Plasma NEFA Research Articles

Increasing the proportion of plasma MUFA, as a result of dietary intervention, is associated with a modest improvement in insulin sensitivity.

The effect of modifying dietary fatty acid (FA) composition on insulin sensitivity remains unclear. We aimed to investigate whether changes in plasma phospholipid (PL) FA composition, as a result of dietary intervention, correspond with changes in insulin sensitivity. The RISCK study was a 6-month randomised controlled dietary intervention study, which assessed the effect of modifying dietary fat and the glycaemic index (GI) of carbohydrates on insulin sensitivity. Total NEFA levels, fasting plasma PL FA profiles and an insulin sensitivity index (Si), derived from intravenous glucose tolerance minimal-model analysis, were available from 533 participants, all at elevated risk of type 2 diabetes. Bivariate correlations between changes in saturated PL FA (SFA), MUFA (as a percentage of total plasma NEFA) and changes in Si were assessed according to treatment group. Age, sex, ethnicity, percentage change in body mass and change in dietary GI were controlled for. Increasing total NEFA concentration was associated with worsening Si (r -0·152; P = 0·001). In the high-MUFA/low-GI diet group, change in PL-MUFA was positively and independently associated with change in Si (r 0·297; P = 0·002). Among MUFA, change in oleic acid (18 : 1) was most strongly correlated with change in Si (r 0·266; P = 0·005), as was change in minor FA 24 : 1 (r 0·244; P = 0·011) and 17 : 1 (r 0·196; P = 0·042). In the high-SFA/high-GI group, change in SFA concentration was not significantly associated with change in Si. In conclusion, increases in the proportion of plasma PL-MUFA following a high-MUFA dietary intervention were associated with improvements in insulin sensitivity.

Effect of Soybean Oil and Fish Oil on Lipid-Related Transcripts in Subcutaneous Adipose Tissue of Dairy Cows.

Simple SummaryThe objective of this study was to determine the effects of degree of unsaturation of dietary lipids on lipid-related metabolites and transcription of genes involved in lipid metabolism in subcutaneous adipose tissue (SAT) of mid-lactating dairy cows. The objective was achieved by supplementing dairy cows with soybean oil (high in linoleic acid) or fish oil (high in polyunsaturated fatty acids) for 63 days (nine weeks). Results revealed effects of oil supplement on lipid metabolism but a mild effect on the transcriptome of the adipose tissue. Compared to soybean oil, fish oil had a higher lipogenic effect in SAT.The objective of this study was to determine the effect of long-term supplementation of unsaturated oil on lipid metabolism and transcription of genes involved in lipid metabolism in subcutaneous adipose tissue (SAT) of mid-lactating dairy cows. The objective was achieved by supplementing dairy cows with soybean oil (SO; high in linoleic acid) or fish oil (FO; high in EPA and DHA) for 63 days (nine weeks). Cows were fed a control diet with no added lipid, or diets containing SO or FO (n = 5 cows/group). At the onset of the experiment (day 0) and on days 21, 42, and 63 of supplementation, blood and SAT samples were collected from each animal. Oil supplementation increased cholesterol and NEFA in plasma, with a greater effect of SO compared to FO. Concentration of BUN was lower in SO compared to control and FO at the end of the trial. Transcription of few genes was affected by dietary lipids: FABP4 had lowest expression in FO followed by SO and control. ACACA and FASN had higher expression in FO. Transcription of SCAP was higher but expression of INSIG1 was lower in SO. Overall, results revealed that compared to control, SO and FO had lipogenic effect in SAT.

Circulating palmitoleic acid is an independent determinant of insulin sensitivity, beta cell function and glucose tolerance in non-diabetic individuals: a longitudinal analysis.

Experimental studies suggest that the fatty acid palmitoleate may act as an adipocyte-derived lipid hormone (or 'lipokine') to regulate systemic metabolism. We investigated the relationship of circulating palmitoleate with insulin sensitivity, beta cell function and glucose tolerance in humans. Plasma NEFA concentration and composition were determined in non-diabetic individuals from the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study cohort at baseline (n = 1234) and after a 3 year follow-up (n = 924). Glucose tolerance, insulin secretion and beta cell function were assessed during an OGTT. Whole-body insulin sensitivity was measured by a hyperinsulinaemic-euglycaemic clamp (M/I) and OGTT (oral glucose insulin sensitivity index [OGIS]). The liver insulin resistance index was calculated using clinical and biochemical data. Body composition including fat mass was determined by bioelectrical impedance. Circulating palmitoleate was proportional to fat mass (r = 0.21, p < 0.0001) and total NEFA levels (r = 0.19, p < 0.0001). It correlated with whole-body insulin sensitivity (M/I: standardised regression coefficient [std. β] = 0.16, p < 0.0001), liver insulin resistance (std. β = -0.14, p < 0.0001), beta cell function (potentiation: std. β = 0.08, p = 0.045) and glucose tolerance (2 h glucose: std. β = -0.24, p < 0.0001) after adjustment for age, sex, BMI, adiposity and other NEFA. High palmitoleate concentrations prevented the decrease in insulin sensitivity associated with excess palmitate (p = 0.0001). In a longitudinal analysis, a positive independent relationship was observed between changes in palmitoleate and insulin sensitivity over time (std. β = 0.07, p = 0.04). We demonstrated that plasma palmitoleate is an independent determinant of insulin sensitivity, beta cell function and glucose tolerance in non-diabetic individuals. These results support the role of palmitoleate as a beneficial lipokine released by adipose tissue to prevent the negative effects of adiposity and excess NEFA on systemic glucose metabolism.

