Intraperitoneal Glucose Tolerance Test Research Articles

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.

Human Soluble Prorenin Receptor Expressed in Adipose Tissue Improves Insulin Sensitivity and Endothelial Function in Obese Female Mice

Increased circulating levels of the soluble prorenin receptor (sPRR), a component of the renin angiotensin system (RAS), plays a role in obesity, glucose, and insulin balance. Additionally, studies show that elevated plasma sPRR in diabetic patients is correlated with hyperglycemia in women but not men. Hence, the current study sought to understand the functional role of circulating human sPRR (HsPRR) produced by the adipose tissue (Adi) on adipogenesis and obesity, glucose homeostasis and insulin sensitivity. Adi-HsPRR mice were generated by breeding human sPRR-Myc-tag transgenic mice with mice expressing Adiponectin/Cre. The mouse model was validated by detecting myc-tagged HsPRR in western blot at 28kD. Adi-HsPRR male and female mice were kept on a low-fat (10% kcal from fat; n=4-9/group) or high-fat diet (60% kcal from fat; n=8-13/group) for 20 weeks. Body weight was recorded weekly and body composition (EchoMRI) was assessed monthly. Intraperitoneal glucose tolerance test (ipGTT) was performed at 12 weeks and insulin tolerance test (ITT) at 14 weeks. At 16 weeks, mice were implanted with radio telemeter to measure blood for 5 consecutive days. At the end of the study, tissues and plasma were collected for biochemical analysis and vascular studies. Adipose HsPRR expression did not change circulating sPRR between groups in mice fed a low-fat diet mouse (M: 3.5±0.5 vs 3.9±0.2 ng/ml, F: 2.3±0.2 vs 3.0±0.2 ng/ml) and high fat-fed females (4.3±0.3 vs 5.4±0.5 ng/ml) but increased plasma sPRR in HFD Adi-HsPRR male mice compared to HFD CTL (5.3±0.4 vs 8.7±0.7 ng/ml p<0.05). Yet, Adi-HsPRR expression did not change body weight and composition, glucose, and insulin balance, nor blood pressure and vascular function in male mice regardless the diet. However, Adi-HsPRR improved insulin sensitivity (438±22 vs 360±14 AUC p<0.05) and endothelium-dependent vascular relaxation (11.7±2.6 vs 19.4±2.5 % p<0.05) in Adi-HsPRR female mice fed an HFD. Blood pressure was similar between groups in males and females on both LFD and HFD. Further analysis showed that Adi-HsPRR increased vasodilator agent, Ang 1-7 (5.1±1.6 vs 16.2±3.0 pmol/L p<0.05) in HFD females which was unchanged in HFD males (10.2±2.4 vs 5.2±1.7 pmol/L). Moreover, Adi-HsPRR reduced gene expression of SREBP1C (1.3±0.2 vs 0.7±0.1 2−ΔΔCT p<0.05) and CD36 (1.5±0.3 vs 0.6±0.1 2−ΔΔCT p<0.05), in gonadal white adipose of HFD females but not in males. Additionally, PPAR gamma mRNA was reduced in HFD Adi-HsPRR females (1.1±0.1 vs 0.6±0.1 2−ΔΔCT p<0.05). Our findings suggest that HsPRR in adipose tissue exerts sex-specific protective effects on insulin sensitivity and endothelial function during obesity, despite similar plasma sPRR levels between control and Adi-HsPRR mice. Thus, our model could be a useful tool to investigate potential antidiabetic effect of adipose sPRR in obese women. This work was supported by National Institutes of Health grants (R01-HL-142969 and R01-HL-1647 to ASL); the National Institute of General Medical Sciences (P30 GM127211); and the University of Kentucky, Center for Clinical and Translational Sciences (UL1TR001998). 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.

