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Transporting epithelial cells optimize their morphology for solute uptake by building an apical specialization: a dense array of microvilli that serves to increase membrane surface area. In the intestinal tract, individual cells build thousands of microvilli, which pack tightly to form the brush border. Recent studies implicate adhesion molecule CDHR2 in the regulation of microvillar packing via the formation of adhesion complexes between the tips of adjacent protrusions. To gain insight on how CDHR2 contributes to brush border morphogenesis and enterocyte function under native in vivo conditions, we generated mice lacking CDHR2 expression in the intestinal tract. Although CDHR2 knockout (KO) mice are viable, body weight trends lower and careful examination of tissue, cell, and brush border morphology revealed several perturbations that likely contribute to reduced functional capacity of KO intestine. In the absence of CDHR2, microvilli are significantly shorter, and exhibit disordered packing and a 30% decrease in packing density. These structural perturbations are linked to decreased levels of key solute processing and transporting factors in the brush border. Thus, CDHR2 functions to elongate microvilli and maximize their numbers on the apical surface, which together serve to increase the functional capacity of enterocyte.
Treatments for metabolic diseases, such as diet and therapeutics, often provide short-term therapy for metabolic stressors, but relapse is common. Repeated bouts of exposure to, and relief from, metabolic stimuli results in a phenomenon we call "metabolic cycling." Recent human and rodent data suggest metabolic cycling promotes an exaggerated response and ultimately worsened metabolic health. This is particularly evident with cycling of body weight and hypertension. The innate and adaptive immune systems have a profound impact on development of metabolic disease, and current data suggest that immunologic memory may partially explain this association, especially in the context of metabolic cycling. In this Brief Review, we highlight recent work in this field and discuss potential immunologic mechanisms for worsened disease prognosis in individuals who experience metabolic cycling.
Copyright © 2018 by The American Association of Immunologists, Inc.
Genome-wide association study (GWAS) data have linked the gene to variations in fasting blood glucose (FBG). encodes an islet-specific glucose-6-phosphatase catalytic subunit that forms a substrate cycle with the beta cell glucose sensor glucokinase. This cycle modulates the glucose sensitivity of insulin secretion and hence FBG. GWAS data have not linked to variations in body weight but we previously reported that female C57BL/6J -knockout (KO) mice were lighter than wild-type littermates on both a chow and high-fat diet. The purpose of this study was to compare the effects of deletion on FBG and body weight in both chow-fed and high-fat-fed mice on two other genetic backgrounds. FBG was reduced in KO mice largely independent of gender, genetic background or diet. In contrast, the effect of deletion on body weight was markedly influenced by these variables. Deletion of conferred a marked protection against diet-induced obesity in male mixed genetic background mice, whereas in 129SvEv mice deletion of had no effect on body weight. deletion also reduced plasma cholesterol levels in a manner dependent on gender, genetic background and diet. An association between and plasma cholesterol was also observed in humans through electronic health record-derived phenotype analyses. These observations suggest that the action of G6PC2 on FBG is largely independent of the influences of environment, modifier genes or epigenetic events, whereas the action of G6PC2 on body weight and cholesterol are influenced by unknown variables.
© 2017 Society for Endocrinology.
Polymorphisms in the SLC30A8 gene, which encodes the ZnT8 zinc transporter, are associated with altered susceptibility to type 2 diabetes (T2D), and SLC30A8 haploinsufficiency is protective against the development of T2D in obese humans. SLC30A8 is predominantly expressed in pancreatic islet β-cells, but surprisingly, multiple knockout mouse studies have shown little effect of Slc30a8 deletion on glucose tolerance or glucose-stimulated insulin secretion (GSIS). Multiple other Slc30a isoforms are expressed at low levels in pancreatic islets. We hypothesized that functional compensation by the Slc30a7 isoform, which encodes ZnT7, limits the impact of Slc30a8 deletion on islet function. We therefore analyzed the effect of Slc30a7 deletion alone or in combination with Slc30a8 on in vivo glucose metabolism and GSIS in isolated islets. Deletion of Slc30a7 alone had complex effects in vivo, impairing glucose tolerance and reducing the glucose-stimulated increase in plasma insulin levels, hepatic glycogen levels, and pancreatic insulin content. Slc30a7 deletion also affected islet morphology and increased the ratio of islet α- to β-cells. However, deletion of Slc30a7 alone had no effect on GSIS in isolated islets, whereas combined deletion of Slc30a7 and Slc30a8 abolished GSIS. These data demonstrate that the function of ZnT8 in islets can be unmasked by removal of ZnT7 and imply that ZnT8 may affect T2D susceptibility through actions in other tissues where it is expressed at low levels rather than through effects on pancreatic islet function.
