Validation of different measures of insulin sensitivity of glucose metabolism in dairy cows using the hyperinsulinemic euglycemic clamp test as the gold standard

TG/HDL-c ratio as a predictor of progressive infarction in patients with anterior circulation single subcortical infarction

BACKGROUND

The contributors predicting progressive infarction (PI) in patients with anterior circulation single subcortical infarction (ACSSI) and pontine single infarction (PSI) may be unidentical. The role of triglyceride to high-density lipoprotein cholesterol (TG/HDL-c) ratio on PI is unclear. The purpose of our study is to evaluate the correlation between TG/HDL-c ratio and PI in patients with ACSSI or PSI.

METHODS

Between January 2020 and October 2022, we retrospectively enrolled 738 patients including 638 ACSSI patients and 100 PSI patients to analyze. Demographic characteristics, clinical information, and laboratory data were collected within 24 h of admission.

RESULTS

PI occurred in 143 (19.4%) patients. In univariate analysis, patients with PI had higher initial National Institutes of Health Stroke Scale (NIHSS) scores, higher discharge NIHSS scores, higher levels of fasting glucose, total cholesterol, TG, low-density lipoprotein cholesterol, and TG/HDL-c ratio, but lower levels of creatinine compared to patients with non-PI (p < .05). Furthermore, the results of the subgroup analyses revealed the independent association between TG/HDL-c ratio and PI in ACSSI patients (OR 1.079, 95% CI 1.009-1.153, p = .026) rather than in PSI patients. Additionally, a receiver operating characteristic curve indicated that the optimal predictive cutoff value of the TG/HDL-c ratio was 3.985, and a TG/HDL-c ratio ≥3.985 was more likely to experience PI in ACSSI patients.

CONCLUSION

In conclusion, the TG/HDL-c ratio was independently associated with PI in patients with ACSSI.

Association of glucose metabolism and insulin resistance with feed efficiency and production traits of finishing beef steers

Increasing nutrient utilization efficiency is an important component of enhancing the sustainability of beef cattle production. The objective of this experiment was to determine the association of glucose metabolism and insulin resistance with dry matter intake (DMI), average daily gain (ADG), gain:feed ratio (G:F), and residual feed intake (RFI). Steers (n = 54; initial body weight = 518 ± 27.0 kg) were subjected to an intravenous glucose tolerance test (IVGTT) where glucose was dosed through a jugular catheter and serial blood samples were collected. Three days after the last group's IVGTT, steers began a 63-d DMI and ADG test. Body weight was measured on days 0, 1, 21, 42, 62, and 63, and DMI was measured using an Insentec Roughage Intake Control system (Hokofarm Group, Emmeloord, the Netherlands). To examine relationships between DMI, ADG, G:F, and RFI with IVGTT measurements, Pearson correlations were calculated using Proc Corr of SAS 9.4 (SAS Inst. Inc., Cary, NC). Additionally, cattle were classified based on DMI, ADG, RFI, and G:F, where the medium classification was set as mean ± 0.5 SD, the low classification was < 0.5 SD from the mean, and the high classification was > 0.5 SD from the mean. No associations between DMI and IVGTT parameters were observed, and no differences were detected when classifying cattle as having low, medium, or high DMI. Peak insulin concentration in response to the IVGTT tended to be correlated with ADG (r = 0.28; P = 0.07), indicating cattle with greater ADG tend to have a greater insulin release in response to glucose. Glucose nadir concentrations tended to be positively correlated with ADG (r = 0.26; P = 0.10). Additionally, the glucose nadir was greater in high-ADG steers (P = 0.003). The association of greater glucose nadir with high-ADG could indicate that high-ADG steers do not clear glucose as efficiently as low-ADG steers, potentially indicating increased insulin resistance. Further, RFI was not correlated with IVGTT measurements, but low RFI steers had a greater peak glucose concentration (P = 0.040) and tended to have a greater glucose area under the curve (P = 0.09). G:F was correlated with glucose area under the curve (r = 0.33; P = 0.050), glucose nadir (r = 0.35; P = 0.011), and insulin time to peak (r = 0.39; P = 0.010). These results indicate that glucose metabolism and insulin signaling are associated with growth and efficiency, but the molecular mechanisms that drive these effects need to be elucidated.

Transition cow clusters with distinctive antioxidant ability and their relation to performance and metabolic status in early lactation

