Resilience-Informed Community Violence Prevention and Community Organizing Strategies for Implementation: Protocol for a Hybrid Type 1 Implementation-Effectiveness Trial

BACKGROUND

Community violence is a persistent and challenging public health problem. Community violence not only physically affects individuals, but also its effects reverberate to the well-being of families and entire communities. Being exposed to and experiencing violence are adverse community experiences that affect the well-being and health trajectories of both children and adults. In the United States, community violence has historically been addressed through a lens of law enforcement and policing; the impact of this approach on communities has been detrimental and often ignores the strengths and experiences of community members. As such, community-centered approaches to address violence are needed, yet the process to design, implement, and evaluate these approaches is complex. Alternatives to policing responses are increasingly being implemented. However, evidence and implementation guidance for community-level public health approaches remain limited. This study protocol seeks to address community violence through a resilience framework-Adverse Community Experiences and Resilience (ACE|R)-being implemented in a major US city and leveraging a strategy of community organizing to advance community violence prevention.

OBJECTIVE

The objective of this research is to understand the impact of community-level violence prevention interventions. Furthermore, we aim to describe the strategies of implementation and identify barriers to and facilitators of the approach.

METHODS

This study uses a hybrid type 1 effectiveness-implementation design. Part 1 of the study will assess the effectiveness of the ACE|R framework plus community organizing by measuring impacts on violence- and health-related outcomes. To do so, we plan to collect quantitative data on homicides, fatal and nonfatal shootings, hospital visits due to nonaccidental injuries, calls for service, and other violence-related data. In Part 2 of the study, to assess the implementation of ACE|R plus community organizing, we will collect process data on community engagement events, deliver community trainings on community leadership and organizing, and conduct focus groups with key partners about violence and violence prevention programs in Milwaukee.

RESULTS

This project received funding on September 1, 2020. Prospective study data collection began in the fall of 2021 and will continue through the end of 2023. Data analysis is currently underway, and the first results are expected to be submitted for publication in 2024.

CONCLUSIONS

Community violence is a public health problem in need of community-centered solutions. Interventions that center community and leverage community organizing show promise in decreasing violence and increasing the well-being of community members. Methods to identify the impact of community-level interventions continue to evolve. Analysis of outcomes beyond violence-specific outcomes, including norms and community beliefs, may help better inform the short-term and proximal impacts of these community-driven approaches. Furthermore, hybrid implementation-effectiveness trials allow for the inevitable contextualization required to disseminate community interventions where communities drive the adaptations and decision-making.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/50444.

Media representation, perception and stigmatisation of race, sexuality and HIV among young black gay and bisexual men

Young Black gay and bisexual men who have sex with men experience stigma related to race, gender expression, sexuality and HIV status. Stigma impacts access to HIV care and prevention as well as interactions with healthcare providers. The amplification of stigma through popular media is under-researched in the health sciences. HealthMpowerment is a mobile phone optimised intervention to reduce sexual risk and support community-building for young Black gay and bisexual men (age 18-30). We analysed Forum conversations from 48 participants, 45.8% living with HIV. Of 322 stigma-relevant conversations, 18.9% referenced the media (e.g. television, news, social media) as a source of stigma. Forum conversations covered media representations of Black gay and bisexual men, media's influence on identity, and the creation of stigma by association with media representations. Cultural messages embedded in the media may accentuate stereotypes that influence perceptions of Black gay and bisexual men and disregard intersectional identities. HealthMpowerment provided a space to challenge stigmatising representations. Participants used HealthMpowerment to garner social support and celebrate positive media representations. Interventions for young Black gay and bisexual men should consider the influential role of media and include spaces for participants to process and address stigma.

"I refused to drink but they still forced me": A mixed-methods approach to understanding the pathways to reduce alcohol use among Vietnamese people with HIV

AIMS

This study explores the effects of two evidence-based alcohol reduction counseling interventions on readiness to change, alcohol abstinence self-efficacy, social support, and alcohol abstinence stigma among people with HIV (PWH) who have hazardous alcohol use in Vietnam.