Characterization of ANGPTL4 function in macrophages and adipocytes using Angptl4-knockout and Angptl4-hypomorphic mice

Angiopoietin-like protein (ANGPTL)4 regulates plasma lipids, making it an attractive target for correcting dyslipidemia. However, ANGPTL4 inactivation in mice fed a high fat diet causes chylous ascites, an acute-phase response, and mesenteric lymphadenopathy. Here, we studied the role of ANGPTL4 in lipid uptake in macrophages and in the above-mentioned pathologies using Angptl4-hypomorphic and Angptl4-/- mice. Angptl4 expression in peritoneal and bone marrow-derived macrophages was highly induced by lipids. Recombinant ANGPTL4 decreased lipid uptake in macrophages, whereas deficiency of ANGPTL4 increased lipid uptake, upregulated lipid-induced genes, and increased respiration. ANGPTL4 deficiency did not alter LPL protein levels in macrophages. Angptl4-hypomorphic mice with partial expression of a truncated N-terminal ANGPTL4 exhibited reduced fasting plasma triglyceride, cholesterol, and NEFAs, strongly resembling Angptl4-/- mice. However, during high fat feeding, Angptl4-hypomorphic mice showed markedly delayed and attenuated elevation in plasma serum amyloid A and much milder chylous ascites than Angptl4-/- mice, despite similar abundance of lipid-laden giant cells in mesenteric lymph nodes. In conclusion, ANGPTL4 deficiency increases lipid uptake and respiration in macrophages without affecting LPL protein levels. Compared with the absence of ANGPTL4, low levels of N-terminal ANGPTL4 mitigate the development of chylous ascites and an acute-phase response in mice.

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.

Association between breakfast skipping and postprandial hyperglycaemia after lunch in healthy young individuals.

Breakfast skipping has become an increasing trend in the modern lifestyle and may play a role in obesity and type 2 diabetes. In our previous studies in healthy young individuals, a single incident of breakfast skipping increased the overall 24-h blood glucose and elevated the postprandial glycaemic response after lunch; however, it was difficult to determine whether this response was due to breakfast omission or the extra energy (i.e. lunch plus breakfast contents). The present study aimed to assess the postprandial glycaemic response and to measure their hormone levels when healthy young individuals had identical lunch and dinner, and the 24-h average blood glucose as a secondary outcome. Nine healthy young men (19-24 years) participated in two-meal trials: with breakfast (three-meal condition) or without breakfast (breakfast skipping condition). During the meals, each individual's blood glucose was continuously monitored. Skipping breakfast resulted in a significantly higher (P < 0·001) glycaemic response after lunch as compared with the glycaemic response after an identical lunch when breakfast was consumed. Despite the difference in the total energy intake, the 24-h average blood glucose was similar between the two-meal conditions (P = 0·179). Plasma NEFA level was significantly higher (P < 0·05) after lunch when breakfast was omitted, and NEFA level positively correlated with the postprandial glycaemic response (r 0·631, P < 0·01). In conclusion, a single incident of breakfast skipping increases postprandial hyperglycaemia, and associated impaired insulin response, after lunch. The present study showed that skipping breakfast influences glucose regulation even in healthy young individuals.

