Altered Glucose Tolerance Research Articles

CiBAR1 loss in mice causes laterality defects, pancreatic degeneration, and altered glucose tolerance.

Bin/Amphiphysin/Rvs (BAR) domains are highly conserved domains found in all eukaryotes. BAR domain proteins form crescent-shaped dimers that sense and sculpt curved lipid membranes and play key roles in various cellular processes. However, their functions in mammalian development are poorly understood. We previously demonstrated that Chibby1-interacting BAR domain-containing 1 (ciBAR1, formerly known as FAM92A) localizes to the ciliary base and plays a critical role in ciliogenesis. Here, we report ciliopathy phenotypes of ciBAR1-KO mice. We found that ∼28% of ciBAR1-KO mice show embryonic lethality because of randomized left-right asymmetry; the rest survive into adulthood with no gross morphological abnormalities. Histological assessments of ciliated tissues revealed exocrine pancreatic lesions. Although overall endocrine islet morphology appeared to be normal, ciBAR1-KO mice showed impaired glucose tolerance. Examination of ductal and islet cilia revealed that cilia number and length were significantly reduced in ciBAR1-KO pancreata. ciBAR1-KO MEFs also exhibited ciliary defects. Our findings indicate that ciBAR1 plays a critical role in ciliogenesis depending on the tissue and cell type in mice.

Bictegravir alters glucose tolerance in vivo and causes hepatic mitochondrial dysfunction

Growing evidence associates antiretroviral therapies containing integrase strand transfer inhibitors or tenofovir alafenamide (TAF) with increased weight gain and metabolic diseases, but the underlying mechanisms remain unclear. This study evaluated the impact of lamivudine, dolutegravir (DTG), bictegravir (BIC), tenofovir disoproxil fumarate, and TAF on metabolic alterations, and explored glucose homeostasis and mitochondrial stress as potential mechanisms. These pathways were analyzed both in vivo (C57BL/6J mice treated with the abovementioned drugs or vehicle for 16 weeks) and in vitro (in Hep3B cells). Mice treated with BIC exhibited higher glucose levels and a slower decrease during a glucose tolerance test. Functional enrichment analyses of livers from antiretroviral-treated mice revealed that only BIC altered the cellular response to insulin and induced a gluconeogenic-favoring profile, with Fgf21 playing a significant role. In vitro, BIC significantly reduced hepatocyte glucose uptake in a concentration-dependent manner, both under basal conditions and post-insulin stimulation, while the other drugs produced no significant changes. Hep3B cells treated with clinically relevant concentrations of BIC exhibited significant alterations in the mRNA expression of enzymes related to glucose metabolism. Both DTG and BIC reduced mitochondrial dehydrogenase activity, but only BIC increased reactive oxygen species, mitochondrial membrane potential, and cellular granularity, thereby indicating mitochondrial stress. BIC promoted mitochondrial dysfunction, modified carbohydrate metabolism and glucose consumption in hepatocytes, and altered glucose tolerance and gluconeogenesis regulation in mice. These findings suggest that BIC contributes to insulin resistance and diabetes in people living with HIV, warranting clinical studies to clarify its association with carbohydrate metabolism disorders.

High-fat diet impact on prostate gland from adiponectin knockout mice: Morphometric, metabolic and inflammatory cytokines analyses

AimsObesity is a global public health issue, and some studies have linked it to an increased risk of prostatic diseases. This study aimed to evaluate the effects of a high-fat diet on metabolic parameters and prostate morphology in wild-type (WT) and adiponectin knockout (KO) mice. Main methodsMale WT and KO mice were fed a control diet (CD) or high-fat diet (HFD) for 6 months. Serum metabolic parameters, inflammatory cytokines in epididymal fat tissue, dorsal prostatic lobe morphometry and histopathology were analyzed. Key findingsCD WT and CD KO mice did not exhibit altered metabolic or prostatic parameters. However, HFD WT mice showed altered glucose and insulin tolerance even without excessive weight gain. On the other hand, HFD KO mice developed obesity, with an increase in low-density lipoprotein (11.8 ± 5.1 vs. 31.4 ± 3.6 mg/dL), high-density lipoprotein (73.4 ± 7.4 vs. 103.4 ± 2.5 mg/dL), and total cholesterol levels (126.2 ± 16.1 vs. 294.6 ± 23.2 mg/dL), a decrease in insulin levels (28.7 ± 12.2 vs. 4.6 ± 2.3 μIU/mL), and glucose and insulin resistance. We also observed that HFD KO animals display an increase in inflammatory cytokines, such as IL6, IL1β, and IL1RA. The dorsal prostate from HFD KO animals also presented significant increases in the mast cells (1.9 ± 0,7 vs. 5,3 ± 1.5 cells/field) and Ki67 index (2.91 ± 0.6 vs. 4.7 ± 0.4 %). SignificanceThe above findings highlight the complex interactions between adiponectin, metabolism, malnutrition, and prostate health. Metabolic deregulation combined with adipose inflammation potentially induces a proliferative and inflammatory microenvironment in the prostate gland under conditions of low adiponectin production, potentially impairing prostate morphophysiology in the context of obesity and aging.

