Adipose Tissue Inflammation: Linking Physiological Stressors to Disease Susceptibility

Meta-analysis to determine the effects of supplementation of niacin during the transition or lactation period on performance in dairy cows

Niacin, a key component of pyridine nucleotides, plays a vital role in over 200 metabolic reactions, including carbohydrate, lipid, and AA metabolism. This meta-analysis aimed to evaluate the effects of niacin supplementation on lactational performance in dairy cows. We hypothesized that niacin supplementation during the transition or lactation period would enhance the productive performance of dairy cows. A systematic review identified 41 experiments, comprising 128 treatment means and 1,992 cows, which were included in the meta-analysis. Each experiment featured a nonsupplemented control (CON) group and a supplemented group, with niacin provided as either rumen-unprotected niacin (RUPN) or rumen-protected niacin (RPN). Supplementation was initiated during either the transition or lactation period, resulting in the categorization of data into 4 distinct cohorts: cows supplemented with RUPN or RPN during either the transition or lactation period. Cows supplemented with RUPN during the transition (CON; n = 13 treatment means vs. RUPN; n = 14 treatment means) and lactation periods (CON; n = 33 treatment means vs. RUPN; n = 40 treatment means) had average niacin intakes (mean ± SD) of 13.9 ± 10.8 g/d and 9.1 ± 3.5 g/d, respectively. Cows supplemented with RPN during the transition (CON; n = 4 treatment means vs. RPN; n = 4 treatment means) and lactation periods (CON; n = 8 treatment means vs. RPN; n = 12 treatment means) had niacin intakes of 11.7 ± 7.3 g/d and 4.6 ± 2.0 g/d, respectively. Mixed models were used to investigate the linear and quadratic effects of RUPN or RPN. Meta-analytical statistics in STATA estimated the weighted mean difference (WMD) of milk yield for treatment comparisons (CON vs. RUPN and CON vs. RPN). All models included the random effect of experiment and weighting by the inverse of the SEM squared. Supplementation of niacin, whether RUPN or RPN, during the transition period did not improve performance in dairy cows. However, RUPN supplementation during the regular lactation period led to linear increases in DMI, yields of milk, ECM, protein and lactose, and increments of 0.50, 0.90, 0.70, 0.04, and 0.05 kg/d, respectively, were observed when cows were supplemented with 9.1 g/d RUPN. In 38 treatment comparisons from 20 experiments evaluating RUPN supplementation during the lactation period, the mean response indicated that RUPN cows produced 0.83 kg/d more milk than CON cows (WMD = 0.83; 95% CI = 0.35-1.31), with moderate (I2 = 61.7%) heterogeneity observed. Similarly, RPN supplementation during the lactation period led to linear increases in DMI and yields of milk, ECM, fat and lactose, with respective increases of 0.60, 1.10, 0.70, 0.06, and 0.05 kg/d when cows were supplemented with 4.7 g/d niacin. Across 12 treatment comparisons from 8 experiments, RPN-supplemented cows produced 0.96 kg/d more milk than CON cows (WMD = 0.96; 95% CI = 0.62-1.31), with no heterogeneity observed. Overall, feeding 9.1 g/d of niacin from RUPN or 4.7 g/d of niacin from RPN during the lactation period improved milk production without improving feed efficiency in dairy cows.

Neutralization of acyl CoA binding protein (ACBP) for the experimental treatment of osteoarthritis

