The effect of housing temperature and a high-fat, high-carbohydrate diet on maternal interscapular brown adipose tissue

AlHarethi, Enas (2019) The effect of housing temperature and a high-fat, high-carbohydrate diet on maternal interscapular brown adipose tissue. MPhil thesis, University of Nottingham.

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Brown adipose tissue (BAT) has a role in energy balance and the utilization of fatty acids and glucose, but the extent to which its composition may be modulated by housing temperature is unknown, especially during gestation. BAT activity decline during gestation to enable conservation of maternal energy. This study aimed to investigate the effect of the standard housing temperature (20°C) as compared to a thermoneutral environment (~27°C) on obesity during gestation. The hypothesis is the impact of gestation and high-fat, high-sucrose (HFHS) diet on BAT and white adipose tissue (WAT) would be pronounced on thermoneutral temperature conditions and these changes would be mediated by changes in BAT.

Several methods were employed in this study to produce the outcomes, including immunohistochemistry on a BAT for visualisation and quantification of mitochondrial UCP1 abundance. The qPCR (quantitative polymerase chain reaction) was performed to investigate the mRNA expression of several BAT-related genes, including UCP1, proximal proliferator-activated receptor (PPARγ), PPARγ coactivator (PGC1α), beta-3 adrenergic receptor (β3-ARs) and transient receptor potential vanilloid subfamily 1 (TRPV1). Other genes were also investigated, such as the lipid-transporter gene adipocyte triglycerides lipase (ATGL), the energy-sensing gene (leptin) and the UCP1-independent thermogenesis sarco/endoplasmic reticulum ATPase2b (SERCA2b). Some plasma metabolites were measured including the use of enzyme linked immune assay for plasma insulin hormone.

The HFHS diet had the greatest effect on body weight gain and fat mass deposition in the gestational group. Throughout gestation, both HFHS diet and housing at 20°C increased interscapular BAT weight. The mitochondrial UCP1 abundance in the animals housed at 20°C increased in the pre-gestation and 10-days gestation groups. Before gestation, the mRNA expression of the UCP1 followed a similar pattern to the UCP1 protein abundance, PGC1 mRNA expression increased and leptin expression decreased as compared to 27°C. In the 19-day gestation group, the mRNA expression of PPARγ decreased and the expression of PGC1α increased. The (ATGL) mRNA expression increased at 27 °C in the pre-gestation and 19-day gestational groups.

In conclusion, these results suggest that the standard housing temperature conditions under which rat are normally maintained impact UCP1 abundance and fat mass deposition although this effect is partially modified by gestation. Only modest changes were shown in plasma metabolites, which emphasize the subtle but important role of housing temperature when examining the effect of HFHS diet. Standard housing temperature do not reflect rat thermoneutrality and may have consequences for metabolic research results. Therefore, thermoneutrality remains the ideal housing temperature that could model human conditions for metabolic research.

Item Type: Thesis (University of Nottingham only) (MPhil)
Supervisors: Symonds, Michael
Budge, Helen
Keywords: Brown adipose tissue; Temperature; Gestation; Rats
Subjects: Q Science > QL Zoology
W Medicine and related subjects (NLM Classification) > WD Disorders of systemic, metabolic or environmental origin
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Medicine
Item ID: 56586
Depositing User: AlHarethi, Enas
Date Deposited: 30 Oct 2019 09:39
Last Modified: 06 May 2020 13:33

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