Ester-related volatile compounds reveal the diversity and commonalities of different types of late-ripening peaches.

To recognize the key ester-related volatile compounds, 5 types of peaches including 54 late-ripening peach materials were examined by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry and E-nose. Here, a large number of esters were identified to be released by ripe peach fruits and were mainly characterized by fruity, green, and fatty notes. The variety and content of esters had greatly changed within or between cultivars, indicating that the fruit volatiles were highly differentiated depending on the specific genotypes and cultivation conditions. The ester types showed that fatty acid-derived C6 alcohols and methyl-/ethyl- short-chain alcohol were the main ester precursors, which were more likely to be utilized and well selected by alcohol acyltransferases, whereas the preference of acyl donors was not observed. The common peach type, which exhibited a unique volatile profile, displayed broader diversity and more abundant characteristics in ester-related volatiles than the other four types. A total of 19 key esters were identified as the main components and the content of most esters showed no significant difference among different peach types. Some key esters had even been enriched in nectarines. Moreover, the multiple discriminant analysis revealed a possible relationship between peach types and the domestication of the peach evolution. This study investigated ester-related volatiles released by different types of peach fruits and can be further used to evaluate the peach qualities, providing an important reference for peach breeding and processing.

Relationship of circulating levels of long-chain fatty acids to persistent organ failure in acute pancreatitis.

During acute pancreatitis (AP), free fatty acids (FFAs) are liberated from circulating triglycerides (TG) and injured adipocytes by pancreatic lipase. Circulating FFAs have been suspected as a source of systemic lipotoxicity in AP. However, assessment of FFAs is difficult and time-consuming, and little is known about relative levels of FFAs between patients with different severities of AP and controls. This study's aims were to assess early circulating levels of FFAs, (both saturated and unsaturated) in patients with AP vs. controls, and associations between FFA levels and AP severity. Serum samples from patients with AP were collected at enrollment (day 1 of hospital stay); serum samples were also collected from controls. FFAs including palmitic, palmitoleic, stearic, oleic, and linoleic acid were extracted and quantitated using gas chromatography separation. Severity of AP was determined by Revised Atlanta Classification. Differences in FFA levels and percentages of total FFAs were assessed between patients with AP and controls and patients with AP of different severity grades. A total of 93 patients with AP (48 female, 52%) and 29 controls (20 female, 69%) were enrolled. Of the patients with AP, 74 had mild/moderate and 19 had severe AP. Serum levels of all FFAs except stearic acid were significantly higher in patients with AP compared with controls. A strong and independent association between elevated palmitoleic acid levels and severe AP was found. Serum unsaturated FFA levels, specifically palmitoleic acid, appear to correlate with severe AP. These findings have potential clinical implications for targeted AP therapies.NEW & NOTEWORTHY Drivers of the inflammatory response in acute pancreatitis remain incompletely understood. Unsaturated fatty acids, specifically palmitoleic, appear to have an association with more severe acute pancreatitis. This finding presents a new clinical understanding of fatty acid toxicity and highlights a potential future target for treatment in severe acute pancreatitis.

The Hypolipidemic Characteristics of a Methanol Extract of Fermented Green Tea and Spore of Eurotium cristatum SXHBTBU1934 in Golden Hamsters.

Fuzhuan brick tea (FBT), a distinctive Chinese dark tea with the predominant fungus of Eurotium cristatum, offered significant health benefits to Chinese people. In the current study, the in vivo bioactivities of E. cristatum (SXHBTBU1934) fermented green tea and spores of E. cristatum fermented on wheat were investigated, respectively. The methanol extract of fermented green tea and spore of E. cristatum both showed potent lipid-lowering activity in the blood of a high-fat diet induced hyperlipidemia model in golden hamsters and significantly reduced the accumulation of fat granules in the liver. These results indicated that the key active components were produced by E. cristatum. Chemical investigations suggested similar components in the two extracts and led to the identification of a new alkaloid, namely variecolorin P (1), along with four known structurally related compounds, (-)-neoechinulin A (2), neoechinulin D (3), variecolorin G (4), and echinulin (5). The structure of the new alkaloid was elucidated by HRESIMS, 1H, 13C, and 2D NMR analysis. The lipid-lowering activity of these compounds was evaluated using an oleic acid-induced HepG2 cell line model. Compound 1 significantly reduced the lipid accumulation in the HepG2 cell line with an IC50 value of 0.127 µM.