The plasma concentrations of acyl CoA binding protein (ACBP) encoded by the gene diazepam binding inhibitor (DBI) are increased in patients with severe osteoarthritis (OA). Here, we show that knee OA induces a surge in plasma ACBP/DBI in mice subjected to surgical destabilization of one hind limb. Knockout of the Dbi gene or intraperitoneal (i.p.) injection of a monoclonal antibody (mAb) neutralizing ACBP/DBI attenuates OA progression in this model, supporting a pathogenic role for ACBP/DBI in OA. Furthermore, anti-ACBP/DBI mAb was also effective against OA after its intraarticular (i.a.) injection, as monitored by sonography, revealing the capacity of ACBP/DBI to locally reduce knee inflammation over time. In addition, i.a. anti-ACBP/DBI mAb improved functional outcomes, as indicated by the reduced weight imbalance caused by OA. At the anatomopathological level, i.a. anti-ACBP/DBI mAb mitigated histological signs of joint destruction and synovial inflammation. Of note, i.a. anti-ACBP/DBI mAb blunted the OA-induced surge of plasma ACBP/DBI, as well as that of other inflammatory factors including interleukin-1α, interleukin-33, and tumor necrosis factor. These findings are potentially translatable to OA patients because joints from OA patients express both ACBP/DBI and its receptor GABAARγ2. Moreover, a novel mAb against ACBP/DBI recognizing an epitope conserved between human and mouse ACBP/DBI demonstrated similar efficacy in mitigating OA as an anti-mouse ACBP/DBI-only mAb. In conclusion, ACBP/DBI might constitute a promising therapeutic target for the treatment of OA.

Hesperetin mitigates adipose tissue inflammation to improve obesity-associated metabolic health

Metabolically unhealthy obesity (MUO) poses significant health risks, including increased susceptibility to type 2 diabetes and cardiovascular diseases. Hesperetin is a key bioactive compound found in citrus fruits. Previous studies have shown that hesperetin can correct metabolic abnormalities and mitigate the progression of various metabolic disorders, but the underlying mechanisms remain unclear. Here, we explored the impact of hesperetin on MUO using ob/ob mice and investigated its potential pharmacological mechanisms. The present data indicated that administration of hesperetin for 12 weeks led to notable improvements in metabolic parameters, including reduced fasting blood glucose, fasting insulin levels, and the HOMA-IR index in ob/ob mice. Glucose and insulin tolerance tests demonstrated that hesperetin effectively enhanced insulin sensitivity, with high-dose effects comparable to metformin. Hesperetin treatment decreased inguinal white adipose tissue (iWAT) weight and improved insulin signaling by increasing AKT phosphorylation. Additionally, it reduced the expression of pro-inflammatory cytokines (Il-6 and Il-1β), chemokine Ccl2 and its receptor Ccr2, and macrophage activation markers Nos2 and Ptgs2 within iWAT of ob/ob mice, likely by inhibiting NF-κB activation and macrophage-mediated inflammation. In vitro studies further confirmed hesperetin's anti-inflammatory effects in LPS-stimulated macrophages, where it suppressed cytokine production and NF-κB signaling. Hesperetin also impaired CCL2-induced macrophage chemotaxis, reducing migration velocity and distance. Mechanistically, hesperetin directly interacts with and inhibits IKKβ kinase activity by binding to key residues (LEU21, VAL465, CYS99, and GLU97) and stabilizing the complex, as demonstrated by molecular docking and molecular dynamics simulations. These findings underscore hesperetin's therapeutic potential in mitigating metabolically unhealthy obesity, obesity-induced insulin resistance, and inflammation through direct modulation of the IKKβ and NF-κB pathways.

Associations of body condition score, body condition score change, and hyperketonemia with mastitis, reproduction, and milk production

