Glucose Clearance Research Articles

1590-P: Post-Oral Glucose Load Hyperinsulinemia in Individuals with Metabolic Syndrome and Metabolic-Associated Fatty Liver Disease—First Steps toward the Development of Type 2 Diabetes?

Introduction: Metabolic associated fatty liver disease (MAFLD) increases the risk of incident type 2 diabetes (T2D), but mechanisms involved have not been clearly elucidated. Objective: To assess post-oral glucose tolerance test (OGTT) glucose metabolism, insulin resistance, secretion and clearance in individuals with metabolic alterations, with or without increased liver fat. Methods: Individuals with a BMI >25 kg/m2 and at least 1 criteria for metabolic syndrome were included in this analysis. Liver fat was quantified using MRI and participants were assigned to 2 groups according to > 5% liver fat (MAFLD group) or ≤ 5%. A 3h frequently-sampled OGTT was performed and oral minimal model was used to measure insulin sensitivity, secretion and disposition index. Results: Fifty participants were included in this analysis and 50% had a liver fat > 5%. Post-OGTT glucose concentrations and iAUC glucose were not different between groups (p -≥ 0.50), whereas post-OGTT insulin concentrations and iAUC were significantly higher in the MAFLD group (p < 0.03) and significantly associated with liver fat. The components of insulin secretion (dynamic, static and total) were not different between groups (p -≥ 0.27). Insulin sensitivity and dynamic disposition indices were lower in the MAFLD group and significantly associated with liver fat. but in a multivariable regression model including sex and BMI, liver fat was not statistically associated with these indices. Insulin clearance indices were significantly lower in the MAFLD group, and liver fat statistically explained most of the variance in the multivariate model (p< 0.02). Conclusion: Among individuals with metabolic alterations, the presence of MAFLD is associated with impaired insulin clearance and post-oral glucose load hyperinsulinemia. Insulin sensitivity and dynamic beta-cell function are also altered, features of the early pathophysiology of T2D. Disclosure G.Trépanier: None. T.Gignac: None. M.Pradeau: None. A.Morissette: None. A.Agrinier: None. C.Gagnon: Advisory Panel; Novo Nordisk, Other Relationship; Ascendis Pharma A/S, Research Support; Novo Nordisk. M.Vohl: None. A.Marette: Advisory Panel; Valbiotis, Amancia, Plexus, Acasti. A.Carreau: Advisory Panel; Novartis, Consultant; Valbiotis, Speaker's Bureau; Novo Nordisk Canada Inc.

233-OR: The Beta-Cell Specific Deletion of Complement 1q-Like-3 Secreted Protein Improves Beta-Cell Function and Glucose Homeostasis

Using bioinformatics network analysis, we identified complement-1q like-3 (C1ql3) as a secreted protein that affects pancreatic islet function in obese mice. Previously, we showed that the recombinant C1ql3 protein inhibits insulin secretion stimulated by exendin-4 (an agonist for GLP-1 receptor) from human and mouse islets. Currently, we are elucidating the role of C1ql3 in pancreatic β-cell function by using mice with β-cell-specific deletion of the C1ql3 (βKO) gene on a standard chow diet. C1ql3βKO mice showed significantly improved glucose clearance after oral glucose challenge than the control mice, whereas no difference in insulin sensitivity was observed. Moreover, the plasma insulin levels were significantly increased at 15 min after the glucose challenge in the C1ql3 βKO vs. control mice. However, islets isolated from C1ql3βKO significantly increased insulin secretion stimulated by cAMP and Exendin-4 than control islets. These results suggest that the loss of C1ql3 in β-cells increases insulin secretion to improve glucose tolerance. Adenovirus-mediated overexpression of C1ql3 in islets showed increased ER stress and decreased expression of genes involving β-cell function and maintenance. In pathophysiological conditions, increased C1ql3 expression coupled to secretion was observed from both T2D donor islets and obese mouse islets. Interestingly, reduction in C1ql3 secretion is inversely correlated with increased glucose-stimulated insulin secretion from islets of C1ql3βKOLeptinob/ob compared to Leptinob/ob control mice. These findings suggest that the loss of β-cell C1ql3 maintains ER stress and increases insulin secretion to maintain glucose homeostasis. Our work shows that an autocrine regulation of the C1ql3-signaling pathway contributes to β-cell dysfunction in obesity and type 2 diabetes. Disclosure M.Rahman: None. H.Alsharif: None. A.Michl: None. S.Bhatnagar: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (1R01DK120684-01)

