First-pass metabolism of alcohol occurs in women's stomachs, study finds
Research helps explain heightened sensitivity to the effects of alcohol experienced by bariatric surgery patients
Date:
March 22, 2022
Source:
University of Illinois at Urbana-Champaign, News Bureau
Summary:
Research identifies the stomach, not the liver, as the site
of alcohol first-pass metabolism in women who underwent sleeve
gastrectomy surgery.
FULL STORY ========================================================================== While scientists have broadly agreed that a fraction of the alcohol
people consume is broken down before it reaches the bloodstream in a
process called first-pass metabolism, they have been uncertain whether
this process occurs in the stomach or the liver.
========================================================================== Published online in the journal JAMA Network Open, a new study of alcohol metabolism in women who underwent sleeve gastrectomy and peers who had not
had weight loss surgery indicates that this process occurs in the stomach.
In addition to clarifying where FPM occurs, the findings also explain
why some patients' sensitivity to alcohol increases dramatically
after bariatric surgery, significantly heightening their risks of alcohol-related disorders.
A team of researchers led by food science and human nutrition professor M.
Yanina Pepino at the University of Illinois Urbana-Champaign compared
alcohol metabolism in 12 sleeve gastrectomy patients with that of nine
women of similar ages, body mass indices and drinking habits who had
not undergone weight loss surgery.
Once absorbed, most of the alcohol a person ingests is broken down in
the liver by an enzymatic process that is saturable.
The challenge in identifying the site of FPM was that the stomach could
play dual roles, both serving as the site where alcohol was broken down
before being released to the liver and affecting a saturable FPM in the
liver by modulating the speed at which the dose of alcohol was being
delivered, if the liver were the site where FPM was occurring instead,
Pepino said.
==========================================================================
That is, the slower the stomach emptied, the more efficient the liver
would be in metabolizing alcohol during FPM, she said. If, however,
FPM occurred in the stomach, the slower the gastric emptying, the more
time the stomach would have to break down the alcohol.
Previous findings from this research team and other laboratories showed
that sleeve gastrectomy and gastric bypass surgery decreased the FPM of
alcohol by accelerating gastric emptying, causing more rapid and higher
peak blood alcohol concentrations than those patients experienced when
they drank the same amount of alcohol prior to their surgeries.
In the current study, the researchers took advantage of sleeve gastrectomy
to determine the site of FPM. Sleeve gastrectomy removes 80% of the
patient's stomach but preserves the pylorus, the valve that controls
the passage of stomach contents to the intestine.
"The data help clarify where alcohol FPM occurs and provide a plausible mechanism for the observed increase in alcohol-related diseases among
many patients who have undergone bariatric surgery," Pepino said.
Co-authors of the paper included Dr. Blair Rowitz, the associate dean
for clinical affairs of the Carle Illinois College of Medicine; Vijay A.
Ramchandani, the senior principal investigator of human psychopharmacology
with the National Institute on Alcohol Abuse and Alcoholism; and
Dr. Martin H.
Plawecki, a professor of psychiatry at the Indiana University School
of Medicine.
==========================================================================
A week apart, the women in the study participated in two experiments that assessed their metabolism of alcohol -- an oral challenge in which they
drank alcohol, and an alcohol clamp session in which it was administered through an IV catheter so their blood alcohol concentrations could be
precisely controlled by removing the variable process of absorption.
For the oral challenge, after fasting overnight the participants drank
0.5 grams of alcohol per kilogram of their fat-free body mass over
a 10-minute period. Through an IV catheter inserted in a hand vein,
the scientists obtained blood samples at regular intervals to measure participants' blood alcohol concentration and the time it took for each
person to reach peak concentration.
In the alcohol clamp session, participants were administered 6% alcohol
in a saline solution through an IV catheter. Using a computer-assisted
alcohol infusion system developed by Indiana University's Neural Systems Laboratory, participants reached a target breath alcohol concentration
of 60 mg/dl within 15 minutes.
That level was maintained for the next 135 minutes, allowing the
researchers to estimate how quickly each person was eliminating the
alcohol from their bloodstream, Pepino said.
The alcohol clamp session helped ensure that the differences found
between the two groups of women during the ingested alcohol session were
not due to variations in their livers' alcohol elimination rates.
"Despite the overnight fast, which minimizes alcohol FPM, the amount of
the ingested alcohol dose that reached their bloodstreams -- that is, the alcohol bioavailability -- increased by 34% in the gastrectomy patients compared with their peers in the control group," said lead author Neda Seyedsadjadi, a postdoctoral researcher at the U. of I.
"This increased bioavailability was not explained by a decrease in their alcohol elimination rate or gastric emptying rate -- differences between
the groups remained when subsets of the participants were matched on the
time it took to reach peak blood alcohol concentrations." A limitation of
the current study was that the participants were all women, who represent
the majority of patients undergoing these surgeries. The researchers
said future research should include men to determine if sex differences
exist in the site of alcohol FPM.
Additional co-authors of the current paper were postdoctoral research
associate Maria Belen Acevedo and doctoral student Raul Alfaro Leiva,
both of the U. of I.
The research was supported by grants from the National Institutes of
Health and the Indiana Alcohol Research Center. Ramchandani's work was supported by the NIAAA Division of Intramural Clinical and Biological
Research.
========================================================================== Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign,_News_Bureau.
Original written by Sharita Forrest. Note: Content may be edited for
style and length.
========================================================================== Journal Reference:
1. Neda Seyedsadjadi, M. Belen Acevedo, Raul Alfaro, Vijay
A. Ramchandani,
Martin H. Plawecki, Blair Rowitz, Marta Yanina Pepino. Site of
Alcohol First-Pass Metabolism Among Women. JAMA Network Open,
2022; 5 (3): e223711 DOI: 10.1001/jamanetworkopen.2022.3711 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220322122530.htm
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