Plasma Non-esterified Free Fatty Acids Research Articles

PMON244 Alterations in Nonesterified Free Fatty Acids (NEFA) Trafficking Rather Than Hyperandrogenism Contribute to Variations in Insulin Sensitivity Among Obese Women with Polycystic Ovary Syndrome

Abstract Objectives To compare the metabolic and hormonal features of metabolically unhealthy obese PCOS women (MU-PCOS) vs. metabolically healthy obese PCOS women (MH-PCOS) and determine whether alterations in non-esterified free fatty acids (NEFA) response to hyperinsulinemia contribute to variations in insulin sensitivity between MU-PCOS and MH-PCOS. Design Prospective cross-sectional study. Setting Tertiary-care academic center. Methods Insulin resistance (IR) in the basal state was assessed by HOMA-IR in 125 consecutive obese oligo-ovulatory PCOS women (BMI≥ 30 kg/m2; NIH 1990 or Rotterdam 2003 Phenotype A/B) undergoing an oral glucose tolerance test (oGTT); and IR in the dynamic state assessed by the modified frequently sampled intravenous glucose tolerance test (mFSIVGTT) in a subgroup of 16 non-diabetic obese PCOS women. Main Outcome Measures: Primary outcome measures were: 1) IR in AT was assessed in the basal state by the Adipose Insulin Resistance Index [Adipo-IR]) and dynamically by the mFSIVGTT-derived indices of insulin-mediated NEFA suppression [NEFAnadir, TIMEnadir, and %NEFAsupp]); 2) peak lipolysis rate [SNEFA]; and 3) peak NEFA uptake rate [KNEFA]. Secondary outcome measures were levels of insulin and glucose during oGTT, HOMA-β%, and degree of hyperandrogenism (i.e. mF-G score, free testosterone [T], total T, DHEAS). Results Eighty-five obese PCOS participants undergoing oGTT had a HOMA-IR index of ≥2.5 (MU-PCOS) and 40 had a HOMA-IR of <2.5 (MH-PCOS). MU-PCOS had higher mean HOMA-β%, levels of fasting, 1-hr and 2-hr. glucose and insulin, and peak insulin during the oGTT, and higher prevalence of prediabetes and elevated 1-hr. glucose and a trend towards higher prevalence of type 2 diabetes mellitus (T2DM), than MH-PCOS. Alternatively, measures of HA were similar between the groups. Assessing IR dynamically, subjects were subdivided into MU-PCOS by an insulin sensitivity index [Si] ≤1.7 [mU/L]−1·min−1 (n=8) or MH-PCOS by an Si ≥5.6 [mU/L]−1·min−1 (n=8), matched for age and BMI. MU-PCOS had lower Si and KNEFA, smaller %NEFAsupp, longer TIMEnidar, and higher NEFAnidar and Adipo-IR than MH-PCOS, although fasting plasma NEFA levels and SNEFA were similar. In bivalent analysis, Si correlated strongly and negatively with NEFAnadir, weakly and negatively with TIMEnadir, and positively and strongly with KNEFA and NEFAsupp, in MUO-PCOS only. Conclusion Independent of age and BMI, metabolically unhealthy obese PCOS women, compared with metabolically healthy obese PCOS women, had lower rates of NEFA uptake and altered insulin-mediated plasma NEFA suppression in response to mFSIVGTT-determined endogenous insulin secretion, rather than disparities in HA and rate of lipolysis, mechanism that may contribute to variations in insulin sensitivity among obese PCOS women. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Senolytic Drugs, Dasatinib and Quercetin, Attenuate Adipose Tissue T Lymphocyte Infiltration and Improve Metabolic Function in Old Mice

