How antigen specificity directs regulatory T-cell function: self, foreign and engineered specificity.

Regulatory T cells (Tregs) are a suppressive subset of T cells that have important roles in maintaining self-tolerance and preventing immunopathology. The T-cell receptor (TCR) and its antigen specificity play a dominant role in the differentiation of cells to a Treg fate, either in the thymus or in the periphery. This review focuses on the effects of the TCR and its antigen specificity on Treg biology. The role of Tregs with specificity for self-antigen has primarily been studied in the context of autoimmune disease, although recent studies have focused on their role in steady-state conditions. The role of Tregs that are specific for pathogens, dietary antigens and allergens is much less studied, although recent data suggest a significant and previously underappreciated role for Tregs during memory responses to a wide range of foreign antigens. The development of TCR- or chimeric antigen receptor (CAR)-transduced T cells means we are now able to engineer Tregs with disease-relevant antigen specificities, paving the way for ensuring specificity with Treg-based therapies. Understanding the role that antigens play in driving the generation and function of Tregs is critical for defining the pathophysiology of many immune-mediated diseases, and developing new therapeutic interventions.

Muscle insulin receptor concentrations in obese patients post bariatric surgery: relationship to hyperinsulinemia.

OBJECTIVE: Obesity results in insulin resistance. Bariatric surgery for obese individuals induces weight loss, improves insulin sensitivity, and lowers insulin levels. We investigated the mechanisms of this improvement. DESIGN: Insulin receptor (IR) content, IR signaling, and adiponectin levels were measured in nine morbidly obese subjects before and after bariatric surgery. SUBJECTS: Seven female and two male, average age 44+/-2y, BMI >40 kg/m(2) and/or at least 100 lbs over ideal body weight, undergoing elective bariatric surgery. MEASUREMENTS: Before surgery BMI, fasting plasma glucose, adiponectin, and insulin levels were measured. A fasting muscle biopsy was obtained from the vastus lateralis for IR concentration and autophosphorylation activity measurements. These procedures were repeated 1 y after surgery. RESULTS: At 1 y after surgery, the subjects had lost an average of 48.3+/-5.6 kg (P<0.001), insulin sensitivity had significantly increased as determined by the minimal model (SI 0.72+/-0.18 vs 3.86+/-1.43, P<0.05), and IR content had increased two-fold in muscle (2.1+/-0.4 vs 4.3+/-0.7 ng/mg protein, P<0.01). The increase in IR content was related to fasting insulin levels. In the subjects with the lowest IR function, there was also an increase in IR function. Plasma adiponectin increased by 40% following weight loss (7.4+/-1.6 pre vs 10.3+/-1.3 mg/ml post, P<0.05). There was no significant change in muscle content of the IR inhibitor, PC-1. CONCLUSION: Increased IR content, most likely regulated by insulin levels, may be one contributor to the increased insulin sensitivity that occurs when morbidly obese patients undergo bariatric surgery.

Increased protein kinase C theta in skeletal muscle of diabetic patients.

In this study we have investigated whether protein kinase C (PKC) protein and activity are increased in skeletal muscle of human diabetic patients. The protein content of different PKC isoforms (beta, Theta, epsilon, delta, mu, and zeta) in the particulate fraction was measured, using Western analysis, in human rectus abdominus skeletal muscle from obese (hyperinsulinemic, normoglycemic) and obese diabetic (hyperinsulinemic, hyperglycemic) subjects. PKC Theta protein content was significantly higher in the particulate fraction of muscle from diabetic patients compared with the nondiabetic controls. PKC Theta was immunoprecipitated and its activity was measured in muscle from diabetic and nondiabetic controls. There was a significant increase in PKC Theta activity in muscle from diabetic patients compared with muscle from nondiabetic controls. Therefore, both PKC Theta protein content and activity were significantly increased in the particulate fraction in muscle from diabetic patients, suggesting the involvement of this isoform in diabetes. Most of the PKC Theta protein was found in the cytosol. There was no change in cytosolic PKC Theta protein content in muscle from diabetic patients compared with muscle from nondiabetic controls. Thus, the increase in particulate-associated PKC Theta was likely due to translocation and activation rather than an increase in protein mass.

Substrate utilization during exercise in formerly morbidly obese women.

