Glucose and Norepinephrine Challenges During the Abomasal Infusion of Cis or Trans Octadecenoates in Holstein Cows1

Glucose and Norepinephrine Challenges During Abomasal Infusion of Cis or Trans Octadecenoates in Holstein Cows' P. J. GAYNOR,"J R. A. E R D M A N , * PB. ~ ~ B. ~ TETER,*q4 A. V. CAPUC0,t15 and D. R. 'University of Maryland, College Park 20742 YUSDA, Agricultural Research Service, Beltsville, MD 20705

ABSTRACT

INTRODUCTION

This experiment determined the effects of infusion of mixtures of fat containing predominantly cis-C18:1 or trans-Clg1 fatty acids into the abomasum on responses of cows to glucose and norepinephrine challenges administered i.v. Six lactating Holstein cows, each with a rumen cannula, were arranged in two Latin squares with 21-d periods. The common basal diet contained 40% forage and 60% concentrate. Treatments were the uninfused control, 750 g/d of a cis fat mixture (65% high oleic sunflower oil and 35% cocoa butter), and 750 g/d of a trans fat mixture (93% shortening and 7% corn oil) infused into the abomasum via a tube that passed through the rumen cannula. Glucose challenges (0.4 mgkg of BW, administered i.v.1 were conducted on d 18, and norepinephrine challenges (0.7 pgkg of BW, administered i.v.1 were conducted on d 19 of each experimental period. Despite a lower percentage of fat in milk for trans than for cis treatment, disappearance rates of glucose, secretion of insulin after glucose challenge, and appearance rates of NEFA and triglycerides after norepinephrine challenge were similar between treatments. Thus, these data support the hypothesis that trans-Clg:1 fatty acids affect the synthesis of milk fat in the mammary gland of lactating cows. ( Key words: glucose, norepinephrine, trans-Cig:1 fatty acids, milk fat depression)

Dietary fat affects the yield and composition of milk fat of dairy cows ( 5 , 10). Specifically, supplementation of diets with long-chain fatty acids ( FA; 18 or more carbons) oRen increases the proportion of long-chain FA and decreases the proportion of shortchain FA (de novo synthesized FA) in milk fat (18). The addition of moderate amounts of fat to diets usually has little effect on total yield of milk fat ( 18). However, substitution of trans-C 18:1 geometric isomers for cis-C18:l FA depressed both the percentage and yield of milk fat (4, 12, 1 5 ) . The exact reasons for divergent effects of geometric Cl8:1 FA isomers on the secretion of milk fat have not been determined but may include differences in metabolism of these FA in liver, adipose, or mammary tissues. Glucose and norepinephrine ( NE) challenges may provide useful information for determining how geometric C18:1 FA isomers exert different effects on milk fat synthesis. Glucose challenges have been used to detect differences in rates of secretion of insulin and utilization of glucose for diets that contained varying amounts of fat and for cows at different stages of lactation (3, 11, 13). In addition, challenges with catecholamines (epinephrine or NE 1 have been used to evaluate lipolytic responsiveness of adipose tissue in vivo and in vitro ( 7 , 8, 9).Therefore, our objective was t o determine whether infusion of fat mixtures containing predominantly cis-C18:1 or trans-Cl8:i FA into the abomasum affected responses of lactating dairy cows to glucose and NE challenges. Other data from this experiment were published previously (41.

Abbreviation key: FA = fatty norepinephrine, TG = triglycerides.

acid, NE

=

Received October 4, 1995. Accepted April 8, 1996. 'Scientific Article A7826, Contribution Number 9153 of the Maryland Agricultural Experiment Station. No endorsements are herein implied. ZDepartment of Animal Science. 3Reprint requests. 4Department of Chemistry and Biochemistry. SMilk Secretion and Mastitis Laboratory. 6Nutrient Conservation and Metabolism Laboratory. 1996 J Dairy Sci 79:1590-15!35

MATERIALS AND METHODS

Six multiparous rumen-cannulated Holstein cows averaging 55 DIM were assigned randomly t o treatment sequences balanced for residual effects in two 3 x 3 Latin squares. The three experimental periods were 21 d each. A single diet (40% forage and 60% concentrate, DM basis; 23.4% CP, 15.6% ADF) was fed for ad

