Blood changes of spontaneously ketotic cows before and four hours after administration of glucose, xylitol, 1,2-propanediol, or magnesium propionate

Hepatic metabolomics and transcriptomics to study susceptibility to ketosis in response to prepartal nutritional management

Background

Ketosis in dairy cows is associated with body fat mobilization during the peripartal period. Sub-clinical and clinical ketosis arise more frequently in cows that are overfed energy during the entire dry (last 50 to 45 days prior to parturition) or close-up period (last ~ 28 days prepartum).

Methods

A retrospective analysis was performed on 12 cows from a larger cohort that were fed a higher-energy diet [1.54 Mcal/kg of dry matter (DM); 35.9% of DM corn silage and 13% of DM ground corn] during the close-up dry period, of which 6 did not develop clinical ketosis (OVE, 0.83 mmol/L plasma hydroxybutyrate; BHB) and 6 were diagnosed with clinical ketosis (KET, 1.4 mmol/L BHB) during the first week postpartum. A whole-transcriptome bovine microarray (Agilent Technologies) and metabolomics (GC-MS, LC-MS; Metabolon® Inc.) were used to perform transcript and metabolite profiling of liver tissue harvested at − 10 days relative to parturition which allowed to establish potential associations between prepartal transcriptome/metabolome profiles and susceptibility to clinical ketosis postpartum.

Results

Cows in KET had greater (P = 0.01) overall body weight between − 2 and 1 week around parturition, but similar body condition score than OVE. Although dry matter intake (DMI) did not differ prepartum, KET cows had lower (P < 0.01) DMI and similar milk yield as OVE cows during the first week postpartum. Transcriptome analysis revealed a total of 3065 differentially expressed genes (DEG; P ≤ 0.05) in KET. Metabolomics identified 15 out of 313 total biochemical compounds significantly affected (P ≤ 0.10) in KET. Among those, greater concentrations (P ≤ 0.06, + 2.3-fold) of glycochenodeoxycholate in KET cows also have been detected in humans developing non-alcoholic fatty liver disease. Bioinformatics analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database and the DEG revealed that, among the top 20 most-impacted metabolic pathway categories in KET, 65% were overall downregulated. Those included ‘Metabolism of cofactors and vitamins’, ‘Biosynthesis of other secondary metabolites’, ‘Lipid’, ‘Carbohydrate’, and ‘Glycan biosynthesis and metabolism’. The lower relative concentration of glucose-6-phosphate and marked downregulation of fructose-1,6-bisphosphatase 2 and pyruvate dehydrogenase kinase 4 support a strong impairment in gluconeogenesis in prepartal liver of cows developing KET postpartum. Among the top 20 most-impacted non-metabolic pathways, 85% were downregulated. Pathways such as ‘mTOR signalling’ and ‘Insulin signalling’ were among those. ‘Ribosome’, ‘Nucleotide excision repair’, and ‘Adherens junctions’ were the only upregulated pathways in cows with KET.

Conclusions

The combined data analyses revealed more extensive alterations of the prepartal liver transcriptome than metabolome in cows overfed energy and developing ketosis postpartum. The causative link between these tissue-level adaptations and onset of clinical ketosis needs to be studied further.

Sugar alcohol sweeteners as alternatives to sugar with special consideration of xylitol

INTRODUCTION

Dental caries is a diet-associated disease which continues to be a serious health problem in most industrialized and developing countries. Strategies to maximize caries prevention should automatically consider the use of sugar substitutes. It is important that public health authorities are made cognizant of the availability of new polyol-type sugar substitutes.

REVIEW SUMMARY

Clinical studies have shown that xylitol, a natural, physiologic sugar alcohol of the pentitol type, can be used as a safe and effective caries-limiting sweetener. Habitual use of xylitol-containing food and oral hygiene adjuvants has been shown to reduce the growth of dental plaque, to interfere with the growth of caries-associated bacteria, to decrease the incidence of dental caries, and to be associated with remineralization of caries lesions. Numerous public regulatory bodies have endorsed the use of xylitol as a caries-limiting agent. Other sugar alcohols that have been successfully used as sugar substitutes include D-glucitol (sorbitol), which, however, owing to its hexitol nature, normally has no strong effect on the mass and adhesiveness of bacterial plaque and on the growth of mutans streptococci. A tetritol-type alditol, erythritol, has shown potential as a non-cariogenic sugar substitute. Combinations of xylitol and erythritol may reduce the incidence of caries more effectively than either alditol alone.