The purpose of this study was to compare substrate utilization during fasting and submaximal exercise in morbidly obese women after weight loss (WL) with that in weight-matched controls (C). WL were studied in the weight-stable condition approximately 24 mo after gastric bypass surgery. Energy intake (self-reported) and expenditure ((2)H(2)(18)O) were also compared. The respiratory exchange ratio during exercise at the same absolute (15 W) workload was significantly (P < or = 0.05) elevated in WL vs. C (0.90 +/- 0.02 vs. 0.83 +/- 0.03); this was reflected as lower fat utilization in WL (29.7 +/- 4.8 vs. 53.2 +/- 9.7% of energy from fat). Respiratory exchange ratio during exercise at the same relative (65% of maximal O(2) uptake) intensity was also significantly (P < 0.05) elevated in WL (0.96 +/- 0.01 vs. 0.89 +/- 0.02), and fat use was concomitantly depressed (12.4 +/- 3.0 vs. 34.3 +/- 9.9% of energy from fat). Resting substrate utilization, daily energy expenditure, and self-reported relative macronutrient intake did not differ between groups. These data suggest that lipid oxidation is depressed during physical activity in WL. This defect may, at least in part, contribute to a propensity for the development of morbid obesity.

Involvement of protein kinase C in human skeletal muscle insulin resistance and obesity.

This study was conducted to investigate the possible involvement of protein kinase C (PKC) and serine/threonine phosphorylation of the insulin receptor in insulin resistance and/or obesity. Insulin receptor tyrosine kinase activity was depressed in muscle from obese insulin-resistant patients compared with lean insulin-responsive control subjects. Alkaline phosphatase treatment resulted in a significant 48% increase in in vitro insulin-stimulated receptor tyrosine kinase activity in obese but not lean muscle. To investigate the involvement of PKC in skeletal muscle insulin resistance and/or obesity, membrane-associated PKC activity and the protein content of various PKC isoforms were measured in human skeletal muscle from lean, insulin-responsive, and obese insulin-resistant patients. Membrane-associated PKC activity was not changed; however, PKC-beta protein content, assayed by Western blot analysis, was significantly higher, whereas PKC-theta, -eta, and -mu were significantly lower in muscle from obese patients compared with muscle from lean control subjects. Incubation of muscle strips with insulin significantly increased membrane-associated PKC activity in muscle from obese but not lean subjects. PKC-delta, -beta, and -theta were translocated from the cytosol to the membrane fraction in response to insulin treatment. These results suggest that in skeletal muscle from insulin-resistant obese patients, insulin receptor tyrosine kinase activity was reduced because of hyperphosphorylation on serine/threonine residues. Membrane-associated PKC-beta protein was elevated under basal conditions, and membrane-associated total PKC activity was increased under insulin-stimulated conditions in muscle from obese insulin-resistant patients. Thus, we postulate that the decreased tyrosine kinase activity of the insulin receptor may be caused by serine/threonine phosphorylation by PKC.

Impact of insulin resistance on lipoprotein subpopulation distribution in lean and morbidly obese nondiabetic women.

The purpose of this study was to examine the effects of insulin resistance on the lipoprotein subpopulation distribution of very-low-density, low-density, and high-density lipoproteins (VLDL, LDL, and HDL) in lean and morbidly obese nondiabetic women. Lean women (body mass index [BMI], 20 to 27 kg/m2) stratified by BMI were divided into insulin-sensitive (SL, n = 12) and insulin-resistant (RL, n = 8) groups according to Bergman's minimal model, SI. A group of obese women (BMI, 30 to 53 kg/m2), also stratified by BMI, were divided into insulin-sensitive (SO, n = 10) and insulin-resistant (RO, n = 11) groups in a similar fashion. Resistant groups were similar to sensitive groups (SL v RL and SO vRO) in age, weight, percent body fat, and waist circumference, ie, total and regional adiposity. VLDL, LDL, and HDL subpopulation distributions were determined in fasting plasma samples by nuclear magnetic resonance (NMR) spectroscopy. The average particle sizes of all 3 classes of lipoproteins were similar for the SL and RL groups. In contrast, RO subjects had larger VLDL, smaller LDL, and smaller HDL, than SO subjects (P < .05). Lower concentrations of large LDL and large HDL were found in RO compared with SO subjects (P < .05). In obese women, but not in lean women, VLDL size was associated with plasma insulin (r = .60, P < .005), while LDL size and HDL size were negatively correlated with plasma insulin (r = -.39, P < .05 and r = -.38, P < .05) and positively correlated with SI (r = .54, P < .01 and r = .42, P < .05). These results suggest that in obese women, insulin resistance may be involved in the formation of lipoprotein subpopulation distributions that are associated with vascular disease.

A new paradigm for type 2 diabetes mellitus: could it be a disease of the foregut?