1590

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GLUCOSE AND NOREPINEPHRINE CHALLENGES

libitum intake throughout the 9-wk experiment. Orts were removed daily a t 0500 h, and cows were fed at 0730 h daily. The three treatments were an uninfused control, 750 gld of a cis fat mixture, and 750 g/d of a trans fat mixture. The cis fat mixture contained 65% high oleic sunflower oil (SVO Enterprises, East Lake, OH) and 35% cocoa butter (Wilbur Chocolate Co., Lititz, PA). The trans fat mixture contained 93% shortening (Auth Brothers, Washington, D C ) and 7% corn oil (Continental Smelkinson, Jessup, MD). Proportions of fat from each source were chosen to equalize the quantities of as many FA as possible except for cisc18:1and tFUnS-C:lg:lFA. The amounts of cis-Cls:l and trans-C18:1 FA consumed were 63 and 2 g/d, respectively, for the uninfused control; 545 and 2 gfd, respectively, for the cis treatment; and 211 and 308 g/ d, respectively, for the trans treatment ( 4 ) . Amounts of C16:0, CIS:^, and c18:2FA consumed were similar among treatments ( 4 ) . Abrupt changes in the treatment administered to each cow occurred on d 1 of each 21-d experimental period. For the cis and the trans treatments, fat (250 g ) was infused at 0800, 1400, and 1900 h through Tygon@ tubing (0.45 cm i.d.; Norton Performance Plastics, Akron, OH) that passed through the rumen and omasum and ended within the abomasum. Sample Collection and Laboratory Analyses

-

ately on ice and centrifuged a t 1750 x g within 1 to 2 h. On d 19, NE (Arterenol; 0.7 p g k g of BW; 0.1 mg/ ml of stock solution; Sigma Chemical Co., St. Louis, MO) was injected through jugular cannulas over 45 s at 2 to 3 h after removal of orts. Injections were followed by 10 ml of saline and 5 ml of sodium citrate solution to rinse cannulas. Blood samples were collected from jugular cannulas ( 10 ml, sodium citrate monovettes) at -15, -7, -1, 5 , 7, 10, 15, 20, 30, 45, and 60 min relative to the initiation of the NE injection.

14 12

A

-

-

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2

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8 -

v

Q

a

8 ii

6 -

4-

2t ,

0

10

20

100 30

45

60

120

75

Time relative to start of glucose challenge (min) On d 17 of each experimental period, a catheter (16 gauge x 19.6 cm; Delmed, New Brunswick, N J ) was inserted into a jugular vein of each cow. Patency was maintained with 3.5% sodium citrate in sterile saline. Glucose challenges were performed on d 18, apfrom the feeding proximately 4 h after removal of o r t ~ of the previous day. A sterile solution of glucose (50%, wt/vol) was injected i.v. through the catheter (0.4 g/ kg of BW) at a constant rate of 1 myS. This dose of glucose was used previously to determine effects of dietary fat on glucose and insulin metabolism ( 11). Injections were complete within 6 to 9 min. After injections of glucose, 5 ml of a sodium citrate solution were injected to rinse catheters. An additional 5 ml. of blood were withdrawn from the catheter and disI I I I I carded immediately before collection of blood samples ( 1 0 ml, sodium citrate monovettes; Sarstedt Inc., Newton, N C ) at -15, -7, -1, 10, 15, 20, 30, 45, 60, 75, 100, and 120 min relative to the start of glucose Figure 1. Predicted concentrations of glucose ( A ) and insulin injection. At 5 and 7 min of glucose injection, blood ( B ) in plasma after a glucose challenge ( 0 . 4 g k g of BW) adwas collected from a coccygeal vein into a vacutainer ministered i.v. for uninfused control (-), cis ( - - - -), and trans (. . .) treatments ( 6 cows per treatment). Parameter estimates containing sodium citrate (Becton Dickinson, Ruther- ( * SE) for comparisons among treatments are presented in ford, N J ) . After collection, blood was placed immedi- Table 1.

