Lipolytic response of bovine adipose tissue to alpha and beta adrenergic agents 30 days pre- and 120 days postpartum

Effects of phytonutrients alone or in combination with monensin on productivity in lactating dairy cows

This experiment was conducted to investigate the effects of phytonutrients, compared with monensin as a positive control, on productivity, milk fatty acids, fat mobilization, and blood cells in lactating dairy cows. Thirty-six Holstein cows were used in a 9-wk randomized complete block design study. Following a 2-wk covariate period, cows were blocked by days in milk, parity, and milk yield and randomly assigned to 1 of 3 treatments (12 cows/treatment): 450 mg/cow per day of monensin (MO), 250 mg/cow per day of capsicum plus 450 mg/cow per day of MO (MOCAP), and 1,000 mg/cow per day of a mixture of cinnamaldehyde, eugenol, and capsicum (CEC). Dry matter intake and milk yield were not affected by treatment. Supplementation of CEC increased feed efficiency compared with MO, but did not affect feed efficiency on an energy-corrected milk basis. Milk composition (fat, protein, and lactose), milk fatty acid profile, and blood concentrations of nonesterified fatty acids and β-hydroxybutyrate were also not affected by treatment. The expression of hormone-sensitive lipase in adipose tissues tended to increase for MOCAP compared with MO. Counts of total white blood cell, neutrophils, lymphocytes, eosinophils, and basophils were not affected by treatment, although monocytes count tended to be decreased by CEC. Treatments had no effect on red blood cells, hemoglobin, and platelets. Results indicate that dietary supplementation of CEC and capsicum had no production or other effects in dairy cows, compared with MO, except CEC increased feed efficiency and tended to decrease blood monocytes count.

Responses of body fat mobilization to isoproterenol or epinephrine challenge in adult cows: influence of energy level, breed, and body fatness

The sustainability of livestock production systems facing climatic or economic changes is linked in part to the potential of the female ruminants to adapt to feeding constraints through metabolic and hormonal regulation, notably responses of body fat mobilization, depending on adipose tissue (AT) lipolysis. Our hypothesis was that these responses could change according to genotype (breed) and body fatness. Six fat, nonpregnant, nonlactating Charolais cows, six fat Holstein cows, and six lean Holstein cows were used in a 2 × 2 crossover design with two treatments (underfeeding or overfeeding, at 62% [low] or 128% [high] of maintenance energy requirements [MER], respectively) and two periods. Isoproterenol (ISO, a nonselective β-adrenergic agonist) or epinephrine (EPI, a β- and α2-adrenergic agonist) was injected (6 nmol/kg of lean mass). Blood samples were collected regularly from -20 to 75 min after the injection and then were analyzed for NEFA, glycerol, glucose, and L-lactate. Underfeeding greatly increased (P < 0.001) basal plasma NEFA concentrations (+467%, +264%, and +600% for fat Charolais, fat Holstein, and lean Holstein cows, respectively). For each drug, underfed cows had higher NEFA or glycerol responses to adrenergic challenges than overfed cows. Fat Charolais cows had higher basal plasma NEFA (P < 0.05) concentrations (+64.9%) than fat Holstein cows. The plasma NEFA or glycerol response at 5 min (P < 0.05) was higher for fat Charolais than for fat Holstein cows, whatever the injected drug. Basal plasma lactate concentration and lactate response to ISO or EPI were higher (P < 0.05) for fat Charolais cows than for fat Holstein cows. Fat Holstein cows had higher (P < 0.01) basal glycerol (+18.4%) than lean Holstein cows. This increase could be linked to the increased AT mass. ISO increased more lipolytic responses in fat than in lean Holstein cows, whereas EPI increased more these responses in lean than in fat Holstein cows (drug × fatness interaction), suggesting an increased antilipolytic effect due to α2-AR stimulation in fat cows. Breed had a significant effect on basal and stimulated fat mobilization as well as lactate concentrations, suggesting that the Charolais breed could be more sensitive to stress.

