Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PROPIONATES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
PubMed2002

Propionate formation by Opitutus terrae in pure culture and in mixed culture with a hydrogenotrophic methanogen and implications for carbon fluxes in anoxic rice paddy soil.

Propionate-forming bacteria seem to be abundant in anoxic rice paddy soil, but biogeochemical investigations show that propionate is not a correspondingly important intermediate in carbon flux in this system. Mixed cultures of Opitutus terrae strain PB90-1, a representative propionate-producing bacterium from rice paddy soil, and the hydrogenotrophic Methanospirillum hungatei strain SK maintained hydrogen partial pressures similar to those in the soil. The associated shift away from propionate formation observed in these cultures helps to reconcile the disparity between microbiological and biogeochemical studies.

Anaerobiosis↗
PubMed2003

Metabolic pathway for propionate utilization by phosphorus-accumulating organisms in activated sludge: 13C labeling and in vivo nuclear magnetic resonance.

In vivo 13C and 31P nuclear magnetic resonance techniques were used to study propionate metabolism by activated sludge in enhanced biological phosphorus removal systems. The fate of label supplied in [3-13C]propionate was monitored in living cells subjected to anaerobic/aerobic cycles. During the anaerobic phase, propionate was converted to polyhydroxyalkanoates (PHA) with the following monomer composition: hydroxyvalerate, 74.2%; hydroxymethylvalerate, 16.9%; hydroxymethylbutyrate, 8.6%; and hydroxybutyrate, 0.3%. The isotopic enrichment in the different carbon atoms of hydroxyvalerate (HV) produced during the first anaerobic stage was determined: HV5, 59%; HV4, 5.0%; HV3, 1.1%; HV2, 3.5%; and HV1, 2.8%. A large proportion of the supplied label ended up on carbon C-5 of HV, directly derived from the pool of propionyl-coenzyme A (CoA), which is primarily labeled on C-3; useful information on the nature of operating metabolic pathways was provided by the extent of labeling on C-1, C-2, and C-4. The labeling pattern on C-1 and C-2 was explained by the conversion of propionyl-CoA to acetyl-CoA via succinyl-CoA and the left branch of the tricarboxylic acid cycle, which involves scrambling of label between the inner carbons of succinate. This constitutes solid evidence for the operation of succinate dehydrogenase under anaerobic conditions. The labeling in HV4 is explained by backflux from succinate to propionyl-CoA. The involvement of glycogen in the metabolism of propionate was also demonstrated; moreover, it was shown that the acetyl moiety to the synthesis of PHA was derived preferentially from glycogen. According to the proposed metabolic scheme, the decarboxylation of pyruvate is coupled to the production of hydrogen, and the missing reducing equivalents should be derived from a source other than glycogen metabolism.

Aerobiosis↗
PubMed1978

Pathway of succinate and propionate formation in Bacteroides fragilis.

Cell suspensions of Bacteroides fragilis were allowed to ferment glucose and lactate labeled with (14)C in different positions. The fermentation products, propionate and acetate, were isolated, and the distribution of radioactivity was determined. An analysis of key enzymes of possible pathways was also made. The results of the labeling experiments showed that: (i) B. fragilis ferments glucose via the Embden-Meyerhof pathway; and (ii) there was a randomization of carbons 1, 2, and 6 of glucose during conversion to propionate, which is in accordance with propionate formation via fumarate and succinate. The enzymes 6-phosphofrucktokinase (pyrophosphate-dependent), fructose-1,6-diphosphate aldolase, phosphoenolpyruvate carboxykinase, malate dehydrogenase, fumarate reductase, and methylmalonyl-coenzyme A mutase could be demonstrated in cell extracts. Their presence supported the labeling results and suggested that propionate is formed from succinate via succinyl-, methylmalonyl-, and propionyl-coenzyme A. From the results it also is clear that CO(2) is necessary for growth because it is needed for the formation of C4 acids. There was also a randomization of carbons 1, 2, and 6 of glucose during conversion to acetate, which indicated that pyruvate kinase played a minor role in pyruvate formation from phosphoenolpyruvate. Phosphoenolpyruvate carboxykinase, oxaloacetate decarboxylase, and malic enzyme (nicotinamide adenine dinucleotide phosphate-dependent) were present in cell extracts of B. fragilis, and the results of the labeling experiments agreed with pyruvate synthesis via oxaloacetate and malate if these acids are in equilibrium with fumarate. The conversion of [2-(14)C]- and [3-(14)C]lactate to acetate was not associated with a randomization of radioactivity.

