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Human intervention stuides have shown that consumption of soft-fruits (berries) reduce postprandial glycaemia. The proposed mechanisms for the reduced postprandial glycaemia are inhibition of carbohydrate digestive enzymes (α-amylase, α-glucosidase), intestinal sugar absorption and transport across small intestine (as assessed via CaCo-2 cell model system). Soft-fruits were selected due to their differences in anthocyanin contents; the compounds which were hypothesised as being the bioactive metabolites. Further, the digestion of the soft-fruits was modeled using in vitro gastrointestinal digestion, where the digested metabolites were identified by LC-MS/MS. The effect of the digested metabolites on α-glucosidase activity and on the activity of cytoplasmic protein; PTP1B was determined using in vitro and in-silico methods. Mirtoselect and black currants, both of which are high in anthocyanins and their digested extracts inhibited yeast α-glucosidase activity at levels lower than Acarbose, whereas wild type bilberry and green currant, which are lower in anthocyanins showed no inhibition. All the soft-fruits showed significant inhibition on salivary α-amylase, glucose uptake, mRNA expressions of sugar transporters (SGLT1, GLUT2, GLUT5) and PTP1B. Selected anthocyanins and 'other phenolics' identified in these soft-fruits by LC-MS/MS analysis were independently evaluated for their inhibitory activity against the same targets. Both the anthocyanins and the 'other phenolics' were shown to inhibit salivary α-amylase, glucose uptake and PTP1B but only the 'other phenolics' were able to inhibit the intestinal sugar transporters (SGLT1, GLUT2, GLUT5). Specific anthocyanins identified in the soft fruits inhibited α-glucosidase, more than Acarbose. Of the selected phenolics, malvidin-3-glucoside and gallic acid demonstrated the highest inhibition of PTP1B, where their mode of inhibition and binding energies were determined using in-silic In summary, anthocyanins, as well as 'other phenolics' identified in the selected soft-fruits were effective in regulating postprandial hyperglycaemia and could lower the associated risk of developing type-2 diabetes.

Background: People with gestational diabetes mellitus (GDM) and impaired glucose regulation (IGR) are at increased risk of developing type 2 diabetes but lifestyle change can help to delay or prevent type 2 diabetes in these groups. Aims: This thesis comprises five publications which inform the development of lifestyle interventions for people with IGR and GDM by describing the epidemiology, progression to type 2 diabetes, and patient views and perceptions associated with these conditions. Methods: Publications one and two used systematic review and meta-analysis methods to describe the prevalence of IGR and GDM in Europe. A retrospective cohort design utilising routinely collected health care data from one region in Scotland was used in publications three and four to describe the incidence of IGR, and the progression from GDM and IGR to type 2 diabetes. Publication five explored women's perceptions and experiences of GDM using semi-structured interviews informed by behaviour change theory. Results: Mean prevalence of IGR and GDM in developed Europe was 22.3% and 5.4% respectively. Rates of progression to type 2 diabetes were 9% in a mean time of 34 months for IGR and 25% in a mean time of eight years for GDM. Older people with IGR living in deprived areas and women with GDM who were overweight and with higher fasting plasma glucose levels were at most risk of developing type 2 diabetes. Publication five highlighted how perceptions about the consequences of GDM and timeline and consequences of type 2 diabetes may be linked to the lifestyle change women make after diagnosis of GDM and their lack of success in maintaining these changes postnatally. Conclusions: This thesis provides a clear understanding of the prevalence of IGR and GDM, rates of progression to type 2 diabetes, and patient views and perceptions on which to base intervention planning and health care delivery.