Xiaozhi formula attenuates non-alcoholic fatty liver disease by regulating lipid metabolism via activation of AMPK and PPAR pathways

BackgroundXiaozhi formula (XZF) is a practical Chinese herbal formula for the treatment of non-alcoholic fatty liver disease (NAFLD), which possesses an authorized patent certificate issued by the State Intellectual Property Office of China (ZL202211392355.0). However, the underlying mechanism by which XZF treats NAFLD remains unclear. PurposeThis study aimed to explore the main component of XZF and its mechanism of action in NAFLD treatment. MethodsUHPLC-Q-Orbitrap HRMS was used to identify the components of the XZF. A high-fat diet (HFD)-induced NAFLD mouse model was used to demonstrate the effectiveness of XZF. Body weight, liver weight, and white fat weight were recorded to evaluate the therapeutic efficacy of XZF. H&E and Oil Red O staining were applied to observe the extent of hepatic steatosis. Liver damage, lipid metabolism, and glucose metabolism were detected by relevant assay kits. Moreover, the intraperitoneal insulin tolerance test and the intraperitoneal glucose tolerance test were employed to evaluate the efficacy of XZF in insulin homeostasis. Hepatocyte oxidative damage markers were detected to assess the efficacy of XZF in preventing oxidative stress. Label-free proteomics was used to investigate the underlying mechanism of XZF in NAFLD. RT-qPCR was used to calculate the expression levels of lipid metabolism genes. Western blot analysis was applied to detect the hepatic protein expression of AMPK, p-AMPK, PPARɑ, CPT1, and PPARγ. Results120 compounds were preliminarily identified from XZF by UHPLC-Q-Orbitrap HRMS. XZF could alleviate HFD-induced obesity, white adipocyte size, lipid accumulation, and hepatic steatosis in mice. Additionally, XZF could normalize glucose levels, improve glucolipid metabolism disorders, and prevent oxidative stress damage induced by HFD. Furthermore, the proteomic analysis showed that the major pathways in fatty acid metabolism and the PPAR signaling pathway were significantly impacted by XZF treatment. The expression levels of several lipolytic and β-oxidation genes were up-regulated, while the expression of fatty acid synthesis genes declined in the HFD + XZF group. Mechanically, XZF treatment enhanced the expression of p-AMPK, PPARɑ, and CPT-1 and suppressed the expression of PPARγ in the livers of NAFLD mice, indicating that XZF could activate the AMPK and PPAR pathways to attenuate NALFD progression. ConclusionXZF could attenuate NAFLD by moderating lipid metabolism by activating AMPK and PPAR signaling pathways.

Intrauterine and early-life malnutrition in rats disrupts the circadian rhythm programming of energy metabolites through adulthood.

Maternal malnutrition plays a crucial role in functional development, resulting in behavioral, cognitive, and metabolic abnormalities and disturbances. "Cafeteria diet" has been linked to obesity, metabolic syndrome, diabetes, and other metabolic disruptions in the mammalian lifespan. However, there are very few reports about the effect of intrauterine and early postnatal malnutrition on the circadian rhythm programming of energy metabolites. In mammals, circadian rhythm central control is fundamental for correct interaction with the environment and physiological regulation. Exposure to malnutrition during development imprints metabolic programming throughout life on the central nervous system and peripheral systems. Lifespan studies exploring the effect of high fat/low protein diet administered during critical periods of development are scarce. The present study explored the effect of intrauterine and perinatal malnutrition induced by a high fat/low protein diet (Cafeteria Diet) on circadian and peripheral oscillators controlling glucose, insulin, and triglycerides in rats at 40 and 90 days of age. We evaluated plasma glucose and triglyceride levels in 6 Zeitgeber times, in addition to an intraperitoneal glucose tolerance test (IpTGT) and homeostasis model assessment of insulin resistance (HOMA-IR) at two time-points over 24h. Our results show that offspring of malnourished dams fed cafeteria diet present alterations in circadian rhythmicity of glucose and triglycerides associated with a change in glucose tolerance and insulin sensibility differentially regulated at the development stage and time of day. Intrauterine and early malnutrition due to a cafeteria diet produces maladaptive responses and programs energetic metabolism at several developmental stages during the lifespan.

Captopril pretreatment augments diabetogenic response to streptozotocin administration: experimental in vivo rat model

