Intraperitoneal Glucose Tolerance Test Research Articles

Abstract 4135662: Dietary Inulin Improves Glucose Metabolism and Energy Balance in Obese Mice via Adipocyte Free Fatty Acid Receptor 2 (FFAR2)

Background: Inulin is a non-digestible prebiotic dietary fiber that can promote metabolic health including reduced body weight and improved glucose metabolism via effects on gut microbiota. We hypothesize that inulin prevents obesity-associated cardiometabolic alterations by augmenting the production of short-chain fatty acids (SCFA) from gut microbiota, which activate free fatty acid receptor 2 (FFAR2), a major SCFA receptor, in murine adipose tissue. Methods: 8-week-old male C57BL/6J (wild-type, WT; n=34) and adipocyte FFAR2-knockout (Ad-FFAR2 KO; n=25) mice were fed a high-fat high-sucrose (HFHS) diet for 8 weeks, then randomized into experimental groups to receive either continued HFHS (n=8-13), or HFHS containing inulin (10% w/w chicory root inulin; n=17-21) for a further 5 weeks. Body weight was recorded weekly, food intake, body composition, and indirect calorimetry were assessed before and after the inulin intervention, and intraperitoneal glucose and insulin tolerance tests were performed. Subcutaneous and visceral white adipose tissue (WAT) samples were collected at the study termination. Results: HFHS-fed Ad-FFAR2 KO mice showed higher body weight (7.4%), fat mass, and WAT weight due to increased food intake, with worse glucose tolerance compared to WT mice. In WT mice, inulin significantly reduced body weight gain and body adiposity. These effects were associated with reduced locomotor activity and respiratory quotient (RQ) without effects on energy expenditure and were accompanied by improvements in glucose tolerance. Strikingly, inulin had no effect on body weight or body adiposity in Ad-FFAR2 KO mice but reduced RQ, locomotor activity, and improved glucose tolerance similar to WT mice. Conclusions: Our findings suggest that FFAR2 signaling in adipose tissue is crucial for improving cardiometabolic outcomes in obesity and that gut metabolites responsive to dietary interventions, such as inulin, are potential targets for obesity treatment strategies.

Host Genetics Background Affects Intestinal Cancer Development Associated with High-Fat Diet-Induced Obesity and Type 2 Diabetes.

Obesity and type 2 diabetes (T2D) promote inflammation, increasing the risk of colorectal cancer (CRC). High-fat diet (HFD)-induced obesity is key to these diseases through biological mechanisms. This study examined the impact of genetic background on the multimorbidity of intestinal cancer, T2D, and inflammation due to HFD-induced obesity. A cohort of 357 Collaborative Cross (CC) mice from 15 lines was fed either a control chow diet (CHD) or HFD for 12 weeks. Body weight was tracked biweekly, and blood glucose was assessed at weeks 6 and 12 via intraperitoneal glucose tolerance tests (IPGTT). At the study's endpoint, intestinal polyps were counted, and cytokine profiles were analyzed to evaluate the inflammatory response. HFD significantly increased blood glucose levels and body weight, with males showing higher susceptibility to T2D and obesity. Genetic variation across CC lines influenced glucose metabolism, body weight, and polyp development. Mice on HFD developed more intestinal polyps, with males showing higher counts than females. Cytokine analysis revealed diet-induced variations in pro-inflammatory markers like IL-6, IL-17A, and TNF-α, differing by genetic background and sex. Host genetics plays a crucial role in susceptibility to HFD-induced obesity, T2D, CRC, and inflammation. Genetic differences across CC lines contributed to variability in disease outcomes, providing insight into the genetic underpinnings of multimorbidity. This study supports gene-mapping efforts to develop personalized prevention and treatment strategies for these diseases.

