R Jeffcoat

Louisiana State University, Baton Rouge, Louisiana, United States

Are you R Jeffcoat?

Claim your profile

Publications (44)247.92 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Energy values of high amylose corn starches high in resistant starch (RS) were determined in vivo by two different methodologies. In one study, energy values were determined according to growth relative to glucose-based diets in rats fed diets containing RS(2), heat-treated RS(2) (RS(2)-HT), RS(3), and amylase predigested versions to isolate the RS component. Net metabolizable energy values ranged from 2.68 to 3.06 kcal/g for the RS starches, and 1.91-2.53 kcal/g for the amylase predigested versions. In a second study, rats were fed a diet containing RS(2)-HT and the metabolizable energy value was determined by bomb calorimetry. The metabolizable energy value was 2.80 kcal/g, consistent with Study 1. Thus, high amylose corn based RS ingredients and their amylase predigested equivalents have energy values approximately 65-78% and 47-62% of available starch (Atwater factor), respectively, according to the RS type (Garcia, T. A.; McCutcheon, K. L.; Francis, A. R.; Keenan, M. J.; O'Neil, C. E.; Martin, R. J.; Hegsted, M. The effects of resistant starch on gastrointestinal organs and fecal output in rats. FASEB J. 2003, 17, A335).
    Journal of Agricultural and Food Chemistry 09/2009; 57(18):8474-9. DOI:10.1021/jf900971c · 3.11 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: 1Hepatocytes were isolated by perfusion of the liver with collagenase/salt solutions and incubated in culture after attachment to plastic culture dishes for periods up to 48 h.2The cells, when incubated in serum-free culture medium in the presence of insulin, showed enhanced stearoyl-CoA desaturase activity which was not observed when 50 uM cycloheximide was included. When insulin was omitted from the medium, the cells lost 80% of their original desaturase activity.3Cells isolated from animals fed 20% (w/w) sucrose for two weeks prior to sacrifice, showed high levels of fatty acid synthesis, stearoyl-CoA desaturase activity and triacylglycerol synthesis when compared with cells isolated from animals fed a corn oil supplemented diet.4The observations are discussed in terms of the influence of stearoyl-CoA desaturase activity on hepatic lipogenesis.
    06/2008; 101(2):439 - 445. DOI:10.1111/j.1432-1033.1979.tb19737.x
  • Source
    Roger Jeffcoat
    [Show abstract] [Hide abstract]
    ABSTRACT: Many factors affect the onset of obesity including satiety control, reduced levels of physical exercise as well as hormonal and genetic parameters which influence the metabolic pathways leading to the net accumulation of triacylglycerol (TAG). The predominant fatty acid of human adipose tissue TAGs is oleic acid, reflecting primarily the composition of the diet but also the product of de novo lipogenesis. Consequently, both carbohydrates and lipids are potential sources of these stored fats. Many studies have been carried out using a variety of differing experimental protocols on healthy, obese or diabetic humans and animals in positive or neutral energy balance to establish the underlying molecular basis for obesity particularly in humans. This short review discusses the interdependence and control of the metabolism of lipids and carbohydrates as it relates to lipogenesis and proposes a unified hypothesis for obesity which brings together a number of different approaches focusing on (i) the interaction of dietary fat and carbohydrate, which typically represent approximately 80% of the daily caloric intake, and their role in the synthesis of TAGs, (ii) the biochemical pathways which control the amount of TAG produced by controlling the composition of their fatty acids via the action of stearoyl-CoA desaturase (SCD), (iii) the control of lipogenesis and SCD by dietary polyunsaturated fatty acid (PUFA) and (iv) the interaction of PUFAs with the transcription factors, peroxisome proliferator activated receptors (PPAR) alpha and gamma, which maintain the balance between oxidation and storage of lipids. The hypothesis focuses on the central role of stearoyl-CoA desaturase (SCD) and its inhibition by polyunsaturated fatty acids (PUFAs) acting via transcription factors based upon data obtained from both animal and human studies. From these observations it should be possible to determine the relevance of the hypothesis to humans and to speculate how these aspects of metabolism may impact the risk of developing related diseases such as coronary heart disease, Type 2 diabetes and certain forms of cancer.