BackgroundStreptozotocin (STZ) is a glucose analogue commonly used for inducing diabetes in experimental animals. This study is intended to investigate the ability of captopril (Cap) pretreatment to augment STZ-induced diabetogenic effect in an experimental rat model. If this hypothesis were proven, Cap administration to rats could reduce the dosage of STZ by augmenting its effect and resulting in a subsequent reduction in STZ cost. Forty-two adult male Wistar rats were randomly divided into seven groups: a control group that fed a normal diet, whereas the other six experimental groups were fed a high-fat diet (HFD). The six groups were then divided into STZ-30, STZ-30-Cap, STZ-40, STZ-40-Cap, STZ-50, and STZ-50-Cap. All Cap-received groups were supplemented with 50 mg/kg Cap orally one hour just before intraperitoneal (I.P.) injection of STZ. 30-STZ, 40-STZ, and 50-STZ-treated groups were injected once with STZ I.P. at doses of 30, 40, and 50 mg/kg, respectively. An intraperitoneal glucose tolerance test (IPGTT) was done. Pancreatic tissue was obtained to measure Tumor necrosis factor alpha (TNF-α), interleukin one beta (IL-1β), and nitric oxide (NO) by enzyme-linked immunosorbent assay (ELISA) and glucose transporter 2 (GLUT2) gene expression by reverse transcription polymerase chain reaction (RT-PCR). Pancreatic sections were examined by hematoxylin and eosin (H&E) stain, and immunohistochemical staining by anti-insulin and anti-TNF-α antibodies.ResultsResults indicated that administration of Cap before STZ in different doses significantly augmented the hyperglycemic state that was evident by intraperitoneal glucose tolerance test, and markedly increased pancreatic pro-inflammatory markers. Histological analysis of islets of Langerhans indicated degeneration with extensive vacuolations associated with a significant decrease in mean area % of insulin immunoreactivity and an increase in optical density of TNF-α immunoreactivity.ConclusionThese findings pointed to the ability of captopril pretreatment to augment the hyperglycemic state and the diabetogenic response that was induced secondary to STZ injection in an experimental rat model.

Investigation of the effects and mechanisms of berberine on a mouse model of polycystic ovary syndrome: based on intestinal flora analysis

Objective: To examine the impact of berberine on polycystic ovary syndrome (PCOS) in mice, and to investigate the effects of berberine on the intestinal flora and the intestinal flora on PCOS. Methods: A mouse model of PCOS was established by administering dehydroepiandrosterone in combination with high fat diet, and the mouse model was given a berberine treatment. The study consisted of a blank control group (C group), a PCOS model group (M group) and a berberine treatment group (T group). During the experiment, the mice were closely monitored through timed body weight measurements and estrous cycle monitoring; intraperitoneal glucose tolerance test and insulin tolerance test were done. Upon completion of the pharmacological intervention, the wet weights of liver, ovary and fat deposits of mice were assessed and subjected to HE staining to confirm the success of PCOS modeling and the efficacy of berberine. Additionally, fecal samples were analyzed for intestinal flora through 16S rRNA analysis. Results: The PCOS model was established successfully, berberine alleviated the disturbance of estrous cycle in mice, and significantly alleviated fat accumulation and metabolic abnormalities of glucose in mice. The cross-sectional area of fat pad cells in T group was (2 858±146) μm², which was significantly lower than that in M group [(9 518±347) μm²], and the difference was statistically significant (P<0.001). The blood glucose levels in T group were significantly lower than those in M group (P<0.05). The composition and structure of intestinal flora in mice of M group with PCOS (compared with C group) and in mice of T group after berberine intervention (compared with M group) were significantly altered. However, alpha diversity did not change significantly among three groups (P>0.05). Conclusion: Berberine could alleviate PCOS by intervening in the alterations of gut microbiota.