8780 The Role of Nuclear Receptor Corepressors 1 and 2 on Intestinal Carbohydrate Transport in Mice

Abstract Disclosure: M.J. Ritter: None. I. Amano: None. A.H. van der Spek: None. H.E. Daniel: None. A.N. Hollenberg: None. The nuclear receptor corepressors NCoR1 and NCoR2 are two critical regulators of metabolism that are required for maintaining metabolic homeostasis. Both NCoR1 and NCoR2 (also known as the silencing mediator of retinoic acid and thyroid hormone receptors; SMRT) recruit histone deacetylase 3 (HDAC3) to their deacetylase domain (DAD) to repress nuclear receptor (NR) target gene expression. Interruption of the DAD of NCoR1 in mice leads to lower body weight, decreased whole-body fat mass, insulin sensitization with altered oscillatory patterns of key metabolic genes (1). On the other hand, total body knock-out (KO) of SMRT leads to weight gain, insulin resistance, and hepatic steatosis with an increase in hepatic lipogenesis (2). Previously, we showed that the KO of NCoR1 and SMRT in tandem from adult mice led rapidly to weight loss, hypoglycemia, hypothermia and was lethal. Reductions in intestinal carbohydrate transporters were seen, including sodium-glucose linked transporter-1 (SGLT1), glucose transporter 2 (GLUT2), and glucose transporter 5 (GLUT5) (3). Thus, we hypothesized that NCoR1 and SMRT play unique roles in regulating intestinal carbohydrate metabolism, in turn controlling metabolic parameters including body mass and glucose levels. We then generated a novel model to enable KO of NCoR1 and SMRT throughout intestinal epithelial cells (IECs) in adult mice using a tamoxifen inducible cre under control of the villin 1 promoter. Mice were injected with tamoxifen and body weight and glucose were monitored daily. This was followed by both oral and intraperitoneal glucose tolerance testing (GTT) and metabolic phenotyping. Preliminary data showed that NCoR1 and SMRT KO leads to sustained weight loss and hypoglycemia with 50% survivability. Metabolic phenotyping confirmed reduction in body mass without concomitant reduction in food intake. Oral GTT showed a blunted peak in response to glucose gavage compared to intraperitoneal administration. Gene expression analysis showed reduction in SGLT1, GLUT2, and GLUT5 in addition to changes in metabolic pathways associated with fatty acid metabolism. Here, we show that NCoR1 and SMRT are critical regulators of body mass and glucose in part via their actions on carbohydrate transporters in the intestine. With the global burden of metabolic diseases, including obesity and diabetes, ever-rising, NCoR1 and SMRT represent an overlooked but important area of study to better our understanding of disease processes and identify new targets for treatment. We next aim to determine the functional mechanism by which weight loss and hypoglycemia develop in addition to identifying molecular targets and pathways regulated by NCoR1 and SMRT in IECs.

8488 Sex-Specific Differences in an Alstrom Syndrome Mouse Model

Abstract Disclosure: Y. Carcamo-Bahena: None. J. Youn: None. E. Lartigue: None. S. Sisley: None. Background: Alström syndrome is a monogenic autosomal recessive disorder caused by loss of the ALMS1 gene that affects 1 in 1 million. Loss of a functional ALMS1 protein leads to global disorganization of microtubules. Patients are affected by progressive vision and hearing loss and are at risk of developing obesity and type 2 diabetes. Aside from reproductive system anomalies, no clinical reports have identified sex-specific difference in patients with Alström syndrome. Methods: Male and female Alms1tvrm[1]02/tvrm[1]02 (null), Alms1tvrm[1]02/+ (heterozygous) and wildtype littermate mice were weaned onto standard chow diet. At 16 weeks of age, they were changed to a 45% high fat diet (HFD). Weekly body weights were collected and intraperitoneal glucose tolerance tests (GTTs, 1.5 g/kg D20W) were performed at three different time points (11, 16, 25 weeks of age). Results:Alms1 null mice were heavier than wildtype and heterozygous mice on standard chow diet. In males, significant changes in weight gain in null mice occurred by 10 weeks compared to wildtype and heterozygous mice (p<0.05). In females, compared to null, this change was observed by 13 weeks (p<0.05). Although female mice are typically protected from diet-induced obesity, the null females weighed the same as the null males (65.0 ± 2.0 vs 67.7 ± 2.8 g) after 9 weeks on HFD. We observed sex and diet specific differences in GTT outcomes. On chow diet, Alms1 deficiency did not affect glucose levels during a GTT in female mice. However, after 9 weeks of HFD (25 weeks of age), baseline fasting glucose levels were higher in the null females compared to wildtype (p<0.05) and heterozygotes (p<0.01). Additionally, the GTT curve was monophasic, indicating onset of diabetes whereas wildtype and heterozygotes (p<0.0001) had normal curves. Null male mice showed an impaired glucose response at 11 weeks of age on chow diet compared to wildtype and heterozygous males (p<0.001) and by 16 weeks, the GTT glucose curve for Alms1 null mice was monophasic. After 9 weeks of HFD, no differences were observed in glucose levels during a GTT. Conclusions: We observed sex-specific differences in this Alms1 null mouse model related to body weight and glucose tolerance with male null mice exhibiting earlier obesity and impaired glucose tolerance and female mice showing more pronounced effects on a HFD. Future research should investigate if these sex-specific effects alter responses to dietary or pharmaceutical interventions. Presentation: 6/1/2024