    Medical Hypotheses 02/2007; 68(5):1159-71. DOI:10.1016/j.mehy.2006.06.009 · 1.15 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The objective of the present study was to investigate the effects of starches with differing rates of hydrolysis on exposure to pancreatin in vitro on postprandial carbohydrate metabolism in healthy subjects and in subjects with type 2 diabetes. Two test starches, prepared from uncooked native granular starch products, and naturally enriched with 13C, were consumed in a randomized crossover design by eight healthy and thirteen type 2 diabetic subjects. One starch was characterized in vitro as being rapidly hydrolysed (R, 94% after 180 min), and the other was more slowly hydrolysed (S, 51% after 180 min). Each subject consumed 50 g of each test starch. In addition, the type 2 diabetic subjects consumed 89.7 g of the S starch on a separate occasion. Blood samples were taken at 10 min intervals for 3 h, and at 20 min intervals for a further 3 h during a 6 h postprandial period. Breath 13CO2 enrichment was measured at the same time points, and indirect calorimetry was performed for seven 20 min sessions immediately before and during the 6 h postprandial period. With the R starch, plasma glucose concentrations and serum insulin concentrations rose faster and the maximum glucose change was approximately 1.8 times that for the S starch, averaged across both subject groups. The areas under the curves for glucose and insulin were, respectively, 1.7 and 1.8 times higher for the R starch compared with the S starch, averaged across both subject groups. The rate of 13CO2 output and the proportion of 13C recovered in breath after consumption of the R starch was similar for both subject groups. The results provide evidence that starches which have different rates of hydrolysis in vitro result in different patterns of glycaemia and insulinaemia in both healthy adults and in diet-controlled type 2 diabetic subjects. Data from the hydrolysis of novel starch products in vitro, therefore, are useful in predicting glycaemic responses in vivo.
    British Journal Of Nutrition 12/2003; 90(5):853-64. DOI:10.1079/BJN2003972 · 3.34 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The use of unmodified starches in frozen foods is severely limited by the undesirable textural changes that occur after freezing and thawing. Retrogradation of glucan chains leads to syneresis, a separation of the starch gel and water phases. Stabilization of the starch structure is normally achieved by chemical modification to prevent these changes from occurring. We have now created a freeze-thaw-stable potato starch by alteration of starch composition and structure by genetic modification. An amylose-free starch with short-chain amylopectin was produced by simultaneous antisense downregulation of three starch synthase genes. This starch is extremely freeze-thaw-stable and shows no syneresis even after five freeze-thaw cycles. The use of this starch has potential for environmental and consumer benefits because its production requires no chemical modification.
    Nature Biotechnology 04/2002; 20(3):295-9. DOI:10.1038/nbt0302-295 · 39.08 Impact Factor
  • 12/2000; 25(12). DOI:10.1557/mrs2000.249
  • [Show abstract] [Hide abstract]
    ABSTRACT: High-amylose starch is in great demand by the starch industry for its unique functional properties. However, very few high-amylose crop varieties are commercially available. In this paper we describe the generation of very-high-amylose potato starch by genetic modification. We achieved this by simultaneously inhibiting two isoforms of starch branching enzyme to below 1% of the wild-type activities. Starch granule morphology and composition were noticeably altered. Normal, high-molecular-weight amylopectin was absent, whereas the amylose content was increased to levels comparable to the highest commercially available maize starches. In addition, the phosphorus content of the starch was increased more than fivefold. This unique starch, with its high amylose, low amylopectin, and high phosphorus levels, offers novel properties for food and industrial applications.