The association of obesity on survival among patients with colorectal cancer (CRC) has not been well characterized. We investigated the association of prediagnostic body mass index (BMI)/waist-hip ratio (WHR) and total/cause-specific mortality in CRC patients. Our study included 1,452 patients who participated in two large cohort studies and were diagnosed with CRC during follow-up period. Participants were measured for anthropometrics and interviewed to collect relevant information at baseline, prior to any cancer diagnosis. Data on site-specific cancer incidence and cause-specific mortality were obtained via in-person surveys and annual record linkage with cancer and vital statistics registries. Cox proportional hazard models were used to evaluate the associations of BMI and WHR with survival. A total of 547 participants died during the follow-up period, including 499 who died of CRC. Relative to normal BMI (18.5 to <25.0 kg/m ), obesity (BMI ≥ 30 kg/m ) was associated with increased mortality resulting from all causes [hazard ratio (HR) = 1.5, 95% confidence interval (CI): 1.1-2.1] and CRC (HR = 1.5, 95% CI: 1.1-2.1). Elevated risk of death was also found among underweight patients (BMI < 18.5 kg/m ), although not all risk estimates were statistically significant. Overweight BMI (25.0 to <30.0 kg/m ) was not associated with risk of death among CRC patients, nor was WHR. In conclusion, prediagnostic BMI was associated with survival among CRC patients following a U-shape pattern; obesity was associated with high mortality after CRC diagnosis. These findings provide support for maintaining healthy weight to improve the survival of CRC patients.
© 2016 UICC.
Individuals with type 2 diabetes (T2D) have a higher fracture risk compared to non-diabetics, even though their areal bone mineral density is normal to high. Identifying the mechanisms whereby diabetes lowers fracture resistance requires well-characterized rodent models of diabetic bone disease. Toward that end, we hypothesized that bone toughness, more so than bone strength, decreases with the duration of diabetes in ZDSD rats. Bones were harvested from male CD(SD) control rats and male ZDSD rats at 16 weeks (before the onset of hyperglycemia), at 22 weeks (5-6 weeks of hyperglycemia), and at 29 weeks (12-13 weeks of hyperglycemia). There were at least 12 rats per strain per age group. At 16 weeks, there was no difference in either body weight or glucose levels between the two rat groups. Within 2 weeks of switching all rats to a diet with 48 % of kcal from fat, only the ZDSD rats developed hyperglycemia (>250 mg/dL). They also began to lose body weight at 21 weeks. CD(SD) rats remained normoglycemic (<110 mg/dL) on the high-fat diet and became obese (>600 g). From micro-computed tomography (μCT) analysis of a lumbar vertebra and distal femur, trabecular bone volume did not vary with age among the non-diabetic rats but was lower at 29 weeks than at 16 weeks or at 22 weeks for the diabetic rats. Consistent with that finding, μCT-derived intra-cortical porosity (femur diaphysis) was higher for ZDSD following ~12 weeks of hyperglycemia than for age-matched CD(SD) rats. Despite an age-related increase in mineralization in both rat strains (μCT and Raman spectroscopy), material strength of cortical bone (from three-point bending tests) increased with age only in the non-diabetic CD(SD) rats. Moreover, two other material properties, toughness (radius) and fracture toughness (femur), significantly decreased with the duration of T2D in ZDSD rats. This was accompanied by the increase in the levels of the pentosidine (femur). However, pentosidine was not significantly higher in diabetic than in non-diabetic bone at any time point. The ZDSD rat, which has normal leptin signaling and becomes diabetic after skeletal maturity, provides a pre-clinical model of diabetic bone disease, but a decrease in body weight during prolonged diabetes and certain strain-related differences before the onset of hyperglycemia should be taken into consideration when interpreting diabetes-related differences.
Obesity is associated with insulin resistance and reduced transport of insulin through the blood-brain barrier (BBB). Reversal of high-fat diet-induced obesity (HFD-DIO) by dietary intervention improves the transport of insulin through the BBB and the sensitivity of insulin in the brain. Although both insulin and estrogen (E2), when given alone, reduce food intake and body weight via the brain, E2 actually renders the brain relatively insensitive to insulin's catabolic action. The objective of these studies was to determine if E2 influences the ability of insulin to be transported into the brain, since the receptors for both E2 and insulin are found in BBB endothelial cells. E2 (acute or chronic) was systemically administered to ovariectomized (OVX) female rats and male rats fed a chow or a high-fat diet. Food intake, body weight and other metabolic parameters were assessed along with insulin entry into the cerebrospinal fluid (CSF). Acute E2 treatment in OVX female and male rats reduced body weight and food intake, and chronic E2 treatment prevented or partially reversed high-fat diet-induced obesity. However, none of these conditions increased insulin transport into the CNS; rather, chronic E2 treatment was associated less-effective insulin transport into the CNS relative to weight-matched controls. Thus, the reduction of brain insulin sensitivity by E2 is unlikely to be mediated by increasing the amount of insulin entering the CNS.