8433 Elucidation of the Molecular Basis of Human and Mouse Pancreatic β-Cell Senescence Induced by Hyperglycemia

Abstract Disclosure: K. Iwasaki: None. P. Carapeto: None. C. Aguayo-Mazzucato: None. Background and AIM: Senescent cells accumulate with age and contribute to the development of chronic diseases, including Type 2 Diabetes (T2D). Whereas senescence is an important pathogenic mechanism in diabetes, the role of hyperglycemia as a metabolic driver of pancreatic β-cells has not been clarified. The aim of this study is to elucidate the molecular basis of hyperglycemia-induced pancreatic β-cell senescence using human and rodent islets. Methods: 1) Human islets were cultured for 2 weeks in 20.2 mM high (HG) or 2.8mM low glucose (LG), and analyzed by qPCR and glucose-responsive insulin secretion (GSIS) to explore the molecular basis of senescence in ex vivo. To test the effects of senescent cell removal, senolytics Dasatinib (1μM) and Quercetin (20μM) (DQ) were used. 2) To evaluate the effects of hyperglycemia in vivo, we transplanted mouse and human islets under the kidney capsule of normoglycemic (NG) or streptozocin-induced hyperglycemic (Stz-Db) immunodeficient mice for two weeks. Graft function was evaluated by intraperitoneal glucose tolerance test and cellular identity using qPCR or immunohistochemistry. DQ (5mg/kg/day + 50mg/kg/day) was used to evaluate the effects of removing senescent cells in transplantation (Tx). To investigate the effect of specific removal of p16-positive senescent β-cells in transplanted islets, INK-ATTAC mice islets (p16Ink4a-mediated apoptosis by targeted activation of caspases) were transplanted into Stz-Db and treated with BB homodimer (BB) to remove p16+ cells or vehicle. Results: (1) Human islets from 5 healthy donors cultured in HG had an increased senescence index (mean of senescence markers p16, p21 and HMGB1 mRNA) when compared to LG islets (p<0.05) and lost glucose responsiveness as evaluated by ex vivo GSIS compared to LG (p<0.05). 2) Human islets (1000IEQ) were transplanted to Stz-Db or NG mice. In Stz-Db graft, P21 mRNA significantly increased with decreased expression of β-cell genes when compared to NG. Stz-Db mice treated with DQ (Db-DQ) for 5 days after Tx, significantly decreased expression of senescence index (p<0.05) and increased in β-cell index (mean of β-cell hallmark genes) (p<0.05) at mRNA levels. Stz-Db mice transplanted with INK-ATTAC mice islets had lower fed glucose levels, decreased p16 mRNA, increased expression β-cell hallmark genes and improved insulin secretion ex vivo after removal of p16+ cells. Conclusion: Sustained exposure of human islets to hyperglycemia induced cellular senescence, leading to pancreatic β-cell dysfunction and loss of cellular identity. Furthermore, elimination of senescent cells may protect pancreatic β-cells from hyperglycemia-induced functional decline, which may have potential clinical application in both Type 1 Diabetes and T2D. Presentation: 6/2/2024

Maternal ingestion of cannabidiol (CBD) in mice leads to sex-dependent changes in memory, anxiety, and metabolism in the adult offspring, and causes a decrease in survival to weaning age

RationaleThe consequences of perinatal cannabidiol (CBD) exposure are severely understudied, but are important, given its widespread use and believed safety as a natural supplement. ObjectiveThe objective of this study was to test the health, metabolic, and behavioral consequences of perinatal CBD exposure on dams and their offspring raised to adult. MethodsPrimiparous female C57BL/6 J mice were orally administered 100 mg/kg CBD in strawberry jam to expose offspring during gestation, lactation, or both using a cross-fostering design. Adult offspring were metabolically profiled using indirect calorimetry and intraperitoneal glucose tolerance testing. Adults were behaviorally phenotyped, video recorded, and mouse position tracked using DeepLabCut. ResultsCBD was detected in maternal plasma using LC-MS 10-min post consumption (34.2 ± 1.7 ng/ul) and peaked within 30 min (371.0 ± 34.0 ng/ul). Fetal exposure to CBD significantly decreased survival of the pups, and decreased male postnatal development, but did not alter litter size, maternal body weight or pup birth weight. We observed many sex-dependent effects of perinatal CBD exposure. Exposure to CBD during gestation and lactation increased meal size, caloric intake, and respiratory exchange ratio for adult male offspring, while exposure during lactation decreased fasting glucose, but had no effect on clearance. Adult female offspring exposed to CBD during lactation showed increased drink size. Perinatal CBD exposure increased obsessive compulsive- and decreased anxiety-like behaviors (marble burying, light-dark box, elevated-plus maze) in female mice, decreased long-term object memory in male mice, and had no effect on attention tasks for either sex. ConclusionsWe conclude that orally-administered CBD during pregnancy affects behavior and metabolism in a sex-dependent manner, and mice are differentially sensitive to exposure during gestation vs. lactation, or both. Because long-term changes are observed following perinatal exposure to the drug, and exposure significantly decreases survival to weaning, more research during development is warranted.

The Influence of Strain and Sex on High Fat Diet-Associated Alterations of Dopamine Neurochemistry in Mice.

Objective: The objective of this study was to determine the influence of sex and strain on striatal and nucleus accumbens dopamine neurochemistry and dopamine-related behavior due to a high-saturated-fat diet (HFD). Methods: Male and female C57B6/J (B6J) and Balb/cJ (Balb/c) mice were randomly assigned to a control-fat diet (CFD) containing 10% kcal fat/g or a mineral-matched HFD containing 60% kcal fat/g for 12 weeks. Results: Intraperitoneal glucose tolerance testing (IPGTT) and elevated plus maze experiments (EPM) confirmed that an HFD produced marked blunting of glucose clearance and increased anxiety-like behavior, respectively, in male and female B6J mice. Electrically evoked dopamine release in the striatum and reuptake in the nucleus accumbens (NAc), as measured by ex vivo fast scan cyclic voltammetry, was reduced for HFD-fed B6J females. Impairment in glucose metabolism explained HFD-induced changes in dopamine neurochemistry for B6J males and, to a lesser extent, Balb/c males. The relative expressions of protein markers associated with the activation of microglia, ionized calcium binding adaptor molecule (Iba1) and cluster of differentiation molecule 11b (CD11b) in the striatum were increased due to an HFD for B6J males but were unchanged or decreased amongst HFD-fed Balb/c mice. Conclusions: Our findings demonstrate that strain and sex influence the insulin- and microglia-dependent mechanisms of alterations to dopamine neurochemistry and associated behavior due to an HFD.