1727-P: Mitochondrial-Encoded Peptide MOTS-c Prevents Senescence-Induced Diabetes

A polymorphism MOTS-c, a mitochondrial-derived miniprotein, was reported to be associated with longevity in humans. Previous reports showed that MOTS-c regulates senescence in cells, enhances physical capacity in old mice and in humans. However, it is still unknown how MOTS-c is able to intervene the cellular senescence, what tissue or cell-type MOTS-c targets, and whether the regulation of aging by MOTS-c can lead to the prevention of aging- or senescence-induced disorders. Here, using S961 (or senescence)-induced mouse model, we show that MOTS-c is capable of targeting pancreas and is able to prevent senescence-induced diabetes. To test how MOTS-c is associated with β cell senescence, we firstly assess whether β cell senescence is associated with MOTS-c expression using pancreatic β cells isolated from 12-week-old mice. After isolation, pancreatic β cells were treated with H2O2 in concentration-dependent manner. Treatment of H2O2 lowered MOTS-c expression in concentration-dependent manner, but increased other senescence-related markers such as β-gal expression. Furthermore, MOTS-c treatment decreased H2O2-induced senescence-associated β-gal expression and SASPs (i.e., IL-1). To understand the inhibitory effect of MOTS-c against β cell senescence in vivo, we have transplanted S961-osmotic pump in 28-week-old mice with or without MOTS-c for 2 weeks. Mice treated with MOTS-c showed lowered random glucose level (310 mg/dL versus 180 mg/dL) and decreased level of pancreatic β-gal expression compared to S961-treated mice. Also, an i.p. glucose tolerance test (IPGTT) in 30-week-old mice revealed that MOTS-c treatment significantly improved glucose clearance. As a result, we showed that senescence/S961-induced diabetes were inhibited by MOTS-c treatment. Disclosure B.Kong: None. S.Hong: None. Y.Cho: Consultant; LG Chem. Funding Ministry of Health & Welfare, Republic of Korea (HI14C1277)

Acute sub-diaphragmatic anterior vagus nerve stimulation increases peripheral glucose uptake in anaesthetized rats

The sub-diaphragmatic vagus innervates various organs involved in the control of glucose homeostasis including the liver, pancreas and the intestines. In the current study, we investigated the effect of acute electrical stimulation of the anterior trunk of the sub-diaphragmatic vagus on glucose fluxes in anaesthetized adult male rats.After overnight fast, rats underwent either vagus nerve stimulation (VNS+, n = 11; rectangular pulses at 5 Hz, 1.5 mA, 1 msec pulse width) or sham stimulation (VNS-; n = 11) for 120 min under isoflurane anesthesia. Before stimulation, the rats received an i.v. bolus of 1 mL/kg of a sterilized aqueous solution containing 125 mg/mL of D-[6,6-2H2] glucose. Endogenous glucose production (EGP) and glucose clearance rate (GCR) were calculated by kinetic analysis from the wash-out of injected D-[6,6–2H2]glucose from the circulation.VNS+ resulted in lower glucose levels compared to the VNS- group (p < 0.05), with similar insulin levels. EGP was similar in both groups, but the GCR was higher in the VNS+ group compared to the VNS- group (p < 0.001). Circulating levels of the sympathetic transmitter norepinephrine were reduced by VNS+ relative to VNS- treatment (p < 0.01).It is concluded that acute anterior sub-diaphragmatic VNS causes stimulation of peripheral glucose uptake, while plasma insulin levels remained similar, and this is associated with lower activity of the sympathetic nervous system.

Dietary Docosahexaenoic Acid and Glucose Systemic Metabolic Changes in the Mouse.

The endocannabinoid system (ECS) participates in regulating whole body energy balance. Overactivation of the ECS has been associated with the negative consequence of obesity and type 2 diabetes. Since activators of the ECS rely on lipid-derived ligands, an investigation was conducted to determine whether dietary PUFA could influence the ECS to affect glucose clearance by measuring metabolites of macronutrient metabolism. C57/blk6 mice were fed a control or DHA-enriched semi-purified diet for a period of 112 d. Plasma, skeletal muscle, and liver were collected after 56 d and 112 d of feeding the diets for metabolomics analysis. Key findings characterized a shift in glucose metabolism and greater catabolism of fatty acids in mice fed the DHA diet. Glucose use and promotion of fatty acids as substrate were found based on levels of metabolic pathway intermediates and altered metabolic changes related to pathway flux with DHA feeding. Greater levels of DHA-derived glycerol lipids were found subsequently leading to the decrease of arachidonate-derived endocannabinoids (eCB). Levels of 1- and 2-arachidonylglcerol eCB in muscle and liver were lower in the DHA diet group compared to controls. These findings demonstrate that DHA feeding in mice alters macronutrient metabolism and may restore ECS tone by lowering arachidonic acid derived eCB.

