John G. Kral

A Review of the Microcirculation of Adipose Tissue: Anatomic, Metabolic, and Angiogenic Perspectives

Adipose tissue microcirculation is unique within the vascular system because of a capacity for this tissue to grow throughout most of adult life. A review of the microcirculation of adipose tissue has included a historical review of the early studies, which served as a foundation for later investigations on this topic, including basic hemodynamic measurements in mammalian adipose tissue. The various methods for measuring blood flow in white and brown adipose tissue are discussed with respect to studies of transport of substrates involved in adipose tissue metabolism. The role of innervation and vascular adrenergic receptors and the effects of diet and exercise on adipose tissue blood flow are also included. An in‐depth analysis of the development of adipose tissue microvasculature indicates that angiogenesis often precedes adipogenesis. The clinical effects of hemodynamic adaptations to adipose tissue expansion are discussed in view of an epidemic increase in the prevalence of obesity and its co‐morbidities. The recent discovery of sites of nuclear regulation of adipocyte differentiation, together with the identification of growth factors in adipose tissue, is an indication of the progress that is being made in the further understanding of molecular and cellular events that affect adipose tissue growth and, ultimately, adipose tissue microcirculation.

Large maternal weight loss from obesity surgery prevents transmission of obesity to children who were followed for 2 to 18 years.

OBJECTIVE. Our aim was to compare the prevalence of obesity in 172 children who were aged 2 to 18 years and born to 113 obese mothers (BMI: 31 ± 9 kg/m2) with substantial weight loss after biliopancreatic bypass surgery with 45 same-age siblings who were born before maternal surgery (mothers’ BMI: 48 ± 8 kg/m2) and with current population standards. METHODS. In this case series, with >88% follow-up in a tertiary referral center, crosssectional office chart and telephone data on childhood and adolescent weights were transformed to z scores. RESULTS. After maternal surgery, the prevalence of obesity in the offspring decreased by 52% and severe obesity by 45.1%, with no increase in the prevalence of underweight. The z score reduction in obesity was gender specific, with boys reducing from 1.4 ± 1.3 before to 0.57 ± 1.7 after maternal surgery, corrected for birth order. The difference was not significant in girls (0.8 ± 1.3 vs 0.8 ± 1.2). Among children of both genders who were aged 6 to 18 years of age and born after maternal surgery, the prevalence of overweight was reduced to population levels. CONCLUSIONS. Contrary to outcomes after intrauterine under- and overnutrition, the prevalence of overweight and obesity in children of mothers with large voluntary postsurgical weight loss was similar to that in the general population, with no increase in underweight. The results demonstrate the importance of potentially modifiable epigenetic factors in the cause of obesity.

Does Intra-Abdominal Adipose Tissue in Black Men Determine Whether NIDDM Is Insulin-Resistant or Insulin-Sensitive?

Insulin resistance in black Americans with non-insulin-dependent diabetes mellitus (NIDDM) is found in only 60% of those with a body mass index (BMI) of <30 kg/m2, suggesting that NIDDM can occur independent of peripheral insulin resistance. When insulin resistance is present, it is not necessarily correlated with obesity. Numerous studies have shown that increased amounts of intra-abdominal adipose tissue are associated with various metabolic abnormalities. We therefore investigated whether the occurrence of insulin resistance in black NIDDM men could be explained by the pattern of body adipose tissue distribution rather than total adiposity. Twenty-two near-normoglycemic black men (fasting plasma glucose [mean ± SD] = 104 ± 10 mg/dl, HbA1c = 4.6 ± 0.78%, age 48.9 ± 9.2 years, and BMI 26.5 ± 2.4 kg/m2) were studied. The euglycemic insulin clamp with 1 mU · kg−1 · min−1 insulin infusion and D-[3-3H]glucose was used to measure insulin action. Whole-body computed tomography with 22 scans was used to determine body composition. Total body adipose tissue was 19.6 ± 7.5 1, and the percentage of body fat was 27 ± 7. Glucose disposal ranged from 2.5 to 8.1 mg · kg−1 · min−1 (10 men were insulin-sensitive and 12 were insulin-resistant). There was a strong inverse correlation between glucose disposal and the proportion of total adipose tissue in the intra-abdominal region (r = −0.78, P < 0.001), while there was no correlation between glucose disposal and total muscle volume, BMI, total adipose tissue volume, or total subcutaneous adipose tissue volume. When insulin resistance is present, it is highly correlated with an increase in the proportion of intra-abdominal adipose tissue. The data raise the possibility that insulin resistance in black NIDDM men may be a consequence of increased intra-abdominal adipose tissue mass.