METHODS

PWH receiving antiretroviral therapy (ART) were screened for hazardous drinking and randomized to one of three study arms: combined intervention (CoI), brief intervention (BI), and standard of care (SOC). A quantitative survey was conducted at baseline (N = 440) and 3-month post-intervention (N = 405), while in-depth interviews were conducted with a subset of BI and CoI participants at baseline (N = 14) and 3 months (N = 14). Data was collected from March 2016 to August 2017. A concurrent mixed-methods model was used to triangulate quantitative and qualitative data to cross-validate findings.

RESULTS

At 3 months, receiving the BI and CoI arms was associated with 2.64 and 3.50 points higher in mean readiness to change scores, respectively, compared to the SOC group (BI: β = 2.64, 95% CI: 1.17-4.12; CoI: β = 3.50, 95% CI 2.02-4.98). Mean alcohol abstinence self-efficacy scores were 4.03 and 3.93 points higher among the BI and CoI arm at 3 months, compared to SOC (BI: β = 4.03, 95% CI: 0.17-7.89; CoI: β = 3.93, 95% CI: 0.05-7.81). The impacts of the interventions on social support and alcohol abstinence stigma were not significant. Perceived challenges to refusing drinks at social events remained due to strong alcohol abstinence stigma and perceived negative support from family and friends who encouraged participants to drink posed additional barriers to reducing alcohol use.

CONCLUSIONS

Both the CoI and BI were effective in improving readiness to change and alcohol abstinence self-efficacy among PWH. Yet, participants still faced significant barriers to reducing their drinking due to social influences and pressure to drink. Interventions at different levels addressing social support and alcohol abstinence stigma are warranted.

Implementation of mandatory opioid prescribing limits in North Carolina: healthcare administrator and prescriber perspectives

BACKGROUND

Recent increases in state laws to reduce opioid prescribing have demonstrated a need to understand how they are interpreted and implemented in healthcare systems. The purpose of this study was to explore the systems, strategies, and resources that hospital administrators and prescribers used to implement the 2017 North Carolina Strengthen Opioid Prevention (STOP) Act opioid prescribing limits, which limited initial prescriptions to a five (for acute) or seven (for post-surgical) days' supply.

METHODS

We interviewed 14 hospital administrators and 38 prescribers with degrees in medicine, nursing, pharmacy, business administration and public health working across North Carolina. Interview guides, informed by the Consolidated Framework for Implementation Research, explored barriers and facilitators to implementation. Interview topics included communication, resources, and hospital system support. Interviews were recorded and transcribed, then analyzed using flexible coding, integrating inductive and deductive coding, to inform analytic code development and identify themes.

RESULTS

We identified three main themes around implementation of STOP act mandated prescribing limits: organizational communication, prescriber education, and changes in the electronic medical record (EMR) systems. Administrators reflected on implementation in the context of raising awareness and providing reminders to facilitate changes in prescriber behavior, operationalized through email and in-person communications as well as dedicated resources to EMR changes. Prescribers noted administrative communications about prescribing limits often focused on legality, suggesting a directive of the organization's policy rather than a passive reminder. Prescribers expressed a desire for more spaces to have their questions answered and resources for patient communications. While hospital administrators viewed compliance with the law as a priority, prescribers reflected on concerns for adequately managing their patients' pain and limited time for clinical care.

CONCLUSIONS

Hospital administrators and prescribers approached implementation of the STOP act prescribing limits with different mindsets. While administrators were focused on policy compliance, prescribers were focused on their patients' needs. Strategies to implement the mandate then had to balance patient needs with policy compliance. As states continue to legislate to prevent opioid overdose deaths, understanding how laws are implemented by healthcare systems and prescribers will improve their effectiveness through tailoring and maximizing available resources.

The Cost-Effectiveness of Adapting and Implementing a Brief Intervention to Target Frequent Alcohol Use Among Persons with HIV in Vietnam

Brief interventions to reduce frequent alcohol use among persons with HIV (PWH) are evidence-based, but resource-constrained settings must contend with competition for health resources. We evaluated the cost-effectiveness of two intervention arms compared to the standard of care (SOC) in a three-arm randomized control trial targeting frequent alcohol use in PWH through increasing the percent days abstinent from alcohol and viral suppression. We estimated incremental cost per quality-adjusted life year (QALY) gained from a modified societal perspective and a 1-year time horizon using a Markov model of health outcomes. The two-session brief intervention (BI), relative to the six-session combined intervention (CoI), was more effective and less costly; the estimated incremental cost-effectiveness of the BI relative to the SOC, was $525 per QALY gained. The BI may be cost-effective for the HIV treatment setting; the health utility gained from viral suppression requires further exploration.

