Untargeted metabolomic profiling of serum from dogs with chronic hepatic disease

Changes in free amino acid profile in goats with pregnancy toxemia

Pregnancy toxemia is a metabolic disorder that afflicts goats when the heightened energy requirements preceding parturition are not sufficiently satisfied. At present, the potential association between pregnancy toxemia and the free amino acid composition in hair goats remains uncharted territory. The purpose of this study is to investigate the free amino acid profile in goats during the pivotal three weeks preceding delivery, distinguishing among those with subclinical pregnancy toxemia (SPT), clinical pregnancy toxemia (CPT), and those in the control group (CG). Additionally, the study aims to investigate any potential relationship between the amino acid profile and beta hydroxy butyric acid (BHBA) levels. The researchers analyzed a total of 50 goats, comprising 20 goats with SPT, 20 with CPT, and 10 in the CG. The serum free amino acid profile was determined using a gas chromatography flame ionization detector (GC-FID) device. BHBA concentration in goats with CPT and SPT was significantly higher than KG (p < 0.001). Furthermore, in goats with CPT, the glucose concentration was significantly lower than in CG (p < 0.012). In goats with CPT and SPT, the concentration of valine, one of the gluconeogenic amino acids, was significantly higher than in control group (p < 0.001), while histidine concentration was significantly lower (p < 0.020) than in control group. Specifically in goats with CPT, the concentrations of alanine (p < 0.002), serine (p < 0.001), and threonine (p < 0.043) were significantly lower than in control group. Moreover, the concentration of phenylalanine, which is both a glycogenic and ketogenic amino acid, was significantly lower (p < 0.028) in goats with SPT compared to the control group. The Fisher ratio (p < 0.010) and Glycine/Alanine ratio (p < 0.001) were significantly higher in pregnancy toxemia goats with than in control group goats, indicating a poor nutritional and energy status of the goats during the prepartum period. In summation, the findings of this study underscore that amino acids exhibiting marked concentration variations hold considerable promise in the diagnosis, prognosis, and therapeutic management of pregnancy toxemia.

Faecal metabolome responses to an altered dietary protein:carbohydrate ratio in adult dogs

High-protein diets may aid weight loss and weight maintenance programs in both humans and dogs, although the effect of dietary protein levels on gut metabolism and functionality has not been studied in depth. The current study aimed to investigate the effect of an altered dietary protein:carbohydrate ratio on gut function in adult dogs by means of faecal metabolomic fingerprinting. More specifically, functional metabolic differences in dogs fed a high-protein/low-carbohydrate (HPLC) vs. low-protein/high-carbohydrate (LPHC) diet were studied by equally allocating twelve clinically healthy (6 lean and 6 obese) Beagles into two groups in a cross-over design, with each group receiving two isocaloric diets for four weeks. The faecal metabolome revealed that different protein:carbohydrate ratio can influence host and/or gut microbiome metabolism and function, while no effect was observed on the body condition. Targeted analysis demonstrated that the HPLC diet significantly increased the concentration of indole, spermidine, and pipecolinic acid and decreased the concentration of azelaic acid, D-fructose, mannose, and galactose (p < 0.05). Multivariate modelling (OPLS-DA) of the untargeted faecal metabolome revealed distinctly different metabolomic profiles following the HPLC vs. LPHC diet, with 18 altered pathways. The HPLC diet influenced amino acid and lipid metabolism, potentially promoting weight loss and immune function, whereas the LPHC diet affected carbohydrate fermentation and may promote anti-oxidative function.

Serum Amino Acids Imbalance in Canine Chronic Hepatitis: Results in 16 Dogs

Simple Summary

Human chronic liver disease is reported to be associated with alterations in amino acids metabolism, with a decrease in serum branched-chain amino acids and an increase in aromatic amino acids. A decreased Fischer ratio (branched to aromatic amino acids ratio) has showed prognostic significance and is a therapeutic target in human cirrhosis. In dogs, few studies have been performed, and the Fischer ratio seems to be reduced in animals with congenital portosystemic shunts. The aim of this study was to evaluate serum amino acids in dogs with chronic hepatic inflammation compared with healthy dogs. The serum amino acids in dogs with chronic hepatitis were also evaluated in relation to their histological severity. Eighteen amino acidic metabolites were measured using the leftover serum samples of 16 dogs with histological chronic hepatitis and 25 healthy dogs. Several amino acid concentrations were significantly different between dogs diagnosed with chronic hepatitis and healthy controls. In human medicine, aromatic amino acids seem to increase during chronic hepatitis, whereas isoleucine decreases. The Fischer ratio was significantly reduced if higher grades of fibrosis were present. Even if total serum proteins did not significantly differ between groups, we observed qualitative imbalances in serum amino acids among dogs presenting with chronic hepatitis.