Role of human Kallistatin in glucose and energy homeostasis in mice

ObjectiveKallistatin (KST), also known as SERPIN A4, is a circulating, broadly acting human plasma protein with pleiotropic properties. Clinical studies in humans revealed reduced KST levels in obesity. The exact role of KST in glucose and energy homeostasis in the setting of insulin resistance and type 2 diabetes is currently unknown. MethodsKallistatin mRNA expression in human subcutaneous white adipose tissue (sWAT) of 47 people with overweight to obesity of the clinical trial “Comparison of Low Fat and Low Carbohydrate Diets With Respect to Weight Loss and Metabolic Effects (B-SMART)” was measured. Moreover, we studied transgenic mice systemically overexpressing human KST (hKST-TG) and wild type littermate control mice (WT) under normal chow (NCD) and high-fat diet (HFD) conditions. ResultsIn sWAT of people with overweight to obesity, KST mRNA increased after diet-induced weight loss. On NCD, we did not observe differences between hKST-TG and WT mice. Under HFD conditions, body weight, body fat and liver fat content did not differ between genotypes. Yet, during intraperitoneal glucose tolerance tests (ipGTT) insulin excursions and HOMA-IR were lower in hKST-TG (4.42 ± 0.87 AU, WT vs. 2.20 ± 0.27 AU, hKST-TG, p < 0.05). Hyperinsulinemic euglycemic clamp studies with tracer-labeled glucose infusion confirmed improved insulin sensitivity by higher glucose infusion rates in hKST-TG mice (31.5 ± 1.78 mg/kg/min, hKST-TG vs. 18.1 ± 1.67 mg/kg/min, WT, p < 0.05). Improved insulin sensitivity was driven by reduced hepatic insulin resistance (clamp hepatic glucose output: 7.7 ± 1.9 mg/kg/min, hKST-TG vs 12.2 ± 0.8 mg/kg/min, WT, p < 0.05), providing evidence for direct insulin sensitizing effects of KST for the first time. Insulin sensitivity was differentially affected in skeletal muscle and adipose tissue. Mechanistically, we observed reduced Wnt signaling in the liver but not in skeletal muscle, which may explain the effect. ConclusionsKST expression increases after weight loss in sWAT from people with obesity. Furthermore, human KST ameliorates diet-induced hepatic insulin resistance in mice, while differentially affecting skeletal muscle and adipose tissue insulin sensitivity. Thus, KST may be an interesting, yet challenging, therapeutic target for patients with obesity and insulin resistance.

Anti-diabetic effect of a combination of black seed (Nigella sativa) and cumin (Cuminum cyminum), a two-step study from bench to bed

Background: Type 2 Diabetes mellitus (T2DM) is a prevalent chronic condition causing one-fifth million deaths globally. Standard treatments for diabetes are not sufficiently effective, highlighting the need to find adjunctive treatments to improve glycemic control. Nigella sativa (NS) and Cuminum cyminum (CC) are two herbal medicines known for their antioxidant, anti-inflammatory, and antidiabetic properties. Objective: This study aims to assess the impact of supplementation with a combination of NS and CC on glycemic regulation among individuals with T2DM. The research was conducted in two phases, pre-clinical and clinical. Methods: In the in-vivo phase, thirty-two male mice were allocated into four groups, each comprising eight mice. These groups were categorized as follows: control, diabetic-type 2, diabetic-intervention-NS, and diabetic-intervention-NS+CC. Following the induction of diabetes using Streptozotocin, the mice in NS and NS-CC groups received 400 mg/kg/d or 360 mg/kg/d NS oil plus 40 mg/kg/d CC oil respectively for 30 days. An insulin tolerance test (ITT), an intraperitoneal glucose tolerance test (IPGTT), and blood glucose were conducted subsequently. In the clinical study, eighty patients who have been clinically diagnosed with type 2 diabetes were randomly assigned to two distinct groups to receive a daily dosage of 2000 mg NS-CC soft gel or sunflower oil soft gel for 12 weeks. The examination of fasting blood glucose (FBG) and hemoglobin A1C (HbA1C) was performed both before and after the completion of the intervention. Results: Preclinical findings exhibited a notable decrease in glucose levels in NS (decrease from 271.1±21.71 to 167.6±8.14 mg/dl) and NS-CC (decrease from 275.4±25.57 to 136±13.07 mg/dl). Also, ITT and IPGTT levels showed significantly more reduction in NS and NS-CC compared to the non-treated diabetic group. Treating with NS-CC, but not NS alone decreased ITT to a normal level with no significant difference with the non-diabetic group. In phase 2, supplementation with NS-CC led to a significantly greater reduction of the mean of fasting blood sugar (FBS) (P=0.001) concentration and HbA1C (P&lt;0.001) compared to placebo. Conclusions: NS-CC oil may reduce insulin resistance and blood glucose levels in murine models and individuals with T2DM. Keywords: Nigella sativa, Cuminum cyminum, Type 2 diabetes mellitus, Glycemic control, Diabetic mice

Differential effects of fish-oil and cocoa-butter based high-fat/high-sucrose diets on endocrine pancreas morphology and function in mice.