90 The influence of supplemental zinc, zinc source, and dietary energy level on performance measures of beef steers

Abstract The objective was to determine if steer performance improved with supplemental Zn above recommended concentrations with increasing growth rate. Angus steers (n = 72; 324 ± 2.1kg BW) were blocked by BW within growing diets to one of three Zn strategies (ZNTRT) 1) no supplemental Zn (analyzed 36 mg Zn/kg DM; CON), 2) supranutritional Zn as ZnSO4(CON + 120 mg Zn/kg DM; INZN), or 3) supranutritional Zn blend (CON + 60 mg Zn/kg as ZnSO4 + 60 mg Zn/kg as Zn-amino acid complex; ZNBLD) fed for 60 d, then assigned to dietary energy strategies (ENERGY) targeting growth rates of 1.6 (LOW) or 2 kg/d (HI). On d 60, HI steers were transitioned for 7 d and all animals received respective treatments for an additional 91 d finishing period (n = 12). Data were analyzed as a 3×2 factorial in Proc Mixed of SAS with block as fixed effect; steer was experimental unit. After 60 d of dietary treatment BW tended to be greater in Zn-fed steers vs. CON (P = 0.07). Finishing DMI within HI was similar between INZN and ZNBLD, which were greater than CON, while within LOW no differences were detected due to ZNTRT (ZNTRT×ENERGY; P = 0.01). Neither ZNTRT×ENERGY nor ZNTRT effects (P ≥ 0.37) were detected for finishing ADG, HCW, marbling score, yield grade or backfat. However, finishing period ADG, hot carcass weight, marbling score, yield grade, and back fat were greater in HI vs. LOW (P ≤ 0.05). Plasma NEFA concentrations were lesser for steers receiving HI vs. LOW (P = 0.02), while BUN was unaffected by ZNTRT or ENERGY (P ≥ 0.42). Steer performance was influenced by supranutritional Zn and dietary energy.

Active immune system and dry matter intake during the transition period are associated with postpartum fertility in lactating Zebu cows

The aim of the present study was to assess if the metabolic adaptation and immune status during transition period influence the postpartum reproductive performance in dairy cattle. We assessed the levels of innate immune molecules (Haptoglobin: Hp, Serum Amyloid A: SAA, IL-6, TNF-α, IL-1β, and IL-8) and energy balance indicators [NEFA and Dry Matter Intake (DMI)] in transition Zebu (Deoni breed) cows that became pregnant within breeding period (n = 7) and remained non-pregnant (n = 10) even after the breeding period (i.e. from 45 to 180 days postpartum). Blood samples were collected at weekly intervals during transition period (−21 d before to 21 d after calving) and plasma variables were estimated using commercially available bovine specific ELISA kits. Plasma Hp concentration was significantly (P < 0.01) higher in cows that became pregnant during breeding period as compared to those that remained non-pregnant. While plasma TNF-α concentrations differed significantly (P = 0.05) between groups, such difference was not observed with SAA concentrations. Group x time interaction had a significant effect on plasma IL-6 (P < 0.01), IL-1β (P = 0.05), IL-8 (P = 0.05) concentrations and DMI (P = 0.001). Plasma NEFA concentrations differed significantly (P = 0.03) between groups, although all the experimental cows had NEFA concentrations within the physiological limits. Days in milk had a significant effect on milk yield (P = 0.001) and fat percentage (P = 0.03). It is concluded that active functioning of immune system, stable dry matter intake, and limited fat mobilization during transition period enabled the cows to conceive early during postpartum period.

270-OR: Adipocyte Integrin-Linked Kinase Is Necessary for the Development of Diet-Induced Adipose Insulin Resistance

The remodeling of the extracellular matrix (ECM) in tissues including adipose tissue, and the expression of collagen binding integrin α2β1 have been associated with the development of insulin resistance. Integrin-linked Kinase (ILK), an adaptor protein and a key component of the IPP (ILK-Parvin-PINCH) complex mediates integrins linking the ECM with intracellular signalling. This study determines the role of ILK in adipose function and insulin resistance in chow and high fat (HF)-fed mice. HF feeding increased adipose ILK expression in mice (2.7 ±0.62 vs. 1±0.23; p=0.01). Adipocyte-specific deletion of ILK resulted in a decrease in fat mass (21.6±1.6% vs. 27.3±1.4%; p=0.009) and epididymal tissue weight (eWAT) (1.04±0.07g vs. 1.62±0.11g; p&amp;lt;0.001) in HF-fed mice, but not in chow-fed mice. During the hyperinsulinemic-euglycemic clamp, HF-fed ILK deficient mice showed increased glucose uptake (66.22±p=0.028) in the brown adipose tissue (BAT) compared with the wild type littermate controls. Increased glucose uptake in BAT is associated with increased phosphorylation of AKT (1.96±0.16 vs. 1±0.28 fold change; p=0.01), and decreased phosphorylation of p38 and JNK (0.23 ± 0.17 vs. 1±0.48; p=0.024 and 0.41 ±0.12 vs. 1±0.17; p=0.025 respectively). The inhibition of lipolysis by insulin was also improved in HF-fed ILK deficient mice determined by plasma NEFA level during the clamp. This could be attributed to decreased cell size (0.85±0.042 vs. 1±0.06; p=0.0001), decreased collagen deposition (22.8±0.98 vs. 30.28± 2.05; p=0.01) and a trend increase in vascularization (3.47±1.26 vs. 1±0.23; p=0.07) in the eWAT. These data suggest that adipocyte ILK plays an important role in regulating adipocyte morphology, signaling and glucose and lipid homeostasis, therefore representing a potential target for obesity, insulin resistance and diabetes. Disclosure A. Bugler-Lamb: None. C. Hennayake: None. A. Hasib: None. M.L. Ashford: None. L. Kang: None. Funding Diabetes UK; Diabetes Research &amp; Wellness Foundation