Building Community in the HIV Online Intervention Space: Lessons From the HealthMPowerment Intervention

BACKGROUND

Mobile health platforms can facilitate social support and address HIV (human immunodeficiency virus) stigma but pose challenges for intervention design and participant engagement. Giddens's structuration theory, that individuals are shaped by-and shape-their communities through rules and resources that give them power to operate within these environments, provides a useful analytic framework for exploring these dynamic intervention spaces.

METHOD

Data were drawn from an online randomized controlled trial intervention (HealthMpowerment) for young Black men who have sex with men to reduce condomless anal intercourse. We applied a conversational analysis informed by structuration theory to 65 user-generated conversations that included stigma content. We aimed to understand how the interdependent relationship between the intervention space and participants' contributions might contribute to behavior change.

RESULTS

Thirty five intervention participants contributed to the analyzed conversations. Our analysis identified three types of conversational processes that may underlie behavior change: (1) Through intervention engagement, participants established norms and expectations that shaped their discussions; (2) participants used anecdotes and anonymity to reinforce norms; and (3) intervention staff members sought to improve engagement and build knowledge by initiating discussions and correcting misinformation, thus playing an integral role in the online community.

CONCLUSIONS

The lens of structuration theory usefully reveals potential behavior change mechanisms within the social interactions of an online intervention. Future design of these interventions to address HIV stigma should explicitly characterize the context in which individuals (study staff and participants) engage with one another in order to assess whether these processes are associated with improved intervention outcomes.

Implementation of two alcohol reduction interventions among persons with hazardous alcohol use who are living with HIV in Thai Nguyen, Vietnam: a micro-costing analysis

BACKGROUND

Hazardous alcohol use is detrimental to persons with HIV (PWH), impacting medication adherence and liver function, yet globally resources to target alcohol use behavior in this population are limited. Few studies have identified the costs of integrating alcohol reduction interventions into HIV care.

OBJECTIVE

To estimate the costs of implementing and delivering two evidence-based behavioral counseling interventions targeting hazardous alcohol use among persons with HIV and to estimate the costs of scale-up in ART clinics in Thai Nguyen, Vietnam.

METHODS

We undertook a micro-costing approach to determine the costs of delivering two adapted evidence-based interventions to reduce alcohol use: an intensive combined cognitive behavioral therapy and motivational enhancement therapy-informed intervention (CoI) and an abbreviated brief alcohol intervention (BI). A total of 294 participants with hazardous alcohol use were identified through a brief screening tool and received the CoI (n = 147) and the BI (n = 147) over 3 months. We estimated costs using time and motion studies, budget analysis, staff interviews, and participant questionnaires. Data were collected from 2016 to 2018 in VND and converted to USD.

RESULTS

The total cost of implementation and administration of the intervention to 147 participants receiving the CoI was $13,900 ($95 per participant) and to 147 participants receiving the BI was $5700 ($39 per participant). Implementation and startup costs including training accounted for 27% of costs for the CoI and 28% for the BI. Counselor costs accounted for a large proportion of both the CoI (41%) and the BI (30%).

CONCLUSIONS

Implementing and delivering alcohol reduction interventions to people with HIV in Vietnam with appropriate fidelity is costly. These costs may be reduced, particularly counselor labor costs, by using an evidence-based brief intervention format. Future research should explore the budgetary impact of brief and combined interventions to reduce hazardous alcohol use, particularly among vulnerable populations.

"Stay strong! keep ya head up! move on! it gets better!!!!": resilience processes in the healthMpowerment online intervention of young black gay, bisexual and other men who have sex with men