Acetates↗
PubMed1997

Propionate catabolism in Salmonella typhimurium LT2: two divergently transcribed units comprise the prp locus at 8.5 centisomes, prpR encodes a member of the sigma-54 family of activators, and the prpBCDE genes constitute an operon.

We present the initial genetic and biochemical characterization of the propionate (prp) locus at 8.5 centisomes of the Salmonella typhimurium LT2 chromosome (T. A. Hammelman et al., FEMS Microbiol. Lett. 137: 233-239, 1996). In this paper, we report the nucleotide sequences of two divergently transcribed transcriptional units. One unit is comprised of the prpR gene (1,626 bp) encoding a member of the sigma-54 family of transcriptional activators; the second unit contains an operon of four genes designated prpB (888 bp), prpC (1,170 bp), prpD (1,452 bp), and prpE (1,923 bp). The heme biosynthetic gene hemB was shown by DNA sequencing to be located immediately downstream of the prpBCDE operon; hemB is divergently transcribed from prpBCDE and is separated from prpE by a 66-bp gap. In addition, we demonstrate the involvement of PrpB, PrpC, and PrpD in propionate catabolism by complementation analysis of mutants using plasmids carrying a single prp gene under the control of the arabinose-responsive P(BAD) promoter. Expression of prpB to high levels was deleterious to the growth of a prp+ strain on minimal medium supplemented with propionate as a carbon and energy source. We also report the cloning and overexpression of prpB, prpC, prpD, and prpE in the T7 system. PrpB, PrpC, PrpD, and PrpE had molecular masses of ca. 32, ca. 44, ca. 53, and ca. 70 kDa, respectively. PrpB showed homology to carboxyphosphonoenolpyruvate phosphonomutase of Streptomyces hygroscopicus and to its homolog in the carnation Dianthus caryophyllus; PrpC was homologous to both archaeal and bacterial citrate synthases; PrpD showed homology to yeast and Bacillus subtilis proteins of unknown function; PrpE showed homology to acetyl coenzyme A synthetases. We identified a sigma-54 (RpoN)-dependent promoter with a consensus RpoN binding site upstream of the initiating methionine codon of prpB, the promoter-proximal gene of the prp operon. Consistent with this finding, an rpoN prp+ mutant failed to use propionate as carbon and energy source. Finally, we report the location of MudI1734 elements inserted in prpC or prpD and of a Tn10delta16delta17 element in prpB and provide genetic evidence supporting the conclusion that the prpBCDE genes constitute an operon.

Amino Acid Sequence↗
PubMed1999

Salmonella typhimurium LT2 catabolizes propionate via the 2-methylcitric acid cycle.

We previously identified the prpBCDE operon, which encodes catabolic functions required for propionate catabolism in Salmonella typhimurium. Results from (13)C-labeling experiments have identified the route of propionate breakdown and determined the biochemical role of each Prp enzyme in this pathway. The identification of catabolites accumulating in wild-type and mutant strains was consistent with propionate breakdown through the 2-methylcitric acid cycle. Our experiments demonstrate that the alpha-carbon of propionate is oxidized to yield pyruvate. The reactions are catalyzed by propionyl coenzyme A (propionyl-CoA) synthetase (PrpE), 2-methylcitrate synthase (PrpC), 2-methylcitrate dehydratase (probably PrpD), 2-methylisocitrate hydratase (probably PrpD), and 2-methylisocitrate lyase (PrpB). In support of this conclusion, the PrpC enzyme was purified to homogeneity and shown to have 2-methylcitrate synthase activity in vitro. (1)H nuclear magnetic resonance spectroscopy and negative-ion electrospray ionization mass spectrometry identified 2-methylcitrate as the product of the PrpC reaction. Although PrpC could use acetyl-CoA as a substrate to synthesize citrate, kinetic analysis demonstrated that propionyl-CoA is the preferred substrate.

Carbon Isotopes↗
PubMed1969

Role of pyruvate metabolism in the growth of Streptococcus faecalis in the presence of propionate.