Age-related metabolic dysfunction is accompanied by accumulation of senescent cells and the senescence-associated secretory phenotype (SASP) leading to chronic sterile inflammation. Recent evidence suggests that using a genetic approach to clear senescent cells improves metabolic function in old mice. However, the underlying mechanisms and if/how these findings can be translated into clinical practice are largely unknown. Here, we evaluated the impact of treatment with the FDA-approved drugs, dasatinib and quercetin (D&Q), on tissue senescence burden, T lymphocyte infiltration and systemic metabolic function in 22-24 month old C57Bl/6 mice. Administration of D&Q resulted in ~50% reduction in expression of the senescence marker p16 in perigonadal white adipose tissue (pgWAT) (p=0.004) and liver (p=0.003) (Fig 1A), but not skeletal muscle (p=0.76). D&Q treatment also resulted in 1 to 4-fold reduction in expression of pro-inflammatory SASP genes (i.e., mcp1, cxcl2, il-6 and il-1β) in pgWAT (all p≤0.04; Fig 1B), but not in liver and skeletal muscle (all p≥0.19), suggesting an adipose specific effect of D&Q. Using flow cytometry, we found that the reduced expression of p16 and SASP genes was associated with 30-50% lower infiltration of total (CD3+), cytotoxic (CD8+) and helper (CD4+) T cells in pgWAT (all p≤0.04; Fig 1C). Treatment with D&Q ameliorated glucose tolerance (2 g/kg, ip) as demonstrated by a lower time response curve (group: p=0.007, interaction: p=0.03, Fig 1D) and reduced area under the curve (p=0.01, Fig 1E). To explore the underlying mechanisms, we assessed glucose-stimulated (2 g/kg, ip) insulin secretion and insulin tolerance (1 U/kg, ip) and found no differences between groups (both p≥0.19). To assess the impact of D&Q on metabolic function in the liver, we performed a pyruvate tolerance (2 g/kg, ip) test and found that this treatment resulted in improved pyruvate tolerance (group: p=0.08, interaction: p=0.04, Fig 2A) and thus attenuated hepatic gluconeogenesis. Biochemical analysis revealed that phosphorylation of a gluconeogenic transcription factor, cAMP response element binding protein, and transcript level expression of gluconeogenic genes (pck1, pck2, fbp2 and g6pc) were lower in D&Q treated mice compared to vehicle treated mice (all p≤0.04; Fig 2B-D), further supporting our findings of diminished hepatic gluconeogenesis. D&Q treatment also reduced plasma triglycerides (113 ± 5 vs 94 ± 5 mg/dL, p=0.02) and improved adipose tissue sensitivity to insulin as indicated by lower insulin-stimulated ((1 U/kg, ip) plasma non-esterified free fatty acids (fasted: 0.63 ± 0.02 vs 0.62 ± 0.06 mmol/L, p=0.87; 15 min: 0.54 ± 0.05 vs 0.33 ± 0.02 mmol/L, p=0.006). Taken together, these results suggest that D&Q improve glucose tolerance and lipid metabolism, associated with an attenuation of adipose inflammation (i.e., reduced SASP gene expression and T cell infiltration) and reduced hepatic gluconeogenesis in old mice.

Autocrine negative feedback regulation of lipolysis through sensing of NEFAs by FFAR4/GPR120 in WAT

ObjectivesLong-chain fatty acids (LCFAs) released from adipocytes inhibit lipolysis through an unclear mechanism. We hypothesized that the LCFA receptor, FFAR4 (GPR120), which is highly expressed in adipocytes, may be involved in this feedback regulation. Methods and resultsLiquid chromatography mass spectrometry (LC-MS) analysis of conditioned media from isoproterenol-stimulated primary cultures of murine and human adipocytes demonstrated that most of the released non-esterified free fatty acids (NEFAs) are known agonists for FFAR4. In agreement with this, conditioned medium from isoproterenol-treated adipocytes stimulated signaling strongly in FFAR4 transfected COS-7 cells as opposed to non-transfected control cells. In transfected 3T3-L1 cells, FFAR4 agonism stimulated Gi- and Go-mini G protein binding more strongly than Gq, effects which were blocked by the selective FFAR4 antagonist AH7614. In primary cultures of murine white adipocytes, the synthetic, selective FFAR4 agonist CpdA inhibited isoproterenol-induced intracellular cAMP accumulation in a manner similar to the antilipolytic control agent nicotinic acid acting through another receptor, HCAR2. In vivo, oral gavage with the synthetic, specific FFAR4 agonist CpdB decreased the level of circulating NEFAs in fasting lean mice to a similar degree as nicotinic acid. In agreement with the identified anti-lipolytic effect of FFAR4, plasma NEFAs and glycerol were increased in FFAR4-deficient mice as compared to littermate controls despite having elevated insulin levels, and cAMP accumulation in primary adipocyte cultures was augmented by treatment with the FFAR4 antagonist conceivably by blocking the stimulatory tone of endogenous NEFAs on FFAR4. ConclusionsIn white adipocytes, FFAR4 functions as an NEFA-activated, autocrine, negative feedback regulator of lipolysis by decreasing cAMP though Gi-mediated signaling.