A high-fat/high-sucrose diet leads to adverse metabolic changes that affect insulin sensitivity, function, and secretion. The source of fat in the diet might inhibit or increase this adverse effect. Fish oil and cocoa butter are a significant part of our diets. Yet comparisons of these commonly used fat sources with high sucrose on pancreas morphology and function are not made. This study investigated the comparative effects of a fish oil-based high-fat/high-sucrose diet (Fish-HFDS) versus a cocoa butter-based high-fat/high-sucrose diet (Cocoa-HFDS) on endocrine pancreas morphology and function in mice. C57BL/6 male mice (n=12) were randomly assigned to dietary intervention either Fish-HFDS (n=6) or Cocoa-HFDS (n=6) for 22 weeks. Intraperitoneal glucose and insulin tolerance tests (IP-GTT and IP-ITT) were performed after 20-21 weeks of dietary intervention. Plasma concentrations of c-peptide, insulin, glucagon, GLP-1, and leptin were measured by Milliplex kit. Pancreatic tissues were collected for immunohistochemistry to measure islet number and composition. Tissues were multi-labelled with antibodies against insulin and glucagon, also including expression on Pdx1-positive cells. Fish-HFDS-fed mice showed significantly reduced food intake and body weight gain compared to Cocoa-HFDS-fed mice. Fish-HFDS group had lower fasting blood glucose concentration and area under the curve (AUC) for both GTT and ITT. Plasma c-peptide, insulin, glucagon, and GLP-1 concentrations were increased in the Fish-HFDS group. Interestingly, mice fed the Fish-HFDS diet displayed higher plasma leptin concentration. Histochemical analysis revealed a significant increase in endocrine pancreas β-cells and islet numbers in mice fed Fish-HFDS compared to the Cocoa-HFDS group. Taken together, these findings suggest that in a high-fat/high-sucrose dietary setting, the source of the fat, especially fish oil, can ameliorate the effect of sucrose on glucose homeostasis and endocrine pancreas morphology and function.

Antidiabetic Effect of Urolithin A in Cultured L6 Myotubes and Type 2 Diabetic Model KK-Ay/Ta Mice with Glucose Intolerance.

Diabetes is caused by abnormal glucose metabolism, and muscle, the largest tissue in the human body, is largely involved. Urolithin A (UroA) is a major intestinal and microbial metabolite of ellagic acid and ellagitannins and is found in fruits such as strawberry and pomegranate. In this present study, we investigated the antidiabetic effects of UroA in L6 myotubes and in KK-Ay/Ta, a mouse model of type 2 diabetes (T2D). UroA treatment elevated the glucose uptake (GU) of L6 myotubes in the absence of insulin. This elevation in GU by UroA treatment was partially inhibited by the concurrent addition of LY294002, an inhibitor of phosphatidylinositol 3-kinase (PI3K) which activates Akt (PKB: protein kinase B) or Compound C, an inhibitor of 5'-adenosine monophosphate-activated protein kinase (AMPK). Moreover, UroA was found to activate both pathways of Akt and AMPK, and then to promote translocation of glucose transporter 4 (GLUT4) from the cytosol to the plasma membrane in L6 myotubes. Based on these in vitro findings, an intraperitoneal glucose tolerance test (IPGTT) was performed after the oral administration of UroA for 3 weeks to KK-Ay/Ta mice with glucose intolerance. UroA was demonstrated to alleviate glucose intolerance. These results suggest that UroA is a biofactor with antihyperglycemic effects in the T2D state.

Mechanisms by which sheep milk consumption ameliorates insulin resistance in high-fat diet-fed mice

Sheep milk is rich in fat, protein, vitamins and minerals and is also one of the most important sources of natural bioactives. Several biopeptides in sheep milk have been reported to possess antibacterial, antiviral and anti-inflammatory properties, and they may prevent type 2 diabetes (T2D), disease and cancer. However, the precise mechanism(s) underlying the protective role of sheep milk against T2D development remains unclear. Therefore, in the current study, we investigated the effect of sheep milk on insulin resistance and glucose intolerance in high-fat diet (HFD)-fed mice, by conducting intraperitoneal glucose tolerance tests, metabolic cage studies, genomic sequencing, polymerase chain reaction, and biochemical assays. Hyperinsulinemic–euglycemic clamp-based experiments revealed that mice consuming sheep milk exhibited lower hepatic glucose production than mice in the control group. These findings further elucidate the mechanism by which dietary supplementation with sheep milk alleviates HFD-induced systemic glucose intolerance.