137-OR: The Selective Human Beta 3 Adrenergic Receptor Mirabegron Potently Activates Lipolysis in Human White Adipocytes

Human obesity is an increasing burden worldwide. Lipids stored as metabolic fuel in white adipose tissue (WAT) can be rapidly mobilized through lipolysis. In rodent adipocytes, activation of the β3-adrenergic receptors (β3-ARs) leads to lipolysis. The physiological role of the β3-AR in human adipocytes remains controversial due to its reported low expression and previous access only to partial β3-AR agonists. Mirabegron, an FDA-approved drug for overreactive bladder, is a highly-selective human β3-AR agonist. In clinical trials, mirabegron treatment led to activation of human brown adipose tissue (BAT) thermogenesis and increased plasma NEFA’s. Therefore, we investigated if mirabegron directly mediates lipolysis in human white adipocytes. We found similar gene expression of the three β-ARs in human immortalized and primary white adipocytes, with β2-AR being the most expressed, followed by β1-AR and β3-AR. Next, to assess the functionally of the β3-AR in human adipocytes, we established dose-response curves and found that mirabegron increased the release of glycerol, a lipolytic product, in the picomolar range. To identify the molecular mechanism controlling mirabegron-induced lipolysis, we assessed the regulation of key downstream lipolytic proteins. Mirabegron mediated lipolysis by rapidly phosphorylating hormone sensitive lipase (HSL), as well as the mitogen activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK). Moreover, acute inhibition of either the PKA or MAPK/ERK pathways decreased lipolysis. In summary, we identify a major role played by the β3-AR in the regulation of human WAT lipolysis. Mirabegron acts as a potent pro-lipolytic effector, signaling through the canonical adrenergic receptor pathway as well as the MAPK/ERK pathway. Due to the comparatively minimal effects previously reported of mirabegron on the cardiovascular system, mirabegron may be the optimal choice for targeted lipid mobilization in human WAT. Disclosure C. Cero: None. J.W. Johnson: None. A. O’Mara: None. J.D. Linderman: None. A.M. Cypess: None. Funding National Institutes of Health

2,4-Thiazolidinedione in Well-Fed Lactating Dairy Goats: I. Effect on Adiposity and Milk Fat Synthesis.

Background: In a prior experiment, treatment of goats with the putative PPARγ agonist 2,4-thiazolidinedione (2,4-TZD) did not affect milk fat or expression of milk-fat related genes. The lack of response was possibly due to deficiency of vitamin A and/or a poor body condition of the animals. In the present experiment, we tested the hypothesis that PPARγ activation affects milk fat synthesis in goats with a good body condition and receiving adequate levels of vitamin A. Methods: Lactating goats receiving a diet that met NRC requirements, including vitamin A, were injected with 8 mg/kg BW of 2,4-TZD (n = 6) or saline (n = 6; CTR) daily for 26 days. Blood metabolic profiling and milk yield and components were measured including fatty acid profile. Expression of genes related to glucose and lipid metabolism was measured in adipose tissue and in mammary epithelial cells (MEC). Size of adipocytes was assessed by histological analysis. Results: NEFA, BHBA, and fatty acids available in plasma decreased while glucose increased in 2,4-TZD vs. CTR. Size of cells and expression of insulin signaling and glucose metabolism-related genes were larger in 2,4-TZD vs. CTR in adipose tissue. In MEC, expression of SCD1 and desaturation of stearate was lower in 2,4-TZD vs. CTR. Conclusions: Overall data revealed a lack of PPARγ activation by 2,4-TZD and no effect on milk fat synthesis despite a strong anti-lipolysis effect on adipose tissue.

Association between prepartum metabolic status and resumption of postpartum ovulation in dairy cows