Ketogenic diet but not free-sugar restriction alters glucose tolerance, lipid metabolism, peripheral tissue phenotype, and gut microbiome: RCT

Restricted sugar and ketogenic diets can alter energy balance/metabolism, but decreased energy intake may be compensated by reduced expenditure. In healthy adults, randomization to restricting free sugars or overall carbohydrates (ketogenic diet) for 12weeks reduces fat mass without changing energy expenditure versus control. Free-sugar restriction minimally affects metabolism or gut microbiome but decreases low-density lipoprotein cholesterol (LDL-C). In contrast, a ketogenic diet decreases glucose tolerance, increases skeletal muscle PDK4, and reduces AMPK and GLUT4 levels. By week 4, the ketogenic diet reduces fasting glucose and increases apolipoprotein B, C-reactive protein, and postprandial glycerol concentrations. However, despite sustained ketosis, these effects are no longer apparent by week 12, when gut microbial beta diversity is altered, possibly reflective of longer-term adjustments to the ketogenic diet and/or energy balance. These data demonstrate that restricting free sugars or overall carbohydrates reduces energy intake without altering physical activity, but with divergent effects on glucose tolerance, lipoprotein profiles, and gut microbiome.

Elevated Plasma Levels of Growth Arrest Specific 6 (Gas6) Protein in Severe Obesity: Implications for Adipose Tissue and Inflammation.

BACKGROUND Preliminary data suggest an adipogenic role for growth arrest-specific 6 (Gas6), a pleiotropic molecule involved in inflammation, proliferation, and hemostasis through its Tyro3, Axl, and MerTK (TAM) receptors. This study compares Gas6 expression in plasma and visceral and subcutaneous adipose tissue in 42 adults with obesity (body mass index ≥40 kg/m²) and 32 normal-weight controls to elucidate its role in obesity and related metabolic alterations. MATERIAL AND METHODS Using a case-control design, we measured Gas6 levels in plasma via a validated sandwich enzyme-linked immunosorbent assay and in adipose tissues through quantitative polymerase chain reactio with specific probes. Medians and correlations were analyzed using Mann-Whitney and Spearman tests. A general linear model assessed the impact of covariates on the Gas6-anthropometric relationship, with statistical significance determined by P values. RESULTS Plasma Gas6 levels were significantly higher in the obese group than in controls (P=0.0006). While Gas6 mRNA expression did not significantly differ in subcutaneous adipose tissue between groups, it was notably higher in visceral than subcutaneous adipose tissue in controls (P<0.05). A significant correlation was found between plasma Gas6 levels and body mass index (P=0.001). CONCLUSIONS Gas6 plasma levels are elevated in morbid obesity, particularly in visceral adipose tissue, and are linked to altered glucose tolerance in female patients. These findings highlight the role of Gas6 in obesity-related metabolic complications and suggest avenues for further research and potential therapies.

Early life consumption of a "processed" diet high in advanced glycation end products impairs memory function and alters the gut microbiome in rats

Recent evidence indicates that “ultra-processed” foods constitute ~65% of total energy intake among children in the U.S. The impacts of excessive processed food consumption during development are poorly understood, in part because there are neither clear definitions of, nor a robust classification system accounting for, the complexity of food processing variables and how they interrelate in final food products. Heat treatment, a common form of food processing, can induce the chemical Maillard reaction and lead to foods rich in advanced glycation end products (AGEs). The neurocognitive implications of high levels of AGE consumption, particularly during early life, are unknown. Here, we used a rat model to evaluate the effects of adolescent consumption of a heat-treated diet high in AGEs on cognition and the gut microbiome in adulthood. In a series of studies, rats received either an otherwise healthy AGE-rich diet (AGE rats; AIN-93G diet heated at 160ºC for 60min) or a non-AGE-rich diet (CTL rats; AIN-93G diet without heat treatment) during adolescence (postnatal days 26-60). Metabolic, behavioral, and gut microbiome assessments were performed in adulthood. Results revealed that AGE rats exhibited hippocampal (HPC)-dependent memory deficits relative to CTL rats in the absence of altered body weight, body composition, glucose tolerance, and behavioral measures of anxiety. Administering a drug to break down AGEs (alagebrium; 1mg/kg/day) concomitantly with the heat-treated diet prevented memory impairments, supporting a causal role of AGEs in early life diet-induced HPC dysfunction. Microbiome sequencing analyses revealed that AGE rats had substantially reduced abundance of the bacterial genus Lactococcus relative to controls, and Lactococcus abundance was strongly correlated with memory performance. Administration of Lactococcus lactis by oral gavage (109 colony forming units/day) from PN 26-40 during exposure to the heat-treated diet rescued the AGE diet-induced memory impairments. Collective findings from this work identify a connection between a specific food processing variable (i.e., increased dietary AGEs through heat treatment), the gut microbiome, and impaired neurocognition. This work was supported by the National Institute of Diabetes and Digestive and Kidney Diseases under grant DK123423 (awarded to SEK and AAF); the National Institute on Aging through a Postdoctoral Ruth L. Kirschstein National Research Service Award under grant F32AG077932 (awarded to AMRH); and a National Science Foundation Graduate Research Fellowship (awarded to LT). 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.