Overexpression of lncRNA HEM2M alleviates liver injury in mice with non-alcoholic fatty liver disease

To explore the effects of long non-coding RNA (lncRNA) HEM2M overexpression on liver injury in mice with non-alcoholic fatty liver disease (NAFLD). Wild-type C57BL/6 (WT) mice and myeloid cell-specific HEM2M knock-in (MYKI) mice were fed normal (ND) or high-fat diet (HFD) for 12 weeks. After intraperitoneal glucose tolerance and insulin tolerance tests, the mice were euthanized for detection of liver function indicators in the serum and liver tissue. HE staining and F4/80 immunohistochemical staining were used to examine liver pathologies, and the levels of IL-6, IL-1β, and TNF-α in the liver tissues were determined with ELISA. The mRNA expressions of HEM2M and the markers of M1 macrophages (TNF-α, iNOS, and IL-6) and M2 macrophages (Arg-1, YM-1, and IL-10) were detected using qRT-PCR, and the protein expressions of P-AKT, T-AKT, NLRC4, caspase-1 and GSDMD were assayed using immunoblotting. Caspase-1 activity in the liver tissues was determined with colorimetric measurement and immunofluorescence assay. Compared with HFD-fed WT mice, MYKI mice with HFD feeding showed milder liver function damage (P < 0.01), alleviated hepatic steatosis, and reduced liver macrophage infiltration, glucose tolerance impairment and insulin resistance (P < 0.01). The levels of IL-6, IL-1β, and TNF-α and mRNA expressions of M1 type macrophage markers were significantly decreased (P < 0.01) and those of M2 type markers increased (P < 0.01) in the liver tissues of HFD-fed MYKI mice, which also showed reduced NLRC4 inflammasome activity, caspase-1 activation, and GSDMD-N protein expression compared with their WT counterparts (P < 0.05). Overexpression of HEM2M reduces the production of hepatic inflammatory factors, improves insulin resistance and inhibits hepatic NLRC4 inflammasome activation, which leads to reduced hepatic pyroptosis and liver injury in NAFLD mice.

Comparison of the effects of monounsaturated fatty acids and polyunsaturated fatty acids on the lipotoxicity of islets.

Monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) have been reported to combat saturated fatty acid (SFA)-induced cellular damage, however, their clinical effects on patients with metabolic diseases such as diabetes and hyperlipidemia are still controversial. Since comparative studies of the effects of these two types of unsaturated fatty acids (UFAs) are still limited. In this study, we aimed to compare the protective effects of various UFAs on pancreatic islets under the stress of SFA-induced metabolic disorder and lipotoxicity. Rat insulinoma cell line INS-1E were treated with palmitic acid (PA) with or without UFAs including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), arachidonic acid (AA), and oleic acid (OA) to determine cell viability, apoptosis, endoplasmic reticulum (ER) stress, and inflammatory. In vivo, male C57BL/6 mice were fed a 60% high-fat diet (HFD) for 12w. Then the lard in HFD was partially replaced with fish oil (FO) and olive oil (OO) at low or high proportions of energy (5% or 20%) to observe the ameliorative effects of the UFA supplement. All UFAs significantly improved PA-induced cell viability impairment in INS-1E cells, and their alleviation on PA induced apoptosis, ER stress and inflammation were confirmed. Particularly, OA had better effects than EPA, DHA, and AA on attenuating cellular ER stress. In vivo, the diets with a low proportion of UFAs (5% of energy) had limited effects on HFD induced metabolic disorder, except for a slight improved intraperitoneal glucose tolerance in obese mice. However, when fed diets containing a high proportion of UFAs (20% of energy), both the FO and OO groups exhibited substantially improved glucose and lipid metabolism, such as decrease in total cholesterol (TC), low-density lipoprotein (LDL), fasting blood glucose (FBG), and fasting blood insulin (FBI)) and improvement of insulin sensitivity evidenced by intraperitoneal glucose tolerance test (IPGTT) and intraperitoneal insulin tolerance test (IPITT). Unexpectedly, FO resulted in abnormal elevation of the liver function index aspartate aminotransferase (AST) in serum. Pathologically, OO attenuated HFD-induced compensatory hyperplasia of pancreatic islets, while this effect was not obvious in the FO group. Both MUFAs and PUFAs can effectively protect islet β cells from SFA-induced cellular lipotoxicity. In particular, both OA in vitro and OO in vivo showed superior activities on protecting islets function and enhance insulin sensitivity, suggesting that MUFAs might have greater potential for nutritional intervention on diabetes.

Antidiabetic and antioxidant potential of Crocin in high-fat diet plus streptozotocin-induced type-2 diabetic rats.