Insulin sensitization by Feronia elephantum in fructose-induced hyperinsulinemic rats: Insights from computational and experimental pharmacology

Ethnopharmacological relevanceFeronia elephantum corr. (synonym: Feronia limonia, Murraya odorata, Schinus Limonia, or Limonia acidissima; common names: Bela, Kath, Billin, and Kavitha), belonging to the family Rutaceae has been known for clinical conditions such as pruritus, diarrhea, impotence, dysentery, heart diseases, and is also used as a liver tonic. However, the effect of the fruit pulp of F. elephantum on insulin resistance has yet not been reported. Aim of the studyThe present study aimed to assess the effect of hydroalcoholic extract/fraction of F. elephantum fruit pulp on fasting blood glucose, oral glucose tolerance test, and glucose uptake in fructose-induced insulin-resistant rats and predict the gene-set enrichment of lead hits of F. elephantum with targets related to insulin resistance. Material and methodsSystem biology tools were used to predict the best category of fraction and propose a possible mechanism. Docking was carried out with adiponectin and its receptor (hub genes). Further, fructose supplementation was used for the induction of insulin resistance. Later, three doses of extract (400, 200, and 100 mg/kg) and a flavonoid-rich fraction (63 mg/kg) were used for treatment along with metformin as standard. The physical parameters like body weight, food intake, and water intake were measured along with oral glucose tolerance test, insulin tolerance test, glycogen content in skeletal muscles and liver, glucose uptake by rat hemidiaphragm, lipid profiles, anti-oxidant biomarkers, and histology of the liver and adipose tissue. ResultsNetwork pharmacology reflected the potency of F. elephantum to regulate adiponectin which may promote the reversal of insulin resistance and inhibit α-amylase and α-glucosidase. Vitexin was predicted to modulate the most genes associated with diabetes mellitus. Further, F. elephantum ameliorated the exogenous glucose clearance, promoted insulin sensitivity, reduced oxidative stress, and improved glucose and lipid metabolism. HPLC profiling revealed the presence of apigenin and quercetin in the extract for the first time. ConclusionThe fruit pulp of F. elephantum reverses insulin resistance by an increase in glucose uptake and a decrease in gluconeogenesis which may be due to the regulation of multiple proteins via multiple bio-actives.

Colostrum insulin supplementation to neonatal Holstein bulls affects small intestinal histomorphology, mRNA expression, and enzymatic activity with minor influences on peripheral metabolism

The objectives of this study were to evaluate how varying colostral insulin concentrations influenced small intestinal development and peripheral metabolism in neonatal Holstein bulls. Insulin was supplemented to approximately 5× (70.0 μg/L; n = 16) or 10× (149.7 μg/L; n = 16) the basal colostrum insulin (12.9 μg/L; BI, n = 16) concentration to maintain equivalent macronutrient intake (crude fat: 4.1 ± 0.06%; crude protein: 11.7 ± 0.05%; and lactose: 1.9 ± 0.01%) among treatments. Colostrum was fed at 2, 14, and 26 h postnatal and blood metabolites and insulin concentration were measured at 0, 30, 60, 90, 120, 180, 240, 360, 480, and 600 min postprandial respective to the first and second colostrum meal. At 30 h postnatal, a subset of calves (n = 8/treatment) were killed to excise the gastrointestinal and visceral tissues. Gastrointestinal and visceral gross morphology and dry matter and small intestinal histomorphology, gene expression, and carbohydrase activity were assessed. Insulin supplementation tended to linearly reduce the glucose clearance rate following the first meal, whereas after the second meal, supplementation linearly increased the rate of glucose absorption and nonesterified fatty acid clearance rate, decreased the time to maximum glucose concentrations, and decreased the time to reach minimum nonesterified fatty acid concentrations. Additionally, insulin clearance rate was linearly increased by insulin supplementation following the second colostrum feeding. However, there were no overall differences between treatments in the concentrations of glucose, nonesterified fatty acids, or insulin in plasma or serum. With respect to macroscopic intestinal development, dry rumen tissue mass linearly decreased when insulin was supplemented in colostrum, and supplementation linearly increased duodenal dry tissue density (g dry matter/cm) while tending to increase duodenal dry tissue weight. Increasing the colostrum insulin concentration improved small intestinal histomorphological development in the distal small intestine, as ileal villi height and mucosal-serosal surface area index were increased by supplementing insulin. Lactase enzymatic activity linearly increased in the proximal jejunum while ileal isomaltase activity linearly decreased with insulin supplementation. These data indicate that changes in colostrum insulin concentrations rapidly affect gastrointestinal growth prioritization and carbohydrase activity. The changes in gastrointestinal ontology result in minor changes in postprandial metabolite availability and clearance.