Investigating the role of the gut in fructose induced glucose intolerance

Background: Obesity and type 2 diabetes (T2D) are global health challenges linked to the consumption of ultra processed foods high in sucrose. The latter sugar is one key source of excess dietary fructose. Although evidence indicates that excess fructose can negatively impact metabolic health and blood glucose regulation, the mechanisms are ill-defined. Excess dietary fructose overwhelms enterocyte absorption in the small intestine and spills over the distal gut. Interestingly, excess fructose has been linked to an expansion of the gut's absorptive surface and increased fat absorption. However, it remains uncertain whether excess dietary fructose impairs glucose tolerance by increasing gut absorptive surface and gut glucose absorption (GGA). Aims and Hypothesis: We hypothesized that dietary fructose impairs glucose tolerance by expanding gut surface and upregulating glucose transport machinery, which promotes increased GGA and glucose intolerance. We aim to (i) map the onset of altered glucose tolerance, plasma insulin, and altered GGA in mice fed a high-fructose diet, and (ii) investigate whether fructose driven increase in GGA correlates with an expansion of absorptive surface. Methodology: C57BL6J male mice were fed a high-sucrose (HS, with 8.5 %Kcal fructose) or a sucrose-free (CTL) diet. Oral glucose tolerance tests (OGTT) and 3-O-methyl-glucose (3-OMG) tests were conducted at weeks 1, 4, and 7 weeks after introduction of diets. Results: We found that 4 weeks, but not 1 week, on HS diet is suffcient to cause glucose intolerance, which persists, but is not aggravated, at week 7. Interestingly, HS-mice did not become insulin resistant, as revealed by plasma insulin levels, homa-ir, and insulin resistance index comparable to that of CTL-mice. HS-fed mice had longer small intestines than CTL-fed counterparts, which is indicative of increased absorptive surface. Furthermore, HS-fed mice presented higher plasma 3-OMG than CTL-mice at weeks 4 and 7, but not at week 1, indicating higher GGA that parallels the trajectory of deteriorated glucose tolerance. Conclusion: Changes in GGA and gut surface are early fructose-induced manifestations relevant to blood glucose control. We will next assess the expression of glucose transporters and perform morphometric analysis in the small intestine of these mice. We will also analyze how gut microbial populations correlate with fructose-induced changes to gut homeostasis. This study uncovers novel mechanisms by which dietary fructose contributes to impaired blood glucose control and elevates the risk of T2D. The findings from this work will lay the groundwork for novel approaches to address the growing burden of metabolic disorders worldwide. Laval university, CRIUCPQ, Fonds de recherche santé Québec. 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.

ROLE OF KATHAKAKHADIRADI KASHAYA IN PREVENTIVE DIABETOLOGY; A CASE REPORT

Diabetes mellitus is an abnormal scenario of altered glucose tolerance due to inadequate insulin action. Small blood vessels are susceptible to the complications of diabetes mellitus, such as basal lamina thickening and endothelial cell proliferation called diabetic microangiopathy, frequently causing retinal and renal damage. Microangiopathy affecting the kidney is called diabetic nephropathy and is the second leading cause of death due to diabetes mellitus after myocardial infarction. Due to the persistent hyperglycemic status of microcapillaries in the kidney, some histological changes occur in the nephron level detected by electron microscopy only after a few years of onset of diabetes [1]. This is a case report of a known diabetic and hypertensive patient who complained of frothy urine and was diagnosed as type 2 diabetes-induced microalbuminuria and intervened with Kathaka Khadiradi Kashaya, a traditional antidiabetic formulation famous in South India. Two months of administration of the medicine reduced the urine microalbumin and albumin creatinine ratio to a significant normalcy, hence proved to be a choice for a clinical trial in the preventive aspect of diabetic nephropathy.