Nonesterified free fatty acids enhance the inflammatory response in renal tubules by inducing extracellular ATP release.

In proteinuric renal diseases, excessive plasma nonesterified free fatty acids bound to albumin can leak across damaged glomeruli to be reabsorbed by renal proximal tubular cells and cause inflammatory tubular cells damage by as yet unknown mechanisms. The present study was designed to investigate these mechanisms induced by palmitic acid (PA; one of the nonesterified free fatty acids) overload. Our results show that excess PA stimulates ATP release through the pannexin 1 channel in human renal tubule epithelial cells (HK-2), increasing extracellular ATP concentration approximately threefold compared with control. The ATP release is dependent on caspase-3/7 activation induced by mitochondrial reactive oxygen species. Furthermore, extracellular ATP aggravates PA-induced monocyte chemoattractant protein-1 secretion and monocyte infiltration of tubular cells, enlarging the inflammatory response in both macrophages and HK-2 cells via the purinergic P2X7 receptor-mammalian target of rapamycin-forkhead box O1-thioredoxin-interacting protein/NOD-like receptor protein 3 inflammasome pathway. Hence, PA increases mitochondrial reactive oxygen species-induced ATP release and inflammatory stress, which cause a "first hit," while ATP itself is a "second hit" in amplifying the renal tubular inflammatory response. Thus, inhibition of ATP release or the purinergic P2X7 receptor may be an approach to reduce renal inflammation and improve renal function.

Potentiation of Ecstasy-induced hyperthermia and FAT/CD36 expression in chronically exercised animals

ABSTRACTFatal hyperthermia as a result of 3,4-methylenedioxymethamphetamine (MDMA) use involves non-esterified free fatty acids (NEFA) and the activation of mitochondrial uncoupling proteins (UCP). NEFA gain access into skeletal muscle via specific transport proteins, including fatty acid translocase (FAT/CD36). FAT/CD36 expression is known to increase following chronic exercise. Previous studies have demonstrated the essential role of NEFA and UCP3 in MDMA-induced hyperthermia. The aims of the present study were to use a chronic exercise model (swimming for two consecutive hours per day, five days per wk for six wk) to increase FAT/CD36 expression in order to: 1) determine the contribution of FAT/CD36 in MDMA (20 mg/kg, s.c.)-mediated hyperthermia; and 2) examine the effects of the FAT/CD36 inhibitor, SSO (sulfo-N-succinimidyl oleate), on MDMA-induced hyperthermia in chronic exercise and sedentary control rats. MDMA administration resulted in hyperthermia in both sedentary and chronic exercise animals. However, MDMA-induced hyperthermia was significantly potentiated in the chronic exercise animals compared to sedentary animals. Additionally, chronic exercise significantly reduced body weight, increased FAT/CD36 protein expression levels and reduced plasma NEFA levels. The FAT/CD36 inhibitor, SSO (40 mg/kg, ip), significantly attenuated the hyperthermia mediated by MDMA in chronic exercised but not sedentary animals. Plasma NEFA levels were elevated in sedentary and exercised animals treated with SSO prior to MDMA suggesting attenuation of NEFA uptake into skeletal muscle. Chronic exercise did not alter skeletal muscle UCP3 protein expression levels. In conclusion, chronic exercise potentiates MDMA-mediated hyperthermia in a FAT/CD36 dependent fashion.

Matured Hop Bittering Components Induce Thermogenesis in Brown Adipose Tissue via Sympathetic Nerve Activity.