Crocin, the principal water-soluble active constituent of saffron, possesses numerous pharmacological activities. The present investigation examined the potential antidiabetic and antioxidant characteristics of Crocin in rats with type-2 diabetes by administering it orally and intraperitoneally (i.p.). After 2weeks of a high-fat diet, streptozotocin (STZ) (i.p., 40mg/kg) was administered to male adult rats to induce type-2 diabetes mellitus. Body weight and fasting blood glucose (FBG) were measured on days zero, weeks 1, and 2. At the end of 2 weeks of drug administration in their respective groups, fasting insulin and glucose levels were estimated, and insulin resistance (HOMA-IR) was determined. Intraperitoneal glucose (IPGTT) and insulin tolerance tests (ITT) were carried out. Histopathological investigation and biochemical parameters were estimated in pancreatic tissues. The Crocin (100mg/kg) treatment has significantly improved body weight, abatement of FBG, fasting insulin, and HOMA-IR. Likewise, Crocin treatment significantly improved the glucose and insulin challenges. We observed a significantly marked elevation in endogenous antioxidant enzymes in Crocin-treated groups. Similarly, Crocin treatment reversed the histopathological changes and restored the normal integrity and function of the pancreas. The overall finding indicates that intraperitoneal administration of Crocin demonstrated better control of glycemic level and body weight. Further, it has improved insulin levels in the serum and potentiated antioxidant properties.

Protective Effect of Monoterpene Isoespintanol in a Rat Model of Prediabetes Induced by Fructose.

A high-fructose diet (HFD) induces murine alterations like those recorded in human prediabetes. Protective effects of isoespintanol (monoterpene isolated from Oxandra cf. xylopioides) on changes induced by HFD were evaluated. Animals were maintained for 21 days with a standard diet (C), 10% fructose (F), and F plus isoespintanol (FI, 10 mg/kg, i.p.). Glycemia, triglyceridemia, total and HDL-cholesterol, and insulin resistance index (IRX) were determined. Intraperitoneal glucose tolerance test (IGTT) was performed. In the liver, we measured glycogen, lipogenic gene expression (SREBP-1c, GPAT, FAS, and CPT1), oxidative stress (GSH and 3'-nitrotyrosine content), inflammation markers (iNOS, TNF-α, and PAI-1 gene expression; iNOS and COX-2 protein levels), p-eNOS, p-Akt, and p-GSK3β protein levels. Isoespintanol corrected enhanced triglycerides, lipogenic genes, and IRX, and reduced HDL-cholesterol induced by HFD. Increased liver glycogen and inflammatory markers and decreased GSH, p-Akt, and p-GSK3β measured in F rats were reversed by isoespintanol, and p-eNOS/e-NOS and iNOS/GADPH ratios were normalized. Isoespintanol restored glucose tolerance (IGTT) compared to F rats. These results demonstrate for the first time that isoespintanol prevents endocrine-metabolic alterations induced by HFD in prediabetic rats. These effects could be mediated by Akt/eNOS and Akt/GSK3β pathways, suggesting its possible use as a therapeutic tool for the prevention of diabetes at early stages of its development (prediabetes).

Carotid body denervation improves hyperglycemia in obese mice.

The carotid bodies (CBs) have been implicated in glucose abnormalities in obesity via elevation of activity of the sympathetic nervous system. Obesity-induced hypertension is mediated by insulin receptor (INSR) signaling and by leptin, which binds to the leptin receptor (LEPRb) in CB and activates transient receptor potential channel subfamily M member 7 (TRPM7). We hypothesize that in mice with diet-induced obesity, hyperglycemia, glucose intolerance, and insulin resistance will be attenuated by the CB denervation (carotid sinus nerve dissection, CSND) and by knockdown of Leprb, Trpm7, and Insr gene expression in CB. In series of experiments in 75 male diet-induced obese (DIO) mice, we performed either CSND (vs. sham) surgeries or shRNA-induced suppression of Leprb, Trpm7, or Insr gene expression in CB, followed by blood pressure telemetry, intraperitoneal glucose tolerance and insulin tolerance tests, and measurements of fasting plasma insulin, leptin, corticosterone, glucagon and free fatty acids (FFAs) levels, hepatic expression of gluconeogenesis enzymes phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6-phosphatase (G-6-Pase) mRNA and liver glycogen levels. CSND decreased blood pressure, fasting blood glucose levels and improved glucose tolerance without any effect on insulin resistance. CSND did not affect any hormone levels and gluconeogenesis enzymes, but increased liver glycogen level. Genetic knockdown of CB Leprb, Trpm7, and Insr had no effect on glucose metabolism. We conclude that CB contributes to hyperglycemia of obesity, probably by modulation of the glycogen-glucose equilibrium. Diabetogenic effects of obesity on CB in mice do not occur via activation of CB Leprb, Trpm7, and Insr.NEW & NOTEWORTHY This paper provides first evidence that carotid body denervation abolishes hypertension and improves fasting blood glucose levels and glucose tolerance in mice with diet-induced obesity. Furthermore, we have shown that this phenomenon is associated with increased liver glycogen content, whereas insulin sensitivity and enzymes of gluconeogenesis were not affected.