A135 Increased renal mRNA expression of CYP27B1 and improved glucose clearance with sclerostin antibody in ovariectomized mice following Roux-en-Y Gastric Bypass Surgery

A135 Increased renal mRNA expression of CYP27B1 and improved glucose clearance with sclerostin antibody in ovariectomized mice following Roux-en-Y Gastric Bypass Surgery

Dual amylin and calcitonin receptor agonist treatment improves insulin sensitivity and increases muscle-specific glucose uptake independent of weight loss

Dual amylin and calcitonin receptor agonists (DACRAs) are known to induce significant weight loss as well as improve glucose tolerance, glucose control, and insulin action in rats. However, to what extent DACRAs affect insulin sensitivity beyond that induced by weight loss and if DACRAs affect glucose turnover including tissue-specific glucose uptake is still unknown. Hyperinsulinemic glucose clamp studies were carried out in pre-diabetic ZDSD and diabetic ZDF rats treated with either the DACRA KBP or the long-acting DACRA KBP-A for 12 days. The glucose rate of disappearance was assessed using 3-3H glucose and tissue-specific glucose uptake was evaluated using 14C-2-deoxy-D-glucose (14C-2DG). In diabetic ZDF rats, KBP treatment significantly reduced fasting blood glucose and improved insulin sensitivity independent of weight loss. Furthermore, KBP increased the rate of glucose clearance, likely by increasing glucose storage, but without altering the endogenous glucose production. This was confirmed in pre-diabetic ZDSD rats. Direct assessment of tissue-specific glucose uptake showed, that both KBP and KBP-A significantly increased glucose uptake in muscles. In summary, KBP treatment significantly improved insulin sensitivity in diabetic rats and markedly increased glucose uptake in muscles. Importantly, in addition to their well-established weight loss potential, the KBPs have an insulin-sensitizing effect independent of weight loss, highlighting DACRAs as promising agents for the treatment of type 2 diabetes and obesity.

Effect of &lt;i&gt;Gymnema sylvestre&lt;/i&gt; Extract on the Regulation of AMPK-GLUT4 Mediated Signaling Pathway on Insulin Resistance in a PCOS Rat Model

This study was intended to assess the effect of Gymnema sylvestre leaf extract on the AMPK-GLUT4 mediated signalling pathway on insulin resistance in polycystic ovarian syndrome-induced rats. For the induction of PCOS in rats, 1 mg/kg of letrozole was given orally for 21 days, after that metformin (300 mg/kg), Gymnema sylvestre leaf extract (200 mg/kg, and 400 mg/kg p. o.) were administered for further 28 days. Letrozole-induced PCOS rats illustrated significant estrus irregularity, and sex hormonal abnormality, and developed insulin resistance as indicated by increased fasting glucose levels, an increased rate of glucose clearance, and also decreases in GLUT4 and AMPK mRNA expression in ovarian cells. Ovarian histology in PCOS rats also showed many follicular cysts, atretic follicles, and the absence of the corpus luteum. These changes were significantly reversed by the treatment of G. sylvestre in a dose-dependent manner. It might be mediated through its insulin resistance modulating property by the activation of AMPK &amp; GLUT4 expression on ovarian endometrial cells.

Sensitivity schemes for dynamic glucose-enhanced magnetic resonance imaging to detect glucose uptake and clearance in mouse brain at 3T.

The article from this special issue was previously published in NMR In Biomedicine , Volume 35, Issue 3, 2022. For completeness we are including the title page of the article below. The full text of the article can be read in Issue 35:3 on Wiley Online Library: https://doi.org/10.1002/nbm.4640.