Histone deacetylase inhibitors (HDACi) increase expression of KCa2.3 (SK3) in primary microvascular endothelial cells.

The small conductance calcium-activated potassium channel (KCa2.3) has long been recognized for its role in mediating vasorelaxation through the endothelium-derived hyperpolarization (EDH) response. Histone deacetylases (HDACs) have been implicated as potential modulators of blood pressure and histone deacetylase inhibitors (HDACi) are being explored as therapeutics for hypertension. Herein, we show that HDACi increase KCa2.3 expression when heterologously expressed in HEK cells and endogenously expressed in primary cultures of human umbilical vein endothelial cells (HUVECs) and human intestinal microvascular endothelial cells (HIMECs). When primary endothelial cells were exposed to HDACi, KCa2.3 transcripts, subunits, and functional current are increased. Quantitative RT-PCR (qPCR) demonstrated increased KCa2.3 mRNA following HDACi, confirming transcriptional regulation of KCa2.3 by HDACs. By using pharmacological agents selective for different classes of HDACs, we discriminated between cytoplasmic and epigenetic modulation of KCa2.3. Biochemical analysis revealed an association between the cytoplasmic HDAC6 and KCa2.3 in immunoprecipitation studies. Specifically inhibiting HDAC6 increases expression of KCa2.3. In addition to increasing the expression of KCa2.3, we show that nonspecific inhibition of HDACs causes an increase in the expression of the molecular chaperone Hsp70 in endothelial cells. When Hsp70 is inhibited in the presence of HDACi, the magnitude of the increase in KCa2.3 expression is diminished. Finally, we show a slower rate of endocytosis of KCa2.3 as a result of exposure of primary endothelial cells to HDACi. These data provide the first demonstrated approach to increase KCa2.3 channel number in endothelial cells and may partially account for the mechanism by which HDACi induce vasorelaxation.

High Sugar-Sweetened Beverage Consumption Is Associated with Increased Health Care Utilization in Patients with Inflammatory Bowel Disease: A Multiyear, Prospective Analysis.

BACKGROUND: Dietary factors like sugar-sweetened beverage (SSB) consumption are known to influence disease course in a variety of illnesses; however, long-term outcomes are not well documented for inflammatory bowel disease. OBJECTIVE: Does high consumption of SSBs lead to high healthcare utilization (ie, hospitalizations and emergency department visits), inflammation, and disease severity in patients with inflammatory bowel disease? DESIGN: A prospective cohort study was conducted from 2015 to 2019. Patients enrolled in the discovery study cohort were followed for 3 years, whereas patients in the validation cohort were followed for 2 years. They underwent nutrition assessment and received routine care. Dietary intakes of SSBs and fiber were quantified by a validated, self-reported questionnaire. PARTICIPANTS/SETTING: For the discovery study cohort, 1133 adult patients were recruited from the University of Pittsburgh Medical Center Digestive Disease Clinic in Pittsburgh, PA. Eligible patients had a preexisting diagnosis of Crohn's disease or ulcerative colitis and had at least annual follow-up at this tertiary referral center. High SSB consumption was defined as 7 or more SSBs per week. Moderate was defined as > 2 but < 7 SSBs per week. Low SSB consumption was defined as 2 or fewer SSBs per week. MAIN OUTCOME MEASURES: Primary outcome was time to hospitalization and emergency department visits. Secondary outcomes assessed laboratory markers of disease severity and inflammation. Tertiary outcomes assessed time to hospitalization and emergency department visits in a subsequent independent cohort of patients. STATISTICAL ANALYSIS PERFORMED: Multivariable logistic regression, Kaplan-Meier, and Cox proportional hazards modeling RESULTS: The discovery cohort included of 1,133 adult patients with inflammatory bowel disease (58% women, 70% with Chron's disease, 30% with ulcerative colitis, median age 46 years). Low SSB consumption, moderate SSB consumption, and high SSB consumption occurred in 57%, 17%, and 26% in the discovery cohort, respectively. Among patients without active disease at enrollment, high SSB consumption was associated with decreased time to hospitalization and emergency department visits when compared with low SSB consumption (hazard ratio 1.55, 95% CI 1.06 to 2.27; and hazard ratio 1.53, 95% CI 1.10 to 2.13). In terms of disease severity and inflammatory biomarkers, high SSB consumption was associated with increase odds of elevated erythrocyte sedimentation rate (odds ratio 2.04, 95% CI 1.31 to 3.18), elevated C-reactive protein level (odds ratio 1.60, 95% CI, 1.07-2.37), eosinophilia (odds ratio 1.88, 95% CI 1.06 to 3.335), and monocytosis (odds ratio 1.81, 95% CI 1.18 to 2.79) when compared with low SSB consumption after adjusting for baseline differences. Lastly, the validation cohort produced similar results to our primary outcome (ie, high SSB consumption was associated with decreased time to hospitalization and emergency department visits when compared with low SSB consumption). CONCLUSIONS: High SSB consumption was associated with decreased time to hospitalization and emergency department visits. Furthermore, high SSB consumption is associated with disease severity biomarkers and inflammation. Prospective studies assessing the therapeutic influence of nutrition counseling and decreased SSB consumption on long-term inflammatory bowel disease clinical course are warranted.

