Type 2 diabetes mellitus (T2DM) is a heterogeneous disease affecting millions of people worldwide. Both genetic and environmental factors contribute to the pathogenesis. The disease is characterized by alterations in many genes and their products. Historically, genomic alterations have mainly been studied at the transcriptional level in diabetes research. However, transcriptional changes do not always lead to altered translation, which makes it important to measure changes at the protein level. Proteomic techniques offer the possibility of measuring multiple protein alterations simultaneously. In this thesis, the proteomic technique surface enhanced laser desorption ionization time-of-flight mass spectrometry (SELDI-TOF MS) has been applied and evaluated in the context of T2DM research. Protocols for pancreatic islet and serum/plasma protein profiling and identification have been developed. In addition, the technique was used to analyze the influence of genetic background versus diabetic environment by determining serum protein profiles of individuals with normal glucose tolerance (NGT) and T2DM with or without family history of diabetes. In total thirteen serum proteins displayed different levels in serum from persons with NGT versus patients with T2DM. Among these proteins, apolipoprotein CIII, albumin and one yet unidentified protein could be classified as being changed because of different genetic backgrounds. On the other hand, ten proteins for instance transthyretin, differed as a result of the diabetic environment. When plasma protein patterns of NGT and T2DM individuals characterized by differences in early insulin responses (EIR) were compared, nine proteins were found to be varying between the two groups. Of these proteins five were identified, namely two forms of transthyretin, hemoglobin α-chain, hemoglobin β-chain and apolipoprotein H. However no individual protein alone could explain the differences in EIR. In conclusion, SELDI-TOF MS has been successfully used in the context of T2DM research to identify proteins associated with family history of diabetes and β-bell function.

Att lägga om sin livsstil är inte lätt, men i många fall kan det vara nödvändigt för att bibehålla en god hälsa. Ett exempel på ett sådant tillfälle är vid en diabetesdiagnos, där förstahandsbehandlingen består i livsstilsförändring, som främst innefattar kost, motion och rökstopp. Resultat från tidigare forskning visar att det är viktigt att patienten är motiverad att genomföra en livsstilsförändring, och även diabetessköterskorna i den här studien är av den uppfattningen. Det är viktigt att patienten själv tar ansvaret för sin sjukdom, det är bara han eller hon som kan förändra sin livsstil. Syftet med studien var att undersöka hur diabetessköterskorna hjälpte sina patienter att hitta motivation till livsstilsförändring. En kvalitativ intervjumetod användes för att samla material, fem diabetessköterskor intervjuades. Den efterföljande analysen är inspirerad av hermeneutisk metod. Resultatet av studien visar att patienten själv måste hitta sin motivation, det finns inget sätt för diabetessköterskan att konkret hjälpa sin patient att hitta den. Diabetessköterskans uppgift är att finnas där när patienten själv hittat sin motivation, och leda patienten rätt. / To change your way of living is not easy, but in many cases it might be necessary to sustain a good health. An example of this is when you get a diagnosis of diabetes and the first treatment is a change of lifestyle, especially concerning diet, exercise and no smoking. Former studies have shown that the patient has to be motivated to change their lifestyle and this is the opinion of diabetes nurses in this study as well. It is important that the patient takes the responsibility for the disease because it’s only himself who can change the lifestyle. The aim of this study was to look into how the diabetes nurses helped the patients to find motivation to a change of lifestyle. Five nurses were interviewed. A qualitative field survey has been used to gather the material and the following analysis is inspired of the hermeneutic method. Results of the study show that the patients have to find the motivation on their own and that the diabetes nurse doesn’t have a concrete way of helping him or her. The nurse’s task is to be there when the patient has found the motivation and lead them on to the right track.

