Prolactin and insulin ultradian secretion and adipose tissue lipoprotein lipase expression in severely obese women after bariatric surgery.
BACKGROUND
Hyperprolactinemia is associated with obesity. Furthermore, in human adipose tissue cultured in vitro, prolactin (PRL) inhibited lipoprotein lipase (LPL) activity via functional PRL receptors.


OBJECTIVE
To study PRL and insulin ultradian rhythm and subcutaneous adipose tissue LPL mRNA and protein expressions in severely obese women before and after malabsorptive bariatric surgery.


METHODS
Seven severely obese, fertile women were studied twice, once before and the second time 1 year after bilio-pancreatic diversion (BPD), when the weight was stable for at least 3 months. Metabolizable energy intake and 24-h energy expenditure (EE) were measured. Fourier and PULSEFIT analyses were applied to 24-h hormonal time-series to study daily fluctuations and hormonal clearance. Insulin sensitivity was assessed by euglycemic-hyperinsulinemic clamp. Quantitative-competitive reverse transcriptase-PCR and western blot analysis were used to measure LPL gene expression.


RESULTS
Spontaneous 24-h PRL secretion was significantly reduced after BPD (mean-daily release, 128.4 +/- 28.1 microg/l vs. 67.2 +/- 9.2 microg/l distribution volume (Vd/l.24 h), P = 0.02); insulin secretion also was significantly reduced (499.9 +/- 204.0 microg/Vd/l.24 h vs. 85.6 +/- 21.0 microg/Vd/l.24 h, P = 0.0001). Metabolizable energy/kg(FFM) did not change significantly after BPD. Twenty-four-hour EE, but not 24-h EE/FFM, was significantly decreased after BPD (P < 0.05). Insulin sensitivity significantly (P < 0.0001) increased after BPD from 21.41 +/- 1.92 to 68.62 +/- 5.03 micromol/kg(FFM)/min. LPL mRNA concentration (from 42.63 +/- 4.21% to 19.00 +/- 2.74% of cyclophilin mRNA, P = 0.001) as well as LPL protein level (from 8.94 +/- 2.73 to 3.16 +/- 1.05 as ratios of protein of interest vs. housekeeping protein, P = 0.038) significantly decreased after BPD. The major determinant of PRL secretion was insulin secretion, whereas the best predictors of LPL expression were insulin and PRL secretion rates.


CONCLUSIONS
The restriction of lipid metabolizable energy rather than weight loss seems to be responsible for both reduction in PRL circulating levels and normalization of its secretion rhythm after bariatric surgery. Furthermore, the reduced adipose tissue LPL expression, being significantly correlated with the decrease in insulin and PRL, suggests a role of hyperinsulinemia and hyperprolactinemia in inducing and sustaining obesity.
Mingrone
Geltrude
G
Department of Internal Medicine, Università Cattolica S. Cuore, Rome, Italy. gmingrone@rm.unicatt.it
Manco
Melania
M
Iaconelli
Amerigo
A
Gniuli
Donatella
D
Bracaglia
Roberto
R
Leccesi
Laura
L
Calvani
Menotti
M
Nolfe
Giuseppe
G
Basu
Subhabrata
S
Berria
Rachele
R
D000273:Adipose Tissue / Q000201:enzymology* / Q000473:pathology; D000328:Adult; D050110:Bariatric Surgery; D001706:Biopsy; D002940:Circadian Rhythm / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D005500:Follow-Up Studies; D005583:Fourier Analysis; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology; D000078790:Insulin Secretion; D008071:Lipoprotein Lipase / Q000235:genetics / Q000378:metabolism*; D009767:Obesity, Morbid / Q000378:metabolism* / Q000601:surgery*; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism
D007328:Insulin; D012333:RNA, Messenger; D012738:Sex Hormone-Binding Globulin; D004958:Estradiol; D011388:Prolactin; D005640:Follicle Stimulating Hormone; D008071:Lipoprotein Lipase