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GAYNOR ET AL.

(lower bound of 0). Areas under the response curves were calculated as AdK, and half-lives of response variables were calculated as log(2)/K. Iteratively derived parameter estimates (Ao, D, and K), calculated half-life, and areas under the response curves were then analyzed by ANOVA for a Latin square design (17 1. Mean comparisons were 1) uninfused control versus the mean of cis plus trans treatments and 2 ) cis versus trans treatment. Changes in concentrations of insulin, NEFA, and TG in plasma aRer NE challenge did not fit a simple model of exponential decay. Therefore, areas under curves between 5 and 60 min after injection of NE Calculations and Statistics were estimated as the sum of areas of trapezoids Nonlinear regression was used to estimate between adjacent sampling times. The mean concenparameters of glucose (10 t o 120 min postinjection) trations before injection of NE were calculated as the and insulin ( 15 to 120 min postinjection) response to means of concentrations a t -15, -7, and -1 min. glucose challenge using SAS ( 14). The model, fit by Preinjection mean, maximum concentrations after insubgroups of cow, period, and treatment ( n = 18), jection of NE, and total areas under the response was curves aRer injection of NE were analyzed by ANOVA, and means were compared as previously described. Significance was determined at P I 0.05. where Y = concentration of glucose or insulin in plasma, & = maximum response of Y (peak value), K RESULTS = exponential decay rate of response, t = time of sample collection relative to the start of glucose injec- Glucose Challenge tion, c = constant used t o adjust t for minutes elapsed The concentrations of glucose and insulin in before peak concentration occurred ( 1 0 for glucose and 15 for insulin), and D = postinjection baseline plasma after a glucose challenge administered i.v. are

Concentrations of glucose in plasma were determined using a glucose analyzer (model 27; Yellow Springs Instruments, Yellow Springs, OH). Concentrations of NEFA in plasma were determined using a modified ( '7 ) NEFA-C procedure (WAKO Pure Chemicals Industries, Ltd., Osaka, Japan), concentrations of triglycerides ( TG) were determined using a triglycerides G kit (WAKO), and concentrations of insulin were determined using a double-antibody radioimmunoassay ( 1) . All intraassay and interassay coefficients of variation were between 5 and 10%.

TABLE 1. Response of lactating Holstein cows to glucose challenge (0.4g/kg of BW) administered i.v. Contrast Treatment Control

cis

trans

SE

Control vs. cis + trans

cis vs. trans

-PCows, no. 6 6 6 Glucose 261 283 270 Area under curve1 19.7 18.0 Half-life, min 19.2 0.040 0.036 Rate of decline, mmoVL per min 0.038 9.9 10.1 Maximum increase, mmoVL 9.8 Posttest baseline, mmoyL 2.3 2.3 2.4 0.992 0.994 0.988 Mean R* Insulin Area under curve2 3618 5592 5270 25.7 40.1 25.1 Half-life, min Rate of decline, m U L 0.030 0.027 0.030 144.9 140.6 Maximum increase, m U L 104.3 Posttest baseline, mU/L 10.5 6.2 8.9 0.912 0.928 Mean Rz 0.949

20 1.4 0.003 0.3 0.2

603 10.1 0.004 21.3 1.8

0.04

*Area bounded by curve and x-axis from 10 to 120 min, measured in (millimoles per liter) x minutes. ZArea bounded by curve and x-axis from 15 to 120 min, measured in (milliunits per liter) x minutes. Journal of Dairy Science Vol. 79, No. 9, 1996

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GLUCOSE AND NOREPINEPHRINE CHALLENGES 4.5 -

NE Challenge

T

-15

-7 -1

5 10 15 20

The concentrations of glucose and insulin in plasma before and after a NE challenge administered i.v. are presented in Figure 2. Parameters of glucose response to NE challenge were similar among treatments (Table 2). Areas under the insulin curves after injection of NE were greater for cis and trans treatments than for the uninfused control. However, areas under the insulin curves after injection of NE were similar for cis and trans treatments.