OR31-05 Long-Term Effects Of Gender Affirming Hormone Therapy On Insulin Sensitivity, Insulin Secretion, And Glucose Tolerance

Abstract Disclosure: S. Pinkson: None. J. Trejo: None. A. Mendoza: None. L. Gondin Hernandez: None. S. Chen: None. S. ahuja: None. D. Tripathy: None. Over the past 15 years, transgender veterans seeking Gender Affirming Hormone Therapy (GAHT) have increased significantly. The metabolic effects of long-term GAHT have been controversial possibly because of multiple confounding factors and different methodologies. We examined long-term effects of estradiol and testosterone on insulin sensitivity and insulin secretion in nondiabetic transwomen and transmen. A total of 4 groups (i) 7 transwomen (age 50 ± 4 yr, BMI 31 ± 2 kg/m2) (ii) 6 transmen (age 38 ± 4yr, BMI 33 ± 2 mg/m2) followed for 52 ± 9 months and as a control group (iii) six cisgender men (age 36 ± 4 yrs, BMI 32 ± 2 kg/m2) and (iv) 8 cisgender women (age 39 ± 4 yr, BMI 28 ± 2 kg/m2) participated in an OGTT and Botnia clamp (IV glucose tolerance test: IVGTT followed by hyperinsulinemic (80 mU.m2/min euglycemic clamp). Total testosterone (by equilibration dialysis method), estradiol, sex hormone binding globulin (SHBG) and lipid profile was measured in all subjects. Insulin, and C-peptide were measured every 30 min during the OGTT. Insulin sensitivity was measured as the M-value form last 30 minutes of insulin clamp and as Matsuda index of insulin sensitivity from the OGTT. Indices of insulin secretion (data pending) was calculated as the first phase insulin response from IVGTT (FPIR: 2-10min) and as indices of beta cell function from OGTT: Insulin secretion/insulin resistance index (Insulin 0-120/Glucose 0-120 X Matsuda index). Plasma estradiol in transwomen was 209 ± 92 pg/ml vs. 32 ± 6 pg/ml in cisgender men. Similarly, the total testosterone level in transmen was 319 ± 57 vs. 19 ± 4 ng/dl in cisgender women. There was no difference in SHBG levels between the groups. The body fat content was not different between trans or cis men (36 ± 3 vs 35 ± 1.4 % ) while it was higher in trans vs cis women (40 ± 0.8 vs 30 ± 3%). There was no difference in HbA1c (5.4 ± 0.2 vs 5.2 ± 0.2%, p=ns) between transwomen and cismen and (5.6 ± 0.1 vs 5.5 ± 0.1, p=ns) transmen and ciswomen. The glucose AUC was higher in transmen vs cisgender women (5,487 ± 994 vs. 3,420 ± 533; P &amp;lt; 0.05). There was no difference in glucose AUC between the transwomen and cismen. There was no difference in insulin sensitivity (M-value) between transwomen and cisgender men (6.9 ± 1.2 vs 7.0 ± 1.4 mg.kg/min, p=ns), while it tended to be worse in transmen compared to cisgender women ( 6.03 ± 1.0 vs 7.7± 0.6 mg.kg/min, p=0.1). In both groups M-Value was inversely related to BMI (r=-0.59; p&amp;lt;0.05). There was no relationship between insulin sensitivity and plasma total testosterone level. HDL cholesterol was lower in transmen (41 ± 2.5 vs 55 ± 4 mg/dL, p&amp;lt;0.05) versus cisgender women though there was no difference in triglyceride, total or LDL cholesterol between the groups. In conclusion long-term GAHT therapy does not adversely affect insulin sensitivity in trans men or women and the mildly altered glucose tolerance is likely a result of higher BMI in transmen. Presentation: Sunday, June 18, 2023

Gestational exposure to ambient fine particulate matter disrupts maternal hepatic lipid metabolism

Pregnancy is a unique physiological stage for females as well as a vulnerable period for pollutant exposure. The effect of gestational ambient fine particulate matter (PM2.5) exposure on maternal lipid metabolism during pregnancy is rarely observed, and the mechanism is unknown. In the current study, pregnant C57BL/6 mice were randomly assigned to either ambient PM2.5 or filtered air exposure chambers since gestational day (GD) 0. Meanwhile, non-pregnant female mice were housed as controls in each exposure chamber. PM2.5 exposure exerted no significant effect on body weight gain or the body composition during pregnancy. Pregnant mice exposed to PM2.5 demonstrated improved glucose tolerance, whereas non-pregnant mice showed an increased fasting blood glucose level after PM2.5 exposure with no alterations in glucose tolerance. PM2.5 exposure exerted no significant effect on total lipid content in serum during pregnancy, while an increased serum total lipid level was found in non-pregnant mice exposed to PM2.5. PM2.5 exposure had no effect on total liver lipid levels, it increased several triacylglycerol (TAG) species and total cholesterol esters (CEs) in pregnant mice but lowered a considerable amount in non-pregnant mice’ livers. Furthermore, gestational exposure to PM2.5 enhanced the expression of key enzymes in fatty acid uptake, de novo lipid synthesis, and β oxidation, and inhibited molecules for lipid export in mice liver. Conversely, PM2.5 exposure upregulated proteins involved in hepatic lipolysis and lipid export in non-pregnant mice. These results suggest that the interference of PM2.5 exposure during pregnancy on the lipid metabolism, particularly the hepatic lipid metabolism, differs from that during non-pregnancy. This study provides toxicological evidence that PM2.5 exposure during pregnancy disrupts the lipid metabolism of the liver and provides a basis for protecting vulnerable populations.