Overlapping stigmas related to sexual minority-, race/ethnicity-, and HIV-status pose barriers to HIV prevention and care and the creation of supportive social networks for young, Black, gay, bisexual, and other men who have sex with men (GBMSM). A risk-based approach to addressing the HIV epidemic focuses on what is lacking and reinforces negative stereotypes about already-marginalized populations. In contrast, a strengths-based approach builds on Black GBMSM’s existing strengths, recognizing the remarkable ways in which they are overcoming barriers to HIV prevention and care. HealthMpowerment (HMP) is an online, mobile phone optimized intervention that aimed to reduce condomless anal intercourse and foster community among young Black GBMSM (age 18–30). Applying a resilience framework, we analyzed 322 conversations contributed by 48 HMP participants (22/48 living with HIV) on the intervention website. These conversations provided a unique opportunity to observe and analyze dynamic, interpersonal resilience processes shared in response to stigma, discrimination, and life challenges experienced by young Black GBMSM. We utilized an existing framework with four resilience processes and identified new subthemes that were displayed in these online interactions: (1) Exchanging social support occurred through sharing emotional and informational support. (2) Engaging in health-promoting cognitive processes appeared as reframing, self-acceptance, endorsing a positive outlook, and agency and taking responsibility for outcomes. (3) Enacting healthy behavioral practices clustered into modeling sex-positive norms, reducing the risk of acquiring or transmitting HIV, and living well with HIV. (4) Finally, empowering other gay and bisexual youth occurred through role modeling, promoting self-advocacy, and providing encouragement. Future online interventions could advance strengths-based approaches within HIV prevention and care by intentionally building on Black GBMSM’s existing resilience processes. The accessibility and anonymity of online spaces may provide a particularly powerful intervention modality for amplifying resilience among young Black GBMSM.

Characteristics of persons who inject drugs and who witness opioid overdoses in Vietnam: a cross-sectional analysis to inform future overdose prevention programs

BACKGROUND

Persons who use opioids have a high risk of overdose and associated mortality. In Vietnam, little is known about the characteristics of this population and the persons who are witness to those overdoses. One approach to combatting fatal overdose has been the use of peer interventions in which a friend or injecting partner administers overdose reversal medication, but availability in Vietnam of these medications is limited to pilot programs with aims to expand in the future (Le Minh and V.F. Go, Personal Communication, 2016). The primary objective of this paper is to explore the characteristics associated with witnessing three or more overdoses in a lifetime.

METHODS

This cross-sectional analysis used baseline data from a four-arm randomized control trial conducted in Thai Nguyen, Vietnam, known as the Prevention for Positives project. One thousand six hundred seventy-three PWID were included in the analysis. We conducted bivariable and multivariable logistic regression to identify characteristics associated with witnessing three or more overdoses in a lifetime. Characteristics explored included education, employment, marital status, risky drug use behaviors, locations for accessing syringes, recent overdose, history of incarceration, drug treatment, and having slept outside in the past 3 months.

RESULTS

Seventy-two percent (n = 1203) of participants had witnessed at least one overdose in their lifetime, and 46% had witnessed three or more overdoses (n = 765). In the multivariable model, having less than secondary education (AOR 0.70; 95% CI 0.57, 0.86), having slept outside in the past 3 months (AOR 1.77; 95% CI 1.31, 2.40), having a history of incarceration (AOR 1.33; 95% CI 1.07, 1.65), having a history of drug treatment (AOR 1.41; 95% CI 1.12, 1.77), experiencing a recent non-fatal overdose (AOR 3.84; 95% CI 2.36, 6.25), injecting drugs daily (AOR 1.79; 95% CI 1.45, 2.20), receptive needle sharing (AOR 1.30; 95% CI 1.04, 1.63), and number of years injecting (AOR 1.04; 95% CI 1.02, 1.07) were significantly associated with witnessing three or more overdoses.

CONCLUSIONS

Targeted interventions are needed to train persons witnessing an overdose to administer overdose-reversal medication. This includes targeting persons prior to release from prisons, drug treatment centers, and those accessing syringe exchange programs. Additional research should assess the burden of witnessing an overdose as well as locations for medication distribution. Assessments of the training capacity and needs for implementing these programs among drug using peers in Vietnam are of the utmost importance.

Improving Screening Methods for Hepatitis C Among People Who Inject Drugs: Findings from the HepTLC Initiative, 2012-2014

OBJECTIVE

People who inject drugs (PWID) are at increased risk for hepatitis C virus (HCV) infection. We examined HCV testing outcomes among PWID through CDC's Hepatitis Testing and Linkage to Care initiative, which promoted viral hepatitis B and hepatitis C screening, posttest counseling, and linkage to care at 34 U.S. sites during 2012-2014. Ten grantees in nine geographically diverse cities conducted HCV testing among PWID.