Cows transitioning from late gestation to early lactation experience an increase in energy demands, which lead to a negative energy balance (NEB) because the greater energy requirement is not fully synchronized with the intake of dry matter. In this context, there is an increase in plasma NEFA and ghrelin concentrations and a decrease in plasma insulin and glucose-dependent insulinotropic polypeptide (GIP) concentrations. This situation could have a negative impact on the return to cyclicity because some of these variables have been associated with reduced GnRH and LH pulsatility (high NEFA and low insulin concentrations). However, there are no studies showing the relationship between ghrelin or GIP and reproductive performance. It is known that these hormones are related with lipolysis and NEB, with NEB being one of the main determinants of GnRH pulse generator activity. Thus, the objective of the present study was to evaluate the association between plasma NEFA concentration and metabolic hormones (insulin, ghrelin, and GIP) before parturition and their associations with the resumption of postpartum ovulations in dairy cows. A completely randomized block design was used in a commercial dairy herd with sampling day (visit to farm) as the blocking criteria. Holstein cows (n = 92) were screened for plasma NEFA concentration −5 d (±2 d) relative to the expected parturition day, and top and bottom quartiles were considered as high (H-NEFA) and low (L-NEFA) NEFA groups. Data were analyzed with correlation, linear regression, and proportional hazard regression models. Plasma NEFA concentration (H-NEFA mean = 294 μM, SD = 141.2; and L-NEFA mean = 122 μM, SD = 25.3) was correlated (P < 0.01) with plasma insulin (r = −0.374) and ghrelin (r = −0.346) concentrations but not with plasma GIP concentration (P = 0.64). The greater the concentration of insulin, the lesser the prepartum NEFA concentration (for each 1 μU/mL of plasma insulin increase, there is a decrease of 1.223 ± 0.62 μM of NEFA). Plasma ghrelin and GIP concentrations were not associated with plasma NEFA concentration. Finally, H-NEFA prepartum cows were less likely to resume ovulation than L-NEFA cows (hazard ratio [HR] = 0.563, 95% confidence interval [CI] = 0.314–1.011), whereas high ghrelin cows were more likely to resume ovulation than low ghrelin cows (HR = 1.873, 95% CI = 0.846–4.145). Conversely, resumption of ovulation was not associated with prepartum insulin and GIP concentrations. Prepartum NEFA and possibly ghrelin are associated with the return to postpartum cyclicity; however, insulin and GIP are not related to the resumption of ovulation in dairy cows.

Supplementation with eicosapentaenoic and docosahexaenoic acids in late gestation in ewes changes adipose tissue gene expression in the ewe and growth and plasma concentration of ghrelin in the offspring1.

Omega-3 long chain fatty acids have a positive impact on production. When consumed during late gestation, it might have fetal programming effects on the fetus, which will have lifelong impacts on development and production. The objectives of the present study were to evaluate the effect of increasing doses of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the diet of ewes in the last third of gestation on their body weight (BW), subcutaneous adipose tissue relative mRNA abundance of genes associated with adipose tissue metabolism, and growth performance and plasma metabolites and hormones of their offspring during the finishing phase. Ewes (n = 72) were blocked by BW and allotted to pens (8 per treatment) with 3 ewes per pen. Ewes were supplemented with an EPA and DHA source (Strata G113) at concentrations of 0, 1, or 2% of dry matter intake during the last 50 d of gestation. At lambing, all ewes were penned together and offered the same diet. After weaning at 60 d of age, lambs were blocked by BW and sex and fed for 56 d. All lambs were fed the same pellet diet (61.09% ground corn, 24.08% soy hulls, 11.09% soybean meal, 1.48% Ca salt of palm oil, and 2.26% mixed mineral vitamin), and were weighed every 14 d until the end of the trial. Blood samples were collected on the weight sampling days. Dry matter intake and refusals were weighed daily. Data were analyzed as a randomized complete block design with repeated measurements (SAS 9.4). Polynomial contrast (linear-L and quadratic-Q) was used for mean separation. There were no differences in ewe body condition score, milk production, milk fat, or milk protein, but there was a trend for increased (L, P = 0.06) lactose concentration, and also differences in DGAT1 (L, P = 0.04), Δ5-desaturase (Q, P = 0.06) and Δ6-desaturase (Q, P = 0.07), PPARα (Q, P = 0.03), ELOVL2 and 5 (Q, P < 0.07), FABP4 (Q, P = 0.04), FATP1 (Q, P = 0.06), leptin (Q, P = 0.02), and resistin (L, P = 0.05). Feeding pregnant ewes an increased amount of EPA and DHA in late gestation increased final BW (L, P = 0.01), ADG (L, P = 0.04; Q, P = 0.01), DMI (Q, P ≤ 0.01), plasma glucose concentration (L, P = 0.04), and trended to decrease ghrelin concentrations (L, P = 0.07) in offspring during the finishing period. Dam supplementation did not affect G:F, nor plasma NEFA concentration (P ≥ 0.53) of lambs. Therefore, increasing supplementation of EPA and DHA in pregnant ewes has an impact on offspring performance, increasing DMI, ADG, and BW.

SAT-152 Loss of Hepatocyte PPARγ Expression Ameliorates Steatosis in Mice Fed a High-Fat, Cholesterol, and Fructose Diet, but Not in Mice Fed a Methionine- and Choline-Deficient Diet

