Effect of a very low negative dietary cation-anion difference (DCAD) diet on plasma and urine metabolomics of prepartum Holstein cows.

The objectives of this cross-sectional, nonintervention, observational study were to compare urine and blood parameters between cows consuming a positive dietary cation-anion difference (DCAD) diet [early dry cows, DCAD + 250 mEq/kg of dry matter (DM), n = 15] with the same cows consuming a negative DCAD diet (-220 mEq/kg of DM) 10 d after moving them from the early dry to the prepartum group. The most remarkable finding was that cows consuming the anionic diet had very low urine pH and very low base excess in blood, suggestive of uncompensated metabolic acidosis. Importantly, the metabolomics data revealed that only urine concentrations of essential and aromatic amino acids were decreased, and that concentrations of total nonessential amino acids and glucogenic amino acids were increased in plasma and reciprocally decreased in urine, suggesting that the cows fed anionic salts were attempting to meet a high glucose demand by mobilizing gluconeogenic amino acid reserves. Notably, the dietary anionic salts exerted marked effects on glycerophospholipids, with a reduction in most phosphatidylcholine containing diacyl (PC aa) and acyl-alkyl (PC ae) moieties in plasma and urine. Further characterization of these metabolomic profiles may lead to the development of novel biomarkers to identify cows susceptible to metabolic acidosis and other metabolic diseases.

Markers of muscle atrophy and impact of treatment with pergolide in horses with pituitary pars intermedia dysfunction and muscle atrophy.

Pituitary pars intermedia dysfunction (PPID) is a common endocrine disorder of aged horses, with muscle atrophy as one of the clinical signs. We sought to compare muscle mass and regulation of skeletal muscle proteolysis between horses with PPID and muscle atrophy to older horses without PPID, and to assess the impact of treatment with pergolide (dopaminergic agonist) on PPID horses. We hypothesized that PPID-associated muscle atrophy is a result of increased proteolysis, and that markers of muscle atrophy and proteolysis would improve over time with pergolide treatment. Markers of muscle atrophy, adiposity, insulin regulation, skeletal muscle composition, and proteolysis (muscle atrophy F- box/atrogin 1 [MAFbx1], muscle RING finger 1 [MuRF1], Bcl2/adenovirus EIV 19kD interacting protein 3 [Bnip3], and microtubule-associated light chain 3 [LC3]) were compared between PPID and control horses. PPID horses were treated for 12 weeks with either pergolide or placebo. Dose of pergolide was adjusted based upon monthly measurement of adrenocorticotropin, and markers of muscle atrophy, adiposity, insulin regulation, skeletal muscle composition, and proteolysis were compared after 12 weeks of treatment. Horses with PPID exhibited increased transcript abundance of MuRF1 (P= 0.04) compared to control. However, no difference was observed in transcript abundance of markers of proteolysis with treatment (P ≥ 0.25). Pergolide treated horses lost weight (P = 0.02) and improved fasting insulin (P = 0.02), while placebo treated horses gained weight and rump fat thickness (P = 0.02). Findings from this study suggest that treatment with pergolide may promote weight loss and improve insulin regulation in horses with PPID, but does not impact muscle mass or markers of muscle proteolysis.

Circulating concentrations of glucagon-like peptide 1, glucose-dependent insulinotropic peptide, peptide YY, and insulin in client-owned lean, overweight, and diabetic cats.

Our objectives were to measure plasma concentrations of glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and peptide YY (PYY) in client-owned newly diagnosed diabetic cats and nondiabetic lean or overweight cats and to determine whether circulating concentrations of these hormones differed between study groups and if they increased postprandially as seen in other species. A total of 31 cats were recruited and placed into 1 of 3 study groups: lean (body condition score 4-5 on a scale of 1-9; n = 10), overweight (body condition score 6-8; n = 11), or diabetic (n = 10). Diabetics were newly diagnosed and had not had prior insulin therapy. Preprandial (fasting) and postprandial (60 min after meal) plasma hormone and glucose concentrations were measured at baseline and 2 and 4 wk. All cats were exclusively fed a commercially available high-protein and low-carbohydrate diet commonly prescribed to feline diabetic patients for 2 wk before the 2-wk assessment and continued through the 4-wk assessment. Results showed that plasma concentrations of GLP-1, GIP, PYY, and insulin increased in general after a meal in all study groups. Plasma PYY concentrations did not differ (P > 0.10) between study groups. Diabetics had greater plasma concentrations of GLP-1 and GIP compared with the other study groups at baseline (P < 0.05), and greater preprandial and postprandial GLP-1 concentrations than lean cats at 2 and 4 wk (P < 0.05). Preprandial plasma GIP concentrations were greater in diabetics than obese and lean (P < 0.05) cats at week 4. Postprandial plasma GIP concentrations in diabetics were greater than lean (P < 0.05) at week 2 and obese and lean cats (P < 0.05) at week 4. Together, our findings suggest that diabetic status is an important determinant of circulating concentrations of GLP-1 and GIP, but not PYY, in cats. The role of GLP-1, GIP, and PYY in the pathophysiology of feline obesity and diabetes remains to be determined.