Metabolic and Endocrine Role of Adipose Tissue During Lactation

The adipose tissue serves an essential role for survival and reproduction in mammals, especially females. It serves primarily as an energy storage organ and is directly linked to the reproductive success of mammals. In wild animals, adipose tissue function is linked to seasonality of the food supply to support fetal growth and milk production. Adipose tissue depots in ruminants and non-ruminants can secrete many signal molecules (adipokines) that act as hormones and as pro- and anti-inflammatory cytokines. The visceral adipose tissue especially appears to be more endocrinologically active than other adipose depots. The endocrine function is important for the overall long-term regulation of energy metabolism and plays an important role in the adaptation to lactation in many mammalian species, including humans. Furthermore, endocrine signals from adipose tissue depots contribute to fertility modulation, immune function, and inflammatory response. Energy homeostasis is modulated by changes in feed intake, insulin sensitivity, and energy expenditure, processes that can be influenced by adipokines in the brain and in peripheral tissues.

Dose- and type-dependent effects of long-chain fatty acids on adipogenesis and lipogenesis of bovine adipocytes

Differentiation and lipid metabolism of adipocytes have a great influence on milk performance, health, and feed efficiency of dairy cows. The effects of dietary long-chain fatty acids (FA) on adipogenesis and lipogenesis of dairy cows are often confounded by other nutritional and physiological factors in vivo. Therefore, this study used an in vitro approach to study the effect of dose and type of long-chain FA on adipogenesis and lipogenesis of bovine adipocytes. Stromal vascular cells were isolated from adipose tissue of dairy cows and induced into mature adipocytes in the presence of various long-chain FA including myristic, palmitic, stearic, oleic, or linoleic acid. When concentrations of myristic, palmitic, and oleic acids in adipogenic mediums were 150 and 200 μM, the induced mature adipocytes had greater lipid content compared with other concentrations of FA. In addition, mature adipocytes induced at 100 μM stearic acid and 300 μM linoleic acid had the greatest content of lipid than at other concentrations. High concentrations of saturated FA were more toxic for cells than the same concentration of unsaturated FA during the induction. When commitment stage was solely treated with FA, the number of differentiated mature adipocytes was greater for oleic and linoleic acids than other FA. When the maturation stage was treated with FA, the number of mature adipocytes was not affected, but the lipid content in adipocytes was affected and ranked oleic > linoleic > myristic > stearic > palmitic. In summary, this study showed that adipogenesis and lipogenesis of bovine adipocytes were differentially affected by long-chain FA, with unsaturated FA more effective than saturated FA.

Changes in lipid metabolism and β-adrenergic response of adipose tissues of periparturient dairy cows affected by an energy-dense diet and nicotinic acid supplementation

Dairy cattle will mobilize large amounts of body fat during early lactation as an effect of decreased lipogenesis and increased lipolysis. Regulation of lipid metabolism involves fatty acid synthesis from acetate and β-adrenergic-stimulated phosphorylation of hormone-sensitive lipase (HSL) and perilipin in adipocytes. Although basic mechanisms of mobilizing fat storage in transition cows are understood, we lack a sufficiently detailed understanding to declare the exact regulatory network of these in a broad range of dairy cattle. The objective of the present study was to quantify 1) protein abundance of fatty acid synthase (FAS), 2) extent of phosphorylation of HSL and perilipin in vivo, and 3) β-adrenergic stimulated lipolytic response of adipose tissues in vitro at different stages of the periparturient period. We fed 20 German Holstein cows an energy-dense or an energetically adequate diet prepartum and 0 or 24 g/d nicotinic acid (NA) supplementation. Biopsy samples of subcutaneous and retroperitoneal adipose tissue were obtained at d 42 prepartum (d -42) and at d 1, 21, and 100 postpartum (d +1, d +21, d +100, respectively). To assess β-adrenergic response, tissue samples were incubated with 1 μ isoproterenol for 90 min at 37°C. The NEFA and glycerol release, as well as HSL and perilipin phosphorylation, was measured as indicators of in vitro stimulated lipolysis. In addition, protein expression of FAS and extent of HSL and perilipin phosphorylation were measured in fresh, nonincubated samples. There was no effect of dietary energy density or NA on the observed variables. The extent of HSL and perilipin phosphorylation under isoproterenol stimulation was strongly correlated with the release of NEFA and glycerol, consistent with the functional link between β-adrenergic-stimulated protein phosphorylation and lipolysis. In the nonincubated samples, FAS protein expression was decreased at d +1 and d +21, whereas HSL and perilipin phosphorylation increased from d -42 to d +1 and remained at an increased level throughout the first 100 d of lactation. In vitro lipolytic response was significant in prepartum samples at times when in vivo lipolysis was only minimally activated by phosphorylation. These data extend our understanding of the complex nature of control of lipolysis and lipogenesis in dairy cows and could be useful to the ongoing development of systems biology models of metabolism to help improve our quantitative knowledge of the cow.