Obesity and type-2 diabetes are major global health crises. The synthetic retinoid compound 4-hydroxy(phenyl)retinamide (Fenretinide, FEN), has been shown to inhibit adiposity and reverse insulin resistance in pre-clinical studies. Fenretinide acts via several different mechanisms, including induction of retinoid signalling and increased hepatic lipid oxidation to exert its metabolic effects. However, the signalling mechanisms behind these effects have yet to be fully elucidated. A number of approaches were taken in this thesis to investigate the signalling mechanisms of Fenretinide. To characterise the relationship between Fenretinide and leptin signalling, Fenretinide treatment was administered in two different leptin-deficient mouse models. Fenretinide effects on hepatic signalling mechanisms were further characterised by performing global transcriptomics analysis in liver from mice receiving HFD ± Fenretinide. In this analysis, the important metabolic hormone fibroblast growth factor (FGF) 21 was identified as a novel retinoid-dependent target of Fenretinide signalling, which was further characterised in multiple mouse models. Retinoic-acid receptor-specific ChIP-sequencing was performed in order to identify other liver genes that are regulated by Fenretinide via retinoid-dependent signalling mechanisms. This work has shown that the beneficial effects of Fenretinide on adiposity occur via a mechanism independent of that through which Fenretinide mediates effects on glucose homeostasis. Fenretinide effects on insulin sensitivity and glucose homeostasis are most likely mediated via the inhibition of ceramide synthesis in the liver and other metabolically active tissues. This work also shows that Fenretinide can normalise the effects of chronic HFD-feeding by targeting the expression of a set of PPARα-target genes in the liver via a retinoid-dependent signalling mechanism. Overall, the work described in this thesis both uncovers more detail about the signalling mechanisms of Fenretinide and identifies novel target genes that may be exploited for the development of new therapeutics to treat obesity and type 2 diabetes.

Genome wide association studies (GWAS) have transformed the study of the heritability of complex diseases such as type 2 diabetes (T2D), with the current tally of established risk loci close to ninety. Each of these loci has the potential to offer novel insights into the biology of this disease, and opportunities for clinical exploitation. However, the complexity of T2D has often frustrated efforts to achieve these functional and translational advances. This thesis aims to delve into the functional characterisation of two known susceptibility loci, KLF14 and ADCY5, and describe findings relevant to disease pathology. KLF14 and ADCY5 are two loci associated with T2D predisposition working through disparate mechanisms. Variants at the maternally imprinted KLF14 locus are associated with measures of insulin resistance and expression data has implicated KLF14 as a master regulator of genes in adipose tissue. In contrast, variation at the ADCY5 locus is associated with impaired beta cell function, high fasting glucose, and low birth weight suggesting ADCY5 is having an effect on insulin secretion. In this thesis, ENU mouse models of these two genes are investigated functionally to elucidate more about the pathology of common human variation at these loci. A mouse model was derived with an ENU point mutation at Adcy5 Y1064C. Phenotyping of this model revealed improved oral glucose tolerance, and secretion studies from isolated islet cells demonstrated impaired glucagon secretion from mice homozygous for the Y1064C mutation in the presence of adrenaline. These results suggest that Adcy5 is involved in glucagon regulation in the alpha cell. The Adcy5 Y1064C confers a protective effect against hyperglycaemia in mouse indicating that the T2D risk allele at the ADCY5 locus in humans may have the opposite direction of effect. A mouse model containing the ENU point mutation Klf14 R238L predicted to be disruptive to KLF14 protein function showed no significant difference in body weight, measures of insulin resistance, or blood cholesterol. However, expression of several genes associated in trans with variation near KLF14 in humans was changed in adipose tissue and skeletal muscle when the R238L mutation was inherited maternally compared to mice which had inherited the mutation paternally or carried two wild type alleles. This result suggests a mechanism by which Klf14 is regulating genes across metabolic tissues.

n-3 polyunsaturated fatty acids (n-3 PUFA) have been postulated to improve the insulin resistance associated with type 2 diabetes since the 1960s when observational studies in the Alaskan Inuit noted a reduced prevalence of type 2 diabetes when this population consumed a traditional diet. These findings were supported by animal studies but results of human intervention studies have been variable with most showing no change in glucose metabolism. More recent studies in growing farm animals suggested that muscle membrane phospholipids required to be enriched to a minimum of 14% n-3 PUFA in order for a change in insulin sensitivity to occur. This study sought to establish the effect of long-term (9 month) high-dose (3g/day) supplement of the n-3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on insulin sensitivity of glucose and protein metabolism. Thirty-three subjects with impaired glucose regulation underwent hyperinsulinaemic-euglycaemic-euaminoacidaemic clamps pre- and postintervention of n-3 PUFA or a control (maize) oil. A second cohort who all received n-3 PUFA supplementation underwent pre- and post-intervention muscle biopsies. Secondary outcomes included an assessment of inflammatory status and determining whether erythrocyte membrane phospholipid could act as a surrogate for muscle membrane phospholipid. In the clamp cohort, there were no changes in glucose metabolism postintervention; however, there was an increase in insulin-stimulated protein metabolism following the fish oil intervention. In the biopsy cohort, no subject achieved 14% PUFA enrichment in muscle membrane phospholipids; however, all subjects who received n-3 PUFA supplementation did achieve a minimum of 14% enrichment of n-3 PUFA in erythrocyte membrane phospholipid. In agreement with the majority of the literature, n-3 PUFA did not affect glucose metabolism. Insulin-stimulated protein metabolism was improved supporting the findings of another recent human study. These changes in protein metabolism may reduce the sarcopenia associated with aging, potentially delaying the progression of frailty.