The growth of Streptococcus faecalis is inhibited by propionate, and the inhibition is reversed by lipoic acid or acetate. A study of the role of pyruvate oxidation in S. faecalis showed that propionate inhibited the lipoic acid-dependent aerobic oxidation of pyruvate in resting cells. Pyruvate dehydrogenation with neotetrazolium as a hydrogen acceptor in cell-free extracts also required lipoic acid and was markedly inhibited by propionyl phosphate as well as sodium propionate. Some lipid substances, such as palmitate, oleate, behenate, and lecithin, had a lipoic acid-replacing effect on growth of the organism. Biotin or bicarbonate promoted the lipoic acid-dependent growth. Acetate-2-(14)C added to the medium was mainly incorporated into the lipid fraction of the cells. Evolution of (14)CO(2) from pyruvate-2-(14)C was not observed in resting cells of the organism, even under aerobic conditions. From the above findings, it is concluded that lipid synthesis through pyruvate oxidation plays a very important role in bacterial growth in medium containing propionate.

Acetates↗
PubMed1993

14C-labeled propionate metabolism in vivo and estimates of hepatic gluconeogenesis relative to Krebs cycle flux.

Purposes of this study were 1) to estimate in humans, using 14C-labeled propionate, the rate of hepatic gluconeogenesis relative to the rate of Krebs cycle flux; 2) to compare those rates with estimates previously made using [3-14C]lactate and [2-14C]acetate; 3) to determine if the amount of ATP required for that rate of gluconeogenesis could be generated in liver, calculated from that rate of Krebs cycle flux and splanchnic balance measurements, previously made, and 4) to test whether hepatic succinyl-CoA is channeled during its metabolism through the Krebs cycle. [2-14C]propionate, [3-14C]-propionate, and [2,3-14C]succinate were given along with phenyl acetate to normal subjects, fasted 60 h. Distributions of 14C were determined in the carbons of blood glucose and of glutamate from excreted phenylacetylglutamine. Corrections to the distributions for 14CO2 fixation were made from the specific activities of urinary urea and the specific activities in glucose, glutamate, and urea previously found on administering [14C]-bicarbonate. Uncertainties in the corrections and in the contributions of pyruvate and Cori cyclings limit the quantitations. The rate of gluconeogenesis appears to be two or more times the rate of Krebs cycle flux and pyruvate's decarboxylation to acetyl-CoA, metabolized in the cycle, less than one-twenty-fifth the rate of its decarboxylation. Such estimates were previously made using [3-14C]lactate. The findings support the use of phenyl acetate to sample hepatic alpha-ketoglutarate. Ratios of specific activities of glucose to glutamate and glucose to urinary urea and expired CO2 indicate succinate's extensive metabolism when presented in trace amounts to liver. Utilizations of the labeled compounds by liver relative to other tissues were in the order succinate = lactate > propionate > acetate. ATP required for gluconeogenesis and urea formation was approximately 40% of the amount of ATP generated in liver. There was no channeling of succinyl-CoA in the Krebs cycle in the hepatic mitochondria.

Adult↗
PubMed1980

Failure of the normal ureagenic response to amino acids in organic acid-loaded rats. Proposed mechanism for the hyperammonemia of propionic and methylmalonic acidemia.

Propionic and methylmalonic acidemia are both known to be associated with hyperammonemia. Rats injected with 10 or 20 mmol/kg of propionate or 20 mmol/kg of methylmalonate, along with 1.5 g/kg of a mixture of amino acids, developed severe hyperammonemia, whereas rats administered the same dosages of acetate did not. In vitro, neither propionyl nor methylmalonyl CoA affected the activity of carbamyl phosphate synthetase I, ornithine transcarbamylase, nor the activation constant (K(A)) of carbamyl phosphate synthetase I for N-acetyl glutamate. Furthermore, rats injected with propionate showed no alteration of liver amino acid concentrations, which could explain impaired ureagenesis. Animals injected with methylmalonate showed an increase in both citrulline and aspartate, suggesting that argininosuccinic acid synthetase may also have been inhibited. Liver ATP levels were unchanged. Citrullinogenesis, measured in intact mitochondria from livers of injected animals, was reduced 20-25% by 20 mmol/kg of propionate or methylmalonate (compared with acetate). This effect was attributable to an impairment in the normal rise of liver N-acetyl glutamate content after amino acid injection. Thus, carbamyl phosphate synthetase I activation was reduced. Liver levels of acetyl CoA and free CoA were reduced. Levels of unidentified acyl CoA derivatives rose, presumably reflecting the accumulation of propionyl and methylmalonyl CoA. Thus, the principal mechanism for hyperammonemia induced by these acids is depletion of liver N-acetyl glutamate, which is in turn attributable to depletion of acetyl CoA and/or competitive inhibition by propionyl and methylmalonyl CoA of N-acetyl glutamate synthetase. Injection of methylmalonate may also have an additional inhibitory effect on argininosuccinic acid synthetase.