A simplified method for the quantitation of short-chain fatty acids in human stool.

A one-vial extraction method for the quantitation of short-chain fatty acids (SCFAs) in human stool was developed. Samples were extracted with an acidified aqueous internal standard solution, sodium sulfate, and diethyl ether, followed by analysis with GC-FID. Accuracy, in terms of relative recovery, was typically between 90 and 110% for most analytes; without internal standard, the accuracy was about 5-34%; the linear dynamic range (LDR) was 0.05-50 µmol per gram; the limit of detection (LOD) was less than or equal to 0.05 µmol per gram; and the (lower) limit of quantitation (LOQ) was 1 µmol per gram. The method is suitable for quantitating acetic acid, propanoic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid, isohexanoic acid, hexanoic acid, and heptanoic acid. It is not suitable for the quantitation of formic acid. Application to human biological research was tested by the measurement of SCFA in heathy humans. This confirmed that the method performed adequately, and even better than expected, with values up to 150 µmol per gram.

Diet and the Human Gut Microbiome: An International Review.

This review summarizes the key results of recently published studies on the effects of dietary change and nutritional intervention on the human microbiome from around the world, focusing on the USA, Canada, Europe, Asia, and Africa. It first explores mechanisms that might explain the ability of fiber-rich foods to suppress the incidence and mortality from westernized diseases, notably cancers of the colon, breast, liver, cardiovascular, infectious, and respiratory diseases, diabetes, and obesity (O'Keefe in Lancet Gastroenterol Hepatol 4(12):984-996, 2019; Am J Clin Nutr 110:265-266, 2019). It summarizes studies from Africa which suggest that disturbance of the colonic microbiome may exacerbate chronic malnutrition and growth failure in impoverished communities and highlights the importance of breast feeding. The American section discusses the role of the microbiome in the swelling population of patients with obesity and type 2 diabetes and examines the effects of race, ethnicity, geography, and climate on microbial diversity and metabolism. The studies from Europe and Asia extoll the benefits of whole foods and plant-based diets. The Asian studies examine the worrying changes from low-fat, high-carbohydrate diets to high-fat, low-carbohydrate ones and the increasing appearance of westernized diseases as in Africa and documents the ability of high-fiber traditional Chinese diets to reverse type 2 diabetes and control weight loss. In conclusion, most of the studies reviewed demonstrate clear changes in microbe abundances and in the production of fermentation products, such as short-chain fatty acids and phytochemicals following dietary change, but the significance of the microbiota changes to human health, with the possible exception of the stimulation of butyrogenic taxa by fiber-rich foods, is generally implied and not measured. Further studies are needed to determine how these changes in microbiota composition and metabolism can improve our health and be used to prevent and treat disease.

A prospective cohort analysis of gut microbial co-metabolism in Alaska Native and rural African people at high and low risk of colorectal cancer.