Background Anthropometric measurements are useful in clinical practice since they are non-invasive and cheap. Previous studies suggest that sagittal abdominal diameter (SAD) may be a better measure of visceral fat depots. The aim of this study was to prospectively explore and compare how laboratory and anthropometric risk markers predicted subclinical organ damage in 255 patients, with type 2 diabetes, after four years. Methods Baseline investigations were performed in 2006 and were repeated at follow-up in 2010. Carotid intima-media thickness (IMT) was evaluated by ultrasonography and aortic pulse wave velocity (PWV) was measured with applanation tonometry over the carotid and femoral arteries at baseline and at follow-up in a cohort of subjects with type 2 diabetes aged 55–65 years old. Results There were significant correlations between apolipoprotein B (apoB) (r = 0.144, p = 0.03), C - reactive protein (CRP) (r = 0.172, p = 0.009) at baseline and IMT measured at follow-up. After adjustment for sex, age, treatment with statins and Hba1c, the associations remained statistically significant. HbA1c, total cholesterol or LDL-cholesterol did not correlate to IMT at follow-up. Baseline body mass index (BMI) (r = 0.130, p = 0.049), waist circumference (WC) (r = 0.147, p = 0.027) and sagittal Abdominal Diameter (SAD) (r = 0.184, p = 0.007) correlated to PWV at follow-up. Challenged with sex, SBP and HbA1c, the association between SAD, not WC nor BMI, and PWV remained statistically significant (p = 0.036). In a stepwise linear regression, entering both SAD and WC, the association between SAD and PWV was stronger than the association between WC and PWV. Conclusions We conclude that apoB and CRP, but not LDL-cholesterol predicted subclinical atherosclerosis. Furthermore, SAD was more independent in predicting arterial stiffness over time, compared with WC, in middle-aged men and women with type 2 diabetes. / <p>Funding Agencies|Medical Research Council of Southeast Sweden||Center for Medical Image Science and Visualization (CMIV)||Linkoping University||Futurum||King Gustaf V and Queen Victoria Freemason Foundation||GE Healthcare||Swedish Heart-Lung Foundation||Swedish Research Council Grant|12661|</p>

An important mechanism involved in the pathogenesis of type 2 diabetes is elevation of plasma free fatty acids which induce insulin resistance and may impair both β-cell function and mass (β-cell lipotoxicity). The objective of my thesis was to investigate the role of oxidative stress in β-cell lipotoxicity, using in vivo, ex vivo, and in vitro models. I used in vivo models of 48h i.v. oleate or olive oil infusion in Wistar rats followed by hyperglycemic clamps, or islet secretion studies ex vivo, and in vitro models of 48h exposure to oleate in isolated islets. My first study showed that 48h oleate infusion decreased the insulin response to a hyperglycemic clamp, an effect prevented by coinfusion of the antioxidants N-acetylcysteine and taurine. Similar to the findings in vivo, 48h infusion of oleate decreased glucose stimulated insulin secretion (GSIS) ex vivo, and induced oxidative stress in isolated islets, effects prevented by coinfusion of the antioxidants N-acetylcysteine, taurine, or tempol. Islets exposed to oleate or palmitate showed a decreased insulin response to high glucose and increased levels of oxidative stress, effects prevented by taurine. Therefore, my data are the first demonstration that oxidative stress plays a role in the decrease in β-cell secretory function induced by prolonged exposure to FFA, in vitro and in vivo. My second study addressed downstream effects of oxidative stress involving inflammation. A 48h infusion of oleate or olive oil decreased β-cell function during a hyperglycemic clamp, an effect prevented by coinfusion of the IKKβ inhibitor salicylate. GSIS in isolated islets was impaired by olive oil or oleate and restored by salicylate. These results suggest a potential role for both oxidative stress and inflammation in lipid-induced β-cell dysfunction. My third study addressed downstream effects of oxidative stress involving β-cell insulin signalling. A 48h infusion of oleate or olive oil decreased β-cell function during a hyperglycemic clamp, an effect prevented by coinfusion of the tyrosine phosphatase inhibitor bisperoxovanadate. GSIS in isolated islets was impaired by olive oil or oleate and restored by bisperoxovanadate, suggesting a role of FFA in decreasing β-cell function by induction of β-cell insulin resistance.