Ileal transposition surgery produces ileal length-dependent changes in food intake, body weight, gut hormones and glucose metabolism in rats.

BACKGROUND: Enhanced stimulation of the lower gut is hypothesized to play a key role in the weight loss and resolution of diabetes following bariatric surgeries. Ileal transposition (IT) permits study of the effects of direct lower gut stimulation on body weight, glucose homeostasis and other metabolic adaptations without the confounds of gastric restriction or foregut exclusion. However, the underlying mechanisms and the length of the ileum sufficient to produce metabolic benefits following IT surgery remain largely unknown. OBJECTIVE: To determine the effects of transposing varying lengths of the ileum to upper jejunum on food intake, body weight, glucose tolerance and lower gut hormones, and the expression of key markers of glucose and lipid metabolism in skeletal muscle and adipose tissue in rats. METHODS: Adult male Sprague-Dawley rats (n=9/group) were subjected to IT surgery with translocation of 5, 10 or 20 cm of the ileal segment to proximal jejunum or sham manipulations. Daily food intake and body weight were recorded, and an intraperitoneal glucose tolerance test was performed. Blood samples were assayed for hormones and tissue samples for mRNA (RT-qPCR) and/or protein abundance (immunoblotting) of regulatory metabolic markers. RESULTS: We demonstrate that IT surgery exerts ileal length-dependent effects on multiple parameters including: (1) decreased food intake and weight gain, (2) improved glucose tolerance, (3) increased tissue expression and plasma concentrations of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), and decreased leptin concentrations and (4) upregulation of key markers of glucose metabolism (glucose transporter-4 (GLUT-4), insulin receptor substrate 1 (IRS-1), adenosine monophosphate-activated protein kinase (AMPK), hexokinase (HK) and phosphofructokinase (PFK)) together with a downregulation of lipogenic markers (fatty acid synthase (FAS)) in muscle and adipose tissue. CONCLUSIONS: Together, our data demonstrate that the reduction in food intake and weight gain, increase in lower gut hormones, glycemic improvements and associated changes in tissue metabolic markers following IT surgery are dependent on the length of the transposed ileum.

Effects of sleeve gastrectomy and ileal transposition, alone and in combination, on food intake, body weight, gut hormones, and glucose metabolism in rats.

Bariatric surgeries are hypothesized to produce weight loss and improve diabetes control by multiple mechanisms including gastric restriction and lower gut stimulation; the relative importance of these mechanisms remains poorly understood. We compared the effects of a typical foregut procedure, sleeve gastrectomy, (SG) with a primarily hindgut surgery, ileal transposition (IT), alone and together (SGIT), or sham manipulations, on food intake, body weight, gut hormones, glucose tolerance, and key markers of glucose homeostasis in peripheral tissues of adult male Sprague-Dawley rats (450-550 g, n = 7-9/group). SG, IT, and SGIT surgeries produced transient reduction in food intake and weight gain; the effects of SG and IT on intake and body weight were nonadditive. SG, IT, and SGIT surgeries resulted in increased tissue expression and plasma concentrations of the lower gut hormones glucagon-like peptide-1 and peptide YY and decreased plasma glucose-dependent insulinotropic peptide, insulin, and leptin concentrations. Despite transient effects on intake and weight gain, the SG, IT, and SGIT surgeries produced a significant improvement in glucose tolerance. In support of glycemic improvements, the protein abundance of key markers of glucose metabolism (e.g., GLUT4, PKA, IRS-1) in muscle and adipose tissue were increased, whereas the expression of key gluconeogenic enzyme in liver (G-6-Pase) were decreased following the surgeries. Therefore, our data suggest that enhanced lower gut stimulation following SG, IT, and SGIT surgeries leads to transient reduction in food intake and weight gain together with enhanced secretion of lower gut hormones and improved glucose clearance by peripheral tissues.

Short communication: expression of peptide YY, proglucagon, neuropeptide Y receptor Y2, and glucagon-like peptide-1 receptor in bovine peripheral tissues.