Hepatic PPARγ expression is positively associated with the progression of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis (NASH) in mice and humans. Although PPARγ agonists, thiazolidinediones (TZD), could be used to treat patients with NASH, these drugs reduced steatosis only in some patients with NASH, while it exacerbated steatosis in obese mice. Several mouse models with congenital knockout or overexpression of hepatic PPARγ have been used to study the actions and relevance of hepatocyte PPARγ in the development of steatosis. However, the mechanisms that hepatocyte PPARγ regulates to promote steatosis are not fully understood. Our group has previously reported that adult-onset hepatocyte-specific PPARγ knockout (aHepPPARγKO) mice fed a high fat diet (60% Kcal from fat) developed adiposity similar to PPARγ-intact controls, but aHepPPARγKO mice showed a dramatic reduction in steatosis, associated with reduced hepatic Cd36-mediated fatty acid uptake. Here, we fed aHepPPARγKO mice two different diets that produce steatosis and NASH to determine if loss of hepatocyte PPARγ expression reduced hepatic lipid levels associated with a reduction in Cd36 expression. Specifically, aHepPPARγKO and control mice were generated by injecting 10 wk-old male PPARγ-floxed littermate mice with a single dose of adeno-associated virus serotype 8 (AAV8) expressing hepatocyte-specific Cre recombinase or a AAV8-null vector, respectively. Two weeks later, aHepPPARγKO and control mice were fed either a methionine- and choline-deficient diet (MCD) for 3 weeks or a high-fat, cholesterol and fructose diet (HFCFD) diet for 8 weeks. The expression of hepatic PPARγ and Cd36 was significantly increased in MCD- and HFCF-fed control mice as compared to their respective control diet-fed controls. Of note, aHepPPARγKO reduced the expression of hepatic PPARγ (by >85%) and Cd36 (by >35-65%). Overall, MCD-fed mice showed reduced body weight, fat mass, and plasma cholesterol levels, while HFCFD-fed mice showed increased body weight and gonadal fat mass, and reduced plasma NEFA levels as compared to their respective control diet-fed littermates. Independent of diet, aHepPPARγKO did not alter body weight, adiposity, or the levels of plasma lipids. However, aHepPPARγKO reduced steatosis in HFCFD-fed mice, but not in MCD-fed mice. Interestingly, the levels of hepatic oleic [18:1(n-9)] and linoleic [18:2(n-6)] acids were, in fact, increased in MCD-fed aHepPPARγKO mice, while the levels of hepatic palmitoleic [16:1(n-7)] and oleic [18:1(n-9)] acids were reduced in HFCFD-fed aHepPPARγKO mice. Taken together, these data suggest that hepatocyte PPARγ serves as a steatogenic factor only in HFCFD-fed mice and not in MCD-fed mice, and this may be due to diet-dependent effects: nature of the development of steatosis and/or changes in adipose tissue.

Postprandial incorporation of EPA and DHA from transgenic Camelina sativa oil into blood lipids is equivalent to that from fish oil in healthy humans.

EPA and DHA are important components of cell membranes. Since humans have limited ability for EPA and DHA synthesis, these must be obtained from the diet, primarily from oily fish. Dietary EPA and DHA intakes are constrained by the size of fish stocks and by food choice. Seed oil from transgenic plants that synthesise EPA and DHA represents a potential alternative source of these fatty acids, but this has not been tested in humans. We hypothesised that incorporation of EPA and DHA into blood lipids from transgenic Camelina sativa seed oil (CSO) is equivalent to that from fish oil. Healthy men and women (18-30 years or 50-65 years) consumed 450 mg EPA + DHA from either CSO or commercial blended fish oil (BFO) in test meals in a double-blind, postprandial cross-over trial. There were no significant differences between test oils or sexes in EPA and DHA incorporation into plasma TAG, phosphatidylcholine or NEFA over 8 h. There were no significant differences between test oils, age groups or sexes in postprandial VLDL, LDL or HDL sizes or concentrations. There were no significant differences between test oils in postprandial plasma TNFα, IL 6 or 10, or soluble intercellular cell adhesion molecule-1 concentrations in younger participants. These findings show that incorporation into blood lipids of EPA and DHA consumed as CSO was equivalent to BFO and that such transgenic plant oils are a suitable dietary source of EPA and DHA in humans.

Probiotic supplementation improves total and exogenous CHO oxidation in trained male cyclists: A randomized, double‐blind, placebo‐controlled cross‐over trial

