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Original Studies |
The UKK Institute for Health Promotion and Research (M.F., K.K.-H., A.N.), Tampere; and the Departments of Clinical Nutrition (R.V., V.H., M.U.) and Medicine (M.L.), University of Kuopio, Kuopio, Finland
Address all correspondence and requests for reprints to: Dr. Mikael Fogelholm, The UKK Institute, POB 30, 33501 Tampere, Finland. E-mail: mikael.fogelholm{at}helsinki.fi
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Abstract |
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 Top Abstract IntroductionSubjects and MethodsResultsDiscussionReferences |
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G
mutation in the uncoupling protein-1 (UCP-1) genes have associations
with weight loss and subsequent weight maintenance. Seventy-seven obese
(body mass index range, 29–46 kg/m2), clinically healthy,
premenopausal women were studied. A 12-wk weight reduction by very low
calorie diet (VLCD) was followed by a 40-wk weight maintenance phase.
The subjects were divided into four groups according to their
ß3AR and UCP-1 genotype: no mutation (control; n =
37), only Trp64Arg mutation in the ß3AR gene
(n = 12), only AG mutation in the UCP-1 gene (n = 23), and
both mutations (n = 5). Subjects with both mutations had a lower
weight reduction during VLCD than the controls [-10.5 ± 0.6
(±SEM) vs. -14.0 ± 0.5 kg;
P = 0.051, by ANOVA]. During the maintenance
phase, weight in subjects with both mutations increased by 5.8 ±
1.5 kg, but remained unchanged in the controls (-0.5 ± 0.8 kg;
P = 0.041). The changes in weight in subjects with
only one of the mutation were close to the results in the controls.
Resting energy expenditure, adjusted for fat mass, fat-free mass, and
maximal aerobic power, did not change differently between the groups
throughout the study. The results suggest that a combination of the
Trp64Arg mutation in the ß3AR and the AG
mutation in the UCP-1 genes may be associated with faster weight gain
after a VLCD. |
Introduction |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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The search for candidate genes for obesity and related metabolic
disorders, such as insulin resistance, has been active during the past
decades (2). Mutations of certain genes have also been studied in
relation to weight changes. Two such variants are the
Trp64Arg mutation in the
ß3-adrenergic receptor (ß3AR) and the AG
mutation in the uncoupling protein 1 (UCP-1) gene.
Two studies with a retrospective study design have found the
Trp64Arg mutation in the ß3AR gene
to predict a larger weight gain (3, 4). Similar results have also been
reported for the AG mutation in the UCP-1 gene (5, 6). Simultaneous
existence of the mutations in the ß3AR and UCP-1 genes
might have an additive effect on weight gain (5). In contrast, Nagase
et al. (7) reported a smaller weight gain in unselected
Japanese men with the Trp64Arg mutation in the
ß3AR gene compared with subjects with normal alleles. In
another Japanese study (8), the Trp64Arg mutation
in the ß3AR gene was associated with difficulty in
loosing weight, whereas two other studies did not find an association
between the mutation in the ß3AR gene and weight loss (4, 9). Finally, Fumeron et al. (9) reported a smaller weight
loss for subjects with the AG mutation in the UCP-1 gene than for
those without the mutation.
In the present study, we examined whether the
Trp64Arg mutation in the ß3AR gene
and the AG mutation in the UCP-1 gene are associated with initial
weight loss induced by VLCD and weight maintenance after initial weight
loss in obese premenopausal women.
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Subjects and Methods |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Eighty-five healthy obese (body mass index range, 29–46 kg/m2), premenopausal (29–46 yr old) women volunteered for this study. All subjects had been weight stable (±3 kg) for at least 3 months before the study. None of the subjects was physically active, smoking, pregnant, or lactating. Suspected binge eaters (symptom scores >20 in the Bulimic Investigatory Test of Edinburgh by Henderson and Freeman) (10) were excluded from the study. Informed consent was given by all the volunteers. The study was approved by the ethical committee of the UKK Institute.
The subjects were not using any regular medication, except for 8–13
persons taking contraceptive hormones during various phases of the
study. About two thirds of the hormone users had intrauterine devices
with levonorgestrel, and the rest took contraceptive hormones with both
estrogen and progestagens. Nine hormone users had normal genotype,
three had the AG mutation of the UCP-1 gene, and one had the
Trp64Arg mutation in the ß3AR
gene.