Body condition score and hyperketonemia (HYK) have been associated with diseases, fertility, and culling, but data are contradictory about their association with pregnancy loss. Our objective was to conduct a retrospective cohort study to investigate associations between BCS, BCS change (ΔBCS), blood BHB, and HYK with mastitis, pregnancy per artificial insemination (P/AI), pregnancy loss (PGL), milk yield, and risk of leaving the herd on a Michigan dairy farm that uses an automated milking system (AMS). We recorded BCS for cows prepartum (14 d before calving) and postpartum (14-21 DIM), and multiparous cows were evaluated for HYK between 3 and 7 DIM. Records were gathered from herd management software. Univariable associations of BCS (prepartum n = 826, postpartum n = 956) ΔBCS (n = 819), and BHB (n = 628) with mastitis, P/AI, PGL, and risk of leaving the herd were evaluated. Survival analyses investigated the association of BCS, ΔBCS, and HYK within parity with mastitis, pregnancy, and hazard of leaving the herd during lactation. We examined the association of BCS, ΔBCS, and HYK with whole lactation milk yield using repeated-measures mixed models. Thinner cows both pre- (BCS < 3.25) and postpartum (BCS < 2.75) had greater risk of leaving the herd (odds ratio [OR] = 1.48 and 2.16, respectively) compared with their moderate BCS herd mates. Cows who lost ≥0.375 units of BCS after calving had greater risk of PGL (OR = 4.99). Cows that lost ≥0.75 units of BCS had greater risk of being culled (OR = 1.80). Cows with HYK were at greater risk of mastitis (risk ratio = 1.34) and being culled (OR = 2.27). Cows with increasing BHB had greater risk of PGL and being culled such that a 1 mmol/L increase in BHB resulted in 2.32 and 1.67 greater risk, respectively. Hyperketonemic cows within third+ parity made 5.4 kg/d ± 1.04 kg/d (difference ± standard error of difference) less milk yield over their lactation compared with non-HYK third+ parity cows. Our data support previous findings that BHB and HYK had adverse associations with mastitis, fertility, leaving the herd, and milk yield. Our data also suggest that BCS loss after calving and BHB during wk 1 of lactation are risk factors associated with incidence of PGL.

Characterization of an in vitro model to study CD4+ T cell metabolism in dairy cows

Dairy cows are susceptible to several health disorders throughout their lactation. Objectives were to characterize an in vitro model to study bioenergetic measures in CD4+ T lymphocytes in dairy cows. Twenty-four healthy mid-lactation multiparous Holstein dairy cows were enrolled at a mean (±SD) of 234 ± 22 DIM. Cows were blocked according to DIM and blood was collected to isolate peripheral blood mononuclear cells followed by magnetic separation of CD4+ T lymphocytes using bovine-specific monoclonal antibodies. The isolated CD4+ T lymphocytes from each cow were split into 2 tubes and randomly assigned to incubate in an assay medium as control (CON) or with a combination of phorbol myristate acetate and ionomycin (PMA+IMY) to evaluate metabolic function under a resting and activated state. Mitochondrial and glycolytic functional kinetics were recorded in CD4+ T lymphocytes based on real-time measurement of oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) under basal conditions and in response to complex V inhibitor (oligomycin), a protonophore uncoupler (BAM 15), and complex I and complex III inhibitors (rotenone and antimycin A). The mean (±SD) viability and purity of CD4+ T lymphocytes was 92.5 ± 2.9% and 95.2 ± 2.9%, respectively. The basal OCR in CD4+ T lymphocytes treated with PMA+IMY was greater than CON; nevertheless, the maximal respiration rate (CON = 58.0 vs. PMA+IMY = 47.3 ± 5.7 pmol/min) and sparing respiratory capacity rate (CON = 42.0 vs. PMA+IMY = 28.7 ± 4.2 pmol/min) were decreased in activated CD4+ T lymphocytes. The ECAR in CD4+ T lymphocytes increased progressively over time in PMA+IMY compared with CON, which indicated an increase in aerobic glycolysis in PMA+IMY compared with CON (CON = 46.9 vs. PMA+IMY = 86.4 ± 7.0 pmol/min). Activated CD4+ T lymphocytes exhibit a metabolic switch from oxidative phosphorylation to aerobic glycolysis, which may support rapid cell proliferation. The results observed in this experiment demonstrate the sensitivity of the technique to detect changes in metabolic function under different cellular conditions, providing a robust framework to study immuno-metabolism in dairy cattle.

