Supplementary information
In an attempt to better understand the physiologic factors underlying the
dramatic weight gain and response to bariatric surgery, hormones important
for appetite and energy balance were studied after Institutional Review Board
approval was obtained.
INSULIN RESPONSES
Serum insulin values were measured during a 24 h period including three
meal challenges before and at intervals following gastric bypass surgery.
Preoperatively, we documented fasting hyperinsulinemia, an exaggerated
insulin response to meal challenge, and markedly increased insulin
excursions between meals (Supplementary Figure 1). By 10 days following
operation, fasting levels of insulin had decreased, but remained exaggerated
postprandially (Supplementary Table 1). By 7 months following operation,
fasting insulin levels had completely normalized, and, although peak
postprandial levels remained high, these excursions were not sustained. By
14 months postoperatively, despite a plateau of weight loss, there was no
recurrence of hyperinsulinemia. In fact, insulin concentrations peaked very
modestly following meals and rapidly returned to baseline.
GHRELIN RESPONSES
Four dominant meal-associated ghrelin peaks were observed both preceding
and following gastric bypass surgery (Supplementary Figure 1). While gastric
bypass did not affect the overall ghrelin profile, there was a steady decrease
in peak and basal active ghrelin concentrations postoperatively, as predicted
from prior studies.17 Preoperatively, mean active ghrelin concentration after an
overnight fast was 62.6 ± 15.3 ng/l, compared with 32.7 ± 4.2 at 14 months
postoperatively. Fasting ghrelin levels became suppressed following breakfast
at preoperative and postoperative study visits (Supplementary Table 1). In
contrast, total ghrelin concentration did not show distinct peaks (data not
shown). Specific analysis of active ghrelin levels might remove ‘background
noise’ and allow for a more sensitive monitoring of circulating ghrelin in clinical
medicine.
LEPTIN RESPONSES
As seen in Supplementary Figure 1, before gastric-bypass-induced weight
loss, fasting leptin level was elevated 4-fold (expected range 30–40 [micro]g/l
for obese adolescents18). Despite an elevated baseline, a 24 h leptin profile
displayed a diurnal variation with mean levels (0600 and 1800h) of 117 ± 6
[micro]g/l, as compared with 124 ± 9 [micro]g/l between 1800 and 0600h
(p<0.02). As early as 10 days following gastric bypass, after loss of 5 kg on
very low calorie intake (500–700 kcal/day), fasting leptin level had fallen
precipitously from 119.8 ± 4.5 to 50.8 [micro]g/l (Supplementary Table 1).
Leptin values further decreased to 20.1 ± 2.7 [micro]g/l by 14 months after
loss of nearly 50 kg. In summary, leptin was elevated before operation and fell
dramatically by 10 days after gastric bypass, even prior to significant weight
loss. With major weight loss, leptin levels decreased even further, ultimately
falling below the level expected for the patient’s degree of obesity. Taken
together, factor(s) other than weight loss per se improved leptin
concentrations in this patient, starting as early as 10 days after gastric
bypass.19
According to the current model of molecular energy balance regulation,
afferent hormones, nutrients and neuronal signals constantly supply multiple
circuits in the central nervous system with information about the status of
energy metabolism. In response, the control centers in the hypothalamus,
brainstem, ventral tegmentum and other brain areas constantly modulate
feeding behavior, thermogenesis and peripheral cell metabolism via efferent
endocrine and neuronal signals, in order to achieve energy homeostasis. Gut
hormones represent an essential afferent component within this model and
include the hunger-inducing hormone ghrelin as well as the centrally acting
satiety factors insulin, cholecystokinin, glucagon-like peptide 1, and pancreatic
polypeptide or peptide YY.20
Ghrelin is considered to be the body’s dominant orexigenic gastric peptide,
and increased levels have been shown to promote hyperphagia in both
rodents21 and humans.22 In genetic and diet-induced human obesity,
circulating ghrelin levels are usually found to be slightly decreased, although
not as low as reported in some studies after gastric bypass.23–25
Significant reduction in the preprandial rise in ghrelin level occurs following
gastric bypass,17 and probably contributed to the markedly reduced food
cravings measured in this patient. Despite the possible disruption of the
ghrelin-responsive circuitry in the ventromedial hypothalamic region after
hypothalamic damage, ghrelin’s primary targets are believed to be situated in
the arcuate nucleus.20 Other ghrelin-responsive neuronal circuits exist in the
brainstem26 or the midbrain27 which would also be unharmed by a
craniopharyngioma or related invasive treatments. These ghrelin-responsive
targets could play a role in the complex neuroendocrine interactions
responsible for weight loss following gastric bypass in this patient and
potentially in neurologically normal patients as well.
Supplementary Figure 1 24 h excursions of insulin, active ghrelin, and leptin
before and after gastric bypass. Following an overnight fast, a 1 l full strength
Pediasure mixed meal challenge was administered preoperatively, (after
discontinuation of octreotide), and at 7 months, and 14 months
postoperatively. The Pediasure mixed meal challenges were offered at typical
mealtimes between 0800 and 0830 h, 1200 and 1230 h, and 1730 and 1800
h. At the 7 and 14 month study dates, because of the small gastric pouch, the
patient was only able to ingest 0.4–0.7 l of the 1 l volume challenge within the
allotted 30 min meal period, as a result of early satiety. Blood samples were
drawn at baseline (0800 h), and at every half hour from 0800 until 2100; after
2100, blood samples were drawn hourly until 0800 the following day. For
hormone assays, plasma was separated by centrifugation and stored at
–80°C. Samples were thawed and human insulin, active ghrelin, and leptin
levels were measured using commercially available ELISA kits from
Diagnostic Systems Laboratories (Webster, TX, USA). All measurements
were performed in duplicate, following the manufacturer’s instructions.
Supplementary Table 1 Fasting and postprandial gut hormone levels of the
patient before and after bariatric surgery.a
Before surgery
10 daysb
7 months
14 months
Fasting
165 ±197
25
20.0 ± 2.5
15 ± 1
Postprandial
2,582 ±1,350
2,003 ± 905 165 ± 180
55 ± 73
Hormone
Insulin (mIU/l)
Active Ghrelin (ng/l)
Fasting
62.6 ± 15.3
55.1
40.0 ± 7.4
32.7 ± 4.2
Postprandial
23.1 ± 4.2
32.5 ± 1.5
31.9 ± 4.4
18.9 ± 1.0
Fasting
119.8 ± 4.5
50.8
45.1 ± 1.5
20.1±2.7
Postprandial
111.4 ± 6.4
43.7 ± 2.5
52.2 ± 1.6
16.7 ± 3.4
Leptin ([micro]g/l)
aHormone
levels were measured 3 h before and 3 h after a 0800 breakfast
meal. Data represent mean values ± S.D. bThe fasting measurements at 10
days were derived from a single serum sample as technical difficulties with
the intravenous catheter in this extremely obese patient precluded acquisition
of additional samples at this timepoint.
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