Abstract

In humans, chronic liver disease may cause alterations in amino acids (AAs) metabolism, with serum branched-chain AAs (BCAAs) decreasing and aromatic AAs (AAAs) increasing. A reduced Fischer ratio (BCAAs/AAAs) has been found to be associated with hepatic fibrosis and is useful for assessing prognosis in human patients. In veterinary medicine, few studies have been performed, and in contrast to human patients, dogs with different kinds of hepatopathy tend to show both increased AAAs and BCAAs. In dogs, the association between histological scores and serum AAs has not been previously investigated. The aim of this study was to evaluate serum AAs in dogs with chronic hepatitis (CH) compared with a healthy control group (C) and, among CH dogs, in relation to their histological fibrosis and necroinflammatory activity scores. Leftover serum samples of 16 dogs with histological CH and 25 healthy dogs were employed. Serum AAs were measured by high performance liquid chromatography. Proline and the AAAs phenylalaine and tyrosine progressively increased with the histological severity. In contrast, cysteine, tryptophan and BCAA isoleucine progressively reduced. Lysine and the BCAAs leucine and valine showed a non-linear trend with the histological findings. The BCAAs/AAAs ratio was significatively reduced if higher grades of liver fibrosis were present.

Metabolomic serum abnormalities in dogs with hepatopathies

Hepatopathies can cause major metabolic abnormalities in humans and animals. This study examined differences in serum metabolomic parameters and patterns in left-over serum samples from dogs with either congenital portosystemic shunts (cPSS, n = 24) or high serum liver enzyme activities (HLEA, n = 25) compared to control dogs (n = 64). A validated targeted proton nuclear magnetic resonance spectroscopy platform was used to assess 123 parameters. Principal component analysis of the serum metabolome demonstrated distinct clustering among individuals in each group, with the cluster of HLEA being broader compared to the other groups, presumably due to the wider spectrum of hepatic diseases represented in these samples. While younger and older adult control dogs had very similar metabolomic patterns and clusters, there were changes in many metabolites in the hepatopathy groups. Higher phenylalanine and tyrosine concentrations, lower branched-chained amino acids (BCAAs) concentrations, and altered fatty acid parameters were seen in cPSS dogs compared to controls. In contrast, dogs with HLEA had increased concentrations of BCAAs, phenylalanine, and various lipoproteins. Machine learning based solely on the metabolomics data showed excellent group classification, potentially identifying a novel tool to differentiate hepatopathies. The observed changes in metabolic parameters could provide invaluable insight into the pathophysiology, diagnosis, and prognosis of hepatopathies.

The Serum and Fecal Metabolomic Profiles of Growing Kittens Treated with Amoxicillin/Clavulanic Acid or Doxycycline

Simple Summary

This study investigated the impact of antibiotic treatment οn the serum and fecal metabolome (the collection of all small molecules produced by the gut bacteria and the host) of young cats. Thirty 2-month-old cats with an upper respiratory tract infection were treated with either amoxicillin/clavulanic acid for 20 days or doxycycline for 28 days. In addition, another 15 control cats that did not receive antibiotics were included. Blood was collected on days 0 (before treatment), 20/28 (last day of treatment), and 300 (10 months after the end of treatment), while feces were collected on days 0, 20/28, 60, 120, and 300. Seven serum and fecal metabolites differed between cats treated with antibiotics and control cats at the end of treatment period. Ten months after treatment, no metabolites differed from healthy cats, suggesting that amoxicillin/clavulanic acid or doxycycline treatment only temporarily affects the abundance of the serum and fecal metabolome.

Abstract

The long-term impact of antibiotics on the serum and fecal metabolome of kittens has not yet been investigated. Therefore, the objective of this study was to evaluate the serum and fecal metabolome of kittens with an upper respiratory tract infection (URTI) before, during, and after antibiotic treatment and compare it with that of healthy control cats. Thirty 2-month-old cats with a URTI were randomly assigned to receive either amoxicillin/clavulanic acid for 20 days or doxycycline for 28 days, and 15 cats of similar age were enrolled as controls. Fecal samples were collected on days 0, 20/28, 60, 120, and 300, while serum was collected on days 0, 20/28, and 300. Untargeted and targeted metabolomic analyses were performed on both serum and fecal samples. Seven metabolites differed significantly in antibiotic-treated cats compared to controls on day 20/28, with two differing on day 60, and two on day 120. Alterations in the pattern of serum amino acids, antioxidants, purines, and pyrimidines, as well as fecal bile acids, sterols, and fatty acids, were observed in antibiotic-treated groups that were not observed in control cats. However, the alterations caused by either amoxicillin/clavulanic acid or doxycycline of the fecal and serum metabolome were only temporary and were resolved by 10 months after their withdrawal.