Chronic hyperglycemia, a hallmark of type 2 diabetes, can decrease β-cell function and mass (β-cell glucotoxicity); however, the mechanisms are incompletely understood. The objective was to examine the mechanisms of β-cell glucotoxicity using in vivo and ex vivo models. The hypothesis is that oxidative stress plays a causal role in high glucose-induced β-cell dysfunction in vivo via pathways that involve endoplasmic reticulum (ER) stress and JNK. The model of β-cell glucotoxicity was achieved by prolonged i.v. glucose infusion (to achieve hyperglycemia). In Study 1, 48h glucose infusion increased total and mitochondrial superoxide levels in islets, and impaired β-cell function in vivo and ex vivo. Co-infusion of the superoxide dismutase mimetic Tempol decreased total and mitochondrial superoxide, and prevented high glucose-induced β-cell dysfunction in vivo and ex vivo. These results suggest that increased superoxide generation plays a role in β-cell glucotoxicity. In Study 2, 48h glucose infusion increased activation of the unfolded protein response (XBP-1 mRNA splicing and phospho-eIF2α levels). This was partially prevented by Tempol. Co-infusion of the chemical chaperone 4-phenylbutyrate with glucose decreased spliced XBP-1 levels, and prevented high glucose-induced β-cell dysfunction in vivo and ex vivo. Co-infusion of 4-phenylbutyrate also decreased total and mitochondrial superoxide induced by high glucose. These results suggest that 1) ER stress plays a causal role in high glucose-induced β-cell dysfunction, and 2) there is a link between oxidative stress and ER stress in high glucose-induced β-cell dysfunction in vivo. In Study 3, JNK inhibition using the inhibitor SP600125 in rats or JNK-1 null mice prevented high glucose-induced β-cell dysfunction ex vivo and in vivo. SP600125 prevented high-glucose-induced β-cell dysfunction without decreasing total and mitochondrial superoxide levels. Both Tempol and 4-phenylbutyrate prevented JNK activation induced by high glucose. These results suggest a role of JNK activation in high glucose-induced β-cell dysfunction downstream of increased superoxide generation and ER stress in vivo. Together, the results suggest that 1) oxidative stress, ER stress and JNK activation are causally involved in β-cell glucotoxicity, and 2) High glucose-induced oxidative stress and ER stress are linked, and both impair β-cell dysfunction via JNK activation in vivo.

PI3K signaling in pancreatic β cells has been shown to be important in modulating β cell mass and function under basal condition. Evidence suggests that a specific group of insulin promoter-expressing neurons also modulates glucose metabolism and energy homeostasis through their PI3K signaling. Thus we hypothesize that PI3K activation via PTEN deletion under the control of rat insulin promoter (RIP) in pancreatic β cells and RIP-expressing neurons will protect against hyperglycemia and diabetes in experimentally induced mouse models of type 2 diabetes. In Chapter IV, we showed that RIP-mediated PTEN deletion in pancreatic β cells led to PI3K activation and subsequent increased β cell mass and function, thus protected the mice from high fat diet (HFD)-induced diabetes. Furthermore in the absence of global leptin signaling, β cell-specific PTEN deletion maintained β cell function in the setting of severe insulin resistance, therefore prevented diabetes development. Interestingly, RIP-mediated PTEN deletion also resulted in increased peripheral insulin sensitivity due to PI3K activation in central nervous system. In Chapter V, we showed this increased insulin sensitivity was maintained after HFD feeding, which also contributed to the protection against diabetes. These mice also showed increased visceral adipogenesis and subcutaneous adiposity on HFD, which were dramatically attenuated in the absence of leptin signaling, indicated the essential role of peripheral leptin action in mediating the insulin sensitive phenotype from neuronal RIP PTEN deletion. Finally, we demonstrated that the insulin sensitizing phenotype in these mice was not mediated through ventromedial hypothalamic nuclei (VMH), such that VMH-specific PTEN deletion did not alter energy homeostasis or glucose metabolism. Together, the data from this thesis points to an inhibitory role of PTEN in both central nervous system and pancreatic β cells in glycemic control. Therefore, PTEN may represent a potential target for diabetes prevention and treatment.