    Nature Biotechnology 06/2000; 18(5):551-4. DOI:10.1038/75427 · 39.08 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Full length cDNAs encoding a second starch branching enzyme (SBE A) isoform have been isolated from potato tubers. The predicted protein has a molecular mass of 101 kDa including a transit peptide of 48 amino acids. Multiple forms of the SBE A gene exist which differ mainly in the length of a polyglutamic acid repeat at the C-terminus of the protein. Expression of the mature protein in Escherichia coli demonstrates that the gene encodes an active SBE. Northern analysis demonstrates that SBE A mRNA is expressed at very low levels in tubers but is the predominant isoform in leaves. This expression pattern was confirmed by Western analysis using isoform specific polyclonal antibodies raised against E. coli expressed SBE A. SBE A protein is found predominantly in the soluble phase of tuber extracts, indicating a stromal location within the plastid. Transgenic potato plants expressing an antisense SBE A RNA were generated in which almost complete reductions in SBE A were observed. SBE activity in the leaves of these plants was severely reduced, but tuber activity was largely unaffected. Even so, the composition and structure of tuber starch from these plants was greatly altered. The proportion of linear chains was not significantly increased but the average chain length of amylopectin was greater, resulting in an increase in apparent amylose content as judged by iodine binding. In addition, the starch had much higher levels of phosphorous.
    The Plant Journal 05/1999; 18(2):163-71. · 6.82 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Full length cDNAs encoding a second starch branching enzyme (SBE A) isoform have been isolated from potato tubers. The predicted protein has a molecular mass of 101 kDa including a transit peptide of 48 amino acids. Multiple forms of the SBE A gene exist which differ mainly in the length of a polyglutamic acid repeat at the C-terminus of the protein. Expression of the mature protein in Escherichia coli demonstrates that the gene encodes an active SBE. Northern analysis demonstrates that SBE A mRNA is expressed at very low levels in tubers but is the predominant isoform in leaves. This expression pattern was confirmed by Western analysis using isoform specific polyclonal antibodies raised against E. coli expressed SBE A. SBE A protein is found predominantly in the soluble phase of tuber extracts, indicating a stromal location within the plastid. Transgenic potato plants expressing an antisense SBE A RNA were generated in which almost complete reductions in SBE A were observed. SBE activity in the leaves of these plants was severely reduced, but tuber activity was largely unaffected. Even so, the composition and structure of tuber starch from these plants was greatly altered. The proportion of linear chains was not significantly increased but the average chain length of amylopectin was greater, resulting in an increase in apparent amylose content as judged by iodine binding. In addition, the starch had much higher levels of phosphorous.
    The Plant Journal 03/1999; 18(2):163 - 171. DOI:10.1046/j.1365-313X.1999.00441.x · 6.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Antibiotics are being proposed for the treatment of cardiovascular disease. In the past, antibiotics were advocated for the control of hypercholesterolemia. We have therefore investigated the relation between colonic bacterial activity and serum lipids. In a four-phase randomized crossover study, we fed a different starch supplement during each 2-week phase to 24 healthy subjects. In two phases, supplements containing resistant starches were fed that reach the colon and are largely fermented by colonic bacteria. Fecal starch recovery therefore reflects the metabolic activity of colonic microflora. The control treatments were conventional starches. Blood lipid levels were obtained at the start and 4-day fecal collections at the end of each phase. Resistant starch supplements increased fecal starch excretion by 3.8 +/- 1.2 g/d more than conventional starches (P = .006). Mean starch excretion was related positively to pretreatment serum high-density lipoprotein (HDL) cholesterol (r = -.57, P = .003) and negatively to low-density lipoprotein (LDL) cholesterol (r = -.57, P = .004), apolipoprotein B:AI (r = -.56, P = .005), and fecal output of fusobacteria (r = -.73, P = .003) and bacteroides (r = -.72, P = .003). The ratio of fusobacteria to total anaerobes was also related to pretreatment LDL cholesterol (r = .56, P = .037). Differences in starch excretion between healthy subjects, as a measure of bacterial activity, accounted for 32% of the variation in pretreatment LDL cholesterol. The activity of colonic microflora therefore appears to influence serum lipid levels. Alterations of bacterial number and activity may provide an additional strategy to control serum lipid risk factors for cardiovascular disease.