BACKGROUND: Alaska Native (AN) people have the world's highest recorded incidence of sporadic colorectal cancer (CRC) (∼91:100,000), whereas rural African (RA) people have the lowest risk (<5:100,000). Previous data supported the hypothesis that diet affected CRC risk through its effects on the colonic microbiota that produce tumor-suppressive or -promoting metabolites. OBJECTIVES: We investigated whether differences in these metabolites may contribute to the high risk of CRC in AN people. METHODS: A cross-sectional observational study assessed dietary intake from 32 AN and 21 RA healthy middle-aged volunteers before screening colonoscopy. Analysis of fecal microbiota composition by 16S ribosomal RNA gene sequencing and fecal/urinary metabolites by 1H-NMR spectroscopy was complemented with targeted quantification of fecal SCFAs, bile acids, and functional microbial genes. RESULTS: Adenomatous polyps were detected in 16 of 32 AN participants, but not found in RA participants. The AN diet contained higher proportions of fat and animal protein and less fiber. AN fecal microbiota showed a compositional predominance of Blautia and Lachnoclostridium, higher microbial capacity for bile acid conversion, and low abundance of some species involved in saccharolytic fermentation (e.g., Prevotellaceae, Ruminococcaceae), but no significant lack of butyrogenic bacteria. Significantly lower concentrations of tumor-suppressive butyrate (22.5 ± 3.1 compared with 47.2 ± 7.3 SEM µmol/g) coincided with significantly higher concentrations of tumor-promoting deoxycholic acid (26.7 ± 4.2 compared with 11 ± 1.9 µmol/g) in AN fecal samples. AN participants had lower quantities of fecal/urinary metabolites than RA participants and metabolite profiles correlated with the abundance of distinct microbial genera in feces. The main microbial and metabolic CRC-associated markers were not significantly altered in AN participants with adenomatous polyps. CONCLUSIONS: The low-fiber, high-fat diet of AN people and exposure to carcinogens derived from diet or environment are associated with a tumor-promoting colonic milieu as reflected by the high rates of adenomatous polyps in AN participants.

Fiber, Fat, and Colorectal Cancer: New Insight into Modifiable Dietary Risk Factors.

PURPOSE OF REVIEW: To review recent data on the role and interactions of fiber and fat as dietary risk factors associated with colorectal cancer (CRC) risk in humans. RECENT FINDINGS: Fiber intake shows convincing and linear dose-response negative correlation with CRC risk. Dietary fiber stimulates butyrogenic activity of the gut microbiota, providing high amounts of butyrate that shows extensive anti-neoplastic effects. A high-fat diet promotes CRC risk through stimulated bile acid metabolism, facilitating bile acid conversion by the gut microbiota to tumor-promoting deoxycholic acid. Comprehensive interactions of these microbial metabolites are likely to underlie mechanisms driving diet-dependent CRC risk in different populations, but require further experimental investigation. Dietary fiber and fat shape the composition and metabolic function of the gut microbiota, resulting in altered amounts of butyrate and deoxycholic acid in the colon. Fiber supplementation and restriction of fat intake represent promising strategies to reduce CRC risk in healthy individuals.

Lack of reinforcement enhancing effects of nicotine in non-dependent smokers.

RATIONALE: Recent animal research has shown that, aside from its primary and secondary reinforcing effects, nicotine may enhance reinforcement from stimuli unrelated to nicotine intake. Little human research has directly examined this potentially important influence of nicotine. OBJECTIVES: We report two virtually identical studies examining the influence of nicotine, via nasal spray (study 1) and cigarettes (study 2), on the reinforcing effects of rewards unrelated to nicotine intake. MATERIALS AND METHODS: Both studies involved young adults with some past smoking exposure but no history of nicotine dependence. Reinforcement was assessed by responses on a simple operant computer task reinforced by: money, music, the termination of aversive noise, or no reward (control). Participants responded for rewards on three separate sessions, involving intermittent dosing of 0, 5, or 10 microg/kg nicotine via nasal spray (study 1) or the smoking of 0.05 or 0.6 mg nicotine cigarettes or no smoking (study 2). RESULTS: Results showed no effects of nicotine, by nasal spray or cigarette smoking, on reinforced responses, although nicotine increased some subjective responses (e.g. head rush/buzzed, liking). Nicotine via smoking also did not influence affect or hedonic ratings of slides varying in mood valence in an exploratory trial in study 2. CONCLUSIONS: These results do not support the notion that nicotine per se enhances the reinforcing value of other reinforcers in humans. Any reinforcement enhancing effects of nicotine in humans may be specific to dependent smokers or may be relatively narrow and dependent upon procedural conditions different from those in the current studies.

Mood, nicotine, and dose expectancy effects on acute responses to nicotine spray.