Copyright © 2016 Elsevier Inc. All rights reserved.
BACKGROUND - The American Cancer Society (ACS) publishes behavioral guidelines for cancer prevention, including standards on body weight, physical activity, nutrition, alcohol, and tobacco use. The impact of these guidelines has been rarely studied in low-income and African American populations.
METHODS - The study included 61,098 racially diverse, mainly low-income adults who participated in the Southern Community Cohort Study and were followed for a median of 6 years. Cox models were used to estimate HRs for cancer incidence associated with behaviors and with an ACS physical activity/nutrition 0-to-4 compliance score indicating the number of body weight, physical activity, healthy eating, and alcohol guidelines met.
RESULTS - During the study period, 2,240 incident cancers were identified. Significantly lower cancer incidence was found among never smokers and non/moderate alcohol drinkers, but not among those meeting guidelines for obesity, physical activity, and diet. The ACS compliance score was inversely associated with cancer risk among the 25,509 participants without baseline chronic disease. HRs for cancer incidence among those without baseline chronic diseases and who met one, two, three, or four guidelines versus zero guidelines were 0.93 (95% confidence intervals, 0.71-1.21), 0.85 (0.65-1.12), 0.70 (0.51-0.97), and 0.55 (0.31-0.99), respectively. Associations were consistent in analyses stratified by sex, race, household income, and smoking status.
CONCLUSIONS - Meeting the ACS smoking and body weight/physical activity/dietary/alcohol guidelines for cancer prevention is associated with reductions in cancer incidence in low-income and African American populations.
IMPACT - This study provides strong evidence supporting lifestyle modification to lower cancer incidence in these underserved populations. Cancer Epidemiol Biomarkers Prev; 25(5); 846-53. ©2016 AACR.
©2016 American Association for Cancer Research.
Selective serotonin reuptake inhibitor (SSRI) antidepressants are widely prescribed for depression and other disorders. SSRIs have become one of the most commonly used drugs in the United States, particularly by women. Acute effects on body composition and carbohydrate metabolism have been reported, but little is known regarding the effects of chronic SSRI use. We evaluated the effects of chronic administration of a commonly prescribed SSRI, sertraline HCl, on body weight and composition, fat distribution, carbohydrate metabolism, as well as activity, in adult female depressed and nondepressed cynomolgus monkeys (Macaca fascicularis; n=42) using a placebo-controlled, longitudinal, randomized study design. Phenotypes were evaluated prior to and after 18 months of oral sertraline (20mg/kg) or placebo. Over the 18 month treatment period, the placebo group experienced increases in body weight, body fat (visceral and subcutaneous) fasting insulin concentrations, and homeostasis model assessment of insulin resistance scores (HOMA-IR). Sertraline treatment prevented increases in body weight, fat, insulin, and HOMA-IR (all p<0.05), without significantly altering activity levels. Sertraline treatment altered adiponectin in an unusual way - reducing circulating adiponectin in depressed monkeys without affecting fat mass or body weight. Deleterious effects on adiponectin, a potentially insulin-sensitizing and atheroprotective protein, may result in adverse effects on cardiovascular health despite otherwise beneficial effects on body composition and carbohydrate metabolism.
Copyright © 2016. Published by Elsevier Ltd.
Most biomedical facilities that use rhesus macaques (Macaca mulatta) limit the amount of blood that may be collected for experimental purposes. These limits typically are expressed as a percentage of blood volume (BV), estimated by using a fixed ratio of blood (mL) per body weight (kg). BV estimation ratios vary widely among facilities and typically do not factor in variables known to influence BV in humans: sex, age, and body condition. We used indicator dilution methodology to determine the BV of 20 adult rhesus macaques (10 male, 10 female) that varied widely in body condition. We measured body composition by using dual-energy X-ray absorptiometry, weight, crown-to-rump length, and body condition score. Two indicators, FITC-labeled hydroxyethyl starch (FITC-HES) and radioiodinated rhesus serum albumin ((125)I-RhSA), were injected simultaneously, followed by serial blood collection. Plasma volume at time 0 was determined by linear regression. BV was calculated from the plasma volume and Hct. We found that BV calculated by using FITC-HES was consistently lower than BV calculated by using (125)I-RhSA. Sex and age did not significantly affect BV. Percentage body fat was significantly associated with BV. Subjects categorized as having 'optimal' body condition score had 18% body fat and 62.1 mL/kg BV (by FITC-HES; 74.5 mL/kg by (125)I-RhSA). Each 1% increase in body fat corresponded to approximately 1 mL/kg decrease in BV. Body condition score correlated with the body fat percentage (R(2) = 0.7469). We provide an equation for calculating BV from weight and body condition score.