Timeliness and use of antibiotic prophylaxis in selected inpatient surgical procedures

BACKGROUND Twenty-five percent of all nosocomial infections are wound infections. Professional guidelines support the timely use of preoperative prophylaxis for prevention of postoperative wound infections. Barriers exist in implementing this practice. IPRO, the New York State peer review organization, as part of the Health Care Financing Administrations Health Care Quality Improvement Program, sought to determine the proportion of patients receiving timely antibiotic prophylaxis for aortic grafts, hip replacements and colon resections in 44 hospitals in New York State. METHODS IPRO conducted a retrospective medical record review of 44 hospitals through out New York State stratified for teaching, nonteaching status. A sample was drawn of 2651 patients, 2256 from Medicare and 395 from Medicaid, undergoing either abdominal aortic aneurysm repair, partial or total hip replacement or large bowel resection. The study determined the proportion of patients who had documentation of receiving antibiotics and those who received antibiotics timely, that is less than or equal to 2 hours preoperatively. RESULTS Eighty-six percent of patients had documentation of receiving an antibiotic. Forty-six percent of aneurysm repairs and 60% of hip replacements had evidence of receiving timely antibiotic prophylaxis, that is within 2 hours prior to surgery. For colon resections, 73% of cases had either oral prophylaxis or timely parenteral therapy. An increased proportion of patients had received parenteral antibiotics prematurely as the surgical start time occurred later in the day. A total of 44 different antibiotics were recorded for prophylaxis. CONCLUSIONS Antibiotic prophylaxis was performed in 81% to 94% of cases, however, anywhere from 27% to 54% of all cases did not receive antibiotics in a timely fashion. By delegating implementation of ordered antibiotic prophylaxis to the anesthesia team, timing may be improved and the incidence of postoperative wound infections may decrease.

Differential methylation in glucoregulatory genes of offspring born before vs. after maternal gastrointestinal bypass surgery

Obesity and overnutrition during pregnancy affect fetal programming of adult disease. Children born after maternal bariatric gastrointestinal bypass surgery (AMS) are less obese and exhibit improved cardiometabolic risk profiles carried into adulthood compared with siblings born before maternal surgery (BMS). This study was designed to analyze the impact of maternal weight loss surgery on methylation levels of genes involved in cardiometabolic pathways in BMS and AMS offspring. Differential methylation analysis between a sibling cohort of 25 BMS and 25 AMS (2–25 y-old) offspring from 20 mothers was conducted to identify biological functions and pathways potentially involved in the improved cardiometabolic profile found in AMS compared with BMS offspring. Links between gene methylation and expression levels were assessed by correlating genomic findings with plasma markers of insulin resistance (fasting insulin and homeostatic model of insulin resistance). A total of 5,698 genes were differentially methylated between BMS and AMS siblings, exhibiting a preponderance of glucoregulatory, inflammatory, and vascular disease genes. Statistically significant correlations between gene methylation levels and gene expression and plasma markers of insulin resistance were consistent with metabolic improvements in AMS offspring, reflected in genes involved in diabetes-related cardiometabolic pathways. This unique clinical study demonstrates that effective treatment of a maternal phenotype is durably detectable in the methylome and transcriptome of subsequent offspring.