Potential relationships between apelin and metabolic-associated indices in transition dairy cows

Metabolic disorders pose significant challenges in transition dairy cows. Numerous parameters have been investigated in this context, and apelin has recently emerged as a potential metabolic indicator. Accordingly, this study aimed to assess the associations between this hormone and other metabolic parameters. Twenty-two adult Holstein-Friesian dairy cows, 21 days before their expected calving date, were selected for blood sampling and serum separation at four time points: 21 and 10 days before calving and 10 and 21 days after parturition. Serum concentrations of apelin, leptin, insulin, cortisol, T3, T4, non-esterified fatty acids, glucose, total protein, albumin, globulin, aspartate aminotransferase, alanine transaminase, triglycerides, cholesterol, high, low and very low-density lipoproteins, total, direct and indirect bilirubin were measured in these samples. Surrogate indices for insulin resistance, body condition score, and milk production were also evaluated. Throughout the transition period, a significant increase in apelin levels was observed. Various models were employed to identify associations between apelin and the studied metabolic parameters. Notably, significant correlations between apelin and Leptin, Insulin, Cortisol, T3, T4, NEFA, Cholesterol, LDL, VLDL, Total Protein, Albumin, Globulin, Total Bilirubin, Direct Bilirubin and Indirect Bilirubin were observed, with some being immediate while others developed over time. These findings indicate a mutual influence between apelin and specific metabolic indices. Changes in any component of the metabolic profile at one stage can lead to alterations in apelin levels in subsequent stages. The correlations uncovered between apelin and other components of the metabolic profile in transitioning dairy cows offer valuable insights, contributing to a better understanding of the potential effects of apelin on the studied indicators and vice versa.

Cytokine production by bovine adipose tissue stromal vascular fraction cells upon Neospora caninum stimulation

In bovines few studies addressed the contribution of adipose tissue to the host immune response to infection. Here we evaluated the in vitro response of bovine adipose tissue stromal vascular fraction (SVF) cells to the protozoan parasite Neospora caninum, using live and freeze-killed tachyzoites. Live N. caninum induced the production of IL-6, IL-1β and IL-10 by SVF cells isolated from subcutaneous adipose tissue (SAT), while in mesenteric adipose tissue (MAT) SVF cell cultures only IL-1β and IL-10 production was increased, showing slight distinct responses between adipose tissue depots. Whereas a clear IL-8 increase was detected in peripheral blood leucocytes (PBL) culture supernatants in response to live N. caninum, no such increase was observed in SAT or MAT SVF cell cultures. Nevertheless, in response to LPS, increased IL-8 levels were detected in all cell cultures. IL-10 levels were always increased in response to stimulation (live, freeze-killed N. caninum and LPS). Overall, our results show that bovine adipose tissue SVF cells produce cytokines in response to N. caninum and can therefore be putative contributors to the host immune response against this parasite.

Endotoxin-induced alterations of adipose tissue function: a pathway to bovine metabolic stress

During the periparturient period, dairy cows exhibit negative energy balance due to limited appetite and increased energy requirements for lactogenesis. The delicate equilibrium between energy availability and expenditure puts cows in a state of metabolic stress characterized by excessive lipolysis in white adipose tissues (AT), increased production of reactive oxygen species, and immune cell dysfunction. Metabolic stress, especially in AT, increases the risk for metabolic and inflammatory diseases. Around parturition, cows are also susceptible to endotoxemia. Bacterial-derived toxins cause endotoxemia by promoting inflammatory processes and immune cell infiltration in different organs and systems while impacting metabolic function by altering lipolysis, mitochondrial activity, and insulin sensitivity. In dairy cows, endotoxins enter the bloodstream after overcoming the defense mechanisms of the epithelial barriers, particularly during common periparturient conditions such as mastitis, metritis, and pneumonia, or after abrupt changes in the gut microbiome. In the bovine AT, endotoxins induce a pro-inflammatory response and stimulate lipolysis in AT, leading to the release of free fatty acids into the bloodstream. When excessive and protracted, endotoxin-induced lipolysis can impair adipocyte's insulin signaling pathways and lipid synthesis. Endotoxin exposure can also induce oxidative stress in AT through the production of reactive oxygen species by inflammatory cells and other cellular components. This review provides insights into endotoxins' impact on AT function, highlighting the gaps in our knowledge of the mechanisms underlying AT dysfunction, its connection with periparturient cows' disease risk, and the need to develop effective interventions to prevent and treat endotoxemia-related inflammatory conditions in dairy cattle.