    Metabolism 03/1999; 48(2):264-8. DOI:10.1016/S0026-0495(99)90045-8 · 3.61 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To assess the effects on fecal bulking, fecal short chain fatty acid (SCFA) production, blood lipids and glycemic indices of two different forms of resistant starch (RS2 and RS3) from a high-amylose cornstarch. Twenty-four healthy subjects (12 men; 12 women) consumed four supplements taken for 2 weeks in random order separated by 2-week washout periods. The supplements were a low-fiber (control) and supplements providing an additional 30 g dietary fiber as wheat bran (high-fiber control) or the equivalent amount of resistant starch analyzed gravimetrically as dietary fiber from RS2 or RS3. Four-day fecal collections and 12-hour breath gas collections were obtained at the end of each period. Fasting blood was taken at the beginning and end of each period. Glycemic indices of supplements were also assessed. The wheat bran supplement increased fecal bulk 96+/-14 g/day compared with the low-fiber control (p<0.001) with the mean for both resistant starches also being greater (22+/-8 g/day) than the low-fiber control (p=0.013). On the resistant starch phases, the mean fecal butyrate:SCFA ratio, which has been suggested to have positive implications for colonic health, was significantly above the low-fiber control by 31+/-14% (p=0.035). Resistant starches did not alter serum lipids, urea or breath H2 or CH4. No significant differences in glycemic index were seen between the RS and control supplements. The potential physiological benefits of the resistant starches studied appear to relate to colonic health in terms of effects on fecal bulk and SCFA metabolism.
    Journal of the American College of Nutrition 01/1999; 17(6):609-16. DOI:10.1080/07315724.1998.10718810 · 1.68 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper examines the effect of changes in fine structure due to hybrid breeding on gel formation and gel properties of high-amylose maize starches. Both small-strain oscillatory testing and uniaxial-compression testing ranked G' and texture/strength, respectively, in the same order of HYLON(R) V starch <HYLON(R) VII starch <low-amylopectin starch (LAPS). The starch gels became more rigid and stronger as amylose content of the hybrids increased from HYLON V starch to LAPS. It was also noted in these studies that LAPS had the quickest onset of gelation and HYLON V starch had the slowest. The effect of preparation temperature on gel properties was also studied by cooking high-amylose starches at 250 degrees, 270 degrees, 290 degrees, 310 degrees, 330 degrees F in a mini-jet cooker with minimal steam Temperature of jet cooking had an impact on the rate of sol-to-gel transformation of the starches, which in turn influenced the final gel properties. All three hybrids were strongest (highest fracture stress and strain values) when prepared at 270 degrees F. HYLON V had the narrowest cooking tolerance forming self-supporting gels from 270 degrees to 310 degrees F, while LAPS was the most robust, forming acceptable gels throughout the range of temperatures tested. (C) 1998 Academic Press Limited.
    Journal of Cereal Science 05/1998; 27(3):301-314. DOI:10.1006/jcrs.1997.0164 · 1.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The molecular structure of two commercially available high-amylose maize starches, HYLON® V starch and HYLON® VII starch, and of a newly developed low-amylopectin starch (LAPS) was examined. These high-amylose starches give three apparent fractions as determined by gel-permeation chromatography: a high-molecular weight (mol.wt) amylopectin fraction, a low-mol.wt amylose fraction, and an intermediate-mol.wt fraction which contains both linear and branched components. The low-mol.wt amylose fraction increases from 9·4% in HYLON V starch to 17·7% in HYLON VII starch and 26·5% in LAPS, whereas the high-mol.wt amylopectin fraction decreases from 31·1% in HYLON V starch to 13·8% in HYLON VII starch and 2·5% in LAPS. The percentage of linear components in HYLON V starch, HYLON VII starch, and LAPS are 42, 54, and 80%, respectively. High-amylose starches have a large proportion of long chains in their branched fractions compared to waxy-maize and normal-maize starch. Both HYLON VII starch and the LAPS give B plus V-type X-ray diffraction patterns, but the LAPS has even a higher gelatinization temperature, lower swelling power in hot water, and is more resistant to acid digestion. With the lack of amylopectin, amylose accounts for at least part of the double helical structure in the LAPS granules.