SUMMARY BACKGROUND DATA: We previously reported, in a study of 608 patients, that the gastric bypass operation (GB) controls type 2 diabetes mellitus in the morbidly obese patient more effectively than any medical therapy. Further, we showed for the first time that it was possible to reduce the mortality from diabetes; GB reduced the chance of dying from 4.5% per year to 1% per year. This control of diabetes has been ascribed to the weight loss induced by the operation. These studies, in weight-stable women, were designed to determine whether weight loss was really the important factor. METHODS: Fasting plasma insulin, fasting plasma glucose, minimal model-derived insulin sensitivity and leptin levels were measured in carefully matched cohorts: six women who had undergone GB and had been stable at their lowered weight 24 to 30 months after surgery versus a control group of six women who did not undergo surgery and were similarly weight-stable. The two groups were matched in age, percentage of fat, body mass index, waist circumference, and aerobic capacity. RESULTS: Even though the two groups of patients were closely matched in weight, age, percentage of fat, and even aerobic capacity, and with both groups maintaining stable weights, the surgical group demonstrated significantly lower levels of serum leptin, fasting plasma insulin, and fasting plasma glucose compared to the control group. Similarly, minimal model-derived insulin sensitivity was significantly higher in the surgical group. Finally, self-reported food intake was significantly lower in the surgical group. CONCLUSIONS: Weight loss is not the reason why GB controls diabetes mellitus. Instead, bypassing the foregut and reducing food intake produce the profound long-term alterations in glucose metabolism and insulin action. These findings suggest that our current paradigms of type 2 diabetes mellitus deserve review. The critical lesion may lie in abnormal signals from the gut.

The gastric bypass operation reduces the progression and mortality of non-insulin-dependent diabetes mellitus.

Of 232 morbidly obese patients with non-insulin-dependent diabetes mellitus referred to East Carolina University between March 5, 1979, and January 1, 1994, 154 had a Roux-en-Y gastric bypass operation and 78 did not undergo surgery because of personal preference or their insurance company"s refusal to pay for the procedure. The surgical and the nonoperative (control) groups were comparable in terms of age, weight, body mass index, sex, and percentage with hypertension. The two groups were compared retrospectively to determine differences in survival and the need for medical management of their diabetes. Mean length of follow-up was 9 years in the surgical group and 6.2 years in the control group. The mean glucose levels in the surgical group fell from 187 mg/dl preoperatively and remained less than 140 mg/dl for up to 10 years of follow-up. The percentage of control subjects being treated with oral hypoglycemics or insulin increased from 56.4% at initial contact to 87.5% at last contact (P = 0.0003), whereas the percentage of surgical patients requiring medical management fell from 31.8% preoperatively to 8.6% at last contact (P = 0.0001). The mortality rate in the control group was 28% compared to 9% in the surgical group (including perioperative deaths). For every year of follow-up, patients in the control group had a 4.5% chance of dying vs. a 1.0% chance for those in the surgical group. The improvement in the mortality rate in the surgical group was primarily due to a decrease in the number of cardiovascular deaths.

The workup for bariatric surgery does not require a routine upper gastrointestinal series.

BACKGROUND: Morbid obesity is a serious disease that afflicts over five million Americans, threatening their health with such co-morbidities as diabetes, arthritis, pulmonary failure and stroke. Surgery is the only effective therapy, providing long-term control of weight, diabetes, pulmonary failure, and hypertension for as long as 14 years. Because the operation presents a major expense, this study examined whether X-ray examination of the gut could be omitted safely as a cost-saving measure. METHODS: The records of 814 consecutive morbidly obese patients who underwent gastric bypass were reviewed to determine: (1) whether these individuals had undergone an upper gastro-intestinal (GI) series, and (2) if these studies influenced therapy or caused cancellation or postponement of surgery. RESULTS: Of the 814 patients, 657 (80.7%) underwent a preoperative GI radiography. Of these examinations, 393 (59.8%) were normal, with the following abnormalities in the remaining 264: hiatal hernia, 164; esophageal reflux, 39; Schatzki's ring, 18; small bowel diverticula, four; renal stones, four; malrotation, three; gall stones, two; pyloric ulcer, one; possible pelvic mass, one; calcified leiomyoma, one; and dysphagial lusoria, one. None of these findings resulted in cancellation or a delay in surgery. CONCLUSIONS: The upper GI series can be safely omitted from the routine preoperative evaluation of patients undergoing gastric bypass. At a cost of $741.00 per examination, this change represents significant potential savings. Similar evaluations of other routine preoperative tests may well provide a better basis for the evaluation of these complex patients.

Physicians' perspective on quality of life: an exploratory study of oncologists.