Intragastric botulinum toxin injection directly regulates ghrelin expression via reactive oxygen species and NF-κB signaling

AimsOne effective clinical strategy to combat obesity is intragastric botulinum toxin (BTX) injection, which increases gastric emptying time and regulates appetite. However, it remains unknown if and how BTX affects ghrelin levels. Materials and methodsAn obese animal model was established by feeding male mice with high-fat diet (HFD). BTX was administered by subserosal injection in the antrum via an upper midline laparotomy. The mice were monitored in terms of body weight and blood biochemical parameters. Glucose utility and insulin sensitivity were measured by intraperitoneal glucose and insulin tolerance tests. Additionally, stomach and liver were histologically examined after BTX treatment. AGS gastric adenocarcinoma cells were used to investigate the molecular mechanism by which BTX affects ghrelin expression. Key findingsIn HFD-fed mice, BTX injection significantly decreased both food intake and body weight over a 3-week monitoring period. Moreover, HFD-induced hyperglycemia, hyperinsulinemia, dyslipidemia and obesity readouts were improved after BTX injection. Importantly, mice also exhibited decreased plasma and gastric ghrelin levels after BTX injection. In cultured AGS cells, BTX significantly increased reactive oxygen species (ROS) levels and activated nuclear factor-κB (NF-κB), which led to decreased ghrelin expression. Pre-treatment with inhibitors of either ROS or NF-κB reversed the effects of BTX on ghrelin expression in the cultured cells. SignificanceBTX decreases ghrelin expression in HFD-fed animals and in AGS cells through an ROS/NF-κB-dependent pathway. This mechanism may contribute to decreased food intake in obese subjects receiving intragastric BTX injection for weight control.

Swimming training prevents obesity installation and normalizes hypothalamic expressions of GLP1 and leptin receptors in adult offspring born in small litters.

Glucagon-like peptide-1 (GLP1) and leptin (Lep) are afferent signals that regulate energy metabolism. Lactational hypernutrition results in hyperphagia and adiposity in adult life, and these events can be prevented by exercise. We evaluated the effects of swimming training on hypothalamic (GLP1-R) and Lep receptor (Lep-R) gene expressions in lactational hypernutrition-induced obesity. On the 3rd postnatal day, the litter sizes of lactating dams were adjusted to small litters (SL; 3 pups/dams) or normal litters (NL; 9 pups/dams). After weaning (21 days), NL and SL male rats were randomly distributed to sedentary (Sed) and exercised (Exe) groups. Exercised mice swam (30 min/3 times/week) for 68 days. Food intake and body weight gain were registered. At 92 days, intraperitoneal glucose and insulin tolerance tests were performed and rats were euthanized at 93 days; adipose tissue depots were weighed, and blood counts and plasma biochemical analyses performed. Hypothalamus were isolated to evaluate Lep-R and GLP1-R gene expressions. Small litters sedentary rats presented increased body weight gain, adiposity, insulin sensibility and higher fasting values of glucose and triglycerides, besides higher hypothalamic gene expressions of Lep-R and GLP1-R, compared to NLSed animals. SLExe rats did not develop obesity or metabolic abnormalities and Lep-R and GLP1-R hypothalamic gene expressions were normalized. Lactational hypernutrition induces obesity and metabolic dysfunction in adult life, in association with higher hypothalamic expressions of the Lep-R and GLP1-R genes. Exercise prevented obesity and improved metabolic state in SL overnourished rats, and normalized their hypothalamic Lep-R and GLP1-R gene expressions.

Long-term Metabolic Dysfunction Programming in Female Mice by Serial Moderate Restriction of a High-fat High-sucrose Diet.

While intermittent fasting leads to weight loss and improved glucose metabolism, food insecurity, the insufficient access to food for a healthy life, is associated with obesity and adverse cardiometabolic health, especially in women. We aimed to characterize the effects of intermittently restricted feeding on energy balance and glucose tolerance in female mice. Female C57BL/6J mice were fed a high-fat, high-sucrose diet and intermittently food restricted to 60% of control littermates' ad libitum intake, starting at weaning and until week 19. Restricted mice were subsequently allowed ad libitum access to the same diet. Body composition and energy balance were measured at weeks 18.5, 19, 30, and 40. At week 42, mice underwent an intraperitoneal glucose tolerance test and plasma appetitive hormones measurements after nutrient gavage. During the food restriction phase, restricted mice accrued lower weight and fat mass than controls despite periodic ad libitum food access. Reintroduction of continuous ad libitum food caused increased food intake during the light phase and increased body mass in restricted mice. Minor differences in body composition-adjusted energy expenditure between groups were observed at week 40. At week 42, glucose tolerance was impaired in restricted mice compared to controls, and trends toward lower levels of postprandial anorexigenic hormones glucagon-like peptide-1 and pancreatic polypeptide were observed. Our findings suggest that repeated intermittent food restriction leads to changes in eating behavior that predispose to glucose intolerance when food is freely available. Future studies are needed to elucidate the specific mechanisms underlying these changes.