The study lasted for 1 yr and consisted of two phases, a 12-week weight reduction phase and a subsequent 40-wk weight maintenance phase. The weight reduction consisted of three parts: week 1 and weeks 10–12, low energy diet, based on a meal exchange system; and weeks 2–9, VLCD (Nutrilett, Nycomed Pharma AS, Oslo, Norway), prescribed to cover 40% of measured resting energy expenditure. The estimated mean (±SD) energy intakes, calculated from 4-day food records by Micronutrica software (The Social Insurance Institution, Turku, Finland), were: week 1, 4.2 ± 0.9 MJ/day (one record); weeks 2–9, 2.7 ± 0.3 MJ/day (three records); and weeks 10–12, 4.6 ± 1.2 MJ/day (one record). The subjects met weekly in small groups and were counselled by a nutritionist. The meeting topics included instructions for the VLCD and the meal exchange system, general knowledge on diet and weight maintenance, and relapse prevention techniques (11).
After the weight reduction, the subjects participated in a 40-week weight maintenance program for which they were randomly assigned to either dietary or exercise groups (prescribed walking, 2–3 or 5–6 h/wk). In weekly group meetings, all subjects were instructed to follow a low fat diet to prevent weight relapse. In addition, the subjects used self-monitoring (recording) to improve their control over high risk situations for overeating (11).
Data collection
With the exceptions of physical activity and eating control, all data were collected 4–7 days before the start of weight reduction (study month 0), 4–7 days after the weight reduction (study month 3), and at the end of the weight maintenance program (study month 12). Body weight was measured in underwear after an overnight fast using a high precision scale (F150S-D2, Sartorius GmBh, Goettingen, Germany). Body density was measured by underwater weighing after full exhalation (presumably at residual lung volume), as previously described (12). Body composition was calculated from body density by Siri’s two-compartment equation (13).
Resting energy expenditure (REE) was assessed in the morning after a 12-h fast, using a Sensor Medics 3000Z energy measurement system (Sensor Medics Corp., Anaheim, CA) in a dilution mode. The subject was in a semirecumbent position with a constantly ventilated canopy over her head. The oxygen and carbon dioxide concentrations in the diluted gas, integrated over 1-min periods, were measured for 45 min. The first 15 min were excluded from the analyses. Using the formula of Weir (14), energy expenditure was calculated for the last two 15-min periods. The lower of these two values was used as the REE.
Maximal oxygen consumption (VO2max) was determined during an uphill walk on the treadmill until symptom-free volitional maximum (15). Expiratory gases were analyzed by Sensor Medics 3000Z and integrated for 1-min periods.
Blood collected by venipuncture after 12 h of fasting. An ethylenediamine tetraacetate blood sample for genetic analysis was taken 1 yr after the end of the weight maintenance phase and was stored at -20 C until analyzed. Plasma for insulin and glucose determinations was divided after centrifugation into aliquots and stored at -70 C until analyzed.
Daily physical activity was estimated as the total number of steps during the last 7 days of the weight maintenance program. The number of daily steps was calculated with a pedometer (Fitty3 Electronic Pedometer, Kasper & Richter, Uttenreuth, Germany) placed on the subject’s belt. The tendency for uncontrolled overeating (binge eating) was assessed by symptoms score of the Bulimic Investigatory Test of Edinburgh (10) in the middle and at the end of the weight maintenance program. The mean value of the two scores were used as an index for poor control over eating habits.
Analytical methods
The Trp64Arg mutation in the
ß3AR gene and the AG mutation in the UCP-1 gene were
detected by PCR-RFLP assays as previously described (16, 17). The
plasma insulin determinations were performed by RIA (Phadeseph Insulin,
Pharmacia Biotech, Uppsala, Sweden). Plasma glucose was
analyzed using the glucose dehydrogenase method (Merck Diagnostica,
Darmstadt, Germany).
Statistical analyses
Blood samples for genetic analyses, taken 1 yr after the end of
intervention, were obtained from 77 subjects. These subjects were
divided into 4 groups according to their ß3AR and UCP-1
genotype: no mutation (control group; n = 37), only
Trp64Arg mutation in the ß3AR gene
(n = 12), only AG mutation in the UCP-1 gene (n = 23), and
both mutations (n = 5). The between-group differences were tested
by the ANOVA, followed by post-hoc Tukey’s tests. To
control for the effects of physical activity and overeating, the data
from the weight maintenance period were also tested by analysis of
covariance (ANCOVA), with the number of daily steps and the binge
eating score as covariates. However, the results and statistical
significances after ANOVA and ANCOVA were not markedly different.