There is an implicit assumption that physicians incorporate quality of life (QOL) information in clinical decision-making. However, very limited data exists on how physicians view QOL information and how they actually use it. To explore this issue, an in-depth study was conducted using a semi-structured interview guide, with 60 oncologists in Canada and the USA. While the majority of respondents perceived QOL as important they reported a tendency to use it informally and not in all situations. Key findings include the belief expressed by 88% of respondents that the term QOL could be defined, although they differed in their definitions. Although 85% stated that QOL can be formally measured, only a third perceived that the current instruments provide valid and reliable data. Respondents noted a number of significant benefits and drawbacks of using QOL data in their clinical practice that had not been previously noted in the literature. For example, its use as an endpoint in clinical trials was generally perceived to enhance both physician and patient participation. A drawback noted was that including QOL might adversely affect the decision-making process. These findings have been used to develop a self-administered questionnaire (MD-QOL) which will test the generalizability of these findings.

A sociobehavioural perspective on genetic testing and counselling for heritable breast, ovarian and colon cancer.

Testing for susceptibility to heritable breast, ovarian and colon cancer has unique psychosocial costs. Negative test results may not be sufficient to relieve anxiety, and positive results can cause sufficient distress to compromise patient compliance with surveillance and risk reduction measures. More needs to be learned about how sociocultural factors affect the understanding of risk, how decisions to undergo testing are made and how information about increased risk affects family dynamics. As the demand for testing and counselling grows, health care providers will be faced with new challenges and dilemmas. A better understanding of genetics by the public is needed to mitigate deterministic attitudes that can lead to the neglect of health promotion. Also of concern are the socioeconomic implications of being identified as having a high risk for heritable cancer and the dangers inherent in using genetics to explain sociological phenomena. Health care providers must take the lead in ensuring that developments in genetics are used to the benefit of all.

Who would have thought it? An operation proves to be the most effective therapy for adult-onset diabetes mellitus.

OBJECTIVE: This report documents that the gastric bypass operation provides long-term control for obesity and diabetes. SUMMARY BACKGROUND DATA: Obesity and diabetes, both notoriously resistant to medical therapy, continue to be two of our most common and serious diseases. METHODS: Over the last 14 years, 608 morbidly obese patients underwent gastric bypass, an operation that restricts caloric intake by (1) reducing the functional stomach to approximately 30 mL, (2) delaying gastric emptying with a c. 0.8 to 1.0 cm gastric outlet, and (3) excluding foregut with a 40 to 60 cm Roux-en-Y gastrojejunostomy. Even though many of the patients were seriously ill, the operation was performed with a perioperative mortality and complication rate of 1.5% and 8.5%, respectively. Seventeen of the 608 patients (< 3%) were lost to follow-up. RESULTS: Gastric bypass provides durable weight control. Weights fell from a preoperative mean of 304.4 lb (range, 198 to 615 lb) to 192.2 lb (range, 104 to 466) by 1 year and were maintained at 205.4 lb (range, 107 to 512 lb) at 5 years, 206.5 lb (130 to 388 lb) at 10 years, and 204.7 lb (158 to 270 lb) at 14 years. The operation provides long-term control of non-insulin-dependent diabetes mellitus (NIDDM). In those patients with adequate follow-up, 121 of 146 patients (82.9%) with NIDDM and 150 of 152 patients (98.7%) with glucose impairment maintained normal levels of plasma glucose, glycosylated hemoglobin, and insulin. These antidiabetic effects appear to be due primarily to a reduction in caloric intake, suggesting that insulin resistance is a secondary protective effect rather than the initial lesion. In addition to the control of weight and NIDDM, gastric bypass also corrected or alleviated a number of other comorbidities of obesity, including hypertension, sleep apnea, cardiopulmonary failure, arthritis, and infertility. Gastric bypass is now established as an effective and safe therapy for morbid obesity and its associated morbidities. No other therapy has produced such durable and complete control of diabetes mellitus.

Gastrogastric fistulas. A complication of divided gastric bypass surgery.

OBJECTIVE: This report warns that gastrogastric fistulas may follow the division of the stomach in bariatric surgery. SUMMARY BACKGROUND DATA: Although surgery is the most effective therapy for morbid obesity, the procedures are still undergoing evolution. One of the key elements in bariatric surgery is the partition of the stomach to develop a much smaller reservoir. The partition has been done with single layers of staples with almost universal failure and with double layers of staples with a failure rate of 11.8% when observed for a 12-year follow-up. METHODS: This report details the experience with a series of 100 consecutive patients in whom the partition was created by dividing the stomach. RESULTS: The course of six patients was complicated by gastrogastric fistulas. One of the patients had the gastric bypass as the initial bariatric operation; in the other five, the gastric bypasses were carried out to revise failed staple lines. Although one of the patients required drainage for a subphrenic abscess, two had only self-limited signs of infection. In the remaining three patients, there was no evidence of any complication. CONCLUSION: Gastrogastric fistulas followed division of the stomach in 6% of our gastric bypass operations. Methods for avoiding this complication include oversewing staple lines, using strong bites of tissue during the anastomosis, avoiding obstruction of the Roux-en-Y jejunal segment, and testing of the integrity of the anastomosis with methylene blue dyes. The ideal method for partition of the stomach remains to be developed.