Susceptibility to Low Vitamin B6 Diet-induced Gestational Diabetes Is Modulated by Strain Differences in Mice.

Gestational diabetes is a common pregnancy complication that adversely influences the health and survival of mother and child. Pancreatic islet serotonin signaling plays an important role in β-cell proliferation in pregnancy, and environmental and genetic factors that disrupt serotonin signaling are associated with gestational diabetes in mice. Our previous studies show that pregnant C57BL/6J mice fed a diet that is low in vitamin B6, a critical co-factor in serotonin synthesis, develop hyperglycemia and glucose intolerance, phenotypes that are consistent with gestational diabetes in humans. The current study shows that, unlike in the C57BL/6J mice, low vitamin B6 diet does not alter glucose tolerance and insulin secretion in pregnant DBA/2J mice. The hypothesis to be tested in the current study is that pregnant DBA/2J mice are protected against low vitamin B6-induced gestational diabetes due to their higher expression and enzymatic activities of tissue nonspecific alkaline phosphatase (ALPL) relative to C57BL/6J. ALPL is a rate-limiting enzyme that regulates vitamin B6 bioavailability. Interestingly, treating pregnant DBA/2J mice with 7.5 mg/kg/day of the ALPL inhibitor SBI-425 is associated with glucose intolerance in low vitamin B6-fed mice, implying that inhibition of ALPL activity is sufficient to modulate resilience to low vitamin B6-induced metabolic impairment.

Impact of chemogenetic activation of dorsal vagal complex astrocytes in mice on adaptive glucoregulatory responses.

The dorsal vagal complex (DVC) regulates diverse aspects of physiology including food intake and blood glucose homeostasis. Astrocytes play an active role in regulating DVC function and, by extension, physiological parameters. DVC astrocytes in ex vivo slices respond to low tissue glucose. The response of neurons to low glucose is conditional on intact astrocyte signalling in slice preparations, suggesting astrocytes are primary sensors of glucose deprivation (glucoprivation). Based on these published findings we hypothesised that in vivo DVC astrocyte manipulation with chemogenetics would be sufficient to alter physiological responses that control blood glucose. We found that 2-h after systemic 2-DG-induced glucoprivation there were no observable changes in morphology of glial fibrillary acidic protein (GFAP)-immunoreactive DVC cells, specifically those in the nucleus of the solitary tract (NTS). Chemogenetic activation of DVC astrocytes was sufficient to suppress nocturnal food intake by reducing both meal size and meal number and this manipulation also suppressed 2-DG-induced glucoprivic food intake. Chemogenetic activation of DVC astrocytes did not increase basal blood glucose nor protect against insulin-induced hypoglycaemia. In male mice, chemogenetic DVC astrocyte activation did not alter glucose tolerance. In female mice, the initial glucose excursion was reduced in a glucose tolerance test, suggesting enhanced glucose absorption. Based on our data and published work, we propose that DVC astrocytes may play an indispensable homeostatic role, that is, are necessary to maintain the function of glucoregulatory neuronal circuitry, but alone their bulk activation is not sufficient to result in adaptive glucoregulatory responses. It is possible that there are state-dependent effects and/or DVC astrocyte subsets that have this specialised role, but this was unresolvable using the experimental approaches employed here.

1587-P: The NADPH Oxidase 4 Regulates Anti-inflammatory Signals to Modulate Lipid Depot Distribution between Adipose Tissue and Liver

Excessive white adipose tissue (WAT) expansion and lipid load is associated with the onset of insulin resistance and Type 2 diabetes. In addition, lipid storage may “overflow” into the liver triggering the apparition of nonalcoholic fatty liver disease (NAFLD). Two major components linking white adipose tissue (WAT) dysfunction and NAFLD to insulin resistance are the deregulation of cellular redox homeostasis and the onset of chronic, low-grade inflammation. NADPH oxidases (NOX-es) produce oxidant molecules that control redox homeostasis and cytokine signaling in inflammatory cells. In particular, NOX4 is essential for the signal transduction of the transcription factor, Stat6 that mediates anti-inflammatory actions of IL-4 and IL-13. In order to elucidate the in vivo interaction between NOX4 and Stat6 and to assess their relevance in the onset of “obese” WAT and NAFLD, we created mice with double knock-out for NOX4 and Stat6 (DKO) and compared their metabolic phenotype to littermates with single NOX4 deletion (NOX4KO) upon a 13-week high-fat diet feeding (60 % of calorie from fat). DKO and NOX4KO mice displayed similar food intake. By contrast, DKO mice displayed less body weight gain than NOX4KO mice due to lower energy efficiency leading to reduced WAT accumulation. DKO mice shifted lipid deposition away from the WAT and enhanced lipid storage in the liver. DKO mice displayed similar fed and starved glucose levels with no alterations in glucose tolerance assessed by intra-peritoneal glucose tolerance tests. Gene expression analysis confirmed a less inflammatory state of both WAT and liver of DKO mice. Our results demonstrate that anti-inflammatory signaling is modulated by NOX4-derived signals in vivo in mice, and that NOX4 and IL-4/IL-13 interaction is a critical component in the regulation surplus lipid storage distribution between WAT and the liver. Disclosure I. Szanto: None. Funding Insuleman Foundation (ISZ-1); Foundation for the Innovation in Research in Cancer and Biological Sciences

