Write a five page (body; double spaced) review of the topic Metabolic Syndrome from a public health biology perspective. In your review, include the following: Discuss the biological basis of energy...

A syndrome is defined as "The aggregate of signs and symptoms associated with
any morbid process, and constituting together the picture of the disease". The
metabolic syndrome represents a heterogeneous group of metabolic disorders,
the central component of which is insulin resistance. It can involve multiple
metabolic pathways that culminate in dyslipidaemia , abdominal obesity,
microalbuminuria and hypertension.

The WHO has defined the metabolic syndrome as impaired insulin sensitivity,
glucose intolerance or diabetes mellitus in combination with at least two other
metabolic derangements, including abdominal obesity, dyslipidaemia (HDL-
cholesterol levels and/or elevated plasma triacylglycerol (TAG)
concentrations) and urinary microalbuminuria.

The National Cholesterol ducation Program Adult Treatment Panel III (Expert
Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in
Adults, 2001) have proposed that individuals with the metabolic syndrome have
three or more of the following metabolic derangements, including central obesity
(waist girth >1020mm in men or >880mm in women), low HDL-cholesterol
concentrations (<1.1 mmol/l for men or <1.3 mmol/l for women),
hypertriacylglycerolaemia (>1.7 mmol/l), hypertension (blood pressure
>130/85mmHg) or fasting hyperglycaemia (>6.1 mmol/l). Thus, the metabolic
syndrome represents a genetically-heterogeneous group of metabolic disorders
sharing insulin resistance.
Abnormalities associated with the metabolic syndrome (modified from Reaven,
2002) are as follows :-
The core cluster
Central obesity, Dyslipidemia, hypertriglyceridemia,low HDL cholesterol,small
dense LDL particles,postprandial lipemia,Glucose intolerance-impaired fasting
glucose,impaired glucose tolerance,type 2 diabetes,Insulin resistance,Hypertension
Other often associated features
Microalbuminuria,Hyperuricemia and gout,Impaired fibrinolysis and increased
coagulability,elevated PAI-1,elevated fibrinogen,increased levels of von
Willebrand factor,Signs of chronic inflammation-elevated CRP, Endothelial
dysfunction,-impaired endothelium-dependent vasodilatation,Low
cardiorespiratory fitness,Fatty liver disease,Polycystic ovary syndrome,Increased
sympathetic activity,low heart rate variability.

Genetic and environmental components of the metabolic syndrome

The global increase in the incidence of the metabolic syndrome and T2DM over
the last few decades is a salient example of how the interaction between lifestyle
and genotype can dramatically impact on health. The familial nature the marked
difference in the prevalence among various racial groups and the difference in
concordance rates between monozygotic twins is clearly consistent with a genetic
component to disease susceptibility.
Heritability studies demonstrate a marked genetic influence on several features of
the insulin resistance syndrome. One study has shown that the heritability
estimates
for fasting glucose concentration and the homeostasis model assessment of
pancreatic b-cell function are 0.72 and 0.78 respectively. On the other hand,
another
study has reported heritability estimates for fasting glucose, insulin, TAG and
HDLcholesterol concentrations of 20, 23, 20 and 43% respectively.
Diet-related environmental factors and the risk of the metabolic syndrome
Obesity has been identified as the key aetiological condition that predisposes to the
development of the metabolic syndrome. There are at least two ways whereby
adipose tissue may influence glucose homeostasis and act as the key aetiological
factor in the development of insulin resistance and the metabolic syndrome. First,
excessive adipose tissue energy storage results in increased fatty acid flux to other
tissues and increased TAG storage in peripheral tissues, which interferes with
insulin signalling, inhibits glucose uptake and promotes insulin resistance. Second,
adipose tissue is an important endocrine organ that secretes several inflammatory
factors,collectively known as adipocytokines or adipokines, many of which have a
direct effect on insulin sensitivity.
Approaches for identifying the genetic determinants of the metabolic
syndrome
The candidate-gene approach has been the traditional approach for identifying the
genes involved in the metabolic syndrome. The candidate genes can be identified
according to biological function and/or linkage studies, and association tests for
significant differences in their allele frequencies between a patient group and a
control population. Given the number of metabolic pathways involved in the
metabolic syndrome it is immediately apparent that the number of potential
candidate genes is tremendous. Overall, there has not been a high extent of success
from candidate-gene studies in terms of defining the genetic determinants of the
metabolic syndrome.
Genetic-disease-association studies are fraught with difficulties,and a number of
the positive results have not been replicated in subsequent studies. The main
reasons for the disparity are inadequate statistical power, multiple hypothesis
testing, population stratification, publication bias and phenotypic differences.It is
becoming increasingly evident that the identification of true genetic associations in
common...