Characterization of the dynamics of fat cell turnover in different bovine adipose tissue depots

In many but not all high producing cows, the energy requirements for milk yield and maintenance exceed energy intake by voluntary feed intake during early lactation. Prioritizing milk secretion, body reserves mainly from adipose tissue are mobilized and imply an increased risk for metabolic diseases. Reducing the energy output via milk by decreasing the milk fat content through feed supplements containing conjugated linoleic acids (CLAs) may attenuate the negative energy balance during this period. In two separate trials, variables characterizing fat cell turnover were investigated in different subcutaneous and visceral fat depots from primiparous heifers (n = 25) during early lactation, and subcutaneous fat from non-lactating, over-conditioned heifers (n = 12) by immunohistochemistry. The portion of apoptotic adipocytes was consistently greater than that of proliferating cells and preadipocytes; the sporadically observed effects of CLA were limited to visceral fat. Lactating heifers had more apoptosis and less preadipocytes than non-lactating heifers.

Effects of Chromium Propionate on Response to an Intravenous Glucose Tolerance Test in Growing Holstein Heifers

To test the effect of chromium propionate on glucose utilization in growing dairy heifers, 0, 5, 10, or 15 mg of chromium/d were fed to 20 Holstein heifers of 11 to 14 mo of age, in a replicated Latin square. A 2-wk adaptation period was followed by 4 periods of 2 wk each with a 2-wk flush out period between treatments. Treatments were allotted to periods in a design balanced for potential carryover effects. Chromium propionate was fed in 0.25 kg/d of ground corn individually. After 14 d on each treatment, animals were fitted with an indwelling jugular catheter, and an intravenous glucose tolerance test was conducted the following morning. Body weights increased throughout the experiment, but weights and condition scores were unaffected by treatment. Chromium supplementation increased basal glucose and decreased basal insulin and nonesterified fatty acids (NEFA) in serum in a dose-dependent, quadratic manner. Chromium increased glucose clearance rate as measured by half-life, time to nadir, and area under the curve. Over all periods, insulin concentrations tended to be lower in treated animals whereas clearance rates were unchanged. Serum NEFA levels were negatively correlated with glucose, such that treated animals with increased glucose had lower NEFA overall. There was an apparent long-term effect of chromium, because heifers in period 4 on the control diet had reduced insulin concentrations than those in the other control periods. Chromium propionate may increase glucose utilization in growing dairy heifers.

Insulin-like growth factors-I and -II, somatotropin, prolactin, and placental lactogen are not acute effectors of lipolysis in ruminants