196-LB: Heterogeneity in Elevated Glucose and A1C as Predictors of the Prediabetes-to-Diabetes Transition—Framingham Heart Study, Multiethnic Study on Atherosclerosis, Jackson Heart Study, and Atherosclerosis Risk In Communities

The clinical utility of the elevated altered glucose tolerance and prediabetes, and novel phenotypes of diabetes risk is a hotly debated. The heterogeneity of risk and incidence across diverse cohorts needs to be considered when developing new approaches for screening and when communicating the uncertainty in the transition rate. How the definition of prediabetes relates to cohort-level sources of variation and predicts the transition from prediabetes to overt diabetes has not been well characterized. Here, we study the range and heterogeneity in the absolute incidence and the relative risk for diabetes across competing definitions of prediabetes in participants from four large US cohorts, the Framingham Heart Study (FHS), Multi-Ethnic Study on Atherosclerosis (MESA), Jackson Heart Study (JHS), and Atherosclerosis Risk in Communities (ARIC). We computed the incidence rates across prediabetes (fasting glucose, A1C%; ADA or WHO), outcome definition (elevated glucose or overt T2D), body mass index, blood pressure, age, race, sex and cohort. The cross-cohort meta-analytic estimate rate for transition to diabetes for FBG 100-125 mg/dL, 110-125 mg/dL, and A1C 5.7-6.4% were 4.2, 8.2, 2.8 cases per 100 person-years, respectively. This contrasts with incidence rates of 0.6, 1.0, and 0.6 for the individuals with FBG less than 100, FBG less than 110, and A1C% less than 5.7% respectively. All the meta-analytic estimates had I2 greater than 93%. The between-cohort range FBG 110-125 mg/dL was 4 (FHS Generation 3), 5 (FHS Generation 2), 5.5 (ARIC), 12.5 (JHS), and 14.8 (MESA). In contrast, the range of the incidence rate for A1C 5.7-6.4% was 1.6 (ARIC) to 5.2 (JHS). We found that these inter-cohort differences cannot be explained by body mass index or ethnic differences and reporting of rates need to consider the wide prediction interval between cohorts. Disclosure C. Patel: None. Funding National Institutes of Health (R01ES032470)

Effects of PCSK9 inhibition on glucose metabolism and β-cell function in humans: a pilot study.

Anti-PCSK9 monoclonal antibodies are effective in reducing LDL-C and cardiovascular events by neutralizing circulating PCSK9. PCSK9, however, is also expressed in tissues, including the pancreas, and studies on PCSK9 KO mice have shown impaired insulin secretion. Statin treatment is already known to affect insulin secretion. Our aim was to conduct a pilot study to evaluate the effect of anti-PCSK9 mAb on glucose metabolism and β-cell function in humans. Fifteen non-diabetic subjects, candidates for anti-PCSK9 mAb therapy, were enrolled. All underwent OGTT at baseline and after 6 months of therapy. During OGTT, insulin secretion parameters were derived from C-peptide by deconvolution (β cell glucose sensitivity). Surrogate insulin sensitivity indices were also obtained from OGTT (Matsuda). Glucose levels during OGTT were unchanged after 6 months of anti-PCSK9 mAb treatment, as well as insulin and C-peptide levels. The Matsuda index remained unchanged, while β-cell glucose sensitivity improved post-therapy (before: 85.3 ± 65.4; after: 118.6 ± 70.9 pmol min-1m-2mM-1; p<0.05). Using linear regression, we found a significant correlation between βCGS changes and BMI (p=0.004). Thus, we compared subjects with values above and below the median (27.6 kg/m2) and found that those with higher BMI had a greater increase in βCGS after therapy (before: 85.37 ± 24.73; after: 118.62 ± 26.83 pmol min-1m-2mM-1; p=0.007). There was also a significant correlation between βCGS change and Matsuda index through linear regression (p=0.04), so we analyzed subjects who had values above and below the median (3.8). This subgroup analysis showed a slight though not significant improvement in βCGS in more insulin resistant patients, (before: 131.4 ± 69.8; after: 170.8 ± 92.7 pmol min-1m-2mM-1; p=0.066). Our pilot study demonstrates that six-month treatment with anti-PCSK9 mAb improves β-cell function, and does not alter glucose tolerance. This improvement is more evident in patients with greater insulin-resistance (low Matsuda) and higher BMI.