Metabolic and oxidative stress have been characterized as risk factors during the transition period from pregnancy to lactation. Although mutual relations between both types of stress have been suggested, they rarely have been studied concomitantly. For this, a total of 99 individual transition dairy cows (117 cases, 18 cows sampled during 2 consecutive lactations) were included in this experiment. Blood samples were taken at -7, 3, 6, 9, and 21 d relative to calving and concentrations of metabolic parameters (glucose, β-hydroxybutyric acid (BHBA), nonesterified fatty acids, insulin, insulin-like growth factor 1, and fructosamine) were determined. In the blood samples of d 21, biochemical profiles related to liver function and parameters related to oxidative status were determined. First, cases were allocated to 2 different BHBA groups (ketotic vs. nonketotic, N:n = 20:33) consisting of animals with an average postpartum BHBA concentration and at least 2 out of 4 postpartum sampling points exceeding 1.2 mmol/L or remaining below 0.8 mmol/L, respectively. Second, oxidative parameters [proportion of oxidized glutathione to total glutathione in red blood cells (%)], activity of glutathione peroxidase, and of superoxide dismutase, concentrations of malondialdehyde and oxygen radical absorbance capacity were used to perform a fuzzy C-means clustering. From this, 2 groups were obtained [i.e., lower antioxidant ability (LAA80%, n = 31) and higher antioxidant ability (HAA80%, n = 19)], with 80% referring to the cutoff value for cluster membership. Increased concentrations of malondialdehyde, decreased superoxide dismutase activity, and impaired oxygen radical absorbance capacity were observed in the ketotic group compared with the nonketotic group, and inversely, the LAA80% group showed increased concentrations of BHBA. In addition, the concentration of aspartate transaminase was higher in the LAA80% group compared with the HAA80% group. Both the ketotic and LAA80% groups showed lower dry matter intake. However, a lower milk yield was observed in the LAA80% group but not in the ketotic group. Only 1 out of 19 (5.3%) and 3 out of 31 (9.7%) cases from the HAA80% and LAA80% clusters belong to the ketotic and nonketotic group, respectively. These findings suggested that dairy cows vary in oxidative status at the beginning of the lactation, and fuzzy C-means clustering allows to classify observations with distinctive oxidative status. Dairy cows with higher antioxidant capacity in early lactation rarely develop ketosis.

Oversupplying metabolizable protein during late gestation to beef cattle does not influence ante- or postpartum glucose-insulin kinetics but does affect prepartum insulin resistance indices and colostrum insulin content

The objective of this study was to evaluate whether oversupplying metabolizable protein (MP) during late gestation influences glucose and insulin concentrations, and insulin resistance (IR) in late gestation and early lactation. Crossbred Hereford, first-lactation heifers were individually fed diets to supply 133% (HMP, n = 11) or 100% (CON, n = 10) of their predicted MP requirements for 55 ± 4 d (mean ± SD) prior to calving. All heifers received a common lactation ration formulated to meet postpartum requirements (103% MP and 126% ME). After feed was withheld for 12 h, cattle underwent an intravenous glucose tolerance test (IVGTT) on d -6.7 ± 0.9 and 14.3 ± 0.4 by infusing a 50% dextrose solution (1.36 g glucose/kg BW 0.75) through a jugular catheter with plasma collected at -10, 0 (immediately after infusion), 5, 10, 15, 20, 25, 30, 45, 60, 75, 90, and 120 min, respective to the infusion. Glucose and insulin concentrations were assessed. Insulin resistance indices (homeostasis model of insulin resistance [HOMA-IR], quantitative insulin sensitivity check index [QUICKI], revised quantitative insulin sensitivity check index [RQUICK], and RQUICKI incorporating serum beta-hydroxybutyrate concentrations [RQUICKIBHB]) were calculated from measurements of serum non-esterified fatty acids and beta-hydroxybutyrate and plasma glucose and insulin concentrations on d -34 ± 4, -15 ± 4, 7 ± 1, 28 ± 3, 70 ± 3, and 112 ± 3. Colostrum samples were collected within an hour of calving (prior to suckling) and analyzed for insulin concentration. Data were analyzed as a randomized block design using the PROC GLIMMIX of SAS, accounting for repeated measurements when necessary. Baseline (-10 min) plasma glucose and insulin concentrations were elevated (P ≤ 0.038) for HMP heifers during the antepartum IVGTT, but not (P ≥ 0.25) during the postpartum IVGTT. Plasma glucose and insulin concentrations throughout the antepartum or postpartum IVGTT did not differ (P ≥ 0.18) by prepartum treatment, nor did other glucose and insulin IVGTT parameters (i.e., max concentration and time to reach max concentration, nadir values, clearance rates and half-lives, area-under-the-curve, and insulin sensitivity index; P ≥ 0.20). Antepartum IVGTT IR indices indicated that HMP heifers were more (P ≤ 0.011) IR than their counterparts. Similarly, the prepartum HOMA-IR was greater (P = 0.033) for HMP heifers, suggesting increased IR. Postpartum IR indices did not (P ≥ 0.25) indicate that prepartum MP consumption impacted postpartum IR. Colostrum insulin concentration was increased (P = 0.004) by nearly 2-fold for HMP relative to CON heifers. These data demonstrate that prepartum MP overfeeding alters baseline glucose-insulin concentrations in late-pregnant beef heifers and increases colostrum insulin content without having carry-over effects on postpartum glucose-insulin concentrations and IR.