Acyl Coenzyme A↗
PubMed1976

Effect of propionic acid on fatty acid oxidation and ureagenesis.

Propionic acid significantly inhibited 14CO2 production from [1-14C] palmitate at a concentration of 10 muM in control fibroblasts and 100 muM in methylmalonic fibroblasts. This inhibition was similar to that produced by 4-pentenoic acid. Methylmalonic acid also inhibited 14CO2 production from [1-14C] palmitate, but only at a concentration of 1 mM in control cells and 5 mM in methylmalonic cells. Propionic acid (5 mM) also inhibited ureagenesis in rat liver slices when ammonia was the substrate but not with aspartate and citrulline as substrates. Propionic acid had no direct effect on either carbamyl phosphate synthetase or ornithine transcarbamylase. These findings may explain the fatty degeneration of the liver and the hyperammonemia in propionic and methylmalonic acidemia.

Ammonia↗
PubMed1989

[Studies on the beneficial effect of levocarnitine chloride (LC-80) on organic acidemias, especially propionic acidemia and methylmalonic acidemia].

The beneficial effect of LC-80 in the therapy for organic acidemias, especially propionic acidemia and methylmalonic acidemia, was compared with those of its optical isomers, d-carnitine chloride (d-isomer) and dl-carnitine chloride (dl-isomer) in rat liver mitochondria. LC-80 at concentrations of 5 and 10 mM did not inhibit the mitochondrial function, while the d-isomer at a concentration of 5 mM significantly reduced the respiratory control ratio (RCR) of mitochondria. In addition, the dl-isomer at concentrations of 10 and 20 mM also significantly reduced RCR in a concentration-dependent manner. Thus, it seems likely that the d-isomer inhibits the mitochondrial function. On the other hand, the inhibition of mitochondrial function induced by a preincubation with propionate (4.76 mM) was significantly reversed by LC-80 (5 and 10 mM) in a concentration-dependent manner, while the d-isomer (5 mM) had no effect on the inhibitory effect of propionate. Moreover, although the dl-isomer (10 and 20 mM) significantly reversed the inhibitory effect of propionate as compared with the d-isomer, its effect was significantly weaker as compared with the effect of LC-80. The substrate specificity of rat liver mitochondrial carnitine acetyltransferase (CAT) was more potent with propionyl CoA than with acetyl CoA. Kinetic studies indicate that the d-isomer is a competitive inhibitor of CAT. These results suggest that LC-80 is useful in the clinical treatment of organic acidemias, whereas the d-isomer has a harmful effect in clinical application.

Amino Acid Metabolism, Inborn Errors↗
PubMed1982

Comparison of cytosolic and mitochondrial enzyme alterations in the livers of propionic or methylmalonic acidemia: a reduction of cytochrome oxidase activity.

The activities of mitochondrial, cytosolic and microsomal enzymes in liver specimens obtained from three patients with propionic or methylmalonic acidemia were compared with those of control patients who had died from unrelated causes. Only the activity of cytochrome oxidase (mitochondrial enzyme) was significantly reduced in the patients of propionic acidemia and methylmalonic acidemia who were in the state of metabolic acidosis; in two patients the activity was less than 30% of that in controls, but in the other patient of propionic acidemia, who was under the treatment with a low protein diet (0.8 g/kg/day), the activity was 50% of that in controls. The metabolites of branched chain amino acids (tiglic acid, propionic acid, methylmalonic acid, succinic acid, tiglyl-CoA and propionyl CoA) exhibited no inhibitory effect on the cytochrome oxidase activity of the sonicated rat liver mitochondria. The reduction of cytochrome oxidase activity found in these organic acidemias may be caused secondarily by some unknown mechanism.

Amino Acid Metabolism, Inborn Errors↗
PubMed2026

Prognostic value of genes associated with metastasis and propionate metabolism in rectal cancer.