Because the unadjusted model did not result in any false positive
results (as judged by the statistical significances in ANCOVA), only
the ANOVA results are presented.
According to multiple linear regressions, REE was positively related to fat-free mass, fat mass, and VO2max (liters per min) before (r2 = 0.45) and after (r2 = 0.58) the weight reduction and after the weight maintenance program (r2 = 0.57). Adjusted REE was calculated as: group mean REE + (measured REE - REE predicted by regression using fat mass, fat-free mass, and VO2max) (18). The change in weight (D weight) during the weight maintenance program was positively related to weight loss during WR (r2 = 0.24). Adjusted D weight (during weight maintenance) was calculated as: group mean D weight (during weight maintenance) + [measured D weight (during weight maintenance) - D weight (during weight maintenance) predicted by D weight (during weight reduction)].
The results are presented as the mean and SEM of the estimate. All statistical analyses were performed using the SPSS statistical software package, version 6.1.3 (SPSS, Inc., Chicago, IL).
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Results |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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G mutation of the
UCP-1 gene were 0.12 and 0.19, respectively. Normal genotype was found
in 37 (48%) of the subjects, the Trp64Arg
mutation of the ß3AR gene was found in 12 (16%), the
AG mutation of the UCP-1 gene was found in 23 (30%), and mutations
in both genes were found in 5 (6%). One subject was homozygous for the
ß3AR mutation, and two subjects were homozygous for the
UCP-1 mutation.
The between-group variation in body weight before the study was large
(from 89.0–96.3 kg), but not statistically significant (Table 1
and Fig. 1). Similarly, the body composition and
metabolic variables did not differ significantly across the four
groups. All of the subjects were normoglycemic (<6.4 mmol/L) except
for one in the control group. The proportion of fasting
hyperinsulinemia (>15 mU/L) ranged from 9% (subjects with the AG
mutation of the UCP-1 gene) to 25% (subjects with the
Trp64Arg mutation of the ß3AR
gene).
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and Fig. 1
). There was a tendency for
the largest weight loss in the controls and the smallest weight loss in
subjects with both the Trp64Arg mutation of the
ß3AR gene and the AG mutation of the UCP-1 gene
(P = 0.051). Moreover, the subjects with both mutations
showed a tendency to lose the smallest amount of fat mass. Initial
hyperglycemia (plasma glucose, >6.4 mmol/L) found in one person with a
normal genome was normalized during weight reduction. The number of
hyperinsulinemic women was decreased to one person (with both
mutations) at the end of weight reduction, and her state remained
unchanged during the weight maintenance phase. The change in the
fasting plasma insulin concentration tended to be the smallest in the
subjects with both mutations (P = 0.09). The responses
in the remaining metabolic variables were not significantly different
among the groups.
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G mutation of the UCP-1 gene, and 6,064 ±
1,013 in the subjects with both mutations (P = 0.26, by
ANOVA). The high mean result in the control group was apparently caused
by one outlier (23,764 steps). Walking group assignment did not
significantly affect any of the outcome variables analyzed in the
present study. The binge eating scores during the weight maintenance
program were highest in the subjects with the
Trp64Arg mutation of the ß3AR gene
and lowest among those with both mutations. The group mean scores
(±SEM) were 8.8 ± 0.7 in the control group,
10.5 ± 1.0 in subjects with the Trp64Arg
mutation of the ß3AR gene, 7.6 ± 0.9 in the
subjects with the AG mutation of the UCP-1 gene, and 7.1 ± 1.3
in the subjects with both mutations (P = 0.23, by
ANOVA).
Weight increased during the weight maintenance phase in the subjects
with both the Trp64Arg mutation of the
ß3AR gene and the AG mutation of the UCP-1 gene,
whereas changes were minor in all other groups (Table 3 and Fig. 1). The unadjusted weight
change during weight maintenance in the subjects with both mutations
was different (P < 0.05) from that in the control
group, but this significance disappeared when the results were adjusted
for weight change during weight reduction. However, the between-group
pattern (clearly increased weight only in subjects with both mutations)
remained even after the adjustment. The overall body weight change
(from 0–12 months) was larger in the control group [-14.5 ±
1.1 kg (±SEM)] than in the subjects with both mutations
(-4.7 ± 1.5 kg; P = 0.02, by ANOVA;
P < 0.05, by Tukey’s test). The weight change was
-11.5 ± 2.2 kg in the subjects with the
Trp64Arg mutation of the ß3AR gene
and -11.6 ± 1.3 kg in the subjects with the AG mutation of
the UCP-1 gene. In the repeated measures ANOVA, the polymorphism by
time interaction was highly significant (P =
0.004).