Coffee pulp improves glucose and lipid metabolism disorder in high-fat diet-induced diabetic mice

BackgroundCoffee berry extracts are anti-lipogenic and lipolytic. This study aims to investigate the effect and mechanism of coffee pulp on high-fat diet (HFD)-induced glucose and lipid metabolism disorder in mice. MethodsThe type 2 diabetes (T2D) mouse model was established by feeding the C57BL/6 J mice with HFD. Mice were administered with coffee pulp diluted in drinking water before or after the establishment of the T2D mouse model. After treatment, the body weight and fasting blood glucose (FBG) of mice were monitored; the intraperitoneal glucose tolerance test (IPGTT) of mice was performed; plasma insulin was determined by ELISA; serum total cholesterol (TC), triglyceride (TG) and liver TG were determined by biochemical analysis; hematoxylin-eosin (H&E) staining was used to evaluate organ histomorphology. Gene expression of key genes in de novo lipogenesis (DNL) in the liver was examined by quantitative reverse transcription PCR (RT-qPCR). ResultsMice that consumed coffee pulp after modeling showed reduced FBG and liver TG, improved IPGTT, and alleviated fatty liver. Consuming coffee pulp before modeling prevented HFD-induced blood glucose and plasma TG increases. Mice consuming coffee pulp also had lower body fat and liver TG compared to the model group. qPCR results showed that the expression of transcription factors (Srebp1, PPARγ) and genes (Fasn, CideA, Plin3, Plin4, Plin5) related to DNL and lipid droplets (LD) formation in the liver of mice consuming coffee pulp were significantly lower than those of the control group. ConclusionsOur study demonstrated that coffee pulp can attenuate HFD-induced disorders of glucose and lipid metabolism, and this effect may be related to the key pathways of lipid synthesis DNL and LD formation pathways in the liver.

Propagermanium as a Novel Therapeutic Approach for the Treatment of Endothelial Dysfunction in Type 2 Diabetes.

Propagermanium (PG) has immune modulating activity and anti-inflammatory properties. This work aimed to study the therapeutic efficacy of PG on endothelial and perivascular dysfunction associated with type 2 diabetes. Non-obese type 2 diabetic Goto-Kakizaki (GK) rats were divided into four groups: (1) the control group; (2) the group treated with 50 mg/kg PG; (3) the group fed a high-fat diet (GKHFD); and (4) the group of GKHFD treated with 50 mg/kg PG. PG was given orally for 3 months. Several in vivo parameters and endothelial function were studied in aortas with perivascular adipose tissue PVAT (+) or without PVAT (-). We also determined the vascular inflammation and levels of CD36 in PVAT. In diabetic GK rats, PG did not affect the lipid profile or the results of the intraperitoneal glucose tolerance test. Instead, it improved the fasting glucose levels (18%, p < 0.01), insulin resistance (32%, p < 0.05), endothelial function (33 and 25% in aortas mounted with (+) or without PVAT (-), p < 0.05), and restored the anticontractile effect of the perivascular adipose tissue by reducing its inflammation (56%, p < 0.05) and oxidative stress profile (55%, p < 0.05). Due to its anti-inflammatory characteristics, PG likely improved endothelial dysfunction and restored the perivascular adipose tissue's anticontractile properties.

Gut microbiota mediates ambient PM2.5 exposure-induced abnormal glucose metabolism via short-chain fatty acids

PM2.5 exposure has been found to cause gut dysbiosis and impair glucose homeostasis in human and animals, yet their underlying biological connection remain unclear. In the present study, we aim to investigate the biological significance of gut microbiota in PM2.5-induced glucose metabolic abnormalities. Our results showed that microbiota depletion by antibiotics treatment significantly alleviated PM2.5-induced glucose intolerance and insulin resistance, as indicated by the intraperitoneal glucose tolerance test, glucose-induced insulin secretion, insulin tolerance test, insulin-induced phosphorylation levels of Akt and GSK-3β in insulin sensitive tissues. In addition, faecal microbiota transplantation (FMT) from PM2.5-exposed donor mice successfully remodeled the glucose metabolism abnormalities in recipient mice, while the transplantation of autoclaved faecal materials did not. Faecal microbiota analysis demonstrated that the composition and alpha diversity of the gut bacterial community were altered by PM2.5 exposure and in FMT recipient mice. Furthermore, short-chain fatty acids levels analysis showed that the circulating acetate was significantly decreased in PM2.5-exposed donor and FMT recipient mice, and supplementation of sodium acetate for 3 months successfully improved the glucose metabolism abnormalities induced by PM2.5 exposure. These results indicate that manipulating gut microbiota or its metabolites could be a potential strategy for preventing the adverse health effects of ambient PM2.5.

Lingonberry (Vaccinium vitis-idaea L.) Skin Extract Prevents Weight Gain and Hyperglycemia in High-Fat Diet-Induced Model of Obesity in Mice.

