Anatomical fat distribution and accumulation and lipotoxicity in lean and obese pregnancy

Jarvie, Eleanor M.K. (2015) Anatomical fat distribution and accumulation and lipotoxicity in lean and obese pregnancy. PhD thesis, University of Glasgow.

Abstract

Maternal obesity has been at the forefront of pregnancy-related research in recent times. The impact of this chronic health condition has been highlighted in reports on maternal mortality (CEMACH, 2007, CEMACH, 2011), where 30% of mothers who died from pregnancy related causes were obese (CEMACH, 2011). The importance of maternal obesity and how it affects maternal adaptation to pregnancy is well documented with obese women exhibiting low grade inflammation, greater coagulability and poorer improvement in vascular function during pregnancy compared to lean women (Stewart et al., 2007a). These findings suggest that obese women display similar characteristics to the non-pregnant adult metabolic syndrome and these attributes may be important in explaining why obese pregnancies have higher rates of obstetric complications including gestational diabetes (GDM) and pre-eclampsia (PET). In non-pregnant adult obesity it has been found that central or truncal adiposity is associated with increased NEFA (non-esterified fatty acids) turnover and ectopic fat (especially liver) deposition. It has been suggested that obese pregnant women may also preferentially gain fat in central depots and this may be the mechanism by which poor vascular improvement and inflammation are initiated.
The aims of this thesis were to assess subcutaneous fat accumulation and distribution throughout pregnancy in both lean and OW/OB women. Furthermore this thesis aimed to acquire a better understanding of the impact of anatomical fat deposition on metabolic and vascular function during pregnancy. A final aim was to assess vascular function and evidence of lipotoxicity during pregnancy and test whether the site of fat accumulation and distribution was associated with gestational improvement of vascular function.

A longitudinal study was performed and anthropometric data was collected from 26 lean and 16 OW/OB women at three antenatal time points (15, 25 and 35 weeks’ gestation) during pregnancy. Direct measurements of energy metabolism (basal metabolic rate, substrate utilisation, physical activity and diet) were also collected to assess the impact of energy metabolism on fat accumulation and distribution. A comprehensive panel of plasma markers of carbohydrate and lipid metabolism (fasting glucose, fasting insulin, total cholesterol [TC], total triglyceride [TG], high density lipoprotein [HDL] and NEFA) and inflammatory
(C-reactive protein [CRP], interleukin-6 [IL6] and tumour necrosis factor alpha [TNF]) were quantitated at each study appointment. Endothelial function was measured using laser Doppler imaging (LDI). Measurement of plasma and urinary biomarkers of endothelial function and lipotoxicity including soluble intracellular adhesion molecule 1 (sICAM-1), soluble vascular adhesion molecule-1 (sVCAM-1), oxidised low density lipoprotein (oxLDL), plasma superoxide and urinary isoprostanes were undertaken.

Lean and OW/OB women gained similar amounts of total body weight and fat mass during pregnancy. Only in lean women was there an anatomical preference for site of fat storage and this was in the upper peripheral subcutaneous depots. In healthy OW/OB pregnancy no such anatomical preference of fat deposition was found.

The study of energy metabolism found that OW/OB women had higher basal metabolic rate and higher fat oxidation than lean women, whilst lean women had higher rates of carbohydrate oxidation and physical activity than OW/OB women. In the lean and OW/OB groups dietary macronutrient intakes were similar. Overall the parameters of energy metabolism were not associated with overall fat mass accumulation or distribution.

During pregnancy, OW/OB women were more insulin resistant and pro-inflammatory (CRP and TNFα) than lean women and lean women had higher concentrations of plasma HDL. Interestingly the lean group had higher plasma concentrations of IL6 which may be a result of higher rates of vascular remodelling and may reflect a physiological rather than pathological process. In both lean and OW/OB pregnancies the gestational increase in subcutaneous adipose depots was not associated with the gestational changes in markers of carbohydrate, lipid or inflammatory profiles.

Both lean and OW/OB women exhibited similar gestational improvement in endothelial microvascular function. During pregnancy both groups showed an increase in markers of lipotoxicity but levels were not associated with vascular function. Changes in anatomical subcutaneous fat distribution were also not associated with the changes in vascular function during pregnancy.
In conclusion, in pregnancy, only lean women exhibit an anatomical site-specific fat accumulation. Although the OW/OB group displayed some aspects of the metabolic syndrome in general the OW/OB women studied here adapted to pregnancy in a similar way to lean women in terms of vascular function and levels of lipotoxicity. However, visceral adiposity was not assessed and OW/OB women with larger visceral adipose stores may exhibit a more lipotoxic phenotype and more pathological adaptation to pregnancy that may make them susceptible to metabolic complications of pregnancy. This study highlights the heterogeneity of maternal obesity and suggests that further studies into ‘metabolically healthy’ and ‘metabolically unhealthy’ lean and OW/OB women is warranted.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: maternal obesity, anatomical fat, lipotoxicity, obese pregnancy
• Subjects: R Medicine > RG Gynecology and obstetrics
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
• Supervisor's Name: Freeman, Dr Dilys
• Date of Award: 2015
• Depositing User: Dr Eleanor MK Jarvie
• Unique ID: glathesis:2015-6310
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 13 May 2015 15:13
• Last Modified: 13 May 2015 15:39
• URI: https://theses.gla.ac.uk/id/eprint/6310