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). No
between-group differences were found when REE was adjusted for body
composition and VO2max (liters per min). |
Discussion |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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G mutation in the UCP-1 genes with weight regain after a rapid
weight reduction by VLCD. The simultaneous existence of the two
mutations was associated with a weight change with a remarkably
different pattern than the change in all other groups: the initial
weight reduction tended to be smaller, the weight gain during
maintenance was larger, and the overall weight loss was less than those
in the remaining subjects.
Using a retrospective design, Clement et al. (5) studied
weight gain during adulthood in morbidly obese subjects. Weight gain
was most remarkable in subjects with both the
Trp64Arg mutation in the ß3AR and
the AG mutation in the UCP-1 genes and was slightly less in subjects
with only one mutation. Although long term, spontaneous weight gain is
usually much slower than weight regain after weight reduction therapy,
the present results agree with the above findings. Although our
subjects with only one mutation did not differ significantly from the
control group, both the weight loss during VLCD and overall success
(weight change from months 0–12) were intermediate between the control
group and the subjects with both mutations.
Fumeron et al. (9) reported an association between the AG
mutation in the UCP-1 gene and a smaller weight loss during a 2.5-month
low energy diet regimen. We are not aware of any other studies on
weight loss and UCP-1 gene mutation. Two studies found weight loss to
be unrelated to ß3AR genotype (9, 14). In contrast,
Sakane et al. (8) reported that the
Trp64Arg mutation in the ß3AR gene
was associated with difficulty in losing weight in noninsulin-dependent
diabetic patients.
The divergent results on the independent association between the ß3AR genotype and obesity are not restricted to prospective studies. Even two recent meta-analyses came to different conclusions, Fujisawa et al. (19) found an association between the Trp64Arg mutation in the ß3AR and body mass index, whereas Allison et al. (20) did not find the mutation to have a role in predisposition to higher body mass index.
Both ß3AR and UCP-1 play a role in thermogenesis (8).
Therefore, reduced REE could be the mechanism by which these genes
could affect energy balance. The present study and two other studies
(21, 22) did not find significant differences in REE among different
genotype groups. Nevertheless, the adjusted REE, as measured before and
after the weight reduction, was 90–220 kJ higher in our controls than
in the groups with one or two mutations. The power of the present study
was clearly too weak to allow any conclusions regarding REE and gene
polymorphism; judged from the 95% confidence intervals of the
between-group differences (not shown), a roughly 300–400 kJ difference
in REE (or change in REE) between the control group and the subjects
with both mutations would have been needed to reach a difference at the
P < 0.05 level. Some studies have indeed found lower
REE in subjects with the ß3AR variant (16, 23). We have
also shown that Trp64Arg mutation in the
ß3AR and the AG mutation in the UCP-1 genes may have
additive effects on lower REE in obese Finns (17).
The allele frequency of the AG mutation in the UCP-1 gene was higher
than the frequency of the Trp64Arg mutation in
the ß3AR gene. The present results agree with the view
that the AG mutation in UCP-1 gene is more common than the
Trp64Arg mutation in the ß3AR gene
in Caucasian populations (5). The present allele frequency of the
mutation in the ß3AR gene was close to the frequencies
(0.07–0.12) reported among Finnish subjects (4, 16, 21, 24). In the
study by Clement et al. (5), 4% of the subjects (10 of 230
morbidly obese patients) had a mutation in both ß3AR and
UCP-1 genes. The corresponding prevalence in less obese women was also
low (6%; 5 subjects) in the present study.
Our results suggest that a combination of the
Trp64Arg mutation in the ß3AR gene
and the AG mutation in the UCP-1 gene might be associated with
faster weight gain after a VLCD. The results should be interpreted
cautiously because of the limited number of subjects with both
mutations. Despite doubtful conclusions regarding the
independent role of ß3AR in obesity (2, 20), the possible
additive effects of the Trp64Arg mutation in the
ß3AR and the AG mutation in the UCP-1 (or mutation of
the UCP-2) genes warrant further studies.
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Footnotes |
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Received July 6, 1998.
Revised August 13, 1998.
Accepted August 17, 1998.
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References |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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G (-3826) variant of the uncoupling
protein gene and the Trp64Arg mutation of the
ß3-adrenergic receptor gene on weight gain in morbid
obesity. Int J Obes. 20:1062–1066.
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