Effects of increasing calcium propionate in a finishing diet on dry matter intake and glucose metabolism in steers

The objective of this study was to determine if increasing propionate alters dry matter intake (DMI), glucose clearance rate, blood metabolites, insulin concentrations and hepatic gene expression in steers fed a finishing diet. Holstein steers (n = 15; BW = 243 ± 3.6 kg) were individually fed a finishing diet ad-libitum. Steers were allocated by body weight (BW) to receive: no Ca propionate (Control), 100 g/d Ca propionate (Low), or 300 g/d Ca propionate (High) in the diet. Orts were collected and weighed daily to determine DMI. Blood samples were collected on d 0, 7, and 21, and BW recorded on d 0, 14, and 28. An intravenous glucose tolerance test (IVGTT) was conducted on d 14 and 28 of the trial. Liver biopsies were collected on d 33 for gene expression analysis. Blood samples were analyzed for whole blood glucose and lactate, plasma non-esterified fatty acids (NEFA) and insulin concentrations. Data were analyzed using a mixed model with treatment, day and their interaction included, with day and minute as a repeated measure. The control treatment had greater (P < 0.01) DMI than low and high steers. Body weight was increased in control steers on d 14 and 28 compared to the steers receiving the High treatment (P = 0.03 for the interaction). Blood glucose concentrations tended (P = 0.09) to be higher on d 21 than d 0 and 7 but was not affected by treatment (P = 0.58). Plasma NEFA concentrations were lower (P = 0.05) for control steers than other treatments, and greater (P = 0.002) on d 0 than d 7 and 21. Blood lactate concentrations were greater (P = 0.05) on d 7, than d 0 and 21, but not affected by treatment (P = 0.13). High steers had greater plasma insulin concentrations in response to the IVGTT than steers on the other treatments (P = 0.001). There was no treatment (P ≥ 0.16) or day effect (P ≥ 0.36) on glucose peak, plateau, or clearance rate. High steers had greater expression of solute carrier family 16 member 1 (SLC16A1; P = 0.05) and tended to have greater hepatic expression of solute carrier family 2 member 2 (SLC2A2; P = 0.07). These data indicate that increased propionate may decrease DMI and insulin sensitivity.

Insulin resistance indexes of grazing cows and mineral or vitamin supplementation under tropical conditions

Background

During the transition period in dairy cows, metabolic changes occur, many of which are related to energy metabolism, which causes metabolic diseases or productive alterations.

Aim

The objective of the present work was to evaluate two mineral and vitamin supplementations related to metabolic regulation mechanisms associated with insulin during the transition period and the first phase of lactation in grazing cows under tropical conditions through metabolic indicators and insulin resistance indexes.

Methods

Twenty-one animals were distributed in three groups: control (CTR), iodine supplementation (SUPP-1), and mixed mineral and vitamin supplementation (SUPP-2). The experimental period was from day 30 prepartum to day 45 postpartum. Evaluation of the body condition score and the blood samples' collection by coccygeal venipuncture was carried out for serum analysis of metabolites, such as beta-hydroxybutyrate (BHB), glucose, and non-esterified fatty acids (NEFA), and hormones, such as insulin, thyroxine, triiodothyronine, and cortisol. Variables related to energy and hormone metabolism were analyzed. Four proposed indexes were calculated to identify insulin resistance: Homeostasis Model Assessment (HOMA), Quantitative Insulin Sensitivity Check Index (QUICKI), Revised Quantitative Insulin Sensitivity Check Index, and QUICKI-BHB. Through linear regression, the effect of metabolites and hormones on the indexes of insulin resistance studied was estimated.

Results

The groups with supplementation did not show significant changes in the mobilization of body reserves, NEFA, or triiodothyronine for interaction between treatments and periods. HOMA and QUICKI indexes used to estimate insulin resistance showed an inverse correlation (-0.97; p<0.001), and a greater capacity of linear adjustment to estimate the evaluated metabolites.

Conclusion

The indexes' values of insulin sensitivity in the present work constitute a starting point in tropical dairy cows to characterize insulin resistance and metabolic alterations. Vitamins and mineral supplementation did not show a positive effect on the metabolism of dairy cows during the transition period and the first phase of lactation in the study.

Comparison of measures of insulin sensitivity in early-lactation dairy goats

This experiment aimed to investigate the correlations between surrogate indices of insulin resistance (IR)-namely, the homeostasis model of IR, the quantitative insulin sensitivity check index, and the revised quantitative insulin sensitivity check index-and measures of IR obtained from an intravenous glucose tolerance test (IVGTT) performed in early-lactation dairy goats. Saanen goats (n = 26) with varying levels of milk production (1.7-4.8 kg/d) were selected and underwent an IVGTT on 43 ± 0.7 d postpartum (mean ± standard deviation). Data from the IVGTT were fitted in the minimal model to calculate parameters of glucose-insulin dynamics such as insulin sensitivity index and acute insulin response to glucose. Surrogate indices were computed using the average of the IVGTT basal samples. Correlation analysis revealed no relationship between surrogate indices of IR and measures of IR derived from the IVGTT (e.g., insulin sensitivity index, glucose clearance rate, glucose area under the curve). Therefore, our results suggest that surrogate indices of IR are not suitable for assessing the insulin sensitivity of peripheral tissue in early-lactation goats.

