FACTORS INFLUENCING INSULIN BIOCHEMISTRY IN UK DIABETIC PATIENTS: SYSTEMATIC REVIEW

ABSTRACT

BACKGROUND: Diabetes Mellitus has proved to become a global public health issue, given the growing burden of the disease (prevalence) and associated metabolic diseases. Empirical evidence from clinical studies demonstrates the influence of insulin biochemistry (parameters) – insulin resistance, insulin secretion and insulin sensitivity – in the development of Diabetes Mellitus; however, the factors underlying the biochemical behaviour these insulin parameters and their associated impact level are note worthy. Therefore, the aim of this systematic review is to assess the factors influencing Insulin Biochemistry in UK diabetic patients (diagnosed and undiagnosed).

METHOD: This systematic review identified primary research articles associated with the factors influencing insulin biochemistry (parameters), published in the UK over the last 20 years (between 1993 and 2013). Database-searched articles (using Advanced search with Boolean operators and the key search terms) and manually-searched articles (Using Basic search and the key search terms) that passed the predetermined inclusion/exclusion criteria were selected, critically appraised (using a CASP checklist), and the data analysed and synthesised using a narrative evidence synthesis. The search databases include: EBSCOhost (Discover), Pubmed (Medline), Medline with full text and CINAHL Plus with full text; Microsoft office Excel application was used as the data extraction matrix for individual studies included.

FINDINGS: 1074 articles were identified for Title/Abstract and Full text screening, with 14 articles included for analysis, after the inclusion/exclusion criteria-based screening process. 11 of the studies focused on insulin resistance; while, the other 3 studies, focused on insulin sensitivity and insulin secretion. Physical, Dietary, Biochemical, Genetic, and Morbidity factors were significantly associated and correlated with insulin resistance; while, Exercise/Fitness and Medication/Supplementation factors were associated with insulin sensitivity and insulin secretion, across different population groups in UK.

CONCLUSION: Insulin parameters are influenced by both intrinsic and extrinsic biological factors; with the most predominant influence exerted by Biochemical, Genetic and Medication (Supplementation) factors. The impact of these influences, results in the development of Diabetes mellitus, Insulin resistance syndrome, Beta-cell dysfunction and other related metabolic diseases.

TABLE OF CONTENTS

DECLARATION2

DEDICATION3

ACKNOWLEDGEMENTS4

ABSTRACT8

KEY WORDS9

ABBREVIATIONS9

1.0 CHAPTER ONE10

1.1 INTRODUCTION10

1.2 BACKGROUND11

1.2.1 Types of Diabetes Mellitus11

1.2.2 Risks Factors of Diabetes Mellitus13

1.2.3 Statistical Variations of Diabetes Mellitus13

1.3 STUDY RATIONALE14

1.4 RESEARCH (REVIEW) QUESTION16

1.5 AIM AND OBJECTIVES16

2.0 CHAPTER TWO – LITERATURE REVIEW17

2.1 INTRODUCTION17

2.1.1 Inclusion Criteria17

2.1.2 Exclusion Criteria17

2.2 REVIEW OF LITERATURE18

2.3 INSULIN RESISTANCE18

2.3.1 Influence of Biochemical Components18

2.3.2 Influence of Medication (Supplementation)20

2.3.3 Influence of Psychological Factors21

2.3.4 Ethnic Variations and Insulin Resistance21

2.3.5 Influence of Dietary Factors21

2.3.6 Physical factors/Fitness and Insulin Resistance22

2.4 INSULIN SECRETION22

2.4.1 Influence of Biochemical Components22

2.4.2 Influence of Medication (Supplementation)24

2.4.3 Physical Factors/Fitness and Insulin Resistance25

2.5 INSULIN SENSITIVITY25

2.5.1 Influence of Biochemical Components26

2.5.2 Influence of Dietary factors27

2.5.3 Influence of Medication (Supplementation)28

2.5.4 Influence of Physical Activities, Morbidity and Ethnicity29

2.6 CHAPTER SUMMARY30

CHAPTER THREE – METHODOLOGY32

3.1 INTRODUCTION32

3.2 BACKGROUND32

3.3 SYSTEMATIC REVIEW METHODOLOGY33

3.3.1 Methodological Protocol34

3.4 RESEARCH (REVIEW) QUESTION AND INCLUSION/EXCLUSION CRITERIA35

3.4.1 Inclusion/Exclusion Criteria and Rationale35

3.5 SEARCH STRATEGY FOR IDENTIFYING LITERATURE36

3.5.1 Search Terms and Boolean Operators37

3.5.2 Strategy for Screening Studies37

3.5.3 Framework of Selection37

3.5.4 Study Outcome Measures39

3.5.5 Flow Chart of Searches and Screening40

3.6 DATA EXTRACTION41

3.7 QUALITY APPRAISAL41

3.8 ANALYSIS OF DATA42

3.9 DATA PROTECTION AND SAFE KEEPING43

3.10 THE REVIEW (RESEARCH) ETHICAL CONSIDERATIONS43

3.11 RESEARCH TIMELINE AND BUDGET44

3.12 CHAPTER SUMMARY44

CHAPTER FOUR – RESULTS47

4.1 INTRODUCTION47

4.2 FACTORS INFLUENCING INSULIN RESISTANCE47

4.2.1 Physical Factors47

4.2.2 Dietary Factor49

4.2.3 Biochemical Factors49

4.2.4 Genetic Factors50

4.2.5 Morbidity Factor51

4.3 FACTORS INFLUENCING INSULIN SENSITIVITY AND INSULIN SECRETION52

4.3.1 Exercise (Fitness) Factor52

4.3.2 Medication (Supplementation) Factors52

4.4 CHAPTER SUMMARY53

CHAPTER FIVE – DISCUSSION62

5.1 INTRODUCTION62

5.2 DISCUSSION OF FINDINGS62

5.2.1 Factors Influencing Insulin Resistance62

5.2.2 Factors Influencing Insulin Sensitivity and Insulin Secretion64

5.2.3 Author’s Conclusion65

5.3 IMPLICATIONS OF FINDINGS67

5.4 LIMITATIONS OF REVIEW69

5.4.1 Strengths and Weaknesses of Included Studies69

5.4.2 Strengths and Weaknesses of Review69

5.5 DISSEMINATION70

5.6 FUTURE RESEARCH71

5.7 CHAPTER SUMMARY72

6.0 CONCLUSION74

6.1 REFLECTION ON LEARNING79

7.0 REFERENCES80

8.0 BIBLIOGRAPHY97

9.0 APPENDICES98

9.1 APPENDIX 1 – DATA EXTRACTION MATRIX (MICROSOFT EXCEL SPREADSHEET)98

9.2 APPENDIX 2 – CASP APPRAISAL TOOL98

9.3 APPENDIX 3 – DISSERTATION TIMELINE100

9.4 APPENDIX 4 – ETHICAL APPROVAL LETTER102

FIGURES

Figure 1 – Flow-chart for Searches40

TABLES

Table 1 – Grading Profile of Quality Appraisal42

Table 2 – Synopsis of Selected Studies55