INTRODUCTION: We recently showed effects of nicotine dose and nicotine expectancy on some responses to cigarette smoking, with generally no influence of induced mood on these effects. The present study extended this line of research to Nicotrol nasal spray, to determine whether formulation (spray vs. smoking) alters responses. METHODS: Smokers abstained overnight before each of two virtually identical sessions, involving negative or positive mood induction. They were randomized to one of five groups, four comprising the 2 x 2 balanced placebo design, varying actual and expected dose of nicotine in the nasal spray, and the fifth group a no-spray control. Dependent measures included self-reported affect, craving, withdrawal, and spray ratings of "liking" and "how much nicotine." Analyses were limited to those whose nicotine expectancies were manipulated successfully (N = 48). RESULTS: The following results matched those from our smoking study: expecting nicotine increased liking; expected, but not actual, nicotine dose increased dose perception; neither actual nor expected nicotine dose had much influence on affect or withdrawal; and mood had no influence on these effects. However, both actual and expected nicotine dose decreased craving in response to spray, contrary to our prior study with smoking. DISCUSSION: Formulation made little difference in some effects of nicotine and expectancies, but other effects differed by formulation. Some of these findings, particularly for craving reduction, may have implications for enhancing the acute therapeutic effects of nasal spray and, perhaps, other medications in smokers trying to maintain abstinence after quitting.

Variability in initial nicotine sensitivity due to sex, history of other drug use, and parental smoking.

Initial sensitivity to nicotine's effects during early exposure to tobacco may relate to dependence vulnerability. We examined the association of initial nicotine sensitivity with individual difference factors of sex, other drug use history (i.e. cross-tolerance or cross-sensitization), and parental smoking status in young adult nonsmokers (N=131). Participants engaged in 4 sessions, the first 3 to assess the dose-response effects of nasal spray nicotine (0, 5, 10 microg/kg) on rewarding, mood, physiological, sensory processing, and performance effects, and the fourth to assess nicotine reinforcement using a choice procedure. Men had greater initial sensitivity than women to some self-reported effects of nicotine related to reward and incentive salience and to impairment in sensory processing, but men and women did not differ on most other effects. Prior marijuana use was associated with greater nicotine reward, nicotine reinforcement was greater in men versus women among those with prior marijuana use, and having parents who smoked was related to increased incentive salience. However, history of other drug use and parental smoking were not otherwise associated with initial nicotine sensitivity. These findings warrant replication with other methods of nicotine administration, especially cigarette smoking, and in more diverse samples of subjects naïve to nicotine. Yet, they suggest that sex differences in initial sensitivity to nicotine reward occur before the onset of dependence. They also suggest that parental smoking may not increase risk of nicotine dependence in offspring by altering initial nicotine sensitivity, and that cross-tolerance between other drugs and nicotine may not be robust in humans.

Initial nicotine sensitivity in humans as a function of impulsivity.

RATIONALE: Impulsivity is related to greater risk of nicotine dependence, perhaps by enhancing sensitivity to nicotine's reinforcing and rewarding effects during initial smoking experiences. OBJECTIVE: We examined the influence of impulsivity characteristics on acute sensitivity to nicotine reward, reinforcement, and other effects in 131 young adult nonsmokers. MATERIALS AND METHODS: Participants engaged in four sessions: the first three to assess dose-response effects of nasal spray nicotine (0, 5, 10 microg/kg) on reward, as well as mood, physiological, and performance effects, and the fourth to assess nicotine reinforcement using a choice procedure. Five impulsivity factors, derived from factor analysis of self-report (e.g., Barratt Impulsivity Scale, Sensation-Seeking Scale, Novelty seeking) and computer (stop-go, delay discounting, probability discounting) measures of impulsivity, were labeled "novelty seeking", "response disinhibition", "extraversion", "inhibition", and "probability/delay discounting". RESULTS: The associations of novelty seeking with nicotine reinforcement and reward tended to move in opposite directions by sex, generally being directly related in men but inversely or unrelated in women. Similarly, response disinhibition was associated with reward and some mood responses to nicotine that differed by sex. Extraversion was inversely associated with nicotine reinforcement. Characteristics loading on to the other impulsivity factors had little association with nicotine sensitivity. CONCLUSIONS: These results are preliminary, but they suggest that characteristics broadly related to impulsivity, especially novelty seeking and response disinhibition, are associated with initial sensitivity to some effects of acute nicotine, including reinforcement and reward, and may do so differentially between men and women.

The influence of caffeine on nicotine's discriminative stimulus, subjective, and reinforcing effects.