Relative Late Gestational Muscle and Adipose Thickness Reflect the Amount of Mobilization of These Tissues in Periparturient Dairy Cattle

Due to insufficient dry matter intake and heightened nutrient requirements in early lactation, periparturient dairy cows mobilize adipose and muscle tissues to bridge energy and amino acid gaps, respectively. Our objective was to evaluate the relationship between the relative muscle thickness of late pregnant cows and their early lactation performance. At 35 d before expected calving (BEC), longissimus dorsi muscle thickness (LDT) was measured in forty-one multiparous Holstein cows via ultrasound. Tissue mobilization was evaluated via ultrasound images of LDT and backfat thickness (BFT) at 21 and 7 d BEC as well as at 0, 10, 30, and 60 DIM. Plasma concentrations of 3-methylhistidine (3-MH), creatinine (CRE), non-esterified fatty acids (NEFA), and β-hydroxybutyrate (BHB) were evaluated weekly. Milk yield and milk component data were collected through 60 DIM. Cattle were assigned post hoc to high-muscle (HM; n = 20; LDT > 4.49 cm) or low-muscle (LM; n = 21; ≤4.37 cm) groups, with mean LDT at 35 d BEC greater in HM (5.05 ± 0.49) than in LM (3.52 ± 0.65) animals. Between 35 and 21 d BEC, LM cows gained LDT, whereas HM cows gained BFT. HM cows mobilized more muscle from 21 d BEC to 30 DIM, as reflected by a greater loss of LDT, greater 3-MH concentrations (532 vs. 438 ± 30 ng/mL), and a greater 3-MH:CRE ratio (0.164 vs. 0.131 ± 0.008) in the first three weeks postpartum. The LDT and BFT at 21 d BEC were related to the amount of respective tissue mobilized through 30 DIM (R² = 0.37 and 0.88, respectively). Although calves born to HM cattle were larger (45.2 vs. 41.8 ± 0.7 kg), HM cows produced less milk (38.8 vs. 41.6 ± 0.8 kg/d) with a tendency towards higher fat content (4.33 vs. 4.05 ± 0.12%), likely related to the mobilization of more backfat from 0 to 60 DIM (1.78 vs. 0.68 ± 0.34 mm), compared to LM cattle. These findings suggest that a cow's metabolic status, as measured by LDT and BFT prepartum, may influence the metabolic strategy the animal uses to meet energy and amino acid requirements in late gestation and early lactation.

Surrogate Indexes of Insulin Resistance in Dairy Goats: Transitional Variation in Subclinical Hyperketonemia

Background: Dairy goats are highly susceptible to subclinical hyperketonemia (SCHK) during the transition period. This study aimed to compare the variation in metabolic parameters and surrogate indexes of insulin resistance (sIR) between goats with SCHK and clinically healthy (HEAL) goats during the transition period. Methods: Twenty Guanzhong dairy goats were assorted to HEAL (n = 10) and SCHK (n = 10) groups according to the blood β-hydroxybutyrate (BHBA) concentrations. The blood samples were taken from the jugular vein of each goat at −3, −2, −1, 0 (partum), +1, +2, and +3 weeks relative to kidding to analyses GLU and INS. The sIR was calculated from blood metabolic parameters. Results: Compared with the HEAL goats, the insulin concentrations were significantly higher in SCHK goats during the first three weeks postpartum. The QUICKI, revised QUICKI (RQUICKI), and RQUICKI_BHBA were significantly lower in goats with SCHK at 1 week postpartum, while the homeostasis model assessment-IR (HOMA-IR) was significantly higher. Conclusion: Goats with SCHK made more efforts through elevated insulin levels at early lactation than HEAL goats, thereby maintaining the normal glucose concentrations.

Chronic prepartum light-dark phase shifts in cattle disrupt circadian clocks, decrease insulin sensitivity and mammary development, and are associated with lower milk yield through 60 days postpartum

Circadian and metabolic systems are interlocked and reciprocally regulated. To determine if the circadian system regulates glucose homeostasis and mammary development, the function of the circadian system was disrupted by exposing cattle to chronic light-dark cycle phase shifts from 5 wk before expected calving (BEC) to parturition. Multiparous Holstein cows were exposed to 16 h of light and 8 h of dark (CON, n = 8) or phase shifting (PS, n = 8) the light cycle 6 h every 3 d beginning 35 d BEC. After calving, both treatments were exposed to CON lighting. Mammary biopsies were taken at 21 d BEC and 21 d in milk (DIM), and histological analysis indicated PS treatment decreased the ratio of lumen to alveolar area and percentage of proliferating epithelial cells in the prepartum period. Intravenous glucose tolerance test was performed at 14 d BEC and 7 DIM by administering 50% dextrose. Blood glucose, β-hydroxybutyrate, insulin, and nonesterified fatty acids were consequently measured over 3 h. At 14 d BEC no treatment differences were observed in baseline glucose or insulin. Treatment had no effect on blood glucose or glucose area under the curve at 14 d BEC and 7 DIM. Insulin area under the curve was higher in PS versus CON at 14 d BEC and 7 DIM. The PS cows produced less milk than CON cows through 60 DIM (40.3 vs. 42.6 kg/d). Exposure to chronic light-dark PS in late gestation decreased mammary development and increased insulin resistance in periparturient cows, which may have caused subsequent lower milk yield.

