Changes in lipid metabolism and β-adrenergic response of adipose tissues of periparturient dairy cows affected by an energy-dense diet and nicotinic acid supplementation1

Abstract

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.

Niacin nutrition and rumen-protected niacin supplementation in dairy cows: an updated review

“…Milk yield and milk protein percentage were not affected by either RPN or free niacin supplement in early lactation in several studies (16,17,44,(46)(47)(48) , which is in line with most of the earlier studies investigating the effects of free niacin supplementation on milk yield and milk protein percentage (5) . Supplementation of RPN in early lactation decreased milk fat percentage in two studies (17,44) .…”

“…Those authors suggested that stimulating HCA 2 by nicotinic acid triggers the anti-lipolytic pathway. However, supplementing niacin in feed did not influence the HCA 2 mRNA abundance in the liver (16,17) or the extent of HSL phosphorylation in early lactation (48) . The short half-life of nicotinic acid or the ruminal degradation probably explains the lack of effect of niacin on HCA 2 mRNA abundance or HSL phosphorylation.…”

“…It is likely that niacin supplementation level may play a role in the antilipolytic effect in dairy cows. In early lactation, the relatively low dosages of free nicotinic acid or nicotinamide supplementation (6-24 g/d) in studies summarised by Niehoff et al (5) and two more recent studies (47,48) demonstrated only minor effects, whereas 12 g/d of RPN (16,44) , 45 g/d of nicotinamide (46) or 120 g/d of nicotinic acid (45) supplementation demonstrated a greater influence on plasma NEFA concentration. The extensive degradation of free niacin in the rumen may partly explain the lack of effects when a low level of nicotinic acid was supplemented.…”

“…Circulating NEFA is an important indicator of adipose mobilisation and metabolic health in dairy cows (43) . In some studies (44)(45)(46) , supplementation of nicotinic acid, RPN or nicotinamide during transition periods was reported to decrease the plasma NEFA concentration, but in some other studies (17,47,48) supplementation had no influence (Table 4). Additionally, Morey et al (16) reported that 12 g/d RPN supplementation in early lactation decreased peak plasma NEFA concentration but did not affect the average plasma NEFA concentration.…”

Effects of energy supply and nicotinic acid supplementation on serum anti‐oxidative capacity and on expression of oxidative stress‐related genes in blood leucocytes of periparturient primi‐ and pluriparous dairy cows

“…Nicotinic acid is hereby readily transformed into nicotinamide that is a precursor of the coenzymes β‐nicotinamide adenine dinucleotide (NAD + ) and nicotinamide adenine dinucleotide phosphate (NADP + ), which participate in anabolic and catabolic pathways. Niacin is well known for its anti‐lipolytic effect (Carlson, ), and nicotinic acid was shown in the bovine to downregulate lipolysis in vitro (Kenez, Locher, Rehage, Danicke, & Huber, ) while in vivo results are inconsistent showing either an anti‐lipolytic effect (Morey et al., ; Pires & Grummer, ; Yuan, Shaver, Bertics, Espineira, & Grummer, ) or no protective effects (Kenez et al., ; Tienken, Kersten, Frahm, Meyer, et al., ). Nicotinamide participates in the cellular energy metabolism and influences oxidative stress.…”