Genetic deletion of skeletal muscle iPLA2γ results in mitochondrial dysfunction, muscle atrophy and alterations in whole-body energy metabolism

Skeletal muscle is the major site of glucose utilization in mammals integrating serum glucose clearance with mitochondrial respiration. To mechanistically elucidate the roles of iPLA2γ in skeletal muscle mitochondria, we generated a skeletal muscle-specific calcium-independent phospholipase A2γ knockout (SKMiPLA2γKO) mouse. Genetic ablation of skeletal muscle iPLA2γ resulted in pronounced muscle weakness, muscle atrophy, and increased blood lactate resulting from defects in mitochondrial function impairing metabolic processing of pyruvate and resultant bioenergetic inefficiency. Mitochondria from SKMiPLA2γKO mice were dysmorphic displaying marked changes in size, shape, and interfibrillar juxtaposition. Mitochondrial respirometry demonstrated a marked impairment in respiratory efficiency with decreases in the mass and function of oxidative phosphorylation complexes and cytochrome c. Further, a pronounced decrease in mitochondrial membrane potential and remodeling of cardiolipin molecular species were prominent. Collectively, these alterations prevented body weight gain during high-fat feeding through enhanced glucose disposal without efficient capture of chemical energy thereby altering whole-body bioenergetics.

Unraveling the Host Genetic Background Effect on Internal Organ Weight Influenced by Obesity and Diabetes Using Collaborative Cross Mice.

Type 2 diabetes mellitus (T2DM) is a severe chronic epidemic that results from the body's improper usage of the hormone insulin. Globally, 700 million people are expected to have received a diabetes diagnosis by 2045, according to the International Diabetes Federation (IDF). Cancer and macro- and microvascular illnesses are only a few immediate and long-term issues it could lead to. T2DM accelerates the effect of organ weights by triggering a hyperinflammatory response in the body's organs, inhibiting tissue repair and resolving inflammation. Understanding how genetic variation translates into different clinical presentations may highlight the mechanisms through which dietary elements may initiate or accelerate inflammatory disease processes and suggest potential disease-prevention techniques. To address the host genetic background effect on the organ weight by utilizing the newly developed mouse model, the Collaborative Cross mice (CC). The study was conducted on 207 genetically different CC mice from 8 CC lines of both sexes. The experiment started with 8-week-old mice for 12 weeks. During this period, one group maintained a standard chow diet (CHD), while the other group maintained a high-fat diet (HFD). In addition, body weight was recorded bi-weekly, and at the end of the study, a glucose tolerance test, as well as tissue collection (liver, spleen, heart), were conducted. Our study observed a strong effect of HFD on blood glucose clearance among different CC lines. The HFD decreased the blood glucose clearance displayed by the significant Area Under Curve (AUC) values in both populations. In addition, variation in body weight changes among the different CC lines in response to HFD. The female liver weight significantly increased compared to males in the overall population when exposed to HFD. Moreover, males showed higher heritability values than females on the same diet. Regardless of the dietary challenge, the liver weight in the overall male population correlated positively with the final body weight. The liver weight results revealed that three different CC lines perform well under classification models. The regression results also varied among organs. Accordingly, the differences among these lines correspond to the genetic variance, and we suspect that some genetic factors invoke different body responses to HFD. Further investigations, such as quantitative trait loci (QTL) analysis and genomic studies, could find these genetic elements. These findings would prove critical factors for developing personalized medicine, as they could indicate future body responses to numerous situations early, thus preventing the development of complex diseases.

Conditioning-induced expression of novel glucose transporters in canine skeletal muscle homogenate.

Athletic conditioning can increase the capacity for insulin-stimulated skeletal muscle glucose uptake through increased sarcolemmal expression of GLUT4 and potentially additional novel glucose transporters. We used a canine model that has previously demonstrated conditioning-induced increases in basal, insulin- and contraction-stimulated glucose uptake to identify whether expression of glucose transporters other than GLUT4 was upregulated by athletic conditioning. Skeletal muscle biopsies were obtained from 12 adult Alaskan Husky racing sled dogs before and after a full season of conditioning and racing, and homogenates from those biopsies were assayed for expression of GLUT1, GLUT3, GLUT4, GLUT6, GLUT8, and GLUT12 using western blots. Athletic conditioning resulted in a 1.31 ± 0.70 fold increase in GLUT1 (p <0.0001), 1.80 ± 1.99 fold increase in GLUT4 (p = 0.005), and 2.46 ± 2.39 fold increase in GLUT12 (p = 0.002). The increased expression of GLUT1 helps explain the previous findings of conditioning-induced increases in basal glucose clearance in this model, and the increase in GLUT12 provides an alternative mechanism for insulin- and contraction-mediated glucose uptake and likely contributes to the substantial conditioning-induced increases in insulin sensitivity in highly trained athletic dogs. Furthermore, these results suggest that athletic dogs can serve as a valuable resource for the study of alternative glucose transport mechanisms in higher mammals.