METHODS

Among those testing positive for HCV antibody (anti-HCV), we calculated the proportion who were offered a confirmatory HCV ribonucleic acid (RNA) test, positively diagnosed, and referred to a specialist for care. We stratified anti-HCV-positive people who completed each step by same-day testing (i.e., an HCV RNA test administered on the same date as an anti-HCV test) vs. person not receiving same-day testing to evaluate whether the need for follow-up testing affected diagnosis of chronic infection and linkage to care.

RESULTS

A total of 15,274 people received an anti-HCV test at 84 testing sites targeting PWID. Of those, 11,159 (73%) reported having injected drugs in their lifetime, 7,789 (51%) reported injecting drugs in the past 12 months, and 3,495 (23%) tested anti-HCV positive. A total of 1,630 people received testing for HCV RNA, of whom 1,244 (76%) were HCV RNA positive. When not receiving both tests on the same day, 601 of 2,465 (24%) anti-HCV-positive people received an HCV RNA test.

CONCLUSION

Strategies to diagnose PWID for HCV infection are needed to reduce associated morbidity and mortality. Agencies can substantially increase the number of PWID who are diagnosed and informed of their HCV infection by administering both anti-HCV and HCV RNA tests during a single testing event.

Past-year prevalence of prescription opioid misuse among those 11 to 30years of age in the United States: A systematic review and meta-analysis

BACKGROUND

There are high levels of prescription and consumption of prescription opioids in the US. Misuse of prescription opioids has been shown to be highly correlated with prescription opioid-related morbidity and mortality including fatal and non-fatal overdose. We characterized the past-year prevalence of prescription opioid misuse among those 11-30years of age in the US.

METHODS

A systematic review and meta-analysis were carried out following a published protocol and PRISMA guidelines. We searched electronic databases; reports were eligible if they were published between 1/1/1990-5/30/2014, and included data on individuals 11-30years of age from the US. Study quality was assessed using the Newcastle-Ottawa Scale.

RESULTS

A total of 3211 abstracts were reviewed for inclusion; after discarding duplicates and identifying non-eligible reports, a total of 19 unique reports, providing 34 estimates, were included in the final systematic review and meta-analysis. The range of past-year prescription opioid misuse prevalence the reports was 0.7%-16.3%. An increase in prevalence of 0.4% was observed over the years of data collection.

CONCLUSIONS

This systematic review and meta-analysis found a high prevalence of past-year prescription opioid misuse among individuals 11-30years of age. Importantly, we identified an increase in past-year prevalence 1990-2014. Misuse of prescription opioids has played an important role in national increases of fatal and non-fatal drug overdose, heroin use and injection, and HIV and HCV infection among young people. The observed high and increasing prevalence of prescription opioid misuse is an urgent public health issue.

A comparison of the effects of controlled-release levodopa (Madopar CR) with conventional levodopa in late Parkinson's disease

In this multicentre study a controlled-release formulation of levodopa and the decarboxylase inhibitor benserazide (Madopar CR) was evaluated in patients with Parkinson's disease exhibiting dose-related fluctuations in motor performance in response to conventional levodopa preparations. The effect of Madopar CR, with or without conventional levodopa/benserazide, on the proportion of time spent "on", "off" or "intermediate" was compared with that of previous conventional levodopa/decarboxylase inhibitor therapy. Evaluation of the two periods of optimum therapy was based on both patient diary data and investigator opinion. Forty seven patients completed the study but full patient diaries were available for only 37. The mean optimum total daily dosage of conventional Madopar was 820 mg taken in a mean of 6.4 doses, compared with a mean optimum daily dosage of combined Madopar CR and conventional Madopar of 1088 mg, taken in a mean of 5.2 doses. Conventional Madopar was taken in addition to Madopar CR in all but eight patients. Madopar CR was felt to be advantageous in 83% and disadvantageous in 11% of patients completing the study. Considering the 37 patients for whom diary data were available, Madopar CR therapy resulted in an increase in the mean time spent "on" (p = 0.016) and a decrease in the mean time spent "off" (p = 0.029) compared with conventional Madopar alone. Individually 25 out of 37 had an increase in "on" time and 19 out of 37 experienced a decrease in "off" time. Thus Madopar CR was found to be beneficial in a significant proportion of patients experiencing fluctuations in response to conventional levodopa.