Ghrelin: Integrative Neuroendocrine Peptide in Health and Disease

Objective:Ghrelin is a novel gastric hormone recognized in 1999 as a mediator of growth hormone release. Since growth hormone is anabolic, an important function of ghrelin may be to coordinate energy needs with the growth process. Newly discovered biologic roles of ghrelin imply that it may have other important physiological functions as well. This is a review of recent clinically relevant, yet less well-known, physiologic actions of ghrelin. Summary Background Data:Ghrelin has profound orexigenic, adipogenic, and somatotrophic properties, increasing food intake and body weight. Secreted predominantly from the stomach, ghrelin is the natural ligand for the growth hormone secretagogue receptor in the pituitary gland, thus fulfilling criteria of a brain-gut peptide. The brain-gut axis is the effector of anabolism by regulating growth, feeding, and metabolism via vagal afferents mediating ghrelin signaling. However, the wide tissue distribution of ghrelin suggests that it may have other functions as well. Methods:Systematic literature review of all PubMed citations between 1999 and August 2003 focusing on clinically relevant biochemical and physiological characteristics of ghrelin. Results:Ghrelin is an important component of an integrated regulatory system of growth and metabolism acting via the vagus nerve, and is implicated in a variety of altered energy states such as obesity, eating disorders, neoplasia, and cachexia. It also enhances immune responses and potentially down-regulates anti-inflammatory molecules. Ghrelins role as a brain-gut peptide emphasizes the significance of afferent vagal fibers as a major pathway to the brain, serving the purpose of maintaining physiologic homeostasis. Conclusions:The discovery of ghrelin has increased our understanding of feeding regulation, nutritional homeostasis, and metabolic processes. Further characterization of ghrelins functions will likely generate new pharmacological approaches to diagnose and treat different disease entities including those related to the over-nutrition of obesity and the catabolic response to surgical trauma.

Early-Life Stress and the Development of Obesity and Insulin Resistance in Juvenile Bonnet Macaques

Stress is a risk factor for chronic illnesses such as obesity, type 2 diabetes, and hypertension and has been postulated to cause the metabolic syndrome via perturbation of the hypothalamo-pituitary-adrenal (HPA) axis. In our model of early-life stress (variable foraging demand [VFD]), food insecurity is imposed on monkey mothers for 16 weeks beginning when their nursing offspring are 3–5 months of age. Under VFD, food availability is never restricted, and the infants growth is unaffected. VFD rearing does, however, cause a range of neurobiological abnormalities, including dysregulation of the HPA axis, manifested in abnormal cerebrospinal fluid cortisol and corticotropin-releasing factor levels. We previously reported spontaneous occurrence of metabolic syndrome in 14% of normally reared peripubertal bonnet macaques given ad libitum access to standard monkey chow. Here, we show that compared with normally reared monkeys, peripubertal VFD juveniles exhibit greater weight, BMI, abdominal circumference, and glucagon-like peptide-1 and decreased glucose disposal rates during hyperinsulinemic-euglycemic clamps. Our data suggest that early-life stress during a critical period of neuro development can result in the peripubertal emergence of obesity and insulin resistance.

Gene Variants and Binge Eating as Predictors of Comorbidity and Outcome of Treatment in Severe Obesity

Melanocortin-4 receptor gene (MC4R) variants are associated with obesity and binge eating disorder (BED), whereas the more prevalent proopiomelanocortin (POMC) and leptin receptor gene (LEPR) mutations are rarely associated with obesity or BED. The complete coding regions of MC4R, POMC, and leptin-binding domain of LEPR were comparatively sequenced in 300 patients (233 women and 67 men; mean ± SEM age, 42 ± 1 years; mean ± SEM body mass index, 43.5 ± 0.3 kg/m2) undergoing laparoscopic gastric banding. Eating behavior, esophagogastric pathology, metabolic syndrome prevalence, and postoperative weight loss and complications were retrospectively compared between carriers and noncarriers of gene variants with and without BED during 36 ± 3-month follow-up. Nineteen patients (6.3%) carried 8 MC4R variants, 144 (48.0%) carried 13 POMC variants, and 247 (82.3%) carried 11 LEPR variants. All MC4R variant carriers had BED, compared with 18.1% of noncarriers (P <0.001). BED rates were similar among POMC and LEPR variant carriers and noncarriers. Gastroscopy revealed more erosive esophagitis in bingers than in nonbingers before and after banding (P < 0.04), regardless of genotype. MC4R variant carriers lost less weight (P < 0.003), showed less improvement in metabolic syndrome (P < 0.001), had dilated esophagi (P < 0.001) and more vomiting (P < 0.05), and had fivefold more gastric complications (P < 0.001) than noncarriers. Overall outcome was poorest in MC4R variant carriers, better in noncarriers with BED (P < 0.05), and best in noncarriers without BED (P < 0.001). MC4R variants influence comorbidities and treatment outcomes in severe obesity.