Glucocorticoid excess and insulin resistance in aged spontaneously hypertensive rats/stroke-prone

Vascular diseases cause chronic cerebral hypoperfusion and neuronal injury and are the second most common cause of dementia. A significant cause of chronic cerebral hypoperfusion is hypertension. Insulin resistance is an important risk factor for hypertension. Aside from age, insulin resistance is also the most important risk factor for the development of dementia. While Insulin resistance is considered an important risk factor for the development of hypertension and dementia, little consideration has been given to the idea that hypertension could initiate insulin resistance and fuel a destructive cycle that hastens dementia. We hypothesized that hypertension initiates insulin resistance through sustained activation of the hypothalamic-pituitary-adrenal axis. To test this hypothesis, we measured corticosterone and the expression of steroid biosynthetic genes in six-month-old spontaneously hypertensive rat/stroke-prone (SHRSP) and normotensive Sprague Dawley (SD) rats. To measure glycemic control, rats were subjected to glucose tolerance and insulin tolerance tests. SHRSP were hypertensive and cognitively impaired. SHRSPs had increased corticosterone compared to SD (Male SD vs. SHRSP: 167±29 pg/g vs.1091±166 pg/g, P&lt;0.0001; Female SD vs. SHRSP: 134±19 pg/g vs. 376±47 pg/g, P=0.0017). Adrenal CYP11B1 mRNA expression was increased in SHRSP (Males 14.44±1.44, P=0.0009; Females 710±59, P=0.0016). STARD1 mRNA expression provided a marker of HPA negative feedback. Male SHRSPs had decreased STARD1 mRNA expression (0.56±0.09, P = 0.0217). However, female SHRSPs had increased STARD1 mRNA expression (12.5± 2.25, P=0.0028). Female, but not male, SHRSPs had increased fasting blood glucose, decreased fasting insulin, and reduced rates of glucose clearance (SD vs. SHRSP: 73±6 vs. 92±4 mg/dL glucose, P=0.0045; 33±2.0 vs. 12±5 pmol/L insulin, P=0.0111; AUC 185±37 vs. 279±27 mg/dL/h, P=0.0368). When fasting rats were challenged with insulin, both male and female SHRSPs had decreased clearance of glucose compared to SDs (Male SD vs. SHRSP AUC 87 ± 2 vs. 58 ± 4 mg/dL/h, P&lt; 0.0001, Female SD vs. SHRSP AUC 82 ± 2 vs. 68 ± 3 mg/dL/h, P=0.0007). These results indicate that hypertension is associated with impaired HPA function and insulin resistance, with female SHRSP succumbing faster to hyperglycemia than males. Alzheimer's Association Research Fellowship This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Oleic acid abomasal infusion limits lipolysis and improves insulin sensitivity in adipose tissue from periparturient dairy cows

Excessive adipose tissue (AT) lipolysis around parturition in dairy cows is associated with impaired AT insulin sensitivity and increased incidence of metabolic diseases. Supplementing cows with oleic acid (OA) reduces circulating biomarkers of lipolysis and improves energy balance. Nevertheless, it is unclear if OA alters lipid trafficking in AT. In the liver and skeletal muscle, OA improves mitochondrial function and promotes lipid droplet formation by activating perilipin 5 (PLIN5) and peroxisome proliferator-activated receptor α (PPARα). However, it is unknown if this mechanism occurs in AT. The objective of this study was to determine the effect of OA on AT lipolysis, systemic and AT insulin sensitivity, and AT mitochondrial function in periparturient dairy cows. Twelve rumen-cannulated Holstein cows were infused abomasally following parturition with ethanol (CON) or OA (60 g/d) for 14 d. Subcutaneous AT samples were collected at 11 ± 3.6 d before calving (-12 d), and 6 ± 1.0 d (7 d) and 13 ± 1.4 d (14 d) after parturition. An intravenous glucose tolerance test was performed on d 14. Adipocyte morphometry was performed on hematoxylin and eosin-stained AT sections. The antilipolytic effect of insulin (1 μg/L) was evaluated using an ex vivo explant culture following lipolysis stimulation. PLIN5 and PPARα transcription and translation were determined by real-time quantitative PCR and capillary electrophoresis, respectively. RNA sequencing was used to evaluate the transcriptomic profile of mitochondrial gene networks. In CON cows, postpartum lipolysis increased the percentage of smaller (<3,000 µm2) adipocytes at 14 d compared with -12 d. However, OA limited adipocyte size reduction at 14 d. Likewise, OA decreased lipolysis plasma markers nonesterified free fatty acids and β-hydroxybutyrate at 5 and 7 d. Over the 14-d period, compared with CON, OA increased the concentration of plasma insulin and decreased plasma glucose. During the glucose tolerance test, OA decreased circulating glucose concentration (at 10, 20, 30, 40 min) and the glucose clearance rate. Moreover, OA increased insulin at 10 and 20 min and tended to increase it at 30 min. Following lipolysis stimulation, OA improved the antilipolytic effect of insulin in the AT at 14 d. PLIN5 and PPARA gene expression decreased postpartum regardless of treatment. However, OA increased PLIN5 protein expression at 14 d and increased PPARA at 7 and 14 d. Immunohistochemical analysis of AT and RNA sequencing data showed that OA increased the number of mitochondria and improved mitochondrial function. However, OA had no effect on production and digestibility. Our results demonstrate that OA limits AT lipolysis, improves systemic and AT insulin sensitivity, and is associated with markers of mitochondrial function supporting a shift to lipogenesis in AT of periparturient dairy cows.