Obesity is the principal symptom of metabolic syndrome, which refers to a group of risk factors that increase the likelihood of atherosclerosis. In recent decades there has been a sharp rise in the incidence of obesity throughout the developed world. Iso-α-acids, the bitter compounds derived from hops in beer, have been shown to prevent diet-induced obesity by increasing lipid oxidation in the liver and inhibition of lipid absorption from the intestine. Whereas the sharp bitterness induced by effective dose of iso-α-acids precludes their acceptance as a nutrient, matured hop bittering components (MHB) appear to be more agreeable. Therefore, we tested MHB for an effect on ameliorating diet-induced body fat accumulation in rodents. MHB ingestion had a beneficial effect but, compared to iso-α-acids and despite containing structurally similar compounds, acted via different mechanisms to reduce body fat accumulation. MHB supplementation significantly reduced body weight gain, epididymal white adipose tissue weight, and plasma non-esterified free fatty acid levels in diet-induced obese mice. We also found that uncoupling protein 1 (UCP1) expression in brown adipose tissue (BAT) was significantly increased in MHB-fed mice at both the mRNA and protein levels. In addition, MHB administration in rats induced the β-adrenergic signaling cascade, which is related to cAMP accumulation in BAT, suggesting that MHB could modulate sympathetic nerve activity innervating BAT (BAT-SNA). Indeed, single oral administration of MHB elevated BAT-SNA in rats, and this elevation was dissipated by subdiaphragmatic vagotomy. Single oral administration of MHB maintained BAT temperature at a significantly higher level than in control rats. Taken together, these findings indicate that MHB ameliorates diet-induced body fat accumulation, at least partly, by enhancing thermogenesis in BAT via BAT-SNA activation. Our data suggests that MHB is a useful tool for developing functional foods or beverages to counteract the accumulation of body fat.

Elevated maternal cortisol leads to relative maternal hyperglycemia and increased stillbirth in ovine pregnancy.

In normal pregnancy, cortisol increases; however, further pathological increases in cortisol are associated with maternal and fetal morbidities. These experiments were designed to test the hypothesis that increased maternal cortisol would increase maternal glucose concentrations, suppress fetal growth, and impair neonatal glucose homeostasis. Ewes were infused with cortisol (1 mg·kg(-1)·day(-1)) from day 115 of gestation to term; maternal glucose, insulin, ovine placental lactogen, estrone, progesterone, nonesterified free fatty acids (NEFA), β-hydroxybutyrate (BHB), and electrolytes were measured. Infusion of cortisol increased maternal glucose concentration and slowed the glucose disappearance after injection of glucose; maternal infusion of cortisol also increased the incidence of fetal death at or near parturition. The design of the study was altered to terminate the study prior to delivery, and post hoc analysis of the data was performed to test the hypothesis that maternal metabolic factors predict the fetal outcome. In cortisol-infused ewes that had stillborn lambs, plasma insulin was increased relative to control ewes or cortisol-infused ewes with live lambs. Maternal cortisol infusion did not alter maternal food intake or plasma NEFA, BHB, estrone, progesterone or placental lactogen concentrations, and it did not alter fetal body weight, ponderal index, or fetal organ weights. Our study suggests that the adverse effect of elevated maternal cortisol on pregnancy outcome may be related to the effects of cortisol on maternal glucose homeostasis, and that chronic maternal stress or adrenal hypersecretion of cortisol may create fetal pathophysiology paralleling some aspects of maternal gestational diabetes.

Postprandial inflammatory responses and plasma‐free fatty acids: effects of blueberry intake (1034.6)

We studied whether a high‐fat (HF) meal‐induced postprandial (PP) lipemia affects inflammatory responses in blood monocytes, and whether blueberry intake suppresses the PP inflammatory responses in healthy human subjects. A HF breakfast increased PP plasma triglycerides and insulin, but non‐esterified free fatty acid (NEFA) levels were decreased compared to fasting levels. TNF‐α , IL‐6 and IL‐8 in PP plasma were decreased compared to fasting levels. Cytokine and NEFA levels in PP plasma were not affected by blueberry intake. To determine whether endogenous NEFAs derived from the HF diet stimulate monocyte activation, whole blood or peripheral blood mononuclear cells (PBMC) were treated with lipoprotein lipase (LPL). LPL treatment of whole blood increased NEFA levels and secretion of IL‐1β, IL‐6, and TNF‐α. IL‐1β in LPL‐treated PP whole blood was elevated compared to fasting control. Blueberry intake suppressed IL‐1β and IL‐6 production without affecting levels of NEFAs released in LPL‐treated PP blood when fasting controls were used as a covariate. LPL treatment also increased NEFA and cytokine levels in PBMC. Together, these results demonstrate that NEFA levels in plasma or whole blood are an important determinant affecting pro‐inflammatory cytokine production. Therefore, modulation of levels of plasma NEFA by dietary means could be an effective strategy to suppress HF diet‐induced inflammatory responses.Grant Funding Source: Supported by USDA‐ARS‐WHNRC Funds and US Highbush Blueberry Council grant