The acute regulation of lipolysis in the adipose tissue of ruminants was evaluated with lactating cows (n = 4) and growing ewe lambs (n = 11). Subcutaneous adipose tissue was obtained by biopsy or at slaughter and was incubated with varying concentrations of biologically active insulin-like growth factors-I and -II (IGF-I, IGF-II), somatotropin (ST), prolactin (PRL), or placental lactogen (PL) to determine the effect of these hormones on lipolysis. Complimentary studies were conducted to examine the effects of IGF-I and IGF-II on the acute regulation of lipolysis in adipose tissue from lactating ewes and wethers under a variety of incubation conditions. Isoproterenol (ISO), a beta-adrenergic agonist known to rapidly stimulate lipolysis, was used as a positive control. Incubation with ISO for 3 hr resulted in a significant increase in the rates of lipolysis. However, there was no stimulation of lipolysis over the 3-hr incubation at any concentration or under any conditions for IGF-I or IGF-II. Furthermore, ST, PRL, or PL had no acute effects on the rates of lipolysis in adipose tissue. These data demonstrate that IGF-I, IGF-II, ST, PRL, and PL are not acute effectors of the lipolytic rate in the adipose tissue of ruminants.

Effects of lactation on the signal transduction systems regulating lipolysis in sheep subcutaneous and omental adipose tissue

The effect of lactation on the regulation of lipolysis by beta- and alpha 2-adrenergic agents and by adenosine has been investigated. When changes in adipocyte mean cell volume (which decreases with lactation) are allowed for, lactation increased the maximum response both to beta-adrenergic agents and to the adenosine analogue N6-phenylisopropyladenosine, but had no apparent effect on the responsiveness of the alpha 2-adrenergic system in both subcutaneous and omental adipocytes. For subcutaneous adipocytes, there was no significant change in the number of beta-adrenergic or alpha 2-adrenergic receptors, but the amount of Gs and the maximum (forskolin-stimulated) adenylate cyclase activity were increased by lactation. In contrast, in omental adipocytes, the number of beta- (but not alpha 2-) adrenergic receptors and the amount of Gs were increased, whereas forskolin-stimulated adenylate cyclase activity was unchanged by lactation. In both types of adipocyte, cyclic AMP phosphodiesterase and total protein kinase A activities were unchanged. Lactation had no effect on the number of adenosine receptors but increased the amounts of the Gi isoforms expressed in both types of adipocyte. These various adaptations differ markedly in a number of respects from those described previously in the rat. Lactation, then, while having a similar overall effect on the response to beta-adrenergic agonists of adipocytes, achieves this by depot-specific mechanisms. In contrast, changes in response to adenosine appear to involve the same mechanism in the two depots investigated.

Glycerolipid biosynthesis in adipose tissue of the bovine during growth

1. Rates of palmitate esterification in tissue slices and glycerophosphate acyltransferase activity in homogenates were determined in bovine subcutaneous and intermuscular adipose tissue at 340, 418 or 498 kg of live weight. 2. Lower rib section fat accretion rates were observed from 340 to 418 kg than from 418 to 498 kg. 3. Changes in palmitate esterification rates at different body weights were consistent with reduced rib section fat accretion as well as with reported differences in fat accretion in subcutaneous and intermuscular fat depots. 4. Glycerophosphate acyltransferase activity was increased at 418 kg and remained elevated whereas palmitate esterification was decreased at 418 and then increased at 498 kg. 5. Differences between palmitate esterification and glycerophosphate acyltransferase in vitro may have been related to differences in substrate supply.

Effect of adipose tissue site, animal size, and fasting on lipolysis in bovine adipose tissue in vitro

1. Lipolytic rates expressed as mumol glycerol released per mg protein increased with body weight in Holstein steers. 2. Lipolytic rates were greatest in both inner and outer back fat and lowest in omental, perirenal, and intermuscular fat depots. 3. Epinephrine stimulated overall glycerol release 3-5-fold. 4. Fasting resulted in greater basal lipolytic rates but epinephrine-stimulated rates tended to be greater for nonfasted steer adipose tissue. 5. Lipolytic activity in adipose tissue seems to increase with growth and fattening, and differences in lipolytic rates between various depots diminish with growth.