Caffeine may acutely alter the discriminative stimulus and subjective effects of nicotine, perhaps explaining the association of coffee intake with smoking status. In this study, smokers were initially trained to discriminate 20 microg/kg nicotine by nasal spray from placebo (0). Then, generalization of nicotine discrimination was tested, using both 2- and 3-choice ("novel" option) procedures, across a range of doses (0-20 microg/kg) following pretreatment with 0, 2.5, and 5.0 mg/kg caffeine p.o. Nicotine reinforcement was assessed after the end of generalization testing using a choice procedure. Caffeine pretreatment did not alter nicotine discrimination and self-administration. Caffeine and nicotine influenced some subjective and cardiovascular responses, but there were no interaction effects except for diastolic blood pressure. These results do not support the notion that caffeine acutely alters nicotine's discriminative stimulus, subjective, or reinforcing effects.

The discriminative stimulus, subjective, cardiovascular, and reinforcing effects of nicotine as a function of light physical activity.

Smokers often experience the acute effects of cigarette smoking while they are engaged in the light physical activity of routine tasks. However, virtually all laboratory-based research on these effects is conducted under conditions of quiet rest and, thus, may not generalize to effects in the natural environment. We examined changes in the discriminative stimulus, subjective, cardiovascular, and reinforcing effects of nicotine in humans as a function of the level of concurrent physical activity. Men and women smokers (N = 17) were initially trained to discriminate 20 microg/kg nicotine by nasal spray from placebo (0 microg/kg) at rest. Three sessions then followed, in which the generalization of discrimination was tested across a range of doses (0-20 microg/kg) while at rest or engaged in very light or light physical activity (15% and 30% of heart rate reserve, respectively) via bicycle ergometer. Generalization testing involved both two- and three-choice ("novel" option) quantitative procedures. Self-reported mood via the Profile of Mood States and visual analog scales, and cardiovascular measures of heart rate and blood pressure were obtained concurrent with discrimination responding. Nicotine reinforcement was assessed after the end of generalization testing using a choice procedure under the same rest or activity conditions. Results showed that physical activity did not significantly alter nicotine discrimination or reinforcement, as no interactions between activity and nicotine were observed. When activity and nicotine influenced the same subjective and cardiovascular responses, they acted in a generally additive fashion. These findings suggest that research on the acute effects of nicotine conducted under typical resting laboratory conditions generally are not altered by light physical activity and so may generalize to the effects of nicotine under conditions common in the natural environment.

In vitro remifentanil metabolism: the effects of whole blood constituents and plasma butyrylcholinesterase.

UNLABELLED: We designed this in vitro study to determine whether the half-life of remifentanil was altered in butyrylcholinesterase-deficient patients. Test tubes containing Krebs buffered solution, whole blood, plasma, or red cells from both normal and butyrylcholinesterase-deficient patients were incubated with remifentanil. Remifentanil concentrations were determined by using gas chromatography and mean half-lives were calculated by using a nonlinear regression analysis. There were no differences in whole blood, red cells, or plasma half-life between normal and butyrylcholinesterase-deficient volunteers. In both normal and butyrylcholinesterase-deficient volunteers, whole blood and plasma had a significantly longer half-life than the red cell component. Extrapolation to the in vivo setting would suggest that a butyrylcholinesterase-deficient patient should not have altered remifentanil kinetics. IMPLICATIONS: This was a test-tube-designed study to determine whether an enzyme deficiency (butyrylcholinesterase deficiency) changes the way remifentanil is metabolized. It seems that remifentanil dosage does not need to be changed in patients with butyrylcholinesterase deficiency.

Acute nicotine reinforcement, but not chronic tolerance, predicts withdrawal and relapse after quitting smoking.

Little research has examined the association of tobacco dependence with nicotine tolerance or reinforcement in a clinical sample. Smokers preparing to quit smoking participated in laboratory sessions to assess nicotine tolerance on subjective, cardiovascular, and performance measures and to assess nicotine reinforcement using a choice procedure. Participants were then provided with individual counseling (but no medication), made a quit attempt, and were followed for 1 year to determine clinical outcome, as determined by postquit withdrawal and days to relapse. Nicotine tolerance was unrelated to either withdrawal or relapse. However, acute nicotine reinforcement was significantly related to both greater withdrawal and faster relapse. Results challenge the common assumption that nicotine tolerance is closely related to dependence but suggest that nicotine reinforcement may have theoretical and clinical significance for dependence.