Autoimmune diabetes is a disorder in which the (3-cells in the pancreatic islets of Langerhans are specifically destroyed resulting in absolute insulin deficiency; typically this is a childhood-onset disease, Type 1 Diabetes (T1D). Type 2 Diabetes (T2D) is a metabolic disorder usually developing in adults resulting from defects in insulin secretion and action. Latent Autoimmune Diabetes in Adults (LADA) is a form of diabetes that shares autoimmune disease pathology with T1D but a clinical presentation similar to T2D; LADA patients develop diabetes as adults (>25 years) and do not immediately require insulin treatment for survival. They are therefore often misdiagnosed with T2D. The aims of this work were to characterise immunological and genetic aspects of LADA using a large cohort collected from various patient repositories the United Kingdom to determine if it is a separate disease entity or an age-related extension of T1D. Both T1D and LADA are characterised by autoantibodies to the islet cell protein glutamic acid decarboxylase 65 (GADA) at diagnosis. The persistence and titre of GADA post-diagnosis in LADA was examined at 0.5, 3 and 6 years. GADA persisted in 93% of patients for 6 years; GADA litres decreased between 0.5 and 3 years post-diagnosis and either stabilised or increased again between 3 and 6 years. GADA titre was not associated with age at diagnosis, glycaemic control, β-cell function or other clinical features. GADA titre at 0.5 years was associated with a greater likelihood of requiring more intensive antihyperglycaemic therapy but did not predict therapy or insulin requirement at 3 and 6 years. Autoantibodies against IA-2 plus GADA compared to GADA alone at diagnosis predicted increased therapy requirement by 3 and 6 years and insulin requirement by 3 years postdiagnosis. Variants of the Human Leukocyte Antigen (HLA) genes DRB1 and DQB1, are associated with susceptibility for T1 D. An analysis of these variants in LADA (n = 378) revealed that the predisposing and protective variants in LADA are similar to those reported in T1D; DR3 (in linkage disequilibrium, LD with DQ2) and DR4 (in LD with DQ8) were the main predisposing variants whereas DR2 (in LD with DQ6) was most the protective against LADA. 85% of LADA patients possessed the DR3 and DR4 specificities, compared with 95% seen in T1D, suggesting a reduced predisposition in LADA compared with T1D. Synergistic effects of the DR3 and DR4 specificities occurred in LADA and the DRB1*0401 allele within the DR4 specificity was predisposing to disease, as seen in T1D. No other predisposing variants were identified in LADA. As reported for T1D, DR11, DR13, DQ5, DQ7 and DQ9 were protective against LADA; DQ6 was positively correlated with age at diagnosis. Association analysis of the insulin gene region in LADA (n = 400) showed that the variable number of tandem repeats (VNTR) locus primarily confers susceptibility to disease. Overall, the short Class I alleles predisposed to disease whereas longer Class III alleles conferred dominant protection, as reported in T1D. Fine-structure analysis showed that the Class I haplotypes 'IC+/ID+' and 'ID-' both conferred susceptibility for LADA - unlike in T1D, where the ID- haplotype has been reported to have protective effects. The Class III 'Protective' and Very Protective' haplotypes, conferred equal protection in LADA, as reported forTID. In conclusion; GADA persist post-diagnosis but are not markers for disease progression of LADA. Patterns of susceptibility at the HLA and insulin gene regions in LADA are similar to that reported for T1 D. LADA is likely to represent an age-related extension of T1D rather than a separate disease entity.