Elevated plasma free fatty acids are associated with sudden death: A prospective community-based evaluation at the time of cardiac arrest

In cohort studies, elevated levels of plasma nonesterified free fatty acids (NEFAs) have been associated with increased risk of sudden cardiac death (SCD) in men, but blood samples were drawn several years before SCD. To confirm this relationship by evaluating levels of plasma NEFAs at the time of the SCD event in a group of both men and women. From the ongoing Oregon Sudden Unexpected Death Study, we compared levels of plasma NEFAs in 149 SCD cases presenting with ventricular fibrillation (mean age 64 ± 12 years; 73% men) and 149 age- and sex-matched controls with coronary artery disease. Plasma was processed from blood drawn at the time of arrest (cases) and at a routine visit (controls). The levels of plasma NEFAs were compared after categorizing into quartiles on the basis of control values. Conditional logistic regression was used to predict adjusted odds ratio for SCD associated with plasma NEFA levels per increased quartile. The plasma NEFA levels were significantly higher in SCD cases than in controls (median 0.39 mmol/L [interquartile range 0.28-0.60 mmol/L] vs 0.32 mmol/L [interquartile range 0.20-0.49 mmol/L]; P = .002). There were no significant differences in body mass index, smoking, and diabetes. The odds ratio for SCD was 1.42 (95% confidence interval 1.14-1.78) per quartile increase in the plasma NEFA level (P = .002). Individuals with plasma NEFA levels above the prespecified cutoff point of 0.32 mmol/L were at increased risk of SCD (odds ratio 2.00; 95% confidence interval 1.20-3.34; P = .008). These findings strengthen the role of plasma NEFA as a potential biomarker for the assessment of SCD risk.

Palm Olein and Olive Oil Cause a Higher Increase in Postprandial Lipemia Compared with Lard but Had No Effect on Plasma Glucose, Insulin and Adipocytokines

Postprandial lipemia impairs insulin sensitivity and triggers the pro-inflammatory state which may lead to the progression of cardiovascular diseases. A randomized, crossover single-blind study (n = 10 healthy men) was designed to compare the effects of a high-fat load (50 g fat), rich in palmitic acid from both plant (palm olein) or animal source (lard) versus an oleic acid-rich fat (virgin olive oil) on lipemia, plasma glucose, insulin and adipocytokines. Serum triacylglycerol (TAG) concentrations were significantly lower after the lard meal than after the olive oil and palm olein meals (meal effect P = 0.003; time effect P < 0.001). The greater reduction in the plasma non-esterified free fatty acids levels in the lard group compared to the olive oil meal was mirrored by the changes observed for serum TAG levels (P < 0.05). The magnitude of response for plasma glucose, insulin and adipocytokines [interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and leptin] were not altered by the type of dietary fats. A significant difference in plasma IL-1β was found over time following the three high fat loads (time effect P = 0.036). The physical characteristics and changes in TAG structure of lard may contribute to the smaller increase in postprandial lipemia compared with palm olein. A high fat load but not the type of fats influences concentrations of plasma IL-1β over time but had no effect on other pro-inflammatory markers tested in the postprandial state.

A Polymorphism Exon 1 Variant at the Locus of the Scavenger Receptor Class B Type I (SCARB1) Gene Is Associated with Differences in Insulin Sensitivity in Healthy People during the Consumption of an Olive Oil-Rich Diet

Scavenger receptor class B type I (SCARB1) was described as the first high-density lipoprotein receptor. Increasing evidence indicates that SCARB1 plays additional roles particularly in type 2 diabetes mellitus. Our aim was to determine whether the presence of an exon 1 (G-->A) polymorphism at the SCARB1 gene modifies the insulin sensitivity to dietary fat. We studied 59 healthy volunteers (30 men and 29 women, 42 G/G homozygous and 17 G/A heterozygous). Subjects consumed three diets for 4 wk each: a saturated fatty acid (SFA)-rich diet (38% fat, 20% SFA), followed by a carbohydrate (CHO)-rich diet (30% fat, 55% CHO) or a monounsaturated fatty acid (MUFA)-rich diet (38% fat, 22% MUFA) after a randomized crossover design. For each diet, we investigated peripheral insulin sensitivity with the insulin suppression test. Steady-state plasma glucose after the MUFA diet was lower in G/A compared with G/G subjects (P = 0.030). This effect was not observed after CHO and SFA diets (P = 0.177 and 0.957, respectively). Plasma nonesterified free fatty acid values were lower in subjects carrying the A allele for all the diet periods. Our findings show that carriers of the G/A genotype have significant increases in insulin sensitivity after a MUFA-rich diet compared with G/G individuals.