Metabolic Stress in the Transition Period of Dairy Cows: Focusing on the Prepartum Period

All modern, high-yielding dairy cows experience a certain degree of reduced insulin sensitivity, negative energy balance, and systemic inflammation during the transition period. Maladaptation to these changes may result in excessive fat mobilization, dysregulation of inflammation, immunosuppression, and, ultimately, metabolic or infectious disease in the postpartum period. Up to half of the clinical diseases in the lifespan of high-yielding dairy cows occur within 3 weeks of calving. Thus, the vast majority of prospective studies on transition dairy cows are focused on the postpartum period. However, predisposition to clinical disease and key (patho)physiological events such as a spontaneous reduction in feed intake, insulin resistance, fat mobilization, and systemic inflammation already occur in the prepartum period. This review focuses on metabolic, adaptive events occurring from drying off until calving in high-yielding cows and discusses determinants that may trigger (mal)adaptation to these events in the late prepartum period.

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

As the precursor to NAD+ and NADP+, niacin is important for catabolic and anabolic redox reactions. In addition, niacin is known for its anti-lipolytic action via a hydroxycarboxylic acid-2-receptor-dependent mechanism. The anti-lipolytic effects of traditional free niacin supplementation during transition periods had been studied extensively, but the reported effects are ambiguous. In the past decade, a series of studies were conducted to evaluate the effects of rumen-protected niacin (RPN) on production performance and metabolic status in early lactation and on heat stress in dairy cows. Feeding RPN seems more effective than free niacin regarding increasing circulating niacin concentration. The rebound of plasma NEFA was found after termination of niacin abomasal infusion. Feeding RPN or infusion of niacin via the abomasum could suppress lipolysis and reduce insulin resistance in early lactation. Additionally, RPN supplementation could possibly relieve heat stress through vasodilation during moderate to severe heat stress condition. However, these beneficial effects of niacin supplementation have not always been observed. The inconsistent results across studies may be related to dosages of niacin supplementation, rebound of plasma NEFA concentration, stage of lactation or severity of heat stress. Overall, the current review is to present updated information on niacin nutrition in dairy cows and the recommendations are given for future research.

Effects of body condition score on direct and indirect measurements of insulin sensitivity in periparturient dairy cows

Reductions in insulin sensitivity in periparturient dairy cows develop as a means to support lactation; however, excessive mobilization of fatty acids (FA) increases the risk for peripartal metabolic disorders. Our objectives were to investigate the effect of prepartum body condition score (BCS) on systemic glucose and insulin tolerance, and to compare direct and indirect measurements of insulin sensitivity in peripartal lean and overweight dairy cows. Fourteen multiparous Holstein cows were allocated into two groups according to their BCS at day -28 prepartum: lean (n = 7; BCS ≤ 3.0) or overweight; (n = 7; BCS ≥ 4.0). Liver biopsies were performed on day -27, -14 and 4, relative to expected parturition. Intravenous insulin or glucose tolerances tests were performed following each liver biopsy. Relative to lean cows, overweight cows exhibited lower dry matter intake, lost more BCS and displayed increased plasma FA and β-hydroxybutyrate concentrations and elevated liver lipid content during peripartum. Glucose clearance rate was lower for all cows postpartum. Prepartum BCS had minimal effects on insulin and glucose tolerance; however, the ability of the cow to restore blood glucose levels following an insulin challenge was suppressed by increased BCS. Glucose-dependent parameters of insulin and glucose tolerance were not correlated with surrogate indices of insulin sensitivity. We conclude that prepartum BCS had minimal effect on systemic insulin sensitivity following parturition. The observed inconsistency between surrogate indices of insulin sensitivity and direct measurements of insulin and glucose tolerance adds support to growing concerns regarding their usefulness as tools to estimate systemic insulin action in periparturient cows.

Insulin resistance: Relationship between indices during late gestation in dairy cows and effects on newborn metabolism

To investigate the relationship between insulin resistance indices ["Revised quantitative insulin sensitivity check index" (RQUICKI; RQ), "Revised quantitative insulin sensitivity check index - β-hydroxybutyrate" (RQUICKI_BHB ; RQ_BHB ), and "Homeostasis model assessment-insulin resistance" (HOMA-IR; HR)], and metabolic parameters in dams during late gestation, and their newborn calves. Blood was sampled twice weekly during the experimental period in 30 dry Holstein cows. In calves, blood sampling and body weight measurements were performed immediately after birth, and in 1-week-old male calves, liver and muscle biopsy samples were obtained for determining metabolic factor mRNA levels. RQ and RQ_BHB were negatively correlated with insulin, nonesterified fatty acid, BHB, and albumin and were positively correlated with leptin levels in blood during late gestation (p < .05). RQ, rather than RQ_BHB , reflected metabolism of dams, while stronger positive correlations were present between HR and blood insulin concentrations than other parameters, and calves of dams with high HR had low body weight, and high liver and muscle expression of growth hormone and insulin receptor mRNA (p < .05). RQ and HR of dams during late gestation could serve as indicators of dam metabolism and predictors of metabolism in newborn calves respectively.