The role of distal gut signals in control of feed intake and metabolism in cattle has received scant attention. Peptide YY (PYY) and glucagon-like peptide-1, which are secreted from enteroendocrine cells of the distal gut in monogastrics have several functions, including regulation of energy balance. However, little is known of the tissue expression of these peptides and their receptors in cattle. The aim of the current study was to characterize the tissue distribution of PYY, neuropeptide Y receptor Y2 (Y2), proglucagon (GCG), and glucagon-like peptide-1 receptor (GLP1R) in various peripheral tissues of cattle. Four male 7-wk-old dairy calves were euthanized and 16 peripheral tissues were collected. Conventional PCR and quantitative real-time PCR were performed to confirm tissue expression and quantify the transcript abundance in various tissues. The results of conventional PCR revealed that mRNA for both PYY and Y2 was detectable in the rumen, abomasum, duodenum, jejunum, ileum, and colon but not in other tissues. Quantitative real-time PCR data demonstrated that PYY mRNA was 2- to 3-fold greater in the pancreas, kidney, and heart relative to the liver. By conventional PCR, GCG mRNA was detected in the abomasum, duodenum, jejunum, ileum, and colon and GLP1R mRNA was expressed in all gut segments, pancreas, spleen, and kidney. Quantitative real-time PCR data demonstrated that, relative to transcript abundance in the liver, GCG mRNA was 4- to 40-fold higher from abomasum to colon, and GLP1R mRNA was 50- to 300-fold higher from the rumen to colon, 14-fold greater in the pancreas, 18-fold higher in the spleen, and 166-fold greater in the kidney. The tissue distribution of PYY, GCG, and their receptors observed in the current study is, in general, consistent with expression patterns in monogastrics. The predominant expression of PYY, Y2, and GCG in the gut, and the presence of GLP1R in multiple peripheral tissues suggest a role for PYY in controlling gut functions and for GLP-1 in regulating multiple physiological functions in cattle.

Gastric distention induced functional magnetic resonance signal changes in the rodent brain.

Investigating the localization of gastric sensation within the brain is important for understanding the neural correlates of satiety. Previous rodent studies have identified the brain-stem and hypothalamus as key mediators of gastric distention-induced satiation. Although, recent blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) studies in humans have identified a role for higher cortico-limbic structures in mediating the satiation effects of gastric distention, the role of these regions in rodents remains to be characterized. We determined the effects of gastric distention on global spatio-temporal BOLD fMRI signal changes in the rodent brain. Brain images were acquired with a high resolution 9.4 T magnet during gastric distention with continuous monitoring of blood pressure in adult male Sprague Dawley rats (n=8-10). Distention of the stomach with an intragastric balloon, at rates which mimicked the rate of consumption and emptying of a mixed nutrient liquid meal, resulted in robust reduction in food intake and increase in blood pressure. Gastric distention increased BOLD fMRI activity within homeostatic regions such as the hypothalamus and nucleus tractus solitarius, as well as non homeostatic regions including the hippocampus, amygdala, thalamus, cerebellum and the cortex (cingulate, insular, motor and sensory cortices). Further, the increase in BOLD fMRI activity following distention was strongly correlated to an increase in blood pressure. These results indicate that gastric distention, mimicking the rate of intake and emptying of a liquid meal, increases BOLD fMRI activity in both homeostatic and non homeostatic brain circuits which regulate food intake, and that these BOLD fMRI signal changes may in part be attributable to transient increases in blood pressure.

Effects of dietary energy and protein density on plasma concentrations of leptin and metabolic hormones in dairy heifers.