BACKGROUND: Research indicates that alterations in propionate metabolic pathways play a critical role in cancer development and invasion. Postoperative metastatic recurrence remains a major cause of mortality in patients with rectal cancer. However, propionate metabolism-related genes (PMRGs) in rectal cancer remain insufficiently characterized. Therefore, this study aimed to identify prognostic biomarkers associated with lymph node metastasis and propionate metabolism and construct a risk‑prediction model for rectal cancer via bioinformatic analyses. METHODS: The Cancer Genome Atlas-Rectum Adenocarcinoma (TCGA-READ) and GSE87211 datasets, together with a curated PMRGs gene set, were used in this study. Pearson correlation analysis was performed to assess associations between overlapping genes (differentially expressed genes between READ and normal tissues, as well as between N0 and N1-N2 stages) and PMRGs, leading to the identification of candidate genes. Functional enrichment analyses were subsequently conducted to characterize the biological roles of these candidates. Prognostic biomarkers were identified using univariate Cox regression combined with least absolute shrinkage and selection operator (LASSO) regression, and a prognostic model was constructed accordingly. Independent prognostic validation was then performed. In addition, immune checkpoint profiling and immunotherapy response analyses were conducted across risk subgroups. Single-gene Gene Set Enrichment Analysis (GSEA) was applied to elucidate the pathways associated with the identified biomarkers. Finally, drug sensitivity analyses were performed. RESULTS: A total of 157 candidate genes were identified through the analytical pipeline. Functional enrichment analysis indicated that these genes were primarily involved in inflammatory response regulation and tumor necrosis factor (TNF) signaling pathways. Five prognostic biomarkers were subsequently identified and incorporated into a predictive model. External validation using the GSE87211 cohort confirmed the robustness of the model. Risk score and disease status were identified as independent prognostic factors. Six immune checkpoint molecules exhibited differential expression between risk groups. Correlation analyses revealed that the risk score was positively associated with most immune checkpoint genes. Single-gene GSEA demonstrated that the biomarkers were mainly enriched in ribosomal biogenesis and cell adhesion molecule-related pathways. Furthermore, 51 therapeutic agents exhibited significantly different half-maximal inhibitory concentration (IC50) values between risk subgroups. CONCLUSIONS: This study identified five biomarkers (CCL24, IGFBP3, ODC1, PYGM, and VKORC1) associated with lymph node metastasis and propionate metabolism pathways, providing a potential foundation for prognostic prediction in patients with rectal cancer.

Rectal cancer↗
PubMed1994

Influence of a propionate load in fed or unfed lambs on blood metabolites and hormone patterns.

Six crossbred wether lambs were used in a crossover design to determine the effects of a 3-d feed and water deprivation period on metabolite and hormonal response to a propionate load. During each period of the crossover design all lambs were limit-fed (700 g/d) a 36% concentrate diet for 16 d, then three of the six lambs were deprived of feed and water for 3 d. All lambs were then limit-fed (700 g/d) the 36% concentrate diet (realimentation). Propionate loading tests were performed 4 h before feeding on d 1, 5, and 9 of the realimentation period. A 1.84 M propionate solution (3 mmol/kg BW) was infused into the right jugular vein and blood samples were obtained from the left jugular vein at intervals for 4 h after infusion. At the end of the 3-d feed and water deprivation period, fed lambs had greater serum insulin (P < .02), acetate (P < .01), and glucose (P < .05) concentrations and lower plasma-free fatty acids (P < .01) and urea N (P < .05) concentrations than unfed lambs. On d 1 of realimentation, previously unfed lambs had greater postinfusion growth hormone (P < .05), free fatty acid (P < .01), propionate (P < .07), lactate (P < .04), and urea N (P < .05) concentrations and lower serum insulin (P < .02), and acetate (P < .03) concentrations than fed lambs. Serum prolactin concentrations increased (P < .02) postinfusion in unfed lambs but not in fed lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1982

Effect of factor B on vitamin B12 status and propionate metabolism in sheep.