Propionate Affects Insulin Signaling and Progesterone Profiles in Dairy Heifers

Emerging data highlighting gut microbiome influences on health support evaluation of how microbial fermentation end-products influence postabsorptive systems. This study aimed to investigate the effect of increased propionate status on progesterone profiles and insulin sensitivity in dairy heifers. Eleven Holstein heifers, synchronized in estrus, were assigned to one of two continuous, 5-day IV treatments: sodium propionate (PRO; n = 5) or saline (CON; n = 6). These infusions culminated in a hyperglycemic clamp with daily blood samples for an additional 7 days. Plasma propionate concentrations increased over the first 9 h in PRO heifers, then decreased until day 3 when they matched CON heifers. Maximum plasma progesterone concentrations tended to be greater in PRO heifers than CON heifers (4.19 vs 3.73 ng/mL; P = 0.087). Plateau insulin concentrations in CON animals were significantly greater than those in PRO animals (249.4 ± 25.1 vs 123.9 ± 35.8; P = 0.008) with a trend for an increased insulin sensitivity index in PRO heifers compared to CON heifers (P = 0.06). These changes in plasma propionate clearance leading to increased progesterone response and changes in insulin sensitivity suggest a role for SCFA metabolism in reproductive hormone regulation.

Effects of overconditioning on pancreatic insulin secretory capacity, fat infiltration, and the number and size of islets in dairy cows at the end of the dry period

In the present study, we tested the hypothesis that overconditioning in dairy cows at the end of the dry period leads to infiltration of fat and alterations of the insulin secretory capacity of the pancreas. Pregnant Holstein Friesian dairy cows were selected based on body condition score (BCS) at the start of the dry period. Body condition score varied between cows to have optimal conditioned (2.5 < BCS ≤3.5, n = 5) and overconditioned (3.5 < BCS ≤5, n = 5) cows. All animals underwent an intravenous glucose tolerance test (IVGTT) at an average of 260 d of gestation to measure the pancreatic insulin secretory capacity and assess peripheral insulin sensitivity regarding glucose metabolism. Eight days after the IVGTT, animals were slaughtered. The pancreas was dissected and weighed and tissue samples were taken for histological analysis. Results revealed that overconditioning in dairy cows led to fat infiltration in the pancreas and an increase in size of pancreatic islets expressed relative to the total area of pancreatic tissue. In addition, results revealed a positive correlation between serum fatty acid concentration and peak insulin concentration and area and number of pancreatic islets expressed relative to the total area of pancreatic tissue. The IVGTT revealed that overconditioned animals have a higher insulin secretory capacity of the pancreas, as demonstrated by higher peak insulin concentration, higher acute insulin response to glucose, and higher area under the curve (AUC) for insulin compared with optimal conditioned cows. A higher AUC for glucose during the first 60 min following administration of the glucose bolus in overconditioned cows indicates an insulin-resistant state regarding glucose metabolism. Our results suggest that the pancreas of overconditioned dairy cows at the end of gestation compensates for the concomitantly elevated level of peripheral insulin resistance by greater secretion of insulin.

Evaluation of surrogate measures of insulin sensitivity - correlation with gold standard is not enough

Background

Impaired insulin sensitivity is a key abnormality underlying the development of type 2 diabetes. Measuring insulin sensitivity is therefore of importance in identifying individuals at risk of developing diabetes and for the evaluation of diabetes-focused interventions. A number of measures have been proposed for this purpose. Among these the hyperinsulinemic euglycemic clamp (HEC) is considered the gold standard. However, as the HEC is a costly, time consuming and invasive method requiring trained staff, there is a need for simpler so called surrogate measures.

Main message

A frequently used approach to evaluate surrogate measures is through correlation with the HEC. We discuss limitations with this method. We suggest other aspects to take into consideration, such as repeatability, reproducibility, systematic biases and discrimination ability. In addition, we focus on three frequently used surrogate measures. We argue that they are one-to-one transformations of each other, and therefore question the benefits of further comparison between them. They give the same results in all rank-based methods, for instance Spearman correlations, Mann-Whitney tests and receiver operating characteristic (ROC) analysis.

Conclusions

We suggest investigating further aspects than correlation alone when evaluating a surrogate measure of insulin sensitivity. We recommend choosing one of the three surrogate measures HOMA-IR, QUICKI and FIRI for analysis of a clinical study.

Electronic supplementary material

The online version of this article (10.1186/s12874-018-0521-y) contains supplementary material, which is available to authorized users.

Effects of TNF receptor blockade on in vitro cell survival and response to negative energy balance in dairy cattle

Background

Associative data and some controlled studies suggest that the inflammatory cytokine tumor necrosis factor (TNF) α can induce fatty liver in dairy cattle. However, research demonstrating that TNFα is a necessary component in the etiology of bovine fatty liver is lacking. The aim of this work was to evaluate whether blocking TNFα signaling with a synthetic cyclic peptide (TNF receptor loop peptide; TRLP) would improve liver metabolic function and reduce triglyceride accumulation during feed restriction.