Development of a human adipocyte synthetic polymer scaffold.

Because of the need for methods for successful transplantation of autologous fat, the differentiation of human preadipocytes on surgical mesh coated with various extracellular matrix components was investigated. Biopsy specimens of human adipose tissue were collected from seven different patients and were subjected to collagenase digestion and selective filtration, resulting in primary cultures of human preadipocytes. Fluortex monofilament-expanded polytetrafluoroethylene (52-/xm pore size) was as a template for coating with either human collagen, albumin, or fibronectin, followed by sodding with established cultures of human preadipocytes. Sodding efficiency on the different matrices was determined by trypsinization of attached cells at different time periods. Preadipocytes did not attach to uncoated polytetrafluoroethylene, but did attach to protein-coated mesh, and in a variable manner. Fibronectin-coating resulted in the highest efficiency of sodding, with differentiation of preadipocytes to adipocytes as assessed by scanning electron -microscopy and conventional Oil Red O staining. Similar results were achieved by using rat (n = 6) perirenal adipose tissue. This new method of adipocyte scaffolding may be used for improving soft-tissue augmentation and serving as a delivery system for growth factors important in wound healing.

Metabolic correlates of eating behavior in severe obesity.

BACKGROUND: The benefit of spreading energy intake over many small meals (‘nibbling’) rather than few large ones (‘gorging’) for control of blood glucose, serum lipids and body fat accretion has been known for 60 y, but the mechanisms are poorly understood. Men exhibit more of a gorging eating pattern than women and are also more prone to the metabolic complications of obesity, as are women with a ‘male’, central distribution of adipose tissue. We have shown correlations between central fat distribution, and other components of the metabolic ‘Syndrome X’ and fatty infiltration of the liver. Here we study relationships between eating rate and fat distribution and test the hypothesis that gorging might be associated with fatty liver.SUBJECTS AND METHODS: In 30 non-alcoholic, non-diabetic, severely obese women (body mass index, BMI=47±1 kg/m2; mean±s.e.m.) with a mean age of 36±1 y and 16 men (BMI: 52±3) age 38±2 y, who were candidates for anti-obesity surgery, we measured eating rate using an eating monitor, and fat distribution by the waist–hip circumference ratio (WHR). In addition in the 17 women and 11 men who had surgery, serum lipids were analyzed and routine liver biopsies were evaluated for steatosis by a pathologist blinded to the conditions of the study.RESULTS: Men ate significantly faster than women (188±28 vs 123±9 g/min; P<0.01), and had more liver fat (score: 2.7±03 vs 1.5±0.3; P<0.01), with no statistically significant sex differences in s-cholesterol or s-triglycerides. Eating rate correlated with WHR (r=0.46; P<0.01, n=46), liver fat (r=0.55; P<0.01), and s-triglycerides (r=0.42; P<0.05) adjusting for sex. Liver fat correlated with WHR (r=0.50; P<0.05), s-triglycerides (r=0.70; P<0.01) and s-cholesterol (r=0.50; P<0.05), while there were no significant correlations with BMI or body weight. In multivariate analysis eating rate (32%), meal size (8%) and WHR (6%) contributed 46% of the variance in liver fat.CONCLUSION: We showed increased eating rates in severely obese men and women with central fat distribution. Furthermore, increased eating rates were associated with fatty liver and elevated serum lipids. Eating rate in severely obese women and men may be a determinant of the metabolic syndrome.