The nighttime problems of Parkinson's disease

In a national survey conducted among 220 patients with Parkinson's disease (PD), 215 reported experiencing disabilities at night or on waking. The most common problems were inability to turn over or get out of bed and a frequent need to pass urine during the night. For the majority of patients, sleep was disrupted. Despite these difficulties, two-thirds of patients rated sleep quality as acceptable or good. The average duration of sleep was 6.5-7 h but approximately 8% of patients reported less than 5 h sleep per night. Hypnotic or sedative drugs were used by 29% of patients to help them sleep but only 6% took any antiparkinsonian medication during the night. Just over half the patients had told their doctor of nocturnal problems; prescription of hypnotic drugs or changes to antiparkinsonian therapy were the remedies most frequently tried. Problems at night are common in PD and, because of their debilitating effect on performance during the daytime, merit special attention.

Viscosity of food gums determined in vitro related to their hypoglycemic actions

Experiments were carried out in vitro and in normal human subjects to evaluate alternative food-grade viscous polysaccharides as agents for reducing postprandial hyperglycemia and to assess the relationship between the in vitro and in vivo performance of the polysaccharides. A 1:1 mixture of xanthan and locust bean gum (X/LBG) had the greatest viscosity at equivalent concentrations and shear rates and was more effective than guar gum, xanthan, or locust-bean gum at inhibiting glucose movement in vitro. It was not, however, more efficient in lowering postprandial blood glucose and plasma insulin in human subjects when incorporated in a drink containing 50 g glucose. When the different gums were acidified and reneutralized to mimic conditions in the gut, there was a better correlation between viscosity and blood glucose and plasma insulin levels. This effect may explain why X/LBG was no more effective than the other gums in reducing postprandial hyperglycemia in man.

Does guar gum improve post-prandial hyperglycaemia in humans by reducing small intestinal contact area?

The possibility that viscous polysaccharides, such as guar gum, could lower post-prandial blood glucose levels in part by restricting carbohydrate solutions to a smaller area of small intestine was investigated in twenty healthy human volunteers. Addition of guar gum (22.5 g/l) delayed the mouth-to-caecum transit time of a hypotonic lactulose drink, but did not affect gastric emptying. When a 250 ml solution containing 50 g glucose was confined to a 550 mm length of intestine by an occluding balloon attached to an intestinal tube, maximum blood glucose response was significantly reduced (P less than 0.05) though only by 0.9 mmol/l. Addition of guar gum (36 g/l) had no effect on the distribution of a radio-labelled glucose drink (250 ml; 200 g glucose/l) in the small intestine, monitored using a gamma camera, although it significantly delayed gastric emptying (t 1/2 (min): guar gum v. control 115 (SE 15) v. 73 (SE 8)). Reduced contact area is unlikely to be one of the mechanisms by which guar gum improves glucose tolerance.

The effect of ispaghula (Fybogel and Metamucil) and guar gum on glucose tolerance in man

The effects of incorporating Fybogel (3.5 and 7 g doses), Metamucil (7 g) or guar gum (2.5 and 14.5 g doses) in a drink containing 50 g glucose on plasma glucose, plasma insulin and gastric emptying were studied in thirty-eight normal volunteers. In addition, the effects of Fybogel (7 g) on glucose tolerance, plasma insulin and gastric emptying were measured in fourteen non-insulin-dependent diabetics. Both doses of guar gum significantly lowered plasma glucose and plasma insulin responses to the oral glucose load in normal subjects, although 14.5 g guar gum did not delay the half-time for gastric emptying. Neither Fybogel nor Metamucil had significant effects on plasma glucose responses in normal subjects. In addition, Fybogel (at either dose) had no significant effects on plasma insulin levels, or on gastric emptying in normal subjects or on plasma glucose and insulin responses in diabetic patients. The viscosity of ispaghula solutions ( Fybogel ) was lower than that of guar gum solutions.