BackgroundIn vitro and animal studies suggest probiotic supplementation can enhance intestinal absorption and whole body oxidation rates of glucose.ObjectiveThis study investigated the effects of multi‐strain probiotics supplementation on substrate utilization, markers of gastrointestinal permeability and damage and subjective symptoms of discomfort and performance during endurance cycling.Methods and DesignNine male cyclists (age 23 ± 4 yrs, V̇O2max 62.1 ± 4.7 mL·kg−1·min−1) were randomized to two periods of daily supplementation with a probiotics capsule (25 billion CFU of Lactobacillus acidophilus (CUL60 and CUL21), Bifidobacterium bifidum (CUL20), Bifidobacterium animalis subsp. lactis (CUL34), Proven Probiotics) or placebo for four weeks, separated by a 14‐day washout period (double‐blind cross‐over trial). After each supplementation period, cyclists consumed a 10% maltodextrin solution (initial 8 mL·kg−1 bolus at commencement of exercise and 2 mL·kg−1 every subsequent 15 min) while exercising for 120 minutes at 55% Wmax. This was followed immediately by a 100 kJ time trial performance test. Markers of GI permeability, damage and GI discomfort were assessed. Oxidation rates of the ingested maltodextrin drinks were calculated from the 13C‐enrichment of plasma glucose and breath 13CO2 production during the 120 minutes exercise period.ResultsProbiotic supplementation resulted in an increase of total carbohydrate (CHO) oxidation (2.12 ± 0.30 vs 1.81 ± 0.44 g·min1, P = 0.019) and the peak oxidation of an ingested maltodextrin drink (0.84 ± 0.10 vs 0.77 ± 0.09 g·min−1 of glucose equivalents, P = 0.016) during exercise. Total fat oxidation was reduced following probiotic supplementation compared to placebo (P = 0.004). There were also significant differences in plasma insulin, NEFA and glycerol between trials. Differences between markers of GI damage and permeability were not significant, as was time trial performance (P &gt; 0.05).ConclusionsProbiotic supplementation enhances total and ingested CHO oxidation while simultaneously attenuating total fat oxidation during moderate intensity cycling. Probiotic supplementation did not change GI symptoms, time trial performance and markers of intestinal damage and permeability.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A controlled heat stress during late gestation affects thermoregulation, productive performance, and metabolite profiles of primiparous sow

Heat stress (HS) alters metabolic parameters and reduces productive performance in lactating sows. However, the impact of HS on metabolomic profiles of sows during late gestation is not fully understood. We present here, a study investigating the productive performance and metabolic responses in sows when exposed to HS during late gestation. Twelve first-parity Landrace × Large White F1 sows were randomly assigned into two environmental treatments including the thermoneutral (TN) (18–22 °C; n = 6) and HS (28–32 °C; n = 6) conditions from 85 d of gestation until farrowing. Rectal temperature (RT), respiration rates (RR), and surface temperature (ST) were measured every 4 h from 0800 h to 2000 h during the 2nd week. Farrowing and litter Data, as well as duration of eating, were monitored to assess sows’ productive performance. Blood biochemical parameters and urinary metabolomic profiles were measured on d107 of gestation to analyze the host metabolic responses. Our results show that HS increased RT, RR, and ST (P < 0.0001). Duration of parturition was prolonged during the delivery in HS group (P < 0.05). Piglet body weight (BW) at d 10 and weaning were reduced by 18% and 17% respectively due to maternal HS (P < 0.001). Duration of eating increased as a result of HS (P < 0.001), consistent with the significant changes observed in serum ghrelin (P < 0.05). Moreover, serum ACTH, cortisol, insulin, creatinine, and BUN saw increase as well (P < 0.05). Plasma NEFA were elevated by HS (P < 0.001). Additionally, HS elevated (VIP>1, log2fold change>0.585, and P < 0.05) the relative concentrations of 5-aminovaleric acid, β-alanine, cysteine, isoleucine, glyceric acid, erythronic acid, mannitol, erythritol, 2-methyl-1,3-butanediol, and pantothenic acid in urine. These ten metabolites mainly affected the pantothenate and CoA biosynthesis, β-alanine metabolism, and glycerolipid metabolism in pregnant sows. In summary, our study suggests that the controlled HS during late gestation elevates thermal responses, reduces productive performance, and more importantly, enhances the catabolism of lipid and protein of first-parity pregnant sow.

Increased NEFA levels reduce blood Mg2+ in hypertriacylglycerolaemic states via direct binding of NEFA to Mg2+

Aims/hypothesisThe blood triacylglycerol level is one of the main determinants of blood Mg2+ concentration in individuals with type 2 diabetes. Hypomagnesaemia (blood Mg2+ concentration <0.7 mmol/l) has serious consequences as it increases the risk of developing type 2 diabetes and accelerates progression of the disease. This study aimed to determine the mechanism by which triacylglycerol levels affect blood Mg2+ concentrations.MethodsUsing samples from 285 overweight individuals (BMI >27 kg/m2) who participated in the 300-Obesity study (an observational cross-sectional cohort study, as part of the Human Functional Genetics Projects), we investigated the association between serum Mg2+ with laboratory variables, including an extensive lipid profile. In a separate set of studies, hyperlipidaemia was induced in mice and in healthy humans via an oral lipid load, and blood Mg2+, triacylglycerol and NEFA concentrations were measured using colourimetric assays. In vitro, NEFAs harvested from albumin were added in increasing concentrations to several Mg2+-containing solutions to study the direct interaction between Mg2+ and NEFAs.ResultsIn the cohort of overweight individuals, serum Mg2+ levels were inversely correlated with triacylglycerols incorporated in large VLDL particles (r = −0.159, p ≤ 0.01). After lipid loading, we observed a postprandial increase in plasma triacylglycerol and NEFA levels and a reciprocal reduction in blood Mg2+ concentration both in mice (Δ plasma Mg2+ −0.31 mmol/l at 4 h post oral gavage) and in healthy humans (Δ plasma Mg2+ −0.07 mmol/l at 6 h post lipid intake). Further, in vitro experiments revealed that the decrease in plasma Mg2+ may be explained by direct binding of Mg2+ to NEFAs. Moreover, Mg2+ was found to bind to albumin in a NEFA-dependent manner, evidenced by the fact that Mg2+ did not bind to fatty-acid-free albumin. The NEFA-dependent reduction in the free Mg2+ concentration was not affected by the presence of physiological concentrations of other cations.Conclusions/interpretationThis study shows that elevated NEFA and triacylglycerol levels directly reduce blood Mg2+ levels, in part explaining the high prevalence of hypomagnesaemia in metabolic disorders. We show that blood NEFA level affects the free Mg2+ concentration, and therefore, our data challenge how the fractional excretion of Mg2+ is calculated and interpreted in the clinic.

