Indiana University-Purdue University Indianapolis (IUPUI) / Insulin resistance in liver, muscle, and adipose tissue almost invariably occurs during obesity. To compensate, the insulin-producing β-cell increases insulin production by expanding cellular mass. The inability of the β-cell to fully compensate leads to hyperglycemia and ultimately type 2 diabetes. The enzyme deoxyhypusine synthase (DHS) catalyzes the spermidine-dependent posttranslational modification of Lys50 of eukaryotic translation initiation factor 5A (eIF5A) to form hypusine (Hyp). Studies have demonstrated this modification of eIF5A to contribute to cellular proliferation in cancerous cells, but its role in the physiologic proliferation of islet β-cells is unknown. I hypothesized eIF5A-Hyp to be required for the proliferation of islet β cells during the early phase of insulin resistance, allowing the β-cell to respond to the increased demand for insulin to maintain glucose homeostasis. To test this hypothesis, deletion of DHS was induced post-developmentally in β-cells by crossing Dhs-fl/fl mice with MIP1-CreERT mice, and animals were fed for 1 or 4 weeks with a 60% kcal from fat diet (HFD) or normal chow diet (NCD, 16% kcal from fat diet). NCD-fed and HFD-fed animals had normal glucose homeostasis after one week feeding, regardless of genotype. However, after 4 weeks of HFD, KO mice had significantly worse glucose intolerance compared to control mice. eIF5A-Hyp levels increased in β-cells of control animals and as expected remained low in the KO mice. β-cell proliferation was significantly increased after 1 week of HFD as measured by PCNA staining, however KO mice showed no increase. Cyclin D2 protein, but not mRNA, was increased in control animals fed a HFD; this protein increase was not observed in KO animals. Furthermore, polyribosomal profile of isolated islets of 1 week HFD-fed mice showed the Ccnd2 mRNA bound to the monoribosome fractions in the KO animals compared to the controls, resulting in changes of global translation. Interestingly, Ccnd1 polyribosome to monoribosome ratio showed no changes in translation compared to Ccnd2. Taken together, these results suggest that DHS (and, consequently, eIF5A-Hyp) is necessary for the adaptive proliferative and functional response of β-cells during high fat diet induced obesity and glucose intolerance.

No description available.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24795号 / 医博第4987号 / 新制||医||1066(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 小林 恭, 教授 波多野 悦朗, 教授 羽賀 博典 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

<p>  </p> <p>In modern society, continuous light exposure and obesity are increasingly prevalent, especially in women of childbearing age. Circadian, metabolic, and reproductive systems have a complex, inter-regulated relationship. Thus, the disruption of one system likely impedes another. Excessive adiposity and circadian disruption alter normal behavior and physiology and disrupt the endocrine milieu. The overall goal of the studies described in this thesis was to develop and test a model system that could tease apart the influence of prepregnancy obesity and circadian disruption, as well as study the combined effects on female reproductive competence. </p> <p>The first study focuses on the prepregnancy period and aims to determine the effect of high fat diet feeding on diurnal eating pattern, body weight over the four-week period, the body composition at the end of the four-week period, hair corticosterone levels, and circadian fecal corticosterone patterns on female ICR mice. Five-week-old female ICR mice were randomly assigned to control (CON; 10% fat) or high fat (HF; 60%) diets and fed for four weeks to achieve adequate adiposity. During this four-week time period, mice had routine light exposure of 12h light and 12h dark. Feed was weighed at 0600 and 1745 Monday-Friday to determine diurnal feed intake. The mice were weighed on a weekly basis. After four weeks on respective diets, mice were anesthetized with isoflurane to measure crown-rump length to calculate BMI and hair was shaved for corticosterone extraction. Once mice recovered from anesthesia, body composition was measured with EchoMRI. After 1 week on diets, HF mice consumed more (P<0.05) during the day than CON mice, which is typically when mice are inactive. After two weeks on diets, HF mice weighed more (P<0.05) than CON, as well as had higher BMI and percent body fat (P<0.05) than CON after four weeks on diets. After four weeks on diets, HF mice had high hair corticosterone (P<0.05). Sampling feces over a 48h period at the end of the four weeks demonstrated that HF mice had elevated basal corticosterone, attenuated circadian rhythms, and a shift in corticosterone amplitude. The prepregnancy period demonstrated that high fat diets alone alter circadian eating pattern and corticosterone rhythms.</p> <p>The remainder of the study continued the dietary treatments assigned during the prepregnancy period, as well as implemented light conditions to create a 2Χ3 factorial study design. There were three light conditions: 12h light and 12h dark (LD), 24h dim light (L5), or 24h bright light (L100). Mice were moved into experimental light conditions after the observation of a vaginal plug or after 5 days with males. This portion of the study aimed to determine the effect of diet (CON or HF) and light exposure (LD, L5, or L100) on gestation length, number of pups born, milk composition, litter weight on postnatal day 12, as well as dam feed intake, hair corticosterone levels, and plasma prolactin. Continuous light exposure increased gestation length, with L5 (19.1 d ± 0.23) and L100 (18.9 d ± 0.21) having longer gestation lengths (P<0.05) than LD (18.1 d ± 0.25). Diet affected the number of pups born (P<0.05), with HF dams having fewer pups (9.99 ± 0.4) than CON (11.4 ± 0.4). Despite no difference in birth weight of standardized litters (n=8 pus/litter), litters of HF dams weighed more than CON by day 4 postnatal. The greater litter weight of HF dams continued until the end of the study on day 12 of lactation (P<0.05). Light had a tendency to increase litter weight (P=0.07). Diet, light, and stage of reproduction influenced dam feed intake (P<0.05). L100 dams had higher plasma prolactin, as well as final dam and mammary wet weights (P<0.05). Constant light exposure decreased ATP content in the mammary gland (P<0.05) and decreased milk lactose concentration (P<0.05). Pearson’s correlation analysis showed a positive relationship between mammary weight, fat pad weight, BMI, kcal of feed intake, and gestation length (P<0.05). In CON mice, hair corticosterone was negatively correlated with litter weight on lactation day 12. Liver weight was positively correlated with d 12 litter weight in HF mice. Together, these studies demonstrate that feeding high fat diets and continuous light alter maternal behavior and physiology, which may impact offspring health and development, however continuous light may not be the best approach to studying circadian disruption. Elevated maternal plasma prolactin and increased dam weight suggests a long day photoperiod was likely induced, thus potentially mitigating the circadian disruptive effects from constant light. Other model systems should be considered, such as using a chronic jet lag model that changes the light exposure every 3 d. </p>

京都大学 / 新制・課程博士 / 博士(農学) / 甲第24109号 / 農博第2514号 / 新制||農||1093(附属図書館) / 学位論文||R4||N5400(農学部図書室) / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 佐藤 健司, 教授 菅原 達也, 准教授 木下 政人 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

No description available.

No description available.

No description available.

No description available.

No description available.