The percentage of obese people is increasing worldwide, causing versatile health problems. Obesity is connected to diseases such as diabetes and cardiovascular diseases, which are preceded by a state called metabolic syndrome. Diets rich in fruits and vegetables have been reported to decrease the risk of metabolic syndrome and type 2 diabetes. Berries with a high polyphenol content, including lingonberry (Vaccinium vitis-idaea L.), have also been of interest to possibly prevent obesity-induced metabolic disturbances. In the present study, we prepared an extract from the by-product of a lingonberry juice production process (press cake/pomace) and investigated its metabolic effects in the high-fat diet-induced model of obesity in mice. The lingonberry skin extract partly prevented weight and epididymal fat gain as well as a rise in fasting glucose level in high-fat diet-fed mice. The extract also attenuated high-fat diet-induced glucose intolerance as measured by an intraperitoneal glucose tolerance test (IPGTT). The extract had no effect on the levels of cholesterol, triglyceride or the adipokines adiponectin, leptin, or resistin. The results extend previous data on the beneficial metabolic effects of lingonberry. Further research is needed to explore the mechanisms behind these effects and to develop further health-promoting lingonberry applications.

Long term administration of thiamine disulfide improves FOXO1/PEPCK pathway in liver to reduce insulin resistance in type 1 diabetes rat model

ObjectiveThe main objective of this study was to find if thiamine disulfide (TD) lowers blood glucose level and improves insulin resistance (IR) in liver and muscle in rats with chronic type 1 diabetes (T1DM) using euglycemic-hyperinsulinemic clamp technique. MethodsA total of fifty male Wistar rats were assigned to five groups consisted of: non-diabetic control (NDC), diabetic control (DC), diabetic treated with thiamine disulfide (D-TD), diabetic treated with insulin (D-insulin), and diabetic treated with both TD and insulin (D-insulin+TD). Diabetes was induced by a 60 mg/kg dose of streptozotocin. Blood glucose levels, pyruvate tolerance test (PTT), intraperitoneal glucose tolerance test (IPGTT), levels of glycosylated hemoglobin (HbA1c), glucose infusion rate (GIR), liver and serum lipid profiles, liver glycogen stores, liver enzymes ([ALT], [AST]), and serum calcium and magnesium levels. were evaluated. Additionally, gene expression levels of phosphoenolpyruvate carboxykinase (Pepck), forkhead box O1 (Foxo1), and glucose transporter type 4 (Glut4) were assessed in liver and skeletal muscle tissues. ResultsBlood glucose level was reduced by TD treatment. In addition, TyG index, HOMA-IR, serum and liver lipid profiles, HbA1c levels, and expressions of Foxo1 and Pepck genes were decreased significantly (P<0.05) in all the treated groups. However, TD did not influence Glut4 gene expression, but GIR as a critical index of IR were 5.0±0.26, 0.29±0.002, 1.5±0.07, 0.9±0.1 and 1.3±0.1 mg.min−1Kg−1 in NDC, DC, D-TD, D-insulin and D-insulin+TD respectively. ConclusionsTD improved IR in the liver primarily by suppressing gluconeogenic pathways, implying the potential use of TD as a therapeutic agent in diabetes.

Myofiber-specific lipidomics unveil differential contributions to insulin sensitivity in individuals of African and European ancestry

AimsIndividuals of African ancestry (AA) present with lower insulin sensitivity compared to their European counterparts (EA). Studies show ethnic differences in skeletal muscle fiber type (lower type I fibers in AA), muscle fat oxidation capacity (lower in AA), whilst no differences in total skeletal muscle lipids. However, skeletal muscle lipid subtypes have not been examined in this context. We hypothesize that lower insulin sensitivity in AA is due to a greater proportion of type II (non-oxidative) muscle fibers, and that this would result in an ancestry-specific association between muscle lipid subtypes and peripheral insulin sensitivity. To test this hypothesis, we examined the association between insulin sensitivity and muscle lipids in AA and EA adults, and in an animal model of insulin resistance with muscle-specific fiber types. MethodsIn this cross-sectional study, muscle biopsies were obtained from individuals with a BMI ranging from normal to overweight with AA (N = 24) and EA (N = 19). Ancestry was assigned via genetic admixture analysis; peripheral insulin sensitivity via hyperinsulinaemic–euglycemic clamp; and myofiber content via myosin heavy chain immunohistochemistry. Further, muscle types with high (soleus) and low (vastus lateralis) type I fiber content were obtained from high-fat diet-induced insulin resistant F1 mice and littermate controls. Insulin sensitivity in mice was assessed via intraperitoneal glucose tolerance test. Mass spectrometry (MS)-based lipidomics was used to measure skeletal muscle lipid. ResultsCompared to EA, AA had lower peripheral insulin sensitivity and lower oxidative type 1 myofiber content, with no differences in total skeletal muscle lipid content. Muscles with lower type I fiber content (AA and vastus from mice) showed lower levels of lipids associated with fat oxidation capacity, i.e., cardiolipins, triacylglycerols with low saturation degree and phospholipids, compared to muscles with a higher type 1 fiber content (EA and soleus from mice). Further, we found that muscle diacylglycerol content was inversely associated with insulin sensitivity in EA, who have more type I fiber, whereas no association was found in AA. Similarly, we found that insulin sensitivity in mice was associated with diacylglycerol content in the soleus (high in type I fiber), not in vastus (low in type I fiber).Conclusions; Our data suggest that the lipid contribution to altered insulin sensitivity differs by ethnicity due to myofiber composition, and that this needs to be considered to increase our understanding of underlying mechanisms of altered insulin sensitivity in different ethnic populations.