Lifelong CD8+ T cell deficiency does not ameliorate liver inflammation or alter glucose tolerance in old mice

Previously, we have demonstrated that T cells accumulate in the liver of old animals and that these cells produce inflammatory cytokines. Additionally, we have demonstrated that short term (28d) pharmacological depletion of total (CD3+) and cytotoxic (CD8+) T cells ameliorates this inflammation and results in improved glucose tolerance in old (22-24mo), but not young (4-6mo) mice. We therefore sought to determine if lifelong CD8+ deficiency using a genetic knockout would result in improved glucose tolerance in old mice. We hypothesized that old CD8KO mice would exhibit better glucose tolerance compared to their old T cell intact counterparts due to the amelioration of CD8+ specific inflammation. Young (4-6mo) and old (22-24mo) CD8KO (n=14 Y; 18 O) and C56BL6 (control; n=9 Y; 19 O) of both sexes underwent a glucose tolerance test (GTT) via an i.p. injection (2g/kg) and blood glucose was measured over 2hrs using a handheld glucometer. 24hrs following the GTT, mice were euthanized, and liver T cell number and phenotype was assessed by flow cytometry. Group differences were assessed by two-way ANOVA and Tukey’s post-hoc test. Data shown as mean±SD. Contrary to our hypothesis, there were no effects of age or strain on glucose tolerance (expressed as area under curve (arbitrary units (AU)) young control: 39525±5544 AU, young CD8KO: 39454±12244 AU, old Control: 41245±10733 AU, Old CD8KO:39580±10859 AU). We therefore hypothesized that there may have been accumulation of non-CD8+ T cell populations within the CD8KO livers potentially explaining the lack of GTT strain differences. Within the liver, there was an effect of age, but not strain on total T cell accumulation. Old mice exhibited greater liver CD4+ counts regardless of strain. We found that there was an effect of both age (p=0.0019) and strain (p=0.0167) on liver double negative T cell (CD3+/CD4-/CD8-; DNT) accumulation. Old CD8KO mice exhibited greater DNT accumulation compared to old controls (Control: 131060±97089 cells/g, CD8KO: 283163±211110 cells/g; p=0.03). Additionally, CD8KO mice exhibited age-related accumulation of DNT (young: 98728±94624 cells/g, Old: 283163±211110 cells/g; p=0.0061), while control mice did not exhibit age-related DNT accumulation. Due to this overcompensation of DNTs in the livers of CD8KO mice, we assessed the liver-to-bodyweight ratio, to determine if this overcompensation had any effects on the liver itself. Surprisingly, we found that old CD8KO mice had significantly higher liver-to-body weight ratios compared to the old control mice (Control:0.042±0.006, CD8KO: 0.047±0.005; p=0.0320). These results suggest that old CD8KO mice may have impaired liver function due to the DNT mediated inflammation. Further, accumulation of DNTs may explain why, in contrast to short term CD8+ depletion, lifelong CD8 deficiency does not result in improved glucose tolerance in old mice. Funding: NIH: R01AG060395 K01AG061271 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.

Exploring the role of FXR signaling in maintaining ileal mucosa integrity in subjects with altered glucose tolerance conditions

Aim: Treatment with the FXR agonist obeticholic acid (OCA) has been found to improve glucose metabolism in type 2 diabetes (T2DM) subjects with mechanisms not completely elucidated. In the gut, FXR is mainly expressed in the ileum where promotes transcription of fibroblast growth factor-19 (FGF19) having positive effects on glucose homeostasis, and maintains gut barrier integrity by regulating tight-junction (TJ) proteins expression. Herein, we evaluate whether subjects with dysglycemic conditions exhibit a down-regulation of the intestinal FXR-FGF19-TJ axis and whether treatment with OCA may revert this aberration. Methods: Levels of FXR, FGF19 and TJ proteins and pro-inflammatory cytokines were assessed in ileal mucosa specimens collected during colonoscopy from 53 subjects subdivided according to their glucose tolerance in: NGT (n=26), prediabetes (n=12) and T2DM (n=15). Effects of OCA treatment was assessed on ileal mucosa specimens of subjects with prediabetes or T2DM cultured in absence or presence of OCA for 6h. Results: Ileal FXR protein and mRNA levels were progressively decreased in prediabetes (-26%) and T2DM (-34%) as compared to the NGT group (both P&lt;0.05). Ileal FXR downregulation was paralleled by lower FGF19 expression and circulating levels (both P&lt;0.05). Additionally, we observed a progressive decrease of proteins and mRNA levels of the TJ zonulin (ZO)-1, occludin and claudin-1 (P&lt;0.05 for all) with an activation of pro-inflammatory pathways in the ileal mucosa of subjects with prediabetes and T2DM as compared to the NGT group. OCA treatment resulted in an up-regulation of FGF19 expression and release (both P&lt;0.01), mRNA and protein levels of the TJ ZO-1, occludin and claudin-1 and in reduced pro-inflammatory cytokines synthesis and release (P&lt;0.05 for all). Conclusion: FXR stimulation by OCA treatment reverts the altered FGF-19/TJ axis in subjects with prediabetes and T2DM, indicating intestinal FXR signaling as a novel target for prevention and/or treatment of T2DM.