30

60

45

Time relative to start of norepinephrine challenge (mln)

300

T

280 260

A

-

$240 -

60

B

3 LL W

= 200

5 E

.--a 40 - 30

180 160

C

-15

-7

-1

5 10 15 20

30

45

60

Time relative to start of norepinephrine challenge (min) 20

-15

-7

-1

5 10 15 20

30

45

60

-

Figure 2 . Concentrations of glucose ( A ) and insulin (B) in plasma before and after norepinephrine challenge (0.7 p&g of BW) administered i.v. for uninfused control (-1, cis ( - - -1, and trans ( , , .) treatments ( 6 cows per treatment). Errors bars show a positive value for standard error for each treatment at each sampling time.

220

B

I!I

Time relative to start of norepinephrine challenge (mln) -

i ol

d 200 n 0

E

-m*

180160140

c

120'

presented in Figure 1.Parameters of glucose response were similar among treatments (Table 1).The areas under insulin curves between 15 and 120 min after injection of glucose were greater for cis and trans treatments than for the uninfused control. All other parameters of insulin response to i.v. glucose challenge were similar among treatments.

I

,

,

,

,

-15 -7 -1 5 10 15 20 30 45 60 Time relative to start of norepinephrine challenge (mln)

Figure 3. Concentrations of NEFA ( A ) and triglycerides ( B ) in plasma before and after norepinephrine challenge (0.7 p g k g of BW) administered i.v. for uninfused control (-1, cis ( - - -1, and trans (. . .) treatments ( 6 cows per treatment). Error bars show positive value for standard error for each treatment at each sampling time. Journal of Dairy Science Vol. 79, No. 9, 1996

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GAYNOR ET AL.

Parameters of NEFA response t o i.v. NE challenge were similar among treatments (Figure 3A; Table 2). Areas under the TG curves after injection of NE tended ( P = 0.08) to be greater for cis and trans treatments than for the uninfused control, but values were similar for cis and trans treatments (Figure 3B; Table 2 ) . DISCUSSION

Supplemental dietary fat depresses the synthesis of short- and medium-chain FA in mammary tissue of lactating dairy cows and alters the proportions of specific FA present in milk fat (5, 10, 18). In addition, although supplemental tFmS-C18:1 FA depressed the percentage of fat in milk (12, 15, 211, the exact mechanisms mediating this effect have not been determined. In this experiment, mixtures of predominantly cisc 1 8 : 1 or trans-C18:1 FA were infused directly into the abomasum to determine the effects of geometric C l 8 :1 FA isomers on milk fat synthesis and responses to glucose and NE challenges administered i.v. Gaynor et al. ( 4 1 previously reported that milk yields were similar, but milk fat percentage was lower, for the trans treatment than for the cis treatment (47.0 vs. 46.3 1.1 kg/d and 2.59vs. 3.27 f. 0.21%,respectively, for trans and cis treatments). Concentrations of trUn.S-C18:1 FA in plasma samples collected immediately before infusion of fat were greater for cows

*

receiving the trans treatment than for cows receiving the cis treatment or cows that were not infused l2.6, 0.7, and 0.4 0.2 g / l O O g of FA methyl ester, respectively ( 4 ) l . Lactating cows may use as much as 80% of available glucose for the synthesis of lactose in the mammary gland ( 2 ) . In addition, a-glycerol phosphate used for synthesis of TG in adipose tissue is derived from glucose ( 6 , 1 6 ) . Increased dietary fat content decreased oxidation of glucose in adipose tissue of lambs and sheep ( 2 2 ) and decreased uptake of [U14Clglucose and oxidation of lipids in bovine adipose tissue in vitro ( 3 ) . In the current experiment, however, rates of glucose disappearance from blood after a glucose challenge were similar among all treatments. Thus, neither supplemental fat nor the geometric C18:1 FA isomer available affected rates of glucose disappearance from blood of these lactating cows. The absence of increased rates of glucose disappearance in response to increased secretion of insulin is referred t o as insulin resistance. Areas under the insulin curves after a glucose challenge may reflect rates of insulin secretion from the pancreas, binding capacity of insulin receptors, or rates of insulin degradation (11, 19). Increased insulin resistance t o glucose challenge for treated cows than for the uninfused cows in this experiment agrees with results of Palmquist and Moser ( 11) . In addition, lack of differences in rates of glucose disappearance or of insulin secre-