BCG Vaccination Suppresses Glucose Intolerance Progression in High-Fat-Diet-Fed C57BL/6 Mice.

Background and Objectives: Mycobacterium bovis Bacillus Calmette-Guérin (BCG) vaccine administration has been suggested to prevent glucose metabolism abnormalities and fatty liver in genetically obese ob/ob mice; however, it is not clear whether the beneficial effects of BCG are also observed in the progression of glucose intolerance induced by a high-fat diet (HFD). Therefore, the effects of BCG vaccination on changes in glucose tolerance and insulin response were investigated in HFD-fed C57BL/6 mice. Materials and Methods: We used the BCG Tokyo 172 strain to determine effects on abnormalities in glucose metabolism. For vaccination, five-week-old male mice were injected intraperitoneally with BCG and maintained on a HFD for three weeks. The mice were regularly subjected to intraperitoneal glucose tolerance and insulin tolerance tests (IGTTs and ITTs). These tests were also performed in mice transplanted with bone marrow cells from BCG-vaccinated donor mice. Results: Significant effects of BCG vaccination on blood glucose levels in the IGTTs and ITTs were observed from week 12 of the experiment. BCG vaccination significantly improved changes in fasting glucose and insulin levels, insulin resistance indexes, and glucagon-to-insulin ratios in conjunction with the HFD at the end of the experiment. Significant inhibitory effects in the IGTTs and ITTs on glucose intolerance were also observed with transplantation with bone marrow cells derived from BCG-vaccinated donor mice. Conclusions: BCG vaccination significantly delayed glucose intolerance progression, suggesting a beneficial effect of BCG on the pathogenesis of type 2 diabetes. It has also been suggested that the effects of BCG vaccination may be at least partially due to an immune memory (trained immunity) for hematopoietic stem and progenitor cells of the bone marrow.

Aged garlic extract preserves beta-cell functioning via modulation of nuclear factor kappa-B (NF-κB)/Toll-like receptor (TLR)-4 and sarco endoplasmic reticulum calcium ATPase (SERCA)/Ca2+ in diabetes mellitus

BackgroundPeripheral insulin resistance and compromised insulin secretion from pancreatic β-cells are significant factors and pathogenic hallmarks of diabetes mellitus (DM). NF-κβ/TLR-4 and SERCA/Ca2+ pathways have been identified as potential pathways regulating insulin synthesis by preserving pancreatic β-cell functioning. The current study aimed to evaluate the therapeutic effect of aged garlic extract (AGE) against DM in a streptozotocin (STZ)-induced rat model with particular emphasis on pancreatic β-cell functioning.MethodsAGE was characterized by gas chromatography-mass spectrometry (GC-MS), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) to evaluate its physio-chemical characteristics followed by in-vitro anti-diabetic and antioxidant potential. This was followed by the induction of DM in laboratory animals for investigating the therapeutic action of AGE by evaluating the role of NF-κβ/TLR-4 and the SERCA/Ca2+ pathway. The parameters assessed in the present experimental setup encompassed antioxidant parameters, metabolic indicators, insulin concentration, intracellular calcium levels, apoptotic markers (CCK-8 and Caspase Glo-8), and protein expression (P-62 and APACHE-II).ResultsAGE characterization by SEM, GC-MS, and X-ray diffraction (XRD) revealed the presence of phenylalanine, alliin, S-allylmercaptocysteine (SAMC), tryptophan, 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid as major bioactive constituents of AGE. Metabolic studies, including intraperitoneal glucose tolerance test (IPGTT), revealed significantly lower blood glucose levels in the AGE group compared to the disease control group. In contrast, the intraperitoneal insulin tolerance test (ITT) exhibited no significant difference in insulin sensitivity between the AGE supplementation group and the DM control group. Interestingly, AGE was found to have no significant effect on fasting glucose and serum insulin levels. In contrast, AGE supplementation was found to cause significant hypoglycaemia in postprandial blood glucose and insulin levels. Importantly, AGE causes restoration of intracellular Ca2+ levels by modulation of SERCA/Ca2 functioning and inhibition NF-κB/TLR-4 pathway. AGE was found to interact with and inhibit the DR-5/ caspase-8/3 apoptotic complex. Furthermore, microscopic studies revealed degeneration and apoptotic changes in pancreatic β-cells of the DM control group, while supplementation of AGE resulted in inhibition of apoptotic pathway and regeneration of pancreatic β-cells.ConclusionThe current study suggests that AGE enhance glucose homeostasis by exerting their effects on pancreatic β-cells, without ameliorating peripheral sensitivity. Moreover, AGEs promote an increase in β-cell mass by mitigating the apoptosis of pancreatic β-cells. These findings suggest that AGE could aid in developing a viable alternative therapy for diabetes mellitus (DM).