Reduced glucose tolerance and insulin sensitivity after prolonged exercise in endurance athletes.

The purpose of this study was to 1. investigate if glucose tolerance is affected after one acute bout of different types of exercise; 2. assess if potential differences between two exercise paradigms are related to changes in mitochondrial function; and 3. determine if endurance athletes differ from nonendurance-trained controls in their metabolic responses to the exercise paradigms. Nine endurance athletes (END) and eight healthy nonendurance-trained controls (CON) were studied. Oral glucose tolerance tests (OGTT) and mitochondrial function were assessed on three occasions: in the morning, 14 h after an overnight fast without prior exercise (RE), as well as after 3 h of prolonged continuous exercise at 65% of VO2 max (PE) or 5 × 4 min at ~95% of VO2 max (HIIT) on a cycle ergometer. Glucose tolerance was markedly reduced in END after PE compared with RE. END also exhibited elevated fasting serum FFA and ketones levels, reduced insulin sensitivity and glucose oxidation, and increased fat oxidation during the OGTT. CON showed insignificant changes in glucose tolerance and the aforementioned measurements compared with RE. HIIT did not alter glucose tolerance in either group. Neither PE nor HIIT affected mitochondrial function in either group. END also exhibited increased activity of 3-hydroxyacyl-CoA dehydrogenase activity in muscle extracts vs. CON. Prolonged exercise reduces glucose tolerance and increases insulin resistance in endurance athletes the following day. These findings are associated with an increased lipid load, a high capacity to oxidize lipids, and increased fat oxidation.

Ormdl3 regulation of specific ceramides is dispensable for mouse β-cell function and glucose homeostasis under obesogenic conditions.

Chronic elevation of sphingolipids contributes to β-cell failure. ORMDL3 has been identified as a key regulator of sphingolipid homeostasis, however, its function in pancreatic β-cell pathophysiology remains unclear. Here, we generated a mouse model lacking Ormdl3 within pancreatic β-cells (Ormdl3 β-/-). We show that loss of β-cell Ormdl3 does not alter glucose tolerance, insulin sensitivity, insulin secretion, islet morphology, or cellular ceramide levels on standard chow diet. When challenged with a high fat diet, while Ormdl3 β-/- mice did not exhibit any alteration in metabolic parameters or islet architecture, lipidomics analysis revealed significantly higher levels of very long chain ceramides in their islets. Taken together, our results reveal that loss of Ormdl3 alone is not sufficient to impinge upon β-cell function or whole-body glucose and insulin homeostasis, however, β-cell-specific loss of Ormdl3 does significantly alter levels of specific sphingolipid species in islets upon high fat feeding.

Dietary Soy Isoflavones Prevent Metabolic Disturbs Associated with a Deleterious Combination of Obesity and Menopause.

This study aimed to evaluate the effects of soy isoflavone supplementation (25 mg/kg) on insulin resistance and inflammation in adipose tissue in an experimental model of menopause-obesity. Twenty-four female Wistar rats were ovariectomized (O) and distributed among the groups: OSD-ovariectomized rats submitted to normocaloric standard diet (n = 6); OHF-ovariectomized rats submitted to high-fat diet (n = 9); and OHFI-ovariectomized rats submitted to high-fat diet with isoflavones (n = 9). Weight gain, body adiposity, food and caloric intake, blood pressure, and glucose tolerance were assessed. After 24 weeks, the rats were euthanized; the thoracic blood collected for serum insulin determination and the homeostatic model assessment-insulin resistance) (HOMA-IR) and homeostatic model assessment-β cell (HOMA-β) indices were calculated. Abdominal adipose tissues were removed, weighed, and fixed for immunohistochemical and morphometric studies. Isoflavones decreased weight gain and blood pressure without changing the food and caloric intake (P < .05). Isoflavones did not affect the weight of the abdominal adipose tissue depots (P < .05). Although they did not alter glucose tolerance, the isoflavones reduced HOMA-IR and HOMA-β, serum insulin levels, in addition to reducing adipocytes' size (P < .05). The number of macrophages, lymphocytes, and crown-like structures in adipose tissue was lower in the group treated with isoflavones (P < .05). In conclusion, our data show that dietary soy isoflavones' supplementation prevents many of well-known deleterious combination of obesity and menopause on metabolism, such as body overweight, adipocyte hypertrophy, and hypertension, as well as insulin resistance and adipose tissue inflammation.