CONCLUSIONS

Partial sugar substitution with polyols is an important dietary tool in the prevention of dental caries that should be used to enhance existing fluoride-based caries prevention programmes. The most effective method of conveying this information to the public is through a proper health claim for these alditols in food labelling. The present review summarizes clinical and biochemical aspects of the above three dietary polyols and emphasizes the role of sugar substitution as a potential health-promoting strategy.

Invited review: pathology, etiology, prevention, and treatment of fatty liver in dairy cows

Fatty liver (i.e., hepatic lipidosis) is a major metabolic disorder of many dairy cows in early lactation and is associated with decreased health status and reproductive performance. In severe cases, milk production and feed intake are decreased. Therefore, a practical preventative or an efficacious treatment of fatty liver could save millions of dollars yearly in treatment, replacement, and production losses for dairy farmers. Fatty liver develops when the hepatic uptake of lipids exceeds the oxidation and secretion of lipids by the liver, which usually is preceded by high concentrations of plasma NEFA mobilized from adipose tissue. Excess lipids are stored as triacylglycerol in the liver and are associated with decreased metabolic functions of the liver. Liver can be categorized into normal liver or mild, moderate, or severe fatty liver; the latter can be subdivided further into nonencephalopathic severe fatty liver and hepatic encephalopathy. Insufficient or unbalanced dietary intake, obesity, and elevated estrogen concentrations are involved in the etiology of fatty liver, which is associated with greater incidence of dystocia, diseases, infections, and inflammations. Because even mild fatty liver is associated with decreased health status and reproductive performance of dairy cows, prevention of fatty liver by supplying cows with sufficient nutrients and a clean and health-promoting environment in the peripartal period would reduce production losses of cows more than would any treatment of fatty liver. This, however, might not be enough for cows that are obese or do not eat well, had calving difficulties or twins, have metabolic or infectious diseases, or are in severe negative energy balance because of high milk production immediately after calving. Potential and commonly used preventatives, as well as treatments, are discussed in the review. Currently, detection of fatty liver is possible only by minor surgery. Ultrasonic techniques offer a potential tool to noninvasively detect fatty liver. Future gene-array and proteomic studies may provide means to detect early molecular events in the etiology of fatty liver plus their connection with immune function and reproductive performance so that more effective treatments and preventatives of fatty liver can be developed. Such advances hopefully will make fatty liver a problem of the past.

Glucose and xylitol tolerance tests for ketotic and healthy dairy cows

Intravenous administration of 500 ml of 50% glucose solution to 10 nonketotic dairy cows increased the blood glucose and insulin concentrations 7-fold immediately following administration. Blood glucose and insulin concentrations of ketotic cows were about 6- and 3-fold higher, respectively, immediately following glucose administration. Administration of 1000 ml of 25% xylitol (xylo-pentane-1,2,3,4,5-pentol) in nonketotic cows increased blood glucose and insulin concentrations 2- and 9-fold, respectively. Ketotic cows treated with xylitol exhibited blood insulin concentration 12-fold higher following administration. This insulin increase might be explained by a decrease in insulin degradation because of the diffusion of xylitol, which is not dependent on insulin in peripheral tissues. For ketotic cows given xylitol, serum concentrations of free fatty acid decreased, and triglyceride concentrations and aspartic acid aminotransferase activity increased, but values were unchanged by xylitol administration to nonketotic cows. Thus, for ketotic cows, the responses of the blood glucose and insulin concentrations to xylitol administration were better than those responses to glucose administration. Improvements in clinical signs, i.e., disappearance of urinary ketone bodies and recovery to normal feed consumption, also suggested the usefulness of xylitol administration for the treatment of ketosis.