Long-term recombinant porcine somatotropin (PST) treatment mitigates the responses to subchronic lipopolysaccharide in swine

The effect of multiple lipopolysaccharide (LPS) challenges in swine undergoing long-term treatment with porcine somatotropin (PST) was determined. Changes in aspartate serine transaminase (AST) occurred only at 24 h following the first LPS challenge dose ( P<0.05), while PST treatment moderated any change from occurring. Nonesterified free fatty acid (NEFA) levels were elevated in PST treated animals for the first 3 days following daily LPS treatment ( P<0.05), while LPS treatment alone had no effect on plasma NEFA levels. Plasma urea nitrogen (PUN) levels were unchanged by LPS following the initial LPS challenge, but were decreased following the second challenge dose ( P=0.014). These changes were long lasting, with a return to normal PUN levels not evident until Day 6. The PST treatment mitigated changes in PUN ( P<0.05) when LPS was administered. Haptoglobin plasma levels, along with lipid peroxide production were not affected by LPS challenge or PST administration. LPS challenge reduced the levels of immunoreactive heat shock protein 70 (HSP70) throughout the entire challenge period ( P<0.001). PST–LPS animals had normal levels of this protein. The results of the present study demonstrate that long-term PST treatment mitigates the adverse effects of subchronic LPS administration.

Levels of oxidative stress are associated with C-reactive protein levels in patients with stable and unstable angina

In cohort studies, elevated levels of plasma nonesterified free fatty acids (NEFAs) have been associated with increased risk of sudden cardiac death (SCD) in men, but blood samples were drawn several years before SCD.To confirm this relationship by evaluating levels of plasma NEFAs at the time of the SCD event in a group of both men and women.From the ongoing Oregon Sudden Unexpected Death Study, we compared levels of plasma NEFAs in 149 SCD cases presenting with ventricular fibrillation (mean age 64 ± 12 years; 73% men) and 149 age- and sex-matched controls with coronary artery disease. Plasma was processed from blood drawn at the time of arrest (cases) and at a routine visit (controls). The levels of plasma NEFAs were compared after categorizing into quartiles on the basis of control values. Conditional logistic regression was used to predict adjusted odds ratio for SCD associated with plasma NEFA levels per increased quartile.The plasma NEFA levels were significantly higher in SCD cases than in controls (median 0.39 mmol/L [interquartile range 0.28–0.60 mmol/L] vs 0.32 mmol/L [interquartile range 0.20–0.49 mmol/L]; P = .002). There were no significant differences in body mass index, smoking, and diabetes. The odds ratio for SCD was 1.42 (95% confidence interval 1.14–1.78) per quartile increase in the plasma NEFA level (P = .002). Individuals with plasma NEFA levels above the prespecified cutoff point of 0.32 mmol/L were at increased risk of SCD (odds ratio 2.00; 95% confidence interval 1.20–3.34; P = .008).These findings strengthen the role of plasma NEFA as a potential biomarker for the assessment of SCD risk.

Acute elevation of NEFA causes hyperinsulinemia without effect on insulin secretion rate in healthy human subjects.