Growing lambs fed diets containing two concentrations of Co (basal and basal plus 1 ppm) were injected with Factor B (cobinamide) or saline during an 8-wk trial conducted to determine the effects of Factor B on liver B12 levels and on propionate metabolism. At the end of the trial, lambs given Factor B had lower (P less than .05) liver vitamin B12 concentrations and higher (P less than .05) Factor B concentrations than controls fed the high Co diet. The high Co diet did not enhance liver B12 levels in the lambs treated with Factor B. Feed intake and body weight gain were not significantly affected by treatment. Plasma propionate increased (P less than .05) with time on experiment, and concentrations during the final period were negatively correlated (r = -.45; P less than .05) with liver B12 levels. When the lambs were loaded with propionate, a similar correlation (r = -.59; P less than .05) was observed between log plasma level at t = 20 and liver B12 levels. Liver B12 levels (.2 to 1.1 micrograms/g) were all within what is usually considered a normal range. . No significant relationship between plasma propionate and liver Factor B levels were observed.

Acetates↗
PubMed1984

Acetate and propionate production in the cecum and proximal colon of lambs.

A modified single-injection isotope dilution technique measured acetate and propionate production rates in the cecum and proximal colon of 14 lambs fed a forage (hay) or high corn (concentrate) diet. The modified isotope dilution appeared to have merit. Volatile fatty acid pool sizes were stable and apparently absorption of fermentation products occurred to prevent end product inhibition. Propionate pool sizes were greater (P less than .01) while acetate pool sizes were not significantly greater when lambs received the concentrate diet. Apparent acetate production was higher (P less than .05) in lambs fed the concentrate diet than in forage-fed lambs (239.4 vs 189.5 mmol/d, respectively). Apparent propionate production was also greater (P less than .01) when lambs were fed the concentrate diet rather than the forage diet (431.4 vs 180.7 mmol/d, respectively). These results indicate that acetate and propionate produced in the cecum and proximal colon may be a considerable source of energy and glucose precursors for the growing lamb.

Acetates↗
PubMed2000

Microbial populations, fermentation end-products, and aerobic stability of corn silage treated with ammonia or a propionic acid-based preservative.

We studied the effects of ammonia treatment on microbial populations during the fermentation of corn silage. We also compared the effects of ammonia to a preservative containing buffered propionic acid and other antifungal compounds on the fermentation and aerobic stability of corn silage. In the first experiment, whole-plant corn was ensiled without treatment or treated with ammonia-N to supply an additional 0.3% N (fresh-forage basis). The addition of ammonia immediately increased silage pH and had no effect on numbers of lactic acid bacteria, but delayed their growth compared with untreated silage. Numbers of enterobacteria declined more slowly, but numbers of yeasts and molds declined more quickly in silage treated with ammonia. During the early stages of ensiling, lactic acid increased more rapidly in untreated than in treated silage. The reverse was true for acetic acid concentrations. When exposed to air, growth of yeasts and molds was delayed in ammonia-treated silage. In a second experiment, various levels (0.1 to 0.3%, fresh weight) of ammonium-N or a preservative with buffered propionic acid were added to whole-plant corn and allowed to ensile for 106 d. Silage treated with ammonia had a greater ratio of L- to D-lactic acid than did other silages. Untreated silage was aerobically stable for 32.3 h, whereas the low (42 h) and moderate (52.7 h) concentrations of both additives numerically improved aerobic stability. High concentrations of ammonia-N (0.3%) or a buffered propionic acid preservative (0.3%), markedly improved the aerobic stability of corn silage (82 and 69 h for ammonia and propionic acid-treated silage, respectively).

Ammonia↗
PubMed1983

Propionate for fatty acid synthesis by the mammary gland of the lactating goat.

Isolated mammary glands of lactating goats were perfused with heparinized and oxygenated blood for 8 to 15 h. Adequate quantities of glucose, acetate, and amino acid were added to the perfusate. After addition of propionate to the perfusion blood, concentrations of odd-numbered and of monomethyl-substituted fatty acids other than those with iso and anteiso configuration increased in the milk fat. These acids seem to be synthesized de novo in the mammary gland. The increase of C17:0 concentration was weak and problematic. We suggest that propionate is acting as a precursor for monomethyl-substituted fatty acids by way of methylmalonyl-CoA. The activating effect of propionate administration upon milk fatty acid production was largest for odd-numbered followed by monomethyl-substituted fatty acids. No increase of iso acids was observed in milk fat in the propionate-infused glands whereas the increase of anteiso acids was extremely small. This agrees with the conception that iso and anteiso fatty acids are synthesized by rumen bacteria.

Animals↗
PubMed1984

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%).

3-Hydroxybutyric Acid↗