Sexual dimorphism in the peripheral metabolic homeostasis and behavior in the TgF344-AD rat model of Alzheimer's disease.

Alzheimer's disease (AD), a prevalent form of dementia, is characterized by the decline of cognitive abilities with age. Available treatment options for AD are limited, making it a significant public health concern. Recent research suggests that metabolic dysfunction plays a role in the development of AD. In addition, insulin therapy has been shown to improve memory in patients with cognitive decline. In this study, we report the first examination of body composition, peripheral insulin sensitivity, and glucose tolerance in relation to behavioral assessments of learning, memory, and anxiety in the TgF344-AD rat model of AD. Results from glucose and insulin tolerance tests show that female TgF344-AD rats exhibit impaired glucose clearance and reduced insulin sensitivity at both 9 and 12 months of age, while males display no differences at 9 months and even improved glucose clearance at 12 months. Results from the Morris Water Maze assessment of learning and memory reveal that male TgF344-AD rats display impairments at both 9 and 12 months of age, while female TgF344-AD rats only show impairments at 12 months. Furthermore, results from open field and elevated plus maze tests suggest that female TgF344-AD rats display increased anxiety at 9 months of age; however, no differences were detected in males or at 12 months of age. Overall, our findings suggest that impairments in metabolism, commonly associated with type 2 diabetes, occur before or simultaneously with cognitive decline and anxiety in a sexually dimorphic manner in the TgF344-AD rat model.

Age and diet modulate the insulin-sensitizing effects of exercise: a tracer-based oral glucose tolerance test

Diet modulates the development of insulin resistance during aging. This includes tissue-specific alterations in insulin signaling and mitochondrial function, which ultimately affect glucose homeostasis. Exercise stimulates glucose clearance, mitochondrial lipid oxidation and enhances insulin sensitivity. It is not well known how exercise interacts with age and diet in the development of insulin resistance. To investigate this, oral glucose tolerance tests (OGTT) with a tracer were conducted in mice ranging from 4 to 21 months of age, fed a low- (LFD) or high-fat diet (HFD), with or without life-long voluntary access to a running wheel (RW). We developed a computational model to derive glucose fluxes, which were commensurate with independent values from steady-state tracer infusions. Both insulin sensitivity indices derived for peripheral tissues and liver (IS-P and IS-L, respectively) were steeply decreased by aging and a HFD. This preceded the age-dependent decline in the mitochondrial capacity to oxidize lipids. In LFD young animals, RW access enhanced the IS-P concomitantly with the muscle β- oxidation capacity. Surprisingly, RW access completely prevented the age-dependent IS-L decrease, but only in LFD animals. This study indicates, therefore, that endurance exercise can improve the age-dependent decline in organ-specific IS mostly in the context of a healthy diet.