Insulin and glucose tolerance assessment in guanylyl cyclase/natriuretic peptide receptor-A gene-targeted mutant mice

Atrial natriuretic peptide (ANP), acting through guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) regulates blood pressure and cardiac homeostasis. The disruption of Npr1 (encoding NPRA) in mice exhibits hypertension and provokes renal and cardiac disorder. However, the underlying mechanisms are not yet precisely determined. The objective of this study was to determine whether Npr1 plays a role in regulating glucose homeostasis in global Npr1 gene-disrupted mice. The adult male (14-18 wks) Npr1 haplotype gene-knockout ( Npr1+/-, 1-copy), wild-type ( Npr1+/+, 2-copy), and gene-duplicated ( Npr1+ +/+ +, 4-copy) mice were fasted overnight (16 h) and given free access to water. The mice were administered with glucose both orally and intraperitoneally (2 g/kg body weight) to determine the oral glucose tolerance test (OGTT) and intraperitoneal glucose tolerance test (IPGTT). For the insulin tolerance test (ITT), mice were also fasted for 16 h and then received an ip-injection of insulin (1.0 UI/kg body weight). Blood glucose levels were determined by performing tail bleeds at 0, 15, 30, 60, 90, and 120 min using the AlphaTRAK blood glucose monitoring system. The results showed that administration of glucose resulted in a greater increases in blood glucose levels at 120 mins in 1-copy mice (OGTT: 237 ± 5 mg/dL, IPGT: 246 ± 6 mg/dL, ITT; 239 ± 7 mg/dL) than 2-copy male (OGTT: 131 ± 3 mg/dL, IPGT: 126 ± 6 mg/dL, ITT; 127 ± 6 mg/dL), respectively. The blood glucose was also significantly lower in 4-copy mice (OGTT: 113 ± 5 mg/dL, IPGT: 108 ± 7 mg/dL, ITT; 107 ± 3 mg/dL) than in 2-copy mice. Systolic blood pressure (SBP) was determined by non-invasive tail-cuff method (Visitech 2000). SBP was significantly greater in 1-copy mice (130 ± 4 mmHg) than 2-copy mice (100 ± 3 mmHg). Similarly, SBP was also significantly lower in 4-copy mice (90 ± 2) than 2-copy mice. The increase in plasma glucose levels was significantly lower in OGTT than in IPGTT. The present results suggest that decreased Npr1 gene copy number predisposes to hyperglycemia, insulin resistance, and hypertension. These results indicate that the Npr1 gene might regulate blood glucose homeostasis. This work was supported by the NIH grant (DK133833). This is the full abstract presented at the American Physiology Summit 2024 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.

Deletion of Mitogen-inducible gene-6 (Mig6) in the Liver Alters Glucose Homeostasis and Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) Progression

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a spectrum of chronic liver disease that can progress from benign steatosis to metabolic dysfunction-associated steatohepatitis (MASH) - both of which, if left untreated, can progress to cirrhosis and hepatocellular carcinoma. The strongest risk factor for progression of MASLD to MASH is insulin resistance. Previous work in our lab identified that the adaptor protein mitogen-inducible gene-6 (Mig6) is increased in obese mice and that deletion of Mig6 in the liver (LKO) improves glucose tolerance and insulin action during hyperinsulinemic-euglycemic clamps in diet-induced obese mice. Mig6 is an endogenous feedback inhibitor of epidermal growth factor receptor activation (EGFR) and regulates cellular repair and survival. Thus, we sought to elucidate the extent to which loss of Mig6 modulates the progression of MASLD to MASH. We hypothesized that liver-specific loss of Mig6 during early MASLD improves whole-body glucose homeostasis and protects against MASLD-mediated liver damage. LKO mice and matched, control littermates (CON) were fed a MASH diet (40% fat, 40% carbohydrate, 2% cholesterol; CON n=13-19, LKO n=16-22) or a low-fat-matched diet (LFD; 10% fat, 70% carbohydrate; CON n=8-16, LKO n=16-21) for up to 40 weeks. Body weights were recorded weekly, and body composition assessment, glucose and insulin tolerance tests, and hepatic histological analysis were performed after 20-, 30- and 40-weeks on each diet. Compared to the MASH-fed CON mice, MASH-fed LKO mice had lower body weights starting at 10-weeks and persisting throughout the study. Body composition analysis established these differences in body weight were due to decreases in fat, but not lean, mass. Interestingly, whereas intraperitoneal glucose tolerance tests did not identify significant differences in glucose handling between the LFD and MASH fed mice, oral glucose tolerance was significantly improved in 10- and 20-week MASH-fed LKO mice, suggesting alterations in the incretin response in this MASH model. Lastly, histological analysis revealed MASH-fed LKO mice had a preservation of hepatic lipid zonation and blunted levels of circulating alanine aminotransferase (ALT) compared to MASH-fed CON, indicating less hepatic damage in LKO mice. These results suggest that liver-specific loss of Mig6 improves whole-body glucose handling, which in turn ameliorates hepatic damage during MASLD progression. In conclusion, Mig6 prevents, or at least delays, the progression of MASLD, which may reveal a new therapeutic area for the prevention and treatment of MASH. MS was supported by a National Cancer Institute Cancer Metabolism Training Program Postdoctoral Fellowship (T32CA221709). This is the full abstract presented at the American Physiology Summit 2024 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.