24-h severe energy restriction impairs postprandial glycaemic control in young, lean males.

Intermittent energy restriction (IER) involves short periods of severe energy restriction interspersed with periods of adequate energy intake, and can induce weight loss. Insulin sensitivity is impaired by short-term, complete energy restriction, but the effects of IER are not well known. In randomised order, fourteen lean men (age: 25 (sd 4) years; BMI: 24 (sd 2) kg/m2; body fat: 17 (4) %) consumed 24-h diets providing 100 % (10 441 (sd 812) kJ; energy balance (EB)) or 25 % (2622 (sd 204) kJ; energy restriction (ER)) of estimated energy requirements, followed by an oral glucose tolerance test (OGTT; 75 g of glucose drink) after fasting overnight. Plasma/serum glucose, insulin, NEFA, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP) and fibroblast growth factor 21 (FGF21) were assessed before and after (0 h) each 24-h dietary intervention, and throughout the 2-h OGTT. Homoeostatic model assessment of insulin resistance (HOMA2-IR) assessed the fasted response and incremental AUC (iAUC) or total AUC (tAUC) were calculated during the OGTT. At 0 h, HOMA2-IR was 23 % lower after ER compared with EB (P<0·05). During the OGTT, serum glucose iAUC (P<0·001), serum insulin iAUC (P<0·05) and plasma NEFA tAUC (P<0·01) were greater during ER, but GLP-1 (P=0·161), GIP (P=0·473) and FGF21 (P=0·497) tAUC were similar between trials. These results demonstrate that severe energy restriction acutely impairs postprandial glycaemic control in lean men, despite reducing HOMA2-IR. Chronic intervention studies are required to elucidate the long-term effects of IER on indices of insulin sensitivity, particularly in the absence of weight loss.

Pleiotrophin deletion alters glucose homeostasis, energy metabolism and brown fat thermogenic function in mice.

Pleiotrophin, a developmentally regulated and highly conserved cytokine, exerts different functions including regulation of cell growth and survival. Here, we hypothesise that this cytokine can play a regulatory role in glucose and lipid homeostasis. To test this hypothesis, we performed a longitudinal study characterising the metabolic profile (circulating variables and tissue mRNA expression) of gene-targeted Ptn-deficient female mice and their corresponding wild-type counterparts at different ages from young adulthood (3months) to older age (15months). Metabolic cages were used to investigate the respiratory exchange ratio and energy expenditure, at both 24°C and 30°C. Undifferentiated immortalised mouse brown adipocytes (mBAs) were treated with 0.1μg/ml pleiotrophin until day 6 of differentiation, and markers of mBA differentiation were analysed by quantitative real-time PCR (qPCR). Ptn deletion was associated with a reduction in total body fat (20.2% in Ptn+/+ vs 13.9% in Ptn-/- mice) and an enhanced lipolytic response to isoprenaline in isolated adipocytes from 15-month-old mice (189% in Ptn+/+ vs 273% in Ptn-/- mice). We found that Ptn-/- mice exhibited a significantly lower QUICKI value and an altered lipid profile; plasma triacylglycerols and NEFA did not increase with age, as happens in Ptn+/+ mice. Furthermore, the contribution of cold-induced thermogenesis to energy expenditure was greater in Ptn-/- than Ptn+/+ mice (42.6% and 33.6%, respectively). Body temperature and the activity and expression of deiodinase, T3 and mitochondrial uncoupling protein-1 in the brown adipose tissue of Ptn-/- mice were higher than in wild-type controls. Finally, supplementing brown pre-adipocytes with pleiotrophin decreased the expression of the brown adipocyte markers Cidea (20% reduction), Prdm16 (21% reduction), and Pgc1-α (also known as Ppargc1a, 11% reduction). Our results reveal for the first time that pleiotrophin is a key player in preserving insulin sensitivity, driving the dynamics of adipose tissue lipid turnover and plasticity, and regulating energy metabolism and thermogenesis. These findings open therapeutic avenues for the treatment of metabolic disorders by targeting pleiotrophin in the crosstalk between white and brown adipose tissue.