Duodenal rapeseed oil infusion in early and midlactation cows. 4. In vivo and in vitro adipose tissue lipolytic responses

In vitro glycerol and FFA releases from adipose tissue were studied in early (wk 3, trial 1) and midlactation (wk 19 to 26, trial 2) multiparous Holstein Friesian cows receiving a duodenal rapeseed oil infusion (1.0 to 1.1 kg/d). In trial 2, in vitro basal FFA release, basal FFA: glycerol ratio, and isoproterenol-stimulated FFA and glycerol releases were higher in perirenal adipose tissue from oil-infused cows. Plasma FFA concentration also was higher in oil-infused cows before and after intravenous isoproterenol injection. In trail 1, basal and stimulated glycerol and FFA releases from perirenal (but not subcutaneous) adipose tissue tended to be lower in oil-infused cows. This was probably linked to a lower milk production potential of oil-infused than of control cows which introduced a bias in energy balance. The basal FFA:glycerol ratio tended to be higher in oil-infused cows in both adipose tissues, suggesting a lower rate of reesterification inducted by oil, as was the case in trial 2. The alpha 2-agonist clonidine decreased perirenal adipose tissue glycerol release in cows and treatments in which the responses to 4 x 10(-7) M isoproterenol were higher. In vivo and in vitro lipolytic responses were lower in trial 2 than in trial 1, except the in vitro maximally stimulated lipolytic rate, which probably reflected a long lasting teleophoretic adaptation to ensure energy needs of lactation. This study indicated that oil infusion affected both beta- and alpha 2-adrenergic responses and that postpartum lipid mobilization did not seem to be reduced by the exogenous unsaturated fatty acid supply.

Regulation of adipose tissue metabolism in support of lactation

In the dairy cow, adipose tissue lipid accumulates during pregnancy, and catabolism begins prior to parturition and increases dramatically afterward. After peak lactation, body lipid is replenished. The duration and magnitudes of these adaptations depend on milk energy secretion, net energy intake, genotype, and endocrine environment. Recent research efforts have focused on endocrine, genetic, and biochemical mechanisms underlying metabolic adaptations in cows of high production potential. Adipose tissue lipid synthesis is decreased and lipolysis is increased in early lactation. The magnitude and duration of these adaptations are increased in animals either consuming relatively less energy or producing more milk. Adipose tissue is more responsive to catecholamines in early and midlactation and in animals with higher production. This is more of an increase in maximal response than in sensitivity. In vivo and in vitro rates of adipose tissue lipolysis correlate positively with milk energy secretion, whereas lipid synthesis rates correlate with energy intake. Thus, mammary metabolic activity, within and among lactations, correlates with that in adipose tissue. Likely mechanisms include adaptations in receptors for homeostatic signals and modulation of postreceptor responses. Research is needed into neural, genetic, and hormone regulation of nutrient utilization and body fat use and recovery during lactation. Research should describe mechanistic relationships among nutrients in animals of high production as well as investigate cellular and molecular mechanisms suitable to genetic manipulation.

Regulation of bovine adipose tissue metabolism during lactation. 6. Cellularity and hormone-sensitive lipase activity as affected by genetic merit and energy intake

Subcutaneous adipose tissue cell size and density and hormone-sensitive lipase activity were determined during late pregnancy and first lactation in Holstein heifers. Animals were daughters of bulls with either +791 (high line) or +390 (low line) kg Predicted Difference (1974 base) for milk. Each line consumed either a 71%: 29% (high energy) or a 36%:63% (low energy) barley concentrate and alfalfa hay diet from 0 to 140 d lactation. Heifers fed the low energy ration ate 33% less NE1 and produced 20% less milk with 52.7% greater milk fat percentage during 28 to 140 d of lactation than heifers fed the high energy ration. Prepartum, animals of the high line had similar adipocyte volume and density to low line animals. However, during early lactation, high line animals had a greater decrease in volume and a larger increase in density than low line animals. There was a delayed recovery of volume in high line, compared with low line animals in late lactation. Adipocyte volume also was decreased by dietary energy restriction. Hormone-sensitive lipase activity was similar in both genetic lines prepartum and increased in all groups at 60 d postpartum. Animals of high line or fed low energy rations had increased activity per gram during early, but not later, lactation. Activity per cell and per milligram cytoplasm protein increased in all groups in early lactation and were highest in high line animals fed the low energy ration.