    Journal of Cereal Science 05/1998; 27(3):289-299. DOI:10.1006/jcrs.1997.9998 · 1.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In order to determine the reasons for the differences in structure between starch from a normal and a low-amylopectin maize variety the activities of all the enzymes in the committed pathway of starch synthesis were studied throughout kernel development. Levels of ADP glucose pyrophosphorylase and starch synthase activity were found to be broadly similar between the two varieties but the low-amylopectin starch (LAPS) maize variety showed dramatically reduced starch branching enzyme activity, with an almost total absence of the branching enzyme II isoform. Scanning electron microscopy showed a significant alteration in the morphology of the starch granules of the low-amylopectin maize. The results suggest that the increased amylose and the reduction of high molecular weight amylopectin in the LAPS starch results from the absence of the branching enzyme II isoform. This evidence supports the theory that the different branching enzyme isoforms contribute separately to the synthesis and final structure of amylopectin.
    Journal of Cereal Science 05/1998; 27(3):279-287. DOI:10.1006/jcrs.1997.0170 · 1.94 Impact Factor
  • R Jeffcoat
    Biochemical Society Transactions 01/1990; 17(6):1137-8. · 3.24 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Two galactomannan polysaccharides (guar gum, locust bean gum) are commonly used in foods and other applications to manipulate aqueous rheology. Locust bean gum (23% galactose, 77% mannose) is more functional and more expensive than guar gum (38% galactose, 62% mannose). We have investigated the enzymic (α-galactosidase) removal of side-chain galactose residues from guar gum to yield galactomannans similar in chemical composition and functional properties to locust bean gum. The optimum concentration for α-galactosidase action increased from ∼ 2% w/w (solution state) at 35°C to ∼ 10% w/w (gel-like state) at 42°C to 20–30% w/w (semi-solid particulate state) at 50°C due to increased enzymic temperature tolerance at high substrate concentrations. Galactomannans varying in galactose content were prepared by manipulating reaction time, temperature and enzyme/guar gum ratio. Enzymically modified guar galactomannans with 22–24% galactose contents were found to reproduce the rheological and stabilisation properties of locust bean gum. These findings form the basis for a feasible biotechnological route for the upgrading of guar gum to galactomannan polymers with enhanced functionality.
    Carbohydrate Polymers 01/1990; 12(2-12):155-168. DOI:10.1016/0144-8617(90)90016-L · 3.92 Impact Factor
  • N M Lindner, R Jeffcoat, C R Lowe
    [Show abstract] [Hide abstract]
    ABSTRACT: A 330-fold one-step purification of alkaline phosphatase from a crude calf intestinal extract has been achieved using specific elution with inorganic phosphate (5 mM) from a purpose designed adsorbent comprising a terminal ring phosphonate analogue of C.I. Reactive Blue 2 coupled to Sepharose CL-6B-200. The resulting alkaline phosphatase preparation displayed a specific activity in excess of 1000 U/mg and was of equivalent purity to commercial "high purity" preparations as deduced by sodium dodecyl sulphate polyacrylamide gel electrophoresis and specific activity comparisons.