Results

Capability of TRLP to inhibit TNFα signaling was confirmed on primary bovine hepatocytes treated with recombinant bovine TNFα and 4 doses of TRLP (0, 1, 10, 50 μmol/L) over 24 h. Next, 4 lactating Holstein cows (parity 1.4 ± 0.5, 433 ± 131 d in milk) in an incomplete Latin rectangle design (3 × 2) were subcutaneously administered with different TRLP doses (0, 1.5, 3.0 mg/kg BW) every 4 h for 24 h, followed by an intravenous injection of TNFα (5 μg/kg BW). Before and for 2 h after TNFα injection, TRLP decreased plasma non-esterified fatty acid (NEFA) concentration (P ≤ 0.05), suggesting an altered metabolic response to inflammation. Finally, 10 non-pregnant, non-lactating Holstein cows (3.9 ± 1.1 yr of age) were randomly assigned to treatments: control (carrier: 57% DMSO in PBS) or TRLP (1.75 mg TRLP /kg BW per day). Treatments were administrated every 4 h for 7 d by subcutaneous injection to feed-restricted cows fed 30% of maintenance energy requirements. Daily blood samples were analyzed for glucose, insulin, β-hydroxybutyrate, NEFA, and haptoglobin concentrations, with no treatment effects detected. On d 7, cows completed a glucose tolerance test (GTT) by i.v. administration of a dextrose bolus (300 mg glucose/kg BW). Glucose, insulin, and NEFA responses failed to demonstrate any significant effect of treatment during the GTT. However, plasma and liver analyses were not indicative of dramatic lipolysis or hepatic lipidosis, suggesting that the feed restriction protocol failed to induce the metabolic state of interest. Injection site inflammation, assessed by a scorer blinded to treatment, was enhanced by TRLP compared to control.

Conclusions

Although the TRLP inhibited bovine TNFα signaling and altered responses to i.v. administration of TNFα, repeated use over 7 d caused apparent local allergic responses and it failed to alter metabolism during a feed restriction-induced negative energy balance. Although responses to feed restriction seemed atypical in this study, side effects of TRLP argue against its future use as a tool for investigating the role of inflammation in metabolic impacts of negative energy balance.

Effect of prepartum supplementation with niacin, choline and cod liver oil on postpartum insulin sensitivity and the redox status in cows with subclinical ketosis

There have been limited field trials exploring the potential ameliorative effect of B-complex vitamin or antioxidant therapy in cows with prolonged insulin resistance (IR). The purpose of this study was to explore the effect of prepartum supplementation of niacin, choline and cod liver oil on metabolic status, indices of insulin sensitivity (IS) as well as markers of oxidative stress in cows with subclinical ketosis (SCK). For this purpose, 24 apparently healthy cows at ~3 weeks before the expected time of calving were studied. Based on their serum concentration of non-esterified fatty acid (NEFA) and β-hydroxybutyrate (BHBA), the studied cows were classified as having SCK (n = 20) or normal (n = 4). The diseased cows were then randomly allocated into four equal-sized groups and received the following feed supplements for subsequent 6 weeks: rumen-protected niacin, (RPN – group; n = 5); rumen-protected choline (RPC – group; n = 5); and cod liver oil (CLO-group; n = 5); or remained without treatment (SCK – group; n = 5). Serum samples were collected from all animals (n = 24) in two occasions i.e. before and after treatment to quantify concentrations of BHBA, NEFA, glucose, insulin, cortisol, and triglyceride, malondialdehyde and superoxide dismutase. Indices of IS were also calculated. The findings of this study suggest benefits of prepartum supplementation to cattle with SCK, particularly RPC which demonstrated great effect on BHBA, triglyceride, and very low-density lipoprotein; but it showed a minimal effect on IS. On the other side, RPN and CLO exhibited a marked effect on serum cortisol and potentiated IS with minimal effect on BHBA. All dietary supplements had nearly equal effect on NEFA, glucose, insulin, and markers of oxidative stress. The information provided in this study could support the advancement of the future investigations in animal welfare and production.

Adipose tissue insulin receptor and glucose transporter 4 expression, and blood glucose and insulin responses during glucose tolerance tests in transition Holstein cows with different body condition