Increased circulating levels of nonesterified free fatty acids (NEFA) have been observed in such hyperinsulinemic states as obesity, impaired glucose tolerance, diabetes, and dyslipidemia where they have been causally linked to the development of insulin resistance and hyperinsulinemia. The concentration of NEFA in plasma is believed to have direct modifying effects on insulin secretion and clearance. It remains controversial whether acute increases in NEFA potentiate insulin secretion in human subjects. We studied the effect of an acute elevation of NEFA during lipid-heparin infusion compared to a glycerol-only control on glucose-stimulated insulin secretion and clearance during a 120-min hyperglycemic (10 mM) clamp in 7 healthy normoglucose-tolerant volunteers. The metabolic clearance rate of C-peptide (MCR(CP)) was measured in each subject during the study by simultaneous infusion of C-peptide. Insulin secretion rate (ISR) was calculated from deconvolution of C-peptide data after correction for the rate of C-peptide infusion. Clearance rate of insulin (MCR(INS)) was calculated based upon endogenous ISR. Plasma glucose (mg/dL): basal (90-115 min) 90.2 +/- 2.8 vs. 90.2 +/- 2.3; clamp (150-240 min) 180.5 +/- 2.8 vs. 180.9 +/- 1.3. Plasma insulin (pmol/L): prebasal (fasting) 29.6 +/- 10.0 vs. 29.8 +/- 10.6; basal (90-115 min) 30.1 +/- 9.2 vs. 34.5 +/- 12.1; second phase clamp (210-240 min) 127.6 +/- 18.2 vs. 182.5 +/- 17.3*. Plasma NEFA (mM): prebasal 0.47 +/- 0.08 vs. 0.52 +/- 0.09; basal 0.35 +/- 0.05 vs. 0.98 +/- 0.02*; clamp (122-240 min) 0.06 +/- 0.02 vs. 0.77 +/- 0.06*. ISR (pmol/min): prebasal 72.7 +/- 7.5 vs. 72.0 +/- 7.9; second phase clamp (210-240 min) 268.5 +/- 27.2 vs. 200.2 +/- 23.7. MCR(INS) (mL/min): prebasal 3393 +/- 488 vs. 3370 +/- 511; clamp 2284 +/- 505 vs. 1214 +/- 153* (*p < 0.05 glycerol vs. intralipid/heparin). This study demonstrates that acute NEFA elevation causes hyperinsulinemia due to a significant decrease in systemic insulin clearance without increasing rates of insulin secretion.

Preoperative feeding does not reverse postoperative insulin resistance in skeletal muscle in the rat

Metabolic studies on injured and postoperative patients have shown impaired glucose disposal in peripheral tissues after trauma. Using small-bowel resection as a model of surgical trauma, we investigated whether substrate availability could ameliorate the changes in muscle glucose uptake induced by trauma. We also studied the effect of preoperative feeding on postoperative insulin-stimulated insulin receptor substrate-1 (IRS-1)-associated phosphatidylinositol (PI) 3-kinase activity in both Wistar rats and genetically non-insulin-dependent diabetic Goto-Kakazaki rats (GK rats). Serum glucose, insulin, plasma epinephrine, lactate, and plasma nonesterified free fatty acids (NEFAs) were measured as indicators of the metabolic state and surgical stress. Insulin-stimulated glucose transport was significantly reduced in fed traumatized Wistar rats compared with fed nontraumatized rats (P < .05). Significant increases in in vivo insulin-stimulated IRS-1-associated PI 3-kinase activity were found in fed traumatized Wistar rats compared with fed nontraumatized Wistar rats and fasted traumatized Wistar rats, as well as fed traumatized GK rats compared with fed nontraumatized GK animals (all P < .017). Serum insulin concentrations were significantly reduced in fed traumatized Wistar and GK rats compared with the respective fed nontraumatized groups (both P < .01). Serum glucose levels were significantly elevated in fed traumatized GK rats compared with fed nontraumatized animals (P < .01). In the present study, preoperative feeding did not prevent a postoperative reduction in insulin-stimulated glucose transport in skeletal muscle. The finding that insulin-stimulated PI 3-kinase activity increased after trauma in both Wistar and GK rats indicates that postoperative insulin resistance is not caused by an impairment in the early steps of the insulin signaling pathway. The postoperative decreases in serum insulin despite high blood glucose suggest that trauma impairs the insulin response to hyperglycemia.