The hormonal and metabolic signals that communicate the level of body energy reserves to the reproductive-mammary axis remain undefined in dairy cattle; consequently, our hypothesis was that leptin may fulfill this role. Our objectives were to determine the effects of diets differing in energy and protein density on dry matter intake (DMI), growth traits [body weight (BW), body condition score (BCS), back-fat (BF) thickness], and temporal changes in plasma concentrations of leptin, insulin, growth hormone (GH), insulin-like growth factor-1 (IGF-1), glucose, and nonesterified fatty acids (NEFA) in dairy heifers during the pre- and postpubertal periods. In period 1, heifers were randomly allotted (n = 10/diet) at 103 kg of BW to diets for a predicted average daily gain of 1.10 (high, H), 0.80 (medium, M), or 0.50 kg/d (low, L). Five heifers in each of the H and L groups were further studied during period 2, either at 12 mo of age (HA, LA) or at 330 kg of BW (HW, LW). The data provide evidence that 1) DMI (18%), BW (17%), and BF (5%) together explained 40% of the variation in plasma leptin concentrations (r(2) = 0.396); 2) unlike the acute postprandial increase in plasma insulin as a result of increased nutrient density (H 1.42 +/- 0.09, M 1.02 +/- 0.09, L 0.68 +/- 0.11 ng/mL), plasma leptin concentrations did not respond acutely with a distinct postprandial profile; 3) although plasma leptin concentrations increased with age, leptin at puberty did not differ among treatment groups (H 5.63 +/- 2.48, M 4.28 +/- 0.55, L 4.12 +/- 0.72 ng/mL) and there was no evidence of an abrupt transition in prepubertal plasma leptin concentrations; 4) plasma leptin concentrations may not be a critical trigger for puberty in rapidly growing heifers, but are apparently essential for puberty in heifers with normal or restricted growth rates; and 5) plasma concentrations of insulin (H 0.59 +/- 0.07, M 0.43 +/- 0.09, L 0.30 +/- 0.09 ng/mL), IGF-1 (H 151.08 +/- 16.47, L 82.51 +/- 17.47 ng/mL), and glucose (H 81.35 +/- 3.39, M 73.59 +/- 2.34, L 68.25 +/- 3.39 mg/dL) reflected nutrient density, whereas GH (H 1.82 +/- 0.23, L 5.87 +/- 0.45 ng/mL) and NEFA (H 209.54 +/- 50.83, L 234.93 +/- 48.97 microM) were inversely related to the plane of nutrition. Collectively, these data suggest that plasma concentrations of leptin may play a role in long-term regulation of energy reserves and puberty in growing Holstein heifers.

PYY(3-36) induces Fos in the arcuate nucleus and in both catecholaminergic and non-catecholaminergic neurons in the nucleus tractus solitarius of rats.

Peptide YY (3-36) [PYY(3-36)] inhibits feeding in rodents, nonhuman primates and humans, yet the neural circuits underlying this action remain to be determined. Here we assessed whether PYY(3-36) inhibits feeding by activating neurons in forebrain and hindbrain sites containing Y2 receptors and linked to control of food intake, or in hindbrain sites immediately downstream of vagal afferent neurons. Rats received an anorexigenic dose of PYY(3-36), and the number of neurons expressing Fos, an indicator of neuronal activation, was determined in anterior hypothalamus (AH), arcuate nucleus (ARC), dorsomedial hypothalamus (DMH), lateral hypothalamus (LH), ventromedial hypothalamus (VMH), central nucleus of the amygdala (CeA), area postrema (AP), and caudal medial nucleus tractus solitarius (cmNTS), commissural NTS (cNTS), and gelatinosus NTS (gNTS). Expression of tyrosine hydroxylase (TH), an indicator of catecholamine synthesis, was also measured in the cmNTS. PYY(3-36) increased Fos in ARC, cmNTS, gNTS and AP. Approximately 10% of Fos+ neurons in the cmNTS were TH+. These results suggest that PYY(3-36) inhibits feeding through direct activation of ARC neurons, and direct and/or indirect activation via vagal afferent nerves of cmNTS, gNTS and AP, including some catecholaminergic neurons in the cmNTS.

Effect of short-term fasting on plasma concentrations of leptin and other hormones and metabolites in dairy cattle.

We determined the effects of short-term fasting and refeeding on temporal changes in plasma concentrations of leptin, insulin, insulin-like growth factor- 1 (IGF-1), growth hormone (GH), glucose, and nonesterified fatty acids (NEFA), in early lactating cows, non-lactating pregnant cows, and postpubertal heifers. In experiment 1, Holstein cows in early lactation were either fed ad libitum (Control, n=5) or feed deprived for 48 h (Fasted, n=6). Plasma leptin, insulin, and glucose concentrations rapidly declined (P<0.05) within 6h, and IGF-1 by 12h, but all these variables sharply returned to control levels (P>0.10) within 2h of refeeding. Plasma NEFA and GH concentrations were elevated (P<0.05) by 4 and 36 h of fasting and returned to control levels (P>0.10) by 8 and 24h after refeeding, respectively. In experiment 2, four ruminally cannulated pregnant non-lactating Holstein cows were used in a cross-over design and were fasted for 48 h (Fasted) or fasted with partial evacuation of rumen contents (Fasted-Evac). The plasma variables measured did not differ (P>0.10) between Fasted and Fasted-Evac cows. Plasma leptin, insulin, and IGF-1 concentrations were reduced by 10, 6, and 24h of fasting, respectively, in Fasted-Evac cows; and these variables were reduced by 24h in Fasted cows (P<0.05). Plasma glucose levels were reduced (P<0.05) by 48 h of fasting in both groups of fasted animals. Plasma NEFA and GH levels were increased (P<0.05) by 12 and 48 h of fasting, respectively. In experiment 3, postpubertal Holstein heifers were either fed ad libitum (Control, n=4) or feed deprived for 72 h (Fasted, n=5). Concentrations of leptin, insulin, IGF-1, and glucose in plasma were reduced (P<0.05) by 24, 10, 24, and 48 h of fasting, respectively. Plasma NEFA concentrations increased (P<0.05) by 4h, of fasting while GH levels were not significantly (P>0.10) affected by fasting. Collectively, our data provide evidence that plasma leptin concentrations are reduced with short-term fasting and rebound on refeeding in dairy cattle with the response dependent on the physiological state of the animals. Compared to the rapid induction of hypoleptinemia with fasting of early lactation cows, the fasting-induced hypoleptinemia was delayed in non-lactating cows and postpubertal heifers.