Persistent hypercobalaminemia three months after successful gradual attenuation of extrahepatic shunts in dogs: a prospective cohort study

Background

Deficiencies in vitamin A and D and disorders in the vitamin B complex are often present in people with chronic liver diseases. So far, the serum concentrations of these vitamins have not yet been studied in dogs with congenital extrahepatic portosystemic shunts (EHPSS), who also have some degree of liver dysfunction. The objective was to assess serum vitamin concentrations in dogs with EHPSS from diagnosis to complete closure. A prospective cohort study was performed using ten client-owned dogs with EHPSS, closed after gradual surgical attenuation. Serum concentrations of vitamin A, 25-hydroxyvitamin D, folic acid, cobalamin and methylmalonic acid (MMA) were measured at diagnosis prior to institution of medical therapy, prior to surgery, and three months after gradual attenuation and complete closure of the EHPSS.

Results

At diagnosis, median serum concentrations of vitamin A, 25-hydroxyvitamin D and folic acid were 18.2 μg/dL (8.8 - 79.5 μg/dL), 51.8 ng/mL (19.4 - 109.0 ng/mL), and 8.1 μg/L (5.2 - 14.5 μg/L), respectively, which increased significantly postoperatively (88.3 μg/dL (51.6 - 182.2 μg/dL, P=0.005), 89.6 ng/mL (49.3 - >150.0 ng/mL, P =0.005), and 14.8 μg/L (11.5 - 17.7 μg/L, P <0.001), respectively). Median serum cobalamin concentrations were 735.5 ng/L (470 - 1388 ng/L) at diagnosis and did not significantly decrease postoperatively (P =0.122). Both at diagnosis and three months postoperatively 7/10 dogs had hypercobalaminemia.

Conclusions

Serum concentrations of vitamin A, 25-hydroxyvitamin D and folic acid significantly increase after surgical attenuation. Nevertheless, persistent hypercobalaminemia is suggestive of ongoing liver dysfunction, despite successful surgery.

Approach to the Diagnosis of Hepatocutaneous Syndrome in Dogs: A Retrospective Study and Literature Review

Superficial necrolytic dermatitis (SND) is a rare and often fatal disease in dogs that has been associated with pancreatic neuroendocrine neoplasia (SND/EN) and hepatocutaneous syndrome (SND/HCS). Although various combinations of diagnostics have been used to differentiate these two causes of SND, there are currently no data on which combination would enable the most timely and noninvasive way to diagnose HCS. Medical records were reviewed retrospectively (2004-2018) for dogs with SND/HCS (n = 24) and SND/EN (n = 1). These data were compared with cases found by review of the literature of dogs with SND/HCS (n = 105) and SND/EN (n = 13). The most consistent findings with SND were dermatological lesions affecting paw pads or mucocutaneous junctions (143/143, 100%) and marked plasma hypoaminoacidemia (58/58, 100%). On ultrasound, a honeycomb liver was seen in 62/63 (98%) dogs with SND/HCS but none with SND/EN. Six out of 23 (26%) dogs in the retrospective study with SND/HCS had marked keratinocyte apoptosis, a finding that was associated with diabetes mellitus. This study suggests that in dogs with characteristic skin lesions, an amino acid profile permits a noninvasive diagnosis of SND. An abdominal ultrasound can then assist in the differentiation of SND/HCS and SND/EN.

A novel canine nuclear magnetic resonance spectroscopy-based metabolomics platform: Validation and sample handling

BACKGROUND

Metabolomics has been proven to be an invaluable research tool by providing comprehensive insight into systemic metabolism. However, the lack of scalable and quantitative methods with known reference intervals (RIs) and documented reproducibility has prevented the use of metabolomics in the clinical setting.

OBJECTIVE

The objective of this study was to validate the developed quantitative nuclear magnetic resonance (NMR) spectroscopy-based metabolomics platform for canine serum and plasma samples and determine optimal sample handling conditions for its use.

METHODS

Altogether, 8247 canine samples were analyzed using a Bruker's 500 MHz NMR spectrometer. Using statistical approaches derived from international guidelines, we studied method precision, measurand stability in various long- and short-term storage conditions, as well as the effect of prolonged contact with red blood cells (RBCs), and differences among blood collection tubes. We also screened interferences with lipemia, hemolysis, and bilirubinemia. The results were compared against routine clinical chemistry methods, and RIs were defined for all measurands.