Genetics and diet explain sex differences in glucose metabolism and cognitive function

AbstractBackgroundDiabetes and cognitive impairment occur together more often than would be expected by chance [1–6]. Individuals diagnosed with type 2 diabetes have a 1.4–2.2‐fold higher risk of dementia than those without diabetes [2,6,7]. Epidemiological research has demonstrated shared risk factors, metabolic disorders, and comorbidities[5,8], shared genetics[9], and evidence of causality assessing glycemic traits [4,10–12]. We set out to determine how glucose metabolism modifies normal aging‐related cognitive decline in comparison to Alzheimer’s Disease (AD)‐related decline, given genetic diversity and controlled diet (GxD).MethodWe studied an innovative, genetically diverse mouse population (AD‐BXDs, Fig. 1) to determine GxD effects on metabolic function and the transition to cognitive impairment [13]. The data were collected longitudinally from a cohort of ∼650 AD‐BXD mice (39 unique strains) fed either a low‐fat chow diet or a high‐fat, high sucrose diet (HFD:45% fat,17.5% sucrose). Glucose metabolism was assessed by measuring the area under the curve of an intraperitoneal glucose tolerance test (IPGTT). In general, faster clearance of glucose (smaller area under the curve) reflects better glycemic control. Contextual fear memory (CFM) at 6 and 14 months of age was the measure of cognitive function. We used multivariable linear regression to model the relationship between overall CFM and an IPGTT by strain effect.ResultWe found that there was heterogeneity in IPGTT by sex, strain, and diet, accounting for more than 50% of the variation explained (Fig. 2). Females generally exhibit faster glucose metabolism than males (Fig.2, left), while the magnitude of the effect of sex and diet on IPGTT differs by strain (Fig. 2, x‐axis). For our research question of how glucose metabolism affects cognitive function, we identified strains that exhibited resilience to cognitive dysfunction as predicted by their glucose metabolism, with a broad‐sense heritability of 0.81 (Fig. 3). These early findings establish a foundation to identify quantitative trait loci (QTLs) and GxD‐type QTLS based on glucose tolerance and cognitive function associations.ConclusionBy examining the effect of diet on AD‐BXD strains and incorporating metabolic measures associated with diabetes, we will be able to evaluate and validate cause in these relationships for the first time.

Insulin-like growth factor-1 short-period therapy improves Non-Alcoholic Fatty Liver Disease (NAFLD) in obese mice

This study seeks to evaluate Insulin-like Growth Factor 1 (IGF-1) short-period therapy in Non-Alcoholic Fatty Liver Disease (NAFLD) as it relates to western diet-induced obesity. For this purpose, 21-day-old male Swiss mice were divided into a control group (CG, N=8), which was fed a standard diet, and an obese group (GO, N=16), which was fed a western diet, rich in saturated fat and simple carbohydrates, for 12 weeks. In the 11th week, part of the animals in the obese group (N=8) received a daily subcutaneous injection of recombinant human IGF-1 (100µg/kg/day) during seven consecutive days (GO+IGF-1). Biometric and metabolic parameters, intraperitoneal glucose tolerance test (IGTT), quantitative analysis of liver steatosis, quantitative analysis of collagen in liver and expression of immunoperoxidase of alpha-smooth muscle actin (a-SMA) were analyzed. Our data demonstrated that IGF-1 short-term treatment was able to improve obesity-related biometric and metabolic parameters. In addition, it promoted the recovery of liver parenchyma, thereby reducing steatosis and fibrosis, thus demonstrating an important hepatoprotective action.