Glucose uptake in tissues is mediated by insulin receptor (INSR) and glucose transporter 4 (GLUT4). The aim of this study was to examine the effect of body condition during the dry period on adipose tissue mRNA and protein expression of INSR and GLUT4, and on the dynamics of glucose and insulin following the i.v. glucose tolerance test in Holstein cows 21 d before (d -21) and after (d 21) calving. Cows were grouped as body condition score (BCS) ≤3.0 (thin, T; n = 14), BCS = 3.25 to 3.5 (optimal, O; n = 14), and BCS ≥3.75 (overconditioned, OC; n = 14). Blood was analyzed for glucose, insulin, fatty acids, and β-hydroxybutyrate concentrations. Adipose tissue was analyzed for INSR and GLUT4 mRNA and protein concentrations. During the glucose tolerance test 0.15 g/kg of body weight glucose was infused; blood was collected at -5, 5, 10, 20, 30, 40, 50, and 60 min, and analyzed for glucose and insulin. On d -21 the area under the curve (AUC) of glucose was smallest in group T (1,512 ± 33.9 mg/dL × min) and largest in group OC (1,783 ± 33.9 mg/dL × min), and different between all groups. Basal insulin on d -21 was lowest in group T (13.9 ± 2.32 µU/mL), which was different from group OC (24.9 ± 2.32 µU/mL. On d -21 the smallest AUC 5-60 of insulin in group T (5,308 ± 1,214 µU/mL × min) differed from the largest AUC in group OC (10,867 ± 1,215 µU/mL × min). Time to reach basal concentration of insulin in group OC (113 ± 14.1 min) was longer compared with group T (45 ± 14.1). The INSR mRNA abundance on d 21 was higher compared with d -21 in groups T (d -21: 3.3 ± 0.44; d 21: 5.9 ± 0.44) and O (d -21: 3.7 ± 0.45; d 21: 4.7 ± 0.45). The extent of INSR protein expression on d -21 was highest in group T (7.3 ± 0.74 ng/mL), differing from group O (4.6 ± 0.73 ng/mL), which had the lowest expression. The amount of GLUT4 protein on d -21 was lowest in group OC (1.2 ± 0.14 ng/mL), different from group O (1.8 ± 0.14 ng/mL), which had the highest amount, and from group T (1.5 ± 0.14 ng/mL). From d -21 to 21, a decrease occurred in the GLUT4 protein levels in both groups T (d -21: 1.5 ± 0.14 ng/mL; d 21: 0.8 ± 0.14 ng/mL) and O (d -21: 1.8 ± 0.14 ng/mL; d 21: 0.8 ± 0.14 ng/mL). These results demonstrate that in obese cows adipose tissue insulin resistance develops prepartum and is related to reduced GLUT4 protein synthesis. Regarding glucose metabolism, body condition did not affect adipose tissue insulin resistance postpartum.

Comparison of surrogate indices for insulin sensitivity with parameters of the intravenous glucose tolerance test in early lactation dairy cattle

The aim of this study was to investigate the correlation between different surrogate indices and parameters of the intravenous glucose tolerance test (IVGTT) in dairy cows at the start of their lactation. Ten dairy cows underwent IVGTT on Days 3 to 7 after calving. Areas under the curve during the 90 min after infusion, peak and nadir concentrations, elimination rates, and times to reach half-maximal and basal concentrations for glucose, insulin, nonesterified fatty acids, and β-hydroxybutyrate were calculated. Surrogate indices were computed using the average of the IVGTT basal samples, and their correlation with the IVGTT parameters studied through the Spearman's rank test. No statistically significant or strong correlation coefficients (P > 0.05; |ρ| < 0.50) were observed between the insulin sensitivity measures derived from the IVGTT and any of the surrogate indices. Therefore, these results support that the assessment of insulin sensitivity in early lactation cattle cannot rely on the calculation of surrogate indices in just a blood sample, and the more laborious tests (ie, hyperinsulinemic euglycemic clamp test or IVGTT) should be employed to predict the sensitivity of the peripheral tissues to insulin accurately.

Relationship between serum adiponectin concentration, body condition score, and peripheral tissue insulin response of dairy cows during the dry period

The aim of the present study was to describe the relationship between serum adiponectin concentration and peripheral tissue insulin response in dairy cows with a variable body condition score (BCS) during the dry period. Cows were selected at the beginning of the dry period based on BCS (BCS <3.75, n = 4; BCS >3.75, n = 5). Animals were followed from the beginning of the dry period by weekly blood sampling and assessment of BCS and backfat thickness. Weekly blood samples were analyzed for adiponectin concentration using a bovine specific ELISA. Hyperinsulinemic euglycemic clamp tests were performed at the end of the dry period to measure peripheral tissue insulin response. Insulin dose response curves were established for both glucose and fatty acid metabolism. Regression analysis revealed that the serum concentrations of adiponectin dropped at the end of the dry period (P < 0.05) and were negatively associated with BCS (P < 0.05). At the level of the glucose metabolism, serum concentrations of adiponectin were positively correlated with insulin responsiveness (reflecting the maximal effect of insulin; r = 0.76, P < 0.05), but not with insulin sensitivity (reflecting the insulin concentration needed to achieve halfmaximal effect; r = -0.54, P = 0.13). At the level of the fatty acid metabolism, greater adiponectin concentrations were negatively correlated with lower NEFA levels during the HEC test reflecting the insulin responsiveness of the NEFA metabolism (r = -0.61, P = 0.08), whereas there was no association with the insulin sensitivity of the NEFA metabolism (r = -0.16, P = 0.67). In conclusion, serum concentrations of adiponectin were negatively associated with the BCS of dairy cows during the dry period and positively associated with insulin responsiveness of the glucose and fatty acid metabolism.