    Journal of Chromatography A 07/1989; 473(1):227-40. DOI:10.1016/S0021-9673(00)91304-9 · 4.26 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Over 20 gram-positive bacteria were isolated by elective culture with (+/-)-alpha-pinene as the sole carbon source. One of these strains, Nocardia sp. strain P18.3, was selected for detailed study. alpha-Pinene-grown cells oxidized, without lag, alpha-pinene, alpha-pinene oxide (epoxide), and the cis and trans isomers of 2-methyl-5-isopropylhexa-2,5-dienal. No other tested terpene was oxidized at a significant rate. alpha-Pinene was not metabolized by cell extracts in the presence or absence of NADH or NADPH. Cell extracts catalyzed a rapid decyclization of alpha-pinene oxide, in the absence of added cofactors, with the formation of cis-2-methyl-5-isopropylhexa-2,5-dienal. Further oxidation of the aldehyde to the corresponding acid occurred in the presence of NAD. Both activities were induced by growth with alpha-pinene. A rapid, nonenzymic transformation of the cis aldehyde into the trans isomer occurred in glycine buffer. The trans isomer was also a substrate for the NAD-linked aldehyde dehydrogenase. The distribution of the alpha-pinene oxide lyase in alpha-pinene-utilizing Pseudomonas spp. was also investigated and was compatible with the two alternative ring-cleavage sequences that have been proposed on the basis of accumulated metabolites.
    Journal of Bacteriology 12/1987; 169(11):4972-9. · 2.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: alpha-Pinene oxide is an intermediate in the degradation of alpha-pinene by Nocardia sp. strain P18.3 and some Pseudomonas strains. The epoxide is cleaved by a lyase which catalyzes a concerted reaction in which both rings of the bicyclic structure are cleaved with the formation of cis-2-methyl-5-isopropylhexa-2,5-dienal. The enzyme has been purified to homogeneity from Nocardia sp. strain P18.3. It was induced by growth with alpha-pinene and constituted 6 to 7% of the soluble protein of cell extracts. The apparent molecular weight of the native enzyme was 50,000 by ultracentrifugal analysis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis gave two dissimilar subunits with apparent molecular weights of 17,000 and 22,000. The enzyme was devoid of prosthetic groups, had no cofactor requirement, and had a broad pH activity range, a Km for alpha-pinene oxide of 9 microM, and a turnover number of 15,000. Inhibitors included sulfhydryl reactive compounds, terpene epoxides, and pinane derivatives with substituent groups at carbon 3. A mechanism for the concerted reaction has been proposed in which decyclization is initiated by donation of a proton from the catalytic center to the oxygen of the epoxide with consequent destabilization. In vitro the enzyme was inactivated during catalysis, and a reactive cationic intermediate may be responsible for this phenomenon. The enzyme should be classified as a lyase EC 4.99.-.-.
    Journal of Bacteriology 12/1987; 169(11):4980-3. · 2.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The interaction of rat mammary gland medium-chain thioesterase with yeast fatty acid synthetase has been investigated. Medium-chain thioesterase interacts with yeast fatty acid synthetase causing premature chain termination of the fatty acids synthesized from acetyl-CoA and malonyl-CoA. This effect is most marked under conditions of rate-limiting malonyl-CoA availability. Immobilized yeast fatty acid synthetase specifically binds rat mammary gland medium-chain thioesterase. This interaction has been used to purify medium-chain thioesterase to near homogeneity from samples of rat mammary gland cytosol. The stoichiometry of binding of medium-chain thioesterase to yeast fatty acid synthetase has been investigated. Yeast fatty acid synthetase binds 5.7 +/- 1 mol medium-chain thioesterase/mol yeast fatty acid synthetase. It is concluded that yeast fatty acid synthetase has a medium-chain thioesterase binding site.
    European Journal of Biochemistry 08/1983; 134(1):27-32. DOI:10.1111/j.1432-1033.1983.tb07526.x · 3.58 Impact Factor

Publication Stats

1k Citations
247.92 Total Impact Points

Institutions

  • 2009
    • Louisiana State University
      • School of Human Ecology
      Baton Rouge, Louisiana, United States
  • 1977–2008
    • Unilever
      • Bioscience
      Londinium, England, United Kingdom
  • 1999
    • St. Michael's Hospital
      Toronto, Ontario, Canada
  • 1987
    • The Royal Institution of Great Britain
      Londinium, England, United Kingdom
  • 1974
    • University of Oxford
      • Department of Biochemistry
      Oxford, England, United Kingdom