Therapeutic exploration of polyherbal formulation against letrozole induced PCOS rats: A mechanistic approach

ObjectiveThis study aimed to develop an effective alternative medicine with multi potential herbs against polycystic ovarian syndrome (PCOS) in rats induced by letrozole treatment. Materials and methodPolyherbal syrup was prepared with a combination of S. asoca bark, G. sylvestre leaves, P. daemia aerial parts, C. zeylanium stem bark, C. bonduc seeds, and W. somnifera roots ethanolic extract. In vitro cell viability study, adenosine monophosphate-activated protein kinase (AMPK), and glucose transporter 4 (GLUT4) gene expression assay were carried out on the Chinese Hamster Ovarian (CHO) cell line. For the PCOS induction letrozole (1 mg/kg p. o.) was given for 21 consecutive days. The PCOS induction was confirmed by measuring estrus irregularity, insulin resistance by oral glucose tolerance test (OGTT), and hyperandrogenism by measuring serum total testosterone level 21 days after completion of letrozole treatment. After induction of PCOS, metformin (155 mg/kg p. o.), and polyherbal syrup (100 mg/kg, 200 mg/kg, and 400 mg/kg p. o.) were administered for further 28 days. The treatment efficacy was measured by measuring serum lipid profile, fasting insulin level, sex hormones level, ovarian steroidogenic enzymes, ovarian tissue insulin receptor, AMPK, and GLUT4 protein expression levels, and histomorphological studies. The post-treatment effect was confirmed by reproductive performance studies. ResultsLetrozole-induced PCOS rats showed significant estrus irregularity, abnormal sex hormones levels, and hyperandrogenism indicated by showing increased free androgenic index and decreased sex hormones binding globulin (SHBG) level. The insulin resistance in PCOS rats was indicated by increased fasting glucose levels with impaired glucose clearance in the OGT test. Homeostasis Model Assessment Index of Insulin Resistance (HOMA-IR) increased level, also decreases INSR, GLUT4, and AMPK mRNA expression in ovarian cells confirming the insulin resistance in PCOS rats. Ovarian histology in PCOS rats also showed many follicular cysts, atretic follicles, and the absence of corpus luteum. The administration of polyherbal syrup, in a dose-dependent manner, effectively restored these alterations. The treatment of polyherbal formulation 400 mg/kg possesses highly significant efficacy over the treatment of metformin in PCOS rats. It mainly acts by reducing peripheral and ovarian hyperandrogenism and improves insulin sensitivity via activating the insulin receptor and AMP-activated kinase-mediated transcription and translation of GLUT4 from the cytoplasm to the ovarian membrane improves glucose uptake and promotes the follicular development and ovulation. The higher fertility rate, delivery index, and survival of delivered pups confirm the broader and superior efficacy of PCOS. These beneficial actions are mainly attributable to the formulation's inclusion of the key secondary metabolites flavonoids and phytosterols. In conclusion, the prepared polyherbal syrup was found to be the safest and most effective alternative medicine for both endocrinal and metabolic complications of PCOS women.

Impact of ergot alkaloid and steroidal implant on whole-body protein turnover and expression of mTOR pathway proteins in muscle of cattle.

Holstein steers (n = 32) were used to determine if the ergot analog, bromocriptine decreases muscle protein synthesis through inhibitory action on the mTOR pathway via a direct effect on signal proteins, and if these negative effects can be alleviated with anabolic agents. Steers were treated with intramuscular administration of bromocriptine (vehicle or 0.1 mg/kg BW) and a subdermal commercial steroidal implant containing trenbolone acetate (TBA) and estradiol 17β (with or without), in a 2×2 factorial design. During the 35 day experiment, intake was restricted to 1.5 times maintenance energy requirement. On days 27 through 32, steers were moved to metabolism stalls for urine collection, and whole-body protein turnover was determined using a single pulse dose of [15N] glycine into the jugular vein on day 28. On day 35, skeletal muscle samples were collected before (basal state) and 60 min after (stimulated state) an i.v. glucose challenge (0.25 g glucose/kg). Blood samples were collected at regular intervals before and after glucose infusion for determination of circulating concentrations of glucose and insulin. Bromocriptine reduced insulin and glucose clearance following the glucose challenge, indicating decreased insulin sensitivity and possible disruption of glucose uptake and metabolism in the skeletal muscle. Conversely, analysis of whole-body protein turnover demonstrated that bromocriptine does not appear to affect protein synthesis or urea excretion. Western immunoblot analysis of skeletal muscle showed that it did not affect abundance of S6K1 or 4E-BP1, so bromocriptine does not appear to inhibit activation of the mTOR pathway or protein synthesis. Estradiol/TBA implant decreased urea excretion and protein turnover but had no effect on protein synthesis, suggesting that steroidal implants promote protein accretion through unchanged rates of synthesis and decreased degradation, even in the presence of bromocriptine, resulting in improved daily gains. Implanted steers likely experienced increased IGF-1 signaling, but downstream activation of mTOR, S6K and 4E-BP1, and thus increased protein synthesis did not occur as expected. Overall, this data suggests that bromocriptine does not have a negative impact on muscle protein synthetic pathways independent of DMI.