*

TABLE 2. Responses of lactating Holstein cows to norepinephrine challenge (0.7 p g k g of BW administered i.v. Contrast Treatment Control

SE

trans

cis

Control vs. cis + trans

- P Cows, no. Glucose, mmol/L Baseline1 Total area2 Maximum value Insulin, m U L Baseline Total area Maximum value NEFA,, peqL Baseline Total area Maximum value Triglycerides, mg/L Baseline Total area Maximum value

6

6

6

3.16 205.9 4.29

3.13 198.2 4.19

3.19 200.8 4.18

20.6 1424 51.4

23.2 1695 62.2

22.8 1812 58.2

184 11,485 259

185 12,876 270

174 11,112 234

134 8574 187

155 10,389 219

154 9581 196

0.06 6.9 0.14 1.5 123

6.1 695 25 12 596 27

1Mean concentration of samples collected at -15, -7, and -1 min. Wnits x 55 min between 5 and 60 min postinjection.

Journal of Dairy Science Vol. 79, No. 9, 1996

0.05

6

0.08

cis vs. trans

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GLUCOSE AND NOREPINEPHRINE CHALLENGES

tion between cis and trans treatments suggests that these parameters are not related to differences in milk fat percentage and yield between these two treatments. Stimulation of catecholamine receptors with epinephrine produced transient hyperglycemia (presumably from glycogenolysis) and increased lipolysis in lactating dairy cows ( 7 ) . Similar to results for glucose challenge, results from the NE challenge also indicated insulin resistance of cows treated with cis or trans FA compared with the response of uninfused controls. Rates of release of FA from adipose tissue depend on numerous factors, including rates of TG hydrolysis, FA oxidation, and reesterification of FA to TG within adipose tissue ( 2 0). In addition, concentrations of NEFA and TG in blood are functions of rates of intestinal absorption, rates of formation in adipose tissue or liver, and rates of clearance. Although this experiment was not designed to determine specifically which of these parameters was affected, lack of differences in NEFA or TG concentrations among treatments after NE challenge suggests that neither supplemental cis-C18:1 nor trans-C18.1 FA exerted a net effect on these parameters in lactating Holstein cows. Our inability t o determine the effects of cis-C18:1 or truns-C18:1 FA on NEFA or TG metabolism in response to NE challenge may be because the effects of truns-C:l8:1 FA on milk fat synthesis occur within the mammary gland. Other investigations to clarify the role of trunsC18:l FA i n the synthesis of milk fat should include their effects on rates of oxidation of long-chain FA in the liver, their effects on acetate metabolism, and their effects on activities of enzymes associated with milk fat s,ynthesis in mammary tissue. CONCLUSIONS Supplemental fat containing predominantly cis or truns geometric isomers of Cl8:1 FA had similar effects on rates of glucose disappearance and insulin secretion after a glucose challenge and on rates of appearance of NEFA and TG after a n i.v. NE challenge. These data support the hypothesis that trans- C18:1 FA affect the synthesis of milk fat in the mammary gland of lactating cows. ACKNOWLEDGMENTS

Charlotte Kirk, Donald Carbaugh, Sheila Andrew, and Will I’otts provided valuable assistance. The excellent help of Tom Moreland, Tommy Junis, and the staff a t the Central Maryland Research and Education Center is appreciated. The authors thank G. B. Huntington for use of the glucose analyzer and the University of Maryland Computer Sciences Center for

