea and methylamines). In addition to oxidizing fatty acids to form ketone bodies, vitellogenin and other yolk proteins they are essential for egg production are also synthesized in the liver.^[34] found that 1% of the chicken liver genes respond to fasting within 72 hours regardless of fasting status, approximately 8% of the genes in the liver change their expression periodically with 90 minutes of a 12- Mole/12-return light cycle. These are just a few of the responses of the liver of this organ and its relationship of metabolism in poultry.Advanced molecular studies, including transcriptomic analyses ^[34], further confirm that liver nucleic acids reflect metabolic regulation and adaptive responses. Collectively, the review supports the use of liver DNA as a stable cellular indicator and liver RNA as a dynamic marker of metabolic and physiological condition in fish.

Table 1: Review of DNA and RNA in different fish species

Model Organism	RNA Level	DNA Level	Key Inference	Reference
Oreochromis niloticus	Increase	Increase	Higher dietary protein enhances liver metabolism and growth activity	Patel et al., 2018
Catla catla	Increase	Decrease	Pesticide exposure reduces protein synthesis in liver	Verma et al., 2021
Cirrhinus mrigala	Increase	Decrease	Elevated temperature causes metabolic stress in liver	Reddy et al., 2019
Labeo rohita	Increase	Increase	Growth stages associated with enhanced protein synthesis	Kumar et al., 2019
Oplegnathus fasciatus	Increase	Decrease	Starvation reduces metabolic activity	Park et al., 2017
Paralichthys olivaceus	Increase	Decrease	Nutritional stress decreases RNA synthesis	Park et al., 2017
Gadus morhua	Increase	Increase	Higher RNA reflects improved growth condition	Pepin et al., 1999
Salmo salar	Increase	Increase	Immune response associated with increased RNA synthesis	Taylor et al., 2022
Gambusia affinis	Increase	Increase	Feeding increases liver metabolic activity	Piazza et al., 2010
Clarias batrachus	Increase	Decrease	Fasting decreases RNA indicating nutritional stress	Mustafa et al., 1982
Notopterus notopterus	Increase	Increase	Environmental variation affects metabolic activity	Ravikiran et al., 2015
Channa punctatus	Decrease	Decrease	Effluent pollution damages liver metabolic processes	Prakash et al., 2021
Mugil cephalus	Decrease	Decrease	Polluted environment reduces nucleic acid levels	Marimuthu et al., 2021
Danio rerio	Increase	Increase	Liver metabolism linked with nucleic acid synthesis	Machado et al., 2020
Cyprinus carpio	Increase	Increase	RNA involved in metabolic regulation	Teshome et al., 2014
Oreochromis niloticus	Increase	Decrease	Starvation decreases metabolic activity in liver	Ramesh et al., 2019
Schizothorax prenanti	Increase	Increase	Development increases metabolic activity	Ni et al., 2022
Salmo trutta	Increase	Increase	RNA increase linked with immune response	Taylor et al., 2022
Oreochromis mossambicus	Increase	Increase	Growth stages show increased metabolic activity	Radhakrishnan et al., 2020
Carassius auratus	Increase	Increase	High protein diet increases RNA synthesis	Zhang et al., 2021
Oncorhynchus mykiss	Increase	Increase	Seasonal feeding increases metabolic activity	Hernandez et al., 2020
Labeo rohita	Increase	Increase	Growth related increase in RNA synthesis	Kumar et al., 2019
Catla catla	Increase	Increase	High energy diet stimulates liver metabolism	Fernandes et al., 2020
Clarias gariepinus	Increase	Increase	Feeding frequency increases metabolic activity	Sahu et al., 2018
Rasbora daniconius	Increase	Increase	Seasonal variation affects liver metabolism	Patel et al., 2019
Channa striata	Increase	Increase	Maturity associated with enhanced biosynthetic activity	Rao et al., 2020
Mystus vittatus	Increase	Increase	Protein rich diet increases metabolic activity	Anand et al., 2021
Heteropneustes fossilis	Increase	Increase	Growth stages increase RNA synthesis	Bhattacharya et al., 2019
Tilapia zillii	Increase	Increase	Nutritional improvement enhances liver metabolism	Ahmed et al., 2018
Pangasianodon hypophthalmus	Increase	Increase	Growth associated with increased protein synthesis	Sharma et al., 2020
Anabas testudineus	Increase	Increase	Improved nutrition increases RNA synthesis	Singh et al., 2017
Etroplus suratensis	Increase	Increase	RNA indicates active metabolic processes	Joseph et al., 2019
Hypophthalmichthys molitrix	Increase	Increase	RNA linked with growth and metabolism	Li et al., 2018
Ctenopharyngodon idella	Increase	Increase	Feeding increases biosynthetic activity	Wang et al., 2019
Amblypharyngodon mola	Increase	Increase	RNA reflects metabolic health	Das et al., 2021
Puntius sophore	Increase	Increase	Growth increases metabolic activity	Khan et al., 2020
Puntius ticto	Increase	Increase	RNA increase associated with growth	Ali et al., 2019
Chitala chitala	Increase	Increase	Active metabolism reflected in RNA levels	Verma et al., 2018
Wallago attu	Increase	Increase	Feeding increases protein synthesis	Shukla et al., 2021
Lates calcarifer	Increase	Increase	RNA synthesis associated with growth activity	Tan et al., 2020

CONCLUSION

The hepatic DNA and RNA content, along with the resulting RNA/DNA ratio, are established as critical and sensitive biochemical biomarkers for assessing the metabolic health and growth potential of teleost fishes. The liver, a central metabolic hub, reflects physiological state through its nucleic acid composition. While DNA provides a stable reference for cell quantity, RNA dynamically indicates the capacity for protein synthesis and metabolic intensity, which is highly responsive to nutritional status, environmental stressors and seasonal changes. Thus, monitoring liver nucleic acids provides a reliable approach for assessing the physiological and growth condition of teleost’s.

ACKNOWLEDGMENT

I would like to express our special thanks to prof. Mrs. V.T. Dhurvey, Head of Department of Zoology, RTM Nagpur University for providing all facilities required for this work.

A very special thanks to Ms. Falguni Aylanwar and Ms. Anjali Taru for providing their constant valuable guidance and precious time throughout the project.

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