Insulin, growth hormone, glucose, and fatty acids in gilts selected for rapid vs. slow growth rate

Twelve-hour plasma profiles of growth hormone (GH), insulin, glucose, and nonesterified free fatty acids (NEFA), as well as GH, insulin, and glucose responses to saline, glucose, arginine, and human pancreatic growth hormone-releasing factor (GRF) infusion were examined in 15 crossbred gilts, selected for rapid vs. slow growth. For experiment 1 GH and insulin patterns differed (P less than 0.05) between the rapid growth line (RGL) and slow growth line (SGL). Mean GH concentrations in SGL and RGL gilts were 4.1 and 3.2 ng/ml, respectively (P less than 0.05). Plasma GH profile area was greater (P less than 0.08) for SGL than RGL gilts. Glucose level, glucose area, and insulin level were higher (P less than 0.05) for RGL than SGL gilts. Plasma NEFA levels and area were greater (P less than 0.05) for SGL gilts. In experiment 2 responses of GH, insulin, and glucose to saline, glucose, arginine, and GRF infusions varied (P less than 0.05) between and within lines relative to control values. These results indicate that selection for growth rate results in concomitant changes in endocrine and metabolic status.

The role of "diabetogenic" hormones on carbohydrate and lipid metabolism following oral glucose loading in insulin dependent diabetics: effects of acute hormone administration.

To evaluate the relative role of "diabetogenic" hormones as insulin antagonists in severe derangements of diabetic control, glucagon, cortisol, growth hormone and adrenaline were administered by continuous intravenous infusion, separately and in combination, to ketosis-prone insulin-dependent diabetics (n = 11). The amount of insulin required for the assimilation of a 50 g glucose load during the various hormone infusions was determined by means of an automated glucose-controlled insulin infusion system and used as an index of insulin effectiveness. Raising plasma hormone concentrations acutely into the range seen in severe diabetic states (glucagon 517 +/- 70 pg/ml; cortisol 32 +/- 3 micrograms/dl; growth hormone 14 +/- 3 ng/ml) did not alter significantly blood glucose profile and insulin requirement (control 11.3 +/- 1.1 U; glucagon 11.6 +/- 2.0 U; cortisol 11.1 +/- 0.4 U; growth hormone 12.9 +/- 1.4 U), except for adrenaline (plasma level 550 +/- 192 pg/ml), which caused a marked rise in blood glucose levels and a threefold increase in insulin demand (31.1 +/- 3.7 U). Combined infusion of all hormones did not potentiate significantly the latter effect (38.3 +/- 4.7 U). The effectiveness of metabolic control by insulin was assessed by a marked decrease in plasma nonesterified free fatty acids and ketone bodies upon its administration after glucose ingestion in all groups studied. It is concluded that from the hormones investigated within this study adrenaline exerts the strongest diabetogenic action during its short term administration followed by that of growth hormone. Whereas it may well be that over-insulinization of the patients by the glucose controlled insulin infusion system has overcome and disguised the smaller diabetogenic effects of cortisol and glucagon.

Mechanism of hypertriglyceridaemia in diabetic patients with fasting hyperglycaemia.

Several aspects of lipid metabolism were studied to define the mechanism of hypertriglyceridaemia in insulin-independent diabetic patients with fasting hyperglycaemia. Patients with insulin-independent diabetes were more obese (p < 0.001) and had a significantly (p < 0.001) higher mean (+/- SEM) fasting plasma triglyceride concentration (387 +/- 66 mg/dl) than did either insulin-dependent diabetics (133 +/- 11 mg/dl) or normal (73 +/- 1 mg/dl) subjects. Very low density lipoprotein secretion rate was also significantly (p < 0.01 - < 0.001) higher in patients with insulin-independent diabetes (14.65 +/- 1.37 mg/kg/h) as compared to 7.64 +/- 0.60 mg x kg/h and 9.86 +/- 0.75 mg/kg/h in normal subjects and patients with insulin-dependent diabetes, respectively. However, the relationship between plasma triglyceride concentration and very low density lipoprotein-triglyceride secretion was similar in diabetics and in normals. The diabetic groups had equivalent degrees of fasting and postprandial hyperglycaemia, and comparable elevations of fasting plasma nonesterified free fatty acid levels (insulin-independent = 0.72 +/- 0.07 mmol/L, insulin-dependent = 0.63 +/- 0.08 mmol/L). Postprandial plasma insulin concentrations, however, reached normal levels in insulin-independent diabetics and were higher (p < 0.001) than in insulin-dependent diabetics. Thus, hypertriglyceridaemia in insulin-independent diabetics with fasting hyperglycaemia was associated with increased hepatic very low density lipoprotein-triglyceride secretion, and normal plasma insulin levels. The lower triglyeride levels in the insulin-dependent diabetics is assumed to be due to their relative hypoinsulinaemia.