The mechanism of action of guar gum in improving glucose tolerance in man

Experiments were carried out in human volunteers to investigate the mechanism by which guar gum improves glucose tolerance. Guar reduced both plasma glucose and insulin responses to an oral glucose load, and delayed gastric emptying. However, there was no correlation between changes in individual blood glucose responses and changes in gastric emptying rates induced by guar. With a steady-state perfusion technique, glucose absorption was found to be significantly reduced during perfusion of the jejunum with solutions containing guar, but returned to control values during subsequent guar-free perfusions. Preperfusing the intestine with guar did not affect electrical measurements of unstirred layer thickness in the human jejunum in vivo. Experiments in vitro established that glucose diffusion out of a guar/glucose mixture was delayed under conditions of constant stirring. We conclude that guar improves glucose tolerance predominantly by reducing glucose absorption in the small intestine. It probably does this by inhibiting the effects of intestinal motility on fluid convection.

The influence of guar gum on intestinal cholesterol transport in the rat

Everted sacs of rat proximal small intestine were used to determine the effect of guar gum (5 g/l) on the uptake of cholesterol (0.1 mM) from a solution of micelles. The uptake of cholesterol was found to be linear both in the presence and absence of guar gum. When guar was present throughout the whole of the incubation medium, the uptake of cholesterol was reduced to approximately 40% of control values. Sacs which had been pre-incubated in guar gum before exposure to cholesterol in a guar-free medium also showed a reduction in cholesterol uptake but this was less pronounced. A two-stage perfusion technique, previously described (Blackburn & Johnson, 1981), was used to determine the effect of a guar layer adsorbed to the mucosal surface on cholesterol absorption in vivo. Such a layer leads to a reduction of approximately 36%; it was concluded that guar slows the absorption of cholesterol from micelles by a mechanism, or mechanisms, involving an increased resistance to diffusion in the aqueous medium. Groups of rats were meal-fed for at least 30 d on semi-synthetic diets with or without the inclusion of guar gum (20 g/kg). Rates of intestinal absorption of cholesterol, glucose and fluid were then determined by the perfusion technique in vivo. There was no reduction in absorption in the test animals compared with the controls. It is proposed that guar gum is able to slow the intestinal transport of cholesterol from a suspension of pre-formed micelles, but only when both are present in the lumen together. No evidence was obtained to suggest that the consumption by rats of a diet containing guar gum, at a level similar to that used in human studies, leads to any adaptive reduction in their rates of cholesterol or glucose absorption.

The influence of guar gum on the movements of inulin, glucose and fluid in rat intestine during perfusion in vivo

A two-stage perfusion technique was used to study the effect of guar gum on the inulin-accessible space and the uptake of water and glucose in rat intestine. Pre-perfusion of test loops with low concentrations of guar, dispersed in saline, modified the rate of equilibration of inulin with the mucosal fluid space during a subsequent perfusion. The glucose absorption rate in such loops was reduced at a concentration of 50 mM, but not at 100 or 150 mM glucose. Fluid absorption was inhibited by pre-treatment with guar gum at all glucose concentrations tested. These results suggest that guar forms a layer closely associated with the mucosal surface which modifies the viscosity of the immediate fluid compartment, so that its resistance to diffusion is increased by means of an unstirred layer effect.

The effect of guar gum on the viscosity of the gastrointestinal contents and on glucose uptake from the perfused jejunum in the rat

1. Male Wistar rats were meal-fed for at least 10 d a control semi-synthetic diet containing no guar gum, or one of three similar test diets containing 3, 10 or 20 g dry guar gum/kg. 2. Rats were killed 6 h after feeding, and contents of stomach, small and large intestine were collected separately. The apparent viscosities of stomach and small intestine contents from animals fed on diets containing 10 and 20 g guar gum/kg were increased relative to control animals, but large intestine contents were unchanged. 3. In the second part of this study, male Wistar rats were anaesthetized and two consecutive lengths of jejunum were perfused, initially with Ringer only (control) or Ringer plus 5 or 6 g guar gum/1 (test). Following this pre-perfusion, both segments were perfused with Ringer containing glucose (10 mM), [3H]glucose and [14C]inulin, and the rate of glucose absorption was determined. 4. The rate of glucose absorption was decreased relative to control values in segments pre-perfused with both 5 and 6 g guar gum/1 solution, but this reduction was significant only in the instance of the 6 g/l solution (P less than 0.001). 5. These results provide evidence to support previous assumptions that ingestion of guar gum will increase the apparent viscosity of the contents of the stomach and small intestine. We propose that a possible mechanism by which guar reduces post-prandial glycaemia is a reduction of glucose absorption from the small intestine, resulting from an increase in viscosity of the contents.