Therapeutic effects of simultaneous use of glucose and insulin in ketotic dairy cows

A glucose tolerance test was carried out on 8 ketotic dairy cows and 5 healthy dairy cows after injection of 500 ml of 50% glucose solution into the jugular vein. The blood insulin concentration increased from 6.3 microU/ml before glucose injection to 62.5 microU/ml after injection in the healthy group and from 3.0 to 22.9 microU/ml in the ketotic group. Insulin concentration before glucose injection was lower, and its increase after glucose injection was smaller, in the ketotic group. Five hundred milliliters of 50% glucose solution were administered to 15 ketotic cows by intravenous infusion once daily from d 1 to 6, and 200 U of insulin were injected subcutaneously in 8 of these cows from d 2 to 6. In the group administered insulin with glucose, the blood glucose concentration, insulin concentration, and insulin to glucagon ratio (50.5 mg/dl, 6.2 microU/ml, and .09, respectively) on d 6 were significantly higher than those for cows administered glucose only (36.3 mg/dl, 3.0 microU/ml, and .04, respectively). Also, the blood ketone bodies and free fatty acid concentrations on d 6 were significantly lower in the group receiving glucose plus insulin (22.1 microU/ml and .79 meq/L, respectively) than in the group receiving glucose alone (63.8 microU/ml and .98 meq/L, respectively). Thus, the simultaneous use of glucose and insulin is considered to be useful for the treatment of ketosis in dairy cows.

Therapy of diseases of ruminant intermediary metabolism

Diseases of intermediary metabolism include ketosis and fatty liver of dairy cattle and pregnancy toxemia of ewes. These conditions occur when there is a failure of the homeostatic mechanisms regulating the mobilization of fats and the conservation of carbohydrates. The therapeutic approach is to reestablish the normal homeostatic patterns of fuel utilization. Suppression of excessive ketogenesis is the most important factor in reestablishing homeostasis. Ketogenesis can be suppressed by a number of therapeutic agents that act either by suppressing the mobilization of fatty acids or by inhibiting the transport of fatty acids into the hepatic mitochondria, the site at which fatty acids are converted to ketone bodies. Useful therapies include bolus glucose infusions, glucose precursors, and glucocorticoids.

Clinical ketosis

A diagnosis of primary ketosis is based on clinical signs, clinical pathology, and ruling-out disorders that cause secondary ketosis. Various treatments can be used alone or in combination during the management of clinical ketosis. A treatment should be based on drugs with a mechanism of action that will eliminate the pathogenesis of the clinical signs observed.

Counteractive effects of propionate or 1,2-propanediol against hypoglycemia and ketonemia of tributyrin-treated cows

We administered tributyrin (500 ml), tributyrin (500 ml) plus magnesium propionate (400 g), tributyrin (500 ml) plus sodium propionate (400 g), or tributyrin (500 ml) plus 1,2-propanediol (400 ml) as a single dose into rumens of lactating cows and then measured in blood the plasma concentrations of glucose, acetoacetate, 3-hydroxybutyrate, free fatty acids, and insulin as a function of time. Tributyrin administration caused hypoglycemia and hyperketonemia similar to the ketotic condition in less than 3 h and was a negative correlation of --.88 between glucose and ketone concentrations in blood plasma. Administration of either magnesium propionate, sodium propionate, or 1,2-propanediol could counteract the hypoglycemia and hyperketonemia induced by tributyrin administration without significantly changing the insulin response. Of the two propionate compounds, magnesium propionate was more effective than sodium propionate for alleviating hypoglycemia and hyperketonemia.

Effect of propionic acid on ketogenesis in lactating sheep fed restricted rations or deprived of food

Propionic acid was used as a possible preventive agent against ketogenesis. A total of 12 Suffolk lactating sheep were allocated to groups of 4 and fed isocaloric isonitrogenous rations containing 0, 5 and 10% propionic acid for 2 wk at 1.25 kg twice daily, followed by 4 days of food restriction to .5 kg/day and 2 days of food deprivation to induce ketogenesis. During the restricted feeding, concentrations of glucose in blood plasma were higher (50 to 57 versus 41 to 53 mg/dl) and concentrations of D (--)-3-hydroxybutyrate and acetoacetate lower (3.0 to 5.9 versus 3.9 to 7.6 mg/dl; .39 to .83 versus .43 to .92 mg/dl) in animals fed propionic acid. Propionic acid did not change free fatty acid concentrations of blood plasma or milk and subcutaneous fatty acid composition. Restricted feeding and fasting markedly lowered glucose and elevated concentrations of ketone bodies and free fatty acids in plasma. Furthermore, during these periods proportions of milk fatty acids containing 4 to 14 carbon atoms were decreased and those of stearic and oleic acid (18:0 and 18:1) were increased (16.6 versus 6.5%; and 41.0 versus 17.4%).