Short communication: Tissue distribution of leptin and leptin receptor mRNA in the bovine.

Detection of leptin and leptin receptor mRNA in various tissues is crucial to an understanding of leptin physiology in dairy cattle. We report here evidence of leptin receptor gene expression in central and peripheral tissues of the bovine by reverse transcription and polymerase chain reaction analysis. Leptin mRNA was detectable in mammary parenchyma and in adipose tissue with similar transcript abundance among the subcutaneous, pericardial, perirenal, and mesenteric adipose depots. The mRNA for the long-form of the leptin receptor, Ob-Rb, was detectable in all four adipose depots, mammary parenchyma, semintendinosus muscle, liver, adrenal cortex, spleen, kidney, testis, mesenteric lymph node, lung, aorta, abomasum, duodenum, jejunum, ileum, hypothalamus, pituitary, brain stem, cerebral cortex, cerebellar cortex, pons, and pineal gland. The mRNA for the short form of the leptin receptor, Ob-Ra, was detectable in the liver, adrenal cortex, spleen, pituitary, and brain stem, but not in the other tissues surveyed. The wide spectrum of tissues expressing the leptin receptor gene reveals that leptin may have multiple physiological functions in the bovine.

Effect of dietary energy and protein density on body composition, attainment of puberty, and ovarian follicular dynamics in dairy heifers.

The objectives were to examine the effects of dietary energy and protein density on age and body composition at puberty, and on ovarian follicular dynamics during the pre- and peripubertal periods in Holstein heifers. In Phase 1, heifers were randomly allotted (n=10 per diet) at 100 kg body weight (BW) to diets with either low (P1L), medium (P1M) or high (P1H) energy and protein formulated for an average daily gain (ADG) of 0.5, 0.8 or 1.1 kg per day, respectively. During Phase 2 (P2), all heifers were fed ad libitum a common diet formulated for an ADG of 0.8 kg per day. Half the animals within the high (n=5) and low groups (n=5) entered P2 either at 12 months of age (P2H-12; P2L-12) or at 330 kg BW (P2H-330; P2L-330). Heifers fed P1H, P1M, P1L, and P2L-12 diets attained puberty at approximately 9, 11, 16, and 14 months of age, respectively (P<0.01). Urea space estimates of body fat and protein percent, and back-fat thickness, were lower in P1L heifers compared to P1H or P1M heifers at similar chronological ages (P<0.05) but did not differ at puberty (P>0.10). Compared to P1L heifers, P1H heifers had high amplitude LH pulses at 8 months, and high frequency low amplitude LH pulses at 10 months of age (P<0.05). The mean diameter (mm) of the dominant follicle was smaller (P<0.05) in P1L heifers (10.6) compared to P1H (12.8) or P1M (12.2) heifers at 8 months. Maximum size and growth rate of the nonovulatory dominant follicle increased with age (P<0.05) but did not differ between P1H and P1M heifers at puberty. The diameter (mm) of the nonovulatory dominant follicle, and the first and second ovulatory follicles were larger in P2L-12 heifers (14.0, 14.7, and 14.9) compared to P1M heifers (13.1, 12.5, and 11.9), while the peak progesterone levels and CL growth were lower (P<0.05) in the first cycle. In conclusion, dairy heifers attained puberty at a constant body weight and body composition independent of dietary manipulation, the size of dominant follicles increased with age in association with increased LH support, and heifers realimented from a low energy diet developed larger first ovulatory follicles and smaller CL with lower peak progesterone concentrations in the first cycle.