Why Insulin in Type 2 DM?

Why is Insulin used in Type 2 Diabetes Mellitus?

Let's begin with the basics on how Insulin works:

https://s.hswstatic.com/gif/diabetes-glucose-regulation.gif
TYPES OF DIABETES MELLITUS
TYPE 1 DIABETES MELLITUS
TYPE 2 DIABETES MELLITUS


Commonly 2nd and 3rd decades of life
Commonly 6th and 7th decades of life
Caused by autoimmune destruction of pancreatic beta cells
Caused by insulin resistance at peripheral adipose and muscle tissues
Insulin levels- Decreased
Insulin levels- increased

Based on the common differences between the two entities, it would seem that the mainstay of treatment for Type 1 DM is insulin (which it is) and that for Type 2 DM would be anything other than insulin ( given the already elevated insulin levels).
Conventional treatment of Type II Diabetes Mellitus starts with:

 1.Lifestyle modifications - Exercise, eating healthy, decreased consumption of alcohol and tobacco.

 2.Oral hypoglycemics – some of which decrease insulin resistance and some of which increase pancreatic secretion of insulin.

 3.Insulin
Now answering your specific question:
Why is Insulin used in Type 2 Diabetes Mellitus?
This can also be paraphrased to – why are oral hypoglycemics such as sulfonylureas (which increase pancreatic secretion of insulin), used in Type 2 DM, given that there’s already increased insulin levels within the body??
The answer to this question is not simple but stems from research-hypothesized theories of the pathophysiology of Type 2 DM.
The pathophysiology of type 2 DM is more complex than it appears. Multiple studies done on Pima Indians[1] [2] (a group of Native Americans living in an area consisting of what is now central and southern Arizona, known to be the most genetically predisposed race to Type 2 Diabetes Mellitus) , illustrate the complex pathophysiology of Type 2 DM. The entire spectrum of pathophysiology appears to be based of the image given below.
As is evident from the diagram, the pathophysiology of Type 2 DM in its it's most severe stage involves a failure of beta- pancreatic cells which causes a net insulin deficit in the body, (this stage was prevalent in Pima Indians.) Thus arises the need for insulin and insulin secreting hypoglycemics in type 2 DM
Image result for paTHOPHYSIOLOGY OF dm TYPE 2
By Dr Jason D'Cruz
References:

1)Weyer C, Bogardus C, Mott DM, Pratley RE
The natural history of insulin secretory dysfunction and insulin resistance in the pathogenesis of type 2 diabetes mellitus. J Clin Invest 1999; 104:787–794pmid:10491414
Baier LJ, Hanson RL


2)Genetic studies of the etiology of type 2 diabetes in Pima Indians: hunting for pieces to a complicated puzzle. Diabetes 2004; 53:1181–1186pmid:15111484

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