Specific SNPs in intronic regions of the human TCF7L2 gene are associated with an elevated risk of T2D development and progression. Several investigations have suggested a role of TCF7L2 in pancreatic β-cells. Whether this transcription factor is indeed expressed in the pancreatic islets of rodent species, however, has been a controversial issue. Here, we found that TCF7L2 mRNA level was significantly lower in the pancreas compared to the gut or Ins-1 cell line. In addition, TCF7L2 mRNA abundance in the pancreas was decreased by insulin. Finally, both TCF7 and TCF7L1 but not LEF-1 could be detected in the mouse pancreas. mRNA abundance for these two transcription factors was also decreased by insulin, and the level of TCF7, TCF7L1, and TCF7L2 mRNAs could be down-regulated by HFD. We speculate that reduced expression of these TCF genes during hyperinsulinemia may alter the Wnt signalling pathway and therefore impair the function of β-cells.

The unfolded protein response, which is activated during ER stress, counteracts stress conditions by increasing folding capacity and by increasing the degradation of misfolded ER proteins by the ER-Associated Degradation (ERAD) system. Studies using an engineered insulinoma cell line with inducible expression of the Akita folding-deficient insulin have shown a large induction of Herp, a protein that has been implicated in the ERAD pathway. We hypothesized that Herp is an essential protein that regulates the degradation of misfolded insulin during the ER stress response. Indeed, we found that the degradation of mutant insulin is Herp-dependent and that maintaining Herp expression is vital for maintaining cell survival. We have also observed that the expression of Herp mRNA and protein is induced in various cell culture and animal models of diabetes. These results suggest that Herp is an important ER stress response protein that is induced under diabetic conditions in pancreatic β-cells.

Specific SNPs in intronic regions of the human TCF7L2 gene are associated with an elevated risk of T2D development and progression. Several investigations have suggested a role of TCF7L2 in pancreatic β-cells. Whether this transcription factor is indeed expressed in the pancreatic islets of rodent species, however, has been a controversial issue. Here, we found that TCF7L2 mRNA level was significantly lower in the pancreas compared to the gut or Ins-1 cell line. In addition, TCF7L2 mRNA abundance in the pancreas was decreased by insulin. Finally, both TCF7 and TCF7L1 but not LEF-1 could be detected in the mouse pancreas. mRNA abundance for these two transcription factors was also decreased by insulin, and the level of TCF7, TCF7L1, and TCF7L2 mRNAs could be down-regulated by HFD. We speculate that reduced expression of these TCF genes during hyperinsulinemia may alter the Wnt signalling pathway and therefore impair the function of β-cells.

The unfolded protein response, which is activated during ER stress, counteracts stress conditions by increasing folding capacity and by increasing the degradation of misfolded ER proteins by the ER-Associated Degradation (ERAD) system. Studies using an engineered insulinoma cell line with inducible expression of the Akita folding-deficient insulin have shown a large induction of Herp, a protein that has been implicated in the ERAD pathway. We hypothesized that Herp is an essential protein that regulates the degradation of misfolded insulin during the ER stress response. Indeed, we found that the degradation of mutant insulin is Herp-dependent and that maintaining Herp expression is vital for maintaining cell survival. We have also observed that the expression of Herp mRNA and protein is induced in various cell culture and animal models of diabetes. These results suggest that Herp is an important ER stress response protein that is induced under diabetic conditions in pancreatic β-cells.