the use of computer resources. Research was conducted with approval of the Maryland Agricultural Experiment Station Animal Care Committee (protocol number R010). REFERENCES 1Barnes, M. A., G. W. Kazmer, R. M. Akers, and R. E Pearson. 1985. Influence of selection for milk yield on endogenous hormones and metabolites in Holstein heifers and cows. J. Anim. Sci. 60:271. 2 Bauman, D. E., and W. B. Currie. 1980. Partitioning of nutrients during pregnancy and lactation: a review of mechanisms involving homeostasis and homeorhesis. J . Dairy Sci. 63: 1514. 3 C u m i n s , K. A., and R. W. Russell. 1985. Effects of feeding whole cottonseed to lactating dairy cows on glucose and palmitate metabolism. J. Dairy Sci. 68:2009 4Gaynor, P. J., R. A. Erdman, B. B. Teter, J. Sampugna, A. V. Capuco, D. R. Waldo, and M. Hamosh. 1994. Milk fat yield and composition during abomasal infusion of cis or trans octadecenoates in Holstein cows. J. Dairy Sci. 77:157. 5 Grummer, R. R. 1991. Effect of feed on the composition of milk fat. J. Dairy Sci. 74:3244. 6 Hood, R. L., E. H. Thompson, and C. E. Allen. 1982. The role of acetate, propionate, and glucose as substrates for lipogenesis in bovine tissues. Int. J. Biochem. 3:598. 7 McCutcheon, S. N., and D. E. Bauman. 1986. Effect of chronic growth hormone treatment on responses to epinephrine and thyrotropin-releasing hormone in lactating cows. J. Dairy Sci. 69:44. 8 McNamara, J. P., and J. K. Hillers. 1986. Regulation of bovine adipose tissue metabolism during lactation. 2. Lipolysis response to milk production and energy intake. J. Dairy Sci. 69: 3042. 9 Metz, H. M., and S. G. van den Berg. 1972. Effects of volatile fatty acids, ketone bodies, glucose, and insulin on lipolysis in bovine adipose tissue. FEBS Lett. (Fed. Eur. Biochem. Soc. Lett.) 21:203. lOPalmquist, D. L., A. D. Beaulieu, and D. M. Barbano. 1993. Feed and animal factors influencing milk fat composition. J. Dairy Sci. 76:1753. llPalmquist, D. L., and W. Moser. 1981. Dietary fat effects on blood insulin, glucose utilization, and milk protein content of lactating cows. J. Dairy Sci. 64:1664. 12 Romo, G., D. Casper, and R. Erdman. 1993. Energy utilization of abomasally infused cis versus trans fatty acid isomers in lactating dairy cows. J. Dairy Sci. 76(Suppl. 1): 185.(Abstr.) 13Sartin, J. L., K. A. C u m i n s , R. J. Kemppainen, D. N. Marple. C. H. Rahe, and J. C. Williams. 1985. Glucagon, insulin, and growth hormone responses to glucose infusion in lactating dairy cows. Am. J. Physiol. 248:E108. 14 SASa User’s Guide: Statistics. Version 5 Edition. 1985. SAS Inst., I n c , Cary, NC. 15Selner. D. R.. and L. H Schultz. 1980 Effect of feedine oleic acid or hydrogenated vegetable oils to lactating cows. J.-Dairy Sci. 63:1235. 16 Sidhu, K. S., and R. S. Emery. 1972. Regulation of blood fatty acids and glycerol in lactating cows. J. Dairy Sci. 55:926. 17Soka1, R. R., and F. J. Rohlf. 1981. Biometry. W. H. Freeman and Co., San Francisco, CA. 18Sutton, J. D. 1989. Altering milk composition by feeding. J. Dairy Sci. 72:2801. 19 Vernon, R. G. 1989. Endocrine control of metabolic adaptation during lactation. Proc. Nutr. Soc. 48:23. 20Vernon, R. G., and D. J. Flint. 1984. Adipose tissue: metabolic adaptation during lactation. Symp. 2001. Soc. Lond. 51:119. 21 Wonsil, B. J., J. H. Herbein, and B. A. Watkins. 1994. Dietary and ruminally derived trans-Clp,l fatty acids alter bovine milk lipids. J. Nutr. 124:556. 22 Yang, Y. T., R. L. Baldwin, and W. N. Garrett. 1978. Effects of dietary lipid supplementation on adipose tissue metabolism in lambs and steers. J. Anim. Sci. 47:686. ~

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