RESULTS

We determined RIs for 123 measurands, most of which were previously unpublished. The reproducibility of the results of the NMR platform appeared generally outstanding, and the integrity of the results can be ensured by following standard blood drawing and processing guidelines.

CONCLUSIONS

Owing to the advantages of quantitative results, high reproducibility, and scalability, this canine metabolomics platform holds great potential for numerous clinical and research applications to improve canine health and well-being.

Plasma amino acid profiles in dogs with closed extrahepatic portosystemic shunts are only partially improved 3 months after successful gradual attenuation

BACKGROUND

Dogs with portosystemic shunts have an altered blood amino acid profile, with an abnormal branched-chained amino acid (BCAA)-to-aromatic amino acid (AAA) ratio being the most common abnormality. Different liver diseases have distinctive amino acid profiles.

OBJECTIVES

Determine the changes in plasma amino acid profiles in dogs with extrahepatic portosystemic shunts (EHPSS) from diagnosis to complete closure.

ANIMALS

Ten client-owned dogs with EHPSS closed after surgical attenuation.

METHODS

Prospective cohort study. Medical treatment was instituted in dogs diagnosed with EHPSS. At least 4 weeks later, gradual surgical attenuation was performed. Three months postoperatively, EHPSS closure was confirmed by transsplenic portal scintigraphy. Clinical signs were scored and blood was taken before institution of medical treatment, at time of surgery, and 3 months postoperatively. At the end of the study, the plasma amino acid profiles were analyzed in batch.

RESULTS

The median BCAA-to-AAA ratio was extremely low (0.6) at time of diagnosis and remained low (0.5) at time of surgery, despite the fact that median neurological score significantly improved from 22 to 2 after starting medical treatment (P = .04). Three months after surgical attenuation, a significantly higher BCAA-to-AAA ratio (1.5) was observed (P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Medical treatment does not improve the BCAA-to-AAA ratio in dogs with EHPSS, despite substantial clinical improvement. Although the ratio significantly increased after EHPSS closure, it was still indicative of moderate to severe hepatic dysfunction in all dogs.

Untargeted metabolomic profiling of serum in dogs with hypothyroidism

Hypothyroidism is one of the most commonly diagnosed endocrine disease in dogs. The clinical signs are caused by a deficiency of the active thyroid hormones triiodothyronine (T3) and thyroxine (T4) and have a negative impact on dog's quality of life. We hypothesized that serum metabolic profile varies between healthy dogs and dogs with hypothyroidism. Twenty serum samples from dogs with hypothyroidism and 20 from healthy dogs were used for untargeted metabolomics analysis performed by LC/MS analysis. Fifteen metabolites showed significant changes between hypothyroid and healthy dogs, being the pentose phosphate pathway (PPP), aminoacyl-tRNA biosynthesis and pyrimidine metabolism the principal pathways altered in hypothyroidism. Specifically, metabolites such as D-gluconic acid and L-Isoleucine may potentially act as biomarkers of disease.

Untargeted metabolomic profiling of serum from dogs with chronic hepatic disease

Background

Chronic hepatopathies present a diagnostic challenge, with different diseases being associated with similar clinical and laboratory findings. Characterization of dogs with chronic hepatopathies can be difficult and require costly diagnostic procedures such as acquisition of a liver biopsy specimen. Noninvasive and inexpensive biomarkers that reliably characterize chronic hepatopathies such as chronic hepatitis or a congenital portosystemic vascular anomaly may decrease the need for costly or invasive diagnostic testing and guide novel therapeutic interventions.

Objective

To investigate differences in the serum metabolome among healthy dogs, dogs with congenital portosystemic shunts, and dogs with chronic hepatitis.

Animals

Stored serum samples from 12 healthy dogs, 10 dogs with congenital portosystemic shunts, and 6 dogs with chronic hepatitis were analyzed.

Methods

The serum metabolome was analyzed with an untargeted metabolomics approach using gas chromatography–quadrupole time of flight mass spectrometry.

Results

Principal component analysis and heat dendrogram plots of the metabolomics data showed clustering among individuals in each group. Random forest analysis showed differences in the abundance of various metabolites including increased aromatic amino acids and xylitol in dogs with congenital portosystemic shunts. Based on the univariate statistics, 50 metabolites were significantly different among groups.

Conclusions and Clinical Importance

The serum metabolome varies among healthy dogs, dogs with congenital portosystemic shunts, and dogs with chronic hepatitis. Statistical analysis identified several metabolites that differentiated healthy dogs from dogs with vascular or parenchymal liver disease. Further targeted assessment of these metabolites is needed to confirm their diagnostic reliability.