A multicenter, placebo-controlled, randomized, double-blind, prospective trial of prophylactic ursodiol for the prevention of gallstone formation following gastric-bypass-induced rapid weight loss.

BACKGROUND: Previous studies have documented a high incidence of gallstone formation following gastric-bypass (GBP)-induced rapid weight loss in morbidly obese patients. This study was designed to determine if a 6-month regimen of prophylactic ursodiol might prevent the development of gallstones. METHODS: A multicenter, randomized, double-blind, prospective trial evaluated 3 oral doses of ursodiol: 300, 600, and 1,200 mg versus placebo beginning within 10 days after surgery and continuing for 6 months or until gallstone development, for patients with a body mass index (BMI) > or = 40 kg/m2. All patients had normal intraoperative gallbladder sonography. Transabdominal sonography was obtained at 2, 4, and 6 months following surgery, or until gallstone formation. RESULTS: Of 233 patients with at least one postoperative sonogram, 56 were randomized to placebo, 53 to 300 mg ursodiol, 61 to 600 mg ursodiol, and 63 to 1,200 mg ursodiol. Preoperative age, sex, race, weight, BMI, and postoperative weight loss were not significantly different between groups. Gallstone formation occurred at 6 months in 32%, 13%, 2%, and 6% of the patients on the respective doses. Gallstones were significantly (P < 0.001) less frequent with ursodiol 600 and 1,200 mg than with placebo. CONCLUSION: A daily dose of 600 mg ursodiol is effective prophylaxis for gallstone formation following GBP-induced rapid weight loss.

Weight loss in severely obese subjects prevents the progression of impaired glucose tolerance to type II diabetes. A longitudinal interventional study.

OBJECTIVE: To determine if weight loss may prevent conversion of impaired glucose tolerance (IGT) to diabetes, because weight loss reduces insulin resistance. The prevalence of IGT in the U.S. population is estimated at 11.2%, more than twice that of diabetes. Furthermore, because an oral glucose tolerance test is needed for its detection, most of these patients are undiagnosed. Screening for IGT would be meaningful if progression to diabetes could be delayed or prevented. RESEARCH DESIGN AND METHODS: For an average of 5.8 years (range 2-10 years), 136 individuals with IGT and clinically severe obesity (> 45 kg excess body weight) were followed. The experimental group included 109 patients with IGT who underwent bariatric surgery for weight loss. The control group was made up of 27 subjects with IGT who did not have bariatric surgery. The criteria of the World Health Organization was used to detect IGT and diabetes in this population. The main outcome measure of this nonrandomized control trial is the incidence density, or number of events (development of diabetes) divided by the time of exposure to risk. RESULTS: Of the 27 subjects in the control group, 6 developed diabetes during an average of 4.8 +/- 2.5 years of postdiagnosis follow-up, yielding a rate of conversion to diabetes of 4.72 cases per 100 person-years. The 109 individuals of the experimental group were followed for an average of 6.2 +/- 2.5 years postbariatric surgery. Based on the 95% confidence interval of the comparison group, we would expect to find that between 22 and 36 subjects in the experimental group developed diabetes over the follow-up period. Only 1 of the 109 experimental-group patients developed diabetes, resulting in a conversion rate of the experimental group of only 0.15 cases per 100 person-years, which is significantly lower (P < 0.0001) than the control group. CONCLUSIONS: Weight loss in patients with clinically severe obesity prevents the progression of IGT to diabetes by > 30-fold.

Large-bore feeding tube occlusion by yeast colonies.

This is a first report of three patients with silicone feeding tubes (two with percutaneous endoscopic gastrostomies and one with a jejunostomy, all 20 French catheters) that have formed a thick yeast crust on the inner luminal surface causing tube occlusion in two cases. Candida species were isolated in all three tubes. The yeast crust could not be removed with a brush or with fungicidal drugs such as nystatin and amphotericin B. Histologic sections through these feeding tubes revealed yeast penetration through the silicone material, explaining the adherent nature of the crust. This complication may also explain the observed material deterioration with subsequent breakage.